JP2017119871A - Adhesive composition, adhesive, and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition which does not exert adverse effects due to an acid component on an adherend such as a transparent conductive film and is excellent in durability, and to provide an adhesive and an adhesive sheet.SOLUTION: The adhesive composition contains: a (meth)acrylate polymer (A) which has a weight-average molecular weight of 1,500,000-2,500,000, contains a hydroxyl group-containing monomer and an aromatic ring-containing monomer as monomer units constituting the polymer, and does not contain a carboxyl group-containing monomer; an isocyanate-based crosslinking agent (B); and a silane coupling agent (C) having a mercapto group as a functional group reactive with an organic material. The (meth)acrylate polymer (A) contains 1-10 mass% of the hydroxyl group-containing monomer and 1-10 mass% of the aromatic ring-containing monomer, as monomer units constituting the polymer.SELECTED DRAWING: Figure 1

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 used for sticking to a transparent conductive film, and particularly to optical members such as polarizing plates. The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that are also suitable for sticking.

  In recent years, in various electronic devices, a touch panel that serves as both a display device and an input unit is often used. The types of touch panels are mainly resistive film type, capacitance type, optical type and ultrasonic type. Resistance film type includes analog resistance film type and matrix resistance film type. There are types and projection types.

  As a touch panel in a mobile electronic device such as a smartphone or a tablet terminal that has been attracting attention recently, a projected capacitive type is often used. As a projected capacitive touch panel in such mobile electronic devices, for example, in order from the bottom, a liquid crystal display (LCD), an adhesive layer, a transparent conductive film (tin-doped indium oxide: ITO), a glass substrate, a transparent conductive film ( ITO) and a laminate of protective layers such as tempered glass have been proposed.

  A liquid crystal cell is generally used as an optical component constituting the liquid crystal display device. In general, the liquid crystal cell is arranged such that the alignment layers of the two transparent electrode substrates on which the alignment layers are formed are placed inside, with a predetermined interval by a spacer, and the periphery thereof is sealed to form the two transparent electrode substrates. A liquid crystal material is sandwiched between them. Usually, a polarizing plate is bonded to the outside of two transparent electrode substrates in a liquid crystal cell via an adhesive.

  As an adhesive used by a touch panel, what is shown by patent documents 1 is known, for example. This pressure-sensitive adhesive contains 0.2 to 20 parts by weight of a carboxyl group-containing monomer as a copolymer component with respect to 100 parts by weight of an alkyl (meth) acrylate having an alkyl group having 4 to 14 carbon atoms as a monomer unit. 0.02 to 2 parts by weight of a peroxide and 0.005 to 5 parts by weight of an epoxy crosslinking agent as a crosslinking agent with respect to 100 parts by weight of the (meth) acrylic polymer and (meth) acrylic polymer. Containing.

JP 2009-242786 A

  As above-mentioned, in the touch panel, the structure which bonds the polarizing plate of a liquid crystal display device to a transparent conductive film (ITO) through an adhesive layer is assumed. In such a configuration, the pressure-sensitive adhesive directly contacts ITO. However, since the pressure-sensitive adhesive described in Patent Document 1 contains a carboxyl group (acid component), there is a problem that the ITO is corroded or the resistance value of the ITO is changed. Arise.

  On the other hand, with the recent thinning of mobile electronic devices, the polarizing plate, which is a constituent member, is also becoming thinner. Specifically, a polarizing plate in which the thickness of a protective film that holds polyvinyl alcohol as a polarizer from both sides is reduced has been used. Since such a polarizing plate is inferior in the ability to prevent the thermal contraction of a polarizer by a protective film, the thermal contraction tends to be larger than that in the past. In addition, as a material for the protective film, an optical functional film or the like that easily generates outgas such as a cycloolefin polymer has been applied instead of triacetylcellulose. Therefore, the pressure-sensitive adhesive used for them is required to have higher reliability (durability) than before.

  As a method for improving the durability of the pressure-sensitive adhesive, it is common to copolymerize a monomer having a high glass transition point (Tg) as a constituent component of the (meth) acrylic polymer. . However, as described above, the thin polarizing plate generates a large shrinkage stress under heat-resistant conditions, and the pressure-sensitive adhesive layer designed to have a high glass transition point makes it difficult to reduce the shrinkage stress. Warping will occur. As a result, the cell gap widens at the end of the liquid crystal display device, which may adversely affect display properties.

  The present invention has been made in view of such a situation, and does not give an adverse effect due to an acid component to an adherend such as a transparent conductive film, and has excellent durability, an adhesive composition, and an adhesive. The purpose is to provide a sheet.

  In order to achieve the above object, first, the present invention has a weight average molecular weight of 1,000,000 to 2,500,000, and contains a monomer having a hydroxyl group and a monomer having an aromatic ring as monomer units constituting the polymer. And a (meth) acrylic acid ester polymer (A) not containing a monomer having a carboxyl group and an isocyanate-based crosslinking agent (B), and the (meth) acrylic acid ester polymer (A) Provided is a pressure-sensitive adhesive composition containing 1 to 10% by mass of a monomer having a hydroxyl group and 1 to 10% by mass of a monomer having an aromatic ring as a monomer unit constituting a polymer (Invention 1).

  In the pressure-sensitive adhesive composition according to the invention (Invention 1), the (meth) acrylic ester polymer (A) does not contain a monomer having a carboxyl group. Not give. Moreover, when the (meth) acrylic acid ester polymer (A) contains a predetermined amount of a monomer having a hydroxyl group and a monomer having an aromatic ring, the resulting pressure-sensitive adhesive has high durability.

  In the said invention (invention 1), content of the said isocyanate type crosslinking agent (B) in the said adhesive composition is 0.1 with respect to 100 mass parts of said (meth) acrylic acid ester polymers (A). It is preferable that it is-1 mass part (invention 2).

  In the said invention (invention 1 and 2), it is preferable to further contain the silane coupling agent (C) which has a mercapto group as a functional group which reacts with an organic material (invention 3).

  2ndly this invention provides the adhesive formed by bridge | crosslinking the said adhesive composition (invention 1-3) (invention 4).

  Thirdly, the present invention provides a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer comprises the pressure-sensitive adhesive (invention 4) ( Invention 5).

  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 4), and contacts the said base material of the said adhesive layer. Provided is a pressure-sensitive adhesive sheet for sticking a transparent conductive film, characterized in that a transparent conductive film is attached to a surface opposite to the surface (Invention 6).

  In the said invention (invention 6), it is preferable that the said transparent conductive film consists of tin dope indium oxide (invention 7).

  In the said invention (invention 5-7), it is preferable that the said base material is an optical member (invention 8).

  In the said invention (invention 8), it is preferable that the said optical member is a polarizing plate (invention 9).

  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. The pressure-sensitive adhesive sheet is characterized in that the layer is composed of the pressure-sensitive adhesive (Invention 4) (Invention 10).

In the said invention (invention 5-10), the said adhesive layer and a transparent conductive film are bonded, About the obtained laminated body, the moist heat acceleration test which exposes to the atmosphere of 65 degreeC and 95% RH for 500 hours is done. It is preferable that the resistance value increase rate calculated by the following formula of the transparent conductive film is 10% or less (Invention 11).
Resistance value increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the formula, R ₀ is an initial resistance value before promoting moist heat, and R is a resistance value after promoting moist heat.)

  Since the (meth) acrylic acid ester polymer of the adhesive composition according to the present invention does not contain a monomer having a carboxyl group, the adherend such as a transparent conductive film is not adversely affected by the acid component. Moreover, when the (meth) acrylic acid ester polymer contains a predetermined amount of a monomer having a hydroxyl group and a monomer having an aromatic ring, the resulting pressure-sensitive adhesive has high durability.

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. 10 is a cross-sectional view of a resistance value measurement sample prepared in Test Example 6. FIG. It is a perspective view explaining the test method in Test Example 6.

Hereinafter, embodiments of the present invention will be described.
[Adhesive composition]
The pressure-sensitive adhesive composition according to the present embodiment (hereinafter referred to as “pressure-sensitive adhesive composition P”) has a weight average molecular weight of 1,000,000 to 2,500,000, and a monomer having a hydroxyl group (hydroxyl group) as a monomer unit constituting the polymer. Containing monomer), a monomer having an aromatic ring (aromatic ring-containing monomer), a (meth) acrylic acid ester polymer (A) not containing a monomer having a carboxyl group (carboxyl group-containing monomer), and an isocyanate type A crosslinking agent (B). Moreover, the (meth) acrylic acid ester polymer (A) contains 1 to 10% by mass of a hydroxyl group-containing monomer and 1 to 10% by mass of an aromatic ring-containing monomer as monomer units constituting the polymer. In this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. Further, the “polymer” includes the concept of “copolymer”.

  In the above-mentioned adhesive composition P, since the (meth) acrylic acid ester polymer (A) does not contain a carboxyl group-containing monomer that is an acid component, the transparent conductive film that is the subject of application is corroded, or the transparent conductive film Changing the resistance value of is suppressed. In addition, since the (meth) acrylic acid ester polymer (A) contains a predetermined amount of a hydroxyl group-containing monomer and an aromatic ring-containing monomer, the resulting pressure-sensitive adhesive has both cohesive strength and stress relaxation properties and high durability. It will be a thing.

  The (meth) acrylic acid ester polymer (A) is a (meth) acryl having 1 to 20 carbon atoms in the alkyl group, in addition to the hydroxyl group-containing monomer and aromatic ring-containing monomer, as the monomer unit constituting the polymer. An acid alkyl ester is preferably contained, and particularly preferably contained as a main component. Moreover, you may contain another monomer (except a carboxyl group-containing monomer) if desired.

  The (meth) acrylic acid ester polymer (A) contains a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. Can be expressed. Examples of the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and (meth) acrylic acid n-. Butyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylic acid Examples include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, and the like. Among these, from the viewpoint of further improving the adhesiveness, (meth) acrylic acid esters having 1 to 4 carbon atoms in the alkyl group are preferable, and methyl (meth) acrylate and n-butyl (meth) acrylate are particularly preferable. In addition, these may be used independently and may be used in combination of 2 or more type.

  The (meth) acrylic acid ester polymer (A) may contain 50 to 98% by mass of a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. The content is preferably 70 to 96% by mass, more preferably 80 to 94% by mass.

  The (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, and the hydroxyl group is highly reactive with the isocyanate group of the isocyanate-based crosslinking agent (B), By these reactions, the (meth) acrylic acid ester polymer (A) is crosslinked by the isocyanate-based crosslinking agent (B). With this crosslinked structure, the gel fraction can be controlled to a predetermined value, and the resulting pressure-sensitive adhesive can be made excellent in durability.

  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 ) (Meth) acrylic acid hydroxyalkyl esters such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate, and the like. Among them, from the point of reactivity with the isocyanate-based crosslinking agent (B) (meta ) 2-hydroxyethyl acrylate and 4-hydroxybutyl (meth) acrylate are preferred, and 2-hydroxyethyl (meth) acrylate is particularly preferred. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester polymer (A) contains 1 to 10% by mass, preferably 2 to 8% by mass, particularly preferably 2 to 8% by mass of a hydroxyl group-containing monomer as a monomer unit constituting the polymer. 5 to 5% by mass is contained. When the content of the hydroxyl group-containing monomer is within the above range, the cross-linked structure to be formed becomes favorable, and the resulting pressure-sensitive adhesive has excellent durability. When the content of the hydroxyl group-containing monomer is less than 1% by mass, there are too few crosslinking points, and the resulting adhesive does not exhibit excellent durability. On the other hand, when the content of the hydroxyl group-containing monomer exceeds 10% by mass, there are too many crosslinking points, the resulting pressure-sensitive adhesive is not flexible, and stress relaxation properties are reduced.

  The (meth) acrylic acid ester polymer (A) contains an aromatic ring-containing monomer as a monomer unit constituting the polymer, and the resulting adhesive is particularly a protective film containing a cycloolefin polymer. It is excellent in durability against a polarizing plate (hereinafter, also referred to as “COP polarizing plate”) using the above.

  Examples of the aromatic ring-containing monomer include phenyl (meth) acrylate, 2-phenylethyl (meth) acrylate, benzyl (meth) acrylate, naphthyl (meth) acrylate, phenoxyethyl (meth) acrylate, (meth ) Phenoxybutyl acrylate, ethoxylated o-phenylphenol acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide modified cresol (meth) acrylate, ethylene oxide (EO) modified nonylphenol (meth) acrylate, etc. From this point, 2-phenylethyl (meth) acrylate is preferred. These may be used alone or in combination of two or more.

  The (meth) acrylic acid ester polymer (A) contains 1 to 10% by mass of an aromatic ring-containing monomer, preferably 2 to 8% by mass, and particularly preferably 3 as a monomer unit constituting the polymer. Contains ~ 5% by mass. When the content of the aromatic ring-containing monomer is within the above range, the obtained pressure-sensitive adhesive exhibits excellent stress relaxation properties and cohesive strength, and has excellent durability. When the content of the aromatic ring-containing monomer is less than 1% by mass, a problem of light leakage occurs when the obtained pressure-sensitive adhesive is used for polarizing plates. On the other hand, when the content of the aromatic ring-containing monomer exceeds 10% by mass, the durability of the obtained pressure-sensitive adhesive deteriorates.

  As said other monomer, in order not to prevent the reaction of the hydroxyl group of the hydroxyl group-containing monomer and the isocyanate crosslinking agent (B), there is a monomer that does not contain a functional group having reactivity with the isocyanate crosslinking agent (B). preferable. Such other monomers include, for example, (meth) acrylic acid alkoxyalkyl esters such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, and aliphatic rings such as cyclohexyl (meth) acrylate (meta Non-crosslinkable acrylamide such as acrylic ester, acrylamide, methacrylamide, etc. Non-crosslinkable tertiary such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate Examples thereof include (meth) acrylic acid ester having an amino group, vinyl acetate, and styrene. These may be used alone or in combination of two or more.

  The polymerization mode of the (meth) acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

  The (meth) acrylic acid ester polymer (A) has a weight average molecular weight of 1,000,000 to 2,500,000, preferably 1,500,000 to 2,200,000, particularly preferably 1,800,000 to 2,000,000. 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 (meth) acrylic acid ester polymer (A) is less than 1,000,000, the resulting pressure-sensitive adhesive is inferior in durability. Moreover, when the weight average molecular weight of (meth) acrylic acid ester polymer (A) exceeds 2.5 million, the obtained adhesive will be inferior to stress relaxation property.

  In the adhesive composition P, the (meth) acrylic acid ester polymer (A) may be used singly or in combination of two or more. Moreover, the adhesive composition P may further contain a (meth) acrylic acid ester polymer that does not contain a hydroxyl group-containing monomer and / or an aromatic ring-containing monomer as a constituent monomer unit.

  The pressure-sensitive adhesive composition P contains an isocyanate-based crosslinking agent (B), and the isocyanate-based crosslinking agent (B) is excellent in reactivity with the hydroxyl group of the (meth) acrylic acid ester polymer (A). There are advantages.

  The isocyanate-based crosslinking agent (B) contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate, and the like. And biuret bodies, isocyanurate bodies, and adduct bodies that are a reaction product with a low-molecular active hydrogen-containing compound such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, and the like. Among these, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropylene, are particularly durable when applied to COP polarizing plates. Pan-modified xylylene diisocyanate are preferable. The said isocyanate type crosslinking agent (B) can be used individually by 1 type or in combination of 2 or more types.

  The content of the isocyanate-based crosslinking agent (B) in the adhesive composition P is preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). In particular, it is preferably 0.2 to 0.5 parts by mass, and more preferably 0.3 to 0.4 parts by mass. When the content of the isocyanate-based crosslinking agent (B) is in the above range, a crosslinked structure having excellent stress relaxation properties and consequently excellent durability can be formed in the obtained pressure-sensitive adhesive.

  The adhesive composition P preferably further contains a silane coupling agent, and in particular, a silane coupling agent having a mercapto group as a functional group that reacts with an organic material (hereinafter referred to as “silane coupling agent (C)”). In some cases). Since the mercapto group easily reacts with the isocyanate group of the isocyanate-based cross-linking agent (B), the cross-linkable functional group of the (meth) acrylic acid ester polymer (A) is difficult to work with a general silane coupling agent. Even if it is only a hydroxyl group (even if the (meth) acrylic acid ester polymer (A) does not contain a carboxyl group as a crosslinkable functional group), the coupling effect by the silane coupling agent (C) can be obtained. .

  When the adhesive composition P containing the silane coupling agent (C) is cross-linked, the mercapto group of the silane coupling agent (C) easily forms a thiourethane bond with the isocyanate group of the isocyanate cross-linking agent (B). Then, another isocyanate group of the isocyanate-based crosslinking agent (B) reacts with the hydroxyl group of the (meth) acrylic acid ester polymer (A) to crosslink the (meth) acrylic acid ester polymer (A), and the tertiary Form original network structure. The alkoxysilyl group of the silane coupling agent (C) is a suitable distance from the (crosslinked) (meth) acrylic acid ester polymer (A) (a plurality of isocyanate groups in the isocyanate-based crosslinking agent (B)). It is presumed that the (meth) acrylic acid ester polymer (A) hangs from the distance. Thereby, an excellent coupling effect is exhibited, and the obtained pressure-sensitive adhesive has excellent adhesion durability even under high temperature conditions and wet heat conditions. This effect is particularly prominent when the adhesive is applied to an inorganic material such as glass or metal.

  The silane coupling agent (C) is an organosilicon compound having at least one mercapto group and at least one alkoxysilyl group in the molecule, has good compatibility with the pressure-sensitive adhesive component, and has light transmittance. Those having, for example, substantially transparent ones are preferred.

  Specific examples of the silane coupling agent (C) include mercapto group-containing low molecular silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; Mercapto group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxy Examples include a mercapto group-containing oligomer type silane coupling agent such as a cocondensate with an alkyl group-containing silane compound such as silane. Among these, from the viewpoint of improving durability, a mercapto group-containing oligomer type silane coupling agent is preferable, and a co-condensate of a mercapto group-containing silane compound and an alkyl group-containing silane compound is particularly preferable. A cocondensate of silane and methyltriethoxysilane is preferred. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the silane coupling agent (C) in the adhesive composition P is preferably 0.01 to 1 part by mass with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). In particular, it is preferably 0.05 to 0.8 parts by mass, and more preferably 0.1 to 0.5 parts by mass. When the content of the silane coupling agent (C) is less than 0.01 parts by mass, it is difficult to obtain the effect of the silane coupling agent (C). On the other hand, when content of a silane coupling agent (C) exceeds 1 mass part, there exists a possibility of inhibiting reaction with an isocyanate type crosslinking agent (B) and a (meth) acrylic acid ester polymer (A).

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

[Method for producing adhesive composition]
The pressure-sensitive adhesive composition P was produced by manufacturing the (meth) acrylic acid ester polymer (A), mixing the obtained (meth) acrylic acid ester polymer (A) and the isocyanate-based crosslinking agent (B), If desired, it can be produced by adding an additive.

  The (meth) acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomer units constituting the polymer by an ordinary radical polymerization method. The polymerization of the (meth) acrylic acid ester polymer (A) can be performed 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 organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

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

  When the (meth) acrylic acid ester polymer (A) is obtained, an isocyanate-based crosslinking agent (B), a diluting solvent, and an additive as required are added to the solution of the (meth) acrylic acid ester polymer (A). By sufficiently mixing, an adhesive composition P (coating solution) diluted with a solvent is obtained.

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

  The concentration / viscosity of the coating solution thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. For example, it dilutes so that the density | concentration of the adhesive composition P may be 10-40 mass%. In addition, when obtaining a coating solution, addition of a dilution solvent etc. is not a necessary condition, and if a viscosity etc. which can be coated with the adhesive composition P are not necessary, a dilution solvent does not need to be added. In this case, the adhesive composition P 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 P. The adhesive which concerns on this embodiment makes a transparent conductive film one of sticking object.

  The pressure-sensitive adhesive composition P can be crosslinked by heat treatment. In addition, this heat processing can also serve as the drying process at the time of volatilizing the dilution solvent of the adhesive composition P, etc.

  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 10 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 (meth) acrylic acid ester polymer (A) is crosslinked by the isocyanate-based crosslinking agent (B), and a three-dimensional network structure is formed.

  The storage elastic modulus (G ′) at 23 ° C. of the pressure-sensitive adhesive according to this embodiment is preferably 0.05 to 0.20 MPa, particularly preferably 0.08 to 0.18 MPa, and more preferably 0. It is preferable that it is 0.1-0.15 MPa. Further, the storage elastic modulus (G ′) at 80 ° C. of the pressure-sensitive adhesive according to the present embodiment is preferably 0.05 to 0.15 MPa, particularly preferably 0.07 to 0.15 MPa. Is preferably 0.08 to 0.13 MPa. When the storage elastic modulus (G ′) at 23 ° C. and 80 ° C. is within the above range, desired stress relaxation property and cohesive force can be obtained. When applied to an optical member such as a polarizing plate, It is possible to effectively prevent floating and peeling at the interface with the optical member or at the interface with the glass substrate (for example, at a high temperature of 80 ° C.). The storage elastic modulus is a value measured by a torsional shear method at a measurement frequency of 1 Hz in accordance with JIS K7244-6.

  The gel fraction of the pressure-sensitive adhesive according to this embodiment is preferably 30 to 98%, and particularly preferably 80 to 95%. When the gel fraction is less than 30%, the cohesive force of the pressure-sensitive adhesive is insufficient, and durability and reworkability may be deteriorated. On the other hand, if the gel fraction exceeds 98%, the adhesive strength may be too low and the durability may be lowered.

  In addition, the gel fraction of an adhesive is a value at the time of sticking (after curing period progress). Specifically, it refers to the gel fraction after the adhesive composition is applied to a release sheet, heat-treated, and then stored (cured) for 7 days in an environment of 23 ° C. and 50% RH. This is because the gel fraction of the adhesive fluctuates before the curing period. From this point of view, if it is unclear whether the curing period has elapsed, after storing again for 7 days in an environment of 23 ° C. and 50% RH, the gel fraction should be within the above range. .

[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 P.

  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 an adhesive layer, it is preferably 10 to 50 μm, particularly preferably 15 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 the desired optical member, woven or non-woven fabric using fibers such as rayon, acrylic, polyester, etc .; synthetic paper; paper such as fine paper, glassine paper, impregnated paper, coated paper; metal such as aluminum and copper Foil; Foam such as urethane foam and polyethylene foam; Polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyurethane film, polyethylene film, polypropylene film, cellulose film such as triacetyl cellulose, polyvinyl chloride film , Polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, acrylic resin film, norbornene resin film, cycloolefin Plastic film such as emission resin 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, a liquid crystal polymer film, a diffusion film, and a transflective film. Etc. Among them, a polarizing plate (polarizing film), particularly a COP polarizing plate, is easily shrunk and has a large dimensional change. Therefore, from the viewpoint of demanding durability, a base for forming the pressure-sensitive adhesive (the pressure-sensitive adhesive layer 11) of this embodiment. Suitable as a material.

  Although the thickness of the base material 13 varies depending on the type, for example, in the case of an optical member, it is usually 10 μm to 500 μm, preferably 50 μm to 300 μm, and particularly preferably 80 μm to 150 μm.

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

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

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

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

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

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

  The pressure-sensitive adhesive layer 11 in the pressure-sensitive adhesive sheets 1A and 1B preferably has a haze value (value measured according to JIS K7136: 2000) of 1.0% or less, particularly preferably 0.9% or less. Further, it is preferably 0.8% or less. When the haze value is 1.0% or less, the transparency is very high, which is suitable for optical applications.

  Here, for example, a touch panel including a liquid crystal cell in which a transparent conductive film is formed on one surface, a polarizing plate stacked on the transparent conductive film, and a polarizing plate stacked on the other surface of the liquid crystal cell. The manufacturing method will be described. As a first method, two pressure-sensitive adhesive sheets 1A using a polarizing plate as a base material 13 are prepared, the release sheet 12 of the first pressure-sensitive adhesive sheet 1A is peeled off, and the exposed pressure-sensitive adhesive layer 11 and a liquid crystal cell The transparent conductive film formed on one surface of the first adhesive sheet is bonded, the release sheet 12 of the second pressure-sensitive adhesive sheet 1A is peeled off, and the exposed pressure-sensitive adhesive layer 11 and the other surface of the liquid crystal cell are bonded. Match.

  As a second method, two pressure-sensitive adhesive sheets 1B are prepared, and one release sheet 12a (or 12b) of the first pressure-sensitive adhesive sheet 1B is peeled off to expose the exposed pressure-sensitive adhesive layer 11 and one of the liquid crystal cells. The transparent conductive film formed on the surface is bonded. Moreover, one peeling sheet 12a (or 12b) of the 2nd adhesive sheet 1B is peeled, and the exposed adhesive layer 11 and the other surface of a liquid crystal cell are bonded. Next, the other release sheet 12b (or 12a) of the first pressure-sensitive adhesive sheet 1B is peeled, and the exposed pressure-sensitive adhesive layer 11 and the polarizing plate are bonded together. Similarly, the other release sheet 12b (or 12a) of the second pressure-sensitive adhesive sheet 1B is peeled, and the exposed pressure-sensitive adhesive layer 11 and the polarizing plate are bonded together.

  According to the above pressure-sensitive adhesive sheets 1A and 1B, since the pressure-sensitive adhesive layer 11 is excellent in durability, it floats, peels off, foams and the like between the substrate 13 and the adherend even under high temperature conditions or wet heat conditions. Is prevented / suppressed. In particular, even when the base material 13 is a COP polarizing plate, stress that can be generated by deformation of the COP polarizing plate can be absorbed and relaxed by the pressure-sensitive adhesive layer 11, thereby exhibiting excellent durability.

  The pressure-sensitive adhesive sheets 1A and 1B according to the present embodiment preferably have a transparent conductive film as an adherend. Since the (meth) acrylic acid ester polymer (A) in the adhesive composition P does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer, the transparent conductive film is adversely affected by the acid component. This is because this can be suppressed. Specifically, corrosion of the transparent conductive film or change in the resistance value of the transparent conductive film can be suppressed.

  Examples of the transparent conductive film include metals such as platinum, gold, silver and copper, oxides such as tin oxide, indium oxide, cadmium oxide, zinc oxide and zinc dioxide, tin-doped indium oxide (ITO), and zinc oxide-doped oxide. Examples include composite oxides such as indium, fluorine-doped indium oxide, antimony-doped tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide, and non-oxidized compounds such as chalcogenide, lanthanum hexaboride, titanium nitride, and titanium carbide. It is done.

Regarding the change in the resistance value of the transparent conductive film, the adhesive layer 11 and the transparent conductive film were bonded, and the resulting laminate was subjected to a wet heat durability test that was exposed to an atmosphere of 65 ° C. and 95% RH for 500 hours. The resistance increase rate calculated by the following formula of the transparent conductive film is preferably 10% or less, particularly preferably 9% or less, and more preferably 8% or less.
Resistance value increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the formula, R ₀ is the resistance value before the wet heat durability test, and R is the resistance value after the wet heat durability test.)
If the resistance value increase rate is 10% or less, it is considered that the conductivity of the transparent conductive film does not substantially decrease and the function of the touch panel is not hindered.

  The pressure-sensitive adhesive sheet 1A using a polarizing plate as the base material 13 (hereinafter sometimes referred to as “a polarizing plate with a pressure-sensitive adhesive layer”) has an adhesive strength to an alkali-free glass of 0.1 to 25 N / 25 mm. It is particularly preferably 2 to 20 N / 25 mm. When the adhesive strength is within the above range, it is possible to prevent floating or peeling between the glass plate and the adherend. In addition, although the adhesive force here means the adhesive force measured by the 180 degree peeling method according to JIS Z0237: 2009, the measurement sample has a width of 25 mm and a length of 100 mm, and the measurement sample is attached. After being applied to the body by applying pressure at 0.5 MPa and 50 ° C. for 20 minutes, the sample was left for 24 hours under conditions of normal pressure, 23 ° C. and 50% RH, and then measured at a peeling rate of 300 mm / min. To do.

  The pressure-sensitive adhesive-attached polarizing plate has an adhesive strength of 0.1 to 25 N / 25 mm after being adhered to the adherend and left for 2 days under conditions of normal pressure, 50 ° C. and 50% RH. It is preferable that it is 2-20 N / 25mm especially. Thus, it can be evaluated that it is excellent in rework property by suppressing the raise of the adhesive force with time. The adhesive strength here also means the adhesive strength measured by a 180 ° peeling method in accordance with JIS Z0237: 2009. The measurement sample is 25 mm wide and 100 mm long, and the measurement sample is attached to the adherend. The sample was pressed at 0.5 MPa at 50 ° C. for 20 minutes and then left for 2 days under the above conditions (normal pressure, 50 ° C., 50% RH), and then measured at a peeling rate of 300 mm / min. To do.

  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 (meth) acrylic acid ester polymer In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device and nitrogen inlet tube, 87.5 parts by mass of n-butyl acrylate, 5 parts by mass of methyl acrylate, Charge 5 parts by mass of 2-phenylethyl acrylate, 2.5 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 0.08 parts by mass of 2,2′-azobisisobutyronitrile, and perform the above reaction. The air in the container was replaced with nitrogen gas. While stirring in this nitrogen atmosphere, the reaction solution was heated to 60 ° C., reacted for 16 hours, and then cooled to room temperature. Here, the molecular weight of a part of the obtained solution was measured by a method described later, and production of a (meth) acrylic acid ester polymer (A) having a weight average molecular weight of 2 million was confirmed.

2. Preparation of adhesive composition 100 parts by mass (solid content converted value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step (1) and the isocyanate-based crosslinking agent (B) 0.20 parts by mass of methylolpropane-modified xylylene diisocyanate (trade name “Takenate D110N”, manufactured by Mitsui Takeda Chemical Co., Ltd.) and, as a silane coupling agent (C), 3-mercaptopropyltrimethoxysilane and methyltriethoxysilane Co-condensate (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “X41-1810”) is mixed with 0.30 part by mass, sufficiently stirred, and diluted with ethyl acetate to obtain a coating solution of an adhesive composition It was.

Here, Table 1 shows the composition of the adhesive composition. Details of the abbreviations and the like described in Table 1 are as follows.
[(Meth) acrylic acid ester polymer]
BA: n-butyl acrylate MA: methyl acrylate PhEA: 2-phenylethyl acrylate HEA: 2-hydroxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate AA: acrylic acid

3. Production of polarizing plate with pressure-sensitive adhesive layer A release sheet (SP-PET3811, manufactured by Lintec Corporation, thickness: 38 μm) obtained by subjecting one surface of a polyethylene terephthalate film to a release treatment with a silicone-based release agent. Then, after applying with a knife coater such that the thickness after drying was 25 μm, a pressure-sensitive adhesive layer was formed by heat treatment at 90 ° C. for 1 minute.

  Next, a COP polarizing plate having a thickness of 100 μm formed by protecting one surface of a polarizer made of a polyvinyl alcohol film with a triacetyl cellulose film and the other surface with a cycloolefin polymer film is exposed to the adhesive layer. The polarizing plate with the adhesive layer was obtained by pasting with the said adhesive layer so that the surface and the surface of a cycloolefin polymer film may contact, and curing at 23 degreeC and 50% RH for 7 days.

[Examples 2-14, Comparative Examples 1-4]
Except for changing the type and ratio of each monomer constituting the (meth) acrylic acid ester polymer (A) and the amount of the isocyanate-based cross-linking agent (B) as shown in Table 1, the same as in Example 1 was carried out. A polarizing plate with an adhesive layer was produced.

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

[Test Example 1] (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 is subjected to a release treatment on the exposed adhesive layer of the release sheet / adhesive layer (thickness: 25 μm) obtained in the production process of the example or the comparative example. The layers were laminated so that the surface side was in contact. Thereby, the adhesive sheet which consists of a structure of a peeling sheet / adhesive layer / release sheet was produced.

  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.

  Next, the pressure-sensitive adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 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 1.

[Test Example 2] (Measurement of haze value)
As a measurement sample, an adhesive sheet (cured for 7 days) similar to the adhesive sheet used for measuring the gel fraction was prepared. About the adhesive layer (thickness: 25 micrometers) of the said adhesive sheet, haze value (%) was measured according to JISK7136: 2000 using the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH2000). The results are shown in Table 1.

[Test Example 3] (Measurement of adhesive strength)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was cut to prepare samples having a width of 25 mm and a length of 100 mm. After peeling the release sheet from this sample and pasting the sample on alkali-free glass (Corning, Eagle XG) through the exposed adhesive layer, 0.5 MPa at 50 ° C. in an autoclave manufactured by Kurihara Seisakusho, Pressurized for 20 minutes. Then, after leaving for 24 hours under conditions of normal pressure, 23 ° C., and 50% RH, using a tensile tester (Orientec, Tensilon), according to JIS Z0237: 2009, a peeling rate of 300 mm / min, The adhesive strength (adhesive strength 1 day after application; N / 25 mm) was measured under the condition of a peeling angle of 180 °.

  Further, as described above, the sample was pressurized at 0.5 MPa and 50 ° C. for 20 minutes and pasted on the alkali-free glass, and then left for 2 days under conditions of normal pressure, 50 ° C. and 50% RH, The adhesive strength at that time (adhesive strength after 2 days after sticking; N / 25 mm) was measured in the same manner as described above. The results are shown in Table 1, respectively.

[Test Example 4] (Durability evaluation)
The pressure-sensitive adhesive layer-attached polarizing plate obtained in Examples or Comparative Examples was cut to produce a sample having a size of 233 mm × 309 mm. As a sample, a sample after storage for 7 days in an environment of 23 ° C. and 50% RH was prepared from preparation of a polarizing plate with an adhesive layer (adhesive layer formation). The release sheet is peeled off from this sample and attached to an alkali-free glass (Corning Corp., Eagle XG) through the exposed adhesive layer, and then applied at 0.5 MPa and 50 ° C. for 20 minutes in an autoclave manufactured by Kurihara Seisakusho. Pressed.

Then, it put into the environment of the following durable conditions, and the presence or absence of the float or peeling was confirmed using the 10 time magnifier 250 hours later. The evaluation criteria are as follows. The results are shown in Table 1.
A: No lifting or peeling was confirmed.
○: Lifting or peeling of a size of 0.5 mm or less was confirmed.
X: Floating or peeling of a size of 0.6 mm or more was confirmed.
<Durability conditions>
・ 85 ℃ dry
・ 60 ℃, relative humidity 90% RH

[Test Example 5] (Measurement of storage elastic modulus)
In the same manner as in Test Example 1, a pressure-sensitive adhesive sheet composed of a release sheet / pressure-sensitive adhesive layer / release sheet was produced. The release sheet was peeled from the pressure-sensitive adhesive sheet, and a plurality of pressure-sensitive adhesive layers were laminated to a thickness of 3 mm. A cylindrical body (height 3 mm) having a diameter of 8 mm was punched out from the obtained laminate of the pressure-sensitive adhesive layer, and this was used as a sample.

About the said sample, based on JISK7244-6, the storage elastic modulus (MPa) was measured on condition of the following by the torsional shear method using the viscoelasticity measuring device (the REOMETRIC company make, DYNAMIC ANALAYZER). The results are shown in Table 1.
Measurement frequency: 1Hz
Measurement temperature: 23 ° C, 80 ° C

[Test Example 6] (Measurement of resistance value increase rate)
About the polarizing plate with an adhesive layer obtained by the Example or the comparative example, the electrical resistance value was measured with the following test methods, and resistance value increase rate was computed.

  FIG. 3 shows a cross-sectional view of the resistance value measurement sample S. A polyethylene terephthalate (PET) film 21 having an ITO film 22 provided on one surface 21 a is prepared by sputtering, and a surface 21 b of the PET film 21 on which the ITO film 22 is not provided and one surface 23 a of the glass plate 23. Were joined via a joining tape 24 (product name “Tackliner TL-70”, manufactured by Lintec Corporation).

  Next, a conductive resin material containing silver (trade name, manufactured by Fujikura Kasei Co., Ltd.) is formed on the surface 22a of the ITO film 22 opposite to the surface in contact with the PET film 21 (hereinafter referred to as "one surface"). After applying “FA-301CA” (Dotite touch panel circuit type) so as to have a rectangular electrode shape of 20 mm × 5 mm, the electrode 25 is heated at a temperature of 80 ° C. for 20 minutes and dried to be a resistance measurement point. Two points were formed. At that time, the positions of the two electrodes 25 and 25 were adjusted so that the distance between them was slightly larger than 20 mm.

  Meanwhile, the pressure-sensitive adhesive layer-attached polarizing plate 1A ′ obtained in Examples or Comparative Examples was cut into a size of 20 mm × 250 mm and the release sheet was peeled off (at this time, the pressure-sensitive adhesive layer-attached polarizing plate 1A ′ was It is a laminate comprising a polarizing plate 13 'and an adhesive layer 11). Then, the adhesive layer is formed on one surface 22a of the ITO film 22 so that the adhesive layer 11 of the polarizing plate 1A ′ with the adhesive layer is aligned with the two electrodes 25, 25 (so as not to be in contact with the edges). Attached polarizing plate 1A ′ was affixed to produce a resistance value measurement sample S shown in FIG.

Subsequently, as shown in FIG. 4, an initial resistance value R ₀ (Ω) between the electrodes 25 and 25 was measured using a digital high tester (manufactured by Hioki Electric Co., Ltd., trade name “3802-50”) 30. Further, the resistance value measurement sample S was left in an environment of 60 ° C. and 90% RH for 500 hours, and then the resistance value R (Ω) after wet heat promotion was measured. Based on the obtained initial resistance value _R0 and resistance value R after the promotion of moist heat, the resistance value increase rate of the resistance value measurement sample S was calculated according to the following equation. The results are shown in Table 1.
Resistance value increase rate (%) = {(R−R ₀ ) / R ₀ } × 100

  As can be seen from Table 1, the pressure-sensitive adhesive of the pressure-sensitive adhesive layer obtained in the examples was able to suppress changes in the resistance value of the transparent conductive film, and was excellent in durability.

  The pressure-sensitive adhesive and pressure-sensitive adhesive sheet of the present invention are suitable for adhesion between a transparent conductive film, particularly a transparent conductive film made of tin-doped indium oxide (ITO), and an optical member, particularly a polarizing plate.

DESCRIPTION OF SYMBOLS 1A, 1B ... Adhesive sheet 1A '... Adhesive layer-attached polarizing plate 11 ... Adhesive layer 12, 12a, 12b ... Release sheet 13 ... Base material 13' ... Polarizing plate 21 ... PET film 21a, 21b ... Surface 22 ... ITO film 22a ... surface 23 ... glass plate 23a ... surface 24 ... bonding tape 25 ... electrode 30 ... digital high tester S ... sample for resistance measurement

Claims (10)

(Meth) acrylic acid having a weight average molecular weight of 1,000,000 to 2,500,000, containing a monomer having a hydroxyl group and a monomer having an aromatic ring as a monomer unit constituting the polymer, and no monomer having a carboxyl group An ester polymer (A);
An isocyanate-based crosslinking agent (B) ;
A silane coupling agent (C) having a mercapto group as a functional group that reacts with an organic material, and
The (meth) acrylic acid ester polymer (A) contains 1 to 10% by mass of a monomer having a hydroxyl group as a monomer unit constituting the polymer, and 1 to 10% by mass of a monomer having an aromatic ring. Containing adhesive composition.   Content of the said isocyanate type crosslinking agent (B) in the said adhesive composition is 0.1-1 mass part with respect to 100 mass parts of said (meth) acrylic acid ester polymers (A). The pressure-sensitive adhesive composition according to claim 1. Adhesive obtained by crosslinking the adhesive composition according to claim 1 or 2. 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 3 , The adhesive sheet characterized by the above-mentioned. A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer is made of the pressure-sensitive adhesive according to claim 3 ,
A pressure-sensitive adhesive sheet for sticking a transparent conductive film, wherein a transparent conductive film is attached to a surface of the pressure-sensitive adhesive layer opposite to the surface in contact with the substrate. The adhesive sheet for sticking a transparent conductive film according to claim 5 , wherein the transparent conductive film is made of tin-doped indium oxide. The pressure-sensitive adhesive sheet according to claim 4 , wherein the base material is an optical member. The pressure-sensitive adhesive sheet according to claim 7 , wherein the optical member is a polarizing plate. 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 3 , The adhesive sheet characterized by the above-mentioned. The pressure-sensitive adhesive layer and the transparent conductive film were bonded together, and the resulting laminate was subjected to a moist heat acceleration test in which it was exposed to an atmosphere of 65 ° C. and 95% RH for 500 hours. The pressure-sensitive adhesive sheet according to any one of claims 4 to 9 , wherein the rate of increase in resistance value calculated by is 10% or less.
Resistance value increase rate (%) = {(R−R ₀ ) / R ₀ } × 100
(In the formula, R ₀ is an initial resistance value before promoting moist heat, and R is a resistance value after promoting moist heat.)

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