JP2017179076A - Adhesive composition and polarizer with adhesive layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition capable of forming an adhesive layer excellent in tolerance to deterioration and suppression of voids in use environment regardless of moisture content of a polarizer and a polarizer with an adhesive layer.SOLUTION: There is provided an adhesive composition containing a (meth)acrylic polymer containing a constitutional unit derived from a monomer having a carboxyl group of 0.1 mass% to 5 mass% based on all the constitutional units, an isocyanate compound of 8 pts.mass to 30 pts.mass based on 100 pts.mass of the (meth)acrylic polymer and a carbodiimide compound of 0.1 pts.mass to 0.5 pts.mass based on 100 pts.mass of the (meth)acrylic polymer.SELECTED DRAWING: None

Description

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

Many electronic devices such as mobile phones and mobile terminals incorporate a liquid crystal display device. In general, a liquid crystal display device includes a liquid crystal cell and an optical film such as a polarizing plate, a retardation plate, and a brightness enhancement film. A liquid crystal cell and an optical film, or optical films are bonded through the adhesive layer formed from an adhesive composition. In order to ensure the visibility of the liquid crystal display device, a transparent acrylic pressure-sensitive adhesive is generally used for forming the pressure-sensitive adhesive layer.
An optical film such as a polarizing plate is usually formed by laminating members having different shrinkage rates. Therefore, the optical film may be warped due to changes in temperature and humidity, and may float, peel off, and foam at the interface between the pressure-sensitive adhesive layer and the optical film. In addition, stress is generated as the optical film shrinks or expands due to changes in temperature and humidity. When this stress is not relieved by the pressure-sensitive adhesive layer, the stress remains in the pressure-sensitive adhesive layer. If the stress remaining in the pressure-sensitive adhesive layer becomes non-uniform, for example, light leakage may occur in a liquid crystal display device, and so-called white spots may occur.
From the above, the pressure-sensitive adhesive composition is required to be capable of forming a pressure-sensitive adhesive layer that is excellent in the ability to suppress floating, peeling, and foaming and in the suppression of white spots.

  As a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer as described above, 0 to 9 parts by mass of a carboxyl group-containing monomer, 0 to 1.8 parts by mass of a hydroxyl group-containing (meth) acrylic monomer, and 99.9 to It consists of 89.2 parts by mass of (meth) acrylic acid ester (however, the total amount of carboxyl group-containing monomer and hydroxyl group-containing (meth) acrylic monomer is not 0 part by mass), and the weight average molecular weight is 1,000,000- Proposed pressure-sensitive adhesive composition containing 100 parts by weight of a (meth) acrylic copolymer of 2 million and 0.05 to 5 parts by weight of a carbodiimide-based crosslinking agent and having a gel fraction of 77 to 93% after 7 days of application (For example, refer to Patent Document 1). This pressure-sensitive adhesive composition is said to be excellent in properties capable of suppressing floating, peeling and foaming and light leakage resistance when used for sticking a polarizing plate.

  Further, 100 parts by weight of an acrylic copolymer produced from a predetermined monomer, 4 to 12 parts by weight of a tolylene diisocyanate crosslinking agent, and 0.05 to 1 part by weight of a silane coupling agent having reactivity with a carboxyl group And a pressure-sensitive adhesive composition having a gel fraction of 91% or more has been proposed (for example, see Patent Document 2). When this pressure-sensitive adhesive composition is used for sticking a polarizing plate having a water content of 0.5 to 5% by mass, it is said to be excellent in the property of suppressing floating, peeling and foaming and in suppressing white spots.

Japanese Patent Laying-Open No. 2015-4072 International Publication No. 2010/0779653

The pressure-sensitive adhesive composition described in Patent Literature 1 is said to be excellent in properties capable of suppressing floating, peeling, and foaming, and light leakage resistance (suppression of white spots). However, in recent years, in addition to use in high temperature and low humidity environments and high temperature and high humidity environments, it floats, peels off, and foams even in severe environments that are repeatedly exposed to high and low temperature environments. Therefore, it is required to have excellent properties (that is, resistance to deterioration in a use environment) and to suppress white spots at a higher level.
Further, as a result of investigations by the inventors, the pressure-sensitive adhesive composition described in Patent Document 2 can be used because the moisture content of the polarizing plate may significantly deteriorate the resistance to deterioration in the usage environment and white spots. Is limited. In particular, when the water content of the polarizing plate exceeds 5% by mass, the isocyanate compound reacts with moisture and deactivates, the crosslinking reaction does not proceed sufficiently, and the resistance to deterioration in the use environment and the suppression of white spots are inferior. . Therefore, the pressure-sensitive adhesive composition described in Patent Document 2 cannot be used for a polarizing plate having a moisture content exceeding 5% by mass.
Thus, no pressure-sensitive adhesive composition is known which satisfies the resistance to deterioration in the use environment and the suppression of white spots at a high level, regardless of the moisture content of the polarizing plate.

  The present invention has been made in view of the circumstances as described above, and can be used to form a pressure-sensitive adhesive layer excellent in resistance to deterioration in a use environment and suppression of white spots regardless of the moisture content of a polarizing plate. And it aims at providing the polarizing plate with an adhesive layer.

Specific means for solving the problems include the following aspects.
<1> A (meth) acrylic polymer containing 0.1% by mass to 5% by mass of a structural unit derived from a monomer having a carboxy group with respect to all structural units, and the (meth) acrylic heavy 8 parts by mass to 30 parts by mass of an isocyanate compound with respect to 100 parts by mass of the coalescence, and 0.1 parts by mass to 0.5 parts by mass of a carbodiimide compound with respect to 100 parts by mass of the (meth) acrylic polymer. An adhesive composition comprising.

<2> The pressure-sensitive adhesive composition according to <1>, wherein a ratio of the isocyanate compound to the carbodiimide compound is 25 to 150 on a mass basis.
<3> Furthermore, the adhesive composition as described in <1> or <2> containing 0.05 mass part-3 mass parts silane coupling agent with respect to 100 mass parts of said (meth) acrylic-type polymers.
<4> The (meth) acrylic polymer contains 0.1% by mass to 0.5% by mass of a structural unit derived from a monomer having a hydroxyl group based on all structural units. > The pressure-sensitive adhesive composition according to any one of the above.

<5> The pressure-sensitive adhesive composition according to any one of <1> to <4>, wherein the (meth) acrylic polymer has a weight average molecular weight of 700,000 to 2,000,000.
<6> The pressure-sensitive adhesive composition according to any one of <1> to <5>, wherein the gel fraction after crosslinking is 65% by mass to 92% by mass.
<7> The pressure-sensitive adhesive composition according to any one of <1> to <6>, which is used when a polarizing plate having a water content of more than 5% by mass is attached to an adherend.

A polarizing plate with an adhesive layer provided with a <8> polarizing plate and an adhesive layer formed from the adhesive composition as described in any one of <1>-<7>.

  ADVANTAGE OF THE INVENTION According to this invention, regardless of the moisture content of a polarizing plate, the adhesive composition which can form the adhesive layer excellent in the tolerance with respect to deterioration in a use environment and suppression of a white spot, and a polarizing plate with an adhesive layer can be provided. .

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.

In the present specification, a numerical range indicated using “to” means a range including the numerical values described before and after “to” as a minimum value and a maximum value, respectively.
In this specification, the amount of each component in the composition is the total amount of the plurality of substances present in the composition unless there is a specific indication when there are a plurality of substances corresponding to each component in the composition. Means.

In the present specification, the “pressure-sensitive adhesive composition” refers to a composition before the crosslinking reaction is completed, for example, a liquid, paste, or powder composition.
In the present specification, the “pressure-sensitive adhesive layer” means a layer after being substantially cross-linked, for example, a solid or gel layer.

In the present specification, “(meth) acrylic polymer” means a monomer having at least a main component of (meth) acrylic polymer among monomers constituting the (meth) acrylic polymer. Means a polymer. The monomer as the main component here means a monomer having the largest content (mass%) among monomers constituting the polymer. In an embodiment of the (meth) acrylic polymer in the present invention, the content of the structural unit derived from the monomer having the (meth) acryloyl group as the main component is 50% by mass or more of the total structural units.
In the present specification, “(meth) acryl” is a concept including both the meanings of “acryl” and “methacryl”, and “(meth) acrylate” includes both the meanings of “acrylate” and “methacrylate”. It is a concept, and “(meth) acryloyl” is a concept including both the meanings of “acryloyl” and “methacryloyl”.

<Adhesive composition>
The pressure-sensitive adhesive composition of the present invention comprises a (meth) acrylic polymer containing 0.1% by mass to 5% by mass of a structural unit derived from a monomer having a carboxy group, based on the total structural unit, 8 parts by mass to 30 parts by mass of an isocyanate compound with respect to 100 parts by mass of the (meth) acrylic polymer, and 0.1 parts by mass to 0.5 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer. And a carbodiimide compound.

The reason why the pressure-sensitive adhesive composition of the present invention is excellent in resistance to deterioration in use environment and suppression of white spots is not clear, but is presumed as follows.
If the substrate contains a large amount of water such as a polarizing plate, the water derived from the substrate reacts with the isocyanate compound, the isocyanate compound is deactivated, and the crosslinking reaction of the (meth) acrylic polymer is difficult to proceed. Become. Therefore, regardless of the moisture content of the base material, it is resistant to deterioration in the usage environment, that is, a harsh environment that is repeatedly exposed to a high temperature and low humidity environment, a high temperature and high humidity environment, and a high temperature environment and a low temperature environment. No pressure-sensitive adhesive layer has been known which has the property of not easily floating, peeling off and foaming when used underneath and excellent in suppressing white spots.
Since the pressure-sensitive adhesive composition of the present invention contains a specific amount of an isocyanate compound and a specific amount of a carbodiimide compound with respect to a specific (meth) acrylic polymer, a crosslinking reaction of the (meth) acrylic polymer. In this case, even if the isocyanate compound is deactivated by moisture, the crosslinking reaction between the carboxy group and the carbodiimide compound proceeds. For this reason, it is considered that the crosslinking reaction of the (meth) acrylic polymer due to moisture hardly occurs. Moreover, even if there is little water | moisture content and an isocyanate compound does not deactivate, the crosslinking reaction advances and the adhesive layer which has moderate cohesion force can be formed. Therefore, it is considered that a pressure-sensitive adhesive layer excellent in resistance to deterioration in the use environment (hereinafter also referred to as durability) and suppression of white spots can be formed regardless of the moisture content of a substrate such as a polarizing plate.

The pressure-sensitive adhesive composition may contain components other than the (meth) acrylic polymer, the isocyanate compound, and the carbodiimide compound.
Below, each component contained in an adhesive composition is demonstrated.

[(Meth) acrylic polymer]
The pressure-sensitive adhesive composition of the present invention includes a (meth) acrylic polymer containing 0.1% by mass to 5% by mass of a structural unit derived from a monomer having a carboxy group with respect to all the structural units.
When the pressure-sensitive adhesive composition contains the (meth) acrylic polymer, the (meth) acrylic polymer reacts with at least one of the isocyanate compound described below and the carbodiimide compound described below to react with the (meth) acrylic polymer. Crosslinking of the polymer proceeds. Therefore, the pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer.
The (meth) acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from an alkyl (meth) acrylate, in addition to the structural unit derived from a monomer having a carboxy group. Preferably, it may further contain structural units derived from other monomers.

(Structural unit derived from monomer having carboxy group)
The (meth) acrylic polymer in the present invention contains 0.1% by mass to 5% by mass of a structural unit derived from a monomer having a carboxy group with respect to all the structural units.
The carboxy group of the structural unit derived from the monomer having a carboxy group can react with an isocyanate group of an isocyanate compound described later and a carbodiimide group of a carbodiimide compound. For this reason, in the pressure-sensitive adhesive composition of the present invention, crosslinking of the (meth) acrylic polymer proceeds to form a pressure-sensitive adhesive layer.

The kind of monomer having a carboxy group is not particularly limited.
Specific examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citraconic acid, cinnamic acid, and 2- (meth) acryloyloxy. Ethyl succinic acid, monohydroxyethyl (meth) acrylate maleate, monohydroxyethyl (meth) acrylate fumarate, monohydroxyethyl (meth) acrylate phthalate, 1,2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate, ( And (meth) acrylic acid dimer and ω-carboxy-polycaprolactone mono (meth) acrylate.
The monomer which has a carboxy group may be used individually by 1 type, and may use 2 or more types together.

  The monomer having a carboxy group is selected from acrylic acid, methacrylic acid, ω-carboxy-polycaprolactone monoacrylate, and monohydroxyethyl phthalate from the viewpoint of adhesive strength and adhesion to a substrate such as a polarizing plate. At least one selected from the above is preferred, and acrylic acid is more preferred.

The content rate of the structural unit derived from the monomer which has a carboxy group in a (meth) acrylic-type polymer is 0.1 mass%-5 mass% with respect to all the structural units.
Since the content of the structural unit derived from the monomer having a carboxy group is 0.1% by mass or more, the crosslinking reaction between the carboxy group and at least one of the later-described isocyanate compound and carbodiimide compound effectively proceeds. To do. For this reason, the pressure-sensitive adhesive composition of the present invention is excellent in durability. On the other hand, when the content of the structural unit derived from the monomer having a carboxy group is 5% by mass or less, the pressure-sensitive adhesive composition of the present invention can be applied without gelation.

  The content of the structural unit derived from the monomer having a carboxy group in the (meth) acrylic polymer is preferably 0.5% by mass to 5% by mass with respect to all the structural units from the same viewpoint as described above. 1% by mass to 3% by mass is more preferable.

(Constitutional unit derived from a monomer having a hydroxyl group)
The (meth) acrylic polymer in the present invention preferably contains a structural unit derived from a monomer having a hydroxyl group in addition to the structural unit derived from the monomer having a carboxy group.
The hydroxyl group of the structural unit derived from the monomer having a hydroxyl group can react with an isocyanate group of an isocyanate compound described later and a carbodiimide group of a carbodiimide compound. Therefore, the pressure-sensitive adhesive composition of the present invention increases the gel fraction after cross-linking as compared with the case where it does not contain a structural unit derived from a monomer having a hydroxyl group, and more foams and white spots in various use environments. There is a tendency to be able to suppress.

The kind of monomer having a hydroxyl group is not particularly limited.
Examples of the monomer having a hydroxyl group include alkyl (meth) acrylate having a hydroxyl group as a substituent and polyalkylene glycol (meth) acrylate having a hydroxyl group.

  The alkyl part of the alkyl (meth) acrylate having a hydroxyl group as a substituent may be linear, branched or cyclic. As for carbon number of the alkyl part of the alkyl (meth) acrylate which has a hydroxyl group as a substituent, 1-12 are preferable. Adhesiveness with a base material is excellent in the carbon number of an alkyl part being in said range. From the same viewpoint as described above, the number of carbon atoms in the alkyl moiety of the alkyl (meth) acrylate having a hydroxyl group as a substituent is more preferably 2-6, and still more preferably 2-4.

  Examples of the alkylene glycol that forms the polyalkylene glycol portion of the polyalkylene glycol (meth) acrylate having a hydroxyl group include ethylene glycol, propylene glycol, and a combination of ethylene glycol and propylene glycol.

Specific examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-hydroxybutyl (Meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, Glycerol mono (meta Acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, and poly - include (ethylene glycol propylene glycol) mono (meth) acrylate.
Monomers having a hydroxyl group may be used alone or in combination of two or more.

  The monomer having a hydroxyl group is preferably an alkyl (meth) acrylate having a hydroxyl group as a substituent from the viewpoint of appropriate adhesive strength to the substrate, durability, and suppression of white spots, and 2-hydroxyethyl (meth) acrylate. , 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate are more preferable, More preferred is at least one selected from hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and 6-hydroxyhexyl (meth) acrylate.

The (meth) acrylic polymer in the present invention preferably contains 0.01% by mass to 1% by mass of a structural unit derived from a monomer having a hydroxyl group with respect to all the structural units.
When the content of the structural unit derived from a single unit having a hydroxyl group is 0.01% by mass or more, the reaction with an isocyanate compound described later proceeds effectively, and white spots in the case of a pressure-sensitive adhesive layer are further suppressed. There is a tendency to be able to. On the other hand, when the content of the structural unit derived from a single unit having a hydroxyl group is 1% by mass or less, the cohesive force of the pressure-sensitive adhesive layer does not become too high, and peeling in various use environments is further suppressed, resulting in durability. There is a tendency to excel.

  The content rate of the structural unit originating in the monomer which has a hydroxyl group in the (meth) acrylic-type polymer in this invention is 0.05 mass%-0.6 with respect to all the structural units from a viewpoint similar to the above. % By mass is more preferable, and 0.1% by mass to 0.5% by mass is even more preferable.

(Structural unit derived from alkyl (meth) acrylate)
The (meth) acrylic polymer in the present invention preferably further contains a structural unit derived from an alkyl (meth) acrylate. Adhesive force can be easily adjusted because a (meth) acrylic-type polymer contains the structural unit derived from alkyl (meth) acrylate.
In the present specification, the “structural unit derived from alkyl (meth) acrylate” means a structural unit formed by addition polymerization of alkyl (meth) acrylate.

  When the (meth) acrylic polymer contains a structural unit derived from an alkyl (meth) acrylate, the type of the alkyl (meth) acrylate that forms the structural unit derived from the alkyl (meth) acrylate is not particularly limited. However, unsubstituted alkyl (meth) acrylate is preferred. The alkyl group of the alkyl (meth) acrylate may be linear, branched or cyclic. Moreover, 1-18 are preferable and, as for carbon number of an alkyl group, 1-12 are more preferable. There exists a tendency which is excellent in adhesive force and adhesiveness with a base material as carbon number of an alkyl group exists in said range.

Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, s-butyl (meth) acrylate, t -Butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i-nonyl (meth) acrylate, n-decyl Examples include (meth) acrylate, n-dodecyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate.
Alkyl (meth) acrylate may be used individually by 1 type, and may use 2 or more types together.

  Alkyl (meth) acrylate is preferably at least one selected from methyl acrylate, n-butyl acrylate, t-butyl acrylate, and 2-ethylhexyl acrylate because cohesion and adhesion are easily adjusted.

Since the (meth) acrylic polymer adjusts the elastic modulus of the pressure-sensitive adhesive layer to improve durability and adhesive strength, the structural unit derived from alkyl (meth) acrylate is 50 masses based on the total structural units. % Or more, preferably 65% by mass or more, more preferably 80% by mass or more.
Moreover, it is preferable that a (meth) acrylic-type polymer contains 99.5 mass% or less of structural units derived from alkyl (meth) acrylate with respect to all the structural units from a viewpoint of cohesion force and adhesive force.

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

(Other structural units)
The type of monomer constituting other structural units is not particularly limited.
As the monomer constituting the other structural unit, specifically, (meth) acrylate having a cyclic group represented by benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, And an alkoxyalkyl (meth) acrylate represented by ethoxyethyl (meth) acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and aromatic monovinyl represented by vinyltoluene, Examples thereof include vinyl cyanides represented by acrylonitrile and methacrylonitrile, vinyl formate, vinyl acetate, vinyl propionate, and vinyl esters represented by vinyl versatate. Moreover, various derivatives of these monomers are mentioned. Moreover, the monomer which has functional groups other than a hydroxyl group, such as a glycidyl group, an amide group or an N-substituted amide group, and a tertiary amino group, is mentioned.

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

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

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

~ Physical properties of (meth) acrylic polymers ~
The weight average molecular weight (Mw) of the (meth) acrylic polymer in the present invention is not particularly limited, but is preferably 700,000 to 2,000,000.
When the weight average molecular weight (Mw) of the (meth) acrylic polymer is 700,000 or more, the cohesive force of the pressure-sensitive adhesive layer increases, foaming in various use environments can be suppressed, and durability tends to be excellent. On the other hand, when the weight average molecular weight (Mw) is 2 million or less, the workability during application tends to be excellent.

  The weight average molecular weight (Mw) of the (meth) acrylic polymer is preferably 750,000 to 1,800,000, more preferably 800,000 to 1,500,000 or more, from the same viewpoint as described above.

  The dispersity (Mw / Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the (meth) acrylic polymer is not particularly limited. For example, the dispersity (Mw / Mn) of the (meth) acrylic polymer can be 1-30.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the (meth) acrylic polymer are values measured by the following method. Specifically, the measurement is performed according to the following (1) to (3).
(1) A solution of a (meth) acrylic polymer is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like (meth) acrylic polymer.
(2) Using the film-like (meth) acrylic polymer obtained in (1) and tetrahydrofuran, a sample solution having a solid content concentration of 0.2% by mass is obtained.
(3) Using gel permeation chromatography (GPC), the weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth) acrylic polymer are measured as standard polystyrene conversion values under the following conditions.

~conditions~
Measuring device: High-speed GPC (model number: HLC-8220 GPC, manufactured by Tosoh Corporation)
Detector: differential refractometer (RI) (built in HLC-8220, manufactured by Tosoh Corporation)
Column: 4 TSK-GEL GMHXL (manufactured by Tosoh Corporation) connected in series Column temperature: 40 ° C
Eluent: Tetrahydrofuran Sample concentration: 0.2% by mass
Injection volume: 100 μL
Flow rate: 0.6 mL / min

  The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably −30 ° C. or lower. When the glass transition temperature of the (meth) acrylic polymer is −30 ° C. or lower, the tackiness is excellent while maintaining the viscosity, and the polarizing plate tends to adhere to the adherend.

  The Tg of the (meth) acrylic polymer is preferably −50 ° C. or higher. When the Tg of the (meth) acrylic polymer is −50 ° C. or higher, suitable elasticity is obtained, and there is a tendency to be excellent in durability and suppression of white spots.

  The glass transition temperature of the (meth) acrylic polymer is a value obtained by converting the absolute temperature (K) obtained by calculation from the following formula into Celsius temperature (° C.).

_{Tg 1,} Tg 2 in the formula, ... and Tg _n is the glass transition temperature represented by (meth) absolute temperature of the homopolymer of each monomer constituting the acrylic polymer (K) It is. m ₁ , m ₂ ,..., and _mn each represent the molar fraction of each monomer constituting the (meth) acrylic polymer, and m ₁ + m ₂ +... m _n = 1. It is.
The absolute temperature (K) can be converted to Celsius temperature (° C) by subtracting 273 from the absolute temperature (K), and the Celsius temperature (° C) can be converted to absolute temperature (K) by adding 273 to the Celsius temperature (° C). Can be converted to

The glass transition temperature of the (meth) acrylic polymer can be adjusted by the type and amount of the monomer that forms the (meth) acrylic polymer.
The glass transition temperatures of typical monomer homopolymers are shown below. The glass transition temperature of the monomer homopolymer is expressed in Celsius temperature (° C.).

  The “glass transition temperature represented by the Celsius temperature (° C.) of a homopolymer” of typical monomers is −57 ° C. for n-butyl acrylate, −76 ° C. for 2-ethylhexyl acrylate, n -Dodecyl methacrylate is -65 ° C, octyl acrylate is -65 ° C, isooctyl acrylate is -58 ° C, isononyl acrylate is -58 ° C, isomyristyl acrylate is -56 ° C, methyl The acrylate is 5 ° C, 4-hydroxybutyl acrylate is -39 ° C, 2-hydroxyethyl acrylate is -15 ° C, acrylic acid is 166 ° C, and phenoxyethyl acrylate is -22 ° C.

  The “glass transition temperature represented by the Celsius temperature (° C.) of the homopolymer” means the glass transition represented by the Celsius temperature (° C.) of the homopolymer produced by polymerizing the monomer alone. Refers to temperature. The glass transition temperature represented by the Celsius temperature (° C.) of the homopolymer is determined using a differential scanning calorimeter (DSC) (model number: EXSTAR6000, manufactured by Seiko Instruments Inc.) in a nitrogen stream. The measurement is performed under the conditions of 10 mg of a measurement sample and a heating rate of 10 ° C./min, and the inflection point of the obtained DSC curve is defined as the glass transition temperature of the homopolymer.

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

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

  Examples of the organic solvent used in the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Aliphatic or alicyclic typified by aromatic hydrocarbons, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil Hydrocarbons, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, esters represented by methyl benzoate, acetone, methyl ethyl ketone, Methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohex Ketones represented by non, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and glycol ethers represented by diethylene glycol monobutyl ether, and methyl alcohol, Examples include alcohols represented by ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol. These organic solvents may be used individually by 1 type, and may use 2 or more types together.

  In the synthesis of the (meth) acrylic polymer, it is preferable to use an organic solvent that hardly causes chain transfer during the polymerization reaction of esters, ketones, and the like. In particular, from the viewpoint of the solubility of the (meth) acrylic polymer, the ease of the polymerization reaction, etc., the organic solvent is preferably at least one selected from the group consisting of ethyl acetate, methyl ethyl ketone, and acetone.

As the polymerization initiator, an organic peroxide, an azo compound, or the like used in usual solution polymerization can be used.
Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydi. Carbonato, t-butylperoxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) propane, 2,2-bis (4,4 -Di-t-butylperoxycyclohexyl) butane, and 2,2 Bis (4,4-di -t- octyl peroxy cyclohexyl), and butane.
Examples of the azo compound include 2,2′-azobis-i-butylnitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis-4-methoxy-2,4-dimethyl. Examples include valeronitrile, 1,1′-azobis-cyclohexane-1-carbonitrile, and 2,2′-azobis (methyl isobutyrate).

  In the synthesis of the (meth) acrylic polymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and an azobis-based polymerization initiator is particularly preferable.

  In the synthesis of the (meth) acrylic polymer, the polymerization initiator is used in an amount of 0.01 part by mass or more and 2 parts by mass with respect to 100 parts by mass of the total amount of monomers forming the (meth) acrylic polymer. The range of not more than 0.1 parts by mass is preferable, and the range of not less than 0.1 parts by mass and not more than 1 part by mass is more preferable.

  The polymerization temperature is preferably in the range of 30 ° C to 180 ° C, more preferably in the range of 50 ° C to 150 ° C, still more preferably in the range of 50 ° C to 100 ° C, and particularly preferably in the range of 60 ° C to 90 ° C.

[Isocyanate compound]
The pressure-sensitive adhesive composition in the present invention contains 8 to 30 parts by mass of an isocyanate compound with respect to 100 parts by mass of the (meth) acrylic polymer.
The isocyanate compound in the present invention functions as a crosslinking agent.
The isocyanate compound undergoes a crosslinking reaction with the carboxy group. For this reason, in the adhesive composition of this invention, an isocyanate compound and the carboxy group of the said (meth) acrylic-type polymer carry out a crosslinking reaction, and an adhesive layer is formed.
Furthermore, the isocyanate compound undergoes a crosslinking reaction with a hydroxyl group. For this reason, when the (meth) acrylic polymer in the pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group, an isocyanate compound and a hydroxyl group of the (meth) acrylic polymer, Undergoes a cross-linking reaction, and the gel fraction after cross-linking increases as compared with the case where the structural unit derived from the monomer having a hydroxyl group is not contained. As a result, when containing a structural unit derived from a monomer having a hydroxyl group, foaming and white spots in various usage environments are more pronounced than when not containing a structural unit derived from a monomer having a hydroxyl group. Can be suppressed.
The pressure-sensitive adhesive composition of the present invention has a high cohesive force because it contains a larger amount of isocyanate compound than the conventional pressure-sensitive adhesive composition, and can suppress changes in the dimensions of a substrate such as a polarizing plate. And an adhesive layer excellent in suppression of white spots can be formed. Furthermore, by using together the above-mentioned specific amount of isocyanate compound and the specific amount of carbodiimide compound described later, it is excellent in durability and suppression of white spots regardless of the water content of the substrate.

Examples of the isocyanate compound include xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, aromatic polyisocyanate compounds represented by tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenation of the above-described aromatic polyisocyanate compound. Chain or cyclic aliphatic polyisocyanate compounds typified by products, biuret, dimer, trimer or pentamer of these polyisocyanate compounds, these polyisocyanate compounds and polyols such as trimethylolpropane Examples include adducts with compounds.
An isocyanate compound may be used individually by 1 type, and may use 2 or more types together.

  From the viewpoint of transparency of the pressure-sensitive adhesive composition, the isocyanate compound in the present invention is a linear or cyclic aliphatic polyisocyanate compound, and a biuret, dimer, or 3 of a linear or cyclic aliphatic polyisocyanate compound. Preferred is at least one selected from the group consisting of a trimer, a pentamer and an adduct, an isocyanate compound having an isocyanurate structure, which is a trimer of hexamethylene diisocyanate, an adduct of hexamethylene diisocyanate, and hexamethylene diisocyanate. More preferred is at least one selected from the group consisting of biuret bodies. Since these isocyanate compounds do not have a structure derived from an aromatic ring, the pressure-sensitive adhesive layer after the heat treatment is hardly yellowed, and a pressure-sensitive adhesive layer that is superior in transparency can be formed.

  A commercially available product may be used as the isocyanate compound in the present invention. Examples of commercially available isocyanate compounds include “Coronate HX”, “Coronate HL-S”, “Coronate L”, “Coronate 2031”, “Coronate 2030”, “Coronate 2234”, and “Coronate 2785” manufactured by Tosoh Corporation. ”,“ Aquanate 200 ”and“ Aquanate 210 ”,“ Sumijour N3300 ”,“ Death Module N3400 ”and“ Sumijoule N-75 ”manufactured by Sumika Covestro Urethane Co., Ltd., manufactured by Asahi Kasei Chemicals Corporation "Duranate E-405-80T", "Duranate 24A-100", and "Duranate TSE-100" as well as "Takenate D-110N", "Takenate D-120N", "Takenate M-" manufactured by Mitsui Chemicals, Inc. 631N "and" MT-Olestar NP1 " 00 "can be suitably used those which are commercially available by the trade name.

Content of the isocyanate compound in the adhesive composition of this invention is 8-30 mass parts with respect to 100 mass parts of said (meth) acrylic-type polymers.
When the content of the isocyanate compound is 8 parts by mass or more, the cohesive force of the pressure-sensitive adhesive layer is increased, and the change in the dimensions of a substrate such as a polarizing plate can be suppressed. On the other hand, the content of the isocyanate compound is 30 parts by mass or less, so that tackiness can be secured, so that when adhering a polarizing plate to an adherend such as a liquid crystal cell, it has excellent adhesion with the adherend, Excellent durability.

  From the viewpoint similar to the above, the content of the isocyanate compound in the pressure-sensitive adhesive composition is preferably 10 parts by mass to 25 parts by mass, and 12 parts by mass to 20 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer. Part is more preferable, and 12 parts by mass to 16 parts by mass is even more preferable.

In the pressure-sensitive adhesive composition, the ratio (NCO / NCN) of the isocyanate compound (NCO) to the carbodiimide compound (NCN) described later is preferably 25 to 150, more preferably 30 to 130, and even more preferably 40 to 110 on a mass basis. preferable.
When the ratio (NCO / NCN) is 25 or more, the durability is further improved. On the other hand, when the ratio (NCO / NCN) is 150 or less, the white spots are more effectively suppressed.

[Carbodiimide compound]
The pressure-sensitive adhesive composition of the present invention contains 0.1 to 0.5 parts by mass of a carbodiimide compound with respect to 100 parts by mass of the (meth) acrylic polymer.
The carbodiimide compound in the present invention functions as a crosslinking agent.
The carbodiimide compound undergoes a crosslinking reaction with a carboxy group. For this reason, in the adhesive composition of this invention, a carbodiimide compound and the carboxy group of the said (meth) acrylic-type polymer carry out a crosslinking reaction, and an adhesive layer is formed.
Furthermore, the carbodiimide compound undergoes a crosslinking reaction with a hydroxyl group. Therefore, when the (meth) acrylic polymer in the pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group, the carbodiimide compound and the hydroxyl group of the (meth) acrylic polymer are The gel fraction after crosslinking is increased as compared with the case where a structural unit derived from a monomer having a hydroxyl group due to a crosslinking reaction is not included. As a result, when containing a structural unit derived from a monomer having a hydroxyl group, foaming and white spots in various usage environments are more pronounced than when not containing a structural unit derived from a monomer having a hydroxyl group. Can be suppressed.
The pressure-sensitive adhesive composition of the present invention further improves durability and suppresses white spots regardless of the moisture content of the base material by using a specific amount of the carbodiimide compound and the specific amount of the isocyanate compound described above in combination. Excellent.

The carbodiimide compound in the present invention is not particularly limited as long as it is a compound having a carbodiimide group (—N═C═N—) in the molecule. Specifically, in molecules such as p-phenylene-bis (2,6-xylylcarbodiimide), tetramethylene-bis (t-butylcarbodiimide), and cyclohexane-1,4-bis (methylene-t-butylcarbodiimide). A compound having two or more carbodiimide groups, 1-vinyl-3-ethyl-carbodiimide, 1-vinyl-3-propyl-carbodiimide, 1-vinyl-3-methoxypropyl-carbodiimide, 1-vinyl-3-isobutyl Carbon-carbon doubles such as -carbodiimide, 1-propenyl-3-ethyl-carbodiimide, 1-propenyl-3-propyl-carbodiimide, 1-propenyl-3-methoxypropyl-carbodiimide, 1-propenyl-3-isobutyl-carbodiimide Compound having bond and carbodiimide group And the like.
Furthermore, the polymer of these compounds, and polycarbodiimide which is a copolymer of a monomer copolymerizable with these compounds, etc. are mentioned.
A carbodiimide compound may be used individually by 1 type, and may use 2 or more types together.

  Examples of copolymerizable monomers that form polycarbodiimide include aromatic vinyl monomers represented by styrene, α-methylstyrene, monochlorostyrene, and vinyltoluene, and methyl acrylate, methyl methacrylate, and acrylic acid. Examples thereof include α, β-ethylenically unsaturated monocarboxylic acid ester monomers represented by ethyl and butyl acrylate.

  A commercially available product may be used as the carbodiimide compound in the present invention. As a commercially available carbodiimide compound, for example, a carbodilite series manufactured by Nisshinbo Chemical Co., Ltd. can be used. Specifically, “SV-02”, “V-02”, “V-02-L2” can be used. "," V-04 "," E-01 "," E-02 "," V-01 "," V-03 "," V-07 "," V-09 ", and" V-05 " Etc.

Content of the carbodiimide compound in the adhesive composition of this invention is 0.1 mass part-0.5 mass part with respect to 100 mass parts of said (meth) acrylic-type polymers.
When the content of the carbodiimide compound is 0.1 parts by mass or more, cross-linking proceeds sufficiently regardless of the moisture content of the substrate, so that white spots can be suppressed. On the other hand, when the content of the carbodiimide compound is 0.5 parts by mass or less, tackiness can be ensured, and therefore, when the polarizing plate is adhered to an adherend such as a liquid crystal cell, the adhesion to the adherend is excellent. Excellent durability.

  The content of the carbodiimide compound in the pressure-sensitive adhesive composition is preferably 0.15 parts by mass to 0.45 parts by mass and more preferably 0.2 parts by mass to 0.4 parts by mass from the same viewpoint as described above.

[Silane coupling agent]
The pressure-sensitive adhesive composition of the present invention may further contain a silane coupling agent. When an adhesive composition contains a silane coupling agent, durability at the time of setting it as an adhesive layer can be improved more.

Examples of the silane coupling agent in the present invention include polymerizable unsaturated group-containing silane compounds represented by vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxy. Thiol group-containing silane compounds represented by silane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane, and 2- (3,4-epoxycyclohexyl) Epoxy group-containing silane compounds represented by ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, and N- (2-aminoethyl) -3 -Aminopro Amino group-containing silane compound represented by methyl dimethoxy silane, and tris - (3-trimethoxysilylpropyl) isocyanurate.
These may be used individually by 1 type and may be used in combination of 2 or more type.

  A commercial item may be used for the silane coupling agent in this invention. Examples of commercially available silane coupling agents include trade names “KBM-803”, “KBM-802”, “X-41-1810”, “X-41-1805” manufactured by Shin-Etsu Chemical Co., Ltd., and Silane coupling agents having a thiol group represented by “X-41-1818”, trade names “KBM-403”, “KBM-303”, “KBM-402”, “KBE-” manufactured by Shin-Etsu Chemical Co., Ltd. 402 ”and silane coupling agents having an epoxy group represented by“ KBE-403 ”.

The content of the silane coupling agent in the pressure-sensitive adhesive composition of the present invention is preferably 0.05 parts by mass to 3 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer, and 0.05 parts by mass to 1 part. A mass part is more preferable, and 0.05 mass part-0.5 mass part is still more preferable.
When the content of the silane coupling agent is within the above range, the durability when the pressure-sensitive adhesive layer is obtained can be further improved.

[Other ingredients]
The pressure-sensitive adhesive composition may contain components other than the above-mentioned (meth) acrylic polymer, the above-mentioned isocyanate compound, the above-mentioned carbodiimide compound, and the above-mentioned silane coupling agent contained as necessary. . Examples of other components include a crosslinking catalyst, a chelating agent, a solvent, a weather resistance stabilizer, a plasticizer, a softening agent, a dye, a pigment, an inorganic filler, an antioxidant, and a polymer other than a (meth) acrylic polymer. Is mentioned.
When the pressure-sensitive adhesive composition contains these other components, the content of the other components can be appropriately set within the range in which the effect of the present invention is exhibited.

~ Physical properties of adhesive composition ~
The gel fraction after crosslinking of the pressure-sensitive adhesive composition of the present invention is preferably 65% by mass to 92% by mass.
When the gel fraction is 65% by mass or more, it is more excellent in suppressing white spots. On the other hand, if the gel fraction is 92% by mass or less, the durability is more excellent.
From the same viewpoint as described above, the gel fraction after crosslinking of the pressure-sensitive adhesive composition is more preferably 70% by mass to 90% by mass, and further preferably 75% by mass to 90% by mass.

In the present specification, the gel fraction after crosslinking of the pressure-sensitive adhesive composition is a ratio of a solvent-insoluble component measured using ethyl acetate as an extraction solvent. Specifically, the measurement is performed according to the following (1) to (4).
(1) About 0.15 g of the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer) after crosslinking is attached to a 250-mesh wire mesh (100 mm × 100 mm) whose mass is accurately measured with a precision balance so that the gel content does not leak. Then, with the adhesive layer affixed to the inside, the wire mesh is folded five times to obtain a sample. Thereafter, the mass is accurately measured with a precision balance.
(2) The obtained sample is immersed in 80 ml of ethyl acetate for 3 days.
(3) A sample is taken out, washed with a small amount of ethyl acetate, and dried at 120 ° C. for 24 hours. Thereafter, the mass is accurately measured with a precision balance.
(4) The gel fraction is calculated by the following formula.
Gel fraction (mass%) = (Z−X) / (Y−X) × 100
Where X is the mass (g) of the wire mesh, Y is the mass (g) before immersion of the wire mesh with the adhesive layer attached, and Z is the mass (g) of the wire mesh with the adhesive layer attached after drying. is there.

-Use of adhesive composition-
The use of the pressure-sensitive adhesive composition of the present invention is not particularly limited, but it is preferably used for a purpose of sticking a polarizing plate to an adherend through a pressure-sensitive adhesive layer. Specifically, the use which sticks a polarizing plate to a liquid crystal cell, and the use which sticks a polarizing plate to optical films, such as retardation film, are mentioned, for example. Especially, it can use suitably for the use which sticks a polarizing plate to a liquid crystal cell in which especially durability and suppression of a white spot are requested | required.

The pressure-sensitive adhesive composition of the present invention can form a pressure-sensitive adhesive layer excellent in durability and suppression of white spots regardless of the water content of the polarizing plate. Therefore, it is not necessary to use different pressure-sensitive adhesive compositions depending on the water content of the polarizing plate, and the economy is excellent.
In particular, in the case of the conventional pressure-sensitive adhesive composition, when the water content of the polarizing plate exceeds 5% by mass, the isocyanate compound is deactivated by moisture derived from the polarizing plate, and the crosslinking reaction of the (meth) acrylic polymer is difficult to proceed. Therefore, it is inferior in durability and suppression of white spots. On the other hand, the pressure-sensitive adhesive composition of the present invention hardly inhibits the crosslinking reaction of the (meth) acrylic polymer due to moisture. Therefore, even when the water content of the polarizing plate exceeds 5% by mass, durability and white spots are eliminated. It is possible to form a pressure-sensitive adhesive layer that is excellent in suppressing the above. For this reason, the adhesive composition of this invention can be used suitably also with respect to the polarizing plate in which a moisture content exceeds 5 mass%.

The water content of the polarizing plate can be measured by the following method.
The polarizing plate is cut into 1.0 cm × 4.0 cm to form a test piece, and the mass F of the test piece is measured accurately. Using a moisture vaporizer (for example, VA-200, manufactured by Mitsubishi Chemical Analytech Co., Ltd.), moisture was vaporized from the test piece at 150 ° C., and the vaporized water amount W was measured using a Karl Fischer moisture meter (for example, Mitsubishi Chemical Corporation). (Analytech, CA-200 type).
The moisture content of the polarizing plate can be calculated by substituting the mass F and water content W of the test piece measured above into the following formula.
Moisture content (% by mass) of polarizing plate = 0.1 × (W / F) Formula W: Water content (μg) indicated by the moisture meter
F: Mass of the weighed test piece (mg)

<Polarizing plate with adhesive layer>
The polarizing plate with an adhesive layer in the present invention includes a polarizing plate and an adhesive layer formed from the adhesive composition of the present invention described above.
Since the polarizing plate with the pressure-sensitive adhesive layer includes the above-mentioned pressure-sensitive adhesive layer, it is excellent in durability and suppression of white spots regardless of the water content of the polarizing plate.

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

As a layer structure of the polarizing plate with an adhesive layer of this invention, an adhesive layer / polarizer, an adhesive layer / polarizer / protective film, an adhesive layer / protective film / polarizer / protective film, and an adhesive, for example Layer / protective film / polarizer.
In addition, between a polarizer and a protective film, between a protective film and an adhesive layer, and between a polarizer and an adhesive layer, optical functional layers, such as retardation film, an adhesive layer, and an easily bonding layer And so on.
The outermost surface of the pressure-sensitive adhesive layer-attached polarizing plate may be protected with a release film.

  Examples of the polarizer include a polyvinyl alcohol (PVA) film.

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

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

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

The moisture content of the polarizing plate in the present invention is not particularly limited, but may exceed 5% by mass or 6% by mass or more.
Further, the water content of the polarizing plate may be 20% by mass or less, 15% by mass or less, or 10% by mass or less.
The water content of the polarizing plate can be measured by the method described above.

  The method for producing the polarizing plate with the pressure-sensitive adhesive layer of the present invention is not particularly limited, and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention described above can be provided on at least one surface of the polarizing plate. A well-known method is mentioned.

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

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof.

<Production Example A>
In a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a reflux condenser, n-butyl acrylate (BA) 88.65 parts by mass, methyl acrylate (MA) 9.50 parts by mass, 2-hydroxyethyl After mixing 0.15 parts by mass of acrylate (2HEA), 1.70 parts by mass of acrylic acid (AA) and 110 parts by mass of ethyl acetate as an organic solvent, the inside of the reactor was purged with nitrogen. Thereafter, the temperature of the mixture in the reactor was increased to 70 ° C. with stirring, 0.04 parts by mass of azobisdimethylvaleronitrile (AIBN) and 40 parts by mass of ethyl acetate were successively added, and the polymerization reaction was maintained for 6 hours. I let you. After completion of the polymerization reaction, the solid content was adjusted to 24.0% by mass by dilution with ethyl acetate. In this way, a (meth) acrylic polymer solution was obtained.

<Production Examples B to J>
In each of Production Examples B to J, the composition of the monomer in Production Example A was changed as shown in Table 1, and the amount of the organic solvent was adjusted to show (meth) acrylic as shown in Table 1. A (meth) acrylic polymer solution was prepared in the same manner as in Production Example A except that the weight average molecular weight of the polymer was adjusted.
Table 1 shows the monomer composition (unit: mass%) and weight average molecular weight (Mw, unit: 10,000) of the obtained (meth) acrylic polymer.
The weight average molecular weight (Mw) is measured by the method described above.
“PHEA” in Table 1 represents phenoxyethyl acrylate.

Example 1
-Preparation of adhesive composition-
The solution of the (meth) acrylic polymer obtained in Production Example A as the (meth) acrylic polymer was 416.67 parts by mass (100.0 parts by mass as the solid content), and 18.7 of the coronate L as the isocyanate compound. Part by mass (manufactured by Tosoh Corporation, adduct of tolylene diisocyanate and trimethylolpropane, 14.0 parts by mass as an active ingredient) and 0.3 part by mass of carbodilite V-05 as a carbodiimide compound (manufactured by Nisshinbo Chemical Co., Ltd.) And 0.3 parts by weight as an active ingredient) and 0.1 parts by weight of KBM-403 as a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltriethoxysilane, 0 as an active ingredient) And 1 part by mass) were sufficiently stirred and mixed to obtain an adhesive composition.

―Preparation of polarizing plate with adhesive layer―
On the surface-treated surface of a release film (100E-0010NO23, manufactured by Fujimori Kogyo Co., Ltd.) obtained by surface-treating the pressure-sensitive adhesive composition obtained above with a silicone-based release agent, the coating amount after drying is 20 g / cm ^2. It was applied as follows.
Next, this was dried using a hot-air circulating drier at 100 ° C. for 90 seconds to form a coating layer on the release film. Subsequently, one surface of the polarizing plate of triacetyl cellulose (TAC) / polyvinyl alcohol (PVA) / TAC structure and the coating layer on the release film were laminated and bonded together under the conditions of 35 ° C. and 45% RH. The film was cured for 96 hours to prepare a polarizing plate with a pressure-sensitive adhesive layer having a laminate structure of release film / pressure-sensitive adhesive layer / polarizing plate.
In addition, the polarizing plate with an adhesive layer uses the polarizing plate A with a moisture content of 6.5 mass%, and the polarizing plate B with a moisture content of 2.8 mass%, and two types of polarizing plates with an adhesive layer are used. Produced.
The water content of the polarizing plate was adjusted by the time for holding the polarizing plate in an atmosphere of 23 ° C. and 50% RH. The water content of the polarizing plate was calculated by the method described above. In calculating the water content, a VA-200 model manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used as the moisture vaporizer, and a CA-200 model manufactured by Mitsubishi Chemical Analytech Co., Ltd. was used as the Karl Fischer moisture meter.
The gel fraction of the pressure-sensitive adhesive layer formed on the polarizing plate A and the gel fraction of the pressure-sensitive adhesive layer formed on the polarizing plate B were measured. Table 1 shows the measurement results of the gel fraction.

―Durability Evaluation Method―
The polarizing plate with the pressure-sensitive adhesive layer obtained above was cut so that the long side was 45 ° with respect to the absorption axis, and a 54 mm × 96 mm (long side) test piece (4.3 inches) was prepared. The release film was peeled from this test piece. The surface of the pressure-sensitive adhesive layer exposed by peeling is adhered to one surface of a 1.1 mm-thick non-alkali glass plate (EagleXG, manufactured by Corning), so that the test piece is stacked on the glass plate and pasted using a laminator. To obtain a laminate. Next, this laminate was subjected to autoclave treatment (50 ° C., 5 kg / cm ² , 20 minutes), and allowed to stand at 23 ° C. and 65% RH for 24 hours. Then, it was left for 500 hours in a Dry environment (80 ° C., 0% RH) under high temperature and low humidity conditions or a WET environment (60 ° C., 90% RH) under high temperature and high humidity conditions. Alternatively, the high temperature and low temperature were repeated (there was 30 minutes at −40 ° C. and then 30 minutes at 85 ° C., which was repeated for 300 cycles). After the standing time had elapsed, the state of foaming, floating and peeling was visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.

Evaluation criteria A: Foaming, floating and peeling were not observed at all.
B: Although foaming, floating, and peeling were slightly observed, it was within an allowable range.
C: Foaming, floating, and peeling were noticeable.

―Evaluation method for white spots―
Two test pieces having the test piece size changed to 230 mm × 410 mm (18.5 inches) in the durability evaluation method are prepared, and Twisted Nematic (TN) so that the absorption axes of the test pieces are orthogonal to each other. A sample for white spot evaluation was prepared by laminating on both sides of the liquid crystal panel of the system using a laminator. Next, this sample was subjected to autoclaving (50 ° C., 5 kg / m ² , 20 minutes), and allowed to stand for 24 hours at 23 ° C. and 50% RH. Then, it was left for 500 hours in a dry environment (70 ° C., 0% RH). After standing, each was placed on the backlight of a liquid crystal monitor under the conditions of 23 ° C. and 50% RH, and the white spots were visually observed. The evaluation results are shown in Table 1.

Evaluation criteria A: No white spots were observed.
B: Some white spots were recognized, but were within an allowable range.
C: Large white spots were recognized.

(Examples 2 to 14 and Comparative Examples 1 to 9)
In Examples 2 to 14 and Comparative Examples 1 to 7, the types and blending amounts of the (meth) acrylic polymer, isocyanate compound, and carbodiimide compound in Example 1 were changed to those shown in Table 1. Except for this, a pressure-sensitive adhesive composition was obtained in the same manner as in Example 1.
In Comparative Examples 8 and 9, a pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that an epoxy compound or a chelate compound was used in the amount shown in Table 1 instead of the carbodiimide compound in Example 1. It was.
Using each obtained adhesive composition, it carried out similarly to Example 1, produced the polarizing plate with an adhesive layer, and performed each evaluation. The results are shown in Table 1.

“-” In Table 1 means that there is no corresponding item.
Details of each component in Table 1 are as follows.
Coronate L: Trade name Coronate L, manufactured by Tosoh Corporation, adduct of tolylene diisocyanate and trimethylolpropane (derivative of tolylene diisocyanate)
V-05: trade name Carbodilite V-05, manufactured by Nisshinbo Chemical Co., Ltd., carbodiimide compound V-07: trade name Carbodilite V-07, manufactured by Nisshinbo Chemical Co., Ltd., carbodiimide compound V-09: trade name Carbodilite V-09, Nisshinbo Chemical Corporation, carbodiimide compound TX: Trade name TETRAD-X, Mitsubishi Gas Chemical Co., Ltd., epoxy-based crosslinking agent TC-100: Trade name Olga-Tix TC-100, Matsumoto Fine Chemical Co., Ltd., titanium acetylacetonate (Metal chelate crosslinking agent)

  As shown in Table 1, it can be seen that the polarizing plate with the pressure-sensitive adhesive layer produced using the pressure-sensitive adhesive compositions of Examples 1 to 14 has good evaluation results for durability and suppression of white spots.

Claims (8)

A (meth) acrylic polymer containing 0.1% by mass to 5% by mass of a structural unit derived from a monomer having a carboxy group, based on the total structural unit;
8 to 30 parts by mass of an isocyanate compound with respect to 100 parts by mass of the (meth) acrylic polymer;
0.1 to 0.5 parts by mass of a carbodiimide compound with respect to 100 parts by mass of the (meth) acrylic polymer;
A pressure-sensitive adhesive composition comprising:   The pressure-sensitive adhesive composition according to claim 1, wherein a ratio of the isocyanate compound to the carbodiimide compound is 25 to 150 on a mass basis.   Furthermore, the adhesive composition of Claim 1 or Claim 2 containing 0.05 mass part-3 mass parts silane coupling agent with respect to 100 mass parts of said (meth) acrylic-type polymers.   The said (meth) acrylic-type polymer contains 0.1 mass%-0.5 mass% of structural units derived from the monomer which has a hydroxyl group with respect to all the structural units. The pressure-sensitive adhesive composition according to claim 1.   The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the (meth) acrylic polymer has a weight average molecular weight of 700,000 to 2,000,000.   The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the gel fraction after crosslinking is from 65% by mass to 92% by mass.   The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive composition is used when a polarizing plate having a moisture content exceeding 5% is adhered to an adherend.   A polarizing plate with an adhesive layer comprising: a polarizing plate; and an adhesive layer formed from the adhesive composition according to any one of claims 1 to 7.