JP7823328B2 - Polyester-based pressure-sensitive adhesive composition, polyester-based pressure-sensitive adhesive, and pressure-sensitive adhesive sheet - Google Patents

Description

The present invention relates to a polyester-based pressure-sensitive adhesive composition, a polyester-based pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet, and more particularly to a polyester-based pressure-sensitive adhesive composition, a polyester-based pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a double-sided pressure-sensitive adhesive sheet that, when used as a pressure-sensitive adhesive, have excellent initial adhesive strength and shear strength.

It has been known that polyester resins can be made to have excellent chemical resistance, plasticizer resistance, mechanical strength, etc. by combining a polycarboxylic acid component with a polyol component, and this has also been studied in the field of pressure-sensitive adhesives (adhesives).

Furthermore, in recent years, with the miniaturization and thinning of parts and components, there is a demand for adhesives with high adhesive strength even over a small area. As a method for improving adhesive strength, for example, Patent Document 1 proposes a polyester-based adhesive composition containing a polyester-based resin and a tackifier.
Patent Document 2 proposes a polyester-based pressure-sensitive adhesive composition containing a polyester-based resin and a fatty acid ester.

JP 2014-169419 A Japanese Patent Application Laid-Open No. 2015-196822

The technology disclosed in Patent Document 1 incorporates a tackifier with a high softening point such as a rosin ester or terpene resin. Generally, a tackifier with a high softening point is incorporated to impart cohesive strength at high temperatures, but such a tackifier reduces the initial adhesive strength at room temperature, leaving issues with adhesive strength and shear strength immediately after lamination.

Furthermore, in the technology disclosed in Patent Document 2, a fatty acid ester is blended with a polyester resin. Although fatty acid esters can impart wettability to an adherend, they are low-molecular-weight components and therefore have poor cohesive strength, leaving issues with respect to adhesive strength and shear strength.

Therefore, under such circumstances, an object of the present invention is to provide a polyester-based pressure-sensitive adhesive composition which, when used as a pressure-sensitive adhesive, has excellent adhesive strength immediately after lamination (initial adhesive strength) and also has excellent shear strength.

However, the present inventors have conducted extensive research in light of the above circumstances and have found that polycarboxylic acids (
They have found that, in a pressure-sensitive adhesive composition containing a polyester resin (A) having structural units derived from polyol (a1) and structural units derived from polyol (a2), by using a polyester resin (A) having a high glass transition temperature in combination with a polyester plasticizer (B), a polyester pressure-sensitive adhesive composition excellent in initial adhesive strength and shear strength can be obtained when made into a pressure-sensitive adhesive,
The present invention has been completed.

That is, the gist of the present invention is the following [1] to [15].
[1] A polyester-based pressure-sensitive adhesive composition comprising a polyester-based resin (A) having structural units derived from a polycarboxylic acid (a1) and structural units derived from a polyol (a2), and a polyester-based plasticizer (B), wherein the polyester-based plasticizer (B) has structural units derived from a polycarboxylic acid (b1), structural units derived from a polyol (b2), and structural units derived from a reactive molecule end-capping agent (b3), and wherein the glass transition temperature (TgA) of the polyester-based resin (A) is −25 to 35° C.
[2] The weight average molecular weight of the polyester resin (A) is 15,000 to 200,000
0. The polyester-based pressure-sensitive adhesive composition according to [1].
[3] The polyester-based pressure-sensitive adhesive composition according to [1] or [2], wherein the acid value of the polyester-based resin (A) is 5 mgKOH/g or less.
[4] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the polyester-based plasticizer (B) contains an aromatic structure in at least one of a structural unit derived from a polycarboxylic acid (b1), a structural unit derived from a polyol (b2), and a reactive molecular end-capping agent (b3).
[5] The weight average molecular weight of the polyester plasticizer (B) is 1,000 to 12,000
[5] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [4],
[6] The content of the polyester-based plasticizer (B) is 100% of the polyester-based resin (A).
The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [5], characterized in that the amount is 0.1 to 180 parts by weight based on the total weight of the polyester-based pressure-sensitive adhesive composition.
[7] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the acid value of the polyester-based plasticizer (B) is 5 mg KOH/g or less.
[8] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [7], wherein the glass transition temperature (TgB) of the polyester-based plasticizer (B) is −80 to 0° C.
[9] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [8], wherein the glass transition temperature (TgA) of the polyester-based resin (A) is higher than the glass transition temperature (TgB) of the polyester-based plasticizer (B).
[10] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [9], further comprising a hydrolysis inhibitor (C).
[11] The polyester-based pressure-sensitive adhesive composition according to any one of [1] to [10], which contains a crosslinking agent (D).
[12] A polyester-based pressure-sensitive adhesive obtained by crosslinking the polyester-based pressure-sensitive adhesive composition according to any one of [1] to [11].
[13] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the polyester-based pressure-sensitive adhesive according to [12].
[14] A pressure-sensitive adhesive sheet having a substrate and a pressure-sensitive adhesive layer obtained from the polyester-based pressure-sensitive adhesive according to [12], wherein the pressure-sensitive adhesive layer is provided on at least one surface of the substrate.
[15] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the polyester-based pressure-sensitive adhesive according to [12], characterized in that the pressure-sensitive adhesive sheet is a substrate-less type having no substrate.

In general, a tackifier is blended into a pressure-sensitive adhesive to improve shear strength. In this case, it is common to use a resin with a low glass transition temperature that has adhesiveness as the main component, and then blend a tackifier resin with a high softening point to further increase cohesive strength. However, in the present invention, by blending a polyester resin with a specific glass transition temperature and a polyester plasticizer having a repeating structural unit consisting of an ester bond, it unexpectedly has excellent compatibility with the main component, does not cause bleeding, and when made into a pressure-sensitive adhesive, it has excellent initial adhesive strength,
Furthermore, a pressure-sensitive adhesive composition having excellent shear strength can be obtained.

The polyester-based pressure-sensitive adhesive composition of the present invention, when used as a pressure-sensitive adhesive, has excellent effects in terms of initial adhesive strength and shear strength, and is particularly useful as a pressure-sensitive adhesive for electronic components.

The configuration of the present invention will be described in detail below, but these are merely examples of preferred embodiments.

The polyester-based pressure-sensitive adhesive composition of the present invention is a polyester-based pressure-sensitive adhesive comprising a polyester-based resin (A) and a polyester-based plasticizer (B),
has a structural unit derived from a polycarboxylic acid (a1) and a structural unit derived from a polyol (a2), and has a glass transition temperature (TgA) of −25 to 35° C., and a polyester-based plasticizer (B)
has a structural unit derived from a polycarboxylic acid (b1), a structural unit derived from a polyol (b2), and a structural unit derived from a reactive molecular end-capping agent (b3).
Each of the constituent components used in the polyester-based pressure-sensitive adhesive composition of the present invention will be described in detail below.

<Polyester Resin (A)>
The polyester resin usable in the present invention is usually obtained by copolymerizing copolymerization components containing polycarboxylic acids (a1) and polyols (a2) as constituent raw materials, and the polyester resin has structural units derived from the polycarboxylic acids (a1) and structural units derived from the polyols (a2) as its resin composition. From the viewpoint of excellent shear strength, it is preferable that the polyester resin contains an aromatic structural unit in at least one of the structural units derived from the polycarboxylic acids (a1) and the structural units derived from the polyols (a2), and it is particularly preferable that the structural units derived from the polycarboxylic acids (a1) have an aromatic structural unit.
In the present invention, the term "carboxylic acids" includes not only carboxylic acids but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters.

[Structural units derived from polycarboxylic acids (a1)]
Examples of the structural unit derived from the polycarboxylic acid (a1) include a structural unit derived from a dicarboxylic acid and a structural unit derived from a trivalent or higher polycarboxylic acid. It is preferable that the structural unit derived from a dicarboxylic acid is contained in order to stably obtain a polyester resin.
The polyvalent carboxylic acids (a1) can be used alone or in combination of two or more kinds.

Examples of the structural units derived from dicarboxylic acids include structural units derived from aliphatic dicarboxylic acids such as malonic acids, dimethylmalonic acids, succinic acids, glutaric acids, adipic acids, trimethyladipic acids, pimelic acids, 2,2-dimethylglutaric acids, azelaic acids, sebacic acids, fumaric acids, maleic acids, itaconic acids, thiodipropionic acids, diglycolic acids, and 1,9-nonanedicarboxylic acids;
Phthalic acids, terephthalic acids, isophthalic acids, benzylmalonic acids, diphenic acids,
Structural units derived from aromatic dicarboxylic acids such as 4,4'-oxydibenzoic acids, and further naphthalenedicarboxylic acids such as 1,8-naphthalenedicarboxylic acids, 2,3-naphthalenedicarboxylic acids, and 2,7-naphthalenedicarboxylic acids;
1,3-cyclopentanedicarboxylic acids, 1,2-cyclohexanedicarboxylic acids, 1
,3-cyclopentanedicarboxylic acids, 1,4-cyclohexanedicarboxylic acids, 2,5
-structural units derived from alicyclic dicarboxylic acids such as norbornanedicarboxylic acids and adamantanedicarboxylic acids;
Structural units derived from dimer acids (mainly those having 36 to 44 carbon atoms) derived from oleic acid, linoleic acid, linolenic acid, erucic acid, etc.; and the like.
Examples of the structural units derived from trivalent or higher polyvalent carboxylic acids include structural units derived from trimellitic acids, pyromellitic acids, adamantanetricarboxylic acids, trimesic acids, and the like.
These structural units derived from polycarboxylic acids (a1) may be contained alone or in combination of two or more.

Among the structural units derived from the polycarboxylic acids (a1), it is preferred to contain a structural unit derived from an aromatic polycarboxylic acid, in particular a structural unit derived from an asymmetric aromatic dicarboxylic acid (a1-1), in terms of reducing the crystallinity of the polyester resin and achieving excellent cohesive strength,
Examples of structural units derived from asymmetric aromatic dicarboxylic acids (a1-1) include structural units derived from phthalic acids, isophthalic acids, 1,8-naphthalenedicarboxylic acids, 2,3-naphthalenedicarboxylic acids, 2,7-naphthalenedicarboxylic acids, etc. Among these, in terms of reactivity, it is particularly preferable to contain a structural unit derived from an isophthalic acid.

The content of such structural units derived from aromatic polycarboxylic acids, particularly structural units derived from asymmetric aromatic dicarboxylic acids (a1-1), is preferably 5 to 100 mol%, more preferably 10 to 95 mol%, even more preferably 20 to 90 mol%, particularly preferably 40 to 85 mol%, and especially preferably 60 to 95 mol%, based on the total structural units derived from polycarboxylic acids (a1).
The content is 0 to 80 mol %. If the content is too low, the shear force tends to decrease, the polyester resin tends to crystallize, and sufficient adhesive performance tends to be lost. If the content is too high, the initial adhesive strength tends to decrease.

In the present invention, from the viewpoint of improving the initial adhesive strength, the structural unit derived from the polyvalent carboxylic acid (a1) preferably contains a structural unit derived from an aliphatic dicarboxylic acid (a1-2) having 4 or more carbon atoms (including the carbon atom of the carboxy group), and more preferably contains an aliphatic dicarboxylic acid having 6 to 12 carbon atoms (including the carbon atom of the carboxy group),
It is particularly preferred that the copolymer contains structural units derived from adipic acids, sebacic acids, or azelaic acids.

The content of the structural units derived from the aliphatic dicarboxylic acids (a1-2) having 4 or more carbon atoms is preferably 5 to 90 mol %, more preferably 10 to 80 mol %, and even more preferably 15 to 60 mol %, based on the total structural units derived from the polycarboxylic acids (a1).
If the content is too low, the glass transition temperature of the polyester resin becomes too high, and the initial adhesive strength tends to decrease, whereas if the content is too high, the shear strength tends to decrease, or the polyester resin tends to crystallize, making it difficult to obtain sufficient adhesive performance.

In the present invention, from the viewpoint of adhesive properties, it is also preferable that the structural units derived from the polyvalent carboxylic acids (a1) include structural units derived from asymmetric aromatic dicarboxylic acids (a1-1) and structural units derived from aliphatic dicarboxylic acids (a1-2) having 4 or more carbon atoms. In this case, the content ratio (molar ratio) of the structural units derived from the asymmetric aromatic dicarboxylic acids (a1-1) to the structural units derived from the aliphatic dicarboxylic acids (a1-2) having 4 or more carbon atoms is (a1-1)/(
a1-2) is preferably 1/99 to 99/1, more preferably 40/60 to 9
0/10, and more preferably 55/45 to 80/20.

In the present invention, the polyester resin may contain structural units derived from trivalent or higher polyvalent carboxylic acids (a1-3) for the purpose of increasing the number of branching points. In particular, it is preferable that the polyester resin contains structural units derived from trimellitic acids, since gelation is less likely to occur during production.

The content of the structural units derived from such trivalent or higher polycarboxylic acids (a1-3) is preferably 10 mol % or less, particularly preferably 0.1 to 5 mol %, and particularly preferably 0.5 to 3 mol %, based on the total structural units derived from the polycarboxylic acids (a1), in order to enhance the cohesive strength of the resulting adhesive. If the content is too high, gelation tends to occur during the production of the polyester resin, or the acid value tends to increase.

[Structural units derived from polyol (a2)]
The structural unit derived from the polyol (a2) may be a structural unit derived from a dihydric alcohol or a structural unit derived from a trihydric or higher polyol.
More than one species can be used in combination.

Examples of the structural unit derived from the dihydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,3-propanediol, 1,4-methyl-1,3-propanediol, 1,5-methyl-1,3-propanediol, 1,4-methyl-1,3-propanediol, 1,5-methyl-1,3-propanediol, 1,6 ...4-methyl-1,3-propanediol, 1,5-methyl-1,3-propanediol, 1,4-methyl-1,3-propanediol, 1,5-methyl-1,3-propanediol, 1,4-methyl-1,3-propanediol, 1,5-methyl-1,3-propanediol, 1,4-methyl-1
structural units derived from aliphatic diols such as 2,2,4-trimethyl-1,5-pentanediol and 2,2,4-trimethyl-1,6-hexanediol;
1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4
- structural units derived from alicyclic diols such as cyclohexanedimethanol, spiroglycol, tricyclodecanedimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol;
Examples include structural units derived from aromatic diols such as 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and ethylene oxide adducts and propylene oxide adducts thereof.
Further examples include structural units derived from fatty acid esters derived from castor oil, structural units derived from dimer diols derived from oleic acid, linoleic acid, linolenic acid, erucic acid, etc., and structural units derived from glycerol monostearate.
Examples of the structural unit derived from the trivalent or higher polyol include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, 1,3,6-hexanetriol,
Examples include structural units derived from adamantanetriol.
These structural units derived from polyol (a2) may be contained alone or in combination of two or more.

In the present invention, in order to lower the glass transition temperature of the polyester resin and improve the initial adhesive strength, a linear aliphatic diol (a
2-1), more preferably contains structural units derived from an aliphatic diol having a linear structure and having 2 to 18 carbon atoms, and particularly preferably contains structural units derived from ethylene glycol, 1,4-butanediol, or 1,6-hexanediol.

The content of the structural unit derived from the linear aliphatic diol (a2-1) is
The content of the structural units derived from the above-mentioned copolymer is preferably 5 to 100 mol %, more preferably 10 to 95 mol %, even more preferably 15 to 90 mol %, particularly preferably 20 to 80 mol %, and especially preferably 30 to 70 mol % based on all structural units derived from the above-mentioned copolymer. If the content is too low, it tends to be difficult to obtain stable resin formation.

Among the structural units derived from the polyol (a2), it is preferable to contain a structural unit derived from a diol (a2-2) having a hydrocarbon group on the side chain, since this can disrupt the crystallinity. Examples of the structural unit derived from such a diol (a2-2) having a hydrocarbon group on the side chain include dipropylene glycol, 2,4-dimethyl-2-ethylhexane-1,4-diol ...
,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-
Propanediol (neopentyl glycol), 2-methyl-2-ethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-
Isobutyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,5
structural units derived from aliphatic diols having a branched structure, such as 1,2-cyclohexanedimethanol, 1,
Examples include structural units derived from alicyclic diols having a branched structure, such as 3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and structural units derived from dimer diols derived from oleic acid, erucic acid, etc. Among these, structural units derived from aliphatic diols having a branched structure are preferred, and 2-
Structural units derived from methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), and 3-methyl-1,5-pentanediol are particularly preferred.

The content of the structural units derived from the diol (a2-2) having a hydrocarbon group in the side chain is preferably 5 to 95 mol %, more preferably 10 to 90 mol %, even more preferably 15 to 80 mol %, and particularly preferably 20 to 30 mol %, based on the total structural units derived from the polyol (a2).
If the content is too low, the resin tends to crystallize and it becomes difficult to obtain sufficient adhesive properties, whereas if the content is too high, the reaction time in the production of the polyester resin tends to become long.

Furthermore, in the present invention, it is also preferable that the structural unit derived from the polyol (a2) contains a structural unit derived from a trivalent or higher polyol (a2-3) in order to form a reaction site with the crosslinking agent (D) described below in the polyester resin and increase the cohesive strength. Among the structural units derived from the trivalent or higher polyol (a2-3), trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-
Structural units derived from pentanetriol and 1,2,6-hexanetriol are preferred, and structural units derived from trimethylolpropane are particularly preferred because they are relatively less likely to produce gel.

The content of the structural units derived from the trivalent or higher polyol (a2-3) is preferably 10 mol % or less, more preferably 0.1 to 5 mol %, and even more preferably 0.5 to 3 mol %, based on the total structural units derived from the polyol (a2). If the content of the structural units derived from the trivalent or higher polyol is too high, production of the polyester resin tends to be difficult.

Here, the proportion of structural units (compositional proportion) derived from each component of the polyester resin can be determined, for example, by NMR.

The polyester resin used in the present invention is produced by appropriately selecting the polyvalent carboxylic acid (a1) and the polyol (a2) within the above content ranges and subjecting them to a polycondensation reaction in the presence of a catalyst by a known method.

The blending ratio of the polyvalent carboxylic acids (a1) and the polyol (a2) is preferably 1 to 2 equivalents of the polyol (a2) per equivalent of the polyvalent carboxylic acids (a1),
If the blending ratio of polyol (a2) is too low, the acid value will be high and it will tend to be difficult to obtain a high molecular weight, whereas if it is too high, the yield will tend to decrease.

During the polycondensation reaction, an esterification reaction is carried out first, followed by the polycondensation reaction.

In such an esterification reaction, a catalyst is usually used, and specific examples include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, antimony-based catalysts such as antimony trioxide, germanium-based catalysts such as germanium dioxide, and catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide, and one or more of these are used. Among these, antimony trioxide, tetrabutyl titanate, germanium dioxide, and zinc acetate are preferred from the perspective of the balance between high catalytic activity and color.

The amount of the catalyst to be added is preferably 1 to 10,000 ppm by weight, more preferably 10 to 5,000 ppm, and even more preferably 20 to 3,000 ppm, based on the weight of all copolymerization components.
If the blending amount is too small, the polymerization reaction tends to proceed poorly.
If the amount is too large, there is no advantage such as shortening the reaction time, and side reactions tend to occur.

The reaction temperature during the esterification reaction is preferably 200 to 300°C, particularly preferably 210 to 280°C, and even more preferably 220 to 260°C. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, while if it is too high, side reactions such as decomposition tend to occur easily. The pressure during the reaction is usually normal pressure.

After the esterification reaction, a polycondensation reaction is carried out.
The reaction conditions for the polycondensation reaction are as follows:
Further, the same amount is compounded, and the reaction temperature is preferably 220 to 280°C, particularly preferably 23
It is preferable to set the reaction temperature at 0 to 270° C., gradually reduce the pressure of the reaction system, and finally carry out the reaction at 5 hPa or less. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if it is too high, side reactions such as decomposition tend to occur easily.

In this way, the polyester resin (A) used in the present invention is obtained.

The polyester resin (A) described above preferably has the following physical properties:

The glass transition temperature (TgA) of the polyester resin (A) is, from the viewpoint of adhesive properties,
The temperature must be 25 to 35°C, preferably -20 to 30°C, and more preferably -1
The temperature is preferably 5 to 28° C., more preferably −10 to 26° C., particularly preferably −5 to 24° C., particularly preferably 0 to 22° C., and most preferably 3 to 20° C. By setting the glass transition temperature (TgA) within the above range, it is possible to obtain a pressure-sensitive adhesive having excellent initial adhesive strength and shear strength, which are the effects of the present invention.
If the glass transition temperature is too high, flexibility will be lost, the initial adhesive strength will decrease, and adhesive strength will not be exerted easily even with pressure equivalent to finger pressure, which will tend to reduce workability, while if the glass transition temperature is too low, shear strength will tend to decrease.

Here, the glass transition temperature (TgA) of the polyester resin (A) is a value measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments.
The measurement temperature range was −90 to 100° C., and the temperature rise rate was 10° C./min.

From the viewpoint of adhesive properties, the glass transition temperature (TgA) of the polyester resin (A) is preferably higher than the glass transition temperature (TgB) of the polyester plasticizer (B) described below. Furthermore, the glass transition temperature of the polyester resin (A) is more preferably 3 to 80°C higher than the glass transition temperature of the polyester plasticizer (B), even more preferably 5 to 60°C higher, particularly preferably 10 to 50°C higher, and especially preferably 15 to 45°C higher.
By setting the content within the above range, a pressure-sensitive adhesive having excellent initial adhesive strength and shear strength can be obtained.

The weight average molecular weight of the polyester resin (A) is usually 15 to 2000 kJ/g from the viewpoint of the cohesive strength of the adhesive.
It is preferably 20,000 to 150,000, particularly preferably 30,000 to 140,000, and further preferably 40,000 to 130,000.
The number is 000.
By setting the content within the above range, a pressure-sensitive adhesive having excellent adhesion to the substrate and shear strength can be obtained.
If the weight average molecular weight is too small, the adhesive will not have sufficient cohesive strength and the shear strength will tend to decrease, whereas if the weight average molecular weight is too large, the adhesiveness to the substrate will tend to decrease.

The weight average molecular weight of the polyester resin is a weight average molecular weight converted into a standard polystyrene molecular weight, and is measured by a high performance liquid chromatograph (Waters, "ACQUITY A"
The column was ACQUITY APC XT 450, and the column was ACQUITY APC XT 450.
Measurements are performed using one ACQUITY APC XT 200 and two ACQUITY APC XT 45 in series, for a total of four.

The number average molecular weight of the polyester resin (A) is usually 5.0 in view of the cohesive strength of the adhesive.
It is preferably 7,500 to 40,000, particularly preferably 10,000 to 35,000, and further preferably 12,000 to 30,000.
By setting the content within the above range, a pressure-sensitive adhesive having excellent adhesion to the substrate and shear strength can be obtained.
If the number average molecular weight is too small, the adhesive will not have sufficient cohesive strength and will tend to have reduced shear strength, whereas if the number average molecular weight is too large, the adhesiveness to the substrate will tend to be reduced.
The number average molecular weight can be measured by the same method as that for the weight average molecular weight of the polyester resin described above for the polyester resin (A).

The hydroxyl value of the polyester resin (A) is preferably 0.1 to 50 mgKOH/g, more preferably 1 to 30 mgKOH/g, and even more preferably 2 to 20 mgKOH/g.
If the hydroxyl value is too high, the efficiency of crosslinking with the crosslinking agent (D) tends to decrease.

The acid value of the polyester resin (A) is preferably 10 mgKOH/g or less, more preferably 5 mgKOH/g or less, even more preferably 3 mgKOH/g or less, particularly preferably 1 mgKOH/g or less, particularly preferably 0.5 mgKOH/g or less, and most preferably 0.3 mgKOH/g or less. By setting the acid value within the above range, hydrolysis of the polyester resin (A) can be suppressed, resulting in excellent shear strength and, further, corrosion when laminated to a metal can be suppressed.
If the acid value is too high, hydrolysis tends to proceed more easily, and when a layer of metal or the like is attached to one side of the pressure-sensitive adhesive layer, it tends to corrode the layer.

Here, the hydroxyl value and acid value in the present invention are determined by neutralization titration in accordance with JIS K 0070.

<Polyester-based plasticizer (B)>
The polyester plasticizer (B) exhibits a plasticizer effect and has a structural unit derived from a polycarboxylic acid (b1), a structural unit derived from a polyol (b2), and a structural unit derived from a reactive molecular end-capping agent (b3). For example, it is obtained by blocking at least one reactive molecular end of a polyester resin with the reactive molecular end-capping agent (b3).
In addition, it is preferable that at least one of the structural unit derived from the polyvalent carboxylic acid (b1), the structural unit derived from the polyol (b2), and the reactive molecular end-capping agent (b3) contains an aromatic structural unit, from the viewpoint of excellent adhesive strength, tackiness, and stain resistance.
It is more preferable that the structural unit derived from b1) and/or the reactive molecular end-capping agent (b3) contains an aromatic structural unit, and it is particularly preferable that the reactive molecular end-capping agent (b3) contains an aromatic structural unit.

The polyester plasticizer (B) contains polycarboxylic acids (b1) as reactive molecular terminals.
The polyester-based plasticizer has at least one of a carboxyl group terminal derived from the polyol (b1) and a hydroxyl group terminal derived from the polyol (b2), and the reactive molecular ends of the polyester-based plasticizer are capped with a reactive molecular end-capping agent (b3) described later.
The polyester plasticizer (B') before the reactive molecule ends are blocked (hereinafter, sometimes referred to as "pre-endblocked polyester plasticizer (B')") will be described below.

[Polyester-based plasticizer (B') before end-capping]
The polyester plasticizer (B') before end-blocking is usually obtained by copolymerizing copolymerization components containing polycarboxylic acids (b1) and polyol (b2) as constituent raw materials, and the polyester plasticizer (B') before end-blocking has, as its resin composition, structural units derived from the polycarboxylic acids (b1) and structural units derived from the polyol (b2).

[Structural units derived from polycarboxylic acids (b1)]
The structural unit derived from the polycarboxylic acid (b1) includes the structural unit derived from the polycarboxylic acid (a1)
) structural units derived from the same as those described above.

Among the structural units derived from the polyvalent carboxylic acids (b1), structural units derived from aromatic polyvalent carboxylic acids,
In particular, it is preferable that a structural unit derived from an asymmetric aromatic dicarboxylic acid (b1-1) is contained, and examples of the structural unit derived from an asymmetric aromatic dicarboxylic acid (b1-1) include structural units derived from phthalic acids, isophthalic acids, 1,8-naphthalenedicarboxylic acids, 2,3-naphthalenedicarboxylic acids, and 2,7-naphthalenedicarboxylic acids. Among these, structural units derived from isophthalic acids are particularly preferable in terms of reactivity.

The content of such structural units derived from aromatic polycarboxylic acids, particularly structural units derived from asymmetric aromatic dicarboxylic acids (b1-1), is preferably 0.1 to 100 mol %, more preferably 1 to 80 mol %, based on the total structural units derived from polycarboxylic acids (b1).
, more preferably 3 to 70 mol %, particularly preferably 5 to 60 mol %, and even more preferably 10 to 55 mol %. If the content is too low, the cohesive strength tends to decrease, or the polyester plasticizer (B) tends to crystallize, making it difficult to obtain sufficient adhesive performance.
If the amount is too large, the initial adhesive strength tends to decrease.

In addition, as the structural unit derived from the polycarboxylic acid (b1), from the viewpoint of improving the initial adhesive strength, aliphatic dicarboxylic acids (b1-) having 4 or more carbon atoms (including the carbon atoms of the carboxy group) are preferably used.
2), and more preferably contains a structural unit derived from an aliphatic dicarboxylic acid having 6 to 12 carbon atoms (including the carbon atom of the carboxy group),
It is particularly preferred that the copolymer contains structural units derived from adipic acids, sebacic acids, or azelaic acids.

The content of structural units derived from such aliphatic dicarboxylic acids (b1-2) having 4 or more carbon atoms is preferably 10 to 100 mol% relative to the total structural units derived from polycarboxylic acids (b1). It is particularly preferably 20 to 95 mol%, more preferably 30 to 90 mol%, and particularly preferably 40 to 80 mol%. If the content is too low, the glass transition temperature of the polyester plasticizer (B) tends to be too high, making it difficult to obtain sufficient adhesive strength. Furthermore, if the content is within the preferred range, crystallization of the polyester plasticizer (B) is suppressed, and the adhesive tends to have excellent initial adhesive strength.

In the present invention, from the viewpoint of adhesive properties, it is also preferable to contain, as the structural units derived from polyvalent carboxylic acids (b1), structural units derived from asymmetric aromatic dicarboxylic acids (b1-1) and structural units derived from aliphatic dicarboxylic acids (b1-2) having 4 or more carbon atoms. In this case, the content ratio (molar ratio) of the structural units derived from asymmetric aromatic dicarboxylic acids (b1-1) to the structural units derived from aliphatic dicarboxylic acids (b1-2) having 4 or more carbon atoms is (b1-1)/(
b1-2) is preferably 1/99 to 99/1, and particularly preferably 5/95 to 90
/10, more preferably 20/80 to 80/20, and particularly preferably 30/70 to 70/
It's 30.
By setting the content within the above range, it is possible to obtain a pressure-sensitive adhesive that is excellent in compatibility with the polyester resin (A) and has excellent initial adhesive strength and shear strength.

In addition, in order to increase the branching points in polyester resins, trivalent or higher polycarboxylic acids (
Structural units derived from b1-3) can also be used, and among these, trimellitic acids are preferably used because they are relatively less likely to gel during production.

The content of the structural units derived from such trivalent or higher polycarboxylic acids (b1-3) is preferably 10 mol% or less, particularly preferably 5 mol% or less, particularly preferably 3 mol% or less, and most preferably 1 mol% or less, based on the total polycarboxylic acids (b1), in order to enhance the cohesive strength when used as a pressure-sensitive adhesive. If the content is too high, gelation tends to occur during the production of the polyester resin, or the acid value tends to increase.

[Polyol (b2)]
Examples of the structural unit derived from the polyol (b2) include the same structural units as those explained above as the structural unit derived from the polyol (a2).

The structural unit derived from the polyol (b2) may contain a structural unit derived from a linear aliphatic diol (b2-1) from the viewpoint of lowering the glass transition temperature (TgB) of the polyester plasticizer (B) and improving the initial adhesive strength, and more preferably contains a structural unit derived from a linear aliphatic diol having 2 to 18 carbon atoms, and particularly preferably contains a structural unit derived from ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol.

The content of the structural unit derived from the linear aliphatic diol (b2-1) is
The content of the structural units derived from the polyester resin (A) is preferably 1 to 80 mol %, more preferably 3 to 60 mol %, even more preferably 5 to 40 mol %, and particularly preferably 10 to 30 mol % relative to all structural units derived from the polyester resin (A). If the content is too high, the polyester resin tends to crystallize, making it difficult to obtain sufficient adhesive properties.

Among the structural units derived from the polyol (b2), it is preferable to contain a structural unit derived from a diol (b2-2) having a hydrocarbon group in the side chain, since this can disrupt crystallinity. Examples of the structural unit derived from the diol (b2-2) having a hydrocarbon group include those described above for the diol (a2-2) having a hydrocarbon group. Among these, it is preferable to contain a structural unit derived from an aliphatic diol having a branched structure, since this inhibits crystallization and provides excellent initial adhesive strength, and 2-methyl-1,3-propanediol, 2,2-dimethyl-
It is particularly preferred that the copolymer contains structural units derived from 1,3-propanediol (neopentyl glycol) or 3-methyl-1,5-pentanediol.

The content of the structural units derived from the diol (b2-2) having a hydrocarbon group in the side chain is preferably 5 to 100 mol%, particularly 15 to 100 mol%, further 30 to 100 mol%, particularly 45 to 100 mol%, and most preferably 60 to 100 mol%, based on all structural units derived from the polyol (b2). If the content is too low, the polyester plasticizer (B) will crystallize, tending to reduce the initial adhesive strength of the pressure-sensitive adhesive.

Furthermore, as the structural unit derived from the polyol (b2), a trivalent or higher polyol (b2-
The content of the structural units derived from the trivalent or higher polyol (b2-3) is 10 to 10% based on the total structural units derived from the polyol (b2).
% or less, more preferably 0.01 to 5 mol %, and particularly preferably 0.0
The content of the structural unit (b2-3) derived from a trivalent or higher polyol is preferably 5 to 3 mol %, and particularly preferably 0.1 to 1 mol %. If the content of the structural unit (b2-3) derived from a trivalent or higher polyol is too high, the initial adhesive strength tends to decrease.

The polyvalent carboxylic acids (b1) and the polyol (b2) are reacted by a method similar to the method for producing the polyester resin described above, thereby producing a polyester plasticizer (
B') is obtained.

The blending ratio of the polyvalent carboxylic acid (b1) and the polyol (b2) in the polyester plasticizer (B') before end-capping is as follows:
In this case, the amount of polyol (b2) per equivalent of polyvalent carboxylic acid (b1) is preferably 1 to 2 equivalents, particularly preferably 1.03 to 1.8 equivalents, more preferably 1.05 to 1.7, and particularly preferably 1.1 to 1.6. If the blending ratio of polyol (b2) is too low, the compatibility with polyester resin (A) tends to decrease, whereas if it is too high, the cohesive strength of the pressure-sensitive adhesive tends to decrease, resulting in a decrease in shear strength.
In addition, when preparing a pre-endblocked polyester-based plasticizer (B') having a carboxy terminal, the amount of the polyvalent carboxylic acid (b1) is preferably 1 to 2 equivalents, particularly preferably 1.03 to 1.8 equivalents, and more preferably 1.05 to 1 equivalents, per equivalent of the polyol (b2).
If the blending ratio of the polycarboxylic acid (b1) is too low, the compatibility with the polyester resin (A) tends to decrease, whereas if the blending ratio is too high, the cohesive strength of the adhesive tends to decrease, resulting in a decrease in shear strength.

The polyester plasticizer (B') obtained before end-blocking typically has at least one reactive molecular end selected from the group consisting of a carboxyl group end derived from the polycarboxylic acid (b1) and a hydroxyl group end derived from the polyol (b2), and from the viewpoint of hydrolysis resistance, it is more preferable that the reactive molecular end has a hydroxyl group end.

The glass transition temperature (Tg'B) of the polyester plasticizer (B') before end-capping is usually -80 to 30°C, preferably -75 to 20°C, more preferably -70 to 0°C, particularly preferably -65 to -20°C, and especially preferably -60 to -40°C, from the viewpoint of adhesive properties.
is.
If the glass transition temperature (TgB) is too high, flexibility is lost and the initial adhesive strength decreases.
The glass transition temperature of the polyester plasticizer (B') before end-capping can be measured by the same method as that for the glass transition temperature of the polyester resin described above for the polyester resin (A).

The number average molecular weight of the polyester plasticizer (B') before end-capping is usually 200 to 12,000, preferably 300 to 10,000, particularly preferably 400 to 8,000, even more preferably 600 to 6,000, especially preferably 800 to 5,000, and more preferably 1,000 to 4,000, from the viewpoint of the cohesive strength of the adhesive.
If the number average molecular weight is too small, the adhesive will not have sufficient cohesive strength and the shear strength will tend to decrease.
Furthermore, if the number average molecular weight is too large, the compatibility with the polyester resin (A) tends to decrease. The number average molecular weight can be measured by the same method as that for the weight average molecular weight of the polyester resin described above for the polyester resin (A).

The weight average molecular weight of the polyester plasticizer (B') before end-capping is 800 to 12,000, preferably 1,000 to 10,000, from the viewpoint of the cohesive strength of the pressure-sensitive adhesive.
Particularly preferably 1,500 to 8,000, and even more preferably 2,000 to 7,5000
, particularly preferably 2,500 to 7,000, more preferably 3,000 to 6,500.
If the weight-average molecular weight is too small, when the polyester plasticizer (B) is used as a plasticizer, the adhesive will not have sufficient cohesive strength, and the shear strength will tend to decrease. Also, if the weight-average molecular weight is too large, the compatibility with the polyester resin (A) will tend to decrease. The weight-average molecular weight can be measured by the same method as the weight-average molecular weight of the polyester resin described above for the polyester resin (A).

The hydroxyl value of the polyester plasticizer (B') before end-capping is 5 to 200 mgKOH/g when the polyester plasticizer (B') before end-capping has a hydroxyl terminal.
Preferably 10 to 150 mgKOH/g or less, more preferably 15 to 100 mgKOH
If the hydroxyl value is too high, the cohesive strength tends to decrease, whereas if it is too low, the compatibility with the polyester resin (A) tends to decrease.
In addition, when the polyester plasticizer (B') before end-blocking has a carboxyl group terminal, the amount of KOH is 10 mgKOH/g or less, preferably 5 mgKOH/g or less, more preferably 3 mgKOH/g or less, particularly preferably 1 mgKOH/g or less, and especially preferably 0.5 mgKOH/g or less.
The hydroxyl value is 0.0 mgKOH/g or less. The lower limit is 0.0 mgKOH/g. If the hydroxyl value is too high, the initial adhesive strength tends to decrease.

The acid value of the polyester plasticizer (B') before end-blocking is 10 mgKOH/g or less, preferably 5 mgKOH/g or less, more preferably 3 mgKOH/g or less, and particularly preferably 1 mgKOH/g or less, when the polyester plasticizer (B') before end-blocking has a hydroxyl group terminal.
The lower limit is 0.0 mg KOH/g or less, particularly 0.5 mg KOH/g or less.
If the acid value is too high, the cohesive strength tends to decrease and hydrolysis tends to proceed easily.
Furthermore, in the case of a pre-endblocked polyester plasticizer (B') having a terminal carboxy group, the acid value is 5 to 200 mgKOH/g, preferably 10 to 150 mgKOH/g, and more preferably 15 to 100 mgKOH/g. If the acid value is too high, the cohesive strength tends to decrease, hydrolysis tends to proceed more easily, and when a layer of metal or the like is laminated to one side of the pressure-sensitive adhesive layer, corrosion tends to occur.

As described above, the polyester plasticizer (B') before end-blocking usually has at least one of a carboxyl group terminal and a hydroxyl group terminal as a reactive molecular terminal. The polyester plasticizer (B) used in the present invention is the polyester plasticizer (B') before end-blocking.
) by blocking at least one of the reactive molecular ends with a reactive molecular end-blocking agent (b3).

[Structural unit derived from reactive molecular end-capping agent (b3)]
The reactive molecular end-capping agent (b3) is a polyester plasticizer (B') before end-capping.
The reactive end of the polyester plasticizer (B') before end-capping reacts with the functional group of the reactive end-capping agent (b3), thereby blocking the reactive end group.
Examples thereof include isocyanate group-containing compounds, carbodiimide group-containing compounds, epoxy group-containing compounds, oxazoline group-containing compounds, carboxy group-containing compounds, hydroxy group-containing compounds, etc. These may be used alone or in combination of two or more.

In the present invention, the isocyanate group-containing compound is preferably a monoisocyanate having one isocyanate group in the molecular structure.
Examples of the monoisocyanate compound include methyl isocyanate, ethyl isocyanate, propyl isocyanate, n-butyl isocyanate, t-butyl isocyanate, isobutyl isocyanate, pentyl isocyanate, neopentyl isocyanate, 2-ethyl-hexyl isocyanate, 2-isocyanatoethyl methacrylate,
Examples of suitable monoisocyanate compounds include aliphatic monoisocyanate compounds such as 2-isocyanatoethyl acrylate and octadecyl isocyanate, and aromatic monoisocyanate compounds such as phenyl isocyanate, tolyl isocyanate, 1-naphthyl isocyanate, 2-naphthyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. These may be used alone or in combination of two or more. Among these, aromatic monoisocyanate compounds are preferred in terms of excellent reactivity, initial adhesive strength, and shear strength, and phenyl isocyanate is particularly preferred.

In the present invention, the carbodiimide group-containing compound is a compound having a carbodiimide group (—N
Monocarbodiimides having one =C=N-) in the molecule are preferred.
Examples of the monocarbodiimide compound include dicyclohexylcarbodiimide,
Examples thereof include diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, diphenylcarbodiimide, and naphthylcarbodiimide, which may be used alone or in combination of two or more.

In the present invention, the epoxy group-containing compound is preferably a monofunctional epoxy compound having one epoxy group in the molecular structure, such as a monoglycidyl ester compound or a monoglycidyl ether compound, which can be used alone or in combination of two or more.

Examples of the monoglycidyl ester compound include benzoic acid glycidyl ester,
t-Bu-benzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycyl ester, lauric acid glycidyl ester, palmitic acid glycidyl ester,
Examples include behenic acid glycidyl ester, versatic acid glycidyl ester, oleic acid glycidyl ester, linoleic acid glycidyl ester, linolenic acid glycidyl ester, behenolic acid glycidyl ester, and stearolic acid glycidyl ester, and these can be used alone or in combination of two or more.

Examples of the monoglycidyl ether compounds include phenyl glycidyl ether,
o-phenylglycidyl ether, etc., which may be used alone or in combination of two or more.

In the present invention, the oxazoline group-containing compound is preferably a monofunctional oxazoline compound having one oxazoline group in its molecular structure, such as 2-phenyl(2-oxazoline) or 2-ethyl-2-oxazoline, which may be used alone or in combination of two or more.

In the present invention, the carboxy group-containing compound is preferably a monocarboxylic acid having one carboxy group in the molecular structure, and particularly preferably a saturated monocarboxylic acid.
Examples of the monocarboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid,
Valeric acid, isovaleric acid, 2-methylbutanoic acid, pivalic acid, hexanoic acid, 4-methylpentanoic acid, 2-ethylbutanoic acid, 2,2-dimethylbutanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid,
Examples of the monocarboxylic acid include aliphatic monocarboxylic acids such as hexacosanoic acid and triacontanoic acid, and aromatic monocarboxylic acids such as benzoic acid, toluic acid, naphthalenecarboxylic acid, methylnaphthalenecarboxylic acid, and phenylacetic acid, which may be used alone or in combination of two or more. Among these, aromatic monocarboxylic acids are preferred because of their excellent reactivity and shear strength.

In the present invention, the hydroxy group-containing compound is preferably a monoalcohol having one hydroxy group in the molecular structure.
Examples of the monoalcohol include butanol, hexanol, pentanol, heptanol, octanol, nonanol, decanol, undecanol, and dodecanol.
aliphatic monoalcohols such as tridecanol, benzyl alcohol, 3-phenyl-1-
Examples of the alcohol include aromatic monoalcohols such as propanol, and these may be used alone or in combination of two or more.

In the present invention, in addition to the compounds having one functional group as described above, compounds having two or more functional groups can also be used as the reactive molecular end-capping agent (b3) within a range that does not impair the effects of the present invention.

Among the reactive molecular end-capping agents (b3), the polyester plasticizer before end-capping (B
An isocyanate group-containing compound is preferred in view of its excellent reactivity with the hydroxyl group terminal of the copolymer (a).

Furthermore, in order to achieve excellent adhesive properties, the reactive molecular end-capping agent (b3) preferably has a number average molecular weight of 50 to 5,000, more preferably 60 to 3,000, particularly preferably 70 to 1,000, even more preferably 80 to 500, and particularly preferably 90 to 300. If the molecular weight is too small, volatility tends to increase, while if it is too large, compatibility with the polyester resin (A) tends to decrease.

In view of excellent adhesive properties, the polyester plasticizer (B) used in the present invention is preferably one in which at least one reactive molecular end is blocked with the reactive molecular end-blocking agent (b3), and more preferably, all reactive molecular ends are blocked.

Polyester plasticizer (B') before end-capping with the reactive molecular end-capping agent (b3)
The blocking of the reactive molecule terminals may be carried out by a known method, for example, by reacting the pre-terminally blocked polyester plasticizer (B') with the reactive molecule terminal blocking agent (b3) in an organic solvent.

The reaction ratio of the polyester plasticizer (B') before end-capping to the reactive molecular end-capping agent (b3) is set to the following ratio depending on the hydroxyl value and acid value of the polyester plasticizer (B') before end-capping:
That is, it is preferable to optimize the ratio depending on the carboxyl groups and hydroxyl groups of the polyester plasticizer (B') before end-capping. The functional groups reactive with the reactive molecular terminals of the reactive molecular terminal blocking agent (b3) are usually 80 to 120 mol%, preferably 90 to 110 mol%, more preferably 95 to 105 mol%, and particularly preferably 97 to 110 mol%, based on 100 mol% of the carboxyl groups or 100 mol% of the hydroxyl groups of the polyester plasticizer (B') before end-capping.
For example, when an isocyanate group-containing compound is used as the reactive molecular end-blocking agent (b3), the isocyanate group-containing compound is reactive with carboxy groups and hydroxy groups, and therefore, the isocyanate group-containing compound may be used in the above range relative to the total of 100 mol % of the carboxy groups and hydroxy groups in the polyester plasticizer (B') before end-blocking.

The organic solvent may be any one that does not exhibit reactivity with the reactive molecular end-capping agent (b3), and examples thereof include esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatics such as toluene and xylene. These may be used alone or in combination of two or more.

The reaction temperature of the polyester plasticizer (B') before end-capping with the reactive molecular end-capping agent (b3) is usually 20 to 240°C, preferably 25 to 180°C, more preferably 30 to 180°C.
The reaction temperature is 20° C., particularly preferably 40 to 80° C., and the reaction time is usually 0.1 to 24 hours, preferably 0.5 to 12 hours, more preferably 0.5 to 3 hours.

By the above method, a polyester plasticizer (B) in which at least one reactive molecular end is blocked can be obtained.

The glass transition temperature (TgB) of the polyester plasticizer (B) is preferably −80 to 30°C, more preferably −70 to 25°C, even more preferably −60 to 20°C, particularly preferably −55 to 0°C, especially preferably −50 to −10°C, and most preferably −40 to −15°C. By adjusting the temperature within the above range, a pressure-sensitive adhesive having excellent initial adhesive strength and shear strength can be obtained. If the glass transition temperature of the polyester plasticizer (B) is too low, the cohesive strength tends to decrease and the adhesive strength tends to decrease. If the glass transition temperature is too high, flexibility is lost, the initial adhesive strength decreases, and the adhesive strength tends to be difficult to exert even with pressure equivalent to finger pressure. As already mentioned, in relation to the glass transition temperature of the polyester resin (A), the glass transition temperature (TgA) of the polyester resin (A) is preferably higher than the glass transition temperature (TgB) of the polyester plasticizer (B).

The polyester plasticizer (B) is preferably amorphous. If it is crystalline, the heat of fusion of the crystal is preferably 20 J/g or less, more preferably 10 J/g or less, particularly preferably 5 J/g or less, even more preferably 3 J/g or less, and particularly preferably 1 J/g or less. If the heat of fusion of the crystal is too high, the storage stability and initial adhesive strength tend to decrease, and the compatibility with the polyester resin (A) tends to be poor.

Here, the heat of crystalline fusion of the polyester-based plasticizer (B) is a value measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments.
The measurement temperature range was −90 to 100° C., and the temperature rise rate was 10° C./min.
The temperature was raised to 0°C to completely melt the crystal, then the temperature was lowered to -90°C, and the heat of exothermic melting when the temperature was raised again to 100°C was taken as the heat of crystal fusion.

The number average molecular weight of the polyester plasticizer (B) is 3.0 or less from the viewpoint of the cohesive strength of the adhesive.
It is preferably 400 to 10,000, and particularly preferably 6
00 to 8,000, more preferably 1,000 to 6,000, and particularly preferably 1.20
The number average molecular weight is preferably 0 to 5,000, more preferably 1,500 to 4,000. By adjusting the number average molecular weight to within the above range, a PSA having excellent initial adhesive strength and shear strength can be obtained. If the number average molecular weight is too small, when a polyester plasticizer (B) is used as a plasticizer, sufficient cohesive strength of the PSA cannot be obtained, and the initial adhesive strength tends to decrease. Furthermore, if the number average molecular weight is too large, compatibility with the polyester resin (A) tends to decrease. The number average molecular weight can be measured using the same method as the weight average molecular weight of the polyester resin described above for the polyester resin (A).

The weight average molecular weight of the polyester plasticizer (B) is 1.0 to 1.5 times as large as possible in terms of the cohesive strength of the adhesive.
The weight average molecular weight is preferably 1,200 to 10,000, particularly preferably 1,500 to 8,000, even more preferably 2,000 to 7,500, especially preferably 2,500 to 7,000, and even more preferably 3,000 to 6,500. By adjusting the weight average molecular weight within the above range, a PSA having excellent initial adhesive strength and shear strength can be obtained. If the weight average molecular weight is too small, when a polyester plasticizer (B) is used as a plasticizer, sufficient cohesive strength of the PSA tends to be insufficient, and shear strength tends to decrease. Furthermore, if the weight average molecular weight is too large, compatibility with the polyester resin (A) tends to decrease. The weight average molecular weight can be measured using the same method as the weight average molecular weight of the polyester resin described above for the polyester resin (A).

The hydroxyl value of the polyester resin (B) is preferably 15 mgKOH/g or less, more preferably 10 mgKOH/g or less, even more preferably 8 mgKOH/g or less, and particularly preferably 5 mgKOH/g or less, and more preferably 3 mgKOH/g or less.
/g or less is particularly preferred, and 1 mgKOH/g or less is most preferred.
The lower limit is 0 mgKOH/g. If the hydroxyl value is too high, the polyester resin (A
) and tends to crosslink, reducing the initial adhesive strength.

The acid value of the polyester resin (B) is preferably 10 mgKOH/g or less, more preferably 5 mgKOH/g or less, even more preferably 3 mgKOH/g or less, and particularly preferably 1 mgKOH/g or less, and is preferably 0.5 mgKOH/g or less.
It is particularly preferable that the acid value is 0 mgKOH/g or less. The lower limit is 0 mgKOH/g. By setting the acid value in the above range, hydrolysis of the polyester resin (A) can be suppressed, and a pressure-sensitive adhesive having excellent initial adhesive strength can be obtained. If the acid value is too high, crosslinking with the polyester resin (A) tends to occur, resulting in a decrease in initial adhesive strength and a decrease in hydrolysis resistance.

The sum of the acid value and hydroxyl value of the polyester plasticizer (B) is preferably 20 mgKOH/g or less, more preferably 15 mgKOH/g or less, and more preferably 10 mgKOH/g or less.
The total acid value and hydroxyl value of the polyester (A) is preferably 0 mgKOH/g or less, more preferably 5 mgKOH/g or less, particularly preferably 3 mgKOH/g or less, and most preferably 1 mgKOH/g or less. The lower limit is 0 mgKOH/g. If the total acid value and hydroxyl value is too high, crosslinking with the polyester (A) tends to occur, resulting in a decrease in initial adhesive strength and a decrease in hydrolysis resistance.

The content of the polyester plasticizer (B) is preferably 0.1 to 180 parts by weight, more preferably 1 to 175 parts by weight, even more preferably 5 to 170 parts by weight, particularly preferably 10 to 160 parts by weight, more preferably 30 to 150 parts by weight, even more preferably 40 to 140 parts by weight, particularly preferably 50 to 130 parts by weight, and more preferably 60 to 150 parts by weight, based on 100 parts by weight of the polyester resin (A).
A content of 120 parts by weight is particularly preferred, and a content of 70 to 110 parts by weight is most preferred. By setting the content within the above range, a pressure-sensitive adhesive having excellent adhesive strength, initial adhesive strength, and shear strength can be obtained. If the content of the polyester-based plasticizer (B) is too high, the cohesive strength tends to decrease and the shear strength tends to decrease, whereas if the content is too low, the adhesive strength and initial adhesive strength tend to decrease.

The content of the polyester plasticizer (B) is 100% by weight of the pressure-sensitive adhesive composition (active ingredient amount).
The content of the polyester plasticizer (B) is preferably 0.1 to 75% by weight, more preferably 1 to 70% by weight, even more preferably 5 to 65% by weight, particularly preferably 10 to 60% by weight, especially preferably 20 to 55% by weight, and most preferably 30 to 50% by weight, relative to 0% by weight. If the content of the polyester plasticizer (B) is too high, the cohesive strength and shear strength tend to decrease, whereas if the content is too low, the adhesive strength and initial adhesive strength tend to decrease.

<Hydrolysis inhibitor (C)>
The pressure-sensitive adhesive composition of the present invention preferably further contains a hydrolysis inhibitor (C) which is contained in order to ensure long-term durability.

As the hydrolysis inhibitor (C), a conventionally known one can be used, for example,
Examples of the hydrolysis inhibitor (C) include compounds that react with and bond to the carboxyl terminal groups of the polyester resin (A), specifically compounds containing functional groups such as carbodiimide groups, epoxy groups, and oxazoline groups. The hydrolysis inhibitor (C) can be used alone or in combination of two or more. Among these, carbodiimide group-containing compounds are preferred because of their high effect of eliminating the catalytic activity of protons derived from carboxylic acid terminal groups.

The carbodiimide group-containing compound is generally a compound having a carbodiimide group (-N=C=N-
) in the molecule, and among them, compounds containing two or more carbodiimide groups in the molecule, i.e., polyvalent carbodiimide compounds, are preferred, and particularly compounds containing three or more, further five or more, carbodiimide groups in the molecule,
In particular, a compound containing 7 or more carbodiimide groups is preferred. The number of carbodiimide groups contained in the molecule of the polyvalent carbodiimide compound is usually 50 or less, and if the number of carbodiimide groups is too large, the molecular structure tends to be too large, which is undesirable as it reduces the compatibility with the polyester resin (A).

As the carbodiimide group-containing compound, it is also preferable to use a high molecular weight polycarbodiimide produced by subjecting a diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimidization catalyst.

Such high molecular weight polycarbodiimides may be synthesized or commercially available products may be used. When synthesizing high molecular weight polycarbodiimides, for example, those obtained by subjecting the following diisocyanates to a decarboxylation condensation reaction may be used.

Examples of such diisocyanates 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, etc., which can be used alone or in combination of two or more kinds.

Furthermore, in terms of storage stability, the high-molecular-weight polycarbodiimide is preferably one in which the terminal isocyanate groups are blocked with a blocking agent. Examples of the blocking agent include compounds having active hydrogen that reacts with isocyanate groups, or compounds having an isocyanate group. Examples include monoalcohols, monocarboxylic acids, monoamines, and monoisocyanates each having one substituent selected from a carboxy group, an amino group, and an isocyanate group.

The carbodiimide equivalent of the carbodiimide group-containing compound is preferably 50 to 100
00, particularly 100 to 1000, and further preferably 150 to 500.
The carbodiimide equivalent weight refers to the chemical formula weight per carbodiimide group.

In addition, the carbodiimide group-containing compound may be a commercially available product. Examples of commercially available carbodiimide group-containing compounds include the Carbodilite (registered trademark) series manufactured by Nisshinbo Chemical Inc., and among them, Carbodilite (registered trademark) "V-01",
"V-02B", "V-03", "V-04K", "V-04PF", "V-05", "
V-07, V-09 and V-09GB are preferred because they have excellent compatibility with the polyester resin (A).

Examples of the epoxy group-containing compound include glycidyl ester compounds, glycidyl ether compounds, etc. These can be used alone or in combination of two or more.
Examples of the glycidyl ester compound include benzoic acid glycidyl ester, t-
Bu-benzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, lauric acid glycidyl ester, palmitic acid glycidyl ester, behenic acid glycidyl ester, versatic acid glycidyl ester, oleic acid glycidyl ester, linoleic acid glycidyl ester, linolenic acid glycidyl ester, behenolic acid glycidyl ester, stearolic acid glycidyl ester, terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, phthalic acid diglycidyl ester Examples of the glycidyl ester include esters, naphthalenedicarboxylic acid diglycidyl ester, methyl terephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecanedioic acid diglycidyl ester, octadecanedicarboxylic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester. These may be used alone or in combination of two or more.

Examples of the glycidyl ether compound include phenyl glycidyl ether, o-
Phenyl glycidyl ether, 1,4-bis(β,γ-epoxypropoxy)butane, 1
,6-bis(β,γ-epoxypropoxy)hexane, 1,4-bis(β,γ-epoxypropoxy)benzene, 1-(β,γ-epoxypropoxy)-2-ethoxyethane, 1-
(β,γ-epoxypropoxy)-2-benzyloxyethane, 2,2-bis-[p-(
and bisglycidyl polyethers obtained by reacting epichlorohydrin with bisphenols such as 2,2-bis-(4-hydroxyphenyl)propane, 2,2-bis-(4-hydroxyphenyl)methane, and 2,2-bis-(4-hydroxyphenyl)propane. These may be used alone or in combination of two or more.

The oxazoline group-containing compound is preferably a bisoxazoline compound. Specifically, for example, 2,2'-bis(2-oxazoline), 2,2'-bis(4-methyl-
2-oxazoline), 2,2'-bis(4,4-dimethyl-2-oxazoline), 2,2
'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2
-oxazoline), 2,2'-bis(4-propyl-2-oxazoline), 2,2'-bis(4-butyl-2-oxazoline), 2,2'-bis(4-hexyl-2-oxazoline), 2,2'-bis(4-phenyl-2-oxazoline), 2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline)
, 2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-o-phenylenebis(2-oxazoline), 2,2'
-p-phenylenebis(4-methyl-2-oxazoline), 2,2'-p-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4-methyl-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'-decamethylenebis(2-oxazoline), 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'-
Examples thereof include tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), and 2,2'-diphenylenebis(2-oxazoline), and these can be used alone or in combination of two or more.

The hydrolysis inhibitor (C) is preferably low in volatility, and therefore it is preferable to use one having a high number average molecular weight, usually 300 to 10,000, preferably 1
,000 to 5,000 are used.
From the viewpoint of hydrolysis resistance, it is preferable to use a hydrolysis inhibitor (C) having a high weight average molecular weight.
It is preferable that the molecular weight is 2,000 to 20,000 or more, more preferably 3,000 to 15,000 or more, and even more preferably 4,000 to 10,000.
00 is particularly preferred.
If the molecular weight of the hydrolysis inhibitor (C) is too small, the hydrolysis resistance tends to decrease.
If the molecular weight is too large, the compatibility with the polyester resin (A) tends to decrease.

The content of the hydrolysis inhibitor (C) is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, further preferably 0.3 to 3 parts by weight, and particularly preferably 0.5 to 2 parts by weight, relative to 100 parts by weight of the polyester resin (A). If the content is too high, the initial adhesive strength with the polyester resin (A) tends to decrease and turbidity tends to occur due to poor compatibility, while if the content is too low, sufficient durability tends to be difficult to obtain.

The content of the hydrolysis inhibitor (C) is preferably optimized depending on the acid value of the polyester resin (A).
For example, when the polyester resin (A) is a polyester resin, the molar ratio ((Y)/(X)) of the total number of moles (Y) of functional groups of the hydrolysis inhibitor (C) in the pressure-sensitive adhesive composition to the total number of moles (X) of acidic functional groups of the polyester resin in the pressure-sensitive adhesive composition is 0.5≦
(Y)/(X) is preferably 1≦(Y)/(X)≦1000, and particularly preferably 1≦(Y)/(X)≦1000.
More preferably, 1.5≦(Y)/(X)≦100.
If the molar ratio of (Y) to (X) is too low, the moist heat resistance tends to decrease, whereas if the molar ratio of (Y) to (X) is too high, the compatibility with the polyester resin (A) tends to decrease, and the adhesive strength, cohesive strength, and durability tend to decrease.

<Crosslinking agent (D)>
The pressure-sensitive adhesive composition of the present invention preferably further contains a crosslinking agent (D).
Examples of the crosslinking agent (D) include compounds having a functional group that reacts with at least one of the hydroxyl group and the carboxyl group contained in the polyester resin (A), such as polyisocyanate compounds and polyepoxy compounds. Among these, it is particularly preferable to use polyisocyanate compounds, as they can achieve a good balance between initial adhesive strength, mechanical strength, and heat resistance.

Examples of such polyisocyanate compounds include polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, and triphenylmethane triisocyanate. Other examples include adducts of the above polyisocyanates with polyol compounds such as trimethylolpropane, and biuret and isocyanurate forms of these polyisocyanate compounds. The above polyisocyanate compounds may also be used in which the isocyanate moiety is blocked with phenol, lactam, or the like. These crosslinking agents (D) may be used alone or in combination of two or more.

The content of the crosslinking agent (D) can be appropriately selected depending on the molecular weight of the polyester resin (A) and the intended use. Usually, the content of the reactive group contained in the crosslinking agent (D) is 0.2 to 1 equivalent of at least one of the hydroxyl group and the carboxyl group contained in the polyester resin (A).
It is preferable that the crosslinking agent (D) is contained in an amount of 0.5 to 10 equivalents, and particularly preferably 0.5 to 10 equivalents.
The amount is preferably from 0.5 to 5 equivalents, more preferably from 0.5 to 3 equivalents.
If the equivalent number of the reactive group contained in the crosslinking agent (D) is too small, the cohesive strength tends to decrease, whereas if it is too large, the flexibility tends to decrease.

The content of the crosslinking agent (D) is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, particularly preferably 1 to 10 parts by weight, even more preferably 1.5 to 8 parts by weight, and especially preferably 2 to 6 parts by weight, relative to 100 parts by weight of the polyester resin (A). If the content of the crosslinking agent (D) is too high, the initial adhesive strength tends to decrease, and if the content is too low, the shear strength tends to decrease.

In the reaction between the polyester resin (A) and the crosslinking agent (D), an organic solvent that does not have a functional group that reacts with the polyester resin (A) and the crosslinking agent (D) component, for example, an ester such as ethyl acetate or butyl acetate, a ketone such as methyl ethyl ketone or methyl isobutyl ketone, or an aromatic such as toluene or xylene, can be used.
These may be used alone or in combination of two or more.

<Urethanization catalyst (E)>
The pressure-sensitive adhesive composition of the present invention preferably further contains a urethanization catalyst (E).
As the urethanization catalyst (E), for example, an organometallic compound, a tertiary amine compound, etc. These may be used alone or in combination of two or more kinds.

Examples of the organometallic compounds include zirconium compounds, iron compounds, tin compounds, titanium compounds, lead compounds, cobalt compounds, and zinc compounds.
Examples of zirconium compounds include zirconium naphthenate and zirconium acetylacetonate.
Examples of iron compounds include iron acetylacetonate and iron 2-ethylhexanoate.
Examples of tin compounds include dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate.
Examples of titanium compounds include dibutyltitanium dichloride, tetrabutyltitanate, and butoxytitanium trichloride.
Examples of lead compounds include lead oleate, lead 2-ethylhexanoate, lead benzoate,
Examples include lead naphthenate.
Examples of the cobalt-based compounds include cobalt 2-ethylhexanoate and cobalt benzoate.
Examples of zinc compounds include zinc naphthenate and zinc 2-ethylhexanoate.

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

Among these urethane catalysts (E), the following are preferred in terms of reaction rate and pot life of the PSA layer:
Organometallic compounds are preferred, zirconium compounds are particularly preferred, and zirconium acetylacetonate is particularly preferred.

[Catalytic inhibitor]
In the pressure-sensitive adhesive composition of the present invention, it is preferable to incorporate a catalytic action inhibitor into the urethanation catalyst (E) in order to extend the pot life and improve the coatability.
Examples of the catalytic inhibitor include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; and β-ketoesters such as acetylacetone, 2,4-hexanedione, and benzoylacetone.
These are keto-enol tautomeric compounds that protect the urethanization catalyst (E), thereby reducing the catalytic activity of the urethanization catalyst (E) in a solution state, suppressing excessive viscosity increase and gelation of the PSA composition after blending, and enabling the pot life of the PSA composition to be extended.
Among these, acetylacetone is preferably used as the catalyst inhibitor from the viewpoint of the balance between pot life and curing speed. These catalyst inhibitors can be used alone or in combination of two or more.

The blending ratio (weight ratio) of the catalytic inhibitor to the urethanization catalyst (E) is preferably in the range of catalytic inhibitor:urethanization catalyst (E) = 0.001:1 to 15:1, more preferably 0.005:1 to 13:1, and particularly preferably 0.01:1 to 10:1. If the content of the catalytic inhibitor relative to the content of the urethanization catalyst (E) is too low, the pot life tends to be short and the coatability tends to be reduced, whereas if it is too high, the curing rate tends to be reduced.

The pressure-sensitive adhesive composition of the present invention contains, in addition to the polyester resin (A), polyester plasticizer (B), hydrolysis inhibitor (C), crosslinking agent (D), urethanization catalyst (E), etc.
Additives such as antioxidants such as hindered phenols, softeners, ultraviolet absorbers, silane coupling agents, stabilizers, antistatic agents, tackifiers, and other additives, such as inorganic or organic fillers, metal powders, pigments, and other powders or particulate additives, can be blended within the range that does not impair the effects of the present invention. These can be used alone or in combination of two or more.

The tackifier is not particularly limited, and conventionally known tackifiers can be used, such as terpene-based tackifiers, phenol-based tackifiers, rosin-based tackifiers, petroleum-based tackifiers, xylene-based tackifiers, epoxy-based tackifiers, polyamide-based tackifiers, ketone-based tackifiers, and elastomer-based tackifiers.
In view of excellent initial adhesive strength and adhesive strength, it is preferable to use a petroleum-based tackifying resin or a terpene-based tackifying resin, and in particular, a styrene-based tackifying resin or a terpene-phenol-based tackifying resin is preferable. These can be used alone or in combination of two or more.

When the tackifier is blended, it is preferably 0.01 to 50 parts by weight, more preferably 0.1 to 30 parts by weight, even more preferably 1 to 20 parts by weight, and particularly preferably 3 to 10 parts by weight, relative to 100 parts by weight of the polyester resin (A), which is preferred in terms of excellent initial adhesive strength.

In addition to the additives, the pressure-sensitive adhesive composition of the present invention may also contain small amounts of impurities contained in the raw materials for producing the components of the pressure-sensitive adhesive composition.

Such a pressure-sensitive adhesive composition can be obtained, for example, by preparing the polyester resin (A), polyester plasticizer (B) and necessary optional components, etc., and mixing and dispersing them during the production of the polyester resin (A), or by mixing them into a solution of the polyester resin (A) dissolved in an organic solvent and dispersing them using a mixing roller.

The pressure-sensitive adhesive according to the present invention is made of the pressure-sensitive adhesive composition, that is, is obtained by crosslinking (curing) the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive.
The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a supporting substrate, or may be a substrate-less double-sided pressure-sensitive adhesive sheet that does not have a substrate.
The pressure-sensitive adhesive sheet of the present invention is particularly suitable as a pressure-sensitive adhesive sheet for electronic components used for bonding electronic components.
In the present invention, the term "sheet" also includes "film" and "tape."

<Adhesive sheet>
The pressure-sensitive adhesive sheet can be produced, for example, as follows.
Such a pressure-sensitive adhesive sheet can be produced according to a known general method for producing a pressure-sensitive adhesive sheet. For example, the pressure-sensitive adhesive composition is applied to one surface of a substrate, followed by drying,
A pressure-sensitive adhesive layer is formed, a release sheet is attached to its surface (the surface opposite to the surface that contacts the substrate), and if necessary, cured, thereby obtaining the pressure-sensitive adhesive sheet of the present invention, which has a substrate and a pressure-sensitive adhesive layer and is provided on at least one surface of the substrate.

Alternatively, the pressure-sensitive adhesive composition is applied to a release sheet and dried to form a pressure-sensitive adhesive layer;
The pressure-sensitive adhesive sheet of the present invention can also be obtained by laminating a substrate to the surface (the surface opposite to the surface in contact with the release sheet) and curing it as necessary.

Alternatively, a pressure-sensitive adhesive layer may be formed on a release sheet, and the surface (the surface opposite to the surface in contact with the release sheet)
By laminating the release sheet and another release sheet to the above, a substrate-less double-sided PSA sheet of the substrate-less type can be produced.

When using the obtained pressure-sensitive adhesive sheet or substrate-less double-sided pressure-sensitive adhesive sheet, the release sheet is peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is attached to an adherend.

Examples of the substrate that can be used include resin films, paper, cloth, rubber sheets, foam sheets, metal foils, and composites of these.
Examples of the resin film include polyethylene (PE) and polypropylene (PP).
Examples of the resin include polyolefin films such as ethylene-propylene copolymers; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; polyurethane films; and cellophane.
Examples of the paper include Japanese paper, kraft paper, glassine paper, wood-free paper, synthetic paper, and top-coated paper.
Examples of the fabric include woven fabrics and nonwoven fabrics made of various fibrous materials, either alone or in combination, such as cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber.
Examples of the rubber sheet include a natural rubber sheet and a butyl rubber sheet.
Examples of the foam sheet include a foamed polyurethane sheet, a foamed polyacrylic sheet, and a foamed polyolefin sheet.
Examples of the metal foil include aluminum foil and copper foil.
These substrates can be used as a single layer or as a multi-layer structure in which two or more types are laminated.

Among these, substrates made of polyethylene terephthalate, polyimide, foamed polyurethane sheet, foamed polyacrylic sheet, or foamed polyolefin sheet are particularly preferred, and polyethylene terephthalate is particularly preferred because of its excellent adhesion to the adhesive, and because it has excellent adhesive strength between the substrate and the adhesive, allowing the effects of the adhesive used in the present invention to be significantly exhibited.

The release sheet can be, for example, a release-treated resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or a composite thereof, as exemplified above as the substrate. Among these, it is preferable to use a silicone-based release sheet as the release sheet.

When a resin film is used as the substrate, the thickness of the resin film substrate is not particularly limited. In order to prevent the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the substrate film can be, for example, 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less. Furthermore, depending on the purpose and mode of use of the pressure-sensitive adhesive sheet, the thickness of the substrate film can be
It may be 70 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. By reducing the thickness of the substrate film, the thickness of the adhesive layer can be increased even if the total thickness of the pressure-sensitive adhesive sheet is the same. This can be advantageous from the viewpoint of improving adhesion to the substrate. There is no particular lower limit for the thickness of the substrate film, but from the viewpoint of the handleability and processability of the pressure-sensitive adhesive sheet, it is usually 0.5 μm or more, preferably 2 μm or more, and particularly preferably 4 μm or more.

When a foam substrate is used as the substrate, the thickness of the foam substrate is not particularly limited and can be appropriately set depending on the strength and flexibility of the pressure-sensitive adhesive sheet, the intended use, etc. From the viewpoint of thinning the bonding portion, the thickness of the foam substrate is usually 0.70 mm or less, and 0.40 mm or less.
From the viewpoint of impact resistance, the thickness of the foam substrate is preferably 0.05 mm or more, more preferably 0.06 mm or more, particularly preferably 0.07 mm or more, and particularly preferably 0.
A thickness of 10 mm or more is particularly preferred. As the thickness of the foam substrate increases, impact resistance tends to be exhibited.

The pressure-sensitive adhesive composition may be applied using, for example, a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, or the like.

As for the drying conditions after coating the pressure-sensitive adhesive composition, the drying temperature is preferably 60 to 140° C., particularly preferably 80 to 120° C. The drying time is preferably 0.5 to 30 minutes, particularly preferably 1 to 5 minutes.

The conditions for the curing treatment are usually room temperature (23°C) to 70°C, and the time is usually 1 to 3 hours.
0 days, specifically, for example, 1 to 20 days at 23°C, preferably 3 to 14 days at 23°C.
The incubation may be carried out under conditions such as 1 to 10 days at 40°C.

The thickness of the pressure-sensitive adhesive sheet and the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet is not particularly limited, but is preferably 0.5 to 500 μm, and particularly preferably 1 to 300 μm.
The thickness of the pressure-sensitive adhesive layer is preferably 10 to 100 μm, more preferably 5 to 200 μm, and particularly preferably 10 to 100 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, the adhesive strength tends to decrease, whereas if the thickness is too thick, it becomes difficult to apply the pressure-sensitive adhesive layer uniformly and problems such as bubbles being trapped in the coating film tend to occur.

The thickness of the adhesive layer was measured using a Digimatic Indicator (Mitutoyo Corporation, ID-C1
12B) and subtracting the measured thickness of the constituent members other than the pressure-sensitive adhesive layer from the measured thickness of the entire pressure-sensitive adhesive sheet.

The gel fraction of the pressure-sensitive adhesive layer is preferably 5% by weight or more, particularly preferably 10 to 80% by weight, and further preferably 15 to 70% by weight, from the viewpoint of adhesive strength and initial adhesive strength.
The gel fraction is particularly preferably 20 to 65% by weight, and most preferably 25 to 60% by weight. If the gel fraction is too low, the shear strength tends to decrease. If the gel fraction is too high, the initial adhesive strength tends to decrease.

The gel fraction is an index of the degree of crosslinking and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (without a separator) consisting of a substrate polymer sheet (e.g., a PET film) on which a pressure-sensitive adhesive layer is formed is wrapped in a 200-mesh SUS wire netting and immersed in toluene at 23°C for 24 hours, and the gel fraction is calculated as the weight percentage of the insoluble pressure-sensitive adhesive component remaining in the wire netting after immersion relative to the weight of the pressure-sensitive adhesive component before immersion, excluding the weight of the substrate.

Furthermore, such a pressure-sensitive adhesive sheet may, if necessary, be provided with a release sheet on the outer side of the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer. Also, in a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is formed on one side of a substrate, it is possible to protect the pressure-sensitive adhesive layer by applying a release treatment to the side of the substrate opposite the pressure-sensitive adhesive layer, thereby utilizing the release-treated surface.

The pressure-sensitive adhesive of the present invention can be used to bond various members, and is particularly preferably used as a pressure-sensitive adhesive for optical members, which is used to bond optical members, or as a pressure-sensitive adhesive for labels.

The optical member with the pressure-sensitive adhesive layer preferably further has a release film on the surface of the pressure-sensitive adhesive layer opposite to the optical member surface, and when used in practice, the release film is peeled off and the pressure-sensitive adhesive layer is attached to an adherend. As such a release film, a silicone-based release film is preferably used.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.
Unless otherwise specified, all values are by weight.
In the following examples, the glass transition temperature, weight average molecular weight, number average molecular weight, acid value,
The hydroxyl value and the like were measured according to the above-mentioned method.

The components were prepared as follows:
The mol % of each component, which is a polycarboxylic acid, described in the following polyester resin production examples
indicates a molar ratio when the total amount of polycarboxylic acids is taken as 100 mol %.
Furthermore, the mol % of each polyol component described in the following production examples indicates the molar ratio when the total amount of polyols is taken as 100 mol %.

[Polyester Resin (A)]
[Production of Polyester Resin (A-1)]
A reactor equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was installed.
As polyvalent carboxylic acids (a1), 355 parts of isophthalic acid, 185 parts of sebacic acid, as polyol (a2), 286 parts of neopentyl glycol, 137 parts of 1,4 butanediol, 1
31 parts of 6-hexanediol, 5 parts of trimethylolpropane, 0.5 parts of zinc acetate as a catalyst.
The internal temperature was raised to 250°C, and the esterification reaction was carried out over 4 hours.
Thereafter, the internal temperature was raised to 260°C, 0.05 parts of tetrabutyl titanate was charged as a catalyst, the pressure was reduced to 1.33 hPa, and a polycondensation reaction was carried out over 3 hours to produce a polyester resin (
A-1) was obtained.
The resulting polyester resin (A-1) had a glass transition temperature (Tg) of 1° C., a number average molecular weight of 18,000, and a weight average molecular weight (Mw) of 90,000.
The final component ratio was 70 mol%/30 mol% of isophthalic acid/sebacic acid as polycarboxylic acids (a1), and 10 mol%/10 mol% of neopentyl glycol as polyol (a2).
The ratio was 58.5 mol %/34 mol %/6.2 mol %/1.3 mol %.

[Production of Polyester Resins (A-2) and (A'-1)]
Polyester resins (A-2) and (A'-1) were obtained in the same manner as A-1, except that the resin compositions were changed as shown in Table 1.

The resin compositions and physical properties of the polyester resins (A-1), (A-2) and (A'-1) obtained above are shown in Table 1.

[Polyester-based plasticizer (B-1)]
[Production of Polyester-Based Plasticizer (B'-1) Before End-Capping]
A reactor equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was installed.
As shown in Table 2 below, isophthalic acid (IPA; b1) is used as the polycarboxylic acid (b1).
290 parts of α-1), 255 parts of adipic acid (AdA; b1-2), and polyol (b2)
454 parts of 3-methylpentanediol (MPD; b2-2) as a catalyst and 0.05 parts of tetrabutyl titanate as a catalyst were charged, the internal temperature was raised to 250° C., and an esterification reaction was carried out over 4 hours.
Thereafter, the internal temperature was raised to 260°C, the pressure was reduced to 100 hPa, and an esterification reaction was carried out over 1 hour to obtain a polyester resin (B'-1) before end-capping. The resulting polyester plasticizer (B'-1) before end-capping had a final component ratio of isophthalic acid/adipic acid = 50/50 mol% as the polycarboxylic acid (a1) and 3-methyl-1,5-pentanediol = 100 mol% as the polyol (a2). The acid value was 0.1 mgKOH/
The hydroxyl value was 56.0 mgKOH/g.
The physical properties of the resulting polyester resin (B'-1) before end-blocking are shown in Table 2 below.

[Production of Polyester-Based Plasticizer (B-1)]
4 parts of ethyl acetate per 100 parts of the polyester plasticizer (B'-1) before end-blocking
11.8 parts of phenyl isocyanate as a blocking agent were charged and reacted at an internal temperature of 60°C for 4 hours to obtain a polyester resin (B-1) in which the reactive molecular ends were blocked. The acid value of the resulting polyester resin (B-4) was 0.1 mgKOH/g and the hydroxyl value was 0.6 mg
The obtained polyester resin (B-1) had a heat of fusion (J
/g) peak was not observed, and there was no melting point.

The physical properties of the polyester resin (B-1) having the reactive molecular ends blocked obtained above are shown in Table 3 below.

[Hydrolysis inhibitor (C)]
(C-1): Polycarbodiimide compound (manufactured by Nisshinbo Chemical Inc., "Carbodilite V-0"
9GB"; Number average molecular weight 3,700; Weight average molecular weight 9,200; (A-1) Y/X = 1
4.0; (A-2)Y/X=9.3)

[Crosslinking agent (D)]
(D-1): Trimethylolpropane/tolylene diisocyanate adduct (manufactured by Tosoh Corporation,
"Coronate L55E")

[Urethanization catalyst (E)]
(E-1): Zirconium-based compound diluted with acetylacetone to a solids concentration of 1% ("Orgatics ZC-150" manufactured by Matsumoto Fine Chemical Co., Ltd.)

Example 1
The polyester resin (A-1) obtained above was diluted with ethyl acetate to a solid content concentration of 50%, and 50 parts of a polyester plasticizer (B-1), 0.5 parts (solid content) of a hydrolysis inhibitor (C-1), and a crosslinking agent (D
3.5 parts (solid content) of urethane-forming catalyst (E-1) and 0.02 parts (solid content) of urethane-forming catalyst (E-1) were blended.
The mixture was stirred and mixed to obtain a pressure-sensitive adhesive composition.

Example 2
In Example 1, 50 parts of polyester plasticizer (B-1) and 100 parts of crosslinking agent (D-
1) A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the amount was changed from 3.5 parts to 6.5 parts.

Example 3
In Example 1, 50 parts of polyester plasticizer (B-1) and 150 parts of crosslinking agent (D-
1) A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the amount was changed from 3.5 parts to 9.5 parts.

Example 4
In Example 1, the polyester resin (A-1) was replaced with (A-2), and the crosslinking agent (D-1) was replaced with 3
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the amount of hydroxybenzoate was changed from 5 parts to 6 parts.

Example 5
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the polyester resin (A-1) was changed to (A-2), the polyester resin (B-1) was changed from 50 parts to 100 parts, and the crosslinking agent (D-1) was changed from 3.5 parts to 10 parts.

Example 5
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the polyester resin (A-1) was changed to (A-2), the polyester resin (B-1) was changed from 50 parts to 150 parts, and the crosslinking agent (D-1) was changed from 3.5 parts to 13 parts.

(Comparative Example 1)
In Example 1, the polyester plasticizer (B-1) was not added, and the crosslinking agent (D-1) was added in an amount of 3
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the amount of 0.5 parts was changed to 1.5 parts.

(Comparative Example 2)
The same procedure as in Example 1 was repeated except that the polyester resin (A-1) was changed to (A-2), the polyester plasticizer (B-1) was not added, and the crosslinking agent (D-1) was changed from 3.5 parts to 3 parts.
In the same manner as above, a pressure-sensitive adhesive composition was obtained.

(Comparative Example 3)
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the polyester resin (A-1) was changed to (A'-1), the polyester plasticizer (B-1) was not added, and the crosslinking agent (D-1) was changed from 3.5 parts to 1.5 parts.

(Comparative Example 4)
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the polyester resin (A-1) was changed to (A'-1).

(Comparative Example 5)
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the polyester resin (A-1) was changed to (A'-1), the polyester plasticizer (B-1) was changed from 50 parts to 100 parts, and the crosslinking agent (D-1) was changed from 3.5 parts to 6.5 parts.

(Comparative Example 6)
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1, except that the polyester resin (A-1) was changed to (A'-1), the polyester plasticizer (B-1) was changed from 50 parts to 150 parts, and the crosslinking agent (D-1) was changed from 3.5 parts to 9.5 parts.

Using the pressure-sensitive adhesive compositions obtained in the above Examples and Comparative Examples, pressure-sensitive adhesive sheets were produced as follows, and evaluated as follows.

<Preparation of adhesive sheet with one-sided release film>
The pressure-sensitive adhesive compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were applied to a 38 μm-thick PET film ("Lumirror T60" manufactured by Toray Industries, Inc.) using an applicator, and dried at 100°C for 3 minutes to obtain pressure-sensitive adhesive sheets with PET film having pressure-sensitive adhesive composition layer thicknesses of 25 μm and 100 μm.
Next, the surface of the pressure-sensitive adhesive composition layer of the obtained pressure-sensitive adhesive sheet with a PET film was coated with a 38 μm thick film.
The sample was covered with a PET release film (Mitsui Chemicals Tocello, SP-PET-01-BU) and then cooled to 4°C.
Aging treatment was carried out at 0° C. for 4 days to obtain a pressure-sensitive adhesive sheet with a release film on one side.

<Preparation of adhesive sheet with double-sided release film>
The pressure-sensitive adhesive compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were applied using an applicator to a 38 μm-thick PET release film (manufactured by Mitsui Chemicals Tocello Inc., "SP-PET-03-BU") and dried at 100°C for 3 minutes to obtain pressure-sensitive adhesive sheets with a release film, the pressure-sensitive adhesive composition layer of which was 100 μm thick.
Next, the surface of the pressure-sensitive adhesive composition layer of the obtained pressure-sensitive adhesive sheet with release film was covered with a 38 μm-thick PET release film (manufactured by Mitsui Chemicals Tocello, Inc., SP-PET-01-BU), and the sheet was heated for 40
The sheet was subjected to aging treatment at 4° C. for 4 days to obtain a pressure-sensitive adhesive sheet with double-sided release films.

[Gel fraction]
The pressure-sensitive adhesive sheet with a release film on one side obtained above was cut into a size of 50 mm x 50 mm, the release film was peeled off, the sheet was wrapped in a 200-mesh SUS wire netting, and the sheet was placed in toluene for 2
The wire mesh was immersed at 3°C for 24 hours, and the weight of the adhesive component before immersion and the weight of the undissolved adhesive component remaining in the wire mesh after immersion were measured. The percentage was calculated according to the following formula, which was taken as the gel fraction (%).
However, the weight of the substrate was subtracted.
Weight of undissolved adhesive component remaining in the wire mesh after immersion/weight of adhesive component before immersion×1
00 (%)

(Adhesive sheet evaluation)
[Initial adhesive strength]
The pressure-sensitive adhesive sheet with one-sided release film obtained above was left in an environment of 23°C and 50% RH for 2
After cutting into a size of 5 mm x 200 mm, the release film was peeled off, and the adhesive layer side was pressed and attached to a mirror-finished stainless steel plate (SUS-BA plate) by reciprocating a 2 kg roller. After leaving it to stand for 30 seconds in the same atmosphere, it was then measured using an Autograph (Shimadzu Corporation, "Autograph AG-
x 50N") at a peeling speed of 300 mm/min and a 180-degree peel adhesive strength (N/25
The evaluation criteria are as follows:
(Evaluation criteria)
◎: Greater than 5 N/25 mm, and peeling occurred at the adherend interface. ○: Greater than 3 N/25 mm but not greater than 5 N/25 mm, and peeling occurred at the adherend interface. △: Greater than 1 N/25 mm but not greater than 3 N/25 mm, and peeling occurred at the adherend interface. ×: Less than 1 N/25 mm, or peeling occurred as cohesive peeling or substrate interface peeling.

[Shear force measurement]
The pressure-sensitive adhesive sheet with double-sided release film obtained above was left in an environment of 23°C and 50% RH for 2
After cutting into a size of 5 mm x 12.5 mm, one release film was peeled off and the adhesive layer side was attached to a stainless steel plate. The other release film was peeled off and the adhesive layer side was attached to a stainless steel plate.
The test piece was then aged for 48 hours in the same atmosphere to prepare a measurement sample, and then measured using an autograph (
A Shimadzu Autograph AG-X 5kN was used at a peel rate of 10 mm/m.
A tensile test was carried out in the vertical direction at 100 mm to measure the shear strength. The evaluation criteria are as follows:
(Evaluation criteria)
◎: More than 1.5 MPa ○: More than 1 MPa and 1.5 MPa or less △: More than 0.5 MPa and 1 MPa or less ×: 0.5 MPa or less

The results in Table 4 above show that the pressure-sensitive adhesive sheets obtained from the pressure-sensitive adhesive compositions of Examples 1 to 6 are excellent in both initial adhesive strength and shear strength.
On the other hand, the pressure-sensitive adhesive sheets obtained from the pressure-sensitive adhesive compositions of Comparative Examples 1 and 2, which did not contain the polyester-based plasticizer (B), were excellent in shear strength but poor in initial adhesive strength.
Furthermore, the pressure-sensitive adhesive sheets obtained from the pressure-sensitive adhesive compositions of Comparative Examples 3 to 6, in which a polyester resin with a low glass transition temperature was used, had excellent initial adhesive strength but poor shear strength.
From the above, it can be seen that a polyester-based pressure-sensitive adhesive composition having a specific glass transition temperature and further containing a polyester-based plasticizer has well-balanced and excellent adhesive properties when used as a pressure-sensitive adhesive.

The pressure-sensitive adhesive composition of the present invention is excellent in initial adhesive strength and shear strength, and therefore pressure-sensitive adhesives and pressure-sensitive adhesive sheets using the same can be used for bonding electronic components.

Claims (13)

A polyester-based pressure-sensitive adhesive composition comprising a polyester-based resin (A) having a structural unit derived from a polycarboxylic acid (a1) and a structural unit derived from a polyol (a2), a polyester-based plasticizer (B), and a crosslinking agent (D),
the polyester plasticizer (B) has a structural unit derived from a polycarboxylic acid (b1), a structural unit derived from a polyol (b2), and a structural unit derived from a reactive molecule end-capping agent (b3), and the content of the polyester plasticizer (B) is 10 to 180 parts by weight per 100 parts by weight of the polyester resin (A);
A polyester-based pressure-sensitive adhesive composition, characterized in that the polyester-based resin (A) has a glass transition temperature (TgA) of -25 to 35°C and a hydroxyl value of 1 to 30 mgKOH/g. The polyester-based pressure-sensitive adhesive composition according to claim 1, wherein the weight-average molecular weight of the polyester-based resin (A) is 15,000 to 200,000. The polyester-based pressure-sensitive adhesive composition according to claim 1 or 2, characterized in that the acid value of the polyester-based resin (A) is 5 mg KOH/g or less. The polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 3, characterized in that the polyester-based plasticizer (B) contains an aromatic structure in at least one of the structural units derived from polycarboxylic acids (b1), the structural units derived from polyol (b2), and the reactive molecular end-capping agent (b3). The polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 4, characterized in that the weight-average molecular weight of the polyester-based plasticizer (B) is 1,000 to 12,000. The polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 5, characterized in that the acid value of the polyester-based plasticizer (B) is 5 mgKOH/g or less. The polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 6, characterized in that the glass transition temperature (TgB) of the polyester-based plasticizer (B) is -80 to 0°C. The polyester-based pressure-sensitive adhesive composition described in any one of items 1 to 7, wherein the glass transition temperature (TgA) of the polyester-based resin (A) is higher than the glass transition temperature (TgB) of the polyester-based plasticizer (B). The polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 8, characterized in that it contains a hydrolysis inhibitor (C). A polyester-based pressure-sensitive adhesive obtained by crosslinking the polyester-based pressure-sensitive adhesive composition according to any one of claims 1 to 9. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the polyester-based pressure-sensitive adhesive of claim 10. A pressure-sensitive adhesive sheet having a substrate and a pressure-sensitive adhesive layer obtained from the polyester-based pressure-sensitive adhesive of claim 10, wherein the pressure-sensitive adhesive layer is provided on at least one surface of the substrate. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer obtained from the polyester-based pressure-sensitive adhesive of claim 10, characterized in that the pressure-sensitive adhesive sheet is a substrate-less type that does not have a substrate.