JP5595034B2 - Adhesive composition, adhesive and adhesive sheet - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition, a method for producing 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 is particularly suitable for optical members such as polarizing plates. The present invention relates to an adhesive composition, a method for producing an adhesive composition, an adhesive, and 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 or the like. 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. However, conventionally, when it was attempted to form such an adhesive layer having excellent stress relaxation properties, it was necessary to extremely reduce the crosslinking density in the adhesive layer. If it does so, there existed a problem that the intensity | strength of adhesive layer itself fell and durability deteriorated.

  Therefore, in Patent Documents 2 to 4, the pressure-sensitive adhesive composition obtained by adding a plasticizer, liquid paraffin, urethane elastomer or the like to the acrylic pressure-sensitive adhesive instead of extremely reducing the cross-linking density of the pressure-sensitive adhesive layer is moderate. The pressure-sensitive adhesive layer is imparted with stress relaxation properties, thereby obtaining light leakage resistance and durability.

JP 2006-235568 A Japanese Patent Laid-Open No. 5-45517 Japanese Patent Laid-Open No. 9-137143 JP 2005-194366 A

  However, the pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition to which a plasticizer or liquid paraffin is added has various problems such as the plasticizer and liquid paraffin bleed out over time and the liquid crystal cell is contaminated. It was happening. In addition, in the pressure-sensitive adhesive composition to which urethane elastomer is added, since the amount of urethane elastomer added is limited from the viewpoint of compatibility with other components, the improvement of stress relaxation is insufficient, and acrylic Depending on the compatibility between the adhesive and the urethane elastomer, problems such as white turbidity have occurred. As described above, it has been difficult for the conventional technology to fundamentally improve the light leakage resistance and durability of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for optical members.

  The present invention has been made in view of such a situation, and when applied to an optical member such as a polarizing plate, the pressure-sensitive adhesive composition excellent in both light leakage resistance and durability, the pressure-sensitive adhesive composition It aims at providing the manufacturing method of this, an adhesive, and an adhesive sheet.

  In order to achieve the above object, first, the present invention provides a first (meth) acrylate copolymer (A) having a weight average molecular weight of 700,000 to 2,500,000, and a weight average molecular weight of 8,000 to 250,000. The second (meth) acrylic acid ester copolymer (B) and the crosslinking agent (C), and the first (meth) acrylic acid ester copolymer (A) with respect to 100 parts by mass. 2 (meth) acrylic acid ester copolymer (B) is a pressure-sensitive adhesive composition having a ratio of 5 to 50 parts by mass, wherein the second (meth) acrylic acid ester copolymer (B) is: A monomer having a functional group (b1) highly reactive with the crosslinking agent (C) is contained as a constituent component, and the proportion of the monomer is the second (meth) acrylic acid ester copolymer ( B) copolymer in excess of 1% by weight Yes, the first (meth) acrylic acid ester copolymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent component, or the second (meth) acrylic ester copolymer (A). ) A monomer having a functional group (a1) having a lower reactivity with the cross-linking agent (C) than the functional group (b1) of the acrylic ester copolymer (B) is contained as a constituent component. An adhesive composition is provided (Invention 1).

  In the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the invention (Invention 1), a low-molecular-weight copolymer (B) conventionally used as a plasticizer forms a three-dimensional network structure by crosslinking. By entanglement of the uncrosslinked high molecular weight copolymer (A) with the three-dimensional network structure, excellent stress relaxation properties are exhibited. By using this pressure-sensitive adhesive having excellent stress relaxation properties, a pressure-sensitive adhesive sheet excellent in both light leakage resistance and durability can be obtained when applied to an optical member such as a polarizing plate.

  In the said invention (invention 1), the said 1st (meth) acrylic acid ester copolymer (A) does not contain the monomer which has a functional group with high reactivity with the said crosslinking agent (C) as a structural component. Is preferred (Invention 2).

  In the said invention (invention 1 and 2), the functional group (a1) with low reactivity with the said crosslinking agent (C) in said 1st (meth) acrylic acid ester copolymer (A) is a carboxyl group. The functional group (b1) having high reactivity with the crosslinking agent (C) in the second (meth) acrylic acid ester copolymer (B) is a hydroxyl group, and the crosslinking agent (C) is an isocyanate. A cross-linking agent is preferable (Invention 3).

  In the said invention (invention 3), the said 1st (meth) acrylic acid ester copolymer (A) contains 0-15 mass% of carboxyl group-containing monomers as a monomer unit which comprises the said copolymer. Is preferred (Invention 4). Thereby, the obtained adhesive sheet is excellent in reworkability.

  In the said invention (invention 3 and 4), the said 2nd (meth) acrylic acid ester copolymer (B) contains 3-40 mass% of hydroxyl-containing monomers as a monomer unit which comprises the said copolymer. (Invention 5) Thereby, the obtained adhesive sheet becomes more excellent in durability.

  In the above inventions (Inventions 3 to 5), the content of the isocyanate crosslinking agent is such that the isocyanate group of the isocyanate crosslinking agent is the crosslinking agent (B) in the second (meth) acrylate copolymer (B). The amount is preferably 0.1 to 5 equivalents relative to the amount of the functional group (b1) having high reactivity with C) (Invention 6).

  In the said invention (invention 1-6), it is preferable to contain a silane coupling agent (D) further (invention 7).

  In the said invention (invention 7), content of the said silane coupling agent (D) is 0.05-0.5 with respect to 100 mass parts of said 1st (meth) acrylic acid ester copolymers (A). It is preferable that it is a mass part (invention 8).

  2ndly this invention is a method of manufacturing the said adhesive composition (invention 1-6), Comprising: The monomer which comprises the said 1st (meth) acrylic acid ester copolymer (A) is converted. Step (1) for producing the first (meth) acrylic acid ester copolymer (A) by radical polymerization at 50 to 90%, and the first (meth) acrylic acid ester copolymer (A ) And a monomer having a functional group (b1) having high reactivity with the crosslinking agent (C), and the presence of the first (meth) acrylate copolymer (A). And a step (2) of producing the second (meth) acrylic ester copolymer (B) by radical copolymerization, and a step (3) of adding the crosslinking agent (C). The manufacturing method of the adhesive composition characterized by this is provided (invention 9).

  In the said invention (invention 9), in the process (2) which manufactures said 2nd (meth) acrylic acid ester copolymer (B), said 1st (meth) acrylic acid ester copolymer (A) It is preferable to radically copolymerize the monomer remaining at the time of polymerization and the monomer having the functional group (b1) having high reactivity with the crosslinking agent (C) at a conversion rate of 70 to 100% (Invention 10).

  In the said invention (invention 9 and 10), when manufacturing the said adhesive composition (invention 7 and 8), it further has the process of adding the said silane coupling agent (D) (invention 11).

  3rdly, this invention provides the adhesive formed by bridge | crosslinking the said adhesive composition (invention 1-8) (invention 12).

  4thly this invention is an adhesive sheet provided with the base material and the adhesive layer, Comprising: The said adhesive layer consists of the said adhesive (invention 12), The adhesive sheet characterized by the above-mentioned is provided. Invention 13).

  In the said invention (invention 13), it is preferable that the said base material is an optical member (invention 14).

  Fifthly, 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 12) (invention 15).

  In the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the present invention, a three-dimensional network structure is formed by crosslinking with a low molecular weight copolymer that has been conventionally used as a plasticizer. By entanglement with a non-crosslinked high molecular weight copolymer, excellent stress relaxation properties are exhibited. By using this pressure-sensitive adhesive having excellent stress relaxation properties, a pressure-sensitive adhesive sheet excellent in both light leakage resistance and durability can be obtained when applied to an optical member such as a polarizing plate.

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 which shows the measurement area | region of the light leak test 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 includes a first (meth) acrylic acid ester copolymer (A) having a weight average molecular weight of 700,000 to 2,500,000, and a second one having a weight average molecular weight of 8,000 to 250,000. It contains a (meth) acrylic acid ester copolymer (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.

  The second (meth) acrylic acid ester copolymer (B) is composed of a monomer having a functional group (b1) having a high reactivity with the crosslinking agent (C), and the copolymer of the monomer (B ) Exceeds 1% by mass.

  On the other hand, the first (meth) acrylic ester copolymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent unit, or the second (meth) A monomer having a functional group (a1) that is less reactive with the crosslinking agent (C) than the functional group (b1) of the acrylic ester copolymer (B) is used as a constituent component.

  The (meth) acrylic acid ester copolymer (A) or (B) is a monomer having a reactive functional group and a (meth) acrylic acid ester having 1 to 20 carbon atoms in the alkyl moiety of the ester moiety. Copolymer of a functional functional group-containing monomer) and other monomers used as desired. In addition, what does not contain the said reactive functional group containing monomer as a structural unit is also preferable for a 1st (meth) acrylic acid ester copolymer (A).

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

  On the other hand, the reactive functional group-containing monomer includes a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), and a monomer having an amino group in the molecule (amino group). Preferred monomer).

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

  Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, and vinyl acetate. These may be used alone or in combination of two or more.

  Examples of amino group-containing monomers include aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and t- (meth) acrylate. And butylaminoethyl. These may be used alone or in combination of two or more.

  Furthermore, as said other monomer, (meth) acrylic acid ester which has aromatic rings, such as (meth) acrylic acid ester which has aliphatic rings, such as (meth) acrylic acid cyclohexyl, and (meth) acrylic acid phenyl, for example Non-crosslinkable acrylamide such as acrylamide and methacrylamide, styrene and the like. These may be used alone or in combination of two or more.

  The reactive functional group (a1) -containing monomer used in the first (meth) acrylic acid ester copolymer (A) and the second (meth) acrylic acid ester copolymer (B) are used. The selection of the reactive functional group (b1) -containing monomer is determined by the reactivity relationship with the crosslinking agent (C) used. Details will be described later.

  Here, the second (meth) acrylic acid ester copolymer (B) contains the reactive functional group (b1) -containing monomer in excess of 1% by mass, and the upper limit is usually 50% by mass. . Preferably, the reactive functional group (b1) -containing monomer is contained in an amount of 3 to 40% by mass, particularly preferably 5 to 25% by mass. By containing the reactive functional group (b1) -containing monomer in the above range, the degree of crosslinking of the second (meth) acrylic acid ester copolymer (B) becomes preferable, and the first (meth) acrylic acid ester In combination with the copolymer (A), the resulting pressure-sensitive adhesive has excellent stress relaxation properties. Further, when the content of the reactive functional group (b1) -containing monomer is 1% by mass or less, the second (meth) acrylic acid ester copolymer (B) is not sufficiently cross-linked, thereby reducing durability. . On the other hand, when the content of the reactive functional group (b1) -containing monomer exceeds 50% by mass, the second (meth) acrylic acid ester copolymer (B) is excessively cross-linked, thereby to the adherend. There is a possibility that the bonding suitability of the resin may decrease. In addition, durability of the adhesive sheet obtained becomes more excellent by making the upper limit of content of a reactive functional group (b1) containing monomer into 40 mass%.

  In this embodiment, said 2nd (meth) acrylic-ester type copolymer (B) may be used individually by 1 type, and may be used in combination of 2 or more type.

  The weight average molecular weight of the second (meth) acrylic acid ester copolymer (B) is 8000 to 250,000, preferably 20,000 to 150,000. That is, the second (meth) acrylic acid ester copolymer (B) is a low 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.

  When the weight average molecular weight of the second (meth) acrylic acid ester copolymer (B) is within the above range, a three-dimensional network structure peculiar to the adhesive composition according to this embodiment is formed, which is excellent. This contributes to stress relaxation. That is, when the weight average molecular weight of the second (meth) acrylic acid ester copolymer (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 copolymer (B) exceeds 250,000, the compatibility is lowered, and the copolymer (A) and the copolymer (B) are good. It is difficult to form an intertwined state, the formation of a target specific network structure is difficult, and the durability and reworkability are inferior.

  The first (meth) acrylic acid ester copolymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent component, or the second (meth) acrylic acid ester copolymer. It contains a monomer having a functional group (a1) that is less reactive with the crosslinking agent (C) than the functional group (b1) of the polymer (B) as a constituent component, and preferably, with the crosslinking agent (C) A monomer having a highly reactive functional group is not contained as a constituent component.

  The first (meth) acrylate copolymer (A) may not contain a monomer having a functional group reactive with the crosslinking agent (C), but the second (meth) acrylate ester When a monomer having a reactive functional group (a1) that is less reactive than the reactive functional group (b1) of the copolymer (B) is contained, the second (meth) acrylic acid ester copolymer (B) When the reaction with the crosslinking agent (C) is promoted or when the silane coupling agent (D) is used, the reactive functional group (a1) of the first (meth) acrylic acid ester copolymer (A) ) Reacts with the alkoxysilyl group or the like of the silane coupling agent (D), and the degree of aggregation of the first (meth) acrylic acid ester copolymer (A) can be adjusted. May be preferred and may be preferred.

  When the first (meth) acrylic acid ester copolymer (A) contains the reactive functional group (a1) -containing monomer, the content is usually 20% by mass or less and 15% by mass or less. It is preferable that it is 10 mass% or less especially. When the content of the reactive functional group (a1) -containing monomer exceeds 20% by mass, the first (meth) acrylic acid ester copolymer (A) is excessively aggregated and the desired stress relaxation property cannot be obtained. There is a fear. In addition, from the viewpoint of imparting reworkability, the content of the reactive functional group (a1) -containing monomer is preferably 15% by mass or less.

  The first (meth) acrylic acid ester copolymer (A) is reactive with the crosslinking agent (C) and has a reactive functional group (b1) of the second (meth) acrylic acid ester copolymer (B). It is preferable not to contain a monomer having a functional group equal to or greater than that in the molecule, but if it is contained, the content of the monomer having the functional group in the molecule is determined in the copolymer (A). It 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) acrylic acid ester copolymer (B) to be preferentially reacted and the crosslinking agent (C) may be inhibited.

  In this embodiment, said 1st (meth) acrylic acid ester copolymer (A) may be used individually by 1 type, and may be used in combination of 2 or more type.

  The weight average molecular weight of the first (meth) acrylic acid ester copolymer (A) is 700,000 to 2,500,000, preferably 1,000,000 to 2,000,000. That is, the first (meth) acrylic acid ester copolymer (A) is a high molecular weight polymer component.

  A three-dimensional network structure formed by the second (meth) acrylate copolymer (B) when the weight average molecular weight of the first (meth) acrylate copolymer (A) is within the above range. The first (meth) acrylic acid ester copolymer (A) is entangled well and contributes to excellent stress relaxation properties, and adherence to the adherend and under high heat / humidity conditions. Adhesive durability is sufficient, and floating and peeling can be prevented.

  Here, when the weight average molecular weight of the first (meth) acrylic acid ester copolymer (A) is less than 700,000, the cohesive force of the component (A) is lowered, and the durability and reworkability are inferior. There is a risk. On the other hand, if the weight average molecular weight of the first (meth) acrylic acid ester copolymer (A) exceeds 2.5 million, the resulting pressure-sensitive adhesive becomes too hard and the desired stress relaxation property may not be obtained.

  The ratio of the second (meth) acrylic acid ester copolymer (B) to 100 parts by mass of the first (meth) acrylic acid ester copolymer (A) is 5 to 50 parts by mass, preferably 10 to 10 parts by mass. 30 parts by mass.

  In the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition containing the first (meth) acrylic acid ester copolymer (A) and the second (meth) acrylic acid ester copolymer (B) in the above proportion, 2 (meth) acrylic acid ester copolymer (B) (low molecular weight polymer) forms a three-dimensional network structure via the crosslinking agent (C), and the three-dimensional network structure is not crosslinked to the first Due to the structure involving the (meth) acrylic acid ester copolymer (A) (high molecular weight polymer), excellent stress relaxation properties are exhibited. In addition, the presence of the three-dimensional network structure maintains the strength of the pressure-sensitive adhesive to be obtained, resulting in high durability.

  Preferred examples of the crosslinking agent (C) include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a metal chelate crosslinking agent.

  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 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, castor oil, and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the epoxy-based crosslinking agent include 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, and ethylene glycol diene. Examples thereof include glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the aziridine-based crosslinking agent include diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethanetri-β-aziridinyl. Propionate, toluene-2,4-bis (1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1- (2-methylaziridine), tris-1- (2-methylaziridine) phosphine, And trimethylolpropane tri-β- (2-methylaziridine) propionate. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Metal chelate crosslinking agents include chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., but aluminum chelate compounds are preferred from the viewpoint of performance. Examples of the aluminum chelate compound include diisopropoxy aluminum monooleyl acetoacetate, monoisopropoxy aluminum bis oleyl acetoacetate, monoisopropoxy aluminum monooleate monoethyl acetoacetate, diisopropoxy aluminum monolauryl acetoacetate, diisopropoxy Examples thereof include aluminum monostearyl acetoacetate and diisopropoxy aluminum monoisostearyl acetoacetate. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the crosslinking agent (C) is such that the crosslinking group (for example, isocyanate group) of the crosslinking agent (C) is the reactive functional group (b1) of the second (meth) acrylic acid ester copolymer (B). The amount is preferably 0.1 to 5 equivalents relative to the amount of (for example, hydroxyl group), and particularly preferably 0.2 to 3 equivalents. If the amount of the crosslinkable group is less than 0.1 equivalent, crosslinking may not be performed sufficiently. If the amount of the crosslinkable group exceeds 5 equivalents, the adhesive strength with time increases and reworkability is increased. May be inferior to.

  Further, in the present embodiment, in addition to the crosslinking agent (C), the reactive functional group (a1) of the copolymer (A) and the reactive functional group (b1) of the copolymer (B) Other cross-linking agents exhibiting high reactivity (meaning the remaining types of cross-linking agents excluding the type of cross-linking agent with the largest addition amount when two or more types of cross-linking agents are used in combination) It can also be used in combination as long as the effects of the invention are not impaired. Specifically, the reactive functional group (a1) of the copolymer (A) is a carboxyl group, the reactive functional group (b1) of the copolymer (B) is a hydroxyl group, and the crosslinking agent (C) is In the case of an isocyanate crosslinking agent, a small amount of an epoxy crosslinking agent can be added as another crosslinking agent. Addition of such other crosslinking agents is effective when the copolymer (A) does not sufficiently entangle with the three-dimensional network structure formed by the copolymer (B) and the cohesive force is insufficient.

  When adding another crosslinking agent, it is preferable that the addition amount is 0.01 to 1 part by mass with respect to 100 parts by mass in total of the copolymers (A) and (B).

  Here, as a combination of the crosslinking agent (C) and the (meth) acrylic acid ester copolymers (A) and (B) each of the reactive functional group-containing monomers, the crosslinking agent (C) is an isocyanate crosslinking agent. In this case, the reactive functional group (a1) -containing monomer of the copolymer (A) is a carboxyl group-containing monomer, and the reactive functional group (b1) -containing monomer of the copolymer (B) is a hydroxyl group-containing monomer or an amino group. The containing monomer is preferably selected.

  On the other hand, when the crosslinking agent (C) is an epoxy crosslinking agent, an aziridine crosslinking agent or a metal chelate crosslinking agent, the reactive functional group (a1) -containing monomer of the copolymer (A) is a hydroxyl group-containing monomer, a copolymer As the reactive functional group (b1) -containing monomer of the polymer (B), a carboxyl group-containing monomer is preferably selected.

  The flexibility of the bond formed between the cross-linking agent (C) and the copolymer (B) and the mildness of the cross-linking reaction. Furthermore, the reactive group of the copolymer (B) is converted into a silane coupling agent (D ) And an appropriate amount of the reactive functional group (a1) -containing monomer of the copolymer (A). It is particularly preferable that the carboxyl group-containing monomer and the reactive functional group (b1) -containing monomer of the copolymer (B) be a hydroxyl group-containing monomer.

  The adhesive composition according to this embodiment preferably further contains a silane coupling agent (D). When this silane coupling agent (D) is contained, when the first (meth) acrylic acid ester copolymer (A) has a carboxyl group, the alkoxysilyl group and the like of the silane coupling agent (D) and the first Since the carboxyl group of the (meth) acrylic acid ester copolymer (A) reacts, the degree of aggregation of the first (meth) acrylic acid ester copolymer (A) can be adjusted. Adhesiveness can be obtained. Moreover, when a silane coupling agent (D) is contained, when bonding a polarizing plate to a liquid crystal glass cell etc., the adhesiveness between an adhesive and a liquid crystal glass cell becomes more favorable, for example.

  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 0.05 to 0.5 parts by mass with respect to 100 parts by mass of the first (meth) acrylic acid ester copolymer (A). In particular, 0.1 to 0.3 parts by mass is preferable.

  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, and 3-chloropropyltrimethoxysilane. 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 for acrylic adhesives, for example, tackifiers, antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillers, antistatic agents, are optionally used. An agent, a refractive index adjusting agent, etc. can be added.

[Method for producing adhesive composition]
The said adhesive composition can be manufactured as follows, for example.
That is, first, the (meth) acrylic acid ester copolymers (A) and (B) are prepared separately by a normal radical polymerization method, preferably in a polymerization solvent described later. Next, the obtained solutions of both copolymers are mixed, and a diluting solvent is added so that the solid content concentration is 10 to 40% by mass. Finally, a cross-linking agent (C) and a silane coupling agent (D) are sequentially added and mixed well to obtain a pressure-sensitive adhesive composition diluted with a solvent.

Moreover, it is preferable to manufacture the said adhesive composition by the serial polymerization shown below.
In particular,
(1) A monomer constituting the first (meth) acrylic acid ester copolymer (A) is radically polymerized at a conversion rate of 50 to 90% to obtain a first (meth) acrylic acid ester copolymer (A After manufacturing)
(2) A monomer remaining at the time of polymerization of the first (meth) acrylic acid ester copolymer (A), a monomer having a functional group (b1) highly reactive with the crosslinking agent (C), and optionally used To the second (meth) acrylic polymer in the presence of the first (meth) acrylic acid ester copolymer (A), preferably with a conversion of 70 to 100%. Producing an acid ester copolymer (B);
(3) A crosslinking agent (C) and / or a silane coupling agent (D) (the component (D) is optionally added) is added.

  The monomer which comprises the 1st (meth) acrylic acid ester copolymer (A) in a process (1) is as above-mentioned, Preferably, carbon number of the alkyl group of an ester part is 1-20 (at least). Contains (meth) acrylic acid ester. In this case, in the step (2), the monomer remaining during the polymerization of the first (meth) acrylic ester copolymer (A) is a (meth) acryl having 1 to 20 carbon atoms in the alkyl group of the ester moiety. Acid esters are relevant.

  The above series of polymerizations can be carried out by a solution polymerization method 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 the step (3), when both the crosslinking agent (C) and the silane coupling agent (D) are added, the crosslinking agent (C) and the silane coupling agent (D) are each diluted to a predetermined concentration with a solvent. Thereafter, it is preferable to add them sequentially.

  In the above series polymerization, the ratio of the first (meth) acrylic acid ester copolymer (A) and the second (meth) acrylic acid ester copolymer (B), and the content of the functional group are the same as described above. The amount of each monomer to be used is adjusted as appropriate so that it falls within the above range. Further, the polymerization conditions were set so that the weight average molecular weights of the first (meth) acrylic acid ester copolymer (A) and the second (meth) acrylic acid ester copolymer (B) were in the above-mentioned range. Adjust as appropriate.

[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 copolymer (B) is crosslinked by the crosslinking agent (C) to form a three-dimensional network structure, and the three-dimensional network structure. The first (meth) acrylic acid ester copolymer (A) is entangled with no or very few chemical bonds. When the first (meth) acrylic acid ester copolymer (A) has a carboxyl group, the first (meth) acrylic acid ester copolymer (A) is combined with the silane coupling agent (D). It reacts and aggregates to a predetermined extent.

  The above-described pressure-sensitive adhesive can be preferably used for an optical member. For example, adhesion between a polarizing plate and a retardation plate, or a polarizing plate (polarizing film) or a retardation plate (retardation film) and a glass substrate. Suitable for bonding. The pressure-sensitive adhesive layer formed by the above-mentioned pressure-sensitive adhesive has excellent stress relaxation properties, so even if the dimensional change of the adherend is large, the pressure-sensitive adhesive layer absorbs / relaxes 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.

[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 Foams, foams such as polyethylene foams; polyester films such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyurethane films, polyethylene films, polypropylene films, polyvinyl chloride films, polyvinylidene chloride films, polyvinyl alcohol films, ethylene -Plastic films such as vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin resin film; And the like can be given more of the laminate. 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, and a contrast enhancement film. Among them, the polarizing plate (polarizing film) is easy to shrink and has a large dimensional change, and therefore is suitable as a target for forming 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 Fluorine resin film, liquid crystal polymer film, etc. are 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 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, and then the pressure-sensitive adhesive layer 11 is coated. The base material 13 is laminated. The conditions for the heat treatment are as described 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.

  Examples of the diluent 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 Cellosolve solvents such as are 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.

  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, one of the release sheets 12a (or 12b) of the adhesive sheet 1B is peeled off to expose the adhesive. The adhesive layer 11 and the liquid crystal cell are bonded together, then the other release sheet 12b (or 12a) is peeled off, and the exposed adhesive layer 11 and the retardation plate are bonded together. What is necessary is just to peel the peeling sheet 12 of 1 A of adhesive sheets using a board, and to bond the exposed adhesive layer 11 and phase difference plate.

  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 applied to the pressure-sensitive adhesive layer 11. It can be absorbed and relaxed, thereby exhibiting excellent light leakage resistance and high durability.

  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. Process (1)
In a reaction vessel equipped with 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, 150.0 parts by mass of acetone, and 2, 0.06 part by mass of 2′-azobisisobutyronitrile was 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 6 hours, and then cooled to room temperature. Here, GPC measurement was carried out on a part of the obtained solution by a method described later, and production of a copolymer (A) having a weight average molecular weight of 1,500,000 was confirmed. Further, the conversion rate at this time (a value obtained by dividing the mass of the copolymer obtained by polymerizing the monomer by the total mass of the monomer used as a raw material) was 80%.

2. Process (2)
To the solution of the copolymer (A) obtained by the above step (1), 150 parts by mass of toluene, 2.2 parts by mass of 2-hydroxyethyl acrylate, and 2,2′-azobis (2,4-dimethylvaleronitrile) ) 0.50 part by mass was added, the temperature was raised to 70 ° C., the mixture was reacted for 6 hours, and then cooled to room temperature. Here, a part of the obtained solution was again subjected to GPC measurement, and it was confirmed that there was almost no change in the peak top of the copolymer (A) having a weight average molecular weight of 1,500,000. From the results of this GPC measurement, By subtracting the result of the GPC measurement in the step (1), the production of a copolymer (B) having a weight average molecular weight of 40,000 was newly confirmed. Ethyl acetate was added to this solution to obtain an acrylic polymer solution (a solution of a mixture of copolymer (A) and copolymer (B)) having a solid content of 23.0% by mass. Here, the mixing ratio of the copolymer (A) and the copolymer (B) is a mass ratio of 80:20 because the conversion rate in the above step (1) was 80%.

3. Step (3)
100 parts by mass in terms of solid content of the acrylic polymer solution obtained in the above step (2) was collected and diluted with methyl ethyl ketone so that the solid content concentration was 20% by mass. And as a crosslinking agent (C), an amount of trimethylolpropane tolylene diisocyanate (TDI) adduct corresponding to 1 equivalent of the hydroxyl group of the copolymer (B) (trade name “Coronate L” manufactured by Nippon Polyurethane Co., Ltd.) Was added. Finally, as a silane coupling agent (D), 0.2 part by mass of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM403”) is added, and the mixture is sufficiently stirred, thereby allowing adhesion. A diluted solution of the sex composition was obtained.

Here, Table 1 shows the composition of the adhesive composition. Details of the abbreviations and the like described in Table 1 are as follows.
[Copolymers (A) and (B)]
BA: n-butyl acrylate AA: acrylic acid HEA: 2-hydroxyethyl acrylate HBA: 4-hydroxybutyl acrylate HEMA: 2-hydroxyethyl methacrylate DEM: N, N-2-dimethylaminoethyl methacrylate
[Crosslinking agent (C)]
・ Isocyanate-based cross-linking agent TDI system: Tolylene diisocyanate adduct of trimethylolpropane (trade name “Coronate L”, manufactured by Nippon Polyurethane Co., Ltd.)
Isocyanurate type: Isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name “Coronate HXR”)
・ Other crosslinking agents (epoxy crosslinking agents)
N, N, N ′, N′-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company, trade name “TETRAD-X”)
[Silane coupling agent (D)]
KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM403”)
KBE9007: 3-isocyanatopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBE9007”)
KBE403: 3-glycidoxypropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBE403”)

  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, in which the polarizing film and the viewing angle widening film are integrated, is bonded so that the pressure-sensitive adhesive layer and the discotic liquid crystal layer are in contact with each other. A polarizing plate with an adhesive layer was obtained by curing with RH for 7 days.

[Examples 2-34, Comparative Examples 1-6]
While adjusting the reaction conditions so that the conversion rate of the copolymer (A) becomes the value shown in Table 1, the addition amount of each monomer so that the ratio of each monomer constituting the adhesive composition becomes the value shown in Table 1. A polarizing plate with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1 except that the above was changed.

Example 35
By copolymerizing 97 parts by mass of butyl acrylate and 3 parts by mass of acrylic acid by a normal polymerization method, a copolymer (A) having a weight average molecular weight of 1,500,000 (GPC measurement) was obtained. Similarly, copolymer (B) having a weight average molecular weight of 40,000 (GPC measurement) was obtained by copolymerizing 90 parts by mass of butyl acrylate and 10 parts by mass of 2-hydroxyethyl acrylate.

  80 parts by mass of the obtained copolymer (A) and 20 parts by mass of the copolymer (B) were mixed and diluted with methyl ethyl ketone to a solid content concentration of 20% to obtain an acrylic polymer solution. Thereafter, a diluted solution of the adhesive composition was obtained in the same manner as in Example 1. And the polarizing plate with an adhesive layer was manufactured like Example 1 using the diluted solution of the said adhesive composition.

[Test Example 1] (Adhesive strength measurement-Reworkability evaluation)
A 25 mm wide, 100 mm long sample was cut out from the polarizing plate with the pressure-sensitive adhesive layer obtained in Examples or Comparative Examples, the release sheet was peeled off, and the alkali-free glass (Corning Corp., Eagle) was exposed through the exposed pressure-sensitive adhesive layer. After being attached to XG), it was pressurized with an autoclave manufactured by Kurihara Seisakusho at 0.5 MPa and 50 ° C. for 20 minutes. Then, after leaving for 24 hours under the conditions of 23 ° C. and 50% RH, using a tensile tester (Orientec, Tensilon), in accordance with JIS Z 0237, peeling speed of 300 mm / min, peeling angle of 180 The adhesive strength (N / 25 mm) was measured under the condition of degree.

  Further, after being left for 14 days under conditions of 23 ° C. and 50% RH, the adhesive strength (adhesive strength after 14 days of application; N / 25 mm) was measured in the same manner as described above. In addition, the range of preferable adhesive force is 0.1 N / 25mm or more and less than 25 N / 25mm.

Based on the adhesive strength after 14 days from the pasting, reworkability was evaluated according to the following criteria. The results are shown in Table 2.
Adhesive strength 14 days after application is 20 N / 25 mm or less: ◎
Adhesive strength after 14 days from pasting is over 20 N / 25 mm, less than 25 N / 25 mm: ○
Adhesive strength 14 days after application is 25 N / 25 mm or more: ×

[Test Example 2] (Measurement of gel fraction)
Instead of the polarizing plate used for the production of the polarizing plate with the pressure-sensitive adhesive layer in the examples or comparative examples, a release sheet obtained by peeling one side of the polyethylene terephthalate film with a silicone release agent (manufactured by Lintec Corporation, SP-PET 3801, thickness) S: 38 μm) was used to prepare an adhesive sheet. Specifically, the release sheet / adhesive layer / release sheet is laminated by laminating the release sheet on the 25 μm-thick adhesive layer obtained in Examples or Comparative Examples so that the release treatment surface side is in contact with the release layer. A pressure-sensitive adhesive sheet having a configuration was prepared.

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

  Using a Soxhlet, the pressure-sensitive adhesive sample was immersed in an ethyl acetate solvent, refluxed, and treated for 16 hours. Thereafter, the pressure-sensitive 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. The mass of only the pressure-sensitive adhesive after drying was weighed with a precision balance. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 3] (Measurement of optical performance)
Instead of the polarizing plate used for the production of the polarizing plate with the pressure-sensitive adhesive layer in the examples or comparative examples, a release sheet obtained by peeling one side of the polyethylene terephthalate film with a silicone release agent (manufactured by Lintec Corporation, SP-PET 3801, thickness) S: 38 μm) was used to prepare an adhesive sheet. Specifically, the release sheet / adhesive layer / release sheet is laminated by laminating the release sheet on the 25 μm-thick adhesive layer obtained in Examples or Comparative Examples so that the release treatment surface side is in contact with the release layer. A pressure-sensitive adhesive sheet having a configuration was prepared.

  The obtained pressure-sensitive adhesive sheet was cured for 7 days under the conditions of 23 ° C. and 50% RH. Then, about the adhesive layer of the said adhesive sheet, the haze value (%) was measured according to JISK7105 using the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH2000). The results are shown in Table 2. In addition, the range of a preferable haze value is 0 to 5%.

[Test Example 4] (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 an 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 each following durable conditions, and observed using the 10 time loupe after 500 hours. 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%
・ 80 ℃ dry

[Test Example 5] (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 an 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, after leaving for 500 hours in an 80 ° C. dry environment, light leakage was evaluated by the following method. The results are shown in Table 2.

<Evaluation of light leakage>
Using the MCPD-2000 manufactured by Otsuka Electronics Co., Ltd., the brightness of each region shown in FIG. 3 is measured, and the brightness difference ΔL ^* is expressed by the formula ΔL ^* = [(b + c + d + e) / 4] −a
(Where a, b, c, d, and e are the lightness values at predetermined measurement points (one central portion of each region) in the A region, B region, C region, D region, and E region, respectively. ) To obtain light leakage. A smaller value of ΔL ^* indicates less light leakage.

Here, the above-mentioned weight average molecular weight 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.

  As is apparent from Table 2, the polarizing plate with the pressure-sensitive adhesive layer obtained in the examples has no problem in durability and is excellent in light leakage resistance. Moreover, about Examples 1-30 by which the introduction amount of acrylic acid in a copolymer (A) and the addition amount of a crosslinking agent (C) were adjusted, it is excellent also in rework property and also haze value is also low. It is suppressed and has excellent transparency. In addition, Example 1 which obtained the acrylic polymer solution by serial polymerization was excellent in light leakage resistance, and its haze value was low compared with Example 35 which obtained the acrylic polymer solution by the blend system by the same mixing | blending.

  About the comparative example 1, since the weight average molecular weight of a 1st (meth) acrylic acid ester copolymer (A) is too small, it is inferior to durability and rework property. About the comparative example 2, since there is too little content of the hydroxyl group in a 2nd (meth) acrylic acid ester copolymer (B), a gel fraction (degree of bridge | crosslinking) is low, and it is inferior to durability. About the comparative example 3, since the weight average molecular weight of a 2nd (meth) acrylic acid ester copolymer (B) is too small, it is inferior to durability. About the comparative example 4, since the weight average molecular weight of the 2nd (meth) acrylic acid ester copolymer (B) is too large, it is inferior to durability and rework property. About comparative example 5, since there is too much content of the 2nd (meth) acrylic acid ester copolymer (B), it is inferior to durability. About Comparative Example 6, since the content of the second (meth) acrylic acid ester copolymer (B) is too small, the gel fraction (degree of crosslinking) is low and the durability is inferior.

  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 (14)

A first (meth) acrylic acid ester copolymer (A) having a weight average molecular weight of 700,000 to 2.5 million;
A second (meth) acrylic acid ester copolymer (B) having a weight average molecular weight of 8000 to 250,000,
A crosslinking agent (C),
The adhesive composition whose ratio of the said 2nd (meth) acrylic acid ester copolymer (B) with respect to 100 mass parts of said 1st (meth) acrylic acid ester copolymers (A) is 5-50 mass parts. Because
The second (meth) acrylic acid ester copolymer (B) contains a monomer having a functional group (b1) highly reactive with the cross-linking agent (C) as a constituent component, and It is a copolymer having a monomer ratio of 10% by mass or more in the second (meth) acrylic acid ester copolymer (B),
The first (meth) acrylic acid ester copolymer (A) does not contain a monomer having a functional group reactive with the crosslinking agent (C) as a constituent component or the second (meth) acrylic. A monomer having a functional group (a1) that is less reactive with the crosslinking agent (C) than the functional group (b1) of the acid ester copolymer (B) , and
The first (meth) acrylic acid ester copolymer (A) does not contain a monomer having a functional group (b1) highly reactive with the cross-linking agent (C) as a constituent component. A characteristic adhesive composition. The functional group (a1) having low reactivity with the crosslinking agent (C) in the first (meth) acrylic acid ester copolymer (A) is a carboxyl group,
The functional group (b1) having high reactivity with the crosslinking agent (C) in the second (meth) acrylic acid ester copolymer (B) is a hydroxyl group,
The pressure-sensitive adhesive composition according to claim 1 , wherein the crosslinking agent (C) is an isocyanate-based crosslinking agent. The first (meth) acrylic acid ester copolymer (A), as a monomer unit constituting the copolymer, to claim 2, characterized in that it contains 0 to 15 wt% of the carboxyl group-containing monomer The adhesive composition as described. The second (meth) acrylic acid ester copolymer (B), as monomer units constituting the copolymer, according to claim 2 or 3, characterized in that it contains a hydroxyl group-containing monomer 10-40 wt% The adhesive composition according to 1. The content of the isocyanate-based crosslinking agent is such that the isocyanate group of the isocyanate-based crosslinking agent has a high reactivity with the crosslinking agent (C) in the second (meth) acrylic acid ester copolymer (B). The pressure-sensitive adhesive composition according to any one of claims 2 to 4 , wherein the pressure-sensitive adhesive composition is 0.1 to 5 equivalents relative to the amount of (b1). Adhesive composition according to any one of claims 1 to 5, characterized in that it contains a silane coupling agent (D) further. Content of the said silane coupling agent (D) is 0.05-0.5 mass part with respect to 100 mass parts of said 1st (meth) acrylic acid ester copolymers (A), It is characterized by the above-mentioned. The pressure-sensitive adhesive composition according to claim 6 . A method of making an adhesive composition according to claim 1-5,
The monomer constituting the first (meth) acrylic acid ester copolymer (A) is radically polymerized at a conversion rate of 50 to 90% to obtain the first (meth) acrylic acid ester copolymer (A). A step (1) of producing
The monomer remaining during the polymerization of the first (meth) acrylic acid ester copolymer (A) and the monomer having a functional group (b1) highly reactive with the crosslinking agent (C), A step (2) of producing the second (meth) acrylic acid ester copolymer (B) by radical copolymerization in the presence of the (meth) acrylic acid ester copolymer (A);
And a step (3) of adding the cross-linking agent (C). In the step (2) of producing the second (meth) acrylic acid ester copolymer (B), the monomer remaining during the polymerization of the first (meth) acrylic acid ester copolymer (A), 9. The pressure-sensitive adhesive composition according to claim 8 , wherein the monomer having a functional group (b1) having high reactivity with the crosslinking agent (C) is radical-copolymerized at a conversion rate of 70 to 100%. Method. A method for producing the adhesive composition according to claim 6 or 7 ,
The method for producing an adhesive composition according to claim 8 or 9 , further comprising a step of adding the silane coupling agent (D). Adhesive obtained by crosslinking the adhesive composition according to any one of claims 1-7. 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 11 , The adhesive sheet characterized by the above-mentioned. The pressure-sensitive adhesive sheet according to claim 12 , wherein the substrate 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 11 , The adhesive sheet characterized by the above-mentioned.

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