TWI527871B - Adhesive compositions, adhesives, and adhesive sheets - Google Patents

Description

Adhesive composition, adhesive and adhesive sheet

The present invention relates to an adhesive composition, an adhesive (a material obtained by crosslinking an adhesive composition), and an adhesive sheet, particularly a good adhesive composition for an optical member such as a polarizing plate, an adhesive, and Adhesive tablets.

In general, in the liquid crystal panel, the adhesive layer formed from the adhesive composition is often applied when the polarizing plate and the retardation film are adhered to the glass substrate of the liquid crystal cell. However, the optical members such as the polarizer and the retardation film are easily contracted by heat or the like, that is, thermally contracted, and as a result, the adhesive layer on which the optical member is stacked cannot follow the shrinkage. Peeling occurs at the interface (so-called floating, peeling), and light leakage occurs due to stress at the time of shrinkage of the optical member, causing light leakage (so-called white spot).

As a method for preventing this problem, there is a method in which the adhesive layer having high adhesion and excellent form stability is bonded to an optical member such as a polarizing plate, thereby suppressing shrinkage of the optical member. Or (2) a method of using an adhesive layer having a small stress when shrinking an optical member. As the method of (1), it is effective to use a high adhesive layer having a storage modulus as shown in Patent Document 1. On the other hand, as the method of (2), it is effective to use an adhesive layer which is excellent in soft stress corresponding to the deformation of the optical member.

For the method using the above (2), Patent Document 2 proposes The adhesive for a polarizing plate having the following composition: (A) a copolymer of (A) an alkyl (meth) acrylate and a polymerizable monomer having a functional group for a crosslinking agent, and a weight average molecular weight of 1,000,000 or more 100 parts by weight of the high molecular weight (meth)acrylic copolymer, (B) 20 to 200 parts by weight of the low molecular weight (meth)acrylic (co)polymer having a weight average molecular weight of 30,000 or less, (C) in the molecule A composition of at least two polyfunctional compounds capable of forming a functional group having a crosslinked structure of 0.005 to 5 parts by weight, using [a functional group of a low molecular weight (meth)acrylic (co)polymer] / [high molecular weight (A) The functional group based on the functional group of the acrylic copolymer is an adhesive for polarizing plates having a functional group partition ratio of 0 to 15% by weight.

In the method of the above (2), Patent Document 3 describes an optical adhesive composition comprising: an acrylate copolymer mixture (A) having a weight average molecular weight of 800,000 to 2,000,000. (meth)acrylate copolymer (a) 100 parts by mass and a weight average molecular weight of 50,000 or less (meth)acrylate copolymer (b) 20-100 parts by mass of an acrylate copolymer mixture (A); The crosslinking agent (B), the copolymer (a) contains a monomer unit having a functional group having high reactivity with the crosslinking agent (B), and the copolymer (b) contains the crosslinking agent (B). The single-unit unit of the functional group having a lower reactivity than the functional group of the above copolymer (a).

[Patent Literature]

[Patent Document 1] JP-A-2006-235568

Patent Document 2, Patent No. 3533539

[Patent Document 3] JP-A-2009-108122

The adhesive disclosed in Patent Documents 2 and 3, the high molecular weight (meth)acrylic copolymer is preferentially crosslinked, and attempts to obtain a stress relaxation rate. However, the above-mentioned adhesive has poor durability, and for example, under wet heat conditions, peeling occurs at the adhesive interface. Further, the stress relaxation rate is also insufficient, and when it is applied to an optical member such as a polarizing plate, light leakage may occur. Further, the adhesion tends to increase with time after the attachment, and the reusability is also insufficient.

The present invention is such an actual situation. An object of the present invention is to provide an adhesive composition which is excellent in stress relaxation rate, can prevent light leakage, is excellent in durability, and is excellent in reusability when applied to an optical member such as a polarizing plate. Adhesives and adhesive sheets.

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 500,000 to 3,000,000 and a weight average molecular weight of 8000-30. The second (meth) acrylate polymer (B) and the crosslinking agent (C), wherein the first (meth) acrylate polymer (A) does not substantially contain an acidic group, and The constituent monomer unit constituting the polymer contains a hydroxyl group-containing monomer (a) having reactivity with the crosslinking agent (C) and satisfying the following formula (I), and the second (meth) acrylate polymer (B) substantially does not contain an acidic group, and contains, as a monomer unit constituting the above polymer, a reactivity with the crosslinking agent (C) that satisfies the following formula (I) Body (b) (Invention 1).

Reactivity with crosslinker (C) and: hydroxyl-containing monomer (a) <hydroxyl-containing monomer (b) ‧‧‧(I)

The adhesive obtained by crosslinking the adhesive composition of the above invention (Invention 1) can exhibit an appropriate cohesive force and an excellent stress relaxation rate. The adhesive having an excellent stress relaxation rate is excellent in both light leakage resistance and durability when applied to an optical member such as a polarizing plate, and is further excellent in reusability. Further, when the respective polymers of the above-mentioned adhesive composition do not substantially contain an acidic group and the adherend is composed of a metal or contains a metal, the corrosion of the metal can be suppressed.

In the above invention (Invention 1), (i) a carbon atom in which a hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded to a carbon atom bonded thereto The number of carbon atoms bonded to the carbon atom on which the hydroxyl group in the hydroxyl group-containing monomer (a) of the first (meth)acrylate polymer (A) is bonded is less (inventive 2) or, (ii) the number of carbon atoms bonded to the carbon atom to which the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded, The number of carbon atoms bonded to a carbon atom bonded to a hydroxyl group in the hydroxyl group-containing monomer (a) of the first (meth)acrylate polymer (A) is the same number, and the above second (methyl group) The hydroxyl group-containing monomer (b) of the acrylate polymer (B), the number of carbon atoms constituting the side chain when the polymer is formed, and the hydroxyl group of the first (meth) acrylate polymer (A) The number of carbon atoms in the monomer (a) which form a side chain when the polymer is formed More than (invention 3), or (iii) the hydroxyl group in the hydroxyl group-containing monomer (b) of the above second (meth) acrylate polymer (B) is bonded to a carbon atom bonded thereto The number of carbon atoms is the same as the number of carbon atoms bonded to the carbon atom on which the hydroxyl group in the hydroxyl group-containing monomer (a) of the first (meth)acrylate polymer (A) is bonded Further, the hydroxyl group-containing monomer (b) of the second (meth) acrylate polymer (B) contains the number of carbon atoms constituting the side chain when the polymer is formed, and the first (meth)acrylic acid. The hydroxyl group-containing monomer (a) of the ester polymer (A) contains the same number of carbon atoms constituting the side chain when the polymer is formed, and preferably the above-mentioned second (meth) acrylate polymer (B) The hydroxyl group-containing monomer (b) is a hydroxyalkyl methacrylate, and the hydroxyl group-containing monomer (a) of the above first (meth) acrylate polymer (A) is preferably a hydroxyalkyl acrylate ( Invention 4).

In the above invention (Invention 1-4), the hydroxyl group contained in the first (meth) acrylate polymer (A) and the hydroxy group contained in the second (meth) acrylate polymer (B) are preferred. The molar ratio is 1.0 or more and 15 is not full (Invention 5).

In the above invention (Invention 1-5), the second (meth) acrylate polymer (B) is preferably a constituent monomer unit of the polymer, and the hydroxyl group-containing monomer (b) is preferably 10-40. % by mass (Invention 6).

In the above invention (Invention 1-6), it is preferred that the ratio of the second (meth) acrylate polymer (B) is 100 parts by mass of the first (meth) acrylate polymer (A). 5-50 parts by mass (Invention 7).

In the above invention (Invention 1-7), the above first (meth) acrylate The polymer (A) and the second (meth) acrylate polymer (B) preferably do not contain a functional group reactive with the crosslinking agent (C) except for the hydroxyl group (Invention 8).

In the above invention (Invention 1-8), the crosslinking agent (C) is preferably an isocyanate crosslinking agent (Invention 9).

In the above invention (Invention 9), the content of the isocyanate-based crosslinking agent is preferably the hydroxyl group contained in the isocyanate-based crosslinking agent and the hydroxyl group contained in the second (meth)acrylate polymer (B). The amount is from 0.1 to 3.5 equivalents (Invention 10).

Second, the present invention provides an adhesive obtained by crosslinking the above adhesive composition (Invention 1-10) (Invention 11).

Thirdly, the present invention provides an adhesive sheet comprising a substrate and an adhesive layer, characterized in that the adhesive layer is composed of an adhesive of the above-mentioned adhesive (Invention 11) (Invention 12).

In the above invention (Invention 12), the substrate is preferably an optical member (Invention 13).

Fourthly, the present invention provides an adhesive sheet comprising two release sheets and an adhesive layer held by the two release sheets, whereby the adhesive layer is in contact with the release surface, and the adhesive layer is It is composed of the above adhesive (Invention 11) (Invention 14).

In the adhesive formed by crosslinking the adhesive composition of the present invention, a low molecular weight polymer which has been conventionally used as a plasticizer is preferentially crosslinked. The chemically crosslinked three-dimensional network structure of the above low molecular weight polymer is formed. In the three-dimensional network structure, a plurality of high molecular weight polymers are inserted, the high molecular weight polymer is bound, and the high molecular weight polymer is formed. Quasi-crosslinking structure (presumed). In this way, the obtained adhesive can exhibit an appropriate cohesive force and an excellent stress relaxation rate, and when applied to an optical member such as a polarizer, it can effectively prevent light leakage and excellent durability, and further reusability. Also good. Further, since each of the polymers of the adhesive composition of the present invention does not substantially contain an acidic group, corrosion of the metal can be suppressed when the adherend is composed of a metal or when a metal is contained.

Hereinafter, embodiments of the present invention will be described.

[adhesive composition]

The adhesive composition of the present embodiment contains a first (meth) acrylate polymer (A) having a weight average molecular weight (Mw) of 500,000 to 3,000,000 and a weight average molecular weight (Mw) of 8,000 to 300,000. The 2 (meth) acrylate polymer (B) and the crosslinking agent (C) preferably further contain a decane coupling agent (D). Further, in the present specification, the (meth) acrylate includes both acrylate and methacrylate. The same is true for other similar terms. In addition, the concept of "copolymer" is also included in "polymer".

The first (meth) acrylate polymer (A) does not substantially contain an acidic group, and contains a reactivity with the crosslinking agent (C) as a constituent monomer unit. The hydroxyl group-containing monomer (a) of the following formula (I) is satisfied, and the second (meth) acrylate polymer (B) does not substantially contain an acidic group, and contains a crosslinking agent as a constituent monomer unit ( The reactivity of C) satisfies the hydroxyl group-containing monomer (b) of the following formula (I). Further, the hydroxyl group-containing monomer means a monomer having a hydroxyl group in the molecule.

Reactivity of crosslinker (C) and: hydroxyl-containing monomer (a) < hydroxyl-containing monomer (b). . . (I)

That is, the reactivity of the hydroxyl group-containing monomer (b) of the polymer (B) with the crosslinking agent (C) and the crosslinking agent (C) of the hydroxyl group-containing monomer (a) of the polymer (A) Responsiveness is high.

As the acidic group, a carboxyl group is mainly exemplified, and other examples include a sulfonic acid group and a phosphoric acid group. Since the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) do not substantially contain an acidic group, the adherend is made of a metal (for example, the adherend is When the electrode is formed of indium tin oxide (ITO) or when a metal is contained (for example, when the metal body is contained in the adherend), corrosion of the metal can be suppressed.

Here, the term "substantially does not contain an acidic group" includes a small amount of an acidic group which is allowed to be contained to the extent that it does not corrode the metal, except that it does not contain an acidic group at all. Specifically, the content of the acid group-containing monomer as a constituent unit of the polymer (A) or (B) is usually 1% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass. Not full.

As described above, the second (meth) acrylate polymer (B) contains the crosslinking agent (C) as compared with the first (meth) acrylate polymer (A). a highly reactive hydroxyl group-containing monomer. When the above adhesive composition is crosslinked, the second (meth) acrylate polymer (B) (low molecular weight polymer) and the crosslinking agent (C) are preferentially reacted. The three-dimensional network structure of the crosslinking agent (C) is formed (presumed). Therefore, in the three-dimensional network structure, two or more molecules of the first (meth) acrylate polymer (A) (high molecular weight polymer) are directly inserted without accompanying chemical bonds or with few chemical bonds. In the state in which the polymer (A) is formed to have a certain degree of freedom, it is bound to form a pseudo-crosslinked structure (presumed) (the structure estimated in this way, and the following is "structure X"). The first (meth) acrylate polymer (A) is considered to have a hydroxyl group derived from the low hydroxyl group-containing monomer (a) which is comparatively reactive with the crosslinking agent (C), and it is considered that the three-dimensional network structure can be carried out. Insert well. The adhesive having the above structure X can exert a suitable cohesive force and an excellent stress relaxation rate. When it is applied to an optical member such as a polarizer, the adhesive having such an excellent stress relaxation rate is excellent in light leakage resistance and excellent in durability, and can be floated under conditions of damp heat or the like. It is prevented by peeling off. Further, in the above-described structure X, since the uncrosslinked low molecular weight component or the like which imparts the stress relaxation rate does not exist, the bleeding of the low molecular weight component which is a problem in the conventional stress relaxation rate type adhesive does not occur. As a result, the adhesive obtained from the adhesive composition of the present embodiment is excellent in recyclability.

The first (meth) acrylate polymer (A) is preferably an alkyl (meth) acrylate having a carbon number of 1 to 20, a hydroxyl group-containing monomer (a), and, if necessary, not contained. A copolymer of another monomer having a functional group reactive with the crosslinking agent (C). 2nd (meth) acrylate polymerization The substance (B) is preferably an alkyl (meth) acrylate having a carbon number of 1 to 20, a hydroxyl group-containing monomer (b), and, if necessary, a gum and a binder (C). a copolymer of other monomers having reactive functional groups.

The (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group may, for example, be methyl (meth)acrylate, ethyl (meth)acrylate or propyl (meth)acrylate. N-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, Isooctyl (meth)acrylate, n-aryl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, hexadecane (meth)acrylate A base ester and a stearyl (meth) acrylate. They may be used alone or in combination of two or more.

As the hydroxyl group-containing monomers (a) and (b), 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate may be exemplified. Examples include esters, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and hydroxyalkyl (meth)acrylates such as 4-hydroxybutyl (meth)acrylate. They may be used alone or in combination of two or more.

Here, as a combination of the hydroxyl group-containing monomer (a) and the hydroxyl group-containing monomer (b), the following modes (i) to (iii) can be exemplified.

(i) the number of carbon atoms bonded to the carbon atom to which the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded, and the first (methyl group) The number of carbon atoms bonded to the carbon atom on the hydroxyl group-containing monomer (a) of the acrylate polymer (A) is less In the case where the number of carbon atoms bonded to the carbon atom to which the hydroxy group is bonded is small, the nucleus has high nucleability and the steric hindrance is small, whereby the reactivity of the hydroxy group is high. Therefore, the number of carbon atoms bonded to the hydroxy-bonded carbon atom is a preferred criterion for determining the reactivity with the crosslinking agent (C).

For example, when the hydroxyl group-containing monomer (a) is a secondary hydroxyl group and the hydroxyl group-containing monomer (b) is a primary hydroxyl group, specifically, the hydroxyl group-containing monomer (a) is a (meth)acrylic acid 2-hydroxy group. a propyl ester, 2-hydroxybutyl (meth)acrylate, or 3-hydroxybutyl (meth)acrylate; the hydroxyl-containing monomer (b) is 2-hydroxyethyl (meth)acrylate, When methyl 3-hydroxypropyl methacrylate or 4-hydroxybutyl (meth) acrylate is used.

(ii) the number of carbon atoms bonded to the carbon atom to which the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded, and the first (methyl group) The number of carbon atoms bonded to the carbon atom on the hydroxyl group-containing monomer (a) of the acrylate polymer (A) is the same number, and the second (meth) acrylate polymer ( The hydroxyl group-containing monomer (b) of B) contains the number of carbon atoms of the side chain formed when the polymer is formed, and is more than the hydroxyl group-containing monomer (a) of the first (meth) acrylate polymer (A). When the polymer is formed, the number of carbon atoms constituting the side chain is large. This is because if the number of carbon atoms bonded to a carbon atom to which a hydroxy group is bonded is the same number, the number of carbon atoms constituting the side chain in the monomer when the polymer is formed is far from the main chain. The reason is that the three-dimensional obstruction is small and the degree of freedom is high, so the reactivity is high.

For example, the hydroxyl group-containing monomer (a) and the hydroxyl group-containing monomer (b) are both primary hydroxyl groups and contain a hydroxyl group monomer (a), and the polymer forms a side chain when formed. The number of carbon atoms is two, and the number of carbon-containing monomers (b) is three or four in the case where the number of carbon atoms constituting the side chain when the polymer is formed. In the case of "a side chain formed at the time of polymer formation", for example, a hydroxyalkyl (meth) acrylate, the hydroxyalkyl moiety corresponds to a "side chain formed at the time of polymer formation". Further, the "number of carbon atoms" is the number of carbon atoms in which the atoms constituting the main chain are bonded from the carbon atom bonded to the hydroxyl group, and the number of carbon atoms in the branched portion in the side chain is not calculated. Inside. For example, the number of the above carbon atoms in the 2-hydroxypropyl acrylate is two.

As a specific example of (ii), the hydroxyl group-containing monomer (a) is 2-hydroxyethyl acrylate, the hydroxyl group-containing monomer (b) is 3-hydroxypropyl (meth)acrylate, or (methyl) The case of 4-hydroxybutyl acrylate.

(iii) the number of carbon atoms bonded to the carbon atom to which the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded, and the first (methyl group) The number of carbon atoms bonded to the carbon atom on the hydroxyl group-containing monomer (a) of the acrylate polymer (A) is the same number, and further, the above second (meth) acrylate The hydroxyl group-containing monomer (b) of the polymer (B), the number of carbon atoms constituting the side chain when the polymer is formed, and the hydroxyl group-containing monomer of the first (meth) acrylate polymer (A) a) contains the same number of carbon atoms constituting the side chain when the polymer is formed, and the hydroxyl group-containing monomer (b) of the second (meth) acrylate polymer (B) is a hydroxyalkyl methacrylate The ester, the hydroxyl group-containing monomer (a) of the first (meth) acrylate polymer (A) is a hydroxyalkyl acrylate. This is due to the bonding of carbon atoms on the hydroxy group bonded thereto. The number of carbon atoms is the same. When the number of carbon atoms constituting the side chain when the polymer is formed is also the same number, the one of the hydroxyalkyl methacrylate is compared with the hydroxyalkyl acrylate. In a straight line, the hydroxyl group is exposed, and the reaction with the crosslinking agent (C) is easily carried out.

For example, the hydroxyl group-containing monomer (a) and the hydroxyl group-containing monomer (b) are both a primary hydroxyl group or a secondary hydroxyl monomer, and the hydroxyl group-containing monomer (a) is a hydroxyalkyl acrylate, a hydroxyl group-containing monomer ( b) In the case of a hydroxyalkyl methacrylate. For example, when the hydroxyl group-containing monomer (a) is 2-hydroxyethyl acrylate, the hydroxyl group-containing monomer (b) is 2-hydroxyethyl methacrylate, or the hydroxyl group-containing monomer (a) is acrylic acid 2- Hydroxypropyl ester, when the hydroxyl group-containing monomer (b) is 2-hydroxypropyl methacrylate.

Here, the molar ratio of the hydroxyl group contained in the second (meth) acrylate polymer (B) of the hydroxyl group contained in the first (meth) acrylate polymer (A) in the adhesive composition is 1.0. Above, 15 is not full, especially 2-10 is better, and further 2-8 is preferred.

In this way, the amount of the hydroxyl group contained in the second (meth) acrylate polymer (B) is more than the amount of the hydroxyl group contained in the first (meth) acrylate polymer (A) (the molar ratio is 1.0 or more). When the adhesive composition of the present embodiment is crosslinked, the preferential reaction of the second (meth) acrylate polymer (B) and the crosslinking agent (C) proceeds efficiently, and the structure X can be favorably formed (presumed). On the other hand, when the amount of the hydroxyl group contained in the second (meth) acrylate polymer (B) is larger than the amount of the hydroxyl group contained in the first (meth) acrylate polymer (A) (molar ratio is 15 or more) The crosslinking of the 2nd (meth) acrylate polymer (B) may be excessive, and the stress relaxation rate may be deteriorated. Sexuality, in addition to cross-linking, there are also hydroxyl groups remaining, especially in the case of wet heat conditions, the durability is deteriorated.

The second (meth) acrylate polymer (B) is preferably a hydroxy group-containing monomer (b) in an amount of 10 to 40% by mass, particularly preferably 10 to 30% by mass, and further contains 10 as a constituent monomer unit. -20% by mass is preferred. When the hydroxyl group-containing monomer (b) is in the above range, the degree of crosslinking of the second (meth) acrylate polymer (B) is good, and the combination with the first (meth) acrylate polymer (A) In this case, the stress relaxation rate of the obtained adhesive is more effectively improved. When the content of the hydroxyl group-containing monomer (b) is 10% by mass or less, the crosslinking of the second (meth)acrylate polymer (B) is insufficient, and the gel fraction is low, thereby providing durability. The possibility of deterioration. On the other hand, if the content of the hydroxyl group-containing monomer (b) exceeds 40% by mass, the crosslinking of the second (meth) acrylate polymer (B) may be excessive, and the stress relaxation rate may be deteriorated. In addition, since hydroxyl groups remain after crosslinking, durability in particular under moist heat conditions may be deteriorated. Further, if the upper limit of the content of the hydroxyl group-containing monomer (b) is 30% by mass, the obtained adhesive sheet is more excellent in light leakage resistance.

Further, the preferred content of the hydroxyl group-containing monomer in the first (meth) acrylate polymer (A) is contained in the hydroxyl group-containing monomer in the second (meth) acrylate polymer (B). The amount and the molar ratio of the above hydroxyl groups are automatically determined.

The other monomer may, for example, be an aliphatic ring-containing (meth) acrylate such as cyclohexyl (meth)acrylate or an aromatic ring (methyl group) such as phenyl (meth)acrylate. Acrylate; non-crosslinkable acrylamide such as acrylamide or methacrylamide; (meth) propylene (meth) acrylate having a non-crosslinkable tertiary amino group such as N,N-dimethylaminoethyl acid or N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate Base ester; styrene and the like. They may be used alone or in combination of two or more.

Other monomers having a non-crosslinking property such as N,N-dimethylaminoethyl (meth)acrylate or N,N-dimethylaminopropyl (meth)acrylate An amino (meth) acrylate, particularly N,N-dimethylaminoethyl (meth) acrylate, has a catalytic effect of promoting the reaction of a hydroxyl group in the polymer and a crosslinking agent (C), In the second (meth) acrylate polymer (B), it may be contained as a constituent monomer unit of the above polymer.

In this case, the content of the (meth) acrylate having the non-crosslinkable tertiary amino group in the second (meth) acrylate polymer (B) is preferably 0.01 to 1% by mass, particularly It is preferably 0.1 to 0.5% by mass.

Here, in order to form the structure X as described above, the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) are preferably not substantially in addition to the hydroxyl group. Contains a functional group having reactivity with the crosslinking agent (C). The functional group may, for example, be a cross-linkable primary or secondary amino group, and examples of the monomer having the above functional group include aminoethyl (meth)acrylate and n-butyl (meth)acrylate. An amino group-containing monomer such as aminoethyl ester.

The phrase "substantially does not contain a functional group reactive with the crosslinking agent (C)" means that the reactivity of the hydroxyl group and the crosslinking agent (C) is not impaired, except that the functional group is not contained at all. The extent that can be tolerated Functional group. Specifically, in each of the polymers (A) and (B), the molar ratio of the functional group to the hydroxyl group is preferably 0.2 or less, and particularly preferably 0.1 or less.

The polymerization method of the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) may be a random copolymer or a block copolymer.

The weight average molecular weight of the first (meth) acrylate polymer (A) is from 500,000 to 3,000,000, preferably from 700,000 to 2,500,000, particularly preferably from 1,000,000 to 2,000,000. That is, the first (meth) acrylate polymer (A) is a high molecular weight polymer component. In addition, the weight average molecular weight in this specification is a polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

When the weight average molecular weight of the first (meth) acrylate polymer (A) is within the above range, the polymer (A) has a relatively large molecular weight, and the structure X is favorably formed (presumed).

When the weight average molecular weight of the first (meth) acrylate polymer (A) is less than 500,000, the gel fraction of the obtained adhesive is low, and durability and reusability may be deteriorated. When the weight average molecular weight of the first (meth) acrylate polymer (A) exceeds 3,000,000, the compatibility with the second (meth) acrylate polymer (B) or the like is deteriorated, and the obtained adhesive is obtained. The stress relaxation rate is likely to deteriorate.

On the other hand, the weight average molecular weight of the second (meth) acrylate polymer (B) is from 8,000 to 300,000, preferably from 10,000 to 200,000, particularly preferably from 50,000 to 100,000. That is, the second (meth) acrylate polymer (B) is a low molecular weight polymer component.

If the weight average of the 2nd (meth) acrylate polymer (B) When the amount is within the above range, a unique three-dimensional network structure is formed in the adhesive composition of the present embodiment, and contributes to an excellent stress relaxation rate. That is, if 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, the weight average molecular weight of the second (meth) acrylate polymer (B) is more than 300,000, and the compatibility with the first (meth) acrylate polymer (A) or the like is deteriorated, and the polymer is polymerized. (B) The insertion of the polymer (A) in the formed three-dimensional network structure is insufficient, and as a result, the obtained adhesive may have durability and reusability.

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

The ratio of the second (meth) acrylate polymer (B) to 100 parts by mass of the first (meth) acrylate polymer (A) is preferably 5 to 50 parts by mass, particularly 5 to 40 parts by mass. The portion is preferably further, preferably 10-30 parts by mass.

The above-described structure X is formed well from 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 ( Speculated).

The crosslinking agent (C) may, for example, be an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent or a metal complex compound crosslinking agent, and among them, a polymer and a polymer are preferable. An isocyanate crosslinking agent which is excellent in reactivity of the hydroxyl group which (A) and (B) has.

Isocyanate crosslinking agent, which contains at least a polyisocyanate compound Things. The polyisocyanate compound may, for example, be an aromatic polyisocyanate such as toluene diisocyanate, diphenylmethane diisocyanate or p-xylylene diisocyanate; an aliphatic polyisocyanate such as hexamethylene diisocyanate; or isophorone II. An alicyclic polyisocyanate such as an isocyanate or a hydrogenated diphenylmethane diisocyanate, and a biuret and an isocyanurate thereof, and further, they may be exemplified by ethylene glycol, propylene glycol, and neopentyl glycol. An adduct obtained by reacting a compound containing a low molecular weight active hydrogen such as trimethylolpropane or castor oil.

The above-mentioned crosslinking agent (C) may be used alone or in combination of two or more.

The content of the crosslinking agent (C) is the amount of the crosslinking group (for example, isocyanate group) of the crosslinking agent (C) to the hydroxyl group of the second (meth) acrylate polymer (B), usually An amount of 0.05 to 5 equivalents is preferably 0.1 to 3.5 equivalents, particularly preferably 0.3 to 1.0 equivalents. When the amount of the crosslinkable group is 0.05 equivalent or less, the gel fraction of the obtained adhesive is low, and there is a possibility that sufficient cohesive force cannot be exhibited. In addition, when the amount of the crosslinkable group is 0.1 equivalent or more, and particularly 0.3 equivalent or more, the durability of the obtained adhesive can be further improved. On the other hand, when the amount of the crosslinkable group is 3.5 equivalent or less, the reusability of the obtained adhesive becomes excellent. Further, when the amount of the crosslinkable group is 1.0 equivalent or less, the crosslinking agent (C) contributes only to the formation of the three-dimensional network structure of the polymer (B), and the crosslinking of the polymer (A) can be effectively performed. Joint prevention (presumed). As a result, the obtained adhesive has excellent stress relaxation rate.

The adhesive composition of the present embodiment preferably further contains ruthenium Alkane coupling agent (D). When the decane coupling agent (D) is contained, the alkoxy fluorenyl group of the decane coupling agent (D) acts on an adherend surface such as a glass substrate, and for example, when a polarizing plate is attached to a liquid crystal glass unit or the like, adhesion is performed. The adhesion between the agent and the liquid crystal glass unit will become better.

The decane coupling agent (D) is an organic ruthenium compound having at least one alkoxyfluorenyl group in the molecule, and has good compatibility with an adhesive component and has light permeability, and is, for example, substantially transparent. The amount of the decane coupling agent (D) to be added is preferably from 0.01 to 0.5 parts by mass, particularly preferably from 0.05 to 0.3 parts by mass, per 100 parts by mass of the first (meth) acrylate polymer (A).

Specific examples of the decane coupling agent (D) include a polymerizable unsaturated group such as vinyl trimethoxy decane, vinyl triethoxy decane, and methacryloxypropyl trimethoxy decane. a compound having an epoxy structure such as 3-glycidyl ether propyl trimethoxy decane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxy decane; 3-aminopropyltrimethoxy An amino group such as decane, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane 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 commonly used in acrylic adhesives, such as a charge preventive agent, an adhesion-imparting agent, an oxidation preventive agent, an ultraviolet absorber, a light stabilizer, a softener, and the like, may be added as needed. Filler, refractive index modifier, and the like.

[Method for Producing Adhesive Composition]

The above-mentioned adhesive composition is produced separately from the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B), and may be mixed at the same time as they are mixed. The crosslinking agent (C) and the desired decane coupling agent (D) are added in stages to be produced.

As a preferable specific example, the (meth)acrylate polymers (A) and (B) are each produced 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 using a polymerization initiator as needed. The polymerization solvent may, for example, be ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane or methyl ethyl ketone, and may be used in combination of two or more kinds.

The polymerization initiator may, for example, be an azo compound or an organic peroxide, and may be used in combination of two or more types. As the azo compound, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutylcyano), 1,1'-azobis(cyclohexane) can be exemplified. 1-nitrile), 2,2'-azobis(2,4-dimethylcarbonitrile), 2,2'-azobis(2,4-dimethyl-4-methoxy nitrile), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanoshikimate), 2,2'-azobis(2-hydroxymethyl) Cyanamide) and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

The organic peroxide may, for example, be an acyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate or di-n-propyl peroxydicarbonate. , bis(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxy neopentate, t-butyl peroxypivalate, (3,5,5-trimethylhexyl) Acyl) peroxide, dipropionyl peroxide and diacetyl Peroxide and the like.

Further, in the above polymerization process, a chain shifting agent such as 2-mercaptoethanol is blended to adjust the weight average molecular weight of the obtained polymer.

Then, the obtained solutions of the polymers (A) and (B) are mixed, and a diluted solvent is added. Thereafter, the crosslinking agent (C) and, if necessary, the decane coupling agent (D) are added, and sufficiently mixed to obtain an adhesive composition (coating solution) diluted with a solvent.

The dilute solvent for diluting the adhesive composition to form a coating solution may, for example, be an aliphatic hydrocarbon such as hexane, heptane or cyclohexane; an aromatic hydrocarbon such as toluene or xylene; or dichloromethane; Halogenated hydrocarbon such as dichloroethane; alcohol such as methanol, ethanol, propanol, butanol or 1-methoxy-2-propanol; acetone, methyl ethyl ketone, 2-pentanone, isophorone a ketone such as cyclohexanone; an ester such as ethyl acetate or butyl acetate; a cellosolve solvent such as ethyl cellosolve;

The concentration of the coating solution thus prepared. The viscosity is not particularly limited as long as it is within the range of application, and may be appropriately selected depending on the circumstances. For example, the concentration of the adhesive composition can be diluted to 10 to 40% by mass. Further, when the coating solution is obtained, the addition of a diluent solvent or the like is not a requirement, and the adhesive composition may be a coating viscosity or the like, and a diluent solvent may not be added. In this case, the adhesive composition is used as a coating solution as it is.

(adhesive)

The adhesive of the present embodiment is obtained by crosslinking the above-mentioned adhesive composition. The crosslinking of the above adhesive composition is carried out by heat treatment. another Further, this heat treatment may also be performed by volatilizing a diluted solvent or the like of the adhesive composition to perform a drying treatment.

In the case of heat treatment, the heating temperature is preferably from 50 to 150 ° C, particularly preferably from 70 to 120 ° C. In addition, the heating time is preferably divided into 30 seconds - 3, especially in the range of 50 seconds -2. Further, after the heat treatment, it is particularly preferable to carry out the cooking at a normal temperature (for example, 23 ° C, 50% RH) to the extent of 1-2 weeks.

In the above heat treatment (and aging), the second (meth) acrylate polymer (B) is crosslinked by the crosslinking agent (C), and the first (meth) is in the three-dimensional network structure thereof. The acrylate polymer (A) is inserted, and the above structure X is formed (presumed).

The adhesive of the present embodiment preferably has an adhesion to an alkali-free glass of from 0.1 to 15 N/25 mm, particularly preferably from 1 to 10 N/25 mm. In addition, with this adhesive force, the adhesion force (peeling speed 300 mm/min) of 180° peeling in accordance with JIS Z0237 is preferably 0.5 MPa, and 20 minutes of pressurization at 50 ° C is applied to the adherend, 23 ° C, 50 The measurement was carried out by placing it under the conditions of %RH for 24 hours. When the adhesive force is within the above range, when applied to an optical member such as a polarizing plate or the like, lifting, peeling, and the like can be prevented.

The adhesive of the present embodiment is preferably adhered to the adherend and further adhered at 14° C. and 50% RH for 14 days (adhesive force after 14 days of attachment). 0.1-25N/25mm, especially 2-20N/25mm. Thus, the increase in the adhesive force with time can be suppressed, and the adhesive of the present embodiment is excellent in evaluation of reusability.

The adhesive described above is preferably used as an optical member, for example, for bonding between optical members such as a polarizing plate (polarizing film) and a phase difference plate (phase difference film), or a polarizing plate (polarized light) Film) and adhesion between the phase difference plate (phase difference film) and the glass substrate. In the adhesive layer formed by the adhesive of the present embodiment, the stress relaxation rate is extremely excellent, and when the dimensional change of the adherend is large, the stress generated by the dimensional change can be absorbed and moderated by the adhesive layer. It is difficult to peel off from the adhesive body for a long period of time, and the light leakage when the optical member described above is used can be effectively prevented. That is, the adhesive of the present embodiment can be satisfactorily achieved both in light leakage resistance and durability. Further, the adhesive of the present embodiment has excellent reusability, and when it is acid-free, when the adherend is a metal or when a metal is contained, the adhesive is excellent in corrosion resistance.

(adhesive film)

As shown in Fig. 1, the adhesive sheet 1A of the first embodiment has a structure in which the release sheet 12, the adhesive layer 11 which is laminated on the release surface of the release sheet 12, and the adhesive layer 11 are sequentially formed from the bottom. Stacked substrate 13.

Further, as shown in Fig. 2, the structure of the adhesive sheet 1B of the second embodiment is two peeling sheets 12a and 12b, and an adhesive layer 11 held by the two peeling sheets 12a and 12b, whereby the adhesive is adhered thereto. The agent layer 11 is in contact with the peeling faces of the two peeling sheets 21a and 12b described above. In addition, the peeling surface of the peeling sheet in this specification is a surface which has the peeling property in a peeling sheet, and the surface which apply|coated the peeling process, and the surface which shows the peeling property, without the peeling process.

In the adhesive sheets 1A and 1B, the adhesive layer 11 is adhered as described above. The composition is formed by crosslinking an adhesive obtained.

The thickness of the adhesive layer 11 is appropriately determined depending on the purpose of use of the adhesive sheets 1A, 1B, but is usually in the range of 5 to 100 μm, preferably 10 to 60 μm, for example, as an optical member, particularly a polarizing plate. When the adhesive layer is used, it is preferably from 10 to 50 μm, particularly preferably from 10 to 30 μm.

The substrate 13 is not particularly limited, and can be generally used as a substrate sheet of an adhesive sheet. For example, in addition to optical components, woven fabrics or nonwoven fabrics of rayon, acrylic polymer, and polyester fibers; papers such as upper paper, cellophane, impregnated paper, and copper paper; metal foils such as aluminum and copper Polyurethane foam, foam of polyethylene foam, etc.; polyester film of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. Polyurethane film, polyethylene film, polypropylene film, cellulose film such as triacetyl cellulose, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film A plastic film such as a polystyrene film, a polycarbonate film, an acrylic resin film, a borneol resin film, or a cycloolefin resin film; or a laminate of two or more kinds of the above-mentioned films. Plastic film, either one-axis rolling or two-axis rolling.

Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation film (retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast improving film, a liquid crystal polymer film, a diffusion film, and a half. Through a reflective film or the like. Among them, the polarizing plate (polarizing film) is easily shrunk and has a large dimensional change. Therefore, from the viewpoint of the above-mentioned light leakage resistance, the application of the adhesive (the above-mentioned adhesive layer 11) of the present embodiment is most suitable.

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.

As the release sheets 12, 12a, 12b, for example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinylidene chloride film, a dichloroethylene copolymer can be used. Film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ion exchange resin film, Ethylene. (Meth)acrylic copolymer film, ethylene. A (meth) acrylate copolymer film, a polystyrene film, a polycarbonate film, a polyimide film, a fluororesin film, or the like. In addition, these crosslinked films are also used. Further, these laminated films are also available.

It is preferable to carry out a peeling process on the peeling surface of the said peeling sheet, especially the adhesive layer 11 and the contact surface. The release agent used for the release treatment may, for example, be a release agent of an alkyd, a siloxane, a fluorine, an unsaturated polyester, a polyolefin, or a wax.

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

In the production of the above-mentioned pressure-sensitive adhesive sheet 1A, the release surface of the release sheet 12 is applied with a solution (coating solution) containing the above-mentioned adhesive composition, and heat treatment is performed to form the adhesive layer 11, and then on the adhesive layer 11 The substrate 13 is stacked. After that, it is better to set the ripening period.

In addition, the conditions of the heat treatment and the ripening are as described above.

Further, in the production of the above-mentioned adhesive sheet 1B, on the peeling surface of one of the release sheets 12a (or 12b), the adhesive composition containing the above adhesive composition is used. The coating solution is applied and heat-treated to form the adhesive layer 11, and then the peeling surface of the other release sheet 12b (or 12a) is superposed on the adhesive layer 11.

The method of applying the coating solution may, for example, be a stick coating method, a knife coating method, a roll coating method, a plate coating method, a die coating method, or a gravure coating method.

Here, for example, in the liquid crystal display device including the liquid crystal cell and the polarizing plate, a polarizing plate is used as the base material 13 of the adhesive sheet 1A, and the release sheet 12 of the adhesive sheet 1A is peeled off to expose the adhesive. The layer 11 and the liquid crystal cell may be bonded together.

Further, for example, in the manufacture of a liquid crystal display device in which a phase difference plate is disposed between a liquid crystal cell and a polarizer, as an example, first, one release sheet 12a (or 12b) of the adhesive sheet 1B is peeled off to form an adhesive sheet. The exposed adhesive layer 11 of 1B is bonded to the phase difference plate. Then, the release sheet 12 of the pressure-sensitive adhesive sheet 1A as the polarizing plate used for the substrate 13 is peeled off, and the exposed pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1A is bonded to the phase difference plate. Further, the other release sheet 12b (or 12a) is peeled off from the adhesive layer 11 of the adhesive sheet B, and the exposed adhesive layer 11 of the adhesive sheet B is bonded to the liquid crystal cell.

According to the above adhesive sheets 1A, 1B, the stress relaxation rate of the adhesive layer 11 is very excellent. For example, when it is applied to the bonding of the polarizing plate, the stress generated by the deformation of the polarizing plate can be adhered to the adhesive layer 11 absorb. By easing, it is possible to exhibit excellent light leakage resistance and high durability (presumed).

The embodiment described above is intended to facilitate the rationale of the present invention. The invention is not limited by the invention. Therefore, each element disclosed in the above embodiments includes all design changes and equivalents within the scope of the technology of the present invention.

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

[Examples]

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

[Example 1] 1. Modulation of polymer (A)

99.0 parts by mass of n-butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 2 were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube. 0.08 parts by mass of 2'-azobisisobutyronitrile, and the air in the above reaction vessel was replaced with nitrogen. The reaction solution was heated to 60 ° C while stirring in the nitrogen atmosphere, and the reaction was carried out for 16 hours, followed by cooling to room temperature. Here, one part of the obtained solution was subjected to molecular weight measurement by the following method, and the formation of the polymer (A) having a weight average molecular weight of 1.57 million was confirmed.

2. Modulation of polymer (B)

81.4 parts by mass of n-butyl acrylate, 18.6 parts by mass of 4-hydroxybutyl acrylate, and ethyl acetate 200 were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube. In an amount of 0.16 parts by mass of 2,2'-azobisisobutyronitrile and 0.3 parts by mass of 2-mercaptomethanol, the air in the reaction vessel was replaced with nitrogen. The reaction solution was heated to 70 ° C while stirring in the nitrogen atmosphere, and after 6 hours of reaction, it was cooled to room temperature. Here, the molecular weight was measured by the following method using a part of the obtained solution, and the formation of the polymer (B) having a weight average molecular weight of 60,000 was confirmed.

3. Modulation of adhesive composition

100 parts by mass (solid content converted value) of the polymer (A) obtained in the above item (1) and 20 parts by mass (solid content converted value) of the polymer (B) obtained in the above item (2) are mixed as To the crosslinking agent (C), a xylene diisocyanate adduct of trimethylolpropane in an amount equivalent to 0.6 equivalent of the hydroxyl group of the polymer (B) (manufactured by Mitsui Chemicals, Inc., trade name "TAKENATED-110N") was added. 3.0 parts by mass. Finally, 0.3 parts by mass of 3-glycidyl ether propyl trimethoxy decane (trade name "KBM403" manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a decane coupling agent (D), and the mixture was sufficiently stirred to obtain a diluted composition of the adhesive composition. Solution.

Further, the ratio of the monomer to be blended was such that the amount of the hydroxyl group (H[OH]) in 100 g of the polymer (A) was 8.62 mmol, and the amount of the hydroxyl group (L[OH]) in 20 g of the polymer (B) was 25.84. Mmmol. Therefore, the ratio (L [OH] / H [OH]) of the number of moles of the hydroxyl groups in 100 parts by mass of the polymer (A) to the number of moles of the hydroxyl groups of the polymer (B) is 3.00.

Here, the adhesion of the above adhesive composition is shown in Table 1. In addition, the outlines and the like described in Table 1 are as follows.

[Polymer (A) and (B)]

BA: n-butyl acrylate

AA: Acrylic

DM: N,N-dimethylaminoethyl methacrylate

HEA: 2-hydroxyethyl acrylate

HEMA: 2-hydroxyethyl methacrylate

2HPA: 2-hydroxypropyl acrylate

4HBA: 4-hydroxybutyl acrylate

H[OH] (mmol): the amount of the polymer (A) added (parts by mass) of the number of moles of hydroxyl groups calculated as (g)

L[OH] (mmol): the amount of the polymer (B) added (parts by mass), the number of moles of the hydroxyl group calculated by (g)

[Isocyanate crosslinking agent (C)]

XDI-TMP: a xylene diisocyanate adduct of trimethylolpropane (manufactured by Mitsui Chemicals, Inc., under the trade name "TAKENATED-110N")

[decane coupling agent (D)]

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

The peeling-treated surface of a polyethylene terephthalate film release sheet (SP-PET3811, thickness: 38 μm, manufactured by Linde Co., Ltd.) which was subjected to a release treatment with a decane-based release agent was obtained. The adhesive solution of the adhesive composition was applied by a doctor blade coating method (the thickness of the coating was 25 μm after drying), and thereafter, heat treatment was performed at 90 ° C for 1 minute to form an adhesive layer.

Then, a disk-shaped polarizing film having a liquid crystal layer is obtained, and polarized light is obtained. The film and the viewing angle expansion film are bonded together by an integrated polarizing film, and the exposed surface of the adhesive layer is brought into contact with the surface of the disk-shaped liquid crystal layer, and is aged at 23 ° C and 50% RH for 7 days to obtain A polarizer of the adhesive layer.

(Examples 2-11, Comparative Examples 1-3)

The type and ratio of each constituent monomer of the adhesive composition, the type and amount of the crosslinking agent and the decane coupling agent, and the mixing ratio of the polymer (A) and the polymer (B) were changed as shown in Table 1. A polarizing plate having an adhesive layer was produced in the same manner as in Example 1 except for the above.

Here, the weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC) under the following conditions (GPC measurement).

<Measurement conditions>

. GPC measuring device: manufactured by TOSOH, HLC-8020

. GPC column (the following sequence is passed): TOSOH company

TSK guard columN HXL-H

TSK gel GMHXL (×2)

TSK gel G2000HXL

. Determination of solvent: tetrahydrofuran

. Measuring temperature: 40 ° C

[Experimental Example 1] (Light leakage test)

The polarizing plate having the adhesive layer obtained in the examples or the comparative examples was adjusted to a size of 233 mm × 309 mm by a cutting device (Super Knife, manufactured by Takino Seisakusho Co., Ltd., PN1-600). The peeling sheet was peeled off, and the exposed adhesive layer was attached to the alkali-free glass (manufactured by Corning Co., Ltd., Eagle XG). The kettle prepared by the original production was pressurized at 20 MPa at 50 ° C for 20 minutes. Further, in the above-described bonding, the polarizing plate having the adhesive layer has a polarization axis in a Nicols cross state (polarizing axis: ∠45°, ∠135°). In this state, the film was allowed to stand in a dry environment at 80 ° C for 250 hours, and then placed in an environment of 23 ° C and 50% RH for 2 hours. This was used as a sample, and the light leakage property was evaluated by the method shown below. The results are shown in Table 2.

<Light leakage evaluation: visual inspection>

The above sample was placed on a flat panel illumination lamp (HF-SL-A312LC, illuminance: 26,000 Lux, luminance: 10,000 cd), and a two-dimensional color luminance meter (manufactured by Nika Minolta Co., Ltd., CA- 2000) Shadowing, analysis software (manufactured by Konica Minolta Co., Ltd., CA-S20w) was converted into a luminance distribution image. The luminance distribution image of the obtained sample was evaluated as shown in the evaluation criteria shown in FIG.

(Experimental Example 2) (Durability Evaluation)

The polarizing plate having the adhesive layer obtained in the examples or the comparative examples was adjusted to a size of 233 mm × 309 mm by a cutting device (Super Knife, manufactured by Takino Seisakusho Co., Ltd., PN1-600). The release sheet was peeled off, and the exposed adhesive layer was attached to an alkali-free glass-making company, Eagle XG), and then pressurized in a kettle made by Kurihara Seisakusho Co., Ltd. under conditions of 0.5 MPa and 50 ° C for 20 minutes.

Thereafter, it was placed under the following conditions of endurance conditions, and after 500 hours, it was observed with a magnifying glass of 10 times. Appearance changes are based on the following. The results are shown in Table 2.

◎: 4 sides, no problem

○: No problem in the 4 sides from the outer peripheral end of 0.6 mm or more

×: At least one of the four sides has an appearance of 0.1 mm or more of an adhesive such as floating, peeling, foaming, and streaking from the outer peripheral end portion of 0.6 mm or more.

<endurance condition>

‧60 ° C, relative humidity 90% RH

[Experimental Example 3] (Reusability evaluation)

A polarizing plate having an adhesive layer obtained in the examples or the comparative examples was cut to prepare a sample having a width of 25 mm and a length of 100 mm. The peeling sheet was peeled off from the sample, and the exposed sample was attached to an alkali-free glass (Eagle XG, manufactured by Corning Co., Ltd.), and then the autoclave manufactured by Kurihara Co., Ltd. was placed at 0.5 MPa and 50 ° C. Perform 20 minutes of pressurization. Then, it was allowed to stand under the conditions of drying at 50 ° C for 48 hours, and humidity control was carried out for 3 hours under conditions of 23 ° C and 50% RH. Thereafter, the sample was peeled off from the alkali-free glass by hand, and the stain on the surface of the above alkali-free glass was visually evaluated. The evaluation was carried out on the basis of the following criteria. The results are shown in Table 2.

○: no glass stains ‧ residual adhesive

△: the stain of the glass ‧ the residual of the adhesive is rare

×: The stain of the glass is ‧ the residual of the adhesive is remarkable

[Experimental Example 4] (Evaluation of corrosion resistance)

The release sheet of the polarizing plate having the adhesive layer obtained in the examples or the comparative examples was peeled off, attached to a copper foil (thickness: 80 μm), and then stored in an atmosphere of 60° C. and 90% RH for 500 hours. Thereafter, the polarizing plate having the adhesive layer was peeled off from the copper foil, and the surface of the exposed copper foil was visually observed to confirm the presence or absence of corrosion. The results are shown in Table 2.

○: no corrosion

×: corroded

[Experimental Example 5] (Evaluation of haze value)

A structure composed of a release sheet/adhesive layer (thickness: 25 μm) obtained in the production process of the example or the comparative example (structure before the polarizing plate was attached) was prepared. The surface of the exposed adhesive layer of the structure was bonded to soda lime glass (haze value: 0%), and the release sheet was peeled off to measure the sample preparation.

The measurement sample was measured by a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.), and a haze value (%) (abbreviated as Hz (%)) in accordance with JIS K7105. Further, the haze value is preferably in the range of 0 to 3%, and is within the above range, and is evaluated as × outside the above range. The results are shown in Table 2.

As shown in Table 2, the polarizing plate having the adhesive layer obtained in the examples was excellent in light leakage resistance and durability, and also excellent in recyclability, corrosion resistance, and optical properties.

The adhesive composition and the adhesive of the present invention are most preferably bonded to an optical member such as a polarizing plate and a phase difference plate, and the adhesive sheet of the present invention is used as an optical member such as a polarizing plate or a phase difference plate. Adhesive tablets are most suitable.

1A, 1B‧‧‧Adhesive tablets

11‧‧‧Adhesive layer

12,12a,12b‧‧‧ peeling film

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 graph showing the evaluation criteria of the light leakage test (visual) in the polarizing plate having the adhesive layer.

1A‧‧‧Adhesive tablets

11‧‧‧Adhesive layer

12‧‧‧ peeling layer

13‧‧‧Substrate

Claims (13)

An adhesive composition comprising a first (meth) acrylate polymer (A) having a weight average molecular weight of 500,000 to 3,000,000 and a second (meth) acrylate polymer having a weight average molecular weight of 8,000 to 300,000 (B) and the crosslinking agent (C), wherein the first (meth) acrylate polymer (A) does not substantially contain an acidic group, and is contained as a constituent monomer unit of the polymer. The reactivity of the crosslinking agent (C) satisfies the hydroxyl group-containing monomer (a) of the following formula (I), and the second (meth) acrylate polymer (B) does not substantially contain an acidic group, and The monomer unit constituting the polymer contains 10 to 40% by mass of the hydroxyl group-containing monomer (b) having reactivity with the crosslinking agent (C) and satisfying the following formula (I), and the crosslinking agent (C) Reactivity: hydroxyl group-containing monomer (a) <hydroxy group-containing monomer (b) ‧‧‧(I) The adhesive composition according to claim 1, wherein the carbon atom of the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded thereto. The number of carbon atoms bonded above is a carbon atom bonded to a carbon atom to which a hydroxyl group in the hydroxyl group-containing monomer (a) of the first (meth)acrylate polymer (A) is bonded The number is small. The adhesive composition according to claim 1, wherein the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded to the carbon atom thereon Number of bonded carbon atoms The number of carbon atoms bonded to the carbon atom on which the hydroxyl group in the hydroxyl group-containing monomer (a) of the first (meth)acrylate polymer (A) is bonded is the same, and the second The number of carbon atoms constituting the side chain at the time of formation of the polymer contained in the hydroxyl group-containing monomer (b) of the (meth) acrylate polymer (B) is higher than that of the above first (meth) acrylate polymer (A) The hydroxyl group-containing monomer (a) contains a large number of carbon atoms constituting a side chain at the time of formation of the polymer. The adhesive composition according to claim 1, wherein the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth)acrylate polymer (B) is bonded to the carbon atom thereon The number of carbon atoms bonded to the carbon atom bonded to the carbon atom on the hydroxyl group-containing monomer (a) of the first (meth) acrylate polymer (A) is bonded to the carbon atom The number is the same, and the number of carbon atoms constituting the side chain when the polymer is formed, which is contained in the hydroxyl group-containing monomer (b) of the second (meth) acrylate polymer (B), and the first The hydroxyl group-containing polymer (A) of the acrylate polymer (A) contains the same number of carbon atoms constituting the side chain when the polymer is formed, and the second (meth) acrylate polymer (B) The hydroxyl group-containing monomer (b) is a hydroxyalkyl methacrylate, and the hydroxyl group-containing monomer (a) of the first (meth) acrylate polymer (A) is a hydroxyalkyl acrylate. The adhesive composition according to the first aspect of the invention, wherein the second (meth) acrylate polymer (B) of the hydroxyl group contained in the first (meth) acrylate polymer (A) The molar ratio of the hydroxyl groups contained in the ) is 1.0 or more, and 15 is less than. The adhesive composition according to the first aspect of the invention, wherein the second (meth) acrylate polymer (B) is 100 parts by mass of the first (meth) acrylate polymer (A). The ratio is 5 to 50 parts by mass. The adhesive composition according to claim 1, wherein the first (meth) acrylate polymer (A) and the second (meth) acrylate polymer (B) are other than a hydroxyl group. It does not substantially contain a functional group reactive with the above crosslinking agent (C). The adhesive composition according to claim 1, wherein the crosslinking agent (C) is an isocyanate crosslinking agent. The adhesive composition according to claim 8, wherein the content of the isocyanate crosslinking agent is the amount of the hydroxyl group contained in the second (meth) acrylate polymer (B). The isocyanate group of the above isocyanate crosslinking agent is in an amount of 0.1 to 3.5 equivalents. An adhesive which is obtained by crosslinking an adhesive composition according to any one of claims 1 to 9. 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 release sheets and an adhesive layer held by the release sheet, whereby the adhesive layer and the two release sheets are The peeling surface is in contact with each other, and the adhesive layer is composed of the adhesive described in claim 10 of the patent application.