KR101899373B1 - An adhesive and adhesion sheet - Google Patents

Abstract

A pressure-sensitive adhesive and a pressure-sensitive adhesive sheet excellent in both leakage light resistance and durability when applied to an optical member such as a polarizing plate.
(Meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000 and a second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8,000 to 300,000, A pressure-sensitive adhesive having a stress relaxation rate of 60% or more and a gel fraction of 30 to 90% after being maintained at 900% for 300 seconds in the test.

Description

[0001] An adhesive and an adhesive sheet [0002]

The present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet, and more particularly to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet suitable for an optical member such as a polarizing plate.

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 easily shrunk due to heat or the like, contraction 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 displacement of the optical axis of the optical member due to the stress at the time of contraction 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 method of using a pressure-sensitive adhesive layer having a small stress at the time. 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 having excellent stress relaxation property capable of flexibly coping 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, 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 the light-leak resistance and the 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 difficulty in causing a plasticizer or liquid paraffin to permeate over time in the pressure-sensitive adhesive layer to be formed. As a result, there have been concerns about various problems such as a decrease in adhesion durability and contamination of a liquid crystal cell serving as an adherend. Further, in the pressure-sensitive adhesive composition to which the urethane elastomer is added, when the compatibility is to be maintained, the upper limit of the amount of the urethane elastomer added is limited, so that the improvement of the stress relaxation property tends to become insufficient. Furthermore, when the amount of the urethane elastomer added is too large to improve the stress relaxation property, the compatibility with the acrylic pressure sensitive adhesive is lowered, and problems such as cloudiness are caused. Thus, in the prior 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 pressure-sensitive adhesive and a pressure-sensitive adhesive sheet which are excellent in both light leakage resistance and durability when applied to an optical member such as a polarizing plate.

In order to attain the above object, the first invention is a process for producing a poly (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000 and a second (meth) acrylic acid ester polymer having a weight average molecular weight of 8,000 to 300,000 B), and has a stress relaxation rate of 60% or more and a gel fraction of 30 to 90% after holding at 900% for 300 seconds in the tensile test (invention One).

It is presumed that the pressure-sensitive adhesive according to the invention (invention 1) has a structure in which a plurality of high molecular weight polymers (A) are inserted into a three-dimensional network structure formed by crosslinking a low molecular weight polymer (B) And has a predetermined gel fraction. As a result, the pressure-sensitive adhesive exhibits an appropriate cohesive force and excellent stress relaxation property. By using the pressure-sensitive adhesive having the excellent stress relaxation property, a pressure-sensitive adhesive sheet excellent in both light leakage and durability can be obtained when applied to an optical member such as a polarizing plate.

In the invention (Invention 1), 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 preferably 5 to 50 parts by mass 2).

It is preferable that the second (meth) acrylic acid ester polymer (B) before crosslinking contains more than 1 mass% and less than 50 mass% of the reactive functional group-containing monomer as a constituent component (invention 3 ).

In the invention (Invention 3), it is preferable that the second (meth) acrylic acid ester polymer (B) is crosslinked by a reaction with a crosslinking agent (C) having a crosslinkable group capable of reacting with the reactive functional group (Invention 4).

A second aspect of the present invention provides a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive (Inventions 1 to 4).

In the above invention (Invention 5), it is preferable that the substrate is an optical member (invention 6).

A third aspect of the present invention is an adhesive sheet comprising two release sheets and a pressure-sensitive adhesive layer sandwiched between the release sheets so as to contact the release surfaces of the two release sheets, wherein the pressure-sensitive adhesive layer comprises the pressure- ) Of the pressure-sensitive adhesive sheet (invention 7).

In the pressure-sensitive adhesive according to the present invention, a polymer having a low molecular weight forms a three-dimensional network structure by chemical crosslinking, and a plurality of high molecular weight polymers are inserted into the three-dimensional network structure, It is presumed that a pseudo-crosslinked structure is formed between the high molecular weight polymers. Therefore, the pressure-sensitive adhesive has a large stress relaxation rate and a predetermined gel fraction. As a result, the pressure-sensitive adhesive exhibits an appropriate cohesive force and excellent stress relaxation property. By using the pressure-sensitive adhesive having the excellent stress relaxation property, a pressure-sensitive adhesive sheet excellent in both light leakage and durability can be obtained when applied to an optical member such as a polarizing plate.

1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to a first embodiment of the present invention.
2 is a cross-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 polarizing plate with a pressure-sensitive adhesive layer.
4 is a drawing (color) showing evaluation criteria of a light leakage test (visual inspection) in a polarizer with a pressure-sensitive adhesive layer.

Hereinafter, embodiments of the present invention will be described.

〔adhesive〕

(A) having a weight average molecular weight (Mw) of 500,000 to 3,000,000 and a second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8,000 to 300,000, And a crosslinking agent. 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 " polymer " includes the concept of " copolymer ".

The above-mentioned pressure-sensitive adhesive preferably includes a first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000 and a second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8,000 to 300,000. And a pressure-sensitive adhesive composition containing a crosslinking agent (C), particularly preferably a pressure-sensitive adhesive composition further containing a silane coupling agent (D). In such a pressure-sensitive adhesive, a three-dimensional network structure is formed by chemically crosslinking a low-molecular-weight polymer conventionally used as a plasticizer, and a plurality of high molecular weight polymers are inserted into the three- It is presumed that they bind each other to form a pseudo-crosslinked structure between the high molecular weight polymers. As a result, the resulting pressure-sensitive adhesive can exhibit an appropriate cohesive force and excellent stress relaxation property. Hereinafter, the adhesive composition will be described.

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

The functional group which reacts with the cross-linking 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) It is preferable to use it as a component.

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 preferably higher than the reactivity of the functional group (b2) with the crosslinking agent (C).

The (meth) acrylic acid ester polymer (A) or (B) is obtained by reacting a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group with a monomer having a functional group (reactive functional group-containing monomer) Copolymers with other monomers to be used as desired 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 acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (Meth) acrylate, n-pentyl acrylate, n-pentyl acrylate, n-hexyl acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl 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 monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers) .

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (Meth) acrylic acid hydroxyalkyl esters 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 N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Vinyl acetate, 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) ) Containing monomer is determined by the reactivity relationship with the crosslinking agent (C) to be used. Details will be described later.

Here, it is preferable that the second (meth) acrylic acid ester polymer (B) contains 1% by mass or more of the monomer containing the reactive functional group (b1) and the upper limit thereof is less than 50% by mass. Preferably, the monomer containing the reactive functional group (b1) is contained in an amount of 5 to 30 mass%, particularly preferably 10 to 20 mass%, and still more preferably 12 to 18 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, and the degree of crosslinking of the second (meth) acrylic acid ester polymer (B) The stress relaxation rate of the pressure sensitive adhesive can be set to a predetermined value or more and the gel fraction can be set within a predetermined range. As a result, it becomes a pressure-sensitive adhesive having durability and resistance to light leakage. When the content of the reactive functional group (b1) -containing monomer is 1% by mass or less, crosslinking of the second (meth) acrylic acid ester polymer (B) is insufficient and the gel fraction falls below a predetermined range, There is a concern. On the other hand, if the content of the reactive functional group (b1) -containing monomer is 50% by mass or more, the crosslinking of the second (meth) acrylic acid ester polymer (B) becomes excessive and the gel fraction of the obtained pressure sensitive adhesive becomes higher than a predetermined range, The rate may be lower than a predetermined value. When the upper limit of the content of the reactive functional group (b1) -containing monomer is 30 mass%, the resulting pressure-sensitive adhesive sheet has better light-leak resistance.

The term "substantially the functional group (b1)" in the polymer (B) of the above-mentioned (1) includes the other functional groups reacting with the crosslinking agent (C) to such an extent as not to interfere with the reactivity of the functional group (b1) (In this case, the polymer (B) of (1) and the polymer (B) of (2) are overlapped). That is, the second (meth) acrylic acid ester polymer (B) contains a monomer (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 Is particularly preferable. However, when the monomer containing a reactive functional group (b2) is contained as a component, it is preferably contained in an amount of 1/5 or less, particularly 1/10 or less, of the content of the reactive functional group (b1) .

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 in the mass ratio, the durability of the resulting pressure- There is a concern. 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- It is presumed to cause a change in compatibility with the (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 the reactive functional groups (b2) remain largely restrains the mobility of the first (meth) acrylic acid ester polymer (A) inserted in the three-dimensional network structure excessively. As a result, the stress relieving rate of the obtained pressure sensitive adhesive is lower than a predetermined value, and the durability is sometimes deteriorated.

When the adhesive 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), it is presumed that the adhesion of the second (meth) acrylic acid ester polymer (B) to the high molecular weight first (meth) acrylic acid ester polymer The alkoxysilyl group or the like of the silane coupling agent (D) also reacts with the reactive functional group (b2) (particularly the carboxyl group) of the second (meth) acrylic acid ester polymer (B) , And 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 the glass substrate or the like to which the pressure-sensitive adhesive is adhered, whereby the durability of the pressure-sensitive adhesive layer may be deteriorated.

The polymerization forms of the second (meth) acrylic acid ester polymer (B) obtained by polymerizing a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group and a monomer having a functional group reactive with the crosslinking agent (C) Or may be a block copolymer.

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

The weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is 8,000 to 300,000, preferably 10,000 to 200,000, and particularly preferably 50,000 to 100,000. 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 a gel permeation chromatography (GPC) method.

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 30,000, the compatibility with the first (meth) acrylic acid ester polymer (A) The insertion of the polymer (A) into the dimensional network structure becomes insufficient, and the gel fraction may fall below the predetermined range. As a result, the resulting pressure-sensitive adhesive may have poor durability and reworkability.

The first (meth) acrylic acid ester polymer (A) preferably contains a monomer having a functional group which reacts with the cross-linking agent (C) as a constituent, and the second (meth) acrylic acid ester polymer (a1) having a lower reactivity with the crosslinking agent (C) than the functional group (b1), and particularly preferably a monomer having a functional group having a higher reactivity with the crosslinking agent (C) than the functional group It is not contained as a component.

The first (meth) acrylic acid ester polymer (A) may not contain a monomer having a functional group reactive with the crosslinking agent (C). However, it is more preferable to contain a monomer (reactive functional group (a1) -containing monomer) having a reactive functional group (a1) having lower reactivity than the reactive functional group (b1) of the second (meth) acrylic acid ester polymer (B). When the reactive functional group (a1) is contained in the polymer (A), the reaction between the second (meth) acrylic acid ester polymer (B) and the crosslinking agent (C) is promoted, or when the silane coupling agent (D) The reactive functional group (a1) of the first (meth) acrylic acid ester polymer (A) reacts with the silane coupling agent (D) so that the durability of the obtained pressure sensitive adhesive to the glass surface, such as a liquid crystal cell, .

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, particularly preferably 10 mass% Do. When the content of the reactive functional group (a1) -containing monomer exceeds 20% by mass, the glass transition temperature (Tg) of the first (meth) acrylic acid ester polymer (A) becomes too high and the stress relaxation rate of the obtained pressure- . From the viewpoint of imparting reworkability to the pressure-sensitive adhesive, 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 second (meth) acrylic acid ester polymer (A) in the first (meth) acrylic acid ester polymer (A) is higher than that of the second (meth) acrylic acid ester polymer (B) Is preferably smaller than the ratio in the above. As a result, 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 and the reactive functional group b1) and the cross-linking agent (C) can be reliably reacted. Thereby, the stress relaxation rate and the gel fraction of the resulting pressure-sensitive adhesive can be set to a predetermined value or less.

The first (meth) acrylic acid ester polymer (A) is a polymer which does not contain a monomer having a functional group having a reactivity with the crosslinking agent (C) equal to or more than 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. As a result, a predetermined stress relaxation rate may not be obtained.

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

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 from 500,000 to 3,000,000, preferably from 700,000 to 250,000, and particularly preferably from 1 million 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 first (meth) acrylic acid ester polymer (B) It is presumed that the polymer (A) is well inserted, and more than two molecules of the polymer (A) intervene in a pseudo crosslinking structure, whereby the polymer (A) is constrained in a state having a certain degree of freedom. The polymer (A) has a relatively large molecular weight as described above, and has a high degree of freedom as a molecular chain while maintaining a pseudo-crosslinked state through the three-dimensional network structure formed by the polymer (B). As a result, the pressure-sensitive adhesive to be formed has a predetermined stress relaxation rate and gel fraction, so that it has an appropriate cohesive force and excellent stress relaxation property. As a result, the pressure-sensitive adhesive has excellent resistance to light leakage, and sufficient adhesion durability under high temperature conditions can be prevented, and lifting and peeling can be prevented.

If the weight-average molecular weight of the first (meth) acrylic acid ester polymer (A) is less than 500,000, the gel fraction of the obtained pressure-sensitive adhesive may be lowered and the durability and workability may be deteriorated. When the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) exceeds 3,000,000, compatibility with the second (meth) acrylic acid ester polymer (B) is deteriorated and the stress relaxation rate of the obtained pressure sensitive adhesive .

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 preferably from 5 to 50 parts by mass, more preferably from 5 to 40 parts by mass, To 30 parts by mass is particularly preferable.

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) (Meth) acrylic ester polymer (A) (high molecular weight polymer) is inserted into the three-dimensional network structure through a crosslinking agent (C) It is presumed that the polymers (A) form a constrained pseudo-crosslinked structure in a state of having a certain degree of freedom. As a result, the obtained pressure-sensitive adhesive has a predetermined stress relaxation ratio and a gel fraction. Therefore, the obtained pressure-sensitive adhesive has excellent durability and leak resistance.

Examples of the crosslinking agent (C) include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a metal chelating crosslinking agent.

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 di Alicyclic polyisocyanates such as isocyanate and the like and a reaction product thereof with a low molecular weight active hydrogen-containing compound such as a biuret, an isocyanurate, and ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, And duct bodies.

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- beta -aziridinylpropionate, tetramethylol methanetri- aziridinyl propionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylene melamine, bisisopthaloyl-1- (2-methyl aziridine), tris- -Methyl aziridine) phosphine, trimethylolpropane 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 crosslinking group (for example, an isocyanate group) of the crosslinking agent (C) is the reactive functional group (b1) 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 0.3 to 1.0 equivalents. When the amount of the crosslinkable group is less than 0.05 equivalent, the gel fraction of the resulting pressure-sensitive adhesive becomes less than 30%, and sufficient cohesive force may not be exhibited. When the amount of the crosslinkable group is 0.1 equivalents or more, particularly 0.3 equivalents or more, the resulting pressure-sensitive adhesive can have better durability. On the other hand, when the amount of the crosslinkable group is 3.5 equivalents or less, the resulting pressure-sensitive adhesive can be made excellent in reworkability. Further, when the amount of the crosslinking group is 1.0 equivalent or less, it is presumed that the crosslinking agent (C) contributes only to the formation of the three-dimensional network structure of the polymer (B), thereby effectively preventing crosslinking of the polymer (A). As a result, the pressure-sensitive adhesive obtained is excellent in stress relaxation property.

In the present embodiment, as the cross-linking agent (C), a plurality of kinds of cross-linking agents may be used in combination if the reactivity of the reactive functional group (b1) and the reactive functional group (a1) is the same. From the viewpoint of facilitating the control of the three-dimensional network structure formed by the second (meth) acrylic acid ester polymer (B), it is preferable to use only one type of crosslinking agent as the functional group, for example, It is particularly preferable to use only one crosslinking agent as the compound.

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- As the monomer containing a functional group (a1), a hydroxyl group-containing monomer or an amino group-containing monomer is preferably selected as the carboxyl group-containing monomer and the reactive functional group (b1) -containing monomer of the polymer (B).

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 monomers are preferably selected from carboxyl group-containing monomers.

The flexibility of the bond formed between the crosslinking agent (C) and the polymer (B) and the mildness of the crosslinking reaction and the reactive group of the polymer (A) react appropriately with the silane coupling agent (D) to improve the adhesion durability of the resulting pressure- It is preferable that the crosslinking agent (C) is 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) of the polymer (B) It is particularly preferable to use no monomer containing a reactive functional group (b2).

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 silane coupling agent (D) is mixed with the organic reactive group of the silane coupling agent (D) ) React with the carboxyl group of the silane coupling agent (D), and 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 bonded to a liquid crystal glass cell or the like, adhesion between the pressure-sensitive adhesive and the liquid crystal glass cell becomes better.

As the silane coupling agent (D), an organosilicon compound having at least one alkoxysilyl group in the molecule is preferred because it has good compatibility with the pressure-sensitive adhesive component and has optical transparency, 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-glycidoxypropyltrimethoxy Silane, silicon compounds having an epoxy structure such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) Amino group-containing silicon compounds such as methoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane and 3-isocyanatepropyltriethoxysilane . These may be used singly or in combination of two or more.

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.

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 any stage, mixing the crosslinking agent (C) ). &Lt; / RTI &gt;

As specific preferred examples, 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, for example, 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 compound, an organic peroxide, and the like, and two or more of them may be used in combination. Examples of the azo compound include azo compounds such as 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 peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) Carbonate, 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; Butanol and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone; esters such as ethyl acetate and butyl acetate; And a cellosolve type solvent such as Solv.

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

The pressure-sensitive adhesive described above 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 three-dimensional network structure. The first (meth) acrylic acid ester polymer (A) having two or more molecules in the three-dimensional network structure is not entangled with direct chemical bonding, or is inserted with very little chemical bonding, so that the polymer (A) It is presumed to form a pseudo - bridging structure. In the case where 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) Can be further improved.

The stress relieving rate after holding the pressure-sensitive adhesive according to the present embodiment at 900% by tensile test for 300 seconds is preferably 60% or more, and more preferably 62% or more. This tensile test is carried out using a single adhesive layer not involving a substrate or the like. Since the pressure-sensitive adhesive made of the above-mentioned material has such a large stress relaxation rate, the pressure-sensitive adhesive exhibits excellent stress relaxation property and can be excellent in both the light-leak resistance and the durability.

The stress relieving rate after stretching 900% of the pressure-sensitive adhesive according to the present embodiment in the tensile test for 100 seconds is preferably 50% or more, particularly preferably 52% or more.

Specifically, the tensile test was carried out under the conditions of 23 占 폚 and 50% RH at a speed of 200 mm / min and a 900% elongation . The stress relaxation rate is calculated by the following equation.

Stress relaxation rate (%) = {(900% Stress immediately after stretching - Stress after holding 300 seconds) / 900% Stress immediately after stretching} x 100

It is preferable that the pressure-sensitive adhesive according to the present embodiment is capable of elongating at least 1,500%, particularly at least 3,000%, when stretched under the same conditions as the tensile test.

The stress immediately after elongation at 900% by the tensile test is preferably 10 N or less, particularly preferably 1.5 N or less. The lower the stress immediately after the elongation of 900%, the more preferable the stress to be generated when the adherend (for example, the polarizing plate) is deformed is small, thereby improving the leak resistance. On the other hand, the lower limit of the stress immediately after elongation at 900% is preferably 0.2 N or more, particularly preferably 0.5 N or more. If the maximum stress is too low, the durability may deteriorate.

The gel fraction of the pressure sensitive adhesive according to the present embodiment is 30 to 90%, preferably 40 to 80%, particularly preferably 45 to 75%. When the gel fraction, that is, the degree of crosslinking is in the above range, the three-dimensional network structure of the second (meth) acrylic acid ester polymer (B) is well formed by crosslinking so that the pressure sensitive adhesive is excellent in both the light leakage resistance and durability . The gel fraction of the pressure-sensitive adhesive is a value at the time of pasting (after elapse of the aging period). Specifically, the gel fraction refers to the gel fraction after the adhesive composition is applied to a release sheet, heat-treated, and then stored at 23 캜 and 50% RH for 7 days. This is because the value of the gel fraction of the pressure-sensitive adhesive varies before aging. From this point of view, if it is unclear whether or not the aging period has elapsed, it is sufficient that the gel fraction is maintained within the above range after being stored for 7 days under the environment of 23 ° C and 50% RH.

The above-described pressure-sensitive adhesive 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 film (retardation film) to a glass substrate. Since the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive has a very excellent stress relaxation property, even when the dimensional change of the adherend is great, the pressure that can be generated by the dimensional change can be absorbed and relaxed by the pressure- It is possible to effectively prevent light leakage when used in the optical member as described above. That is, the pressure sensitive adhesive according to the present embodiment achieves compatibility between light leakage and durability when used in an optical member.

[Adhesive sheet]

1, the pressure-sensitive adhesive sheet 1A according to the first embodiment comprises a release sheet 12, a pressure-sensitive adhesive layer 11 laminated on the release surface of the release sheet 12, And a substrate 13 laminated on the pressure-sensitive adhesive layer 11. [

2, the pressure-sensitive adhesive sheet 1B according to the second embodiment has two sheets of peeling sheet 12a and 12b and two peeling sheets 12a and 12b, And a pressure-sensitive adhesive layer 11 sandwiched between two release sheets 12a and 12b. The release surface of the release sheet in the present specification means a surface having release properties in the release sheet and includes both the surface subjected to the release treatment and the surface exhibiting the release property without performing the release treatment.

In any of the pressure-sensitive adhesive sheets 1A, 1B, the pressure-sensitive adhesive layer 11 is a pressure-sensitive adhesive obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition.

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, It is preferably 10 to 50 占 퐉, more preferably 10 to 30 占 퐉.

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 coated paper, glossy paper, impregnated paper, and coated paper; Metal foil such as aluminum or copper; Foams such as urethane foams and polyethylene foams; A polyurethane film, a polyethylene film, a polypropylene film, a polyvinyl chloride film, a polyvinylidene chloride film, a polyvinylidene chloride film, a polyvinylidene chloride film, a polyvinylidene chloride film, a polyethylene terephthalate film, A plastic film such as a vinyl alcohol film, an ethylene-vinyl acetate copolymer film, a polystyrene film, a polycarbonate film, an acrylic resin film, a norbornene resin film, and a cycloolefin resin film; A laminate of two or more kinds thereof, and the like. 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 easily shrunk 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 resistance to light leakage.

The thickness of the substrate 13 differs depending on the kind thereof, but it 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. These may be laminated films.

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 an alchid type, a silicone type, a fluorine type, an unsaturated polyester type, a polyolefin type, and a wax type releasing agent.

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, A base material (13) is laminated on the layer (11). After that, it is preferable to set a curing period.

Conditions for the heat treatment and curing 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 a method for applying the coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a braid coating method, a die coating method, a gravure coating method, or 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- And the exposed pressure-sensitive adhesive layer 11 and the liquid crystal cell may be laminated.

For example, 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 as an example, The exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive layer 1B and the retarder are bonded. Next, the release sheet 12 of the pressure-sensitive adhesive sheet 1A using the polarizing plate as the base material 13 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1A is bonded to the retarder. The other release sheet 12b (or 12a) is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet B and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet B is bonded to the liquid crystal cell.

According to the above-mentioned pressure-sensitive adhesive sheets 1A, 1B, the pressure-sensitive adhesive layer 11 has excellent stress relaxation properties. Therefore, even when the pressure-sensitive adhesive sheet 11 is applied to the adhesion of a polarizing plate, for example, 11, it is presumed that excellent light-resistance leakage resistance and high durability are exerted.

The above-described embodiments 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)

To a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube, 97.0 parts by mass of n-butyl acrylate, 3.0 parts by mass of acrylic acid, 200 parts by mass of ethyl acetate, and 2,2'-azobisisobutyl 0.08 parts by mass of nitrile were introduced, 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)

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, 20.0 parts by mass of 2,2'-azobisisobutyronitrile were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, 0.16 parts by mass of bisisobutyronitrile and 0.3 parts by mass of 2-mercaptoethanol were introduced, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in the nitrogen atmosphere, the reaction solution was heated to 70 캜, 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 following method to confirm the production of the polymer (B) having a weight average molecular weight of 60,000.

3. Preparation of adhesive composition

After mixing 100 parts by mass (solid content conversion value) of the polymer (A) obtained in the above step (1) and 15 parts by mass (solid content conversion value) of the polymer (B) obtained in the above step (2) 2.21 parts by mass of a tolylene diisocyanate (TDI) adduct of trimethylol propane in an amount corresponding to 0.6 equivalents of the hydroxyl group of the polymer (B) (trade name "Colonate L", trade name, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added. 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 the abbreviations and the like described in Table 1 are as follows.

[Polymers (A) and (B)]

BA: n-butyl acrylate

AA: Acrylic acid

HEA: 2-hydroxyethyl acrylate

4HBA: 4-hydroxybutyl acrylate

[Plasticizer]

Adekaizer C-8: trimellitic acid ester plasticizer (tris (2-ethylhexyl) trimellitate) (trade name "Adekaizer C-8" manufactured by Asahi Denka Kogyo Co., Ltd.)

[Crosslinking agent (C)]

· Isocyanate-based crosslinking agent

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

Takenate D-110N: A xylene diisocyanate adduct of trimethylol propane (trade name "Takenate D-110 N" manufactured by Mitsui Chemicals, Inc.)

· Epoxy crosslinking agent

TETRAD-X: N, N, N ', N'-tetraglycidyl-m-xylenediamine (trade name "TETRAD-X" manufactured by Mitsubishi Chemical Corporation)

[Silane coupling agent (D)]

KBM403: 3-glycidoxypropyltrimethoxysilane (trade name: KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.)

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

The diluted solution of the obtained sticky composition was applied to the release surface of a release sheet (SP-PET3811, thickness: 38 mu m) of a release sheet (one side of the polyethylene terephthalate film was peeled off with a silicone-based release agent) Coated with 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 composed of a polarizing film with a discotic liquid crystal layer and an integrated polarizing film and a viewing angle enlarging film was attached so as to be in contact with the pressure sensitive adhesive layer and the discotic liquid crystal layer, and cured at 23 DEG C and 50% RH for 7 days, Thereby obtaining a polarizing plate with a pressure-sensitive adhesive layer.

[Examples 2 to 13 and Comparative Examples 1 to 5]

Except that the types and ratios of the respective monomers constituting the adhesive composition, the type and amount of the plasticizer, 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 in the same manner as in Example 1.

Here, the weight average molecular weight (Mw) described above 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 ℃

[Test Example 1] (Measurement of gel fraction)

(SP-PET 3801 manufactured by LINTEC CORPORATION, thickness: 38 mu m) obtained by peeling one side of a polyethylene terephthalate film with a silicone-based releasing agent was used in place of the polarizer used in the production of the polarizer with a pressure- , Thereby producing 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 surrounded with a polyester mesh (mesh size 200), and the mass of the pressure-sensitive adhesive alone was measured with a precision balance. The mass at this time is denoted by M1.

Next, the pressure sensitive adhesive surrounded by the polyester mesh was immersed in ethyl acetate at room temperature (23 DEG C) for 24 hours. Thereafter, the pressure-sensitive adhesive was taken out and air-dried for 24 hours under an environment of a temperature of 23 ° C and a relative humidity of 50%, and further dried in an oven at 80 ° C for 12 hours. The mass of the adhesive after drying was measured with a precision scale. 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 2] (Measurement of optical performance)

As a measurement sample, an adhesive sheet (cured for 7 days) similar to the adhesive sheet used for measuring the gel fraction was prepared. The haze value (%) (sometimes abbreviated as Hz (%)) of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was measured according to 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 3] (Evaluation of durability)

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

Thereafter, the mixture was placed under an environment of an endurance condition of 80 캜 dry, and after 500 hours, observation was carried out using a 10-fold magnifying glass. 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 of the four sides has a defect in appearance of the adhesive of 0.1 mm or more such as peeling, peeling, foaming, streaking or the like at a portion of 0.6 mm or more from the outer peripheral end.

[Test Example 4] (Light leakage test)

The polarizing plate with a pressure-sensitive adhesive layer obtained in Example or Comparative Example was made into a size of 233 mm 309 mm by using a cutting device (Super Cutter, PN1-600, manufactured by Oginosei Co., Ltd.). The peeled sheet was peeled off and attached to alkali-free glass (Eagle XG, manufactured by Corning) through the exposed pressure-sensitive adhesive layer, followed by pressurization at 0.5 MPa and 50 캜 for 20 minutes in an autoclave made by Kurarasa 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, the sample was allowed to stand in a dry environment at 80 占 폚 for 250 hours, and left for 2 hours under an environment of 23 占 폚 and 50% RH. Using the sample as a sample, the light leakage property was evaluated by the following method. The results are shown in Table 2.

<Evaluation of light leakage property:? L ^* >

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

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

(Where a, b, c, d and e are brightness 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 leaky. The smaller the value of? L ^*, the smaller the light leakage. And L ^* max represents the maximum brightness in all the areas.

<Evaluation of Light Leakage Property: Visual>

The sample was placed on a flat illuminator (HF-SL-A312LC, illuminance: 26,000 Lux, luminance: 10,000 cd) and photographed with a two-dimensional color luminance meter (CA-2000, Konica Minolta) Manufactured by Konica Minolta, CA-S20w). The luminance distribution images of the obtained samples were evaluated based on the evaluation criteria shown in Fig.

[Test Example 5] (Tensile test)

The adhesive compositions prepared in Examples and Comparative Examples were coated on the release treated surface of a release sheet (SP-PET3811, manufactured by LINTEC CO., LTD.) In which one surface of a polyethylene terephthalate film was peeled off with a silicone release agent so that the coating thickness after drying was 25 占 퐉 And heated at 100 DEG C for 1 minute to form a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer and a peeled-off surface of another release sheet (SP-PET3801, manufactured by LINTEC CO., LTD.) Having one side of the polyethylene terephthalate film peeled off with a silicone-based release agent were laminated to obtain a pressure-sensitive adhesive sheet.

A plurality of the above-mentioned pressure-sensitive adhesive layers were laminated so that the total thickness of the pressure-sensitive adhesive layers in the pressure-sensitive adhesive sheet was 500 탆 and only the release sheet in the outermost layer of the laminate remained, and left for 2 weeks in an atmosphere of 23 캜 and 50% RH . Thereafter, a sample of 10 mm (width) x 75 mm (length) was cut out from the pressure-sensitive adhesive sheet having a plurality of the pressure-sensitive adhesive layers laminated to peel off the release sheet laminated on the outermost layer of the laminate, × 20 mm (length), stretched in the longitudinal direction at a tensile speed of 200 mm / min using a tensile tester (Tensilon Co., Ltd., Orientech) under conditions of 23 ° C. and 50% RH, The stress (N) after holding for 100 seconds, 300 seconds, or 1200 seconds and the stress (N) immediately after 900% elongation were measured. From the measurement results, the stress relaxation rate (%) after keeping the pressure-sensitive adhesive for 100 seconds and the stress relaxation rate (%) after 300 seconds were calculated. The results are shown in Table 2.

As can be seen from Table 2, in the polarizing plate with a pressure-sensitive adhesive layer obtained in the examples, the stress relaxation rate after holding for 300 seconds at 900% elongation of the pressure-sensitive adhesive was 60% or more. On the other hand, in the polarizing plate with a pressure-sensitive adhesive layer obtained in the comparative example, the stress relaxation rate after holding for 300 seconds at 900% elongation of the pressure-sensitive adhesive was less than 60%, and both of durability and resistance to light leakage were reduced.

The pressure sensitive adhesive of the present invention is suitable for bonding an optical member, for example, a polarizing plate or a retardation plate, and the pressure sensitive adhesive sheet of the present invention is suitable as an adhesive sheet for optical members such as a polarizing plate and a retardation plate.

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

Claims (7)

A first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000,
(B) a second (meth) acrylic acid ester polymer having a weight average molecular weight of 8000 to 300000,
In the tensile test, the stress relaxation rate after holding for 300 seconds at a rate of 200 mm / min at 900% is at least 60%
And a gel fraction of 30 to 90%. The method according to claim 1,
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 50 parts by mass. The method according to claim 1,
Wherein the second (meth) acrylic acid ester polymer (B) before crosslinking contains more than 1% by mass and less than 50% by mass of a reactive functional group-containing monomer as a constituent component. The method of claim 3,
Wherein the second (meth) acrylic acid ester polymer (B) is crosslinked by a reaction with a crosslinking agent (C) having a crosslinkable group capable of reacting with the reactive functional group. A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive. 6. The method of claim 5,
Wherein the substrate is an optical member. Two release sheets,
And a pressure-sensitive adhesive layer sandwiched between the release sheets so as to come into contact with the release surfaces of the two release sheets,
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive.

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