JP2021046499A - Pressure-sensitive adhesive, and pressure-sensitive adhesive sheet - Google Patents

Abstract

To provide a pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having good releasability even if under a more extreme environment than before, a pressure-sensitive adhesive sheet using the same, a pressure-sensitive adhesive having excellent curving properties and low adhesiveness, and a pressure-sensitive adhesive sheet using the same.SOLUTION: The problem is solved by a pressure-sensitive adhesive including: polyurethanepolyol (A) which is a reaction product of polyol (x) and polyisocyanate (y); a polyfunctional isocyanate compound (B); and a compound (C) having a hydroxy group, and a steroid skeleton.SELECTED DRAWING: None

Description

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

Conventionally, as a surface protection sheet for various members, an adhesive sheet in which an adhesive layer is formed on a base material sheet has been widely used. Examples of the pressure-sensitive adhesive include an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a urethane-based pressure-sensitive adhesive. Acrylic adhesives have excellent adhesive strength, but because of their strong adhesive strength, they do not have good re-peelability after being attached to an adherend. In particular, after a lapse of time in a high-temperature and high-humidity environment, the re-peelability is further reduced due to the increase in adhesive strength, and the adhesive tends to remain on the surface of the adherend after re-peeling. .. Silicone adhesives tend to contaminate the adherend, and silicone resins with relatively low molecular weight may volatilize and adsorb to the surface of devices such as electronic devices, causing problems. On the other hand, the urethane-based adhesive has good adhesion to the adherend, has relatively excellent removability, and is difficult to volatilize.

Patent Document 1 discloses a urethane-based pressure-sensitive adhesive in which a polyfunctional isocyanate compound is blended with a polyurethane polyol obtained by reacting a polyester polyol, a polyether polyol, and an organic polyisocyanate in the presence of two types of catalysts. (Claim 1). It is described that this urethane-based pressure-sensitive adhesive has good removability after being left on the adherend under the condition of 40 ° C.-65% RH (paragraph 0051 and Table 2). Examples 1-6 etc.).
In the present specification, "RH" indicates relative humidity unless otherwise specified.

Patent Document 2 discloses a urethane-based pressure-sensitive adhesive containing a polyurethane polyol, a polyfunctional isocyanate compound, and a fatty acid ester having 10 to 30 carbon atoms (claim 1). It is described that this urethane-based adhesive has good removability after being left on the adherend under the condition of 40 ° C.-80% RH for 24 hours (paragraphs 0049 and Table 1). Examples 1 to 4 etc.).

Patent Document 3 discloses a urethane-based pressure-sensitive adhesive containing a polyurethane polyol, a polyfunctional isocyanate compound, and at least one compound selected from a polyalkylene glycol-based compound, an epoxy-based compound, and a phosphoric acid ester-based compound. (Claim 1). It is described that this urethane-based pressure-sensitive adhesive has good removability after being left on the adherend under the condition of 60 ° C.-90% RH for 96 hours (paragraph 0061 and Table 1). Examples 1 to 18 etc.).

Japanese Unexamined Patent Publication No. 2000-73040 Japanese Unexamined Patent Publication No. 2011-190420 Japanese Unexamined Patent Publication No. 2015-7226

Flat panel displays such as liquid crystal displays (LCDs) and organic electroluminescence displays (OELDs), as well as touch panel displays that combine such flat panel displays and touch panels, include televisions, personal computers (PCs), mobile phones, and personal digital assistants. Widely used in electronic devices such as terminals.
Urethane-based adhesive sheets are suitably used as surface protective sheets for flat panel displays and touch panel displays, as well as substrates and optical members manufactured or used in these manufacturing processes.
The range of use of the above electronic devices is expanding, and there is a possibility that they will be placed in a hot and humid environment that is harsher than before.

In a display such as OLED, it is possible to make it flexible by using a plastic film as a substrate. In such an application, it is preferable that the adhesive layer does not peel off from the base sheet even when the structure in which the adhesive sheet is attached to the flexible adherend is repeatedly curved, and has good curvature. Further, in order to avoid damage to the optical member when the adhesive sheet is peeled off, the adhesive sheet preferably has low adhesiveness.

The present invention has been made in view of the above circumstances, and is a pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having good removability even when placed in a harsher high-temperature and high-humidity environment than before. It is an object of the present invention to provide an adhesive sheet using this.
It is also an object of the present invention to provide a pressure-sensitive adhesive having excellent curvature and low tackiness, and a pressure-sensitive adhesive sheet using the same.

The present inventors have reached the present invention as a result of diligent studies in order to solve the above problems.
That is, the present invention comprises a polyurethane polyol (A), which is a reaction product of a polyol (x) and a polyisocyanate (y), a polyfunctional isocyanate compound (B), and a compound (C) having a hydroxyl group and a steroid skeleton. Regarding adhesives contained.

The present invention also relates to the pressure-sensitive adhesive, which comprises 0.5 to 20 parts by mass of the compound (C) with respect to 100 parts by mass of the polyurethane polyol (A).

The present invention also relates to the pressure-sensitive adhesive, wherein the compound (C) has one hydroxyl group in one molecule.

The present invention also relates to a pressure-sensitive adhesive sheet including a base material sheet and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive.

In the present specification, "Mw" is a polystyrene-equivalent weight average molecular weight determined by gel permeation chromatography (GPC) measurement. "Mn" is a polystyrene-equivalent number average molecular weight determined by GPC measurement. These can be measured by the method described in the [Examples] section.

According to the present invention, there is provided an adhesive capable of forming an adhesive layer having good removability even when placed in a harsher high temperature and high humidity environment than before, and an adhesive sheet using the same. can do.
According to the present invention, it is also possible to provide a pressure-sensitive adhesive capable of achieving both excellent curvature and low adhesiveness, and a pressure-sensitive adhesive sheet using the same.

Embodiments of the present invention will be described in detail below, but the following description is an example (representative example) of embodiments of the present invention, and the present invention is not limited to these contents as long as the gist thereof is not exceeded.

≪Adhesive≫
The pressure-sensitive adhesive of the present invention contains a polyurethane polyol (A), which is a reaction product of a polyol (x) and a polyisocyanate (y), a polyfunctional isocyanate compound (B), and a compound (C) having a hydroxyl group and a steroid skeleton. Including.
As a result, it is possible to obtain a pressure-sensitive adhesive having good re-peelability, low adhesiveness, and excellent curvature even when placed in a harsher high-temperature and high-humidity environment than before.

<Polyurethane polyol (A)>
The polyurethane polyol (A) is a reaction product obtained by copolymerizing one or more polyols (x) with one or more polyisocyanates (y). The copolymerization reaction can be carried out in the presence of one or more catalysts, if necessary. If necessary, one or more kinds of solvents can be used for the copolymerization reaction.

[Polycarbonate (x)]
The polyol (x) is preferably a known polyol having two or more hydroxyl groups. Examples of the polyol (x) include polyacrylic polyol, polyether polyol, polyester polyol, polybutadiene-modified polyol, polycaprolactone polyol, polycarbonate polyol, castor oil-based polyol and the like. Among these, polyether polyols, polyester polyols, polycaprolactone polyols and polycarbonate polyols are preferable, and polyether polyols and polyester polyols are more preferable.

As the polyester polyol, a known polyester polyol is used. The polyester polyol requires, for example, an acid component and a glycol component, and can be synthesized by an esterification reaction using the polyol component if necessary. Examples of the acid component include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid and the like. Further, as a glycol component, ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexaneglycol, 3-methyl-1,5-pentanediol, 3,3'- Dimethylol heptane, butyl ethylpentanediol, polyoxyethylene glycol, polyoxypropylene glycol, and examples of the polyol component include glycerin, trimethylolpropane, and pentaerythritol.

The molecular weight of the polyester polyol is preferably a number average molecular weight of 500 to 5,000, as it can be used without particular limitation. When a number average molecular weight of 500 to 5,000 is used, appropriate reactivity can be obtained, and a resin having better cohesive force can be easily obtained. When two or more kinds of the polyol (x) are used, the polyester polyol is preferably 0 to 100 mol%, more preferably 30 to 80 mol% in 100 mol% of the polyol (a).

As the polyether polyol, a known polyether polyol is used. The polyether polyol is obtained by polymerizing an oxylan compound such as ethylene oxide, propylene oxide, butylene oxide or tetrahydrofuran using, for example, a low molecular weight polyol such as water, ethylene glycol, propylene glycol, glycerin or trimethylolpropane as an initiator. can get. As the polyether polyol, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like having two or more hydroxyl groups are preferable, and polypropylene glycol is more preferable.
Polypropylene glycol can be obtained by addition polymerization of propylene oxide, but most of the propylene oxide is β-cleaved to become a secondary hydroxyl group having low reactivity with isocyanate at the end. Therefore, in order to increase the reactivity with the polyfunctional isocyanate compound (B), a known method for obtaining polypropylene glycol having a primary hydroxyl group at the terminal by addition polymerization of ethylene oxide or α cleavage of propylene oxide with a specific catalyst. There is.
The molecular weight of the polyether polyol is preferably a number average molecular weight of 500 to 5,000, as it can be used without particular limitation. When a number average molecular weight of 500 to 5,000 is used, appropriate reactivity can be obtained, and a resin having good cohesive force can be easily obtained. When two or more kinds of the polyol (a) are used, the polyether polyol is preferably 10 to 100 mol% in 100 mol% of the polyol (a), more preferably 20 to 90 mol%.

Further, in the present invention, if necessary, a part of the polyether polyol may be ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylpropane, glycols such as pentaerythritol, ethylenediamine, etc. It can be used in combination with polyvalent amines such as N-aminoethylethanolamine, isophoronediamine, and xylylenediamine.

Polybutadiene-modified polyols have, for example, two or more hydroxyl ends and have a 1,2-vinyl site, a 1,4-cis site, a 1,4-trans site or a structure in which they are hydrogenated, and are direct. It is a chain or branched polybutadiene.

The number average molecular weight (Mn) of the polybutadiene-modified polyol is preferably 200 to 6,000, more preferably 500 to 6,000, even more preferably 500 to 4,000, and particularly preferably 500 to 3,000. By setting the number average molecular weight in the above range, appropriate reactivity can be obtained, and a resin having good cohesive force can be easily obtained.

To the extent that the polybutadiene-modified polyol is hydrogenated, it is preferable that all of the double bond sites existing before hydrogenation are hydrogenated, but in the present invention, some double bond sites remain. Is also good.

The polycaprolactone polyol is preferably, for example, a caprolactone-based polyester diol obtained by ring-opening polymerization of a cyclic ester monomer such as ε-caprolactone or σ-valerolactone.

The molecular weight of the polycaprolactone polyol is preferably a number average molecular weight of 500 to 5,000, as it can be used without particular limitation. By setting the number average molecular weight in the above range, appropriate reactivity can be obtained, and the adhesive force and the cohesive force can be further improved. When two or more kinds of the polyol (x) are used, the polycaprolactone polyol is preferably 0 to 80 mol%, more preferably 5 to 60 mol% in 100 mol% of the polyol (a).

The polycarbonate polyol is, for example, a polycarbonate polyol obtained by subjecting the above polyol component and phosgen to a polycondensation reaction; the above polyol component and dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, ethylbutyl carbonate, ethylene carbonate, propylene. Polycarbonate polyol obtained by ester exchange condensation with carbonic acid diesters such as carbonate, diphenyl carbonate, dibenzyl carbonate; copolymerized polycarbonate polyol obtained by using two or more of the above polyol components in combination; the various polycarbonate polyols and carboxyl group-containing compounds Polycarbonate polyol obtained by esterifying the above-mentioned various polycarbonate polyols; polycarbonate polyol obtained by etherifying the above-mentioned various polycarbonate polyols with a hydroxyl group-containing compound; polycarbonate obtained by performing an ester exchange reaction between the above-mentioned various polycarbonate polyols and an ester compound. Polycarbonate; Polycarbonate polyol obtained by ester-exchange reaction of various polycarbonate polyols with hydroxyl group-containing compound; Polycarbonate-based polycarbonate polyol obtained by polycondensation reaction of various polycarbonate polyols with dicarboxylic acid compound; Examples thereof include a copolymerized polyether polycarbonate polyol obtained by copolymerizing with an alkylene oxide.

The molecular weight of the polycarbonate polyol is preferably a number average molecular weight of 500 to 5,000, as it can be used without particular limitation. By setting the number average molecular weight in the above range, appropriate reactivity can be obtained, and a resin having good cohesive force can be easily obtained. When two or more kinds of the polyol (x) are used, the polycarbonate polyol is preferably 0 to 70 mol%, more preferably 5 to 60 mol% in 100 mol% of the polyol (a).

As the polyol (a) used in the present invention, it is preferable to use two or more kinds of polyols (a). When two or more types of polyols are used, the molecular weight distribution can be easily adjusted and the cohesive force can be arbitrarily adjusted, so that the adhesive force and the curvability can be balanced at a high level.

Further, in the present invention, it is preferable to use a polyol (x) having three or more hydroxyl groups in combination. The polyol having three or more hydroxyl groups is preferably contained in an amount of 10 to 95% by mass in 100% by mass of the polyol (x). When the polyol having three or more hydroxyl groups is set in a predetermined range, the coatability of the pressure-sensitive adhesive is further improved, the good cross-linking density of the formed pressure-sensitive adhesive layer is further improved, and the removability is further improved.

[Polyisocyanate (y)]
As the polyisocyanate (y), known ones can be used, and examples thereof include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

Examples of the aromatic polyisocyanate include 1,3-phenylenediocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylenediocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, and 2,6-triisocyanate. Range isocyanate, 4,4'-toluidin diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4', 4 "-Triphenylmethane triisocyanate, ω, ω'-diisocyanate-1,3-dimethylbenzene, ω, ω'-diisocyanate-1,4-dimethylbenzene, ω, ω'-diisocyanate-1,4-diisocyanate, 1, , 4-Tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate and the like.

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

Examples of the alicyclic polyisocyanate include 3-isocyanate methyl-3,5,5-trimethylcyclohexylisocyanate, 1,3-cyclopentanediisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, and methyl-2,4. -Cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,4-bis (isocyanatemethyl) cyclohexane, 1,4-bis (isocyanatemethyl) cyclohexane and the like can be mentioned. ..

In addition, examples of the polyisocyanate include a trimethylolpropane adduct form, a biuret form, and a trimer of the above-mentioned polyisocyanate (the trimer contains an isocyanurate ring) and the like.

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

[catalyst]
Known catalysts can be used, and examples thereof include tertiary amine compounds and organometallic compounds.

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

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 acetate. , Triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate and the like.
Non-tin compounds include titanium-based compounds such as dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride; lead-based compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; 2 -Iron-based such as iron ethylhexanoate and iron acetylacetonate; cobalt-based such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc-based such as zinc naphthenate and zinc 2-ethylhexanoate; Examples include zirconium.

One kind or two or more kinds of catalysts can be used.
When a plurality of types of polyols (x) having different reactivity are used in combination, the difference in reactivity may cause poor polymerization stability or white turbidity of the reaction solution in a single catalyst system. In this case, by using two or more kinds of catalysts, the reaction (for example, reaction rate) can be easily controlled, and the above problem can be solved. In a system in which a plurality of types of polyols (x) having different reactivity are used in combination, it is preferable to use two or more types of catalysts. The combination of two or more kinds 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. is there. When the mass ratio is less than 1, the balance of catalytic activity is good, 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 1.0 mass with respect to the total amount of one or more polyols (x) and one or more polyisocyanates (y). It is a department.

[solvent]
If necessary, one or more kinds of solvents can be used for the polymerization of the polyurethane polyol (A). Known solvents can be used, and examples thereof include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Ethyl acetate, toluene and the like are particularly preferable from the viewpoint of the solubility of the polyurethane polyol (A) and the boiling point of the solvent.

[Polymerization method]
The polymerization method of the polyurethane polyol (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.
Procedure 1) A procedure in which one or more polyols (x), one or more polyisocyanates (y), one or more catalysts if necessary, and one or more solvents as necessary are collectively charged into a flask. ;
Step 2) One or more polyols (x), one or more catalysts as needed, and one or more solvents as needed are placed in a flask, and one or more organic polyisosianates (y) are charged therein. Can be mentioned as a procedure for dropping and adding.
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 85 to 95 ° C. When the reaction temperature is 100 ° C. or higher, it becomes difficult to control the reaction rate, polymerization stability, etc., and it may be difficult to produce the polyurethane polyol (A) having a desired molecular weight.
The reaction temperature when no catalyst is used is preferably 100 ° C. or higher, more preferably 110 ° C. or higher. The reaction time when no catalyst is used is preferably 3 hours or more.

The weight average molecular weight (Mw) of the polyurethane polyol (A) is preferably 10,000 to 500,000, more preferably 30,000 to 400,000, and particularly preferably 50,000 to 350,000. When the Mw of the polyurethane polyol (A) is in an appropriate range, good coatability can be easily obtained. The molecular weight dispersion (Mw / Mn) is preferably 1 to 15, more preferably 4 to 12.

<Polyfunctional isocyanate compound (B)>
As the polyfunctional isocyanate compound (B), known compounds can be used, and the compounds exemplified as the polyisocyanate (y) which is the raw material of the polyurethane polyol (A) (specifically, aromatic polyisocyanate, aliphatic polyisocyanate, Aromatic aliphatic polyisocyanates, alicyclic polyisocyanates, and trimetylolpropane adducts / burettes / trimerics thereof) can be used.

<Compound (C) having a hydroxyl group and a steroid skeleton>
The compound (C) having a hydroxyl group and a steroid skeleton is a compound having a hydroxyl group and having a cyclopentano-perhydrophenanthrene nucleus (synonymous with a steroid nucleus) as a basic skeleton. It can have various structures depending on the type, and many of them are present in plants.

Examples of the compound (C) having a hydroxyl group and a steroid skeleton include a compound having a cyclopentano-perhydrophenanthrene nucleus having a hydroxyl group, a compound having a double bond in the alicyclic of the nucleus, and a compound having a substituent thereof. Specific examples of the compound (C) include compounds represented by the following formulas [1] to [9] and the like. (In the following equation, the broken line indicates that C = C double bond may be used.)

（式中、ｎは１〜５０を表す。）

(In the formula, n represents 1 to 50.)

In the above equations [1] to [9], Ra to Ri are independent of each other.
Hydrogen atom, oxygen atom, alkyl group, alkenyl group, alkynyl group, hydroxyl group, formyl group,
Alkylcarbonyl group, hydroxyalkylcarbonyl group, carboxyalkylcarbonyl group, formaltoalkylcarbonyl group, acetoxyalkylcarbonyl group,
Alkylcarboxy group, hydroxyalkylcarboxy group, carboxyalkylcarboxy group, formaltoalkylcarboxy group, acetoxyalkylcarboxy group,
Alkoxy group, hydroxyalkoxy group, carboxyalkoxy group, formalkoxy group, acetoxyalkoxy group,
It is a benzoyloxy group or a group represented by any of the following formula [10].
Examples of the alkyl group include a methyl group and an ethyl group. Examples of the alkenyl group include a vinyl group and an allyl group. Examples of the alkynyl group include an ethynyl group and a propa-2-in-1-yl group.
("Holmart" means "-O-CH = O". In the following formula, | * | indicates a bond.)

The compound (C) having a hydroxyl group and a steroid skeleton is not limited as long as it is a compound having a cyclopentanoperhydrophenantrene nucleus having a hydroxyl group, but among them, a compound having one hydroxyl group in one molecule is preferable. .. By having one hydroxyl group in one molecule, the cross-linking reaction between the polyol component (A) and the polyisocyanate component (B) can be controlled, and high curvature can be obtained.

The hydroxyl group of the compound (C) having a hydroxyl group and a steroid skeleton is preferably a primary hydroxyl group and / or a secondary hydroxyl group. By being a primary hydroxyl group and / or a secondary hydroxyl group, the reactivity with the polyisocyanate component (B) is improved, and high moist heat resistance and curvability can be obtained.

The molecular weight of the compound (C) having a hydroxyl group and a steroid skeleton is preferably 250 to 800, and more preferably 300 to 500. When the molecular weight is 250 or more, a sufficient cohesive force can be obtained, and the removability in a high temperature and high humidity environment can be improved. When the molecular weight is 800 or less, excessive cohesive force can be suppressed and deterioration of curvature can be suppressed.

In another preferred embodiment, the substituents Ra to Ri in the formulas [1] to [9] are preferably an alkyl group, an alkenyl group, or an alkynyl group having 5 or more carbon atoms. .. When the substituent has an alkyl group, an alkenyl group, or an alkynyl group having 5 or more carbon atoms, the adhesive strength and the heat resistance to moisture and humidity can be improved, and the compatibility with the polyurethane polyol (A) is further improved. ..

Specific examples of the compound (C) having a hydroxyl group and a steroid skeleton described above include
Desoxycorticosterone, 11-dehydrocorticosterone, NIKKOL BPS-X (where X is 5, 10, 20, 30), NIKKOL BPSH-25, NIKKOL DHC-30, etc., which can be obtained from Nikko Chemicals Co., Ltd. Compound having a steroid skeleton having a primary hydroxyl group of
Cholesterol, β-sitosterol, campesterol, stigmasterol, brassicasterol, lanosterol, ergosterol, β-cholestanol, testosterone, estrone, dehydroepiandrosterone, coprostanol, pregnenolone, epicholestanol, 7-dehydrocholesterol, tigogenin , A compound having a steroid skeleton having a secondary hydroxyl group such as hecogenin;
Compounds with a steroid skeleton having a tertiary hydroxyl group such as metandienone, cortisone acetate, and stenolone;
Steroids with polyfunctional hydroxyl groups such as β-estradiol, α-estradiol, bolandiol, cortisone, prednisolone, corticosterone, aldosterone, 18-hydroxycorticosterone, 4-androsten-11α, 17β-diol-3-one. Examples thereof include compounds having a skeleton.
Of these, cholesterol, β-sitosterol, campesterol, stigmasterol, brassicasterol, lanosterol, ergosterol, β-cholestanol, coprostanol, epicholestanol, and 7-dehydrocholesterol are one hydroxyl group in one molecule. It is more preferable because it has a molecular weight of 300 to 500, and the substituent has 5 or more carbon atoms.

As the compound (C) having these hydroxyl groups and a steroid skeleton, one type may be used alone, or two or more types may be used in combination. Examples of the mixture of two or more kinds include phytosterol, which is a mixture of β-sitosterol, campesterol, stigmasterol, brassicasterol and the like.

The adhesive composition of the present invention has an equivalent ratio of an isocyanato group in a polyfunctional isocyanate (B), a hydroxyl group in a polyurethane polyol (A), and a hydroxyl group in a hydroxyl group and a compound (C) having a steroid skeleton (isocyanato group). / Hydroxyl group) is preferably 0.6 to 5.0, more preferably 0.8 to 2.5. When the isocyanato group / hydroxyl ratio is 0.6 or more, high removability can be obtained, and when the isocyanato group / hydroxyl ratio is 5.0 or less, the decrease in curvature due to excessive cohesive force can be suppressed.

<Plasticizer>
Since the wettability can be improved, the pressure-sensitive adhesive of the present invention can further contain one or more plasticizers. Examples of the plasticizer include a fatty acid ester-based plasticizer, a polyether ester-based plasticizer, a hydroxycarboxylic acid ester-based plasticizer, and a phosphoric acid ester-based plasticizer.

Examples of the fatty acid ester include an ester of a monobasic acid or polybasic acid having 6 to 18 carbon atoms and a branched alcohol having 18 or less carbon atoms, and an unsaturated fatty acid or branched acid having 14 to 18 carbon atoms and an alcohol having 4 or less valences. Examples thereof include esters and esters of monobasic acids or polybasic acids having 6 to 18 carbon atoms and polyalkylene glycols.

Examples of the ester of a monobasic acid or polybasic acid having 6 to 18 carbon atoms and a branched alcohol having 18 or less carbon atoms include isostearyl laurate, isopropyl myristate, isosetyl myristate, octyldodecyl myristate, and isostearyl palmitate. Examples thereof include isocetyl stearate, octyldodecyl oleate, diisostearyl adipate, diisocetyl sebacate, trioleyl trimeritate, and triisocetyl trimeritate.

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

Examples of the polyether ester-based plasticizer include polyethylene glycol dihexylate, polyethylene glycol di-2-ethylhexylate, polyethylene glycol dilaurate, polyethylene glycol dioleate, and dipolyethylene glycol methyl ether adipate.

The plasticizer may be a compound containing a fatty acid ester structure and a polyether structure, such as polyoxyethylene ether of a sorbitan fatty acid ester obtained by condensing ethylene oxide with a sorbitan fatty acid ester. For example, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monooleate and the like can be mentioned.

Examples of the hydroxycarboxylic acid ester-based plasticizer include butyl citrate, triethyl citrate, tripropyl citrate, and triethyl o-acetyl citrate.

Examples of the phosphoric acid ester-based plasticizer include tributyl phosphate, tris (2-ethylhexyl) phosphate, triphenyl phosphate, and tricresyl phosphate.

The number average molecular weight (Mn) of the plasticizer is not particularly limited, and is preferably 200 to 1,000, more preferably 230 to 900, still more preferably 250 to 800, and particularly preferably 250 to 250, from the viewpoint of improving the wetting rate. It is 500.

<Antistatic agent>
The pressure-sensitive adhesive of the present invention may further contain an antistatic agent. When an antistatic agent is contained, electrostatic discharge when the adhesive sheet is peeled off is suppressed, and for example, it is easy to prevent damage to parts incorporated in a display or the like. Examples of the antistatic agent include inorganic salts, ionic liquids, surfactants and the like. Of these, ionic liquids are preferred. The "ionic liquid" is also referred to as a molten salt at room temperature, and exhibits the properties of the liquid 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.

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

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, a known ionic liquid in which the cation is a pyrrolidinium salt, a phosphonium salt, a sulfonium salt or the like can be appropriately used.

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

Nonionic types include, for example, glycerin fatty acid ester, polyoxyalkylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene alkyl amine fatty acid ester, fatty acid diethanolamide, polyether ester amide type. , Ethylene oxide-epichlorohydrin type, polyether ester type and the like.
Anionic types include, for example, alkyl sulfonates, alkylbenzene sulfonates, alkyl phosphates, polystyrene sulfonic acid types and the like. Examples of the cationic type include a tetraalkylammonium salt, a trialkylbenzylammonium salt, and a quaternary ammonium base-containing acrylate polymer type.
The amphoteric types include, for example, amino acid amphoteric tenside agents such as alkyl betaine and alkyl imidazolium betaine, higher alkyl aminopropionate, higher alkyl dimethyl betaine, and betaine amphoteric tenside agents such as higher alkyl dihydroxyethyl betaine. Can be mentioned.

The antistatic agent may be used alone or in combination of two or more.

The amount of the antistatic agent blended 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 polyol (A).

<Solvent>
The pressure-sensitive adhesive of the present invention may contain one or more kinds of solvents, if necessary. Known solvents can be used, and examples thereof include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Ethyl acetate, toluene and the like are particularly preferable from the viewpoint of the solubility of the polyurethane polyol (A) and the boiling point of the solvent.

<Other optional ingredients>
The pressure-sensitive adhesive of the present invention may contain one or more other optional components, if necessary, as long as the effects of the present invention are not impaired. Other optional components include catalysts, resins other than urethane resins, fillers, metal powders, pigments, foils, softeners, conductive agents, antioxidants, UV absorbers, light stabilizers, surface lubricants. Examples thereof include agents, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, antifoaming agents, lubricants and the like.

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

Examples of the antioxidant include a radical chain inhibitor such as a phenolic antioxidant; a peroxide decomposition agent such as a sulfur-based antioxidant and a phosphorus-based antioxidant.

As a phenolic antioxidant,
2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stea-β- (3,5-di-t-butyl-). 4-Hydroxyphenyl) Monophenolic antioxidants such as 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), and 3,9-bis [1,1-dimethyl-2- [β- (3-t-butyl-4-hydroxy) -5-Methylphenyl) Propionyloxy] Ethyl] 2,4,8,10-Tetraoxaspiro [5,5] Bisphenol antioxidants such as undecane;
1,1,3-Tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl) -4-Hydroxybenzyl) benzene, tetrakis- [methylene-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane, bis [3,3'-bis- (4') -Hydroxy-3'-t-butylphenyl) butyric acid] glycol ester, and 1,3,5-tris (3', 5'-di-t-butyl-4'-hydroxybenzyl) -S-triazine- Examples thereof include high molecular weight phenolic antioxidants such as 2,4,6- (1H, 3H, 5H) trione and tocophenol.

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

Examples of the phosphorus-based antioxidant include triphenylphosphine, diphenylisodecylphosphine, phenyldiisodecylphosphine and the like.

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

Examples of benzophenone-based ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, and 2,2'-dihydroxy. -4-Dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, and bis (2-methoxy-4-hydroxy-5-benzoylphenyl) Examples include methane.

Examples of the benzotriazole-based ultraviolet absorber include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, and 2- (2'). -Hydroxy-3', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2-( 2'-Hydroxy-3', 5'-di-tert-butylphenyl) 5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-Hydroxy-4'-octoxyphenyl) Benzotriazole, 2- [2'-Hydroxy-3'-(3 ", 4", 5 ", 6",-Tetrahydrophthalimidemethyl)- 5'-Methylphenyl] benzotriazole, 2,2'methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazole-2-yl) phenol], and [2 ( 2'-Hydroxy-5'-metaacryloxyphenyl) -2H-benzotriazole and the like can be mentioned.

Examples of the salicylic acid-based ultraviolet absorber include phenylsalicylate, p-tert-butylphenylsalicylate, and p-octylphenylsalicylate.

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

Examples of the light stabilizer include hindered amine-based light stabilizers and ultraviolet stabilizers.

Hindered amine light stabilizers include [bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate], bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and Examples thereof include methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate.

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

Examples of the leveling agent include an acrylic leveling agent, a fluorine-based leveling agent, and a silicone-based leveling agent. As an acrylic leveling agent, Polyflow No. 36, Polyflow No. 56, Polyflow No. 85HF, Polyflow No. 99C (manufactured by Isuremo Kyoeisha Chemical Co., Ltd.) and the like can be mentioned. Examples of the fluorine-based leveling agent include Megafuck F470N and Megafuck F556 (both manufactured by DIC Corporation). Examples of the silicone-based leveling agent include Grandic PC4100 (manufactured by DIC Corporation) and the like.

<Mixing ratio>
The pressure-sensitive adhesive of the present invention contains a polyurethane polyol (A), a polyfunctional isocyanate compound (B), and a compound (C) having a hydroxyl group and a steroid skeleton as essential components. These compounding ratios are not particularly limited, but preferable compounding ratios are as follows.

The amount of one or more polyfunctional isocyanates (B) with respect to 100 parts by mass of one or more polyurethane polyols (A) is preferably 1 to 25 parts by mass, more preferably 3 to 20 parts by mass. When the amount of one or more types of polyfunctional isocyanate (B) is 1 part by mass or more, the cohesive force of the adhesive layer is good, and when it is 25 parts by mass or less, the curvature of the adhesive layer is good.

The content of the compound (C) having a hydroxyl group and a steroid skeleton is not particularly limited, but is preferably 0.1 part by mass to 20 parts by mass, more preferably 0 parts by mass, based on 100 parts by mass of the polyurethane polyol (A). It is 5 to 16 parts by mass. When the content of the compound (C) having a hydroxyl group and a steroid skeleton is in the above range, low adhesive strength, high curvature, and high removability in a high temperature and high humidity environment can be obtained.

<Adhesive manufacturing method>
The method for producing the pressure-sensitive adhesive of the present invention is not particularly limited.
The method for producing an adhesive according to one aspect of the present invention is as follows.
A step of copolymerizing a polyol (x) and a polyisocyanate (y) to obtain a polyurethane polyol (A), and
It has a step of mixing an isocyanate compound (B) with a polyurethane polyol (A) and a compound (C) having a hydroxyl group and a steroid skeleton.

≪Adhesive sheet≫
The pressure-sensitive adhesive sheet of the present invention includes a base material sheet 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 sheet. 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 sheet is not particularly limited, and examples thereof include a resin sheet, paper, and a metal foil. The base sheet may be a laminated sheet in which any one or more layers are laminated on at least one surface of these base sheets. If necessary, the surface of the base sheet 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 is 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; Amid-based resins; urethane-based resins (including foams); combinations 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 metal of the metal foil is not particularly limited, and examples thereof include aluminum, copper, and combinations thereof.

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 base sheet such as a resin sheet or paper can be used.

The 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 sheet 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 (thickness after drying) varies depending on the application, but is preferably 0.1 to 200 μm.
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 form the present invention. A pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive may be formed, and a base material sheet may be laminated on the exposed surface of the pressure-sensitive adhesive layer.

<Use>
The 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 is suitably used as a surface protective sheet, a cosmetic sheet, a non-slip sheet, and the like.
Flat panel displays such as liquid crystal displays (LCDs) and organic electroluminescence displays (OELDs), as well as touch panel displays that combine such flat panel displays and touch panels, include televisions (TVs), personal computers (PCs), mobile phones, and the like. It is widely used in electronic devices such as mobile information terminals.

The adhesive sheet of the present invention is suitably used as a surface protective sheet for flat panel displays and touch panel displays, as well as substrates and optical members manufactured or used in these manufacturing processes.
The range of use of the above electronic devices is expanding, and there is a possibility that they will be placed in a hot and humid environment that is harsher than before.
The pressure-sensitive adhesive sheet of the present invention is preferable because it has good adhesiveness and can have good removability even when placed in a higher temperature and higher humidity environment than before.

The pressure-sensitive adhesive sheet of the present invention is more excellent in curvature than the conventional one. Therefore, the adhesive sheet of the present invention can be suitably used as a flexible display such as OLED using a plastic film as a substrate, and as a surface protective sheet for a substrate and an optical member manufactured or used in this manufacturing process. it can.

As described above, according to the present invention, an adhesive capable of forming an adhesive layer having good removability even when placed in a high temperature and high humidity environment harsher than the conventional one, and an adhesive thereof. The used adhesive sheet can be provided.
According to the present invention, it is also possible to provide a pressure-sensitive adhesive having excellent curvature and low adhesiveness, and a pressure-sensitive adhesive sheet using the same.

Hereinafter, specific examples of the present invention will be described together with comparative examples, but the present invention is not limited to the following examples. Further, in the following Examples and Comparative Examples, "parts" and "%" represent "parts by mass" and "% by mass", respectively.

<Measurement of non-volatile content>
About 1 g of the sample solution was weighed in a metal container, dried in an oven at 150 ° C. for 20 minutes, the residue was weighed, and the residual rate was calculated to obtain a non-volatile component (nonvolatile component concentration).

<Measurement of Mw>
The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC) method. The measurement conditions were as follows. Both Mw and Mn are polystyrene-equivalent values.
<Measurement conditions>
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: 0.1%,
Sample injection volume: 100 μL.

<Measurement of hydroxyl value (OHV)>
1 g of the sample was precisely weighed in an Erlenmeyer flask with a stopper, and 100 ml of pyridine was added to dissolve the sample. Further, exactly 5 ml of an acetylating agent (a solution obtained by dissolving 25 g of acetic anhydride in pyridine to make a volume of 100 ml) was added, and the mixture was stirred for 1 hour and then titrated with a 0.5 N-alcoholic potassium hydroxide solution. The hydroxyl value (unit: mgKOH / g) was calculated by the following formula. The hydroxyl value was the value of the dried sample.
Hydroxy group value = [{(ba) × F × 28.05} / S] / (nonvolatile content concentration / 100) + D
S: Sample collection amount (g)
a: Consumption of 0.5N-alcoholic potassium hydroxide solution (ml)
b: Consumption (ml) of 0.5N-alcoholic potassium hydroxide solution in the blank experiment
F: Factor of 0.5N-alcoholic potassium hydroxide solution D: Acid value (mgKOH / g)

<Measurement of isocyanato value (NCO value)>
Precisely weigh 10 g of the sample in a stoppered triangular flask, and weigh 25 ml of orthodichlorobenzene, di-n-butylamine / o-dichlorobenzene (mass ratio: di-n-butylamine / o-dichlorobenzene = 1 / 24.8). 10 ml of the mixed solution was added and dissolved. To this solution, 80 g of methanol and a bromphenol blue reagent were added as indicators, and the solution was titrated with a 0.1 N alcoholic hydrochloric acid solution. The end point was when the solution turned yellowish green and was held for 30 seconds or longer. The NCO value (unit:%) was calculated by the following formula.
NCO value = {0.42 x (BC) x F} / W
W: Sample collection amount (g)
B: Consumption of 0.1N alcoholic hydrochloric acid solution required for sample titration (ml)
C: Consumption of 0.1N alcoholic hydrochloric acid solution required for titration of blank test (ml)
F: Factor of 0.1N alcoholic hydrochloric acid solution

[material]
The materials used are as follows.
<Polyprethane (x)>
(X-1): P-1010 (manufactured by Kuraray Co., Ltd.), bifunctional polyester polyol, Mn1000, number of hydroxyl groups 2,
(X-2): P-2010 (manufactured by Kuraray), bifunctional polyester polyol, Mn2000, number of hydroxyl groups 2,
(X-3): PP-1000 (manufactured by Sanyo Chemical Industries, Ltd.), bifunctional polyether polyol, Mn1000, number of hydroxyl groups 2,
(X-4): GI1000 (manufactured by Nippon Soda), hydroxyl-terminated polybutadiene at both ends, Mn1500, number of hydroxyl groups 2,
(X-5): AM302 (manufactured by ADEKA CORPORATION), trifunctional polyether polyol, Mn3000, number of hydroxyl groups 3,
(X-6): F-3010 (manufactured by Kuraray Co., Ltd.), trifunctional polyester polyol, Mn3000, number of hydroxyl groups 3.

<Polyisocyanate (y)>
(Y-1): Death Module H (manufactured by Tosoh Corporation), 1,6-hexamethylene diisocyanate,
(Y-2): Takenate 500 (manufactured by Mitsui Chemicals, Inc.), 1,3-xylylene diisocyanate,
(Y-3): VESTANAT IPDI (manufactured by EVONIK), isophorone diisocyanate.

<Polyfunctional isocyanate compound B>
(B-1): TDI-TMP adduct (trimethylolpropane adduct of tolylene diisocyanate, isocyanato cardinal number = 3, NCO value = 6.5%, non-volatile content = 37.5%)
(B-2): IPDI nurate (isophorone diisocyanate nurate, isocyanato radix = 3, NCO value = 11.8%, non-volatile content = 70.0%)

<Compound (C) having a hydroxyl group and a steroid skeleton>
Phytosterol: (Product name "Phytosterol CO", manufactured by Tama Biochemical Co., Ltd.), Number of hydroxyl groups 1 (secondary hydroxyl group)
Cholesterol: molecular weight 386.7, number of hydroxyl groups 1 (secondary hydroxyl group)
Deoxycorticosterone: molecular weight 330.5, number of hydroxyl groups 1 (primary hydroxyl group)
Dehydroepiandrosterone: molecular weight 288.4, number of hydroxyl groups 1 (secondary hydroxyl group)
Bolandiol: molecular weight 276.4, number of hydroxyl groups 2 (secondary hydroxyl group)
Stenolone: Molecular weight 300.44, number of hydroxyl groups 1 (tertiary hydroxyl group)

<Other compounds>
IPM: Isopropyl myristate W-260: Polyalkylene glycol compound, DIC cholesterol acetate: Molecular weight 428.7

[Synthesis example of polyurethane polyol A]
(Synthesis Example 1)
100 parts of polyol (x-1) (“P-1010” (manufactured by Kuraray Co., Ltd.)) was charged into a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, a thermometer, and a dropping funnel. To this, 77 parts of toluene was added as a solvent, 0.03 part of dibutyltin dilaurate and 0.01 part of tin 2-ethylhexanoate were added as a catalyst, and then the temperature was gradually raised to 90 ° C. under a nitrogen atmosphere. Fifteen parts of polyisocyanate (y-1) (“Death Module H” (manufactured by Tosoh Corporation)) was added dropwise thereto, and the reaction was carried out for 2 hours after the completion of the addition. After confirming the disappearance of the residual isocyanate group by infrared absorption spectrum (IR), the reaction solution was cooled to terminate the reaction. As described above, a solution of polyurethane polyol (A-1) (nonvolatile content: 60%) was obtained. The Mw of the obtained polyurethane polyol (A-1) was 43,000, and the hydroxyl value was 10.7 mgKOH / g.

(Synthesis Examples 2 to 6)
In Synthesis Examples 2 to 6, polyurethane polyols (A-2 to 6) were obtained in the same manner as in Synthesis Example 1 except that the types of polyols and polyisocyanates used and their blending ratios were changed as shown in Table 1. Got Table 1 shows the Mw and hydroxyl value of the obtained polyurethane polyol in each synthesis example.

[Manufacturing of urethane adhesive]
(Example 1)
100 parts of the polyurethane polyol (A-1) obtained in Synthesis Example 1, 5.6 parts of the polyfunctional isocyanate compound (B-1), 1 part of phytosterol as the compound (C), and 50 parts of ethyl acetate as a solvent are blended. Then, the urethane adhesive was obtained by stirring with a disper. The blending amount of each material excluding the solvent indicates a non-volatile content conversion value (the same applies to other examples and comparative examples). Table 2 shows the types of materials used and the compounding ratios.

(Examples 2 to 12, Comparative Examples 1 to 6)
In each of Examples 2 to 12 and Comparative Examples 1 to 6, the urethane adhesive was applied in the same manner as in Example 1 except that the types and compounding ratios of the materials used were changed as shown in Tables 2 and 3. Got

[Manufacturing and evaluation of adhesive sheets]
Using the obtained pressure-sensitive adhesive, the pressure-sensitive adhesive sheet was manufactured and evaluated as follows.
(Manufacturing of adhesive sheet)
As a base sheet, a polyethylene terephthalate (PET) sheet (“Lumilar T-60” manufactured by Toray Industries, Inc., thickness 50 μm) was prepared. Using a comma coater (registered trademark), the obtained urethane-based adhesive was applied to one side of the base sheet so that the coating speed was 3 m / min and the thickness after drying was 12 μm. Next, the formed coating layer was dried at 100 ° C. for 2 minutes to form an adhesive layer. A release sheet having a thickness of 38 μm (“Super Stick SP-PET38” manufactured by Lintec Corporation) was attached onto the adhesive layer to obtain an adhesive sheet. The obtained adhesive sheet was cured under the condition of 23 ° C.-50% RH for 1 week, and then subjected to evaluation of adhesive strength, removability (adhesion contamination inhibitory property), and curvature.

[Evaluation items and evaluation methods]
The evaluation items and evaluation methods are as follows.
(Adhesive force)
Two test pieces having a width of 25 mm and a length of 100 mm were cut out from the adhesive sheet. The release sheets were peeled off from each of the two test pieces in an atmosphere of 23 ° C. to 50% RH, a soda glass plate was attached to the surface of the exposed adhesive layer, and the two test pieces were pressure-bonded with a 2 kg roll.
One of the two obtained laminates was left to stand for 24 hours in an atmosphere of 23 ° C.-50% RH (temperature / humidity condition 1).
The other laminate was left in an oven at 85 ° C.-85% RH for 24 hours (temperature / humidity condition 2), then taken out of the oven and air-cooled in an atmosphere of 23 ° C.-50% RH for 1 hour.
The adhesive strength of each laminated body was measured in accordance with JIS Z 0237 using a tensile tester under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 °. The evaluation criteria are as follows.

◯: Less than 20 mN / 25 mm, good.
Δ: 20 to 100 mN / 25 mm, practically possible.
X: Over 100 mN / 25 mm, not practical.

(Removability (suppression of adherent contamination))
Three test pieces having a width of 70 mm and a length of 100 mm were cut out from the adhesive sheet. For each of the three test pieces, the release sheet was peeled off in an atmosphere of 23 ° C.-50% RH, a caustic soda glass plate was attached to the surface of the exposed adhesive layer, and the three test pieces were pressure-bonded with a laminator.
The three obtained laminates were adjusted to 40 ° C.-90% RH (temperature / humidity condition 1), 60 ° C.-90% RH (temperature / humidity condition 2), and 85 ° C.-85% RH (temperature / humidity condition 3), respectively. It was left in the set oven for 72 hours.
Each of the three laminates was taken out of the oven, air-cooled in an atmosphere of 23 ° C.-50% RH for 1 hour, and then the adhesive sheet was peeled off from the glass plate to evaluate the re-peelability. The surface of the glass plate on the side where the adhesive sheet was attached was irradiated with LED lamp light in a dark room, and evaluated by visual observation. The evaluation criteria are as follows.

⊚: Excellent, with no adhesion of adhesive layer components on the glass surface.
◯: Good, with thin adhesive layer components adhering to one or two places on the glass surface.
Δ: A thin adhesive layer component is observed at three points on the glass surface, which is practical.
X: Thin adhesive layer component is observed at 4 or more points on the glass surface / or thick adhesive layer component is observed at 1 or 2 points on the glass surface, which is not practical.

(Curvability)
A test piece having a width of 20 mm and a length of 15 mm was cut out from the adhesive sheet. In an atmosphere of 23 ° C.-50% RH, peel off the release sheet from the test piece, attach the surface of the exposed adhesive layer around a polypropylene (PP) round bar with a length of 30 cm and a diameter of 60 mmφ, and use your finger. Strongly crimped. At this time, the width direction of the test piece was set to be parallel to the length direction of the round bar. The sample was left in an atmosphere of 23 ° C.-50% RH for 24 hours. Then, the length of the peeling range from the round bar was measured at both ends of the pressure-sensitive adhesive sheet, and the end having the larger peeling range was evaluated according to the following criteria.

⊚: No peeling range / or peeling range is less than 1 mm, excellent.
◯: The peeling range is 1 mm or more and less than 2 mm, which is good.
Δ: Peeling range is 2 mm or more and less than 5 mm, practically possible.
X: The peeling range is 5 mm or more, which is not practical.

[Evaluation results]
The evaluation results are shown in Table 4.

In Comparative Example 1, the curvature was excellent, but the adhesive strength was high and the removability was poor. In Comparative Example 2, by using a trifunctional polyol as a raw material of the polyurethane polyol (A), the crosslink density of the pressure-sensitive adhesive sheet was increased, and the adhesive strength and removability were improved. However, on the other hand, the curvature was poor. In Comparative Examples 3 and 4, by using isopropyl myristate and W-260 as plasticizers, the removability was good, but the curvability was poor. In Comparative Examples 5 and 6, a compound having a steroid skeleton and no hydroxyl value was added, but removability and curvability could not be achieved at the same time.

On the other hand, all of the pressure-sensitive adhesive sheets obtained in Examples 1 to 14 had good or relatively good results in all the evaluation items. Further, when the compound (C) had one hydroxyl value in one molecule, the curvability was better. Further, when the compound (C) has a primary or secondary hydroxyl group, the result shows more excellent adhesiveness, removability and curvability. Further, when the content of the compound (C) is 1 part by mass or more, excellent adhesiveness is exhibited, and when it is 16 parts by mass or less, it is excellent even under more severe conditions such as 60 ° C.-90% and 85 ° C.-85%. The result showed removability.

Claims (4)

A pressure-sensitive adhesive containing a polyurethane polyol (A) which is a reaction product of a polyol (x) and a polyisocyanate (y), a polyfunctional isocyanate compound (B), and a compound (C) having a hydroxyl group and a steroid skeleton. The pressure-sensitive adhesive according to claim 1, wherein the compound (C) having a hydroxyl group and a steroid skeleton is contained in an amount of 0.5 to 20 parts by mass with respect to 100 parts by mass of the polyurethane polyol (A). The pressure-sensitive adhesive according to claim 1 or 2, wherein the compound (C) having a hydroxyl group and a steroid skeleton has one hydroxyl group in one molecule. A pressure-sensitive adhesive sheet comprising a base material sheet and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive according to any one of claims 1 to 3.