JP2019032508A - Adhesive composition for polarizer and polarizer with adhesive layer - Google Patents

Abstract

To provide an adhesive composition for polarizer capable of forming an adhesive layer superior in reworkability and durability and a polarizer with adhesive layer.SOLUTION: The adhesive composition for polarizer contains a (meth)acrylic copolymer which contains a constituent unit derived from a monomer having a carboxy group and a constituent unit derived from an alkyl (meth) acrylate monomer, the content of the constituent unit derived from a monomer having at least one kind of functional group selected from a group consisting of a carboxy group, a hydroxyl group, and an amino group, a range of 0.2 mass% to 0.8 mass% with respect to all constitutional units and a range of weight average molecular weight of 1.25 million to 2 million and an isocyanate compound. The molar equivalent ratio of the amount of isocyanate group in the isocyanate compound to the total amount of carboxy group, hydroxyl group and amino group in the (meth) acrylic copolymer is in the range of 0.15 to 2.5, and the gel fraction after crosslinking is a range of 40% by mass to 75% by mass. And there is provided an application of the adhesive composition for polarizer.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition for polarizing plates and a polarizing plate with a pressure-sensitive adhesive layer.

  Many portable electronic devices such as cellular phones and portable terminals have a liquid crystal display device incorporated therein. In general, a liquid crystal display device includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two glass substrates, and a polarizing plate disposed on both surfaces 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.

A polarizing plate is usually formed by laminating members having different shrinkage rates. Therefore, warpage of the polarizing plate is caused by changes in temperature and humidity, and bubbles, floats, and peeling may occur at the interface between the polarizing plate and the pressure-sensitive adhesive layer. Further, in the polarizing plate, when temperature and humidity change, stress may be generated in an attempt to contract or expand. If the generated stress is not relaxed, the stress remains in the adhesive layer. If the stress remaining in the pressure-sensitive adhesive layer becomes non-uniform, for example, light leakage may occur in a liquid crystal display device, and so-called white spots may occur. Therefore, the pressure-sensitive adhesive used for laminating the liquid crystal cell and the polarizing plate can suppress foaming, floating, and peeling that can occur when exposed to a high temperature environment or a high temperature and high humidity environment (so-called, Durability) and a property capable of suppressing white spots.
Furthermore, in the bonding between the liquid crystal cell and the polarizing plate, a bonding error may occur. When a bonding mistake occurs, it is necessary to re-bond, and therefore the pressure-sensitive adhesive used for bonding the liquid crystal cell and the polarizing plate is required to have a property of being easily re-bonded, so-called reworkability.

  In response to these requirements, for example, Patent Document 1 discloses a pressure-sensitive adhesive for a polarizing film that can sufficiently prevent the occurrence of peeling, bubbles, and white spots, and is excellent in reworkability and recyclability. As a composition, an acrylic copolymer containing a specific amount of a repeating unit having a carboxy group in the molecule and a repeating unit having a hydroxy group, a specific amount of a polyisocyanate compound, and a specific amount of a silane coupling having a specific structure A pressure-sensitive adhesive composition for a polarizing film containing an agent is disclosed.

By the way, in recent years, there is a tendency to increase the viewing angle of the liquid crystal display device by further providing an EWV (Excellent wide view) layer on the triacetyl cellulose (TAC) layer provided on the surface of the polarizing plate. The EWV layer usually includes a discotic liquid crystal compound.
For example, Patent Document 2 discloses a polarizing plate with an optical compensation film having an adhesive layer containing a (meth) acrylic polymer, an optical compensation film containing a discotic liquid crystal compound, and a polarizer.

JP 2004-224873 A JP 2009-258660 A

In general, the EWV layer has extremely poor adhesion to the pressure-sensitive adhesive layer. Therefore, the pressure-sensitive adhesive layer formed on the surface of the EWV layer, when peeled, is applied to the polarizing plate provided with the EWV layer (hereinafter referred to as “EWV polarizing plate” as appropriate). There is a problem that it is easily transferred to a glass substrate of a liquid crystal cell.
In order to improve the reworkability of the EWV polarizing plate, for example, it is conceivable to increase the amount of the crosslinking agent blended in the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer. When the amount of the cross-linking agent added to the pressure-sensitive adhesive increases, the cross-linking agent that does not contribute to cross-linking interacts with the EWV layer, thereby improving the adhesiveness with the EWV layer, thereby improving reworkability.
On the other hand, when there are too many compounding quantities of the crosslinking agent to an adhesive, the softness | flexibility of an adhesive layer will become low by the improvement of the crosslinking density of the adhesive layer formed. When the flexibility of the pressure-sensitive adhesive layer is low, it cannot sufficiently follow the expansion and contraction of the base material accompanying changes in temperature and humidity, which may lead to a decrease in durability.
As described above, in the pressure-sensitive adhesive used for the EWV polarizing plate, it is difficult to improve both reworkability and durability.

  This invention is made | formed in view of the above situations, and is formed with the adhesive composition for polarizing plates which can form the adhesive layer which is excellent in rework property and durability, and the said adhesive composition for polarizing plates. It is providing a polarizing plate with an adhesive layer provided with the made adhesive layer.

Specific means for solving the problems include the following aspects.
<1> A structural unit derived from a monomer having a carboxy group and a structural unit derived from a (meth) acrylic acid alkyl ester monomer, and at least one selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group The content rate of the structural unit derived from the monomer which has a seed | species functional group is the range of 0.2 mass%-0.8 mass% with respect to all the structural units, and the weight average molecular weight is 1.25 million- The said isocyanate compound with respect to the total amount of the carboxy group in the said (meth) acrylic-type copolymer, a hydroxyl group, and an amino group containing the (meth) acrylic-type copolymer which is the range of 2 million, and an isocyanate compound The molar equivalent ratio of the amount of isocyanate groups in the range is in the range of 0.15 to 2.5, and the gel fraction after crosslinking is in the range of 40% by mass to 75% by mass. .
<2> The pressure-sensitive adhesive composition for a polarizing plate according to <1>, wherein the (meth) acrylic copolymer includes a structural unit derived from a monomer having a hydroxyl group.
<3> The content rate of the structural unit derived from the monomer which has the said carboxy group in the said (meth) acrylic-type copolymer is the range of 0.1 mass%-0.8 mass% with respect to all the structural units. <1> or <2> wherein the pressure-sensitive adhesive composition for a polarizing plate is.
<4> The content rate of the structural unit derived from the said (meth) acrylic-acid alkylester monomer in the said (meth) acrylic-type copolymer is 60 mass%-99.8 mass% with respect to all the structural units. The pressure-sensitive adhesive composition for polarizing plates according to any one of <1> to <3>, which is a range.
<5> Any one of <1> to <4>, in which the content of the (meth) acrylic copolymer is in the range of 50% by mass to 99% by mass with respect to the total solid content of the pressure-sensitive adhesive composition. The adhesive composition for polarizing plates as described in 1.
<6> Furthermore, the weight average molecular weight is in the range of 50,000 to 200,000, and contains a (meth) acrylic polymer that does not have any functional group of carboxy group, hydroxyl group, and amino group < The adhesive composition for polarizing plates as described in any one of 1>-<5>.
<7> Furthermore, the adhesive composition for polarizing plates as described in any one of <1>-<6> containing a silane coupling agent.
<8> Furthermore, the adhesive composition for polarizing plates as described in any one of <1>-<7> containing an epoxy compound.
<9> A polarizing plate, disposed on the surface of the polarizing plate, and a layer having a contact angle with water of 90 ° or more and a surface having a contact angle with water of 90 ° or more. A pressure-sensitive adhesive layer-attached polarizing plate comprising: a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition for a polarizing plate according to any one of <1> to <8>.
<10> The polarizing plate with the pressure-sensitive adhesive layer according to <9>, wherein the layer having a contact angle with water of 90 ° or more is a layer containing a discotic liquid crystal compound.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive composition for polarizing plates which can form the adhesive layer which is excellent in rework property and durability, and polarized light with an adhesive layer provided with the adhesive layer formed with the said adhesive composition for polarizing plates A board is provided.

  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 object of the present invention.

In the present specification, a numerical range indicated using “to” means a range including the numerical values described before and after “to” as a minimum value and a maximum value, respectively.
In the numerical ranges described stepwise in the present specification, the upper limit value or lower limit value described in a numerical range may be replaced with the upper limit value or lower limit value of the numerical range described in other steps. . Further, 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 embodiments is a more preferred embodiment.
In the present specification, the amount of each component means the total amount of the plurality of types of substances unless there is a specific notice when there are a plurality of types of substances corresponding to the respective components.

In the present specification, the “pressure-sensitive adhesive composition” means a liquid or paste-like composition after the (meth) acrylic copolymer and a crosslinking agent (for example, an isocyanate compound) are mixed and before the crosslinking reaction is completed. Means a substance.
In the present specification, the “pressure-sensitive adhesive layer” means a substance after the crosslinking reaction in the pressure-sensitive adhesive composition is completed.
In the present specification, the “adherent” means an object in contact with the pressure-sensitive adhesive layer opposite to the polarizing plate when in use, for example, the pressure-sensitive adhesive composition of the present invention provided with an EWV layer. When used for (ie, an EWV polarizing plate), a glass substrate of a liquid crystal cell can be an adherend.
In this specification, “substrate” refers to, for example, a polarizing plate, and the term “substrate” is used separately from the term “adhered body”.

In this specification, “reworkability” means ease of peeling at the time of reattachment, for example, without peeling the adhesive layer to the adherend (so-called adhesive residue) when peeling from the adherend. This means that re-sticking can be performed, and re-working can be performed more easily as the reworkability is improved.
As used herein, “durable” refers to foaming, floating, and the like that can occur when exposed to high temperature (eg, 95 ° C.) environment or high temperature and high humidity (eg, 65 ° C., 95% RH) environment. A property that can prevent peeling.

  In this specification, “(meth) acrylic copolymer” and “(meth) acrylic polymer” are monomers that are at least a main component among monomers constituting the copolymer and the polymer. Means a copolymer and a polymer which are monomers having a (meth) acryloyl group, respectively. The monomer as the main component here means a monomer having the largest content (unit: mass%) among the monomers constituting the copolymer and the polymer. In an embodiment of the (meth) acrylic copolymer in the present invention, the content of the structural unit derived from the monomer having the (meth) acryloyl group as the main component is 50% by mass or more of the total structural units. .

  In the present specification, “(meth) acryl” is a term including both “acryl” and “methacryl”, “(meth) acrylate” is a term including both “acrylate” and “methacrylate”, “(Meth) acryloyl” is a term encompassing both “acryloyl” and “methacryloyl”.

[Adhesive composition for polarizing plate]
The pressure-sensitive adhesive composition for polarizing plates of the present invention (hereinafter referred to as “pressure-sensitive adhesive composition” as appropriate) is a structural unit derived from a monomer having a carboxy group and a (meth) acrylic acid alkyl ester monomer. A structural unit derived from a monomer having a structural unit derived from and having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group (hereinafter referred to as “specific functional group” as appropriate). (Meth) acrylic copolymer having a content ratio of 0.2 to 0.8% by mass and a weight average molecular weight in the range of 1.25 to 2 million with respect to all the structural units (Hereinafter referred to as “specific (meth) acrylic copolymer” as appropriate) and an isocyanate compound, and the total amount of carboxy group, hydroxyl group, and amino group in the (meth) acrylic copolymer. Against the above The amount of molar equivalent ratio of the isocyanate groups of the isocyanate compound is in the range of 0.15 to 2.5, the gel fraction after crosslinking is in the range of 40 wt% to 75 wt%.

In order to improve the reworkability, for example, it is conceivable to increase the amount of the crosslinking agent blended in the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer. When the amount of the cross-linking agent added to the pressure-sensitive adhesive increases, the cross-linking agent that does not contribute to cross-linking interacts with the base material, thereby improving the adhesiveness with the base material, and thus reworkability can be improved.
On the other hand, when there are too many compounding quantities of the crosslinking agent to an adhesive, the adhesive layer becomes hard by the improvement of the crosslinking density of the adhesive layer formed, ie, the softness | flexibility of an adhesive layer becomes low. When the flexibility of the pressure-sensitive adhesive layer is low, it cannot sufficiently follow the expansion and contraction of the base material accompanying changes in temperature and humidity, which may lead to a decrease in durability.

  On the other hand, the pressure-sensitive adhesive composition of the present invention includes a structural unit derived from a monomer having a carboxy group and a structural unit derived from a (meth) acrylic acid alkyl ester monomer, and includes a carboxy group, a hydroxyl group, and The content of the structural unit derived from the monomer having at least one functional group selected from the group consisting of amino groups is in the range of 0.2 mass% to 0.8 mass% with respect to the total structural units. And the weight average molecular weight of the adhesive layer formed by containing the (meth) acrylic-type copolymer (namely, specific (meth) acrylic-type copolymer) which is the range of 1.25 million-2 million Durability can be improved.

Furthermore, the pressure-sensitive adhesive composition of the present invention contains a specific (meth) acrylic copolymer and an isocyanate compound, and contains a carboxy group, a hydroxyl group, and an amino group in the specific (meth) acrylic copolymer. The molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount is in the range of 0.15 to 2.5, and the gel fraction after crosslinking is in the range of 40 to 75% by mass. Thereby, the durability and reworkability of the pressure-sensitive adhesive layer to be formed can be improved.
From the above, according to the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer excellent in both reworkability and durability can be formed.

  For the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive described in Patent Document 2 (Japanese Patent Laid-Open No. 2009-258660) is composed of a carboxy group, a hydroxyl group, and an amino group in a (meth) acrylic copolymer. Isocyanate with respect to the total amount of carboxy groups, hydroxyl groups, and amino groups in the (meth) acrylic copolymer, although the content of structural units derived from monomers having at least one functional group selected from the group is high Since the molar equivalent ratio of the amount of isocyanate groups in the compound is low, it has been found that sufficient crosslink density cannot be obtained, and the reworkability of the pressure-sensitive adhesive layer to be formed is remarkably inferior (for example, Reference Examples described later) 1). That is, the pressure-sensitive adhesive described in JP-A-2009-258660 cannot form a pressure-sensitive adhesive layer having both excellent reworkability and durability.

  Hereinafter, each component of the pressure-sensitive adhesive composition of the present invention will be described.

[Specific (meth) acrylic copolymer]
The (meth) acrylic copolymer (that is, the specific (meth) acrylic copolymer) contained in the pressure-sensitive adhesive composition of the present invention is a structural unit derived from a monomer having a carboxy group and (meth) acrylic. Including the structural unit derived from the acid alkyl ester monomer, the content of the structural unit derived from the monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group is all It is the range of 0.2 mass%-0.8 mass% with respect to a structural unit, and the weight average molecular weight (Mw) is the range of 1.25 million-2 million.

  The carboxy group of the structural unit derived from the monomer having a carboxy group can be crosslinked with an isocyanate group of an isocyanate compound described later. For this reason, in the adhesive composition of this invention, the carboxy group of the structural unit derived from the monomer which has a carboxy group contained in a specific (meth) acrylic-type copolymer, and the isocyanate group of the below-mentioned isocyanate compound A crosslinking reaction advances and an adhesive layer can be formed.

  In the present specification, the “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 kind of monomer having a carboxy group is not particularly limited.
Specific examples of the monomer having a carboxy group include (meth) acrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone (n≈2) mono (Meth) acrylate etc. are mentioned.
Among these, examples of the monomer having a carboxy group include acrylic acid and ω-carboxy-polycaprolactone (n from the viewpoint of the adhesive strength of the adhesive layer and the adhesiveness between the adhesive layer and the substrate. 2) At least one selected from monoacrylates is preferable, and acrylic acid is more preferable.

  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.

The ratio (that is, content) of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is based on the total structural units constituting the specific (meth) acrylic copolymer. The range of 0.1% by mass to 0.8% by mass is preferable, the range of 0.1% by mass to 0.5% by mass is more preferable, and the range of 0.2% by mass to 0.4% by mass is preferable. Is more preferable.
The proportion of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is 0.1% by mass or more based on the total structural units constituting the specific (meth) acrylic copolymer. When it is, the crosslinking reaction of a carboxyl group and the isocyanate group of the below-mentioned isocyanate compound advances effectively, and the adhesive layer excellent in durability can be formed.
By the way, since a carboxy group can be a factor which corrodes a metal, for example, the ratio of the structural unit derived from the monomer which has a carboxy group with respect to the display apparatus provided with the optical member containing a metal like ITO glass. When a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer with a large amount is used, metal corrosion may occur due to the pressure-sensitive adhesive layer formed.
The proportion of the structural unit derived from the monomer having a carboxy group in the specific (meth) acrylic copolymer is 0.8% by mass or less with respect to all the structural units constituting the specific (meth) acrylic copolymer. When it is, the corrosion of the metal by the adhesive layer resulting from a carboxy group can be suppressed.

The specific (meth) acrylic copolymer includes 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 the adjustment of the adhesive strength of the pressure-sensitive adhesive layer.

  In the present specification, the “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.

As a (meth) acrylic-acid alkylester monomer, an unsubstituted (meth) acrylic-acid alkylester monomer is preferable and the kind in particular is not restrict | limited.
The alkyl group of the (meth) acrylic acid alkyl ester monomer may be linear, branched or cyclic. In addition, the number of carbon atoms of the alkyl group is preferably in the range of 1 to 18, more preferably in the range of 1 to 12, from the viewpoint of the adhesive strength of the adhesive layer and the adhesion between the adhesive layer and the substrate. .

As the (meth) acrylic acid alkyl ester monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) 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, 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, as the (meth) acrylic acid alkyl ester monomer, for example, methyl acrylate, n-butyl acrylate, t-butyl acrylate from the viewpoint of easily adjusting the cohesive strength and adhesive strength of the pressure-sensitive adhesive layer. And at least one selected from the group consisting of 2-ethylhexyl acrylate, and more preferably n-butyl acrylate.

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

The proportion (ie, content) of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer is, for example, a viewpoint that it is easy to adjust the adhesive strength of the pressure-sensitive adhesive layer. Therefore, 60 mass% or more is preferable with respect to all the structural units constituting the specific (meth) acrylic copolymer, 70 mass% or more is more preferable, and 80 mass% or more is still more preferable.
The upper limit of the ratio of the structural unit derived from the (meth) acrylic acid alkyl ester monomer in the specific (meth) acrylic copolymer is not particularly limited. For example, the specific (meth) acrylic copolymer is configured. 99.8 mass% or less is preferable with respect to all the structural units.

The specific (meth) acrylic copolymer has a specific (meth) content of a structural unit derived from a monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. In the range of 0.2% by mass to 0.8% by mass with respect to all the structural units constituting the acrylic copolymer, in addition to the structural unit derived from the monomer having a carboxy group, the single unit having a hydroxyl group. It is preferable to include a structural unit derived from a monomer.
The hydroxyl group of the structural unit derived from the monomer having a hydroxyl group can react with an isocyanate group of an isocyanate compound described later.
In the pressure-sensitive adhesive composition of the present invention, when a structural unit derived from a monomer having a hydroxyl group is included, the gel fraction after crosslinking is increased as compared with the case where the structural unit is not included, thereby forming a pressure-sensitive adhesive layer that is more durable. There is a tendency to be able to.

The kind of monomer having a hydroxyl group is not particularly limited.
Specific examples of the monomer having a hydroxyl group include 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 (meta ) Acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, glycerin mono (Meta) a Relate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly (ethylene glycol - propylene glycol) mono (meth) acrylate.

  The monomer having a hydroxyl group is preferably an alkyl (meth) acrylate having a hydroxyl group as a substituent from the viewpoint of appropriate adhesive strength to the substrate, durability, and suppression of occurrence of white spots in the pressure-sensitive adhesive layer to be formed. From the group consisting of 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate At least one selected is more preferable, and at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate is more preferable.

  When the specific (meth) acrylic copolymer includes a structural unit derived from a monomer having a hydroxyl group, the specific (meth) acrylic copolymer may include only one structural unit derived from the monomer having a hydroxyl group, and two or more types. May be included.

When the specific (meth) acrylic copolymer includes a structural unit derived from a monomer having a hydroxyl group, the proportion of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer (that is, , Content) is a specific (meth) acrylic copolymer whose content of structural units derived from a monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. As long as it is in the range of 0.2% by mass to 0.8% by mass with respect to all the structural units constituting the, it is not particularly limited.
For example, from the viewpoint of forming a more durable pressure-sensitive adhesive layer, the proportion of the structural unit derived from the monomer having a hydroxyl group in the specific (meth) acrylic copolymer is the specific (meth) acrylic copolymer. The range of 0.01 mass%-0.8 mass% is preferable with respect to all the structural units which comprise a polymer, and the range of 0.1 mass%-0.6 mass% is more preferable.

The specific (meth) acrylic copolymer has a specific (meth) content of a structural unit derived from a monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group. It is the range of 0.2 mass%-0.8 mass% with respect to all the structural units which comprise an acryl-type copolymer, and the range of 0.3 mass%-0.5 mass% is more preferable.
In addition, an amino group here refers to a primary amino group or a secondary amino group.
A carboxy group, a hydroxyl group, and an amino group can all be crosslinked with an isocyanate group of an isocyanate compound described later.
When the content of the structural unit derived from the monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group is 0.2% by mass or more, the carboxy group, the hydroxyl group, and A crosslinking reaction of at least one functional group selected from the group consisting of an amino group and an isocyanate group of an isocyanate compound proceeds appropriately, the crosslinking density of the formed adhesive layer becomes appropriate, and the adhesive layer Adhesiveness with a base material becomes favorable. Therefore, it is thought that the adhesive composition of this invention can form the adhesive layer excellent in durability.
Further, when the content of the structural unit derived from the monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group is 0.8% by mass or less, the carboxy group, the hydroxyl group , And at least one functional group selected from the group consisting of amino groups and the isocyanate group of the isocyanate compound are not excessively cross-linked, so that a pressure-sensitive adhesive layer showing moderate flexibility is formed. The pressure-sensitive adhesive layer exhibiting moderate flexibility can sufficiently follow the expansion and contraction of the substrate accompanying changes in temperature and humidity. Therefore, it is thought that the adhesive composition of this invention can form the adhesive layer excellent in durability.

  The specific (meth) acrylic copolymer is a structural unit derived from a monomer having a carboxy group and a structure derived from a (meth) acrylic acid alkyl ester monomer within the range in which the effects of the present invention are exhibited. A structural unit other than a structural unit derived from a monomer having a hydroxyl group which is a unit and an arbitrary structural unit (hereinafter, referred to as “other structural unit” as appropriate) may be included.

The type of monomer constituting other structural units is not particularly limited.
As other monomers constituting the structural unit, for example, (meth) acrylate, methoxyethyl (meth) acrylate and ethoxyethyl having a cyclic group represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate ( Alkoxyalkyl (meth) acrylates represented by meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl, acrylonitrile and methacrylo represented by vinyltoluene Examples thereof include vinyl cyanide represented by nitrile, and vinyl esters represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. In addition, examples of monomers constituting other structural units include various derivatives of these monomers. Moreover, as a monomer which comprises other structural units, the monomer which has functional groups, such as a glycidyl group, an amide group or N-substituted amide group, and a tertiary amino group, is mentioned.

  Specific examples of the monomer having a glycidyl group include glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, and glycidyl (meth) allyl ether. , 4-hydroxybutyl acrylate glycidyl ether, and 3,4-epoxycyclohexyl (meth) allyl ether.

  Specific examples of the monomer having an amide group or an N-substituted amide group include acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, and N-methoxymethyl (meth) acrylamide. N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-tert-butylacrylamide, N-octylacrylamide, dimethylacrylamide, diethylacrylamide, isopropylacrylamide, and Examples include diacetone acrylamide.

  Specific examples of the monomer having a tertiary amino group include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and dimethylaminopropyl (meth) acrylamide.

  For example, when the pressure-sensitive adhesive composition of the present invention is used for an IPS (In Plane Switching) type polarizing plate (that is, an IPS polarizing plate), other structural units are configured from the viewpoint of further enhancing the whitening suppression effect. As the monomer, phenoxyethyl (meth) acrylate is preferable.

The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is in the range of 1.25 million to 2 million, preferably in the range of 1.3 million to 1.8 million, and more preferably in the range of 1.4 million to 1.7 million.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 1.25 million or more, an adhesive layer having excellent durability can be formed.
When the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is 2 million 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 satisfactorily.

The weight average molecular weight (Mw) of the specific (meth) acrylic copolymer is a value measured by the following method. Specifically, the measurement is performed according to the following (1) to (3).
(1) A specific (meth) acrylic copolymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like specific (meth) acrylic copolymer.
(2) Using the film-like 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.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight (Mw) 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) (built in HLC-8220, Tosoh Corporation)
Column: 4 TSK-GEL GMHXL (Tosoh Corp.) 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

  The content of the specific (meth) acrylic copolymer in the pressure-sensitive adhesive composition of the present invention is based on the total solid content of the pressure-sensitive adhesive composition from the viewpoint that it is easy to adjust the cohesive strength and pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer. On the other hand, the range of 50% by mass to 99% by mass is preferable.

[Method for producing specific (meth) acrylic copolymer]
The method for producing the specific (meth) acrylic copolymer is not particularly limited. For example, it can be produced by polymerizing monomers by a known polymerization method represented by solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, as the polymerization method, solution polymerization is preferable because the treatment process is relatively simple and can be performed in a short time.

  In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator and, if necessary, a chain transfer agent are generally charged in a polymerization tank, and are stirred for several hours in a nitrogen stream or at the reflux temperature of the organic solvent. Heat reaction. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator, and / or the chain transfer agent may be sequentially added.

Examples of the organic solvent used in the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Aliphatic or alicyclic typified by aromatic hydrocarbons, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil Hydrocarbons, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, esters represented by methyl benzoate, acetone, methyl ethyl ketone, Methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohex Ketones represented by non, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and glycol ethers represented by diethylene glycol monobutyl ether, and methyl alcohol, Examples include alcohols represented by ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.
In the polymerization reaction, these organic solvents may be used alone or in combination of two or more.

  In the production of the specific (meth) acrylic copolymer, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of esters, ketones, etc. In particular, the dissolution of the specific (meth) acrylic copolymer From the viewpoints of properties and ease of polymerization reaction, use of ethyl acetate, toluene, or the like is preferable.

As the polymerization initiator, organic peroxides, azo compounds and the like used in usual solution polymerization can be used.
Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxide. Carbonato, t-butylperoxybivalate, 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- octyl peroxy cyclohexyl), and butane.
Examples of the azo compound include 2,2′-azobisisobutylnitrile (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 (methyl isobutyrate).

  In the production of the 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 azobis-based polymerization initiator.

  The amount of the polymerization initiator used is preferably in the range of 0.001 to 0.1 parts by mass with respect to 100 parts by mass of the total amount of monomers constituting the specific (meth) acrylic copolymer. The range of 0.005 parts by mass to 0.05 parts by mass is more preferable.

In the production of the specific (meth) acrylic copolymer, a chain transfer agent can be used as necessary as long as the purpose and effect of the present invention are not impaired.
Examples of the chain transfer agent include cyanoacetic acid, cyanoacetic acid alkyl esters having 1 to 8 carbon atoms, bromoacetic acid, bromoacetic acid alkyl esters having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, fluorene. And aromatic compounds typified by 9-phenylfluorene, aromatic nitro compounds typified by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, Benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2- Tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloro Halogenated hydrocarbons typified by tan, tribromomethane, and 3-chloro-1-propene, aldehydes typified by chloral and furaldehyde, alkyl mercaptans having 1 to 18 carbon atoms, thiophenol and toluene mercaptan Specific examples include aromatic mercaptans, mercaptoacetic acid, alkyl esters having 1 to 10 carbon atoms of mercaptoacetic acid, hydroxyalkyl mercaptans having 1 to 12 carbon atoms, and terpenes represented by binene and terpinolene.

  When a chain transfer agent is used in the production of the specific (meth) acrylic copolymer, the amount of the chain transfer agent used is, for example, the total amount of monomers constituting the specific (meth) acrylic copolymer is 100. It can be set as the range of 0.005 mass part-1.0 mass part with respect to a mass part.

  The polymerization temperature is preferably in the range of 30 ° C to 120 ° C, more preferably in the range of 50 ° C to 100 ° C, and still more preferably in the range of 60 ° C to 80 ° C.

[Other (meth) acrylic polymers]
The pressure-sensitive adhesive composition of the present invention further has a weight average molecular weight in the range of 50,000 to 200,000 and does not have any functional group of carboxy group, hydroxyl group, and amino group (meth) acrylic It is preferable to contain a polymer (hereinafter referred to as “other (meth) acrylic polymer” as appropriate).
When the pressure-sensitive adhesive composition of the present invention further contains other (meth) acrylic polymer, the occurrence of white spots in the formed pressure-sensitive adhesive layer tends to be further suppressed.

  The other (meth) acrylic polymer may be a homopolymer composed of a specific monomer or a copolymer composed of two or more monomers.

The other (meth) acrylic polymer preferably includes a structural unit derived from a (meth) acrylic acid alkyl ester monomer.
When the specific (meth) acrylic copolymer contains a structural unit derived from a (meth) acrylic acid alkyl ester monomer, the types of (meth) acrylic acid alkyl ester monomers include carboxy groups, hydroxyl groups, and amino acids. There is no particular limitation except that the monomer does not have any functional group. In addition, an amino group here refers to a primary amino group or a secondary amino group.
As a (meth) acrylic-acid alkylester monomer, the thing similar to the unsubstituted (meth) acrylic-acid alkylester monomer in the above-mentioned specific (meth) acrylic-type copolymer is mentioned, for example.
The (meth) acrylic acid alkyl ester monomer in the other (meth) acrylic polymer is preferably at least one selected from the group consisting of methyl acrylate, n-butyl acrylate, and n-butyl methacrylate.

The weight average molecular weight (Mw) of other (meth) acrylic polymers is in the range of 50,000 to 200,000, preferably in the range of 10,000 to 150,000, and more preferably in the range of 50,000 to 150,000. .
When the weight average molecular weight (Mw) of the other (meth) acrylic polymer is 55,000 or more, the durability of the formed pressure-sensitive adhesive layer is further improved.
When the weight average molecular weight (Mw) of the other (meth) acrylic polymer is 200,000 or less, occurrence of white spots in the formed pressure-sensitive adhesive layer is further suppressed.

  The weight average molecular weight (Mw) of the other (meth) acrylic polymer is measured by the same method as the weight average molecular weight (Mw) of the specific (meth) acrylic copolymer described above.

  When the pressure-sensitive adhesive composition of the present invention contains other (meth) acrylic polymers, it may contain only one kind of other (meth) acrylic polymers or two or more kinds.

  When the pressure-sensitive adhesive composition of the present invention contains another (meth) acrylic polymer, the content of the other (meth) acrylic polymer in the pressure-sensitive adhesive composition is white in the pressure-sensitive adhesive layer to be formed. From the viewpoint of suppressing the occurrence, the range of 0.01 to 40 parts by mass is preferable with respect to 100 parts by mass of the specific (meth) acrylic copolymer described above, and the range of 10 to 30 parts by mass is more preferable. The range of 15 to 25 parts by mass is more preferable.

  Other (meth) acrylic polymers can be produced by the same method as the specific (meth) acrylic copolymers described above.

[Isocyanate compound]
The pressure-sensitive adhesive composition of the present invention contains an isocyanate compound.
In the pressure-sensitive adhesive composition of the present invention, the isocyanate compound functions as a crosslinking agent.

  Isocyanate compounds include aromatic polyisocyanate compounds represented by xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate, Linear or cyclic aliphatic polyisocyanate compounds represented by hydrogenated aromatic polyisocyanate compounds, biurets, dimers, trimers or pentamers of these polyisocyanate compounds, and these polyisocyanates Examples thereof include adducts of a compound and a polyol compound such as trimethylolpropane.

A commercially available product can be used as the isocyanate compound.
Examples of commercially available isocyanate compounds include “Coronate (registered trademark) HX”, “Coronate (registered trademark) HL-S”, “Coronate (registered trademark) L”, and “Coronate (registered trademark)” of Tosoh Corporation. 2031 "," Coronate (registered trademark) 2030 "," Coronate (registered trademark) 2234 "," Coronate (registered trademark) 2785 "," Aquanate (registered trademark) 200 ", and" Aquanate (registered trademark) 210 ". "Sumijoule (registered trademark) N3300", "Desmodule (registered trademark) N3400" and "Sumijoule (registered trademark) N-75" of Sumika Covestrourethane Co., Ltd., "Duranate" of Asahi Kasei Corporation (Registered trademark) E-405-80T "," Duranate (registered trademark) 24A-100 ", and" Duranate (registered trademark) " TSE-100 ”and“ Takenate (registered trademark) D-110N ”,“ Takenate (registered trademark) D-120N ”,“ Takenate (registered trademark) M-631N ”and“ MT- ”of Mitsui Takeda Chemical Co., Ltd. "Olestar (registered trademark) NP1200" can be preferably used.

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

The pressure-sensitive adhesive composition of the present invention is a molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxy groups, hydroxyl groups, and amino groups in the specific (meth) acrylic copolymer described above (isocyanate compound). The molar amount of isocyanate group in the total amount of carboxy group, hydroxyl group and amino group in the specific (meth) acrylic copolymer) is in the range of 0.15 to 2.5, and 0.4 to 2 The range of 0.0 is preferable, and the range of 0.6 to 1.5 is more preferable.
In the pressure-sensitive adhesive composition of the present invention, the molar amount of isocyanate group in the isocyanate compound / the total molar amount of carboxy group, hydroxyl group and amino group in the specific (meth) acrylic copolymer is 0.15 or more. In spite of the small amount of carboxy group, hydroxyl group and amino group (so-called group capable of crosslinking with isocyanate group) in the specific (meth) acrylic copolymer, sufficient crosslinking is performed. As a result, it is considered that the pressure-sensitive adhesive layer formed has a moderately high cross-linking density and can form a pressure-sensitive adhesive layer having excellent durability while maintaining excellent reworkability.
On the other hand, in the pressure-sensitive adhesive composition of the present invention, the total molar amount of isocyanate groups in the isocyanate compound / carboxy group, hydroxyl group, and amino group in the specific (meth) acrylic copolymer is 2.5 or less. By being, the isocyanate compound which does not contribute to bridge | crosslinking does not arise excessively. As a result, since the formed pressure-sensitive adhesive layer does not become hard and exhibits appropriate flexibility, it can sufficiently follow the expansion and contraction of the substrate accompanying changes in temperature and humidity. Therefore, it is considered that the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer that is excellent in both reworkability and durability and in which the occurrence of white spots is suppressed.

  The molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxy groups, hydroxyl groups, and amino groups in the specific (meth) acrylic copolymer (molar amount of isocyanate groups in the isocyanate compound / specific (meth) The total molar amount of the carboxy group, the hydroxyl group, and the amino group in the acrylic copolymer is determined by the following calculation formulas (1) to (3). In the following calculation formula, the molar amount of the isocyanate group in the isocyanate compound is expressed as “NCO amount”, and the total molar amount of the carboxy group, the hydroxyl group, and the amino group in the specific (meth) acrylic copolymer is calculated. This is expressed as “total functional group amount”.

NCO amount (unit: mmol / solid content 100 g)
= [Isocyanate group content in isocyanate compound (unit: mass%) / isocyanate compound solid content (unit: mass%) × isocyanate compound content (unit: g)] / isocyanate group molecular weight (unit: g) / Mol) × 1000 (1)

Total functional group amount (unit: mmol / solid content 100 g)
= [Content of structural unit derived from monomer having carboxy group in specific (meth) acrylic copolymer (unit: mass%) / molecular weight of structural unit derived from monomer having carboxy group ( (Unit: g / mol) × number of carboxy groups in the structural unit derived from the monomer having a carboxy group (valence) × 1000] + [single amount having a hydroxyl group in the specific (meth) acrylic copolymer Content of structural unit derived from body (unit: mass%) / molecular weight of structural unit derived from monomer having hydroxyl group (unit: g / mol) × in the structural unit derived from monomer having hydroxyl group Number of hydroxyl groups (valence) × 1000] + [content of structural unit derived from monomer having amino group in specific (meth) acrylic copolymer (unit: mass%) / single unit having amino group Molecular weight of the structural unit derived from the monomer : G / mol) × number of amino groups in the constituent unit derived from a monomer having an amino group (valence) × 1000] ··· (2)

Mole equivalent ratio of the amount of isocyanate groups to the total amount of carboxy groups, hydroxyl groups, and amino groups in the specific (meth) acrylic copolymer = NCO amount / total functional group amount (3)

[Epoxy compound]
The pressure-sensitive adhesive composition of the present invention preferably further contains an epoxy compound as a crosslinking agent in addition to the aforementioned isocyanate compound.
When the pressure-sensitive adhesive composition of the present invention further contains an epoxy compound as a crosslinking agent in addition to the isocyanate compound, the crosslinking density of the formed pressure-sensitive adhesive layer is further increased, so that the durability of the pressure-sensitive adhesive layer is further improved. obtain.

  In the present specification, the “epoxy compound” means a compound having two or more epoxy groups in the molecule (so-called bifunctional or higher functional epoxy compound).

  As epoxy compounds, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneopentyl Glycol diglycidyl ether, Methylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1,3- Examples thereof include bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-1,3-benzenedi (methanamine), and the like.

A commercially available product can be used as the epoxy compound.
Examples of commercially available epoxy compounds include “TETRAD (registered trademark) -X” and “TETRAD (registered trademark) -C” of Mitsubishi Gas Chemical Co., Ltd., and “Denacol (registered trademark)” of Nagase ChemteX Corporation. EX-201 "can be preferably used.

  When the pressure-sensitive adhesive composition of the present invention contains an epoxy compound, it may contain only one kind of epoxy compound or two or more kinds.

When the pressure-sensitive adhesive composition of the present invention contains an epoxy compound, the content of the epoxy compound in the pressure-sensitive adhesive composition is not particularly limited, and is, for example, 0 with respect to 100 parts by mass of the specific (meth) acrylic copolymer. The range of 0.005 parts by mass to 1 part by mass is preferred, the range of 0.01 parts by mass to 0.5 parts by mass is more preferred, and the range of 0.02 parts by mass to 0.1 parts by mass is still more preferred.
When the content of the epoxy compound in the pressure-sensitive adhesive composition is 0.005 parts by mass or more with respect to 100 parts by mass of the specific (meth) acrylic copolymer, for the specific functional group that is not crosslinked by the isocyanate compound, Since the crosslinking density of the pressure-sensitive adhesive layer to be formed is further increased by the reaction of the epoxy compound, the durability of the pressure-sensitive adhesive layer can be further improved.
When the content of the epoxy compound in the pressure-sensitive adhesive composition is 1 part by mass or less with respect to 100 parts by mass of the specific (meth) acrylic copolymer, the epoxy compound has a slower reaction with respect to the specific functional group than the isocyanate compound. Therefore, the storage stability of the pressure-sensitive adhesive composition is less likely to be impaired.

〔Silane coupling agent〕
The pressure-sensitive adhesive composition of the present invention may further contain a silane coupling agent.
When the pressure-sensitive adhesive composition of the present invention further contains a silane coupling agent, durability of the formed pressure-sensitive adhesive layer can be further improved.

Examples of the silane coupling agent include polymerizable unsaturated group-containing silane compounds represented by vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3 Thiol group-containing silane compounds represented by mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane, and 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Epoxy group-containing silane compounds represented by silane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and N- (2-aminoethyl) -3-aminopropyl Methyl dimethyl Amino group-containing silane compound represented by Kishishiran, and tris - (3-trimethoxysilylpropyl) isocyanurate.
Note that the epoxy group-containing silane compound does not function as a crosslinking agent, unlike the epoxy compounds described above.

A commercial item can be used as a silane coupling agent.
As a commercial item of a silane coupling agent, for example, trade names “KBM-803”, “KBM-802”, “X-41-1810”, “X-41-1805” of Shin-Etsu Chemical Co., Ltd., and Thiol group-containing silane compounds represented by “X-41-1818” and trade names “KBM-403”, “KBM-303”, “KBM-402”, “KBE-402” of Shin-Etsu Chemical Co., Ltd. ”,“ KBE-403 ”,“ X-41-1053 ”, and“ X-41-1056 ”, epoxy group-containing silane compounds.

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

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, and for example, 100 parts by mass of the specific (meth) acrylic copolymer On the other hand, the range of 0.01 mass part-5 mass parts is preferable, The range of 0.05 mass part-1 mass part is more preferable, The range of 0.05 mass part-0.5 mass part is still more preferable.
When the content of the silane coupling agent in the pressure-sensitive adhesive composition is within the above range, durability of the formed pressure-sensitive adhesive layer can be further improved.

[Organic solvent]
The pressure-sensitive adhesive composition of the present invention may contain an organic solvent for improving applicability.
As an organic solvent, the organic solvent used at the time of the polymerization reaction of the above-mentioned specific (meth) acrylic-type copolymer is mentioned, for example.

[Other ingredients]
The pressure-sensitive adhesive composition of the present invention may contain components other than those already described (so-called other components) as necessary within a range not impairing the effects of the present invention.
Other components include specific (meth) acrylic copolymers and other polymers other than (meth) acrylic polymers, crosslinking agents other than isocyanate compounds and epoxy compounds, crosslinking catalysts, solvents, antioxidants, and coloring. Various additives such as an agent (for example, a dye and a pigment), a light stabilizer (for example, an ultraviolet absorber), and an antistatic agent are included.
In the pressure-sensitive adhesive composition of the present invention, the specific (meth) acrylic copolymer described above has a carboxy group as a functional group serving as a cross-linking point, so that the cross-linking reaction is terminated even without including a cross-linking catalyst. It is done.

<Gel fraction after crosslinking>
The pressure-sensitive adhesive composition of the present invention has a gel fraction after crosslinking in the range of 40% by mass to 75% by mass, preferably in the range of 40% by mass to 70% by mass, and 50% by mass to 70% by mass. More preferably, it is the range.
When the gel fraction after cross-linking is 40% by mass or more, the cohesive force of the pressure-sensitive adhesive layer is in an appropriate range, and when reworking, the cohesive failure of the pressure-sensitive adhesive layer does not occur, and the substrate and / or adhesion The adhesive residue on the body can be suppressed, and when exposed to a high-temperature environment or a high-temperature and high-humidity environment, the generation of bubbles (that is, foaming) can be suppressed.
When the gel fraction after cross-linking is 75% by mass or less, it can sufficiently follow the expansion and contraction of the substrate accompanying changes in temperature and humidity, and tends to be excellent in durability.

Since the pressure-sensitive adhesive composition of the present invention includes a structural unit derived from a monomer having a carboxy group in the (meth) acrylic copolymer, the gel fraction after crosslinking is 40% by mass or more.
In addition, the gel fraction after cross-linking includes an appropriate amount of a structural unit derived from a monomer having a hydroxyl group in the specific (meth) acrylic copolymer contained in the pressure-sensitive adhesive composition, or the pressure-sensitive adhesive composition If one of the conditions of including a suitable amount of a crosslinking agent is satisfied, it tends to be in the range of 40% by mass to 75% by mass.

In the present specification, the “gel fraction after crosslinking of the pressure-sensitive adhesive composition” is a ratio of a solvent-insoluble component measured using ethyl acetate as an extraction solvent. Specifically, the gel fraction after crosslinking of the pressure-sensitive adhesive composition is measured according to the following (1) to (4).
(1) About 0.15 g of the pressure-sensitive adhesive composition (that is, the pressure-sensitive adhesive layer) after cross-linking is applied to a 250-mesh wire mesh (100 mm × 100 mm) whose mass is accurately measured with a precision balance, and the gel content leaks. The wire mesh is folded 5 times with the attached adhesive layer inside so that there is no sample. Thereafter, the mass is accurately measured with 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. Thereafter, the mass is accurately measured with a precision balance.
(4) The gel fraction is calculated by the following formula.
Gel fraction (unit: mass%) = (Z−X) / (Y−X) × 100
However, X is the mass of the wire mesh (unit: g), Y is the mass before immersion of the wire mesh with the adhesive layer attached (unit: g), Z is the mass of the wire mesh with the adhesive layer attached, dried after immersion. (Unit: g).

[Use of pressure-sensitive adhesive composition]
The pressure-sensitive adhesive composition of the present invention is suitably used for applications in which a polarizing plate is attached to an adherend through a pressure-sensitive adhesive layer. Specifically, the use which sticks a polarizing plate to a liquid crystal cell, the use which sticks a polarizing plate to optical films, such as phase contrast film, etc. are mentioned.
Among these, since the effect of the adhesive composition of this invention is exhibited more, it is preferable to use it for the use which sticks a polarizing plate to a liquid crystal cell especially in which durability and suppression of occurrence of white spots are required.

As described above, since the EWV layer is generally inferior in adhesion to the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer formed on the surface of the EWV layer is transferred to an adherend (for example, a glass substrate of a liquid crystal cell). Easy to wear. On the other hand, since the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer exhibiting good adhesion to the EWV layer and has excellent reworkability, the polarizing plate provided with the EWV layer (that is, the EWV) It is particularly suitably used for the purpose of attaching a polarizing plate to an adherend (for example, a glass substrate of a liquid crystal cell).
When reworking the EWV polarizing plate, if peeling occurs at the interface between the EWV layer and the pressure-sensitive adhesive layer, the reworkability is extremely lowered.

[Polarizing plate with adhesive layer]
The polarizing plate with an adhesive layer in the present invention includes a polarizing plate and an adhesive layer formed from the adhesive composition of the present invention described above.
Since the polarizing plate with an adhesive layer in the present invention includes an adhesive layer formed by the adhesive composition of the present invention, it is excellent in reworkability and durability. Moreover, in the polarizing plate with an adhesive layer in the present invention, white spots are hardly generated.

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

As a layer structure of the polarizing plate with an adhesive layer of this invention, an adhesive layer / polarizer, an adhesive layer / polarizer / protective film, an adhesive layer / protective film / polarizer / protective film, and an adhesive, for example Layer / protective film / polarizer.
A retardation film (for example, an optical functional layer, an adhesive layer, and an easy layer) is provided 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. It may have a layer such as an adhesive layer.
The outermost surface of the pressure-sensitive adhesive layer-attached polarizing plate may be protected with a release film.

  As a polarizer, a polyvinyl alcohol (PVA) film is mentioned, for example.

  Examples of the protective film include a triacetyl cellulose (TAC) film, a polycycloolefin (COP) film, and an acrylic film.

As a release film in contact with the pressure-sensitive adhesive layer, in order to make it easy to peel the release film from the pressure-sensitive adhesive layer, for example, a polyester whose surface is subjected to a release treatment with a release agent such as fluororesin, paraffin wax, silicone, etc. A synthetic resin film is preferred.
When the surface opposite to the surface on the pressure-sensitive adhesive layer side is protected with a release film, examples of the release film include surface protective films such as hard-coated polyethylene terephthalate (PET) films.

As a preferable embodiment of the polarizing plate with the pressure-sensitive adhesive layer of the present invention, the contact angle between the polarizing plate, the layer disposed on the surface of the polarizing plate and having a contact angle with water of 90 ° or more, and the water. And a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, which is disposed on the surface of the layer having an angle of 90 ° or more.
In general, a layer having a contact angle with water of 90 ° or more has extremely poor adhesion to the pressure-sensitive adhesive layer. Therefore, the pressure-sensitive adhesive layer formed on the surface of the layer is easily transferred to the adherend. On the other hand, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention exhibits excellent adhesion even for a layer having a contact angle with water of 90 ° or more, and is excellent in reworkability. It becomes possible to design the polarizing plate with the pressure-sensitive adhesive layer in such an embodiment.

  In this specification, “contact angle with water” refers to the contact angle of water droplets after dropping 2 μm of pure water on the surface of a layer to be measured under an atmosphere temperature of 25 ° C. and leaving it for 30 seconds. The value measured using a contact angle meter. As the measuring device, for example, Drop Master DM-701 (product name) manufactured by Kyowa Interface Science Co., Ltd. can be used. However, the measuring device is not limited to this.

  Examples of the layer having a contact angle with water of 90 ° or more include a layer containing a discotic liquid crystal compound (that is, an EWV layer).

  The thickness of the pressure-sensitive adhesive layer in the present invention can be appropriately set according to the types of the substrate and the adherend, the surface roughness of the substrate and the adherend, and the like. In general, the thickness of the pressure-sensitive adhesive layer is in the range of 1 μm to 100 μm, preferably in the range of 5 μm to 50 μm, and more preferably in the range of 10 μm to 30 μm.

The polarizing plate with an adhesive layer of the present invention can be produced by a known method.
As a known method, for example, the pressure-sensitive adhesive composition of the present invention is applied on a release film, dried, and after forming a coating layer of the pressure-sensitive adhesive composition on the release film, the coating layer is transferred onto a polarizing plate. The method of producing a polarizing plate with an adhesive layer by curing is mentioned.
In addition, after the pressure-sensitive adhesive composition of the present invention is coated on a release film and dried to form a coating layer of the pressure-sensitive adhesive composition on the release film, the exposed surface of the coating layer is further provided with the release film adhered thereto. A double-sided pressure-sensitive adhesive tape without a support is prepared, and after curing the coating layer, one of the release films is peeled off, and the exposed pressure-sensitive adhesive layer is transferred onto the polarizing plate to form a polarizing plate with a pressure-sensitive adhesive layer. The method of producing is mentioned.
Moreover, the method of producing the polarizing plate with an adhesive layer is mentioned by apply | coating the adhesive composition of this invention on a polarizing plate, drying and curing.
In addition, as drying conditions, the conditions of drying for 1 minute-3 minutes at 70 degreeC-120 degreeC using a hot air dryer are mentioned, for example.

  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 thereof is not exceeded.

  In addition, the weight average molecular weight (Mw) of the (meth) acrylic copolymer A and the (meth) acrylic copolymer B produced in this example is the weight of the specific (meth) acrylic copolymer described above. It measured by the method similar to the measuring method of average molecular weight (Mw).

[Example 1]
<Production of (meth) acrylic copolymer A>
In a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser, 81.2 parts by mass of n-butyl acrylate (n-BA; alkyl acrylate monomer), phenoxyethyl acrylate (PHEA) ) 18.0 parts by mass, 2-hydroxyl ethyl acrylate (2HEA; acrylic monomer having a hydroxyl group) 0.6 parts by mass, acrylic acid (AA; acrylic monomer having a carboxy group) 0.2 parts by mass , And 110 parts by mass of ethyl acetate, and after mixing, the inside of the reactor was purged with nitrogen. Next, the temperature of the mixture in the reactor was increased to 70 ° C. with stirring, 0.02 part by mass of 2,2′-azobis (2,4-dimethylvaleronitrile) (ABVN; polymerization initiator) and 40% ethyl acetate. Mass parts were sequentially added, and the polymerization reaction was carried out by maintaining for 6 hours. After completion of the polymerization reaction, the solution was diluted with ethyl acetate to obtain a solution of (meth) acrylic copolymer A having a solid content of 17.3% by mass and a weight average molecular weight (Mw) of 1.6 million. The “solid content” means the amount of residue obtained by removing volatile components such as a solvent from the solution of the (meth) acrylic copolymer A.

<Production of (meth) acrylic copolymer B>
In a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser, 36.0 parts by mass of n-butyl acrylate (n-BA), 20.0 parts by mass of methyl acrylate (MA), n- Butyl methacrylate (n-BMA) 44.0 parts by mass, ethyl acetate 45.6 parts by mass, toluene 136.0 parts by mass, and 2,2′-azobisisobutyronitrile (AIBN; polymerization initiator) 0.20 After mixing and mixing with parts by mass, the mixture in the reactor was heated to 95 ° C. while stirring, and then 2.29 parts by mass of 2,2′-azobisisobutyronitrile (AIBN) and 110 parts by mass of ethyl acetate. And the polymerization reaction was continued for 6 hours. After the completion of the polymerization reaction, the solution was diluted with 176.8 parts by mass of toluene to obtain a solution of (meth) acrylic copolymer B having a solid content of 47.3 parts by mass and a weight average molecular weight (Mw) of 100,000. . The “solid content” means the amount of residue obtained by removing volatile components such as a solvent from the solution of the (meth) acrylic copolymer B.

<Preparation of pressure-sensitive adhesive composition>
100 parts by mass (solid content converted value) of (meth) acrylic copolymer A, 20 parts by mass (solid content converted value) of (meth) acrylic copolymer B, and an isocyanate compound (trade name: Sumijoule (registered trademark) N-75, hexamethylene diisocyanate (HMDI) biuret type, Sumika Cobestrourethane Co., Ltd. (0.65 parts by mass) (solid content conversion value), and silane coupling agent (trade name: X-41-1810, solid content: 100% by mass, Shin-Etsu Chemical Co., Ltd.) 0.1 part by mass was sufficiently stirred and mixed to obtain an adhesive composition.
In the obtained pressure-sensitive adhesive composition, the molar equivalent ratio of the amount of isocyanate group of the isocyanate compound to the total amount of the specific functional group of the (meth) acrylic copolymer [molar amount of isocyanate group of the isocyanate compound / (meta ) Total molar amount of specific functional group possessed by acrylic copolymer] was 0.43.

  The molar equivalent ratio of the amount of the isocyanate group that the isocyanate compound has to the total amount of the specific functional group that the (meth) acrylic copolymer has is calculated using the aforementioned calculation formulas (1) to (3). . Specifically, the calculation was performed as follows. In addition, Sumijoule (registered trademark) N-75, which is an isocyanate compound, has a solid content of 75 mass% and an isocyanate group content of 16.5 mass%. The molecular weight of the isocyanate group is 42. The molecular weight of the structural unit derived from acrylic acid which is a monomer having a carboxy group is 72, and the molecular weight of the structural unit derived from 2-hydroxyethyl acrylate which is a monomer having a hydroxyl group is 116. is there.

Formula (1)
NCO amount (unit: mmol / solid content 100 g)
= Isocyanate group content in isocyanate compound (unit: mass%) / isocyanate compound solid content (unit: mass%) × isocyanate compound content (unit: g) / isocyanate group molecular weight (unit: g / mol) ) X 1000
= 16.5 (mass%) / 75 (mass%) x 0.65 (g) / 42 (g / mol) x 1000 = 3.4

Formula (2)
Total functional group amount (unit: mmol / solid content 100 g)
= [Content of structural unit derived from monomer having carboxy group in (meth) acrylic copolymer (unit: mass%) / molecular weight of structural unit derived from monomer having carboxy group (unit : G / mol) × number of carboxy groups in the structural unit derived from the monomer having a carboxy group (valence) × 1000] + [(meth) acrylic copolymer having a hydroxyl group-containing monomer Content of constituent unit derived (unit: mass%) / molecular weight of constituent unit derived from monomer having hydroxyl group (unit: g / mol) × hydroxyl group in constituent unit derived from monomer having hydroxyl group Number (valence) × 1000] + [content of structural unit derived from monomer having amino group in (meth) acrylic copolymer (unit: mass%) / in monomer having amino group Molecular weight of derived structural unit (unit: g / mo ) The number of amino groups in the constituent unit derived from a monomer having a × amino group (valency) × 1000]
= [0.2 (parts by mass) / 100 (parts by mass) x 100 (%) / 72 (g / mol) x 1 x 1000] + [0.6 (parts by mass) / 100 (parts by mass) x 100 ( %) / 116 (g / mol) × 1 × 1000] = 7.95

Formula (3)
The molar equivalent ratio of the amount of isocyanate groups to the total amount of carboxy groups, hydroxyl groups and amino groups in the (meth) acrylic copolymer = NCO amount / total functional group amount = 3.4 / 7.95 = 0.43

<Preparation of polarizing plate with adhesive layer>
Using the pressure-sensitive adhesive composition obtained above, a pressure-sensitive adhesive layer-attached polarizing plate was produced as follows. Adhesive so that the thickness after drying is 20 μm on the surface-treated surface of a release film (trade name: Film Vina (registered trademark) 100E-0010N023, Fujimori Kogyo Co., Ltd.) surface-treated with a silicone release agent The composition was applied to form a coating layer. Subsequently, the peeling film which has an application layer was dried on 100 degreeC and the drying conditions for 1 minute using the hot air circulation type dryer, and the layer of the adhesive composition was formed on the peeling film. Next, the surface on the EWV layer side of the polarizing plate having the structure of EWV layer / triacetyl cellulose (TAC) layer / polyvinyl alcohol (PVA) layer / TAC layer, and the layer of the pressure-sensitive adhesive composition formed on the release film, A polarizing plate with a pressure-sensitive adhesive layer having a laminate structure of release film / pressure-sensitive adhesive layer / polarizing plate is obtained by laminating and laminating and curing for 168 hours under conditions of 25 ° C. and 50% RH. Produced.
In addition, the contact angle with respect to the water of the surface of the EWV layer which a polarizing plate has was 97.6 degrees.

[Measurement of gel fraction]
On the surface-treated surface of a release film (trade name: Film Vina (registered trademark) 100E-0010N023, Fujimori Kogyo Co., Ltd.) surface-treated with the silicone-based release agent, the pressure-sensitive adhesive composition obtained above. It apply | coated so that the thickness after drying might be set to 20 micrometers, and the coating layer was formed. Subsequently, the peeling film which has an application layer was dried on 100 degreeC and the drying conditions for 1 minute using the hot air circulation type dryer, and the layer of the adhesive composition was formed on the peeling film.
Subsequently, the surface where the layer of the pressure-sensitive adhesive composition was exposed was laminated and bonded to the surface-treated surface of a separately prepared release film (trade name: Film Vina (registered trademark) 100E-0010N023, Fujimori Industry Co., Ltd.). A base material type pressure-sensitive adhesive sheet was prepared.
Next, the sample was allowed to cure for 168 hours under conditions of 25 ° C. and 50% RH, whereby the crosslinking reaction was advanced, and a gel fraction measurement sample having an adhesive layer was obtained.
Using the obtained gel fraction measurement sample, the gel fraction of the pressure-sensitive adhesive layer (that is, the gel fraction of the pressure-sensitive adhesive composition after crosslinking) was measured by the method described above, and was found to be 65.5% by mass. Met.

[Evaluation]
1. Reworkability The polarizing plate with the pressure-sensitive adhesive layer produced above was cut to prepare a test piece having a size of 25 mm × 75 mm (long side).
The peeling film of the test piece was peeled off, and the surface of the pressure-sensitive adhesive layer exposed by peeling was laminated and bonded to one side of soda glass (Matsunami Glass Industry Co., Ltd .; hereinafter simply referred to as “glass”). The laminated body was produced by pressure bonding using a laminator. The prepared laminate was subjected to autoclave treatment (temperature: 50 ° C., pressure: 5 kg / cm ² , treatment time: 20 minutes) and then allowed to stand at 50 ° C. for 96 hours.
After the standing time had elapsed, 180 ° peeling was performed at a peeling speed of 300 mm / min under the condition of 23 ° C. And the surface of the glass and the surface of the peeled adhesive layer were observed visually, and rework property was evaluated according to the following evaluation criteria. The results are shown in Table 3.
If the evaluation result is “A” or “B”, there is no practical problem.

-Evaluation criteria-
A: The pressure-sensitive adhesive layer did not transfer at all on the glass surface.
B: Although the adhesive layer did not transfer at all on the surface of glass, the surface of the adhesive layer after peeling was rough.
C: The pressure-sensitive adhesive layer partially transferred to the glass surface.
D: The entire pressure-sensitive adhesive layer was transferred to the glass surface.

2. Durability (preparation of samples for durability evaluation)
The polarizing plate with the pressure-sensitive adhesive layer produced above was cut so that the long side was 45 ° with respect to the absorption axis, and two test pieces having a size of 50 mm × 89 mm (long side) were prepared.
The release film of the test piece was peeled off, and the surface of the pressure-sensitive adhesive layer exposed by peeling was laminated on one side of the glass and bonded together, followed by pressure bonding using a laminator to prepare a laminate. Autoclave treatment (temperature: 50 ° C., pressure: 5 kg / cm ² , treatment time: 20 minutes) was performed on the produced laminate, and the laminate was left to stand for 1 hour at 23 ° C. and 50% RH. An evaluation sample was produced.

(Evaluation test)
2-1. High temperature and high humidity conditions (65 ° C, 95% RH)
The durability evaluation sample prepared above was left for 500 hours under high temperature and high humidity conditions of 65 ° C. and 95% RH. The appearance of the sample for durability evaluation after standing was visually observed, and the durability of the pressure-sensitive adhesive composition under high temperature and high humidity conditions (65 ° C., 95% RH) was evaluated according to the following evaluation criteria. The results are shown in Table 3.
If the evaluation result is “A”, “B”, or “C”, there is no practical problem.

-Evaluation criteria-
A: Foaming, floating, and peeling were not recognized at all.
B: Foaming, floating, and peeling were hardly recognized.
C: Although foaming, floating, and peeling were slightly observed, they were within an allowable range.
D: Foaming, floating, and peeling were recognized and were outside the allowable range.
E: Foaming, floating, and peeling were remarkably recognized.

2-2. High temperature conditions (95 ° C)
The durability evaluation sample prepared above was left under a high temperature condition of 95 ° C. for 500 hours. The appearance of the sample for evaluating durability after standing was visually observed, and the high temperature of the pressure-sensitive adhesive composition was determined according to the same evaluation criteria as the evaluation criteria for durability under the high temperature and high humidity conditions (65 ° C., 95% RH). Durability under conditions (95 ° C.) was evaluated. The results are shown in Table 3.
If the evaluation result is “A”, “B”, or “C”, there is no practical problem.

3. White spots (Preparation of white spot evaluation samples)
The polarizing plate with an adhesive layer produced above was cut, and two test pieces having a size of 62 mm × 110 mm (long side) were prepared.
The release film of the two test pieces is peeled off, and the surface of the pressure-sensitive adhesive layer exposed by peeling is overlapped on both surfaces of a twisted nematic (TN) type liquid crystal panel so that the absorption axes of the respective test pieces are orthogonal to each other. Bonding and pressure bonding using a laminator produced a laminate. The prepared laminate was subjected to autoclave treatment (temperature: 50 ° C., pressure: 5 kg / cm ² , treatment time: 20 minutes), and then left for 1 hour under the conditions of 23 ° C. and 50% RH. An evaluation sample was produced.

(Evaluation test)
The white spot evaluation sample prepared as described above was left under a high temperature condition of 95 ° C. for 500 hours. The sample for white spot evaluation after being left is placed on the backlight of a liquid crystal monitor under the conditions of 23 ° C. and 50% RH, and the white spot state is visually observed. evaluated. The results are shown in Table 3.
The evaluation result is preferably “A” or “B”.

-Evaluation criteria-
A: No white spots were observed at all.
B: White spots were recognized, but were within an allowable range.
C: Remarkable white spots were recognized.

[Examples 2 to 20]
In Examples 2 to 20, the compositions of the (meth) acrylic copolymer, the crosslinking agent, and the silane coupling agent in Example 1 were the same as in Example 1 except that the compositions shown in Table 1 were used. Operation was performed to prepare a pressure-sensitive adhesive composition, and a polarizing plate with a pressure-sensitive adhesive layer was prepared using the pressure-sensitive adhesive composition obtained.
About the obtained adhesive composition, the gel fraction after bridge | crosslinking was measured by the method similar to Example 1. FIG. Moreover, about the produced polarizing plate with an adhesive layer, by the method similar to Example 1, rework property, durability, and white evaluation were performed. The results are shown in Table 3.

[Comparative Examples 1 to 11]
In Comparative Example 1 to Comparative Example 11, the compositions of the (meth) acrylic copolymer, the crosslinking agent, and the silane coupling agent in Example 1 were the same as in Example 1 except that the compositions shown in Table 2 were used. Operation was performed and the adhesive composition was prepared.
About the comparative example 1- comparative example 7 and the comparative example 9- comparative example 11 among the obtained adhesive compositions, the gel fraction after bridge | crosslinking was measured by the method similar to Example 1. FIG. In Comparative Example 8, the viscosity was very high and the coating could not be performed, so the gel fraction after crosslinking could not be measured. The results are shown in Table 3.
Moreover, about the obtained adhesive composition, about Comparative Example 1- Comparative Example 4, Comparative Example 6, Comparative Example 7, Comparative Example 9, and Comparative Example 11, operation similar to Example 1 was performed, and adhesive was carried out. A polarizing plate with an agent layer was prepared and evaluated for reworkability, durability, and white spot by the same method as in Example 1. In Comparative Example 5 and Comparative Example 10, the gel fraction after crosslinking was very low, and reworkability, durability, and white spots could not be evaluated. The results are shown in Table 3.

[Reference Example 1]
In Reference Example 1, the same operations as in Example 1 were performed except that the composition of the (meth) acrylic copolymer, the crosslinking agent, and the silane coupling agent in Example 1 was changed to the composition shown in Table 2. A pressure-sensitive adhesive composition was prepared, and a polarizing plate with a pressure-sensitive adhesive layer was prepared using the obtained pressure-sensitive adhesive composition.
About the obtained adhesive composition, the gel fraction after bridge | crosslinking was measured by the method similar to Example 1. FIG. Moreover, about the produced polarizing plate with an adhesive layer, by the method similar to Example 1, rework property, durability, and white evaluation were performed. The results are shown in Table 3.

In Tables 1 and 2, “-” in the column of the composition means that the corresponding component is not included.
In Tables 1 and 2, “n-BA” is “n-butyl acrylate”, “PHEA” is “phenoxyethyl acrylate”, “2HEA” is “2-hydroxyethyl acrylate”, “4HBA” is “4-hydroxy “Butyl acrylate” and “AA” represent “acrylic acid”.
“M-5300” in Table 1 and Table 2 is Aronix (registered trademark) M-5300 (ω-carboxy-polycaprolactone (n≈2) monoacrylate; monomer having carboxy group) manufactured by Toa Gosei Co., Ltd. Represents.

The details of each crosslinking agent described in Table 1 and Table 2 are as follows.
<Isocyanate compound>
Sumijoule (registered trademark) N-75: Bimuret type of hexamethylene diisocyanate (HMDI), solid content: 75 mass%, isocyanate group content: 16.5 mass%, Sumika Covestrourethane Co., Ltd.
Coronate (registered trademark) L45E: Tolylene diisocyanate (TDI), solid content: 45% by mass, isocyanate group content: 7.9% by mass, Tosoh Corporation
Takenate (registered trademark) D-110N: xylylene diisocyanate (XDI), solid content: 75 mass%, isocyanate group content: 11.5 mass%, Mitsui Takeda Chemical Co., Ltd.
Duranate (registered trademark) E405-80T: Adduct type of hexamethylene diisocyanate (HMDI), solid content: 80% by mass, isocyanate group content: 7.1% by mass, Asahi Kasei Corporation
<Epoxy compound>
・ TETRAD-X: Mitsubishi Gas Chemical Co., Ltd.
Denacol (registered trademark) EX-201: resorcinol diglycidyl ether, Nagase ChemteX Corporation

Moreover, the detail of each silane coupling agent of Table 1 and Table 2 is as follows.
<Silane coupling agent>
・ X-41-1810: Thiol group-containing silane compound, Shin-Etsu Chemical Co., Ltd.
X-41-1053: Epoxy group-containing silane compound, Shin-Etsu Chemical Co., Ltd.
X-41-1056: Epoxy group-containing silane compound, Shin-Etsu Chemical Co., Ltd.
KBM403: 3-glycidoxypropyltriethoxysilane, epoxy group-containing silane compound, Shin-Etsu Chemical Co., Ltd.
KBM 9659: Tris- (trimethoxysilylpropyl) isocyanurate, Shin-Etsu Chemical Co., Ltd.
Any silane coupling agent has a solid content of 100% by mass.

As shown in Table 3, the pressure-sensitive adhesive layers formed by the pressure-sensitive adhesive compositions of Examples 1 to 20 were all excellent in both reworkability and durability.
Moreover, generation | occurrence | production of white spot was suppressed in the adhesive layer formed with the adhesive composition of Example 1- Example 20. FIG.

According to the comparison between Example 3 and Example 4, the pressure-sensitive adhesive composition is formed by containing a (meth) acrylic copolymer containing a structural unit derived from a monomer having a hydroxyl group. It can be seen that the durability of the pressure-sensitive adhesive layer is improved when exposed to a high-temperature and high-humidity environment.
According to the comparison between Example 3 and Example 13, the pressure-sensitive adhesive composition further has a weight average molecular weight in the range of 50,000 to 200,000, and any of carboxy group, hydroxyl group, and amino group. It turns out that the durability of the adhesive layer formed improves by including the (meth) acrylic-type polymer which does not have a functional group.

  According to the comparison between Example 3 and Examples 15 to 17, the pressure-sensitive adhesive composition is formed by further including an epoxy compound that is also a crosslinking agent in addition to the isocyanate compound that is a crosslinking agent. It can be seen that the durability of the pressure-sensitive adhesive layer is improved.

On the other hand, with the pressure-sensitive adhesive composition of Comparative Example 11 in which the molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxy groups, hydroxyl groups, and amino groups in the (meth) acrylic copolymer is 0.11. The formed pressure-sensitive adhesive layer is compared with the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Example (for example, Example 3) in which the molar equivalent ratio is in the range of 0.15 to 2.5. Both reworkability and durability were remarkably inferior. Also, white spots were noticeable.
Further, Comparative Examples 2 and 2.66 in which the molar equivalent ratio of the amount of isocyanate group in the isocyanate compound to the total amount of carboxy group, hydroxyl group, and amino group in the (meth) acrylic copolymer is 4.32. The pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of Comparative Example 9 is a pressure-sensitive adhesive composition of Examples (for example, Example 3 and Example 11) in which the molar equivalent ratio is in the range of 0.15 to 2.5. Compared with the adhesive layer formed with the thing, durability was remarkably inferior. Also, white spots were noticeable.

The pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of Comparative Example 3 containing an epoxy compound as a crosslinking agent instead of the isocyanate compound is formed of the pressure-sensitive adhesive composition of the example (for example, Example 3) containing the isocyanate compound. Both the reworkability and the durability were significantly inferior to the pressure-sensitive adhesive layer. Also, white spots were noticeable.
Comparative example in which the content of the structural unit derived from the monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group is 0.1% by mass with respect to all the structural units The pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of No. 4 is a pressure-sensitive adhesive composition according to an example (for example, Example 3) in which the content of the structural unit is in the range of 0.2% by mass to 0.8% by mass. Compared with the adhesive layer formed with the thing, durability was remarkably inferior. White spots were noticeable.

The (meth) acrylic copolymer does not contain a structural unit derived from a monomer having a carboxy group, and is a group consisting of a carboxy group, a hydroxyl group, and an amino group in the (meth) acrylic copolymer. The pressure-sensitive adhesive formed of the pressure-sensitive adhesive composition of Comparative Example 5 in which the content of the structural unit derived from the selected monomer having at least one functional group is 0.1% by mass with respect to all the structural units. The layer did not increase in gel fraction and could not be evaluated.
The content rate of the structural unit derived from the monomer which has at least 1 type of functional group chosen from the group which consists of a carboxy group in a (meth) acrylic-type copolymer, a hydroxyl group, and an amino group is with respect to all the structural units. The pressure-sensitive adhesive formed by the pressure-sensitive adhesive composition of Comparative Example 10 in which the (meth) acrylic copolymer does not contain a structural unit derived from a monomer having a carboxy group Regarding the layer, the gel fraction did not increase and could not be evaluated.

Comparative example in which the content of the structural unit derived from the monomer having at least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group is 1.0% by mass with respect to all the structural units. The pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of No. 6 is a pressure-sensitive adhesive composition according to an example (for example, Example 3) in which the content of the structural unit is in the range of 0.2% by mass to 0.8% by mass. Compared with the adhesive layer formed with the thing, durability was remarkably inferior. Also, white spots were noticeable.
The pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of Comparative Example 7 in which the weight average molecular weight of the (meth) acrylic copolymer is 1,200,000 has a weight average molecular weight of the (meth) acrylic copolymer of 1.25 million. Compared with the adhesive layer formed by the adhesive composition of the Example (for example, Example 3) which is the range of 2 million, durability was remarkably inferior.
The pressure-sensitive adhesive composition of Comparative Example 8 in which the weight average molecular weight of the (meth) acrylic copolymer was 2.1 million was too high in viscosity to be applied.
A pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of Reference Example 1 having a low molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxy groups, hydroxyl groups, and amino groups in the (meth) acrylic copolymer. The layer has a remarkably inferior reworkability compared to the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the example (for example, example 3) having a molar equivalent ratio in the range of 0.15 to 2.5. It was.
The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 1 having a gel fraction of 15.6% by mass is an example in which the gel fraction is in the range of 40% by mass to 75% by mass (for example, Example In comparison with the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of 3), both reworkability and durability were significantly inferior. Also, white spots were noticeable.

Claims (10)

At least one functional group selected from the group consisting of a carboxy group, a hydroxyl group, and an amino group, including a structural unit derived from a monomer having a carboxy group and a structural unit derived from a (meth) acrylic acid alkyl ester monomer The content rate of the structural unit derived from the monomer which has group is the range of 0.2 mass%-0.8 mass% with respect to all the structural units, and a weight average molecular weight is 1.25 million-2 million. A range of (meth) acrylic copolymers,
An isocyanate compound,
The molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxy groups, hydroxyl groups, and amino groups in the (meth) acrylic copolymer is in the range of 0.15 to 2.5,
The adhesive composition for polarizing plates whose gel fraction after bridge | crosslinking is the range of 40 mass%-75 mass%.   The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the (meth) acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group.   The content of the structural unit derived from the monomer having a carboxy group in the (meth) acrylic copolymer is in the range of 0.1% by mass to 0.8% by mass with respect to the total structural units. Claim | item 1 or the adhesive composition for polarizing plates of Claim 2.   The content rate of the structural unit derived from the said (meth) acrylic-acid alkylester monomer in the said (meth) acrylic-type copolymer is the range of 60 mass%-99.8 mass% with respect to all the structural units. The adhesive composition for polarizing plates of any one of Claims 1-3.   The content rate of the said (meth) acrylic-type copolymer is the range of 50 mass%-99 mass% with respect to the total solid of an adhesive composition, The any one of Claims 1-4. Pressure-sensitive adhesive composition for polarizing plate.   Furthermore, the weight average molecular weight is in the range of 50,000 to 200,000, and contains a (meth) acrylic polymer that does not have any functional group of carboxy group, hydroxyl group, and amino group. The pressure-sensitive adhesive composition for a polarizing plate according to claim 5.   Furthermore, the adhesive composition for polarizing plates of any one of Claims 1-6 containing a silane coupling agent.   Furthermore, the adhesive composition for polarizing plates of any one of Claims 1-7 containing an epoxy compound. A polarizing plate;
A layer disposed on the surface of the polarizing plate and having a contact angle with water of 90 ° or more;
The adhesive layer formed with the adhesive composition for polarizing plates of any one of Claims 1-8 arrange | positioned on the surface of the layer whose contact angle with the said water is 90 degrees or more, ,
A polarizing plate with an adhesive layer.   The polarizing plate with an adhesive layer according to claim 9, wherein the layer having a contact angle with water of 90 ° or more is a layer containing a discotic liquid crystal compound.