JP5517831B2 - 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 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 of the optical member. However, conventionally, when it was attempted to form such an adhesive layer having excellent stress relaxation properties, it was necessary to design a low 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, by adding a plasticizer, liquid paraffin, urethane elastomer or the like to the acrylic pressure-sensitive adhesive instead of lowering the cross-linking density of the pressure-sensitive adhesive layer, the resulting pressure-sensitive adhesive composition becomes moderately soft. Thus, stress relaxation is imparted to the pressure-sensitive adhesive layer, 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 composition to which a plasticizer or liquid paraffin is added has a drawback that the formed pressure-sensitive adhesive layer bleeds out the plasticizer and liquid paraffin over time. As a result, various problems such as contamination of the liquid crystal cell as an adherend have occurred. Moreover, since the upper limit of the addition amount of a urethane elastomer will be limited if it is going to maintain compatibility, the adhesive composition which added the urethane elastomer is inadequate in improvement of stress relaxation property. Further, when the amount of the urethane elastomer added is increased in order to improve the stress relaxation property, the compatibility with the acrylic pressure-sensitive adhesive is lowered, and problems such as cloudiness 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, a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet that are excellent in both light leakage resistance and durability. The purpose is to provide.

  In order to achieve the above object, first, the present invention includes a first (meth) acrylic acid ester copolymer (A) having a mass average molecular weight of 1,000,000 to 2,500,000, and a mass average molecular weight of 20,000 to 15; A pressure-sensitive adhesive composition containing a second (meth) acrylic acid ester copolymer (B), an isocyanate-based crosslinking agent (C), and a silane coupling agent (D), The ratio of the second (meth) acrylic ester copolymer (B) to 100 parts by mass of the (meth) acrylic ester copolymer (A) is 10 to 30 parts by mass, and the first ( The (meth) acrylic acid ester copolymer (A) contains a monomer having a carboxyl group as a reactive functional group as a constituent component, and the ratio of the monomer having a carboxyl group is the first (meth) acrylic. Acid Este It is 2.0-6.0 mass% in a copolymer (A), and the said 2nd (meth) acrylic acid ester copolymer (B) is a component which has a hydroxyl group as a reactive functional group. Further, the proportion of the monomer having a hydroxyl group is 10.0 to 20.0% by mass in the second (meth) acrylic acid ester copolymer (B), and the isocyanate-based crosslinking agent. The content of (C) is such that the crosslinkable group of the isocyanate-based crosslinking agent (C) is 0.3 to the amount of the hydroxyl group in the second (meth) acrylic ester copolymer (B). An adhesive composition characterized in that the amount is 0.9 equivalent (Invention 1).

  In the pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition according to the above invention (Invention 1), a three-dimensional network structure formed by chemical crosslinking with a low molecular weight copolymer (B) that has been conventionally used as a plasticizer. Form. Then, by inserting a plurality of high molecular weight copolymers (A) into the three-dimensional network structure, the high molecular weight copolymers (A) are constrained, and the high molecular weight copolymers (A) are bound together. A pseudo-crosslinked structure is formed. Thereby, the obtained adhesive exhibits appropriate cohesive force and excellent stress relaxation properties. 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 above invention (Invention 1), the content of the first (meth) acrylic acid ester copolymer (A) in the adhesive composition in the adhesive composition with respect to the content of the monomer having a carboxyl group. The content ratio of the monomer having a hydroxyl group in the second (meth) acrylic acid ester copolymer (B) is preferably 0.3 to 0.9 as a molar ratio (Invention 2).

  In the said invention (invention 1 and 2), content of the said isocyanate type crosslinking agent (C) is 7.5-26 with respect to 100 mass parts of said 2nd (meth) acrylic acid ester copolymers (B). It is preferable that it is the quantity used as a mass part (invention 3).

  Secondly, the present invention provides a pressure-sensitive adhesive obtained by crosslinking the pressure-sensitive adhesive composition (invention 1 to 3) (invention 4).

  In the said invention (invention 4), it is preferable that the gel fraction when it is stored for 7 days under conditions of 23 ° C. and 50% RH after production is 50 to 80% (invention 5).

  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 (inventions 4 and 5). (Invention 6)

  In the said invention (invention 6), it is preferable that the said base material is an optical member (invention 7).

  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. The layer provides the pressure-sensitive adhesive sheet (Invention 8), characterized in that it comprises the above-mentioned pressure-sensitive adhesive (Inventions 4 and 5).

  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 chemical crosslinking with a low molecular weight copolymer conventionally used as a plasticizer. Then, by inserting a plurality of high molecular weight copolymers into the three-dimensional network structure, the high molecular weight copolymers are constrained to form a pseudo cross-linked structure between the high molecular weight copolymers. Thereby, the obtained adhesive exhibits appropriate cohesive force and excellent stress relaxation properties. 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 mass average molecular weight of 1,000,000 to 2,500,000 and a second one having a mass average molecular weight of 20,000 to 150,000. (Meth) acrylic acid ester copolymer (B), an isocyanate type crosslinking agent (C), and 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 first (meth) acrylic acid ester copolymer (A) contains a monomer having a carboxyl group as a reactive functional group (carboxyl group-containing monomer) as a constituent component, and the ratio of the carboxyl group-containing monomer is It is 2.0-6.0 mass% in a 1st (meth) acrylic acid ester copolymer (A).

  On the other hand, the second (meth) acrylic acid ester copolymer (B) contains a monomer having a hydroxyl group as a reactive functional group (hydroxyl group-containing monomer) as a constituent component, and the ratio of the hydroxyl group-containing monomer is It is 10.0-20.0 mass% in 2 (meth) acrylic acid ester copolymer (B).

  The first (meth) acrylic acid ester copolymer (A) is a (meth) acrylic acid ester having 1 to 20 carbon atoms in the alkyl group of the ester moiety, a carboxyl group-containing monomer, and other optionally used A copolymer with a monomer is preferable, and the second (meth) acrylic acid ester copolymer (B) is a (meth) acrylic acid ester having 1 to 20 carbon atoms in the ester group and a hydroxyl group-containing monomer. And a copolymer with other monomers used as desired.

  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.

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

  Examples of the 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.

  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, methacrylamide, styrene, vinyl acetate and the like. These may be used alone or in combination of two or more.

  As described above, the first (meth) acrylic acid ester copolymer (A) contains a carboxyl group-containing monomer as a constituent component. When a carboxyl group-containing monomer is contained, the carboxyl group reacts with the alkoxysilyl group or the like of the silane coupling agent (D) to adjust the degree of aggregation of the first (meth) acrylate copolymer (A). And desired adhesiveness can be obtained. The carboxyl group-containing monomer promotes the reaction between the second (meth) acrylic acid ester copolymer (B) and the isocyanate-based crosslinking agent (C), while the carboxyl group contains the second (meth) acrylic. Since the reactivity with the isocyanate crosslinking agent (C) is lower than the hydroxyl group of the acid ester copolymer (B), the second (meth) acrylic acid ester copolymer (B) and the isocyanate crosslinking agent (C It is estimated that a three-dimensional network structure can be obtained from the second (meth) acrylic acid ester copolymer (B) crosslinked by the isocyanate-based crosslinking agent (C). .

  The content ratio of the carboxyl group-containing monomer in the first (meth) acrylic acid ester copolymer (A) is 2.0 to 6.0% by mass, preferably 3.0 to 5.0% by mass. . If the content of the carboxyl group-containing monomer is less than 2.0% by mass, the durability may be insufficient. On the other hand, if the content of the carboxyl group-containing monomer exceeds 6.0% by mass, the first (meth) acrylic acid ester copolymer (A) may be excessively aggregated and a desired stress relaxation property may not be obtained. There is.

  In order not to prevent the first (meth) acrylate copolymer (A) from interfering with the reaction between the second (meth) acrylate copolymer (B) and the isocyanate-based crosslinking agent (C), It is preferable that a monomer having a functional group having a higher reactivity with the isocyanate-based crosslinking agent (C) than the carboxyl group, such as a hydroxyl group or a thiol group, is not contained as a constituent component. However, if it contains a monomer having a functional group having a higher reactivity with the isocyanate-based crosslinking agent (C) than the carboxyl group, the content of the monomer having the functional group having a higher reactivity in the molecule is It is preferable that it is 1 mass% or less in a copolymer (A), and it is especially preferable that it is 0.5 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 isocyanate-based crosslinking agent (C) may be inhibited. is there.

  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 mass average molecular weight of the first (meth) acrylic acid ester copolymer (A) is 1,000,000 to 2,500,000, preferably 1,200,000 to 2,000,000. That is, the first (meth) acrylic acid ester copolymer (A) is a high molecular weight polymer component. In addition, the mass mean molecular weight in this specification is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

  A three-dimensional network structure formed by the second (meth) acrylate copolymer (B) when the mass average molecular weight of the first (meth) acrylate copolymer (A) is within the above range. A plurality of the first (meth) acrylic acid ester copolymers (A) are sufficiently constrained in the inside, and a pseudo cross-linked structure without a chemical bond is formed between the copolymers (A). I can guess it. As a result, the resulting pressure-sensitive adhesive contributes to excellent stress relaxation properties and is excellent in light leakage resistance. In addition, since the obtained pressure-sensitive adhesive also has an appropriate cohesive force due to the pseudo-crosslinked structure, adhesion with an adherend and adhesion durability under high heat / humid heat conditions are sufficient, and Peeling can be prevented.

  Here, when the mass average molecular weight of the first (meth) acrylic acid ester copolymer (A) is less than 1,000,000, 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 mass 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.

  On the other hand, the second (meth) acrylic acid ester copolymer (B) contains a hydroxyl group-containing monomer as a constituent component. Since the hydroxyl group has higher reactivity with the isocyanate-based crosslinking agent (C) than the carboxyl group of the first (meth) acrylic acid ester copolymer (A), it is preferentially used with the isocyanate-based crosslinking agent (C). It is presumed that it reacts to form a three-dimensional network structure via the crosslinking agent (C).

  The content ratio of the hydroxyl group-containing monomer in the second (meth) acrylic acid ester copolymer (B) is 10.0 to 20.0 mass%, preferably 12 to 17 mass%. By containing the hydroxyl group-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 copolymer (A). In combination, the resulting pressure-sensitive adhesive has excellent stress relaxation properties. On the other hand, when the content of the hydroxyl group-containing monomer is 10.0% 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 hydroxyl group-containing monomer exceeds 20.0% by mass, the second (meth) acrylic acid ester copolymer (B) is excessively cross-linked, thereby being suitable for bonding to an adherend. May decrease.

  In addition, the second (meth) acrylic acid ester copolymer (B) is a monomer having a functional group that is less reactive with the isocyanate-based crosslinking agent (C) than the hydroxyl group, such as a carboxyl group or a sulfonyl group (low It is particularly preferable that the reactive functional group-containing monomer is not contained as a constituent component, but when a low reactive functional group-containing monomer is contained as a constituent component, the amount is 1/5 or less of the content of the hydroxyl group-containing monomer. In particular, it is preferably contained in an amount of 1/10 or less.

  In the present embodiment, if there are too many low-reactive functional group-containing monomers in the copolymer (B), many low-reactive functional groups remain in the three-dimensional network structure formed thereby, and the tertiary It is estimated that the compatibility between the original network structure and the copolymer (A) is changed. As a result, the insertion of the copolymer (A) into the three-dimensional network structure becomes insufficient, the durability of the resulting pressure-sensitive adhesive may be deteriorated, and the haze value may be further increased. It is also presumed that the three-dimensional network structure in which many low-reactive functional groups remain excessively restricts the mobility of the copolymer (A) inserted therein. As a result, the stress relaxation property of the obtained adhesive may be deteriorated.

  On the other hand, the silane coupling agent (D) reacts with the carboxyl group of the first (meth) acrylic acid ester copolymer (A) to produce a high molecular weight first (meth) acrylic acid ester copolymer (A )) Is presumed to be excellent in adhesiveness with a glass substrate or the like as an adherend in the obtained pressure-sensitive adhesive. However, if the second (meth) acrylic acid ester copolymer (B) contains an excessively low-reactive functional group-containing monomer, the alkoxysilyl group of the silane coupling agent (D) is ) Presumed to react with the low-reactive functional group (especially carboxyl group) of the acrylate copolymer (B) to bind to the second (meth) acrylate copolymer (B) having a low molecular weight. Is done. As a result, the obtained pressure-sensitive adhesive is inferior in adhesion to a glass substrate as an adherend, thereby reducing the durability of the pressure-sensitive adhesive layer.

  In addition, the second (meta) in the adhesive composition with respect to the content of the carboxyl group-containing monomer of the first (meth) acrylic acid ester copolymer (A) in the adhesive composition according to the present embodiment. ) The ratio of the hydroxyl group-containing monomer content (hydroxyl group-containing monomer content / carboxyl group-containing monomer content) in the acrylic ester copolymer (B) is preferably 0.3 to 0.9. In particular, it is preferably 0.5 to 0.8.

  When the ratio is too small, the ratio of the carboxyl group of the copolymer (A) is too large compared to the hydroxyl group of the copolymer (B), and the reaction between the hydroxyl group and the isocyanate-based crosslinking agent (C) is inhibited. The durability of the resulting pressure-sensitive adhesive may be deteriorated. Moreover, the quantity of the carboxyl group of a copolymer (A) may increase too much as an absolute quantity, and may worsen the rework property of the adhesive which is obtained.

  On the other hand, if the ratio is too large, the network of the three-dimensional network structure formed by the copolymer (B) becomes too fine and the copolymer (A) is not sufficiently inserted. Even when the properties are deteriorated or inserted, the degree of freedom of the copolymer (A) is excessively limited, and the light leakage resistance of the resulting adhesive may deteriorate. Moreover, the quantity of the carboxyl group of a copolymer (A) becomes too small as an absolute quantity, reaction with a silane coupling agent (D) becomes inadequate, and the durability of the adhesive obtained may be deteriorated.

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

  When the mass 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 mass average molecular weight of the second (meth) acrylic acid ester copolymer (B) is less than 20,000, a good three-dimensional network structure cannot be obtained. On the other hand, when the mass average molecular weight of the second (meth) acrylic acid ester copolymer (B) exceeds 150,000, 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. In addition, when the weight average molecular weight of the copolymer (B) is 50,000 to 120,000, the light leakage resistance can be improved, which is more preferable.

  The ratio of the second (meth) acrylate copolymer (B) to 100 parts by mass of the first (meth) acrylate copolymer (A) is 10 to 30 parts by mass from the viewpoint of durability. , Preferably it is 17-30 mass parts. Furthermore, from the viewpoint of light leakage resistance, the ratio is particularly preferably 22 to 28 parts by mass.

  If the ratio of the copolymer (B) to the copolymer (A) is too small, it is presumed that the pseudo cross-linked site composed of the three-dimensional network structure formed by the copolymer (B) is insufficient. On the other hand, when the ratio of the copolymer (B) to the copolymer (A) is too large, the compatibility is deteriorated, so that the copolymer (A) is sufficient in the three-dimensional network structure of the copolymer (B). It is presumed that the degree of freedom of the copolymer (A) is limited due to excessive insertion of pseudo cross-linking sites.

  In this embodiment, an isocyanate type crosslinking agent (C) is used as a crosslinking agent. This is because the crosslinking agent (C) has a mild crosslinking reaction, is excellent in the reaction selectivity of the carboxyl group and the hydroxyl group, and is excellent in the flexibility of the resulting bond.

  The isocyanate-based crosslinking agent (C) 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. Particularly preferably, a tolylene diisocyanate (TDI) -based adduct of trimethylolpropane is used. This is because the crosslinking rate is suitable for handling and the strength of the resulting crosslinked structure can be made excellent. The said crosslinking agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the isocyanate-based crosslinking agent (C) is 0 with respect to the amount of the hydroxyl group of the second (meth) acrylic acid ester copolymer (B) in which the crosslinking group (isocyanate group) of the crosslinking agent (C) is. .3 to 0.9 equivalent, and preferably 0.4 to 0.7 equivalent. When the amount of the crosslinkable group is less than 0.3 equivalent, crosslinking cannot be performed sufficiently and the durability is poor. When the amount of the crosslinkable group exceeds 0.9 equivalent, desired stress relaxation properties cannot be obtained, and the light leakage resistance is poor when applied to an optical member such as a polarizing plate.

  It is preferable that content of an isocyanate type crosslinking agent (C) is an amount used as 9-28 mass parts with respect to 100 mass parts of 2nd (meth) acrylic acid ester copolymers (B).

  Although the adhesive composition which concerns on this embodiment contains a silane coupling agent (D), when this silane coupling agent (D) is contained, the organic reactive group and 1st of a silane coupling agent (D) are included. The (meth) acrylic acid ester copolymer (A) carboxyl group reacts, and on the other hand, the alkoxysilyl group of the silane coupling agent (D) acts on the adherend surface such as a glass substrate. For this reason, 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 pressure-sensitive adhesive composition comprises a first (meth) acrylic acid ester copolymer (A) and a second (meth) acrylic acid ester copolymer (B) mixed with an isocyanate at any stage. It can manufacture by adding a system crosslinking agent (C) and a silane coupling agent (D).

  As a preferred specific example, the (meth) acrylic acid ester copolymers (A) and (B) are separately prepared by an ordinary radical polymerization method.

  The polymerization of the (meth) acrylic acid ester copolymers (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.

  Next, the obtained solutions of both copolymers (A) and (B) are mixed, and a diluting solvent is added. Thereafter, an isocyanate-based crosslinking agent (C) and a silane coupling agent (D) are added and mixed well to obtain a pressure-sensitive adhesive composition (coating solution) diluted with a solvent.

  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.

[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.

  It is estimated that the second (meth) acrylate copolymer (B) is crosslinked by the isocyanate crosslinking agent (C) by the heat treatment (and curing) to form a dense three-dimensional network structure. Is done. Then, two or more molecules of the first (meth) acrylic acid ester copolymer (A) are inserted into the three-dimensional network structure without any direct chemical bond or with very few chemical bonds. Therefore, it is presumed that the copolymer (A) is constrained and forms a pseudo cross-linked structure. The first (meth) acrylic acid ester copolymer (A) reacts with the silane coupling agent (D) via a carboxyl group 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.

  The pressure-sensitive adhesive according to this embodiment is a gel when stored for 7 days under conditions of 23 ° C. and 50% RH after application and drying of the pressure-sensitive adhesive composition (after formation of the pressure-sensitive adhesive layer = after production of the pressure-sensitive adhesive). The fraction is preferably 50 to 80%, particularly preferably 60 to 77%. When the gel fraction is in the above range, the degree of crosslinking of the second (meth) acrylic acid ester copolymer (B) in the adhesive composition is preferable, and the resulting pressure-sensitive adhesive has stress relaxation properties. It will be very good.

[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 -Plastics such as vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin resin film, triacetyl cellulose, etc. Click film; 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, and a liquid crystal polymer 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 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 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.

  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. Preparation of copolymer (A) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introducing tube, 97.0 parts by mass of n-butyl acrylate, 3.0 parts by mass of acrylic acid, acetic acid 200 parts by mass of ethyl 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, GPC measurement was performed on a part of the obtained solution by a method described later, and production of a copolymer (A) having a mass average molecular weight of 1,500,000 was confirmed.

2. Preparation of copolymer (B) In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen introducing tube, 85.0 parts by mass of n-butyl acrylate, 2-hydroxyethyl acrylate 15.0 A mass part, 200 parts by mass of ethyl acetate, 0.3 part by mass of 2-mercaptoethanol, and 0.16 part by mass of 2,2′-azobisisobutyronitrile are charged, and the air in the reaction vessel is replaced with nitrogen gas. did. 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, GPC measurement was performed on a part of the obtained solution by a method described later, and the production of a copolymer (B) having a mass average molecular weight of 50,000 was confirmed.

3. Preparation of adhesive composition 100 parts by mass of copolymer (A) obtained in the above step (1) (solid content conversion value) and 15 parts by mass of copolymer (B) obtained in the above step (2) (Solid content conversion value) and then, as an isocyanate-based crosslinking agent (C), an amount (2.48 parts by mass) of trimethylolpropane in an amount corresponding to 0.6 equivalent of the hydroxyl group of the copolymer (B). Range isocyanate (TDI-based) adduct (manufactured by Nippon Polyurethane Co., Ltd., trade name “Coronate L”) 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 to thereby adhere. A diluted solution of the sex composition was obtained.

Here, Table 1 shows the composition of the adhesive composition. The details of the abbreviations listed in Table 1 are as follows.
BA: n-butyl acrylate AA: acrylic acid HEA: 2-hydroxyethyl acrylate

  After drying the diluted solution of the obtained adhesive composition on the release treatment surface of a release sheet (SP-PET3811, thickness: 38 μm, manufactured by Lintec Co., Ltd.) on one side of a polyethylene terephthalate film with a silicone 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 made of a polarizing film with a discotic liquid crystal layer and integrated with a polarizing film and a viewing angle widening film is bonded so that the pressure-sensitive adhesive layer and the discotic liquid crystal layer are in contact with each other at 23 ° C., 50%. A polarizing plate with an adhesive layer was obtained by curing with RH for 7 days.

[Examples 2 to 26, Comparative Examples 1 to 7]
Table 1 shows the types and ratios of the respective monomers constituting the adhesive composition, the types and addition amounts of the crosslinking agent and the silane coupling agent, and the blending ratio of the copolymer (A) and the copolymer (B). A polarizing plate with a pressure-sensitive adhesive layer was produced in the same manner as in Example 1 except that the change was made.

[Test Example 1] (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 after preparation (= after formation of the pressure-sensitive adhesive layer). 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, dried in an environment at a temperature of 23 ° C. and a relative humidity of 50% for 24 hours, 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 1.

[Test Example 2] (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 after preparation (= after formation of the pressure-sensitive adhesive layer). Thereafter, the release sheets on both sides were peeled off, and one surface of the pressure-sensitive adhesive layer was bonded to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.) to prepare a measurement sample. In addition, it confirmed separately that the haze value of the said soda-lime glass itself was 0. About the said measurement sample, haze value (%) was measured according to JISK7105 using the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH2000). The results are shown in Table 1. In addition, the range of a preferable haze value is 0 to 5%.

[Test Example 3] (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 1.
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 4] (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 1.

<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. Moreover, let the largest value among the values of b to e be L ^* max. As L ^* max is larger, it means that there is a portion where light leaks strongly locally.

Here, the above-mentioned mass average molecular weight is a polystyrene-reduced mass 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 apparent from Table 1, 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. About the comparative example 1 and the comparative example 2, since the compounding ratio of the 2nd (meth) acrylic ester copolymer (B) with respect to the 1st (meth) acrylic ester copolymer (A) is too large, it is durable. Inferior to sex. About the comparative example 3 and the comparative example 5, since there is too little content of an isocyanate type crosslinking agent (C), it is inferior to durability. About the comparative example 4 and the comparative example 6, since there is too much content of an isocyanate type crosslinking agent (C), it is inferior to light leakage resistance. Since Comparative Example 7 does not contain a silane coupling agent (D), it is inferior in durability.

  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 (8)

A first (meth) acrylic acid ester copolymer (A) having a mass average molecular weight of 1,000,000 to 2.5 million;
A second (meth) acrylic acid ester copolymer (B) having a mass average molecular weight of 20,000 to 150,000,
An isocyanate-based crosslinking agent (C);
A pressure-sensitive adhesive composition containing a silane coupling agent (D),
The ratio of the second (meth) acrylic ester copolymer (B) to 100 parts by mass of the first (meth) acrylic ester copolymer (A) is 10 to 30 parts by mass,
Said 1st (meth) acrylic acid ester copolymer (A) contains the monomer which has a carboxyl group as a reactive functional group as a structural component, Furthermore, the ratio of the monomer which has the said carboxyl group is the said 1st In the (meth) acrylic acid ester copolymer (A) of 2.0 to 6.0% by mass,
The second (meth) acrylic acid ester copolymer (B) contains a monomer having a hydroxyl group as a reactive functional group as a constituent component, and the ratio of the monomer having a hydroxyl group is the second ( In the (meth) acrylic acid ester copolymer (B), it is 10.0-20.0 mass%,
The content of the isocyanate-based crosslinking agent (C) is such that the crosslinking group of the isocyanate-based crosslinking agent (C) is the amount of the hydroxyl group in the second (meth) acrylic acid ester copolymer (B). The pressure-sensitive adhesive composition is characterized in that the amount is 0.3 to 0.9 equivalent.   Said 2nd (meth) acrylic acid in said adhesive composition with respect to content of the monomer which has a carboxyl group of said 1st (meth) acrylic acid ester copolymer (A) in said adhesive composition The pressure-sensitive adhesive composition according to claim 1, wherein the content ratio of the monomer having a hydroxyl group in the ester copolymer (B) is 0.3 to 0.9 as a molar ratio.   Content of the said isocyanate type crosslinking agent (C) is the quantity used as 7.5-26 mass parts with respect to 100 mass parts of said 2nd (meth) acrylic acid ester copolymers (B). The pressure-sensitive adhesive composition according to claim 1 or 2.   The adhesive which bridge | crosslinks the adhesive composition as described in any one of Claims 1-3.   The pressure-sensitive adhesive according to claim 4, wherein the gel fraction is 50 to 80% when stored for 7 days under conditions of 23 ° C and 50% RH. 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 4 or 5, The adhesive sheet characterized by the above-mentioned.   The pressure-sensitive adhesive sheet according to claim 6, 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 4 or 5, The adhesive sheet characterized by the above-mentioned.

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