JP7376400B2 - Adhesive composition and optical member with adhesive layer - Google Patents

Description

The present invention relates to an adhesive composition and an optical member with an adhesive layer.

Many portable electronic devices, such as mobile phones and mobile terminals, incorporate liquid crystal display devices. Generally, a liquid crystal display device includes a liquid crystal cell having a liquid crystal layer sandwiched between two glass substrates, and polarizing plates arranged on both sides of the liquid crystal cell. A liquid crystal cell and a polarizing plate are generally bonded together via an adhesive layer formed of an acrylic adhesive from the viewpoint of ensuring visibility of the liquid crystal display device.
For example, Patent Document 1 discloses an optical adhesive containing 100 parts by weight of an acrylic polymer and 5 to 50 parts by weight of an isocyanate curing agent.

Japanese Patent Application Publication No. 2011-37927

A polarizing plate provided with an adhesive layer (so-called a polarizing plate with an adhesive layer) is sometimes bonded to a liquid crystal cell after being stored for a long period of time (for example, for 6 months; the same applies hereinafter). Therefore, the adhesive layer in a polarizing plate with an adhesive layer is required to have excellent adhesion suitability even after long-term storage. However, in an adhesive layer formed from a so-called hard type adhesive composition that uses a large amount of a polyisocyanate compound as a crosslinking agent, for example, due to the action of a small amount of moisture in the adhesive layer or in the atmosphere, Condensates of water and polyisocyanate compounds may be formed. When this condensation product is formed, the adhesive layer becomes hard, which may cause problems such as deterioration of bubble release properties when bonding a polarizing plate with an adhesive layer to a glass substrate or the like.
Furthermore, in general, when a polarizing plate changes in temperature, stress may be generated as the polarizing plate attempts to contract or expand. If this generated stress is not relieved, stress remains in the adhesive layer. If the stress remaining in the adhesive layer becomes non-uniform, for example, light leakage may occur in a liquid crystal display device, resulting in a white phenomenon, so-called white spots.

In order to realize an adhesive layer that has excellent adhesion suitability even after long-term storage, it is conceivable to prevent the storage modulus (G') of the adhesive layer from increasing excessively over time, for example. On the other hand, as mentioned above, the adhesive layer in a polarizing plate with an adhesive layer is required to have a property that does not easily cause white spots even when exposed to a high temperature environment (for example, 105°C; the same applies hereinafter). However, from the viewpoint of suppressing the occurrence of white spots, it is desirable that the adhesive layer has a storage modulus (G') high enough not to shrink under the stress generated.

The problem to be solved by the present invention is to provide an adhesive composition that has excellent adhesion suitability after long-term storage and can form an adhesive layer with appropriate viscoelasticity immediately after curing and after long-term storage, and An object of the present invention is to provide an optical member with an adhesive layer, which has an adhesive layer that has excellent bonding suitability after storage and has appropriate viscoelasticity immediately after curing and after long-term storage.

Specific means for solving the problem include the following aspects.
<1> A (meth)acrylic copolymer containing a structural unit derived from a (meth)acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group,
a polyisocyanate compound;
A monohydric alcohol compound having 5 to 18 carbon atoms,
The content of the polyisocyanate compound is 6 parts by mass to 30 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer,
An adhesive composition in which the content of the alcohol compound is 0.01 parts by mass to 3 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer.
<2> The content of structural units derived from the monomer having a carboxy group in the (meth)acrylic copolymer is 1% by mass with respect to all structural units of the (meth)acrylic copolymer. The adhesive composition according to <1>, which has a content of ~5% by mass.
<3> The adhesive composition according to <1> or <2>, wherein the (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group.
<4> The content of structural units derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is 0.1 mass by mass with respect to all structural units of the (meth)acrylic copolymer. % to 3% by mass of the adhesive composition according to <3>.
<5> The ratio of the mass content of the alcohol compound to the mass content of the polyisocyanate compound (mass content of the alcohol compound/mass content of the polyisocyanate compound) is 0.04 to 0.15 <1> to The adhesive composition according to any one of <4>.
<6> Optical member;
An adhesive layer provided on the optical member and formed from the adhesive composition according to any one of <1> to <5>;
An optical member with an adhesive layer.

According to the present invention, there is provided an adhesive composition that has excellent adhesion suitability after long-term storage and can form an adhesive layer having appropriate viscoelasticity immediately after curing and after long-term storage; An optical member with a pressure-sensitive adhesive layer is provided, which has a pressure-sensitive adhesive layer that is suitable for bonding and has appropriate viscoelasticity immediately after curing and after long-term storage.

Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not 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, a numerical range indicated using "~" means a range that includes the numerical values listed before and after "~" as the minimum and maximum values, respectively.
In the numerical ranges described step by step in this specification, the upper limit value or lower limit value described in a certain numerical range may be replaced with the upper limit value or lower limit value of another numerical range described step by step. . Moreover, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the value shown in the Examples.
In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.
In this specification, when there are multiple types of substances corresponding to each component, unless otherwise specified, the amount of each component means the total amount of the multiple types of substances.

In the present specification, "(meth)acrylic copolymer" means that the content of structural units derived from a monomer having a (meth)acryloyl group is equal to or less than all structural units [i.e., (meth)acrylic copolymer]. It means a copolymer that accounts for 50% by mass or more of the total structural units of the polymer.

In this specification, "(meth)acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth)acrylate" is a term that includes both "acrylate" and "methacrylate". , "(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 adhesive composition of the present invention comprises a (meth)acrylic copolymer [hereinafter referred to as Also called "specific (meth)acrylic copolymer." ], a polyisocyanate compound, and a monohydric alcohol compound having 5 to 18 carbon atoms [hereinafter also referred to as "specific alcohol compound". ], the content of the polyisocyanate compound is 6 parts by mass to 30 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer, and the content of the specific alcohol compound is ) 0.01 parts by mass to 3 parts by mass per 100 parts by mass of the acrylic copolymer.
According to the adhesive composition of the present invention, it is possible to form an adhesive layer that has excellent adhesion suitability after long-term storage and has appropriate viscoelasticity immediately after curing and after long-term storage.
The reason why the pressure-sensitive adhesive composition of the present invention can exhibit such effects is not clear, but the present inventors speculate as follows. However, the following speculations are not intended to limit the pressure-sensitive adhesive composition of the present invention, but are explained as an example.

The adhesive composition of the present invention contains a relatively large amount of a polyisocyanate compound. When an adhesive layer is formed using an adhesive composition containing a large amount of a polyisocyanate compound, the polyisocyanate compound may interact with a small amount of moisture in the adhesive layer or in the atmosphere during long-term storage. It may react over time and form a hard condensate. When the adhesive layer becomes hard due to the formation of this condensation product, the adhesive force decreases, which may cause a problem that, for example, bubble removal performance is reduced when a polarizing plate with an adhesive layer is bonded to a glass substrate or the like. On the other hand, the adhesive composition of the present invention contains a specific proportion of a monohydric alcohol compound having 5 to 18 carbon atoms (i.e., a specific alcohol compound) in addition to the polyisocyanate compound. By the reaction between the compound and the polyisocyanate compound, the crosslinking reaction between the carboxy group in the specific (meth)acrylic copolymer and the isocyanate group of the polyisocyanate compound is not impaired when forming the adhesive layer. It is considered that the formation of the above-mentioned condensate, which progresses during long-term storage after the formation of the adhesive layer, is appropriately suppressed. Therefore, it is presumed that the adhesive layer formed from the adhesive composition of the present invention has excellent lamination suitability after long-term storage, and has appropriate viscoelasticity immediately after curing and after long-term storage.

In contrast to the adhesive composition of the present invention, the optical adhesive described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2011-37927) is a monohydric alcohol compound having 5 to 18 carbon atoms (i.e., a specific alcohol compound). ), it is thought that when stored for a long period of time, the formed adhesive layer will have poor adhesion strength, debubbling properties, and other problems, resulting in poor adhesion suitability.

[Specific (meth)acrylic copolymer]
The adhesive composition of the present invention comprises a (meth)acrylic copolymer containing a structural unit derived from a (meth)acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group [i.e. specific (meth)acrylic copolymer].
The adhesive composition of the present invention may contain only one type of specific (meth)acrylic copolymer, or may contain two or more types of specific (meth)acrylic copolymer.

<Structural unit derived from (meth)acrylic acid alkyl ester monomer>
The specific (meth)acrylic copolymer contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer.
The structural unit derived from the (meth)acrylic acid alkyl ester monomer contributes to adjusting the adhesive force of the adhesive layer.

As used herein, "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.
Note that the "(meth)acrylic acid alkyl ester monomer" in this specification does not include a (meth)acrylic acid alkyl ester monomer having at least one of a hydroxyl group and a carboxy group.

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 alkyl group preferably has, for example, 1 to 18 carbon atoms, more preferably 1 to 8 carbon atoms, and still more preferably 1 to 4 carbon atoms.

Specific examples of (meth)acrylic acid alkyl ester monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, and s-butyl (meth)acrylate. Acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, Examples include n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.
As the (meth)acrylic acid alkyl ester monomer, at least one selected from n-butyl acrylate and methyl acrylate is preferred, and n-butyl acrylate is more 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 of structural units.

The content of the 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 content of all the structural units of the specific (meth)acrylic copolymer It is preferably 50% by mass or more, more preferably 50% by mass or more and 99% by mass or less, even more preferably 60% by mass or more and 99% by mass or less, and still more preferably 70% by mass or less. It is particularly preferable that the amount is in the range of % or more and 99% by mass or less.
Here, the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic copolymer is 50% of the total structural units of the specific (meth)acrylic copolymer. % by mass or more means that the structural unit derived from the (meth)acrylic acid alkyl ester monomer is contained as the main component of the structural units constituting the specific (meth)acrylic copolymer. do.

<Structural unit derived from a monomer having a carboxy group>
The specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a carboxy group.
When a specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a carboxy group, crosslinking progresses sufficiently immediately after curing, and the adhesive layer tends to have an appropriate elastic modulus. . For this reason, even if the adhesive layer immediately after curing is used for a polarizing plate, white spots tend not to occur when exposed to a high-temperature environment.

As used herein, "a 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, methacrylic acid, crotonic acid , maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [ Examples include ω-carboxy-polycaprolactone (n≈2) monoacrylate] and succinic acid esters [eg, 2-acryloyloxyethyl-succinic acid].
The monomer having a carboxy group is preferably at least one selected from acrylic acid and ω-carboxy-polycaprolactone monoacrylate, and acrylic acid is more preferred.

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 of structural units.

The content of the structural units derived from the monomer having a carboxy group in the specific (meth)acrylic copolymer is not particularly limited, but for example, the content of the structural units derived from the monomer having a carboxy group is, for example, relative to all the structural units of the specific (meth)acrylic copolymer. , preferably 0.5% to 7% by weight, more preferably 1% to 5% by weight, and even more preferably 2% to 4% by weight.
The content of structural units derived from a monomer having a carboxy group in the specified (meth)acrylic copolymer is 0.5% by mass or more based on the total structural units of the specified (meth)acrylic copolymer. If there is, crosslinking will proceed sufficiently immediately after curing, and the adhesive layer will tend to have a more appropriate modulus of elasticity. For this reason, even if the adhesive layer immediately after curing is used for a polarizing plate, white spots tend to be less likely to occur when exposed to a high temperature environment.
The content of structural units derived from a monomer having a carboxy group in the specified (meth)acrylic copolymer is 7% by mass or less based on the total structural units of the specified (meth)acrylic copolymer. , the adhesive layer tends to have better bonding suitability after long-term storage. For example, the pressure-sensitive adhesive layer after long-term storage tends to exhibit higher adhesive strength and has better bubble removal properties when bonded to an adherend.

<Structural unit derived from a monomer having a hydroxyl group>
It is preferable that the specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group.
When the specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group, the adhesive layer tends to have more appropriate viscoelasticity immediately after curing and after long-term storage. Therefore, even if the pressure-sensitive adhesive layer is used immediately after curing or after long-term storage in polarizing plate applications, white spots tend to be less likely to occur when exposed to a high-temperature environment.

As used herein, "a 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 monomer having a hydroxyl group is not particularly limited.
Specific examples of monomers having hydroxyl groups include 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxypropyl (meth)acrylate. 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, N-hydroxyethyl (meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono( Examples include meth)acrylates.
The monomer having a hydroxyl group is preferably a hydroxyalkyl (meth)acrylate, more preferably a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group having 1 to 5 carbon atoms, and a hydroxyalkyl group having 2 to 4 carbon atoms. Hydroxyalkyl (meth)acrylate having the following is more preferred, and at least one selected from 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is particularly preferred.

When the specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group, it may contain only one type of structural unit derived from a monomer having a hydroxyl group, or it may contain two or more types of structural units derived from a monomer having a hydroxyl group. May contain.

When the specified (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group, the content of the structural unit derived from a monomer having a hydroxyl group in the specified (meth)acrylic copolymer is Although not particularly limited, for example, it is preferably 0.05% by mass to 5% by mass, and 0.1% to 3% by mass, based on the total constitutional units of the specific (meth)acrylic copolymer. It is more preferable that the amount is 0.3% by mass to 2% by mass.
The content of structural units derived from a monomer having a hydroxyl group in the specified (meth)acrylic copolymer is 0.05% by mass or more based on the total structural units of the specified (meth)acrylic copolymer. Then, the adhesive layer immediately after curing and after long-term storage tends to have more appropriate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer is used immediately after curing or after long-term storage in polarizing plate applications, white spots tend to be less likely to occur when exposed to a high-temperature environment.
The content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 5% by mass or less based on the total structural units of the specific (meth)acrylic copolymer, The adhesive layer tends to have better bonding suitability after long-term storage. For example, the pressure-sensitive adhesive layer after long-term storage tends to exhibit higher adhesive strength and has better bubble removal properties when bonded to an adherend.

<Other constituent units>
The specific (meth)acrylic copolymer may contain structural units other than the above-mentioned structural units (so-called other structural units) within a range that does not impair the effects of the present invention.

Examples of monomers constituting other structural units (hereinafter also referred to as "other monomers") include aromatic rings such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate. (meth)acrylate, alkoxyalkyl (meth)acrylate represented by methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl represented by vinyltoluene, vinyl cyanide represented by acrylonitrile and methacrylonitrile, and vinyl ester represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. Also included are various derivatives of these monomers.

When the specific (meth)acrylic copolymer contains other structural units, it may contain only one type of other structural units, or it may contain two or more types of other structural units.

When the specific (meth)acrylic copolymer contains other structural units, the content of the other structural units in the specific (meth)acrylic copolymer is not particularly limited and can be set as appropriate depending on the purpose. .

<<Weight average molecular weight of specific (meth)acrylic copolymer>>
The weight average molecular weight (Mw; hereinafter the same) of the specific (meth)acrylic copolymer is not particularly limited, but is preferably from 400,000 to 2,500,000, and preferably from 400,000 to 2,300,000. More preferably, it is from 400,000 to 2,000,000, even more preferably from 400,000 to 1,800,000.
When the weight average molecular weight of the specific (meth)acrylic copolymer is 400,000 or more, it tends to be possible to form an adhesive layer that is less likely to foam when exposed to a high temperature environment.
When the weight average molecular weight of the specific (meth)acrylic copolymer is 2.5 million or less, the viscosity of the pressure-sensitive adhesive composition does not become too high, and the pressure-sensitive adhesive composition tends to be coatable more favorably.

The weight average molecular weight of the specific (meth)acrylic copolymer is a value measured by the following method. Specifically, it is measured according to (1) to (3) below.
(1) A solution of the specific (meth)acrylic copolymer is applied to a 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, a sample solution having a solid content concentration of 0.2% by mass is obtained. Note that the "solid content concentration" herein means the mass proportion of the specific (meth)acrylic copolymer in the sample solution.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight of the specific (meth)acrylic copolymer is measured as a standard polystyrene equivalent value under the following conditions.

～Conditions～
Measuring device: High-speed GPC [Model number: HLC-8220 GPC, Tosoh Corporation]
Detector: Differential refractometer (RI) [Incorporated into HLC-8220, Tosoh Corporation]
Column: 4 TSK-GEL GMHXL [Tosoh Corporation] connected in series Column temperature: 40℃
Eluent: Tetrahydrofuran Injection volume of sample solution: 100 μL
Flow rate: 0.8mL/min

The weight average molecular weight of the specific (meth)acrylic copolymer can be adjusted to a 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.

<<Content of specific (meth)acrylic copolymer>>
The content of the specific (meth)acrylic copolymer in the adhesive composition of the present invention is not particularly limited, but is, for example, 75.0% by mass to 94% by mass based on the total solid content in the adhesive composition. It is preferably 3% by mass, more preferably 80.0% by mass to 94.3% by mass, and particularly preferably 80.0% by mass to 90.0% by mass.

[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 can be obtained by polymerizing the monomers described above using known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. It can be manufactured by
As the polymerization method, a solution polymerization method is preferable because the processing steps are relatively simple and can be performed in a short time in preparing the adhesive composition of the present invention after production.

In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as necessary are generally placed in a polymerization tank, and the mixture is stirred at the reflux temperature of the organic solvent in a nitrogen stream. while heating for several hours. In this case, at least a portion of the organic solvent, monomer, polymerization initiator and/or chain transfer agent may be added sequentially.

Examples of the organic solvent used during the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, and glycol ether compounds.
More specifically, the organic solvent used during the polymerization reaction includes benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic hydrocarbon compounds represented by aromatic naphtha, fats represented by n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil. Group-based 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, ketone compounds represented by acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone, as well as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol Examples include glycol ether compounds represented by monoethyl ether and diethylene glycol monobutyl ether.

When producing a specific (meth)acrylic copolymer, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of aromatic hydrocarbon compounds, ester compounds, ketone compounds, etc. From the viewpoints of solubility of the copolymer, ease of polymerization reaction, etc., it is preferable to use ethyl acetate.

At the time of the polymerization reaction, only one kind of organic solvent may be used, or two or more kinds of organic solvents may be used.

Examples of the polymerization initiator include organic peroxides and azo compounds used in common solution polymerization methods.
Examples of organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, and di-2-ethylhexyl peroxydicarbonate. Carbonate, t-butylperoxypivalate, 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 dimethyl 2,2'-azobis(isobutyrate).
When producing a specific (meth)acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and it is particularly preferable to use an azo compound.

At the time of the polymerization reaction, only one kind of polymerization initiator may be used, or two or more kinds of polymerization initiators may be used.

The amount of the polymerization initiator used is not particularly limited, and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

When producing the specific (meth)acrylic copolymer, a chain transfer agent may be used as necessary.
Examples of chain transfer agents include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, and fluorene. , and aromatic compounds represented by 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds represented by p-nitrotoluene, benzoquinone, and Benzoquinone derivatives represented by 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane , tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and halogenated hydrocarbon compounds represented by 3-chloro-1-propene, aldehyde compounds represented by chloral and furaldehyde, alkyl having 1 to 18 carbon atoms. Mercaptan compounds, aromatic mercaptan compounds represented by thiophenol 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. Typical examples include terpene compounds.

When a chain transfer agent is used in the production of a specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited. It can be set as appropriate.

The polymerization temperature is not particularly limited, and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[Polyisocyanate compound]
The adhesive composition of the present invention contains a polyisocyanate compound. Further, the content of the polyisocyanate compound in the adhesive composition of the present invention is 6 parts by mass to 30 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer described above.
The polyisocyanate compound is a compound having two or more isocyanate groups in the molecule, and functions as a crosslinking agent in the pressure-sensitive adhesive composition of the present invention.

The polyisocyanate compound is not particularly limited.
Examples of polyisocyanate compounds include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), and pentamethylene diisocyanate (PDI). , isophorone diisocyanate, aliphatic or alicyclic polyisocyanate compounds such as hydrogenated aromatic polyisocyanate compounds, and the like.
In addition, examples of the polyisocyanate compound include a dimer, trimer, or pentamer of the above polyisocyanate compound, an adduct of the above polyisocyanate compound and a polyol compound such as trimethylolpropane, and a biuret form of the above polyisocyanate compound. etc. can also be mentioned.
As the polyisocyanate compound, for example, from the viewpoint of coatability, a tolylene diisocyanate compound is preferable.
As used herein, the term "tolylene diisocyanate compound" refers not only to tolylene diisocyanate (TDI), but also tolylene diisocyanate multimers (e.g., dimers, trimers, or pentamers), tolylene diisocyanate, and tolylene diisocyanate. This includes adducts with polyol compounds, biuret forms of tolylene diisocyanate, and the like.

Commercially available products can be used as the polyisocyanate compound.
Examples of commercially available polyisocyanate compounds include "Coronate (registered trademark) HX,""Coronate (registered trademark) HL-S,""Coronate (registered trademark) L," and "Coronate (registered trademark) L-45E." , “Coronate (registered trademark) 2031,” “Coronate (registered trademark) 2030,” “Coronate (registered trademark) 2234,” “Coronate (registered trademark) 2785,” “Aquanate (registered trademark) 200,” and “Aqua Nate (registered trademark) 210'' [all manufactured by Tosoh Corporation], ``Sumidur (registered trademark) N3300'', ``Desmodule (registered trademark) N3400'', and ``Sumidur (registered trademark) N75'' (all manufactured by Tosoh Corporation). Kacobestrowretan Co., Ltd.], “Duranate (registered trademark) E-405-80T”, “Duranate (registered trademark) AE700-100”, “Duranate (registered trademark) 24A-100”, and “Duranate (registered trademark) ) TSE-100'' [Asahi Kasei Corporation], as well as ``Takenate (registered trademark) D-110N'', ``Takenate (registered trademark) D-120N'', ``Takenate (registered trademark) M-631N'', and ``Takenate (registered trademark) M-631N''. MT-Orestar (registered trademark) NP1200” and “Stabio (registered trademark) XD-340N” [all manufactured by Mitsui Chemicals, Inc.].

The adhesive composition of the present invention may contain only one kind of polyisocyanate compound, or may contain two or more kinds of polyisocyanate compounds.

The content of the polyisocyanate compound in the adhesive composition of the present invention is 6 parts by mass to 30 parts by mass, and 7 parts by mass to 28 parts by mass, based on 100 parts by mass of the specific (meth)acrylic copolymer. The amount is preferably from 8 parts by weight to 25 parts by weight, and even more preferably from 10 parts by weight to 20 parts by weight.
When the content of the polyisocyanate compound in the adhesive composition of the present invention is 6 parts by mass or more based on 100 parts by mass of the specific (meth)acrylic copolymer, the adhesive layer immediately after curing and after long-term storage is , tend to have moderate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer is used for a polarizing plate immediately after curing or after long-term storage, white spots tend not to occur when exposed to a high-temperature environment.
When the content of the polyisocyanate compound in the adhesive composition of the present invention is 30 parts by mass or less based on 100 parts by mass of the specific (meth)acrylic copolymer, the adhesive layer after long-term storage will have an excellent It tends to be suitable for bonding. For example, an adhesive layer after long-term storage exhibits high adhesive strength and tends to have excellent bubble removal properties when bonded to an adherend.

[Specific alcohol compound]
The adhesive composition of the present invention contains a monohydric alcohol compound having 5 to 18 carbon atoms (ie, a specific alcohol compound). Further, the content of the specific alcohol compound in the adhesive composition of the present invention is 0.01 parts by mass to 3 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer described above.

The specific alcohol compound may be a straight chain alcohol compound (so-called straight chain alcohol), an alcohol compound having a branched structure (so-called branched alcohol), or an alcohol compound having a cyclic structure (so-called, cyclic alcohol).
As the specific alcohol compound, for example, straight chain alcohol is preferable from the viewpoint of reactivity with polyisocyanate compounds.

The specific alcohol compound has 5 to 18 carbon atoms, preferably 6 to 16 carbon atoms, more preferably 7 to 14 carbon atoms, and even more preferably 8 to 12 carbon atoms.
When the specific alcohol compound has 5 or more carbon atoms, the adhesive layer tends to have appropriate viscoelasticity immediately after curing and after long-term storage. Therefore, even if the pressure-sensitive adhesive layer is used for a polarizing plate immediately after curing or after long-term storage, white spots tend not to occur when exposed to a high-temperature environment.
When the number of carbon atoms in the specific alcohol compound is 18 or less, the adhesive layer after long-term storage tends to have excellent bonding suitability. For example, an adhesive layer after long-term storage exhibits high adhesive strength and tends to have excellent bubble removal properties when bonded to an adherend.

The boiling point of the specific alcohol compound is not particularly limited, but for example, it is preferably 135°C or higher, more preferably 150°C or higher, from the viewpoint of being less likely to volatilize during application and drying of the adhesive composition. The temperature is preferably 200°C or higher, and more preferably 200°C or higher.
The upper limit of the boiling point of the specific alcohol compound is not particularly limited, but is preferably 250° C. or lower, for example.

Specific examples of specific alcohol compounds include 1-pentanol (carbon number: 5, straight chain alcohol), 1-hexanol (carbon number: 6, straight chain alcohol), 1-heptanol (carbon number: 7, straight chain alcohol) ), 1-octanol (carbon number: 8, straight chain alcohol), 1-nonanol (carbon number: 9, straight chain alcohol), 1-decanol (carbon number: 10, straight chain alcohol), 1-undecanol (carbon number: :11, straight chain alcohol), 1-dodecanol (carbon number: 12, straight chain alcohol), 1-tetradecanol (carbon number: 14, straight chain alcohol), 1-hexadecanol (carbon number: 16, straight chain alcohol) chain alcohol), 1-octadecanol (carbon number: 18, straight chain alcohol), 2-hexanol (carbon number: 6, branched alcohol), benzyl alcohol (carbon number: 7, cyclic alcohol), and texanol (carbon number: :12, branched alcohol).
The specific alcohol compound is preferably at least one selected from the group consisting of 1-pentanol, 1-decanol, and 1-octadecanol, and more preferably 1-decanol.

The adhesive composition of the present invention may contain only one type of specific alcohol compound, or may contain two or more types of specific alcohol compounds.

The content of the specific alcohol compound in the adhesive composition of the present invention is 0.01 parts by mass to 3 parts by mass, and 0.05 parts by mass to 100 parts by mass of the specific (meth)acrylic copolymer. The amount is preferably 3 parts by weight, and more preferably 0.7 parts to 1.5 parts by weight.
When the content of the specific alcohol compound in the adhesive composition of the present invention is 0.01 part by mass or more based on 100 parts by mass of the specific (meth)acrylic copolymer, the adhesive layer after long-term storage will be It tends to have excellent lamination suitability. For example, an adhesive layer after long-term storage exhibits high adhesive strength and tends to have excellent bubble removal properties when bonded to an adherend.
When the content of the specific alcohol compound in the adhesive composition of the present invention is 3 parts by mass or less based on 100 parts by mass of the specific (meth)acrylic copolymer, the adhesive layer immediately after curing and after long-term storage is , tend to have moderate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer is used for a polarizing plate immediately after curing or after long-term storage, white spots tend not to occur when exposed to a high-temperature environment.

The ratio of the mass content of the specific alcohol compound to the mass content of the polyisocyanate compound (the mass content of the specific alcohol compound/the mass content of the polyisocyanate compound) is not particularly limited, but may be, for example, 0.0007 to 0.21. It is preferably from 0.01 to 0.21, even more preferably from 0.04 to 0.15, and particularly preferably from 0.05 to 0.12.
When the ratio of the content mass of the specific alcohol compound to the content mass of the polyisocyanate compound (the content mass of the specific alcohol compound/the content mass of the polyisocyanate compound) is 0.0007 or more, the adhesive layer after long-term storage is better. It tends to have good lamination suitability. For example, a pressure-sensitive adhesive layer after long-term storage tends to exhibit higher adhesive strength and has better bubble removal properties when bonded to an adherend.
When the ratio of the content mass of the specific alcohol compound to the content mass of the polyisocyanate compound (contained mass of the specific alcohol compound/contained mass of the polyisocyanate compound) is 0.21 or less, the adhesive layer immediately after curing and after long-term storage is , tend to have more moderate viscoelasticity. Therefore, even if the pressure-sensitive adhesive layer is used immediately after curing or after long-term storage in polarizing plate applications, white spots tend to be less likely to occur when exposed to a high-temperature environment.

〔Silane coupling agent〕
The adhesive composition of the present invention may contain a silane coupling agent.
When the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent, the adhesiveness of the formed pressure-sensitive adhesive layer to glass is improved. Therefore, when the adherend is glass, the adhesive layer tends to exhibit better bonding suitability after long-term storage.

The silane coupling agent is not particularly limited.
Examples of the silane coupling agent include silane compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. - Thiol group-containing silane compounds such as mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane Epoxy group-containing silane compounds represented by, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyl Examples include amino group-containing silane compounds such as dimethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate.

As the silane coupling agent, commercially available products can be used.
Examples of commercially available silane coupling agents include "KBM-403", "X-41-1053", and "KBM-402" (all manufactured by Shin-Etsu Chemical Co., Ltd.).

When the adhesive composition of the present invention contains a silane coupling agent, it may contain only one type of silane coupling agent, or may contain two or more types of silane coupling agent.

When the adhesive composition of the present invention contains a silane coupling agent, the content of the silane coupling agent is not particularly limited, but for example, 0.00 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer. It is preferably from 1 part by weight to 1 part by weight, more preferably from 0.1 part by weight to 0.8 part by weight, even more preferably from 0.1 part by weight to 0.5 part by weight.
When the adhesive composition of the present invention contains a silane coupling agent, and the content of the silane coupling agent is within the above range, when the adherend is glass, the adhesive layer after long-term storage will be They tend to exhibit better bonding suitability.

[Organic solvent]
The adhesive composition of the present invention may contain an organic solvent.
When the adhesive composition of the present invention contains an organic solvent, the coating properties can be improved.
Examples of the organic solvent include those similar to the organic solvents described above, which are used during the polymerization reaction of the specific (meth)acrylic copolymer.
Note that the "organic solvent" in this specification does not include specific alcohol compounds.

When the 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 of organic solvent.

When the 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 depending on the purpose.

[Other ingredients]
The adhesive composition of the present invention may contain components other than those described above (so-called other components), as necessary, within a range that does not impair the effects of the present invention.
Other components include polymers other than the specific (meth)acrylic copolymer, crosslinking catalysts, colorants (for example, dyes and pigments), light stabilizers (for example, ultraviolet absorbers), and the like.

[Application]
The use of the adhesive composition of the present invention is not particularly limited.
The adhesive composition of the present invention can form an adhesive layer having excellent lamination suitability after long-term storage. That is, the adhesive layer formed from the adhesive composition of the present invention exhibits high adhesive strength and excellent bubble release properties even when stored for a long period of time.
Further, the adhesive composition of the present invention can form an adhesive layer having appropriate viscoelasticity both immediately after curing and after long-term storage. Therefore, the adhesive layer formed using the adhesive composition of the present invention causes white spots not only when exposed to a high temperature environment immediately after curing, but also when exposed to a high temperature environment after long-term storage. It's hard to let go.
Since the adhesive composition of the present invention has the above characteristics, it is suitable for use, for example, in adhering an optical member to an adherend (so-called for use in optical members). Specific applications include, for example, applications in which a polarizing plate is attached to a liquid crystal cell (specifically, the glass substrate of a liquid crystal cell), applications in which a polarizing plate is attached to an optical film such as a retardation film, etc. It will be done.

[Optical member with adhesive layer]
The optical member with an adhesive layer of the present invention includes an optical member and an adhesive layer provided on the optical member and formed from the above-described adhesive composition of the present invention. That is, in the optical member with an adhesive layer of the present invention, the optical member and the adhesive layer formed from the adhesive composition of the present invention are laminated.
Since the optical member with an adhesive layer of the present invention includes an adhesive layer formed from the adhesive composition of the present invention, it has excellent bonding suitability after long-term storage. In addition, since the optical member with an adhesive layer of the present invention is provided with an adhesive layer formed from the adhesive composition of the present invention, it is not only exposed to a high temperature environment immediately after curing, but also when exposed to a high temperature environment after long-term storage. Even when exposed to the environment, it is difficult to cause white spots.

The optical member in the optical member with an adhesive layer of the present invention is not particularly limited.
Examples of the optical member include members constituting devices (so-called optical devices) such as image display devices and input devices, and members used in these devices.
Specific examples of optical members include polarizing plates, AG (Anti-Glare) polarizing plates, wave plates, retardation plates including 1/2 and 1/4 wave plates, viewing angle compensation films, optical compensation films, and brightness enhancement. Examples include films, light guide plates, reflective films, antireflection films, transparent conductive films such as ITO (Indium-Tin Oxide) films, prism sheets, lens sheets, and diffusion plates.
Materials for optical components include polyester resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, vinyl chloride resin, and ABS (Acrylonitrile resin). Resins such as Butadiene Styrene resin, fluororesin, etc.

As the optical member in the optical member with an adhesive layer of the present invention, a polarizing plate is preferable.
The polarizing plate is configured to include 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 a protective film on both sides of the polarizer. There may be.
When the optical member in the optical member with an adhesive layer of the present invention is a polarizing plate, the layer structure includes, for example, adhesive layer/polarizer, adhesive layer/polarizer/protective film, adhesive layer/protective film/ Examples include polarizer/protective film and adhesive layer/protective film/polarizer. In addition, between the polarizer and the protective film, between the protective film and the adhesive layer, and between the polarizer and the adhesive layer, a retardation film (for example, an optically functional layer typified by an EWV layer) is provided. , an adhesive layer, and an easily adhesive layer).
Examples of polarizers include polyvinyl alcohol (PVA) films.
Examples of the protective film include triacetyl cellulose (TAC) film, polycycloolefin (COP) film, polyethylene terephthalate (PET) film, and acrylic film.

The exposed adhesive layer in the optical member with an adhesive layer of the present invention may be protected by a release film.
The release film is not particularly limited as long as it can be easily removed from the adhesive layer; for example, a resin film that has been surface-treated with a release agent on one or both sides (so-called easy-release treatment). can be mentioned.
Examples of the resin film include polyester films typified by polyethylene terephthalate (PET) films. Examples of the release agent include fluororesins, paraffin wax, silicones, long-chain alkyl group compounds, and the like.
The release film protects the surface of the adhesive layer until the optical member with the adhesive layer is put into practical use, and is peeled off at the time of use.

The thickness of the adhesive layer in the optical member with an adhesive layer of the present invention is not particularly limited, and can be appropriately set depending on the material, shape, etc. of the adherend.
The thickness of the adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

The optical member with an adhesive layer of the present invention can be produced by a known method.
Examples of the method for producing the optical member with an adhesive layer of the present invention include the following method. A coating film is formed on the release film by applying the adhesive composition of the present invention to the easily peelable surface of the release film. Next, by drying the formed coating film, an adhesive film is formed on the release film. Next, the exposed surface of the formed adhesive film is brought into contact with an optical member and pressurized to transfer the adhesive film to the optical member, thereby forming an adhesive film on the optical member. Next, the formed adhesive film is cured to form an adhesive layer. In the manner described above, an optical member with an adhesive layer of the present invention is obtained.

Another method for producing the optical member with an adhesive layer of the present invention includes, for example, the following method. A coating film is formed on the release film by applying the adhesive composition of the present invention to the easily peelable surface of the release film. Next, by drying the formed coating film, an adhesive film is formed on the release film. Next, the easily peeled surface of a separately prepared release film is placed on the exposed surface of the formed adhesive film and then pressure bonded to produce a double-sided adhesive sheet without a base material. Next, the adhesive film of the produced double-sided adhesive sheet is cured to form an adhesive layer. Next, one of the release films is peeled off, and the exposed adhesive layer is brought into contact with the optical member and pressurized, thereby transferring the adhesive layer to the optical member. In the manner described above, an optical member with an adhesive layer of the present invention is obtained.

Moreover, as another method for producing the optical member with an adhesive layer of the present invention, for example, the following method may be mentioned. A coating film is formed on the optical member by applying the adhesive composition of the present invention to one surface of the optical member. Next, by drying the formed coating film, an adhesive film is formed on the optical member. Next, the formed adhesive film is cured to form an adhesive layer. In the manner described above, an optical member with an adhesive layer of the present invention is obtained.

The method of applying the adhesive composition is not particularly limited.
Examples of methods for applying the adhesive composition include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, knife coater, spray coater, bar coater, applicator, and the like.
The amount of the adhesive composition to be applied is not particularly limited, and is appropriately set, for example, depending on the thickness of the adhesive layer to be formed.

The method of drying the coating film is not particularly limited.
Examples of methods for drying the coating film include methods such as natural drying, heat drying, hot air drying, and vacuum drying.
The drying temperature and drying time of the coating film are not particularly limited, and are appropriately set depending on the thickness of the coating film, the amount of organic solvent in the coating film, and the like.
An example of drying conditions includes drying using a hot air dryer at 70° C. to 120° C. for 30 seconds to 180 seconds.

Curing is performed, for example, for 3 to 7 days at an ambient temperature of 23° C. to 35° C. and 50% RH. By curing, the crosslinking reaction of the adhesive composition is completed and an adhesive layer is formed.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. The present invention is not limited to the following examples unless the scope thereof is exceeded.

[Production of (meth)acrylic copolymer]
[Manufacture example A-1]
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe, and a reflux condenser, 96.5 parts by mass of n-butyl acrylate [n-BA; (meth)acrylic acid alkyl ester monomer], 2- Hydroxyethyl acrylate [2HEA; monomer having a hydroxyl group] 0.5 parts by mass, acrylic acid [AA; monomer having a carboxy group] 3.0 parts by mass, and ethyl acetate [organic solvent] 70.0 parts by mass. were added and mixed to obtain a mixture, and then the inside of the reactor was purged with nitrogen.
Next, the temperature of the mixture in the reactor was raised to 70° C. while stirring, and then 0.2% of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] was added to the mixture in the reactor. 02 parts by mass of ethyl acetate and 120.0 parts by mass of ethyl acetate were successively added thereto and held for 6 hours to cause a polymerization reaction, thereby obtaining 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 a (meth)acrylic copolymer.

The "solid content concentration" herein means the mass proportion of the (meth)acrylic copolymer in the solution of the (meth)acrylic copolymer. The same applies to each solution of the (meth)acrylic copolymer produced in Production Examples A-2 to A-13 shown below.

[Production examples A-2 to A-5 and A-8 to A-13]
In Production Examples A-2 to A-5 and A-8 to A-13, the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 1, and the organic solvent Production Example A- except that the weight average molecular weight of the (meth)acrylic copolymer was adjusted to the weight average molecular weight shown in Table 1 by adjusting at least one of the usage amount of The same operation as in 1 was performed to obtain each solution of a (meth)acrylic copolymer having a solid content concentration of 18.5% by mass.

[Manufacture example A-6]
In Production Example A-6, the weight average molecular weight of the (meth)acrylic copolymer was adjusted to the weight average molecular weight shown in Table 1 by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used. Except for the above, the same operation as in Production Example A-1 was performed to obtain a solution of a (meth)acrylic copolymer having a solid content concentration of 18.5% by mass.

[Manufacture example A-7]
In a reactor equipped with a thermometer, a stirrer, and a reflux condenser, 97.0 parts by mass of n-butyl acrylate [n-BA; (meth)acrylic acid alkyl ester monomer] and acrylic acid [AA; 3.0 parts by mass of a monomer having groups] and 60.0 parts by mass of ethyl acetate [organic solvent] were added and mixed to obtain a mixture.
Next, the temperature of the mixture in the reactor was raised to 95° C. while stirring, and then 0.2% of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] was added to the mixture in the reactor. 1 part by mass and 40.0 parts by mass of ethyl acetate were successively added and held for 5 hours to cause a 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 a (meth)acrylic copolymer.

Monomer composition (unit: mass %) and weight average molecular weight [Mw, unit: 10,000] of the (meth)acrylic copolymers produced in Production Examples A-1 to A-13 ⁴ )] are shown in Table 1.
The weight average molecular weight of the (meth)acrylic copolymers produced in Production Examples A-1 to A-13 was determined by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic copolymer described above. It was measured.

Among the (meth)acrylic copolymers produced in Production Examples A-1 to A-13, the (meth)acrylic copolymers produced in Production Examples A-1 to A-12 are Corresponds to meth)acrylic copolymer.

Details of each monomer listed in Table 1 are as shown below.
<(meth)acrylic acid alkyl ester monomer>
"n-BA": n-butyl acrylate "MA": methyl acrylate <monomer with hydroxyl group>
"2HEA": 2-hydroxyethyl acrylate "4HBA": 4-hydroxybutyl acrylate <monomer having a carboxy group>
"AA": Acrylic acid "M-5300": ω-Carboxy-polycaprolactone (n≒2) monoacrylate <Other monomers>
"PHEA": Phenoxyethyl acrylate

In Table 1, "-" in the monomer composition column means that the monomer corresponding to that column is not included.
In Table 1, "weight average molecular weight" is expressed as "Mw".

[Preparation of adhesive composition]
[Example 1]
540.5 parts by mass (100 parts by mass as solid content) of the (meth)acrylic copolymer solution produced in Production Example A-1 and Coronate (registered trademark) L-45E [trade name, Tri Adduct of diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, Tosoh Corporation] 31.1 parts by mass (14.0 parts by mass as solid content), and a specific alcohol compound 1.0 parts by mass of 1-decanol [carbon number: 10, linear alcohol, boiling point: 233°C, Tokyo Chemical Industry Co., Ltd.] as a silane coupling agent, and KBM-403 [trade name, 3-glycidoxy] as a silane coupling agent. Propyltriethoxysilane, epoxy group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.] 0.3 parts by mass and an appropriate amount of ethyl acetate were thoroughly mixed, A pressure-sensitive adhesive composition was obtained.

[Examples 2 to 26]
In Example 1, the same operation as in Example 1 was performed except that the composition of the adhesive composition was changed to the composition shown in Table 2, and each adhesive composition of Examples 2 to 26 was obtained.

[Comparative Examples 1 to 8]
In Example 1, the same operation as in Example 1 was performed except that the composition of the adhesive composition was changed to the composition shown in Table 3, and each adhesive composition of Comparative Examples 1 to 8 was obtained.

In Tables 2 and 3, the "-" in the composition column means that the component corresponding to that column is not blended.
In Table 2, all numerical values listed in the "parts by mass" column in the column for specific (meth)acrylic copolymer, polyisocyanate compound (X), and silane coupling agent are solid content equivalent values. In addition, in Table 3, the values listed in the "parts by mass" column in the columns for specific (meth)acrylic copolymer, comparative polymer, polyisocyanate compound (X), and silane coupling agent are all solid content. This is a converted value.
In Tables 2 and 3, "Ratio of the content mass of the specific alcohol compound (Y) to the content mass of the polyisocyanate compound (X) [Content mass of the specific alcohol compound (Y)/Content mass of the polyisocyanate compound (X)]" ” was expressed as “content mass ratio (Y)/(X).”
In Table 3, "-" in the column "Contained mass ratio (X)/(Y)" means that there is no corresponding value in that column.

Details of the components listed in Tables 2 and 3 are as shown below.
<Polyisocyanate compound>
"Coronate L-45E" [Product name, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, Tosoh Corporation]
"Coronate 2030" [Product name, isocyanate nurate of tolylene diisocyanate (TDI), solid concentration: 50% by mass, Tosoh Corporation]
"Takenate D-110N" [Product name, adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content concentration: 75% by mass, Mitsui Chemicals, Inc.]
"Sumidur N-75" [Product name, buret of hexamethylene diisocyanate HMDI, solid content concentration: 75% by mass, Sumika Covestrourethane Co., Ltd.]
The above "Coronate", "Takenate", and "Sumidur" are all registered trademarks.

<Alcohol compound>
-Specific alcohol compounds-
"1-Decanol" [Number of carbon atoms: 10, linear alcohol, boiling point: 233°C, Tokyo Chemical Industry Co., Ltd.]
"1-Pentanol" [Number of carbon atoms: 5, linear alcohol, boiling point: 138°C, Fujifilm Wako Pure Chemical Industries, Ltd.]
"1-Octadecanol" [Number of carbon atoms: 18, linear alcohol, boiling point: 210°C, Tokyo Chemical Industry Co., Ltd.]
- Comparative compound -
"1-Butanol" [Number of carbon atoms: 4, linear alcohol, boiling point: 118°C, Mitsubishi Chemical Corporation]
"1-nonadecyl alcohol" [Number of carbon atoms: 19, straight chain alcohol, boiling point: 156°C, Tokyo Chemical Industry Co., Ltd.]
"1,6-hexanediol" [carbon number: 6, dihydric alcohol compound, boiling point: 223°C, Tokyo Chemical Industry Co., Ltd.]

<Silane coupling agent>
"KBM-403" [Product name, 3-glycidoxypropyltriethoxysilane, epoxy group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.]
"X-41-1053" [Product name, epoxy group-containing silane compound, solid content concentration: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.]
"KBM-402" [Product name, 3-glycidoxypropylmethyldiethoxysilane, epoxy group-containing silane compound, solid content concentration: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.]

<Preparation of polarizing plate with adhesive layer>
The 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-based mold release agent to form a coating film. The amount of the adhesive composition applied was such that the thickness of the adhesive film, which will be described later, would be 20 μm. Next, 100° C. air was blown onto the formed coating film at a wind speed of 3 m/sec for 60 seconds using a hot air circulation dryer to form a 20 μm thick adhesive film on the release film. Next, the exposed surface of the formed adhesive film and the surface of one TAC layer of a polarizing plate having the structure of triacetyl cellulose (TAC) layer/polyvinyl alcohol (PVA) layer containing a polarizer/TAC layer are overlapped. After bonding, the adhesive film is left in an environment of 23°C and 50% RH for 7 days to cure the adhesive film, resulting in a release film/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer). A polarizing plate with an adhesive layer having the following structure was produced.

<Preparation of film with adhesive layer>
The 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-based mold release agent to form a coating film. The amount of the adhesive composition applied was such that the thickness of the adhesive film, which will be described later, would be 20 μm.
Next, 100° C. air was blown onto the formed coating film using a hot air circulation dryer at a wind speed of 3 m/sec for 60 seconds to form an adhesive film with a thickness of 20 μm.
Next, the exposed surface of the adhesive film and the surface-treated surface of a separately prepared release film [type: MRF, thickness: 38 μm, Mitsubishi Chemical Corporation] were laminated together, and then the ambient temperature was set at 23°C. By leaving the adhesive film in an environment of 50% RH for 7 days to cure the adhesive film, a film with an adhesive layer having a configuration of release film/adhesive layer/release film was produced.

[evaluation]
1. Bonding Suitability (1) Adhesive Strength Adhesive force was measured as one of the indicators of bonding suitability.
The adhesive layer-coated polarizing plate produced above was left for 6 months in an environment with an ambient temperature of 23° C. and 50% RH. Next, the polarizing plate with the adhesive layer after being left to stand was cut to obtain a test piece A-1 with a size of 25 mm x 75 mm (long side). Next, the release film of the obtained test piece A-1 [composition: release film/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer)] was peeled off, and the surface of the adhesive layer exposed by peeling was , and the surfaces of the adherends listed in Table 4 or Table 5, and then press them using a laminator to form the adherend/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer). A laminate having the following structure was obtained. Next, the obtained laminate was subjected to autoclave treatment (processing temperature: 50°C, processing pressure: 5kg/cm ² , processing time: 20 minutes), and then placed in an environment with an ambient temperature of 23°C and 50% RH. After leaving for 0.5 hour, a test piece A-2 was obtained. Regarding this test piece A-2, when the polarizing plate with the adhesive layer having the configuration of adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer) was peeled 180° in the long side direction from the adherend, Adhesive strength (unit: N/25mm) was measured using a single column material testing machine [model number: STA-1225, A&D Co., Ltd.] as a measuring device, at an ambient temperature of 23°C and 50% RH. Below, measurements were made at a peeling rate of 300 mm/min.
The results are shown in Tables 4 and 5.
If the adhesive strength was 0.7 N/25 mm or more, it was determined that the adhesive layer exhibits high adhesive strength to the adherend even when stored for a long period of time, and the adhesive layer has excellent bonding suitability.
The adhesive force is preferably 0.7 N/25 mm or more, more preferably 1.0 N/25 mm or more, and even more preferably 1.3 N/25 mm or more.

(2) Bubble release after autoclave treatment Bubble release after autoclave treatment was evaluated as one of the indicators of bonding suitability.
The adhesive layer-coated polarizing plate produced above was left for 6 months in an environment with an ambient temperature of 23° C. and 50% RH. Next, the polarizing plate with the adhesive layer after being left to stand was cut to obtain a test piece B-1 with a size of 62 mm x 110 mm. Next, the release film of the obtained test piece B-1 [composition: release film/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer)] was peeled off, and the surface of the adhesive layer exposed by peeling was , and the surfaces of the adherends listed in Table 4 or Table 5, and then press them using a laminator to form the adherend/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer). A laminate having the following structure was obtained. Next, the obtained laminate was subjected to autoclave treatment (processing temperature: 50°C, processing pressure: 5kg/cm ² , processing time: 20 minutes), and then placed in an environment with an ambient temperature of 23°C and 50% RH. After standing for 0.5 hour, a test piece B-2 was obtained. Regarding this test piece B-2, the edges of the polarizing plate were visually observed to see whether or not air bubbles were removed, specifically, the presence and extent of air bubbles was observed. Then, based on the observation results, bubble removal after autoclave treatment (hereinafter also referred to as "after A/C") was evaluated according to the following evaluation criteria.
The results are shown in Tables 4 and 5.
If the evaluation result is "A", "B", or "C", the adhesive layer has excellent bubble release properties when bonded to an adherend, even after long-term storage, and has excellent bonding suitability. It was determined that it was a chemical layer.

-Evaluation criteria-
A: No bubbles were observed at the edges of the polarizing plate.
B: Almost no air bubbles were observed at the edges of the polarizing plate.
C: A few bubbles were observed at the edges of the polarizing plate, but within an acceptable range.
D: Air bubbles were noticeably observed at the edges of the polarizing plate, which was outside the acceptable range.

2. White spots The polarizing plate with the adhesive layer immediately after curing was cut to obtain a test piece C-1 with a size of 62 mm x 110 mm (long side).
Moreover, the polarizing plate with an adhesive layer produced above was left for 6 months in an environment with an ambient temperature of 23° C. and 50% RH. Next, the adhesive layer-coated polarizing plate after being left to stand was cut to obtain a test piece D-1 with a size of 62 mm x 110 mm.
For test piece C-1 and test piece D-1, the release film of the test piece [composition: release film/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer)] was peeled off, and the adhesive exposed by peeling was removed. After overlapping the surfaces of the agent layers on both sides of a twisted nematic (TN) type liquid crystal panel so that the absorption axes of each test piece are perpendicular to each other, they were crimped using a laminator to form the laminate C-1 and the laminate. I got D-1.
Next, the obtained laminate C-1 and laminate D-1 were subjected to autoclave treatment (treatment temperature: 50° C., treatment pressure: 5 kg/cm ² , treatment time: 20 minutes). Next, the laminates after the autoclave treatment were left for 24 hours in an environment with an ambient temperature of 23° C. and 50% RH to obtain a laminate C-2 and a laminate D-2.
Next, the obtained laminate C-2 and laminate D-2 were left in an environment with an ambient temperature of 105° C. for 500 hours to obtain a test piece C-2 and a test piece D-2. Test piece C-2 and test piece D-2 were placed on the backlight of a liquid crystal monitor at an ambient temperature of 23° C. and 50% RH, and the presence or absence and degree of white spots were visually observed. Based on the observation results, white spots were evaluated according to the following evaluation criteria.
The results are shown in Tables 4 and 5.
If the evaluation result was "A", "B", or "C", it was determined that the adhesive layer was unlikely to cause white spots even when exposed to a high temperature environment.

-Evaluation criteria-
A: No white spots were observed.
B: Almost no white spots were observed.
C: Slight white spots were observed, but within an acceptable range.
D: Significant white spots were observed, which was outside the acceptable range.

3. Viscoelasticity Storage modulus (G') was measured as one of the indicators of viscoelasticity.
After peeling off the release film of the film with an adhesive layer immediately after curing to expose the adhesive layer, the adhesive layers are pasted together by folding in two, and the release film/adhesive layer (thickness: 40 μm A laminate having a laminate structure of )/release film was obtained. Next, one release film of the obtained laminate is peeled off to expose the adhesive layer, and then the adhesive layers are bonded together by folding in two, and the release film/adhesive layer (thickness: A laminate having a laminate structure of 80 μm)/release film was obtained. The above operations (peeling off the release film and bonding the adhesive layers together) were repeated until the thickness of the adhesive layer became 500 μm, and the resulting laminate was used as sample E for storage modulus measurement. -1.
Further, the film with the adhesive layer produced above was left for 6 months in an environment with an ambient temperature of 23° C. and 50% RH. Next, the same operation as above was performed on the film with the adhesive layer after being left to stand, and the obtained laminate was designated as sample E-2 for storage modulus measurement.
Using a dynamic viscoelasticity measurement device (product name: Physica MCR301, Anton Paar) as a measurement device, the sample for storage modulus measurement was evaluated at 25°C, cone used: 8mmφ, and measurement gap: 0.6mm. The storage modulus (G') (unit: Pa) was measured for E-1 and E-2 while applying shear stress at a frequency of 1 Hz.
The results are shown in Tables 4 and 5.
If the storage modulus (G') was 1.1×10 ⁵ Pa to 12.0×10 ⁵ Pa, it was determined that the adhesive layer had appropriate viscoelasticity. The storage modulus (G') is preferably 1.1×10 ⁵ Pa to 12.0×10 ⁵ Pa, more preferably 4.0×10 ⁵ Pa to 12.0×10 ⁵ Pa. It is preferably 7.0×10 ⁵ Pa to 12.0×10 ⁵ Pa, and more preferably 7.0×10 5 Pa to 12.0×10 5 Pa.

In Tables 4 and 5, "-" means that the evaluation corresponding to that column has not been performed.
Details of the adherends listed in Tables 4 and 5 are as follows.
"Glass" [soda glass, Matsunami Glass Industry Co., Ltd.]
"BASUS" [Stainless steel plate, product name: SUS304, Paltech Co., Ltd.]
"PET": polyethylene terephthalate film, product name: Teijin (registered trademark) Tetron (registered trademark) film HPE, thickness: 50 μm, Teijin Film Solutions Ltd.

As shown in Table 4, (meth)acrylic copolymers containing structural units derived from (meth)acrylic acid alkyl ester monomers and structural units derived from monomers having a carboxy group [i.e., specific ( meth)acrylic copolymer], a polyisocyanate compound, and a monohydric alcohol compound having 5 to 18 carbon atoms (i.e., a specific alcohol compound), and the content of the polyisocyanate compound is a specific ( The content of the specific alcohol compound is 6 parts by mass to 30 parts by mass based on 100 parts by mass of the meth)acrylic copolymer, and the content of the specific alcohol compound is 0.01 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer. The pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 26 in an amount of 3 parts to 3 parts by mass have high adhesive strength after long-term storage and excellent bubble release after autoclave treatment, and are suitable for long-term storage. It was confirmed that the film had excellent bonding suitability even when In addition, the adhesive layers formed from the adhesive compositions of Examples 1 to 26 had appropriate viscoelasticity both immediately after curing and after long-term storage, and when exposed to high temperature environments. However, it has become clear that it is difficult to cause white spots.

On the other hand, as shown in Table 5, the adhesive composition formed from the adhesive composition of Comparative Example 1 in which the content of the polyisocyanate compound was less than 6 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer. It was confirmed that the storage modulus (G') of the agent layer was extremely low both immediately after curing and after long-term storage, and that white spots were likely to occur when exposed to a high temperature environment.
When the adhesive layer formed of the adhesive composition of Comparative Example 2 in which the content of the polyisocyanate compound exceeds 30 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer, when used after long-term storage, It was confirmed that the adhesive force was excessively low, and bubble removal after autoclave treatment was poor, resulting in poor adhesion suitability.
The adhesive layer formed from the adhesive composition of Comparative Example 3 in which the content of the specific alcohol compound is less than 0.01 parts by mass based on 100 parts by mass of the specific (meth)acrylic copolymer is When used, it was confirmed that the adhesive strength was excessively low, and bubble removal after autoclave treatment was poor, resulting in poor adhesion suitability.
The adhesive layer formed by the adhesive composition of Comparative Example 4 in which the content of the specific alcohol compound exceeds 3 parts by mass per 100 parts by mass of the specific (meth)acrylic copolymer was used immediately after curing and after long-term storage. It was confirmed that in each case, the storage modulus (G') was excessively low and white spots were likely to occur when exposed to a high temperature environment.
Formed by the adhesive composition of Comparative Example 5 containing a (meth)acrylic copolymer that does not contain a structural unit derived from a monomer having a carboxy group instead of the specific (meth)acrylic copolymer. It was confirmed that the adhesive layer had an extremely low storage modulus (G') immediately after curing, and was likely to cause white spots when exposed to a high temperature environment. The reason is considered to be that crosslinking has not progressed sufficiently immediately after curing.
The adhesive layer formed by the adhesive composition of Comparative Example 6 containing a monohydric alcohol compound having less than 5 carbon atoms in place of the specific alcohol compound did not exhibit storage stability either immediately after curing or after long-term storage. It was confirmed that the elastic modulus (G') was excessively low and white spots were likely to occur when exposed to a high temperature environment.
The adhesive layer formed by the adhesive composition of Comparative Example 7 containing a monohydric alcohol compound having more than 18 carbon atoms instead of the specific alcohol compound has excessively low adhesive strength when used after long-term storage. In addition, it was confirmed that bubble removal after autoclave treatment was poor and the suitability for bonding was poor.
The adhesive layer formed by the adhesive composition of Comparative Example 8, which contains a dihydric alcohol compound having 5 to 18 carbon atoms instead of the specific alcohol compound, exhibits excessive adhesive strength when used after long-term storage. It was confirmed that the bonding properties were low, and bubble removal after autoclave treatment was poor, resulting in poor bonding suitability.

Claims (6)

A (meth)acrylic copolymer containing a structural unit derived from a (meth)acrylic acid alkyl ester monomer and a structural unit derived from a monomer having a carboxy group (however, it has a functional group that reacts with an isocyanate group). (Excluding (meth)acrylic copolymers containing structural units derived from nitrogen-containing monomers that do not contain nitrogen-containing monomers.)
a polyisocyanate compound;
A monohydric alcohol compound having 5 to 18 carbon atoms,
The content of the polyisocyanate compound is 6 parts by mass to 30 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer,
A pressure-sensitive adhesive composition in which the content of the alcohol compound is 0.01 parts by mass to 3 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer. The content of structural units derived from the monomer having a carboxy group in the (meth)acrylic copolymer is 1% by mass to 5% by mass based on the total structural units of the (meth)acrylic copolymer. % of the adhesive composition according to claim 1. The adhesive composition according to claim 1 or 2, wherein the (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group. The content of structural units derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is 0.1% by mass to 3% by mass based on the total structural units of the (meth)acrylic copolymer. The pressure-sensitive adhesive composition according to claim 3, which is % by mass. The adhesive composition according to any one of claims 1 to 4, wherein the ratio of the content mass of the alcohol compound to the content mass of the polyisocyanate compound is 0.04 to 0.15. an optical member;
an adhesive layer provided on the optical member and formed from the adhesive composition according to any one of claims 1 to 5;
An optical member with an adhesive layer.