KR101863664B1 - adhesion composition, an adhesive and adhesion sheet - Google Patents

Abstract

A pressure sensitive adhesive composition excellent in both light leakage and durability when applied to an optical member such as a polarizing plate, a process for producing the pressure sensitive adhesive composition, a pressure sensitive adhesive and a pressure sensitive adhesive sheet are provided.
(Meth) acrylic acid ester polymer (A) having a weight average molecular weight of 700,000 to 2,550,000 and a second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 250,000 and a crosslinking agent , The proportion of the second (meth) acrylic acid ester polymer (B) relative to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is 5 to 40 parts by mass, The ester polymer (B) contains a monomer having a functional group (b1) reacting with the crosslinking agent (C) as a constituent component, and the ratio of the monomer having the functional group (b1) The functional group which reacts with the crosslinking agent (C) contained in the second (meth) acrylic acid ester polymer (B) is more than 1% by mass and less than 50% by mass in the ester polymer (B) Only the functional group (b1) is present, and among the first (meth) acrylic acid esters (A) does not contain a monomer having a functional group which reacts with the crosslinking agent (C) as a constituent component or does not contain the crosslinking agent (C) more than the functional group (b1) of the second (meth) acrylic acid ester polymer As a constituent component, a monomer having a low-reactivity functional group (a1).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an adhesive composition, an adhesive and an adhesive sheet,

The present invention relates to a pressure-sensitive adhesive composition, a method for producing a pressure-sensitive adhesive composition, a pressure-sensitive adhesive (a material obtained by crosslinking a pressure-sensitive adhesive composition) and a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive composition suitable for an optical member such as a polarizing plate, Sheet.

Generally, in a liquid crystal panel, a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition is often used to adhere a polarizing plate or a retardation plate to a glass substrate or the like. However, since optical members such as a polarizing plate and a retarder are liable to shrink due to heat, shrinkage occurs due to thermal history, and as a result, the pressure-sensitive adhesive layer laminated on the optical member does not follow shrinkage thereof, (So-called white peeling) due to the shift of the optical axis of the optical member due to the stress at the time of shrinkage of the optical member.

As a method for preventing this, there are (1) a method of suppressing shrinkage of the optical member by bonding a pressure-sensitive adhesive layer having a high adhesive force and excellent in shape stability to an optical member such as a polarizing plate, or (2) And a pressure-sensitive adhesive layer having a small stress at the time of shrinkage is used. As the method (1), it is effective to use a pressure-sensitive adhesive layer having a high storage modulus as shown in Patent Document 1. [ On the other hand, as the method (2), it is effective to use a pressure-sensitive adhesive layer excellent in stress relaxation property which can flexibly cope with the deformation of the optical member. However, conventionally, when attempting to form a pressure-sensitive adhesive layer having excellent stress relaxation properties, it has been necessary to design the crosslinking density in the pressure-sensitive adhesive layer to be low. In this case, there is a problem that the strength of the pressure-sensitive adhesive layer itself is lowered and the durability is deteriorated.

Therefore, in Patent Documents 2 to 4, the pressure-sensitive adhesive composition to be obtained is moderately softened by adding a plasticizer, liquid paraffin, urethane elastomer or the like to the acrylic pressure-sensitive adhesive instead of lowering the crosslink density of the pressure-sensitive adhesive layer to give stress- , Thereby obtaining a light leakage property and a durability.

[Patent Document 1] JP-A-2006-235568 [Patent Document 2] JP-A-5-45517 [Patent Document 3] JP-A-9-137143 [Patent Document 4] JP-A-2005-194366

However, a pressure-sensitive adhesive composition to which a plasticizer or liquid paraffin is added has a drawback that the pressure-sensitive adhesive layer to be formed exudes a plasticizer or liquid paraffin over time. This causes various problems such as contamination of the liquid crystal cell as the adherend. Further, in the pressure-sensitive adhesive composition to which the urethane elastomer is added, if the compatibility is to be maintained, the upper limit of the amount of the urethane elastomer to be added is limited, and the improvement of the stress relaxation property is insufficient. In addition, when the amount of the urethane elastomer is increased in order to improve the stress relaxation property, the compatibility with the acrylic pressure sensitive adhesive is lowered, and problems such as opacity are caused. Thus, in the conventional art, it is difficult to fundamentally improve the light-leak resistance and durability of the pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition for optical members.

An object of the present invention is to provide a sticky composition excellent in both light leakage and durability when applied to an optical member such as a polarizing plate which has been made in view of this real image, a method for producing the sticky composition, a pressure sensitive adhesive and a pressure sensitive adhesive sheet The purpose.

(A) having a weight average molecular weight of 700000 to 250000 and a second (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 8000 to 250000. In order to achieve the above object, The ratio of the second (meth) acrylic acid ester polymer (B) to the first 100 parts by mass of the (meth) acrylic acid ester polymer (A) And the second (meth) acrylic acid ester polymer (B) contains a monomer having a functional group (b1) capable of reacting with the crosslinking agent (C) as a constituent component and the functional group (B) in the second (meth) acrylic acid ester polymer (B) is more than 1% by mass and less than 50% by mass in the second (meth) acrylic acid ester polymer The functional group which reacts with the functional group (C) is substantially only the functional group (b1) The first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group that reacts with the crosslinking agent (C) as a constituent component, and the functional group of the second (meth) acrylic acid ester polymer (a1) having a lower reactivity with the crosslinking agent (C) than the crosslinking agent (b1) as a constituent component (Invention 1).

(Meth) acrylic acid ester polymer (A) having a weight average molecular weight of 700,000 to 2,500,000 and a second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 250,000 and a crosslinking agent Wherein the ratio of the second (meth) acrylic acid ester polymer (B) to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is 5 to 40 parts by mass, (Meth) acrylic ester polymer (B) of the present invention contains a monomer having a functional group (b1) satisfying the following formula (I) as a reactive component with the crosslinking agent (C) (B) of the second (meth) acrylic acid ester polymer (B) is more than 1% by mass and less than 50% by mass in the second (meth) acrylic acid ester polymer (B) A monomer having a functional group (b2) having a reactivity with the crosslinking agent (C) satisfying the following formula (I) (Meth) acrylic ester polymer (A) is contained as a component in an amount of not more than 1/5 (mass ratio) of the content of the monomer having the group-containing functional group (b1) (A1) having a lower reactivity with the crosslinking agent (C) than the functional group (b1) of the second (meth) acrylic acid ester polymer (B) is used as the constituent component (Invention 2).

Reactivity with crosslinking agent (C): Functional group (b2) <Functional group (b1) (I)

In the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the invention (inventions 1 and 2), a three-dimensional network structure is formed by chemical cross-linking to the low molecular weight polymer (B) conventionally used as a plasticizer. A high molecular weight polymer (A) is constrained to form a pseudo crosslinked structure between polymers (A) having a high molecular weight by inserting a plurality of high molecular weight polymers (A) into the three dimensional network structure. As a result, the obtained pressure-sensitive adhesive exhibits an appropriate cohesive force and excellent stress relaxation property. By using the pressure-sensitive adhesive having this excellent stress relaxation property, when applied to an optical member such as a polarizing plate, a pressure-sensitive adhesive sheet excellent in both light leakage and durability can be obtained.

In the above invention (Invention 1 or 2), it is preferable that the first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent component (invention 3) .

(A1) in the first (meth) acrylic acid ester polymer (A) is a carboxyl group, and in the second (meth) acrylic acid ester polymer (B) The functional group (b1) is preferably a hydroxyl group, and the crosslinking agent (C) is preferably an isocyanate crosslinking agent (invention 4).

In the invention (Invention 2 or 3), the functional group (a1) in the first (meth) acrylic acid ester polymer (A) is a carboxyl group and the functional group Preferably, the functional group (b1) is a hydroxyl group, the functional group (b2) is a carboxyl group, and the crosslinking agent (C) is an isocyanate crosslinking agent (invention 5).

In the invention (Invention 4 or 5), it is preferable that the first (meth) acrylic acid ester polymer (A) contains 0 to 15 mass% of a carboxyl group-containing monomer as a monomer unit constituting the polymer ).

In the above invention (Invention 4 to 6), it is preferable that the second (meth) acrylic acid ester polymer (B) contains 3 to 40 mass% of a hydroxyl group-containing monomer as a monomer unit constituting the polymer ).

In the invention (Invention 4 to 7), the content of the isocyanate-based crosslinking agent is preferably 0.1 to 0.1, based on the amount of the functional group (b1) in the second (meth) acrylic acid ester polymer (B) To 3.5 equivalents (invention 8).

The third aspect of the present invention is a method for producing the adhesive composition (Invention 1 to 8), wherein the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (C) is added at an arbitrary stage. (Invention 9) The present invention provides a process for producing a pressure-sensitive adhesive composition,

A fourth aspect of the present invention provides a pressure-sensitive adhesive obtained by crosslinking the adhesive compositions (inventions 1 to 8) (invention 10).

A fifth aspect of the present invention provides a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive (invention 10).

In the invention (invention 11), it is preferable that the substrate is an optical member (invention 12).

A sixth aspect of the present invention is an adhesive sheet comprising two peeling sheets and a pressure-sensitive adhesive layer sandwiched between the peeling sheets so as to contact the peeling surfaces of the two peeling sheets, wherein the pressure-sensitive adhesive layer comprises the pressure- (Claim 13).

In the pressure-sensitive adhesive in which the pressure-sensitive adhesive composition according to the present invention is crosslinked, a three-dimensional network structure is formed by chemical crosslinking to a low molecular weight polymer conventionally used as a plasticizer. By inserting a plurality of high molecular weight polymers into the three-dimensional network structure, high molecular weight polymers are constrained to form a pseudo crosslinked structure between the high molecular weight polymers. As a result, the obtained pressure-sensitive adhesive exhibits an appropriate cohesive force and excellent stress relaxation property. By using the pressure-sensitive adhesive having this excellent stress relaxation property, when applied to an optical member such as a polarizing plate, a pressure-sensitive adhesive sheet excellent in both light leakage and durability can be obtained.

1 is a sectional view of a pressure-sensitive adhesive sheet according to a first embodiment of the present invention.
2 is a sectional view of a pressure-sensitive adhesive sheet according to a second embodiment of the present invention.
3 is a view showing a measurement area of a light leakage test in a polarizer with a pressure-sensitive adhesive layer.

Hereinafter, embodiments of the present invention will be described.

[Adhesive composition]

(A) having a weight average molecular weight of 700000 to 250000 and a second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 250000. The first (meth) acrylic acid ester polymer And a crosslinking agent (C), and preferably further contains a silane coupling agent (D). In the present specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same is true of other similar terms. The term &quot; polymer &quot; includes the concept of &quot; copolymer &quot;.

The second (meth) acrylic acid ester polymer (B)

The functional group reactive with the crosslinking agent (C) contained in the polymer (B) is a monomer having a functional group (b1) reacting with the crosslinking agent (C)

(2) a monomer having a functional group (b1) satisfying the following formula (I) and a functional group (b2) having a reactivity with the crosslinking agent (C) satisfying the following formula (I) As a constituent.

Reactivity with crosslinking agent (C): Functional group (b2) <Functional group (b1) (I)

That is, in the polymer (B) of (2), the reactivity of the functional group (b1) with the crosslinking agent (C) is higher than the reactivity of the functional group (b2) with the crosslinking agent (C).

In the polymer (B) of the above (1) and (2), the proportion of the monomer having the functional group (b1) in the polymer (B) is more than 1% by mass and less than 50% by mass. The polymer (B) of the above-mentioned (2) contains the monomer having the functional group (b2) as a component in an amount (mass ratio) of not more than 1/5 of the content of the monomer having the functional group (b1).

The term "substantially the functional group (b1)" in the polymer (B) of the above-mentioned (1) means that the other functional group reacting with the crosslinking agent (C) . Therefore, the polymer (B) containing the small amount of the functional group (b2) is also included in the polymer (B) of the above-mentioned (1), and the polymer (B) .

On the other hand, the first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constitutional unit, (a1) having a lower reactivity with the crosslinking agent (C) than the crosslinking agent (b1).

The (meth) acrylic acid ester polymer (A) or (B) is obtained by reacting a (meth) acrylic ester having an alkyl group of an alkyl group having 1 to 20 carbon atoms in the ester moiety with a monomer having a functional group (reactive functional group containing monomer) And other monomers to be used as required are preferred. It is also preferable that the first (meth) acrylic acid ester polymer (A) does not contain the above-mentioned reactive functional group-containing monomer as a constitutional unit.

Examples of the (meth) acrylic esters having 1 to 20 carbon atoms in the alkyl moiety of the ester moiety include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (Meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate and the like. These may be used alone or in combination of two or more.

Examples of the reactive functional group-containing monomer include a monomer having a hydroxyl group in the molecule (a hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (a carboxyl group-containing monomer), a monomer having an amino group in the molecule (an amino group-containing monomer) .

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (Meth) acrylate such as 3-hydroxybutyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid. These may be used alone or in combination of two or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate and n-butylaminoethyl (meth) acrylate. These may be used alone or in combination of two or more.

Examples of the other monomer include (meth) acrylic acid esters having an aliphatic ring such as cyclohexyl (meth) acrylate, (meth) acrylic acid esters having an aromatic ring such as phenyl (meth) acrylate, acrylamide, (Meth) acrylic acid esters having a non-crosslinkable tertiary amino group such as (meth) acrylic acid N, N-dimethylaminoethyl, N, N-dimethylaminopropyl (meth) Vinyl, styrene, and the like. These may be used alone or in combination of two or more.

The monomer containing a reactive functional group (a1) used in the first (meth) acrylic acid ester polymer (A) and the reactive functional group (b1) used in the second (meth) acrylic acid ester polymer (B) The selection of the b2) containing monomer is determined in relation to the reactivity with the crosslinking agent (C) to be used. Details will be described later.

Here, the second (meth) acrylic acid ester polymer (B) contains more than 1% by mass of the monomer containing the reactive functional group (b1), and the upper limit thereof is less than 50% by mass. Preferably, the monomer contains the reactive functional group (b1) -containing monomer in an amount of 3 to 40 mass%, particularly preferably 5 to 25 mass%. The degree of crosslinking of the second (meth) acrylic acid ester polymer (B) is preferred by containing the reactive functional group (b1) -containing monomer within the above range. In combination with the first (meth) acrylic acid ester polymer (A) The resulting pressure-sensitive adhesive exhibits excellent stress relaxation properties. When the content of the reactive functional group (b1) -containing monomer is 1% by mass or less, the crosslinking of the second (meth) acrylic acid ester polymer (B) is insufficient, thereby decreasing the durability. On the other hand, if the content of the reactive functional group (b1) -containing monomer is 50% by mass or more, crosslinking of the second (meth) acrylic acid ester polymer (B) becomes excessive and there is a fear that the adhesiveness to the adherend may deteriorate . When the upper limit of the content of the reactive functional group (b1) -containing monomer is 40 mass%, the resulting pressure-sensitive adhesive sheet has better durability.

The second (meth) acrylic acid ester polymer (B) preferably contains a monomer (a monomer containing a reactive functional group (b2)) having a functional group (b2) having a lower reactivity with the crosslinking agent (C) than the functional group (B2) -containing monomer is contained as the constituent component, the amount of the reactive functional group (b1) -containing monomer is preferably not more than 1/5 of the content of the reactive functional group (b1) -containing monomer, .

When the second (meth) acrylic acid ester polymer (B) contains the reactive functional group (b2) -containing monomer in an amount exceeding 1/5 of the content of the reactive functional group (b1) -containing monomer as a mass ratio, the durability . When the amount of the reactive functional group (b2) in the second (meth) acrylic acid ester polymer (B) is too large, a large amount of the reactive functional group (b2) remains in the three- 1 (meth) acrylic acid ester polymer (A). As a result, the haze value may increase. It is also presumed that the three-dimensional network structure in which a large amount of the reactive functional group (b2) remains excessively restricts the mobility of the first (meth) acrylic acid ester polymer (A) inserted in the three-dimensional network structure. As a result, durability may deteriorate.

When the sticking composition according to the present embodiment contains the silane coupling agent (D), the silane coupling agent (D) can be obtained by reacting the reactive functional group (a1) (particularly the carboxyl group) of the first (meth) acrylic acid ester polymer (Meth) acrylic acid ester polymer (B) reacts with the first (meth) acrylic acid ester polymer (A) having a high molecular weight, (B2) (particularly the carboxyl group) of the second (meth) acrylic acid ester polymer (B), the alkoxysilyl group and the like of the silane coupling agent (D) may contain an excess of the reactive functional group It is presumed to react with the second (meth) acrylic acid ester polymer (B) having a low molecular weight. As a result, the pressure-sensitive adhesive obtained is inferior in adhesion with a glass substrate or the like to which the pressure-sensitive adhesive is adhered, whereby the durability of the pressure-sensitive adhesive layer is lowered.

The polymerization type (B) of the second (meth) acrylic acid ester polymer (B) obtained by polymerizing a (meth) acrylic acid ester having an alkyl group of an alkyl group of 1 to 20 in the ester portion and a monomer having a functional group reactive with the crosslinking agent May be a random copolymer or a block copolymer. Particularly, when the second (meth) acrylic acid ester polymer (B) is a block copolymer, the size of the network of the three-dimensional network structure can be controlled, so that the second (meth) acrylic acid ester polymer (B) Chain is also desirable. Specifically, in the second (meth) acrylic acid ester polymer (B), a monomer having a reactive functional group (b1) at both terminals may be copolymerized with a (meth) acrylic acid ester having a carbon number of 1 to 20 .

In the present embodiment, the second (meth) acrylic ester polymer (B) may be used singly or in combination of two or more kinds.

The weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is from 8000 to 250,000, preferably from 20,000 to 150,000. That is, the second (meth) acrylic acid ester polymer (B) is a low molecular weight polymer component. In the present specification, the weight average molecular weight is a polystyrene reduced value measured by gel permeation chromatography (GPC).

Since the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is within the above range, a three-dimensional network structure peculiar to the adhesive composition according to the present embodiment is formed and contributes to excellent stress relaxation property. That is, when the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is less than 8,000, a satisfactory three-dimensional network structure can not be obtained. On the other hand, when the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) exceeds 25,000, the compatibility is lowered and the insertion of the polymer (A) into the three-dimensional network structure formed by the polymer (B) Resulting in insufficient durability and reworkability.

The first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent. The functional group (b1) of the second (meth) acrylic acid ester polymer (A1) having a lower reactivity with the crosslinking agent (C) than the above-mentioned functional group (b1), and preferably contains a monomer having a functional group higher in reactivity with the crosslinking agent (C) than the above-mentioned functional group Not included.

The first (meth) acrylic acid ester polymer (A) may not contain a monomer having a functional group reactive with the crosslinking agent (C), but may be more reactive than the reactive functional group (b1) of the second (meth) acrylic acid ester polymer (Meth) acrylic ester polymer (B) and the cross-linking agent (C) when the monomer having a low reactive functional group (a1) (monomer containing a reactive functional group (a1) (D) is used, the reactive functional group (a1) of the first (meth) acrylic acid ester polymer (A) reacts with the alkoxysilyl group or the like of the silane coupling agent (D) The degree of agglomeration of the ester polymer (A) can be adjusted, and desired adhesiveness can be obtained, which is preferable.

When the first (meth) acrylic acid ester polymer (A) contains the above-mentioned reactive functional group (a1) containing monomer, its content is usually 20 mass% or less, preferably 15 mass% or less, more preferably 10 mass% desirable. If the content of the reactive functional group (a1) -containing monomer exceeds 20 mass%, the first (meth) acrylic acid ester polymer (A) may agglomerate too much and the desired stress relaxation property may not be obtained. From the viewpoint of imparting reworkability, the content of the reactive functional group (a1) -containing monomer is preferably 15% by mass or less.

In comparison with the monomer containing a reactive functional group (b1) contained in the second (meth) acrylic acid ester polymer (B), the content of the reactive functional group (a1) contained in the first (meth) acrylic acid ester polymer (A) The proportion of the monomer in the first (meth) acrylic acid ester polymer (A) is preferably such that the ratio of the second (meth) acrylic acid ester polymer (A) contained in the second (meth) acrylic acid ester polymer (B) Acrylic acid ester polymer (B). Thereby, the reaction between the reactive functional group (a1) and the crosslinking agent (C) contained in the first (meth) acrylic acid ester polymer (A) is inhibited, The functional group (b1) and the crosslinking agent (C) can be reliably reacted.

The first (meth) acrylic acid ester polymer (A) contains a monomer having a functional group having a reactivity with the crosslinking agent (C) equal to or higher than that of the reactive functional group (b1) of the second (meth) acrylic acid ester polymer However, if contained, the content of the monomer having the functional group in the molecule is preferably 1% by mass or less, more preferably 0.5% by mass or less, in the polymer (A). If the content of the monomer exceeds 1% by mass, the reaction between the second (meth) acrylic acid ester polymer (B) to be reacted with the crosslinking agent (C) may be inhibited.

Here, the polymerization forms of the first (meth) acrylic acid ester polymer (A) obtained by polymerizing the (meth) acrylic acid ester having 1 to 20 carbon atoms in the alkyl moiety of the ester moiety and the monomer having a reactive functional group may be a random copolymer, A copolymer may be used.

In the present embodiment, the first (meth) acrylic acid ester polymer (A) may be used singly or in combination of two or more kinds.

The weight average molecular weight of the first (meth) acrylic acid ester polymer (A) is 700,000 to 250,000, preferably 1,000,000 to 2,000,000. That is, the first (meth) acrylic acid ester polymer (A) is a high molecular weight polymer component.

When the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) is within the above range, the three-dimensional network structure formed by the second (meth) acrylic acid ester polymer (B) ) Acrylic ester polymer (A) is favorably inserted, and it is presumed that two or more molecules of the polymer (A) are constrained to a state having a certain degree of freedom through a pseudo crosslinking structure. As a result, the pressure-sensitive adhesive to be formed has appropriate cohesive force and excellent stress relaxation property. As a result, the pressure-sensitive adhesive has an excellent resistance to light leakage, a sufficient durability under high temperature and wet heat conditions, have.

Here, when the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) is less than 700,000, the cohesive force of the component (A) is lowered and the durability and workability may be deteriorated. When the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) is more than 250,000, the compatibility with the second (meth) acrylic acid ester polymer (B) is deteriorated, There is a possibility that the stress relaxation property is not obtained.

The ratio of the second (meth) acrylic acid ester polymer (B) to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is 5 to 40 parts by mass, preferably 10 to 30 parts by mass.

In the pressure-sensitive adhesive obtained from the adhesive composition containing the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B) in the above ratio, the second (meth) acrylic acid ester polymer (B) (Low molecular weight polymer) forms a three-dimensional network structure through the crosslinking agent (C), and two or more molecules of the first (meth) acrylic acid ester polymer (A) (high molecular weight polymer) are inserted into the three- It is presumed that the polymers (A) form a pseudo-crosslinked structure constrained in a state having a certain degree of freedom by the structure. As a result, the resulting pressure-sensitive adhesive exhibits excellent cohesion and excellent stress relaxation property. Therefore, the obtained pressure-sensitive adhesive has excellent durability and leak resistance.

As the crosslinking agent (C), an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent and a metal chelating crosslinking agent are preferably used.

The isocyanate-based crosslinking agent includes at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane Alicyclic polyisocyanates such as diisocyanate and the like, and a reaction product thereof with a low molecular active hydrogen-containing compound such as a biuret, an isocyanurate, or an ethylene glycol, propylene glycol, neopentyl glycol, trimethylol propane or castor oil And a duct duct body.

Examples of the epoxy crosslinking agent include 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane, N, N, N ', N'-tetraglycidyl-m- , Ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylol propane diglycidyl ether, diglycidyl aniline, and diglycidyl amine.

Examples of the aziridine crosslinking agent include diphenylmethane 4,4'-bis (1-aziridinecarboxamide), trimethylolpropane tri- (3-aziridinylpropionate, tetramethylolmethanetri- Aziridinyl propionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylene melamine, bisisophthaloyl-1- (2-methyl aziridine) Methyl aziridine) phosphine, trimethylol propane tri- beta - (2-methyl aziridine) propionate, and the like.

As the metal chelate-based crosslinking agent, chelate compounds such as aluminum, zirconium, titanium, zinc, iron and tin can be used as the metal atom, but aluminum chelate compounds are preferable from the viewpoint of performance. Examples of the aluminum chelate compound include diisopropoxy aluminum monooleate acetoacetate, monoisopropoxy aluminum bisoleyl acetoacetate, monoisopropoxy aluminum monooleate monoethylacetoacetate, diisopropoxy aluminum Mono lauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, diisopropoxyaluminum monoisostearyl acetoacetate, and the like.

The content of the crosslinking agent (C) is preferably such that the crosslinkable group (for example isocyanate group) of the crosslinking agent (C) is the reactive functional group (b1) (for example, hydroxyl group) of the second (meth) acrylic acid ester polymer (B) The amount is usually 0.05 to 5 equivalents, preferably 0.1 to 3.5 equivalents, and particularly preferably 0.2 to 1.8 equivalents. When the amount of the crosslinkable group is 0.1 equivalent or more, the gel fraction of the obtained pressure sensitive adhesive becomes 40% or more and sufficient cohesive force can be exhibited. When the amount is 0.2 equivalent or more, the obtained pressure sensitive adhesive can be made more excellent in durability. On the other hand, when the amount of the crosslinkable group is not more than 3.5 equivalents, the resulting pressure-sensitive adhesive can exhibit excellent reworkability, and when it is 1.8 or less, the haze value of the obtained pressure-sensitive adhesive can be suppressed to a low value.

In the present embodiment, a plurality of types of crosslinking agents may be used together as the crosslinking agent (C), if the crosslinking agent (C) is a crosslinking agent of a kind having a matching reactivity with both the reactive functional group (b1) and the reactive functional group (a1). From the viewpoint of facilitating control of the three-dimensional network structure formed by the second (meth) acrylic acid ester polymer (B), it is preferable to use only one kind of crosslinking agent, for example, only an isocyanate crosslinking agent is used And it is particularly preferable to use only one crosslinking agent.

On the other hand, as another form, it is preferable to use one type of crosslinking agent, particularly preferably one crosslinking agent, as the crosslinking agent (C), and to have a relationship of reactivity with both the reactive functional group (b1) and the reactive functional group (CR) different from that of the crosslinking agent (C) may be used in an amount of preferably 1/20 or less, particularly preferably 1/30 or less, in terms of mass ratio to the crosslinking agent (C). For example, the crosslinking agent (C) is preferably an isocyanate crosslinking agent, and the other crosslinking agent (CR) is a small amount of an epoxy crosslinking agent. The addition of such another crosslinking agent is effective when the polymer (A) is not sufficiently inserted into the three-dimensional network structure constituted by the polymer (B), and the cohesive force is insufficient. The other crosslinking agent (CR) is not included in the crosslinking agent (C), and is excluded from the crosslinking agent (C) in the above quantitative relationship.

Here, the combination of the cross-linking agent (C) and the reactive functional group-containing monomer of each of the (meth) acrylic acid ester polymer (A) and the (meth) acrylic acid ester polymer (B) is preferably such that, in the case of the isocyanate- Examples of the monomer containing a functional group (a1) include a carboxyl group-containing monomer, a monomer containing a reactive functional group (b1) of the polymer (B), a monomer containing a hydroxyl group or an amino group, and a monomer containing a reactive functional group (b2) Is preferably selected.

On the other hand, when the crosslinking agent (C) is an epoxy crosslinking agent, an aziridine crosslinking agent or a metal chelating crosslinking agent, the reactive functional group (a1) containing monomer of the polymer (A) Containing monomer as the reactive functional group (b2) -containing monomer of the polymer (B), a hydroxyl group-containing monomer is preferably selected.

The flexibility of the bond formed between the crosslinking agent (C) and the polymer (B), the mildness of the crosslinking reaction and the reactivity of the polymer (A) contribute to the cohesive force of the polymer (A) by appropriately reacting with the silane coupling agent The crosslinking agent (C) is reacted with an isocyanate crosslinking agent, a monomer containing a reactive functional group (a1) of the polymer (A) and a monomer containing a reactive functional group (b1) Containing functional group (b2) as a carboxyl group-containing monomer is particularly preferable.

The adhesive composition according to the present embodiment preferably further contains a silane coupling agent (D). When the first (meth) acrylic acid ester polymer (A) has a carboxyl group, the organic reactive group of the silane coupling agent (D) and the like can be mixed with the first (meth) acrylic acid ester polymer The carboxyl group of the silane coupling agent (A) reacts, while the alkoxysilyl group of the silane coupling agent (D) acts on the surface of the adherend such as a glass substrate. For this reason, for example, when the polarizing plate is attached to a liquid crystal glass cell or the like, adhesion between the pressure-sensitive adhesive and the liquid crystal glass cell becomes better.

The silane coupling agent (D) is preferably an organosilicon compound having at least one alkoxysilyl group in the molecule, good compatibility with the pressure-sensitive adhesive component, and light-transmitting property, for example, substantially transparent. The amount of the silane coupling agent (D) to be added is preferably 0.01 to 0.5 parts by mass, more preferably 0.05 to 0.3 parts by mass with respect to 100 parts by mass of the first (meth) acrylic acid ester polymer (A).

Specific examples of the silane coupling agent (D) include a polymerizable unsaturated group-containing silicon compound such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane (3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyl) silane compounds having an epoxy structure such as methoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, Amino group-containing silicon compounds such as trimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, have. These may be used singly or in combination of two or more kinds.

As the adhesive composition, various additives commonly used in acrylic pressure sensitive adhesives such as a tackifier, an antioxidant, an ultraviolet absorber, a light stabilizer, a softening agent, a filler, an antistatic agent and a refractive index adjuster may be added.

[Production method of adhesive composition]

The adhesive composition is prepared by mixing the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B), and at the optional step, a crosslinking agent (C) D).

As a preferred specific example, the (meth) acrylic acid ester polymers (A) and (B) are separately prepared by a conventional radical polymerization method. The polymerization of the (meth) acrylic acid ester polymers (A) and (B) can be carried out by a solution polymerization method or the like, using a polymerization initiator if desired. As the polymerization solvent, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like may be used.

Examples of the polymerization initiator include an azo-based compound, an organic peroxide, and the like, or two or more of them may be used in combination. Examples of the azo based compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane- (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxy valeronitrile), dimethyl 2,2 ' Azobis (2-methylpropionate), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile) -Azobis [2- (2-imidazolin-2-yl) propane].

Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxy dicarbonate, di-n-propyl peroxy dicarbonate, di (2- Peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybibarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide and diacetyl peroxide. .

Next, the solutions of the obtained polymers (A) and (B) are mixed, and a diluting solvent is added. Thereafter, a crosslinking agent (C) and, if desired, a silane coupling agent (D) are added and thoroughly mixed to obtain a sticky composition (coating solution) diluted with a solvent.

Examples of the diluting agent for diluting the adhesive composition to prepare a coating solution include aliphatic hydrocarbons such as hexane, heptane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; Ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone, esters such as ethyl acetate and butyl acetate, esters such as ethyl cell And cellosolve solvents such as Rosolv.

The concentration and viscosity of the coating solution thus prepared are not particularly limited and may be suitably selected according to the circumstances. For example, it is diluted so that the concentration of the adhesive composition is 10 to 40% by mass. Further, when obtaining a coating solution, it is not necessary to add a diluting solvent or the like, and it is not necessary to add a diluting solvent if the viscosity is such that the adhesive composition can be coated. In this case, the adhesive composition is directly used as a coating solution.

[adhesive]

The pressure-sensitive adhesive according to the present embodiment is obtained by crosslinking the pressure-sensitive adhesive composition. The crosslinking of the adhesive composition can be carried out by heat treatment. This heat treatment may also be used as a drying treatment for volatilizing a diluting solvent or the like of the adhesive composition.

In the case of performing the heat treatment, the heating temperature is preferably 50 to 150 占 폚, particularly preferably 70 to 120 占 폚. The heating time is preferably 30 seconds to 3 minutes, more preferably 50 seconds to 2 minutes. Further, it is particularly preferable to leave a curing period of about 1 to 2 weeks at room temperature (for example, 23 DEG C, 50% RH) after the heat treatment.

It is presumed that the second (meth) acrylic acid ester polymer (B) is crosslinked by the crosslinking agent (C) by the above heat treatment (and curing) to form a dense three-dimensional network structure. The first (meth) acrylic acid ester polymer (A) having two or more molecules in the three-dimensional network structure is inserted with no direct chemical bonding or with very little chemical bonding, whereby the polymer (A) To form a pseudo-cross-linked structure. When the first (meth) acrylic acid ester polymer (A) has a carboxyl group, the first (meth) acrylic acid ester polymer (A) reacts with the silane coupling agent (D) to coagulate to a predetermined degree.

The pressure-sensitive adhesive described above can be preferably used for an optical member, and is suitable, for example, for adhesion of a polarizing plate and a retardation plate or adhesion of a polarizing plate (polarizing film) or a retardation plate (retardation film) to a glass substrate. Since the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive is excellent in stress relaxation property, even if the dimensional change of the adherend is great, the pressure that can be caused by the dimensional change can be absorbed and alleviated in the pressure- It is difficult to peel from the adherend all the time, and light leakage can be effectively prevented when the optical member is used in such an optical member. That is, the pressure sensitive adhesive according to the present embodiment achieves compatibility between light leakage and durability.

[Adhesive sheet]

1, the pressure-sensitive adhesive sheet 1A according to the first embodiment comprises a pressure-sensitive adhesive layer 11 laminated on the release face of the release sheet 12 and the release sheet 12 in order from below, (13) laminated on the substrate (11).

2, the pressure-sensitive adhesive sheet 1B according to the second embodiment is formed so as to contact two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b And a pressure-sensitive adhesive layer 11 sandwiched between the two release sheets 12a and 12b. The peeling surface of the peeling sheet in the present specification refers to a peeling surface in the peeling sheet, and includes both the surface subjected to the peeling treatment and the surface showing the peeling property without performing the peeling treatment.

In any of the pressure-sensitive adhesive sheets 1A, 1B, the pressure-sensitive adhesive layer 11 becomes a pressure-sensitive adhesive that is crosslinked with the pressure-sensitive adhesive composition described above.

The thickness of the pressure-sensitive adhesive layer 11 is appropriately determined according to the intended use of the pressure-sensitive adhesive sheets 1A and 1B, but is usually in the range of 5 to 100 占 퐉, preferably 10 to 60 占 퐉, And when it is used as a pressure-sensitive adhesive layer for a polarizing plate, it is preferably 10 to 50 탆, particularly 10 to 30 탆.

The substrate 13 is not particularly limited and any substrate used as a base sheet of a conventional adhesive sheet can be used. For example, in addition to a desired optical member, a woven or nonwoven fabric using fibers such as rayon, acrylic, and polyester; Papers such as high temperature paper, glassine paper, impregnated paper, and coated paper; Metal foil such as aluminum or copper; Foams such as urethane foams and polyethylene foams; Polyester films such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyurethane films, polyethylene films, polypropylene films, polyvinyl chloride films, polyvinylidene chloride films, polyvinyl alcohol films, A plastic film such as a copolymer film, a polystyrene film, a polycarbonate film, an acrylic resin film, a norbornene resin film, and a cycloolefin resin film; And a laminate of two or more of these. The plastic film may be uniaxially or biaxially stretched.

Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation film (phase difference film), a viewing angle compensating film, a luminance improving film, a contrast enhancing film and a liquid crystal polymer film. Among them, the polarizing plate (polarizing film) is easy to shrink and has a large dimensional change, so that it is suitable as an object for forming the pressure-sensitive adhesive (the pressure-sensitive adhesive layer 11) of the present embodiment from the viewpoint of light-

The thickness of the base material 13 differs depending on the type thereof, but is usually from 10 탆 to 500 탆, preferably from 50 탆 to 300 탆 in the case of optical members, for example.

Examples of the release sheets 12, 12a and 12b include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film , Ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, , A polycarbonate film, a polyimide film, a fluororesin film and the like are used. These crosslinked films are also used. Further, these laminated films may be used.

It is preferable that a peeling treatment is performed on the peeling surface of the peeling sheet (in particular, the surface in contact with the peeling layer 11). Examples of the releasing agent used in the peeling treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based releasing agents.

The thickness of the release sheets 12, 12a, 12b is not particularly limited, but is usually about 20 to 150 占 퐉.

In order to produce the pressure-sensitive adhesive sheet 1A, a solution (coating solution) containing the pressure-sensitive adhesive composition is applied to the release surface of the release sheet 12 and heat treatment is performed to form the pressure-sensitive adhesive layer 11, The base material 13 is laminated on the pressure-sensitive adhesive layer 11. [ Conditions for the heat treatment are as described above.

In order to produce the pressure-sensitive adhesive sheet 1B, a coating solution containing the pressure-sensitive adhesive composition is applied to the release surface of one release sheet 12a (or 12b) and heat treatment is performed to form the pressure- , The peeling surface of the other release sheet 12b (or 12a) is superimposed on the pressure-sensitive adhesive layer 11.

As the method of applying the coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method and the like can be used.

Here, for example, in order to manufacture a liquid crystal display device comprising a liquid crystal cell and a polarizing plate, a polarizing plate is used as the base material 13 of the pressure-sensitive adhesive sheet 1A, and the release sheet 12 of the pressure- Peeled, and the exposed pressure-sensitive adhesive layer 11 and the liquid crystal cell are laminated.

For example, in order to manufacture a liquid crystal display device in which a phase difference plate is disposed between a liquid crystal cell and a polarizing plate, one of the release sheets 12a (or 12b) of the pressure-sensitive adhesive sheet 1B is peeled off and the exposed pressure- And then the other release sheet 12b (or 12a) is peeled off, and the exposed pressure-sensitive adhesive layer 11 and the retarder are bonded to each other. Further, the polarizing plate is used as the base material 13 The release sheet 12 of the pressure-sensitive adhesive sheet 1A is peeled off, and the exposed pressure-sensitive adhesive layer 11 and the retarder are bonded.

According to the pressure-sensitive adhesive sheets 1A and 1B described above, the pressure-sensitive adhesive layer 11 has excellent stress relaxation properties. Therefore, even when the pressure-sensitive adhesive layer 11 is applied to the adhesion of a polarizing plate, for example, It can be absorbed and relaxed in the resin layer 11, whereby it is estimated that an excellent resistance to light leakage and a high durability are exhibited.

The embodiments described above are described for the purpose of facilitating understanding of the present invention and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design modifications and equivalents falling within the technical scope of the present invention.

For example, the release sheet 12 of the pressure-sensitive adhesive sheet 1A may be omitted, and either one of the release sheets 12a and 12b in the pressure-sensitive adhesive sheet 1B may be omitted.

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]

1. Preparation of Polymer (A)

A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 95.0 parts by mass of n-butyl acrylate, 5.0 parts by mass of acrylic acid, 200 parts by mass of ethyl acetate and 2,2'-azobisisobutyl And 0.08 part by mass of nitrile, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in the nitrogen atmosphere, the reaction solution was heated to 60 占 폚, allowed to react for 16 hours, and then cooled to room temperature. Here, a part of the obtained solution was subjected to GPC measurement by the below-mentioned method to confirm formation of polymer (A) having a weight average molecular weight of 1.5 million.

2. Preparation of Polymer (B)

A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 85.0 parts by mass of n-butyl acrylate, 15.0 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, 0.16 parts by mass of bisisobutylonitrile and 0.3 parts by mass of 2-mercaptoethanol were placed, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 70 占 폚, allowed to react for 6 hours, and then cooled to room temperature. Here, a part of the obtained solution was subjected to GPC measurement by the method described below to confirm the production of the polymer (B) having a weight average molecular weight of 50,000.

3. Preparation of adhesive composition

After mixing 100 parts by mass of the polymer (A) obtained in the above step (1) (solid content conversion value) and 20 parts by mass (solid content conversion value) of the polymer (B) obtained in the above step (2) (TDI type) adduct of trimethylol propane in an amount corresponding to 0.8 equivalents of the hydroxyl group of the polymer (B) (trade name &quot; Colonate L &quot; manufactured by Nippon Polyurethane Industry Co., Ltd.). Finally, 0.2 part by mass of 3-glycidoxypropyltrimethoxysilane (trade name: KBM403 available from Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent (D) was added and sufficiently stirred to obtain a diluted solution of the adhesive composition.

Table 1 shows the composition of the adhesive composition. Details of abbreviations and the like in Table 1 are as follows.

[Polymers (A) and (B)]

BA: n-butyl acrylate

AA: Acrylic acid

HEA: 2-hydroxyethyl acrylate

HBA: 4-hydroxybutyl acrylate

HEMA: 2-hydroxyethyl methacrylate

[Crosslinking agent (C)]

· Isocyanate-based crosslinking agent

TDI system: Tolylene diisocyanate adduct of trimethylol propane (trade name &quot; Colonate L &quot; manufactured by Nippon Polyurethane Industry Co., Ltd.)

   Isocyanurate: isocyanurate of hexamethylene diisocyanate (trade name &quot; Colonate HXR &quot;, trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.)

· Other crosslinking agents (epoxy crosslinking agents)

N, N, N ', N'-tetraglycidyl-m-xylenediamine (trade name "TETRAD-X" manufactured by Mitsubishi Gas Chemical Co.,

[Silane coupling agent (D)]

KBM403: 3-glycidoxypropyltrimethoxysilane (trade name &quot; KBM403 &quot; manufactured by Shinetsu Kagaku)

KBE9007: 3-isocyanate propyltriethoxysilane (trade name: KBE9007, manufactured by Shin-Etsu Chemical Co., Ltd.)

KBE403: 3-glycidoxypropyltriethoxysilane (trade name &quot; KBE403 &quot; manufactured by Shinetsu Kagaku)

The diluted solution of the obtained sticky composition was applied to the release treatment surface of a release sheet (SP-PET3811, thickness: 38 mu m) of a release sheet (one side of polyethylene terephthalate film was peeled off with a silicone release agent) By a knife coater, and then heat-treated at 90 DEG C for 1 minute to form a pressure-sensitive adhesive layer.

Then, a polarizing plate as a polarizing film with a discotic liquid crystal layer integrated with a polarizing film and a viewing angle enlarging film was laminated so that the pressure-sensitive adhesive layer and the discotic liquid crystal layer were in contact with each other, and cured at 23 DEG C and 50% RH for 7 days, Thereby obtaining a layer-attached polarizing plate.

[Examples 2 to 32, Comparative Examples 1 to 7]

Except that the types and ratios of respective monomers constituting the adhesive composition, the kind and amount of the crosslinking agent and the silane coupling agent, and the blending ratio of the polymer (A) and the polymer (B) were changed as shown in Table 1, A polarizing plate with a pressure-sensitive adhesive layer was produced.

[Test Example 1] (Adhesive strength measurement - Evaluation of reworkability)

A sample of 25 mm (width) and 100 mm (length) was cut out from the polarizer with a pressure-sensitive adhesive layer obtained in the example or comparative example and the release sheet was peeled off and exposed to the alkali-free glass (Eagle XG manufactured by Corning) After the application, it was pressurized at 0.5 MPa and 50 캜 for 20 minutes in an autoclave made by Kurihara Seisakusho Co., Ltd. (N / 25 mm) under the conditions of a peeling speed of 300 mm / min and a peeling angle of 18 degrees using a tensile tester (Tensilon Co., Ltd., manufactured by Orientech) after leaving for 24 hours under the conditions of 23 캜 and 50% RH. . Conditions other than those described herein were measured in accordance with JIS Z0237: 2009.

After 14 days under the conditions of 23 ° C and 50% RH, the adhesive strength (adhesion after 14 days of attachment: N / 25 mm) was measured in the same manner as described above. The preferable range of the adhesive force is more than 0.1 N / 25 mm and less than 25 N / 25 mm.

Based on the adhesive force after 14 days from the above attachment, the reworkability was evaluated according to the following criteria. The results are shown in Table 2.

Adhesion after 14 days with 20N / 25mm or less: ◎

Adhesion after 14 days after attachment: 20N / 25mm or more, less than 25N / 25mm: ○

Adhesion after 14 days after attachment: 25N / 25mm or more: x

[Test Example 2] (Measurement of gel fraction)

(SP-PET3801, thickness: 38 mu m) obtained by peeling one surface of a polyethylene terephthalate film with a silicone-based releasing agent was used in place of the polarizer used in the production of the polarizing plate with a pressure-sensitive adhesive layer in Examples and Comparative Examples To prepare a pressure-sensitive adhesive sheet. Specifically, the peeling sheet was laminated on the pressure-sensitive adhesive layer on which the constitution comprising the release sheet / pressure-sensitive adhesive layer (thickness: 25 占 퐉) obtained in the manufacturing process of the example or the comparative example was exposed. Thus, a pressure-sensitive adhesive sheet having a configuration of a release sheet / pressure-sensitive adhesive layer / release sheet was produced.

The obtained pressure-sensitive adhesive sheet was cured for 7 days under conditions of 23 캜 and 50% RH. Thereafter, the pressure-sensitive adhesive sheet was sampled at a size of 80 mm x 80 mm, the pressure-sensitive adhesive layer was wrapped with a polyester mesh (mesh size 200), and the mass of the pressure-sensitive adhesive alone was weighed with a precision balance. The mass at this time is defined as M1.

A sample of the pressure-sensitive adhesive was immersed in an ethyl acetate solvent using a sieve, and refluxed for 16 hours. Thereafter, the pressure-sensitive adhesive was taken out and dried by wind for 24 hours under an environment of a temperature of 23 DEG C and a relative humidity of 50%, and further dried in an oven at 80 DEG C for 12 hours. The mass of the adhesive after drying was weighed with a precision balance. Let the mass at this time be M2. The gel fraction (%) is expressed by (M2 / M1) x100. The results are shown in Table 2.

[Test Example 3] (Measurement of optical performance)

As a measurement sample, an adhesive sheet (7 days cured) similar to the adhesive sheet used for measuring the gel fraction was prepared. The haze value (%) of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was measured in accordance with JIS K7105 using a haze meter (NDH2000, manufactured by Nippon Denshoku Chemical Co., Ltd.). The results are shown in Table 2. The range of the haze value is preferably 0 to 5%.

[Test Example 4] (Evaluation of durability)

The polarizing plate with a pressure-sensitive adhesive layer obtained in Examples or Comparative Examples was adjusted to a size of 233 mm 309 mm using a cutting device (Super Cutter, PN1-600 manufactured by Oginosei Co., Ltd.). The peel-off sheet was peeled off and attached to alkali-free glass (Eagle XG made by Corning) through the exposed pressure-sensitive adhesive layer, followed by pressurization at 0.5 MPa and 50 ° C for 20 minutes in an autoclave made by Kuraray Seisakusho.

Thereafter, they were placed under the conditions of the following durability conditions, and observation was carried out using a 10-fold magnifier after 500 hours. The appearance change was based on the following. The results are shown in Table 2.

◎: No defect in 4 sides

?: No defects at the sides of 0.6 mm or more from the peripheral edge at four sides

X: At least one side of four sides has a defect in appearance or appearance of a pressure-sensitive adhesive of 0.1 mm or more such as peeling, peeling, foaming and streaking on a portion of 0.6 mm or more from the outer peripheral edge

&Lt; Durability condition &

· 60 ° C, relative humidity 90%

· Drying at 80 ℃

[Test Example 5] (Light leakage test)

The polarizing plate with a pressure-sensitive adhesive layer obtained in Examples or Comparative Examples was adjusted to a size of 233 mm 309 mm using a cutting device (Super Cutter, PN1-600 manufactured by Oginosei Co., Ltd.). The peel-off sheet was peeled off and attached to a non-alkali glass (Eagle XG made by Corning) through the exposed pressure-sensitive adhesive layer, followed by pressurization at 0.5 MPa and 50 ° C for 20 minutes in an autoclave made by Kurihara Seisakusho. The bonding was performed so that the polarization axis of the polarizing plate with a pressure-sensitive adhesive layer was in the cross-Nicol state (polarizing axis: 45 deg., 135 deg.) On the front and back of the alkali-free glass. In this state, after leaving for 500 hours under a drying condition of 80 캜, light leakage property was evaluated by the following method. The results are shown in Table 2.

&Lt; Evaluation of light leakage property &

Using MCPD-2000 manufactured by Otsuka Denshi Co., Ltd., the brightness of each area shown in Fig. 3 was measured, and the brightness difference DELTA L ^*

? L ^* = [(b + c + d + e) / 4] -a

(Where a, b, c, d and e are luminances at a predetermined measurement point (one central portion of each region) of the A region, B region, C region, D region and E region) I made it into the castle. The smaller the value of DELTA L ^*, the smaller the light leakage.

Here, the above-mentioned weight average molecular weight is a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement).

<Measurement Conditions>

GPC measurement apparatus: HLC-8020 manufactured by Tosoh Corporation

GPC column (passed in the following order): manufactured by Toso Co., Ltd.

TSK guard column HXL-H

TSK gel GMHXL (× 2)

TSK gel G2000HXL

Measurement solvent: tetrahydrofuran

· Measuring temperature: 40 ℃

As can be clearly seen from Table 2, the polarizing plate with a pressure-sensitive adhesive layer obtained in the Example had no problem in durability and excellent leakage light resistance. Further, in Example 30, since the content of the carboxyl group in the first (meth) acrylic acid ester polymer (A) is slightly larger than the preferable amount, the reworkability is inferior. Further, in Examples 31 and 32, the content of the isocyanate-based crosslinking agent is slightly larger than the preferable amount, resulting in poor reworkability.

In Comparative Example 1, since the content of hydroxyl groups in the second (meth) acrylic acid ester polymer (B) was too large, the durability was poor. In Comparative Example 2, the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) was too small, resulting in poor durability and reworkability. In Comparative Example 3, since the content of hydroxyl groups in the second (meth) acrylic acid ester polymer (B) was too small, the gel fraction (degree of crosslinking) was low and durability was poor. In Comparative Example 4, since the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) was too small, the durability was poor. In Comparative Example 5, the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) was too large, resulting in poor durability and reworkability. In Comparative Example 6, since the content of the second (meth) acrylic acid ester polymer (B) was too large, the durability was poor. In Comparative Example 7, since the content of the second (meth) acrylic acid ester polymer (B) was too small, the gel fraction (degree of crosslinking) was low and the durability was poor.

The pressure-sensitive adhesive composition and pressure-sensitive adhesive of the present invention are suitable for bonding optical members such as a polarizing plate and a retardation plate, and the pressure-sensitive adhesive sheet of the present invention is suitable as a pressure-sensitive adhesive sheet for optical members such as a polarizing plate and a retardation plate.

1 A, 1 B ... Adhesive sheet
11 ... The pressure-
12, 12a, 12b ... Peeling sheet
13 ... materials

Claims (13)

A first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 700,000 to 2,500,000,
A second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 250,000,
And a cross-linking agent (C)
The ratio of the second (meth) acrylic acid ester polymer (B) to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is 5 to 40 parts by mass,
The second (meth) acrylic acid ester polymer (B) contains as a constituent component a monomer having a functional group (b1) reacting with the crosslinking agent (C), and the ratio of the monomer having the functional group Is more than 1% by mass and less than 50% by mass in the second (meth) acrylic acid ester polymer (B)
The functional group which reacts with the crosslinking agent (C) contained in the second (meth) acrylic acid ester polymer (B) is substantially only the functional group (b1)
The first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group that reacts with the crosslinking agent (C) as a constituent component, and the functional group of the second (meth) acrylic acid ester polymer (a1) having a lower reactivity with the crosslinking agent (C) than the crosslinking agent (b1) as a constituent component. A first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 700,000 to 2,500,000,
A second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 250,000,
And a cross-linking agent (C)
The ratio of the second (meth) acrylic acid ester polymer (B) to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is 5 to 40 parts by mass,
Wherein the second (meth) acrylic acid ester polymer (B) contains as a constituent component a monomer having a functional group (b1) satisfying the following formula (I) in reactivity with the crosslinking agent (C) ) Is more than 1% by mass and less than 50% by mass in the second (meth) acrylic acid ester polymer (B)
The second (meth) acrylic acid ester polymer (B) is obtained by reacting a monomer having a functional group (b2) having a reactivity with the crosslinking agent (C) satisfying the following formula (I) As a constituent component in an amount of not more than 1/5 (mass ratio)
The first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group that reacts with the crosslinking agent (C) as a constituent component, and the functional group of the second (meth) acrylic acid ester polymer (a1) having a lower reactivity with the crosslinking agent (C) than the crosslinking agent (b1) as a constituent component.
Reactivity with crosslinking agent (C): Functional group (b2) <Functional group (b1) (I) 3. The method according to claim 1 or 2,
Wherein the first (meth) acrylic acid ester polymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent component. The method according to claim 1,
The functional group (a1) in the first (meth) acrylic acid ester polymer (A) is a carboxyl group,
The functional group (b1) in the second (meth) acrylic acid ester polymer (B) is a hydroxyl group,
Wherein the cross-linking agent (C) is an isocyanate-based cross-linking agent. 3. The method of claim 2,
The functional group (a1) in the first (meth) acrylic acid ester polymer (A) is a carboxyl group,
(B1) in the second (meth) acrylic acid ester polymer (B) is a hydroxyl group, the functional group (b2) is a carboxyl group,
Wherein the cross-linking agent (C) is an isocyanate-based cross-linking agent. The method according to claim 4 or 5,
Wherein the first (meth) acrylic acid ester polymer (A) contains 0 to 15 mass% of a carboxyl group-containing monomer as a monomer unit constituting the polymer. The method according to claim 4 or 5,
Wherein the second (meth) acrylic acid ester polymer (B) contains 3 to 40 mass% of a hydroxyl group-containing monomer as a monomer unit constituting the polymer. The method according to claim 4 or 5,
The content of the isocyanate crosslinking agent is such that the isocyanate group of the isocyanate crosslinking agent is 0.1 to 3.5 equivalents based on the amount of the functional group (b1) in the second (meth) acrylic acid ester polymer (B) Tacky composition. A method for producing the adhesive composition according to any one of claims 1 to 3,
(A) and the second (meth) acrylic acid ester polymer (B) are mixed together and the crosslinking agent (C) is added at an optional step, wherein the crosslinking agent &Lt; / RTI &gt; A pressure-sensitive adhesive which is crosslinked with the pressure-sensitive adhesive composition according to claim 1 or 2. A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive sheet according to claim 10, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive according to claim 10. 12. The method of claim 11,
Wherein the substrate is an optical member. Two peeling sheets,
And a pressure-sensitive adhesive layer sandwiched between the release sheets so as to contact the release surfaces of the two release sheets,
The pressure-sensitive adhesive sheet according to claim 10, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive according to claim 10.

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