JP2014098144A - Pressure sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure sensitive adhesive sheet which does not corrode a metal surface even if affixed to the metal surface, is inhibited from peeling due to bubbles and from bubbling in an adhesive layer under high temperature when affixed to a resin panel, and inhibits the adhesive layer from becoming cloudy under high temperature and high humidity.SOLUTION: A pressure sensitive adhesive sheet is used for affixing a resin member and a metal surface to each other and comprises an adhesive layer containing a (meth)acrylate ester copolymer containing, as monomer components, an alkoxyalkyl (meth)acrylate ester monomer and an alkyl (meth)acrylate ester having an acryl group having 1 to 4 carbon atoms, in which the content of the alkoxyalkyl (meth)acrylate ester monomer is 50 mass% or more, the content of the alkyl (meth)acrylate ester having an acryl group having 1 to 4 carbon atoms is 1 to 45 mass%, and the content of a carboxyl group-containing monomer is 1% or less, and an acyclic aliphatic isocyanate-based crosslinking agent, and having a gel fraction of 30 to 80%.

Description

  The present invention relates to an adhesive sheet that can be used, for example, for bonding a resin member and a surface made of a conductive layer.

In recent years, touch sensors have begun to be mounted on electronic devices. The touch sensor includes a resistive film type touch panel that detects the contact location (contents of instructions to the electronic device) by pressure when a finger, a touch pen, or the like touches, and the static electricity when touched by the finger. Capacitive touch panels that detect contact points are known, and the electrostatic capacitive method is becoming mainstream due to the multi-functionality of input methods including multi-touch.
As the touch panel, generally, a transparent conductive film provided with a conductive layer having good conductivity on the surface of a transparent film or glass plate is used. The surface of the conductive film is fixed to a protective panel or the like in contact with the pressure-sensitive adhesive layer constituting the double-sided pressure-sensitive adhesive sheet.

  However, when the adhesive layer is in contact with the surface of the conductive layer constituting the transparent conductive film for a long period of time, the conductive layer is oxidized by the influence of the adhesive layer, and the conductivity of the transparent conductive film is increased. There was a case where the problem of the touch panel not working properly occurred.

As a method for preventing a decrease in conductivity of the transparent conductive film or the like, a method for imparting a performance to prevent corrosion of the conductive layer to the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet is known. For example, corrosion of the conductive layer There is known a double-sided pressure-sensitive adhesive sheet that does not have an acid component, which is a factor that causes oxidization (see, for example, Patent Document 1).
However, since the double-sided pressure-sensitive adhesive sheet is not sufficient in terms of adhesive strength, the adherend may be peeled off over time. In particular, when two or more adherends of different materials are bonded, the adhesive force is remarkably reduced. For example, even if an attempt is made to bond a member made of resin and a member made of metal, it is used for the manufacture of electrical equipment and the like. In some cases, a possible level of adhesion could not be applied.
In addition, when the adhesive bonded using the double-sided PSA sheet is left at a high temperature of about 85 ° C. for a long period of time, it causes peeling of the adhesive interface due to the influence of gas (gas) generated from the resin member. In some cases, the pressure-sensitive adhesive layer may become cloudy.

JP 2010-215794 A

  The problem to be solved by the present invention is that even when affixed to the surface having the conductive layer constituting the adherend, the surface having the conductive layer is not corroded, and is stuck to the resin surface constituting the adherend. Even so, it is possible to provide a pressure-sensitive adhesive sheet having excellent adhesive force that hardly causes peeling due to a gas (gas) that can be generated from the resin surface and hardly causes white turbidity of the pressure-sensitive adhesive layer due to bubbles due to the gas. That is.

  As a result of studies to solve the above problems, the present inventors have found that a gel component formed using an acrylic pressure-sensitive adhesive containing a (meth) acrylic acid ester copolymer and an acyclic aliphatic isocyanate crosslinking agent. The pressure-sensitive adhesive layer has a rate of 30% by mass to 80% by mass, and the (meth) acrylic acid ester copolymer is obtained by polymerizing the monomer component, and is contained in the monomer component ( The content of the (meth) acrylic acid alkoxyalkyl ester (A) is 50% by mass or more, and the content of the (meth) acrylic acid alkyl ester (B) having an acrylic group having 1 to 4 carbon atoms is 1 mass. It has been found that the above-mentioned problems can be solved if the pressure-sensitive adhesive sheet has a carboxyl group-containing vinyl monomer (C) content of 1% by mass or less.

  That is, the present invention is a pressure-sensitive adhesive sheet used for bonding a surface made of a resin and a surface having a conductive layer, wherein the pressure-sensitive adhesive sheet comprises a (meth) acrylic acid ester copolymer and an acyclic aliphatic isocyanate. It has a pressure-sensitive adhesive layer having a gel fraction of 30% by mass to 80% by mass formed using an acrylic pressure-sensitive adhesive containing a crosslinking agent, and the (meth) acrylic acid ester copolymer has a monomer component. An acrylic group which is obtained by polymerization and has a (meth) acrylic acid alkoxyalkyl ester (A) content of 50% by mass or more and 1 to 4 carbon atoms contained in the monomer component. The content of the (meth) acrylic acid alkyl ester (B) having 1 to 45% by mass and the content of the vinyl monomer (C) having a carboxyl group is 1% by mass or less. Features The present invention relates to a pressure-sensitive adhesive sheet to be.

  Since the pressure-sensitive adhesive sheet of the present invention has an excellent adhesive force, it can be suitably used for bonding two or more adherends having different materials, for example. In addition, the adhesive sheet is attached to the resin surface constituting the adherend without corroding the surface having the conductive layer even if it is attached to the surface having the conductive layer constituting the adherend, for example. However, it is difficult to cause peeling due to the gas (gas) that can be generated from the resin, and it is difficult to cause white turbidity of the pressure-sensitive adhesive layer due to bubbles caused by the gas.

It is the schematic which shows the structural example of the image display apparatus to which the adhesive sheet of this invention is applied. It is the schematic which shows the structural example of the image display apparatus to which the adhesive sheet of this invention is applied.

  The pressure-sensitive adhesive sheet of the present invention has a gel fraction of 30% by mass to 80% by mass formed using an acrylic pressure-sensitive adhesive containing a (meth) acrylic acid ester copolymer and an acyclic aliphatic isocyanate crosslinking agent. A (meth) acrylic acid alkoxyalkyl ester (A) having a pressure-sensitive adhesive layer and obtained by polymerizing the monomer component of the (meth) acrylic acid ester copolymer (A). ) Content is 50% by mass or more, the content of (meth) acrylic acid alkyl ester (B) having an acrylic group having 1 to 4 carbon atoms is 1% by mass to 45% by mass, and , Wherein the content of the vinyl monomer (C) having a carboxyl group is 1% by mass or less, and a surface composed solely of a resin constituting the adherend, and a surface composed of a metal For pasting It is intended to use.

  The pressure-sensitive adhesive sheet of the present invention may be composed of, for example, a structure having a pressure-sensitive adhesive layer on one or both sides of a substrate, and is composed of only a pressure-sensitive adhesive layer without having a substrate. Also good. The pressure-sensitive adhesive layer may be a single layer or a laminate of a plurality of pressure-sensitive adhesive layers.

The pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet having only the pressure-sensitive adhesive layer without the base material in order to maintain excellent transparency and shape followability.
Even if the pressure-sensitive adhesive sheet without the substrate is printed on the surface of the adherend, it can follow the level difference on the surface of the adherend due to the printing, so that it peels over time, etc. Can be further prevented.

  The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet of the present invention preferably has a gel fraction of 30% by mass to 80% by mass, more preferably 40% by mass to 80% by mass, and 55% by mass to More preferably, it is 80 mass%. The pressure-sensitive adhesive layer having a gel fraction in the above range is particularly difficult to cause peeling from the surface made of metal constituting the adherend, can follow the unevenness of the adherend surface, and has bubbles or the like at the interface. It can be prevented from remaining. In addition, the said gel fraction points out the value computed by the method described in the Example of this-application specification.

  Moreover, what is necessary is just to select the thickness of the adhesive sheet of this invention suitably by the aspect to be used, but it is preferable that they are 5 micrometers-500 micrometers. In particular, when the pressure-sensitive adhesive sheet is applied to the smooth surface of the adherend, the use of a pressure-sensitive adhesive sheet having a thickness in the range of 10 μm to 250 μm contributes to the thinning of a laminate such as a touch panel device. can do. Moreover, when sticking the said adhesive sheet on the surface which has a level | step difference or an unevenness | corrugation, it is preferable to use the adhesive sheet which has a thickness of 20 micrometers or more, and uses the adhesive sheet which has the thickness of the range of 25 micrometers-150 micrometers. More preferably.

  The pressure-sensitive adhesive sheet of the present invention preferably has a total light transmittance of 80% or more and a haze of 1.0% or less, a total light transmittance of 90% or more and a haze of 0.5%. It is more preferable to use the following. By using an adhesive sheet having a total light transmittance within the above range, excellent transparency of the display equipped with the touch panel device can be maintained.

The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet of the present invention can be formed by using an acrylic pressure-sensitive adhesive containing a (meth) acrylic acid ester copolymer and an acyclic aliphatic isocyanate crosslinking agent.
As the (meth) acrylic acid ester copolymer contained in the acrylic pressure-sensitive adhesive, among those obtained by polymerizing the monomer component, (meth) acrylic acid alkoxyalkyl ester ( The content of (meth) acrylic acid alkyl ester (B) having an acrylic group having a content of A) of 50% by mass or more and having 1 to 4 carbon atoms is 1% by mass to 45% by mass, And what is obtained by superposing | polymerizing the monomer component whose content of the vinyl monomer (C) which has a carboxyl group is 1 mass% or less can be used.
Examples of the (meth) acrylic acid alkoxyalkyl ester (A) include, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-methoxytriethylene glycol acrylate, 3-methoxypropyl acrylate, 3-acrylic acid 3- Ethoxypropyl, 4-methoxybutyl acrylate, 4-ethoxybutyl acrylate and the like can be used. Among them, as the (meth) acrylic acid alkoxyalkyl ester (A), use of 2-methoxyethyl acrylate and 2-ethoxyethyl acrylate imparts more excellent cohesive force to the pressure-sensitive adhesive layer. Can do. Moreover, since the hydrophilicity of the pressure-sensitive adhesive layer is increased, white turbidity of the pressure-sensitive adhesive layer that can occur under high-temperature and high-humidity conditions can be prevented. In the present specification, acrylic acid and methacrylic acid are collectively referred to as (meth) acrylic acid, and these derivatives are also represented in the same manner.

The said (meth) acrylic-acid alkoxyalkylester (A) is used in 50 mass% or more with respect to the whole quantity of the monomer component used for manufacture of the said (meth) acrylic acid ester copolymer. Thereby, the further outstanding cohesion force can be provided to an adhesive layer. Moreover, since the hydrophilicity of the pressure-sensitive adhesive layer is increased, white turbidity of the pressure-sensitive adhesive layer that can occur under high-temperature and high-humidity conditions can be prevented.
The (meth) acrylic acid alkoxyalkyl ester (A) is used in the range of 50% by mass to 95% by mass with respect to the total amount of the monomer components used in the production of the (meth) acrylic acid ester copolymer. It is preferable to use in the range of 60% by mass to 95% by mass, and it is more preferable to use in the range of 70% by mass to 90% by mass. By using the (meth) acrylic acid alkoxyalkyl ester (A) within the above range, more excellent cohesive force can be imparted to the pressure-sensitive adhesive layer. Moreover, since the hydrophilicity of the pressure-sensitive adhesive layer is increased, white turbidity of the pressure-sensitive adhesive layer that can occur under high-temperature and high-humidity conditions can be prevented.

  Moreover, as said (meth) acrylic-acid alkylester (B) which has a C1-C4 alkyl group used for manufacture of the said (meth) acrylic acid ester copolymer, said (meth) acrylic-acid alkoxyalkylester is mentioned above. (Meth) acrylic acid alkyl esters other than (A) can be used, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, T-butyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, t-butyl methacrylate and the like can be used.

  Among these, as the (meth) acrylic acid alkyl ester (B), it is preferable to use n-butyl acrylate for forming a pressure-sensitive adhesive layer having even more excellent cohesive strength.

  The said (meth) acrylic-acid alkylester (B) is used in 1 mass%-45 mass% with respect to the whole quantity of the monomer component used for manufacture of the said (meth) acrylic acid ester copolymer. In particular, the (meth) acrylic acid ester (B) is more preferably used in the range of 5% by mass to 45% by mass, and more preferably in the range of 10% by mass to 35% by mass. It is particularly preferable to use in the range of% to 25% by mass. By using the (meth) acrylic acid ester (B) within the above range, the adhesive layer has more excellent adhesive force and cohesive force, and is attached to the resin surface constituting the adherend. However, it is possible to obtain a pressure-sensitive adhesive sheet that hardly causes peeling due to a gas (gas) that can be generated from the resin surface and hardly causes white turbidity of the pressure-sensitive adhesive layer due to bubbles due to the gas.

  The vinyl monomer (C) having a carboxyl group that may be used for the production of the (meth) acrylic acid ester copolymer is not particularly limited, but acrylic acid, methacrylic acid, itaconic acid, maleic acid. , Crotonic acid, acrylic acid dimer, ethylene oxide-modified succinic acid acrylate, and the like can be used. When the vinyl monomer (C) having a carboxyl group is used, it is preferable to use acrylic acid because of its high versatility.

  The vinyl monomer (C) having a carboxyl group is used in an amount of 1% by mass or less based on the total amount of monomer components used for the production of the (meth) acrylic acid ester copolymer. In particular, the vinyl monomer (C) having a carboxyl group is preferably used in a range of 0.5% by mass or less, more preferably 0.1% by mass or less, and not used. Is more preferable. Thereby, corrosion of the metal surface which comprises a to-be-adhered body can fully be prevented.

The (meth) acrylic acid ester copolymer has a functional group capable of reacting with the isocyanate group of the crosslinking agent when used in combination with a crosslinking agent such as the acyclic aliphatic isocyanate crosslinking agent. It is preferable to use one. Examples of the functional group include a hydroxyl group.
The hydroxyl group can be introduced into the (meth) acrylic acid ester copolymer by using a vinyl monomer having a hydroxyl group as the monomer component.
Examples of the vinyl monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, and the like.

  The vinyl monomer having a hydroxyl group may be used in the range of 0.1% by mass to 10% by mass with respect to the total amount of monomer components used for the production of the (meth) acrylic acid ester copolymer. Preferably, it is more preferably used in the range of 0.5% by mass to 5% by mass.

  The (meth) acrylic acid ester copolymer can be produced by, for example, a thermal polymerization method such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, or a polymerization method performed by irradiating active energy rays such as light or radiation. It can be produced by polymerizing the monomer component. In that case, it is preferable to employ the solution polymerization method among the polymerization methods in order to improve workability, quality stability, and the like in the production process of the (meth) acrylic acid ester copolymer.

When the solution polymerization method is employed, the monomer component is supplied into a reaction vessel containing a solvent together with a polymerization initiator and the like. At that time, either a batch charging method in which the whole amount of the monomer component is supplied to the reaction vessel in a batch and polymerized, or a dropping method in which the monomer component is continuously or divided and supplied to the reaction vessel to be polymerized is adopted. May be.
As the solvent that can be used in the solution polymerization method, various organic solvents generally used in the solution polymerization method can be used, and it is preferable to use a non-toluene organic solvent.
Examples of the organic solvent include ethyl acetate, hexane, cyclohexane, methylcyclohexane, isopropyl alcohol, and the like. Examples of other organic solvents that can be preferably used include 1-butanol, secondary butanol, tertiary butanol, tertiary butyl methyl ether, methyl ethyl ketone, acetylacetone, 1,2-dichloroethane, and the like.

  The (meth) acrylic acid ester copolymer obtained by the above method preferably has a weight average molecular weight in the range of 300,000 to 1.6 million, and has a weight average molecular weight in the range of 400,000 to 1.3 million. More preferably, having a weight average molecular weight in the range of 500,000 to 1,000,000 is adhesion to the metal surface constituting the adherend and following the unevenness of the metal to be attached and the display panel. It is preferable because the properties can be suitably imparted.

  The molecular weight distribution (weight average molecular weight / number average molecular weight) of the (meth) acrylic acid ester copolymer is preferably 10-50, more preferably 10-30, and still more preferably 10-20. By adjusting the molecular weight distribution (weight average molecular weight / number average molecular weight) of the (meth) acrylic acid ester copolymer to the above range, it is possible to impart followability to the unevenness of the metal surface and display panel constituting the adherend, It is difficult to leave bubbles in the display screen portion, and further, peeling from the metal surface can be suppressed.

In addition, the weight average molecular weight of the said (meth) acrylic acid ester copolymer points out the value measured by the gel permeation chromatograph (GPC). More specifically, it is a value obtained by measuring “SC8020” manufactured by Tosoh Corporation as a GPC measurement device, and measuring the polystyrene conversion value under the following GPC measurement conditions.
(GPC measurement conditions)
Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μL
・ Eluent: Tetrahydrofuran (THF)
・ Flow rate: 1.0 mL / min
Column temperature (measurement temperature): 40 ° C
Column: “TSKgel GMHHR-H” manufactured by Tosoh Corporation
・ Detector: Differential refraction

  As the acrylic pressure-sensitive adhesive, an acyclic aliphatic isocyanate crosslinking agent is used in combination with the (meth) acrylic acid ester copolymer. Thereby, the outstanding adhesive force and cohesion force of an adhesive layer can be reconciled.

As the acyclic aliphatic isocyanate crosslinking agent, an isocyanate compound having a so-called linear or branched chain structure that does not have a cyclic structure can be used. Specifically, it is preferable to use hexamethylene diisocyanate.
By using hexamethylene diisocyanate, it is possible to achieve both excellent adhesive force and cohesive force of the pressure-sensitive adhesive layer, and it is difficult to cause peeling due to gas (gas) that can be generated from the resin surface constituting the adherend. It is possible to make it difficult to cause white turbidity or the like of the pressure-sensitive adhesive layer due to bubbles caused by the gas.

  The acyclic aliphatic isocyanate crosslinking agent is preferably used in the range of 0.03 parts by mass to 2 parts by mass with respect to 100 parts by mass of the acrylate copolymer. It is more preferable to use in the range of 5 parts by mass, and use in the range of 0.1 to 1 part by mass results in peeling due to gas (gas) that can be generated from the resin surface constituting the adherend. It is further preferable in order to achieve the effect of suppressing the above.

As the acrylic pressure-sensitive adhesive, a mixture of the (meth) acrylic acid ester copolymer and an acyclic aliphatic isocyanate crosslinking agent can be used. Among these, as the acrylic pressure-sensitive adhesive, it is possible to use a solution in which the (meth) acrylic acid ester copolymer and the acyclic aliphatic isocyanate crosslinking agent are dissolved or dispersed in a solvent. Since it can improve, it is preferable.
The acrylic pressure-sensitive adhesive is produced, for example, by mixing a solvent solution or dispersion of a (meth) acrylic acid ester copolymer obtained by the solution polymerization method with an acyclic aliphatic isocyanate crosslinking agent. Can do.

As the acrylic pressure-sensitive adhesive, in addition to the above-described components, other additives can be used as necessary.
Examples of the additive include an ultraviolet absorber, a light stabilizer, an anti-aging agent, a release modifier, a tackifier, a plasticizer, a softener, a filler, a colorant (such as a pigment and a dye), and a surfactant. Can be used.

The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by forming a pressure-sensitive adhesive layer on a film substrate or a release sheet. Specifically, the pressure-sensitive adhesive sheet of the present invention can be produced by applying the acrylic pressure-sensitive adhesive on the surface of a film substrate and drying or curing it.
In the pressure-sensitive adhesive sheet of the present invention, the acrylic pressure-sensitive adhesive is applied to the surface of a release sheet, and a pressure-sensitive adhesive layer is formed by drying or curing, and then a film substrate is applied to the surface of the pressure-sensitive adhesive layer. Can be manufactured by a method.
Moreover, the adhesive sheet of this invention produces two what formed the adhesive layer by apply | coating the said acrylic adhesive to the surface of a release sheet, and drying or hardening, The surface of those adhesive layers It can manufacture by bonding together.

The pressure-sensitive adhesive sheet of the present invention can be used for adhesion of various adherends. In particular, the pressure-sensitive adhesive sheet of the present invention is excellent in adhesiveness to a surface made of a resin constituting the adherend and a surface made of a metal constituting the adherend. Even when the pressure-sensitive adhesive sheet of the present invention is attached to a surface made of the resin, it is difficult to cause peeling due to a gas that can be generated from the surface made of the resin. Less likely to cause white turbidity of the agent layer. Moreover, even if the adhesive sheet of this invention is a case where it affixes on the surface which consists of the said metal, it can prevent the corrosion of the said metal surface.
Therefore, the pressure-sensitive adhesive sheet of the present invention is exclusively used for bonding a surface made of resin and a surface made of metal. More specifically, the pressure-sensitive adhesive sheet of the present invention is a metal having good conductivity on the surface of a transparent film or glass plate constituting an image display panel, a touch panel, etc. comprising a transparent resin panel constituting the image display device. It can be suitably used for fixing a transparent metal film or the like provided with a layer. In particular, the pressure-sensitive adhesive sheet of the present invention is preferably used for fixing an image display panel composed of the transparent resin panel because the image visibility of the image display device can be improved.
Examples of the adherend to which the pressure-sensitive adhesive sheet of the present invention can be applied include an adherend having a surface made of resin. All of the adherend may be made of one or more resins, or a part of the adherend may be made of a resin.
The adherend is preferably a film, a sheet, or a panel. In particular, when the adherend is used for an image display panel or the like, it is preferably highly transparent, and its total light transmittance is preferably 85% or more, and 90% or more. Is more preferable.
The surface made of resin constituting the adherend may have a shape such as a flat surface, a curved surface, a bent surface, a smooth surface, or a rough surface.
Examples of the resin constituting the resin surface of the adherend include resins such as an acrylic resin and a polycarbonate resin. Among them, the acrylic resin is less likely to cause peeling due to the gas and has excellent adhesion. It is preferable because the force can be maintained.
If it is the adhesive sheet of this invention, peeling of the adhesive sheet by the influence of the gas generated from the surface which consists of the said resin, the cloudiness of the adhesive layer by the bubble derived from the said gas, etc. can be prevented.

Examples of the adherend to which the adhesive sheet of the present invention can be attached include an adherend having a surface made of a conductive layer. A transparent conductive film in which a conductive layer is provided on the surface of a transparent resin film, a glass plate, or the like can be used.
The adherend is preferably a film, a sheet, or a panel. In particular, when the adherend is used for a transparent conductive film constituting a touch panel or the like, it is preferable to use a highly transparent one.

  Examples of the surface made of the conductive layer include indium tin oxide, indium oxide, tin oxide, zinc oxide, cadmium oxide, gallium oxide, and titanium oxide. As a member having such a metal surface, ITO glass or ITO film provided with indium tin oxide (ITO) on the surface of glass or film, or silver or copper wiring provided on the surface of glass or film. The member which has a conductive layer surface used for image display apparatuses, such as touch panels, such as a metal wiring film, can be illustrated.

  Since the adhesive sheet of the present invention does not corrode the surface made of the conductive layer, ITO glass or ITO film provided with indium tin oxide (ITO) on the surface of the glass or film, or silver or silver on the surface of the glass or film. It can be suitably used for fixing a member having a metal surface such as a metal wiring film provided with copper wiring. Especially, it can use suitably for fixation of the member which has a conductive layer surface where high transparency is calculated | required and the stable electroconductivity is calculated | required. Moreover, since peeling at the resin panel interface at high temperature and generation of bubbles in the pressure-sensitive adhesive layer can be suppressed, it can be suitably used when fixing a resin panel such as an acrylic plate.

  As a suitable configuration example to which the pressure-sensitive adhesive sheet of the present invention is applied, for example, ITO is vapor-deposited on one side in a touch sensor used in an image display unit of an electronic device that requires high transparency and stable conductivity. The polyethylene terephthalate film made can be suitably used for fixing a resin image display panel. As a specific example of the image display device having such a configuration, the configuration as shown in FIG. 1 can be preferably exemplified. In the application example in FIG. 1, the resin-made transparent image display panel 2 having the printing layer 3 and the ITO film 4 having the ITO surface 4 b on the transparent resin film 4 a are formed by the adhesive sheet 1 of the present invention without a substrate. The adhesive sheet of the present invention can be suitably used for such applications. In addition, an image display module 6 such as an LCD module is provided in the housing 5, and the housing and the transparent resin film 4 a side of the ITO film 4 ′ are fixed by an adhesive member 7 such as an adhesive tape or an adhesive tape. The ITO surface 4b ′ of the ITO film 4 ′ and the transparent resin film 4a surface of the ITO film 4 can be suitably used for fixing the substrate with the pressure-sensitive adhesive sheet “1” of the present invention.

  Furthermore, it is suitable as a pressure-sensitive adhesive film for the purpose of fixing glass and surface protection panels with acid value indium tin deposited on one side, or preventing scattering when glass is broken, in touch sensors used in image display parts of electronic devices. Can be used for As a specific example of the image display device having such a configuration, the configuration shown in FIG. 2 can be preferably exemplified. The application example in FIG. 2 is an application in which the surface protection panel 12 having the printed layer 13 and the ITO glass 14 having the ITO surfaces 14b and 14c on the transparent glass 14a are fixed by the adhesive sheet 11 of the present invention without a substrate. Thus, the pressure-sensitive adhesive sheet of the present invention can be suitably applied as in the embodiment of FIG. Moreover, in order to prevent cracking of ITO glass, the pressure-sensitive adhesive sheet 11 may be a double-sided pressure-sensitive adhesive sheet having a substrate. In the configuration example, a scattering prevention adhesive sheet 15 having an adhesive layer 15a is provided on one surface of the hard coat film 15b for preventing the ITO glass 14 from scattering, and the hard coat film 15b of the scattering prevention adhesive sheet 15 is provided. The housing 16 having the image display module 17 such as an LCD module is fixed by an adhesive member 18.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
<Adhesive composition (A)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 75 parts by mass of 2-methoxyethyl acrylate, 24 parts by mass of n-butyl acrylate, 1 mass of 2-hydroxyethyl acrylate Part and 0.22 parts by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (A) of solid content 45 mass%.

<Adhesive composition (B)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 85 parts by mass of 2-methoxyethyl acrylate, 14 parts by mass of n-butyl acrylate, 1 mass of 2-hydroxyethyl acrylate Part and 0.22 parts by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (B) of solid content 45 mass%.

<Adhesive composition (C)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 95 parts by mass of 2-methoxyethyl acrylate, 1 part by mass of n-butyl acrylate, 4 parts by mass of 2-hydroxyethyl acrylate Part and 0.22 parts by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (C) of 45 mass% of solid content.

<Adhesive composition (D)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 2-methoxyethyl acrylate 50 parts by mass, n-butyl acrylate 49 parts by mass, 2-hydroxyethyl acrylate 1 part by mass Part and 0.22 parts by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and after substitution with nitrogen, polymerization was carried out at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (D) of 45 mass% of solid content.

<Adhesive composition (E)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel, and nitrogen gas inlet, 70 parts by mass of 2-methoxyethyl acrylate, 29 parts by mass of 2-ethylhexyl acrylate, 1 part by mass of 2-hydroxyethyl acrylate Then, 0.2 part by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator was dissolved in 100 parts by mass of ethyl acetate, and after nitrogen substitution, polymerization was carried out at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (E) of solid content 45 mass%.

<Adhesive composition (F)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 70 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of 2-hydroxyethyl acrylate, and 2,2 as a polymerization initiator '-Azobisisobutylnitrile (0.2 part by mass) was dissolved in ethyl acetate (100 parts by mass), purged with nitrogen, and then polymerized at 80 ° C for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (F) with a solid content of 35 mass%.

<Adhesive composition (G)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 65 parts by mass of n-butyl acrylate, 5 parts by mass of 2-ethylhexyl acrylate, 30 parts by mass of 2-hydroxyethyl acrylate Then, 0.2 part by mass of 2,2′-azobisisobutylnitrile as a polymerization initiator was dissolved in 100 parts by mass of ethyl acetate, and after nitrogen substitution, polymerization was carried out at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (G) of solid content 30 mass%.

<Adhesive composition (H)>
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 85 parts by mass of n-butyl acrylate, 15 parts by mass of methyl methacrylate, 4 parts by mass of acrylic acid, and a polymerization initiator 0.22 parts by mass of 2,2′-azobisisobutylnitrile was dissolved in 100 parts by mass of ethyl acetate, purged with nitrogen, and polymerized at 80 ° C. for 8 hours. Then, it diluted with ethyl acetate and obtained the adhesive composition (H) of solid content 25 mass%.

Abbreviations for blending in the table are as follows.
MEA: methoxyethyl acrylate BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate HEA: 2-hydroxyethyl acrylate MA: methyl acrylate MMA: methyl methacrylate AA: acrylic acid

Example 1
To 100 parts by mass of the pressure-sensitive adhesive composition (A), 0.08 parts by mass of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) is added as an acyclic aliphatic isocyanate crosslinking agent and stirred for 15 minutes. Thus, an acrylic pressure-sensitive adhesive (A) was prepared.
Next, the acrylic pressure-sensitive adhesive (A) is applied to a dried pressure-sensitive adhesive layer on a 50 μm-thick polyester film (hereinafter, abbreviated as “# 50 release film”) having one surface peel-treated with a silicone compound. The coating was applied to a thickness of 50 μm and dried at 80 ° C. for 5 minutes. A 38 μm thick polyester film (hereinafter abbreviated as “# 38 release film”) having one side peeled with a silicone compound was bonded to the surface of the pressure-sensitive adhesive layer formed after the drying. Thereafter, by aging at 23 ° C. for 7 days, a base material-less pressure-sensitive adhesive sheet (thickness 50 μm) in which the gel fraction of the pressure-sensitive adhesive layer was 52 mass% was obtained.

(Example 2)
Example 1 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.25 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 77 mass% was obtained.

(Example 3)
The gel fraction of the pressure-sensitive adhesive layer is 52% by mass in the same manner as in Example 1 except that 100 parts by mass of the pressure-sensitive adhesive composition (B) is used instead of the pressure-sensitive adhesive composition (A). A substrate-less pressure-sensitive adhesive sheet (thickness 50 μm) was obtained.

(Example 4)
Example 3 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.25 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 77 mass% was obtained.

(Example 5)
The gel fraction of the pressure-sensitive adhesive layer is 48% by mass in the same manner as in Example 1 except that 100 parts by mass of the pressure-sensitive adhesive composition (C) is used instead of the pressure-sensitive adhesive composition (A). A substrate-less pressure-sensitive adhesive sheet (thickness 50 μm) was obtained.

(Example 6)
Example 5 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.1 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 55 mass% was obtained.

(Example 7)
Example 5 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.12 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 62 mass% was obtained.

(Example 8)
Example 5 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.14 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 65 mass% was obtained.

(Comparative Example 1)
Example 1 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.04 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 28 mass% was obtained.

(Comparative Example 2)
Example 1 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.08 parts by mass to 0.4 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 90 mass% was obtained.

(Comparative Example 3)
Instead of Coronate HL (Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent, 0.1 part by mass of Coronate HX (Nippon Polyurethane Industry Co., Ltd., xylene diisocyanate compound) is used. A base material-less pressure-sensitive adhesive sheet (thickness 50 μm) having a gel fraction of the pressure-sensitive adhesive layer of 50% by mass was obtained in the same manner as in Example 1 except that it was used.

(Comparative Example 4)
Comparative Example 3 except that the addition amount of Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd., xylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.1 parts by mass to 0.24 parts by mass. In the same manner, a baseless pressure-sensitive adhesive sheet (thickness: 50 μm) having a gel fraction of the pressure-sensitive adhesive layer of 72% by mass was obtained.

(Comparative Example 5)
Comparative Example 3 except that the addition amount of Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd., xylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.1 parts by mass to 0.4 parts by mass. In the same manner, a baseless pressure-sensitive adhesive sheet (thickness 50 μm) having a gel fraction of the pressure-sensitive adhesive layer of 90% by mass was obtained.

(Comparative Example 6)
The gel fraction of the pressure-sensitive adhesive layer is 25% by mass in the same manner as in Comparative Example 1 except that 100 parts by mass of the pressure-sensitive adhesive composition (C) is used instead of the pressure-sensitive adhesive composition (A). A substrate-less pressure-sensitive adhesive sheet (thickness 50 μm) was obtained.

(Comparative Example 7)
100 parts by mass of the pressure-sensitive adhesive composition (C) is used in place of the pressure-sensitive adhesive composition (A), and coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate type) is used as an acyclic aliphatic isocyanate crosslinking agent. The gel fraction of the pressure-sensitive adhesive layer is the same as that of Comparative Example 1 except that 0.3 parts by mass of Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd., xylene diisocyanate compound) is used instead of the compound). A substrate-less pressure-sensitive adhesive sheet (thickness: 50 μm), which was 85% by mass, was obtained.

(Comparative Example 8)
100 parts by mass of the pressure-sensitive adhesive composition (D) is used instead of the pressure-sensitive adhesive composition (A), and coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate type) is used as an acyclic aliphatic isocyanate crosslinking agent. Except for changing the addition amount of the compound) from 0.04 parts by mass to 0.1 parts by mass, in the same manner as in Comparative Example 1, the gel fraction of the pressure-sensitive adhesive layer is 52% by mass. An adhesive sheet (thickness 50 μm) was obtained.

(Comparative Example 9)
100 parts by mass of the pressure-sensitive adhesive composition (E) is used in place of the pressure-sensitive adhesive composition (A), and coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate type) is used as an acyclic aliphatic isocyanate crosslinking agent. Except for changing the addition amount of the compound) from 0.04 parts by mass to 0.1 parts by mass, in the same manner as in Comparative Example 1, the gel fraction of the pressure-sensitive adhesive layer is 50% by mass. An adhesive sheet (thickness 50 μm) was obtained.

(Comparative Example 10)
100 parts by mass of the pressure-sensitive adhesive composition (F) is used in place of the pressure-sensitive adhesive composition (A), and coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate type) is used as an acyclic aliphatic isocyanate crosslinking agent. Except for changing the addition amount of the compound) from 0.04 parts by mass to 0.0.3 parts by mass, the gel fraction of the pressure-sensitive adhesive layer is 35% by mass in the same manner as in Comparative Example 1. A material-less adhesive sheet (thickness 50 μm) was obtained.

(Comparative Example 11)
Comparative Example 10 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.03 parts by mass to 0.05 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 50 mass% was obtained.

(Comparative Example 12)
Comparative Example 10 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.03 parts by mass to 0.08 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 73 mass% was obtained.

(Comparative Example 13)
Comparative Example 10 except that the addition amount of Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate compound) as an acyclic aliphatic isocyanate crosslinking agent is changed from 0.03 parts by mass to 0.3 parts by mass. By the same method, the base material-less adhesive sheet (50 micrometers in thickness) whose gel fraction of an adhesive layer is 90 mass% was obtained.

(Comparative Example 14)
100 parts by mass of the pressure-sensitive adhesive composition (G) is used instead of the pressure-sensitive adhesive composition (A), and coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate type) is used as an acyclic aliphatic isocyanate crosslinking agent. Except for changing the addition amount of the compound) from 0.08 parts by mass to 0.0.4 parts by mass, the gel fraction of the pressure-sensitive adhesive layer is 53% by mass in the same manner as in Example 1. A material-less adhesive sheet (thickness 50 μm) was obtained.

(Comparative Example 15)
100 parts by mass of the pressure-sensitive adhesive composition (H) is used in place of the pressure-sensitive adhesive composition (A), and coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd., hexamethylene diisocyanate type) is used as an acyclic aliphatic isocyanate crosslinking agent. The gel fraction of the pressure-sensitive adhesive layer is the same as in Example 1 except that 0.6 parts by mass of E-2XM (manufactured by Soken Chemical Co., Ltd., epoxy crosslinking agent) is used instead of the compound). A substrate-less pressure-sensitive adhesive sheet (thickness: 50 μm), which was 60% by mass, was obtained.

  The following evaluation was performed about the adhesive sheet obtained by the said Example and comparative example. The results obtained are shown in the table below.

(Peeling resistance after leaving in high temperature environment)
The test piece 1 was obtained by peeling off the release film (# 38 release film) on one side of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and pasting it on a polyethylene terephthalate film having a thickness of 100 μm, a length of 50 mm, and a width of 50 mm. The release film (# 50 release film) on the other side constituting the test piece 1 is peeled off and bonded to an acrylic plate (MR-200 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 2 mm, a length of 50 mm, and a width of 5 mm. The test piece 2 was subjected to heat and pressure treatment at 70 ° C. for 20 minutes and left at 85 ° C. for 250 hours.
Next, the whole test piece 2 was observed from the polyethylene terephthalate film side with a microscope (100 times magnification), and it was confirmed whether there was peeling due to bubble expansion. The evaluation criteria were as follows.
○: No peeling ×: There is peeling

(Foam resistance after leaving in high temperature environment)
The test piece 3 was obtained by peeling off the release film (# 38 release film) on one side of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and bonding the film to a polyethylene terephthalate film having a thickness of 100 μm, a length of 50 mm, and a width of 50 mm. The release film (# 50 release film) on the other side constituting the test piece 3 is peeled off and bonded to an acrylic plate (MR-200 manufactured by Mitsubishi Rayon Co., Ltd.) having a thickness of 2 mm, a length of 50 mm, and a width of 5 atm. A test piece 4 was prepared by heating and pressurizing under conditions of 70 ° C. for 20 minutes and then leaving it under conditions of 85 ° C. for 250 hours.
Next, the entire test piece 4 was observed with a microscope (100 times magnification), and it was confirmed whether air bubbles were mixed in the adhesive layer. The evaluation criteria for bubble contamination were as follows.
◎: No bubbles with a diameter of 5 μm or more ○: No bubbles with a diameter of 10 μm or more ○ △: No bubbles with a diameter of 30 μm or more △: No bubbles with a diameter of 50 μm or more X: Bubbles with a diameter of 50 μm or more

(White turbidity resistance after standing under high temperature and high humidity conditions)
A test piece 5 was obtained by peeling off the release film (# 38 release film) on one side of the pressure-sensitive adhesive sheet and bonding it to a polyethylene terephthalate film having a thickness of 100 μm, a length of 50 mm, and a width of 40 mm. A test sample prepared by peeling off the release film (# 50 release film) on the other side constituting the test piece 4 and attaching it to a glass plate having a thickness of 1 mm, a length of 50 mm, and a width of 40 mm was obtained at 60 ° C. and 90% RH. The haze immediately after the test sample was taken out from the above conditions was measured using “HR-100 Model” manufactured by Murakami Color Research Laboratory.
○: Haze 1.0% or less △: Haze 1.0% to 3.0%
X: Haze 3.0% or more

Metal corrosivity evaluation method (measurement of electrical resistance of indium tin oxide film)
A test piece 6 was obtained by peeling off the release film (# 38 release film) on one side of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, bonding a polyethylene terephthalate film (100 μm), and cutting the film into 50 mm × 50 mm.
Next, a polyethylene terephthalate film (100 mm long × 100 mm long) with indium tin oxide deposited on the surface thereof was prepared, and the pressure-sensitive adhesive layer from which the other release film (# 50 release film) of the test piece 5 was removed and the oxidized film A test piece 7 was obtained by attaching the surface of a film (layer) made of indium tin.
The electrical resistance value measuring machine “Lorestar GP” manufactured by Mitsubishi Chemical Corporation was used to measure the initial electrical resistance values (R1) at both ends of the pressure-sensitive adhesive layer constituting the test piece 7.
Next, the electrical resistance value (R2) of the test piece 7 after the test piece 6 is allowed to stand for 250 hours under the conditions of 60 ° C. and 90% RH and then for 1 hour under the conditions of 23 ° C. and 50% RH. Was measured by the same method as the initial electrical resistance value (R1). The electric resistance value change rate of the indium tin oxide (ITO) film was calculated by the following formula.
Change rate of electric resistance value of ITO film (%) = ((R2−R1) / R1) × 100
○: Electrical resistance value change rate of 90% or more and less than 110% ×: Electrical resistance value change rate of less than 90% or 110% or more

  As shown in the above table, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 8 did not peel off or foam in the pressure-sensitive adhesive layer under a high temperature environment. Moreover, it was confirmed that it does not become cloudy under high-temperature and high-humidity conditions, and the electrical resistance value does not change excessively. On the other hand, the pressure-sensitive adhesive composition is the same as in the examples, but Comparative Examples 1 and 6 having a gel fraction of less than 30% foam in the pressure-sensitive adhesive layer after standing in a high temperature environment, and the gel fraction exceeds 80%. In Comparative Example 2 and Comparative Example 7, peeling at the interface was confirmed after leaving in a high temperature environment. Moreover, in Comparative Examples 3 to 5 using xylene diisocyanate as a crosslinking agent, foaming in the pressure-sensitive adhesive layer or peeling at the interface was confirmed after leaving in a warm environment. Further, in Comparative Example 8 in which the content of n-butyl acrylate having 4 carbon atoms is 49% by mass and Comparative Example 9 using 2-ethylhexyl acrylate having 8 carbon atoms, haze increases under high temperature and high humidity conditions. The cloudiness was confirmed. In Comparative Examples 10 to 13 containing no alkoxyalkyl acrylate, foaming in the pressure-sensitive adhesive layer or peeling at the interface was confirmed after leaving the environment. In Comparative Example 15 having acrylic acid which is a monomer having a carboxyl group, an increase in the electrical resistance value of ITO was confirmed.

1, 1 ', 11 Adhesive sheet 2, 12 Surface protection panel 3, 13 Print layer 4, 4' ITO film 4a, 4a 'Transparent resin film 4b, 4b' ITO
5,16 Case 6,17 Image display module 7,18 Adhesive member 14 ITO glass 14a Transparent glass 14b, 14c ITO
15 scattering prevention pressure sensitive adhesive sheet 15a pressure sensitive adhesive layer 15b hard coat film

Claims (5)

A pressure-sensitive adhesive sheet used for bonding a surface made of a resin and a surface made of a conductive layer, wherein the pressure-sensitive adhesive sheet contains a (meth) acrylic acid ester copolymer and an acyclic aliphatic isocyanate crosslinking agent. It has a pressure-sensitive adhesive layer with a gel fraction of 30% by mass to 80% by mass formed using an acrylic pressure-sensitive adhesive,
The (meth) acrylic acid ester copolymer is obtained by polymerizing a monomer component, and the content of the (meth) acrylic acid alkoxyalkyl ester (A) contained in the monomer component is 50 mass. The content of the (meth) acrylic acid alkyl ester (B) having an alkyl group having 1 to 4 carbon atoms is 1% by mass to 45% by mass and having a carboxyl group. The pressure-sensitive adhesive sheet, wherein the content of the monomer (C) is 1% by mass or less.   The pressure-sensitive adhesive sheet according to claim 1, wherein the (meth) acrylic acid alkyl ester (B) having an alkyl group having 1 to 4 carbon atoms is n-butyl acrylate.   The pressure-sensitive adhesive sheet according to claim 1, wherein the acyclic aliphatic isocyanate crosslinking agent is hexamethylene diisocyanate.   The pressure-sensitive adhesive sheet according to claim 1, wherein the (meth) acrylic acid ester copolymer has a weight average molecular weight of 300,000 to 1,600,000.   The pressure-sensitive adhesive sheet according to claim 1, wherein the resin member having a surface made of resin is an acrylic panel, and the member having a surface made of the conductive layer is a transparent conductive film.

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