Pressure sensitive adhesive sheet, optical member with adhesive layer and picture display unit

Abstract

To provide a pressure sensitive adhesive sheet with reduced low dielectric constant to lower noises, having sufficient adhesive strength as well as drop impact resistance.SOLUTION: A pressure sensitive adhesive sheet includes an adhesive layer. The adhesive layer causes no peelings at a drop impact resistance test under a prescribed condition, has a dielectric constant of 4 or less at a frequency 100 kHz, and a glass adhesive strength of 10 N / 20 mm or more under a condition of a peeling angle 180° and a tensile speed 300 mm / min at least on one side thereof, and is to be used for an optical member.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive layer-attached optical member, and an image display device. [Background technology]

[0002] In recent years, image display devices such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs), as well as touch panels incorporating touch sensors in these image display devices, have come to be widely used in various fields. Such image display devices and touch panels have a configuration in which various optical members such as a polarizing film, a retardation film, an optical compensation film, a touch sensor film, and a cover film are laminated on an image display panel. Adhesive sheets having an adhesive layer are used to bond these optical members. For example, transparent adhesive sheets are used to bond various optical members in image display devices (see, for example, Patent Documents 1 to 3).

[0003] In particular, for adhesive sheets used in touch panels, in addition to the above, there has been a demand for adhesive sheets that achieve a low dielectric constant in order to reduce malfunctions caused by noise. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-238915 A [Patent Document 2] JP 2003-342542 A [Patent Document 3] JP 2004-231723 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional adhesive sheets, when the dielectric constant is reduced, the polarity of the adhesive sheet surface is reduced, which can result in insufficient adhesion at the interface with the adherend, particularly in insufficient drop impact resistance.

[0006] Therefore, the present invention was devised under these circumstances, and its object is to provide an adhesive sheet which has a low dielectric constant, thereby reducing noise, has sufficient adhesive strength to an adherend, and also has drop impact resistance. [Means for solving the problem]

[0007] As a result of intensive research into achieving the above-mentioned object, the inventors have found that if an adhesive layer has an adhesive layer which does not peel off in a specific drop impact resistance test, has a dielectric constant of 4 or less at a frequency of 100 kHz, and has an adhesion to glass of 10 N / 20 mm or more at a peel angle of 180° and a tensile speed of 300 mm / min on at least one surface, then the dielectric constant is reduced, thereby reducing noise, providing sufficient adhesion to an adherend, and providing drop impact resistance.

[0008] That is, the present invention provides an adhesive sheet for use with optical components, which has an adhesive layer, which does not peel off in the drop impact resistance test described below, has a dielectric constant of 4 or less at a frequency of 100 kHz, and has an adhesion to glass of 10 N / 20 mm or more on at least one surface at a peel angle of 180° and a tensile speed of 300 mm / min. <Drop impact resistance test> A first glass plate (length 100 mm x width 75 mm, thickness 500 μm), the adhesive layer (length 75 mm x width 45 mm), a printed layer (thickness 30 μm) formed within a range of 15 mm around the edge of the second glass plate, and the second glass plate (length 100 mm x width 50 mm, thickness 500 μm) are laminated in this order, and a bonded body is produced by heat treatment under conditions of 50 ° C, 0.5 MPa, and 30 minutes. The bonded body is placed on a support table so that only the protruding parts at both ends in the width direction of the first glass plate are supported by the support table and the second glass plate is not in contact with the support table, and the first glass plate is placed on the upper side of the bonded body. A metal ball having a mass of 15 g is dropped from a height of 300 mm onto the first glass plate to check whether or not the adhesive layer peels off from the first glass plate or the printed layer.

[0009] The pressure-sensitive adhesive layer does not peel off even in the drop impact resistance test, and has a glass adhesion strength of 10 N / 20 mm or more under conditions of a peel angle of 180° and a tensile speed of 300 mm / min, so that the pressure-sensitive adhesive layer has sufficient adhesion strength and can exhibit drop impact resistance. In addition, the dielectric constant at a frequency of 100 kHz is 4 or less, so that noise can be reduced.

[0010] It is preferable that the pressure-sensitive adhesive layer does not peel off even after being left for one week at 80° C. after the drop impact resistance test. By having the above-mentioned configuration, the pressure-sensitive adhesive layer can be suitably used even under high temperature conditions.

[0011] The present invention also provides an optical member with a pressure-sensitive adhesive layer, comprising the above-mentioned pressure-sensitive adhesive sheet attached to at least one surface of the optical member.

[0012] The present invention also provides an image display device having the pressure-sensitive adhesive layer-attached optical member.

[0013] The present invention also provides a touch panel having the pressure-sensitive adhesive layer-attached optical member. Effect of the Invention

[0014] The pressure-sensitive adhesive sheet of the present invention reduces noise due to its low dielectric constant, has sufficient adhesive strength, and also has drop impact resistance. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram showing a specific example of a preferred embodiment of the pressure-sensitive adhesive sheet of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a specific example of a preferred embodiment of the pressure-sensitive adhesive layer-attached optical member of the present invention. [Diagram 3] FIG. 3 is a schematic diagram showing a specific example of a preferred embodiment of the image display device of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a specific example of a preferred embodiment of the touch panel of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [Adhesive sheet] The adhesive sheet of the present invention has an adhesive layer, which does not peel off from an adherend in the drop impact resistance test described below, has a dielectric constant of 4 or less at a frequency of 100 kHz, and has an adhesion to glass of 10 N / 20 mm or more on at least one surface at a peel angle of 180° and a tensile speed of 300 mm / min, and is suitable for use as an optical component. <Drop impact resistance test> A first glass plate (length 100 mm x width 75 mm, thickness 500 μm), the adhesive layer (length 75 mm x width 45 mm), a printed layer (thickness 30 μm) formed within a range of 15 mm around the edge of the second glass plate, and the second glass plate (length 100 mm x width 50 mm, thickness 500 μm) are laminated in this order, and a bonded body is produced by heat treatment under conditions of 50 ° C, 0.5 MPa, and 30 minutes. The bonded body is placed on a support table so that only the protruding parts at both ends in the width direction of the first glass plate are supported by the support table and the second glass plate is not in contact with the support table, and the first glass plate is placed on the upper side of the bonded body. A metal ball having a mass of 15 g is dropped from a height of 300 mm onto the first glass plate to check whether or not the adhesive layer peels off from the first glass plate or the printed layer.

[0017] The pressure-sensitive adhesive sheet is used for adhering optical components such as polarizing films, retardation films, optical compensation films, touch sensor films, and cover films to image display panels in image display devices such as liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDs), and in touch panels in which a touch sensor is incorporated into these image display devices, or for adhering these optical components to each other. In this specification, when referring to an "image display device", it is intended to include a "touch panel" unless otherwise specified.

[0018] The pressure-sensitive adhesive sheet may be a double-sided pressure-sensitive adhesive sheet in which both sides are pressure-sensitive adhesive layer surfaces, or a single-sided pressure-sensitive adhesive sheet in which only one side is a pressure-sensitive adhesive layer surface. In particular, from the viewpoint of bonding two members together, a double-sided pressure-sensitive adhesive sheet is preferable. In this specification, the term "pressure-sensitive adhesive sheet" also includes a tape-like one, i.e., an "adhesive tape". In this specification, the pressure-sensitive adhesive layer surface may be referred to as the "adhesive surface".

[0019] (Adhesive layer) The pressure-sensitive adhesive layer is not particularly limited, but preferably has a low dielectric constant controlled from the viewpoint of preventing malfunction of a touch panel having the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer has a dielectric constant of 4 or less at 20° C. and a frequency of 100 kHz, preferably 3.9 or less, more preferably 3.8 or less. The lower limit of the dielectric constant at a frequency of 100 kHz is not particularly limited, but is preferably 1.5 or more, more preferably 1.8 or more, and even more preferably 2.0 or more. The lower limit of the dielectric constant at a frequency of 100 kHz may be 2.1 or more, 2.2 or more, 2.3 or more, 2.4 or more, or 2.5 or more. The lower limit of the dielectric constant is 1.5 or more, which makes it easier for the pressure-sensitive adhesive layer to exhibit adhesion. The dielectric constant is measured in accordance with JIS K 6911.

[0020] The adhesive layer has an adhesive strength of 10N / 20mm or more on at least one side with a glass plate measured under conditions of 23°C and 50% RH using a tensile tester at a peel angle of 180° and a tensile speed of 300mm / min, and can be easily bonded. It is preferably 12N / 20mm or more, more preferably 14N / 20mm or more. The upper limit is not particularly limited, but may be, for example, 30N / 20mm or less. From the viewpoint of exhibiting reworkability, it is preferably 24N / 20mm or less, more preferably 22N / 20mm or less, and particularly preferably 20N / 20mm or less. When the adhesive layer is used as a double-sided adhesive sheet, it is preferable that the adhesive strength of both sides is within the above range.

[0021] The pressure-sensitive adhesive layer does not peel off even in the above-mentioned drop impact resistance test, preferably in the above-mentioned drop impact resistance test changed to a height of 400 mm. A pressure-sensitive adhesive layer that does not peel off from an adherend in the above-mentioned drop impact resistance test has good drop impact resistance.

[0022] Furthermore, after the drop impact resistance test, it is preferable that no peeling occurs when the adhesive layer is left for one week at 80° C. A pressure-sensitive adhesive layer having such properties can be suitably used even under high temperature conditions.

[0023] Furthermore, after the drop impact resistance test, it is preferable that no peeling occurs when the adhesive layer is left for one week at −10° C. A pressure-sensitive adhesive layer having such properties can be suitably used even under low temperature conditions.

[0024] Furthermore, it is preferable that the adhesive layer does not peel off when left for one month at room temperature after the drop impact resistance test. A pressure-sensitive adhesive layer having such properties tends to have excellent storage stability.

[0025] The pressure-sensitive adhesive layer has a compressibility of 1.0×10 at 20° C. according to JIS K 6911. 3 ~10 4 The lower limit of the dielectric tangent in Hz is preferably 0.75 or more, more preferably 0.85 or more, even more preferably 0.95 or more, and particularly preferably 1.15 or more. The upper limit is preferably 2.6 or less, more preferably 2.4 or less, even more preferably 2.2 or less, and particularly preferably 2.0 or less. 3 ~10 4 A dielectric tangent of 0.75 or more in the high-speed region of 100 Hz makes it easy to exhibit drop impact resistance, while a dielectric tangent of 2.6 or less makes it easy to prevent cohesive failure of the adhesive layer.

[0026] The thickness of the pressure-sensitive adhesive layer is preferably 5 to 300 μm, more preferably 8 to 200 μm, and particularly preferably 10 to 100 μm. When the thickness is 5 μm or more, drop impact resistance is easily exhibited, and when the thickness is 300 μm or less, handleability and manufacturability are excellent.

[0027] The method for producing the pressure-sensitive adhesive layer is not particularly limited. For example, the pressure-sensitive adhesive composition described below is prepared, and applied (coated) onto a substrate or a release liner, and then, if necessary, irradiated with active energy rays, dried by heating, or the like.

[0028] The pressure-sensitive adhesive composition may be applied (coated) by a known coating method, for example, a coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, or a direct coater.

[0029] In addition, the pressure-sensitive adhesive composition preferably does not contain or does not substantially contain an organic solvent. The organic solvent is not particularly limited as long as it is an organic compound used as a solvent, and examples thereof include hydrocarbon solvents such as cyclohexane, hexane, and heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, butanol, and isopropyl alcohol. The organic solvent may be a mixed solvent containing two or more organic solvents.

[0030] In the above pressure-sensitive adhesive composition, "substantially free of organic solvent" means that the organic solvent is not actively blended, except when the organic solvent is inevitably mixed in. Specifically, a pressure-sensitive adhesive composition having an organic solvent content of 1.0 mass % or less (preferably 0.5 mass % or less, more preferably 0.2 mass % or less) relative to the total amount (100 mass %) of the pressure-sensitive adhesive composition can be said to be substantially free of organic solvent.

[0031] The adhesive composition forming the adhesive layer is preferably an adhesive composition containing an acrylic polymer as a base polymer. It may also contain hydrogenated polyolefin resin, polyfunctional (meth)acrylate, silane coupling agent, and other additives, which will be described later. The acrylic polymer may be used alone or in combination of two or more kinds.

[0032] The content of the acrylic polymer is not particularly limited, but is preferably 30 to 90 mass %, more preferably 40 to 80 mass %, relative to the total amount (100 mass %) of the pressure-sensitive adhesive composition.

[0033] The adhesive composition for forming the adhesive layer containing an acrylic polymer as the main component is not particularly limited, and examples thereof include a composition containing an acrylic polymer as an essential component; a mixture of monomer components constituting an acrylic polymer (sometimes referred to as a "monomer mixture") or a composition containing a partial polymer thereof as an essential component. The former includes, for example, a so-called water-dispersed composition (emulsion type composition), and the latter includes, for example, a so-called active energy ray curable composition. Among them, the adhesive composition is preferably a composition containing the above-mentioned monomer mixture or a partial polymer thereof as an essential component.

[0034] In this specification, the above-mentioned "mixture of monomer components" includes a case where the mixture is composed of a single monomer component and a case where the mixture is composed of two or more monomer components. Also, the above-mentioned "partially polymerized product of the mixture of monomer components" means a composition in which one or more of the constituent monomer components of the above-mentioned "mixture of monomer components" are partially polymerized.

[0035] An acrylic polymer is a polymer containing an acrylic monomer as an essential monomer unit. In other words, an acrylic polymer is a polymer containing a constituent unit derived from an acrylic monomer as a constituent unit. That is, an acrylic polymer is a polymer constituted (formed) with an acrylic monomer as an essential monomer component. In this specification, "(meth)acrylic" refers to either one or both of "acrylic" and "methacrylic", and the same applies to the others. The weight average molecular weight of the acrylic polymer is not particularly limited, but is preferably 100,000 to 5,000,000.

[0036] The acrylic polymer in the pressure-sensitive adhesive composition is preferably a polymer containing, as a monomer unit, a (meth)acrylic acid alkyl ester having a linear or branched alkyl group (hereinafter, sometimes simply referred to as "(meth)acrylic acid alkyl ester").

[0037] Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate (n-butyl (meth)acrylate), isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, Examples of the (meth)acrylic acid alkyl ester include those having an alkyl group having 1 to 24 carbon atoms, such as nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. The (meth)acrylic acid alkyl ester may be used alone or in combination of two or more kinds.

[0038] As the (meth)acrylic acid alkyl ester, an acrylic acid alkyl ester is more preferable than a methacrylic acid alkyl ester in that it can shorten the polymerization time of the acrylic polymer and improve the productivity. In particular, when the acrylic polymer is cured by radiation polymerization, an acrylic acid alkyl ester is suitable.

[0039] Among these, the (meth)acrylic acid alkyl ester is preferably a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 18 carbon atoms, from the viewpoint of exhibiting a low dielectric constant and drop impact resistance, more preferably methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isostearyl acrylate (ISTA), and particularly preferably 2-ethylhexyl acrylate (2EHA).

[0040] The content (proportion) of the (meth)acrylic acid alkyl ester in all monomer units of the acrylic polymer (total amount of monomer components constituting the acrylic polymer) is not particularly limited, but in order to exhibit a low dielectric constant and drop impact resistance, it is preferably 30 to 95 mass%, more preferably 35 to 90 mass%, and even more preferably 40 to 85 mass%, relative to the total amount of monomer components constituting the acrylic polymer (100 mass%).

[0041] In this specification, the term "the total amount of monomer components constituting the acrylic polymer" is intended to include monomer components that are added separately to the pressure-sensitive adhesive composition containing the acrylic polymer for the purpose of adjusting the dielectric constant of the pressure-sensitive adhesive layer or the like in the above-mentioned pressure-sensitive adhesive composition.

[0042] In the pressure-sensitive adhesive composition, the acrylic polymer may contain, as a monomer unit, a functional group-containing monomer capable of copolymerization (copolymerizable functional group-containing monomer) in addition to the (meth)acrylic acid alkyl ester. That is, the acrylic polymer may contain a functional group-containing monomer as a constituent monomer component. The functional group-containing monomer may be used alone or in combination of two or more kinds.

[0043] The functional group-containing monomer is preferably a hydroxyl group-containing monomer. When the acrylic polymer contains a hydroxyl group-containing monomer as a monomer unit, the monomer components constituting the polymer are easily polymerized, and the cohesive force can be increased. In addition, the interaction with the adherend interface can be increased. Therefore, strong adhesion can be easily obtained.

[0044] The hydroxyl group-containing monomer means a monomer having at least one hydroxyl group in the molecule. A monomer having at least one hydroxyl group and at least one carboxyl group in the molecule is a carboxyl group-containing monomer, but not a hydroxyl group-containing monomer. The hydroxyl group-containing monomer is not particularly limited, but specifically includes, for example, hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl) (meth)acrylate; vinyl alcohol, allyl alcohol, and the like. Among them, the hydroxyl group-containing monomer is preferably a hydroxyl group-containing (meth)acrylic acid ester, more preferably 2-hydroxyethyl acrylate (HEA), 2-hydroxypropyl (meth)acrylate (HPA), or 4-hydroxybutyl acrylate (4HBA), from the viewpoint of easily obtaining good cohesive strength and easily obtaining adhesive reliability at high temperatures. The hydroxyl group-containing monomer may be used alone or in combination of two or more kinds.

[0045] Furthermore, the functional group-containing monomer is preferably a nitrogen atom-containing monomer. When the acrylic polymer contains a nitrogen atom-containing monomer as a monomer unit, it is easy to obtain a moderate cohesive force, so that it is easy to obtain strong adhesion and excellent foaming peeling resistance.

[0046] The nitrogen atom-containing monomer means a monomer having at least one nitrogen atom in the molecule (per molecule). However, the above-mentioned hydroxyl group-containing monomer does not include the above-mentioned nitrogen atom-containing monomer. That is, in this specification, a monomer having a hydroxyl group and a nitrogen atom in the molecule is included in the nitrogen atom-containing monomer. Also, a monomer having at least one nitrogen atom in the molecule and at least one carboxyl group in the molecule is a carboxyl group-containing monomer, but is not a nitrogen atom-containing monomer.

[0047] As the nitrogen atom-containing monomer, from the viewpoint of exerting strong adhesive strength, N-vinyl cyclic amide, (meth)acrylamide, etc. The nitrogen atom-containing monomer may be used alone or in combination of two or more kinds.

[0048] As the N-vinyl cyclic amide, from the viewpoint of facilitating obtaining good cohesive strength and facilitating obtaining adhesive reliability at high temperatures, the N-vinyl cyclic amide represented by the following formula (1) is preferable. [ka] (In formula (1), R 1 represents a divalent organic group.

[0049] R in the above formula (1) 1 is a divalent organic group, preferably a divalent saturated or unsaturated hydrocarbon group, and more preferably a divalent saturated hydrocarbon group (for example, an alkylene group having 3 to 5 carbon atoms).

[0050] As the N-vinyl cyclic amide represented by the above formula (1), from the viewpoint of exerting even stronger adhesiveness, N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, etc. are preferred, more preferably N-vinyl-2-pyrrolidone, N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

[0051] Examples of the (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of the N-alkyl(meth)acrylamide include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, and N-octylacrylamide. Furthermore, the N-alkyl(meth)acrylamide also includes (meth)acrylamides having an amino group, such as dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide. Examples of the N,N-dialkyl(meth)acrylamide include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide.

[0052] The (meth)acrylamides also include, for example, various N-hydroxyalkyl (meth)acrylamides. Examples of the N-hydroxyalkyl (meth)acrylamides include N-methylol (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, and N-methyl-N-2-hydroxyethyl (meth)acrylamide.

[0053] The (meth)acrylamides also include, for example, various N-alkoxyalkyl (meth)acrylamides, such as N-methoxymethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

[0054] Examples of nitrogen atom-containing monomers other than the N-vinyl cyclic amides and the (meth)acrylamides include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, N- Examples of the monomer include heterocyclic ring-containing monomers such as methylvinylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; and succinimide-based monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate-based monomers such as 2-(meth)acryloyloxyethylisocyanate.

[0055] Examples of copolymerizable monomers in acrylic polymers include, in addition to the above-mentioned nitrogen atom-containing monomers and hydroxyl group-containing monomers, alicyclic structure-containing monomers [e.g., cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate]; (meth)acrylic acid alkoxyalkyl esters [e.g., 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxy (meth)acrylate, propyl, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, etc.]; epoxy group-containing monomers [e.g., glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, etc.]; sulfonic acid group-containing monomers [e.g., sodium vinyl sulfonate, etc.]; phosphate group-containing monomers; (meth)acrylic acid esters having aromatic hydrocarbon groups [e.g., phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc.]; vinyl esters [e.g., vinyl acetate, vinyl propionate, etc.]; aromatic vinyl compounds [e.g., styrene, vinyl toluene, etc.]; olefins or dienes [e.g., ethylene, propylene, butadiene, isoprene, isobutylene, etc.]; vinyl ethers [e.g., vinyl alkyl ethers, etc.]; vinyl chloride, etc.

[0056] The pressure-sensitive adhesive composition preferably does not contain or substantially does not contain a carboxyl group-containing monomer as a monomer component constituting an acrylic polymer. By not containing or substantially not containing a carboxyl group-containing monomer, a corrosion prevention effect on metal wiring can be obtained in a touch panel to which an optical member (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film is attached. The content of the carboxyl group-containing monomer is 1 ng / cm based on the total amount of the pressure-sensitive adhesive composition. 2 Less than (e.g., 0 to 1 ng / cm 2 ) is preferred, and 0.8 ng / cm is more preferred. 2 Less than (e.g., 0 to 0.8 ng / cm 2 ), more preferably 0.5 ng / cm 2 Less than (e.g., 0 to 0.5 ng / cm 2 ) is not substantially contained. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like. The carboxyl group-containing monomer also includes, for example, acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride.

[0057] The content (ratio) of the functional group-containing monomer relative to the total amount (100% by mass) of monomer components constituting the acrylic polymer is not particularly limited, but in terms of exerting appropriate adhesion, it is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass.

[0058] When the acrylic polymer contains a hydroxyl group-containing monomer and a nitrogen atom-containing monomer as functional group-containing monomer components constituting the polymer, the content of the functional group-containing monomer contained in a larger amount among the hydroxyl group-containing monomer and the nitrogen atom-containing monomer is preferably 60 mass% or more, more preferably 65 mass% or more, and even more preferably 70 mass% or more, based on the total amount (100 mass%) of the hydroxyl group-containing monomer and the nitrogen atom-containing monomer.

[0059] In addition, when polymerizing the acrylic polymer, a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator (photoinitiator) may be used depending on the type of polymerization reaction. The polymerization initiator may be used alone or in combination of two or more kinds.

[0060] The photopolymerization initiator is not particularly limited, and examples thereof include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, etc. The photopolymerization initiators may be used alone or in combination of two or more kinds.

[0061] Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone. Examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc.

[0062] The amount of the photopolymerization initiator used is not particularly limited, but is preferably 0.001 to 1 part by mass, and more preferably 0.01 to 0.50 parts by mass, per 100 parts by mass of all monomer units of the acrylic polymer (total amount of monomer components constituting the acrylic polymer).

[0063] The thermal polymerization initiator is not particularly limited, but examples thereof include azo polymerization initiators, peroxide polymerization initiators (e.g., dibenzoyl peroxide, tert-butyl permaleate, etc.), redox polymerization initiators, etc. Among them, the azo polymerization initiators disclosed in JP-A-2002-69411 are preferred. Examples of the azo polymerization initiators include 2,2'-azobisisobutyronitrile (hereinafter sometimes referred to as "AIBN"), 2,2'-azobis-2-methylbutyronitrile (hereinafter sometimes referred to as "AMBN"), 2,2'-azobis(2-methylpropionate) dimethyl, and 4,4'-azobis-4-cyanovaleric acid.

[0064] The amount of the thermal polymerization initiator used is not particularly limited. For example, in the case of the azo-based polymerization initiator, the amount is preferably 0.05 to 0.5 parts by mass, and more preferably 0.1 to 0.3 parts by mass, per 100 parts by mass of all monomer units of the acrylic polymer (total amount of monomer components constituting the acrylic polymer).

[0065] The pressure-sensitive adhesive composition preferably contains the acrylic polymer as a main component, and further contains a monomer component other than the acrylic polymer (hereinafter, sometimes referred to as "monomer added separately") from the viewpoint of lowering the dielectric constant and exhibiting drop impact resistance. The monomer added separately may be used alone or in combination of two or more kinds.

[0066] As the monomer to be added separately, from the viewpoint of achieving low dielectric constant and drop impact resistance, the above-mentioned (meth)acrylic acid alkyl ester and / or the compound presented as the above-mentioned functional group-containing monomer are preferable, and the above-mentioned (meth)acrylic acid alkyl ester and / or the compound presented as the above-mentioned hydroxyl group-containing monomer are more preferable. Specifically, the above-mentioned (meth)acrylic acid alkyl ester includes methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isostearyl acrylate (ISTA), etc. Examples of hydroxyl group monomers include hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and 4-hydroxymethylcyclohexyl (meth)acrylate; vinyl alcohol, and allyl alcohol.

[0067] The amount of the monomer to be added separately is not particularly limited, but from the viewpoint of exerting a low dielectric constant and drop impact resistance, the lower limit is preferably 25% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, and particularly preferably 40% by mass or more, based on 100% by mass of all monomer units of the acrylic polymer (total amount of monomer components constituting the acrylic polymer).The upper limit is preferably 75% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less, and particularly preferably 60% by mass or less.

[0068] The pressure-sensitive adhesive composition is preferably a pressure-sensitive adhesive composition containing an acrylic polymer as a main component and a hydrogenated polyolefin resin. The hydrogenated polyolefin resin is a material with a low dielectric constant, and by blending it with the acrylic polymer, the dielectric constant is reduced, and in a touch panel to which an optical member (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film is bonded, a malfunction of a touch operation can be suppressed. In addition, it is also preferable that a highly flexible pressure-sensitive adhesive layer can be realized without requiring a low molecular weight acrylic polymer, and that even when an optical member (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film is bonded, the stress with the metal wiring can be sufficiently relaxed to prevent display unevenness. In addition, the hydrogenated polyolefin resin is also excellent in compatibility with the acrylic polymer, and is therefore preferable in that the transparency of the pressure-sensitive adhesive layer can be maintained to a higher degree. The hydrogenated polyolefin resin can be used alone or in combination of two or more kinds.

[0069] Hydrogenated polyolefin resins are preferred because they can realize a highly flexible adhesive layer and can sufficiently relieve stress with the metal wiring and prevent display unevenness even when bonded to an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, and therefore exhibit liquid fluidity at 25°C. A hydrogenated polyolefin resin exhibiting liquid fluidity at 25°C means that its viscosity measured at 25°C using a Brookfield viscometer is 10,000 mPa s or less.

[0070] The hydrogenated polyolefin resin is obtained by reducing the carbon-carbon double bonds contained in the polyolefin resin by hydrogenation reaction. Since the hydrogenated polyolefin resin has a reduced number of carbon-carbon double bonds in the molecule, for example, when the pressure-sensitive adhesive composition is cured by UV irradiation, polymerization inhibition is unlikely to occur, and the polymerization rate is unlikely to decrease and the molecular weight is unlikely to decrease, so that the pressure-sensitive adhesive composition can maintain a high level of adhesive reliability at high temperatures.

[0071] The hydrogenation rate of the hydrogenated polyolefin resin is preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more, from the viewpoint of preventing polymerization inhibition and improving adhesive reliability at high temperatures. The upper limit of the hydrogenation rate is not particularly limited, but is theoretically 100%, and may be 99.9% or less or 99.8% or less in practice. The hydrogenation rate of the hydrogenated polyolefin resin is 1 It can be determined by, for example, quantifying the amount of double bonds remaining in the hydrogenated polyolefin resin by H-NMR measurement.

[0072] The iodine value (Ig / 100g) of the hydrogenated polyolefin resin is preferably 30 or less, more preferably 25 or less, and even more preferably 20 or less, from the viewpoint of preventing polymerization inhibition and improving adhesive reliability at high temperatures. The lower limit of the iodine value is not particularly limited, but may be 0.1 or more, or 0.2 or more. The iodine value is a value measured in accordance with JIS K 0070-1992.

[0073] The number average molecular weight (Mn) of the hydrogenated polyolefin resin is preferably 1000 to 5000 in terms of imparting appropriate stress relaxation properties and fluidity to the pressure-sensitive adhesive layer and improving compatibility with the acrylic polymer. The number average molecular weight (Mn) is preferably 1000 or more in terms of being able to impart appropriate stress relaxation properties and fluidity to the pressure-sensitive adhesive composition, more preferably 1500 or more, and even more preferably 1800 or more. The number average molecular weight (Mn) is preferably 5000 or less in terms of improving compatibility with the acrylic polymer and maintaining a higher degree of transparency of the pressure-sensitive adhesive composition, more preferably 4800 or less, and even more preferably 4600 or less.

[0074] The polydispersity (Mw / Mn) of the hydrogenated polyolefin resin is preferably 2.0 or less, more preferably 1.8 or less, in order to provide the pressure-sensitive adhesive layer with appropriate stress relaxation properties and fluidity, improve compatibility with the acrylic polymer, maintain high transparency, and suppress haze. The lower limit of the polydispersity is not particularly limited, but may be 1.0 or 1.1 or more in practical use. The number average molecular weight (Mn) and polydispersity (Mw / Mn) of the hydrogenated polyolefin resin are values ​​measured by gel permeation chromatography (GPC) and calculated based on polystyrene standard.

[0075] The hydrogenated polyolefin resin contains a hydrogenated polyolefin. The pressure-sensitive adhesive composition contains a hydrogenated polyolefin as the hydrogenated polyolefin resin, which is preferable from the viewpoint of reducing the dielectric constant and suppressing malfunctions of touch operations in a touch panel.

[0076] The hydrogenated polyolefin is a hydrogenated product of a polymer (polyolefin) having a structural unit derived from an olefin. The hydrogenated polyolefin includes hydrogenated homopolymers and copolymers of α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene; diene compounds such as butadiene and isoprene; and aromatic vinyl compounds such as styrene. The hydrogenated polyolefin is preferably a hydrogenated homopolymer or copolymer of a diene compound, such as hydrogenated polybutadiene and hydrogenated polyisoprene. The hydrogenated polyolefin can be used alone or in combination of two or more kinds.

[0077] From the viewpoint of reducing the dielectric constant and suppressing malfunctions during touch operations on a touch panel, the hydrogenated polyolefin resin preferably further contains a hydrogenated polyolefin polyol in addition to the hydrogenated polyolefin.

[0078] The hydrogenated polyolefin polyol is a compound in which the end of the hydrogenated polyolefin is modified with a hydroxyl group. The hydrogenated polyolefin polyol is preferably a hydroxyl group modified product of a homopolymer or copolymer of a diene compound, such as hydrogenated polybutadiene polyol, hydrogenated polyisoprene polyol, etc. The hydrogenated polyolefin polyol can be used alone or in combination of two or more kinds.

[0079] As the hydrogenated polyolefin and hydrogenated polyolefin polyol, hydrogenated polybutadiene polyol and hydrogenated polybutadiene polyol are preferred, respectively, in that they can realize a highly flexible adhesive layer and can sufficiently relieve stress with the metal wiring and prevent display unevenness even when an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film is attached.

[0080] The hydrogenated polybutadiene is preferably one represented by the following formula (2), and the hydrogenated polybutadiene polyol is preferably one represented by the following formula (3). [ka] In the above formula, m represents the degree of polymerization of the hydrogenated polybutadiene.

[0081] Commercially available hydrogenated polyolefins and hydrogenated polyolefin polyols can be used. Commercially available hydrogenated polyolefins include those under the trade names "BI-2000" and "BI-3000" (all manufactured by Nippon Soda Co., Ltd.). Commercially available hydrogenated polyolefin polyols include those under the trade names "GI-1000", "GI-2000", and "GI-3000" (all manufactured by Nippon Soda Co., Ltd.) and those under the trade name "EPOL" (manufactured by Idemitsu Kosan Co., Ltd.).

[0082] The content of the hydrogenated polyolefin resin is not particularly limited, but from the viewpoint of reducing the dielectric constant and suppressing malfunction of touch operation in a touch panel, it is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, relative to 100 parts by mass of the acrylic polymer. On the other hand, from the viewpoint of suppressing an increase in haze and ensuring higher transparency, and from the viewpoint of being able to maintain high adhesive strength and adhesive reliability at high temperatures, the content of the hydrogenated polyolefin resin is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less.

[0083] The content of the hydrogenated polyolefin polyol is not particularly limited, but from the viewpoint of reducing the dielectric constant and suppressing malfunction of touch operation in a touch panel, it is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, relative to 100 parts by mass of the acrylic polymer. On the other hand, from the viewpoint of suppressing an increase in haze and ensuring higher transparency, and from the viewpoint of being able to maintain high adhesive strength and adhesive reliability at high temperatures, the content of the hydrogenated polyolefin polyol is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less.

[0084] The weight ratio of the hydrogenated polyolefin content to the hydrogenated polyolefin polyol content in the pressure-sensitive adhesive composition (hydrogenated polyolefin / hydrogenated polyolefin polyol) is not particularly limited, but from the viewpoint of reducing the dielectric constant and suppressing malfunction of touch operation in a touch panel, it is preferably 1 / 99 or more, more preferably 2 / 98 or more, 3 / 98 or more, or may be 4 / 96 or more. In addition, from the viewpoint of suppressing an increase in haze and ensuring higher transparency, the above ratio is preferably 90 / 10 or less, more preferably 80 / 20 or less, even more preferably 70 / 30 or less, and may be 55 / 45 or less, 45 / 55 or less, or 30 / 70 or less.

[0085] The pressure-sensitive adhesive composition preferably further contains a polyfunctional (meth)acrylate, which acts as a cross-linking component and makes it easier for the pressure-sensitive adhesive composition to have an appropriate cohesive strength.

[0086] Examples of the polyfunctional (meth)acrylate include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, etc. The polyfunctional (meth)acrylate may be used alone or in combination of two or more.

[0087] The content (ratio) of the polyfunctional (meth)acrylate is not particularly limited, but from the viewpoint that the adhesive layer has an appropriate cohesive force, it is preferably 0.001 parts by mass or more, more preferably 0.002 parts by mass or more, even more preferably 0.005 parts by mass or more, and may be 0.01 parts by mass or more, relative to 100 parts by mass of the acrylic polymer. In addition, the content (ratio) of the polyfunctional (meth)acrylate is preferably 0.5 parts by mass or less, more preferably 0.35 parts by mass or less, even more preferably 0.2 parts by mass or less, and may be 0.1 parts by mass or less, relative to 100 parts by mass of the acrylic polymer, from the viewpoint that a highly flexible adhesive layer can be realized, and the stress with the metal wiring can be sufficiently relaxed to prevent display unevenness.

[0088] The pressure-sensitive adhesive composition preferably further contains an ultraviolet absorbing agent. The ultraviolet absorbing agent is not particularly limited, but may be, for example, a triazine-based ultraviolet absorbing agent, a benzotriazole-based ultraviolet absorbing agent, a benzophenone-based ultraviolet absorbing agent, an oxybenzophenone-based ultraviolet absorbing agent, a salicylic acid ester-based ultraviolet absorbing agent, a cyanoacrylate-based ultraviolet absorbing agent, etc., which may be used alone or in combination of two or more.

[0089] Specific examples of triazine-based ultraviolet absorbers include 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (TinosorbS, manufactured by BASF), 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (TINUVIN460, manufactured by BASF), ), 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane reaction products (TINUVIN400, BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydro 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester reaction product (TINUVIN 405, BASF), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (TINUVIN 1577, BASF) ), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (ADKSTABLA46, manufactured by ADEKA), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenyl)-1,3,5-triazine (TINUVIN479, manufactured by BASF), etc. can be used.

[0090] Benzotriazole-based UV absorbers include 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN928, manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (TINUVINPS, manufactured by BASF), benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5 -(1,1-dimethylethyl)-4-hydroxy (C7-9 side chain and straight chain alkyl) ester compound (TINUVIN384-2, BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN900, BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl) Phenol (TINUVIN928, BASF), methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 reaction product (TINUVIN1130, BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (TINUVINP, BASF), 2(2H-benzotriazol-2-yl)-4-6-bis(1-methyl) 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (TINUVIN 326, BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (TINUVIN 328, BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN329, manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate with polyethylene glycol 300 (TINUVIN213, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (TINUVIN571, manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimido-methyl)-5-methylphenyl]benzotriazole (Sumisorb250, manufactured by Sumitomo Chemical Co., Ltd.), etc. can be used.

[0091] Examples of benzophenone-based ultraviolet absorbers (benzophenone-based compounds) and oxybenzophenone-based ultraviolet absorbers (oxybenzophenone-based compounds) include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (anhydrous and trihydrate), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, and 2,2'-dihydroxy-4,4-dimethoxybenzophenone.

[0092] Examples of salicylic acid ester-based ultraviolet absorbers (salicylic acid ester-based compounds) include phenyl-2-acryloyloxybenzoate, phenyl-2-acryloyloxy-3-methylbenzoate, phenyl-2-acryloyloxy-4-methylbenzoate, phenyl-2-acryloyloxy-5-methylbenzoate, phenyl-2-acryloyloxy-3-methoxybenzoate, phenyl-2-hydroxybenzoate, phenyl-2-hydroxy-3-methylbenzoate, phenyl-2-hydroxy-4-methylbenzoate, phenyl-2-hydroxy-5-methylbenzoate, phenyl-2-hydroxy-3-methoxybenzoate, and 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate (TINUVIN120, manufactured by BASF).

[0093] Examples of cyanoacrylate-based ultraviolet absorbers (cyanoacrylate-based compounds) include alkyl-2-cyanoacrylates, cycloalkyl-2-cyanoacrylates, alkoxyalkyl-2-cyanoacrylates, alkenyl-2-cyanoacrylates, and alkynyl-2-cyanoacrylates.

[0094] The content (ratio) of the ultraviolet absorber is not particularly limited, but from the viewpoint that the pressure-sensitive adhesive layer has an appropriate cohesive force, it is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.05 parts by mass or more, and may be 0.1 parts by mass or more, relative to 100 parts by mass of the acrylic polymer. The content (ratio) of the ultraviolet absorber is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, even more preferably 5 parts by mass or less, and may be 3 parts by mass or less, relative to 100 parts by mass of the acrylic polymer.

[0095] The pressure-sensitive adhesive composition may further contain a photopolymerization initiator other than that contained in the acrylic polymer. As the photopolymerization initiator other than that contained in the acrylic polymer, the photopolymerization initiator exemplified as that used in the acrylic polymer described above can be used. The photopolymerization initiator other than that contained in the acrylic polymer can be used alone or in combination of two or more kinds.

[0096] The content (ratio) of the photopolymerization initiator other than that contained in the acrylic polymer is not particularly limited, but is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.05 parts by mass or more, and may be 0.1 parts by mass or more, relative to 100 parts by mass of the acrylic polymer. The content (ratio) of the photopolymerization initiator is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 1 part by mass or less, and may be 0.5 parts by mass or less, relative to 100 parts by mass of the acrylic polymer.

[0097] The above-mentioned adhesive composition may contain, as necessary, known additives such as crosslinking agents, crosslinking accelerators, tackifier resins (rosin derivatives, polyterpene resins, oil-soluble phenols, etc.), antioxidants, fillers, colorants (pigments, dyes, etc.), chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, rust inhibitors, antioxidants, etc., within the range that does not impair the characteristics of the present invention. Such additives may be used alone or in combination of two or more.

[0098] The glass transition temperature (Tg) calculated from the acrylic polymer and the separately added monomer in the pressure-sensitive adhesive composition is preferably -5°C or higher, more preferably -4°C or higher, and particularly preferably -3°C or higher. The glass transition temperature (Tg) of -5°C or higher makes it easier for the pressure-sensitive adhesive layer to have a low dielectric constant and to exhibit reworkability in the high-speed (low-temperature) range. The upper limit is not particularly limited, but is preferably 20°C or lower from the viewpoint of exhibiting a minimum adhesive strength, more preferably 15°C or lower, and even more preferably 10°C or lower.

[0099] The glass transition temperature (Tg) is a calculated glass transition temperature calculated from the following Fox formula: This calculated glass transition temperature is calculated based on the type and amount of each monomer component constituting the pressure-sensitive adhesive composition, and therefore can be adjusted by selecting the type and amount of each monomer component.

[0100] The calculated glass transition temperature (calculated Tg) can be calculated from the following Fox formula [1]. 1 / Calculation Tg=W1 / Tg(1)+W2 / Tg(2)+···+Wn / Tg(n) [1] Here, W1, W2, ...Wn mean the weight fractions (% by weight) of monomer component (1), monomer component (2), ...monomer component (n) constituting the pressure-sensitive adhesive composition relative to the total monomer components, and Tg(1), Tg(2), ...Tg(n) mean the glass transition temperatures (units: absolute temperature: K) of homopolymers of monomer component (1), monomer component (2), ...monomer component (n). In this specification, the term "glass transition temperature (Tg) of homopolymer" (sometimes simply referred to as "Tg of homopolymer") means "glass transition temperature (Tg) of a homopolymer of the monomer", and specifically, the numerical values ​​are listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1987). The Tg of the homopolymer of a monomer not described in the above literature refers to, for example, a value obtained by the following measurement method (see JP 2007-51271 A) except for a monomer having a polyorganosiloxane skeleton. That is, 100 parts by mass of monomer, 0.2 parts by mass of 2,2'-azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as a polymerization solvent are charged into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser tube, and stirred for 1 hour while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by mass. The homopolymer solution is then cast onto a release liner and dried to prepare a test sample (homopolymer sheet) with a thickness of about 2 mm. The test sample is then punched out into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity is measured in a shear mode at a temperature range of -70 to 150°C and a heating rate of 5°C / min while applying a shear strain of 1 Hz using a viscoelasticity tester (product name "ARES", manufactured by Rheometrics Co., Ltd.). The peak top temperature of tan δ is taken as the Tg of the homopolymer.

[0101] The pressure-sensitive adhesive composition can be prepared by mixing the acrylic polymer and, if necessary, a monomer component, a hydrogenated polyolefin resin, a polyfunctional (meth)acrylate, a silane coupling agent, and other additives, and stirring the mixture uniformly.

[0102] The pressure-sensitive adhesive sheet of the present invention may be a so-called "substrate-less type" pressure-sensitive adhesive sheet that does not have a substrate (substrate layer) (hereinafter, may be referred to as a "substrate-less pressure-sensitive adhesive sheet"), or may be a type of pressure-sensitive adhesive sheet that has a substrate (hereinafter, may be referred to as a "substrate-attached pressure-sensitive adhesive sheet"). Examples of the substrate-less pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet consisting of only the pressure-sensitive adhesive layer, and a double-sided pressure-sensitive adhesive sheet consisting of the pressure-sensitive adhesive layer and a pressure-sensitive adhesive layer other than the pressure-sensitive adhesive layer (hereinafter, may be referred to as an "other pressure-sensitive adhesive layer"). On the other hand, examples of the substrate-attached pressure-sensitive adhesive sheet include a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer on at least one side of the substrate. Among these, a substrate-less pressure-sensitive adhesive sheet (substrate-less double-sided pressure-sensitive adhesive sheet) is preferred, and a substrate-less double-sided pressure-sensitive adhesive sheet consisting of only the pressure-sensitive adhesive layer is more preferred. The "substrate (substrate layer)" does not include a release liner that is peeled off when the pressure-sensitive adhesive sheet is used (applied).

[0103] 1 is a schematic diagram (cross-sectional view) showing a specific example of a preferred embodiment of the pressure-sensitive adhesive sheet of the present invention, in which 1 indicates a pressure-sensitive adhesive sheet, 10 indicates a pressure-sensitive adhesive layer, and 11 and 12 indicate release liners. In Fig. 1, the pressure-sensitive adhesive sheet 1 is a substrate-less double-sided pressure-sensitive adhesive sheet, and the adhesive surfaces on both sides of the pressure-sensitive adhesive layer 10 are protected by release liners 11 and 12.

[0104] The thickness (total thickness) of the pressure-sensitive adhesive sheet is not particularly limited, but is preferably 5 to 600 μm, and more preferably 10 to 500 μm. A thickness of at least a certain level is preferable in terms of exhibiting drop impact resistance. A thickness of less than a certain level is also preferable in terms of making it easier to maintain an excellent appearance during production and roll storage, and preventing glue stains during cutting. The thickness of the pressure-sensitive adhesive sheet does not include the thickness of the release liner.

[0105] The pressure-sensitive adhesive sheet is not particularly limited, but is preferably manufactured according to a known or conventional manufacturing method. For example, when the pressure-sensitive adhesive sheet is a substrate-less pressure-sensitive adhesive sheet, it is obtained by forming the pressure-sensitive adhesive layer on a release liner by the above-mentioned method. When the pressure-sensitive adhesive sheet is a substrate-attached pressure-sensitive adhesive sheet, it may be obtained by directly forming the pressure-sensitive adhesive layer on the surface of the substrate (direct transfer method), or it may be obtained by forming the pressure-sensitive adhesive layer on a release liner once, and then transferring (attaching) it to the substrate, thereby providing the pressure-sensitive adhesive layer on the substrate (transfer method).

[0106] The pressure-sensitive adhesive sheet may have other layers in addition to the pressure-sensitive adhesive layer. Examples of the other layers include other pressure-sensitive adhesive layers (pressure-sensitive adhesive layers other than the pressure-sensitive adhesive layer), intermediate layers, undercoat layers, etc. The pressure-sensitive adhesive sheet may have two or more other layers.

[0107] When the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet with a substrate, the substrate is not particularly limited, and examples thereof include various optical films such as plastic films, anti-reflection (AR) films, polarizing plates, and retardation plates. Examples of materials for the plastic films and the like include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymers, and cyclic olefin polymers such as trade names "Arton (cyclic olefin polymer, manufactured by JSR Corporation)" and "ZEONOR (cyclic olefin polymer, manufactured by Zeon Corporation)". These plastic materials may be used alone or in combination of two or more kinds. The "substrate" refers to a portion that is attached to the adherend together with the adhesive layer when the pressure-sensitive adhesive sheet is attached to the adherend. The "substrate" does not include a release liner that is peeled off when the pressure-sensitive adhesive sheet is used (attached).

[0108] The thickness of the substrate is not particularly limited, but is preferably, for example, 12 to 500 μm. The substrate may have either a single layer or a multi-layer structure. The surface of the substrate may be appropriately subjected to a known and commonly used surface treatment, such as a physical treatment such as a corona discharge treatment or a plasma treatment, or a chemical treatment such as an undercoat treatment.

[0109] The pressure-sensitive adhesive sheet may have a release liner on the adhesive surface until use. When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, each adhesive surface may be protected by two release liners, or may be protected by a single release liner having release surfaces on both sides in a rolled form. The release liner is used as a protective material for the pressure-sensitive adhesive layer, and is peeled off when the pressure-sensitive adhesive sheet is attached to the adherend. When the pressure-sensitive adhesive sheet is a substrate-less pressure-sensitive adhesive sheet, the release liner also serves as a support for the pressure-sensitive adhesive layer. The release liner may not necessarily be provided.

[0110] The release liner is not particularly limited, but examples thereof include a release liner having a release layer (release treatment layer) on at least one surface of a release liner substrate, a low-adhesion release liner made of a fluorine-based polymer, and a low-adhesion release liner made of a non-polar polymer. The release treatment agent constituting the release layer is not particularly limited, but examples thereof include silicone-based release treatment agents, fluorine-based release treatment agents, long-chain alkyl-based release treatment agents, and molybdenum sulfide release treatment agents. The fluorine-based polymer is not particularly limited, but examples thereof include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. The non-polar polymer is not particularly limited, but examples thereof include olefin-based resins such as polyethylene (PE) and polypropylene (PP). Among them, it is preferable to use a release liner having a release layer on at least one surface of a release liner substrate.

[0111] The release liner substrate is not particularly limited, but may include plastic films. Examples of such plastic films include plastic films made of polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); olefin resins containing α-olefin as a monomer component, such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer (EVA); polyvinyl chloride (PVC); vinyl acetate resins; polycarbonate (PC); polyphenylene sulfide (PPS); amide resins such as polyamide (nylon) and fully aromatic polyamide (aramid); polyimide resins; and polyether ether ketone (PEEK). Among these, plastic films made of polyester resins are preferred from the viewpoints of processability, availability, workability, dust resistance, cost, and the like, and PET films are more preferred.

[0112] The release liner can be produced by a known method. A carrier material, a conductive treatment layer, and other layers may be laminated on the release layer and / or the back surface of the release liner by a known method. The release liner may also have other layers (e.g., an intermediate layer, an undercoat layer, and the like) within the scope of not impairing the effects of the present invention.

[0113] The thickness of the release liner is not particularly limited, but from the standpoint of cost and ease of handling of the pressure-sensitive adhesive sheet during lamination, it is preferably 12 to 200 μm, more preferably 25 to 150 μm, and even more preferably 38 to 125 μm.

[0114] The pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer (the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition), and therefore has a low dielectric constant, reduced noise, sufficient adhesive strength, and excellent drop impact resistance. Therefore, the pressure-sensitive adhesive sheet is useful for adhering optical members such as polarizing films, retardation films, optical compensation films, touch sensor films, and cover films to image display panels in image display devices and touch panels incorporating touch sensors in these image display devices, or for adhering these optical members to each other.

[0115] The pressure-sensitive adhesive sheet is preferably used in the manufacture of portable electronic devices, such as mobile phones, PHS, smartphones, tablets (tablet computers), mobile computers (mobile PCs), personal digital assistants (PDAs), electronic organizers, portable broadcast receivers such as portable televisions and portable radios, portable game consoles, portable audio players, portable DVD players, cameras such as digital cameras, and camcorder-type video cameras.

[0116] The above-mentioned adhesive sheet is preferably used, for example, for bonding members or modules constituting a portable electronic device to each other, or for fixing members or modules constituting a portable electronic device to a housing. More specifically, examples of the adhesive sheet include bonding a cover glass or lens (particularly a glass lens) to a touch panel or a touch sensor film (particularly a touch sensor film having metal wiring such as a metal mesh film or a silver nanowire film), bonding a polarizing film to a touch panel or a touch sensor, bonding a display panel to a touch panel or a touch sensor film, fixing a cover glass or lens (particularly a glass lens) to a housing, fixing a display panel to a housing, fixing an input device such as a sheet-like keyboard or a touch panel to a housing, bonding a protective panel of an information display unit to a housing, bonding housings together, bonding a housing to a decorative sheet, and fixing or bonding various members and modules constituting a portable electronic device. In this specification, the display panel refers to a structure at least composed of a lens (particularly a glass lens) and a touch panel. In addition, the lens in this specification is a concept that includes both a transparent body that exhibits a light refraction action and a transparent body that does not have a light refraction action. In other words, the lens in this specification also includes a simple window panel that has no refractive effect.

[0117] Furthermore, the pressure-sensitive adhesive sheet is preferably used for optical applications. That is, the pressure-sensitive adhesive sheet is preferably an optical pressure-sensitive adhesive sheet used for optical applications. More specifically, it is preferably used for, for example, bonding optical members (for bonding optical members) or for manufacturing products (optical products) using the optical members.

[0118] [Optical components with pressure-sensitive adhesive layers, image display devices, touch panels] The pressure-sensitive adhesive layer-attached optical member of the present invention is not particularly limited as long as it is an optical member having the pressure-sensitive adhesive layer attached to at least one side of the optical member. The pressure-sensitive adhesive layer-attached optical member is formed by attaching the pressure-sensitive adhesive sheet, so that it has a low dielectric constant, reduces noise, has sufficient adhesive strength, and can exhibit drop impact resistance.

[0119] The pressure-sensitive adhesive layer-attached optical member may be one in which the pressure-sensitive adhesive sheet is attached to an optical member (touch sensor film) having metal wiring such as a metal mesh film, a silver nanowire film, etc. In this case, it is preferable that the pressure-sensitive adhesive sheet is attached to the surface of the touch sensor film on the side having the metal wiring.

[0120] FIG. 2 is a schematic diagram (cross-sectional view) showing a specific example of a preferred embodiment of the pressure-sensitive adhesive layer-attached optical member of the present invention. In Figure 2(a), 2A is an optical member with an adhesive layer, 20 is the adhesive layer, 21 is an optical member, and 22 is a release liner, with the adhesive layer 20 laminated on one side of the optical member 21, and the adhesive surface of the adhesive layer 20 opposite the optical member 21 being protected by the release liner 22. In Figure 2(b), 2B is an optical component with an adhesive layer (touch sensor film with an adhesive layer), 20 is the adhesive layer, 23 is the touch sensor film, 22 is a release liner, and 24 is the metal wiring, with the adhesive layer 20 laminated on the surface of the touch sensor film 23 on which the metal wiring 24 is formed, and the adhesive surface of the adhesive layer 20 opposite the touch sensor film 23 is protected by a release liner 22. Since the adhesive layer 20 is composed of the above-mentioned adhesive layer, the optical member 2A with an adhesive layer and the touch sensor film 2B with an adhesive layer have reduced noise generation, sufficient adhesive strength, and can exhibit drop impact resistance.

[0121] The optical member refers to a member having optical properties (for example, polarization, light refraction, light scattering, light reflectivity, light transmittance, light absorption, light diffraction, optical rotation, visibility, etc.). The substrate constituting the optical member is not particularly limited, but examples thereof include substrates constituting devices (optical devices) such as image display devices and touch panels, or substrates used in these devices, such as polarizing films, wave plates, retardation films, optical compensation films, brightness-enhancing films, light guide plates, reflective films, anti-reflection films, hard-coated films (films in which at least one side of a plastic film such as a PET film has been subjected to a hard-coat treatment), transparent conductive films (for example, plastic films having an ITO layer on the surface (preferably, ITO films such as PET-ITO, polycarbonate, and cycloolefin polymer), etc.), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates (glass substrates such as glass sensors, glass display panels (LCDs, etc.), and glass substrates such as glass plates with transparent electrodes), and substrates on which these are laminated (these may be collectively referred to as "functional films"). These films may also have metal wiring such as a metal nanowire layer or a conductive polymer layer. These films may also have metal thin wires printed in a mesh pattern. The above terms "plate" and "film" each include plate-like, film-like, sheet-like, and other shapes, and for example, "polarizing film" includes "polarizing plate" and "polarizing sheet", etc. Furthermore, "film" includes film sensors, etc.

[0122] The pressure-sensitive adhesive sheet can be suitably used for transparent conductive films (metal mesh films, silver nanowire films) in which the metal wiring is metal mesh wiring or silver nanowires, particularly optical members (touch sensor films) having metal mesh films. When an optical member having metal wiring such as a metal mesh film or a silver nanowire film is bonded via the pressure-sensitive adhesive sheet, the optical member has sufficient adhesive strength and excellent drop impact resistance while suppressing noise generation due to its low dielectric constant.

[0123] Therefore, the image display device or touch panel having the pressure-sensitive adhesive sheet can reduce malfunctions due to noise generation and exhibit drop impact resistance. Examples of the image display device include liquid crystal display devices, organic EL (electroluminescence) display devices, PDPs (plasma display panels), electronic paper, etc.

[0124] FIG. 3 is a schematic diagram (cross-sectional view) showing a specific example of a preferred embodiment of the image display device of the present invention. In Figure 3, 3 indicates an image display device, 30 and 31 indicate the above-mentioned adhesive layer, 32 indicates an image display panel, 33 indicates a polarizing film, and 34 indicates a transparent substrate. The image display device 3 has an image display panel 32, an adhesive layer 30, a polarizing film 33, an adhesive layer 31, and a transparent substrate 34 laminated in this order. Since the pressure-sensitive adhesive layers 30 and 31 are formed of the above-mentioned pressure-sensitive adhesive layer, the image display device 3 can suppress noise generation and exhibit drop impact resistance. Note that one of the pressure-sensitive adhesive layers 30 and 31 does not have to be formed of the pressure-sensitive adhesive layer of the present invention.

[0125] The touch panel of the present invention is an image display device incorporating an optical member (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film.

[0126] FIG. 4 is a schematic diagram (cross-sectional view) showing a specific example of a preferred embodiment of the touch panel of the present invention. In Figure 4, 4 indicates a touch panel, 40 and 41 indicate the above-mentioned adhesive layers, 42 indicates an image display panel, 43 indicates a touch sensor film, 44 indicates a transparent substrate, and 45 indicates metal wiring. The touch panel 4 is formed by laminating an image display panel 42, an adhesive layer 40, a touch sensor film 43, an adhesive layer 41, and a transparent substrate 44 in this order. Since the adhesive layers 40 and 41 are made of the above-mentioned adhesive layer, the touch panel 4 can suppress noise generation and exhibit drop impact resistance. Note that one of the adhesive layers 40 and 41 does not have to be made of the above-mentioned adhesive layer.

[0127] The image display device and touch panel of the present invention may further include optical members such as a wavelength plate, a retardation film, and an optical compensation film. These optical members may be singular or plural. The manner of bonding these optical members is not particularly limited, but examples thereof include (1) a mode in which the optical member with the pressure-sensitive adhesive layer of the present invention is bonded to the optical member with the pressure-sensitive adhesive layer of the present invention via the pressure-sensitive adhesive sheet of the present invention, and (2) a mode in which the optical member with the pressure-sensitive adhesive layer of the present invention is bonded to the optical member with the pressure-sensitive adhesive layer of the present invention via a pressure-sensitive adhesive sheet other than the pressure-sensitive adhesive sheet of the present invention. EXAMPLES

[0128] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0129] [Production Example 1: Preparation of Polymer A] A monomer mixture consisting of 80 parts by mass of 2-ethylhexyl acrylate (2EHA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 5 parts by mass of 2-hydroxyethyl acrylate (HEA) was mixed with 0.035 parts by mass of a photopolymerization initiator (product name "Omnirad184", manufactured by IGM Resins BV) and 0.035 parts by mass of a photopolymerization initiator (product name "Omnirad651", manufactured by IGM Resins BV), and the mixture was then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa s, thereby obtaining Polymer A in which a portion of the monomer components had been polymerized.

[0130] [Production Example 2: Preparation of Polymer B] A monomer mixture consisting of 40 parts by mass of 2-ethylhexyl acrylate (2EHA), 40 parts by mass of isostearyl acrylate (ISTA), 19 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 1 part by mass of 4-hydroxybutyl acrylate (4-HBA) was mixed with 0.05 parts by mass of a photopolymerization initiator (trade name "Omnirad184", manufactured by IGM Resins BV) and 0.05 parts by mass of a photopolymerization initiator (trade name "Omnirad651", manufactured by IGM Resins BV), and the mixture was then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa s, thereby obtaining Polymer B in which a portion of the monomer components had polymerized.

[0131] [Example 1] To 100 parts by mass of Polymer A obtained in Production Example 1, 80 parts by mass of isostearyl acrylate (ISTA), 20 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.1 parts by mass of 1,6-hexanediol diacrylate (product name "NK Ester A-HD-N", manufactured by Shin-Nakamura Chemical Co., Ltd.), 2.0 parts by mass of an ultraviolet absorber (product name "TinosorbS", manufactured by BASF), and 0.3 parts by mass of a photopolymerization initiator (product name "Omnirad819", manufactured by IGM Resins BV) were added and mixed to obtain a pressure-sensitive adhesive composition (pre-cured composition).

[0132] The above adhesive composition was applied onto a polyethylene terephthalate (PET) release liner (first release liner, product name "MRF75", manufactured by Mitsubishi Chemical Corporation) so that the final thickness (adhesive layer thickness) was 100 μm to form a coating layer (adhesive composition layer). Next, a PET release liner (second release liner, product name "MRE75", manufactured by Mitsubishi Chemical Corporation) was provided on the above coating layer to cover the coating layer and block oxygen. Then, a laminate of MRF75 / coating layer (adhesive composition layer) / MRE75 was obtained. Next, a black light (Toshiba Corp.) was used to illuminate the laminate from the top surface (MRF75 side) of the laminate with an illumination intensity of 5 mW / cm. 2The sheet was then irradiated with ultraviolet light of 1000 nm for 300 seconds, and further dried in a dryer at 90° C. for 2 minutes. As a result, a substrate-less double-sided PSA sheet was obtained, which consisted only of a PSA layer and in which both sides of the PSA layer were protected by release liners.

[0133] [Example 2, Comparative Examples 1 and 2] A substrate-less double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was formulated as shown in Table 1. Unless otherwise specified, the units of the values ​​in Table 1 are parts by mass.

[0134] Details of the components shown in Table 1 are as follows: HEA: 2-hydroxyethyl acrylate 1,6-HD: 1,6-Hexanediol diacrylate ISTA: Isostearyl acrylate TMPTA: Trimethylolpropane triacrylate BI-3000: Product name "BI-3000", hydrogenated 1,2-polybutadiene, number average molecular weight (Mn): 2930 (measured value), weight average molecular weight (Mw): 4050 (measured value), polydispersity (Mw / Mn): 1.38 (measured value), hydrogenation rate: 97% or more (catalog value), iodine value: 21 or less (catalog value), manufactured by Nippon Soda Co., Ltd. GI-2000: Product name "GI-2000", hydrogenated 1,2-polybutadiene glycol, number average molecular weight (Mn): 3110 (measured value), weight average molecular weight (Mw): 5090 (measured value), polydispersity (Mw / Mn): 1.64 (measured value), hydrogenation rate: 97% or more (catalog value), iodine value: 21 or less (catalog value), manufactured by Nippon Soda Co., Ltd. TinosorbS: UV absorber, product name "TinosorbS", manufactured by BASF Omnirad819: Photopolymerization initiator, product name "Omnirad819", manufactured by IGM Resins BV

[0135] The actual measured values ​​of the number average molecular weight (Mn), weight average molecular weight (Mw), and polydispersity (Mw / Mn) of the above hydrogenated polyolefin and the above hydrogenated polyolefin polyol were determined by measuring them by gel permeation chromatography (GPC) under the following conditions, and calculating the values ​​in terms of polystyrene. Analytical equipment: GPC: HLC-8320GPC (Tosoh) Measurement conditions: Column: TSKgel SuperHZM-H / HZ4000 / HZ3000 / HZ2000 Column size: 6.0mm I.D. x 150mm Eluent: THF (tetrahydrofuran) Flow rate: 0.6mL / min Detector: Differential refractometer (RI) Column temperature: 40℃ Injection volume: 20μL

[0136] [evaluation] The substrate-less double-sided PSA sheet was subjected to the following evaluations, and the results are shown in Table 1.

[0137] (1) Dielectric constant (Dk) The release liner was peeled off from the substrate-less double-sided PSA sheet obtained in the Examples or Comparative Examples, and the resulting PSA layer was sandwiched between copper foil and an electrode, and the dielectric constant at a frequency of 100 kHz was measured using the following device. Three samples were prepared for the measurement, and the average of the measured values ​​for the three samples was taken as the dielectric constant. The dielectric constant of the pressure-sensitive adhesive layer at a frequency of 100 kHz was measured in accordance with JIS K 6911 under the following conditions. Measurement method: Capacitance method (Apparatus: Agilent Technologies 4294A Precision Impedance Analyzer) Electrode structure: 12.1mmΦ, 0.5mm thick aluminum plate Counter electrode: 3oz copper plate Measurement environment: 23±1℃, 52±1%RH

[0138] (2) Adhesion to glass The substrate-less double-sided adhesive sheet obtained in the examples or comparative examples was cut to a size of 20 mm wide and 80 mm long to prepare a measurement sample. In an environment of 23°C and 50% RH, the adhesive layer surface of the measurement sample was exposed, and the adhesive layer surface was attached to a glass plate (thickness 0.7 mm), and autoclaved at 50°C and 0.5 MPa for 15 minutes to adhere. In an environment of 23°C and 50% RH, a tensile tester was used to measure glass adhesion (10 N / 20 mm) under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm / min. As the tensile tester, a universal tensile compression tester (apparatus name "tensile compression tester, TCM-1kNB", manufactured by Minebea Co., Ltd.) was used. In addition, in the measurement, if necessary (for example, when the substrate is easily deformed, etc.), an appropriate backing material can be attached to the adhesive tape to be measured to reinforce it. As the backing material, for example, a PET film having a thickness of about 50 μm can be used, and this backing material was used in the examples and comparative examples described in this specification.

[0139] (3) Glass transition temperature (Tg) The glass transition temperature (Tg) of the substrate-less double-sided PSA sheets obtained in the Examples and Comparative Examples was calculated using the above-mentioned Fox formula.

[0140] (4) Dielectric tangent The substrate-less double-sided PSA sheets obtained in the examples and comparative examples were subjected to a frequency of 10 3 Hz~10 4 The dielectric loss tangent was measured in the same manner as for the dielectric constant, except that the dielectric loss tangent was measured in Hz.

[0141] (5) Rework The substrate-less double-sided PSA sheets obtained in the examples or comparative examples were subjected to the same treatment as in the above-mentioned glass adhesion measurement. The samples were manually peeled off from the glass plate and the reworkability was evaluated according to the following criteria. The reworkability evaluation was performed three times by preparing three sheets according to the above procedure. ○: The sheet broke in part out of the three sheets, but could be peeled off by peeling again. △: All three sheets broke, but could be peeled off by peeling again. ×: All three sheets had adhesive residue or the film broke and could not be peeled off no matter how many times it was peeled off.

[0142] (6) Drop impact resistance (Preparation of evaluation samples) The substrateless double-sided adhesive sheet obtained in the examples or comparative examples was cut into a length of 75 mm x width of 45 mm, the second release liner was peeled off from the adhesive sheet, and the exposed adhesive sheet was attached to the center of a first glass plate (length 100 mm x width 75 mm, thickness 500 μm) along its four sides. A roll laminator was used for the attachment, with a roll-to-roll pressure of 0.2 MPa and a feed rate of 100 mm / min. Next, the first release liner was peeled off from the adhesive sheet on the first glass plate, and the exposed adhesive layer was attached to the center of a second glass plate (length 100 mm x width 50 mm, thickness 500 μm) with a printed layer along its four sides to obtain a bonded body. The printed layer (thickness 30 μm, black ink layer) was formed on one side of the second glass plate in the thickness direction within a range of 15 mm inward from each end, and in the width direction within a range of 5 mm inward from each end of the first glass plate. The adhesive layer is attached to the center of one surface in the thickness direction of the second glass plate, and the entire edge of the adhesive layer is in contact with the printed layer. That is, the printed layer on the second glass plate is sandwiched between the second glass plate and the adhesive layer within a range of 2.5 mm outward from the inner edge of the printed layer. The bonded body was heat-treated at 50°C, 0.5 MPa, and 30 minutes to prepare an evaluation sample.

[0143] The above evaluation samples were subjected to the following drop impact resistance test. The evaluation sample was placed on the support stand so that the first glass plate in the evaluation sample was located on the upper side, both ends of the first glass plate in the width direction were supported from below by the support stand, and the second glass plate below did not come into contact with the support stand. Next, the evaluation sample on the support stand was fixed to the support stand with adhesive tape. Next, the support stand and the evaluation sample were kept in an environment of -5°C for 24 hours. After the support stand and the evaluation sample were returned to room temperature, a metal ball was dropped onto the evaluation sample on the support stand within 40 seconds, and the metal ball collided with the first glass plate of the evaluation sample. The mass of the metal ball was 15g. The drop position of the metal ball on the evaluation sample was a position 10 mm away from the printing layer in both the length direction and the width direction. Two tests (tests with different samples) were performed for each adhesive sheet (n=2). The drop height of the metal ball in the first test was 300 mm, and the drop height of the metal ball in the second test was 400 mm. Regarding the drop impact resistance of the adhesive sheet, if no peeling of the adhesive layer occurred in the first and second tests, it was rated as "excellent," if peeling did not occur in the first test only, it was rated as "fair," and if peeling occurred in both the first and second tests, it was rated as "poor."

[0144] [Table 1]

[0145] It was confirmed that the pressure-sensitive adhesive sheets disclosed in the examples have a sufficiently low dielectric constant, reduce noise generation, have sufficient adhesion to glass, are easy to attach to an adherend, and exhibit drop impact resistance (Examples 1 and 2). On the other hand, when the Tg of the acrylic polymer is low, it is not possible to achieve a low dielectric constant although it has drop impact resistance (Comparative Example 1), and when the dielectric loss tangent in the high speed region is small, it is possible to achieve a low dielectric constant but is unable to exhibit drop impact resistance (Comparative Example 2). [Explanation of symbols]

[0146] 1 Adhesive sheet 10 Adhesive layer 11, 12 Release liner 2A Optical components with adhesive layer 2B Touch sensor film with adhesive layer 20 Adhesive layer 21 Optical components 22 Release Liner 23 Touch sensor film 24 Metal wiring 3 Image display device 30, 31 Adhesive layer 32 Image display panel 33 Polarizing film 34 Transparent Substrate 4. Touch Panel 40, 41 Adhesive layer 42 Image display panel 43 Touch sensor film 44 Transparent Substrate 45 Metal wiring

Claims

1. A pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer did not peel off in the following drop impact resistance test, The dielectric constant at a frequency of 100 kHz is 4 or less, The adhesive strength to glass of at least one surface is 10 N / 20 mm or more under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min, Adhesive sheets used for optical components. <Drop impact resistance test> A first glass plate (length 100 mm x width 75 mm, thickness 500 μm), the adhesive layer (length 75 mm x width 45 mm), a printed layer (thickness 30 μm) formed within a range of 15 mm around the edge of the second glass plate, and the second glass plate (length 100 mm x width 50 mm, thickness 500 μm) are laminated in this order, and a bonded body is produced by heat treatment under conditions of 50 ° C., 0.5 MPa, and 30 minutes. The bonded body is placed on a support table so that only the protruding parts at both ends in the width direction of the first glass plate are supported by the support table, and the second glass plate is not in contact with the support table, and the first glass plate is placed on the upper side of the bonded body, and a metal ball having a mass of 15 g is dropped from a height of 300 mm toward the first glass plate to check whether or not the adhesive layer peels off from the first glass plate or the printed layer.

2. The pressure-sensitive adhesive sheet according to claim 1, which does not peel off even when left for one week at 80° C. after the drop impact resistance test.

3. 3. An optical member with a pressure-sensitive adhesive layer, comprising the pressure-sensitive adhesive sheet according to claim 1 or 2 attached to at least one surface of the optical member.

4. An image display device comprising the pressure-sensitive adhesive layer-attached optical member according to claim 3 .

5. The image display device according to claim 4 , which is a touch panel.

Images