TWI551661B - Adhesive composition, adhesive and adhesive sheet - Google Patents

Description

Adhesive composition, adhesive and adhesive sheet

The present invention relates to an adhesive composition, a method for producing an adhesive composition, an adhesive (a material for bridging an adhesive composition), and an adhesive sheet, and particularly relates to an optical member which can be suitably used for a polarizing plate or the like. Adhesive composition, method of producing adhesive composition, adhesive, and adhesive sheet.

In general, in a liquid crystal panel, an adhesive layer formed of an adhesive composition is often used in a polarizing plate or a phase difference plate followed by a glass substrate or the like. However, since an optical member such as a polarizing plate or a phase difference plate is likely to shrink due to heat or the like, shrinkage occurs due to heat stagnation, and as a result, the adhesive layer laminated on the optical member cannot follow shrinkage, and peeling occurs at the interface. (so-called foaming and peeling), and the stress caused by shrinkage of the optical member causes the optical axis of the optical member to shift to cause light leakage (so-called white point).

(1) A method of suppressing shrinkage by adhering an adhesive layer having high adhesion and excellent form stability to an optical member optical member such as a polarizing plate; or (2) using an optical member A method of stressing a layer of adhesive with a small stress. The method of (1) is effective as shown in Patent Document 1 using an adhesive layer having a high storage modulus. On the other hand, in the method of (2), it is effective to use an adhesive layer which is soft and elastically compatible with the deformation of the optical member. However, when it is desired to form such an adhesive layer excellent in stress relaxation, it is necessary to design a bridge density in the adhesive layer to be low. Thus, the strength of the adhesive layer itself is lowered, and there is a problem that durability is deteriorated.

Therefore, in Patent Documents 2 to 4, instead of reducing the bridging density of the adhesive layer, a plasticizer, a fluid paraffin, a urethane elastomer, or the like is added to the acrylic adhesive to appropriately change the obtained adhesive composition. The softness imparts stress relaxation to the adhesive layer, and is intended to provide light leakage resistance and durability.

[Advanced technical literature]

[Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent Publication No. 2006-235568

[Patent Document 2] Japanese Patent Laid-Open No. Hei 5-45517

[Patent Document 3] Japanese Patent Laid-Open Publication No. Hei 9-137143

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2005-194366

However, the addition of a plasticizer or a fluid paraffin adhesive composition forms an adhesive layer which is difficult to release a plasticizer or a flowing paraffin over time. Then, as a result, the liquid crystal cell of the object to be inspected is contaminated, and various problems occur. Further, when the urethane elastomer-attached adhesive composition is added, the upper limit of the amount of the urethane elastomer to be added is limited, and the improvement in stress relaxation property is not sufficient. Further, when the amount of addition of the urethane elastomer is increased to improve the stress relaxation property, the compatibility with the acrylic pressure-sensitive adhesive is lowered, and problems such as white turbidity are caused. As described above, according to the prior art, it is difficult for the adhesive layer formed of the adhesive composition for an optical member to fundamentally improve its light leakage resistance and durability.

The present invention provides an adhesive composition which is excellent in both light leakage resistance and durability when used in an optical member such as a polarizing plate, and a method for producing the adhesive composition. Adhesives and adhesive sheets are the target.

In order to achieve the above object, the present invention provides an adhesive composition comprising: a first (meth) acrylate polymer (A) having a weight average molecular weight of 700,000 to 2.5 million; weight average molecular weight a second (meth) acrylate polymer (B) of 8,000 to 250,000; and a bridging agent (C), the second (meth) acrylate polymer (B) to the first (meth) acrylate The ratio of the mass portion of the ester polymer (A) to 100 parts by mass is 5 to 40 parts by mass, and the second (meth) acrylate polymer (B) contains the functional group (b1) reactive with the bridging agent (C). The monomer is a constituent component, and the ratio of the monomer having the functional group (b1) is more than 1% by mass and less than 50% by mass in the second (meth) acrylate polymer (B). The functional group which can be reacted with the bridging agent (C) contained in the second (meth) acrylate polymer (B) is substantially only the functional group (b1), and the first (meth) acrylate is polymerized. The monomer (A) does not contain a monomer having a functional group reactive with the bridging agent (C) as a constituent component, or contains a reactivity with the bridging agent (C) as compared with the second (meth) propylene. Ester polymer (B) of the functional group (b1) of the lower functional group (a1) constituting the monomer component (Invention 1).

Secondly, the present invention provides an adhesive composition comprising: a first (meth) acrylate polymer (A) having a weight average molecular weight of 700,000 to 2.5 million; and a weight average molecular weight of 8,000 to 250,000 a second (meth) acrylate polymer (B); and a bridging agent (C), the second (meth) acrylate polymer (B) to the first (meth) acrylate polymer (A) The ratio of 100 parts by mass is 5 to 40 parts by mass, and the second (meth) acrylate polymer (B) contains a functional group satisfying the following formula (I) with reactivity with the above-mentioned bridging agent (C) ( The monomer of b1) is a constituent component, and the ratio of the monomer having the above functional group (b1) is more than 1% by mass and less than 50% by mass in the second (meth) acrylate polymer (B). And the second (meth) acrylate polymer (B) contains the amount (mass ratio) of 1/5 or less of the content of the monomer having the functional group (b1), and has the above-mentioned bridging agent ( C) Reactivity The monomer satisfying the functional group (b2) of the following formula (I) is a constituent component, and the first (meth) acrylate polymer (A) does not contain a reaction with the above-mentioned bridging agent (C). Single functional group a constituent component or a monomer having a functional group (a1) having a lower reactivity with the above-mentioned functional group (b1) of the second (meth) acrylate polymer (B) than the above-mentioned second (meth) acrylate polymer (B) As a constituent (Invention 2):

Reactivity with bridging agent (C): functional group (b2) < functional group (b1) (I)

The adhesive for bridging the adhesive composition of the above invention (Inventions 1 and 2) was previously formed into a three-dimensional network structure by chemical bridging using a low molecular weight polymer (B) for a plasticizer. Then, by inserting a plurality of high molecular weight polymers (A) into the three-dimensional network structure, the high molecular weight polymers (A) are mutually restrained to form a pseudo between the high molecular weight polymers (A). Bridge construction. Thereby, the obtained adhesive can exert an appropriate agglomeration force and excellent stress relaxation. By using an adhesive having such excellent stress relaxation properties, when applied to an optical member such as a polarizing plate, an adhesive sheet excellent in both light leakage resistance and durability can be obtained.

In the above invention (Inventions 1 and 2), it is preferred that the first (meth) acrylate polymer (A) does not contain a monomer having a functional group reactive with the bridging agent (C). 3).

The invention (Inventions 1 and 3) is characterized in that the functional group (a1) of the first (meth) acrylate polymer (A) has a carboxyl group and the second (meth) acrylate polymer (B) The functional group (b1) is a hydroxyl group, and the bridging agent (C) is preferably an isocyanate bridging agent (Invention 4).

In the above invention (Inventions 2 and 3), the functional group (a1) of the first (meth) acrylate polymer (A) has a carboxyl group in the second (meth) acrylate polymer (B). The functional group (b1) is a hydroxyl group, the functional group (b2) is a carboxyl group, and the bridging agent (C) is preferably an isocyanate bridging agent (Invention 5).

In the above invention (Inventions 4 and 5), the first (meth) acrylate polymer (A) contains 0 to 15% by mass of a monomer having a carboxyl group as a monomer unit constituting the polymer (Invention 6). .

In the above invention (Inventions 4 to 6), the second (meth) acrylate polymer (B) contains 3 to 40% by mass of a monomer having a hydroxyl group as a monomer unit constituting the polymer (Invention 7) ).

In the above invention (Inventions 4 to 7), the content of the isocyanate-based bridging agent is such that the isocyanate group of the isocyanate-based bridging agent is in the functional group (b1) of the second (meth)acrylate polymer (B). The amount is preferably 0.1 to 3.5 equivalents (Invention 8).

Thirdly, the present invention provides a method for producing an adhesive composition, which is a method for producing the above-mentioned adhesive composition (Inventions 1 to 8), characterized in that the first (meth) acrylate polymer (A) The above-mentioned second (meth) acrylate polymer (B) is mixed, and the above-mentioned bridging agent (C) is added at any stage (Invention 9).

Fourth, the present invention provides an adhesive which is obtained by bridging the above adhesive composition (Inventions 1 to 8) (Invention 10).

Fifthly, the present invention provides an adhesive sheet comprising: a substrate; and an adhesive layer, wherein the adhesive layer is composed of the above adhesive (Invention 10) (Invention 11).

In the above invention (Invention 11), the substrate is preferably an optical member (Invention 12).

Sixth, the present invention provides an adhesive sheet comprising: two peeling sheets; and an adhesive layer which is held in contact with the peeling surface of the two peeling sheets to the peeling sheet, The adhesive layer is composed of the above adhesive (Invention 10) (Invention 13).

The adhesive for bridging the adhesive composition of the present invention was previously formed into a chemically bridged three-dimensional network structure using a low molecular weight polymer used as a plasticizer. Then, by inserting a plurality of high molecular weight polymers into the three-dimensional network structure, the high molecular weight polymers are mutually restrained to form a pseudo bridge structure between the high molecular weight polymers. Thereby, the obtained adhesive can exert a suitable agglomeration force and excellent stress relaxation. By using an adhesive having such excellent stress relaxation properties, when applied to an optical member such as a polarizing plate, an adhesive sheet excellent in both light leakage resistance and durability can be obtained.

Hereinafter, embodiments of the present invention will be described.

[Adhesive composition]

The adhesive composition of the present embodiment comprises a first (meth) acrylate polymer (A) having a weight average molecular weight of 700,000 to 2.5 million and a second (methyl) having a weight average molecular weight of 8,000 to 250,000. The acrylate polymer (B); and the bridging agent (C), and preferably further contains a coupling agent (D). In the present specification, the term "(meth)acrylate" means both acrylate and methacrylate. Other similar terms are the same. In addition, the concept of "copolymer" is also included in "polymer".

2nd (meth) acrylate polymer (B),

(1) A monomer having a functional group (b1) reactive with a bridging agent (C), wherein the functional group contained in the polymer (B) which reacts with the bridging agent (C) is substantially only functional Base (b1), or

(2) a monomer having a functional group (b1) satisfying the reactivity of the bridging agent (C) and satisfying the functional group (b1) of the following formula (I), and having a reactivity with the bridging agent (C) satisfying the functional group of the following formula (I) The monomer of (b2) is a constituent component.

Reactivity with bridging agent (C): functional group (b2) < functional group (b1) (I),

That is, the polymer (B) of (2) has a higher reactivity with the bridging agent (C) of the functional group (b2) than the bridging agent (C) of the functional group (b2).

In the polymer (B) according to any one of the above (1) and (2), the monomer having the functional group (b1) is such that the composition ratio of the polymer (B) exceeds 1% by mass and is less than 50% by mass. In addition, the polymer (B) of the above (2) contains a monomer having the above functional group (b2) in an amount (mass ratio) of 1/5 or less of the monomer content of the functional group (b1). ingredient.

Further, the "substantially functional group (b1)" of the polymer (B) of the above (1) means that it is allowed to be contained so as not to interfere with the reactivity of the functional group (b1) and the bridging agent (C). The bridging agent (C) reacts with other functional groups. Therefore, a small amount of the above functional group (b2) is also contained in the polymer (B) of the above (1), in which case the polymer (B) of (1) and the polymer (B) of (2) are repeated.

On the other hand, the first (meth) acrylate polymer (A) is a monomer which does not contain a functional group which can react with the bridging agent (C) in the constituent unit, or contains a bridging agent in the constituent unit ( C) A monomer having a lower functional group (a1) than the functional group (b1) of the second (meth) acrylate polymer (B).

The (meth) acrylate polymer (A) or (B), wherein the alkyl group of the ester moiety has a carbon number of 1 to 20 (meth) acrylate, and has a functional group reactive with the bridging agent (C). A monomer (a monomer having a reactive functional group) and a copolymer of another monomer which is desirably used are preferred. Further, the first (meth) acrylate polymer (A) is preferably a constituent unit which does not contain the above-mentioned monomer having a reactive functional group.

The (meth) acrylate having a carbon number of the alkyl group in the ester portion is 1 to 20, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate. N-butyl acrylate, n-amyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylate Isooctyl ester, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, octadecyl (meth)acrylate Wait. These may be used alone or in combination of two or more.

On the other hand, the monomer having a reactive functional group may be a monomer having a hydroxyl group in the molecule (a monomer having a hydroxyl group), a monomer having a carboxyl group in the molecule (a monomer having a carboxyl group), and a molecule. A monomer having an amine group (a monomer having an amine group) or the like is preferred.

The hydroxyl group-containing monomer may, for example, be 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate or 2-(meth)acrylate. A hydroxyalkyl (meth)acrylate such as hydroxybutyl ester, 3-hydroxybutyl (meth)acrylate or 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 monomer having an amine group include, for example, aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used alone or in combination of two or more.

In addition, examples of the other monomer include an aliphatic ring-containing (meth) acrylate such as cyclohexyl (meth)acrylate and an aromatic ring such as phenyl (meth)acrylate ( Methyl) acrylate; non-branching acrylamide of acrylamide, methacrylamide, etc.; N,N-dimethylaminoethyl (meth)acrylate, N,N (meth)acrylate a (meth) acrylate having a non-branching tertiary amino group such as dimethylaminopropyl ester; vinyl acetate, styrene or the like. These may be used alone or in combination of two or more.

Further, the monomer containing the reactive functional group (a1) of the first (meth) acrylate polymer (A) and the reactivity of the second (meth) acrylate polymer (B) The choice of the monomer of the functional group (b1) and the monomer containing the reactive functional group (b2) is determined by the reactivity with the bridging agent (C) used. Details will be described later.

Here, the second (meth) acrylate polymer (B) contains more than 1% by mass of the above-mentioned monomer having a reactive functional group (b1), and the upper limit thereof is less than 50% by mass. The monomer containing the reactive functional group (b1) is preferably 3 to 40% by mass, particularly preferably 5 to 25% by mass. By including the monomer having a reactive functional group (b1) in the above range, the degree of bridging of the second (meth) acrylate polymer (B) is improved, and the first (meth) acrylate polymer (in the first (meth) acrylate polymer ( In the combination of A), the stress relaxation property of the obtained adhesive becomes excellent. In addition, when the content of the monomer containing the reactive functional group (b1) is at most 1% by mass, the bridging of the second (meth) acrylate polymer (B) is not sufficient, and thus the durability is lowered. On the other hand, when the content of the monomer having a reactive functional group (b1) is 50% by mass or more, bridging of the second (meth) acrylate polymer (B) is excessive, and thus the object is lowered. The adhesiveness of the paste. Further, by setting the upper limit of the content of the monomer containing the reactive functional group (b1) to 40% by mass, the durability of the obtained adhesive sheet can be further improved.

Further, the second (meth) acrylate polymer (B) does not include a monomer having a functional group (b2) having a lower reactivity with the bridging agent (C) than the functional group (b1) in the constituent component. (The monomer containing the reactive functional group (b2)) is particularly preferable, and when the monomer containing the reactive functional group (b2) is contained as a constituent component, the monomer having the reactive functional group (b1) is contained in a mass ratio. The amount of 1/5 or less of the content is particularly preferably 1/10 or less.

The second (meth) acrylate polymer (B) contains a monomer having a reactive functional group (b2) in an amount exceeding 1/5 of the content of the monomer containing the reactive functional group (b1) by mass. The durability of the resulting adhesive layer is lowered. When the number of reactive functional groups (b2) in the second (meth) acrylate polymer (B) is too large, it is presumed that a large amount of reactive functional groups (b2) remain in the three-dimensional network structure formed thereby, The compatibility of the three-dimensional network structure and the first (meth) acrylate polymer (A) is changed. As a result, there is a case where the haze value rises. Further, the ternary network structure in which a large amount of the reactive functional group (b2) remains, it is presumed that the first (meth) acrylate polymer (A) which is excessively restricted to be inserted into the ternary network structure is movable. Sex. As a result, there is a case where the durability is deteriorated.

Further, when the adhesive composition of the present embodiment contains the decane coupling agent (D), the decane coupling agent (D) and the reactive functional group (a1) with the first (meth) acrylate polymer (A) (in particular, a carboxyl group) is bonded to the high molecular weight first (meth) acrylate polymer (A), and the adhesion between the obtained adhesive and the glass substrate to be coated is excellent. When the second (meth) acrylate polymer (B) contains a monomer having a reactive functional group (b2) excessively, it is presumed that the alkoxy fluorenyl group of the decane coupling agent (D) is also the second (A) The reactive functional group (b2) (particularly a carboxyl group) of the acrylate polymer (B) is reacted with a low molecular weight second (meth) acrylate polymer (B). As a result, the adhesion between the obtained adhesive and the glass substrate or the like of the object is deteriorated, so that the durability of the adhesive layer is lowered.

Here, the (meth) acrylate having an alkyl group having an alkyl group of 1 to 20 and a monomer having a functional group reactive with the bridging agent (C) is polymerized to obtain a second (meth)acrylic acid. The polymerized form of the ester polymer (B) may be a random copolymer or a block copolymer. In particular, when the second (meth) acrylate polymer (B) is a block copolymer, the size of the network of the three-dimensional network structure can be controlled, so the second (meth) acrylate polymer (B) ), preferably a block copolymer. Specifically, the second (meth) acrylate polymer (B) may preferably be a monomer having a reactive functional group (b1) at both terminals, and having a carbon number of 1 to 20 ( The state in which the methyl acrylate block is copolymerized.

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

The weight average molecular weight of the second (meth) acrylate polymer (B) is 8,000 to 250,000, preferably 20,000 to 150,000. That is, the second (meth) acrylate polymer (B) is a low molecular weight polymer component. Further, the weight average molecular weight in the present specification is a value measured by a gel permeation chromatography (GPC) method in terms of polystyrene.

When the weight average molecular weight of the second (meth) acrylate polymer (B) is within the above range, a unique three-dimensional network structure is formed in the adhesive composition of the present embodiment, and excellent stress relaxation property is imparted. . That is, when the weight average molecular weight of the second (meth) acrylate polymer (B) is less than 8,000, a good three-dimensional network structure cannot be obtained. On the other hand, when the weight average molecular weight of the second (meth) acrylate polymer (B) exceeds 250,000, the compatibility is lowered, and the three-dimensional network structure of the polymer (A) to the polymer (B) is formed. The insertion in the change is insufficient, and the durability and the reworkability are deteriorated.

The first (meth) acrylate polymer (A) is a monomer which does not contain a functional group having a reaction with the bridging agent (C), or contains a reactivity with the bridging agent (C) in the constituent component. a monomer having a lower functional group (a1) than the above functional group (b1) of the second (meth) acrylate polymer (B), and then preferably, the constituent component does not contain a bridging agent (C) A monomer having a higher reactivity than the above functional group (b1).

The first (meth) acrylate polymer (A) may contain a reactive (2) (meth) acrylate polymer (B), although it may not contain a monomer having a functional group reactive with the bridging agent (C). a monomer having a reactive functional group (b1) having a low reactive functional group (a1) (a monomer having a reactive functional group (a1)), and a second (meth) acrylate polymer (B) The reactive functional group (a1) of the first (meth) acrylate polymer (A) and the alkane of the decane coupling agent (D) when reacting with the bridging agent (C) or using the decane coupling agent (D) The degree of agglomeration of the first (meth) acrylate polymer (A) can be adjusted by a reaction such as an oxyindenyl group, and a desired adhesion can be obtained.

When the first (meth) acrylate polymer (A) contains the monomer having the reactive functional group (a1), the content thereof is usually 20% by mass or less, preferably 15% by mass or less, and preferably 10% by mass or less. Especially good.

When the content of the monomer having a reactive functional group (a1) exceeds 20% by mass, the first (meth) acrylate polymer (A) is excessively agglomerated, and the desired stress relaxation property cannot be obtained. Further, from the viewpoint of imparting remanufacturability, the content of the monomer having a reactive functional group (a1) is preferably 15% by mass or less.

Further, the monomer containing the reactive functional group (b1) contained in the second (meth) acrylate polymer (B) is contained in the first (meth) acrylate polymer (A). The ratio of the monomer containing the reactive functional group (a1) to the first (meth) acrylate polymer (A) is more than that contained in the second (meth) acrylate polymer (B). The ratio of the monomer of the reactive functional group (b1) to the second (meth) acrylate polymer (B) is preferably small. Thereby, the reaction of the reactive functional group (a1) contained in the first (meth) acrylate polymer (A) with the bridging agent (C) can be suppressed, and the second (meth) acrylate polymer can be obtained ( B) The reactive functional group (b1) contained therein does react with the bridging agent (C).

The first (meth) acrylate polymer (A) does not contain a reactive functional group with the bridging agent (C) and a reactive functional group of the second (meth) acrylate polymer (B) in the molecule ( B1) A monomer having an equivalent or more functional group is preferable, and if it is contained, the content of the monomer having the functional group in the molecule is preferably 1% by mass or less, and 0.5% by mass in the polymer (A). The following is especially good. When the content of the monomer exceeds 1% by mass, there is a possibility that the reaction between the second (meth) acrylate polymer (B) which is preferentially reacted and the bridging agent (C) is inhibited.

Here, the (meth) acrylate polymer (A) obtained by polymerizing a monomer having an alkyl group having an alkyl group of 1 to 20 in an ester moiety and a monomer having a reactive functional group The polymerization state may be a random copolymer or a block copolymer.

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

The weight average molecular weight of the first (meth) acrylate polymer (A) is from 700,000 to 2.5 million, preferably from 1,000,000 to 2,000,000. That is, the first (meth) acrylate polymer (A) is a high molecular weight polymer component.

When the weight average molecular weight of the first (meth) acrylate polymer (A) is within the above range, it is presumed that the first (meth) acrylate polymer (A) can be favorably inserted into the second (meth) group. A three-dimensional network structure formed by the acrylate polymer (B), two or more molecules are passed through the pseudo-bridge structure of the polymer (A), and the polymer (A) is subjected to a degree of degree of freedom. Restricted. Thereby, the formed adhesive has an appropriate agglomeration force and excellent stress relaxation property, and as a result, the light leakage resistance is excellent, and further, the durability is sufficiently maintained under high temperature and wet heat conditions, and floating or peeling can be prevented. Wait.

When the weight average molecular weight of the first (meth) acrylate polymer (A) is less than 700,000, the agglomeration power of the component (A) is lowered, and the durability and the reworkability are deteriorated. In addition, when the weight average molecular weight of the first (meth) acrylate polymer (A) exceeds 2.5 million, the compatibility with the second (meth) acrylate polymer (B) or the like is deteriorated, and the haze value is increased. , or the expected stress relaxation can not be obtained.

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

In the adhesive obtained by the adhesive composition containing the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) in the above ratio, it is presumed that the second (A) The acrylate polymer (B) (low molecular weight polymer) forms a three-dimensional network structure via the bridging agent (C), and is composed of two or more molecules of the first (meth) acrylate polymer (A) (high molecular weight) The polymer is inserted into the structure of the three-dimensional network structure, and the polymer (A) forms a pseudo bridge structure in which each of them is restrained in a state of a certain degree of freedom. Thereby, the obtained adhesive has an appropriate agglomeration force and can exhibit excellent stress relaxation. Therefore, the obtained adhesive is excellent in durability and light leakage resistance.

The bridging agent (C) can be well-known as an isocyanate bridging agent, an epoxy bridging agent, a cyclic ethylene imide bridging agent, a metal chelate bridging agent, and the like.

The isocyanate bridging agent is a compound containing at least a polyisocyanate compound. Examples of the polyisocyanate compound include an aromatic polyisocyanate such as tolyl diisocyanate, diphenylmethane diisocyanate or xylylene diisocyanate; an aliphatic polyisocyanate such as hexamethylene diisocyanate; and isophorone II. An alicyclic polyisocyanate such as an isocyanate or a hydrogenated diphenylmethane diisocyanate, and the like, such a diuret, a cyanuric acid, and ethylene glycol, propylene glycol, neopentyl glycol, and hexamethylol An adduct of a reactant of a compound containing a low molecular weight active hydrogen such as propane or castor oil.

The epoxy-based bridging agent may, for example, be a 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl group. Tolyldiamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hexamethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine, and the like.

The bis-ethylenimine-based bridging agent may, for example, be diphenylmethane 4,4′-bis(1-cycloethyliminecarboxamide) or hexamethylolpropane triβ-aziridine propionate. Tetramethylol methane tri-β-aziridine propionate, toluene-2,4-bis(1-cycloethylimine carboxamide), trivinyl melamine, bis-p-benzoquinone-1-(2) -Methylcycloethylimine), tri-1-(2-methylcycloethylimine)phosphine, hexamethylolpropane tri-β-(2-methylcycloethylimine) propionate, and the like.

The metal chelate bridging agent has a chelate compound in which the metal atom is aluminum, zirconium, titanium, zinc, iron, tin, etc., and the aluminum chelate compound is preferred from the viewpoint of performance. The aluminum chelate compound may, for example, be diisopropoxy aluminum monooleyl acetate, monoisopropoxy aluminum dioleyl acetate, monoisopropoxy aluminum monooleate monoethyl acetamidine. Acetate, aluminum diisopropoxide, monolaurylacetate, diisopropoxy aluminum monostearyl acetate, diisopropoxide aluminum monoisostearylacetic acid Ester and the like.

The content of the bridging agent (C) is the reactive functional group (b1) of the bridging agent (C) bridging group (for example, isocyanate group) to the second (meth) acrylate polymer (B) (for example, The amount of the hydroxy group is usually 0.05 to 5 equivalents of 5, preferably 0.1 to 3.5 equivalents, and particularly preferably 0.2 to 1.8 equivalents. When the amount of the bridging group is 0.1 equivalent or more, the gel fraction of the obtained adhesive is 40% or more, and a sufficient agglomeration power can be exhibited. If the amount is more than 0.2 equivalent, the durability of the obtained adhesive can be further improved. By. On the other hand, as long as the amount of the bridging group is 3.5 equivalent or less, the obtained adhesive can be excellent in reworkability, and if it is 1.8 equivalent or less, the haze value of the obtained adhesive can be suppressed to be low.

Further, in the present embodiment, the bridging agent (C) may be a plurality of types of bridging agents in accordance with the reactivity relationship between the reactive functional group (b1) and the reactive functional group (a1). From the viewpoint of easily controlling the three-dimensional network structure formed by the second (meth) acrylate polymer (B), for example, only an isocyanate bridging agent is used, and it is preferred to use only one type of bridging agent, and further, only one is used. A kind of bridging agent is especially good.

On the other hand, as another aspect, the bridging agent (C) is preferably one type of bridging agent, particularly one type of bridging agent, and the reactive functional group (b1) and the reactive functional group (a1). The reactivity of the two parties is the same as the other bridging agent (C) of the bridging agent (C), and the mass ratio of the bridging agent (C) is preferably 1/20 or less, and is particularly preferably 1/30 or less. good. For example, an isocyanate-based bridging agent is used as a bridging agent (C), and an epoxy-based bridging agent is used as a small amount of another bridging agent (CR), and such other bridging agent is added to the polymer (A). The three-dimensional network structure composed of the polymer (B) is not sufficiently inserted, and it is effective when the agglomeration power is insufficient. Further, the other bridging agent (CR) is not included in the bridging agent (C), and the relationship between the above amounts is removed by the bridging agent (C).

Here, when the bridging agent (C) is combined with each of the monomers containing a reactive functional group of the (meth) acrylate polymers (A) and (B), and the bridging agent (C) is an isocyanate bridging agent, The monomer containing the reactive functional group (a1) of the polymer (A) is preferably a monomer having a carboxyl group, and the monomer containing the reactive functional group (b1) of the polymer (B) is a monomer having a hydroxyl group. The monomer having an amine group or the monomer containing the reactive functional group (b2) of the polymer (B) is a monomer having a carboxyl group.

On the other hand, when the bridging agent (C) is an epoxy bridging agent, a cycloethylenimine bridging agent or a metal chelate bridging agent, the monomer of the polymer (A) containing the reactive functional group (a1) may be A monomer having a hydroxyl group is favorably selected, a monomer containing a reactive functional group (b1) of the polymer (B) is a monomer having a carboxyl group, and a monomer containing a reactive functional group (b2) of the polymer (B) A monomer containing a hydroxyl group.

The bonding softness formed between the bridging agent (C) and the polymer (B), and the relaxation of the bridging reaction, and the reactive group of the polymer (A) are appropriately contributed to the reaction with the decane coupling agent (D). To enhance the agglomeration of the polymer (A), the bridging agent (C) is an isocyanate bridging agent, and the monomer containing the reactive functional group (a1) of the polymer (A) is a monomer having a carboxyl group, a polymer ( B) The monomer having a reactive functional group (b1) is a monomer having a hydroxyl group, and the monomer containing a reactive functional group (b2) of the polymer (B) is particularly preferably a monomer having a carboxyl group.

The adhesive composition of the present embodiment further preferably contains a decane coupling agent (D). When the decane coupling agent (D) is contained, when the first (meth) acrylate polymer (A) has a carboxyl group, the organic reactive group of the decane coupling agent (D) and the like (1) (meth) acrylate The carboxyl group of the polymer (A) reacts, and on the other hand, the alkoxy fluorenyl group of the decane coupling agent (D) acts on the surface of the glass substrate or the like. Therefore, for example, when the polarizing plate is adhered to the liquid crystal glass cell, the adhesion between the adhesive and the liquid crystal glass cell is better.

The decane coupling agent (D) is an organic ruthenium compound having only one alkoxy fluorenyl group in the molecule, and is excellent in compatibility with an adhesive component and has light penetrability, for example, substantially transparent. It is better. The amount of the decane coupling agent (D) to be added is preferably 0.01 to 0.5 parts by mass, and particularly preferably 0.05 to 0.3 parts by mass, based on 100 parts by mass of the first (meth) acrylate polymer (A).

Specific examples of the decane coupling agent (D) include a fluorene compound containing a polymerizable unsaturated group such as vinyl trimethoxy decane, vinyl triethoxy decane, or methacryl methoxypropyl trimethoxy decane. An anthracene compound having an epoxy group structure such as 3-propenyloxypropoxytrimethoxydecane or 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane, 3-aminopropyltrimethoxy Decane, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane, etc. The amine group contains an anthracene compound, 3-chloropropyltrimethoxydecane, 3-isocyanatepropyltriethoxydecane, and the like. These may be used alone or in combination of two or more.

In the above adhesive composition, various additives generally used for an acrylic adhesive, such as an adhesive agent, an oxidation preventive agent, an ultraviolet absorber, a light stabilizer, a softener, a filler, and a charge prevention can be added as desired. Agent, refractive index modifier, and the like.

[Method of Manufacturing Adhesive Composition]

In the above adhesive composition, the bridging agent (C) can be mixed at any stage by mixing the first (meth) acrylate polymer (A) with the second (meth) acrylate polymer (B). And manufactured by adding a decane coupling agent (D) as desired.

In a preferred embodiment, the (meth) acrylate polymers (A) and (B) are individually prepared by a usual radical polymerization method. The polymerization of the (meth) acrylate polymers (A) and (B) can be carried out by a solution polymerization method or the like according to the desired use of a polymerization initiator. The polymerization solvent may, for example, be ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane or methyl ethyl ketone, or two or more types may be used in combination.

The polymerization initiator may be a heavy nitrogen compound or an organic peroxide, and two or more types may be used in combination. Examples of the diazo compound include 2,2'-diazobisisobutyronitrile, 2,2'-diazobis(2-methylbutyronitrile), and 1,1'-diazobis(cyclohexane). 1-carbonylnitrile), 2,2'-diazobis(2,4-dimethylvaleronitrile), 2,2'-diazobis(2,4-dimethyl-4-methoxyvaleronitrile) , dimethyl 2,2'-diazobis(2-methylpropionate), 4,4'-diazobis(4-cyanovaleric acid), 2,2'-diazobis(2- Hydroxymethylpropionitrile, 2,2'-diazobis[2-(2-imidazolin-2-yl)propane, and the like.

The organic peroxide may, for example, be benzene peroxide, tert-butyl peroxybenzoic acid, cumene hydroperoxide, diisopropyl peroxycarbonate, di-n-propyl peroxycarbonate, or the like. -ethoxyethyl)peroxycarbonate, tert-butyl peroxy neodecanoate, tert-butyl peroxypivalate, (3,5,5-trimethylhexyl) peroxide, peroxidation Dipropylene, diethyl peroxide, etc.

Next, the solutions of the obtained polymers (A) and (B) are mixed, and a diluent solvent is added.

Thereafter, the bridging agent (C) and the decane coupling agent (D) are added as needed, and sufficiently mixed to obtain an adhesive composition (coating solution) diluted with a solvent.

The diluted adhesive composition may be used as a diluent solvent for the coating solution, for example, an aliphatic hydrocarbon such as hexane, heptane or cyclohexane, an aromatic hydrocarbon such as toluene or xylene, or dichloromethane or dichloroethane. Alcohols such as halogenated hydrocarbons, methanol, ethanol, propanol, butanol, 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, cyclohexanone, etc. An ester such as an ester or a butyl acetate, or a cellosolve such as an ethyl cellosolve.

The concentration ‧ viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and may be appropriately selected according to circumstances. For example, the concentration of the adhesive composition is diluted to 10 to 40% by mass. Further, in the case where a coating solution is obtained, the addition of a diluent solvent or the like is not a requirement, and the adhesion agent may be added without adding a diluent solvent as long as it is a coatable viscosity or the like. At this time, the adhesive composition directly forms a coating solution.

[adhesive]

The adhesive of the present embodiment is obtained by bridging the above-mentioned adhesive composition. The bridging of the above adhesive composition can be carried out by heat treatment. Further, the heat treatment may also serve as a drying treatment for volatilizing a diluent solvent or the like of the adhesive composition.

When the heat treatment is carried out, the heating temperature is preferably 50 to 150 ° C, particularly preferably 70 to 120 ° C. In addition, the heating time is preferably divided into 30 seconds to 3, especially in the range of 50 seconds to 2 minutes. Further, after the heat treatment, it is particularly preferable to set a curing period of about 1 to 2 weeks at normal temperature (for example, 23 ° C, 50% RH).

It is presumed that the second (meth) acrylate polymer (B) is bridged by the bridging agent (C) by the above heat treatment (and curing) to form a dense three-dimensional network structure. Then, it is presumed that two or more molecules of the first (meth) acrylate polymer (A) in the three-dimensional network structure are not accompanied by direct chemical bonding, or are inserted with little chemical bonding, so that the polymer ( A) Being restrained and forming a bridge structure. Further, when the first (meth) acrylate polymer (A) has a carboxyl group, the first (meth) acrylate polymer (A) reacts with the decane coupling agent (D) to agglomerate to a certain extent.

The adhesive described above can be suitably used for an optical member, and is suitable for, for example, a polarizing plate and a phase difference plate, or a polarizing plate (polarizing film) or a phase difference plate (phase difference film) and a glass substrate. . Since the adhesive layer formed of the above adhesive is excellent in stress relaxation property, even if the size of the object is greatly changed, the adhesive layer can absorb and moderate the stress caused by the dimensional change. It is not easy to be peeled off by the body for a long time, and when it is used for the optical member as described above, light leakage can be effectively prevented. In other words, the adhesive of the present embodiment can coexist both light leakage resistance and durability.

[adhesive sheet]

As shown in Fig. 1, the adhesive sheet 1A of the first embodiment is formed by peeling the sheet 12 in the following order; the adhesive layer 11 laminated on the peeling surface of the peeling sheet 12; and laminating on the adhesive sheet The substrate 13 of the agent layer 11 is composed of a substrate 13 .

Further, as shown in Fig. 2, the adhesive sheet 1B of the second embodiment is composed of two peeling sheets 12a and 12b and a peeling surface of the two peeling sheets 12a and 12b. The adhesive layer 11 sandwiched between the sheet peeling sheets 12a and 12b is formed. In addition, the peeling surface of the peeling sheet of the present specification means the surface which peels the peeling sheet, the surface which apply|coated the peeling process, and the surface which shows the peeling property, even if it is a peeling process.

In any of the adhesive sheets 1A, 1B, the adhesive layer 11 is composed of an adhesive formed by bridging the above adhesive composition.

The thickness of the adhesive layer 11 can be appropriately determined according to the purpose of use of the adhesive sheets 1A and 1B, and is usually 5 to 100 μm, preferably in the range of 10 to 60 μm, for example, an optical member, particularly as an adhesive for a polarizing plate. The layer is 10 to 50 μm, particularly preferably 10 to 30 μm.

The substrate 13 is not particularly limited, and is generally used as a substrate sheet for an adhesive sheet. For example, in addition to the desired optical member, a woven or non-woven fabric of enamel, acryl, polyester, or the like; paper of upper quality paper, glossy paper, impregnated paper, coated paper, or the like; aluminum Metal foil such as copper; foam of urethane foam or polyethylene foam; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate Polyester film such as ester, polyurethane film, polyethylene film, polypropylene film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate A plastic film such as an ester film, an acrylic resin film, a norbornene resin film or a cycloolefin resin film; or a laminate of two or more of these. Plastic film, which can be uniaxially extended or biaxially extended.

Examples of the optical member include a polarizing plate (polarizing film), a polarizing plate, a phase difference plate (phase difference film), a viewing angle compensation film, a brightness enhancement film, a contrast lifting film, and a liquid crystal polymer film. Among them, the polarizing plate (polarizing film) has a large dimensional change due to easy shrinkage, and therefore can be favorably used as an adhesive (the above-mentioned adhesive layer 11) of the present embodiment from the viewpoint of light leakage resistance.

The thickness of the substrate 13 varies depending on the type thereof. For example, in the case of an optical member, it is usually 10 μm to 500 μm, preferably 50 μm to 300 μm.

For the peeling sheets 12, 12a, 12b, for example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film can be used. , polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionized resin film, vinyl ‧ (A A) acrylic copolymer film, a vinyl ‧ (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, a fluororesin film, or the like. In addition, such bridging membranes can also be used. Furthermore, it may be such a laminated film.

It is preferable to apply a peeling treatment to the peeling surface of the peeling sheet (particularly, the surface of the adhesive layer 11). The release agent used for the release treatment may, for example, be an alkyd type, a silicone type, a fluorine type, an unsaturated polyester type, a polyolefin type or a wax type release agent.

The thickness of the peeling sheets 12, 12a, and 12b is not particularly limited, and is usually about 20 to 150 μm.

The adhesive sheet 1A is produced by applying a solution (coating solution) containing the above-described adhesive composition to a peeling surface of the peeling sheet 12, and heat-treating to form an adhesive layer 11, and then applying the adhesive layer 11 to the adhesive layer 11 The substrate 13 is laminated.

Further, the conditions regarding the heat treatment are as described above.

Further, the adhesive sheet 1B is produced by applying a coating solution containing the above-described adhesive composition to a release surface of the other release sheet 12a (or 12b), and heat-treating to form the adhesive layer 11, and then The adhesive layer 11 overlaps the peeling surface of the other peeling sheet 12b (or 12a).

A method of applying the above coating solution, for example, a bar coating method, a knife coating method, a roll coating method, a knife coating method, a die coating method, a gravure coating method, or the like.

Here, for example, in the manufacture of a liquid crystal display device comprising a liquid crystal cell and a polarizing plate, a polarizing plate is used as the substrate 13 of the adhesive sheet 1A, and the peeling sheet 12 of the adhesive sheet 1A is peeled off to expose the adhesive. The agent layer 11 can be adhered to the liquid crystal cell.

Further, for example, in manufacturing a liquid crystal display device in which a phase difference plate is disposed between a liquid crystal cell and a polarizing plate, the other peeling sheet 12a (or 12b) of the adhesive sheet 1B is peeled off, and the exposed adhesive layer 11 is The liquid crystal cell is pasted, and then the other peeling sheet 12b (or 12a) is peeled off, and the exposed adhesive layer 11 is adhered to the phase difference plate. Further, the polarizing plate is used as the peeling plate of the adhesive sheet 1A of the substrate 13. The sheet 12 is peeled off, and the exposed adhesive layer 11 is adhered to the phase difference plate.

According to the above-mentioned adhesive sheets 1A and 1B, since the stress relaxation property of the adhesive layer 11 is very excellent, for example, when used in the subsequent step of the polarizing plate, the adhesive layer 11 can absorb and moderate the stress caused by the deformation of the polarizing plate. It is presumed that excellent light leakage resistance and high durability can be exhibited.

The embodiments described above are described for easy understanding of the present invention, and are not intended to limit the present invention. Therefore, all the design changes or equivalents belonging to the technical scope of the present invention are also included in the above-described embodiments.

For example, the peeling sheet 12 of the adhesive sheet 1A can be omitted, and either one of the peeling sheets 12a and 12b of the adhesive sheet 1B can be omitted.

[Examples]

Hereinafter, the present invention will be specifically described by way of Examples and the like, but the scope of the present invention is not limited to the Examples and the like.

[Example 1]

1. Modulation of polymer (A)

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 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'-weight are placed. Nitrogen diisobutyronitrile was used in an amount of 0.08 mass%, and the air in the above reaction vessel was replaced with nitrogen. The mixture was stirred under a nitrogen atmosphere, and the reaction solution was heated to 60 ° C. After reacting for 16 hours, it was cooled to room temperature. Here, a part of the obtained solution was measured by GPC, and it was confirmed that a polymer (A) having a weight average molecular weight of 1.5 million was produced.

2. Modulation of polymer (B)

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 85.0 parts by mass of n-butyl acrylate, 15.0 parts by mass of 2-hydroxyethyl acrylate, and 200 parts by mass of ethyl acetate, 2, 2'-diazobisisobutyronitrile 0.16 parts by mass and 0.2 mass% of 2-mercaptoethanol, and the air in the reaction container was replaced with nitrogen. The mixture was stirred under a nitrogen atmosphere, and the reaction solution was heated to 70 ° C, and after reacting for 6 hours, it was cooled to room temperature. Here, a part of the obtained solution was measured by GPC, and it was confirmed that a polymer (B) having a weight average molecular weight of 50,000 was produced.

3. Modulation of adhesive composition

100 parts by mass (solid content converted value) of the polymer (A) obtained in the above step (1) is mixed with 20 parts by mass (solid content converted value) of the polymer (B) obtained in the above step (2), and then a polymer is added ( The hydroxyl group of B) corresponds to a toluene diisocyanate (TDI-based) adduct of hexamethylolpropane (trade name "CORONATE L" manufactured by Nippon Polyurethane Co., Ltd.) in an amount of 0.8 equivalents as a bridging agent (C). Finally, a 0.2 mass part of 3-propenyl methoxypropane trimethoxy decane (trade name "KBM403" manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a decane coupling agent (D), and the diluted solution of the adhesive composition was obtained by stirring well.

Here, the formulation of the adhesive composition is shown in Table 1. The details of the simple numbers and the like described in Table 1 are as follows.

[Polymers (A) and (B)]

BA: n-butyl acrylate

AA: Acrylic

HEA: 2-hydroxyethyl acrylate

HBA: 4-hydroxybutyl acrylate

HEMA: 2-hydroxyethyl methacrylate

[Bridge agent (C)]

‧Isocyanate bridging agent

TDI system: tolyl diisocyanate adduct of hexamethylolpropane (manufactured by Nippon Polyurethane Co., Ltd., trade name "CORONATE L")

Cyanuric acid system: a cyanuric acid hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE HXR")

‧Other bridging agents (epoxy bridging agent)

N,N,N',N'-tetraglycidyl-xylylenediamine (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD-X")

[decane coupling agent (D)]

KBM403: 3-propenyl methoxypropane trimethoxy decane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM403")

KBE9007: 3-isocyanate propyl triethoxy decane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBE9007")

KBF403: 3-propenyloxypropane triethoxy decane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBE403")

The diluted solution of the obtained adhesive composition was peeled off from the peeling sheet (SP-PET3811, thickness: 38 μm, manufactured by LINTEC Co., Ltd.) which was peeled off by a silicone-based release agent on one side of the polyethylene terephthalate film. The treated surface was applied by a knife coater to a thickness of 25 μm after drying, and then heat-treated at 90 ° C for 1 minute to form an adhesive layer.

Next, a polarizing plate composed of a polarizing film having a disc-shaped liquid crystal layer and a polarizing film integrated with a viewing angle expansion film is adhered to the disc-shaped liquid crystal layer to be cured at 23 ° C, 50% RH. After 7 days, a polarizing plate having an adhesive layer was obtained.

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

The types and ratios of the monomers constituting the adhesive composition, the types and addition amounts of the bridging agent and the decane coupling agent, and the formulation ratios of the polymer (A) and the polymer (B) are changed as shown in Table 1. In Example 1, a polarizing plate having an adhesive layer was produced in the same manner.

[Test Example 1] (Adhesion measurement - Reproducibility evaluation)

From the polarizing plate having the adhesive layer obtained in the examples or the comparative examples, a sample having a width of 25 mm and a length of 100 mm was cut out, and the peeled sheet was peeled off, and adhered to the alkali-free glass via the exposed adhesive layer (EAGLE XG, manufactured by Corning Incorporated) After that, a high-pressure reactor manufactured by Kurihara Seisakusho Co., Ltd. was pressurized at 0.5 MPa and 50 ° C for 20 minutes. Thereafter, it was allowed to stand at 23 ° C, 50% RH for 24 hours, and then a tensile tester (tensilon) was used, and the adhesion was measured at a peeling speed of 300 mm/min and a peeling angle of 180 degrees (N/25 mm). ). The conditions other than the above description were measured in accordance with JIS Z0237:2009.

Further, the film was allowed to stand under the conditions of 23 ° C and 50% RH for 14 days, and the adhesive force (adhesive force after 14 days of adhesion; N/25 mm) was measured in the same manner as above. Furthermore, the preferred range of adhesion is 0.1 N/25 mm or more and less than 25 N/25 mm.

According to the adhesion after 14 days of the above adhesion, the evaluation of the reproducibility was performed on the basis of the following criteria. The results are shown in Table 2.

After 14 days of adhesion, the adhesion is below 20N/25mm: ◎,

Adhesive force after 14 days of bonding exceeds 20N/25mm, less than 25N/25mm: ○

The adhesion after 14 days of bonding is 25N/25mm or more: ×

[Test Example 2] (Measurement of gel fraction)

In place of the polarizing plate used for the production of the polarizing plate having the adhesive layer of the embodiment or the comparative example, a peeling sheet in which one side of the polyethylene terephthalate film is peeled off by a silicone-based release agent is used (LINTEC) Company system, SP-PET3801, thickness: 38μm), making adhesive sheets. Specifically, the peeling sheet was attached to the peeling treatment surface on the exposed adhesive layer of the constituent body composed of the peeling sheet/adhesive layer (thickness: 25 μm) obtained in the production process of the example or the comparative example. Side by side. Thereby, an adhesive sheet composed of a structure of a release sheet/adhesive layer/release sheet was produced.

The obtained adhesive sheet was cured at 23 ° C, 50% RH for 7 days. Thereafter, the adhesive sheet was sampled to a size of 80 mm × 80 mm, and the adhesive layer was wrapped in a polyester mesh (mesh size 200), and only the quality of the adhesive was weighed by a precision balance. At this time, the mass is M1.

A sample of the adhesive was immersed in an ethyl acetate solvent using a Soxhlet Extractor, and refluxed for 16 hours. Thereafter, the adhesive was taken out, air-dried for 24 hours in 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. After drying, only the quality of the adhesive is weighed with a precision balance. The mass at this time is M2. The gel fraction (%) is represented by (M2/M1) × 100. The results are shown in Table 2.

[Test Example 3] (Measurement of optical properties)

An adhesive sheet (for 7 days of curing) similar to the adhesive sheet used for the measurement of the gel fraction was prepared as a measurement sample. The haze value (%) of the adhesive layer of the adhesive sheet was measured using a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7105. The results are shown in Table 2. Further, the preferred haze value ranges from 0 to 5%.

[Trial Example 4] (Durability Assessment)

The polarizing plate having the adhesive layer obtained in the example or the comparative example was adjusted to a size of 233 mm × 309 mm using a cutting device (SUPER CUTTER, PN1-600, manufactured by Takino Seisakusho Co., Ltd.). The peeled sheet was peeled off, and the exposed adhesive layer was adhered to an alkali-free glass (EAGLE XG, manufactured by Corning Incorporated), and then pressurized in a high-pressure reactor manufactured by Kurihara Co., Ltd. at 0.5 MPa at 50 ° C for 20 minutes.

Thereafter, the mixture was subjected to the following durability conditions, and after 500 hours, it was observed with a magnifying glass of 10 times. The appearance changes as follows. The results are shown in Table 2.

◎: On the 4 sides, there are no defects

○: On the 4 sides, there is no defect from the outer peripheral end to the 0.6 mm or more.

X: at least one side of the four sides, from the outer peripheral end to the portion of 0.6 mm or more, there is an abnormality in the appearance of an adhesive having a thickness of 0.1 mm or more such as floating, peeling, foaming, or streaking.

<endurance condition>

‧60 ° C, relative humidity 90%

‧80°C dry

[Trial Example 5] (Light leakage test)

The polarizing plate having the adhesive layer obtained in the example or the comparative example was adjusted to a size of 233 mm × 309 mm using a cutting device (SUPER CUTTER, PN1-600, manufactured by Takino Seisakusho Co., Ltd.). The peeled sheet was peeled off, and the exposed adhesive layer was adhered to an alkali-free glass (EAGLE XG, manufactured by Corning Co., Ltd.), and then pressurized in a high-pressure reactor manufactured by Kurihara Co., Ltd. at 0.5 MPa and 50 ° C for 20 minutes. Further, the above-described pasting is performed by causing the polarizing axis of the polarizing plate having the adhesive layer to be in an orthogonal polarization state (polarizing axis: ∠45°, ∠135°) on the front and back surfaces of the alkali-free glass. In this state, after standing for 500 hours in a dry environment of 80 ° C, the light leakage was evaluated by the method shown below. The results are shown in Table 2.

<Light leakage assessment>

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

△L*=[(b+c+d+e)/4]-a

(These, a, b, c, d, and e are respectively set in the brightness of the measurement points (the central part 1 of each area) of the A area, the B area, the C area, the D area, and the E area in advance.) Obtained as light leakage. The smaller the value of ΔL*, the less light leakage.

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

<Measurement conditions>

‧GPC measuring device: manufactured by TOSO, HLC-8020

‧GPC column (passed in the following order): TOSO company

TSK guard column HXL-H

TSK gel GMHXL (×2)

TSK gel G2000HXL

‧ Determination of solvent: tetrahydrofuran

‧Measurement temperature: 40 ° C

As is clear from Table 2, the polarizing plate having the adhesive layer obtained in the examples has no problem in durability and is excellent in light leakage resistance. Further, in Example 30, the amount of the carboxyl group of the first (meth) acrylate polymer (A) was relatively large, and the reworkability was inferior. Further, in Example 31 and Example 32, the amount of the isocyanate-based bridging agent was relatively high, and the reworkability was inferior.

In Comparative Example 1, since the content of the hydroxyl group of the second (meth) acrylate polymer (B) is too large, the durability is preferable. In Comparative Example 2, since the weight average molecular weight of the first (meth) acrylate polymer (A) was too small, durability and reworkability were inferior. In Comparative Example 3, since the content of the hydroxyl group of the second (meth) acrylate polymer (B) was too small, the gel fraction (degree of bridging) was low and the durability was inferior. In Comparative Example 4, since the weight average molecular weight of the second (meth) acrylate polymer (B) was too small, the durability was inferior. In Comparative Example 5, since the weight average molecular weight of the second (meth) acrylate polymer (B) was too large, durability and reworkability were inferior. In Comparative Example 6, the content of the second (meth) acrylate polymer (B) was too large, and the durability was inferior. In Comparative Example 7, since the content of the second (meth) acrylate polymer (B) was too small, the gel fraction (degree of bridging) was low, and durability was inferior.

[Industry use possibility]

The adhesive composition and the adhesive of the present invention are suitable for an optical member such as a polarizing plate or a phase difference plate, and further, the adhesive sheet of the present invention is suitable for bonding an optical member such as a polarizing plate or a phase difference plate. Plate.

1A, IB. . . Adhesive sheet

11. . . Adhesive layer

12, 12a, 12b. . . Off-board

13. . . Substrate

Fig. 1 is a cross-sectional view showing an adhesive sheet according to a first embodiment of the present invention.

Fig. 2 is a cross-sectional view showing an adhesive sheet according to a second embodiment of the present invention.

Fig. 3 is a view showing a measurement area of a light leakage test of a polarizing plate with an adhesive layer.

1A. . . Adhesive sheet

11. . . Adhesive layer

12. . . Off-board

13. . . Substrate

Claims (13)

An adhesive composition comprising: a first (meth) acrylate polymer (A) having a weight average molecular weight of 700,000 to 2.5 million; and a second (meth) acrylate polymerization having a weight average molecular weight of 8,000 to 250,000 And (B), the bridging agent (C), the ratio of the second (meth) acrylate polymer (B) to 100 parts by mass of the first (meth) acrylate polymer (A) The second (meth) acrylate polymer (B) contains, as a constituent component, a monomer having a functional group (b1) reactive with the bridging agent (C) as a constituent component, and has the above-mentioned The ratio of the monomer of the functional group (b1) is 5% by mass or more and less than 50% by mass based on the second (meth) acrylate polymer (B), and the second (meth) acrylate is polymerized. The functional group which can be reacted with the above-mentioned bridging agent (C) contained in the substance (B) has only the above functional group (b1), and the above first (meth) acrylate polymer (A) does not contain the above-mentioned bridging agent ( C) a monomer having a functional group for the reaction as a constituent component or a functional group having a lower reactivity with the above-mentioned functional group (b1) of the second (meth) acrylate polymer (B) than the above-mentioned second (meth) acrylate polymer (B) (A1) constituting the monomer component, and, the proportion of the monomer having the functional group (a1), the first based on the (meth) acrylate polymer (A), 0 to 5% by mass. An adhesive composition comprising: a first (meth) acrylate having a weight average molecular weight of 700,000 to 2.5 million Polymer (A); second (meth) acrylate polymer (B) having a weight average molecular weight of 8,000 to 250,000; and bridging agent (C) characterized by polymerization of said second (meth) acrylate The ratio of the substance (B) to the first mass portion of the first (meth) acrylate polymer (A) is 5 to 40 parts by mass, and the second (meth) acrylate polymer (B) is contained to have the above The reactivity of the bridging agent (C) is a component which satisfies the functional group (b1) of the following formula (1), and the ratio of the monomer having the above functional group (b1) is based on the second (methyl) 5% by mass or more and less than 50% by mass in the acrylate polymer (B), and the second (meth) acrylate polymer (B) contains a monomer having the above functional group (b1) The amount (mass ratio) of 1/5 or less of the content, the monomer having the reactivity with the bridging agent (C) satisfying the functional group (b2) of the following formula (I) is a constituent component, and the first (meth) group The acrylate polymer (A) is a constituent component which does not contain a functional group reactive with the above-mentioned bridging agent (C), or contains a reactivity with the above-mentioned bridging agent (C) as compared with the above second (methyl) The above acrylate polymer (B) The monomer having a functional group (a1) having a low functional group (b1) is a constituent component: reactivity with a bridging agent (C): a functional group (b2) < a functional group (b1) (I), and further having the above functional group The ratio of the monomer of (a1) is based on the 0 to 5% by mass in the (meth) acrylate polymer (A). The adhesive composition according to claim 1 or 2, wherein the first (meth) acrylate polymer (A) does not contain a functional group capable of reacting with the bridging agent (C) in the constituent component. Base monomer. The adhesive composition according to claim 1, wherein the functional group (a1) in the first (meth) acrylate polymer (A) is a carboxyl group, and the second (meth) acrylate is The functional group (b1) of the ester polymer (B) is a hydroxyl group, and the bridging agent (C) is an isocyanate bridging agent. The adhesive composition according to claim 2, wherein the functional group (a1) in the first (meth) acrylate polymer (A) is a carboxyl group, and the second (meth) acrylate is The functional group (b1) of the ester polymer (B) is a hydroxyl group, the functional group (b2) is a carboxyl group, and the bridging agent (C) is an isocyanate bridging agent. The adhesive composition according to claim 4, wherein the first (meth) acrylate polymer (A) contains 0 to 5% by mass of a monomer having a carboxyl group as a constituent of the polymer. Monomer unit. The adhesive composition according to claim 4, wherein the second (meth) acrylate polymer (B) contains 5 to 40% by mass of a monomer having a hydroxyl group as a polymer constituting the polymer. Monomer unit. An adhesive composition as described in claim 4 or 5, The content of the isocyanate-based bridging agent is such that the isocyanate group of the isocyanate-based bridging agent is in an amount of 0.1 to 3.5 equivalents to the functional group (b1) of the second (meth)acrylate polymer (B). An adhesive composition according to claim 1 or 2, wherein the first (meth) acrylate polymer (A) and the second portion are produced by the method of producing an adhesive composition The (meth) acrylate polymer (B) is mixed, and the above-mentioned bridging agent (C) is added at any stage. An adhesive agent obtained by bridging an adhesive composition according to claim 1 or 2. An adhesive sheet comprising: a substrate and an adhesive layer, wherein the adhesive layer is composed of the adhesive according to claim 10 of the patent application. The adhesive sheet according to claim 11, wherein the substrate is an optical member. An adhesive sheet comprising: two peeling sheets; and an adhesive layer held on the peeling sheet in contact with the peeling surface of the two peeling sheets, wherein the adhesive layer is applied The adhesive composition described in claim 10 of the patent scope.