TWI465535B - Adhesive composition, adhesive and adhesive sheet - Google Patents

Description

Adhesive composition, adhesive and adhesive sheet

The present invention relates to an adhesive composition, an adhesive (a material for bridging an adhesive composition), and an adhesive sheet, and particularly to an adhesive composition, an adhesive, and an optical member which can be suitably used for an optical member such as a polarizing plate. Adhesive plate.

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 described 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. It is soft, 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. As a result, the liquid crystal cells of the adherend are 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 has been completed in view of such a reality to provide use In the case of an optical member such as a polarizing plate, an adhesive composition, an adhesive, and an adhesive sheet which are excellent in both light leakage resistance and durability are intended.

In order to achieve the above object, the present invention provides an adhesive composition comprising: a first (meth) acrylate copolymer (A) having a mass average molecular weight of from 1,000,000 to 2.5 million; and a mass average molecular weight of 20,000. 150,000th (meth) acrylate copolymer (B); isocyanate bridging agent (C); and decane coupling agent (D) characterized by the above (2) (meth) acrylate copolymer (B) The ratio of 100 parts by mass of the first (meth) acrylate copolymer (A) is 10 to 30 parts by mass, and the first (meth) acrylate copolymer (A) contains a carboxyl group as a reactive functional group. The monomer is a constituent component, and the ratio of the monomer having the carboxyl group is 2.0 to 6.0% by mass in the first (meth) acrylate copolymer (A), and the second (meth) acrylate is used. The copolymer (B) contains a monomer having a hydroxyl group as a reactive functional group as a constituent component, and a ratio of a monomer having the above hydroxyl group is 10.0 in the second (meth)acrylate copolymer (B). ~20.0% by mass, the content of the above isocyanate bridging agent (C) is the shelf of the isocyanate bridging agent (C) On the substrate to an amount of 0.3 to 0.9 equivalents of the amount of the hydroxyl groups of the second (meth) acrylate copolymer (B) of the (invention 1).

The adhesive which bridges the adhesive composition of the above invention (Invention 1) is formed into a three-dimensional network structure by chemical bridging in the low molecular weight copolymer (B) previously used as a plasticizer. Then, by inserting the complex high molecular weight copolymer (A) into the three-dimensional network structure, the high molecular weight copolymer (A) is restrained from each other to form a false bond between the high molecular weight copolymer (A). Sexual bridging structure. Thereby, the obtained adhesive can exhibit an appropriate agglomeration power and excellent stress relaxation property. When the optical member having a good stress relaxation property is used and 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 (Invention 1), the content of the monomer having a hydroxyl group of the second (meth) acrylate copolymer (B) in the adhesive composition is the first one in the adhesive composition. The ratio of the content of the monomer having a carboxyl group of the (meth) acrylate copolymer (A) is preferably from 0.3 to 0.9 in terms of a molar ratio (Invention 2).

In the above invention (Inventions 1 and 2), the content of the isocyanate-based bridging agent (C) is preferably 7.5 to 26 parts by mass per 100 parts by mass of the second (meth) acrylate copolymer (B). (Invention 3).

Secondly, the present invention provides an adhesive which is obtained by bridging the above adhesive composition (Inventions 1 to 3) (Invention 4).

In the above invention (Invention 4), the gel fraction at the time of storage at 23 ° C and 50% RH for 7 days after the production is preferably 50 to 80% (Invention 5).

Thirdly, the present invention provides an adhesive sheet comprising: a substrate; and an adhesive layer, wherein the adhesive layer is composed of the above-mentioned adhesive (Inventions 4 and 5) (Invention 6).

In the above invention (Invention 6), the substrate is preferably an optical member (Invention 7).

According to a fourth aspect, the present invention provides an adhesive sheet comprising: two peeling sheets; and an adhesive layer attached to the peeling sheet of the peeling sheets of the two peeling sheets, the adhesive Layer consisting of the above adhesive (Invention 4, 5) Composition (Invention 8).

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 copolymers into the three-dimensional network structure, the high molecular weight copolymers are mutually restrained to form a pseudo bridge structure between the high molecular weight copolymers. Thereby, the obtained adhesive can exhibit appropriate agglomeration power 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 includes a first (meth) acrylate copolymer (A) having a mass average molecular weight of 1,000,000 to 250,000, and a second (mass average molecular weight) of 20,000 to 150,000 (A) Acrylate copolymer (B); isocyanate bridging agent (C); and decane coupling agent (D). In the present specification, the term "(meth)acrylate" means both acrylate and methacrylate. Other similar terms are the same.

The first (meth) acrylate copolymer (A), the constituent component comprising a monomer having a carboxyl group as a reactive functional group (a monomer having a carboxyl group), and a ratio of a monomer having a carboxyl group, in the first (A) Acrylate copolymer (A) It is 2.0 to 6.0% by mass.

On the other hand, the second (meth) acrylate copolymer (B), the constituent component contains a monomer having a hydroxyl group as a reactive functional group (a monomer having a hydroxyl group), and a ratio of a monomer having a hydroxyl group, In the second (meth) acrylate copolymer (B), it is 10.0 to 20.0% by mass.

The first (meth) acrylate copolymer (A), a (meth) acrylate having a carbon number of the alkyl group of the ester moiety of 1 to 20, a monomer having a carboxyl group, and other monomers as desired The copolymer of the body is preferably a second (meth) acrylate copolymer (B), a (meth) acrylate having a carbon number of the alkyl group of the ester moiety of 1 to 20, and a monomer having a hydroxyl group, and Copolymers of other monomers which are desired to be used are preferred.

The (meth) acrylate having 1 to 20 carbon atoms of the alkyl group in the ester moiety may, for example, be methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate or (methyl). Butyl acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, Ethyl (meth)acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, octadecyl (meth)acrylate, and the like. 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.

The hydroxyl group-containing monomer may, for example, be 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate or 3-hydroxypropionate (meth)acrylate. A (meth)acrylic acid hydroxyalkyl ester such as an ester, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate or 4-hydroxybutyl (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 such as acrylamide or methacrylamide; styrene, vinyl acetate, and the like. These may be used alone or in combination of two or more.

As described above, the first (meth) acrylate copolymer (A) contains a monomer having a carboxyl group as a constituent component. When a monomer having a carboxyl group is contained, the carboxyl group is reacted with an alkoxythio group of the decane coupling agent (D) or the like, and the degree of agglomeration of the first (meth) acrylate copolymer (A) can be adjusted to obtain desired The continuity of the. Further, the monomer having a carboxyl group promotes the reaction of the second (meth) acrylate copolymer (B) with the isocyanate bridging agent (C), and on the other hand, the reactivity of the carboxyl group with the isocyanate bridging agent (C). Since the hydroxyl group of the second (meth) acrylate copolymer (B) is lower, the reaction between the second (meth) acrylate copolymer (B) and the isocyanate bridging agent (C) cannot be avoided. The three-dimensional network structure can be obtained by the second (meth) acrylate copolymer (B) bridged by the isocyanate bridging agent (C).

The content ratio of the carboxyl group-containing monomer in the first (meth) acrylate copolymer (A) is preferably 2.0 to 6.0% by mass, and preferably 3.0 to 5.0% by mass. When the content of the monomer having a carboxyl group is less than 2.0% by mass, the durability may be insufficient. On the other hand, when the content of the carboxyl group-containing monomer is more than 6.0% by mass, the first (meth) acrylate copolymer (A) is excessively agglomerated, and the content is not obtained. The expected stress mitigation.

The first (meth) acrylate copolymer (A) does not interfere with the reaction of the second (meth) acrylate copolymer (B) with the isocyanate bridging agent (C), and does not contain an isocyanate-based bridging agent (C). The functional group having a higher reactivity than the carboxyl group is preferably a monomer having a hydroxyl group, a thiol group or the like as a constituent component. However, when a monomer having a functional group having a higher reactivity with an isocyanate-based bridging agent (C) than a carboxyl group is contained, the content of the monomer having a functional group having high reactivity in the molecule is contained in the copolymer (A). The amount is preferably 1% by mass or less, particularly preferably 0.5% by mass or less. When the content of the monomer exceeds 1% by mass, the reaction between the second (meth) acrylate copolymer (B) which is preferentially reacted and the isocyanate-based bridging agent (C) is inhibited.

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

The mass average molecular weight of the first (meth) acrylate copolymer (A) is from 1,000,000 to 2.5 million, preferably from 1.2 million to 2,000,000. That is, the first (meth) acrylate copolymer (A) is a high molecular weight polymer component. Further, the mass average molecular weight in the present specification is a value in terms of polystyrene measured by a gel permeation chromatography (GPC) method.

It is presumed that the first (meth) acrylate copolymer (A) is sufficiently restrained by the second (A) by setting the mass average molecular weight of the first (meth) acrylate copolymer (A) within the above range. In the three-dimensional network structure formed by the acrylate copolymer (B), a pseudo bridge structure in which the copolymer (A) is not chemically bonded to each other is formed. Thereby, the obtained adhesive is excellent in stress relaxation property, and it is excellent in light leakage resistance. In addition, due to the income The adhesive has an appropriate agglomeration force by the pseudo bridge structure, so that the adhesion to the adherend and the adhesion durability under high heat and humidity are sufficient to prevent floating or peeling.

When the mass average molecular weight of the first (meth) acrylate copolymer (A) is less than 1,000,000, the agglomeration power of the component (A) is lowered, and the durability and the reworkability are deteriorated. Further, when the mass average molecular weight of the first (meth) acrylate copolymer (A) exceeds 2.5 million, the obtained adhesive becomes too hard, and the desired stress relaxation property cannot be obtained.

On the other hand, the second (meth) acrylate copolymer (B) contains a monomer having a hydroxyl group as a constituent component. Since the hydroxyl group has higher reactivity with the isocyanate-based bridging agent (C) than the carboxyl group of the first (meth) acrylate copolymer (A), it is presumed that it is preferentially reacted with the isocyanate-based bridging agent (C). The bridging agent (C) forms a three-dimensional network structure.

The content ratio of the hydroxyl group-containing monomer in the second (meth) acrylate copolymer (B) is from 10.0 to 20.0% by mass, preferably from 12 to 17% by mass. By including a hydroxyl group-containing monomer in the above range, the degree of bridging of the second (meth) acrylate copolymer (B) is improved, and in combination with the first (meth) acrylate copolymer (A), The stress relaxation property of the obtained adhesive is excellent. In addition, when the content of the hydroxyl group-containing monomer is 10.0% by mass or less, bridging of the second (meth) acrylate copolymer (B) is not sufficient, and thus durability is lowered. On the other hand, when the content of the hydroxyl group-containing monomer exceeds 20.0% by mass, the bridging of the second (meth) acrylate copolymer (B) becomes excessive, and thus the adhesion to the adherend is lowered.

Further, the second (meth) acrylate copolymer (B) does not contain and The cyanate ester-based bridging agent (C) has a lower reactivity than the hydroxyl group, and for example, a monomer having a carboxyl group, a sulfonyl group or the like (a monomer having a low-reactivity functional group) is particularly preferable as a constituent component, and is contained. When the monomer having a low reactivity functional group is a constituent component, it contains an amount of 1/5 or less of the content of the monomer having a hydroxyl group, and particularly preferably an amount of 1/10 or less.

In the present embodiment, when the monomer having a low reactivity functional group in the copolymer (B) is too much, a large amount of a low-reactivity functional group remains in the three-dimensional network structure formed thereby, and it is presumed that the monomer is required to be three times. The compatibility of the reticular structure with the copolymer (A) changes. As a result, the insertion of the copolymer (A) into the three-dimensional network structure is insufficient, and the durability of the obtained adhesive is deteriorated, and the haze value is increased. Further, it is presumed that the ternary network structure in which a large amount of a low-reactivity functional group remains, the mobility of the copolymer (A) inserted thereto is excessively restricted. As a result, there is a case where the stress relaxation property of the obtained adhesive is deteriorated.

On the other hand, the decane coupling agent (D) is reacted with the carboxyl group of the first (meth) acrylate copolymer (A) to bond with the high molecular weight first (meth) acrylate copolymer (A), and it is presumed that The adhesion between the obtained adhesive and the glass substrate to be adhered is excellent. However, when the second (meth) acrylate copolymer (B) excessively contains a monomer having a low reactivity functional group, the alkoxy thiol group of the decane coupling agent (D) is also the second (meth) group. The reaction of the low-reactivity functional group (particularly a carboxyl group) of the acrylate copolymer (B) is presumed to be bonded to the second (meth) acrylate copolymer (B) having a low molecular weight. As a result, the adhesion between the obtained adhesive and the glass substrate to be adhered becomes poor, and thus the durability of the adhesive layer is lowered.

Further, the hydroxyl group-containing monomer of the second (meth) acrylate copolymer (B) is contained in the first (meth) acrylate copolymer (A) in the adhesive composition of the present embodiment. The content of the monomer of the carboxyl group in the content of the adhesive composition (the content of the monomer having a hydroxyl group / the content of the monomer having a carboxyl group) is preferably 0.3 to 0.9 in mol ratio, particularly 0.5 to 0.5. 0.8 is better.

When the ratio is too small, the ratio of the carboxyl group of the copolymer (A) becomes too large compared to the hydroxyl group of the copolymer (B), and the reaction between the hydroxyl group and the isocyanate bridging agent (C) is hindered, and the resulting adhesive is durable. Sexual deterioration. Further, the amount of the carboxyl group of the copolymer (A) is excessively increased in an absolute amount, which may deteriorate the reproducibility of the obtained adhesive.

On the other hand, if the ratio is too large, the network of the three-dimensional network structure formed by the copolymer (B) becomes too fine, and the copolymer (A) cannot be sufficiently inserted, so that the durability of the obtained adhesive is obtained. Deterioration, even in the case of insertion, the degree of freedom of the copolymer (A) is excessively restricted, and the light leakage resistance of the obtained adhesive is deteriorated. Further, the amount of the carboxyl group of the copolymer (A) is too small in an absolute amount, and the reaction with the decane coupling agent (D) is insufficient, and the durability of the obtained adhesive may be deteriorated.

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

The second (meth) acrylate copolymer (B) has a mass average molecular weight of 20,000 to 150,000, preferably 50,000 to 120,000. That is, the second (meth) acrylate copolymer (B) is a low molecular weight polymer component.

By averaging the molecular weight of the second (meth) acrylate copolymer (B) When the amount is within the above range, a three-dimensional network structure peculiar to the adhesive composition of the present embodiment can be formed, and excellent stress relaxation property can be imparted. In other words, when the mass average molecular weight of the second (meth) acrylate copolymer (B) is less than 20,000, a good three-dimensional network structure cannot be obtained. On the other hand, the second (meth) acrylate copolymer (B) has a mass average molecular weight of more than 150,000, and the compatibility is lowered, and the copolymer (A) and the copolymer (B) are not easily complexed. It is difficult to form a unique mesh structure of the target, resulting in poor durability and reworkability. Further, when the mass average molecular weight of the copolymer (B) is from 50,000 to 120,000, the light leakage resistance is also excellent, which is more preferable.

The ratio of the second (meth) acrylate copolymer (B) to 100 parts by mass of the first (meth) acrylate copolymer (A) is from 10 to 30 parts by mass from the viewpoint of durability, and is 17 to 30 masses. The department is better. Further, from the viewpoint of light leakage resistance, the ratio is particularly preferably 22 to 28 parts by mass.

When the ratio of the copolymer (B) to the copolymer (A) is too small, it is presumed that the pseudo bridging portion composed of the three-dimensional network structure formed by the copolymer (B) is insufficient. On the other hand, when the ratio of the copolymer (B) to the copolymer (A) is too large, it is presumed that the copolymer (A) cannot be sufficiently inserted into the three-dimensional network structure of the copolymer (B) due to deterioration in compatibility. Or the false bridging portion becomes excessive, and the degree of freedom of the copolymer (A) is restricted.

In the present embodiment, an isocyanate bridging agent (C) is used as a bridging agent. Because of the bridging agent (C), the bridging reaction is mild, the reaction selectivity of the carboxyl group and the hydroxyl group is excellent, and the flexibility of the resulting bond is also excellent.

The isocyanate-based bridging agent (C) is a compound containing at least a polyisocyanate compound. The polyisocyanate compound may, for example, be tolylene diisocyanate. An aromatic polyisocyanate such as diphenylmethane diisocyanate or xylyl diisocyanate; an aliphatic polyisocyanate such as hexamethylene diisocyanate; or a lipid such as isophorone diisocyanate or hydrogenated diphenylmethane diisocyanate; a cyclic polyisocyanate or the like; and such a diuret, a cyanuric acid; and a compound containing a low molecular weight active hydrogen such as ethylene glycol, propylene glycol, neopentyl glycol, hexamethylolpropane or castor oil An adduct of the reactants, and the like. In particular, a tolyl diisocyanate (TDI)-based adduct of hexamethylolpropane is preferably used. Because the bridging speed is suitable for operation, the resulting bridging structure can also be made to have excellent strength. The bridging agent may be used alone or in combination of two or more.

The content of the isocyanate bridging agent (C) is such that the amount of the bridging group (isocyanate group) of the bridging agent (C) to the hydroxyl group of the second (meth) acrylate copolymer (B) is 0.3 to 0.9 equivalent. It is preferably in the amount of 0.4 to 0.7 equivalents. The amount of the bridging base is less than 0.3 equivalent, and the bridging cannot be sufficiently performed, and the durability is poor. When the amount of the bridging group is more than 0.9 equivalent, the desired stress relaxation property cannot be obtained, and when it is applied to an optical member such as a polarizing plate, the light leakage resistance is inferior.

The content of the isocyanate-based bridging agent (C) is preferably from 9 to 28 parts by mass based on 100 parts by mass of the second (meth) acrylate copolymer (B).

In the adhesive composition of the present embodiment, the decane coupling agent (D) is contained, and when the decane coupling agent (D) is contained, the organic reactive group of the decane coupling agent (D) is copolymerized with the first (meth) acrylate. The carboxyl group of the substance (A) reacts, and on the other hand, the alkoxy group of the decane coupling agent (D) acts on the surface of the glass substrate or the like. Therefore, for example, when a polarizing plate is adhered to a liquid crystal cell or the like, The adhesion between the adhesive and the liquid crystal glass cell can be improved.

The decane coupling agent (D) is preferably an organic ruthenium compound having at least one alkoxy fluorenyl group in the molecule, which is compatible with an adhesive component and has light penetrability, for example, substantially transparent. . The amount of the decane coupling agent (D) to be added is preferably 0.05 to 0.5 parts by mass, more preferably 0.1 to 0.3 parts by mass, per 100 parts by mass of the first (meth) acrylate copolymer (A).

Specific examples of the decane coupling agent (D) include a fluorene compound containing a polymerizable unsaturated group such as vinyltrimethoxy decane, vinyltriethoxysilane or methacryloxypropyltrimethoxy 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. An amine group-containing compound, 3-chloropropyltrimethoxydecane, 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 copolymer (A) with the second (meth) acrylate copolymer (B). And decane coupling agent (D).

A preferred embodiment is a (meth) acrylate copolymer (A) and (B) is separately prepared by a usual radical polymerization method.

The polymerization of the (meth) acrylate copolymers (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 peroxybenzoate, cumene hydroperoxide, diisopropyl peroxycarbonate, di-n-propyl peroxycarbonate, or the like (2). -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 copolymers (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.

To dilute the adhesive composition into a dilution solvent of the coating solution, for example, an aliphatic hydrocarbon such as hexane, heptane or cyclohexane; or a toluene or xylene; Halogenated hydrocarbons such as aromatic hydrocarbons, dichloromethane, dichloroethane, etc.; alcohols such as methanol, ethanol, propanol, butanol, 1-methoxy-2-propanol; acetone, methyl ethyl ketone, 2-pentanone, and iso A ketone such as phorone or cyclohexanone; an ester such as ethyl acetate or butyl acetate; a cellosolve such as ethyl cellosolve; and the like.

The concentration of the coating solution thus prepared. The viscosity 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, when the coating solution is obtained, the addition of a diluent solvent or the like is not a requirement, and the diluent composition may be omitted as long as the adhesive composition 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 copolymer (B) is bridged by the heat treatment (and curing) by the isocyanate-based bridging agent (C) to form a dense three-dimensional network structure. Then, it is presumed that two or more molecules of the first (meth) acrylate copolymer (A) in the three-dimensional network structure are not accompanied by direct chemical bonding or insertion with little chemical bonding, so that the copolymer (A) is restrained and forms a bridge structure. Further, when the first (meth) acrylate copolymer (A) has a carboxyl group, the first (meth) acrylate copolymer (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. The adhesive layer formed by the above adhesive agent is excellent in stress relaxation, so that even if the size of the adherend varies greatly, it can be absorbed by the adhesive layer. Since the stress due to the dimensional change is alleviated, it can be easily peeled off by the adherend for a long period of time, and when used in 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.

The adhesive of the present embodiment is applied to the adhesive composition. After drying (after the formation of the adhesive layer = after the production of the adhesive), the gel fraction at the time of storage at 23 ° C and 50% RH for 7 days is preferably 50 to 80%, especially 60 to 77%. good. When the gel fraction is in the above range, the bridging degree of the second (meth) acrylate copolymer (B) of the above adhesive composition can be made preferable, and the stress relaxation property of the obtained adhesive is excellent. By.

[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 two peeling sheets attached thereto. The peeling faces of 12a and 12b are constituted by the adhesive layer 11 which is sandwiched between the two peeling sheets 12a and 12b. In addition, the peeling surface of the peeling sheet of this 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 the peeling process is not apply.

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 fibers such as enamel, acryl, polyester, etc.; paper of upper quality paper, glossy paper, impregnated paper, coated paper, etc.; 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, a cycloolefin resin film, or a cellulose triacetate; or a laminate of two or more of these. Plastic film, which can be uniaxially extended or biaxially extended.

The optical member may, for example, be a polarizing plate (polarizing film), a polarizing plate, a phase difference plate (phase difference film), a viewing angle compensation film, a brightness enhancement film, and a comparison Rising film, liquid crystal polymer film, etc. Among them, the polarizing plate (polarizing film) has a large dimensional change due to easy shrinkage, and therefore can be favorably used as the object for forming the above-mentioned adhesive layer 11 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, 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, 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 laminating the peeling surface of the peeling sheet 12, applying a solution containing the above-mentioned adhesive composition, and heat-treating to form the adhesive layer 11, and then laminating the substrate 13 on the adhesive layer 11. . Further, the conditions regarding the heat treatment are as described above.

In addition, the above-mentioned adhesive sheet 1B is manufactured by another peeling sheet. The peeling surface of 12a (or 12b) is coated with a coating solution containing the above adhesive composition, and after heat treatment to form the adhesive layer 11, the other peeling sheet 12b (or 12a) is superposed on the adhesive layer 11. Stripping the surface.

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 adhesive sheets 1A, 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 be absorbed. The stress generated by the deformation of the polarizing plate is alleviated, and 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 copolymer (A)

In a reaction vessel containing a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 97.0 parts by mass of n-butyl acrylate, 3.0 parts by mass of acrylic acid, 200 parts by mass of ethyl acetate, and 2,2'-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 copolymer (A) having a weight average molecular weight of 1.5 million was produced.

2. Modulation of copolymer (B)

In a reaction vessel containing 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- 0.3 parts by mass of mercaptoethanol and 0.16 parts by mass of 2,2'-diazobisisobutyronitrile, and the air in the reaction vessel 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 copolymer (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 15 parts by mass (solid content converted value) of the polymer (B) obtained in the above step (2), and then a polymer is added ( B) The hydroxyl group is equivalent to 0.6 equivalent (2.48 parts by mass) of a toluene diisocyanate (TDI-based) adduct of trimethylolpropane (manufactured by Nippon Polyurethane Co., Ltd., trade name "CORONATE L") 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.

BA: n-butyl acrylate

AA: Acrylic

HEA: 2-hydroxyethyl acrylate

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 26, 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 copolymer (A) and the copolymer (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] (gel fraction) Determination)

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, on the adhesive layer having a thickness of 25 μm obtained in the production process of the examples or the comparative examples, the release sheet was joined to the side of the release-treated surface to be laminated, and a release sheet/adhesive layer/release sheet was produced. An adhesive sheet composed of the composition of the sheet.

The obtained adhesive sheet was cured at 23 ° C, 50% RH for 7 days after its preparation (= after the formation of the adhesive layer). 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 1.

[Test Example 2] (Measurement of optical properties)

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, on the adhesive layer having a thickness of 25 μm obtained in the production process of the examples or the comparative examples, the release sheet was joined to the side of the release-treated surface to be laminated, and a release sheet/adhesive layer/release sheet was produced. An adhesive sheet composed of the composition of the sheet.

The obtained adhesive sheet was cured at 23 ° C, 50% RH for 7 days after its preparation (= after the formation of the adhesive layer). Thereafter, the peeling sheets on both sides were peeled off, and the surface of one side of the adhesive layer was adhered to soda glass (manufactured by Nippon Sheet Glass Co., Ltd.) to prepare a measurement sample. Further, it was confirmed that the haze value of the soda glass itself was 0. For the measurement sample, a haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used, and the haze value (%) was measured in accordance with JIS K7105. The results are shown in Table 1. Further, the preferred haze value ranges from 0 to 5%.

[Test Example 3] (Endurance Evaluation)

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 1.

◎: 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.

×: at least one side of the four sides, from the outer peripheral end portion 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

[Test Example 4] (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 1.

<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* by the formula ΔL*=[(b+c+d+e)/4]-a

(where a, b, c, d, and e are respectively set in the A area in advance The brightness of the measurement points (one at the center of each area) of the domain, the B region, the C region, the D region, and the E region. ) Seek as light leakage. The smaller the value of ΔL*, the less light leakage. Further, the maximum value among the above values b to e is L*max. The larger the L*max, the more the portion where the light leakage is strong.

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): made by TOSO

TSK guard column HXL-H

TSK gel GMHXL (×2)

TSK gel G2000HXL

. Determination of solvent: tetrahydrofuran

. Measuring temperature: 40 ° C

[Table 1]

As is clear from Table 1, the polarizing plate having the adhesive layer obtained in the examples has no problem in durability and is excellent in light leakage resistance. In Comparative Example 1 and Comparative Example 2, the formulation ratio of the second (meth) acrylate copolymer (B) to the first (meth) acrylate copolymer (A) was too large, and the durability was inferior. In Comparative Example 3 and Comparative Example 5, since the content of the isocyanate-based bridging agent (C) was too small, the durability was inferior. In Comparative Example 4 and Comparative Example 6, the content of the isocyanate-based bridging agent (C) was too large, and the light leakage resistance was inferior. Regarding Comparative Example 7, since the decane coupling agent (D) was not contained, the 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, 1B. . . Adhesive sheet

11. . . Adhesive layer

12, 12a, 12b. . . Stripping plate

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 having an adhesive layer.

1A‧‧‧Adhesive sheets

11‧‧‧Adhesive layer

12‧‧‧ peeling sheet

13‧‧‧Substrate

Claims (8)

An adhesive composition comprising: a first (meth) acrylate copolymer (A) having a mass average molecular weight of 1,000,000 to 250,000; and a second (meth) acrylate having a mass average molecular weight of 20,000 to 150,000 Copolymer (B); isocyanate bridging agent (C); and decane coupling agent (D), characterized in that said second (meth) acrylate copolymer (B) is bonded to said first (meth) acrylate The ratio of the mass portion of the copolymer (A) is 10 to 30 parts by mass, and the first (meth) acrylate copolymer (A) contains a monomer having a carboxyl group as a reactive functional group as a constituent component, and has the above-mentioned The ratio of the monomer of the carboxyl group is 2.0 to 6.0% by mass in the first (meth)acrylate copolymer (A), and the second (meth)acrylate copolymer (B) contains a hydroxyl group as a reaction. The monomer having a functional group as a constituent component, and the ratio of the monomer having the above hydroxyl group is from 10.0 to 20.0% by mass in the second (meth)acrylate copolymer (B), and the above isocyanate bridging agent ( The content of C) is such that the isocyanate bridging agent (C) has a bridging group pair in the above second (meth) acrylate The amount of the above hydroxyl group of the polymer (B) is in an amount of from 0.3 to 0.9 equivalent. The adhesive composition according to claim 1, wherein the second (meth) acrylate copolymer in the adhesive composition is the second (meth) acrylate copolymer The ratio of the content of the monomer having a hydroxyl group in (B) to the content of the monomer having a carboxyl group of the above-mentioned first (meth) acrylate copolymer (A) in the above adhesive composition, in terms of molar ratio 0.3~0.9. The adhesive composition according to claim 1, wherein the content of the isocyanate-based bridging agent (C) is 7.5 to 26 in terms of 100 parts by mass of the second (meth) acrylate copolymer (B). The quantity of the quality department. An adhesive composition, which is obtained by applying the adhesive composition according to any one of claims 1 to 3. The adhesive according to claim 4, which has a gel fraction of 50 to 80% when stored at 23 ° C and 50% RH for 7 days after the production. An adhesive sheet comprising: a substrate; and an adhesive layer, wherein the adhesive layer is composed of the adhesive described in claim 4 of the patent application. The adhesive sheet according to claim 6, wherein the substrate is an optical member. An adhesive sheet comprising: two peeling sheets; and an adhesive layer attached to the peeling sheet on the peeling surface of the two peeling sheets, wherein the adhesive layer is patented The adhesive composition of item 4 is composed.