JP6826362B2 - Adhesive sheet - Google Patents

Description

The present invention relates to a migration inhibitor, an adhesive and an adhesive sheet capable of preventing / suppressing the migration of a metal member or the like, for example, a metal electrode of a touch panel or the like.

In recent years, in various mobile electronic devices such as smartphones and tablet terminals, a touch panel is often used as a display. The touch panel method includes a resistive film method, a capacitance method, and the like, but the capacitance method is mainly adopted in the mobile electronic devices as described above.

Recently, the size of touch panels has been increased, and mesh-shaped metal electrodes such as copper electrodes and silver electrodes have been studied as electrode materials for such touch panels. However, when a conventional adhesive is used in contact with a metal electrode, particularly a copper electrode or a silver electrode, ion migration (= electrochemical migration; hereinafter simply referred to as "migration") may occur. Specifically, at the positive electrode, the electrode melts and breaks, and at the negative electrode, dendrites are formed due to the precipitation of the positive electrode component, causing a short circuit.

This migration is particularly likely to occur when a voltage is applied to the electrodes under high temperature and high humidity. If such migration occurs, the touch panel will not drive normally. In particular, in recent years when electrodes have become finer and narrower in pitch, wire breaks and short circuits due to migration are likely to occur.

By the way, Patent Document 1 discloses a pressure-sensitive adhesive composition for a touch panel, which contains a benzotriazole compound as a rust preventive.

Japanese Unexamined Patent Publication No. 2014-177611

However, the benzotriazole compound as a rust preventive could not sufficiently prevent / suppress migration even if it had an effect of preventing corrosion of metal wiring.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a migration inhibitor, an adhesive, and an adhesive sheet capable of effectively preventing / suppressing migration.

In order to achieve the above object, firstly, the present invention provides a migration inhibitor characterized by containing a silane coupling agent having a mercapto group (Invention 1).

According to the above invention (Invention 1), when the material to which the migration inhibitor is added comes into contact with a metal member or the like, for example, a target member such as a metal electrode of a touch panel, migration in the target member is effectively prevented.・ It can be suppressed.

In the above invention (Invention 1), the silane coupling agent is preferably a mercapto group-containing oligomer-type silane coupling agent (Invention 2).

In the above inventions (Inventions 1 and 2), the mercapto group equivalent of the organosilicon compound constituting the silane coupling agent is preferably 100 g / mol or more and 1000 g / mol or less (Invention 3).

Secondly, the present invention provides a pressure-sensitive adhesive obtained from a pressure-sensitive adhesive composition containing the migration inhibitor (Invention 1-3) (Invention 4).

In the above invention (Invention 4), the adhesive composition contains a (meth) acrylic acid ester polymer (A) and a silane coupling agent (B) having a mercapto group as the migration inhibitor. Is preferable (Invention 5).

In the above invention (Invention 5), the (meth) acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer in an amount of 3% by mass or more and 35% by mass or less as a monomer unit constituting the polymer. (Invention 6).

In the above inventions (Inventions 5 and 6), the adhesive composition preferably further contains a cross-linking agent (C) (Invention 7).

In the above inventions (Inventions 5 to 7), the content of the silane coupling agent (B) having a mercapto group in the adhesive composition is 100 parts by mass of the (meth) acrylic acid ester polymer (A). On the other hand, it is preferably 0.01 part by mass or more and 5 parts by mass or less (Invention 8).

Thirdly, the present invention includes 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, and the pressure-sensitive adhesive layer is the pressure-sensitive adhesive. Provided is an adhesive sheet comprising (Invention 4 to 8) (Invention 9).

In the above invention (Invention 9), it is preferable that the pressure-sensitive adhesive layer is arranged so as to be in contact with the electrodes on the touch panel (Invention 10).

According to the migration inhibitor, the pressure-sensitive adhesive and the pressure-sensitive adhesive sheet according to the present invention, migration can be effectively prevented or suppressed.

It is sectional drawing of the adhesive sheet which concerns on one Embodiment of this invention. It is sectional drawing which shows one configuration example of a touch panel. It is a reference image of the evaluation criteria in the evaluation of the migration prevention effect of Test Example 3.

Hereinafter, embodiments of the present invention will be described.
[Migration inhibitor]
The migration inhibitor according to one embodiment of the present invention contains a silane coupling agent having a mercapto group. The migration inhibitor according to the present embodiment may consist only of a silane coupling agent having a mercapto group, or may contain other components.

The migration inhibitor according to the present embodiment is added to a material (hereinafter, may be referred to as “contact material”) that comes into contact with a member (hereinafter, may be referred to as “target member”) that is required to prevent or suppress migration. It is preferable that it is used. Examples of the target member include a metal electrode made of copper, silver, etc. (including a mesh-like one), a transparent conductive film made of tin-doped indium oxide (ITO), etc. (including a patterned one), a metal nanowire film, and the like. Examples include wire grid polarizing films. Among the above metal electrodes, it is preferable to use a metal electrode containing an unoxidized metal as a main component, specifically, a metal electrode made of copper or silver as a target member. Examples of the contact material include an adhesive, a hard coat agent, and the like, in addition to the adhesive described later.

The silane coupling agent having a mercapto group can prevent or suppress the dissolution of the electrode at the positive electrode when the contact material to which the migration inhibitor containing the silane coupling agent is added comes into contact with the target member. It is possible to prevent or suppress the formation of dendrites on the negative electrode. That is, migration in the target member can be effectively prevented / suppressed (this effect may be referred to as "migration prevention effect"). Thereby, for example, even in the target member in which the electrodes are miniaturized and the pitch is narrowed, it is possible to prevent the electrodes from being broken or short-circuited. In particular, when the target member is a touch panel electrode, it is possible to prevent a touch panel drive failure due to a disconnection or short circuit of the electrode.

A silane coupling agent having a mercapto group is composed of an organosilicon compound having at least one mercapto group and at least one alkoxysilyl group in the molecule. When the target member is an optical member such as a touch panel, the silane coupling agent having a mercapto group is preferably one having light transmission, for example, one substantially transparent.

Specific examples of the silane coupling agent having a mercapto group include a mercapto group-containing low molecular weight silane coupling agent such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; Mercapto group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, and methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxy Examples thereof 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 them, a mercapto group-containing oligomer-type silane coupling agent having an excellent migration prevention effect and good workability is preferable, and a cocondensate of a mercapto group-containing silane compound and an alkyl group-containing silane compound is particularly preferable, and further, 3-mercapto is preferable. A cocondensate of propyltrimethoxysilane and methyltriethoxysilane is preferred. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The lower limit of the mercapto group equivalent of the organosilicon compound constituting the silane coupling agent having a mercapto group is preferably 100 g / mol or more, particularly preferably 120 g / mol or more, and further 150 g / mol or more. Is preferable. By setting the lower limit value as described above, when the contact material is used as a pressure-sensitive adhesive, the polarity difference from the polymer component as the main agent is within an appropriate range, and the above-mentioned silane coupling agent is dispersed in the pressure-sensitive adhesive. The sex can be made suitable.

The upper limit of the mercapto group equivalent of the organosilicon compound constituting the silane coupling agent having a mercapto group is preferably 1000 g / mol or less, particularly preferably 800 g / mol or less, and further 500 g / mol or less. Is preferable. By setting the upper limit value as described above, when the contact material is used as an adhesive, it is possible to prevent deterioration of the optical properties due to phase separation from the polymer component as the main agent.

The amount of the migration inhibitor added to the contact material is preferably such that the lower limit of the content of the component derived from the silane coupling agent having a mercapto group in the contact material is 0.01% by mass or more. In particular, the amount is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more. The addition amount is preferably such that the upper limit of the content of the above component in the contact material is 5% by mass or less, and particularly preferably 2.5% by mass or less. Further, the amount is preferably 1% by mass or less. When the amount of the migration inhibitor added is within the above range, the migration prevention effect becomes more excellent.

[Adhesive]
The pressure-sensitive adhesive according to the present embodiment is obtained from a pressure-sensitive adhesive composition containing the above-mentioned migration inhibitor. The type of adhesive is not particularly limited as long as the migration prevention effect of the migration inhibitor is exhibited. For example, acrylic adhesive, rubber adhesive, silicone adhesive, urethane adhesive, polyester adhesive. It may be either a pressure-sensitive adhesive, a polyvinyl ether-based pressure-sensitive adhesive, or the like. Further, the pressure-sensitive adhesive may be an emulsion type, a solvent type or a solvent-free type, and may be either a crosslinked type or a non-crosslinked type. Furthermore, it may be either an active energy ray-curable type or an active energy ray non-curable type.

When the target member is a touch panel electrode, an acrylic adhesive is preferable among the above. In that case, the pressure-sensitive adhesive according to the present embodiment has a pressure-sensitive composition containing a (meth) acrylic acid ester polymer (A) and a silane coupling agent (B) having a mercapto group as the migration inhibitor. It is preferably obtained from a product (hereinafter sometimes referred to as "adhesive composition P"). The adhesive composition P preferably further contains a cross-linking agent (C), in which case the pressure-sensitive adhesive according to the present embodiment is obtained by cross-linking the adhesive composition P. In addition, in this specification, (meth) acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. In addition, the concept of "polymer" shall be included in "polymer".

The pressure-sensitive adhesive layer made of the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P containing the silane coupling agent (B) having a mercapto group not only exhibits the above-mentioned migration prevention effect, but also at the interface with the target member. Due to the presence of the component derived from the silane coupling agent (B) having a mercapto group, the adhesion to the target member is high, and when the target member has a step, the step followability is excellent. Specifically, even when the pressure-sensitive adhesive layer is attached to a target member having a step and exposed to high temperature and high humidity conditions for a predetermined time (for example, at 85 ° C. and 85% RH for 72 hours), the step Bubbles, floats, peeling, etc. are suppressed in the vicinity (excellent step followability under high temperature and high humidity conditions). As a result, when the target member is a touch panel, it is possible to suppress the occurrence of light reflection loss in the vicinity of the step, and it is possible to maintain good image quality of the touch panel.

(1) (Meta) acrylic acid ester polymer (A)
The (meth) acrylic acid ester polymer (A) has a preferable adhesiveness by containing a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a monomer unit constituting the polymer. Can be expressed. From this point of view, the (meth) acrylic acid ester polymer (A) has a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms as a lower limit value of 50 as a monomer unit constituting the polymer. It is preferably contained in an amount of mass% or more, particularly 60% by mass or more, and further preferably 70% by mass or more. When the (meth) acrylic acid alkyl ester is contained in an amount of 50% by mass or more, the (meth) acrylic acid ester polymer (A) can exhibit suitable tackiness. Further, the (meth) acrylic acid ester polymer (A) preferably contains the above (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer in an upper limit of 97% by mass or less, particularly 90% by mass. It is preferably contained in an amount of% or less, and more preferably 85% by mass or less. By containing 97% by mass or less of the above (meth) acrylic acid alkyl ester, a suitable amount of other monomer components can be introduced into the (meth) acrylic acid ester polymer (A).

Examples of the (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, and n- (meth) acrylic acid. Butyl, n-pentyl (meth) acrylic acid, n-hexyl (meth) acrylic acid, 2-ethylhexyl (meth) acrylic acid, isooctyl (meth) acrylic acid, n-decyl (meth) acrylic acid, (meth) acrylic acid Examples thereof include n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and adamantyl (meth) acrylate. Above all, from the viewpoint of further improving the adhesiveness, it is preferable that a (meth) acrylic acid ester having 4 to 8 carbon atoms in the alkyl group is contained. These may be used alone or in combination of two or more. The alkyl group in the (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms of the alkyl group means a linear, branched chain or cyclic alkyl group.

Further, as a (meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group, a hard monomer having a glass transition temperature (Tg) of more than 0 ° C. (preferably 70 ° C. or higher) as a homopolymer and a homopolymer. It is also preferable to use it in combination with a soft monomer having a glass transition temperature (Tg) of 0 ° C. or lower. This is because the step-following property of the display panel (touch panel) can be made more excellent by improving the cohesive force with the hard monomer while ensuring the adhesiveness and flexibility with the soft monomer. In this case, the mass ratio of the hard monomer to the soft monomer is preferably 5:95 to 40:60, and particularly preferably 20:80 to 30:70.

Examples of the hard monomer include methyl acrylate (Tg10 ° C.), methyl methacrylate (Tg105 ° C.), isobornyl acrylate (Tg94 ° C.), isobornyl methacrylate (Tg180 ° C.), adamantyl acrylate (Tg115 ° C.), and methacrylic acid. Adamantane (Tg 141 ° C.) and the like can be mentioned. These may be used alone or in combination of two or more.

Among the above hard monomers, methyl acrylate, methyl methacrylate and isobornyl acrylate are preferable from the viewpoint of further exerting the performance of the hard monomer while preventing adverse effects on other properties such as adhesiveness and transparency. In consideration of adhesiveness, methyl acrylate and methyl methacrylate are more preferable, and methyl methacrylate is particularly preferable.

As the soft monomer, an acrylic acid alkyl ester having a linear or branched alkyl group having 2 to 12 carbon atoms is preferably mentioned. For example, 2-ethylhexyl acrylate (Tg-70 ° C.), n-butyl acrylate (Tg-54 ° C.) and the like are preferably mentioned. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains a reactive functional group-containing monomer as a monomer unit constituting the polymer. The reactive functional group derived from this reactive functional group-containing monomer reacts with the cross-linking agent (C) described later, whereby a cross-linked structure (three-dimensional network structure) is formed, and a pressure-sensitive adhesive having a desired cohesive force is obtained. Be done.

The reactive functional group-containing monomer contained in the (meth) acrylic acid ester polymer (A) as a monomer unit constituting the polymer includes a monomer having a hydroxyl group in the molecule (hydroxyl-containing monomer) and a carboxyl in the molecule. Preferred examples thereof include a monomer having a group (monomer containing a carboxyl group) and a monomer having an amino group in the molecule (monomer containing an amino group). Among these, a hydroxyl group-containing monomer having excellent reactivity with the cross-linking agent (C) and moisture-heat whitening resistance and having little adverse effect on the target member is particularly preferable.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth). ) Hydroxyalkyl esters of (meth) acrylic acid such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylic acid can be mentioned. Among them, 2-hydroxyethyl (meth) acrylate in the obtained (meth) acrylic acid ester polymer (A) from the viewpoint of reactivity with the cross-linking agent (C) of the hydroxyl group and copolymerizability with other monomers. Alternatively, 4-hydroxybutyl (meth) acrylate is preferable. 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. Of these, acrylic acid is preferable from the viewpoint of reactivity of the obtained (meth) acrylic acid ester polymer (A) with the cross-linking agent (C) of the carboxyl group and copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate and the like. These may be used alone or in combination of two or more.

The (meth) acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer as a lower limit value of 3% by mass or more, particularly 10% by mass or more, as a monomer unit constituting the polymer. It is preferable, and it is preferable that the content is 15% by mass or more. Further, the (meth) acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer as an upper limit value of 35% by mass or less, and particularly 30% by mass or less, as a monomer unit constituting the polymer. It is preferably contained in an amount of 25% by mass or less. When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer in the above amount as a monomer unit, a predetermined amount of hydroxyl groups remains in the obtained pressure-sensitive adhesive. Hydroxy groups are hydrophilic groups, and if such hydrophilic groups are present in a predetermined amount of the pressure-sensitive adhesive, even if the pressure-sensitive adhesive is placed under high-temperature and high-humidity conditions, it will penetrate into the pressure-sensitive adhesive under the high-temperature and high-humidity conditions. It has good compatibility with the water content, and as a result, whitening of the adhesive when returned to normal temperature and humidity is suppressed (excellent in moisture-heat whitening resistance).

However, when a predetermined amount of hydrophilic groups are present in the pressure-sensitive adhesive as described above, the pressure-sensitive adhesive tends to take in water, and migration easily occurs in the target member in contact with the pressure-sensitive adhesive. However, the adhesive composition P according to the present embodiment effectively contains migration as a migration inhibitor by containing the silane coupling agent (B) having a mercapto group, so that migration occurs in the target member in contact. Can be prevented / suppressed.

The (meth) acrylic acid ester polymer (A) preferably does not contain a carboxyl group-containing monomer as a monomer unit constituting the polymer, but it is permissible to contain a predetermined amount. Since the carboxyl group is an acid component, there is usually concern about migration of the target member, but the pressure-sensitive adhesive according to the present embodiment is a pressure-sensitive adhesive containing a silane coupling agent (B) having a mercapto group as a migration inhibitor. This is because the effect of preventing migration can be exerted even in the presence of the carboxyl group because it is obtained from the composition P. Specifically, it is permissible to contain a carboxyl group-containing monomer in an amount of 5% by mass or less, preferably 2% by mass or less, as a monomer unit in the (meth) acrylic acid ester polymer (A).

If desired, the (meth) acrylic acid ester polymer (A) may contain another monomer as a monomer unit constituting the polymer. As the other monomer, a monomer containing no reactive functional group is preferable so as not to interfere with the action of the reactive functional group-containing monomer. Examples of such other monomers include (meth) acrylic acid alkoxyalkyl ester such as (meth) acrylate ethyl, (meth) acrylate ethyl, (meth) acrylic acid N, N-dimethylaminoethyl, and (meth). ) N, N-dimethylaminopropyl acrylate, (meth) acrylic acid ester having a non-crosslinkable tertiary amino group such as (meth) acryloylmorpholin, (meth) acrylamide, dimethylacrylamide, vinyl acetate, styrene and the like. Be done. 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 lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 200,000 or more, particularly preferably 300,000 or more, and further preferably 400,000 or more. The weight average molecular weight in the present specification is a standard polystyrene-equivalent value measured by a gel permeation chromatography (GPC) method. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is at least the above value, the pressure-sensitive adhesive has excellent step-following property under high temperature and high humidity conditions.

Further, the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is preferably 1 million or less, particularly preferably 900,000 or less, and further preferably 700,000 or less. preferable. When the upper limit of the weight average molecular weight of the (meth) acrylic acid ester polymer (A) is not more than the above, the adhesive has excellent step-following property at the time of sticking.

In the adhesive composition P, one type of (meth) acrylic acid ester polymer (A) may be used alone, or two or more types may be used in combination.

(2) Silane coupling agent having a mercapto group (B)
The silane coupling agent (B) having a mercapto group contained in the adhesive composition P is the silane coupling agent having a mercapto group as the migration inhibitor described above.

The content of the silane coupling agent (B) having a mercapto group in the adhesive composition P is 0.01 part by mass or more as a lower limit value with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). It is preferably 0.05 parts by mass or more, and further preferably 0.1 parts by mass or more. Further, the upper limit value is preferably 5 parts by mass or less, particularly preferably 1.5 parts by mass or less, and further preferably 1.0 part by mass or less. When the content of the silane coupling agent (B) having a mercapto group is within the above range, the migration prevention effect becomes more excellent.

The lower limit of the number of moles of mercapto groups (amount of mercapto groups) in the silane coupling agent (B) per 100 g of the (meth) acrylic acid ester polymer (A) is preferably 0.01 mmol or more, particularly 0. It is preferably 1 mmol or more, and more preferably 0.2 mmol or more. The upper limit of the number of moles is preferably 30 mmol or less, particularly preferably 5 mmol or less, and further preferably 1.5 mmol or less. When the number of moles of the mercapto group of the silane coupling agent (B) with respect to the (meth) acrylic acid ester polymer (A) is within the above range, the migration prevention effect can be further enhanced.

(3) Crosslinking agent (C)
The adhesive composition P preferably contains a cross-linking agent (C). By containing the cross-linking agent (C), the adhesive composition P cross-links the (meth) acrylic acid ester polymer (A) to form a three-dimensional network structure, and improves the cohesive force of the obtained pressure-sensitive adhesive. It is possible to improve the step followability under high temperature and high humidity conditions.

The cross-linking agent (C) may be any as long as it reacts with the reactive group of the (meth) acrylic acid ester polymer (A). For example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an amine-based cross-linking agent, Melamine-based cross-linking agent, aziridine-based cross-linking agent, hydrazine-based cross-linking agent, aldehyde-based cross-linking agent, oxazoline-based cross-linking agent, metal alkoxide-based cross-linking agent, metal chelate-based cross-linking agent, metal salt-based cross-linking agent, ammonium salt-based cross-linking agent, etc. Can be mentioned. When the (meth) acrylic acid ester polymer (A) contains a hydroxyl group-containing monomer as a monomer unit constituting the polymer, it is preferable to use an isocyanate-based cross-linking agent having excellent reactivity with the hydroxyl group. As the cross-linking agent (C), one type can be used alone, or two or more types can be used in combination.

The isocyanate-based cross-linking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanates, and alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate. , And their biurets, isocyanurates, and adducts, which are reactants with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Of these, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate, is preferable from the viewpoint of reactivity with hydroxyl groups.

The content of the cross-linking agent (C) in the adhesive composition P is preferably 0.001 part by mass or more as a lower limit value with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). In particular, it is preferably 0.01 part by mass or more, and more preferably 0.02 part by mass or more. Further, the upper limit value is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 1 part by mass or less.

When the content of the cross-linking agent (C) is in the above range, the cohesive force of the obtained pressure-sensitive adhesive becomes preferable, and the step-following property of the pressure-sensitive adhesive under high temperature and high humidity conditions is improved.

(4) Various Additives The pressure-sensitive adhesive composition P contains various additives usually used for acrylic pressure-sensitive adhesives, such as antistatic agents, pressure-sensitive adhesives, antioxidants, ultraviolet absorbers, and light stabilizers, if desired. Agents, softeners, fillers, refractive index adjusters and the like can be added. Further, in addition to the above-mentioned silane coupling agent (B) having a mercapto group, another silane coupling agent may be added together. However, it is preferable not to add a rust preventive, particularly a benzotriazole-based rust preventive, because it has an effect of inhibiting the cross-linking of the adhesive composition P.

Further, the adhesive composition P may contain an active energy ray-curable component such as a polyfunctional acrylate-based monomer having a molecular weight of less than 1000, if desired. When the pressure-sensitive adhesive composition P contains an active energy ray-curable component, the pressure-sensitive adhesive layer is attached to a target member, and then the pressure-sensitive adhesive layer is irradiated with active energy rays to cure the pressure-sensitive adhesive layer. An adhesive layer having very excellent properties can be obtained.

The adhesive composition P represents a mixture of various components remaining in the pressure-sensitive adhesive layer as it is or in a reacted state, and is a component removed in a drying step or the like, for example, polymerization described later. The solvent and the diluting solvent are not included in the adhesive composition P.

(5) Production of Adhesive Composition The adhesive composition P produced a (meth) acrylic acid ester polymer (A) and used the obtained (meth) acrylic acid ester polymer (A) and a mercapto group. It can be produced by mixing the silane coupling agent (B) having the mixture and, if desired, adding a cross-linking agent (C) and 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 carried out by a solution polymerization method or the like using a polymerization initiator, if desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone and the like, and two or more of them may be used in combination.

Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane1-carbonitrile), and 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-butylperbenzoate, cumenehydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, and di (2-ethoxyethyl) peroxy. Examples thereof include dicarbonate, t-butylperoxyneodecanoate, t-butylperoxyvivarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

In the above polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

Once the (meth) acrylic acid ester polymer (A) is obtained, the solution of the (meth) acrylic acid ester polymer (A) is mixed with a silane coupling agent (B) having a mercapto group, and optionally a cross-linking agent ( C), an additive and a diluting solvent are added and mixed thoroughly to obtain a tacky composition P (coating solution) diluted with the solvent.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as methylene chloride and ethylene chloride, methanol, ethanol, propanol and butanol. Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

The concentration and viscosity of the coating solution prepared in this manner may be any range as long as it can be coated, and is not particularly limited and can be appropriately selected depending on the situation. For example, the adhesive composition P is diluted to a concentration of 10 to 40% by mass. It should be noted that the addition of a diluting solvent or the like is not a necessary condition when obtaining the coating solution, and the diluting solvent may not be added as long as the adhesive composition P has a coatable viscosity. In this case, the adhesive composition P becomes a coating solution using the polymerization solvent of the (meth) acrylic acid ester polymer (A) as it is as a diluting solvent.

(6) Production of Adhesive An adhesive can be obtained by heat-treating the above-mentioned adhesive composition P. This heat treatment can also be used as a drying treatment for volatilizing the diluting solvent or the like of the adhesive composition P.

When the heat treatment is performed, the heating temperature is preferably 50 to 150 ° C., particularly preferably 70 to 120 ° C. The heating time is preferably 30 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (for example, 23 ° C., 50% RH). If this curing period is required, the adhesive layer is formed after the curing period has elapsed, and if the curing period is not required, after the heat treatment is completed.

The lower limit of the gel fraction of the pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition P is preferably 30% or more, particularly preferably 40% or more, and further preferably 50% or more. When the lower limit of the gel fraction of the pressure-sensitive adhesive is equal to or higher than the above, the cohesive force of the pressure-sensitive adhesive becomes high, and the step followability under high temperature and high humidity conditions becomes excellent. The upper limit of the gel fraction is preferably 90% or less, particularly preferably 85% or less, and further preferably 80% or less. When the upper limit of the gel fraction of the pressure-sensitive adhesive is not more than the above, the pressure-sensitive adhesive does not become too hard, and the step-following property at the time of sticking becomes excellent. Here, the method for measuring the gel fraction of the pressure-sensitive adhesive is as shown in a test example described later.

The pressure-sensitive adhesive according to the present embodiment contains a silane coupling agent having a mercapto group as a migration inhibitor, and thus, for example, a metal electrode made of copper, silver, etc., a transparent conductive material made of tin-doped indium oxide (ITO), or the like. Even if it is attached to a target member such as a film, a metal nanowire film, or a wire grid polarizing film, migration in the target member can be effectively suppressed. In particular, even when the target member is a metal electrode of a touch panel using copper, silver, or the like, which has a higher ionization tendency than a metal oxide such as ITO, it is possible to prevent a touch panel drive failure due to a disconnection or short circuit of the electrode. ..

[Adhesive sheet]
As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 according to the present embodiment is in contact with the two release sheets 12a and 12b and the release surfaces of the two release sheets 12a and 12b. , 12b and the pressure-sensitive adhesive layer 11 sandwiched between the two. However, the release sheets 12a and 12b are not essential components in the pressure-sensitive adhesive sheet 1, and are peeled off and removed when the pressure-sensitive adhesive sheet 1 is used. The peeling surface of the release sheet in the present specification means a surface of the release sheet that has peelability, and includes both a surface that has been peeled and a surface that exhibits peelability without peeling. ..

(1) Adhesive Layer The adhesive layer 11 is composed of the above-mentioned adhesive. The lower limit of the thickness of the pressure-sensitive adhesive layer 11 (value measured according to JIS K7130) is preferably 10 μm or more, particularly preferably 25 μm or more, and further preferably 50 μm or more. When the lower limit of the thickness of the pressure-sensitive adhesive layer 11 is at least the above, excellent adhesive strength is sufficiently exhibited. The upper limit of the thickness of the pressure-sensitive adhesive layer 11 is preferably 300 μm or less, particularly preferably 250 μm or less, and further preferably 100 μm or less. When the upper limit of the thickness of the pressure-sensitive adhesive layer 11 is equal to or less than the above, the workability is improved. The pressure-sensitive adhesive layer 11 may be formed as a single layer, or may be formed by laminating a plurality of layers.

(2) Release sheet The release sheets 12a and 12b are not particularly limited, and known plastic films can be used. 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 acetate. Vinyl films, ionomer resin films, ethylene / (meth) acrylic acid copolymer films, ethylene / (meth) acrylic acid ester copolymer films, polystyrene films, polycarbonate films, polyimide films, fluororesin films and the like are used. In addition, these crosslinked films are also used. Further, these laminated films may be used.

It is preferable that the peeling surfaces (particularly the surfaces in contact with the pressure-sensitive adhesive layer 11) of the release sheets 12a and 12b are subjected to a peeling treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. Of the release sheets 12a and 12b, it is preferable that one release sheet is a heavy release type release sheet having a large release force and the other release sheet is a light release type release sheet having a small release force.

The thickness of the release sheets 12a and 12b is not particularly limited, but is usually about 20 to 150 μm.

(3) Production of Adhesive Sheet As an example of production of the adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a (or 12b) and heat-treated to adhere. After the sex composition P is crosslinked to form a coating layer, the peeling surface of the other release sheet 12b (or 12a) is superposed on the coating layer. If a curing period is required, the curing period is set, and if the curing period is not required, the coating layer becomes the adhesive layer 11 as it is. As a result, the adhesive sheet 1 is obtained. The conditions for heat treatment and curing are as described above.

As another production example of the pressure-sensitive adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one of the release sheets 12a, and heat treatment is performed to crosslink the adhesive composition P to crosslink the coating layer. To obtain a release sheet 12a with a coating layer. Further, the coating liquid of the adhesive composition P is applied to the peeling surface of the other release sheet 12b, and heat treatment is performed to crosslink the adhesive composition P to form a coating layer, which is provided with a coating layer. A release sheet 12b is obtained. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are bonded so that both coating layers are in contact with each other. When the curing period is required, the curing period is set, and when the curing period is not required, the laminated coating layer becomes the pressure-sensitive adhesive layer 11. As a result, the adhesive sheet 1 is obtained. According to this production example, stable production is possible even when the pressure-sensitive adhesive layer 11 is thick.

As a method of applying the coating liquid of the adhesive composition P, 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 and the like can be used.

(4) Adhesive Strength The lower limit of the adhesive strength of the adhesive sheet 1 according to the present embodiment to soda lime glass is preferably 5N / 25mm or more, particularly preferably 8N / 25mm or more, and further 10N / 25mm. It is preferably 25 mm or more. When the lower limit of the adhesive force of the pressure-sensitive adhesive sheet 1 is equal to or higher than the above value, the step followability under high temperature and high humidity conditions becomes excellent. On the other hand, the upper limit of the adhesive strength is not particularly limited, but is preferably 50 N / 25 mm or less, particularly 30 N, in consideration of the ease of peeling the release sheets 12a and 12b from the adhesive layer 11 during use. It is preferably / 25 mm or less. Further, considering the reworkability, it is preferably 26 N / 25 mm or less. In that case, even if a bonding error occurs, the member can be easily reused.

Here, the adhesive strength in the present specification basically means the adhesive strength measured by the 180-degree peeling method according to JIS Z0237: 2009, but the measurement sample is 25 mm wide and 100 mm long, and the measurement sample is used. It is attached to an adherend, pressurized at 0.5 MPa and 50 ° C. for 20 minutes, left at normal pressure, 23 ° C. and 50% RH for 24 hours, and then measured at a peeling speed of 300 mm / min. It shall be.

(5) Use of Adhesive Sheet By using the adhesive sheet 1, for example, the capacitance type touch panel 2 shown in FIG. 2 can be manufactured. The touch panel 2 includes a display module 3, a first film sensor 5a laminated on the display module 3 via an adhesive layer 4, and a second film sensor 5b laminated on the display module 3 via an adhesive layer 11. And a cover material 6 laminated on the adhesive layer 11 via the adhesive layer 11.

The pressure-sensitive adhesive layer 11 in the touch panel 2 is the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1.

Examples of the display module 3 include a liquid crystal (LCD) module, a light emitting diode (LED) module, an organic electroluminescence (organic EL) module, and electronic paper.

The pressure-sensitive adhesive layer 4 may be formed by the pressure-sensitive adhesive layer 11 of the pressure-sensitive adhesive sheet 1, or may be formed by another pressure-sensitive adhesive or a pressure-sensitive adhesive sheet. In the latter case, examples of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer 4 include acrylic pressure-sensitive adhesive, rubber-based pressure-sensitive adhesive, silicone-based pressure-sensitive adhesive, urethane-based pressure-sensitive adhesive, polyester-based pressure-sensitive adhesive, polyvinyl ether-based pressure-sensitive adhesive, and the like. However, acrylic adhesives are particularly preferable.

The first film sensor 5a and the second film sensor 5b in the present embodiment each include a base film 51 and an electrode 52 formed on the base film 51. The base film 51 is not particularly limited, and for example, a polyethylene terephthalate film, an acrylic film, a polycarbonate film, or the like is used.

The electrode 52 is made of, for example, a metal electrode made of copper, silver or the like, a patterned transparent conductive film made of tin-doped indium oxide (ITO) or the like.

One of the electrodes 52 of the first film sensor 5a and the electrode 52 of the second film sensor 5b usually constitutes a circuit pattern in the X-axis direction, and the other constitutes a circuit pattern in the Y-axis direction.

The electrode 52 of the second film sensor 5b in the present embodiment is located above the second film sensor 5b in FIG. On the other hand, the electrode 52 of the first film sensor 5a is located above the first film sensor 5a in FIG. 2, but is not limited to this, and is below the first film sensor 5a. It may be located in.

The cover material 6 is usually mainly composed of a glass plate or a plastic plate. The glass plate is not particularly limited, and for example, chemically strengthened glass, non-alkali glass, quartz glass, soda lime glass, barium / strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium borosilicate glass. And so on. The plastic plate is not particularly limited, and examples thereof include an acrylic plate made of polymethylmethacrylate and the like, a polycarbonate plate, and the like.

Functional layers such as a hard coat layer, an antireflection layer, and an antiglare layer may be provided on one or both sides of the glass plate or the plastic plate, or a hard coat film, an antireflection film, or an antiglare film. Etc. may be laminated.

In the present embodiment, the cover material 6 has a step on the surface on the adhesive layer 11 side, and specifically, the cover material 6 has a step depending on the presence or absence of the print layer 7. The print layer 7 is generally formed in a frame shape on the pressure-sensitive adhesive layer 11 side of the cover material 6.

The material constituting the printing layer 7 is not particularly limited, and a known material for printing is used. The thickness of the print layer 7, that is, the lower limit of the height of the step is preferably 3 μm or more, more preferably 5 μm or more, and particularly preferably 7 μm or more. The upper limit is preferably 50 μm or less, more preferably 25 μm or less, and particularly preferably 15 μm or less.

An example of the manufacturing method of the touch panel 2 will be described below.
As the adhesive sheet 1, a first adhesive sheet 1 and a second adhesive sheet 1 are prepared. One of the release sheets 12a is peeled off from the first adhesive sheet 1, and the exposed adhesive layer 11 (first adhesive layer 11) is brought into contact with the electrode 52 of the second film sensor 5b. It is bonded to the film sensor 5b of. Further, one of the release sheets 12a is peeled off from the second adhesive sheet 1, and the exposed adhesive layer 11 (second adhesive layer) is brought into contact with the electrode 52 of the first film sensor 5a. It is bonded to the film sensor 5a of 1.

Then, the other release sheet 12b of the second adhesive sheet is peeled off, and the exposed second adhesive layer 11 is the side on which the first adhesive layer 11 of the second film sensor 5b is laminated. Both are bonded so as to be in contact with the opposite surface (exposed surface of the base film 51 of the second film sensor 5b). As a result, a laminate obtained by sequentially laminating the release sheet 12b, the first pressure-sensitive adhesive layer 11, the second film sensor 5b, the second pressure-sensitive adhesive layer 11, and the first film sensor 5a is obtained.

Next, the pressure-sensitive adhesive layer 4 provided on the release sheet is bonded to the surface of the laminated body on the first film sensor 5a side (exposed surface of the base film 51 of the first film sensor 5a). Subsequently, the release sheet 12b is peeled off from the laminated body, and the cover material 6 is applied to the exposed first pressure-sensitive adhesive layer 11 so that the printed layer 7 side of the cover material 6 is in contact with the pressure-sensitive adhesive layer 11. Stick them together. As a result, the cover material 6, the first adhesive layer 11, the second film sensor 5b, the second adhesive layer 11, the first film sensor 5a, the adhesive layer 4, and the release sheet are sequentially laminated. The construct is obtained.

Finally, the release sheet is peeled off from the above-mentioned structure, and the structure is attached to the display body module 3 so that the exposed pressure-sensitive adhesive layer 4 is in contact with the display body module 3. As a result, the touch panel 2 shown in FIG. 2 is manufactured.

Even when the touch panel 2 is placed under high temperature and high humidity conditions and a voltage is applied to the electrode 52 in that state, the pressure-sensitive adhesive layer 11 in contact with the electrode 52 is the migration inhibitor (mercapto) according to the present embodiment. By containing a component derived from a silane coupling agent having a group), migration of the electrode 52 is effectively suppressed. This prevents drive failure of the touch panel 2 due to disconnection or short circuit of the electrode 52.

The embodiments described above are described for facilitating the understanding of the present invention, and are 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, either one of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
1. 1. Preparation of (meth) acrylic acid ester copolymer 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate and 20 parts by mass of 2-hydroxyethyl acrylate are copolymerized to obtain a (meth) acrylic acid ester polymer. (A) was prepared. When the molecular weight of this (meth) acrylic acid ester polymer (A) was measured by the method described later, the weight average molecular weight (Mw) was 600,000.

2. 2. Preparation of Adhesive Composition As a silane coupling agent (B) having a mercapto group, 100 parts by mass (solid content conversion value; the same applies hereinafter) of the (meth) acrylic acid ester polymer (A) obtained in the above step 1. 3-Mercaptopropyltrimethoxysilane and methyltriethoxysilane cocondensate (manufactured by Shinetsu Chemical Industry Co., Ltd., trade name "X-41-1810", oligomer type, mercapto group equivalent: 450 g / mol) 0.05 mass 203 parts by mass of trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Coronate L") as a cross-linking agent (C) is mixed, sufficiently stirred, and diluted with methyl ethyl ketone. As a result, a coating solution of the adhesive composition having a solid content concentration of 38% by mass was obtained.

Here, Table 1 shows each formulation (solid content conversion value) of the adhesive composition when the (meth) acrylic acid ester polymer (A) is 100 parts by mass (solid content conversion value). Details of the abbreviations and the like shown in Table 1 are as follows.
[(Meta) Acrylic Ester Polymer (A)]
2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate
[Silane coupling agent having a mercapto group (B)]
X-41-1810: Cocondensate of 3-mercaptopropyltrimethoxysilane and methyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-41-1810", oligomer type, mercapto group equivalent: 450 g / mol )
KBM-803: 3-mercaptopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-803", low molecular weight type, mercapto group equivalent: 196.4 g / mol)
[Other silane coupling agents]
KBM-403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shinetsu Silicone Co., Ltd., trade name "KBM-403", low molecular weight type)
KBE-9007: 3-Isocyanatepropyltriethoxysilane (manufactured by Shinetsu Silicone Co., Ltd., trade name "KBE-9007", low molecular weight type)

3. 3. Manufacture of Adhesive Sheet A heavy release type release sheet (manufactured by Lintec Corporation, trade name "SP-PET382150") in which one side of a polyethylene terephthalate film is peeled off with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. , Thickness: 38 μm) was applied with a knife coater and then heat-treated at 90 ° C. for 1 minute to form a coating layer (thickness: 25 μm). Similarly, a light release type release sheet (manufactured by Lintec Corporation, product name "SP-PET382120") obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent from the coating solution of the adhesive composition obtained in the above step 2. ) Was coated with a knife coater and then heat-treated at 90 ° C. for 1 minute to form a coating layer (thickness: 25 μm).

Next, the heavy-release type release sheet with the coating layer obtained above and the light-release type release sheet with the coating layer obtained above are bonded together so that both coating layers are in contact with each other, and the temperature is 23 ° C. By curing for 7 days under the condition of 50% RH, an adhesive sheet having a structure of a heavy release type release sheet / an adhesive layer (thickness: 50 μm) / a light release type release sheet was prepared.

[Examples 2 to 10, Comparative Examples 1 to 10]
Examples except that the type and ratio of the silane coupling agent (silane coupling agent having a mercapto group (B) and other silane coupling agent) and the ratio of the cross-linking agent (C) are changed as shown in Table 1. An adhesive sheet was produced in the same manner as in 1. In Comparative Examples 7 to 10, N, N-bis (2-ethylhexyl)-(4 or 5) -methyl-1H-benzotriazole-1-methylamine (manufactured by BASF, trade name "" was used as a rust preventive. IRGMET 39 ") was added to the adhesive composition in the proportions shown in Table 1.

Here, the above-mentioned weight average molecular weight (Mw) is a polystyrene-equivalent weight average molecular weight measured under the following conditions (GPC measurement) using gel permeation chromatography (GPC).
<Measurement conditions>
-GPC measuring device: HLC-8020 manufactured by Tosoh Corporation
-GPC column (passed in the following order): TSK guard volume HXL-H manufactured by Tosoh Corporation
TSK gel GMHXL (x2)
TSK gel G2000HXL
・ Measurement solvent: tetrahydrofuran ・ Measurement temperature: 40 ° C

[Test Example 1] (Measurement of gel fraction)
The adhesive sheets obtained in Examples and Comparative Examples were cut into a size of 80 mm × 80 mm, the adhesive layer was wrapped in a polyester mesh (mesh size 200), the mass was weighed with a precision balance, and the above mesh was used. The mass of the pressure-sensitive adhesive alone was calculated by subtracting the mass of a single substance. 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. Then, the adhesive was taken out, air-dried for 24 hours in an environment of a temperature of 23 ° C. and a relative humidity of 50%, and further dried in an oven at 80 ° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. The mass at this time is M2. The gel fraction (%) is represented by (M2 / M1) × 100. The results are shown in Table 2.

[Test Example 2] (Measurement of adhesive strength)
The light release type release sheet is peeled off from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer is a polyethylene terephthalate (PET) film having an easy adhesive layer (manufactured by Toyobo Co., Ltd., product name "PET A4300"). , Thickness: 100 μm), and a laminated body of a heavy-release type release sheet / adhesive layer / PET film was obtained. The obtained laminate was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

In an environment of 23 ° C. and 50% RH, the heavy-release type release sheet is peeled off from the above sample, the exposed adhesive layer is attached to soda lime glass (manufactured by Nippon Sheet Glass Co., Ltd.), and then the autoclave manufactured by Kurihara Seisakusho Co., Ltd. is used. The pressure was increased at 0.5 MPa and 50 ° C. for 20 minutes. Then, after leaving it to stand for 24 hours under the conditions of 23 ° C. and 50% RH, the adhesive strength (N) was set to a peeling speed of 300 mm / min and a peeling angle of 180 degrees using a tensile tester (Tencilon manufactured by Orientec). / 25 mm) was measured. Conditions other than those described here were measured in accordance with JIS Z 0237: 2009. The results are shown in Table 2.

[Test Example 3] (Evaluation of migration prevention effect)
(1) Preparation of wiring board Copper of copper-clad laminate (manufactured by Nikkan Kogyo Co., Ltd., product name "Nikaflex") made by laminating copper foil (thickness: 18 μm) and polyethylene terephthalate film (thickness: 50 μm) An etching resist pattern was printed on the foil surface by a screen printing method. Then, unnecessary copper foil was removed by etching to form a comb-shaped electrode. The line width of each electrode was 300 μm, and the gap between the electrodes was 50 μm.

(2) Evaluation of migration prevention effect A polyethylene terephthalate (PET) film (Toyo Boseki Co., Ltd.) having an easy-adhesive layer was formed by peeling a light-release type release sheet from the adhesive sheets obtained in Examples and Comparative Examples and applying an exposed adhesive layer. A laminate of a heavy peeling type release sheet / adhesive layer / PET film was obtained by laminating with an easy-adhesive layer of (Product), product name “PET A4300”, thickness: 100 μm). Next, the heavy-release type release sheet was peeled off from the laminate, and the exposed pressure-sensitive adhesive layer was attached onto the comb-shaped electrode to prepare a sample.

The above sample was allowed to stand under moist heat conditions of 85 ° C. and 85% RH, and a voltage of 5 V was applied between the electrodes in that state to perform a migration test. After 8 hours, 24 hours, and 48 hours from the start of the test, the comb-shaped electrode was observed with an optical microscope (magnification: 10 times), and the migration prevention effect was evaluated based on the evaluation criteria shown below. The results are shown in Table 2.
⊚: Melting of the electrode (positive electrode) and formation of dendrites at the electrode (negative electrode) are not observed at all.
◯: Dissolution is observed only at the end of the electrode (positive electrode), and no dendrite formation is observed at the electrode (negative electrode).
X: Melting of the electrode (positive electrode) and formation of dendrites at the electrode (negative electrode) can be observed.
A reference image of the above evaluation criteria is shown in FIG.

As can be seen from Table 2, the adhesive sheet obtained in the examples was able to effectively prevent / suppress migration and was excellent in the migration prevention effect.

The migration inhibitor, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet according to the present invention can be suitably used for, for example, a capacitance type touch panel using a copper electrode or a silver electrode.

1 ... Adhesive sheet 11 ... Adhesive layer 12a, 12b ... Release sheet 2 ... Touch panel 3 ... Display module 4 ... Adhesive layer 5a ... First film sensor 5b ... Second film sensor 51 ... Base film 52 ... Electrode 6 ... Cover material 7 ... Printing layer

Claims (3)

Two release sheets and
An adhesive sheet provided with 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 layer
(Meta) acrylic ester polymer (A) and
A pressure-sensitive adhesive obtained from a pressure-sensitive adhesive composition containing a silane coupling agent (B) having a mercapto group as a migration inhibitor.
The (meth) acrylic acid ester polymer (A) is composed of a pressure-sensitive adhesive containing 10% by mass or more and 35% by mass or less of a hydroxyl group-containing monomer as a monomer unit constituting the polymer .
A pressure-sensitive adhesive sheet , wherein the pressure-sensitive adhesive layer is arranged so as to be in contact with electrodes on a touch panel . The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive composition further contains a cross-linking agent (C). The content of the silane coupling agent (B) having a mercapto group in the adhesive composition is 0.01 part by mass or more with respect to 100 parts by mass of the (meth) acrylic acid ester polymer (A). The adhesive sheet according to claim 1 or 2, wherein the amount is 5 parts by mass or less.