JP5611130B2 - Adhesive composition, adhesive and adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive (a material obtained by crosslinking a pressure-sensitive adhesive composition), and a pressure-sensitive adhesive sheet, and particularly, a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, and a pressure-sensitive adhesive suitable for optical members such as polarizing plates. The present invention relates to an adhesive sheet.

  In general, in a liquid crystal panel, a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition is often used to bond a polarizing plate or a retardation plate to a glass substrate of a liquid crystal cell. However, since optical members such as polarizing plates and retardation plates are easily shrunk by heat, etc., shrinkage occurs due to thermal history, and as a result, the adhesive layer laminated on the optical member cannot follow the shrinkage. Problems have been pointed out, such as peeling at the interface (so-called floating or peeling), or light leakage (so-called white spots) due to displacement of the optical axis of the optical member due to stress during contraction of the optical member. .

  As a method for preventing this, (1) a method of suppressing the contraction of the optical member itself by bonding a pressure-sensitive adhesive layer having high adhesive strength and excellent shape stability to an optical member such as a polarizing plate. Or (2) a method using a pressure-sensitive adhesive layer having a small stress when the optical member is contracted. As the method (1), it is effective to use a pressure-sensitive adhesive layer having a high storage elastic modulus as disclosed in Patent Document 1. On the other hand, as the method (2), it is effective to use a pressure-sensitive adhesive layer having excellent stress relaxation properties that can flexibly cope with deformation of the optical member.

  In order to carry out the above method (2), Patent Document 2 includes a copolymer of (A) alkyl (meth) acrylate and 0.5 to 20% by weight of a polymerizable monomer having functionality with respect to a crosslinking agent. And 100 parts by weight of a high molecular weight (meth) acrylic copolymer having a weight average molecular weight of 1 million or more, and (B) a low molecular weight (meth) acrylic (co) polymer 20 having a weight average molecular weight of 30,000 or less. ˜200 parts by weight and (C) 0.005 to 5 parts by weight of a polyfunctional compound having at least two functional groups capable of forming a crosslinked structure in the molecule. ) Polymer functional group] / [Functional group of high molecular weight (meth) acrylic copolymer] A functional group distribution ratio represented by 0 to 15% by weight is proposed. ing.

  Similarly, in order to carry out the method (2) above, Patent Document 3 discloses that 100 parts by weight of a (meth) acrylic acid ester copolymer (a) having a weight average molecular weight of 800,000 to 2,000,000 and a weight average molecular weight of 5 It consists of an acrylic ester copolymer mixture (A) composed of 20 to 100 parts by mass of a (meth) acrylic ester copolymer (b) of not more than 10,000, and a crosslinking agent (B). ) Includes a monomer unit having a functional group highly reactive with the crosslinking agent (B), and the copolymer (b) reacts more than the functional group of the crosslinking agent (B) and the copolymer (a). An optical pressure-sensitive adhesive composition containing a monomer unit having a functional group having low properties has been proposed.

JP 2006-235568 A Japanese Patent No. 3533589 JP 2009-108122 A

  The pressure-sensitive adhesives disclosed in Patent Documents 2 and 3 try to obtain stress relaxation properties by preferentially crosslinking a high molecular weight (meth) acrylic copolymer. However, such an adhesive is inferior in durability, and for example, peeling occurs at the adhesive interface under wet heat conditions. Further, the stress relaxation property is not always sufficient, and light leakage may occur when applied to an optical member such as a polarizing plate. Furthermore, since the adhesive force tends to increase with the lapse of time after application, the reworkability is also insufficient.

  The present invention has been made in view of such a situation, and when applied to an optical member such as a polarizing plate, it has excellent stress relaxation properties and can prevent light leakage, and also has excellent durability. Furthermore, an object is to provide a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet having good reworkability.

In order to achieve the above object, first, the present invention includes a first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000, and a weight average molecular weight of 8,000 to 300,000. An adhesive composition containing a second (meth) acrylic acid ester polymer (B) and a crosslinking agent (C), wherein the first (meth) acrylic acid ester polymer (A) is: As a monomer unit which does not substantially contain an acidic group and constitutes the polymer, a hydroxyl group-containing monomer (a) satisfying the following formula (I) with reactivity with the crosslinking agent (C) is contained, The second (meth) acrylic acid ester polymer (B) does not substantially contain an acidic group, and the reactivity with the crosslinking agent (C) as a monomer unit constituting the polymer is represented by the following formula. Containing a hydroxyl group-containing monomer (b) that satisfies (I) Providing an adhesive composition according to symptoms (invention 1).
Reactivity with crosslinking agent (C): hydroxyl group-containing monomer (a) <hydroxyl group-containing monomer (b) (I)

  The pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the invention (Invention 1) exhibits appropriate cohesive force and excellent stress relaxation properties. By using this pressure-sensitive adhesive with excellent stress relaxation properties, when applied to an optical member such as a polarizing plate, a pressure-sensitive adhesive sheet having both excellent light leakage resistance and durability, and also good reworkability is obtained. It is done. Moreover, since each polymer of the said adhesive composition does not contain an acidic group substantially, when the to-be-adhered body consists of a metal or contains a metal, it can suppress that the said metal corrodes. .

In the above invention (Invention 1),
(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) acrylic acid ester polymer (B) is bonded is the first ( Or less than the number of carbon atoms bonded to the carbon atom to which the hydroxyl group in the hydroxyl group-containing monomer (a) of the (meth) acrylate polymer (A) is bonded (Invention 2),
(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) acrylic acid ester polymer (B) is bonded; The number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded in the hydroxyl group-containing monomer (a) of the (meth) acrylate polymer (A) is the same, and the second (meth) acrylic The number of carbon atoms constituting the side chain during polymer formation contained in the hydroxyl group-containing monomer (b) of the acid ester polymer (B) is the hydroxyl group of the first (meth) acrylate polymer (A). Whether the number of carbon atoms included in the monomer (a) is greater than the number of carbon atoms constituting the side chain during polymer formation (Invention 3)
(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) acrylic acid ester polymer (B) is bonded, and the first ( The number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded in the hydroxyl group-containing monomer (a) of the (meth) acrylate polymer (A) is the same, and the second (meth) The number of carbon atoms constituting the side chain at the time of polymer formation contained in the hydroxyl group-containing monomer (b) of the acrylic ester polymer (B), and the first (meth) acrylic ester polymer (A) In the hydroxyl group-containing monomer (a), the number of carbon atoms constituting the side chain at the time of polymer formation is the same, and the hydroxyl group-containing monomer (B) of the second (meth) acrylate polymer (B) b) A le acid hydroxyalkyl esters, hydroxyl-containing monomer in the first (meth) acrylic acid ester polymer (A) (a) is an acrylic acid hydroxyalkyl ester (Invention 4)
It is preferable.

  In the said invention (invention 1-4), the hydroxyl group contained in the said 2nd (meth) acrylic acid ester polymer (B) with respect to the hydroxyl group contained in the said 1st (meth) acrylic acid ester polymer (A). The molar ratio is preferably 1.0 or more and less than 15 (Invention 5).

  In the said invention (invention 1-5), said 2nd (meth) acrylic acid ester polymer (B) is 10-40 mass% of said hydroxyl-containing monomers (b) as a monomer unit which comprises the said polymer. It is preferable to contain (Invention 6).

  In the said invention (invention 1-6), the ratio of the said 2nd (meth) acrylic acid ester polymer (B) with respect to 100 mass parts of said 1st (meth) acrylic acid ester polymers (A) is 5-5. The amount is preferably 50 parts by mass (Invention 7).

  In the said invention (invention 1-7), said 1st (meth) acrylic acid ester polymer (A) and said 2nd (meth) acrylic acid ester polymer (B) are said crosslinking agents other than a hydroxyl group. It is preferable that the functional group having reactivity with (C) is not substantially contained (Invention 8).

  In the said invention (invention 1-8), it is preferable that the said crosslinking agent (C) is an isocyanate type crosslinking agent (invention 9).

  In the said invention (invention 9), content of the said isocyanate type crosslinking agent is the amount of the said hydroxyl group in which the isocyanate group of the said isocyanate type crosslinking agent is contained in said 2nd (meth) acrylic acid ester polymer (B). The amount is preferably 0.1 to 3.5 equivalents (Invention 10).

  2ndly this invention provides the adhesive formed by bridge | crosslinking the said adhesive composition (invention 1-10) (invention 11).

  Thirdly, the present invention provides a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive (invention 11). Invention 12).

  In the said invention (invention 12), it is preferable that the said base material is an optical member (invention 13).

  Fourthly, the present invention is an adhesive sheet comprising two release sheets and an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets. A layer provides the adhesive sheet characterized by consisting of the said adhesive (invention 11) (invention 14).

  In the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the present invention, the low molecular weight polymer that has been conventionally used as a plasticizer is preferentially cross-linked, so that the low molecular weight polymer is chemically treated. A three-dimensional network structure is formed by a cross-linked structure, and a plurality of high molecular weight polymers are inserted into the three-dimensional network structure to constrain the high molecular weight polymers to each other. It is presumed to form a crosslinked structure. As a result, the obtained pressure-sensitive adhesive exhibits appropriate cohesive force and excellent stress relaxation properties, and can effectively prevent light leakage when applied to an optical member such as a polarizing plate and is durable. In addition, the reworkability is also good. Moreover, since each polymer of the adhesive composition which concerns on this invention does not contain an acidic group substantially, when a to-be-adhered body consists of a metal or contains a metal, it suppresses that the said metal corrodes. be able to.

It is sectional drawing of the adhesive sheet which concerns on the 1st Embodiment of this invention. It is sectional drawing of the adhesive sheet which concerns on the 2nd Embodiment of this invention. It is a figure (color) which shows the evaluation criteria of the light-leakage test (visual observation) in a polarizing plate with an adhesive layer.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition]
The pressure-sensitive adhesive composition according to this embodiment has 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 8000 to 30. It contains tens of second (meth) acrylic acid ester polymer (B) and a crosslinking agent (C), and preferably further contains a silane coupling agent (D). In this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

The first (meth) acrylic acid ester polymer (A) contains substantially no acidic group, and the reactivity with the crosslinking agent (C) as a monomer unit constituting the polymer is represented by the following formula ( A hydroxyl group-containing monomer (a) that satisfies I), the second (meth) acrylic acid ester polymer (B) does not substantially contain an acidic group, and is a monomer unit constituting the polymer. And a hydroxyl group-containing monomer (b) having reactivity with the crosslinking agent (C) satisfying the following formula (I). The hydroxyl group-containing monomer means a monomer having a hydroxyl group in the molecule.
Reactivity with crosslinking agent (C): hydroxyl group-containing monomer (a) <hydroxyl group-containing monomer (b) (I)
That is, the reactivity of the hydroxyl group-containing monomer (b) of the polymer (B) with the crosslinking agent (C) is more than the reactivity of the hydroxyl group-containing monomer (a) of the polymer (A) with the crosslinking agent (C). high.

  Examples of the acidic group include a carboxyl group, and other examples include a sulfonic acid group and a phosphoric acid group. When the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B) contain substantially no acidic group, the adherend is made of metal ( For example, when the adherend is an electrode made of indium tin oxide (ITO) or contains a metal (for example, when the adherend contains a metal mesh), corrosion of the metal can be suppressed. .

  Here, “substantially no acidic group” means that it contains no acidic group at all and a trace amount that does not corrode metals. Specifically, the content of the acidic group-containing monomer as a constituent unit of the polymer (A) or (B) is usually less than 1% by mass, preferably less than 0.5% by mass, particularly preferably. It is less than 0.1% by mass.

  As described above, the second (meth) acrylic acid ester polymer (B) is more reactive with the crosslinking agent (C) than the first (meth) acrylic acid ester polymer (A). By containing a high hydroxyl group-containing monomer, the second (meth) acrylic acid ester polymer (B) (low molecular weight polymer) is preferentially combined with the crosslinking agent (C) when the adhesive composition is crosslinked. It is presumed that it reacts to form a three-dimensional network structure via the crosslinking agent (C). And, in the three-dimensional network structure, two or more molecules of the first (meth) acrylic acid ester polymer (A) (high molecular weight polymer) are not accompanied by a direct chemical bond or with a very small number of chemical bonds. It is presumed that a pseudo-crosslinked structure is formed in which the polymers (A) are inserted and constrained in a state having a certain degree of freedom (the structure thus estimated is hereinafter referred to as “structure”). X "). The first (meth) acrylic acid ester polymer (A) contains a hydroxyl group derived from the hydroxyl group-containing monomer (a) having a relatively low reactivity with the crosslinking agent (C), so that the above three-dimensional network structure is obtained. It is thought that it is inserted well. The pressure-sensitive adhesive having the structure X exhibits appropriate cohesive force and excellent stress relaxation properties. Such an adhesive having excellent stress relaxation properties, when applied to an optical member such as a polarizing plate, is excellent in light leakage resistance, excellent in durability, and does not float or peel even under wet heat conditions. Can be prevented. Furthermore, in the above structure X, there is no uncrosslinked low molecular weight component or the like for imparting stress relaxation properties. Therefore, the low molecular weight component bleed-out, which is a problem with the conventional stress relaxation type pressure-sensitive adhesive, does not occur. As a result, the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition according to this embodiment is also excellent in reworkability.

  The first (meth) acrylic acid ester polymer (A) is a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, a hydroxyl group-containing monomer (a), and a crosslinking agent used as desired. It is preferable that it is a copolymer with (C) and another monomer that does not contain a functional group having reactivity, and the second (meth) acrylic acid ester polymer (B) has an alkyl group having 1 carbon atom. It is a copolymer of ~ 20 (meth) acrylic acid alkyl ester, a hydroxyl group-containing monomer (b), and other monomers that do not contain a functional group reactive with the crosslinking agent (C), which is used as desired. It is preferable.

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

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

  Here, as a combination of a hydroxyl-containing monomer (a) and a hydroxyl-containing monomer (b), the following aspects (i)-(iii) are mentioned, for example.

  (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) acrylic acid ester polymer (B) is bonded is the first (meth) This is a case where the number of carbon atoms bonded to the carbon atom bonded to the hydroxyl group in the hydroxyl group-containing monomer (a) of the acrylic ester polymer (A) is smaller. This is because the smaller the number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded, the higher the nucleophilicity of the hydroxyl group and the lower the steric hindrance, the higher the hydroxyl group reactivity. Therefore, the number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded is a preferential judgment criterion regarding the reactivity with the crosslinking agent (C).

  For example, the hydroxyl group-containing monomer (a) is a secondary hydroxyl group monomer, and the hydroxyl group-containing monomer (b) is a primary hydroxyl group monomer. Specifically, the hydroxyl group-containing monomer (a) is 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, or 3-hydroxybutyl (meth) acrylate, and a hydroxyl group-containing monomer ( In this case, b) is 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, or 4-hydroxybutyl (meth) acrylate.

  (Ii) the number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded in the hydroxyl group-containing monomer (b) of the second (meth) acrylic acid ester polymer (B), and the first (meth) The number of carbon atoms bonded to the carbon atom bonded to the hydroxyl group in the hydroxyl group-containing monomer (a) of the acrylate polymer (A) is the same, and the second (meth) acrylate weight The hydroxyl group-containing monomer (a) of the first (meth) acrylate polymer (A) is included in the hydroxyl group-containing monomer (b) of the coalescence (B), and the number of carbon atoms constituting the side chain at the time of polymer formation is ), Which is larger than the number of carbon atoms constituting the side chain during polymer formation. If the number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded is the same, the number of carbon atoms constituting the side chain at the time of polymer formation in the monomer is larger from the main chain. Because the steric hindrance is small, the degree of freedom is high and the reactivity is high.

  For example, the hydroxyl group-containing monomer (a) and the hydroxyl group-containing monomer (b) are both primary hydroxyl group monomers, and the hydroxyl group-containing monomer (a) has two carbon atoms constituting the side chain at the time of polymer formation. Yes, this is the case when the number of carbon atoms constituting the side chain of the hydroxyl group-containing monomer (b) when the polymer is formed is 3 or 4. For example, in the case of (meth) acrylic acid hydroxyalkyl ester, “the side chain is formed at the time of polymer formation” corresponds to the portion “the side chain is formed at the time of polymer formation”. The “number of carbon atoms” refers to the number of carbon atoms connected from the carbon atom to which the hydroxyl group is bonded to the atom constituting the main chain at the time of polymer formation, and the carbon of the branched chain portion in the side chain. The number is not counted. For example, the number of carbon atoms in 2-hydroxypropyl acrylate is two.

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

  (Iii) the number of carbon atoms bonded to the carbon atom bonded to the hydroxyl group in the hydroxyl group-containing monomer (b) of the second (meth) acrylic ester polymer (B), and the first (meth) The number of carbon atoms bonded to the carbon atom bonded to the hydroxyl group in the hydroxyl group-containing monomer (a) of the acrylate polymer (A) is the same, and the second (meth) acrylic acid The hydroxyl group-containing monomer (b) of the ester polymer (B) contains the number of carbon atoms constituting the side chain at the time of polymer formation and the hydroxyl group content of the first (meth) acrylic ester polymer (A). The monomer (a) has the same number of carbon atoms constituting the side chain during the formation of the polymer, and the hydroxyl group-containing monomer (b) of the second (meth) acrylic acid ester polymer (B) Hydroxy methacrylate Alkyl esters, hydroxyl group-containing monomer of the first (meth) acrylic acid ester polymer (A) (a) is a case of acrylic acid hydroxyalkyl esters. If the number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded is the same, and the number of carbon atoms constituting the side chain at the time of polymer formation is also the same, compared with the hydroxyalkyl ester of acrylic acid. This is because the methacrylic acid hydroxyalkyl ester has a rigid and linear main chain, which exposes the hydroxyl group and easily reacts with the crosslinking agent (C).

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

  Here, the molar ratio of the hydroxyl group contained in the second (meth) acrylate polymer (B) to the hydroxyl group contained in the first (meth) acrylate polymer (A) in the adhesive composition is 1.0 or more and preferably less than 15, particularly preferably 2 to 10, and more preferably 2 to 8.

  Thus, the amount of hydroxyl groups contained in the second (meth) acrylic acid ester polymer (B) is greater than or equal to the amount of hydroxyl groups contained in the first (meth) acrylic acid ester polymer (A) (molar ratio is 1.0 or more), when the adhesive composition according to this embodiment is crosslinked, the second (meth) acrylic acid ester polymer (B) and the crosslinking agent (C) are preferential. It is presumed that the reaction proceeds more effectively and the structure X is well formed. On the other hand, the amount of hydroxyl groups contained in the second (meth) acrylic acid ester polymer (B) is larger than the amount of hydroxyl groups contained in the first (meth) acrylic acid ester polymer (A) (molar ratio is 15 or more), the second (meth) acrylic acid ester polymer (B) is excessively cross-linked, and there is a risk that the stress relaxation property may be lowered. Durability under wet heat conditions may be inferior.

  The second (meth) acrylic acid ester polymer (B) preferably contains 10 to 40% by mass of the hydroxyl group-containing monomer (b) as a monomer unit constituting the polymer, particularly 10 to 30% by mass. It is preferable to contain, Furthermore, it is preferable to contain 10-20 mass%. By containing the hydroxyl group-containing monomer (b) in the above range, the degree of crosslinking of the second (meth) acrylic acid ester polymer (B) becomes preferable, and the first (meth) acrylic acid ester polymer (A )), The stress relaxation property of the obtained pressure-sensitive adhesive can be improved more effectively. When the content of the hydroxyl group-containing monomer (b) is less than 10% by mass, the second (meth) acrylic acid ester polymer (B) is not sufficiently cross-linked, and the gel fraction is low, thereby reducing the durability. There is a fear. On the other hand, when the content of the hydroxyl group-containing monomer (b) exceeds 40% by mass, the second (meth) acrylic acid ester polymer (B) is excessively cross-linked, and the stress relaxation property may be lowered. Further, the residual hydroxyl group after crosslinking may result in poor durability particularly under wet heat conditions. Moreover, the light leakage resistance of the adhesive sheet obtained becomes more excellent by making the upper limit of content of a hydroxyl-containing monomer (b) into 30 mass%.

  In addition, the preferable content of the hydroxyl group-containing monomer in the first (meth) acrylic acid ester polymer (A) is the content of the hydroxyl group-containing monomer in the second (meth) acrylic acid ester polymer (B) and the above-described content. It is naturally determined from the molar ratio of the hydroxyl group.

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

  Among the above-mentioned other monomers, (meth) acrylic acid ester having a non-crosslinking tertiary amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate In particular, since the N, N-dimethylaminoethyl (meth) acrylate has a catalytic effect of promoting the reaction between the hydroxyl group in the polymer and the crosslinking agent (C), the second (meth) acrylic acid ester polymer In (B), it may be contained as a monomer unit constituting the polymer.

  In this case, the content of the (meth) acrylic acid ester having a non-crosslinkable tertiary amino group in the second (meth) acrylic acid ester polymer (B) is 0.01 to 1% by mass. It is preferable that it is 0.1 to 0.5 mass% especially.

  Here, in order to reliably form the structure X, the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B), in addition to the hydroxyl group, It is preferable that the functional group having reactivity with the crosslinking agent (C) is not substantially contained. Examples of such functional groups include crosslinkable primary amino groups or secondary amino groups. Examples of monomers containing such functional groups include aminoethyl (meth) acrylate and (meth) acrylic acid n. -Amino group-containing monomers such as butylaminoethyl.

  “Substantially no functional group having reactivity with the crosslinking agent (C)” means that the functional group does not contain the functional group at all, and does not interfere with the reactivity between the hydroxyl group and the crosslinking agent (C). It is allowed to contain a group. Specifically, in each polymer (A) and (B), the molar ratio of the functional group to the hydroxyl group is preferably 0.2 or less, particularly preferably 0.1 or less.

  The polymerization mode of the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B) may be a random copolymer or a block copolymer, respectively. It may be.

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

  The first (meth) acrylic acid ester polymer (A) has a weight average molecular weight within the above range, and the polymer (A) has a relatively large molecular weight, so that the structure X is favorably formed. It is estimated to be.

  When the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) is less than 500,000, the gel fraction of the resulting pressure-sensitive adhesive may be low, and the durability and reworkability may be deteriorated. . Moreover, when the weight average molecular weight of the first (meth) acrylic acid ester polymer (A) exceeds 3 million, the compatibility with the second (meth) acrylic acid ester polymer (B) and the like deteriorates. There exists a possibility that the stress relaxation property of the adhesive obtained may fall.

  On the other hand, the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is 8000 to 300,000, preferably 10,000 to 200,000, and particularly preferably 50,000 to 100,000. That is, the second (meth) acrylic acid ester polymer (B) is a low molecular weight polymer component.

  When the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is within the above range, a three-dimensional network structure peculiar to the pressure-sensitive adhesive composition according to this embodiment is formed, and excellent stress is obtained. This will contribute to relaxation. That is, when the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) is less than 8000, a good three-dimensional network structure cannot be obtained. On the other hand, when the weight average molecular weight of the second (meth) acrylic acid ester polymer (B) exceeds 300,000, the compatibility with the first (meth) acrylic acid ester polymer (A) and the like decreases, Insertion of the polymer (A) into the three-dimensional network structure formed by the polymer (B) becomes insufficient, and as a result, the resulting pressure-sensitive adhesive may be inferior in durability and reworkability. .

  In the present embodiment, each of the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B) may be used alone. Two or more kinds may be used in combination.

  The ratio of the second (meth) acrylic acid ester polymer (B) to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is preferably 5 to 50 parts by mass, particularly 5 to 5 parts by mass. The amount is preferably 40 parts by mass, and more preferably 10 to 30 parts by mass.

  The pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition containing the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B) in the above proportion has the structure X described above. It is estimated that it forms well.

  Examples of the crosslinking agent (C) include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, etc. Among them, the reaction with the hydroxyl groups of the polymers (A) and (B) An isocyanate-based crosslinking agent having excellent properties is preferred.

  The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and the like. , And their biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil.

  The said crosslinking agent (C) can be used individually by 1 type or in combination of 2 or more types.

  The content of the crosslinking agent (C) is usually relative to the amount of hydroxyl groups of the second (meth) acrylic acid ester polymer (B) in which the crosslinkable group (for example, isocyanate group) of the crosslinking agent (C). The amount is 0.05 to 5 equivalents, preferably 0.1 to 3.5 equivalents, and particularly preferably 0.3 to 1.0 equivalents. When the amount of the crosslinkable group is less than 0.05 equivalent, the gel fraction of the obtained pressure-sensitive adhesive is low, and there is a possibility that sufficient cohesive force cannot be exhibited. Further, when the amount of the crosslinkable group is 0.1 equivalent or more, particularly 0.3 equivalent or more, the obtained pressure-sensitive adhesive can be made more excellent in durability. On the other hand, if the amount of the crosslinkable group is 3.5 equivalents or less, the resulting pressure-sensitive adhesive can be made excellent in reworkability. Furthermore, if 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) is effective. It is estimated that this can be prevented. As a result, the obtained pressure-sensitive adhesive has excellent stress relaxation properties.

  The adhesive composition according to this embodiment preferably further contains a silane coupling agent (D). When this silane coupling agent (D) is contained, the alkoxysilyl group of the silane coupling agent (D) acts on the adherend surface such as a glass substrate, and thus, for example, when a polarizing plate is bonded to a liquid crystal glass cell or the like. In addition, the adhesion between the pressure-sensitive adhesive and the liquid crystal glass cell becomes better.

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

  Specific examples of the silane coupling agent (D) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, Silicon compounds having an epoxy structure such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- Examples include amino group-containing silicon compounds such as (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatopropyltriethoxysilane. These may be used individually by 1 type and may be used in combination of 2 or more type.

  In the above-mentioned adhesive composition, various additives usually used in acrylic adhesives, for example, antistatic agents, tackifiers, antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillings, if desired An agent, a refractive index adjusting agent, etc. can be added.

[Method for producing adhesive composition]
The said adhesive composition manufactures each of the 1st (meth) acrylic acid ester polymer (A) and the 2nd (meth) acrylic acid ester polymer (B), mixes them, and is arbitrary. It can be produced by adding a crosslinking agent (C) and, if desired, a silane coupling agent (D) at the stage.

  As a preferred specific example, the (meth) acrylic acid ester polymers (A) and (B) are separately produced by a normal radical polymerization method. The polymerization of the (meth) acrylic acid ester polymers (A) and (B) can be carried out by a solution polymerization method or the like using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like. Two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more kinds may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2′-azobis (2-methylpropionate) 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-hydroxymethylpropionitrile), 2,2′-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

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

  In addition, in the said superposition | polymerization process, the weight average molecular weight of the polymer obtained can be adjusted by mix | blending chain transfer agents, such as 2-mercaptoethanol.

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

  Examples of the dilution solvent for diluting the adhesive composition to form a coating solution include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane, aromatic hydrocarbons such as toluene and xylene, methylene chloride, and ethylene chloride. Halogenated hydrocarbons, alcohols such as methanol, ethanol, propanol, butanol and 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethyl cellosolve A cellosolve solvent such as is used.

  The concentration / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of an adhesive composition may be 10-40 mass%. In addition, when obtaining an application | coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with an adhesive composition, it is not necessary to add a dilution solvent. In this case, the adhesive composition becomes the coating solution as it is.

[Adhesive]
The pressure-sensitive adhesive according to this embodiment is obtained by crosslinking the pressure-sensitive adhesive composition. Crosslinking of the pressure-sensitive adhesive composition can be performed by heat treatment. In addition, this heat processing can also serve as the drying process at the time of volatilizing the dilution solvent etc. of an adhesive composition.

  When performing heat processing, it is preferable that heating temperature is 50-150 degreeC, and it is especially preferable that it is 70-120 degreeC. The heating time is preferably 30 seconds to 3 minutes, particularly preferably 50 seconds to 2 minutes. Furthermore, it is particularly preferable to provide a curing period of about 1 to 2 weeks at room temperature (for example, 23 ° C., 50% RH) after the heat treatment.

  By the heat treatment (and curing), the second (meth) acrylate polymer (B) is crosslinked by the crosslinking agent (C), and the first (meth) acrylate ester is added to the three-dimensional network structure. It is presumed that the polymer (A) is inserted and the structure X is formed.

  The pressure-sensitive adhesive according to this embodiment preferably has an adhesive strength with respect to alkali-free glass of 0.1 to 15 N / 25 mm, and particularly preferably 1 to 10 N / 25 mm. In addition, adhesive force here refers to 180 degree peeling adhesive force (peeling speed 300 mm / min) according to JIS Z0237, and after applying and applying to 0.5MPa and 50 degreeC for 20 minutes, to a to-be-adhered body, It shall be measured after being left for 24 hours under conditions of 23 ° C. and 50% RH. When the adhesive force is within the above range, it is possible to prevent floating or peeling when applied to an optical member such as a polarizing plate.

  The pressure-sensitive adhesive according to this embodiment has an adhesive strength (adhesive strength after 14 days after application) of 0.1 days after being left on the adherend for 14 days under conditions of 23 ° C. and 50% RH. It is preferably ˜25 N / 25 mm, particularly preferably 2 to 20 N / 25 mm. As described above, the pressure-sensitive adhesive according to this embodiment can be evaluated as having excellent reworkability by suppressing the increase in the adhesive strength with time.

  The pressure-sensitive adhesive described above can be preferably used for an optical member. For example, an adhesive between optical members such as a polarizing plate (polarizing film) and a retardation plate (retarding film), or a polarizing plate (polarizing film) It is suitable for adhesion between a retardation plate (retardation film) and a glass substrate. The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive according to the present embodiment is very excellent in stress relaxation properties. Therefore, even when the dimensional change of the adherend is large, the pressure-sensitive adhesive layer generates stress that can be generated by the dimensional change. Therefore, it becomes difficult to peel off from the adherend over a long period of time, and light leakage can be effectively prevented when used in the optical member as described above. That is, the pressure-sensitive adhesive according to this embodiment achieves both light leakage resistance and durability. Furthermore, since the pressure-sensitive adhesive according to the present embodiment has good reworkability and is acid-free, it has excellent corrosion resistance when the adherend is made of metal or contains metal.

[Adhesive sheet]
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 </ b> A according to the first embodiment is laminated on the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 stacked on the release surface of the release sheet 12, and the pressure-sensitive adhesive layer 11. And the formed base material 13.

  In addition, as shown in FIG. 2, the adhesive sheet 1B according to the second embodiment includes the two release sheets 12a and 12b and the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. And the pressure-sensitive adhesive layer 11 sandwiched between the release sheets 12a and 12b. In addition, the release surface of the release sheet in this specification refers to a surface having peelability in the release sheet, and includes both a surface that has been subjected to a release treatment and a surface that exhibits peelability without being subjected to a release treatment. .

  In any of the pressure-sensitive adhesive sheets 1A and 1B, the pressure-sensitive adhesive layer 11 is made of a pressure-sensitive adhesive formed by crosslinking the above-described pressure-sensitive adhesive composition.

  The thickness of the pressure-sensitive adhesive layer 11 is appropriately determined according to the purpose of use of the pressure-sensitive adhesive sheets 1A and 1B, but is usually in the range of 5 to 100 μm, preferably 10 to 60 μm, for example, for optical members, particularly for polarizing plates. When used as a PSA layer, it is preferably 10 to 50 μm, particularly preferably 10 to 30 μm.

  There is no restriction | limiting in particular as the base material 13, What was used as a base material sheet of a normal adhesive sheet can be used. For example, in addition to desired optical members, woven or non-woven fabrics using fibers such as rayon, acrylic, polyester, etc .; papers such as fine paper, glassine paper, impregnated paper, coated paper; metal foils such as aluminum and copper; urethane Foam, foam such as polyethylene foam; polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyurethane film, polyethylene film, polypropylene film, cellulose film such as triacetylcellulose, polyvinyl chloride film, polychlorinated Vinylidene film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin resin Plastic films such as Irumu; and the like of two or more kinds of those laminates. The plastic film may be uniaxially stretched or biaxially stretched.

  Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation plate (retarding film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, and a transflective film. Etc. Among these, since the polarizing plate (polarizing film) easily shrinks and has a large dimensional change, it is suitable as a target for forming the pressure-sensitive adhesive of the present embodiment (the pressure-sensitive adhesive layer 11) from the viewpoint of light leakage resistance.

  Although the thickness of the base material 13 changes with kinds, for example in the case of an optical member, they are 10 micrometers-500 micrometers normally, Preferably they are 50 micrometers-300 micrometers.

  As the release sheets 12, 12a, 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, Polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film A fluororesin film or the like is used. These crosslinked films are also used. Furthermore, these laminated films may be sufficient.

  The release surface of the release sheet (particularly the surface in contact with the pressure-sensitive adhesive layer 11) is preferably subjected to a release treatment. Examples of the release agent used for the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax release agents.

  Although there is no restriction | limiting in particular about the thickness of the peeling sheets 12, 12a, 12b, Usually, it is about 20-150 micrometers.

In order to manufacture the pressure-sensitive adhesive sheet 1A, a solution (coating solution) containing the pressure-sensitive adhesive composition is applied to the release surface of the release sheet 12, and heat treatment is performed to form the pressure-sensitive adhesive layer 11. A base material 13 is laminated on the agent layer 11. Then, it is preferable to provide a curing period.
In addition, about the conditions of heat processing and curing, it is as having mentioned above.

  Moreover, in order to manufacture the said adhesive sheet 1B, the coating solution containing the said adhesive composition is apply | coated to the peeling surface of one peeling sheet 12a (or 12b), heat processing is performed, and the adhesive layer 11 is formed. After that, the release surface of the other release sheet 12b (or 12a) is overlaid on the adhesive layer 11.

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

  Here, for example, to manufacture a liquid crystal display device composed of a liquid crystal cell and a polarizing plate, a polarizing plate is used as the base material 13 of the pressure-sensitive adhesive sheet 1A, and the release sheet 12 of the pressure-sensitive adhesive sheet 1A is peeled off. What is necessary is just to bond the exposed adhesive layer 11 and a liquid crystal cell.

  For example, in order to manufacture a liquid crystal display device in which a retardation plate is disposed between a liquid crystal cell and a polarizing plate, as an example, first, one release sheet 12a (or 12b) of the adhesive sheet 1B is released. Then, the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1B and the phase difference plate are bonded together. Next, the release sheet 12 of the pressure-sensitive adhesive sheet 1A using a polarizing plate as the base material 13 is peeled off, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet 1A and the retardation plate are bonded. Furthermore, the other release sheet 12b (or 12a) is peeled from the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet B, and the pressure-sensitive adhesive layer 11 exposed from the pressure-sensitive adhesive sheet B is bonded to the liquid crystal cell.

  According to the above pressure-sensitive adhesive sheets 1A and 1B, since the pressure-sensitive adhesive layer 11 is very excellent in stress relaxation properties, even when applied to adhesion of a polarizing plate, for example, the stress that can be generated by deformation of the polarizing plate is generated in the pressure-sensitive adhesive layer 11. It can be assumed that excellent light leakage resistance and high durability can be exhibited.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

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

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention further more concretely, the scope of the present invention is not limited to these Examples etc.

[Example 1]
1. Preparation of polymer (A) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introduction tube, 99.0 parts by mass of n-butyl acrylate, 1.0 mass of 2-hydroxyethyl acrylate Part, 200 parts by mass of ethyl acetate, and 0.08 part by mass of 2,2′-azobisisobutyronitrile were charged, and the air in the reaction vessel was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 60 ° C., reacted for 16 hours, and then cooled to room temperature. Here, the molecular weight of a part of the obtained solution was measured by the method described later, and the production of a polymer (A) having a weight average molecular weight of 1,570,000 was confirmed.

2. Preparation of polymer (B) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introduction tube, 81.4 parts by mass of n-butyl acrylate, 18.6 masses of 4-hydroxybutyl acrylate Part, 200 parts by mass of ethyl acetate, 0.16 parts by mass of 2,2′-azobisisobutyronitrile, and 0.3 parts by mass of 2-mercaptomethanol were charged, and the air in the reaction vessel was replaced with nitrogen gas. . While stirring in this nitrogen atmosphere, the reaction solution was heated to 70 ° C., reacted for 6 hours, and then cooled to room temperature. Here, a molecular weight of a part of the obtained solution was measured by a method described later, and production of a polymer (B) having a weight average molecular weight of 60,000 was confirmed.

3. Preparation of adhesive composition 100 parts by mass (solid content converted value) of the polymer (A) obtained in the step (1) and 20 parts by mass (solid) of the polymer (B) obtained in the step (2) And a trimethylolpropane xylene diisocyanate adduct (trade name, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) in an amount corresponding to 0.6 equivalent of the hydroxyl group of the polymer (B) as a crosslinking agent (C). "Takenate D-110N") 3.0 parts by weight was added. Finally, by adding 0.3 parts by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM403”) as the silane coupling agent (D), and sufficiently stirring, A diluted solution of the adhesive composition was obtained.

  From the ratio of the blended monomers, the amount of hydroxyl group (H [OH]) in 100 g of polymer (A) is 8.62 mmol, and the amount of hydroxyl group (L [OH]) in 20 g of polymer (B) is 25. Calculated as .84 mmol. Accordingly, the ratio of the number of moles of hydroxyl group in 20 parts by mass of the polymer (B) to the number of moles of hydroxyl group in 100 parts by weight of the polymer (A) (L [OH] / H [OH]) is 3.00. .

Here, Table 1 shows the composition of the adhesive composition. Details of the abbreviations and the like described in Table 1 are as follows.
[Polymers (A) and (B)]
BA: n-butyl acrylate AA: acrylic acid DM: N, N-dimethylaminoethyl methacrylate HEA: 2-hydroxyethyl acrylate HEMA: 2-hydroxyethyl methacrylate 2HPA: 2-hydroxypropyl acrylate 4HBA: acrylic acid 4-hydroxybutyl H [OH] (mmol): number of moles of hydroxyl group calculated by adding the amount of polymer (A) (part by mass) as (g) L [OH] (mmol): amount of polymer (B) added ( Number of moles of hydroxyl group calculated with (part by mass) as (g)
[Isocyanate-based crosslinking agent (C)]
XDI-TMP: xylene diisocyanate adduct of trimethylolpropane (trade name “Takenate D-110N” manufactured by Mitsui Chemicals Polyurethanes)
[Silane coupling agent (D)]
KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM403”)

  After drying the diluted solution of the obtained adhesive composition on the release-treated surface of a release sheet (SP-PET3811, thickness: 38 μm, manufactured by Lintec Co., Ltd.) obtained by releasing one side of a polyethylene terephthalate film with a silicone-based release agent After coating with a knife coater so that the thickness of the adhesive layer became 25 μm, a pressure-sensitive adhesive layer was formed by heat treatment at 90 ° C. for 1 minute.

  Next, a polarizing plate composed of a polarizing film with a discotic liquid crystal layer, and a polarizing plate in which a polarizing film and a viewing angle widening film are integrated, are bonded so that the exposed surface of the adhesive layer and the surface of the discotic liquid crystal layer are in contact with each other. A polarizing plate with an adhesive layer was obtained by curing for 7 days at 23 ° C. and 50% RH.

[Examples 2 to 11, Comparative Examples 1 to 3]
As shown in Table 1, the types and ratios of the respective monomers constituting the adhesive composition, the types and blending amounts of the crosslinking agent and the silane coupling agent, and the blending ratio of the polymer (A) and the polymer (B) are shown. A polarizing plate with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1 except for changing.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-reduced weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
GPC measurement device: manufactured by Tosoh Corporation, HLC-8020
GPC column (passed in the following order): TSK guard column HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (× 2)
TSK gel G2000HXL
・ Measurement solvent: Tetrahydrofuran ・ Measurement temperature: 40 ° C.

[Test Example 1] (Light leakage test)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was adjusted to a size of 233 mm × 309 mm using a cutting device (Super cutter manufactured by Hadano Seisakusho, PN1-600). The release sheet was peeled off and attached to alkali-free glass (Corning Corp., Eagle XG) through the exposed adhesive layer, and then pressurized at 0.5 MPa and 50 ° C. for 20 minutes in an autoclave manufactured by Kurihara Seisakusho. In addition, the said bonding was performed on the front and back of non-alkali glass so that the polarizing axis may be in a crossed nicols state (polarizing axis: ∠45 °, ∠135 °). In this state, it was allowed to stand for 250 hours in an 80 ° C. dry environment, and then left for 2 hours in an environment of 23 ° C. and 50% RH. Using this as a sample, light leakage was evaluated by the following method. The results are shown in Table 2.

<Evaluation of light leakage: visual inspection>
The sample was placed on a flat illuminator (Dentsu Sangyo Co., Ltd., HF-SL-A312LC, illuminance: 26,000 Lux, luminance: 10,000 cd), and a two-dimensional color luminance meter (Konica Minolta, CA-2000). ) And converted into a luminance distribution image by analysis software (Konica Minolta, CA-S20w). The luminance distribution image of the obtained sample was evaluated based on the evaluation criteria shown in FIG.

[Test Example 2] (Durability evaluation)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was adjusted to a size of 233 mm × 309 mm using a cutting device (Super cutter manufactured by Hadano Seisakusho, PN1-600). The release sheet was peeled off and attached to alkali-free glass (Corning Corp., Eagle XG) through the exposed adhesive layer, and then pressurized at 0.5 MPa and 50 ° C. for 20 minutes in an autoclave manufactured by Kurihara Seisakusho.

Then, it put into the environment of the following durable conditions, and observed using the 10 time magnifier 500 hours later. Appearance change was based on the following. The results are shown in Table 2.
A: No defects on 4 sides. O: No defects on the sides of 0.6 mm or more from the outer peripheral edge on 4 sides. X: 0.6 mm or more from the outer edge on at least one side of the four sides. There are abnormal appearance defects of adhesives of 0.1 mm or more such as floating, peeling, foaming, streaks, etc. <durability conditions>
・ 60 ℃, relative humidity 90% RH

[Test Example 3] (Reworkability evaluation)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was cut to prepare samples having a width of 25 mm and a length of 100 mm. After peeling the release sheet from this sample and pasting the sample on alkali-free glass (Corning, Eagle XG) through the exposed adhesive layer, 0.5 MPa at 50 ° C. in an autoclave manufactured by Kurihara Seisakusho, Pressurized for 20 minutes. Subsequently, it was left to stand for 48 hours under the condition of 50 ° C. dry, and conditioned for 3 hours under the 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 alkali-free glass was visually evaluated. Evaluation was performed based on the following. The results are shown in Table 2.
○: No glass stains / adhesive residue left △: Slight glass stains / adhesive residue remaining ×: Significant glass stain / adhesive residue remaining

[Test Example 4] (Evaluation of corrosion resistance)
The release sheet of the polarizing plate with the pressure-sensitive adhesive layer obtained in Examples or Comparative Examples was peeled off and bonded to a copper foil (thickness: 80 μm), and then stored in an atmosphere of 60 ° C. and 90% RH for 500 hours. . Then, the polarizing plate with an adhesive layer was peeled off from the copper foil, and the exposed surface of the copper foil was visually observed to confirm the presence or absence of corrosion. The results are shown in Table 2.
○: No corrosion ×: Corrosion

[Test Example 5] (Evaluation of haze value)
A structure (a structure before applying a polarizing plate) composed of a release sheet / adhesive layer (thickness: 25 μm) obtained in the production process of Examples or Comparative Examples was prepared. A measurement sample was prepared by bonding the surface of the pressure-sensitive adhesive layer exposed from this structure and soda lime glass (haze value 0%) and peeling off the release sheet.

  About the said measurement sample, the haze value (%) (it may abbreviate as Hz (%)) was measured according to JISK7105 using the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH2000). In addition, the range of the preferable haze value was 0 to 3%, and the thing in the said range evaluated as (circle) and the thing outside the said range as x. The results are shown in Table 2.

  As is clear from Table 2, in the polarizing plate with the pressure-sensitive adhesive layer obtained in the examples, both the light leakage resistance and the durability are excellent, and the reworkability, the corrosion resistance, and the optical characteristics are all good. Met.

  The pressure-sensitive adhesive composition and pressure-sensitive adhesive of the present invention are suitable for adhesion of optical members such as polarizing plates and retardation plates, and the pressure-sensitive adhesive sheet of the present invention is for optical members such as polarizing plates and phase difference plates. Suitable as an adhesive sheet.

1A, 1B ... Adhesive sheet 11 ... Adhesive layer 12, 12a, 12b ... Release sheet 13 ... Base material

Claims (13)

A first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000,
A second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 300,000,
A pressure-sensitive adhesive composition containing a crosslinking agent (C),
The first (meth) acrylic acid ester polymer (A) is , as a monomer unit constituting the polymer, a hydroxyl group-containing monomer (a) whose reactivity with the crosslinking agent (C) satisfies the following formula (I) ) And the content of the acidic group-containing monomer is less than 1% by mass,
The second (meth) acrylic acid ester polymer (B) is , as a monomer unit constituting the polymer, a hydroxyl group-containing monomer (b) whose reactivity with the crosslinking agent (C) satisfies the following formula (I) ) In an amount of 10 to 40% by mass , and the content of the acidic group-containing monomer is less than 1% by mass .
Reactivity with crosslinking agent (C): hydroxyl group-containing monomer (a) <hydroxyl group-containing monomer (b) (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) acrylic acid ester polymer (B) is bonded is the number of the first (meth) acrylic. The pressure-sensitive adhesive composition according to claim 1, wherein the number of carbon atoms bonded to the carbon atom to which the hydroxyl group in the hydroxyl group-containing monomer (a) of the acid ester polymer (A) is bonded is smaller. . 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) acrylic acid ester polymer (B) is bonded, and the first (meth) acrylic The number of carbon atoms bonded to the carbon atom to which the hydroxyl group is bonded in the hydroxyl group-containing monomer (a) of the acid ester polymer (A) is the same, and the second (meth) acrylic acid ester weight The number of carbon atoms constituting the side chain at the time of polymer formation contained in the hydroxyl group-containing monomer (b) of the coalescence (B) is the hydroxyl group-containing monomer (A) of the first (meth) acrylate polymer (A). The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is more than the number of carbon atoms constituting the side chain during the formation of the polymer contained in a). A first (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 500,000 to 3,000,000,
A second (meth) acrylic acid ester polymer (B) having a weight average molecular weight of 8000 to 300,000,
With a cross-linking agent (C)
An adhesive composition containing
The first (meth) acrylic acid ester polymer (A) is, as a monomer unit constituting the polymer, a hydroxyl group-containing monomer (a) whose reactivity with the crosslinking agent (C) satisfies the following formula (I) ) And the content of the acidic group-containing monomer is less than 1% by mass,
The second (meth) acrylic acid ester polymer (B) is, as a monomer unit constituting the polymer, a hydroxyl group-containing monomer (b) whose reactivity with the crosslinking agent (C) satisfies the following formula (I) ) And the content of the acidic group-containing monomer is less than 1% by mass,
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) acrylic acid ester polymer (B) is bonded, and the first (meth) acrylic The number of carbon atoms bonded to the carbon atom bonded to the hydroxyl group in the hydroxyl group-containing monomer (a) of the acid ester polymer (A) is the same, and the second (meth) acrylic acid ester The number of carbon atoms constituting the side chain during the formation of the polymer and the hydroxyl group-containing monomer of the first (meth) acrylate polymer (A) contained in the hydroxyl group-containing monomer (b) of the polymer (B) The hydroxyl group-containing monomer (b) of the second (meth) acrylic acid ester polymer (B) is the same as the number of carbon atoms constituting the side chain contained in (a) when forming the polymer. , Methacrylic acid It is hydroxyalkyl ester, The hydroxyl-containing monomer (a) of said 1st (meth) acrylic acid ester polymer (A) is acrylic acid hydroxyalkyl ester, The adhesive composition characterized by the above-mentioned.
Reactivity with crosslinking agent (C): hydroxyl group-containing monomer (a) <hydroxyl group-containing monomer (b) (I)   The molar ratio of the hydroxyl group contained in the second (meth) acrylate polymer (B) to the hydroxyl group contained in the first (meth) acrylate polymer (A) is 1.0 or more, 15 It is less than, The adhesive composition as described in any one of Claims 1-4 characterized by the above-mentioned. The ratio of the second (meth) acrylic acid ester polymer (B) to 100 parts by mass of the first (meth) acrylic acid ester polymer (A) is 5 to 50 parts by mass. The pressure-sensitive adhesive composition according to any one of claims 1 to 5 . In the first (meth) acrylic acid ester polymer (A) and the second (meth) acrylic acid ester polymer (B), the functional group having the crosslinking agent other than a hydroxyl group (C) and reactive the molar ratio for the hydroxyl group, the adhesive composition according to any one of claims 1 to 6, characterized in that not more than 0.2. The crosslinking agent (C), the adhesive composition according to any one of claims 1 to 7, characterized in that an isocyanate-based crosslinking agent. The content of the isocyanate-based crosslinking agent is 0.1-3. With respect to the amount of the hydroxyl group in which the isocyanate group of the isocyanate-based crosslinking agent is contained in the second (meth) acrylic acid ester polymer (B). The pressure-sensitive adhesive composition according to claim 8 , wherein the amount is 5 equivalents. Adhesive obtained by crosslinking the adhesive composition according to any one of claims 1-9. A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer,
The said adhesive layer consists of an adhesive of Claim 10 , The adhesive sheet characterized by the above-mentioned. The pressure-sensitive adhesive sheet according to claim 11 , wherein the base material is an optical member. Two release sheets,
An adhesive sheet comprising an adhesive layer sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets,
The said adhesive layer consists of an adhesive of Claim 10 , The adhesive sheet characterized by the above-mentioned.

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