JP7127596B2 - Adhesive, adhesive sheet, and method for producing hydroxyl-terminated urethane prepolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive, an adhesive sheet, and a method for producing a hydroxyl group-terminated urethane prepolymer.

BACKGROUND ART Conventionally, adhesive sheets having an adhesive layer formed on a base sheet have been widely used as surface protection sheets for various members. Examples of adhesives include acrylic adhesives, silicone adhesives, urethane adhesives, and the like. The acrylic pressure-sensitive adhesive has excellent adhesive strength, but because of its strong adhesive strength, it has poor removability after it has been applied to an adherend. In particular, after the passage of time in a high-temperature and high-humidity environment, the removability is further reduced due to an increase in adhesive strength, and there is a tendency for the adherend to be contaminated with the adhesive remaining on the surface of the adherend after re-peeling. . Silicone pressure-sensitive adhesives tend to contaminate adherends, and the relatively low molecular weight silicone resin may volatilize and adhere to the surfaces of equipment such as electronic devices, causing problems. On the other hand, the urethane-based pressure-sensitive adhesive has good adhesion to the adherend, is relatively excellent in removability, and is difficult to volatilize.
In the present specification, the "adhesive" is a removable adhesive (removable adhesive), and the "adhesive sheet" is a removable adhesive sheet (removable adhesive sheet).

Flat panel displays such as liquid crystal displays (LCDs) and organic electroluminescent displays (OELDs), as well as touch panel displays that combine such flat panel displays with touch panels, are widely used in televisions (TVs), personal computers (PCs), mobile phones, and It is widely used in electronic devices such as personal digital assistants.
Urethane pressure-sensitive adhesive sheets are used for flat panel displays and touch panel displays, as well as substrates (glass substrates and ITO/glass substrates in which an ITO (indium tin oxide) film is formed on a glass substrate) that are manufactured or used in these manufacturing processes. etc.) and as a surface protection sheet for optical members and the like.

As a method for producing a urethane-based pressure-sensitive adhesive, there is a method using a hydroxyl group-terminated urethane prepolymer, which is a reaction product of an active hydrogen group-containing compound such as a polyol and a polyisocyanate, and a polyfunctional isocyanate compound, and a method using a hydroxyl group-terminated urethane prepolymer. There is also a method (one-shot method) in which the polyol and the polyfunctional isocyanate compound are reacted at once without any reaction.

A general adhesive sheet manufacturing method includes a coating step of applying an adhesive onto a base sheet, and a heat-drying treatment of the formed coating layer to form an adhesive layer containing a cured product of the adhesive. It includes a heating step, a winding step of winding the obtained adhesive sheet around a core to form an adhesive sheet roll, and a curing step of curing the adhesive sheet roll.

Japanese Patent No. 5501489 JP 2016-138237 A JP 2016-204468 A

Urethane-based adhesives cure immediately after production, but if the initial curing is too high, the pot life will be shortened and the viscosity of the adhesive will become too high before the adhesive is applied to the base sheet. There is a risk that uniform coating will not be possible. If the initial curability of the urethane-based adhesive is too low, the coating layer or the adhesive layer will be subjected to hot air during heat drying of the coating layer, or mechanical damage during winding and curing of the adhesive sheet obtained after heat drying. Under the influence of stress, surface appearance defects such as core step marks, citrus peel, and curling habit may occur on the adhesive layer. The urethane pressure-sensitive adhesive preferably has good initial curability while having a good pot life.

The pressure-sensitive adhesive sheet preferably has good adhesion of the pressure-sensitive adhesive layer to the substrate sheet (also referred to as substrate adhesion). The pressure-sensitive adhesive sheet preferably has good adhesiveness to a substrate and good removability so that it can be easily removed from the adherend when it is removed from the adherend. Even when the pressure-sensitive adhesive sheet is exposed to a high-temperature and high-humidity environment, it is preferable that there is no contamination of the adherend, that is, the pressure-sensitive adhesive component remains on the surface of the adherend after re-peeling.

It is preferable that the adhesive layer has good wettability with respect to an adherend such as glass, and air bubbles are not involved in the adhesion interface when the adhesive sheet is adhered to the adherend. A plasticizer may be added to the urethane pressure-sensitive adhesive in order to improve wettability. However, when the amount of the plasticizer added is large, especially when exposed to a high-temperature and high-humidity environment, there is a risk that the adherend may be contaminated with the adhesive component remaining on the surface of the adherend after the adhesive sheet is removed again. be. Therefore, it is preferable that the amount of the plasticizer to be added is small, and it is more preferable that the amount of the plasticizer to be added is zero. The urethane-based pressure-sensitive adhesive preferably has good wettability even in a compounding composition with a small amount of plasticizer added/preferably no amount of plasticizer added.

Documents related to the present invention include Patent Documents 1 to 3.
Patent Document 1 discloses a polyol (A1) having 3 OH groups and a number average molecular weight (Mn) of 8000 to 20000 and a polyol (A2) having 3 or more OH groups and a number average molecular weight (Mn) of 5000 or less. A urethane-based pressure-sensitive adhesive containing a polyurethane-based resin obtained by curing a composition containing a plurality of types of polyols (A) and a polyfunctional isocyanate compound (B) is disclosed (claim 1).

Patent Document 2 discloses a polyol composition for pressure-sensitive adhesives, which contains the following polyol (A1) and is reacted with a polyisocyanate compound (B) to obtain a pressure-sensitive adhesive (claim 1).
Polyol (A1): polyoxy having 3 or more functional groups, a number average molecular weight (Mn) per functional group of 500 to 2500, and an oxyethylene group content of 16 mol% or more relative to the total amount of oxyalkylene groups Alkylene polyol.
In Patent Document 2,
Having a base composition contained in a first container and a curing agent composition contained in a second container,
The main composition is the polyol composition for pressure-sensitive adhesives,
The curing agent composition contains a polyisocyanate compound (B),
An adhesive kit is disclosed in which one or both of the main composition and the curing agent composition contain a catalyst (C) (claim 5).

In Patent Document 3, a polyether diol A having a degree of unsaturation of 0.07 meq/g or less and a number average molecular weight (Mn) of 3000 to 30000 and a polyisocyanate C are used to obtain a polyisocyanate C and the total amount of OH groups of polyether diol A is in the range of 0.85 to 1.15 (molar ratio). Item 9).
The code of each component described in Patent Documents 1 to 3 is the code described in these documents and has nothing to do with the code used for each component of the present invention.

The urethane-based pressure-sensitive adhesives described in Patent Documents 1 and 2 are urethane-based pressure-sensitive adhesives produced by a one-shot method. In general, an adhesive layer using a urethane-based adhesive obtained by the one-shot method is hard and tends to deteriorate the surface smoothness of the adhesive layer due to cure shrinkage.
In the urethane pressure sensitive adhesive described in Patent Document 3, polyether diol A having a number average molecular weight (Mn) per functional group of 1500 to 15000 is used as a raw material polyol for the urethane prepolymer. When such a relatively long-chain polyol is used as the raw material polyol for the urethane prepolymer, the wettability of the adhesive layer can be improved, but the initial curability of the adhesive decreases, and the removability of the adhesive layer deteriorates. tend to decline.

The present invention has been made in view of the above circumstances, and has good pot life and initial curability, good wettability and substrate adhesion, and is good even when placed in a high-temperature and high-humidity environment. An object of the present invention is to provide a pressure-sensitive adhesive capable of forming a removable pressure-sensitive adhesive layer, and a pressure-sensitive adhesive sheet using the same.

The pressure-sensitive adhesive of the present invention is
A polyether polyol (HA) having a number average molecular weight (Mn) per functional group of 1650 or more and a number average molecular weight (Mn) per functional group of 300 or less having a plurality of active hydrogen groups in one molecule. a hydroxyl group-terminated urethane prepolymer (UPH) which is a reaction product of a plurality of types of active hydrogen group-containing compounds (HX) including an active hydrogen group-containing compound (HB) having and one or more polyisocyanates (N); ,
and a polyfunctional isocyanate compound (I).

The pressure-sensitive adhesive sheet of the present invention includes a base sheet and a pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive of the present invention.

The method for producing a hydroxyl-terminated urethane prepolymer of the present invention comprises one or more polyether polyols (HA) having a number average molecular weight (Mn) of 1650 or more per functional group and one or more polyisocyanates (N). in an excess proportion of isocyanate groups to produce an isocyanate group-terminated urethane prepolymer (UPN);
The obtained isocyanate group-terminated urethane prepolymer (UPN) and one or more active hydrogen group-containing compounds ( HB).

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

According to the present invention, a pressure-sensitive adhesive layer having good pot life and initial curability, good wettability and adhesion to a substrate, and good removability even when placed in a high-temperature and high-humidity environment is provided. A pressure-sensitive adhesive that can be formed and a pressure-sensitive adhesive sheet using the same can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section of the adhesive sheet of 1st Embodiment which concerns on this invention. FIG. 4 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to a second embodiment of the invention;

The adhesive of the present invention comprises a hydroxyl group-terminated urethane prepolymer (UPH) which is a reaction product of multiple active hydrogen group-containing compounds (HX) and one or more polyisocyanates (N), and a polyfunctional isocyanate compound ( I) is a urethane-based pressure-sensitive adhesive containing
In the present invention, multiple types of active hydrogen group-containing compounds (HX) are composed of one or more polyether polyols (HA) having a number average molecular weight (Mn) of 1650 or more per functional group, and and one or more active hydrogen group-containing compounds (HB) having a number average molecular weight (Mn) of 300 or less and having a plurality of active hydrogen groups in one molecule.

The pressure-sensitive adhesive sheet of the present invention is a urethane-based pressure-sensitive adhesive sheet comprising a substrate sheet and an adhesive layer comprising a cured product of the pressure-sensitive adhesive of the present invention.

[Adhesive]
(Hydroxyl group-terminated urethane prepolymer (UPH))
A hydroxyl group-terminated urethane prepolymer (UPH) is a reaction product obtained by copolymerizing multiple types of active hydrogen group-containing compounds (HX) and one or more types of polyisocyanate (N). The copolymerization reaction can be carried out in the presence of one or more catalysts, if desired. One or more solvents may be used in the copolymerization reaction, if desired.
A hydroxyl group-terminated urethane prepolymer (UPH) is preferably an isocyanate group-terminated urethane prepolymer (UPN) which is a reaction product of a polyether polyol (HA) and a polyisocyanate (N), and an active hydrogen group-containing compound (HB). is a reaction product with
In the present invention, the multiple active hydrogen group-containing compounds (HX) include a relatively long-chain polyether polyol (HA) and a relatively short-chain active hydrogen group-containing compound (HB).

<Polyether polyol (HA)>
Polyether polyol (HA) has a number average molecular weight (Mn) of 1650 or more per functional group, and has a higher molecular weight per functional group than active hydrogen group-containing compounds generally used as raw materials for urethane (pre)polymers. It is a relatively long-chain polyether polyol with a large number average molecular weight (Mn).
A known polyether polyol (HA) can be used. The polyether polyol (HA) is a compound (addition polymer) obtained by addition polymerization of one or more oxirane compounds using an active hydrogen group-containing compound having a plurality of active hydrogen groups in one molecule as an initiator. is mentioned.

Examples of initiators include hydroxyl group-containing compounds and amines. Specifically, two compounds 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.
Oxirane compounds include alkylene oxides (AO) such as ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO); tetrahydrofuran (THF), and the like.

The polyether polyol (HA) is preferably an alkylene oxide adduct of an active hydrogen-containing compound (also referred to as "polyoxyalkylene polyol"). Among them, polyethylene glycol (PEG), polypropylene glycol (PPG), PPG with ethylene oxide (EO) added to the end (PPG-EO), and bifunctional polyether polyols such as polyalkylene glycols such as polytetramethylene glycol; Trifunctional polyether polyols such as alkylene oxide adducts of glycerin are preferred.

It is preferred that the polyether polyol (HA) have a low degree of unsaturation. The degree of unsaturation is the total amount of unsaturated groups contained per gram of polyether polyol and corresponds to the amount of impurity monools. By using a high-purity material with a low degree of unsaturation, the initial curing property of the adhesive is good, and especially when exposed to a high-temperature and high-humidity environment, it sticks to the surface of the adherend after the adhesive sheet is removed again. It is possible to suppress the contamination of the adherend where the agent component remains. The degree of unsaturation of the polyether polyol (HA) is preferably 0.07 meq/g or less, more preferably 0.04 meq/g or less, and particularly preferably 0.01 meq/g or less.
In this specification, unless otherwise specified, the degree of unsaturation of polyol is a value measured according to JIS K1557 6.7.

<Active hydrogen group-containing compound (HB)>
The active hydrogen group-containing compound (HB) has a number average molecular weight (Mn) of 300 or less per functional group, and has one functional group more than an active hydrogen group-containing compound generally used as a raw material for urethane (pre)polymers. It is a relatively short-chain active hydrogen group-containing compound with a small number average molecular weight (Mn).
Active hydrogen groups include hydroxy group, mercapto group, and amino group (unless otherwise specified, amino group includes imino group). Active hydrogen group-containing compounds (HB) include polyols having multiple hydroxy groups in one molecule, polyamines having multiple amino groups in one molecule, aminoalcohols having amino groups and hydroxyl groups in one molecule, one molecule Among them are polythiols having multiple mercapto groups. These can be used alone or in combination of two or more. The active hydrogen group-containing compound (HB) may be a non-polymer or a polymer.
Among them, polyols are preferred. Since polyamines and polythiols have high reactivity and short pot lives, they are preferably used in combination with polyols. In addition, when the polyol contains a secondary hydroxyl group, the initial curability of the urethane adhesive is not improved, so from the viewpoint of pot life and initial curability, the active hydrogen group-containing compound (HB) has moderate reactivity. It preferably contains a hydroxyl group.

Non-polymeric polyols include ethylene glycol (EG), propylene glycol (PG), diethylene glycol, triethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol. , 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 (also referred to as "1,3-octanediol"), 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octane Diol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane (TMP), pentaerythritol, hexanetriol, and the like.

Examples of polymer polyols that can be used as the active hydrogen group-containing compound (HB) include polyester polyols, polyether polyols, polyacrylic polyols, polycaprolactone polyols, polycarbonate polyols, and castor oil-based polyols. Among them, polyester polyols, polyether polyols, and combinations thereof are preferred.

A known polyester polyol can be used as the active hydrogen group-containing compound (HB). Examples of polyester polyols include compounds (esterified products) obtained by an esterification reaction between one or more polyol components and one or more acid components.

Examples of raw polyol components include ethylene glycol (EG), propylene glycol (PG), diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3- Hexanediol (1,3-octanediol), 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylol propane, pentaerythritol, hexanetriol, and the like.

Acid components of raw materials include succinic acid, methylsuccinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1, 4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and acid anhydrides thereof etc.

A known polyether polyol can be used as the active hydrogen group-containing compound (HB). Examples of polyether polyols include compounds (addition polymers) obtained by addition polymerization of one or more oxirane compounds using an active hydrogen group-containing compound having a plurality of active hydrogen groups in one molecule as an initiator. . As the initiator and oxirane compound, the same ones as exemplified for the polyether polyol (HA) can be used.
Like the polyether polyol (HA), the polyether polyol that can be used as the active hydrogen group-containing compound (HB) is preferably an alkylene oxide adduct (polyoxyalkylene polyol) of an active hydrogen group-containing compound. Among them, polyethylene glycol (PEG), polypropylene glycol (PPG), PPG with ethylene oxide (EO) added to the end (PPG-EO), and bifunctional polyether polyols such as polyalkylene glycols such as polytetramethylene glycol; Trifunctional polyether polyols such as alkylene oxide adducts of glycerin are preferred.

Examples of polyamines that can be used as the active hydrogen group-containing compound (HB) include ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6 -hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, 1,14-tetradecanediamine, 1,16-hexadecane Diamine, hexamethylenediamine, trimethylhexamethylenediamine, iminobispropylamine, methyliminobispropylamine, 1,5-diamino-2-methylpentane, isophoronediamine, 1,3-bisaminomethylcyclohexane, 1-cyclohexylamino- 3-Aminopropane, 3-aminomethyl-3,3,5-trimethyl-cyclohexylamine, norbornane dimethyleneamine, metaxylylenediamine (MXDA), hexamethylenediamine carbamate, diethylenetriamine, triethylenetetramine, tetraethylenepenta amine, and aliphatic polyamines such as pentaethylenehexamine; 3,3′-dichloro-4,4′-diaminodiphenylmethane (MOCA), 4,4′-diaminodiphenylmethane, 2,4′-diaminodiphenylmethane, 3,3′ -diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2'-diaminobiphenyl, 3,3'-diaminobiphenyl, 2,4-diaminophenol, 2,5-diaminophenol, o-phenylenediamine, m-phenylene Diamines, p-phenylenediamine, 2,3-tolylenediamine, 2,4-tolylenediamine, 2,5-tolylenediamine, 2,6-tolylenediamine, 3,4-tolylenediamine, and diethyltoluene aromatic polyamines such as diamine;

Amino alcohols that can be used as active hydrogen group-containing compounds (HB) include monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tri(hydroxymethyl)aminomethane, and 2-amino-2 -monoamines having a hydroxyl group such as ethyl-1,3-propanediol; diamines having a hydroxyl group such as N-(2-hydroxypropyl)ethanolamine; and the like.

Polythiols that can be used as active hydrogen group-containing compounds (HB) include methanedithiol, 1,3-butanedithiol, 1,4-butanedithiol, 2,3-butanedithiol, 1,2-benzenedithiol, 1, 3-benzenedithiol, 1,4-benzenedithiol, 1,10-decanedithiol, 1,2-ethanedithiol, 1,6-hexanedithiol, 1,9-nonanedithiol, 1,8-octanedithiol, 1,5 -pentanedithiol, 1,2-propanedithiol, 1,3-propadithiol, toluene-3,4-dithiol, 3,6-dichloro-1,2-benzenedithiol, 1,5-naphthalenedithiol, 1,2- benzenedimethanethiol, 1,3-benzenedimethanethiol, 1,4-benzenedimethanethiol, 4,4'-thiobisbenzenethiol, 2,5-dimercapto-1,3,4-thiadiazole, 1,8 -dimercapto-3,6-dioxaoctane, 1,5-dimercapto-3-thiapentane, 2-di-n-butylamino-4,6-dimercapto-s-triazine, and thiol group-terminated polymers (such as polysulfide polymers) etc.

In general, a plasticizer may be added to a urethane-based pressure-sensitive adhesive in order to improve wettability. However, when the amount of the plasticizer added is large, especially when exposed to a high-temperature and high-humidity environment, there is a risk that the adherend may be contaminated with the adhesive component remaining on the surface of the adherend after the adhesive sheet is removed again. be.
In the present invention, a relatively long-chain polyether polyol (HA) having a number average molecular weight (Mn) per functional group of 1650 or more is preferable as a raw material containing active hydrogen groups for the hydroxyl-terminated urethane prepolymer (UPH). By using a relatively long-chain polyether polyol (HA) containing an alkyleneoxy (AO) group, even with a formulation composition with a small amount of plasticizer added / preferably no amount of plasticizer added, It is possible to form an adhesive layer with good wettability. For example, it is possible to form a pressure-sensitive adhesive layer that makes it difficult for air bubbles to be involved in the adhesion interface when the pressure-sensitive adhesive sheet is adhered to an adherend such as a glass substrate and an ITO/glass substrate. A relatively large number of organic groups, preferably alkylene groups, which form the ether bond and are bonded to oxygen atoms, is considered to exhibit the same effect as a plasticizer.

When a relatively long-chain polyether polyol (HA) is used as the raw material for the hydroxyl-terminated urethane prepolymer (UPH), the wettability of the adhesive layer is improved, but the initial curability of the adhesive is reduced, resulting in Removability tends to decrease. This tendency increases as the number average molecular weight (Mn) per functional group of the polyether polyol (HA) increases.
From the viewpoint of improving the wettability of the adhesive layer, the number average molecular weight (Mn) per functional group of the polyether polyol (HA) is preferably 2000 or more, more preferably 3000 or more.
In the present invention, by using a relatively short-chain active hydrogen group-containing compound (HB) together as a raw material for a hydroxyl group-terminated urethane prepolymer (UPH), adhesion by using a relatively long-chain polyether polyol (HA) It is possible to improve the deterioration of the initial curing property of the agent and the deterioration of the removability of the adhesive layer.
From the viewpoint of improving the wettability of the adhesive layer, the initial curability of the adhesive, and the balance of removability of the adhesive layer, the number average molecular weight (Mn) per functional group of the polyether polyol (HA) is preferably 2000 to 2000. 10,000, more preferably 3,000 to 9,000.
Since it is possible to effectively improve the deterioration of the initial curing property of the adhesive and the deterioration of the removability of the adhesive layer due to the use of a relatively long-chain polyether polyol (HA), the monofunctional active hydrogen group-containing compound (HB) The number average molecular weight (Mn) per group is preferably 30-300, more preferably 30-100.

The one or more polyether polyols (HA) can include difunctional polyether polyols and/or trifunctional or higher polyether polyols. Similarly, the one or more active hydrogen group-containing compounds (HB) can include bifunctional active hydrogen group-containing compounds and/or tri- or more functional active hydrogen group-containing compounds.
In general, a bifunctional active hydrogen group-containing compound has two-dimensional crosslinkability and can impart appropriate flexibility to the pressure-sensitive adhesive layer. The trifunctional or higher active hydrogen group-containing compound has three-dimensional crosslinkability and can impart appropriate hardness to the pressure-sensitive adhesive layer.
The adhesive strength, cohesive strength, and properties such as removability can be adjusted. The number of functional groups of each material can be selected so that properties such as adhesive strength, cohesive strength, and removability are within preferred ranges depending on the application. The one or more polyether polyols (HA) preferably contain tri- or higher functional polyether polyols, since it is easy to achieve both adhesive strength and removability. The one or more active hydrogen group-containing compounds (HB) preferably contain a bifunctional active hydrogen group-containing compound because it is easy to achieve both reaction stability and cohesion.

Multiple types of active hydrogen group-containing compounds (HX), which are raw materials for hydroxyl group-terminated urethane prepolymers (UPH), are known active hydrogen group-containing compounds other than the above polyether polyol (HA) and active hydrogen group-containing compounds (HB). It may contain one or more compounds.

Documents related to the present invention include Patent Documents 1 to 3 listed in the “Background Art” section. These documents describe relatively long-chain polyols having a number average molecular weight (Mn) per functional group of 1650 or more, but the number average molecular weight (Mn) per functional group is 300 or less. There is no description or suggestion regarding the combined use of a relatively short-chain active hydrogen group-containing compound (HB). Moreover, the urethane pressure-sensitive adhesives described in Patent Documents 1 and 2 are based on the one-shot method, and do not use hydroxyl group-terminated urethane prepolymers.

<Polyisocyanate (N)>
A known polyisocyanate (N) can be used, including aromatic polyisocyanate, aliphatic polyisocyanate, and alicyclic polyisocyanate.

Aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tri diisocyanate, 4,4′-toluidine diisocyanate, 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, 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-diethylbenzene, 1 ,4-tetramethylxylylene diisocyanate and 1,3-tetramethylxylylene diisocyanate.

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

Alicyclic polyisocyanates include isophorone diisocyanate (IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6 -cyclohexanediisocyanate, 4,4′-methylenebis(cyclohexylisocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane, and the like.

Other polyisocyanates include trimethylolpropane adduct, biuret, allophanate, and trimers of the above polyisocyanates (this trimer contains an isocyanurate ring).

As the polyisocyanate (N), 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) and the like are preferable. As detailed below, the one or more polyisocyanates (N) preferably comprise isophorone diisocyanate (IPDI).

Preferred raw material blending ratios of the hydroxyl group-terminated urethane prepolymer (UPH) are as follows.
The ratio (NCO/H) of the number of moles of isocyanate groups (NCO) possessed by polyisocyanate (N) to the total number of moles of active hydrogen groups (H) possessed by multiple active hydrogen group-containing compounds (HX) is 0.20. It is preferable to determine the blending ratio of the raw materials so that it is 0.84 to 0.84, more preferably 0.40 to 0.80. The closer the NCO/H is to 1, the easier it is to gel during the synthesis of the hydroxyl group-terminated urethane prepolymer (UPH). If the NCO/H is 0.84 or less, it is possible to effectively suppress gelation during synthesis of a hydroxyl group-terminated urethane prepolymer (UPH).

The effect of improving the wettability of the adhesive layer by using polyether polyol (HA), the effect of improving the initial curing property of the adhesive and the removability of the adhesive layer by using the active hydrogen group-containing compound (HB), and the desired hydroxyl group-terminated urethane From the viewpoint of stable synthesis of prepolymer (UPH),
The amount of one or more active hydrogen group-containing compounds (HB) is 0.5 to 40 parts by mass per 100 parts by mass of one or more polyether polyols (HA), and one or more polyisocyanates (N ) is preferably 1.0 to 20 parts by mass.
The amount of one or more active hydrogen group-containing compounds (HB) is 1.0 to 20 parts by mass per 100 parts by mass of one or more polyether polyols (HA), and one or more polyisocyanates (N ) is more preferably 3.0 to 10 parts by mass.

<Catalyst>
If necessary, one or more catalysts can be used for the polymerization of the hydroxyl-terminated urethane prepolymer (UPH). Known catalysts can be used, including tertiary amine compounds and organometallic compounds.
Tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU).
Examples of organometallic compounds include tin-based compounds and non-tin-based compounds.
Tin-based compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, and tributyltin acetate. , triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.
Non-tin compounds include titanium compounds such as dibutyl titanium dichloride, tetrabutyl titanate, and butoxy titanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; - 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; A zirconium system is mentioned.
The type and amount of catalyst to be added can be appropriately designed within a range in which the reaction proceeds well.

Due to the difference in reactivity of multiple types of active hydrogen group-containing compounds (HX), a single catalyst system may easily cause gelation or cloudiness of the reaction solution. In this case, by using two kinds of catalysts, the reaction (for example, reaction rate, etc.) can be easily controlled, and the above problem can be solved. Combinations of two types of catalysts are not particularly limited, and include tertiary amine/organometallic, tin-based/non-tin-based, tin-based/tin-based, and the like. Tin-based/tin-based are preferred, and dibutyltin dilaurate and tin 2-ethylhexanoate are more preferred.
The mass ratio of tin 2-ethylhexanoate and 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 catalyst activity is well balanced, the gelation and cloudiness of the reaction solution are effectively suppressed, and the polymerization stability is further improved.

<Solvent>
If necessary, one or more solvents can be used for the polymerization of the hydroxyl-terminated urethane prepolymer (UPH). A known solvent can be used, including methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Ethyl acetate, toluene and the like are particularly preferred from the viewpoint of the solubility of the hydroxyl group-terminated urethane prepolymer (UPH) and the boiling point of the solvent.

<Polymerization method of hydroxyl group-terminated urethane prepolymer (UPH)>
The polymerization method for the hydroxyl group-terminated urethane prepolymer (UPH) is not particularly limited, and known polymerization methods such as bulk polymerization and solution polymerization can be applied.
As a polymerization procedure for the hydroxyl group-terminated urethane prepolymer (UPH),
Procedure 1) one or more polyether polyols (HA), one or more active hydrogen group-containing compounds (HB), one or more polyisocyanates (N), optionally one or more catalysts, and optionally charging the flask with one or more solvents, as appropriate;
Procedure 2) One or more polyether polyols (HA), one or more active hydrogen group-containing compounds (HB), optionally one or more catalysts, and optionally one or more solvents are added to a flask. A procedure of charging and adding one or more polyisocyanates (N) dropwise thereto;
Step 3) Combine one or more polyether polyols (HA), one or more polyisocyanates (N), optionally one or more catalysts, and optionally one or more solvents into a flask. After preparation, polyisocyanate (N) is reacted with polyether polyol (HA) at a ratio of excess isocyanate groups to generate an isocyanate group-terminated urethane prepolymer (UPN), and then one or more active hydrogen group-containing compounds. a procedure for adding (HB); and the like.

The reaction temperature when using a catalyst is preferably less than 100°C, more preferably 50-95°C, particularly preferably 60-85°C. If the reaction temperature is 100° C. or higher, it may become difficult to control the reaction rate, polymerization stability, and the like, making it difficult to produce a hydroxyl-terminated urethane prepolymer (UPH) 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.

In procedure 1) and procedure 2), relatively long-chain polyether polyol (HA) and relatively short-chain active hydrogen group-containing compound (HB) are simultaneously mixed with polyisocyanate (N). In this method, a relatively short-chain active hydrogen group-containing compound (HB) with high reactivity preferentially polyisocyanate (N) over a relatively long-chain polyether polyol (HA) with low reactivity. tend to react. In this case, relatively long-chain polyether polyol (HA) with low reactivity remains unreacted, and the reaction solution may become cloudy. In order to eliminate relatively long-chain polyether polyol (HA) remaining unreacted, when the number of moles of isocyanate groups is excessive with respect to the total number of moles of active hydrogen groups, relatively short-chain polyether polyol (HA) An isocyanate group-terminated urethane prepolymer produced by first reacting an active hydrogen group-containing compound (HB) and a polyisocyanate (N), and a relatively short-chain active hydrogen group-containing compound (HB) with high reactivity. may occur, resulting in gelation of the reaction solution.

Procedure 3) is preferred because the reaction is easier to control. Polymerization by this procedure involves reacting one or more polyether polyols (HA) with one or more polyisocyanates (N) in an isocyanate excess ratio to produce an isocyanate terminated urethane prepolymer (UPN). and a step of reacting the obtained isocyanate group-terminated urethane prepolymer (UPN) with one or more active hydrogen group-containing compounds (HB).

In procedure 3), in the absence of a relatively short-chain active hydrogen group-containing compound (HB), only a relatively low-reactive long-chain polyether polyol (HA) is first added to the polyisocyanate (N). After the reaction, the obtained isocyanate group-terminated urethane prepolymer (UPN) and the active hydrogen group-containing compound (HB) are reacted. In this method, gelation and cloudiness of the reaction solution are suppressed, and the desired hydroxyl group-terminated urethane prepolymer (UPH) can be stably synthesized.
Therefore, a hydroxyl group-terminated urethane prepolymer (UPH) is an isocyanate group-terminated urethane prepolymer (UPN) which is a reaction product of a polyether polyol (HA) and a polyisocyanate (N), and an active hydrogen group-containing compound (HB). It is preferably a reaction product with
Preferably, in step 3), the one or more polyisocyanates (N) comprise isophorone diisocyanate (IPDI). In this case, the reaction is easy to control, and the desired hydroxyl group-terminated urethane prepolymer (UPH) can be stably synthesized.

(Polyfunctional isocyanate compound (I))
A known compound can be used as the polyfunctional isocyanate compound (I), and the compounds exemplified as the polyisocyanate (N) which is a raw material of the hydroxyl group-terminated urethane prepolymer (UPH) (specifically, aromatic polyisocyanate, aliphatic Polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and their trimethylolpropane adducts/biurets/allophanates/trimers) can be used.

(Plasticizer (P))
As described above, the present invention can provide a pressure-sensitive adhesive having good wettability even in a composition with a small amount of plasticizer (P) added/preferably no amount of plasticizer (P) added. Therefore, in the pressure-sensitive adhesive of the present invention, the plasticizer (P) is not an essential component for improving wettability, but the pressure-sensitive adhesive of the present invention may contain one or more plasticizers (P) as necessary. can be done. However, even when the plasticizer (P) is added, its amount can be suppressed to a low level. The amount of the plasticizer (P) relative to 100 parts by mass of the hydroxyl group-terminated urethane prepolymer (UPH) may be, for example, 50 parts by mass or less (0 to 50 parts by mass), preferably 40 parts by mass or less (0 to 40 parts by mass), More preferably 30 parts by mass or less (0 to 30 parts by mass), more preferably 20 parts by mass or less (0 to 20 parts by mass), particularly preferably 10 parts by mass or less (0 to 10 parts by mass), most preferably 5 parts by mass part or less (0 to 5 parts by mass).

The plasticizer (P) is not particularly limited, and organic acid esters having a molecular weight of 250 to 1,000 are preferable from the viewpoint of compatibility with other components.

Esters of monobasic or polybasic acids with alcohols include, for example, isostearyl laurate, isopropyl myristate, isocetyl myristate, octyldodecyl myristate, isostearyl palmitate, isocetyl stearate, octyldodecyl oleate, and phthalate. Dibutyl acid, dioctyl phthalate, diheptyl phthalate, dibenzyl phthalate, butyl benzyl phthalate, diisodecyl adipate, diisostearyl adipate, dibutyl sebacate, diisocetyl sebacate, acetyl tributyl citrate, tributyl trimellitate, trimellit trioctyl acid, trihexyl trimellitate, trioleyl trimellitate, triisocetyl trimellitate, and the like.

Other esters of acids and alcohols include unsaturated fatty acids or branched acids such as myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid, and ethylene glycol, propylene glycol, glycerin. , trimethylolpropane, pentaerythritol, and esters with alcohols such as sorbitan.

Examples of esters of monobasic or polybasic acids with polyalkylene glycol include polyethylene glycol dihexylate, polyethylene glycol di-2-ethylhexylate, polyethylene glycol dilaurate, polyethylene glycol dioleate, and dipolyethylene glycol methyl adipate. ether and the like.

The molecular weight (formula weight or Mn) of the organic acid ester is preferably 250 to 1,000, more preferably 400 to 900, and particularly preferably 500 to 850 from the viewpoint of improving wettability. If the molecular weight is 250 or more, the heat resistance of the adhesive layer will be good, and if the molecular weight is 1,000 or less, the wettability of the adhesive will be good.

(solvent)
The pressure-sensitive adhesive of the present invention can contain one or more solvents, if desired. A known solvent can be used, including methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Ethyl acetate, toluene, and the like are particularly preferred from the viewpoint of the solubility of the hydroxyl group-terminated urethane prepolymer (UPH) and the boiling point of the solvent.

(Anti-alteration agent)
The pressure-sensitive adhesive of the present invention may optionally contain one or more anti-deterioration agents. Thereby, deterioration of various properties due to long-term use of the adhesive layer can be suppressed. Anti-deterioration agents include anti-hydrolysis agents, antioxidants, UV absorbers, light stabilizers, and the like.

<Hydrolysis resistant agent>
When a hydrolysis reaction occurs in the adhesive layer in a high-temperature, high-humidity environment or the like to generate carboxyl groups, a hydrolysis-resistant agent can be used to block the carboxyl groups. Carbodiimide-based, isocyanate-based, oxazoline-based, epoxy-based, and the like can be used as hydrolysis-resistant agents. Among these, carbodiimide-based compounds are preferable from the viewpoint of the hydrolysis-suppressing effect.

A carbodiimide-based hydrolysis inhibitor is a compound having one or more carbodiimide groups in one molecule.
Examples of monocarbodiimide compounds include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, diphenylcarbodiimide, and naphthylcarbodiimide.
A polycarbodiimide compound can be produced by subjecting a diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimidation catalyst. Here, examples of diisocyanate include 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-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, and the like. Carbodiimidation catalysts include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl- Phosphorene oxides such as 2-phospholene-1-oxide, and 3-phospholene isomers thereof, and the like.

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

Examples of oxazoline-based hydrolysis inhibitors include 2,2′-o-phenylenebis(2-oxazoline), 2,2′-m-phenylenebis(2-oxazoline), 2,2′-p-phenylenebis (2-oxazoline), 2,2′-p-phenylenebis(4-methyl-2-oxazoline), 2,2′-m-phenylenebis(4-methyl-2-oxazoline), 2,2′-p -phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-ethylenebis(2-oxazoline) , 2,2′-tetramethylenebis(2-oxazoline), 2,2′-hexamethylenebis(2-oxazoline), 2,2′-octamethylenebis(2-oxazoline), 2,2′-ethylenebis (4-methyl-2-oxazoline), and 2,2'-diphenylenebis(2-oxazoline).

Examples of epoxy hydrolyzing agents 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 cycloaliphatic polyols such as cyclohexanedimethanol; Diglycidyl or polyglycidyl esters of aliphatic or aromatic polycarboxylic acids; resorcinol, bis-(p-hydroxyphenyl)methane, 2,2-bis-(p-hydroxyphenyl)propane, tris-(p- hydroxyphenyl)methane, and diglycidyl or polyglycidyl ethers of polyhydric phenols such as 1,1,2,2-tetrakis(p-hydroxyphenyl)ethane; N,N-diglycidylaniline, N,N-diglycidyl N-glycidyl derivatives of amines such as toluidine and N,N,N',N'-tetraglycidyl-bis-(p-aminophenyl)methane; triglycidyl derivatives of aminophenols; triglycidyltris(2-hydroxyethyl) isocyanurate and triglycidyl isocyanurate; epoxy resins such as ortho-cresol type epoxy resins and phenol novolac type epoxy resins;

The amount of 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, relative to 100 parts by mass of hydroxyl-terminated urethane prepolymer (UPH). , particularly preferably 0.5 to 3 parts by mass.

<Antioxidant>
Antioxidants include radical scavengers and peroxide decomposers. Examples of radical scavengers include phenol compounds and amine compounds. Examples of peroxide decomposers include sulfur-based compounds and phosphorus-based compounds.

Examples of phenol compounds include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin-β-(3,5 -di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[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)butyric acid]glycol ester, 1,3,5-tris(3 ',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

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

Phosphorus compounds include, for example, triphenylphosphite, diphenylisodecylphosphite, 4,4′-butylidene-bis(3-methyl-6-tert-butylphenylditridecyl)phosphite, cyclic neopentanetetrayl bis(octadecylphosphite), tris(nonylphenyl)phosphite, tris(monononylphenyl)phosphite, tris(dinonylphenyl)phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa- 10-phosphaphenanthrene-10-oxide, 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10 -decyloxy-9,10-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) ) octyl phosphite and the like.

By using an antioxidant, it is possible to prevent thermal deterioration of the hydroxyl-terminated urethane prepolymer (UPH). In addition, bleeding out of the plasticizer (P) from the adhesive layer when using the plasticizer (P) can be effectively suppressed.
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, particularly preferably 0.1 to 3 parts by mass, based on 100 parts by mass of the hydroxyl group-terminated urethane prepolymer (UPH). is 0.2 to 2 parts by mass.

As the antioxidant, from the viewpoint of stability and antioxidant effect, it is preferable to use one or more phenolic compounds that are radical scavengers. One or more phenolic compounds that are radical scavengers and a peroxide decomposer are It is more preferable to use together with one or more phosphorus-based compounds. In addition, as antioxidants, it is particularly preferable to use a combination of a phenolic compound that is a radical scavenger and a phosphorus compound that is a peroxide decomposer, and to use these antioxidants in combination with the above-mentioned anti-hydrolysis agent. .

<Ultraviolet absorber>
Examples of ultraviolet absorbers include benzophenone-based compounds, benzotriazole-based compounds, salicylic acid-based compounds, oxalic acid anilide-based compounds, cyanoacrylate-based compounds, and triazine-based compounds.
The amount of the ultraviolet absorber to be 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, based on 100 parts by mass of the hydroxyl-terminated urethane prepolymer (UPH). Particularly preferably, it is 0.2 to 2 parts by mass.

<Light stabilizer>
Light stabilizers 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, based on 100 parts by mass of the hydroxyl-terminated urethane prepolymer (UPH). Particularly preferably, it is 0.2 to 1 part by mass.

(Antistatic agent)
The pressure-sensitive adhesive of the present invention can contain one or more antistatic agents (AS agents), if necessary. Examples of antistatic agents include inorganic salts, polyhydric alcohol compounds, ionic liquids, surfactants, and the like, with ionic liquids being preferred. Incidentally, the “ionic liquid” is also referred to as a room temperature molten salt, and is a salt that is fluid at 25°C.

Examples of inorganic salts include 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. , sodium carbonate, and sodium thiocyanate.

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

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

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- methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-octyl-4-methylpyridinium bis(fluorosulfonyl)imide, 1-methylpyridinium bis(perfluoroethylsulfonyl)imide, and 1-methylpyridinium bis(perfluorobutylsulfonyl)imide ) imide and the like.

Ionic liquids containing ammonium ions include, for example, trimethylheptylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-propylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl- N-methyl-N-pentylammonium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-heptylammonium bis(trifluoromethanesulfonyl)imide, and tri-n-butylmethylammonium bistrifluoromethanesulfone imide and the like.

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

Surfactants are classified into low-molecular-weight surfactants and high-molecular-weight surfactants. Within each type there are nonionic, anionic, cationic and amphoteric types.

Examples of nonionic low-molecular-weight surfactants include glycerin fatty acid esters, polyoxyalkylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, and fatty acid diethanolamides. be done.
Anionic low-molecular-weight surfactants include alkylsulfonates, alkylbenzenesulfonates, and alkylphosphates.
Cationic low-molecular-weight surfactants include tetraalkylammonium salts, trialkylbenzylammonium salts and the like.
Amphoteric low-molecular-weight surfactants include alkylbetaines and alkylimidazolium betaines.

Nonionic polymeric surfactants include polyether ester amide type, ethylene oxide-epichlorohydrin type, and polyether ester type.
Examples of anionic polymeric surfactants include polystyrene sulfonic acid type surfactants.
Examples of cationic polymeric surfactants include quaternary ammonium base-containing acrylate polymer types.
Examples of amphoteric polymer surfactants include amino acid type amphoteric surfactants such as higher alkylaminopropionates, and betaine type amphoteric surfactants such as higher alkyldimethylbetaines and higher alkyldihydroxyethylbetaines.

The amount of the antistatic agent to be added is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, per 100 parts by mass of the hydroxyl group-terminated urethane prepolymer (UPH).

(leveling agent)
The pressure-sensitive adhesive of the present invention can contain a leveling agent, if desired. By adding a leveling agent, the leveling property of the adhesive layer can be improved. Examples of the leveling agent include acrylic leveling agents, fluorine-based leveling agents, silicone-based leveling agents, and the like. From the viewpoint of suppressing contamination of the adherend after re-peeling of the pressure-sensitive adhesive sheet, acrylic leveling agents and the like are preferable.

The weight average molecular weight (Mw) of the leveling agent is not particularly limited, preferably 500 to 20,000, more preferably 1,000 to 15,000, particularly preferably 2,000 to 10,000. When Mw is 500 or more, the amount of vaporization from the coating layer is sufficiently small during drying by heating of the coating layer, 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 from the viewpoint of suppressing contamination of the adherend after re-peeling of the adhesive sheet and improving the leveling property of the adhesive layer, it is preferably 0.001 to 2 parts by mass, more preferably 0.01 to 1.5 parts by mass, particularly preferably 0.1 to 1 part by mass.

(other optional ingredients)
The pressure-sensitive adhesive of the present invention can optionally contain other optional components within a range that does not impair the effects of the present invention. Other optional components include catalysts, resins other than urethane-based resins, fillers (talc, calcium carbonate, titanium oxide, etc.), metal powders, coloring agents (pigments, etc.), foil-like materials, softening agents, and electrical conductivity. agents, silane coupling agents, lubricants, corrosion inhibitors, heat stabilizers, weather stabilizers, polymerization inhibitors, antifoaming agents and the like.

(blending ratio)
The pressure-sensitive adhesive of the present invention contains one or more hydroxyl-terminated urethane prepolymers (UPH) and one or more polyfunctional isocyanate compounds (I) as essential components, and optionally contains one or more optional components. . The compounding ratio of these components is not particularly limited, but preferred compounding ratios are as follows.
The amount of one or more polyfunctional isocyanate compounds (I) per 100 parts by mass of one or more hydroxyl-terminated urethane prepolymers (UPH) is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass. When the amount of the one or more polyfunctional isocyanate compounds (I) is 3 parts by mass or more, the cohesive force of the adhesive layer is good, and when it is 20 parts by mass or less, the pot life is good.

(Method for producing adhesive)
The method for producing the pressure-sensitive adhesive of the present invention is not particularly limited.
One or more polyfunctional isocyanate compounds (I) and optionally one or more optional components are added to the hydroxyl-terminated urethane prepolymer (UPH) synthesized by the above method (preferably procedure 3)). By mixing, the adhesive of the present invention can be produced.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention includes a base sheet and a pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive of the present invention. The adhesive layer can be formed on one side or both sides of the base sheet. If desired, the exposed surface of the adhesive layer can be covered with a release sheet. The release sheet is released when the pressure-sensitive adhesive sheet is attached to the adherend.

FIG. 1 shows a schematic cross-sectional view of the pressure-sensitive adhesive sheet of the first embodiment according to the present invention. In FIG. 1, reference numeral 10 is an adhesive sheet, reference numeral 11 is a base sheet, reference numeral 12 is an adhesive layer, and reference numeral 13 is a release sheet. The adhesive sheet 10 is a single-sided adhesive sheet in which an adhesive layer is formed on one side of a base sheet.
FIG. 2 shows a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to a second embodiment of the invention. In FIG. 2, reference numeral 20 is an adhesive sheet, reference numeral 21 is a base sheet, reference numerals 22A and 22B are adhesive layers, and reference numerals 23A and 23B are release sheets.

The base sheet is not particularly limited, and examples thereof include resin sheets, paper, and metal foils. 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. The surface of the base sheet on which the adhesive layer is to be formed may be subjected, if necessary, to an easy-adhesion treatment such as corona discharge treatment and application of an anchor coating agent.

The constituent resin of the resin sheet is not particularly limited, and includes ester resins such as polyethylene terephthalate (PET); olefin resins such as polyethylene (PE) and polypropylene (PP); vinyl resins such as polyvinyl chloride; amide-based resins; urethane-based resins (including foams); and combinations thereof.
The thickness of the resin sheet other than the polyurethane sheet is not particularly limited, preferably 15 to 300 μm. The thickness of the polyurethane sheet (including foam) is not particularly limited, preferably 20 to 50,000 μm.

The paper is not particularly limited, and includes plain paper, coated paper, art paper, and the like.
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 obtained by applying a known release treatment such as coating of a release agent to the surface of a base sheet such as a resin sheet or paper can be used.

A 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 a substrate sheet to form a coating layer comprising 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 composed of the cured adhesive of the present invention. The heat drying temperature is not particularly limited, and is preferably about 60 to 150°C. The thickness of the 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.
A single-sided pressure-sensitive adhesive sheet can be produced in the manner described above.
A double-sided pressure-sensitive adhesive sheet can be produced by performing the above operation on both sides.

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

The method for producing an adhesive sheet preferably includes a coating step of applying an adhesive onto a base sheet, and heating to form an adhesive layer containing a cured product of the adhesive by heating and drying the formed coating layer. a winding step of winding the obtained adhesive sheet around a core to form an adhesive sheet roll; and a curing step of curing the adhesive sheet roll.

In the pressure-sensitive adhesive of the present invention, a relatively long-chain polyether polyol (HA) is used as a raw material active hydrogen group-containing compound for hydroxyl-terminated urethane prepolymer (UPH), so that the amount of plasticizer added is small/preferably It is possible to form an adhesive layer having good wettability even with a composition that does not contain a plasticizer.

In the present invention, a relatively long-chain polyether polyol (HA ) can improve the deterioration of the initial curing property of the pressure-sensitive adhesive and the deterioration of the removability of the pressure-sensitive adhesive layer.
The pressure-sensitive adhesive of the present invention can have good initial curability while having a good pot life. Since the adhesive of the present invention has a good pot life, the adhesive does not become too viscous until it is applied to the substrate sheet, enabling uniform application of the adhesive. is. Since the adhesive of the present invention has good initial curability, the coating layer or the adhesive layer is exposed to hot air during heat drying of the coating layer, or during winding and curing of the adhesive sheet obtained after heat drying. It is less likely to be affected by the mechanical stress received, and the occurrence of surface appearance defects such as core step marks, citrus peel, and curl peculiarities on the adhesive layer is suppressed.
In the adhesive of the present invention, the addition of a plasticizer can be reduced or not used, and a relatively short-chain active hydrogen group-containing compound as a raw material active hydrogen group-containing compound for a hydroxyl group-terminated urethane prepolymer (UPH) By using (HB), it is possible to effectively suppress contamination of the adherend by the adhesive component remaining on the surface of the adherend after re-peeling of the pressure-sensitive adhesive sheet, especially when exposed to a high-temperature and high-humidity environment. can.
The pressure-sensitive adhesive of the present invention also has good adhesion to substrates.

As described above, according to the present invention, pot life and initial curability are good, wettability and substrate adhesion are good, and good removability is obtained even when placed in a high-temperature and high-humidity environment. A pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive layer having properties and a pressure-sensitive adhesive sheet using the same can be provided.

[Use]
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 pressure-sensitive adhesive sheet of the present invention is suitable for use as a surface protection sheet, a cosmetic sheet, an anti-slip sheet, and the like.
Flat panel displays such as liquid crystal displays (LCDs) and organic electroluminescent displays (OELDs), as well as touch panel displays combining such flat panel displays and touch panels, are widely used in televisions (TVs), personal computers (PCs), mobile phones, and widely used in electronic devices such as personal digital assistants.
The pressure-sensitive adhesive sheet of the present invention can be used for flat panel displays and touch panel displays (these are also collectively referred to simply as "displays"), substrates manufactured or used in these manufacturing processes (glass substrates, and ITO on glass substrates). (Indium Tin Oxide) film-formed ITO/glass substrate, etc.) and as a surface protective sheet for optical members and the like.

Synthesis examples, examples according to the present invention, and comparative examples are described below. In the description below, unless otherwise specified, "parts" means parts by mass, "%" means % by mass, and "RH" means relative humidity.

[Measurement of Mn and Mw]
Number average molecular weight (Mn) and weight average molecular weight (Mw) were measured by gel permeation chromatography (GPC) method. The measurement conditions were as follows. Both Mn and Mw are polystyrene equivalent values.
<Measurement conditions>
Apparatus: SHIMADZU Prominence (manufactured by Shimadzu Corporation),
Column: Two TSKgelGMH manufactured by TOSOH are connected in series,
Detector: differential refractive index detector (RID-10A),
solvent: tetrahydrofuran (THF),
flow rate: 1 mL/min,
Solvent temperature: 40°C,
Sample concentration: 0.1%,
Sample injection volume: 100 μL.

[material]
The materials used are as follows.
<Polyether polyol (HA) having a number average molecular weight (Mn) of 1650 or more per functional group>
(HA-1): Preminol 5001F (abbreviation in the table: PREM 5001F), manufactured by Asahi Glass Co., Ltd., bifunctional polyether polyol, Mn4000, number of hydroxyl groups: 2, hydroxyl value: 28, degree of unsaturation: 0.02,
(HA-2): Preminol S4013F (abbreviation in the table: PREM S4013F), manufactured by Asahi Glass Co., Ltd., bifunctional polyether polyol, Mn12000, number of hydroxyl groups: 2, hydroxyl value: 9, degree of unsaturation: 0.007,
(HA-3): Preminol S4318F (abbreviation in the table: PREM S4318F), manufactured by Asahi Glass Co., Ltd., bifunctional polyether polyol, Mn 18000, number of hydroxyl groups 2, hydroxyl value 6, degree of unsaturation 0.007,
(HA-4): Excel 828 (abbreviation in the table: EXCE 828), manufactured by Asahi Glass Co., Ltd., trifunctional polyether polyol, Mn 5000, number of hydroxyl groups 3, hydroxyl value 34, degree of unsaturation 0.07,
(HA-5): Preminol S3011 (abbreviation in the table: PREM S3011), manufactured by Asahi Glass Co., Ltd., trifunctional polyether polyol, Mn 10000, number of hydroxyl groups 3, hydroxyl value 17, degree of unsaturation 0.006,
(HA-6): Preminol 3012 (abbreviation in the table: PREM 3012), manufactured by Asahi Glass Co., Ltd., trifunctional polyether polyol, Mn 12000, number of hydroxyl groups 3, hydroxyl value 14, degree of unsaturation 0.020,
(HA-7): EXENOL 838 (abbreviation in the table: EXCE 838), manufactured by Asahi Glass Co., Ltd., tetrafunctional polyether polyol, Mn 8000, number of hydroxyl groups: 4, hydroxyl value: 28, degree of unsaturation: 0.07.
The unit of unsaturation is meq/g.
Table 1 shows the number of functional groups, Mn, Mn per functional group, and degree of unsaturation of each polyether polyol (HA).

<General-purpose polyether polyol (HM) having a number average molecular weight (Mn) of more than 300 and less than 1,650 per functional group>
(HM-1): PP-2000, manufactured by Sanyo Kasei Co., Ltd., bifunctional polyether polyol, Mn2000, number of hydroxyl groups: 2, hydroxyl number: 56,
(HM-2): G-1500, manufactured by Adeka Co., Ltd., trifunctional polyether polyol, Mn1500, number of hydroxyl groups: 3, hydroxyl value: 112,
(HM-3): G-3000B, manufactured by Adeka Co., Ltd., trifunctional polyether polyol, Mn3000, number of hydroxyl groups: 3, hydroxyl value: 56.
Table 1 shows the number of functional groups, Mn, and Mn per functional group of each polyether polyol (HM).

<Active hydrogen group-containing compound (HB) having a number average molecular weight (Mn) of 300 or less per functional group>
(HB-1): ethylene glycol (EG), containing only primary hydroxyl groups,
(HB-2): 1,5-pentanediol, containing only primary hydroxyl groups,
(HB-3): 2-ethyl-1,3-hexanediol (1,3-octanediol), containing primary and secondary hydroxyl groups,
(HB-4): PPG600 (the number indicates Mn, the same applies to PEG), polypropylene glycol, manufactured by Sanyo Kasei Co., Ltd., containing only secondary hydroxyl groups,
(HB-5): PEG300, polyethylene glycol, manufactured by Sanyo Kasei Co., Ltd., containing only primary hydroxyl groups,
(HB-6): PEG600, polyethylene glycol, manufactured by Sanyo Kasei Co., Ltd., containing only primary hydroxyl groups,
(HB-7): glycerin, containing primary and secondary hydroxyl groups,
(HB-8): trimethylolpropane (TMP), containing only primary hydroxyl groups,
(HB-9): SP-750, manufactured by Sanyo Kasei Co., Ltd., hexafunctional polyether polyol, Mn700, 6 hydroxyl groups, containing only secondary hydroxyl groups,
(HB-10): Isophorone diamine.
Table 1 shows the number of functional groups, Mn, and Mn per functional group of each active hydrogen group-containing compound (HB).

<Polyisocyanate (N)>
(N-1): isophorone diisocyanate (IPDI), manufactured by Tokyo Chemical Industry Co., Ltd.,
(N-2): hexamethylene diisocyanate (HDI), manufactured by Tokyo Chemical Industry Co., Ltd.,
(N-3): tolylene diisocyanate (mixture of 2,4-tolylene diisocyanate (80% by mass) and 2,6-tolylene diisocyanate (20% by mass)) (TDI) manufactured by Tosoh Corporation.
Table 1 shows the number of functional groups, Mn, and Mn per functional group of each polyisocyanate (N).

<Polyfunctional isocyanate compound (I)>
(I-1) Coronate HL, manufactured by Tosoh Corporation, hexamethylene diisocyanate (HDI) / trimethylolpropane (TMP) adduct,
(I-2) Sumidule N-3300, manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate (HDI) / isocyanurate,
(I-3) Sumidule N-75, manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate (HDI)/isocyanabiuret,
(I-4) Desmodur Z4470BA, manufactured by Sumika Bayer Urethane Co., Ltd., isophorone diisocyanate (IPDI)/isocyanurate.

<Antioxidant (C)>
(C-1): IRGANOX 1135 (manufactured by BASF).
<Antistatic agent (AS agent) (E)>
(E-1): Elexel AS-804 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).
<Plasticizer (P)>
(P-1): ATBC (manufactured by Mitsubishi Chemical Corporation), tributyl acetylcitrate.

[Synthesis example of hydroxyl group-terminated urethane prepolymer (UPH)]
(Synthesis Example 1) (Two-stage polymerization method)
100 parts by mass of polyether polyol (HA-1), 10 parts by mass of polyisocyanate (N-1), and toluene were placed in a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel. 47 parts by mass and 0.01 part by mass of dioctyltin dilaurate as a catalyst were charged and mixed. The content liquid was gradually heated to 80° C. and reacted for 2 hours to obtain an isocyanate group-terminated urethane prepolymer (first stage reaction). Next, the content liquid was cooled to 60° C., 28 parts by mass of ethyl acetate was added, and then 4 parts by mass of the active hydrogen group-containing compound (HB-2) was added and reacted (second stage reaction). In the entire reaction of the first step and the second step, the active hydrogen groups (H ) was 0.71 (NCO/H).
After confirming the disappearance of the remaining isocyanate groups by infrared spectroscopic analysis (IR analysis), the content liquid was cooled to terminate the reaction, and a colorless and transparent hydroxyl group-terminated urethane prepolymer (60% non-volatile, viscosity 2,100 cps) A solution of UPA-1) was obtained. The obtained hydroxyl group-terminated urethane prepolymer had Mn=16,500 and Mw=43,000.
Compounding composition, the number of moles of isocyanate groups (NCO) possessed by the polyisocyanate (N) used for the reaction relative to the total number of moles of active hydrogen groups (H) possessed by all active hydrogen group-containing compounds (HX) used for the reaction The ratio (NCO/H) and Mn and Mw of the obtained hydroxyl group-terminated urethane prepolymer are shown in Table 2-1. The unit of blending amount is "parts by mass" (the same applies to other tables).

(Synthesis Examples 2 to 42) (Two-stage polymerization method)
In Synthesis Examples 2 to 42, the same procedure as in Synthesis Example 1 was performed except that the types of polyether polyol (HA), active hydrogen group-containing compound (HB), and polyisocyanate (N) used and their blending ratios were changed. Then, solutions of colorless and transparent hydroxyl group-terminated urethane prepolymers (UPA-2) to (UPA-42) were obtained by a two-stage polymerization method.
In each synthesis example, the isocyanate group (NCO ) and the Mn and Mw of the obtained hydroxyl group-terminated urethane prepolymers are shown in Tables 2-1 to 2-5.

(Synthesis Example 43) (One-step polymerization method)
100 parts by mass of polyether polyol (HA-6) and 4 parts by mass of active hydrogen group-containing compound (HB-2) were placed in a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel. 47 parts by mass of toluene, and 0.01 part by mass of dioctyltin dilaurate as a catalyst were charged and mixed, and the temperature was gradually raised to 80°C. 9 parts by mass of polyisocyanate (N-1) and 28 parts by mass of ethyl acetate were added to the content liquid and reacted for 2 hours. Polyisocyanate used in the reaction with respect to the total number of moles of active hydrogen groups (H) possessed by all active hydrogen group-containing compounds (HX) used in the reaction ((HA-6) and (HB-2) in this example) The ratio (NCO/H) of the number of moles of isocyanate groups (NCO) possessed by (N) was 0.58.
After confirming the disappearance of the remaining isocyanate groups by infrared spectroscopic analysis (IR analysis), the content liquid was cooled to terminate the reaction, and the hydroxyl group-terminated urethane prepolymer (nonvolatile content 60%, viscosity 3,300 cps, white opaque hydroxyl group-terminated urethane prepolymer ( A solution of UPA-43) was obtained. The obtained hydroxyl group-terminated urethane prepolymer had Mn=26,500 and Mw=73,000.
Compounding composition, the number of moles of isocyanate groups (NCO) possessed by the polyisocyanate (N) used for the reaction relative to the total number of moles of active hydrogen groups (H) possessed by all active hydrogen group-containing compounds (HX) used for the reaction The ratio (NCO/H) and Mn and Mw of the obtained hydroxyl group-terminated urethane prepolymer are shown in Table 2-5.

(Synthesis Examples C1 to C6) (One-step polymerization method)
In Synthesis Examples C1 to C6, a plurality of types of active hydrogen group-containing compounds (HX) selected from polyether polyols (HA), polyether polyols (HM), and active hydrogen group-containing compounds (HB), poly Colorless and transparent comparative hydroxyl-terminated urethane prepolymers (UPB-1) to ( A solution of UPB-6) was obtained.
In each synthesis example, the isocyanate group (NCO ) and the Mn and Mw of the obtained hydroxyl group-terminated urethane prepolymer are shown in Table 2-6.

(Synthesis Example C7) (Two-stage polymerization method)
In Synthesis Example C7, polyether polyol (HM-3) was used in place of polyether polyol (HA-1), and the types and raw material blending ratios of the active hydrogen group-containing compound (HB) and polyisocyanate (N) were changed. A solution of a colorless and transparent hydroxyl group-terminated urethane prepolymer (UPB-7) for comparison was obtained by a two-stage polymerization method in the same manner as in Synthesis Example 1, except for the above.
Compounding composition, the number of moles of isocyanate groups (NCO) possessed by the polyisocyanate (N) used for the reaction relative to the total number of moles of active hydrogen groups (H) possessed by all active hydrogen group-containing compounds (HX) used for the reaction The ratio (NCO/H) and Mn and Mw of the obtained hydroxyl group-terminated urethane prepolymer are shown in Table 2-6.

(Formulation example D1)
In Formulation Example D1, polyether polyol (HA-6), active hydrogen group-containing compound (HB-3), 47 parts by mass of toluene, 28 parts by mass of ethyl acetate, and 0.01 part by mass of dioctyltin dilaurate as a catalyst were charged. , to obtain a colorless and transparent solution of polyol (PO-1) for comparison (polyol mixed solution). The formulation composition is shown in Tables 2-6.

[Manufacture of urethane adhesive and adhesive sheet]
(Example 1)
100 parts by mass of the solution of the hydroxyl group-terminated urethane prepolymer (UPA-1) obtained in Synthesis Example 1, 10 parts by mass of the polyfunctional isocyanate compound (I-1), 1 part by mass of the antioxidant (C-1), and a solvent 100 parts by mass of ethyl acetate was blended as and stirred with a disper to obtain a urethane-based pressure-sensitive adhesive. In addition, the amount of each material used other than the solvent indicates a non-volatile content conversion value (the same applies to other examples and comparative examples). The formulation composition is shown in Table 3-1. Pot life evaluation was performed on the resulting pressure-sensitive adhesive.
A polyethylene terephthalate (PET) film (Lumirror T-60, manufactured by Toray Industries, Inc.) having a thickness of 50 μm was prepared as a base sheet. Using a comma coater (registered trademark), the obtained urethane pressure-sensitive adhesive was coated on one side of the base sheet so that the thickness after drying was 12 μm. Then, 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 (Superstick SP-PET38, manufactured by Lintec) was adhered to the adhesive layer to obtain an adhesive sheet. Evaluation of initial hardening property was carried out after curing for 3 hours under conditions of 23° C.-50% RH. Other evaluations were carried out after curing for one week under conditions of 23° C.-50% RH.

(Examples 2 to 55, Comparative Examples 1 to 8)
In each of Examples 2 to 55 and Comparative Examples 1 to 8, the same procedure as in Example 1 was performed except that the types and compounding ratios of the materials used were changed as shown in Tables 3-1 and 3-2. , production and evaluation of urethane-based pressure-sensitive adhesives and pressure-sensitive adhesive sheets. Comparative Example 8 is an example in which an adhesive was produced by the one-shot method.

[Evaluation items and evaluation methods]
Evaluation items and evaluation methods for the adhesive and adhesive sheet are as follows.
(pot life)
Immediately after production, the obtained adhesive was placed in a glass bottle with a lid, and the glass bottle was placed in a constant temperature water bath at 40°C. The rate of increase in viscosity after 6 hours relative to that after 1 hour (viscosity after 6 hours/viscosity after 1 hour [times]) was determined. Evaluation criteria are as follows.
Good: Viscosity increase rate is less than 3 times, good.
Δ: Viscosity increase rate is 3 times or more and 5 times or less, practically acceptable.
x: Viscosity increase rate is more than 5 times, not practical.

(initial curability)
A test piece having a width of 30 mm and a length of 100 mm was cut from the pressure-sensitive adhesive sheet after curing for 3 hours in an atmosphere of 23° C.-50% RH. This test piece was attached to a SUS mesh (opening: 0.077 mm, wire diameter: 0.05 mm) and then immersed in ethyl acetate. After extracting at 50°C for 24 hours, it was dried at 100°C for 30 minutes, and the gel fraction (% by mass) was calculated based on the following formula (1).
Gel fraction (% by mass) = (G2/G1) x 100 (1)
In the above formula, each symbol indicates the following parameters.
G1: mass of sticky layer before extraction with ethyl acetate,
G2: Weight of sticky layer after extraction with ethyl acetate and drying.
Evaluation criteria are as follows.
⊚: Excellent with a gel fraction of 80% by mass or more.
◯: Good gel fraction of 50% by mass or more and less than 80% by mass.
Δ: Gel fraction of 20% by mass or more and less than 50% by mass, practically acceptable.
x: Gel fraction is less than 20% by mass, not practical.

(Wettability)
A test piece with a width of 50 mm and a length of 100 mm is cut out from the adhesive sheet after curing for 1 week in an atmosphere of 23 ° C.-50% RH, left for 30 minutes in an atmosphere of 23 ° C.-50% RH, and then peeled from the test piece. The sheet was peeled off. One end in the longitudinal direction of the test piece from which the release sheet was removed was fixed to the end of the glass plate, and the other end, which was not fixed, was lifted by hand to a height of 5 cm from the surface of the glass plate. In this state, the hand was released, and the time until the entire adhesive layer adhered to the surface of the glass plate was measured. Evaluation criteria are as follows.
◯: less than 4 seconds until close contact, good.
Δ: 4 seconds or more and less than 8 seconds until close contact, practically acceptable.
x: 8 seconds or longer until close contact, impractical.

(Substrate adhesion)
After curing for 1 week in an atmosphere of 23 ° C.-50% RH, the adhesive layer of the adhesive sheet was half-cut 11 times at 1 mm intervals in two linear directions perpendicular to each other, and 1 mm square. formed 100 squares of . After rubbing the entire 100 squares with a finger for 1 minute, the number of squares remaining on the base sheet was visually counted. Evaluation criteria are as follows.
A: The number of remaining cells is 81 to 100, excellent.
◯: 61 to 80 remaining squares, good.
Δ: 41 to 60 remaining squares, practically acceptable.
x: 0 to 40 remaining squares, impractical.

(Removability)
Three test pieces each having a width of 70 mm and a length of 100 mm were cut from the pressure-sensitive adhesive sheet after curing for one week in an atmosphere of 23° C.-50% RH. For each of the three test pieces, the release sheet was peeled off in an atmosphere of 23° C.-50% RH, and a caustic soda glass plate was adhered to the surface of the exposed adhesive layer and pressed with a laminator. The resulting three laminates were left in an oven set at 85° C.-85% RH for 72 hours (Condition 1), 120 hours (Condition 2) and 240 hours (Condition 3). Each of the three laminates was removed from the oven and air-cooled in an atmosphere of 23° C.-50% RH for 3 hours. Evaluation criteria are as follows.
⊚: Excellent, with absolutely no adhesive layer component adhering to the glass surface under all conditions.
◯: Under conditions 1 and 2, there was no adhesion of adhesive layer components to the glass surface, but under condition 3, adhesion of adhesive layer components to the glass surface occurred, which was good.
Δ: Under condition 1, there was no adhesion of the adhesive layer components to the glass surface, but under conditions 2 and 3, adhesion of the adhesive layer components to the glass surface occurred, and it was practically acceptable.
x: Adhesion of adhesive layer components to the glass surface occurs under all conditions, impractical.

(Adherend contamination suppression property)
A test piece with a width of 70 mm and a length of 100 mm was cut out from the adhesive sheet after curing for 1 week in an atmosphere of 23 ° C.-50% RH, and the release sheet was peeled off in an atmosphere of 23 ° C.-50% RH to expose the adhesive. A caustic soda glass plate was attached to the surface of the layer and pressed with a laminator. The resulting laminate was left in an oven set at 85° C.-85% RH for 72 hours. The laminate was taken out of the oven and air-cooled in an atmosphere of 23° C.-50% RH for 3 hours. In a dark room, the surface of the glass plate on which the adhesive sheet was pasted was irradiated with light from an LED (light emitting diode) lamp and visually observed for evaluation. Evaluation criteria are as follows.
⊚: Excellent, no adherence of adhesive layer components on the glass surface.
Good: Adherence of a thin adhesive layer component is observed at 1 to 2 locations on the glass surface.
Δ: Adhesion of thin adhesive layer components is observed at three locations on the glass surface, practically acceptable.
x: Adhesion of thin adhesive layer components is observed at 4 or more locations on the glass surface/or adhesion of thick adhesive layer components is observed at 1 to 2 locations on the glass surface, impractical.

[Evaluation results]
Evaluation results are shown in Tables 4-1 and 4-2.
In Examples 1 to 55, a relatively long-chain polyether polyol (HA) having a number average molecular weight (Mn) per functional group of 1650 or more and a number average molecular weight (Mn) per functional group of 300 or less A urethane containing a relatively short-chain active hydrogen group-containing compound (HB), a hydroxyl group-terminated urethane prepolymer (UPH) that is a reaction product of a polyisocyanate (N), and a polyfunctional isocyanate compound (I) A system adhesive was produced.
In all of these examples, a pressure-sensitive adhesive with good pot life and initial curability can be produced. It was possible to produce a pressure-sensitive adhesive sheet having good removability and contamination-inhibiting properties on adherends even when exposed to the bottom.

As the active hydrogen group-containing compound, a hydroxyl group-terminated urethane prepolymer obtained using only multiple kinds of general-purpose polyether polyols (HM) having a number average molecular weight (Mn) of more than 300 and less than 1650 per functional group was used. In Comparative Example 2, the wettability of the pressure-sensitive adhesive sheet obtained was poor because no plasticizer was added.

As the active hydrogen group-containing compound (HX), a relatively long-chain polyether polyol (HA) having a number average molecular weight (Mn) per functional group of 1650 or more, and a number average molecular weight (Mn) per functional group In Comparative Examples 1 and 3 to 5 using a hydroxyl-terminated urethane prepolymer obtained using a general-purpose polyether polyol (HM) having a polyether polyol (HM) of more than 300 and less than 1650, a pressure-sensitive adhesive sheet having good wettability even without the addition of a plasticizer could be manufactured. However, in these comparative examples, a relatively short-chain active hydrogen group-containing compound (HB) having a number average molecular weight (Mn) of 300 or less per functional group was not used as a raw material for the hydroxyl-terminated urethane prepolymer. The adhesive had poor pot life and initial curability, and the removability of the adhesive sheet and the suppression of contamination of the adherend were poor. The pressure-sensitive adhesive sheets obtained in these comparative examples also had poor adhesion to the substrate.

As the active hydrogen group-containing compound (HX), a general-purpose polyether polyol (HM) having a number average molecular weight (Mn) per functional group of more than 300 and less than 1650, and a number average molecular weight (Mn) per functional group of 300 In Comparative Examples 6 and 7 using hydroxyl group-terminated urethane prepolymers obtained using the following relatively short-chain active hydrogen group-containing compound (HB), per functional group Since a relatively long-chain polyether polyol (HA) having a number-average molecular weight (Mn) of 1,650 or more was not used, the obtained pressure-sensitive adhesive sheet had poor wettability. In Comparative Example 6, the urethane prepolymer obtained by the one-stage polymerization method had a mixture of primary and secondary terminal hydroxyl groups, so that the obtained pressure-sensitive adhesive had poor initial curability. In Comparative Example 7, since the terminal hydroxyl group of the urethane prepolymer obtained by the two-stage polymerization method was only primary, the initial curability was improved.

In Comparative Example 8, without using a hydroxyl group-terminated urethane prepolymer (UPH), a relatively long-chain polyether polyol (HA) having a number average molecular weight (Mn) per functional group of 1650 or more and one functional group A relatively short-chain active hydrogen group-containing compound (HB) having a number average molecular weight (Mn) of 300 or less per unit is mixed with a polyfunctional isocyanate compound (I) to produce a urethane-based adhesive by a one-shot method. did. The pressure-sensitive adhesive obtained had poor initial curability, and the pressure-sensitive adhesive sheet using this adhesive had poor removability and resistance to contamination of adherends.

The present invention is not limited to the above-described embodiments and examples, and design changes are possible as appropriate without departing from the gist of the present invention.

10, 20 adhesive sheets 11, 21 base sheet 12, 22A, 22B adhesive layer 13, 23A, 23B release sheet

Claims (9)

A polyether polyol (HA) having a number average molecular weight of 2000 or more per functional group and an active hydrogen group containing a plurality of active hydrogen groups in one molecule having a number average molecular weight of 30 to 100 per functional group. a hydroxyl group-terminated urethane prepolymer (UPH), which is a reaction product of a plurality of active hydrogen group-containing compounds (HX) containing a compound (HB) and one or more polyisocyanates (N);
and a polyfunctional isocyanate compound (I),
The ratio (NCO/H) of the number of moles of isocyanate groups (NCO) possessed by polyisocyanate (N) to the total number of moles of active hydrogen groups (H) possessed by multiple active hydrogen group-containing compounds (HX) is 0.20. ~0.84;
A pressure-sensitive adhesive in which one or more polyether polyols (HA) contain tri- or more functional polyether polyols. The adhesive according to claim 1, wherein the amount of the plasticizer (P) added is 0 to 10 parts by mass with respect to 100 parts by mass of the hydroxyl-terminated urethane prepolymer (UPH). Hydroxyl group-terminated urethane prepolymer (UPH) is an isocyanate group-terminated urethane prepolymer (UPN), which is a reaction product of polyether polyol (HA) and polyisocyanate (N), and an active hydrogen group-containing compound (HB). 3. The adhesive according to claim 1, which is a reaction product. The adhesive according to any one of claims 1 to 3, wherein the one or more polyisocyanates (N) comprise isophorone diisocyanate. The adhesive according to any one of claims 1 to 4, wherein the active hydrogen group-containing compound (HB) contains a primary hydroxyl group. Furthermore, the adhesive according to any one of claims 1 to 5, comprising one or more anti-deterioration agents selected from the group consisting of antioxidants, anti-hydrolysis agents, ultraviolet absorbers, and light stabilizers. agent. The adhesive according to any one of claims 1 to 6, further comprising an antistatic agent. A pressure-sensitive adhesive sheet comprising a base sheet and a pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive according to any one of claims 1 to 7. One or more polyether polyols (HA) having a number average molecular weight per functional group of 2000 or more and one or more polyisocyanates (N) are reacted at a ratio of excess isocyanate groups to prepare an isocyanate group-terminated urethane prepolymer. producing a polymer (UPN);
The obtained isocyanate group-terminated urethane prepolymer (UPN) and one or more active hydrogen group-containing compounds (HB) having a number average molecular weight of 30 to 100 per functional group and having a plurality of active hydrogen groups in one molecule. and a step of reacting with
one or more polyether polyols (HA) comprise trifunctional or higher polyether polyols,
With respect to the total number of moles of active hydrogen groups (H) possessed by multiple active hydrogen group-containing compounds (HX) containing one or more polyether polyols (HA) and one or more active hydrogen group-containing compounds (HB) A method for producing a hydroxyl group-terminated urethane prepolymer in which the molar ratio (NCO/H) of isocyanate groups (NCO) possessed by polyisocyanate (N) is 0.20 to 0.84.

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