JP7275463B2 - Adhesive composition and adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition and an adhesive sheet.

2. Description of the Related Art Many mobile electronic devices such as mobile phones and mobile terminals incorporate a liquid crystal display device. Generally, a liquid crystal display device includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two glass substrates, and polarizing plates arranged on both sides of the liquid crystal cell. From the viewpoint of ensuring the visibility of the liquid crystal display device, the liquid crystal cell and the polarizing plate are generally bonded via an adhesive layer formed of an acrylic adhesive.

For example, Patent Document 1 discloses an optical adhesive characterized by containing 100 parts by mass of an acrylic polymer and 5 to 50 parts by mass of an isocyanate curing agent.

JP 2011-37927 A

In a polarizing plate provided with an adhesive layer (hereinafter also referred to as a "polarizing plate with an adhesive layer"), when cutting, the adhesive adheres to the cutting blade, the polarizing plates with the adhesive layer stick to each other, and there is an adhesive problem. Problems such as floating of the agent layer may occur. Therefore, the pressure-sensitive adhesive composition used for the polarizing plate is required to be capable of forming a pressure-sensitive adhesive layer (so-called pressure-sensitive adhesive layer with excellent workability) that is less likely to cause the above problems.

By the way, generally, a polarizing plate with an adhesive layer is cut into a desired size and used after being stored in a roll state. However, in recent years, from the viewpoint of improving work efficiency, there has been a demand to cut a polarizing plate coated with an adhesive composition in a short period of time after coating, and then to cure the polarizing plate. However, if the polarizing plate is cut in a state in which the cross-linking is insufficient (that is, the curing is insufficient), adhesion of the adhesive to the cutting blades and the like become noticeable.
In order to suppress adhesion of the adhesive to the cutting blade, for example, it is conceivable to use a chelate-based cross-linking agent with a high cross-linking rate to allow the cross-linking reaction to proceed immediately after coating. However, when a chelate-based cross-linking agent is used, the adhesion between the polarizing plate and the pressure-sensitive adhesive layer is extremely lowered.

As described above, it is difficult to realize a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having both excellent adhesion to a substrate (for example, polarizing plate) (hereinafter also referred to as "substrate adhesion") and processability. It was difficult.

The problem to be solved by the present invention is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent adhesion to a substrate and processability, and a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. It is to be.

Specific means for solving the problems include the following aspects.
<1> (Meth) acrylic containing a structural unit derived from a (meth)acrylic acid alkyl ester monomer, a structural unit derived from a monomer having a carboxy group, and a structural unit derived from a monomer having a hydroxyl group a system copolymer;
a metal chelate-based compound;
and a tolylene diisocyanate-based compound,
The content of the metal chelate compound is in the range of 5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic copolymer, and
A pressure-sensitive adhesive composition, wherein the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the (meth)acrylic copolymer is 1.00 or more.
<2> The content of structural units derived from the monomer having a carboxy group in the (meth)acrylic copolymer is 1 mass with respect to all structural units of the (meth)acrylic copolymer. % or more and 5% by mass or less of the pressure-sensitive adhesive composition according to <1>.
<3> The content of structural units derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is 0.1 with respect to the total structural units of the (meth)acrylic copolymer. The pressure-sensitive adhesive composition according to <1> or <2>, which is in the range of 3% by mass or more.
<4> Any one of <1> to <3>, wherein the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the (meth)acrylic copolymer is 10.00 or less The adhesive composition described.
<5> A film with a thickness of 20 μm formed by blowing air at 100° C. for 1 minute at a wind speed of 3 m / sec on the adhesive composition applied on the temporary support is applied in an environment with an ambient temperature of 23° C. and 50% RH. The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the film has a gel fraction of 80% by mass or more when placed under the pressure-sensitive adhesive composition for 3 hours.
<6> A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed from the pressure-sensitive adhesive composition according to any one of <1> to <5>.
<7> The adhesive sheet according to <6>, wherein the substrate is a polarizing plate.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive composition which can form the adhesive layer which is excellent in substrate adhesion and workability, and the adhesive sheet provided with the adhesive layer formed with the said adhesive composition are provided.

Specific embodiments of the present invention will be described in detail below. However, the present invention is by no means limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

In this specification, the numerical range indicated using "to" means a range including the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. . Moreover, in the numerical ranges described in this specification, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the values shown in the examples.
In the present specification, a combination of two or more preferred aspects is a more preferred aspect.
In the present specification, the amount of each component means the total amount of the multiple types of substances unless otherwise specified when there are multiple types of substances corresponding to each component.

As used herein, the term "(meth)acrylic copolymer" means that the content of structural units derived from a monomer having a (meth)acryloyl group is the total structural unit [i.e., (meth)acrylic copolymer 50% by mass or more of the total constituent units].

As used herein, "(meth)acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth)acrylate" is a term that includes both "acrylate" and "methacrylate". and "(meth)acryloyl" is a term that includes both "acryloyl" and "methacryloyl".

As used herein, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention includes a structural unit derived from a (meth)acrylic acid alkyl ester monomer, a structural unit derived from a monomer having a carboxy group, and a structural unit derived from a monomer having a hydroxyl group. (Meth)acrylic copolymer containing [hereinafter also referred to as "specific (meth)acrylic copolymer". ], a metal chelate compound, and a tolylene diisocyanate compound, and the content of the metal chelate compound is 5 parts by mass or more and 18 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer and the equivalent ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the (meth)acrylic copolymer is 1.00 or more.
The pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer having excellent adhesion to a substrate and processability by having the above configuration.
Although it is not clear why the pressure-sensitive adhesive composition of the present invention can exhibit such effects, the present inventors speculate as follows. However, the following assumptions are not intended to limit the interpretation of the pressure-sensitive adhesive composition of the present invention, but are explained as an example.

In the pressure-sensitive adhesive composition of the present invention, the carboxyl group in the (meth)acrylic copolymer reacts quickly with the metal chelate compound, so curing does not require much time. Therefore, even if the adhesive layer formed from the adhesive composition of the present invention is cut in a relatively short time after coating, the adhesive does not adhere to the cutting blade and the adhesive sheets do not stick to each other. Hard to come by. Further, in the pressure-sensitive adhesive composition of the present invention, the isocyanate groups in the tolylene diisocyanate compound are equal to or more than the hydroxyl groups in the specific (meth)acrylic copolymer, and the tolylene diisocyanate type that does not contribute to cross-linking A compound exists. The tolylene diisocyanate-based compound that does not contribute to cross-linking interacts with the base material, thereby forming a pressure-sensitive adhesive layer with excellent adhesion to the base material. By the way, the content of the metal chelate compound contained in the adhesive composition of the present invention is relatively large. A pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a large amount of a metal chelate compound tends to have poor adhesion to a substrate. However, in the pressure-sensitive adhesive composition of the present invention, after the reaction between the carboxyl group in the specific (meth)acrylic copolymer and the metal chelate compound, the hydroxyl group in the specific (meth)acrylic copolymer and tolylene diisocyanate The reaction proceeds with isocyanate groups in the system compound. Therefore, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention satisfactorily suppresses adhesion of the pressure-sensitive adhesive to the cutting blade and sticking of the pressure-sensitive adhesive sheets to each other when cutting in a relatively short time after coating. In addition, it has excellent adhesion to the substrate. In addition, since the content of the metal chelate compound in the pressure-sensitive adhesive composition of the present invention is not more than a specific amount, the formed pressure-sensitive adhesive layer does not become too hard, and the pressure-sensitive adhesive layer is lifted from the substrate due to impact during cutting. hard.
From the above, it is believed that the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer with excellent substrate adhesion and workability.

In contrast, Patent Document 1 (JP 2011-37927 A) includes both structural units derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxy group (meta) An example in which an acrylic copolymer, a tolylene diisocyanate compound, and a metal chelate compound are used in combination is not described. Also, the optical pressure-sensitive adhesive described in Patent Document 1 contains a metal chelate compound, but the content is very small. Therefore, when the pressure-sensitive adhesive layer formed by the optical pressure-sensitive adhesive described in Patent Document 1 is cut in a relatively short time after coating, for example, the adhesion of the pressure-sensitive adhesive to the cutting blade and the pressure-sensitive adhesive sheet It is considered that sticking between them occurs.

Each component of the pressure-sensitive adhesive composition of the present invention will be described below.

[Specific (meth)acrylic copolymer]
The pressure-sensitive adhesive composition of the present invention includes a structural unit derived from a (meth)acrylic acid alkyl ester monomer, a structural unit derived from a monomer having a carboxy group, and a structural unit derived from a monomer having a hydroxyl group. Contains a (meth)acrylic copolymer containing [that is, a specific (meth)acrylic copolymer].
The pressure-sensitive adhesive composition of the present invention may contain only one type of specific (meth)acrylic copolymer, or may contain two or more types.

<Structural unit derived from (meth)acrylic acid alkyl ester monomer>
The specific (meth)acrylic copolymer contains structural units derived from (meth)acrylic acid alkyl ester monomers.
The structural unit derived from the (meth)acrylic acid alkyl ester monomer contributes to the adjustment of adhesive strength.

In the present specification, "a structural unit derived from a (meth)acrylic acid alkyl ester monomer" means a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer.

The type of (meth)acrylic acid alkyl ester monomer is not particularly limited.
As the (meth)acrylic acid alkyl ester monomer, an unsubstituted (meth)acrylic acid alkyl ester monomer is preferable.
The alkyl group of the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic.
The number of carbon atoms in the alkyl group is, for example, preferably 1 to 18, more preferably 1 to 8, and even more preferably 1 to 4, from the viewpoint of adhesive strength and substrate adhesion.

Specific examples of (meth) acrylic acid alkyl ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylates, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and the like.
Among these, the (meth)acrylic acid alkyl ester monomers include, for example, methyl acrylate (MA) and n-butyl acrylate (n-BA) from the viewpoint of facilitating adjustment of cohesive force and adhesive force. At least one selected from the group consisting of is preferred.

The specific (meth)acrylic copolymer may contain only one type of structural unit derived from a (meth)acrylic acid alkyl ester monomer, or may contain two or more types thereof.

The content (i.e., ratio) of structural units derived from the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic copolymer is not particularly limited, but for example, the specific (meth)acrylic copolymer It is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and particularly preferably 80% by mass or more, based on the total structural units of the coalescence. preferable.
Here, the fact that the content of structural units derived from (meth)acrylic acid alkyl ester monomers is 50% by mass or more with respect to all structural units of the specific (meth)acrylic copolymer means that (meth) ) means that a structural unit derived from an acrylic acid alkyl ester monomer is contained as a main component of a structural unit constituting a specific (meth)acrylic copolymer.
The upper limit of the content of structural units derived from (meth)acrylic acid alkyl ester monomers in the specific (meth)acrylic copolymer is not particularly limited. It is preferably 98.5% by mass or less with respect to the constituent units.

<Structural Unit Derived from Monomer Having Carboxy Group>
The specific (meth)acrylic copolymer contains structural units derived from a monomer having a carboxy group.
A carboxy group of a structural unit derived from a monomer having a carboxy group rapidly reacts with a metal chelate compound described below.

As used herein, the term "structural unit derived from a monomer having a carboxy group" means a structural unit formed by addition polymerization of a monomer having a carboxy group.

The type of monomer having a carboxy group is not particularly limited.
Specific examples of monomers having a carboxy group include acrylic acid (AA), methacrylic acid (MAA), crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, and ω-carboxy-polycaprolactone. mono(meth)acrylate [eg ω-carboxy-polycaprolactone (n≈2) monoacrylate], succinic acid ester (eg 2-acryloyloxyethyl-succinic acid) and the like.
Among these, the monomer having a carboxy group is preferably acrylic acid from the viewpoint of copolymerizability.

The specific (meth)acrylic copolymer may contain only one type of structural unit derived from a monomer having a carboxy group, or may contain two or more types thereof.

The content (percentage) of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic copolymer is not particularly limited, but for example, all structural units of the specific (meth)acrylic copolymer is preferably in the range of 1% by mass or more and 5% by mass or less, more preferably in the range of 1% by mass or more and 3% by mass or less, and in the range of 1.5% by mass or more and 3% by mass or less It is even more preferable to have
The content of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic copolymer is 1% by mass or more with respect to all structural units of the specific (meth)acrylic copolymer. There is a tendency that the carboxy group and the metal chelate compound react sufficiently to form an adhesive layer that can further suppress adhesion of the adhesive to the cutting blade and sticking of the adhesive sheets to each other.
The content of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic copolymer is 5% by mass or less with respect to the total structural units of the specific (meth)acrylic copolymer. For example, when the substrate is a polarizing plate, deterioration of the substrate tends to be less likely to occur. In addition, the pressure-sensitive adhesive layer to be formed does not become too hard, and there is a tendency for the pressure-sensitive adhesive layer to be more suppressed from coming off from the base material due to impact during cutting of the pressure-sensitive adhesive sheet.

<Structural Unit Derived from Monomer Having Hydroxyl Group>
A specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group.
A hydroxyl group of a structural unit derived from a monomer having a hydroxyl group is crosslinked with an isocyanate group of a tolylene diisocyanate compound described later.

As used herein, the term “structural unit derived from a monomer having a hydroxyl group” means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

The type of hydroxyl group-containing monomer is not particularly limited.
Specific examples of monomers having a hydroxyl group include 2-hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4- Hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1 -dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3- Hydroxyhexyl (meth)acrylate, hydroxyalkyl (meth)acrylates such as N-hydroxyethyl (meth)acrylamide, 1,4-cyclohexanedimethanol monoacrylate, dicaprolactone 2-acryloyloxy-ethyl ether and the like.
Among these, hydroxyalkyl (meth)acrylates are preferred as monomers having a hydroxyl group, for example, from the viewpoint of good copolymerizability with (meth)acrylic acid alkyl ester monomers.
Hydroxyalkyl (meth)acrylates include, for example, 2-hydroxyethyl acrylate (2HEA) and 4-hydroxybutyl acrylate (4HBA) from the viewpoint of good reactivity with tolylene diisocyanate compounds described later. At least one selected from the group is preferred.

The specific (meth)acrylic copolymer may contain only one type of structural unit derived from a monomer having a hydroxyl group, or may contain two or more types thereof.

The content (percentage) of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer is not particularly limited. On the other hand, it is preferably in the range of 0.1% by mass or more and 3% by mass or less, more preferably in the range of 0.1% by mass or more and 2% by mass or less, and 0.3% by mass or more and 1% by mass or less. is more preferably in the range of
The content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 0.1% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer. There is a tendency that the hydroxyl group and the isocyanate group of the tolylene diisocyanate compound sufficiently react with each other to form a pressure-sensitive adhesive layer having excellent adhesion to a substrate.
When the content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 3% by mass or less with respect to the total structural units of the specific (meth)acrylic copolymer, The pressure-sensitive adhesive layer to be formed does not become too hard, and the pressure-sensitive adhesive layer tends to be more suppressed from lifting from the base material due to the impact during cutting of the pressure-sensitive adhesive sheet.

<Other structural units>
The specific (meth)acrylic copolymer, within the range in which the effect of the present invention is exhibited, has the structural unit described above, that is, the structural unit derived from the (meth)acrylic acid alkyl ester monomer, and the carboxy group. A structural unit (so-called other structural unit) other than a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a hydroxyl group may be included.

The monomers constituting other structural units are not particularly limited as long as they can be copolymerized with the monomers constituting the aforementioned structural units.
Specific examples of monomers constituting other structural units include monomers having an amino group, benzyl (meth)acrylate, and (meth)acrylates having a cyclic group represented by phenoxyethyl (meth)acrylate, Alkoxyalkyl (meth)acrylates typified by methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, typified by styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene aromatic monovinyls, vinyl cyanides typified by acrylonitrile and methacrylonitrile, vinyl esters typified by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate, and various derivatives of these monomers is mentioned.

<<Weight average molecular weight of specific (meth)acrylic copolymer>>
The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is not particularly limited. is more preferable, and more preferably in the range of 600,000 or more and 1,500,000 or less.
When the weight-average molecular weight (Mw) of the specific (meth)acrylic copolymer is 500,000 or more, foaming of the pressure-sensitive adhesive layer that can occur when exposed to a high-temperature environment tends to be reduced.
When the weight-average molecular weight (Mw) of the specific (meth)acrylic copolymer is 2,000,000 or less, the viscosity of the pressure-sensitive adhesive composition does not become too high, so that the pressure-sensitive adhesive composition can be applied more satisfactorily.

The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is a value measured by the following method. Specifically, it is measured according to the following (1) to (3).
(1) A solution of the specific (meth)acrylic copolymer is applied to release paper and dried at 100° C. for 1 minute to obtain a film-like specific (meth)acrylic copolymer.
(2) Using the film-shaped specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, the solid content concentration (i.e., the mass ratio of the specific (meth)acrylic copolymer) is A sample solution is obtained which is 0.2% by weight.
(3) Using gel permeation chromatography (GPC), measure the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer as a standard polystyrene equivalent value under the following conditions.

~Conditions~
Measuring device: high-speed GPC (model number: HLC-8220 GPC, manufactured by Tosoh Corporation)
Detector: Differential refractometer (RI) (built into HLC-8220, manufactured by Tosoh Corporation)
Column: Four TSK-GEL GMHXL (manufactured by Tosoh Corporation) connected in series Column temperature: 40 ° C.
Eluent: Tetrahydrofuran Sample concentration: 0.2% by mass
Injection volume: 100 μL
Flow rate: 0.6 mL/min

<<Specific (meth)acrylic copolymer content>>
The content (percentage) of the specific (meth)acrylic copolymer in the pressure-sensitive adhesive composition of the present invention is not particularly limited. It is preferably in the range of 50% by mass or more and 95% by mass or less, more preferably in the range of 60% by mass or more and 95% by mass or less, and in the range of 70% by mass or more and 95% by mass or less. It is even more preferable to have

As used herein, "total solid content in the pressure-sensitive adhesive composition" means the total mass of the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition does not contain a solvent. When included, it means the mass of the residue after removing the solvent from the pressure-sensitive adhesive composition.

[Method for producing specific (meth)acrylic copolymer]
The method for producing the specific (meth)acrylic copolymer is not particularly limited.
The specific (meth)acrylic copolymer is produced by polymerizing the above-described monomers by a known polymerization method represented by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method. can.

The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer can be adjusted to the desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. can be the value of

As the polymerization method, solution polymerization is preferable in that the processing steps are relatively simple and can be performed in a short period of time when preparing the pressure-sensitive adhesive composition of the present invention after production.
In solution polymerization, a given organic solvent, a monomer, a polymerization initiator, and optionally a chain transfer agent are charged in a polymerization vessel, and the reaction is carried out in a nitrogen stream and/or at the reflux temperature of the organic solvent. Heat and react for several hours while stirring. In this case, at least part of the organic solvent, monomer, polymerization initiator and/or chain transfer agent may be added sequentially.

Organic solvents used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, alcohol compounds and the like.
More specific examples of the organic solvent used during the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic hydrocarbon compounds typified by aromatic naphtha, fats typified by n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine. family or alicyclic hydrocarbon compounds, represented by ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; Ester compounds, acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and ketone compounds represented by methyl cyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ethers and glycol ether compounds typified by diethylene glycol monobutyl ether, and methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t- Alcohol compounds represented by butyl alcohol are mentioned.
At the time of the polymerization reaction, one kind of these organic solvents may be used alone, or two or more kinds thereof may be mixed and used.

In the production of the specific (meth)acrylic copolymer, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction of aromatic hydrocarbon compounds, ester compounds, ketone compounds, alcohol compounds, etc. In particular, the specific ( From the viewpoint of the solubility of the meth)acrylic copolymer, the ease of the polymerization reaction, and the like, it is preferable to use, for example, ethyl acetate.

Examples of the polymerization initiator include organic peroxides, azo compounds, and the like, which are used in ordinary solution polymerization.
Examples of organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, carbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4 -di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane.
Examples of azo compounds include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2,4-dimethylvaleronitrile) (ABVN), 2,2′-azobis(4- methoxy-2,4-dimethylvaleronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile), and 2,2′-azobis(isobutyrate)dimethyl.
At the time of the polymerization reaction, one kind of these polymerization initiators may be used alone, or two or more kinds thereof may be mixed and used.

The amount of the polymerization initiator to be used is not particularly limited, and is appropriately set according to the molecular weight of the desired specific (meth)acrylic copolymer.

If necessary, a chain transfer agent may be used in the production of the specific (meth)acrylic copolymer.
Examples of chain transfer agents include cyanoacetic acid, cyanoacetic acid alkyl ester compounds having 1 to 8 carbon atoms, bromoacetic acid, bromoacetic acid alkyl ester compounds having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, and fluorene. , and aromatic compounds represented by 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone and Benzoquinone derivatives typified by 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives typified by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane Halogenated hydrocarbon compounds typified by , tribromoethylene, trichlorethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds typified by chloral and furaldehyde; alkyls having 1 to 18 carbon atoms; Aromatic mercaptan compounds represented by mercaptan compounds, thiophenols, and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and pinene and terpinolene and terpene compounds represented by.

When using a chain transfer agent in the production of the specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited, depending on the molecular weight of the desired specific (meth)acrylic copolymer , are set accordingly.

The polymerization temperature is not particularly limited, and is appropriately set according to the molecular weight of the desired specific (meth)acrylic copolymer.

[Metal chelate compound]
The adhesive composition of the present invention contains a metal chelate compound.
A metal chelate compound functions as a cross-linking agent.

The metal chelate compound is not particularly limited.
Examples of metal chelate compounds include aluminum chelate compounds represented by aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(ethylacetoacetate), and aluminum tris(acetylacetonate), titanium chelate compounds, and zirconium chelate compounds. , cobalt chelate compounds, and the like.
Among these, aluminum chelate compounds are preferable as metal chelate compounds from the viewpoint that they are stable as compounds and easy to handle.

A commercial item can be used as a metal chelate-type compound.
Examples of commercially available metal chelate compounds include "Aluminum chelate A", "Aluminum chelate D" and "ALCH-TR" [manufactured by Kawaken Fine Chemicals Co., Ltd.].

The pressure-sensitive adhesive composition of the present invention may contain only one kind of metal chelate compound, or may contain two or more kinds.

The content of the metal chelate compound in the adhesive composition of the present invention is in the range of 5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer, and is 6 parts by mass or more. It is preferably in the range of 15 parts by mass or less, and more preferably in the range of 7 parts by mass or more and 12 parts by mass or less.
When the content of the metal chelate compound in the adhesive composition of the present invention is 5 parts by mass or more with respect to 100 parts by mass of the specific (meth)acrylic copolymer, the metal chelate compound and the specific (meth) Since the carboxyl group in the acrylic copolymer reacts sufficiently, it is possible to form a pressure-sensitive adhesive layer in which the adhesion of the pressure-sensitive adhesive to the cutting blade and the sticking of the pressure-sensitive adhesive sheets to each other are suppressed.
If the content of the metal chelate compound in the pressure-sensitive adhesive composition of the present invention is 18 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer, the formed pressure-sensitive adhesive layer becomes too hard. Therefore, it is possible to prevent the pressure-sensitive adhesive layer from lifting from the base material due to impact during cutting of the pressure-sensitive adhesive sheet.

[Tolylene diisocyanate compound]
The adhesive composition of the present invention contains a tolylene diisocyanate compound.
The tolylene diisocyanate-based compound functions as a cross-linking agent.
When the pressure-sensitive adhesive composition of the present invention contains other polyisocyanate-based compounds [e.g., xylylene diisocyanate (XDI) and hexamethylene diisocyanate (HMDI)] instead of the tolylene diisocyanate-based compound, gelation occurs. Coating becomes difficult.

The tolylene diisocyanate compound is not particularly limited.
Examples of the tolylene diisocyanate-based compound include tolylene diisocyanate (TDI) isocyanurate and TDI adduct [that is, an adduct of TDI and a polyol compound [eg, trimethylolpropane (TMP)]].
Among these, the tolylene diisocyanate-based compound is preferably an adduct of TDI from the viewpoint that both the reaction rate and pot life are moderate.

A commercial item can be used as a tolylene diisocyanate type compound.
Commercially available examples of tolylene diisocyanate compounds include "Coronate (registered trademark) L", "Coronate (registered trademark) L-45E", "Coronate (registered trademark) 2030", and "Coronate (registered trademark) 2037". ” [all manufactured by Tosoh Corporation].

The pressure-sensitive adhesive composition of the present invention may contain only one type of tolylene diisocyanate-based compound, or may contain two or more types.

The content of the tolylene diisocyanate compound in the adhesive composition of the present invention is such that the equivalent ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the specific (meth)acrylic copolymer is 1.00 or more. is not particularly limited.
The content of the tolylene diisocyanate compound in the adhesive composition of the present invention is, for example, in the range of 1.5 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer. , preferably in the range of 1.5 to 10 parts by mass, more preferably in the range of 3 to 8 parts by mass.

<Equivalence ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the specific (meth)acrylic copolymer>
In the adhesive composition of the present invention, the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the specific (meth)acrylic copolymer is 1.00 or more and 2.00 or more. is preferred, and 3.00 or more is more preferred.
When the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the specific (meth)acrylic copolymer is 1.00 or more, there is a sufficient amount of tolylene diisocyanate compound that does not contribute to cross-linking. Since the tolylene diisocyanate-based compound that does not contribute to cross-linking interacts with the base material (particularly, the polarizing plate), it is possible to form a pressure-sensitive adhesive layer with better adhesion to the base material.
The upper limit of the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the specific (meth)acrylic copolymer is not particularly limited, but for example, it is preferably 15.00 or less, and 10.00 or less. is more preferably 8.00 or less.
If the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the specific (meth)acrylic copolymer is 15.00 or less, excessive condensates of tolylene diisocyanate compounds that do not contribute to cross-linking Not generated. Therefore, the pressure-sensitive adhesive layer to be formed does not become too hard, and there is a tendency that the pressure-sensitive adhesive layer is more suppressed from lifting from the base material due to impact during cutting of the pressure-sensitive adhesive sheet.

Equivalent ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the specific (meth) acrylic copolymer (molar amount of isocyanate groups in the tolylene diisocyanate compound/specific (meth) acrylic copolymer in The molar amount of hydroxyl groups) is determined by the following formulas (1) to (3).
In the following calculation formula, the molar amount of isocyanate groups in the tolylene diisocyanate compound is referred to as "NCO amount", and the molar amount of hydroxyl groups in the specific (meth)acrylic copolymer is referred to as "OH amount". write.

NCO amount (unit: mmol/solid content 100 g)
= [Isocyanate group content in the tolylene diisocyanate compound (unit: mass%) × [mixture amount of tolylene diisocyanate compound (solid content equivalent, unit: g) / solid content of tolylene diisocyanate compound ( Unit: mass %)]] / formula weight of isocyanate group (unit: g/mol) × 1000 (1)

OH amount (unit: mmol/solid content 100 g)
= [content of structural units derived from monomers having hydroxyl groups in the specific (meth)acrylic copolymer (units: % by mass) / molecular weight of monomers having hydroxyl groups (units: g/mol) × Number of hydroxyl groups in a structural unit derived from a monomer having a hydroxyl group (valence) x 1000] (2)

Equivalent ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the specific (meth)acrylic copolymer = NCO amount/OH amount (3)

〔Silane coupling agent〕
The pressure-sensitive adhesive composition of the invention may contain a silane coupling agent.
The silane coupling agent is not particularly limited, and examples thereof include polymerizable unsaturated group-containing silane compounds represented by vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyl. Thiol group-containing silane compounds represented by trimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl ) epoxy group-containing silane compounds represented by ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)- Examples include amino group-containing silane compounds typified by 3-aminopropylmethyldimethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate.

A commercial item can be used as a silane coupling agent.
Examples of commercially available silane coupling agents include "KBM-403", "X-41-1053", and "KBM-9659" (manufactured by Shin-Etsu Chemical Co., Ltd.).

When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, it may contain only one silane coupling agent, or may contain two or more silane coupling agents.

When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, the content of the silane coupling agent in the pressure-sensitive adhesive composition is not particularly limited. On the other hand, it is preferably in the range of 0.1 parts by mass or more and 1.0 parts by mass or less, more preferably in the range of 0.2 parts by mass or more and 0.8 parts by mass or less, and 0.3 parts by mass or more More preferably, it is in the range of 0.5 parts by mass or less.

[Organic solvent]
The pressure-sensitive adhesive composition of the present invention may contain an organic solvent, for example, from the viewpoint of improving coatability.
Examples of the organic solvent include those similar to those used in the polymerization reaction of the specific (meth)acrylic copolymer described above.

When the pressure-sensitive adhesive composition of the present invention contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types.

When the pressure-sensitive adhesive composition of the present invention contains an organic solvent, the content of the organic solvent is not particularly limited, and can be appropriately set according to the purpose.

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than the components described above (so-called other components), if necessary, as long as the effects of the present invention are not impaired.
Other components include polymers other than specific (meth)acrylic copolymers, crosslinking catalysts, tackifiers, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers ), and various additives such as antistatic agents.

When the pressure-sensitive adhesive composition of the present invention contains these other components, the content of the other components can be appropriately set within the range in which the effects of the present invention are exhibited.

(Gel fraction)
The pressure-sensitive adhesive composition of the present invention preferably exhibits the following physical properties.
A film with a thickness of 20 μm was formed by blowing air at 100° C. for 1 minute at a wind speed of 3 m / sec on the adhesive composition applied on the temporary support, and the film was placed in an environment with an ambient temperature of 23° C. and 50% RH for 3 times. The gel fraction of the film (so-called adhesive film) when left for a long time is 80% by mass or more.
A gel fraction of 80% by mass or more means that the cross-linking reaction proceeds in a short time. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition having a gel fraction of 80% by mass or more, for example, even if it is cut in a relatively short time after coating, the pressure-sensitive adhesive to the cutting blade Adhesion and sticking between adhesive sheets tend to be difficult to occur.

In this specification, for convenience of explanation, the above gel fraction is also referred to as "gel fraction 3 hours after coating".

The gel fraction after 3 hours from application of the pressure-sensitive adhesive composition of the present invention is more preferably 85% by mass or more, and even more preferably 90% by mass or more.
The upper limit of the gel fraction after 3 hours from the coating of the pressure-sensitive adhesive composition of the present invention is not particularly limited. The following are preferable.

The gel fraction 3 hours after the application of the pressure-sensitive adhesive composition of the present invention is measured using the pressure-sensitive adhesive film. As used herein, the "gel fraction of the adhesive film" is the ratio of solvent-insoluble matter measured using ethyl acetate as an extraction solvent.
Specifically, the gel fraction after 3 hours from application of the pressure-sensitive adhesive composition of the present invention is measured according to the following (1) to (4).
(1) About 0.15 g of an adhesive film is attached to a 250-mesh wire mesh (100 mm × 100 mm) whose mass is accurately measured using a precision balance, and the attached adhesive film is placed inside so that the gel content does not leak. Then, fold the wire mesh five times to make a sample. Next, the mass of the sample (that is, the mass of the wire mesh with the adhesive film attached before immersion) is accurately measured using a precision balance.
(2) The obtained sample is immersed in 80 mL of ethyl acetate for 3 days.
(3) A sample is taken out, washed with a small amount of ethyl acetate, and dried at 120° C. for 24 hours. Next, the mass of the sample after drying (that is, the mass of the wire mesh to which the adhesive film is attached and dried after immersion) is accurately measured using a precision balance.
(4) Calculate the gel fraction by the following formula.
Gel fraction (unit: mass%) = (ZX)/(YX) x 100
However, X is the weight of the wire mesh (unit: g), Y is the weight of the wire mesh attached with the adhesive film before immersion (unit: g), and Z is the adhesive film dried after immersion. It is the mass (unit: g) of the attached wire mesh.

[Use of adhesive composition]
Applications of the pressure-sensitive adhesive composition of the present invention are not particularly limited.
The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention not only has excellent adhesion to a substrate, but also adheres to the cutting blade when the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer is cut. Problems such as the sheets sticking together and the pressure-sensitive adhesive layer floating from the substrate hardly occur, and the workability is excellent. Therefore, the pressure-sensitive adhesive composition of the present invention is suitable for use in, for example, attaching a polarizing plate to an adherend via a pressure-sensitive adhesive layer.
Specific uses include the use of attaching a polarizing plate to a liquid crystal cell, the use of attaching a polarizing plate to an optical film such as a retardation film, and the like.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention includes a substrate and a pressure-sensitive adhesive layer provided on the substrate and formed from the above-described pressure-sensitive adhesive composition of the present invention.
Since the pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, it has excellent adhesion to a substrate. In addition, since the pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive adheres to the cutting blade during cutting, the pressure-sensitive adhesive sheets stick to each other, and the base material Problems such as separation of the pressure-sensitive adhesive layer from the surface are unlikely to occur, and workability is excellent.

The substrate is not particularly limited as long as the adhesive layer can be formed on the substrate.
Examples of base materials include polyester-based resins, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, acrylic-based resins, vinyl chloride-based resins, ABS resins, Films containing resins such as fluorine-based resins can be used.

The substrate may contain various additives such as plasticizers, colorants (eg, dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, and the like.
The substrate may be partially or wholly patterned.

The substrate is preferably a polarizing plate.
The polarizing plate in the present invention includes at least a polarizer, and may be a single polarizer or a laminate of a polarizer and a protective film.
That is, the polarizing plate may have a one-layer structure with a polarizer alone, a two-layer structure with a protective film on one side of the polarizer, or a three-layer structure with protective films on both sides of the polarizer. There may be.

When the substrate is a polarizing plate, the layer structure of the pressure-sensitive adhesive sheet of the present invention is, for example, pressure-sensitive adhesive layer/polarizer, pressure-sensitive adhesive layer/polarizer/protective film, pressure-sensitive adhesive layer/protective film/polarizer/protective. films, and adhesive layers/protective films/polarizers.
Between the polarizer and the protective film, between the protective film and the pressure-sensitive adhesive layer, and between the polarizer and the pressure-sensitive adhesive layer, a retardation film (e.g., an optical functional layer represented by an EWV layer, It may have layers such as an adhesive layer and an easy-adhesion layer).

Polarizers include, for example, polyvinyl alcohol (PVA) films.

Protective films include, for example, triacetylcellulose (TAC) films, polycycloolefin (COP) films, polyethylene terephthalate (PET) films, and acrylic films.

The thickness of the substrate is generally 500 μm or less, preferably 300 μm or less, more preferably 200 μm or less.
The lower limit of the thickness of the substrate is not particularly limited, and is preferably 30 μm or more, for example.

The pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition of the present invention and includes a crosslinked product of the pressure-sensitive adhesive composition.
A method for forming the pressure-sensitive adhesive layer is not particularly limited, and a commonly used method can be employed.
As a method for forming the pressure-sensitive adhesive layer on the substrate, for example, the following method can be adopted.
The pressure-sensitive adhesive composition of the present invention is applied on a substrate as it is or after being diluted with a solvent as necessary to form a coating film on the substrate. Next, the formed coating film is dried to remove the solvent, and then cured to form an adhesive layer on the substrate.

The exposed surface of the pressure-sensitive adhesive layer may be protected with a release film.
The release film is not particularly limited as long as it can be easily separated from the surface of the pressure-sensitive adhesive layer. .
Examples of resin films include polyester films typified by polyethylene terephthalate (PET) films.
Examples of release agents include fluorine-based resins, paraffin waxes, silicones, long-chain alkyl group compounds, and the like.
The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put to practical use, and is peeled off during use.

As another method for forming a pressure-sensitive adhesive layer on a substrate, for example, the following method can be adopted.
The pressure-sensitive adhesive composition of the present invention is applied as it is or, if necessary, diluted with a solvent, onto the surface-treated surface of the release film to form a coating film on the release film. do. Next, the formed coating film is dried to remove the solvent. Next, the surface of the release film on which the adhesive layer is formed is brought into contact with the substrate and pressed to transfer the adhesive layer to the substrate, thereby forming the adhesive layer on the substrate. Next, curing is performed.

The method of applying the pressure-sensitive adhesive composition onto the substrate or release film is not particularly limited. A known method using a coater, an applicator, or the like can be mentioned.
The amount of the pressure-sensitive adhesive composition to be applied onto the substrate or release film is appropriately set according to the thickness of the pressure-sensitive adhesive layer to be formed.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be appropriately set according to, for example, the types of substrate and adherend, the surface roughness of the substrate and adherend, and the like.
The thickness of the adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm.

The method for drying the coating film formed on the substrate or the release film is not particularly limited, and examples thereof include natural drying, heat drying, hot air drying, vacuum drying and the like.
The drying temperature and drying time of the coating film are not particularly limited, and are appropriately set according to the thickness of the coating film, the amount of the organic solvent in the coating film, and the like.

Curing is performed, for example, in an environment of 20° C. to 40° C. for 24 hours to 168 hours.
Curing completes the cross-linking reaction of the adhesive composition to form an adhesive layer.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples. The present invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

[Production of (meth)acrylic copolymer]
(Production Example A-1)
Into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 97.5 parts by mass of n-butyl acrylate (n-BA; acrylic acid alkyl ester monomer), 2-hydroxylethyl acrylate (2HEA; a monomer having a hydroxyl group) 0.5 parts by mass, acrylic acid (AA; a monomer having a carboxyl group) 2.0 parts by mass, and 70.0 parts by mass of ethyl acetate were added and mixed to form a mixture. After obtaining, the inside of the reactor was replaced with nitrogen.
Then, the mixture in the reactor was heated to 70° C. while stirring, and then 0.02 parts by mass of 2,2′-azobis(2,4-dimethylvaleronitrile) (ABVN; polymerization initiator) and ethyl acetate. 120.0 parts by mass were successively added, and the mixture was maintained for 6 hours for polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 18.5% by mass, and then cooled to obtain a solution of (meth)acrylic copolymer A-1.

The term "solid content concentration" as used herein means the mass proportion of the (meth)acrylic copolymer A-1 in the solution of the (meth)acrylic copolymer A-1. The same applies to each solution of (meth)acrylic copolymers A-2 to A-15 below.

(Production Examples A-2 to A-5, A-7 to A-11, and A-13 to A-15)
In Production Examples A-2 to A-5, A-7 to A-11, and A-13 to A-15, the monomer composition of the (meth)acrylic copolymer is shown in Table 1. (Meth)acrylic copolymers A-2 to A-5 and A-7 to which the solid content concentration is 18.5% by mass are performed in the same manner as in Production Example A-1, except that they are changed to Solutions of A-11 and A-13 to A-15 were obtained.

(Production Example A-6)
In a reactor equipped with a thermometer, stirrer, and reflux condenser, 32.5 parts by mass of n-butyl acrylate (n-BA; acrylic acid alkyl ester monomer), 2-hydroxyl ethyl acrylate (2HEA; hydroxyl group ), 0.67 parts by mass of acrylic acid (AA; monomer having a carboxyl group), and 60.0 parts by mass of ethyl acetate were added and mixed to obtain a mixture.
Then, after heating the mixture in the reactor to 95° C. while stirring, 65.0 parts by mass of n-butyl acrylate (n-BA), 0.33 parts by mass of 2-hydroxylethyl acrylate (2HEA), 1.33 parts by mass of acrylic acid (AA), 86.0 parts by mass of ethyl acetate, 2,2′-azobis(2,4-dimethylvaleronitrile) (ABVN; polymerization initiator) 0.09 parts by mass, was added successively and maintained for 5 hours for polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 38.0% by mass, and then cooled to obtain a solution of (meth)acrylic copolymer A-6.

(Production Example A-12)
In Production Example A-12, by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used, the weight average molecular weight (Mw) of the (meth)acrylic copolymer was reduced to the weight shown in Table 1. Except for changing the average molecular weight (Mw), the same operation as in Production Example A-6 was performed to obtain a solution of (meth)acrylic copolymer A-12 having a solid content concentration of 38.0% by mass. rice field.

(Meth)acrylic copolymers A-1 to A-15 monomer composition (unit: % by mass) and weight-average molecular weight [Mw, unit: 10,000 (indicated as “×10 ⁴ ” in the table)] are shown in Table 1.
The weight average molecular weight (Mw) of the (meth)acrylic copolymers A-1 to A-15 is determined by the same method as the method for measuring the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer described above. Measured by

Details of each monomer listed in Table 1 are as shown below.
"n-BA": n-butyl acrylate (acrylic acid alkyl ester monomer)
"MA": methyl acrylate (acrylic acid alkyl ester monomer)
"PHEA": phenoxyethyl acrylate (other monomers)
"2HEA": 2-hydroxyethyl acrylate (a monomer having a hydroxyl group)
"4HBA": 4-hydroxybutyl acrylate (a monomer having a hydroxyl group)
"AA": acrylic acid (a monomer having a carboxy group)
"M-5300" [trade name, manufactured by Toagosei Co., Ltd.]: ω-carboxy-polycaprolactone (n≈2) monoacrylate (monomer having a carboxy group)

In Table 1, "-" means that the monomer in the corresponding column was not used.
In Table 1, "weight average molecular weight (Mw)" is simply written as "Mw".

[Preparation of adhesive composition]
[Example 1]
100 parts by mass (solid content conversion value) of a solution of (meth)acrylic copolymer A-1 as a (meth)acrylic copolymer, and Coronate (registered trademark) L-45E as a tolylene diisocyanate compound [trade name] , manufactured by Tosoh Corporation] 5 parts by mass (solid content conversion value), and aluminum chelate A as a metal chelate compound [trade name, aluminum tris (acetylacetonate), aluminum content: 8.3% by mass, Kawa Ken Fine Chemical Co., Ltd.] diluted with acetylacetone at a mass ratio of 1: 20 parts by mass (10 parts by mass as a metal chelate compound), and KBM-403 [trade name, Shin-Etsu Chemical Co., Ltd.] as a silane coupling agent Kogyo Co., Ltd.] 0.3 parts by mass and an appropriate amount of ethyl acetate were sufficiently stirred and mixed to obtain a pressure-sensitive adhesive composition of Example 1.

[Examples 2 to 21]
In Example 1, except that the composition of the adhesive composition was changed to the composition shown in Table 2, the same operation as in Example 1 was performed to obtain each adhesive composition of Examples 2 to 21.

[Comparative Examples 1 to 9]
In Example 1, except that the composition of the adhesive composition was changed to the composition shown in Table 3, the same operation as in Example 1 was performed to obtain adhesive compositions of Comparative Examples 1 to 9.

Composition of each pressure-sensitive adhesive composition of Examples 1 to 21 (unit: parts by mass), and tolylene diisocyanate system for hydroxyl groups in the (meth)acrylic copolymer in each pressure-sensitive adhesive composition of Examples 1 to 21 Table 2 shows the equivalent ratio of isocyanate groups in the compounds.
The composition of each pressure-sensitive adhesive composition of Comparative Examples 1-9 (unit: parts by mass), and the hydroxyl group in the (meth)acrylic copolymer in each of the pressure-sensitive adhesive compositions of Comparative Examples 1-3, 5, and 7 Table 3 shows the equivalent ratio of the isocyanate group in the tolylene diisocyanate compound to the

The equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the (meth)acrylic copolymer in the pressure-sensitive adhesive composition was calculated using the aforementioned formulas (1) to (3). be.

For example, the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the (meth)acrylic copolymer in the adhesive composition of Example 1 was specifically calculated as follows.
In addition, Coronate (registered trademark) L-45E, which is a tolylene diisocyanate compound, has a solid content of 45% by mass (i.e., 0.45) and an isocyanate group content of 7.9% by mass (i.e., 0 .079). The formula weight of the isocyanate group is 42, and the compounding amount (in terms of solid content) of Coronate (registered trademark) L-45E is 5 g.
The molecular weight of 2-hydroxyethyl acrylate (2HEA), which is a monomer having a hydroxyl group, is 116.

Formula (1)
NCO amount (unit: mmol/solid content 100 g)
= [Isocyanate group content in the tolylene diisocyanate compound (unit: mass%) × [mixture amount of tolylene diisocyanate compound (solid content equivalent, unit: g) / solid content of tolylene diisocyanate compound ( Unit: mass %)]] / formula weight of isocyanate group (unit: g / mol) × 1000
= [0.079 x [5/0.45]]/42 x 1000
= 20.90

Formula (2)
OH amount (unit: mmol/solid content 100 g)
= [content of structural units derived from monomers having hydroxyl groups in the specific (meth)acrylic copolymer (units: % by mass) / molecular weight of monomers having hydroxyl groups (units: g/mol) × Number of hydroxyl groups in a structural unit derived from a monomer having a hydroxyl group (valence) × 1000]
= [0.5 (parts by mass) / 100 (parts by mass) × 100 (%) / 116 (g / mol) × 1 × 1000]
= 4.31

Formula (3)
Equivalent ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the (meth)acrylic copolymer = NCO amount/OH amount = 20.90/4.31
= 4.85

In Tables 2 and 3, "-" in the "composition of adhesive composition" column means that the corresponding component is not included.
In Tables 2 and 3, "-" in the column "equivalent ratio of isocyanate groups in the tolylene diisocyanate compound to hydroxyl groups in the (meth)acrylic copolymer" means that there is no corresponding value. .

Details of the components listed in Tables 2 and 3 are as follows.
[Crosslinking agent]
<TDI (tolylene diisocyanate)>
"Coronate L-45E" [trade name, manufactured by Tosoh Corporation]: adduct of TDI and trimethylolpropane (TMP) (so-called adduct of TDI), solid content: 45% by mass, isocyanate group content : 7.9% by mass
"Coronate 2030" [trade name, manufactured by Tosoh Corporation]: isocyanate nurate form of TDI, solid content: 50% by mass, content of isocyanate group: 8.0% by mass
<XDI (xylylene diisocyanate)>
“Takenate D-110N” [trade name, manufactured by Mitsui Chemicals, Inc.]: an adduct of XDI and trimethylolpropane (TMP) (so-called XDI adduct), solid content: 75% by mass
<HMDI (hexamethylene diisocyanate)>
"Sumidule N-75" [trade name, manufactured by Sumika Covestro Urethane Co., Ltd.]: Bullet body of HMDI, solid content: 75% by mass
<Metal chelate compound>
"Aluminum chelate A" [trade name, manufactured by Kawaken Fine Chemicals Co., Ltd.]

"Coronate", "Takenate" and "Sumidule" are all registered trademarks.

〔Silane coupling agent〕
"KBM-403" [trade name, manufactured by Shin-Etsu Chemical Co., Ltd.]: 3-glycidoxypropyltriethoxysilane, epoxy group-containing silane compound, solid content: 100% by mass
"X-41-1053" [trade name, manufactured by Shin-Etsu Chemical Co., Ltd.]: epoxy group-containing silane compound, solid content: 100% by mass
"KBM-9659" [trade name, manufactured by Shin-Etsu Chemical Co., Ltd.]: tris-(trimethoxysilylpropyl) isocyanurate, solid content: 100% by mass

[Measurement of gel fraction 3 hours after coating]
For each adhesive composition of Examples 1 to 21 and Comparative Examples 1 to 5, 7 and 8, the gel fraction after 3 hours from coating was measured by the method shown below. Table 4 shows the results.
The adhesive compositions of Comparative Examples 6 and 9 both gelled and could not be coated, so the gel fraction could not be measured.

[Preparation of sample for gel fraction measurement]
(Example 1)
A pressure-sensitive adhesive composition is applied to a thickness of about 110 μm on the surface-treated surface of a release film [type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation] that has been surface-treated with a silicone release agent. to form a coating film.
Next, air at 100° C. was blown to the formed coating film using a hot air circulation dryer for 1 minute at a wind speed of 3 m/sec to form a film X with a thickness of 20 μm.
Then, the formed film X was left for 3 hours in an environment with an ambient temperature of 23° C. and 50% RH to obtain a laminate having a structure of release film/adhesive film.
Then, the release film of the laminate was peeled off, and the resulting adhesive film was used as a sample for gel fraction measurement.

(Examples 2 to 21 and Comparative Examples 1 to 5, 7, and 8)
A laminate having a release film/adhesive film configuration was obtained in the same manner as in Example 1, except that the coating amount of the adhesive composition was appropriately changed so that the thickness of the film X was 20 μm. rice field.
Then, the release film of the laminate was peeled off, and the resulting adhesive film was used as a sample for gel fraction measurement.

[Gel fraction measurement]
Using the sample for gel fraction measurement (that is, the adhesive film) prepared above, the gel fraction was measured according to the following (1) to (4).
(1) About 0.15 g of an adhesive film is attached to a 250-mesh wire mesh (100 mm × 100 mm) whose mass is accurately measured using a precision balance, and the attached adhesive film is placed inside so that the gel content does not leak. Then, fold the wire mesh five times to make a sample. Next, the mass of the sample (that is, the mass of the wire mesh with the adhesive film attached before immersion) is accurately measured using a precision balance.
(2) The obtained sample is immersed in 80 mL of ethyl acetate for 3 days.
(3) A sample is taken out, washed with a small amount of ethyl acetate, and dried at 120° C. for 24 hours. Next, the mass of the sample after drying (that is, the mass of the wire mesh to which the adhesive film is attached and dried after immersion) is accurately measured using a precision balance.
(4) Calculate the gel fraction by the following formula.
Gel fraction (unit: mass%) = (ZX)/(YX) x 100
However, X is the weight of the wire mesh (unit: g), Y is the weight of the wire mesh attached with the adhesive film before immersion (unit: g), and Z is the adhesive film dried after immersion. It is the mass (unit: g) of the attached wire mesh.

[evaluation]
The adhesive compositions of Examples 1 to 21 and Comparative Examples 1 to 5, 7 and 8 were evaluated as follows. Table 4 shows the results.
The pressure-sensitive adhesive compositions of Comparative Examples 6 and 9 were not evaluated because they gelled and could not be coated.

1. Substrate Adhesion (Preparation of Adhesive Sheet)
A pressure-sensitive adhesive sheet having a polarizing plate as the base material was used for the evaluation of adhesion to the base material.
The pressure-sensitive adhesive composition was applied onto the surface-treated surface of a release film [type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation] that had been surface-treated with a silicone release agent to form a coating film. The amount of the pressure-sensitive adhesive composition applied was such that the thickness of the film Y, which will be described later, was 20 μm.
Next, air of 100° C. was blown to the formed coating film using a hot air circulating dryer at a wind speed of 3 m/sec for 1 minute to form a film Y having a thickness of 20 μm.
Next, the exposed surface of the formed film Y and one TAC layer surface of a polarizing plate having a structure of triacetyl cellulose (TAC) layer/polyvinyl alcohol (PVA) layer containing a polarizer/TAC layer are overlapped. After laminating together, it is left for 3 days in an environment with an atmospheric temperature of 35 ° C. and 50% RH, and cured to promote the cross-linking reaction, and the release film / adhesive layer / polarizing plate (TAC layer / PVA layer /TAC layer) was prepared.

(Evaluation test)
The pressure-sensitive adhesive sheet prepared above was cut into a size of 25 mm×75 mm (long side).
Next, the release film of the cut pressure-sensitive adhesive sheet is peeled off, and the surface of the pressure-sensitive adhesive layer exposed by peeling and soda glass as an adherend [manufactured by Matsunami Glass Industry Co., Ltd.; hereinafter simply referred to as "glass". ] and , were laminated together, and then pressure-bonded using a laminator to produce a laminate.
Next, the produced laminate was subjected to autoclave treatment (temperature: 50°C, pressure: 5 kg/cm ² , treatment time: 20 minutes), and then left in an environment with an ambient temperature of 50°C for 96 hours.
After the standing time had passed, 180° peeling was performed at a peeling speed of 300 mm/min in an environment with an ambient temperature of 23°C. Then, the surface of the glass and the surface of the peeled pressure-sensitive adhesive layer were visually observed, and the adhesiveness to the substrate was evaluated according to the following evaluation criteria. Table 4 shows the evaluation results.
If the evaluation result was "A" or "B", it was judged that there was no practical problem.

-Evaluation criteria-
A: The adhesive layer was not transferred to the surface of the glass at all.
B: The adhesive layer was slightly transferred to the surface of the glass, but within the allowable range.
C: The adhesive layer was clearly transferred to the surface of the glass.

2. Workability 2-1. Adhesion of adhesive to the cutting blade and sticking of adhesive sheets to each other (production of adhesive sheets)
A pressure-sensitive adhesive sheet having a polyethylene terephthalate (PET) film as a base material was used for evaluation of processability based on the adhesion of the pressure-sensitive adhesive to the cutting blade and the sticking of the pressure-sensitive adhesive sheets to each other.
The pressure-sensitive adhesive composition was applied onto the surface-treated surface of a release film [type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation] that had been surface-treated with a silicone release agent to form a coating film. The amount of the adhesive composition applied was such that the thickness of the film Z, which will be described later, was 20 μm.
Next, air at 100° C. was blown to the formed coating film for 1 minute at a wind speed of 3 m/sec using a hot air circulating dryer to form a film Z with a thickness of 20 μm.
Next, in an environment of an ambient temperature of 23° C. and 50% RH, the exposed surface of the film Z and the surface of the base material (PET film, thickness: 50 μm) are overlapped and bonded together, and crimped using a laminator. A laminate having a configuration of "substrate/membrane Z/release film" was produced.
Next, the produced laminate is left in an environment with an atmospheric temperature of 23° C. and 50% RH for 3 hours after coating (that is, formation of film Z), and the structure of “base material/adhesive film/release film” is changed. A pressure-sensitive adhesive sheet having

(Evaluation test)
After stacking five pressure-sensitive adhesive sheets prepared above, they were cut.
After cutting, the cutting blade and the adhesive sheet were visually observed to confirm the presence or absence and degree of adhesion of the adhesive to the cutting blade, and the presence or absence and degree of sticking between the adhesive sheets. Then, the workability was evaluated based on the adhesion of the adhesive to the cutting blade and the sticking of the adhesive sheets to each other according to the following evaluation criteria. Table 4 shows the evaluation results.
If the evaluation result was "A", "B", or "C", it was judged that there was no practical problem.

-Evaluation criteria-
A: Adhesion of the adhesive to the cutting blade and sticking of the adhesive sheets to each other were not observed at all.
B: Adhesion of the adhesive to the cutting blade was slightly confirmed, but sticking of the adhesive sheets to each other was not confirmed at all.
C: Adhesion of the adhesive to the cutting blade and sticking of the adhesive sheets to each other were slightly observed, but both were within the allowable range.
D: Remarkable adhesion of the adhesive to the cutting blade and adhesion of the adhesive sheets to each other were observed.

2-2. Lifting of adhesive layer by cutting (production of adhesive sheet)
A pressure-sensitive adhesive sheet having a polarizing plate as a base material was used for the evaluation of workability based on lifting of the pressure-sensitive adhesive layer by cutting. The pressure-sensitive adhesive sheet was prepared in the same manner as in the preparation of the pressure-sensitive adhesive sheet in "1. Adhesion to substrate".

(Evaluation test)
The pressure-sensitive adhesive sheet prepared above was cut.
After cutting, the interface between the polarizing plate and the adhesive layer at the edge of the adhesive sheet and the cut surface of the adhesive layer are observed to determine the presence and degree of floating of the adhesive layer, and the cut surface of the adhesive layer. The presence or absence of unevenness was confirmed. Then, according to the following evaluation criteria, workability was evaluated based on lifting of the pressure-sensitive adhesive layer due to cutting. Table 4 shows the evaluation results.
If the evaluation result was "A", "B", or "C", it was judged that there was no practical problem.
The cut surface of the pressure-sensitive adhesive layer may be observed to be uneven due to the impact of cutting.

-Evaluation criteria-
A: No lifting of the pressure-sensitive adhesive layer was observed at all, and no unevenness was observed on the cut surface of the pressure-sensitive adhesive layer.
B: No lifting of the pressure-sensitive adhesive layer was observed, but irregularities were observed on the cut surface of the pressure-sensitive adhesive layer.
C: Slight lifting of the pressure-sensitive adhesive layer was confirmed, but within the allowable range.
D: Clear lifting of the pressure-sensitive adhesive layer was confirmed.

As shown in Table 4, the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 21 were all excellent in both substrate adhesion and workability.
Moreover, it was confirmed that the adhesive layers formed from the adhesive compositions of Examples 1 to 21 all had a high gel fraction 3 hours after coating, and the cross-linking reaction proceeded in a short time. In particular, the adhesive compositions of Examples 1 to 17 and 19 to 21 have a gel fraction of 80% by mass or more after 3 hours from coating, and are adhesive compositions that can be cut in a short time after coating. , and according to the adhesive compositions of Examples 1 to 17 and 19 to 21, a significant improvement in workability can be expected.

On the other hand, in the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 1, in which the content of the metal chelate compound is less than 5 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer, the pressure-sensitive adhesive Remarkable adhesion to the cutting blade and sticking of the adhesive sheets to each other were confirmed, indicating poor workability.
In the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 2, in which the content of the metal chelate compound exceeds 18 parts by mass with respect to 100 parts by mass of the (meth)acrylic copolymer, the pressure-sensitive adhesive layer by cutting Clear floating was confirmed, and it turned out that it is inferior to workability.
The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 3, in which the equivalent ratio of the isocyanate groups in the tolylene diisocyanate-based compound to the hydroxyl groups in the (meth)acrylic copolymer is less than 1.00, It was found that the adhesion was poor.
It was found that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 4, which did not contain a tolylene diisocyanate-based compound, had poor adhesion to a substrate.
In the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 5, which does not contain a metal chelate compound, adhesion of the pressure-sensitive adhesive to the cutting blade and adhesion of the pressure-sensitive adhesive sheets to each other were remarkably confirmed, and workability was poor. I found out. In addition, it was confirmed that the pressure-sensitive adhesive composition of Comparative Example 5 had a gel fraction of 3% by mass after 3 hours of application, which was remarkably low.
It was found that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 7, in which the (meth)acrylic copolymer did not contain a structural unit derived from a monomer having a carboxy group, had poor adhesion to the substrate. rice field. Moreover, in the adhesive layer formed from the adhesive composition of Comparative Example 7, adhesion of the adhesive to the cutting blade and sticking between the adhesive sheets were remarkably confirmed, and it was found that the workability was poor. Furthermore, the pressure-sensitive adhesive composition of Comparative Example 7 had a gel fraction of 2% by mass 3 hours after coating, which was confirmed to be remarkably low.
It was found that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of Comparative Example 8, in which the (meth)acrylic copolymer did not contain a structural unit derived from a monomer having a hydroxyl group, had poor adhesion to the substrate. .

Claims (7)

A (meth)acrylic copolymer containing a structural unit derived from a (meth)acrylic acid alkyl ester monomer, a structural unit derived from a monomer having a carboxy group, and a structural unit derived from a monomer having a hydroxyl group coalescence and
a metal chelate compound;
and a tolylene diisocyanate-based compound,
The content of the metal chelate compound is in the range of 5 parts by mass or more and 18 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic copolymer, and
The equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the (meth)acrylic copolymer is 1.00 or more,
A pressure-sensitive adhesive composition used for polarizing plates . The content of structural units derived from the monomer having a carboxy group in the (meth)acrylic copolymer is 1% by mass or more with respect to the total structural units of the (meth)acrylic copolymer 5 The pressure-sensitive adhesive composition according to claim 1, which is in the range of mass% or less. The content of structural units derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is 0.1% by mass or more with respect to the total structural units of the (meth)acrylic copolymer. The pressure-sensitive adhesive composition according to claim 1 or 2, which is in the range of 3% by mass or less. The adhesive according to any one of claims 1 to 3, wherein the equivalent ratio of the isocyanate groups in the tolylene diisocyanate compound to the hydroxyl groups in the (meth)acrylic copolymer is 10.00 or less. agent composition. A film with a thickness of 20 μm was formed by blowing air at 100° C. for 1 minute at a wind speed of 3 m / sec on the adhesive composition applied on the temporary support, and the film was placed in an environment with an ambient temperature of 23° C. and 50% RH for 3 times. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the film has a gel fraction of 80% by mass or more when left for a long time. A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer provided on the base material and formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5. The pressure-sensitive adhesive sheet according to claim 6, wherein the base material is a polarizing plate.