TWI786160B - Adhesive composition for a polarizing plate and polarizing plate with an adhesive layer - Google Patents

Abstract

The invention provides an adhesive composition for a polarizing plate and a polarizing plate with an adhesive layer. The adhesive composition for a polarizing plate includes: a (meth)acrylic copolymer containing a structural unit derived from a monomer having a carboxy group and a structural unit derived from a (meth)acrylic acid alkyl ester monomer, in which a 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 is in a range of from 0.2% by mass to 0.8% by mass with respect to an entire amount of structural units, and a weight average molecular weight of the (meth)acrylic copolymer is in a range of from 1,250,000 to 2,000,000; and an isocyanate compound, wherein a molar equivalent ratio of an amount of isocyanate groups in the isocyanate compound with respect to a total amount of carboxy groups, hydroxyl groups and amino groups in the (meth)acrylic copolymer is in a range of from 0.15 to 2.5, and a gel fraction after crosslinking is in a range of from 40% by mass to 75% by mass.

Description

Adhesive composition for polarizing plate and polarizing plate with adhesive layer

The present invention relates to an adhesive composition for a polarizing plate and a polarizing plate with an adhesive layer.

Mobile electronic devices such as mobile phones and mobile terminals are mostly incorporated with liquid crystal display devices. A general liquid crystal display device includes: a liquid crystal cell (liquid crystal cell) in which a liquid crystal layer is sandwiched between two glass substrates, and polarizing plates arranged on both sides of the liquid crystal cell. A liquid crystal cell and a polarizing plate are generally bonded with an adhesive layer formed of an acrylic adhesive in consideration of securing the visibility of the liquid crystal display device.

Polarizing plates are usually formed by laminating members with different shrinkage rates. Therefore, the polarizing plate may be warped due to changes in temperature and humidity, and bubbles, floating, and peeling may occur at the interface between the polarizing plate and the adhesive layer. Also, when the temperature and humidity change, the polarizing plate tends to shrink or expand, and stress may be generated. When the generated stress is not relieved, stress remains in the adhesive layer. In addition, if the stress remaining in the adhesive layer is not uniform, for example, light leakage may occur in a liquid crystal display device, that is, a so-called white void may occur. Therefore, for the adhesive used for laminating the liquid crystal cell and the polarizing plate, it is required to suppress the foaming, floating, and peeling that may occur when exposed to a high-temperature environment or a high-temperature and high-humidity environment (so-called durability) properties), and the property of suppressing white spots. In addition, the bonding of the liquid crystal cell and the polarizing plate may sometimes cause a bonding error. When a lamination error occurs, it must be pasted again. Therefore, the adhesive used for laminating the liquid crystal cell and the polarizer requires the property of being able to be easily re-pasted, which is the so-called rework.

In response to these requirements, for example, in Japanese Patent Application Laid-Open No. 2004-224873, it is possible to fully prevent the occurrence of peeling, air bubbles, and white spots, and to form a pressure-sensitive adhesive for polarizing films with excellent reworkability and reusability. In terms of materials, a pressure-sensitive adhesive composition for polarizing films is disclosed, which contains: an acrylic copolymer containing a specific amount of repeating units with carboxyl groups and repeating units with hydroxyl groups in the molecule, a specific amount of polyisocyanate compound, A specific amount of silane coupling agent with a specific structure.

In recent years, by further providing an EWV (Excellent wide view) layer on the triacetyl cellulose (TAC) layer provided on the surface of the polarizing plate, the viewing angle of the liquid crystal display device tends to be improved. The EWV layer typically contains a discotic liquid crystal compound. For example, Japanese Patent Laid-Open No. 2009-258660 discloses a polarizing plate with an optical compensation film, which has: an adhesive layer containing a (meth)acrylic polymer, an optical compensation film containing a discotic liquid crystal compound, and a polarizer .

[Problem to be Solved by the Invention]

Generally speaking, the adhesion between the EWV layer and the adhesive layer is very poor. Therefore, in a polarizing plate provided with an EWV layer (hereinafter, appropriately referred to as “EWV polarizing plate”), for example, the adhesive layer formed on the surface of the EWV layer is easily transferred and adhered to the adherend (for example, a liquid crystal cell). glass substrate) problem. In order to improve the reworkability of the EWV polarizing plate, for example, some consider increasing the amount of the crosslinking agent blended in the adhesive forming the adhesive layer. When the amount of the cross-linking agent blended in the adhesive increases, the cross-linking agent not involved in cross-linking interacts with the EWV layer, thereby improving the adhesion between the adhesive layer and the EWV layer, thereby improving reworkability. On the other hand, if the amount of the crosslinking agent blended in the adhesive is too large, the flexibility of the adhesive layer will decrease due to the increase in the crosslink density of the formed adhesive layer. When the flexibility of the adhesive layer is low, it cannot fully follow the expansion and contraction of the base material accompanying changes in temperature and humidity, resulting in a decrease in durability. As mentioned above, it is difficult to simultaneously improve the reworkability and durability of the adhesive used in EWV polarizing plates.

The present invention is made in view of the above circumstances, and aims to provide an adhesive composition for a polarizing plate capable of forming an adhesive layer excellent in reworkability and durability, and a device having an adhesive layer formed of the above adhesive composition for a polarizing plate A polarizing plate with an adhesive layer attached. [Means to solve the problem]

Specific means for solving the problems include the following aspects. <1> An adhesive composition for polarizing plates, comprising: a (meth)acrylic copolymer comprising a structural unit derived from a monomer having a carboxyl group and a structural unit derived from an alkyl (meth)acrylate monomer, and derived from The content of the constituent units of monomers having at least one functional group selected from the group consisting of carboxyl, hydroxyl, and amino groups is in the range of 0.2% by mass to 0.8% by mass relative to all the constituent units, and the weight average The molecular weight is in the range of 1,250,000 to 2,000,000; and an isocyanate compound, the molar equivalent of the amount of isocyanate groups in the above-mentioned isocyanate compound relative to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the above-mentioned (meth)acrylic copolymer The ratio 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 adhesive composition for polarizing plates according to <1>, wherein the above-mentioned (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group. <3> The adhesive composition for polarizing plates according to <1> or <2>, wherein the content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer relative to the total The constituent unit is in the range of 0.1% by mass to 0.8% by mass. <4> The adhesive composition for polarizing plates according to any one of <1> to <3>, wherein the composition derived from the alkyl (meth)acrylate monomer in the (meth)acrylic copolymer is The content of the unit is in the range of 60% by mass to 99.8% by mass relative to all the constituent units. <5> The adhesive composition for polarizing plates according to any one of <1> to <4>, wherein the content of the above-mentioned (meth)acrylic copolymer relative to the total solid content of the adhesive composition is: The range of 50% by mass to 99% by mass. <6> The adhesive composition for polarizing plates according to any one of <1> to <5>, which further has a weight average molecular weight in the range of 5,000 to 200,000, and does not have any of carboxyl, hydroxyl, and amine groups. Any functional group (meth)acrylic polymer. <7> The adhesive composition for polarizing plates according to any one of <1> to <6>, further comprising a silane coupling agent. <8> The adhesive composition for polarizing plates according to any one of <1> to <7>, which further contains an epoxy compound. <9> A polarizing plate with an adhesive layer, comprising: a polarizing plate; a layer disposed on the surface of the polarizing plate and having a contact angle with water of 90° or more; and a layer disposed on the above-mentioned layer whose contact angle with water is 90° The surface of the above layer, and an adhesive layer formed of the adhesive composition for polarizing plates according to any one of <1> to <8>. <10> The polarizing plate with an 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. [Effect of Invention]

According to the present invention, it is possible to provide an adhesive composition for a polarizing plate capable of forming an adhesive layer excellent in reworkability and durability, and a polarizer with an adhesive layer provided with an adhesive layer formed of the adhesive composition for a polarizing plate. plate.

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 appropriately modified and implemented within the scope of the purpose of the present invention.

In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described in subparagraphs in this specification, the upper limit or lower limit described in a certain numerical range may also be replaced with the upper limit or lower limit of the numerical ranges described in other subparagraphs. In addition, in the numerical range described in this specification, the upper limit or the lower limit described in a certain numerical range may be replaced with the value shown in an Example. In this specification, the combination of 2 or more preferable aspects is a more preferable aspect. In the present specification, the amount of each component means the total amount of the plurality of substances unless otherwise specified when there are a plurality of substances corresponding to each component.

In this specification, the term "adhesive composition" refers to a liquid or adhesive composition after mixing a (meth)acrylic copolymer and a crosslinking agent (for example, an isocyanate compound) and before the completion of the crosslinking reaction. Paste-like substance. In this specification, the "adhesive layer" refers to a substance after the crosslinking reaction in the adhesive composition is completed. In this specification, the term "adherent" refers to an object that is in contact with the adhesive layer on the opposite side to the polarizing plate during use. For example, the adhesive composition of the present invention is applied to an EWV layer. In the case of polarizing plates (that is, EWV polarizing plates), the glass substrate of the liquid crystal cell can be an adherend. In this specification, the term "substrate" refers to, for example, a polarizing plate, and the term "substrate" and the term "adherent" are used separately.

In this specification, "reworkability" refers to the ease of peeling during re-adhesive work, for example, it means that when the adhesive layer is peeled off from the adherend, the adhesive layer can be adhered to the adherend without transfer (so-called Re-paste in the case of glue residue), the better the reworkability, the easier it is to re-paste. In this specification, "durability" refers to the ability to suppress foaming, Levitating, and flaking properties.

In this specification, "(meth)acrylic copolymer" and "(meth)acrylic polymer" mean that among the monomers constituting the copolymer and the polymer, at least the main component monomer has ( Copolymers and polymers of methacryl-based monomers. The term "main component monomer" as used herein refers to a monomer having the largest content (unit: mass %) among monomers constituting copolymers and polymers. In one embodiment of the (meth)acrylic copolymer in the present invention, the content rate of the constituent unit derived from the monomer having a (meth)acryl group as the main component is 50% by mass or more of the total constituent units .

In this specification, "(meth)acrylic" is a term that includes both "acrylic" and "methacrylic", and "(meth)acrylate" includes "acrylate" and "methacrylic". The terms "ester" and "(meth)acryl" are terms that include both "acryl" and "methacryl".

[Adhesive composition for polarizing plates] The adhesive composition for polarizing plates (hereinafter, appropriately referred to as “adhesive composition”) of the present invention contains: (meth)acrylic copolymer (hereinafter, appropriately referred to as "Specific (meth)acrylic copolymer"), containing a constituent unit derived from a monomer having a carboxyl group and a constituent unit derived from an alkyl (meth)acrylate monomer, and derived from The content rate of the constituent unit of the monomer of at least one functional group (hereinafter, appropriately referred to as "specific functional group") in the group constituted by the group is in the range of 0.2% by mass to 0.8% by mass relative to all the constituent units , and the weight average molecular weight is in the range of 1,250,000 to 2,000,000; and an isocyanate compound, the amount of the isocyanate group in the above-mentioned isocyanate compound is relative to the total amount of carboxyl, hydroxyl, and amine groups in the above-mentioned (meth)acrylic copolymer The molar equivalent ratio 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.

In order to improve the reworkability, for example, it is considered to increase the amount of the crosslinking agent blended in the adhesive forming the adhesive layer. When the amount of the cross-linking agent blended in the adhesive increases, the cross-linking agent that does not participate in cross-linking will interact with the substrate, thereby improving the adhesion between the adhesive layer and the substrate, thereby improving reworkability. On the other hand, if the amount of the cross-linking agent blended in the adhesive is too large, the adhesive layer will become hard due to the increase of the cross-linking density of the formed adhesive layer, that is, the softness of the adhesive layer will be reduced. Sex will be lower. When the flexibility of the adhesive layer is low, it cannot fully follow the expansion and contraction of the base material accompanying changes in temperature and humidity, resulting in a decrease in durability.

On the other hand, in the adhesive composition of the present invention, by including a constituent unit derived from a monomer having a carboxyl group and a constituent unit derived from an alkyl (meth)acrylate monomer, and a constituent unit derived from a monomer having a carboxyl group, a hydroxyl group, and an amino group The content rate of the structural unit of the monomer of at least one functional group in the constituent group is in the range of 0.2% by mass to 0.8% by mass relative to all the structural units, and the weight average molecular weight is in the range of 1,250,000 to 2,000,000 The (meth)acrylic copolymer (that is, the specific (meth)acrylic copolymer) can improve the durability of the formed adhesive layer.

Furthermore, in the adhesive composition of the present invention, by containing the specific (meth)acrylic copolymer and the isocyanate compound, and the amount of the isocyanate group in the isocyanate compound is relative to the carboxyl group in the specific (meth)acrylic copolymer The molar equivalent ratio of the total amount of hydroxy, hydroxyl, and amino groups 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, which can improve the adhesiveness of the formed adhesive layer. Durability and heavy workability. In view of the above, according to the adhesive composition of the present invention, an adhesive layer excellent in both reworkability and durability can be formed.

With respect to the adhesive composition of the present invention, the adhesive described in Japanese Patent Application Laid-Open No. 2009-258660 is known, although the (meth)acrylic copolymer has a compound selected from carboxyl, hydroxyl, and amino groups. The content rate of the constituent units of monomers with at least one functional group in the group is high, but the amount of the isocyanate group in the isocyanate compound is relative to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the (meth)acrylic copolymer. Since the molar equivalent ratio of the amount is low, sufficient crosslinking density cannot be obtained, and the reworkability of the formed adhesive layer is remarkably poor (for example, refer to Reference Example 1 described later). That is, the adhesive disclosed in JP-A-2009-258660 cannot form an adhesive layer that has both excellent reworkability and durability.

Hereinafter, each component of the adhesive composition of this invention is demonstrated.

[Specific (meth)acrylic copolymer] The (meth)acrylic copolymer contained in the adhesive composition of the present invention (that is, the specific (meth)acrylic copolymer) contains Containing a constituent unit of a body and a constituent unit derived from an alkyl (meth)acrylate monomer, and a constituent unit derived from a monomer having at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, and an amine group The ratio is in the range of 0.2 mass % to 0.8 mass % with respect to all the constituent units, and the weight average molecular weight (Mw) is in the range of 1.25 million to 2 million.

A carboxyl group derived from a constituent unit of a monomer having a carboxyl group can be crosslinked with an isocyanate group of an isocyanate compound described later. Therefore, in the adhesive composition of the present invention, the carboxyl group derived from the constituent unit of the monomer having a carboxyl group contained in the specific (meth)acrylic copolymer and the isocyanate group of the isocyanate compound described later will undergo a crosslinking reaction, and can be An adhesive layer is formed.

In the present specification, "a structural unit derived from a monomer having a carboxyl group" means a structural unit formed by addition polymerization of a monomer having a carboxyl group.

The type of monomer having a carboxyl group is not particularly limited. Specific examples of monomers having carboxyl groups include: (meth)acrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone Ester (n≒2) mono(meth)acrylate, etc. Among them, the monomer having a carboxyl group is preferably selected from acrylic acid and ω-carboxy-polycaprolactone in view of, for example, the adhesive force of the adhesive layer and the adhesion between the adhesive layer and the substrate. (n≒2) at least one of monoacrylates, more preferably acrylic acid.

The specific (meth)acrylic copolymer may contain only 1 type of structural unit derived from the monomer which has a carboxyl group, and may contain 2 or more types.

The ratio (that is, the content) of the structural unit derived from the monomer having a carboxyl group in the specific (meth)acrylic copolymer is preferably 0.1 mass with respect to all the structural units constituting the specific (meth)acrylic copolymer % to 0.8% by mass, more preferably 0.1 to 0.5% by mass, more preferably 0.2 to 0.4% by mass. When the proportion of the structural unit derived from a monomer having a carboxyl group in the specific (meth)acrylic copolymer is 0.1% by mass or more relative to the total structural units constituting the specific (meth)acrylic copolymer, the carboxyl group and the isocyanate described below The cross-linking reaction of the isocyanate group of the compound proceeds efficiently, and an adhesive layer with more excellent durability can be formed. In addition, carboxyl groups are the main cause of corrosion of metals. Therefore, for display devices equipped with optical members containing metals such as ITO glass, (meth)acrylic copolymers containing a large proportion of constituent units derived from monomers having carboxyl groups are used. If the adhesive composition of the object is used, the adhesive layer formed will lead to the occurrence of metal corrosion. When the ratio of the structural unit derived from a monomer having a carboxyl group in the specific (meth)acrylic copolymer is 0.8% by mass or less relative to all the structural units constituting the specific (meth)acrylic copolymer, the Carboxyl metal corrosion due to adhesive layer.

The specific (meth)acrylic copolymer contains the structural unit derived from the alkyl (meth)acrylate monomer. The constituent units derived from the alkyl (meth)acrylate monomer contribute to the adjustment of the adhesive force of the adhesive layer.

In this specification, "the structural unit derived from the alkyl (meth)acrylate monomer" means the structural unit formed by the addition polymerization of the alkyl (meth)acrylate monomer.

The alkyl (meth)acrylate monomer is preferably an unsubstituted alkyl (meth)acrylate monomer, and its type is not particularly limited. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched or cyclic. Also, the carbon number of the alkyl group is preferably in the range of 1-18, more preferably in the range of 1-12, from the viewpoint of, for example, the adhesive force of the adhesive layer and the adhesiveness between the adhesive layer and the substrate.

Alkyl (meth)acrylate monomers include: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, (meth) Secondary butyl acrylate, tertiary butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)acrylate ) n-nonyl acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate Esters, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. Among them, the alkyl (meth)acrylate monomer is preferably selected from methyl acrylate, n-butyl acrylate, tertiary butyl acrylate, etc. in view of the ease of adjusting the cohesion and adhesion of the adhesive layer, for example. At least one of the group consisting of ester and 2-ethylhexyl acrylate, more preferably n-butyl acrylate.

The specific (meth)acrylic copolymer may contain only 1 type of structural unit derived from the alkyl (meth)acrylate monomer, and may contain 2 or more types.

The ratio (that is, the content) of the constituent unit derived from the alkyl (meth)acrylate monomer in the specific (meth)acrylic copolymer is, for example, in consideration of the ease of adjusting the adhesive force of the adhesive layer, relative to the composition The total constituent units of the specific (meth)acrylic copolymer are preferably at least 60% by mass, more preferably at least 70% by mass, and most preferably at least 80% by mass. The upper limit of the proportion of the constituent units derived from the alkyl (meth)acrylate monomer in the specific (meth)acrylic copolymer is not particularly limited, for example, relative to all the constituent units constituting the specific (meth)acrylic copolymer It is preferably 99.8% by mass or less.

For the specific (meth)acrylic copolymer, the content rate of the constituent unit derived from the monomer having at least one functional group selected from the group consisting of carboxyl group, hydroxyl group, and amino group is relative to the constituent specific ( The total constituent units of the meth)acrylic copolymer are in the range of 0.2% by mass to 0.8% by mass, and preferably contain constituent units derived from monomers having a hydroxyl group in addition to constituent units derived from monomers having a carboxyl group. The hydroxyl group derived from the structural unit of the monomer which has a hydroxyl group can react with the isocyanate group of the isocyanate compound mentioned later. In the adhesive composition of the present invention, when the constituent unit derived from the monomer having a hydroxyl group is contained, the gel fraction after crosslinking is increased compared to the case where the constituent unit derived from the monomer having a hydroxyl group is not included. Tendency to form an adhesive layer with better durability.

The type of monomer having a hydroxyl group is not particularly limited. Specific examples of monomers having a hydroxyl group include: (meth)acrylate-2-hydroxyethyl, (meth)acrylate-2-hydroxypropyl, (meth)acrylate-3-hydroxypropyl, (meth)acrylate ) -4-hydroxybutyl acrylate, -6-hydroxyhexyl (meth)acrylate, -10-hydroxydecyl (meth)acrylate, -12-hydroxylauryl (meth)acrylate, (meth)acrylic acid -3-Methyl-3-hydroxybutyl ester, (meth)acrylate-1,1-dimethyl-3-hydroxybutyl ester, (meth)acrylate-1,3-dimethyl-3-hydroxybutyl ester, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, glycerol mono(meth)acrylate, Polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, poly(ethylene glycol-propylene glycol) mono(meth)acrylate, and the like.

As for the monomer having a hydroxyl group, in consideration of the moderate adhesion of the formed adhesive layer to the substrate, durability, and suppression of white spots, it is preferably a (meth)acrylic alkyl group having a hydroxyl group as a substituent. Esters selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxyl (meth)acrylate More preferably at least one of the group consisting of decyl ester and 12-hydroxylauryl (meth)acrylate, selected from 2-hydroxyethyl (meth)acrylate, 4-hydroxylauryl (meth)acrylate, At least one kind selected from the group consisting of hydroxybutyl ester and 6-hydroxyhexyl (meth)acrylate is particularly preferred.

When a specific (meth)acrylic-type copolymer contains the structural unit derived from the monomer which has a hydroxyl group, it may contain only 1 type of structural unit derived from the monomer which has a hydroxyl group, and may contain 2 or more types.

When the specific (meth)acrylic copolymer contains a structural unit derived from a monomer having a hydroxyl group, the proportion of the structural unit derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer (that is, the content rate ), as long as the content rate of the constituent units derived from monomers having at least one functional group selected from the group consisting of carboxyl, hydroxyl, and amino groups is The constituent units are within the range of 0.2% by mass to 0.8% by mass, and are not particularly limited. For example, from the viewpoint of forming an adhesive layer with better durability, the ratio of the constituent unit derived from a monomer having a hydroxyl group in the specific (meth)acrylic copolymer to that of the constituent unit of the specific (meth)acrylic copolymer The total constituent units are preferably in the range of 0.01% by mass to 0.8% by mass, more preferably in the range of 0.1% by mass to 0.6% by mass.

For the specific (meth)acrylic copolymer, the content rate of the constituent unit derived from the monomer having at least one functional group selected from the group consisting of carboxyl group, hydroxyl group, and amino group is relative to the constituent specific ( The range of all the structural units of a meth)acrylic-type copolymer is 0.2 mass % - 0.8 mass %, More preferably, it is the range of 0.3 mass % - 0.5 mass %. In addition, the amine group referred to here refers to a primary amine group or a secondary amine group. Carboxyl groups, hydroxyl groups, and amine groups can all be cross-linked with isocyanate groups of isocyanate compounds described later. Selected from the group consisting of carboxyl, hydroxyl, and amino groups if the content of constituent units derived from monomers having at least one functional group selected from the group consisting of carboxyl groups, hydroxyl groups, and amino groups is 0.2% by mass or more The crosslinking reaction between at least one functional group in the group and the isocyanate group of the isocyanate compound proceeds moderately, the formed adhesive layer has an appropriate crosslinking density, and the adhesion between the adhesive layer and the substrate becomes good. Therefore, it is considered that the adhesive composition of the present invention can form an adhesive layer excellent in durability. In addition, if the content rate of the constituent unit derived from a monomer having at least one functional group selected from the group consisting of carboxyl group, hydroxyl group, and amino group is 0.8% by mass or less, it is selected from carboxyl group, hydroxyl group, and amino group. At least one functional group in the group and the isocyanate group of the isocyanate compound are not excessively cross-linked, so an adhesive layer exhibiting moderate flexibility can be formed. An adhesive layer exhibiting moderate flexibility can fully follow the expansion and contraction of the base material accompanied by changes in temperature and humidity. Therefore, it is considered that the adhesive composition of the present invention can form an adhesive layer excellent in durability.

The specific (meth)acrylic copolymer may contain a constituent unit derived from a monomer having a carboxyl group, a constituent unit derived from an alkyl (meth)acrylate monomer, and an arbitrary constituent within the range in which the effects of the present invention are exerted. The structural unit other than the structural unit derived from the monomer which has a hydroxyl group (Hereinafter, it is suitably called "other structural unit.").

The types of monomers constituting other constituent units are not particularly limited. As monomers constituting other structural units, for example, (meth)acrylates having a cyclic group represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; Base) alkoxyalkyl (meth)acrylate represented by methoxyethyl acrylate and ethoxyethyl (meth)acrylate; styrene, α-methylstyrene, tertiary butylstyrene, Aromatic monoethylene represented by p-chlorostyrene, chloromethylstyrene, and vinyl toluene; vinyl cyanide represented by acrylonitrile and methacrylonitrile; and vinyl formate, vinyl acetate, and vinyl propionate , and vinyl-versatate represented by vinyl esters. Moreover, various derivatives of these monomers are mentioned as a monomer which comprises another structural unit. Further, monomers constituting other structural units also include monomers having functional groups such as glycidyl group, amide group, N-substituted amide group, and tertiary amine group.

As a monomer having a glycidyl group, specifically, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl Ether, 3,4-epoxycyclohexyl vinyl ether, glycidyl (methyl) allyl ether, 4-hydroxybutyl acrylate glycidyl ether, and 3,4-epoxycyclohexyl (methyl) Allyl ether.

As a monomer having an amido group or an N-substituted amido group, specifically, acrylamide, methacrylamide, N-methyl(meth)acrylamide, N-ethyl( Meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide Amine, N-butoxymethyl(meth)acrylamide, N-tertiary butylacrylamide, N-octylacrylamide, dimethylacrylamide, diethylacrylamide, iso Propyl acrylamide, and diacetone acrylamide.

As a monomer having a tertiary amino group, specifically, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylamide.

For example, when the adhesive composition of the present invention is used in an IPS (In Plane Switching) type polarizing plate (that is, an IPS polarizing plate), in consideration of further enhancing the white point suppression effect, the monomers constituting other constituent units are preferably It is phenoxyethyl (meth)acrylate.

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, more preferably in the range of 1.4 million to 1.7 million. When the weight average molecular weight (Mw) of a specific (meth)acrylic-type copolymer is 1.25 million or more, the adhesive layer excellent in 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 adhesive composition does not become too high, so the adhesive composition can be coated well.

The weight average molecular weight (Mw) of a specific (meth)acrylic-type copolymer is the value measured by the following method. Specifically, it is measured according to the following (1)-(3). (1) Coat the solution of the specific (meth)acrylic copolymer on release paper, and dry it at 100° C. for 2 minutes to obtain the specific (meth)acrylic copolymer in the form of a film. (2) Using the film-like specific (meth)acrylic copolymer and tetrahydrofuran obtained in (1) above, a sample solution having a solid content concentration of 0.2% by mass was obtained. (3) The weight average molecular weight (Mw) of a specific (meth)acrylic-type copolymer was measured by the gel permeation chromatography (GPC) under the following conditions as a standard polystyrene conversion value.

~Conditions~ Measuring device: High-speed GPC (model: HLC-8220 GPC, Tosoh Co., Ltd.) Detector: Differential refractometer (RI) (installed in HLC-8220, Tosoh Co., Ltd.) Column: TSK-GEL GMHXL (Tosoh Co., Ltd.) 4 columns connected in series Temperature: 40°C Eluent: THF 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 adhesive composition of the present invention is preferably 50% by mass relative to the total solid content of the adhesive composition in consideration of the ease of adjusting the cohesion and adhesion of the adhesive layer. % to 99% by mass.

[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 conventional polymerization methods represented by solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among them, the polymerization method is preferably solution polymerization in consideration of relatively simple treatment steps and the ability to carry out in a short period of time.

Solution polymerization generally involves adding predetermined organic solvents, monomers, polymerization initiators, and chain transfer agents as needed into the polymerization tank, and heating them while stirring in a nitrogen stream or at the reflux temperature of the organic solvent to make them react several times. Hour. At this time, at least a part of the organic solvent, monomer, polymerization initiator and/or chain transfer agent may be added sequentially.

The organic solvent used in the polymerization reaction, for example, benzene, toluene, ethylbenzene, n-propylbenzene, tertiary butylbenzene, o-xylene, m-xylene, p-xylene, tetrahydronaphthalene, decahydronaphthalene, and Aromatic hydrocarbons represented by aromatic naphtha; aliphatic hydrocarbons represented by n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, naphtha, and turpentine or Alicyclic hydrocarbons; ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and benzoic acid Esters represented by methyl ester; Ketones represented by acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, and methyl cyclohexanone; Glycol ethers represented by alcohol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and methanol, ethanol, n-propylene Alcohols represented by alcohol, isopropanol, n-butanol, isobutanol, secondary butanol, and tertiary butanol. During the polymerization reaction, these organic solvents may be used alone or in combination of two or more.

When producing specific (meth)acrylic copolymers, it is advisable to use organic solvents such as esters and ketones that are not prone to chain transfer during the polymerization reaction, considering the solubility and polymerization reaction of specific (meth)acrylic copolymers Ethyl acetate, toluene, and the like are particularly preferably used from the viewpoint of ease of use.

As a polymerization initiator, organic peroxides, azo compounds, etc. which are generally used in solution polymerization can be used. Examples of organic peroxides include tertiary butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauryl peroxide, hexyl peroxide, Diisopropyl peroxydicarbonate, bis(2-ethylhexyl peroxydicarbonate), tertiary butyl peroxytrimethylacetate, 2,2-bis(4,4-di-tertiary butyl Peroxycyclohexyl) propane, 2,2-bis(4,4-di-tertiary pentylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tertiary octylperoxycyclohexyl) ) propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tertiary butylperoxycyclohexyl)butane alkanes, and 2,2-bis(4,4-di-tertiary octylperoxycyclohexyl)butane. Examples of azo compounds include: 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2 ,2'-Azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-Azobis(cyclohexane-1-carbonitrile), and 2,2'- Azobis(methyl isobutyrate).

When producing a specific (meth)acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and it is especially 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, 0.005 to 0.05 parts by mass relative to 100 parts by mass of the total monomers constituting the specific (meth)acrylic copolymer Better range.

In the production of the specific (meth)acryl-based copolymer, a chain transfer agent may be used as needed, as long as the object and effect of the present invention are not impaired. In terms of chain transfer agents, for example, cyanoacetic acid and alkyl esters with 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid and alkyl esters with 1 to 8 carbon atoms of bromoacetic acid; Aromatic compounds represented by ethylene, anthracene, phenanthrene, fennel, and 9-phenylfenene; p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrobenzoic acid Aromatic nitro compounds represented by nitrotoluene; benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone; Borane derivatives; as carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromochloroform, tribromomethane, and Halogenated hydrocarbons represented by 1-propene; aldehydes represented by chloral and furan formaldehyde; alkyl mercaptans with carbon number 1-18; aromatic mercaptans represented by sulfur phenol and toluene mercaptan; Thioglycolic acid, alkyl esters of thioglycolic acid with 1 to 10 carbon atoms; hydroxyalkylthiols with 1 to 12 carbon atoms; and terpenes represented by pinene and terpinolene .

When a chain transfer agent is used in the production of a specific (meth)acrylic copolymer, the amount of the chain transfer agent used is, for example, 100 mass relative to the total amount of monomers constituting the specific (meth)acrylic copolymer The range of 0.005 mass part - 1.0 mass part may be sufficient.

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 most preferably in the range of 60°C to 80°C.

[Other (meth)acrylic polymers] The adhesive composition of the present invention preferably contains a weight average molecular weight in the range of 5,000 to 200,000, and does not have any functional group among carboxyl, hydroxyl, and amine groups (meth)acrylic polymers (hereinafter, referred to as "other (meth)acrylic polymers" as appropriate.). The adhesive composition of the present invention tends to further suppress the generation of white spots in the formed adhesive layer by further containing other (meth)acrylic polymers.

Other (meth)acrylic polymers may be homopolymers composed of specific monomers or copolymers composed of two or more types of monomers.

Other (meth)acrylic polymers preferably contain a constituent unit derived from an alkyl (meth)acrylate monomer. When the specific (meth)acrylic copolymer contains a constituent unit derived from an alkyl (meth)acrylate monomer, the type of the alkyl (meth)acrylate monomer is as long as it does not have a carboxyl group, a hydroxyl group, and an amine group. The monomer of any functional group is not particularly limited other than this. In addition, the amine group referred to here refers to a primary amine group or a secondary amine group. As an alkyl (meth)acrylate monomer, the thing similar to the unsubstituted alkyl (meth)acrylate monomer in the said specific (meth)acrylic-type copolymer is mentioned, for example. The alkyl (meth)acrylate monomer in other (meth)acrylic polymers 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 5,000 to 200,000, preferably in the range of 10,000 to 150,000, more preferably in the range of 50,000 to 150,000. When the weight average molecular weight (Mw) of other (meth)acryl-type polymers is 50,000 or more, the durability of the adhesive layer formed will be further improved. When the weight average molecular weight (Mw) of another (meth)acryl-type polymer is 200,000 or less, the generation|occurrence|production of the white spot in the adhesive agent layer formed will be suppressed further.

The weight average molecular weight (Mw) of other (meth)acryl-type polymers is measured by the method similar to the weight average molecular weight (Mw) of the said specific (meth)acryl-type copolymer.

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

When the adhesive composition of the present invention contains other (meth)acrylic polymers, the content of other (meth)acrylic polymers in the adhesive composition is considered to suppress white spots in the formed adhesive layer From the viewpoint of the generation of the aforementioned specific (meth)acrylic copolymer, it is preferably in the range of 0.01 to 40 parts by mass, more preferably in the range of 10 to 30 parts by mass, and is 15 parts by mass The range of -25 parts by mass is particularly preferable.

Other (meth)acrylic-type polymers can be manufactured by the method similar to the said specific (meth)acrylic-type copolymer.

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

Isocyanate compounds include: aromatic polyisocyanate compounds represented by xylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and toluene diisocyanate (TDI); Chain or cyclic aliphatic polyisocyanate compounds represented by isocyanate (HMDI), isophorone diisocyanate, hydrogenated products of the aforementioned aromatic polyisocyanate compounds; diurea, dimer, and trimer of these polyisocyanate compounds Compounds or pentamers, adducts of these polyisocyanate compounds and polyol compounds such as trimethylolpropane, etc.

As an isocyanate compound, a commercial item can be used. As commercially available isocyanate compounds, for example, Tosoh Co., Ltd.'s "CORONATE (registered trademark) HX", "CORONATE (registered trademark) HL-S", "CORONATE (registered trademark) L", " CORONATE (registered trademark) 2031", "CORONATE (registered trademark) 2030", "CORONATE (registered trademark) 2234", "CORONATE (registered trademark) 2785", "AQUANATE (registered trademark) 200", and "AQUANATE (registered trademark) )210”; Sumika Covestro Urethane’s “SUMIDUR (registered trademark) N3300”, “DESMODUR (registered trademark) N3400”, and “SUMIDUR (registered trademark) N-75”; Asahi Kasei’s “DURANATE (registered trademark) Trademark) E-405-80T", "DURANATE(registered trademark) 24A-100", and "DURANATE(registered trademark) TSE-100"; and "TAKENATE(registered trademark) D-110N" of Mitsui Takeda Chemical Co., Ltd. , "TAKENATE (registered trademark) D-120N", "TAKENATE (registered trademark) M-631N" and "MT-OLESTER (registered trademark) NP1200".

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

In the adhesive composition of the present invention, the molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the aforementioned specific (meth)acrylic copolymer (isocyanate The molar amount of the isocyanate group in the compound/the total molar amount of the carboxyl group, hydroxyl group, and amino group in the specific (meth)acrylic copolymer) is in the range of 0.15 to 2.5, preferably in the range of 0.4 to 2.0, which is The range of 0.6-1.5 is more preferable. In the adhesive composition of the present invention, the molar amount of the isocyanate group in the isocyanate compound/the total molar amount of the carboxyl group, hydroxyl group, and amino group in the specific (meth)acrylic copolymer is 0.15 or more, although The amount of carboxyl groups, hydroxyl groups, and amine groups (so-called groups capable of crosslinking with isocyanate groups) in the specific (meth)acrylic copolymer is small, and sufficient crosslinking can be performed. As a result, it is thought that the crosslink density of the formed adhesive layer becomes moderately high, and it is possible to form an adhesive layer excellent in durability while maintaining excellent reworkability. On the other hand, in the adhesive composition of the present invention, the molar amount of the isocyanate group in the isocyanate compound/the total molar amount of the carboxyl group, hydroxyl group, and amino group in the specific (meth)acrylic copolymer is Below 2.5, there will be no excessive production of isocyanate compounds that do not participate in crosslinking. As a result, the formed adhesive layer does not become hard, but exhibits moderate flexibility, so it can fully follow the expansion and contraction of the substrate accompanying changes in temperature and humidity. Therefore, it is considered that the adhesive composition of the present invention can form an adhesive layer that is excellent in both reworkability and durability, and in which the generation of white spots is suppressed.

The molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the specific (meth)acrylic copolymer (the molar amount of isocyanate groups in the isocyanate compound/specific ( The total molar amount of carboxyl groups, hydroxyl groups, and amino groups in the meth)acrylic copolymer can be calculated according to the following formulas (1) to (3). In addition, in the following calculation formula, the molar amount of the isocyanate group in the isocyanate compound is marked as "NCO amount", and the total molar amount of the carboxyl group, hydroxyl group, and amino group in the specific (meth)acrylic copolymer is marked as "Total functional basis".

Amount of NCO (unit: mmol/solid content 100 g) = [content rate of isocyanate group in isocyanate compound (unit: mass %)/solid content of isocyanate compound (unit: mass %) × blending amount of isocyanate compound (unit: mass %) g)]/molecular weight of isocyanate group (unit: g/mol)×1000･･･(1)

Amount of total functional groups (unit: mmol/100 g of solid content) = [Content rate (unit: mass %) of a constituent unit derived from a monomer having a carboxyl group in a specific (meth)acrylic copolymer/unit derived from a monomer having a carboxyl group The molecular weight of the constituent unit of the body (unit: g/mol) × the number (valence) of the carboxyl group in the constituent unit from the monomer having a carboxyl group × 1000] + [the specific (meth)acrylic copolymer from Content ratio of the constituent unit of the monomer having a hydroxyl group (unit: mass %)/molecular weight of the constituent unit derived from the monomer having a hydroxyl group (unit: g/mol)×the ratio of the hydroxyl group in the constituent unit of the monomer having a hydroxyl group Number (valence) × 1000] + [Content rate of constituent units derived from monomers having amino groups in specific (meth)acrylic copolymers (unit: mass %)/Amount derived from monomers having amino groups The molecular weight of the constituent unit (unit: g/mol) × the number of amino groups (valence) in the constituent units derived from monomers with amino groups × 1000]･･･(2)

The molar equivalent ratio of the amount of isocyanate groups to the total amount of carboxyl groups, hydroxyl groups, and amine groups in a specific (meth)acrylic copolymer =NCO amount/total functional group amount･･･(3)

[Epoxy Compound] The adhesive composition of the present invention preferably further contains an epoxy compound as a crosslinking agent in addition to the aforementioned isocyanate compound. In the adhesive composition of the present invention, as far as the crosslinking agent is concerned, if the epoxy compound is included in addition to the isocyanate compound, the crosslinking density of the formed adhesive layer will be further increased, so the durability of the adhesive layer can be further improved. sex.

In this specification, an "epoxy compound" means a compound having two or more epoxy groups in a molecule (so-called more than bifunctional epoxy compound).

Epoxy compounds include 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, Glycerin Diglycidyl Ether Ether, Glycerin Triglycidyl Ether, Diglycerol Polyglycidyl Ether, Polyglycerol Polyglycidyl Ether, Resorcinol Diglycidyl Ether, 2,2-Dibromoneopentyl Glycol Diglycidyl Ether , Trimethylolpropane Triglycidyl Ether, Pentaerythritol Polyglycidyl Ether, Sorbitol Polyglycidyl Ether, Diglycidyl Adipate, Diglycidyl Phthalate, Ginseng (Glycidyl) isocyanurate, ginseng (glycidoxyethyl) isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane , N,N,N',N'-tetraepoxypropyl-1,3-benzenedi(methanamine), etc.

A commercial item can be used for an epoxy compound. As commercially available epoxy compounds, for example, "TETRAD (registered trademark)-X" and "TETRAD (registered trademark)-C" of Mitsubishi Gas Chemical Co., Ltd.; and "Denacol (registered trademark) of Nagase ChemteX Co., Ltd. Trademark) EX-201".

When the adhesive composition of the present invention contains an epoxy compound, it may contain only one type of epoxy compound, or may contain two or more types.

When the adhesive composition of the present invention contains an epoxy compound, the content of the epoxy compound in the adhesive composition is not particularly limited. For example, it is preferably 0.005 parts by mass to 100 parts by mass of a specific (meth)acrylic copolymer. The range of 1 part by mass is more preferably in the range of 0.01 to 0.5 parts by mass, and more preferably in the range of 0.02 to 0.1 parts by mass. If the content of the epoxy compound in the adhesive composition is 0.005 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer, the epoxy compound will react with the specific functional group that is not crosslinked by the isocyanate compound , thereby further increasing the cross-linking density of the formed adhesive layer, so the durability of the adhesive layer can be further improved. When the content of the epoxy compound in the adhesive composition is 1 part by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer, the reaction of the epoxy compound to the specific functional group is greater than that of the epoxy compound to the isocyanate compound. The reaction is slow, so it is less prone to damage and the storage stability of the adhesive composition.

[Silane coupling agent] The adhesive composition of the present invention may further contain a silane coupling agent. If the adhesive composition of the present invention further contains a silane coupling agent, the durability of the formed adhesive layer can be further improved.

In terms of silane coupling agents, examples include: vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane containing polymerizable unsaturated Silane compounds containing thiol groups; silanes containing thiol groups represented by 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane Compounds; silane compounds containing epoxy groups represented by 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; 3- Aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyl Amino-containing silane compounds represented by dimethoxysilane; and ginseng-(3-trimethoxysilylpropyl)isocyanurate. In addition, the silane compound containing an epoxy group does not have the function as a crosslinking agent unlike the said epoxy compound.

As a silane coupling agent, a commercial item can be used. Examples of commercially available silane coupling agents include: Shin-Etsu Chemical Co., Ltd.'s trade names "KBM-803", "KBM-802", "X-41-1810", "X-41-1805 ", and "X-41-1818" as representatives of silane compounds containing thiol groups; and the trade names "KBM-403", "KBM-303", "KBM-402", "KBE-402", "KBE-403", "X-41-1053", and "X-41-1056" are representative epoxy group-containing silane compounds.

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

When the adhesive composition of the present invention contains a silane coupling agent, the content of the silane coupling agent in the adhesive composition is not particularly limited, for example, it is preferably 0.01 mass parts relative to 100 mass parts of the specific (meth)acrylic copolymer The range of 0.05-1 mass part is more preferable in the range of 0.05-0.5 mass part, and the range of 0.05-0.5 mass part is more preferable. If the content of the silane coupling agent in the adhesive composition is within the above range, the durability of the formed adhesive layer can be further improved.

[Organic solvent] The adhesive composition of the present invention may contain an organic solvent in order to improve applicability. As an organic solvent, the organic solvent used at the time of the polymerization reaction of the said specific (meth)acryl-type copolymer is mentioned, for example.

[Other Components] The adhesive composition of the present invention may optionally contain components other than the aforementioned components (so-called other components) within the range that does not impair the effect of the present invention. Examples of other components include polymers other than specific (meth)acrylic copolymers and other (meth)acrylic polymers, crosslinking agents other than isocyanate compounds and epoxy compounds, crosslinking catalysts, solvents, and antioxidants , Colorants (for example, dyes and pigments), light stabilizers (for example, ultraviolet absorbers), antistatic agents and other additives. In addition, in the adhesive composition of the present invention, the above-mentioned specific (meth)acrylic copolymer has a carboxyl group as a functional group serving as a crosslinking point, so the crosslinking reaction can be completed even without a crosslinking catalyst.

<Gel fraction after crosslinking> The 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. The range of 50% by mass to 70% by mass is more preferable. If the gel fraction after cross-linking is 40% by mass or more, the cohesive force of the adhesive layer will be in an appropriate range, and cohesion and damage of the adhesive layer will not occur during rework, and it can be suppressed on the substrate and/or by The glue residue of the viscous body can also suppress the generation of air bubbles (ie, foaming) when exposed to a high temperature environment or a high temperature and high humidity environment. When the gel fraction after crosslinking is 75% by mass or less, it can sufficiently follow the expansion and contraction of the base material accompanying changes in temperature and humidity, and tends to be excellent in durability.

In the adhesive composition of the present invention, the (meth)acrylic copolymer contains a structural unit derived from a monomer having a carboxyl group, so the gel fraction after crosslinking is 40% by mass or more. In addition, if any of the conditions that the specific (meth)acrylic copolymer contained in the adhesive composition contains an appropriate amount of constituent units derived from a monomer having a hydroxyl group, or the adhesive composition contains an appropriate amount of a crosslinking agent , the gel fraction after crosslinking tends to fall within the range of 40% by mass to 75% by mass.

In this specification, the "gel fraction after crosslinking of the adhesive composition" refers to the proportion of solvent-insoluble components measured using ethyl acetate as the extraction solvent. The gel fraction after crosslinking of the adhesive composition is specifically measured according to the following (1)-(4). (1) Attach about 0.15 g of the cross-linked adhesive composition (that is, the adhesive layer) to a 250-mesh metal mesh (100mm×100mm) whose mass was accurately measured by a precision balance, so that the gel In such a way as not to leak, make the attached adhesive layer inside, and fold the metal mesh 5 times to make a sample. Afterwards, the mass is accurately determined using precision balances. (2) The obtained sample was immersed in 80 mL of ethyl acetate for 3 days. (3) Take out the sample, wash it with a small amount of ethyl acetate, and dry it at 120° C. for 24 hours. Afterwards, the mass is accurately determined using precision balances. (4) Calculate the gel fraction according to the following formula. Gel fraction (unit: mass %)=(Z-X)/(Y-X)×100 However, X is the mass of the metal mesh (unit: g), and Y is the mass of the metal mesh with the adhesive layer attached before dipping (unit: g), Z is the mass (unit: g) of the metal mesh attached with the adhesive layer after dipping and drying.

[Use of Adhesive Composition] The adhesive composition of the present invention is ideally used for adhering a polarizing plate to an adherend through an adhesive layer. Specifically, the application of affixing a polarizing plate to a liquid crystal cell, the application of affixing a polarizing plate to an optical film such as a phase difference film, etc. are mentioned. Among these, when it is used for adhering a polarizing plate to a liquid crystal cell in which durability and suppressing occurrence of white spots are particularly required, since the effect of the adhesive composition of the present invention can be exhibited more, it is preferable.

As mentioned above, generally speaking, the adhesion between the EWV layer and the adhesive layer is extremely poor, so the adhesive layer formed on the surface of the EWV layer is easily transferred and adhered to the adherend (for example, the glass substrate of the liquid crystal cell). In contrast, the adhesive composition of the present invention can form an adhesive layer that exhibits good adhesion even to the EWV layer, and has excellent reworkability, so it is particularly suitable for use in a polarizing plate to be provided with an EWV layer (that is, an EWV polarizing plate ) is pasted on the adherend (for example, the glass substrate of the liquid crystal unit). In addition, when the EWV polarizing plate is reworked, if peeling occurs at the interface between the EWV layer and the adhesive layer, the reworkability will be significantly reduced.

[Polarizing plate with adhesive layer] The polarizing plate with adhesive layer in the present invention includes a polarizing plate and an adhesive layer formed of the above-mentioned adhesive composition of the present invention. The polarizing plate with an adhesive layer in the present invention has an adhesive layer formed from the adhesive composition of the present invention, so it has excellent reworkability and durability. Moreover, the polarizing plate with the adhesive layer in the present invention is less prone to white spots.

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

The layer structure of the polarizing plate with an adhesive layer of the present invention includes, for example: adhesive layer/polarizer, adhesive layer/polarizer/protective film, adhesive layer/protective film/polarizer/protective film, and adhesive Agent layer/protective film/polarizer. In addition, a retardation film (for example, an optical functional layer, an adhesive layer, and an easy adhesive layer) and other layers. Moreover, the outermost surface of the polarizing plate with an adhesive layer can also be protected with a release film.

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

As a protective film, a triacetyl cellulose (TAC) film, a polycycloolefin (COP) film, and an acrylic film are mentioned, for example.

In terms of the release film in contact with the adhesive layer, it is desirable to release the release film on the surface with a release agent such as fluorine-based resin, paraffin, silicone, etc., in order to easily peel the release film from the adhesive layer. Molded polyester and other synthetic resin films. When protecting the surface opposite to the side of the adhesive layer with a release film, examples of the release film include surface protection films such as hard-coated polyethylene terephthalate (PET) films. .

A preferred aspect of the polarizing plate with an adhesive layer of the present invention includes a polarizing plate, a layer disposed on the surface of the polarizing plate and having a contact angle with water of 90° or more, and a layer disposed on the above-mentioned and The aspect of the adhesive layer formed from the adhesive composition of the present invention on the surface of the layer whose water contact angle is 90° or more. In general, a layer having a contact angle with water of 90° or more has extremely poor adhesion to the adhesive layer, so the adhesive layer formed on the surface of the layer tends to transfer and adhere to the adherend. On the other hand, the adhesive layer formed by the adhesive composition of the present invention exhibits excellent adhesiveness even for a layer with a contact angle with water of 90° or more, and has excellent reworkability, so it is possible to design an attached device as described above. Polarizing plate with adhesive layer.

The "contact angle with water" in this specification refers to the drop of pure water of 2 μm on the surface of the layer to be measured under the condition of ambient temperature of 25°C, and the water drop is measured with a contact angle meter after standing for 30 seconds. The value obtained from the contact angle. As the measurement device, for example, Drop Master DM-701 (product name) of Kyowa Interface Science Co., Ltd. can be used. However, the measurement device is not limited to this.

As a layer whose contact angle with water is 90 degrees or more, the layer containing a discotic liquid crystal compound (ie, EWV layer) is mentioned, for example.

The thickness of the 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. Generally speaking, the thickness of the adhesive layer is in the range of 1 μm to 100 μm, preferably in the range of 5 μm to 50 μm, especially 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 for the known method, for example, the method of applying the adhesive composition of the present invention on the release film and drying it to form a coating layer of the adhesive composition on the release film, and then applying the adhesive composition The layer is transferred to a polarizing plate and cured to produce a polarizing plate with an adhesive layer. In addition, the method of applying the adhesive composition of the present invention on a release film and drying it, forming a coating layer of the adhesive composition on the release film, and then further adhering the exposed surface of the coating layer to set the release film A double-sided adhesive tape without a support is made by using a thin film, and the coating layer is cured, and then one of the peeling films is peeled off, and the exposed adhesive layer is transferred to a polarizing plate to produce a polarizing plate with an adhesive layer. Also, a method of producing a polarizing plate with an adhesive layer by applying the adhesive composition of the present invention on a polarizing plate, drying, and curing it can be mentioned. In addition, drying conditions include, for example, conditions of drying at 70° C. to 120° C. for 1 minute to 3 minutes using a hot air dryer. [Example]

Hereinafter, the present invention will be described more specifically by way of examples. The present invention is not limited to the following examples unless the gist is exceeded.

In addition, the weight average molecular weight (Mw) of the (meth)acrylic copolymer A and the (meth)acrylic copolymer B prepared in this example is based on the combination of the aforementioned specific (meth)acrylic copolymer The measurement method of weight average molecular weight (Mw) was measured by the same method.

[Example 1] <Manufacture of (meth)acrylic copolymer A> In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet pipe, and a reflux cooling pipe, n-butyl acrylate (n-BA; ester monomer) 81.2 parts by mass, 18.0 parts by mass of phenoxyethyl acrylate (PHEA), 0.6 parts by mass of 2-hydroxyethyl acrylate (2HEA; an acrylic monomer having a hydroxyl group), acrylic acid (AA; an acrylic acid having a carboxyl group) After mixing 0.2 parts by mass of monomer) and 110 parts by mass of ethyl acetate, the inside of the reactor was replaced with nitrogen. Then, after heating the mixture in the reactor to 70°C while stirring, 0.02 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN; polymerization initiator) and acetic acid 40 parts by mass of ethyl ester was kept for 6 hours to make it polymerized. After completion|finish of a polymerization reaction, it diluted with ethyl acetate so that solid content might become 17.3 mass %, and the solution of the (meth)acrylic-type copolymer A whose weight average molecular weight (Mw) was 1.6 million was obtained. In addition, "solid content" means the amount of residue obtained by removing volatile components, such as a solvent, from the solution of the (meth)acryl-type copolymer A.

<Manufacture of (meth)acrylic copolymer B> 36.0 parts by mass of n-butyl acrylate (n-BA), methyl acrylate (MA) 20.0 parts by mass, 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; polymerized Initiator) 0.20 parts by mass and mixed, the mixture in the reactor was heated to 95°C while stirring, then, 2,2'- azobisisobutyronitrile (AIBN) 2.29 parts by mass and ethyl acetate were added successively 110 parts by mass, kept for 6 hours and allowed to polymerize. After completion|finish of a polymerization reaction, it diluted with 176.8 mass parts of toluene, and solid content became 47.3 mass parts, and the solution of the (meth)acrylic-type copolymer B whose weight average molecular weight (Mw) was 100,000 was obtained. In addition, "solid content" means the amount of residue obtained by removing volatile components, such as a solvent, from the solution of the (meth)acryl-type copolymer B.

<Preparation of Adhesive Composition> Mix 100 parts by mass of a solution of (meth)acrylic copolymer A (in terms of solid content) and 20 parts by mass of a solution of (meth)acrylic copolymer B (in terms of solid content) , Isocyanate compound (trade name: SUMIDUR (registered trademark) N-75, bisurea type of hexamethylene diisocyanate (HMDI), Sumika Covestro Urethane Co., Ltd.) 0.65 parts by mass (solid content conversion value), silane coupling 0.1 part by mass of agent (trade name: X-41-1810, solid content: 100% by mass, Shin-Etsu Chemical Co., Ltd.) was fully stirred and mixed to obtain an adhesive composition. The molar equivalent ratio of the amount of isocyanate groups possessed by the isocyanate compound in the obtained adhesive composition to the total amount of specific functional groups possessed by the (meth)acrylic copolymer [the isocyanate group possessed by the isocyanate compound The molar amount/the total molar amount of the specific functional groups which the (meth)acrylic-type copolymer has was 0.43.

The molar equivalent ratio of the amount of isocyanate groups that the isocyanate compound has to the total amount of specific functional groups that the (meth)acrylic copolymer has is calculated using the aforementioned calculation formulas (1) to (3). Specifically, it is calculated as follows. In addition, SUMIDUR (registered trademark) N-75 which is an isocyanate compound has a solid content of 75% by mass and an isocyanate group content of 16.5% by mass. Also, the molecular weight of the isocyanate group was 42. Also, the molecular weight of the structural unit derived from acrylic acid which is a monomer having a carboxyl 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.

Calculation formula (1) NCO amount (unit: mmol/solid content 100 g) = content rate of isocyanate group in isocyanate compound (unit: mass %)/solid content of isocyanate compound (unit: mass %) × blending of isocyanate compound Amount (unit: g)/molecular weight of isocyanate group (unit: g/mol) x 1000 = 16.5 (mass %) / 75 (mass %) x 0.65 (g) / 42 (g/mol) x 1000 = 3.4

Calculation formula (2) total functional group amount (unit: mmol/solid content 100g) = [(meth)acrylic copolymer content rate (unit: mass %) of the constituent unit derived from the monomer having a carboxyl group/from The molecular weight of the constituent unit of the monomer having a carboxyl group (unit: g/mol) × the number (valence) of the carboxyl group derived from the constituent unit of the monomer having a carboxyl group × 1000] + [(meth)acrylic copolymer The content of the constituent unit derived from the monomer having a hydroxyl group (unit: mass %)/the molecular weight of the constituent unit derived from the monomer having a hydroxyl group (unit: g/mol) × the constituent unit derived from the monomer having a hydroxyl group The number of hydroxyl groups (valence) × 1000] + [(meth)acrylic copolymer content rate of constituent units derived from monomers having amino groups (unit: mass %)/monomers derived from amino groups The molecular weight of the constituent unit of the monomer (unit: g/mol) × the number (valence) of the amino groups (valence) × 1000] = [0.2 (mass parts) / 100 (mass parts )×100(%)/72(g/mol)×1×1000]＋[0.6(mass parts)/100(mass parts)×100(%)/116(g/mol)×1×1000]＝7.95

Calculation formula (3) The molar equivalent ratio of the amount of isocyanate groups relative to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the (meth)acrylic copolymer = NCO amount/total functional group amount = 3.4/7.95 = 0.43

<Production of a polarizing plate with an adhesive layer> Using the adhesive composition obtained above, a polarizing plate with an adhesive layer was produced as follows. Apply the adhesive composition to a release film (trade name: FILMBYNA (registered trademark) 100E-0010N023, Fujimori Kogyo Co., Ltd. (stock)) surface treatment surface to form a coating layer. Then, the peeling film with the coating layer was dried at 100° C. for 1 minute using a hot air circulation dryer to form a layer of the adhesive composition on the peeling film. Then, the EWV layer side surface of the polarizing plate having the structure of EWV layer/triacetyl cellulose (TAC) layer/polyvinyl alcohol (PVA) layer/TAC layer and the above-mentioned adhesive composition formed on the release film The layers are overlapped and laminated, and aged for 168 hours under the conditions of 25 ° C and 50% RH, so that the cross-linking reaction proceeds, and the attached adhesive with a laminated structure of peeling film/adhesive layer/polarizing plate is obtained. The polarizing plate of the agent layer. In addition, the contact angle with water on the surface of the EWV layer included in the polarizing plate was 97.6°.

[Measurement of Gel Fraction] The above-obtained adhesive composition was applied to a release film (trade name: The surface treatment surface of FILMBYNA (registered trademark) 100E-0010N023, Fujimori Industry Co., Ltd., formed the coating layer. Then, the peeling film with the coating layer was dried at 100° C. for 1 minute using a hot air circulation dryer to form a layer of the adhesive composition on the peeling film. Then, the exposed surface of the adhesive composition layer was laminated on the surface-treated surface of a separate prepared release film (trade name: FILMBYNA (registered trademark) 100E-0010N023, Fujimori Industries Co., Ltd.) to obtain a substrate-free film. type of adhesive sheet. Then, aging was carried out for 168 hours under the conditions of 25° C. and 50% RH, so that the crosslinking reaction proceeded, and a sample for measuring a gel fraction having an adhesive layer was obtained. Using the obtained sample for gel fraction measurement, the gel fraction of the adhesive layer (that is, the gel fraction of the adhesive composition after crosslinking) was measured by the aforementioned method, and the result was 65.5% by mass.

[Evaluation] 1. Reworkability The above-prepared polarizing plate with an adhesive layer was cut to prepare a test piece with a size of 25 mm×75 mm (long side). Peel off the peeling film of the test piece, and laminate the surface of the adhesive layer exposed by the peeling on one side of the blue plate sodium glass (Songnang Glass Industry Co., Ltd.; hereinafter referred to as "glass"), Crimping is performed using a laminator to produce a laminate. The obtained laminate was subjected to autoclave treatment (temperature: 50°C, pressure: 5kg/cm ² , treatment time: 20 minutes), and then left at 50°C for 96 hours. After standing time, 180° peeling was carried out at a peeling speed of 300 mm/min under the condition of 23°C. In addition, the surface of the glass and the surface of the peeled adhesive layer were observed visually, and the reworkability was evaluated according to the following evaluation criteria. The results are shown in Table 3. In addition, if the evaluation result is "A" or "B", there is no practical problem.

-Evaluation Criteria- A: The adhesive layer did not transfer and adhere to the surface of the glass at all. B: Although the adhesive layer was not transferred and adhered to the surface of the glass at all, the surface of the peeled adhesive layer was rough. C: Part of the adhesive layer is transferred and adhered to the surface of the glass. D: The entire surface of the adhesive layer is transferred and adhered to the surface of the glass.

2. Durability (preparation of samples for durability evaluation) Cut the polarizing plate with adhesive layer prepared above so that the long side becomes 45° with respect to the absorption axis, and prepare 50mm×89mm (long side ) of the size of the test piece 2 pieces. The peeling film of the test piece was peeled off, and the surface of the adhesive layer exposed by peeling was laminated on one side of the glass, and bonded by pressure using a laminator to produce a laminated body. For the obtained laminate, it is subjected to autoclave treatment (temperature: 50°C, pressure: 5kg/cm ² , treatment time: 20 minutes), and then placed under the conditions of 23°C and 50%RH for 1 hour to make durable Samples for performance evaluation.

(Evaluation Test) 2-1. High-temperature and high-humidity conditions (65°C, 95%RH) The durability evaluation samples prepared above were left to stand under high-temperature and high-humidity conditions of 65°C and 95%RH for 500 hours. Visually observe the appearance of the samples for durability evaluation after being placed, and evaluate the durability of the adhesive composition under high-temperature and high-humidity conditions (65°C, 95%RH) according to the following evaluation criteria. The results are shown in Table 3. In addition, if the evaluation result is "A", "B", or "C", there is no practical problem.

-Evaluation Criteria- A: No blistering, floating, and peeling were observed at all. B: Blistering, floating, and peeling were hardly observed. C: Blistering, floating, and peeling were observed slightly, but were within the allowable range. D: Blistering, floating, and peeling were observed, and were outside the allowable range. E: Blistering, floating, and peeling were remarkably observed.

2-2. High temperature condition (95° C.) The durability evaluation sample prepared above was left to stand under a high temperature condition of 95° C. for 500 hours. Visually observe the appearance of the sample for durability evaluation after being left to stand, and evaluate the adhesive composition under high temperature conditions ( 95°C) durability. The results are shown in Table 3. In addition, if the evaluation result is "A", "B", or "C", there is no practical problem.

3. White spots (preparation of samples for white spot evaluation) The above-prepared polarizing plate with an adhesive layer was cut to prepare two test pieces with a size of 62 mm×110 mm (long side). Peel off the peeling films of the two test pieces so that the absorption axis of each test piece is perpendicular to each other, and then overlap the surface of the exposed adhesive layer on both sides of the Twisted Nematic (TN) liquid crystal panel , use a laminator to perform crimping to produce a laminated body. The obtained laminate was subjected to autoclave treatment (temperature: 50°C, pressure: 5kg/cm ² , treatment time: 20 minutes), and then placed under the conditions of 23°C and 50%RH for 1 hour to produce a white Samples for point evaluation.

(Evaluation test) The sample for white point evaluation prepared above was left to stand under the high temperature condition of 95 degreeC for 500 hours. Place the white point evaluation sample after standing on the backlight of the LCD screen under the conditions of 23°C and 50% RH, observe the state of the white point visually, and evaluate the white point according to the following evaluation criteria. The results are shown in Table 3. In addition, the evaluation result should be "A" or "B".

-Evaluation Criteria- A: White spots were not observed at all. B: White spots are observed, but within the allowable range. C: White spots are remarkably observed.

[Example 2-Example 20] In Example 2-Example 20, the composition of the (meth)acrylic copolymer, crosslinking agent, and silane coupling agent in Example 1 is changed to Table 1 Except for the composition shown, the same operation as in Example 1 was carried out to prepare an adhesive composition, and a polarizing plate with an adhesive layer was produced using the obtained adhesive composition. With regard to the obtained adhesive composition, the gel fraction after crosslinking was measured by the same method as in Example 1. Moreover, the evaluation of rework property, durability, and a white spot was performed by the method similar to Example 1 about the obtained polarizing plate with an adhesive layer. The results are shown in Table 3.

[Comparative Example 1-Comparative Example 11] In Comparative Example 1-Comparative Example 11, the composition of the (meth)acrylic copolymer, crosslinking agent, and silane coupling agent in Example 1 was changed to Table 2 Except for the composition shown above, the same operation as in Example 1 was carried out to prepare an adhesive composition. In the obtained adhesive composition, for Comparative Examples 1 to 7 and Comparative Examples 9 to 11, the gel fraction after crosslinking was measured by the same method as in Example 1. In addition, the viscosity of Comparative Example 8 was so high that it could not be coated, so the gel fraction after crosslinking could not be measured. The results are shown in Table 3. In addition, among the obtained adhesive composition, for Comparative Example 1 to Comparative Example 4, Comparative Example 6, Comparative Example 7, Comparative Example 9, and Comparative Example 11, the same operation as that of Example 1 was carried out to produce an attached adhesive. Layered polarizing plates were evaluated in the same manner as in Example 1 for reworkability, durability, and white point. In addition, 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 composition of the (meth)acrylic copolymer, crosslinking agent, and silane coupling agent in Example 1 was changed to the composition shown in Table 2, except that , perform the same operation as in Example 1 to prepare an adhesive composition, and use the obtained adhesive composition to manufacture a polarizing plate with an adhesive layer. With regard to the obtained adhesive composition, the gel fraction after crosslinking was measured by the same method as in Example 1. Moreover, the evaluation of rework property, durability, and a white spot was performed by the method similar to Example 1 about the obtained polarizing plate with an adhesive layer. The results are shown in Table 3.

[Table 1]

[Table 2]

In Table 1 and Table 2, "-" recorded in the composition column means that the component is not included. In Table 1 and Table 2, "n-BA" means "n-butyl acrylate", "PHEA" means "phenoxyethyl acrylate", "2HEA" means "2-hydroxyethyl acrylate", and "4HBA" means "4-Hydroxybutyl acrylate", and "AA" means "acrylic acid". "M-5300" in Table 1 and Table 2 means ARONIX (registered trademark) M-5300 (ω-carboxy-polycaprolactone (n≒2) monoacrylate; a monomer with a carboxyl group) of Toagosei Co., Ltd. ).

The details of each crosslinking agent described in Table 1 and Table 2 are as follows. ＜Isocyanate compound＞ ･SUMIDUR (registered trademark) N-75: Diurea type of hexamethylene diisocyanate (HMDI), solid content: 75% by mass, content of isocyanate group: 16.5% by mass, Sumika Covestro Urethane (stock ) ･CORONATE (registered trademark) L45E: Toluene diisocyanate (TDI), solid content: 45% by mass, content of isocyanate group: 7.9% by mass, Tosoh Co., Ltd. ･TAKENATE (registered trademark) D-110N: Xylene Diisocyanate (XDI), solid content: 75% by mass, content of isocyanate group: 11.5% by mass, Mitsui Takeda Chemical Co., Ltd. ･ DURANATE (registered trademark) E405-80T: Added hexamethylene diisocyanate (HMDI) Product type, solid content: 80% by mass, content of isocyanate group: 7.1% by mass, Asahi Kasei Co., Ltd. <Epoxy compound> ･TETRAD-X: Mitsubishi Gas Chemical Co., Ltd. ･Denacol (registered trademark) EX-201 : Resorcinol Diglycidyl Ether, Nagase ChemteX Corporation

In addition, the details of each silane coupling agent described in Table 1 and Table 2 are as follows. ＜Silane coupling agent＞ ･X-41-1810: Silane compound containing thiol group, Shin-Etsu Chemical Co., Ltd. ･X-41-1053: Silane compound containing epoxy group, Shin-Etsu Chemical Co., Ltd. ･X -41-1056: Silane compounds containing epoxy groups, Shin-Etsu Chemical Co., Ltd. KBM403: 3-glycidoxypropyltriethoxysilane, silane compounds containing epoxy groups, Shin-Etsu Chemical Co., Ltd. ) ･KBM9659: Ginseng-(trimethoxysilylpropyl)isocyanurate, Shin-Etsu Chemical Co., Ltd. All silane coupling agents have a solid content of 100% by mass.

[table 3]

As shown in Table 3, the adhesive layers formed from the adhesive compositions of Examples 1 to 20 were excellent in both reworkability and durability. In addition, in the adhesive layer formed from the adhesive composition of Examples 1 to 20, the occurrence of white spots was suppressed.

From the comparison between Example 3 and Example 4, it can be seen that: the adhesive composition contains a (meth)acrylic copolymer containing constituent units derived from a monomer having a hydroxyl group, and the formed adhesive layer is exposed to high temperature and high humidity Durability in ambient conditions has been improved. From the comparison of Example 3 and Example 13, it can be seen that the adhesive composition further contains a weight average molecular weight of 0.5-200,000 in the range of 0.5 million to 200,000, and does not have any functional group in the carboxyl group, hydroxyl group, and amine group ( meth)acrylic polymer, the durability of the formed adhesive layer is improved.

From the comparison of Example 3 and Examples 15 to 17, it can be seen that: in addition to the isocyanate compound which is a cross-linking agent, the adhesive composition also contains an epoxy compound which is also a cross-linking agent. Layer durability is improved.

On the other hand, the 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 carboxyl groups, hydroxyl groups, and amine groups in the (meth)acrylic copolymer is 0.11 Compared with the adhesive layer formed by the adhesive composition of the above-mentioned embodiment (for example, Example 3) in which the molar equivalent ratio is in the range of 0.15 to 2.5, the adhesive layer formed by the compound has remarkable reworkability and durability. poor. Also, white spots were remarkably observed. Also, Comparative Example 2 in which the molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the (meth)acrylic copolymer was 4.32 and Comparative Example 2.66 Compared with the adhesive layer formed by the adhesive composition of 9, the adhesive layer formed by the above-mentioned adhesive composition in the range of the molar equivalent ratio of 0.15 to 2.5 (for example, Example 3 and Example 11) layer, with significantly poorer durability. Also, white spots were remarkably observed.

Compared with the adhesive layer formed by the adhesive composition of Comparative Example 3 containing epoxy compounds instead of isocyanate compounds as crosslinking agents, the adhesive layer formed by the adhesive composition of Examples (for example, Example 3) containing isocyanate compounds Adhesive layer, reworkability and durability are significantly poor. Also, white spots were remarkably observed. Adhesive composition of Comparative Example 4 in which the content of structural units derived from monomers having at least one functional group selected from the group consisting of carboxyl groups, hydroxyl groups, and amino groups is 0.1% by mass relative to all structural units The formed adhesive layer was significantly more durable than the adhesive layer formed of the adhesive composition of the example (for example, Example 3) whose content rate of the above-mentioned structural unit was in the range of 0.2% by mass to 0.8% by mass. poor. White spots were remarkably observed.

The (meth)acrylic copolymer does not contain a constituent unit derived from a monomer having a carboxyl group, and the (meth)acrylic copolymer has at least one unit selected from the group consisting of a carboxyl group, a hydroxyl group, and an amino group. The adhesive layer formed from the adhesive composition of Comparative Example 5 in which the content of the structural unit of monomeric monomers of one functional group was 0.1% by mass relative to all the structural units did not increase the gel fraction, and thus could not be evaluated. The content rate of the constituent unit derived from the monomer having at least one functional group selected from the group consisting of carboxyl group, hydroxyl group, and amino group in the (meth)acrylic copolymer is 0.6 mass with respect to all the constituent units %, but the (meth)acrylic copolymer did not contain a structural unit derived from a monomer having a carboxyl group. The adhesive layer formed by the adhesive composition of Comparative Example 10 did not increase the gel fraction, so it could not be evaluated.

Adhesive composition of Comparative Example 6 in which the content rate of a structural unit derived from a monomer having at least one functional group selected from the group consisting of carboxyl group, hydroxyl group, and amino group is 1.0% by mass relative to all structural units The formed adhesive layer was significantly more durable than the adhesive layer formed of the adhesive composition of the example (for example, Example 3) whose content rate of the above-mentioned structural unit was in the range of 0.2% by mass to 0.8% by mass. poor. Also, white spots were remarkably observed. The adhesive layer formed from the adhesive composition of Comparative Example 7 in which the weight average molecular weight of the (meth)acrylic copolymer was 1.2 million was compared to the adhesive layer formed by the weight average molecular weight of the (meth)acrylic copolymer which was 1.25 million. The durability of the adhesive layer formed by the adhesive composition in the range of ~2 million (for example, Example 3) is significantly poor. The adhesive composition of Comparative Example 8, in which the weight average molecular weight of the (meth)acrylic copolymer was 2.1 million, had too high viscosity and could not be applied. Adhesive composed of the adhesive composition of Reference Example 1 in which the molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound relative to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the (meth)acrylic copolymer is low Compared with the adhesive layer formed from the adhesive composition of the example (for example, Example 3) having a molar equivalent ratio in the range of 0.15 to 2.5, the reworkability of the layer was significantly inferior. Compared with the adhesive layer formed of the adhesive composition of Comparative Example 1 with a gel fraction of 15.6% by mass compared to Examples (for example, Example 1) with a gel fraction of 40% by mass to 75% by mass, 3) The adhesive layer formed by the adhesive composition has significantly poor reworkability and durability. Also, white spots were remarkably observed.

Claims (10)

An adhesive composition for a polarizing plate, comprising: a (meth)acrylic copolymer, comprising a constituent unit derived from a monomer having a carboxyl group and a constituent unit derived from an alkyl (meth)acrylate monomer, and derived from The content rate of the structural unit of the monomer of at least one functional group in the group consisting of carboxyl group, hydroxyl group, and amine group is in the range of 0.2% by mass to 0.8% by mass relative to all the structural units, and the weight average molecular weight is 125 The range of 10,000 to 2 million; and an isocyanate compound, the molar equivalent ratio of the amount of isocyanate groups in the isocyanate compound relative to the total amount of carboxyl groups, hydroxyl groups, and amine groups in the (meth)acrylic copolymer is 0.15 The range of ~2.5, the gel fraction after crosslinking is in the range of 40% by mass to 70% by mass. The adhesive composition for polarizing plates as claimed in Claim 1, wherein the (meth)acrylic copolymer contains a constituent unit derived from a monomer having a hydroxyl group. The adhesive composition for polarizing plates as claimed in claim 1 or 2 of the patent application, wherein the content rate of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer relative to all the structural units It is in the range of 0.1% by mass to 0.8% by mass. For example, the adhesive composition for polarizing plates of claim 1 or 2, wherein the content of the constituent unit derived from the (meth)acrylic acid alkyl monomer in the (meth)acrylic copolymer is relatively It is in the range of 60% by mass to 99.8% by mass in all constituent units. The adhesive composition for polarizing plates as claimed in claim 1 or 2 of the patent application, wherein the content of the (meth)acrylic copolymer is 50% by mass to 99% by mass relative to the total solid content of the adhesive composition % range. For example, the adhesive composition for polarizing plates in item 1 or 2 of the scope of the patent application further contains a weight-average molecular weight in the range of 5,000 to 200,000, and does not have any functional group among carboxyl, hydroxyl, and amine groups ( Meth)acrylic polymers. For example, the adhesive composition for polarizing plates in claim 1 or 2 of the scope of the patent application further contains a silane coupling agent. For example, the adhesive composition for polarizing plates in claim 1 or 2 of the scope of the patent application further contains an epoxy compound. A polarizing plate with an adhesive layer, comprising: a polarizing plate; a layer arranged on the surface of the polarizing plate and having a contact angle with water of 90° or more; and a layer arranged on the layer with a contact angle of 90° or more surface, and an adhesive layer formed of the adhesive composition for polarizing plates according to any one of items 1 to 8 of the scope of application. In the polarizing plate with an adhesive layer as claimed in claim 9, the layer having a contact angle with water of 90° or more is a layer containing a discotic liquid crystal compound.