WO2023157875A1

WO2023157875A1 - Double-sided adhesive sheet, laminate, and method for manufacturing laminate

Info

Publication number: WO2023157875A1
Application number: PCT/JP2023/005212
Authority: WO
Inventors: 真之山本
Original assignee: 王子ホールディングス株式会社
Priority date: 2022-02-18
Filing date: 2023-02-15
Publication date: 2023-08-24
Also published as: TW202338043A

Abstract

The present invention provides a double-sided adhesive sheet by which in a situation where constituent optical members of a display device having a touch panel are equipped with metallic electrically conductive parts, ion migration at the metallic electrically conductive parts can be suppressed when the optical members are pasted together, and changes in resistance value due to a hygrothermal environment and ultraviolet rays can be suppressed. Provided are: a double-sided adhesive sheet for pasting together a first adherend and a second adherend, both of which are constituent optical members of a display device having a touch panel, wherein the first adherend and/or the second adherend has metallic electrically conductive parts, and the adhesive sheet has a sulfur content of 50 mg/kg or less, a spectral transmittance of 30% or less at a wavelength of 380 nm, and a water vapor transmission rate of 400 g/m2/24 h or less or a water absorption rate of 1.0% or less; a laminate; and a method for manufacturing the laminate.

Description

Double-sided pressure-sensitive adhesive sheet, laminate, and method for producing laminate

The present invention relates to a double-sided pressure-sensitive adhesive sheet, a laminate, and a method for producing a laminate.

Display devices such as liquid crystal displays (LCDs) and input devices such as touch panels are widely used in various fields. Touch panel systems include a resistive type, a capacitance type, and the like, but the capacitance type is mainly adopted. In the manufacture of display devices equipped with these touch panels, transparent adhesive sheets are used for laminating optical members, and transparent adhesive sheets are also used for laminating display devices and input devices. there is

In display devices such as smartphones equipped with a small touch panel, metal oxides such as ITO were often used for the mesh-shaped electrode sensor (transparent conductive film) located in the screen part from the viewpoint of transparency. In recent years, in the case of a display device equipped with a touch panel having a large screen of 10 inches or more, such as a notebook PC, ITO has insufficient conductivity and sensitivity may decrease and malfunction may occur. An electrode sensor part with a metallic conductive part is used.

When an optical member constituting a display device equipped with a touch panel has a metal conductive portion, using a conventional transparent adhesive sheet may cause problems.
For example, when a mesh-like electrode sensor having a wiring width of several μm is used as a metal conductive portion, there is a problem that the resistance value increases due to mere corrosion and the sensor sensitivity decreases.
In addition, metal is sometimes used for lead wires in the frame part of the screen, but when the distance between the lead wires is set to about 10 μm as the frame of the touch panel is narrowed, there is a problem that ion migration of the metal occurs. can occur. When ion migration occurs, the positive electrode melts and disconnects, and the negative electrode forms dendrites due to deposition of the positive electrode component, resulting in short circuit. In particular, ion migration is extremely likely to occur on the positive electrode side, and ion migration is less likely to occur on the negative electrode side. When evaluating the ion migration, it is preferable to evaluate the parallel wiring rather than the serial wiring, and it is particularly preferable to evaluate the anode side.

In contrast, adhesive sheets that can effectively prevent and suppress ion migration are known. For example, Patent Literature 1 discloses an adhesive for forming an adhesive for bonding a first display body constituting member having a step on at least the bonded side and a second display body constituting member. The composition, wherein the first display body component and/or the second display body component has an electrode on at least the surface to be bonded, and the adhesive composition contains (meth)acrylic acid ester An adhesive composition containing a polymer (A), a silane coupling agent (B) having a mercapto group, and an active energy ray-curable component (C) is described.

On the other hand, as a method for preventing corrosion of ITO, which is a metal oxide, Patent Document 2 discloses that a homopolymer having a weight average molecular weight of 500,000 has a water vapor transmission rate of 500 g/m at 40°C and 90% RH measured by the cup method. ² ·day or less (meth)acrylic acid alkyl ester (a-1); 50% by weight or more, hydroxyl group-containing monomer (a-2); 0.5 to 10% by weight, nitrogen-containing monomer (a-3) an acrylic polymer (A) having a weight average molecular weight of 50,000 or more and less than 400,000 substantially free of acidic groups obtained by copolymerizing monomers containing 0.1 to 5% by weight, and a cross-linking agent (B ) and is used for bonding conductive films.

Further, Patent Document 3 discloses a conductive sheet having a support and a conductive portion composed of conductive fine lines disposed on the support and containing metallic silver and gelatin, wherein describes a conductive sheet in which gelatin is not substantially contained and the volume ratio (A/B) of the volume A of metallic silver and the volume B of gelatin in the conductive fine wire is 0.3 to 10.0. ing. Furthermore, Patent Document 3 discloses a touch panel including a conductive sheet having this configuration and a transparent adhesive layer disposed on the conductive portion side of the conductive sheet, wherein the adhesive contained in the transparent adhesive layer has an acid value of 100 mgKOH/ g or less, and the pressure-sensitive adhesive has a water absorption rate of 1.0% or less.

JP 2017-014379 A JP 2013-047296 A JP 2014-209332 A

Patent Document 1 describes that ion migration can be suppressed by using a silane coupling agent having a mercapto group. It was found that the suppression of ion migration may be insufficient depending on the composition of the adhesive composition such as. Furthermore, the present inventors have found that a new problem in the case of containing a sulfur component in the pressure-sensitive adhesive sheet, such as when a chain transfer agent or silane coupling agent having a mercapto group (thiol) is used, is caused by corrosion of the conductive portion of the metal. It was found that the resistance value increased, and in particular, the resistance value change remarkably occurred due to moist heat environment and ultraviolet rays.
Patent Document 2 focuses only on preventing acid corrosion by using an adhesive that does not substantially contain an acid component as a method for preventing corrosion of ITO. I was only interested in the relationship between
Patent Document 3 does not consider suppression of resistance value change due to corrosion, and in particular, does not suggest at all about resistance value change due to corrosion of metal conductive parts due to wet heat environment and ultraviolet rays. In addition, Patent Document 3 describes stabilizing metallic silver in the conductive portion by using a migration inhibitor such as an organic mercapto compound, but does not suggest suppression of the sulfur content.

The problem to be solved by the present invention is to suppress the ion migration of the metal conductive portion when the optical members are bonded to each other when the optical members constituting the display device equipped with the touch panel include the metal conductive portion. , to provide a double-sided pressure-sensitive adhesive sheet that can suppress changes in resistance value due to a moist heat environment and ultraviolet rays.

The specific configuration and preferred configuration of the present invention are as follows.

[1] A double-sided pressure-sensitive adhesive sheet for bonding a first adherend and a second adherend, both of which are optical members constituting a display device equipped with a touch panel, comprising:
At least one of the first adherend and the second adherend has a metal conductive portion,
sulfur content is 50 mg / kg or less,
Spectral transmittance at a wavelength of 380 nm is 30% or less,
A double-sided pressure-sensitive adhesive sheet having a water vapor transmission rate of 400 g/m ² /24h or less, or a water absorption rate of 1.0% or less.
[2] The first adherend is a touch panel,
The double-sided pressure-sensitive adhesive sheet according to [1], wherein the second adherend is an image display device or a cover material.
[3] A total light transmittance of 90% to 100%, a haze value of less than 1%, and a chromaticity b* defined by the CIE1976L*a*b* color system of −1 to 1. , [1] or [2].
[4] The double-sided pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer,
The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the pressure-sensitive adhesive layer has a gel fraction of 40% to 90%.
[5] The double-sided pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer contains 70 to 98% by mass of units derived from a (meth)acrylate having a branched chain with 8 to 18 carbon atoms and 1 to 20% by mass of units derived from a hydroxyl group-containing (meth)acrylate. The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [4], which contains a polymer.
[6] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [5];
A laminate comprising a first adherend and a second adherend, both of which are optical members constituting a display device equipped with a touch panel, disposed on both sides of a double-sided pressure-sensitive adhesive sheet,
A laminate, wherein at least one of the first adherend and the second adherend has a metal conductive portion.
[7] The first adherend is a touch panel,
the second adherend is an image display device or a cover material,
At least one of the touch panel and the image display device or the cover material includes a transparent conductive film having a mesh-shaped conductive portion and a lead wire connected to the mesh-shaped conductive portion. Laminate according to [6].
[8] The laminate according to [6] or [7], wherein the conductive portion contains silver or copper.
[9] Any one of [1] to [5] is applied to one surface of each of the first adherend and the second adherend, both of which are optical members constituting a display device equipped with a touch panel. Including a step of applying pressure while the double-sided pressure-sensitive adhesive sheet according to item 1 is in contact,
A method for manufacturing a laminate, wherein at least one of a first adherend and a second adherend has a metal conductive portion.

According to the present invention, when an optical member constituting a display device equipped with a touch panel has a metal conductive portion, ion migration of the metal conductive portion can be suppressed when the optical members are bonded to each other. It is possible to provide a double-sided pressure-sensitive adhesive sheet that can suppress changes in resistance due to ultraviolet rays.

FIG. 1 is a schematic diagram showing an example of a cross section of the configuration of the double-sided pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a cross-sectional view showing an example of the cross-section of the structure of the laminate of the present invention. FIG. 3 is a schematic diagram showing the configuration of a conductive film for evaluation provided with silver wiring. FIG. 4 is a schematic diagram showing the configuration of an evaluation sample for suppressing ion migration. FIG. 5 is a schematic diagram showing a circuit configuration used for evaluating suppression of ion migration. FIG. 6 is a schematic diagram showing the structure of a conductive film for resistance value evaluation provided with silver wiring. FIG. 7 is a schematic diagram showing the configuration of a resistance value evaluation sample.

The present invention will be described in detail below. Although the constituent elements described below may be described based on representative embodiments and specific examples, the present invention is not limited to such embodiments.

[Double-sided adhesive sheet]
The double-sided pressure-sensitive adhesive sheet of this embodiment is a double-sided pressure-sensitive adhesive sheet for bonding a first adherend and a second adherend, both of which are optical members constituting a display device equipped with a touch panel. At least one of the first adherend and the second adherend has a metal conductive portion, has a sulfur content of 50 mg/kg or less, and has a spectral transmittance of 30% or less at a wavelength of 380 nm. and the water vapor transmission rate is 400 g/m ² /24h or less, or the water absorption rate is 1.0% or less.
The double-sided pressure-sensitive adhesive sheet of the present embodiment has the above-described structure, and when optical members constituting a display device equipped with a touch panel include a metal conductive portion, ion migration of the metal conductive portion is prevented when the optical members are bonded to each other. can be suppressed, and the change in resistance value due to a moist heat environment and ultraviolet rays can be suppressed.

In the present embodiment, the sulfur content of the adhesive sheet is set to a specific range or less, the spectral transmittance at a wavelength of 380 nm is also set to a specific range or less, and the water vapor transmission rate or water absorption rate is set to a specific range or less, so that the metal It is possible to suppress the ion migration of the conductive portion of , and suppress the resistance value change due to the moist heat environment and ultraviolet rays. Conventionally, in the technical field of adhesive sheets, ion migration is suppressed using a silane coupling agent having a mercapto group (group containing sulfur) (in addition to Patent Document 1, JP-A-2017-014378, JP-A-2017-014378, 2020-114914, Japanese Patent No. 6170202, etc.) and sulfur-containing organic salts (Japanese Patent Laid-Open No. 2021-504750) to form a crosslinked structure to suppress corrosion. On the other hand, the present embodiment, in which the sulfur content is set to a specific range or less, solves the above-mentioned problems based on knowledge completely different from the conventional knowledge in the technical field of pressure-sensitive adhesive sheets.

Preferred aspects of the double-sided pressure-sensitive adhesive sheet of this embodiment will be described below.

<Characteristics of double-sided adhesive sheet>
(Water vapor transmission rate)
In the first embodiment of the present invention, the double-sided pressure-sensitive adhesive sheet has a water vapor transmission rate of 400 g/m ² /24h or less. The water vapor transmission rate of the double-sided pressure-sensitive adhesive sheet is preferably 300 g/m ² /24h or less, more preferably 200 g/m ² /24h or less. It is preferable that the water vapor transmission rate is within the above range from the viewpoint of easily suppressing migration when the double-sided pressure-sensitive adhesive sheet is used for an optical member having a metal conductive portion. It is preferable that the water vapor transmission rate of only the pressure-sensitive adhesive layer, which will be described later, is within the above range.

(water absorption rate)
In the second embodiment of the present invention, the double-sided pressure-sensitive adhesive sheet has a water absorption rate of 1.0% or less. The water absorption rate of the double-sided pressure-sensitive adhesive sheet is preferably 0.7% or less, more preferably 0.6% or less. It is preferable that the water absorption rate is within the above range from the viewpoint of easily suppressing migration when the double-sided pressure-sensitive adhesive sheet is used for an optical member having a metal conductive portion. It is preferable that the water absorption rate of only the pressure-sensitive adhesive layer, which will be described later, is within the above range.

(Sulfur content)
The sulfur content of the double-sided pressure-sensitive adhesive sheet of this embodiment is 50 mg/kg or less. The sulfur content of the double-sided PSA sheet is preferably 40 mg/kg or less, more preferably 30 mg/kg or less. The sulfur content of the double-sided pressure-sensitive adhesive sheet is preferably 0 mg/kg, ie below the detection limit. It is preferable that the sulfur content is within the above range from the viewpoint of easily suppressing a change in resistance value due to a wet and hot environment when the double-sided pressure-sensitive adhesive sheet is used for an optical member having a metal conductive portion. Conventionally, little attention has been paid to the increase in the resistance value of conductive parts of metals such as silver. The present inventors have found that change is likely to occur as a problem. It is preferable that the sulfur content of only the pressure-sensitive adhesive layer, which will be described later, is within the above range.
There are no particular restrictions on the method for reducing the sulfur content of the double-sided pressure-sensitive adhesive sheet to the above range or less. For example, when using a chain transfer agent when synthesizing the base polymer, using a chain transfer agent other than a sulfur-based chain transfer agent, using an additive that does not contain sulfur, or containing an additive that contains sulfur For example, reducing the amount. Specifically, when using a chain transfer agent during polymerization of the base polymer, use a chain transfer agent that does not contain a thiol such as 2,4-diphenyl-4-methyl-1-pentene, or use a mercapto-based additive as an additive. Examples include using a silane coupling agent other than the silane coupling agent and reducing the content of the mercapto-based silane coupling agent.

(380 nm transmittance)
The spectral transmittance of the double-sided pressure-sensitive adhesive sheet of this embodiment at a wavelength of 380 nm is 30% or less. The spectral transmittance of the double-sided pressure-sensitive adhesive sheet at a wavelength of 380 nm is preferably 25% or less, more preferably 20% or less. It is preferable that the spectral transmittance is within the above range from the viewpoint of easily suppressing a change in resistance value due to UV treatment when the double-sided pressure-sensitive adhesive sheet is used for an optical member having a metal conductive portion. In the past, no attention was paid to the change in resistance caused by UV light. The present inventor found that this is likely to occur as a problem. It is preferable that the spectral transmittance of only the pressure-sensitive adhesive layer, which will be described later, is within the above range.
The spectral transmittance of the double-sided pressure-sensitive adhesive sheet at a wavelength of 380 nm is preferably 0% or more, more preferably 10% or more from the viewpoint of the chromaticity b* value.

(Chromaticity b* value)
In the double-sided pressure-sensitive adhesive sheet of the present embodiment, the chromaticity b* value defined by the CIE1976L*a*b* color system under an environment of 23° C. and a relative humidity of 50% is preferably −1 to 1. , is preferably greater than −1 and less than 1, more preferably greater than −0.5 and less than 0.5. If the b ^* value is within the above range, the transparency and color reproducibility of image display devices required when the double-sided pressure-sensitive adhesive sheet is used as an optical member can be satisfied.

(Total light transmittance)
The double-sided pressure-sensitive adhesive sheet can have a total light transmittance of 80% (value measured according to JIS K 7361-1:1997) in an environment of 23° C. and 50% relative humidity. The total light transmittance of the double-sided pressure-sensitive adhesive sheet of this embodiment is preferably 90% to 100%. When the total light transmittance is within the above range, the transparency is high and it is suitable for optical applications.

(Haze value)
The double-sided pressure-sensitive adhesive sheet can have a haze value of 0% or more and 2% or less in an environment of 23° C. and a relative humidity of 50%. The haze value of the double-sided pressure-sensitive adhesive sheet of this embodiment is more preferably 0% or more and less than 1%. If the haze value is within the above range, the double-faced pressure-sensitive adhesive sheet can satisfy the transparency required when used for optical members, and is suitable for optical applications.

<Structure of double-sided adhesive sheet>
The double-sided pressure-sensitive adhesive sheet of this embodiment may be composed of a pressure-sensitive adhesive layer and other layers, but is preferably composed of only a pressure-sensitive adhesive layer. Other layers include supports, release sheets, and the like.
FIG. 1 is a cross-sectional view showing an example of the configuration of a double-sided pressure-sensitive adhesive sheet with a release sheet. The double-sided pressure-sensitive adhesive sheet 1 shown in FIG. 1 has release sheets (12a, 12b) on both sides of the pressure-sensitive adhesive layer 11 . The double-sided pressure-sensitive adhesive sheet in FIG. 1 is a non-carrier type single-layer pressure-sensitive adhesive sheet, and is a double-sided pressure-sensitive adhesive sheet.

<Support>
Examples of the support include plastic films such as polystyrene, styrene-acrylic copolymer, acrylic resin, polyethylene terephthalate, polycarbonate, polyetheretherketone, and triacetylcellulose; optical films such as antireflection films and electromagnetic wave shielding films; mentioned.

<Release sheet>
The double-sided pressure-sensitive adhesive sheet of this embodiment preferably has a pressure-sensitive adhesive layer, and the surface of the pressure-sensitive adhesive layer is preferably covered with a release sheet. That is, this embodiment may be a double-sided pressure-sensitive adhesive sheet with a release sheet.

As the release sheet, a release laminated sheet having a release sheet substrate and a release agent layer provided on one side of the release sheet substrate, or a polyolefin film such as a polyethylene film or a polypropylene film as a low-polarity substrate. is mentioned.
Papers and polymer films are used as the base material for the release sheet in the release laminated sheet. As the release agent constituting the release agent layer, for example, a general-purpose addition-type or condensation-type silicone-based release agent or a compound containing a long-chain alkyl group is used. In particular, an addition-type silicone-based release agent having high reactivity is preferably used.
Specific examples of silicone release agents include BY24-4527 and SD-7220 manufactured by Toray Dow Corning Silicone Co., Ltd., and KS-3600, KS-774 and X62-2600 manufactured by Shin-Etsu Chemical Co., Ltd. is mentioned. Further, the silicone release agent may contain a silicone resin which is an organosilicon compound having SiO ₂ units and (CH ₃ ) ₃ SiO _1/2 units or CH ₂ ═CH(CH ₃ ) SiO _1/2 units. preferable. Specific examples of silicone resins include BY24-843, SD-7292, SHR-1404, etc. manufactured by Dow Corning Toray Silicone Co., Ltd., and KS-3800, X92-183, etc. manufactured by Shin-Etsu Chemical Co., Ltd.

In the release sheet 12 shown in FIG. 1, it is preferable that the release sheets 12a and 12b have different releasability in order to facilitate their release. In other words, if the releasability from one side and the releasability from the other are different, it becomes easy to peel off only the release sheet 12 with higher releasability first. In that case, the releasability of the release sheets 12a and 12b may be adjusted depending on the lamination method and lamination order.

<Adhesive layer>
The double-sided pressure-sensitive adhesive sheet of this embodiment preferably has a pressure-sensitive adhesive layer.
The thickness of the pressure-sensitive adhesive layer can be appropriately set according to the application, and is not particularly limited. Generally, the thickness of the pressure-sensitive adhesive layer is preferably in the range of 10 µm to 500 µm, more preferably 20 µm to 450 µm, even more preferably 30 µm to 450 µm, and 40 µm to 400 µm. is more preferable, more preferably 40 μm or more and 350 μm or less, and particularly preferably 40 μm or more and 300 μm or less. By setting the thickness of the pressure-sensitive adhesive layer within the above range, it is possible to sufficiently ensure conformability to irregularities and further improve durability. Also, by setting the thickness of the pressure-sensitive adhesive layer within the above range, the production of the double-sided pressure-sensitive adhesive sheet is facilitated.

(Gel fraction)
The gel fraction of the pressure-sensitive adhesive layer is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 65% by mass or more. Moreover, the gel fraction of the pressure-sensitive adhesive layer is preferably 90% by mass or less. It is preferable to make the gel fraction equal to or higher than the lower limit from the viewpoint of easily reducing the water vapor transmission rate and the water absorption rate. Adhesion can be increased by setting the gel fraction to the upper limit or less.

The composition of the adhesive layer is not particularly limited, but it preferably contains the base polymer (A). The pressure-sensitive adhesive layer preferably contains, as optional additives, a crosslinking agent (B), a silane coupling agent (C), and an ultraviolet absorber (D), and further preferably contains a solvent (E).

(Base polymer (A))
The base polymer (A) is not particularly limited, but preferably has units derived from (meth)acrylate. The base polymer (A) preferably has transparency to the extent that the visibility of the display device is not deteriorated. In addition, in this specification, a "unit" is a repeating unit (monomer unit) which comprises a polymer.
The base polymer (A) preferably contains units (a1) derived from a non-crosslinkable (meth)acrylic acid ester and units (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group. .

At least one of the unit (a1) derived from a non-crosslinkable (meth)acrylic acid ester and the unit (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group is a unit derived from a methacrylic acid ester. is preferably For example, when the unit (a1) derived from a non-crosslinkable (meth) acrylic ester is a unit derived from a non-crosslinkable acrylic ester, a unit derived from a (meth) acrylic monomer having a crosslinkable functional group (a2) is preferably a unit derived from a methacrylic monomer having a crosslinkable functional group.
Alternatively, if the unit (a2) derived from a (meth) acrylic monomer having a crosslinkable functional group is a unit derived from an acrylic monomer, the unit (a1 ) preferably contains 50% by mass or more of units derived from a non-crosslinkable methacrylic acid ester.

- Unit (a1) derived from non-crosslinkable (meth) acrylic acid ester -
The unit (a1) derived from a non-crosslinkable (meth)acrylic acid ester is preferably a unit derived from a (meth)acrylate having a branched chain of 8 to 18 carbon atoms. Examples of such (meth)acrylic acid alkyl esters include 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and isononyl (meth)acrylate. These may be used individually by 1 type, and may use 2 or more types together. Among them, it is preferable to use 2-ethylhexyl (meth)acrylate as the non-crosslinkable (meth)acrylate unit (a1). Here, when the unit (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group is a unit derived from an acrylic monomer, a unit derived from a non-crosslinkable (meth)acrylic acid ester ( a1) is preferably a unit derived from a non-crosslinkable methacrylic acid ester. In this case, the unit (a1) derived from a non-crosslinkable (meth)acrylate ester is preferably a unit derived from a methacrylate having a branched chain with 8 to 18 carbon atoms, such as 2-ethylhexyl methacrylate (2EHMA). is more preferred.

The number of carbon atoms in the branched alkyl group of the unit (a1) derived from the non-crosslinkable (meth)acrylic acid ester may be from 8 to 18, preferably from 8 to 10. By setting the number of carbon atoms in the branched alkyl group within the above range, it is possible to easily control the degree of polymerization of the base polymer (A) and obtain a pressure-sensitive adhesive composition excellent in workability.

The content of the units (a1) derived from the non-crosslinkable (meth)acrylic acid ester in the base polymer (A) is preferably 70% by mass or more, based on the total mass of the base polymer (A). It is more preferably 80% by mass or more, more preferably 80% by mass or more. Moreover, the content of the unit (a1) is preferably 95% by mass or less, more preferably 90% by mass or less. The content of the unit (a1) is preferably at least the lower limit of the above range from the viewpoint of controlling water vapor transmission rate and hygroscopicity, and is preferably at most the upper limit of the above range from the viewpoint of controlling adhesive performance.

-Unit (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group-
The unit (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group includes a hydroxyl group (hydroxy group)-containing monomer unit, an amino group-containing monomer unit, a glycidyl group-containing monomer unit, A carboxy group-containing monomer unit and the like are included. One of these monomer units may be used, or two or more of them may be used.
A hydroxyl group-containing monomer unit is a repeating unit derived from a hydroxyl group-containing monomer. Examples of hydroxyl group-containing monomers include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate, ( (Meth)acrylic acid [(mono-, di- or poly)alkylene glycol] such as meth)acrylic acid mono(diethylene glycol), and (meth)acrylic acid lactones such as (meth)acrylic acid monocaprolactone. Here, when the unit (a1) derived from a non-crosslinkable (meth) acrylic ester is a unit derived from a non-crosslinkable acrylic ester, it is derived from a (meth)acrylic monomer having a crosslinkable functional group. The unit (a2) is preferably a unit derived from a methacrylic monomer having a crosslinkable functional group. In this case, the hydroxyl group-containing monomer is preferably a hydroxyl group-containing methacrylate, methacrylic acid [(mono-, di- or poly)alkylene glycol], methacrylic acid lactone, more preferably a hydroxyl group-containing methacrylate, methacrylic acid Particularly preferred is 2-hydroxyethyl (2HEMA).
Examples of amino group-containing monomer units include repeating units derived from amino group-containing monomers such as (meth)acrylamide and allylamine.
Examples of glycidyl group-containing monomer units include repeating units derived from glycidyl group-containing monomers such as glycidyl (meth)acrylate.
Carboxy group-containing monomer units include acrylic acid and methacrylic acid.

The content of units (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group in the base polymer (A) (preferably a hydroxyl group-containing (meth)acrylate) is based on the total mass of the base polymer (A). On the other hand, it is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and particularly preferably 10.0% by mass or more. Moreover, the content of the unit (a2) is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. It is preferable that the content of the unit (a2) is at least the lower limit of the above range from the viewpoint of suppressing the increase in resistance value in a hot and humid environment and controlling the gel fraction, and the water vapor transmission is less than the upper limit of the above range. It is preferable from the viewpoint of controlling the rate and hygroscopicity. Among the units (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group, the content of the hydroxyl group-containing (meth)acrylate is at least the lower limit value of the above range. It is preferable from the viewpoint of controlling the suppression of and the gel fraction, and it is preferable from the viewpoint of controlling the water vapor transmission rate and the hygroscopicity that it is equal to or less than the upper limit of the above range.

-Other monomeric units-
The base polymer (A) optionally contains units other than the unit (a1) derived from a non-crosslinkable (meth)acrylic acid ester and the (meth)acrylic monomer unit (a2) having a crosslinkable functional group. It may have a mer unit. Other monomers include (meth)acrylic acid ester units having 4 or less carbon atoms or 10 or more carbon atoms. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-decyl (meth)acrylate, lauryl (meth)acrylate , stearyl (meth)acrylate, and the like. Moreover, as other (meth)acrylic acid ester units, a (meth)acrylic acid ester unit having a linear alkyl group having from 5 to 9 carbon atoms may be included. Specifically, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, etc. can be mentioned. Furthermore, other (meth)acrylic acid ester units include (meth)acrylic acid ester units having a cyclic group such as cyclohexyl (meth)acrylate and benzyl (meth)acrylate, (meth)acrylonitrile, vinyl acetate, Styrene, vinyl chloride, vinylpyrrolidone, vinylpyridine and the like can be mentioned. The content of other monomer units in the base polymer (A) is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

- Physical properties of base polymer (A) -
The weight average molecular weight of the base polymer (A) is preferably 100,000 or more and 2,000,000 or less, more preferably 300,000 or more and 1,500,000 or less. By setting the weight-average molecular weight within the above range, it is possible to maintain the semi-cured state of the pressure-sensitive adhesive sheet and to ensure sufficient conformability to irregularities. The weight average molecular weight of the base polymer (A) is the value before cross-linking with the cross-linking agent. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and determined based on polystyrene standards. As the base polymer (A), a commercially available one may be used, or one synthesized by a known method may be used.

-Content of base polymer (A)-
The content of the base polymer (A) is preferably 75% by mass or more, more preferably 80% by mass or more, and further preferably 85% by mass or more, relative to the total mass of the pressure-sensitive adhesive composition. preferable. Also, the content of the base polymer (A) is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

(Crosslinking agent (B))
The cross-linking agent (B) is a cross-linking agent that reacts with the base polymer (A) by heat. As the cross-linking agent (B), for example, from known cross-linking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, butylated melamine compounds, cross-linkable functionalities possessed by the base polymer (A) It can be appropriately selected in consideration of reactivity with the group. For example, when a hydroxy group is included as a crosslinkable functional group, an isocyanate compound can be used because of the reactivity of the hydroxy group. From the viewpoint that the units (a2) derived from a (meth)acrylic monomer having a crosslinkable functional group can be easily crosslinked, it is preferable to use an isocyanate compound or an epoxy compound.

Examples of isocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and the like.
Examples of epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diol. glycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. mentioned.

Commercially available products can be used as the cross-linking agent (B) such as an isocyanate compound. Examples of commercially available products include Takenate D-110N (isocyanate compound, manufactured by Mitsui Chemicals, Inc.).

As the cross-linking agent (B), one type may be used alone, or two or more types may be used in combination. The content of the cross-linking agent (B) in the pressure-sensitive adhesive composition is appropriately selected depending on the desired adhesive physical properties, etc., and is not particularly limited. 5 parts by mass or less, and 0.10 parts by mass or more and 3 parts by mass or less.
In addition, the content of the cross-linking agent (B) can be 0.01% by mass or more and 5.0% by mass or less with respect to the total mass of the adhesive composition, and 0.02% by mass or more and 2.0% by mass. % or less.

(Silane coupling agent (C))
As the silane coupling agent, for example, a reactive functional group-containing silane coupling agent can be used. Examples include mercapto-based silane coupling agents, (meth)acrylic silane coupling agents, isocyanate-based silane coupling agents, epoxy-based silane coupling agents, amino-based silane coupling agents, and the like. Mercapto-based silane coupling agents include mercaptoalkoxysilane compounds (eg, mercapto group-substituted alkoxy oligomers, etc.), etc., but it is necessary to pay attention to the content as described later. Other reactive functional group-containing silane coupling agents include those described in [0094] to [0096] of JP-A-2020-114914, which is incorporated herein by reference. be
Among these, (meth)acrylic silane coupling agents, isocyanate silane coupling agents, epoxy silane coupling agents, and amino silane coupling agents are preferred from the viewpoint of reducing the sulfur content of the double-sided PSA sheet. Epoxy silane coupling agents are more preferred.

A commercially available product can be used as the silane coupling agent. Examples of commercially available products include an epoxy-based silane coupling agent (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) and a mercapto-based silane coupling agent (X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd.).

When the double-sided pressure-sensitive adhesive sheet contains a silane coupling agent, the content of the silane coupling agent is preferably 1 part by mass or less and 0.5 parts by mass or less with respect to 100 parts by mass of the base polymer (A). is more preferable. From the viewpoint of reducing the sulfur content of the double-sided PSA sheet, the content of the mercapto-based silane coupling agent is preferably 0.06 parts by mass or less with respect to 100 parts by mass of the base polymer (A). It is more preferable to make it 0.04 mass part or less.

(Ultraviolet absorber (D))
The ultraviolet absorber can be selected from those having a maximum absorption wavelength in the ultraviolet region. In particular, it is preferable to use an ultraviolet absorber having a maximum absorption wavelength of 350 nm or longer. Examples of ultraviolet absorbers having a maximum absorption wavelength of 350 nm or more include benzotriazole-based ultraviolet absorbers and benzotriazine-based ultraviolet absorbers. Moreover, the compound represented by the following general formula (1) or (2) can be mentioned as an ultraviolet absorber.

In the above formula, R ¹ represents a hydrogen atom, a halogen atom, an alkoxy group having 1 to 4 carbon atoms, a nitro group or a cyano group; R ² represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms; ³ represents an alkyl group structure.

In the above formula, R ⁴ , R ⁵ and R ⁶ are hydrogen atoms, hydroxyl groups, alkyl group structures or halogen atoms, and not all of R ⁴ , R ⁵ and R ⁶ are hydrogen atoms. The alkyl group-based structure is a concept including substituted or unsubstituted alkyl groups and substituents mainly composed of alkyl groups such as substituted or unsubstituted alkoxy groups.

The ultraviolet absorber preferably contains at least one compound that is oily or liquid at 23°C. Among them, as the ultraviolet absorber, an ultraviolet absorber exhibiting an oily or liquid state at 23 ° C., which has improved compatibility by introducing an alkyl group with a large molecular weight into the aromatic ring of the basic skeleton, is particularly preferably used. Here, showing an oily or liquid state at 23° C. means a state in which only the ultraviolet absorber has fluidity without a diluent solvent.

Commercially available products can be used as UV absorbers. Examples of commercially available products include triazine-based ultraviolet absorbers (tinuvin 477) and benzotriazole-based ultraviolet absorbers (tinuvin 384-2, tinuvin PS) manufactured by BASF Japan.

The content of the ultraviolet absorber is preferably 0.1 to 8.0 parts by mass, more preferably 0.5 to 4.0 parts by mass, based on 100 parts by mass of the base polymer (A). 1.0 to 3.0 parts by mass is particularly preferred. The ultraviolet absorbers may be used singly or in combination of two or more. When two or more are used in combination, the total mass is preferably within the above range.

(Solvent (E))
The pressure-sensitive adhesive composition may further contain a solvent (E). The solvent (E) is used for improving the coatability of the pressure-sensitive adhesive composition.
Examples of such a solvent (E) include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichlorethylene, tetrachlorethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, etc. ketones; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene Polyols such as glycol monoethyl ether and propylene glycol monomethyl ether acetate, and derivatives thereof.

A solvent (E) may be used individually by 1 type, and may use 2 or more types together. The content of the solvent (E) in the pressure-sensitive adhesive composition is not particularly limited. It can be less than or equal to parts by mass.
Moreover, the content of the solvent (E) can be 10% by mass or more and 90% by mass or less, and can be 20% by mass or more and 80% by mass or less with respect to the total mass of the adhesive composition.

(other ingredients)
The pressure-sensitive adhesive composition may contain components other than the above as long as the effects of the present invention are not impaired. Other components include components known as additives for adhesives, such as plasticizers, monomers, polymerization initiators, antioxidants, metal corrosion inhibitors, tackifiers, and light stabilizers such as hindered amine compounds. etc. can be selected as needed.
A non-functional acrylic polymer can be used as a plasticizer.
Examples of antioxidants include phenol antioxidants, amine antioxidants, lactone antioxidants, phosphorus antioxidants, sulfur antioxidants, and the like. These antioxidants may be used individually by 1 type, and may use 2 or more types together.
Examples of metal corrosion inhibitors include benzotriazole-based resins.
Examples of tackifiers include rosin-based resins, terpene-based resins, terpene-phenolic resins, coumarone-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, petroleum resins, and methacrylic-based resins.

<Method for producing double-sided adhesive sheet>
The method for producing the double-sided pressure-sensitive adhesive sheet of this embodiment is not particularly limited.
The manufacturing process of the double-sided pressure-sensitive adhesive sheet of the present embodiment preferably includes a process of applying a pressure-sensitive adhesive composition onto a release sheet to form a coating film.

The step of forming a coating film by applying the pressure-sensitive adhesive composition onto a release sheet will be described below as a representative example.
By heating the coating film, the reaction between the base polymer (A) and the cross-linking agent (B) proceeds to form a semi-cured product (adhesive sheet). In order to make the pressure-sensitive adhesive composition in a semi-cured state, after removing the solvent after coating, the pressure-sensitive adhesive sheet may be subjected to an aging treatment in which the pressure-sensitive adhesive sheet is allowed to stand at a constant temperature for a certain period of time. The aging treatment can be performed by standing at 23° C. for 7 days, for example.

Coating of the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive sheet can be carried out using a known coating apparatus. Coating devices include, for example, blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, micro gravure coaters, rod blade coaters, lip coaters, die coaters and curtain coaters.
Moreover, the coating film can be heated using a known heating device such as a heating furnace or an infrared lamp.

(How to use the adhesive sheet)
In the method of using the double-sided pressure-sensitive adhesive sheet of the present embodiment, the release sheet on the light release side of the pressure-sensitive adhesive sheet is peeled off and the pressure-sensitive adhesive layer is brought into contact with the surface of the first adherend for lamination, followed by the heavy release side. The release sheet is peeled off, and the pressure-sensitive adhesive layer on the opposite side of the first adherend is brought into contact with the second adherend. When the pressure-sensitive adhesive sheet is a semi-cured pressure-sensitive adhesive sheet having post-curing properties, the pressure-sensitive adhesive layer may be completely cured by irradiating active energy rays in that state.

[Laminate]
The laminate of the present embodiment includes the above-described double-sided pressure-sensitive adhesive sheet, and the first adherend and the second adherend, which are both optical members constituting a display device equipped with a touch panel, disposed on both sides of the double-sided pressure-sensitive adhesive sheet. and an adherend, at least one of the first adherend and the second adherend having a metal conductive portion.

The first adherend and the second adherend are preferably optical members constituting an image display device having a liquid crystal module equipped with a touch panel with a cover material. It preferably has an optical member constituting an image display device having a liquid crystal module equipped with a touch panel. The cover material is a member provided on the opposite side of the touch panel from the image display device. Examples of the cover material include cover glass and resin cover lenses.

The laminate of the present embodiment is produced by contacting the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet to the surface of the adherend, and in this state, pressurizing, heating, and defoaming using an autoclave or the like to improve adhesion. preferably obtained. In the laminate of the present embodiment, the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet does not have to be completely cured after the pressure-sensitive adhesive layer is brought into contact with the surface of the adherend.

FIG. 2 is a cross-sectional view showing an example of the configuration of a laminate 20 in which the double-sided pressure-sensitive adhesive sheet 21 of this embodiment is attached to the first adherend 22 and the second adherend 24. FIG. As shown in FIG. 2, the first adherend 22 and the second adherend 24 may have stepped conductive portions (27a, 27b, 27c, 27d). . In FIG. 2, the first adherend 22 has conductive portions (27a, 27b) and the second adherend 24 has conductive portions (27c, 27d). Incidentally, the thickness of the conductive portions (27a, 27b, 27c, 27d) is usually 5 μm or more and 60 μm or less. As described above, the double-sided pressure-sensitive adhesive sheet 21 of the present embodiment can be attached to a member having a stepped portion, and it is preferable that it can follow the unevenness caused by the stepped portion.

In the present embodiment, the first adherend and the second adherend are optical members arranged on both sides of a double-sided pressure-sensitive adhesive sheet and constituting a display device equipped with a touch panel. At least one of the first adherend and the second adherend has a metal conductive portion.
Examples of optical members include constituent members in optical products such as touch panels and image display devices. As a component of the touch panel, for example, a metal film in which a mesh-shaped metal film or metal wiring is provided on a transparent resin film, or a mesh-shaped metal film or metal wiring is provided on the surface of a glass plate. Metallic glass, ITO film in which an ITO film is provided on a transparent resin film, ITO glass in which an ITO film is provided on the surface of a glass plate, transparent conductive film and hard coat film obtained by coating these transparent resin films with a conductive polymer , anti-fingerprint films, and the like. Examples of constituent members of the image display device include antireflection films, oriented films, polarizing films, retardation films, brightness enhancement films and the like used in liquid crystal display devices.
Materials used for these members include glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, and cellulose acylate.

When the double-sided pressure-sensitive adhesive sheet of this embodiment is a double-sided pressure-sensitive adhesive sheet, it can be used for bonding two adherends. In this case, the double-sided pressure-sensitive adhesive sheet of the present embodiment can be used for lamination of metal films, lamination of a metal film and metallic glass, lamination of a metallic film and an ITO film, and lamination of an ITO film and metallic glass inside the touch panel. , bonding between a metal film of a touch panel and a liquid crystal panel, bonding between a cover material and a metal film, and the like. The double-sided pressure-sensitive adhesive sheet of the present embodiment is particularly preferably used for bonding a cover material and a metal film, and more preferably used for bonding a cover material and a metal film of a touch panel.

In the present embodiment, the first adherend is preferably a touch panel, and the second adherend is preferably an image display device or a cover material (preferably a cover glass). More preferably, at least one of the touch panel, the image display device, and the cover material includes a transparent conductive film having a mesh-shaped conductive portion and lead wires connected to the mesh-shaped conductive portion. It is particularly preferred that the cover material includes a transparent conductive film having a mesh-like conductive portion and lead wires connected to the mesh-like conductive portion.

In this embodiment, the metal conductive portion preferably contains copper, silver, iron, tin, zinc, nickel, molybdenum, chromium, tungsten, lead, and an alloy containing two or more metals selected from these. , copper alloys, silver, silver alloys, and particularly preferably silver or silver alloys. As the conductive portion containing silver, one manufactured from a material containing silver halide is preferable. The double-sided pressure-sensitive adhesive sheet of the present embodiment is a conductive thin wire containing silver produced by exposing and developing a photosensitive material containing silver halide described in [0006] to [0160] of JP-A-2014-209332. It is most suitable for application to adherends with Silver alloys preferably include, for example, silver to which palladium and copper are added. A metal that is not oxidized has a higher ionization tendency than a metal oxide such as ITO, but according to the double-sided pressure-sensitive adhesive sheet of the present embodiment, ion migration can be suppressed even in such a case. As a result, even when the double-sided pressure-sensitive adhesive sheet of the present embodiment comes into contact with electrodes or wirings having finer and narrower pitches, disconnection or short-circuiting of the electrodes or wirings can be prevented.

[Laminate production method]
In the method for producing a laminate of the present embodiment, the present The method includes a step of applying at least one of heating and pressing while the double-sided pressure-sensitive adhesive sheet of the embodiment is in contact, wherein at least one of the first adherend and the second adherend has a metal conductive portion. have.
The step of applying pressure while the double-sided pressure-sensitive adhesive sheet of the present embodiment is in contact with one surface of each of the first adherend and the second adherend is not particularly limited. It is preferable to perform defoaming by a pressurizing step, or to further perform a defoaming step before or after the pressurizing step. Moreover, it is preferable to carry out the pressurizing step while heating, or to further carry out the heating step before or after the pressurizing step. For example, the double-sided pressure-sensitive adhesive sheet is brought into contact with the surface of the first adherend and/or the second adherend, and in that state, pressurization, heating, and defoaming using an autoclave or the like, or in that state It is preferable to include a step of improving adhesion by pressurization and vacuum defoaming.

The features of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below.

[Synthesis example]
<Synthesis of crosslinkable (meth)acrylic copolymer A-1>
AibN (azobisisobutyronitrile ) and polymerized by heating to 60°C. As a result, a solution (a-1) of a crosslinkable (meth)acrylic copolymer (A-1) having a solid content concentration of 50% by mass and a weight average molecular weight of 450,000 was obtained.

<Synthesis of crosslinkable (meth)acrylic copolymer A-2>
A monomer prepared by blending 2-ethylhexyl acrylate (2EHA) and 2-hydroxyethyl methacrylate (2HEMA) in a mass ratio of 85:15 was added to ethyl acetate as a polymerization solvent to form AIBN (azobisisobutyronitrile ) and polymerized by heating to 60°C. As a result, a solution (a-2) of a crosslinkable (meth)acrylic copolymer (A-2) having a solid content concentration of 50% by mass and a weight average molecular weight of 480,000 was obtained.

<Synthesis of crosslinkable (meth)acrylic copolymer A-3>
AibN (azobisisobutyronitrile ) and polymerized by heating to 60°C. As a result, a solution (a-3) of a crosslinkable (meth)acrylic copolymer (A-3) having a solid content concentration of 50% by mass and a weight average molecular weight of 440,000 was obtained.

<Synthesis of crosslinkable (meth)acrylic copolymer A-4>
Monomers containing 2-ethylhexyl acrylate (2EHA) and 2-hydroxyethyl methacrylate (2HEMA) at a weight ratio of 95:5 were mixed in ethyl acetate, the polymerization solvent, to form AIBN (azobisisobutyronitrile ) and polymerized by heating to 60°C. As a result, a solution (a-4) of a crosslinkable (meth)acrylic copolymer (A-4) having a solid content concentration of 50% by mass and a weight average molecular weight of 460,000 was obtained.

<Synthesis of crosslinkable (meth)acrylic copolymer A-5>
AibN (azobisisobutyronitrile ) and polymerized by heating to 60°C. As a result, a solution (a-5) of a crosslinkable (meth)acrylic copolymer (A-5) having a solid content concentration of 50 mass % and a weight average molecular weight of 450,000 was obtained.

<Synthesis of crosslinkable (meth)acrylic copolymer A-6>
Monomers containing butyl acrylate (BA) and 2-hydroxyethyl acrylate (2HEA) at a weight ratio of 85:15 were mixed in ethyl acetate, the polymerization solvent, to form AIBN (azobisisobutyronitrile). Polymerization was carried out by heating to 60° C. in the presence. As a result, a solution (a-6) of a crosslinkable (meth)acrylic copolymer (A-6) having a solid content concentration of 50% by mass and a weight average molecular weight of 500,000 was obtained.

<Weight average molecular weight>
The weight average molecular weights of the crosslinkable (meth)acrylic copolymer (A) and the methyl methacrylate polymer (B) were measured using gel permeation chromatography (GPC) in the following manner. The measurement conditions of GPC are as follows.
・Solvent: Tetrahydrofuran ・Column: Shodex KF801, KF803L, KF800L, KF800D (4 columns manufactured by Showa Denko Co., Ltd. were connected and used)
・Column temperature: 40°C
・Sample concentration: 0.5% by mass
・Detector: RI-2031plus (manufactured by JASCO)
・Pump: RI-2080plus (manufactured by JASCO)
・Flow rate (flow velocity): 0.8 ml/min
・Injection volume: 10 μl
• Calibration curve: standard polystyrene Shodex standard Polystyrene (manufactured by Showa Denko KK) Mw = 1320 to 2,500,000 A calibration curve of 10 samples was used.

[Example 1]
<Adjustment of adhesive composition>
Per 100 parts by mass of the solution (a-1) of the acrylic copolymer (A-1), 0.1 parts by mass of an isocyanate compound (D-110N, manufactured by Mitsui Chemicals, Inc.) as a cross-linking agent, an epoxy silane cup A raw material containing 0.02 parts by mass of a ring agent (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) and 1.2 parts by mass of an ultraviolet absorber (Tinuvin 384-2, manufactured by BSAF) is used so that the concentration of the raw material is 45% by mass. was added to ethyl acetate and stirred to prepare an adhesive composition.

<Production of double-sided adhesive sheet>
The pressure-sensitive adhesive composition prepared as described above was applied to a polyethylene terephthalate film (first release sheet, 50RL-07, manufactured by Oji F-Tex Co., Ltd.) having a thickness of 50 μm and having a release layer treated with a silicone release agent. The surface of (2)) was uniformly coated with an applicator so that the coating thickness after drying was 50 μm to form a coating film. The coating film was dried at 80° C. for 3 minutes in an air circulating constant temperature oven to form a pressure-sensitive adhesive layer (double-sided pressure-sensitive adhesive sheet of Example 1) on the surface of the first release sheet.

<Preparation of adhesive sheet with release sheet>
Next, a second release sheet (38RL-07(L) manufactured by Oji F-Tex Co., Ltd., 38RL-07(L) manufactured by Oji F-Tex Co., Ltd.) having a thickness of 38 μm and having a different release force from the first release sheet was laminated on the surface of the pressure-sensitive adhesive layer, and the temperature was maintained at 23°C. and 50% relative humidity for 14 days. As a result, a pressure-sensitive adhesive sheet with a release sheet having a configuration of a first release sheet/adhesive sheet/second release sheet in which the pressure-sensitive adhesive layer (adhesive sheet) is sandwiched between a pair of release sheets having different peeling strengths is produced. Obtained.

[Example 2]
A release sheet was prepared in the same manner as in Example 1, except that the solution (a-1) of the acrylic copolymer (A-1) was changed to the solution (a-2) of the acrylic copolymer (A-2). A sticky adhesive sheet was obtained.

[Example 3]
The solution (a-1) of the acrylic copolymer (A-1) was changed to the solution (a-2) of the acrylic copolymer (A-2), and an epoxy-based silane coupling agent (KBM403, Shin-Etsu Chemical Co., Ltd. (manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to a mercapto-based silane coupling agent (X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd.) in the same manner as in Example 1 to obtain a pressure-sensitive adhesive sheet with a release sheet.

[Example 4]
A release sheet was prepared in the same manner as in Example 3, except that the solution (a-3) of the acrylic copolymer (A-3) was changed to the solution (a-4) of the acrylic copolymer (A-4). A sticky adhesive sheet was obtained.

[Example 5]
A release sheet was prepared in the same manner as in Example 1 except that the solution (a-1) of the acrylic copolymer (A-1) was changed to the solution (a-5) of the acrylic copolymer (A-5). A sticky adhesive sheet was obtained.

[Example 6]
With a release sheet, the same procedure as in Example 1 except that the amount of the isocyanate compound (D-110N, manufactured by Mitsui Chemicals, Inc.) that is a cross-linking agent was changed from 0.1 parts by mass to 0.04 parts by mass. A sticky sheet was obtained.

[Comparative Example 1]
Peeling in the same procedure as in Example 3, except that the amount of the mercapto-based silane coupling agent (X-41-1810, manufactured by Shin-Etsu Chemical Co., Ltd.) was changed from 0.02 parts by mass to 0.04 parts by mass. A pressure-sensitive adhesive sheet with a sheet was obtained.

[Comparative Example 2]
A pressure-sensitive adhesive sheet with a release sheet was obtained in the same manner as in Example 1, except that 1.2 parts by mass of an ultraviolet absorber (Tinuvin 384-2, manufactured by BSAF) was not added.

[Comparative Example 3]
A release sheet was prepared in the same manner as in Example 1, except that the solution (a-1) of the acrylic copolymer (A-1) was changed to the solution (a-6) of the acrylic copolymer (A-6). A sticky adhesive sheet was obtained.

[Characteristics of double-sided adhesive sheet]
Each property of the double-sided PSA sheets obtained in Examples and Comparative Examples was measured by the following procedures. The results obtained are shown in Table 1 below.

<Water vapor transmission rate>
The separator on the light release side of the 50 μm-thick pressure-sensitive adhesive sheets with a release sheet prepared in Examples and Comparative Examples was peeled off and attached to a non-woven fabric sheet (Nepiwipe, manufactured by Nepia) using a hand roller. Then, the double-sided adhesive sheet from which the separator on the light release side of the 50 μm thick adhesive sheet prepared in Examples and Comparative Examples was removed was applied to the adhesive surface from which the separator on the heavy release side was removed from the adhesive sheet lined with a nonwoven fabric sheet. A sample sheet having a configuration of a nonwoven fabric sheet backed with a nonwoven fabric sheet having an adhesive thickness of 100 μm/adhesive layer (thickness 100 μm)/heavy release separator was prepared. Next, on top of a glass bottle with an opening diameter of 2.5 cm containing 50 ml of distilled water, peel off the separator on the heavy release side of the sample sheet so that the adhesive side faces the bottle side. covered with a lid. Furthermore, a seal tape was used on the edge of the sample sheet covering the opening of the bottle, and the sample sheet was fixed so that the glass bottle was completely sealed so as not to cover the opening. The bottle was placed in an oven set at 40° C. and 20% RH so that the bottle was not tilted (in other words, water did not touch the sample) and treated for 24 hours. By measuring the weight before and after this treatment and finding the weight of the water that was reduced, the water vapor transmission rate of g/m ² /24h was found by calculation.

<Water absorption rate>
Only the adhesive layers of the 50 μm thick double-sided adhesive sheets prepared in Examples and Comparative Examples were superimposed to form a 5 mm thick adhesive layer, which was cut into a 5 cm×5 cm square to prepare a sample for water absorption evaluation. Subsequently, the sample for water absorption evaluation was placed on a pre-weighed glass petri dish and treated in a drying oven at 105° C. for 5 hours. The absolute dry weight of the sample for water absorption evaluation was measured by subtracting the weight of the Petri dish. Subsequently, the sample for evaluation was placed together with the petri dish in a constant temperature and humidity layer of 85°C and 95% RH and treated for 24 hours. The weight of the petri dish was weighed, and the weight of the petri dish was subtracted in the same manner as when determining the absolute dry weight to measure the weight of the sample for water absorption rate evaluation after water absorption. The water absorption was determined by the following formula 1.
(Water absorption rate) = (weight of water absorption rate evaluation sample after water absorption)/(absolutely dried water absorption rate evaluation sample weight) x 100 Formula 1

<Sulfur content>
Three pieces of 5 cm×5 cm were cut out from the 50 μm-thick pressure-sensitive adhesive sheets with a release sheet prepared in Examples and Comparative Examples. Next, the light release side separator and the heavy release side separator of each adhesive sheet with a release sheet were peeled off, and only the adhesive layer was collected and weighed. In addition, pressurized acid decomposition was performed using a microwave decomposition system (MARS5 manufactured by CEM). After the decomposition is completed, three pieces of decomposition solution for each level are mixed as measurement data and quantified to 20 ml, and then the sulfur component is quantified using an ICP emission spectrometer (ICP-OES Rigaku CIROS120). The amount of sulfur (mg) per 1 kg of the pressure-sensitive adhesive sheet was converted into the sulfur content.

<380 nm transmittance>
The adhesive sheet with a 50 μm thick release sheet prepared in Examples and Comparative Examples was cut into 50 mm × 50 mm, and the separator on the light release side was peeled off to prevent air from entering. It was laminated using a hand roller. Next, the separator on the heavy release side was peeled off to prepare a sample for evaluation of the structure of the glass/adhesive layer. Using a self-recording spectrophotometer (model: UV-3100PC, manufactured by Shimadzu Corporation), the spectral transmittance of the evaluation sample at a wavelength of 380 nm was measured.

<Gel fraction>
A 50 μm adhesive sheet with a release sheet prepared in Examples and Comparative Examples was cut into a size of 10 cm×10 cm. Next, peel off the separator on the light release side and the separator on the heavy release side of each adhesive sheet with a release sheet, weigh 0.1 g of only the adhesive layer (double-sided adhesive sheet), collect it in a sample bottle, and add 30 ml of ethyl acetate. It was shaken for 24 hours while being heated to 40°C. Thereafter, the contents of the sample bottle were filtered through a 150-mesh stainless steel wire mesh, and the residue on the wire mesh was dried at 100° C. for 3 hours to measure the dry mass (g). The gel fraction was obtained from the obtained dry mass by the following formula 2.
Gel fraction (% by mass) = (dry mass/collected mass of double-sided pressure-sensitive adhesive sheet) x 100 Equation 2

[Evaluation of double-sided adhesive sheet]
Each evaluation of the pressure-sensitive adhesive sheet with a release sheet obtained in each example and comparative example was performed according to the following procedures. Among the obtained results, the results other than the total light transmittance and the haze value are shown in Table 1 below.

<Suppression of ion migration>
(Preparation of conductive film for evaluation)
A PET film with a thickness of 100 μm (Cosmo Shine A4360 manufactured by Toyobo Co., Ltd.) that has been subjected to an easy adhesion treatment is screen-printed using a silver paste (RAFS059 manufactured by Toyochem Co., Ltd.). The pattern was printed so that each of the wiring lines was straight and parallel. Thereafter, heat treatment was performed at 135° C. for 30 minutes to cure the silver paste, thereby obtaining a conductive film for evaluation having silver wiring as shown in FIG. The width of each of the two wires was 40 μm, and the distance between the wires was 15 μm.

(Preparation of sample for evaluation)
The separator on the light release side of the adhesive sheet with a release sheet prepared in Examples and Comparative Examples was peeled off, and the adhesive surface was laminated to a 100 μm PET film (Cosmoshine A4360 manufactured by Toyobo Co., Ltd.) with a hand roller. A laminate film having a configuration of pressure-sensitive adhesive layer/heavy release side separator was obtained. Next, the separator on the heavy release side was peeled off from this laminated film, and it was laminated on the wiring of the conductive film for evaluation prepared above as shown in FIG. After that, it was left for 24 hours under conditions of 23° C. and 50% relative humidity (RH) to prepare a sample for evaluation.

(Evaluation of ion migration suppression effect)
A circuit configuration was formed by applying wiring (parallel wiring) as shown in FIG. 5 to the evaluation sample. An ion migration test was performed by treating for 240 hours at 85° C. and 95% RH while applying a voltage of DC 15V. The space between the wires in the bonded portion of the pressure-sensitive adhesive layer (double-sided pressure-sensitive adhesive sheet) of the thus-treated evaluation sample was observed with an optical microscope, and the effect of suppressing ion migration was evaluated based on the following evaluation criteria. In addition, in the samples of any of the examples and comparative examples, lifting, peeling, generation of air bubbles, etc. did not occur.
A: Formation of dendrites between wirings and discoloration such as yellow (or orange) bleeding are not observed at all.
B: Discoloration such as yellow (or orange) bleeding is slightly observed between wirings.
C: Formation of dendrites or discoloration such as yellow (or orange) bleeding is observed between wirings.

<Resistance increase>
(Preparation of conductive film for resistance value evaluation)
A silver paste (RAFS059 manufactured by Toyochem Co., Ltd.) was applied to a 100 μm thick PET film (Cosmoshine A4360 manufactured by Toyobo Co., Ltd.) by screen printing on a PET film (manufactured by Toyobo Co., Ltd.) with a thickness of 100 μm that had been subjected to an easy adhesion treatment. A mesh-like pattern having a part) was printed. Thereafter, heat treatment was performed at 135° C. for 30 minutes to cure the silver paste, thereby obtaining a conductive film for resistance value evaluation having silver wiring as shown in FIG. The mesh pattern had a pitch of 500 μm and a line width of 15 μm.

(Preparation of sample for resistance value evaluation)
The separator on the light release side of the adhesive sheet with a release sheet prepared in Examples and Comparative Examples was peeled off, and the adhesive surface was laminated to a 100 μm PET film (Cosmoshine A4360 manufactured by Toyobo Co., Ltd.) with a hand roller. A laminate film having a configuration of pressure-sensitive adhesive layer/heavy release side separator was obtained. Next, the separator on the heavy release side was peeled off from this laminated film, and it was laminated on the wiring of the conductive film for resistance value evaluation prepared above as shown in FIG. After the autoclave treatment, it was left for 24 hours under conditions of 23° C. and 50% RH to prepare a sample for resistance value evaluation.

(Rise in resistance at 85°C, 95% treatment)
A tester was used to measure the initial electrical resistance value between the measurement electrode portions on both ends of the conductive portion of the resistance value evaluation sample. Then, after treating at 85° C. and 95% RH for 240 hours, the electrical resistance value between the electrodes was measured again using a tester. Using the average value of the resistance values before and after the treatment of n=3 measured in this way, the resistance value increase rate was obtained by the following formula 3, and the resistance value increase was evaluated based on the evaluation criteria shown below. In the samples for resistance value evaluation of any of the examples and comparative examples, no floating, peeling, generation of air bubbles, or the like occurred.
(Resistance value increase rate) = (Electrical resistance value after 95% treatment at 85°C)/(Initial electrical resistance value) Equation 3
A: The rate of increase in resistance value is less than 1.0.
B: The rate of increase in resistance value is 1.0 or more and less than 1.05.
C: Resistance value increase rate is 1.05 or more.

(Resistance increase in UV treatment)
Instead of treatment at 85° C. and 95% RH for 100 hours, a xenon super weather meter (super xenon weather meter SX75 manufactured by Suga Test Instruments Co., Ltd.) was used at 70 W/m ² and a black panel temperature of 65° C. for 100 hours. calculated the resistance value increase rate by the following formula 4 in the same manner as in "85°C, 95% treatment", and evaluated the resistance value increase based on the evaluation criteria shown below. In the samples for resistance value evaluation of any of the examples and comparative examples, no floating, peeling, generation of air bubbles, or the like occurred.
(Resistance value increase rate)=(electric resistance value after UV treatment)/(initial electric resistance value) Equation 4
A: The rate of increase in resistance value is less than 1.0.
B: The rate of increase in resistance value is 1.0 or more and less than 1.05.
C: Resistance value increase rate is 1.05 or more.

<Chromaticity b* value>
A sample for evaluation of the structure of the glass/adhesive layer was prepared in the same manner as the sample for evaluation prepared in the measurement of "380 nm transmittance", and was prepared in accordance with JIS Z8781-4: 2013, and CIE1976L*a*b* color specification. The b* in the system was measured.

<Total light transmittance and haze value>
A sample for evaluation of the structure of the glass/adhesive layer was prepared in the same manner as the sample for evaluation prepared in the measurement of "380 nm transmittance", and the total light transmittance of the obtained sample was measured according to JIS K 7361-1. and measured. Also, the haze value of the obtained sample was measured according to JIS K7136. These measurements were performed 3 times, and the average value was used as each measurement value. For the measurement, an integrating sphere type light transmittance measuring device (NDH-5000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used.
As a result, the double-sided pressure-sensitive adhesive sheets produced in Examples and Comparative Examples had a total light transmittance of 90% to 100% in an environment of 23°C and a relative humidity of 50%, and an environment of 23°C and a relative humidity of 50%. The haze value in was less than 1%.

From Table 1 above, it can be seen that the double-sided pressure-sensitive adhesive sheet of the present invention, when optical members constituting a display device equipped with a touch panel have metal conductive portions, prevents ion migration of the metal conductive portions when the optical members are bonded together. It can be seen that the resistance value change due to the wet heat environment and ultraviolet rays can be suppressed.
In Comparative Example 1, the sulfur content of the double-sided pressure-sensitive adhesive sheet exceeded the range specified in the present invention, and the change in resistance value due to the moist heat environment and ultraviolet rays was large.
In Comparative Example 2, the spectral transmittance of the double-sided pressure-sensitive adhesive sheet at a wavelength of 380 nm exceeded the range specified in the present invention, and the change in resistance value due to the ultraviolet treatment was large.
In Comparative Example 3, the water vapor transmission rate and water absorption rate of the double-sided pressure-sensitive adhesive sheet exceeded the ranges specified in the present invention, and ion migration of the conductive portion occurred significantly when the optical members were bonded together.

1 double-sided adhesive sheet with release sheet 11 double-sided adhesive sheet (adhesive layer)
12a, 12b release sheet 20 laminate 21 double-sided adhesive sheet (adhesive layer)
22 first adherend 24 second adherend 27a, 27b, 27c, 27d conductive portion

Claims

A double-sided pressure-sensitive adhesive sheet for bonding a first adherend and a second adherend, both of which are optical members constituting a display device equipped with a touch panel,
At least one of the first adherend and the second adherend has a metal conductive portion,
sulfur content is 50 mg / kg or less,
Spectral transmittance at a wavelength of 380 nm is 30% or less,
A double-sided pressure-sensitive adhesive sheet having a water vapor transmission rate of 400 g/m 2 /24h or less, or a water absorption rate of 1.0% or less.
The first adherend is a touch panel,
The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the second adherend is an image display device or a cover material.
A total light transmittance of 90% to 100%, a haze value of less than 1%, and a chromaticity b* defined by the CIE1976L*a*b* color system of -1 to 1. 2. The double-sided pressure-sensitive adhesive sheet according to 1.
The double-sided pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer,
The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a gel fraction of 40% to 90%.
The double-sided pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer contains 70 to 98% by mass of units derived from a (meth)acrylate having a branched chain of 8 to 18 carbon atoms and 1 to 20% by mass of units derived from a hydroxyl group-containing (meth)acrylate. 2. The double-sided pressure-sensitive adhesive sheet according to claim 1, comprising a base polymer.
A double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 5;
A laminate comprising a first adherend and a second adherend, both of which are optical members constituting a display device equipped with a touch panel, disposed on both sides of the double-sided pressure-sensitive adhesive sheet,
A laminate, wherein at least one of the first adherend and the second adherend has a metal conductive portion.
The first adherend is a touch panel,
The second adherend is an image display device or a cover material,
7. The method according to claim 6, wherein at least one of the touch panel, the image display device, and the cover material includes a transparent conductive film having a mesh-shaped conductive portion and lead wires connected to the mesh-shaped conductive portion. laminate.
The laminate according to claim 6, wherein the conductive portion contains silver or copper.
According to any one of claims 1 to 5, on one surface of each of the first adherend and the second adherend, both of which are optical members constituting a display device equipped with a touch panel. Including a step of applying pressure with the double-sided adhesive sheet of
A method for manufacturing a laminate, wherein at least one of the first adherend and the second adherend has a metal conductive portion.