JP2011201942A - Adhesive for conductive film surface, and adhesive sheet for conductive film surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for a conductive film surface which significantly suppresses a resistance increasing rate of a conductive film which is an object for attachment in a high-humidity and high-temperature environment and does not cause deterioration of the conductive film that causes failure of information terminal equipment even in a high-humidity and high-temperature environment, and to provide the adhesive sheet for a conductive film surface using the same.SOLUTION: The adhesive for a conductive film surface is the adhesive used for the adhesive sheet to be attached to the conductive film surface of a conductive sheet on the surface of which the conductive film is provided. The adhesive includes an acrylic copolymer (A) and a crosslinking agent (B), wherein the acrylic copolymer (A) includes 50-85 mass% of a structural unit (a1) derived from an alkyl acrylate monomer having a 4-20C alkyl group, 10-30 mass% of a structural unit (a2) derived from a heterocyclic group-containing monomer, and 0.1-10 mass% of a structural unit (a3) derived from a hydroxy group-containing monomer.

Description

 The present invention relates to a pressure-sensitive adhesive to be applied to a conductive film, in particular, a pressure-sensitive adhesive for a conductive film surface to be applied to a conductive film used as a part of a member such as a capacitive touch panel, a liquid crystal display, or electronic paper, And it is related with the adhesive sheet for electrically conductive film surfaces using this.

A laminate in which a transparent conductive film made of a conductive material such as tin-doped indium oxide (ITO), zinc oxide, or tin oxide is formed on a transparent polymer substrate or glass is used for touch panels, liquid crystal displays, electronic paper, etc. Widely used as a transparent electrode in information terminal equipment.
In recent years, information terminal devices using such transparent electrodes have been reduced in size and thickness, and the inside of products has a complicated and dense structure. In the information terminal device, for example, a member such as a display device or a substrate and a laminated body having a transparent electrode are directly fixed via an adhesive sheet, thereby eliminating unnecessary space. In the information terminal device having such a structure, the transparent electrode and the adhesive are in direct contact.

Moreover, in an information terminal device, as another example of a structure adopting a structure in which a transparent electrode and an adhesive are in direct contact, a capacitive touch panel can be cited.
For example, as shown in the sectional view of FIG. 4, the capacitive touch panel 100 includes a hard coat layer 101, a resin film layer 102, a decorative print layer 103, an embedding adhesive layer 104, a glass layer 105, and a transparent conductive film. 106 are stacked in this order. The capacitive touch panel 100 is directly fixed to the display surface 108 a of the display device 108 through the adhesive layer 107 in the transparent conductive film 106.
In such a capacitive touch panel 100, a weak voltage is applied to the transparent conductive film 106, and charges are stored on the surface thereof, so that an electric field is formed on the transparent conductive film 106. Therefore, when a conductor such as a finger or a touch pen is brought into contact with the surface 101a of the hard coat layer 101, the electric field of the transparent conductive film 106 changes and the transparent conductive film 106 is discharged. At this time, the display device 108 performs a calculation process on weak current changes flowing in the four corners of the transparent conductive film 106, whereby the contact position on the capacitive touch panel 100 is detected.

When the adhesive is in direct contact with the conductive film in the internal member as in the information terminal device described above, the conventional adhesive is an acrylic acid that forms an acrylic copolymer that is the main component in a high temperature environment. Due to the acidity resulting from the carboxyl group (—COOH), the conductive film to be applied tends to be corroded. If the electrical resistance value of the conductive film increases due to this corrosion, it may cause a failure of the information terminal device.
In particular, in the case of the capacitive touch panel 100, in order to improve the detection of the contact position, the adhesive layer 107 that fixes the transparent conductive film 106 to the display surface 108a of the display device 108 is provided with the transparent conductive film 106. The performance which does not change the electric capacity (electrostatic capacity) of is required. In response to such a demand, an adhesive that can effectively prevent corrosion of the metal layer has been proposed (see, for example, Patent Document 1).

JP 2006-045315 A

 The pressure-sensitive adhesive composition disclosed in Patent Document 1 has an acrylic copolymer, benzotriazole and its derivatives as essential components for the purpose of preventing metal corrosion. However, in this pressure-sensitive adhesive composition, benzotriazole and its derivative are not polymerized on the acrylic copolymer, but benzotriazole and its derivative are formed on the substrate formed by crosslinking the acrylic copolymer. Since it is only dispersed, there is a concern that the adhesive force varies due to bleeding of benzotriazole and its derivatives and discoloration due to aging of these components.

 The present invention has been made in view of the above circumstances, and greatly suppresses the rate of increase in the resistance value of a conductive film to be applied in a high-temperature and high-humidity environment. It aims at providing the adhesive for conductive film surfaces which does not produce the deterioration of the electrically conductive film which causes the failure of an apparatus, and the adhesive sheet for conductive film surfaces using the same.

 The pressure-sensitive adhesive for conductive film surface of the present invention is a pressure-sensitive adhesive used for a pressure-sensitive adhesive sheet for attaching to a conductive film surface of a conductive sheet provided with a conductive film on the surface, and the alkyl group has 4 to 4 carbon atoms. 50 to 85% by mass of the structural unit (a1) derived from the alkyl acrylate monomer which is 20, 10 to 30% by mass of the structural unit (a2) derived from the heterocyclic group-containing monomer, and the structural unit (a3) derived from the hydroxyl group-containing monomer. It contains the acrylic copolymer (A) and 0.1 to 10 mass% of a crosslinking agent (B).

 In the adhesive for conductive film surface of the present invention, it is preferable that the hetero atom contained in the heterocyclic group-containing monomer (a2) is a nitrogen atom.

 In the conductive film surface pressure-sensitive adhesive of the present invention, the heterocyclic group-containing monomer (a2) is preferably acryloylmorpholine.

 The pressure-sensitive adhesive sheet for conductive film surface of the present invention is characterized in that the pressure-sensitive adhesive of the present invention is provided on at least one surface of a base film.

 In the pressure-sensitive adhesive sheet for conductive film surface of the present invention, it is preferable that the base film is a polyethylene terephthalate film and the resin film constituting the conductive sheet is a polyethylene terephthalate film.

 In the pressure-sensitive adhesive sheet for a conductive film surface of the present invention, the conductive film constituting the conductive sheet is preferably made of a metal oxide.

 In the conductive sheet surface pressure-sensitive adhesive sheet of the present invention, the metal oxide is preferably tin-added indium oxide.

 It is preferable that the adhesive sheet for electrically conductive film surfaces of this invention is used as a member of a touch panel.

 In the pressure-sensitive adhesive sheet for a conductive film surface of the present invention, it is preferable that the touch panel is a capacitance type.

 According to the conductive film surface pressure-sensitive adhesive of the present invention, the resistance value of the conductive film of the conductive sheet to which the conductive film surface pressure-sensitive adhesive sheet using the conductive film surface pressure-sensitive adhesive is attached in a high-temperature and high-humidity environment. Therefore, the information terminal device using the pressure-sensitive adhesive sheet for conductive film surface of the present invention can be used in a good state even in a high temperature and high humidity environment.

It is a schematic sectional drawing which shows one Embodiment of the adhesive sheet for electrically conductive film surfaces of this invention. In the Example and comparative example of the adhesive sheet for electrically conductive film surfaces of this invention, it is a schematic sectional drawing which shows an example of the resistance value measurement sample used for an electrical resistance value measurement test. It is explanatory drawing of the electrical resistance value measurement test in the Example and comparative example of the adhesive sheet for electrically conductive film surfaces of this invention. It is a schematic sectional drawing which shows an example of an electrostatic capacitance type touch panel, and its application example.

Embodiments of the pressure-sensitive adhesive for conductive film surface of the present invention and the pressure-sensitive adhesive sheet for conductive film surface using the same will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

 In the present specification and claims, the “structural unit” means a monomer unit (monomer unit) constituting a resin component (polymer, copolymer).

“Surface conductive film adhesive”
The adhesive for conductive film surface of this invention is used for the adhesive sheet for sticking to the electrically conductive film surface of the conductive sheet in which the electrically conductive film was provided in the surface, an acrylic copolymer (A) and a crosslinking agent (B ).
The acrylic copolymer (A) is a structural unit derived from 50 to 85% by mass of a structural unit (a1) derived from an alkyl acrylate monomer having an alkyl group having 4 to 20 carbon atoms and a heterocyclic group-containing monomer. It is a copolymer comprising 10 to 30% by mass of (a2) and 0.1 to 10% by mass of a structural unit (a3) derived from a hydroxyl group-containing monomer.

The alkyl acrylate monomer having 4 to 20 carbon atoms in the alkyl group is a linear or branched alkyl group-containing acrylate monomer, and includes butyl acrylate, pentyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, Examples include isooctyl acrylate, lauryl acrylate, and stearyl acrylate. Among these, butyl acrylate is preferable from the viewpoint that the pressure-sensitive adhesive for conductive film surfaces of the present invention can exhibit appropriate adhesive strength.
The alkyl group here is a substituent obtained by removing one hydrogen from the end of the alkane in accordance with the IUPAC nomenclature, and refers to the one represented by the general formula —C _n H _{2n + 1} .

The content of the structural unit (a1) derived from an alkyl acrylate monomer having 4 to 20 carbon atoms in the alkyl group is 50 to 85% by mass, preferably 55 to 80%, when the total monomer amount is 100% by mass. It is mass%, More preferably, it is 60-80 mass%.
When the content of the structural unit (a1) derived from the alkyl acrylate monomer is within this range, the conductive film surface pressure-sensitive adhesive of the present invention expresses an appropriate adhesive force and contains a heterocyclic group which is an essential component. There is room for containing the structural unit (a2) derived from the monomer and the structural unit (a3) derived from the hydroxyl group-containing monomer.

 That is, when the content of the structural unit (a1) derived from the alkyl acrylate monomer is less than 50% by mass, the conductive film surface pressure-sensitive adhesive of the present invention does not exhibit sufficient adhesive strength. On the other hand, when the content of the structural unit (a1) derived from the alkyl acrylate monomer exceeds 85% by mass, the structural unit (a2) derived from a sufficient amount of the heterocyclic group-containing monomer to express the target function, In addition, the structural unit (a3) derived from the hydroxyl group-containing monomer cannot be contained.

Examples of the heterocyclic group-containing monomer include those in which the hetero atom is a nitrogen atom, an oxygen atom, a sulfur atom, or the like.
Among these heterocyclic group-containing monomers, those in which the hetero atom is a nitrogen atom include (meth) acryloylmorpholine, vinylpyrrolidone, (meth) acryloylpiperidine and the like.
Among the heterocyclic group-containing monomers, examples in which the hetero atom is an oxygen atom include (meth) acryloylmorpholine, furanyl acrylate and the like.
Among the heterocyclic group-containing monomers, examples in which the hetero atom is a sulfur atom include thiophenyl (meth) acrylate.
Among these heterocyclic group-containing monomers, in a high temperature and high humidity environment, the hetero atom is a nitrogen atom from the viewpoint of high corrosion prevention effect of the conductive film to which the adhesive for the conductive film surface of the present invention is applied. Some are preferred, and acryloylmorpholine is more preferred.
Acryloylmorpholine can be copolymerized with an alkyl acrylate monomer or a hydroxyl group-containing monomer having 4 to 20 carbon atoms in the alkyl group constituting the acrylic copolymer (A), and the glass transition of the copolymer. Since the point (Tg) is relatively high (145 ° C.), the conductive film surface pressure-sensitive adhesive of the present invention is more heat-resistant than those using copolymers of other acrylic monomers even in a high-temperature and high-humidity environment. Excellent in properties. Therefore, by using acryloylmorpholine as a monomer for forming the acrylic copolymer (A), the acrylic copolymer (A) is decomposed even in a high-temperature and high-humidity environment. It is estimated that it can prevent corroding the electrically conductive film which is the sticking object of the adhesive for conductive film surfaces of invention.

The content of the structural unit (a2) derived from the heterocyclic group-containing monomer is 10 to 30% by mass, preferably 14 to 26% by mass, more preferably 100% by mass when the total monomer amount is 100% by mass. 17-22 mass%.
If the content of the structural unit (a2) derived from the heterocyclic group-containing monomer is within this range, the conductive film surface-use pressure-sensitive adhesive of the present invention can suppress deformation under high temperature and high humidity, and can be appropriately bonded. Expresses power.

 That is, when the content of the structural unit (a2) derived from the heterocyclic group-containing monomer is less than 10% by mass, the conductive film surface pressure-sensitive adhesive of the present invention cannot suppress deformation under high temperature and high humidity. On the other hand, when the content of the structural unit (a2) derived from the heterocyclic group-containing monomer exceeds 30% by mass, the conductive film surface pressure-sensitive adhesive of the present invention does not exhibit sufficient adhesive force.

As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate And hydroxyalkyl (meth) acrylates such as 4-hydroxybutyl (meth) acrylate.
Among these, 2-hydroxyethyl acrylate is preferable from the viewpoint of increasing the adhesive strength.

The content of the structural unit (a3) derived from the hydroxyl group-containing monomer is 0.1 to 10% by mass, preferably 0.3 to 5% by mass, more preferably 100% by mass when the total monomer amount is 100% by mass. Is 0.5-3 mass%.
When the content of the structural unit (a3) derived from the hydroxyl group-containing monomer is within this range, the pressure-sensitive adhesive for the conductive film surface of the present invention exhibits an appropriate adhesive force, and the acrylic copolymer (A) is Since the crosslinking origin with a crosslinking agent (B) can be ensured, the adhesive for conductive film surfaces of this invention can obtain moderate cohesion force.

 That is, when the content of the structural unit (a3) derived from the hydroxyl group-containing monomer is less than 0.1% by mass, the conductive film surface pressure-sensitive adhesive of the present invention has insufficient cohesive force. On the other hand, when the content of the structural unit (a3) derived from the hydroxyl group-containing monomer exceeds 10% by mass, sufficient adhesive strength is not exhibited.

 The acrylic copolymer (A) is a structural unit derived from a carboxyl group-containing monomer such as acrylic acid, methacrylic acid, crotonic acid, fumaric acid, itaconic acid, maleic acid or 2-carboxyethyl methacrylate. It is preferable not to contain. When the acrylic copolymer (A) contains a carboxyl group-containing monomer, there is a risk of corroding the conductive film of the conductive sheet to which the adhesive for the conductive film surface of the present invention is applied.

 As the crosslinking agent (B), one that reacts with the hydroxyl group of the hydroxyl group-containing monomer to crosslink and develops a cohesive force necessary as an adhesive is used. For example, an organic polyvalent isocyanate compound, an organic polyvalent epoxy compound is used. And organic polyvalent imine compounds. Among these, an organic polyvalent isocyanate compound is preferable from the viewpoint of availability.

Examples of organic polyvalent isocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, diphenylmethane -2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like.
Moreover, the trimer of these polyvalent isocyanate compounds and the terminal isocyanate-retane prepolymer obtained by making these polyvalent isocyanate compounds and a polyol compound react can be used.

 Examples of organic polyvalent epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, 1,3-bis (N, N-diglycidylaminomethyl) toluene, N, N, N ′, N′-tetraglycidyl- Examples include 4,4-diaminodiphenylmethane.

 Examples of organic polyvalent imine compounds include N, N′-diphenylmethane-4,4′-bis (1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri- β-aziridinylpropionate, N, N′-toluene-2,4-bis (1-aziridinecarboxyamide) triethylenemelamine and the like can be mentioned.

 Content of a crosslinking agent is 0.01-10 mass parts with respect to 100 mass parts of solid content of an acrylic copolymer (A) from a viewpoint of raising the adhesive force of the adhesive for conductive film surfaces of this invention. It is preferable that it is 0.03-7 mass parts, and it is especially preferable that it is 0.05-5 mass parts.

 The pressure-sensitive adhesive for conductive film surfaces of the present invention can take the form of various pressure-sensitive adhesive sheets processed into a sheet shape. For example, the pressure-sensitive adhesive for conductive film surface of the present invention can be in the form of a double-sided pressure-sensitive adhesive sheet without a substrate film, in which release sheets are provided on both sides of the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for conductive film surface. By setting it as such a form, the adhesive for conductive film surfaces of this invention is used for fixation of display apparatuses, such as a electrically conductive film which consists of ITO, Ag nanowire, etc., and a liquid crystal display (LCD).

The adhesive for the conductive film surface of the present invention preferably has an adhesive strength to the conductive film of 8 N / 25 mm or more, more preferably 9 N / 25 mm or more.
If the adhesive force of the adhesive for conductive film surface of the present invention to the conductive film is 8 N / 25 mm or more, the conductive sheet is firmly fixed. Therefore, the expansion and contraction of the conductive sheet due to heating or the like is suppressed by fixing with the adhesive force, and the conductive sheet The change in resistance value of the conductive film due to the expansion and contraction of the film can be suppressed.
In addition, in the case where the conductive film is made of a metal oxide, it is preferable that the conductive film formed on the conductive sheet is a metal oxide because the resistance value is likely to change due to expansion and contraction of the conductive sheet.

Next, the manufacturing method of the adhesive for conductive film surfaces of this invention is demonstrated.
First, the alkyl acrylate monomer having an alkyl group having 4 to 20 carbon atoms, the heterocyclic group-containing monomer, and the hydroxyl group-containing monomer are stirred and mixed in a solvent at the predetermined compounding ratio described above, and reacted. Consists of a structural unit (a1) derived from an alkyl acrylate monomer having 4 to 20 carbon atoms in the alkyl group, a structural unit (a2) derived from a heterocyclic group-containing monomer, and a structural unit (a3) derived from a hydroxyl group-containing monomer. An acrylic copolymer (A) to be prepared is synthesized (step A).
In the next step, the obtained acrylic copolymer (A) is used in the form of a solution dissolved in the solvent used in the reaction or in the form from which the solvent used in the reaction is removed.

 In step A, the reaction temperature and reaction time are as follows: a structural unit derived from an alkyl acrylate monomer having an alkyl group having 4 to 20 carbon atoms (a1), a structural unit derived from a heterocyclic group-containing monomer (a2), and a hydroxyl group-containing monomer. It adjusts suitably according to the kind of a structural unit (a3) derived, etc., these compounding ratios, etc.

Although it does not specifically limit as a solvent used at the process A, For example, toluene, ethyl acetate, methyl ethyl ketone, etc. are mentioned.
In Step A, a catalyst may be added as necessary.

Next, 0.01 to 10 parts by mass of a crosslinking agent (B) is added to 100 parts by mass of the solid content of the acrylic copolymer (A), and these are stirred and mixed in a solvent to cause a reaction. The adhesive for conductive film surfaces of the present invention is prepared (Step B).
The obtained conductive film surface pressure-sensitive adhesive is in the form of a solution dissolved in a solvent used at the time of reaction or a solid form from which the solvent used at the time of reaction is removed in the manufacturing process of the conductive film surface pressure-sensitive adhesive sheet described later. Used.

In step B, the reaction temperature and reaction time are appropriately adjusted according to the type of the acrylic copolymer (A), the cross-linking agent (B), the blending ratio thereof, and the like.
In Step B, the same solvent as in Step A is used.

"Adhesive sheet for conductive film surface"
FIG. 1 is a schematic cross-sectional view showing one embodiment of the conductive sheet surface pressure-sensitive adhesive sheet of the present invention.
The pressure-sensitive adhesive sheet 10 for conductive film surface of this embodiment is provided on the base film 11 and one surface 11a of the base film 11, and is composed of a pressure-sensitive adhesive layer 12 made of the pressure-sensitive adhesive for conductive film surface of the present invention, and a pressure-sensitive adhesive. It is schematically configured from a release sheet 13 affixed to a surface (hereinafter referred to as “one surface”) 12 a opposite to the surface in contact with the base material film 11 of the agent layer 12.
This conductive film surface pressure-sensitive adhesive sheet 10 is a single-sided pressure-sensitive adhesive sheet with a base film in which a pressure-sensitive adhesive layer 12 is provided on one surface 11 a of the base film 11.

Although it does not specifically limit as the base film 11, For example, a polyethylene terephthalate, a polyethylene naphthalate, a polyimide, polyetherimide, polyaramid, polyetherketone, polyetheretherketone, polyphenylene sulfide, poly (4-methylpentene-1) ) Polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyethylene terephthalate, polyurethane, ethylene-vinyl acetate copolymer, ionomer resin, ethylene (meth) acrylic acid copolymer, polystyrene Resin films made of polycarbonate, fluororesin, low density polyethylene, linear low density polyethylene, triacetyl cellulose, polymethyl methacrylate, and the like, and Examples thereof include films in which a hard coat layer is provided on the surface of the resin film, films in which a foam structure is provided in these resin films, and paper base materials such as fine paper, coated paper, glassine paper, and laminated paper. .
In general, a polyethylene terephthalate film is often used as the base material of the conductive sheet. If the material of the base film 11 and the conductive sheet used in the present invention is the same, the same stretch behavior is exhibited at the time of temperature change. Stress can be suppressed. Therefore, deterioration of the conductive film can be prevented, and a change in resistance value of the transparent conductive film under high temperature and high humidity can be suppressed.
From such a viewpoint, the base film 11 used in the present invention is preferably a polyethylene terephthalate film.

 The thickness of the base film 11 is preferably 5 μm to 300 μm, more preferably 10 μm to 100 μm.

 Various release sheets are used as the release sheet 13, but a sheet material having peelability on the surface is used. As such a sheet material, polyethylene terephthalate, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polybutylene terephthalate, polyurethane, ethylene-vinyl acetate copolymer, ionomer resin, Resin film made of ethylene (meth) acrylic acid copolymer, polystyrene, polycarbonate, fluororesin, low density polyethylene, linear low density polyethylene, triacetyl cellulose, etc., fine paper, coated paper, glassine paper, laminated paper, etc. Can be mentioned.

In order to impart peelability to the surface of the sheet material used for the release sheet 13, a release agent such as a fluororesin, a silicone resin, or a long-chain alkyl group-containing carbamate is applied to the surface, and these surfaces are applied to the surface. A release agent is attached.
The thickness of the release sheet 13 is preferably 5 μm to 300 μm, more preferably 10 μm to 200 μm. When polyethylene terephthalate is used as the sheet material for the release sheet 13, the thickness of the release sheet 13 is most preferably 10 μm to 100 μm.

Next, the manufacturing method of the adhesive sheet 10 for electrically conductive film surfaces is demonstrated.
First, after coating the adhesive containing composition prepared by dissolving the adhesive for conductive film surface of the present invention in a solvent on one surface 13a of the release sheet 13, the temperature is 80 to 150 ° C for 30 seconds to 5 seconds. Heat for minutes to evaporate the solvent and low boiling components. Thereby, the adhesive layer 12 which consists of the adhesive for electrically conductive film surfaces of this invention is formed in the one surface 13a of the peeling sheet 13 (process C).

In this step C, as a method for applying the pressure-sensitive adhesive-containing composition to one surface 13a of the release sheet 13, a gravure coating method, a bar coating method, a spray coating method, a spin coating method, a roll coating method, a die coating method. A known coating method such as a knife coating method, an air knife coating method, or a curtain coating method is used.
Moreover, it is although it does not specifically limit as a coating device used for application | coating of an adhesive containing composition, A well-known apparatus is used.

Furthermore, it is preferable that the application amount of the adhesive for conductive film surface after drying is 1-100 micrometers, More preferably, it is 5-50 micrometers, Most preferably, it is 10-30 micrometers.
If the coating amount of the adhesive for the conductive film surface after drying is within this range, the pressure-sensitive adhesive layer 12 exhibits a sufficient adhesive force and is punched with a blade in the shape of the object to be deposited (punching process) ), There is no risk of bleeding from the planned shape due to deformation of the adhesive.
That is, if the coating amount of the adhesive for the conductive film surface after drying is less than 1 μm, the adhesive strength of the adhesive layer 12 may be insufficient. On the other hand, when the coating amount of the conductive film surface pressure-sensitive adhesive after drying exceeds 100 μm, the punching suitability decreases.

 Next, the base film 11 is bonded to the surface (hereinafter referred to as “the other surface”) 12 b opposite to the surface in contact with the release sheet 13 of the pressure-sensitive adhesive layer 12, and the adhesive for the conductive film surface. A sheet 10 is obtained (step D).

In this embodiment, the conductive film surface pressure-sensitive adhesive sheet 10, which is a single-sided pressure-sensitive adhesive sheet with a base film provided with a pressure-sensitive adhesive layer 12 on one surface (single side) 11 a of the base film 11, The pressure-sensitive adhesive sheet for conductive film surface of the present invention is not limited to this.
As mentioned above, the pressure-sensitive adhesive sheet for the conductive film surface of the present invention is a double-sided pressure-sensitive adhesive sheet without a base film provided with release sheets on both sides of the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for the conductive film surface of the present invention. You can also.

When the pressure-sensitive adhesive sheet for conductive film surface of the present invention is in the form of a double-sided pressure-sensitive adhesive sheet without a substrate film, two release sheets are required.
That is, in order to constitute a double-sided pressure-sensitive adhesive sheet without a base film, another release sheet is bonded to the surface of the pressure-sensitive adhesive layer coated on one surface of the release sheet, and another laminate sheet is bonded to the laminate. To do. In that case, it is preferable to make a difference between the peeling forces of the two release sheets. If there is a difference between the release forces of the two release sheets, when only the release sheet (light release sheet) side with a lower release force is peeled off, the adhesive is applied from the release sheet (heavy release sheet) side with a higher release force. It is possible to prevent the possibility of the layer floating and the risk of the adhesive layer being stretched and deformed in an attempt to follow both release sheets.
Or in order to comprise a double-sided adhesive sheet without a base film, after providing an adhesive layer in one side of the release sheet which apply | coated the release agent on both surfaces, you may wind it in roll shape.

Moreover, the adhesive sheet for electrically conductive film surfaces of this invention can also be used as the double-sided adhesive sheet with a base film in which the adhesive layer was provided in the one surface and other surface (both surfaces) of a base film.
When the pressure-sensitive adhesive sheet for conductive film surface of the present invention is in the form of a double-sided pressure-sensitive adhesive sheet with a base film, (a) one side of the release sheet of the double-sided pressure-sensitive adhesive sheet without a base film is peeled off on both sides of the base film The double-sided pressure-sensitive adhesive sheet without the base film is laminated to form a laminate. (B) The pressure-sensitive adhesive-containing composition is directly applied to both sides of the base film to form a pressure-sensitive adhesive layer. (C) One side of the release sheet of the double-sided pressure-sensitive adhesive sheet without base film is peeled off, and the double-sided pressure-sensitive adhesive sheet without base film is formed on one side of the base film. In addition, the pressure-sensitive adhesive-containing composition is directly applied to the other surface of the base film to form a pressure-sensitive adhesive layer, and a release sheet is bonded to the pressure-sensitive adhesive layer to form a laminate. The method is adopted .

In the pressure-sensitive adhesive sheet for attaching a conductive film of the present invention, the object to be attached is a conductive sheet in which a conductive film is provided on a base film.
Although it does not specifically limit as an electroconductive sheet, For example, what provided the electrically conductive film which consists of electroconductive materials, such as a metal or a metal oxide, to the base film similar to the above-mentioned base film 11 is mentioned.

The conductive material is not particularly limited, but silver, copper, gold, platinum, indium oxide, zinc oxide, tin oxide, titanium oxide, tin-added indium oxide (ITO), indium oxide / zinc oxide (IZO), gallium added Examples include zinc oxide (GZO) and antimony-doped tin oxide (ATO). Among these conductive materials, a metal oxide is preferable from the viewpoint of high electrical resistivity, and among the metal oxides, tin-added indium oxide (ITO) is most preferable from the viewpoint of transparency.
The tin-added indium oxide (ITO) is a metal oxide in which some indium atoms are substituted with tin atoms in the crystal structure of indium (III) oxide.

 Among conductive sheets, transparent conductive films with dry coating of tin-added indium oxide (ITO) on the surface of polyethylene terephthalate film are more effective than other conductive sheets in terms of reducing manufacturing costs and reducing the thickness of mounted equipment. Is also excellent.

When a transparent conductive film in which tin-doped indium oxide (ITO) is dry-coated on the surface of a polyethylene terephthalate film is used as the conductive sheet, the base film constituting the adhesive sheet for attaching a conductive film of the present invention is also polyethylene terephthalate. A film is preferred. If the material of the base film and the conductive sheet is the same, the same expansion and contraction behavior is exhibited when the temperature changes, so that the stress applied to the conductive film can be suppressed by the difference in the degree of expansion and contraction between the base film and the conductive sheet. Therefore, deterioration of the conductive film can be prevented, and a change in resistance value of the transparent conductive film under high temperature and high humidity can be suppressed.
For touch panels for mobile phones and smartphones where these elements are required, especially for projection type capacitive touch panels, the adhesive sheet for attaching a conductive film of the present invention is formed from tin-added indium oxide (ITO) on the surface of a polyethylene terephthalate film. It is preferable to use what was stuck to the transparent conductive film provided with the electrically conductive film used as a member.

The pressure-sensitive adhesive for conductive film surface of the present invention comprises 50 to 85% by mass of a structural unit (a1) derived from an alkyl acrylate monomer having an alkyl group having 4 to 20 carbon atoms and a structural unit derived from a heterocyclic group-containing monomer ( It contains an acrylic copolymer (A) containing 10 to 30% by mass of a2) and 0.1 to 10% by mass of a structural unit (a3) derived from a hydroxyl group-containing monomer and a crosslinking agent (B).
The pressure-sensitive adhesive sheet for sticking a conductive film of the present invention has a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for the conductive film surface of the present invention, and increases the electrical resistance value of the conductive film to be stuck even in a high-temperature and high-humidity environment. Since the rate can be kept within an allowable range, it is preferably used as a member of a touch panel. Specifically, the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive for the conductive film surface of the present invention has an electrical property of the conductive film to be applied in an environment at a temperature of 80 ° C. or an environment at a temperature of 60 ° C. and a humidity of 90% RH. The increase rate of the resistance value can be suppressed to 20% or less. If the increasing rate of the electrical resistance value of the conductive film is 20% or less, there is no problem in detecting the contact position of the capacitive touch panel described later.

Examples of the touch panel include a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitance method. Among these, the capacitive touch panel is a system that operates the device by detecting a change in the capacitance of the transparent conductive film when a finger or a touch pen is brought into contact with the screen or the like, and the touch panel is applied. The position of the touch on the touch panel is detected by the device calculating the change in capacitance.
From such a principle, in the capacitive touch panel, a slight change in the electric resistance value of the transparent conductive film leads to a decrease in accuracy, resulting in a failure. The adhesive sheet for attaching a conductive film of the present invention is particularly preferably used as a member of a capacitive touch panel because it does not increase the electrical resistance value of the conductive film to be attached even in a high temperature and high humidity environment.
Moreover, although the capacitive touch panel has a surface type and a projection type, the adhesive sheet for attaching a conductive film of the present invention can be used for either type.

 According to the conductive film surface pressure-sensitive adhesive of the present invention and the conductive film surface pressure-sensitive adhesive sheet using the same, the conductive film of the conductive sheet to which the conductive film surface pressure-sensitive adhesive sheet is attached in a high-temperature and high-humidity environment. Since the rate of increase of the resistance value can be significantly suppressed, the information terminal device using the pressure-sensitive adhesive sheet for conductive film surface of the present invention can be used in a good state even in a high temperature and high humidity environment.

 EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example.

"Example 1"
Butyl acrylate (BA), methyl acrylate (MA), 2-hydroxyethyl acrylate (HEA), and acryloylmorpholine (ACMO) in a mass ratio in ethyl acetate, BA: MA: HEA: ACMO = 79: 2: The mixture was stirred and mixed at 2:17, and these monomers were copolymerized to synthesize an acrylate copolymer (BA: MA: HEA: ACMO = 79: 2: 2: 17, molecular weight 900,000).
The obtained acrylic ester copolymer was used in the next step as a solution (solid content concentration 35.1%) dissolved in ethyl acetate.
Next, 0.5 parts by mass of an isocyanate-based crosslinking agent (product name “BHS-8515”, solid concentration 37.5%, manufactured by Toyo Ink Co., Ltd.) is added to 100 parts by mass of the acrylic ester copolymer solution. The mixture was stirred and mixed to prepare an acrylic pressure-sensitive adhesive solution. At this time, the addition amount of the isocyanate crosslinking agent with respect to 100 parts by mass of the solid content of the acrylate copolymer was 0.53 parts by mass.
Next, an acrylic pressure-sensitive adhesive solution was applied to one side of the heavy release sheet (product name “SP-PET38 T103-1” manufactured by Lintec Corporation) so that the thickness of the pressure-sensitive adhesive layer after drying was 25 μm. The mixture was heated at 120 ° C. for 2 minutes to form an adhesive layer made of an acrylic adhesive on one surface of the heavy release sheet.
Next, a light release sheet (product name “SP-PET38 1031” manufactured by Lintec Corporation) was bonded to the adhesive surface of the adhesive layer to obtain a double-sided adhesive sheet without a substrate film.

"Example 2"
Acrylic ester copolymer (BA: MA: HEA: ACMO = 83.5: 2: 0.5: 14, molecular weight 720,000) was synthesized and dissolved in ethyl acetate (solid content concentration 35.7). %) 1.8 parts by mass of an isocyanate-based cross-linking agent (product name “BXX5640”, solid content concentration 35%) manufactured by Toyo Ink Co., Ltd.) is added to 100 parts by mass, and the mixture is stirred and mixed to prepare an acrylic adhesive solution. A double-sided PSA sheet without a substrate film was obtained in the same manner as Example 1 except that it was prepared.
At this time, the addition amount of the isocyanate-based crosslinking agent with respect to 100 parts by mass of the solid content of the acrylate copolymer was 1.76 parts by mass.

"Example 3"
Acrylate ester copolymer (BA: MA: HEA: ACMO = 79: 1: 20, molecular weight 800,000) was synthesized, and 100 parts by mass of an isocyanate solution (solid content concentration 30%) was dissolved in isocyanate. Except that 0.45 parts by mass of a cross-linking agent (manufactured by Soken Chemical Co., Ltd., product name “TD-75”, solid content concentration: 75%) was added, stirred and mixed to prepare an acrylic pressure-sensitive adhesive solution. In the same manner as in Example 1, a double-sided PSA sheet without a substrate film was obtained.
At this time, the addition amount of the isocyanate crosslinking agent with respect to 100 parts by mass of the solid content of the acrylic ester copolymer was 1.13 parts by mass.

"Comparative Example 1"
Butyl acrylate (BA), methyl acrylate (MA) and acrylic acid (AAc) are stirred and mixed at a mass ratio of BA: MA: AAc = 77: 20: 3 in ethyl acetate, and these monomers are mixed. Copolymerized acrylic ester copolymer (BA: MA: AAc = 77: 20: 3, molecular weight 800,000) was synthesized, and 100 parts by mass of a solution (solid content concentration 28%) dissolved in ethyl acetate In addition, 1.75 parts by mass of an isocyanate-based crosslinking agent (product name “BHS-8515”, solid concentration 37.5%, manufactured by Toyo Ink Co., Ltd.) and an aluminum chelate-based crosslinking agent (product name “M- 5A ", solid content concentration 4.95%) 1.75 parts by mass were added, stirred and mixed to prepare an acrylic pressure-sensitive adhesive solution. Adhesive To obtain the door.
At this time, the addition amount of the isocyanate crosslinking agent was 2.34 parts by mass with respect to 100 parts by mass of the solid content of the acrylate copolymer, and the addition amount of the aluminum chelate crosslinking agent was 0.31 parts by mass.

"Comparative Example 2"
Butyl acrylate (BA), ethyl acrylate (EA), and acrylic acid (AAc) are stirred and mixed at a mass ratio of BA: EA: AAc = 77: 20: 3 in ethyl acetate. Copolymerized acrylic ester copolymer (BA: EA: AAc = 77: 20: 3, molecular weight 900,000) was synthesized, and 100 parts by mass of a solution (solid content concentration 30%) dissolved in ethyl acetate 4 parts by mass of an aluminum chelate-based cross-linking agent (product name “M-5A”, solid content concentration 4.95%, manufactured by Soken Chemical Co., Ltd.) was added, stirred and mixed to prepare an acrylic pressure-sensitive adhesive solution. Except for this, a double-sided PSA sheet without a substrate film was obtained in the same manner as Example 1.
At this time, the addition amount of the aluminum chelate crosslinking agent with respect to 100 parts by mass of the solid content of the acrylic ester copolymer was 0.66 parts by mass.

“Comparative Example 3”
Butyl acrylate (BA), trifluoroethyl methacrylate (TFEMA), and hydroxyethyl acrylate (HEA) are stirred and mixed at a mass ratio of BA: TFEMA: HEA = 87: 10: 3 in ethyl acetate. An acrylic acid ester copolymer (BA: TFEMA: HEA = 87: 10: 3, molecular weight 700,000) was synthesized by copolymerizing the above monomers, and a solution (solid content concentration 26.7) dissolved in ethyl acetate was synthesized. %) 2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Toyo Ink Co., Ltd., product name “BHS-8515”, solid content concentration 37.5%) is added to 100 parts by mass, and the acrylic pressure-sensitive adhesive is stirred and mixed. A double-sided PSA sheet without a substrate film was obtained in the same manner as in Example 1 except that the solution was prepared.
At this time, the addition amount of the isocyanate-based crosslinking agent with respect to 100 parts by mass of the solid content of the acrylic ester copolymer was 2.81 parts by mass.

“Comparative Example 4”
Butyl acrylate (BA), methyl acrylate (MA), acrylamide (AAm), and hydroxyethyl acrylate (HEA) in mass ratio in ethyl acetate, BA: MA: AAm: HEA = 68.5: 30: 1 : Stirring and mixing at 0.5, and acrylic acid ester copolymer (BA: MA: AAm: HEA = 68.5: 30: 1: 0.5, molecular weight 900,000) obtained by copolymerizing these monomers Was added to 100 parts by mass of a solution (solid content concentration 29%) dissolved in ethyl acetate, and an isocyanate-based crosslinking agent (product name “TD-75” manufactured by Soken Chemical Co., Ltd., solid content concentration 75%). A double-sided PSA sheet without a substrate film was obtained in the same manner as in Example 1 except that 45 parts by mass were added, stirred and mixed to prepare an acrylic adhesive solution.
At this time, the addition amount of the isocyanate-based crosslinking agent with respect to 100 parts by mass of the solid content of the acrylate copolymer was 1.16 parts by mass.

“Comparative Example 5”
To 100 parts by mass of a silicone-based pressure-sensitive adhesive (manufactured by Toray Dow Corning, SD-4580), 0.9 part by mass of a platinum catalyst (manufactured by Toray Dow Corning, SRX-212) is added, stirred, mixed, and silicone is added. A system adhesive solution was prepared.
Next, a silicone-based pressure-sensitive adhesive solution was directly applied to the easily adhesive surface of a polyethylene terephthalate film (Toyobo Co., Ltd., PET50-A4100) as a heavy release sheet so that the thickness of the pressure-sensitive adhesive layer after drying was 25 μm. The mixture was heated at a temperature of 120 ° C. for 2 minutes to form a pressure-sensitive adhesive layer made of a silicone-based pressure-sensitive adhesive on the easy adhesion surface of the polyethylene terephthalate film.
Next, a light release sheet (SP-PET50D, manufactured by Lintec Corporation) was bonded to the adhesive surface of the adhesive layer to obtain a double-sided adhesive sheet without a substrate film.

"Evaluation"
About the base-material-free double-sided adhesive sheet obtained in Examples 1-3 and Comparative Examples 1-5, the electrical resistance value was measured and the increase rate of the electrical resistance value was calculated by the following test method.
A resistance value measurement sample used in the electrical resistance value measurement test will be described with reference to FIG.
A polyethylene terephthalate film 21 having an ITO film 22 provided on one surface 21a is prepared by sputtering, and a surface 21b of the polyethylene terephthalate film 21 on which the ITO film 22 is not provided and one surface 23a of the glass plate 23 are provided. Bonding was performed via a bonding tape 24 (product name “Tackliner TL-70”, manufactured by Lintec Corporation).
Next, a conductive resin material containing silver (manufactured by Fujikura Kasei Co., Ltd.) is formed on a surface 22a opposite to the surface of the ITO film 22 that is in contact with the polyethylene terephthalate film 21 (hereinafter referred to as "one surface"). , Product name “FA-301CA” Dortite touch panel circuit type) is applied so as to have a rectangular electrode shape of 20 mm × 5 mm, and then heated for 20 minutes at a temperature of 80 ° C. and dried to serve as a resistance measurement point. Two electrodes 25 were produced at a distance. At that time, the position was adjusted so that the distance between the two electrodes 25 and 25 was 2 cm.
Next, the light release sheet of the baseless double-sided pressure-sensitive adhesive sheet obtained in Examples 1 to 3 and Comparative Examples 1 to 5 was peeled, and the exposed adhesive layer of the double-sided pressure-sensitive adhesive sheet without base material was exposed on one surface. As the base film 26, a polyethylene terephthalate film (Toyobo Co., Ltd., “PET50-A4100”, thickness 50 μm) is pasted, and the base film 26 and a double-sided adhesive without a base provided on one surface 26a thereof are attached. A single-sided PSA sheet with a base film having a PSA layer 27 of the sheet was produced.
Next, the obtained single-sided pressure-sensitive adhesive sheet with a base film was cut into a size of 20 mm × 250 mm, the heavy release sheet of the single-sided pressure-sensitive adhesive sheet with a base film was peeled off, and the pressure-sensitive adhesive layer 27 was two points of the electrode 25. A single-sided pressure-sensitive adhesive sheet with a base film was attached to one surface 22a of the ITO 22 film so as to be along the line (so as not to be in contact with the edge), and the resistance value measurement sample of FIG. 2 was produced.
Next, as shown in FIG. 3, an initial resistance value R ₀ between the electrodes 25 and 25 was measured using a digital high tester (manufactured by Hioki Electric Co., Ltd., “3802-50”) 30.
Furthermore, after the resistance value measurement sample was allowed to stand in an environment at a temperature of 80 ° C. for 500 hours, the resistance value R after heat promotion was measured.
Further, the resistance value measurement sample was allowed to stand for 500 hours in an environment of a temperature of 60 ° C. and a humidity of 90% RH, and then the resistance value R after wet heat promotion was measured.
The resistance value increase rate of the resistance value measurement sample in each case was calculated as follows.
Resistance value increase rate (%) = (R−R ₀ ) / R ₀ × 100
The results are shown in Table 1.

From the result of Table 1, since the adhesive layer of the double-sided pressure-sensitive adhesive sheet of Examples 1 to 3 contains 10 to 30% by mass of acryloylmorpholine in the acrylate ester copolymer, heat acceleration and wet heat acceleration Since the increase rate of the resistance value due to is 20% or less, it was found that it is suitably used as a member of a capacitive touch panel.
On the other hand, since the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet of Comparative Examples 1 to 4 does not contain acryloylmorpholine in the acrylate copolymer, the resistance increase rate due to heat promotion or wet heat promotion is 20%. Since it exceeded, it turned out that it is not preferable as a member of a capacitive touch panel.
Moreover, also about the adhesive layer of the base-free double-sided pressure-sensitive adhesive sheet of Comparative Example 5 made of a silicone-based adhesive, since the rate of increase in resistance value due to heat promotion or wet heat promotion exceeds 20%, as a member of a capacitive touch panel Turned out to be undesirable.

DESCRIPTION OF SYMBOLS 10 Adhesive sheet for conductive film surfaces 11 Base film 12 Adhesive layer 13 Release sheet 21 Polyethylene terephthalate film 22 ITO film 23 Glass plate 24 Joining tape 25 Electrode 26 Base film 27 Adhesive layer 30 Digital high tester 100 Capacitance system Touch panel 101 Hard coat layer 102 Resin film layer 103 Cosmetic print layer 104 Embedding adhesive layer 105 Glass layer 106 Transparent conductive film 107 Adhesive 108 Display device

Claims (9)

A pressure-sensitive adhesive used in a pressure-sensitive adhesive sheet for attaching to a conductive film surface of a conductive sheet provided on the surface,
50 to 85% by mass of a structural unit (a1) derived from an alkyl acrylate monomer having 4 to 20 carbon atoms in the alkyl group, 10 to 30% by mass of a structural unit (a2) derived from a heterocyclic group-containing monomer, and a hydroxyl group A pressure-sensitive adhesive for conductive film surfaces, comprising an acrylic copolymer (A) containing 0.1 to 10% by mass of a monomer-derived structural unit (a3) and a crosslinking agent (B).  The adhesive for conductive film surface according to claim 1, wherein the hetero atom contained in the heterocyclic group-containing monomer (a2) is a nitrogen atom.  The pressure-sensitive adhesive for conductive film surfaces according to claim 1 or 2, wherein the heterocyclic group-containing monomer (a2) is acryloylmorpholine.  A pressure-sensitive adhesive sheet for a conductive film surface, wherein the pressure-sensitive adhesive according to any one of claims 1 to 3 is provided on at least one surface of a base film.  The pressure-sensitive adhesive sheet for conductive film surfaces according to claim 4, wherein the base film is a polyethylene terephthalate film, and the resin film constituting the conductive sheet is a polyethylene terephthalate film.  6. The pressure-sensitive adhesive sheet for a conductive film surface according to claim 4 or 5, wherein the conductive film constituting the conductive sheet is made of a metal oxide.  The pressure-sensitive adhesive sheet for a conductive film surface according to claim 6, wherein the metal oxide is tin-added indium oxide.  The pressure-sensitive adhesive sheet for a conductive film surface according to any one of claims 4 to 7, wherein the pressure-sensitive adhesive sheet is used as a member of a touch panel. The pressure-sensitive adhesive sheet for a conductive film surface according to claim 8, wherein the touch panel is a capacitive type.

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