Adhesive sheet, optical component with adhesive layer, and image display device.

Abstract

The present invention provides an adhesive sheet that reduces noise, possesses sufficient adhesive strength, is resistant to drop impacts, and transmits a wide range of light wavelengths. [Solution] The adhesive sheet 1 has an adhesive layer 10. The adhesive layer 10 does not peel off in a drop impact resistance test, has a dielectric constant of 4 or less at a frequency of 100 kHz, has a glass adhesive strength of 10 N / 20 mm or more under conditions of a peel angle of 180° on at least one side and a tensile speed of 300 mm / min, and has a transmittance of 80% or more at a wavelength of 380 nm and a transmittance of 80% or more at a wavelength of 420 nm. The adhesive sheet 1 is used in optical components.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet, an optical component with an adhesive layer, and an image display device. [Background technology]

[0002] In recent years, image display devices such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs), as well as touch panels that incorporate touch sensors into these image display devices, have become widely used in various fields. Such image display devices and touch panels have a structure in which various optical components such as polarizing films, phase difference films, optical compensation films, touch sensor films, and cover films are laminated onto an image display panel. Adhesive sheets having an adhesive layer are used to bond these optical components together. For example, transparent adhesive sheets are used to bond various optical components in image display devices (see, for example, Patent Documents 1 to 3).

[0003] In particular, adhesive sheets used in touch panels were required to achieve a low dielectric constant in order to reduce malfunctions caused by noise generation. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-238915 [Patent Document 2] Japanese Patent Publication No. 2003-342542 [Patent Document 3] Japanese Patent Publication No. 2004-231723 [Overview of the project] [Problems that the invention aims to solve]

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

[0006] Furthermore, lowering the glass transition temperature of the adhesive layer in an adhesive sheet makes the adhesive layer more flexible, resulting in superior adhesion to the adherend and better resistance to drop impact. However, such adhesive sheets have the problem of a narrow wavelength range of light that they transmit. A narrow wavelength range means that, for example, if the adhesive layer is photocurable, the wavelength selectivity of the light used for curing is low, and curing takes a long time at low illumination levels.

[0007] The present invention has been made in view of the above problems, and its object is to provide an adhesive sheet that reduces noise, has sufficient adhesive strength to the adherend, possesses drop impact resistance, and has a wide wavelength range of light transmission. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objectives, the inventors have found that a particular adhesive sheet reduces noise, has sufficient adhesive strength to the adherend, possesses drop impact resistance, and has a wide wavelength range of light transmission.

[0009] In other words, the present invention provides an adhesive sheet for use in optical components, having an adhesive layer, wherein the adhesive layer does not peel off in the following drop impact resistance test, has a dielectric constant of 4 or less at a frequency of 100 kHz, has a glass adhesive strength of 10 N / 20 mm or more under the conditions of a peeling angle of 180° on at least one side and a tensile speed of 300 mm / min, and has a transmittance of 80% or more at both a wavelength of 380 nm and a wavelength of 420 nm. <Drop Impact Resistance Test> A first glass plate (100 mm long x 75 mm wide, 500 μm thick), the adhesive layer (75 mm long x 45 mm wide), a printed layer (30 μm thick) formed within a 15 mm radius around the edge of the second glass plate, and the second glass plate (100 mm long x 50 mm wide, 500 μm thick) are stacked in that order, and a bonded body is produced by heat treatment at 50°C, 0.5 MPa, and 30 minutes. The bonded body is placed on a support base so that only the protruding portions at both ends in the width direction of the first glass plate are supported by the support base, and the second glass plate is not in contact with the support base, with the first glass plate on the upper side of the bonded body. A metal ball with a mass of 15 g is dropped from a height of 300 mm toward the first glass plate, and it is checked whether or not the adhesive layer and the first glass plate or the printed layer peel off.

[0010] The adhesive layer described above did not peel off even in the drop impact resistance test, and the glass adhesive strength was 10N / 20mm or more under the conditions of a peel angle of 180° and a tensile speed of 300mm / min, demonstrating sufficient adhesive strength and demonstrating drop impact resistance. Furthermore, the dielectric constant at a frequency of 100kHz is 4 or less, which makes it possible to reduce noise. In addition, the transmittance at wavelengths of 380nm and 420nm are both 80% or more, resulting in high light transmittance in the 380-420nm wavelength range and a wide range of transmitted light wavelengths.

[0011] It is preferable that no delamination occurs in the drop impact resistance test after the above-mentioned joint has been manufactured and stored at 80°C for one week. The above configuration allows for favorable use even under high-temperature operating conditions.

[0012] It is preferable that the above-mentioned joint does not delaminate after being stored at room temperature for 6 months following its fabrication, as demonstrated in the above-mentioned drop impact resistance test. The above configuration allows for favorable use even after long-term storage.

[0013] The above-mentioned adhesive sheet preferably has a ratio of glass adhesion of 1.0 to 2.0 under the conditions of a peeling angle of 180° of the adhesive layer and a tensile speed of 300 mm / min after the adhesive sheet is bonded to a glass plate and stored at room temperature for 6 months with respect to the above-mentioned glass adhesion. By having the above configuration, even after long-term storage, the adhesive sheet has sufficient adhesion to the adherend, has impact resistance against dropping, and is reworkable, and can be preferably used even after long-term storage.

[0014] In addition, the present invention provides an optical member with an adhesive layer, on which the above-mentioned adhesive sheet is adhered to at least one side of the optical member.

[0015] In addition, the present invention provides an image display device having the above-mentioned optical member with an adhesive layer.

[0016] The above-mentioned optical member with an adhesive layer is preferably a touch panel.

Advantages of the Invention

[0017] The adhesive sheet of the present invention has reduced noise, has sufficient adhesion, has impact resistance against dropping, and has a wide wavelength range of light transmittance.

Brief Description of the Drawings

[0018] [Figure 1] It is a cross-sectional view showing an embodiment of the adhesive sheet of the present invention. [Figure 2] It is a cross-sectional view showing an embodiment of the optical member with an adhesive layer of the present invention. [Figure 3] It is a cross-sectional view showing an embodiment of the image display device of the present invention. [Figure 4] It is a cross-sectional view showing an embodiment of the touch panel of the present invention. [Figure 5] It is a (a) plan view, (b) cross-sectional view in the short side direction, and (c) cross-sectional view in the long side direction of an evaluation sample on which an impact resistance against dropping test was carried out in an example.

Modes for Carrying Out the Invention

[0019] [Adhesive sheet] The adhesive sheet of the present invention comprises at least an adhesive layer. The adhesive layer does not peel off from the adherend in the following drop impact resistance test, has a dielectric constant of 4 or less at a frequency of 100 kHz, has a glass adhesive strength of 10 N / 20 mm or more under the conditions of a peel angle of 180° on at least one side and a tensile speed of 300 mm / min, and has a transmittance of 80% or more at a wavelength of 380 nm and a transmittance of 80% or more at a wavelength of 420 nm. In this specification, the adhesive layer may be referred to as "the adhesive layer of the present invention." <Drop Impact Resistance Test> A first glass plate (100 mm long x 75 mm wide, 500 μm thick), the adhesive layer (75 mm long x 45 mm wide), a printed layer (30 μm thick) formed within a 15 mm radius around the edge of the second glass plate, and the second glass plate (100 mm long x 50 mm wide, 500 μm thick) are stacked in that order, and a bonded body is produced by heat treatment at 50°C, 0.5 MPa, and 30 minutes. The bonded body is placed on a support base so that only the protruding portions at both ends in the width direction of the first glass plate are supported by the support base, and the second glass plate is not in contact with the support base, with the first glass plate on the upper side of the bonded body. A metal ball with a mass of 15 g is dropped from a height of 300 mm toward the first glass plate, and it is checked whether or not the adhesive layer and the first glass plate or the printed layer peel off.

[0020] In this specification, "peeling" in a drop impact resistance test means that one or more voids of 100 μm or more occur in the bonding area between the adhesive layer and the glass plate.

[0021] The above-mentioned adhesive sheet is used for optical components. That is, the adhesive sheet is used by being bonded to optical components. For example, the adhesive sheet is used in image display devices such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs), and in touch panels that incorporate touch sensors into these image display devices, to bond optical components such as polarizing films, phase difference films, optical compensation films, touch sensor films, and cover films to the image display panel, or to bond these optical components to each other. In this specification, when the term "image display device" is used, it includes the concept of "touch panel" unless otherwise specified.

[0022] The adhesive sheet described above may be a double-sided adhesive sheet with adhesive layers on both sides, or a single-sided adhesive sheet with adhesive layers on only one side. Of these, a double-sided adhesive sheet is preferable from the viewpoint of bonding two components together. In this specification, the term "adhesive sheet" also includes tape-like materials, i.e., "adhesive tape." In this specification, the surface of the adhesive layer may be referred to as the "adhesive surface."

[0023] (The adhesive layer of the present invention) The adhesive layer of the present invention is not particularly limited, but from the viewpoint of preventing malfunctions of the touch panel having the adhesive layer of the present invention, it is preferable that the dielectric constant is controlled to be low. The dielectric constant of the adhesive layer at 20°C and a frequency of 100kHz is 4 or less, preferably 3.9 or less, and more preferably 3.8 or less. The lower limit of the dielectric constant at a frequency of 100kHz 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 100kHz may also be 2.1 or more, 2.2 or more, 2.3 or more, 2.4 or more, or 2.5 or more. By setting the lower limit of the dielectric constant to 1.5 or more, the adhesive layer can easily exhibit adhesiveness. The dielectric constant is measured in accordance with JIS K 6911.

[0024] The adhesive layer of the present invention has an adhesive strength (sometimes referred to as "glass adhesive strength") of 10 N / 20 mm or more on at least one side, measured using a tensile testing machine at a peel angle of 180° and a tensile speed of 300 mm / min in an environment of 23°C and 50% RH. This glass adhesive strength of 10 N / 20 mm or more allows for easy adhesion to the substrate. The glass adhesive strength is preferably 12 N / 20 mm or more, and more preferably 14 N / 20 mm or more. There is no particular upper limit, but it may be, for example, 30 N / 20 mm or less. From the viewpoint of exhibiting reworkability, it is preferably 24 N / 20 mm or less, more preferably 22 N / 20 mm or less, and particularly preferably 20 N / 20 mm or less. When the adhesive layer of the present invention is used as a double-sided adhesive sheet, it is preferable that the adhesive strength of both sides is within the above range. In this specification, the glass adhesive strength may be referred to as "glass adhesive strength (immediately after)".

[0025] The adhesive layer of the present invention preferably has an adhesive strength (glass adhesive strength) of 10 N / 20 mm or more, more preferably 14 N / 20 mm or more, and even more preferably 17 N / 20 mm or more, measured on at least one side using a tensile testing machine at 23°C and 50% RH with a peel angle of 180° and a tensile speed of 300 mm / min, after the adhesive sheet has been bonded to a glass plate and stored at room temperature (25 ± 3°C) for 6 months. When the adhesive layer of the present invention is used as a double-sided adhesive sheet, it is preferable that the adhesive strength of both sides is within the above range. In this specification, the above glass adhesive strength may be referred to as "glass adhesive strength (after 6 months)".

[0026] The ratio of the glass adhesive strength (after 6 months) to the glass adhesive strength (immediately after) [glass adhesive strength (after 6 months) / glass adhesive strength (immediately after)] is preferably 1.0 or higher, more preferably 1.1 or higher, even more preferably 1.2 or higher, and particularly preferably 1.3 or higher. When the ratio is 1.0 or higher, the adhesive sheet has sufficient adhesive strength to the adherend even after long-term storage, and also possesses drop impact resistance, making it suitable for use even after long-term storage. The ratio is preferably 2.0 or lower, more preferably 1.8 or lower, and even more preferably 1.7 or lower. When the ratio is 2.0 or lower, it is reworkable even after long-term storage, and can be suitable for use even after long-term storage.

[0027] The adhesive layer of the present invention does not peel off even in the above-mentioned drop impact resistance test, and preferably does not peel off even in the above-mentioned drop impact resistance test when the height is changed to 400 mm. An adhesive layer that does not peel off from the adherend in the above-mentioned drop impact resistance test has good drop impact resistance.

[0028] Furthermore, it is preferable that the above-mentioned bonded structure does not peel off in the above-mentioned drop impact resistance test when stored at 80°C for one week after its manufacture. An adhesive layer having such properties can be preferably used even under high-temperature operating conditions.

[0029] Furthermore, it is preferable that the above-mentioned bonded structure does not peel off in the above-mentioned drop impact resistance test when stored at -10°C for one week after its manufacture. An adhesive layer with such properties can be preferably used even under low-temperature operating conditions.

[0030] Furthermore, it is preferable that the above-mentioned bonded structure does not peel off in the above-mentioned drop impact resistance test when stored at room temperature (25±3℃) for one month after its manufacture. Adhesive layers with such properties tend to have excellent storage stability.

[0031] The adhesive layer of the present invention is preferably such that it does not peel off even after the adhesive sheet has been stored at room temperature (25±3℃) for 6 months, even in the aforementioned drop impact resistance test. An adhesive layer with such properties can be used even after the adhesive sheet has been stored for a long period of time.

[0032] Furthermore, the adhesive layer of the present invention is 1.0 × 10 in 20°C, as required in accordance with JIS K 6911. 3 ~10 4 The dielectric loss tangent (tanδ) at Hz is preferably 0.75 or higher, more preferably 0.85 or higher, even more preferably 0.95 or higher, and particularly preferably 1.15 or higher. Furthermore, the dielectric loss tangent is preferably 2.6 or lower, more preferably 2.4 or lower, even more preferably 2.2 or lower, and particularly preferably 2.0 or lower. 1.0 × 10 3 ~10 4 A dielectric loss tangent of 0.75 or higher in the high-speed region of Hz makes it easier to achieve drop impact resistance. Furthermore, a value of 2.6 or lower makes it easier to prevent cohesive failure of the adhesive layer. It is also preferable that the dielectric loss tangent remains within the above range even after the adhesive sheet has been stored at room temperature for 6 months. (The above "1.0 × 10 3 ~10 4 "The dielectric loss tangent (tanδ) at Hz is 0.75 or greater" means 1.0 × 10⁻⁶ 3 ~10 4 This means that the value is 0.75 or higher across the entire Hz range.

[0033] The light transmittance of the adhesive layer of the present invention at a wavelength of 380 nm is 80% or more, preferably 85% or more, and more preferably 90% or more. The upper limit is not particularly limited and may be 100%. The method for measuring the above transmittance is not particularly limited, but for example, it can be measured using a spectrophotometer U4100 (manufactured by Hitachi High-Tech Corporation).

[0034] The light transmittance of the adhesive layer of the present invention at a wavelength of 420 nm is 80% or more, preferably 85% or more, and more preferably 90% or more. The upper limit is not particularly limited and may be 100%. The method for measuring the above transmittance is not particularly limited, but for example, it can be measured using a spectrophotometer U4100 (manufactured by Hitachi High-Tech Corporation).

[0035] The adhesive layer of the present invention has a transmittance of 80% or more at both a wavelength of 380 nm and a wavelength of 420 nm, resulting in high light transmittance in the 380-420 nm wavelength range and a wide wavelength range of transmitted light. Therefore, it is preferable that the light transmittance in the 380-420 nm wavelength range is within the above range.

[0036] The thickness of the adhesive layer of the present invention is preferably 5 to 300 μm, more preferably 8 to 200 μm, even more preferably 10 to 150 μm, and particularly preferably 10 to 100 μm. A thickness of 5 μm or more facilitates drop impact resistance, while a thickness of 300 μm or less provides excellent handling and manufacturability.

[0037] The adhesive layer of the present invention can be a known or conventional adhesive layer. Preferably, the adhesive layer is a solvent-free adhesive layer containing a photopolymerized polymer as the base polymer. Such an adhesive layer can be manufactured from a solvent-free adhesive composition. When manufacturing the adhesive layer from a solvent-free adhesive composition, there is no need to remove the solvent by volatilizing it from the coating film of the composition. Therefore, an adhesive sheet equipped with the above adhesive layer is suitable for reducing environmental impact.

[0038] The adhesive layer of the present invention is preferably a sheet-like pressure-sensitive adhesive (solvent-free adhesive sheet) formed from a solvent-free adhesive composition. Therefore, the adhesive layer (solvent-free adhesive composition) preferably contains at least a photopolymerizable polymer as a base polymer. A photopolymerizable polymer is a polymer formed by a polymerization method in which the polymerization reaction of polymerizable components is advanced by irradiation with active energy rays such as ultraviolet light.

[0039] The base polymer is an adhesive component that exhibits tackiness in the adhesive layer of the present invention. The base polymer is not particularly limited, but examples include acrylic polymers, rubber polymers (such as natural rubber polymers and synthetic rubber polymers), silicone polymers, polyester polymers, urethane polymers, polyamide polymers, epoxy polymers, vinyl alkyl ether polymers, and fluorine polymers. One or more of the base polymers may be used.

[0040] The content of the base polymer in the adhesive layer of the present invention is not particularly limited, but is preferably 75% by mass or more (for example, 75 to 99.9% by mass) and more preferably 85% by mass or more (for example, 85 to 99.9% by mass) based on the total amount (100% by mass) of the adhesive layer.

[0041] The method for producing the adhesive layer of the present invention is not particularly limited. For example, the adhesive composition described below may be prepared, applied (coated) onto a substrate or release liner, and, if necessary, irradiated with active energy rays, heated and dried, etc.

[0042] Furthermore, known coating methods may be used for applying (coating) the above adhesive composition. For example, coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, and direct coaters may be used.

[0043] Furthermore, it is preferable that the above adhesive composition does not contain or substantially contains an organic solvent. The above organic solvent is not particularly limited as long as it is an organic compound used as a solvent, but examples 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 above organic solvent may be a mixed solvent containing two or more organic solvents.

[0044] In the above-mentioned adhesive composition, "substantially free of organic solvents" means that organic solvents are not actively incorporated except in cases where they are inevitably mixed in. Specifically, an adhesive composition in which the content of organic solvents is 1.0% by mass or less (preferably 0.5% by mass or less, and more preferably 0.2% by mass or less) relative to the total amount of the adhesive composition (100% by mass) can be said to be substantially free of organic solvents.

[0045] The adhesive composition for forming the adhesive layer of the present invention is preferably an adhesive composition containing an acrylic polymer as the base polymer. That is, the adhesive layer of the present invention is preferably an acrylic adhesive layer with an acrylic polymer as the base polymer. It may also contain hydrogenated polyolefin resins, polyfunctional (meth)acrylates, silane coupling agents, and other additives as described later. The acrylic polymer can be used alone or in combination of two or more types.

[0046] The content of the acrylic polymer is not particularly limited, but it is preferably 30 to 90% by mass, and more preferably 40 to 80% by mass, relative to the total amount (100% by mass) of the adhesive layer of the present invention.

[0047] The adhesive composition that forms an adhesive layer containing an acrylic polymer as the main component is not particularly limited, but examples include compositions in which an acrylic polymer is an essential component; and compositions in which a mixture of monomer components constituting the acrylic polymer (sometimes referred to as a "monomer mixture") or a partially polymer thereof is an essential component. Examples of the former include so-called water-dispersible compositions (emulsion-type compositions), and examples of the latter include so-called active energy ray-curable compositions. Among these, adhesive compositions in which the above-mentioned monomer mixture or a partially polymer thereof is an essential component are preferred.

[0048] In this specification, the above-mentioned "mixture of monomer components" includes cases where it is composed of a single monomer component and cases where it is composed of two or more monomer components. Furthermore, the above-mentioned "partially polymerized 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.

[0049] Acrylic polymers are polymers (polymers) that contain acrylic monomers (acrylic monomers) as essential monomer units (monomer units, monomer constituent units). In other words, acrylic polymers are polymers that contain constituent units derived from acrylic monomers as constituent units. That is, acrylic polymers are polymers that are composed (formed) with acrylic monomers as essential monomer components. In this specification, "(meth)acrylic" refers to either or both of "acrylic" and "methacrylic," and the same applies to other terms. The weight-average molecular weight of the acrylic polymer in the adhesive layer is not particularly limited, but is preferably between 100,000 and 5,000,000.

[0050] The acrylic polymer in the above adhesive composition is preferably a polymer containing an alkyl (meth)acrylate (hereinafter sometimes simply referred to as "alkyl (meth)acrylate") having a linear or branched alkyl group as a monomer unit.

[0051] Examples of the above alkyl (meth)acrylate esters 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 include alkyl esters of (meth)acrylates, 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, where the alkyl group has 1 to 24 carbon atoms. Alkyl meth)acrylates may be used alone or in combination of two or more types.

[0052] As for alkyl (meth)acrylate esters, alkyl acrylates are preferred over alkyl methacrylates because they can shorten the polymerization time of the acrylic polymer and improve productivity. In particular, alkyl acrylates are preferred when the above-mentioned acrylic polymer is cured by radiation polymerization.

[0053] Among these, alkyl (meth)acrylate esters with 1 to 18 carbon atoms in the alkyl group are preferred, as they exhibit low dielectric constant and drop impact resistance. More preferably, methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and isostearyl acrylate (ISTA) are preferred.

[0054] The content (percentage) of the alkyl (meth)acrylate in the total monomer units (total amount of monomer components constituting the acrylic polymer) of the above acrylic polymer is not particularly limited, but in order to exhibit a low dielectric constant and drop impact resistance, it is preferably 30 to 99% by mass, more preferably 35 to 95% by mass, and even more preferably 40 to 90% by mass, relative to the total amount of monomer components constituting the acrylic polymer (100% by mass).

[0055] In this specification, when referring to "the total amount of monomer components constituting the acrylic polymer," it also includes monomer components that are separately added to the adhesive composition containing the acrylic polymer for purposes such as adjusting the dielectric constant of the adhesive layer.

[0056] The above monomer component preferably contains an alkyl (meth)acrylate having an alkyl group with 8 or more carbon atoms (sometimes referred to as "alkyl (meth)acrylate (A)"). Alkyl (meth)acrylate (A) has a medium-chain to long-chain alkyl group, making it easy to achieve a low dielectric constant while exhibiting high tackiness.

[0057] Examples of the above-mentioned alkyl (meth)acrylate (A) include alkyl (meth)acrylates with 8 to 24 carbon atoms in the alkyl group, such as octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, 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.

[0058] Of the alkyl (meth)acrylate (A) mentioned above, alkyl acrylate is preferred over alkyl methacrylate in that it can shorten the polymerization time of the acrylic polymer and improve productivity. In particular, alkyl acrylate is preferred from the viewpoint of superior active energy ray curability.

[0059] Among the above alkyl (meth)acrylate (A), it is preferable to include an alkyl (meth)acrylate having a branched alkyl group having 8 or more carbon atoms, more preferably an alkyl (meth)acrylate having a branched alkyl group having 8 or 9 carbon atoms, even more preferably ethylhexyl (meth)acrylate, and particularly preferably ethylhexyl acrylate (2EHA). The number of carbon atoms in the side chain alkyl group of the above branched alkyl group is not particularly limited, but alkyl groups having 1 to 3 carbon atoms (e.g., methyl group, ethyl group, n-propyl group, isopropyl group) are preferred. The "side chain alkyl group" is an alkyl group that is substituted on the side chain of the carbon chain with the longest number of carbon atoms.

[0060] The content of the alkyl (meth)acrylate (A) in the above acrylic adhesive composition is not particularly limited, but from the viewpoint of easily achieving a low dielectric constant while exhibiting high adhesiveness, it is preferably 30 to 99% by mass, more preferably 35 to 95% by mass, and even more preferably 40 to 90% by mass, based on the total amount (100% by mass) of monomer components in the above acrylic adhesive composition.

[0061] If the above alkyl (meth)acrylate (A) includes an alkyl (meth)acrylate having a branched alkyl group having 8 or 9 carbon atoms (hereinafter referred to as alkyl (meth)acrylate (A1) in this specification), it is preferable that it further includes an alkyl (meth)acrylate having a branched alkyl group having 10 to 24 carbon atoms (hereinafter referred to as alkyl (meth)acrylate (A2) in this specification).

[0062] When the above alkyl (meth)acrylate (A) contains alkyl (meth)acrylate (A2) in addition to alkyl (meth)acrylate (A1), the dielectric constant of the adhesive layer can be reduced due to the action of the long-chain branched alkyl group. Therefore, even when it is attached to an optical component (touch sensor film) on which a metal wiring layer such as metal mesh wiring or silver nanowire is formed, malfunctions can be prevented because the adhesive layer has a low dielectric constant.

[0063] The Tg of the (meth)acrylate (A2) homopolymer is preferably -80 to 0°C, and more preferably -70 to -10°C. If the Tg of the homopolymer is -70°C or higher, the elastic modulus of the adhesive layer at room temperature is not too low, and if it is -10°C or lower, the initial tackiness is superior. The Tg of the homopolymer is a value measured by differential scanning calorimetry (DSC). Furthermore, while branched alkyl groups with 10 to 24 carbon atoms are preferred because they satisfy a moderately low dielectric constant and elastic modulus, alkyl (meth)acrylates having appropriately preferred alkyl groups can be selected depending on the method for producing the (meth)acrylic polymer. For example, the alkyl group has more preferably 12 to 18 carbon atoms, and even more preferably 14 to 18 carbon atoms.

[0064] Examples of alkyl esters (A2) (meth)acrylates include isodecyl acrylate (10 carbon atoms, Tg of homopolymer = -60°C, hereinafter simply abbreviated as Tg), isodecyl methacrylate (10 carbon atoms, Tg = -41°C), isomistyryl acrylate (14 carbon atoms, Tg = -56°C), isostearyl acrylate (18 carbon atoms, Tg = -18°C), 2-propylheptyl acrylate, isoundecyl acrylate, isododecyl acrylate, isotridecyl acrylate, isopentadecyl acrylate, isohexadecyl acrylate, and isoheptadecyl acrylate.

[0065] Among the branched alkyl groups having 10 to 24 carbon atoms, those having a branched alkyl group such as a t-butyl group at the end of the ester group are particularly preferred because they are thought to increase the molar volume and decrease the dipole moment, resulting in an adhesive layer with a balance between the two. Preferred branched alkyl groups at the end of the ester group include branched alkyl groups having 4 to 6 carbon atoms, such as a t-butyl group, a neopentyl group, and a t-pentyl group, with the t-butyl group being particularly preferred. A preferred example of an alkyl (meth)acrylate ester (A2) having a t-butyl group at the end of the ester group is isostearyl acrylate, represented by the following formula. [ka]

[0066] The content of the alkyl (meth)acrylate (A1) in the above acrylic adhesive composition is not particularly limited, but from the viewpoint of easily achieving a low dielectric constant while exhibiting high adhesiveness, it is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and may be 30% by mass or more, based on the total amount of monomer components (100% by mass) in the above acrylic adhesive composition. Furthermore, from the viewpoint of lowering the dielectric constant of the adhesive layer and preventing malfunctions, the above content is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

[0067] The content of the alkyl (meth)acrylate (A2) in the above acrylic adhesive composition is not particularly limited, but from the viewpoint of reducing the dielectric constant of the adhesive layer and preventing malfunctions, it is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and may be 30% by mass or more, based on the total amount of monomer components (100% by mass) in the above acrylic adhesive composition. Furthermore, from the viewpoint of easily achieving a low dielectric constant while exhibiting high adhesiveness, the above content is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, even more preferably 50% by mass or less, and particularly preferably 40% by mass or less.

[0068] The mass ratio of the above alkyl methacrylate (A1) to alkyl methacrylate (A2) [(alkyl methacrylate (A2) / (alkyl methacrylate (A1)] is not particularly limited, but from the viewpoint of easily achieving a low dielectric constant while exhibiting high tackiness, it is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. Also, from the viewpoint of reducing the dielectric constant of the adhesive layer to prevent malfunctions, the above mass ratio is preferably 0.2 or more, more preferably 0.4 or more, even more preferably 0.6 or more, and may also be 0.8 or more.

[0069] The above monomer component may also contain alkyl (meth)acrylates other than alkyl (meth)acrylate (A) (hereinafter sometimes referred to as "alkyl (meth)acrylate (B)"). Examples of alkyl (meth)acrylate (B) include alkyl (meth)acrylates having a linear or branched alkyl group with 1 to 7 carbon atoms, such as 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, and heptyl (meth)acrylate.

[0070] The content of the alkyl (meth)acrylate (B) in the above acrylic adhesive composition is not particularly limited, but from the viewpoint of easily achieving a low dielectric constant while exhibiting high adhesiveness, it is preferably 10% by mass or less, and more preferably 7% by mass or less, relative to the total amount of monomer components (100% by mass) in the above acrylic adhesive composition. The above content may be 1% by mass or more, or 3% by mass or more.

[0071] In the above adhesive composition, the acrylic polymer may contain copolymerizable functional group-containing monomers (copolymerizable functional group-containing monomers) in addition to the above-mentioned alkyl (meth)acrylate as monomer units. In other words, the acrylic polymer may contain functional group-containing monomers as constituent monomer components. The functional group-containing monomers may be used alone or in combination of two or more types.

[0072] As the above-mentioned functional group-containing monomers, hydroxyl group-containing monomers are preferred. When an acrylic polymer contains a hydroxyl group-containing monomer as a monomer unit, polymerization of the constituent monomer components becomes easier, and the cohesive force can be increased. Furthermore, the interaction with the adherend interface can be enhanced. As a result, strong adhesion can be easily obtained.

[0073] The above-mentioned hydroxyl group-containing monomers refer to monomers that have at least one hydroxyl group in their molecule. Furthermore, monomers that have at least one hydroxyl group and at least one carboxyl group in their molecule are carboxyl group-containing monomers and not hydroxyl group-containing monomers. The above-mentioned hydroxyl group-containing monomers are not particularly limited, but specifically include, 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, etc. In particular, as the above-mentioned hydroxyl group-containing monomer, hydroxyl group-containing (meth)acrylic acid esters are preferred from the viewpoint of easily obtaining good cohesive force and improving adhesive reliability at high temperatures, and more preferably 2-hydroxyethyl acrylate (HEA), 2-hydroxypropyl (meth)acrylate (HPA), and 4-hydroxybutyl acrylate (4HBA). Note that the hydroxyl group-containing monomer may be used alone or in combination of two or more types.

[0074] Furthermore, nitrogen atom-containing monomers are preferred as the functional group-containing monomers. When an acrylic polymer contains nitrogen atom-containing monomers as monomer units, it becomes easier to obtain appropriate cohesive force, which in turn makes it easier to obtain strong adhesion and excellent foaming resistance.

[0075] The nitrogen atom-containing monomer means a monomer having at least one nitrogen atom in the molecule (within one molecule). However, the above hydroxyl group-containing monomer does not include the 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. Further, 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 and is not a nitrogen atom-containing monomer.

[0076] As the above nitrogen atom-containing monomer, from the viewpoint of exhibiting strong adhesive force, N-vinyl cyclic amides, (meth)acrylamides, etc. are preferable. The nitrogen atom-containing monomer may be used alone or in combination of two or more.

[0077] As the above N-vinyl cyclic amide, from the viewpoint of easily obtaining good cohesive force and easily obtaining adhesive reliability at high temperature, the N-vinyl cyclic amide represented by the following formula (1) is preferable. [Chemical formula] (In formula (1), R 1 represents a divalent organic group)

[0078] R in the above formula (1) 1 is a divalent organic group, preferably a divalent saturated hydrocarbon group or an unsaturated hydrocarbon group, more preferably a divalent saturated hydrocarbon group (for example, an alkylene group having 3 to 5 carbon atoms, etc.).

[0079] From the viewpoint of exhibiting even stronger adhesiveness, the N-vinyl cyclic amide represented by formula (1) above is preferably 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-morpholindione, more preferably N-vinyl-2-pyrrolidone and N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

[0080] Examples of the above (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of the above N-alkyl(meth)acrylamide include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, and N-octylacrylamide. Furthermore, the above 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 above 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.

[0081] Furthermore, the above-mentioned (meth)acrylamides also include, for example, various N-hydroxyalkyl (meth)acrylamides. Examples of the above-mentioned 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.

[0082] Furthermore, the above-mentioned (meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides. Examples of the above-mentioned N-alkoxyalkyl(meth)acrylamides include N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.

[0083] Furthermore, nitrogen atom-containing monomers other than the above N-vinyl cyclic amides and (meth)acrylamides include, for example, amino group-containing monomers such as (meth)aminoethyl acrylate, (meth)dimethylaminoethyl acrylate, (meth)dimethylaminopropyl acrylate, and (meth)butylaminoethyl 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 include heterocyclic monomers such as methylvinylpyrrolidone; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate.

[0084] In addition to the nitrogen atom-containing monomers and hydroxyl group-containing monomers mentioned above, copolymerizable monomers in acrylic polymers include 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]; and alkoxyalkyl esters of (meth)acrylates [e.g., 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxyethyl (meth)acrylate]; Examples include propyl, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, etc.; epoxy group-containing monomers [e.g., glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, etc.]; sulfonic acid group-containing monomers [e.g., sodium vinylsulfonate, etc.]; phosphate group-containing monomers; (meth)acrylate 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, vinyltoluene, etc.]; olefins or dienes [e.g., ethylene, propylene, butadiene, isoprene, isobutylene, etc.]; vinyl ethers [e.g., vinyl alkyl ether, etc.]; vinyl chloride, etc.

[0085] The above adhesive composition preferably does not contain or substantially contains carboxyl group-containing monomers as monomer components constituting the acrylic polymer. By not containing or substantially containing carboxyl group-containing monomers, a corrosion prevention effect on metal wiring can be obtained in touch panels to which optical components (touch sensor films) having metal wiring such as metal mesh films or silver nanowire films are bonded. The content of carboxyl group-containing monomers is 1 ng / cm³ of the total amount of the above adhesive composition. 2 (For example, 0-1 ng / cm²) 2 ) is preferred, and more preferably 0.8 ng / cm³ 2 (For example, 0-0.8 ng / cm²) 2 ), more preferably 0.5 ng / cm 2 (For example, 0-0.5 ng / cm²) 2 Those that are substantially free of carboxyl group-containing monomers can be said to be substantially free of carboxyl group-containing monomers. Examples of carboxyl group-containing monomers include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. Furthermore, the carboxyl group-containing monomers also include acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride.

[0086] The content (percentage) 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 exhibiting appropriate tackiness, it is preferably 5 to 40% by mass, more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass. Furthermore, it is preferable that the total content of hydroxyl group-containing monomers and nitrogen atom-containing monomers is within the above range.

[0087] When the above-mentioned acrylic polymer contains hydroxyl group-containing monomers and nitrogen atom-containing monomers as functional group-containing monomer components constituting the polymer, the proportion of the functional group-containing monomer that is most abundant among the hydroxyl group-containing monomers and nitrogen atom-containing monomers is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total amount (100% by mass) of the hydroxyl group-containing monomers and nitrogen atom-containing monomers.

[0088] Furthermore, when polymerizing the above-mentioned acrylic polymer, polymerization initiators such as thermal polymerization initiators and photopolymerization initiators (photoinitiators) may be used depending on the type of polymerization reaction. The polymerization initiators may be used alone or in combination of two or more types.

[0089] The above-mentioned photopolymerization initiators are not particularly limited, but examples 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, and the like. The photopolymerization initiators may be used alone or in combination of two or more.

[0090] Examples of the above-mentioned benzoin ether-based photopolymerization initiators 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 above-mentioned acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of the above-mentioned α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of the above-mentioned aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of the above-mentioned photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of the above-mentioned benzoin-based photopolymerization initiators include benzoin. Examples of the above-mentioned benzyl-based photopolymerization initiators include benzyl. Examples of the above-mentioned benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone. Examples of the above-mentioned ketal-based photopolymerization initiators include benzyldimethylketal. Examples of the above-mentioned thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, etc.

[0091] The amount of the above-mentioned photopolymerization initiator used is not particularly limited, but for example, it 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 the total monomer units (total amount of monomer components constituting the acrylic polymer) of the acrylic polymer.

[0092] Furthermore, the above-mentioned thermal polymerization initiator is not particularly limited, but examples include azo polymerization initiators, peroxide polymerization initiators (e.g., dibenzoyl peroxide, tert-butyl permaleate, etc.), and redox polymerization initiators. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of the above-mentioned 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-methylpropionic acid)dimethyl, and 4,4'-azobis-4-cyanovaleric acid.

[0093] The amount of the above-mentioned thermal polymerization initiator used is not particularly limited, but for example, in the case of the above-mentioned azo polymerization initiator, it 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 the total monomer units of the acrylic polymer (total amount of monomer components constituting the acrylic polymer).

[0094] The above adhesive composition mainly consists of the above acrylic polymer, and it is preferable to add a monomer component other than the above acrylic polymer (hereinafter sometimes referred to as "separately added monomer") from the viewpoint of lowering the dielectric constant and exhibiting drop impact resistance. The separately added monomer may be used alone or in combination of two or more types.

[0095] As monomers to be added separately as described above, from the viewpoint of achieving low dielectric constant and drop impact resistance, the compounds presented as the above-mentioned alkyl (meth)acrylates and / or functional group-containing monomers are preferred, and more preferably the above-mentioned alkyl (meth)acrylates and / or hydroxyl group-containing monomers are preferred. Specifically, examples of alkyl (meth)acrylates include methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), isostearyl acrylate (ISTA), etc. Furthermore, 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)acrylic acid; vinyl alcohol, allyl alcohol, etc.

[0096] The amount of monomer added separately as described above is not particularly limited, but from the viewpoint of exhibiting 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 the total monomer units of the acrylic polymer (total amount of monomer components constituting the acrylic polymer). Furthermore, 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.

[0097] The adhesive layer of the present invention may contain a hydrogenated polyolefin resin. That is, the above adhesive composition may be an adhesive composition mainly composed of an acrylic polymer with a hydrogenated polyolefin resin added. The hydrogenated polyolefin resin is a material with a low dielectric constant, and by blending it with the above acrylic polymer, the dielectric constant can be reduced, thereby suppressing malfunctions of touch operations in touch panels to which optical components (touch sensor films) having metal wiring such as metal mesh films or silver nanowire films are bonded. Furthermore, it is preferable that a highly flexible adhesive layer can be realized without requiring the molecular weight of the acrylic polymer to be reduced, and that even when optical components (touch sensor films) having metal wiring such as metal mesh films or silver nanowire films are bonded, the stress with the metal wiring can be sufficiently relieved, preventing uneven display. In addition, since the hydrogenated polyolefin resin has excellent compatibility with acrylic polymers, it is preferable that the transparency of the adhesive layer of the present invention can be maintained at a higher level. The hydrogenated polyolefin resin can be used alone or in combination of two or more types.

[0098] Hydrogenated polyolefin resins are preferable because they can create a highly flexible adhesive layer, and when bonded to optical components (touch sensor films) having metal wiring such as metal mesh films or silver nanowire films, they can sufficiently relieve stress with the metal wiring and prevent display unevenness. Therefore, it is preferable that they exhibit liquid fluidity at 25°C. A hydrogenated polyolefin resin exhibiting liquid fluidity at 25°C means that its viscosity measured by a B-type viscometer at 25°C is 10,000 mPa·s or less.

[0099] Hydrogenated polyolefin resins are obtained by reducing the carbon-carbon double bonds contained in polyolefin resins through a hydrogenation reaction. Because hydrogenated polyolefin resins have a reduced number of carbon-carbon double bonds in their molecules, for example, when curing the adhesive composition by ultraviolet irradiation, polymerization inhibition is less likely to occur, and a decrease in polymerization rate and molecular weight reduction is less likely to occur. Therefore, the adhesive reliability of the adhesive composition at high temperatures can be maintained at a high level.

[0100] The hydrogenation rate of hydrogenated polyolefin resins is preferably 90% or higher, more preferably 95% or higher, and even more preferably 97% or higher, from the viewpoint of minimizing polymerization inhibition and ensuring adhesive reliability at high temperatures. The upper limit of the hydrogenation rate is not particularly limited, but theoretically it is 100%, and practically it may be 99.9% or lower, or even 99.8% or lower. The hydrogenation rate of hydrogenated polyolefin resins is... 1 This can be determined by quantitatively determining the amount of remaining double bonds in hydrogenated polyolefin resins using 1H-NMR measurement, among other methods.

[0101] The iodine value (Ig / 100g) of hydrogenated polyolefin resins is preferably 30 or less, more preferably 25 or less, and even more preferably 20 or less, from the viewpoint of minimizing polymerization inhibition and ensuring adhesive reliability at high temperatures. The lower limit of the iodine value is not particularly limited, but may be 0.1 or higher, or 0.2 or higher. The iodine value is measured in accordance with JIS K 0070-1992.

[0102] 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 adhesive layer and improving compatibility with acrylic polymers. The number average molecular weight (Mn) is preferably 1000 or more, more preferably 1500 or more, and even more preferably 1800 or more, in terms of being able to impart appropriate stress relaxation properties and fluidity to the adhesive composition. The number average molecular weight (Mn) is preferably 5000 or less, more preferably 4800 or less, and even more preferably 4600 or less, in terms of improving compatibility with acrylic polymers and being able to maintain a higher level of transparency of the adhesive layer of the present invention.

[0103] The polydispersity (Mw / Mn) of the hydrogenated polyolefin resin is preferably 2.0 or less, and more preferably 1.8 or less, in order to impart appropriate stress relaxation and fluidity to the adhesive layer, improve compatibility with acrylic polymers, maintain high transparency, and suppress haze. The lower limit of polydispersity is not particularly limited, but in practice it may be 1.0 or 1.1 or higher. The number-average molecular weight (Mn) and polydispersity (Mw / Mn) of the hydrogenated polyolefin resin are measured by gel permeation chromatography (GPC) and are values ​​determined on a polystyrene basis.

[0104] The above-mentioned hydrogenated polyolefin resin contains hydrogenated polyolefin. The adhesive layer of the present invention is preferable in that it contains hydrogenated polyolefin as the hydrogenated polyolefin resin, thereby reducing the dielectric constant and suppressing malfunctions of touch operations on a touch panel.

[0105] The above-mentioned hydrogenated polyolefins are hydrogenated polymers (polyolefins) having constituent units derived from olefins. Hydrogenated polyolefins include 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. Hydrogenated polyolefins are preferably hydrogenated homopolymers or copolymers of diene compounds, such as hydrogenated polybutadiene and hydrogenated polyisoprene. Hydrogenated polyolefins can be used alone or in combination of two or more types.

[0106] From the viewpoint of reducing the dielectric constant and suppressing malfunctions in touch operations on touch panels, it is preferable that the hydrogenated polyolefin resin further contains a hydrogenated polyolefin polyol in addition to the hydrogenated polyolefin.

[0107] The above-mentioned hydrogenated polyolefin polyol is a compound in which the terminal ends of the above-mentioned hydrogenated polyolefin are modified with hydroxyl groups. Preferred hydrogenated polyolefin polyols are hydroxyl-modified products of hydrogenated homopolymers or copolymers of diene compounds, such as hydrogenated polybutadiene polyol and hydrogenated polyisoprene polyol. Hydrogenated polyolefin polyols can be used alone or in combination of two or more types.

[0108] Of the above-mentioned hydrogenated polyolefins and hydrogenated polyolefin polyols, hydrogenated polybutadiene polyols and hydrogenated polybutadiene polyols are preferred because they can realize a highly flexible adhesive layer, and even when bonding with optical components (touch sensor films) having metal wiring such as metal mesh films or silver nanowire films, they can sufficiently relieve stress with the metal wiring and prevent uneven display.

[0109] The hydrogenated polybutadiene is preferably represented by the following formula (2), and the hydrogenated polybutadiene polyol is preferably represented by the following formula (3). [ka] In the above formula, m represents the degree of polymerization of hydrogenated polybutadiene.

[0110] Commercially available hydrogenated polyolefins and hydrogenated polyolefin polyols can be used. Examples of commercially available hydrogenated polyolefins include the product names "BI-2000" and "BI-3000" (both manufactured by Nippon Soda Co., Ltd.). Examples of commercially available hydrogenated polyolefin polyols include the product names "GI-1000," "GI-2000," and "GI-3000" (all manufactured by Nippon Soda Co., Ltd.), and "EPOL" (manufactured by Idemitsu Kosan Co., Ltd.).

[0111] The content of hydrogenated polyolefin resin is not particularly limited, but from the viewpoint of reducing the dielectric constant and suppressing malfunctions of touch operations on touch panels, 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, per 100 parts by mass of acrylic polymer. On the other hand, from the viewpoint of suppressing the rise of 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 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.

[0112] The content of hydrogenated polyolefin polyol is not particularly limited, but from the viewpoint of reducing the dielectric constant and suppressing malfunctions of touch operations on touch panels, 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, per 100 parts by mass of acrylic polymer. On the other hand, from the viewpoint of suppressing the rise of haze and ensuring higher transparency, and from the viewpoint of being able to maintain high adhesion strength and adhesive reliability at high temperatures, the content of 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.

[0113] The weight ratio of hydrogenated polyolefin content to hydrogenated polyolefin polyol content (hydrogenated polyolefin / hydrogenated polyolefin polyol) in the above adhesive composition is not particularly limited, but from the viewpoint of reducing the dielectric constant and suppressing malfunctions of touch operations on touch panels, it is preferably 1 / 99 or more, more preferably 2 / 98 or more, and may be 3 / 98 or more, or 4 / 96 or more. Furthermore, from the viewpoint of suppressing the rise of 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.

[0114] The above adhesive composition preferably further contains a polyfunctional (meth)acrylate. That is, the adhesive layer of the present invention preferably contains a structural component derived from a polyfunctional (meth)acrylate. The polyfunctional (meth)acrylate acts as a crosslinking component, making it easier for the adhesive composition to have appropriate cohesive force.

[0115] Examples of the above-mentioned polyfunctional (meth)acrylates 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, and the like. Note that the polyfunctional (meth)acrylates may be used individually or in combination of two or more types.

[0116] The content (percentage) of polyfunctional (meth)acrylate is not particularly limited, but from the viewpoint of the adhesive layer having 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, per 100 parts by mass of acrylic polymer. Furthermore, the content (percentage) of 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, per 100 parts by mass of acrylic polymer, in order to realize a highly flexible adhesive layer and sufficiently relieve stress with metal wiring to prevent uneven display.

[0117] The proportion of ultraviolet absorbers in the adhesive layer of the present invention is preferably less than 0.1% by mass, more preferably 0.05% by mass or less, even more preferably 0.02% by mass or less, and particularly preferably less than 0.01% by mass, relative to the total amount (100% by mass) of the adhesive layer, and preferably substantially absent. The above "substantially absent" means that ultraviolet absorbers are not actively incorporated except in cases where they are inevitably mixed in.

[0118] The above-mentioned UV absorbers are not particularly limited, but examples include triazine-based UV absorbers, benzotriazole-based UV absorbers, benzophenone-based UV absorbers, oxybenzophenone-based UV absorbers, salicylate-based UV absorbers, cyanoacrylate-based UV absorbers, and the like.

[0119] Triazine-based UV absorbers include, specifically, 2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (trade name "TinosorbS", manufactured by BASF) and 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (trade name "TINUVIN460", manufactured by BASF). ), the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl)-5-hydroxyphenyl and [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane (trade name "TINUVIN400", manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropyl [(hexyl)oxy]phenol), reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (trade name "TINUVIN 405", manufactured by BASF), 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]phenol (trade name "TINUVIN 1577", manufactured by BASF), 2 -(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol (trade name "ADKSTABLA46", manufactured by ADEKA Corporation), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenyl)-1,3,5-triazine (trade name "TINUVIN479", manufactured by BASF), etc. can be used.

[0120] Benzotriazole-based UV absorbers include 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN928", manufactured by BASF), 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (trade name "TINUVINPS", manufactured by BASF), benzenepropanoic acid, and 3-(2H-benzotriazole-2-yl)-5-( Ester compounds of 1,1-dimethylethyl)-4-hydroxy(C7-9 side chain and linear alkyl) (trade name "TINUVIN384-2", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN900", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (Trade name "TINUVIN928", manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 (Trade name "TINUVIN1130", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (Trade name "TINUVINP", manufactured by BASF), 2(2H-benzotriazol-2-yl)-4-6-bis(1-methyl- 1-Phenylethyl)phenol (trade name "TINUVIN234", manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (trade name "TINUVIN326", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (trade name "TINUVIN328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN329", manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (trade name "TINUVIN213", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (trade name "TINUVIN571", manufactured by BASF), 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (trade name "Sumisorb250", manufactured by Sumitomo Chemical Co., Ltd.), etc. can be used.

[0121] Examples of benzophenone-based ultraviolet absorbers (benzophenone compounds) and oxybenzophenone-based ultraviolet absorbers (oxybenzophenone 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.

[0122] Examples of salicylic acid ester-based UV absorbers (salicylic acid ester 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).

[0123] Examples of cyanoacrylate-based ultraviolet absorbers (cyanoacrylate compounds) include alkyl-2-cyanoacrylate, cycloalkyl-2-cyanoacrylate, alkoxyalkyl-2-cyanoacrylate, alkenyl-2-cyanoacrylate, and alkynyl-2-cyanoacrylate.

[0124] Furthermore, the adhesive layer of the present invention may also contain a photopolymerization initiator in addition to the one contained in the acrylic polymer. The photopolymerization initiators exemplified above for use with the acrylic polymer can be used as the photopolymerization initiators other than those contained in the acrylic polymer. Note that the photopolymerization initiators other than those contained in the acrylic polymer can be used alone or in combination of two or more types.

[0125] The content (percentage) of photopolymerization initiators other than those contained in the acrylic polymer described above 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, per 100 parts by mass of the acrylic polymer. Furthermore, the content (percentage) of photopolymerization initiators 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, per 100 parts by mass of the acrylic polymer.

[0126] The adhesive layer of the present invention may optionally contain known additives such as crosslinking agents, crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, oil-soluble phenols, etc.), anti-aging agents, fillers, colorants (pigments, dyes, etc.), chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, rust inhibitors, and antioxidants, to the extent that they do not impair the properties of the present invention. Such additives may be used individually or in combination of two or more.

[0127] The glass transition temperature (Tg) calculated from the base polymer and the separately added monomer in the adhesive layer of the present invention is preferably -5°C or higher, more preferably -4°C or higher, and particularly preferably -3°C or higher. A glass transition temperature (Tg) of -5°C or higher makes it easier to achieve a low dielectric constant in the adhesive layer and to exhibit reworkability in the high-speed (low-temperature) range. While there is no particular upper limit, from the viewpoint of exhibiting minimum adhesive strength, it is preferably 20°C or lower, more preferably 15°C or lower, and even more preferably 10°C or lower.

[0128] The glass transition temperature (Tg) mentioned above is a calculated glass transition temperature derived from Fox's formula, which is used to determine the temperature. This calculated glass transition temperature is determined based on the type and amount of each monomer component constituting the adhesive composition, and therefore can be adjusted by selecting the type and amount of each monomer component.

[0129] The calculated glass transition temperature (calculated Tg) can be calculated from the following Fox equation [1]. 1 / Calculation Tg=W1 / Tg(1)+W2 / Tg(2)+···+Wn / Tg(n) [1] Here, W1, W2, ...Wn represent the weight fraction (weight %) of monomer component (1), monomer component (2), ...monomer component (n) that constitute the adhesive composition, relative to the total monomer components, and Tg(1), Tg(2), ...Tg(n) represent the glass transition temperatures (unit: absolute temperature: K) of the homopolymers of monomer component (1), monomer component (2), ...monomer component (n). In this specification, "glass transition temperature (Tg) of homopolymer" (sometimes simply referred to as "Tg of homopolymer") means "glass transition temperature (Tg) of the homopolymer of the monomer," and specifically, the numerical value is given in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1987). For monomer homopolymers not listed in the above literature, the Tg refers to the value obtained by, for example, the following measurement method (see Japanese Patent Publication No. 2007-51271), except for monomers 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 added to a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, and the mixture is 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. Next, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by mass. Then, this homopolymer solution is cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. This test sample is then punched out into a disc shape with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity is measured using a viscoelasticity tester (product name "ARES", manufactured by Rheometrics) in shear mode while applying a shear strain of 1 Hz at a frequency of 1 Hz, in a temperature range of -70 to 150°C, with a heating rate of 5°C / min. The peak top temperature of tanδ is taken as the Tg of the homopolymer.

[0130] The above adhesive composition can be prepared by mixing the above base polymer, and optionally monomer components, polyfunctional (meth)acrylates, silane coupling agents, and other additives, and stirring them uniformly.

[0131] The adhesive sheet of the present invention may be a so-called "substrate-less type" adhesive sheet (hereinafter sometimes referred to as "substrate-less adhesive sheet") that does not have a base material (substrate layer), or it may be an adhesive sheet of the type that has a base material (hereinafter sometimes referred to as "adhesive sheet with base material"). Examples of the above-mentioned substrate-less adhesive sheet include a double-sided adhesive sheet consisting only of the adhesive layer of the present invention, and a double-sided adhesive sheet consisting of the adhesive layer of the present invention and an adhesive layer other than the adhesive layer of the present invention (sometimes referred to as "other adhesive layer"). On the other hand, examples of adhesive sheets with base material include a single-sided adhesive sheet having the adhesive layer of the present invention on one side of the base material, a double-sided adhesive sheet having the adhesive layer of the present invention on both sides of the base material, and a double-sided adhesive sheet having the adhesive layer of the present invention on one side of the base material and another adhesive layer on the other side. Among these, the substrate-less adhesive sheet (substrate-less double-sided adhesive sheet) is preferred, and more preferably, the substrate-less double-sided adhesive sheet consisting only of the above-mentioned adhesive layer. The above-mentioned "substrate (substrate layer)" refers to the support, which is the part that is attached to the adherend together with the adhesive layer when the adhesive sheet of the present invention is used (attached) to an adherend. The release liner that is peeled off when the adhesive sheet is used (attached) is not included in the above-mentioned substrate.

[0132] Figure 1 is a cross-sectional view showing one embodiment of the adhesive sheet of the present invention. 1 is the adhesive sheet, 10 is the adhesive layer of the present invention, and 11 and 12 are release liners. In Figure 1, the adhesive sheet 1 is a substrate-less double-sided adhesive sheet, and the adhesive surfaces on both sides of the adhesive layer 10 of the present invention are protected by release liners 11 and 12.

[0133] The thickness (total thickness) of the adhesive sheet described above is not particularly limited, but is preferably 5 to 600 μm, and more preferably 10 to 500 μm. A thickness above a certain level is preferable for exhibiting drop impact resistance. Conversely, a thickness below a certain level is preferable because it makes it easier to maintain an excellent appearance during manufacturing and roll storage, and prevents adhesive staining during cutting. Note that the thickness of the adhesive sheet does not include the thickness of the release liner.

[0134] The above-mentioned adhesive sheet is not particularly limited, but is preferably manufactured according to known or conventional manufacturing methods. For example, if the adhesive sheet is a substrate-less adhesive sheet, it can be obtained by forming the adhesive layer on a release liner by the method described above. If the adhesive sheet is a substrate-attached adhesive sheet, it can be obtained by directly forming the adhesive layer on the surface of the substrate (direct transfer method), or by first forming the adhesive layer on a release liner and then transferring (bonding) it to the substrate to provide the adhesive layer on the substrate (transfer method).

[0135] The above-mentioned adhesive sheet may have other layers in addition to the adhesive layer of the present invention. Examples of other layers include other adhesive layers (adhesive layers other than the adhesive layer of the present invention), intermediate layers, undercoat layers, etc. The above-mentioned adhesive sheet may have two or more other layers.

[0136] When the above adhesive sheet is an adhesive sheet with a base material, the base material is not particularly limited, but examples include various optical films such as plastic films, anti-reflective (AR) films, polarizing plates, and phase difference plates. Examples of materials for the above plastic films, etc., include polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetylcellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, and cyclic olefin polymers such as the trade name "Arton" (cyclic olefin polymer, manufactured by JSR Corporation) and the trade name "Zeonor" (cyclic olefin polymer, manufactured by Nippon Zeon Co., Ltd.). These plastic materials may be used individually or in combination of two or more. Furthermore, the above "base material" refers to the part that is attached to the adherend together with the adhesive layer when the adhesive sheet is attached to the adherend. The release liner that is peeled off when the adhesive sheet is used (attached) is not included in the "base material".

[0137] The thickness of the above-mentioned substrate is not particularly limited, but is preferably, for example, 12 to 500 μm. The substrate may be in the form of a single layer or multiple layers. Furthermore, the surface of the substrate may be appropriately subjected to known and conventional surface treatments, such as physical treatments like corona discharge treatment or plasma treatment, or chemical treatments like primer treatment.

[0138] The above-mentioned adhesive sheet may have a release liner on the adhesive surface until use. If the above-mentioned adhesive sheet is a double-sided adhesive sheet, each adhesive surface may be protected by two release liners, or it may be protected by a single release liner with both sides being release surfaces, in a roll-like manner. The release liner is used as a protective material for the adhesive layer and is peeled off when it is applied to the substrate. Furthermore, if the above-mentioned adhesive sheet is a substrate-less adhesive sheet, the release liner also serves as a support for the adhesive layer. Note that the release liner is not necessarily required.

[0139] The above-mentioned peel-off liners are not particularly limited, but examples include peel-off liners having a release layer (release treatment layer) on at least one surface of the peel-off liner substrate, low-adhesion peel-off liners made of fluorine-based polymers, and low-adhesion peel-off liners made of non-polar polymers. The release treatment agents constituting the above-mentioned release layer are not particularly limited, but examples include silicone-based release treatment agents, fluorine-based release treatment agents, long-chain alkyl-based release treatment agents, and molybdenum sulfide. The above-mentioned fluorine-based polymers are not particularly limited, but examples include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. The above-mentioned non-polar polymers are not particularly limited, but examples include olefin resins such as polyethylene (PE) and polypropylene (PP). Among these, it is preferable to use a peel-off liner having a release layer on at least one surface of the peel-off liner substrate.

[0140] The above-mentioned peel-off liner substrate is not particularly limited, but examples include plastic films. Examples of such plastic films include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); olefin resins with α-olefins as monomer components such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer (EVA); polyvinyl chloride (PVC); vinyl acetate resin; polycarbonate (PC); polyphenylene sulfide (PPS); amide resins such as polyamide (nylon) and fully aromatic polyamide (aramid); polyimide resin; and polyetheretherketone (PEEK). Among these, plastic films formed from polyester resins are preferred from the viewpoint of processability, availability, workability, dustproofness, and cost, and PET films are more preferred.

[0141] The above-mentioned peel liner can be manufactured by known and conventional methods. In addition, layers such as carrier material and conductive treatment layer may be laminated on the peel layer and / or back surface of the peel liner by known methods, and the above-mentioned peel liner may have other layers (e.g., intermediate layer, undercoat layer, etc.) to the extent that it does not impair the effects of the present invention.

[0142] The thickness of the release liner is not particularly limited, but from viewpoints such as cost and handling of the adhesive sheet during bonding, it is preferably 12 to 200 μm, more preferably 25 to 150 μm, and even more preferably 38 to 125 μm.

[0143] The adhesive sheet of the present invention has an adhesive layer of the present invention, so noise is reduced, it has sufficient adhesive strength, and it has excellent resistance to drop impact. For this reason, the above adhesive sheet is useful in image display devices and touch panels that incorporate touch sensors into such image display devices for attaching optical components such as polarizing films, phase difference films, optical compensation films, touch sensor films, and cover films to the image display panel, or for attaching these optical components to each other.

[0144] The above-mentioned adhesive sheet is preferably used in the manufacture of portable electronic devices. Examples of such portable electronic devices include mobile phones, PHS phones, 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.

[0145] The above-mentioned adhesive sheet is preferably used, for example, for bonding components and modules that make up portable electronic devices to each other, or for fixing components and modules that make up portable electronic devices to the casing. More specifically, examples include bonding cover glass or lenses (especially glass lenses) to touch panels or touch sensor films (especially touch sensor films with metal wiring such as metal mesh films or silver nanowire films), bonding polarizing films to touch panels or touch sensors, bonding display panels to touch panels or touch sensor films, fixing cover glass or lenses (especially glass lenses) to the casing, fixing display panels to the casing, fixing input devices such as sheet keyboards and touch panels to the casing, bonding protective panels for information display sections to the casing, bonding casings to each other, bonding casings to decorative sheets, and fixing or bonding various components and modules that make up portable electronic devices. In this specification, a display panel refers to a structure that is at least composed of a lens (especially a glass lens) and a touch panel. In this specification, a lens is a concept that includes both transparent materials that exhibit light refraction and transparent materials that do not exhibit light refraction. In other words, the term "lens" in this specification also includes simple window panels that do not have a refractive effect.

[0146] Furthermore, the above-mentioned adhesive sheet is preferably used for optical applications. That is, the above-mentioned adhesive sheet is preferably an optical adhesive sheet used for optical applications. More specifically, it is preferably used for applications such as bonding optical components together (for bonding optical components) or for manufacturing products using the above-mentioned optical components (optical products).

[0147] [Optical components with adhesive layer, image display devices, touch panels] The adhesive-coated optical member of the present invention is an optical member having an adhesive sheet of the present invention attached to at least one side of the optical member, and is not particularly limited in any other respect. Because the above adhesive-coated optical member is formed by attaching the adhesive sheet of the present invention, noise is reduced, sufficient adhesive strength is achieved, and drop impact resistance can be exhibited.

[0148] Furthermore, the above-mentioned optical component with an adhesive layer may be an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, to which the adhesive sheet of the present invention is attached. In that case, it is preferable that the adhesive sheet of the present invention is attached to the side of the touch sensor film that has the metal wiring.

[0149] Figure 2 is a cross-sectional view showing one embodiment of the adhesive-layered optical member of the present invention. In Figure 2(a), 2A is the adhesive-layered optical member, 20 is the adhesive layer of the present invention, 21 is the optical member, and 22 is the release liner. The adhesive layer 20 of the present invention is laminated on one side of the optical member 21, and the adhesive surface of the adhesive layer 20 of the present invention opposite the optical member 21 is protected by the release liner 22.

[0150] 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 of the present invention, 23 is the touch sensor film, 22 is the release liner, and 24 is the metal wiring. The adhesive layer 20 of the present invention is 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 of the present invention opposite the touch sensor film 23 is protected by the release liner 22. The optical component with an adhesive layer 2A and the touch sensor film 2B with an adhesive layer, equipped with the adhesive layer 20 of the present invention, reduce noise generation, have sufficient adhesive strength, and exhibit drop impact resistance.

[0151] The above-mentioned optical components refer to components that have optical properties (for example, polarization, refractiveness, scattering, reflectivity, transmission, absorption, diffraction, optical rotation, visibility, etc.). The substrates constituting the optical components described above are not particularly limited, but examples include substrates constituting devices (optical devices) such as image display devices and touch panels, or substrates used in such devices. Examples include polarizing films, waveplates, phase difference films, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflective films, hard coat films (films in which at least one side of a plastic film such as a PET film is hard-coated), transparent conductive films (for example, plastic films having an ITO layer on the surface (preferably ITO films such as PET-ITO, polycarbonate, or cycloolefin polymer)), decorative films, ornamental films, surface protection plates, prisms, lenses, color filters, transparent substrates (glass sensors, glass display panels (LCDs, etc.), glass substrates such as glass plates with transparent electrodes, etc.), and even substrates on which these are laminated (these are sometimes collectively referred to as "functional films"). Furthermore, these films may have metal wiring such as metal nanowire layers or conductive polymer layers. In addition, these films may have fine metal wires printed on them as a mesh. Furthermore, the terms "plate" and "film" above include forms such as plate-like, film-like, and sheet-like shapes, respectively. For example, "polarizing film" includes "polarizing plates" and "polarizing sheets," etc. Also, "film" includes film sensors, etc.

[0152] Furthermore, the adhesive sheet can be suitably used with transparent conductive films (metal mesh films, silver nanowire films) in which the metal wiring is metal mesh wiring or silver nanowires, and especially with optical components (touch sensor films) having a metal mesh film. When optical components having metal wiring such as metal mesh films or silver nanowire films are bonded together via the adhesive sheet, sufficient adhesive strength is achieved while suppressing noise generation, and excellent resistance to drop impacts is obtained.

[0153] Therefore, image display devices and touch panels having the adhesive sheet of the present invention can reduce malfunctions caused by noise generation and exhibit drop impact resistance. Examples of the above-mentioned image display devices include liquid crystal displays, organic EL (electroluminescent) displays, PDP (plasma display panels), and electronic paper.

[0154] Figure 3 is a cross-sectional view showing one embodiment of the image display device of the present invention. In Figure 3, 3 is the image display device, 30 and 31 are the adhesive layers of the present invention, 32 is the image display panel, 33 is the polarizing film, and 34 is the transparent substrate. The image display device 3 is constructed by laminating the image display panel 32, the adhesive layer 30 of the present invention, the polarizing film 33, the adhesive layer 31 of the present invention, and the transparent substrate 34 in this order. The image display device 3 equipped with the adhesive layers 30 and 31 of the present invention suppresses noise generation and exhibits drop impact resistance because it is equipped with the adhesive layers of the present invention. Note that one of the adhesive layers 30 and 31 of the present invention may be composed of an adhesive layer other than the adhesive layer of the present invention.

[0155] The touch panel of the present invention is an image display device that incorporates an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film.

[0156] Figure 4 is a cross-sectional view showing one embodiment of the touch panel of the present invention. In Figure 4, 4 is the touch panel, 40 and 41 are the adhesive layers of the present invention, 42 is the image display panel, 43 is the touch sensor film, 44 is the transparent substrate, and 45 is the metal wiring. The touch panel 4 is constructed by laminating the image display panel 42, the adhesive layer 40 of the present invention, the touch sensor film 43, the adhesive layer 41 of the present invention, and the transparent substrate 44 in this order. The touch panel 4 equipped with the adhesive layers 40 and 41 of the present invention suppresses noise generation and exhibits drop impact resistance because it is equipped with the adhesive layers of the present invention. Note that one of the adhesive layers 40 and 41 of the present invention may be composed of an adhesive layer other than the adhesive layer of the present invention.

[0157] The image display device and touch panel of the present invention may further include optical elements such as waveplates, phase difference films, and optical compensation films. These optical elements may be one or more in number. The manner in which these optical elements are bonded together is not particularly limited, but examples include (1) bonding the adhesive layer-equipped optical elements of the present invention via the adhesive sheet of the present invention, and (2) bonding the adhesive layer-equipped optical elements of the present invention via an adhesive sheet other than the adhesive sheet of the present invention.

[0158] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. [Examples]

[0159] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0160] [Manufacturing 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 (trade name "Omnirad184", manufactured by IGM Resins BV) and 0.035 parts by mass of another photopolymerization initiator (trade name "Omnirad651", manufactured by IGM Resins BV). 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 above monomer components had polymerized.

[0161] [Manufacturing 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 another photopolymerization initiator (trade name "Omnirad651", manufactured by IGM Resins BV). 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 above monomer components had polymerized.

[0162] [Manufacturing Example 3: Preparation of Polymer C] 40 parts by mass of dicyclopentanyl methacrylate (DCPMA, dicyclopentanyl methacrylate) (trade name "FA-513M", manufactured by Resona Corporation) and 60 parts by mass of methyl methacrylate were placed in a four-necked flask as monomer components, 3 parts by mass of thioglycolic acid as a chain transfer agent, and 100 parts by mass of ethyl acetate as a polymerization solvent. The mixture was then stirred at 70°C for 1 hour under a nitrogen atmosphere, and then 0.2 parts by mass of 2,2'-azobisisobutyronitrile was added as a polymerization initiator. The mixture was reacted at 70°C for 2 hours, followed by a reaction at 80°C for 2 hours. The reaction mixture was then placed under a temperature atmosphere of 130°C to dry and remove the ethyl acetate, chain transfer agent, and unreacted monomers, yielding a solid polymer C. The weight-average molecular weight of polymer C was 2500.

[0163] [Example 1] To 100 parts by mass of polymer A obtained in Production Example 1, 80 parts by mass of isostearyl acrylate (ISTA), 10 parts by mass of butyl acrylate (BA), 20 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.2 parts by mass of 1,6-hexanediol diacrylate (trade name "NK Ester A-HD-N", manufactured by Shin Nakamura Chemical Industry Co., Ltd.), 5 parts by mass of polymer C obtained in Production Example 3, 0.35 parts by mass of silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.3 parts by mass of photopolymerization initiator (trade name "Omnirad819", manufactured by IGM Resins BV) were added and mixed to obtain an adhesive composition (pre-curing composition).

[0164] The above adhesive composition was applied to a polyethylene terephthalate (PET) release liner (first release liner, trade name "MRF75", manufactured by Mitsubishi Chemical Corporation) to a final thickness (thickness of the adhesive layer) of 25 μm, forming a coated layer (adhesive composition layer). Next, a PET release liner (second release liner, trade name "MRE75", manufactured by Mitsubishi Chemical Corporation) was placed on the coated layer to cover the coated layer and block oxygen. A laminate of [MRF75 / coated layer (adhesive composition layer) / MRE75] was then obtained. Next, a black light (manufactured by Toshiba Corporation) was used on the top surface of the laminate (MRF75 side) to measure an illuminance of 5 mW / cm². 2 The material was irradiated with ultraviolet light for 300 seconds. It was then dried in a 90°C dryer for 2 minutes. This resulted in a substrate-less double-sided adhesive sheet consisting only of an adhesive layer, with both sides of the adhesive layer protected by a release liner.

[0165] [Comparative Examples 1-3] A substrate-less double-sided adhesive sheet was obtained in the same manner as in Example 1, except that the adhesive composition was as shown in Table 1. Unless otherwise specified, the units of the numerical values ​​in Table 1 represent parts by mass.

[0166] The 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 BA: n-butyl acrylate TMPTA: Trimethylolpropane triacrylate Silane coupling agent: Product name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd. TinosorbS: UV absorber, brand name "TinosorbS", manufactured by BASF. Omnirad819: Photopolymerization initiator, trade name "Omnirad819", manufactured by IGM Resins BV.

[0167] [evaluation] The following evaluations were performed on the substrate-less double-sided adhesive sheets obtained in the examples and comparative examples, and the results are shown in Table 1.

[0168] (1) Dielectric constant (Dk) The adhesive layer obtained by peeling off the release liner from the substrate-less double-sided adhesive sheets obtained in the examples and comparative examples was sandwiched between copper foil and an electrode, and the dielectric constant at a frequency of 100 kHz was measured using the following apparatus. Measurements were performed on three independently prepared samples, and the average of the measured values ​​of these three samples was taken as the dielectric constant. The dielectric constant of the adhesive layer at a frequency of 100 kHz was measured in accordance with JIS K 6911 under the following conditions. Measurement method: Volumetric method (Equipment: Agilent Technologies 4294A Precision Impedance Analyzer) Electrode configuration: 12.1mm diameter, 0.5mm thick aluminum plate Counter electrode: 3oz copper plate Measurement environment: 23±1℃, 52±1%RH

[0169] (2) Glass adhesion Measurement samples were prepared by cutting the substrate-less double-sided adhesive sheets obtained in the examples and comparative examples to a size of 20 mm in width and 80 mm in length. The adhesive layer surface of the measurement samples was exposed in an environment of 23°C and 50% RH, and this adhesive layer surface was bonded to a glass plate (thickness 0.7 mm). The samples were autoclaved at 50°C and 0.5 MPa for 15 minutes to ensure adhesion. After being stored for 1 day in an environment of 23°C and 50% RH, the substrate-less double-sided adhesive sheets were peeled from the glass plate using a tensile testing machine under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min, and the glass adhesive strength (10 N / 20 mm) was measured (glass adhesive strength (immediately after)). Furthermore, the glass adhesive strength (10N / 20mm) of the substrate-less double-sided adhesive sheet was measured in the same manner as the glass adhesive strength (immediately after measurement) after the above substrate-less double-sided adhesive sheet was bonded to a glass plate and stored at room temperature (23°C, 50%RH) for 6 months (glass adhesive strength (after 6 months)). A universal tensile and compression tester (device name "Tensile and Compression Tester TCM-1kNB", manufactured by MinebeaMitsumi Inc.) was used as the tensile testing machine. In addition, if necessary (for example, if the substrate is easily deformed), an appropriate backing material can be attached to the adhesive tape to be measured to reinforce it. As a backing material, for example, a PET film with a thickness of about 50 μm can be used, and this backing material was used in the examples and comparative examples described herein.

[0170] (3) Glass transition temperature (Tg) The glass transition temperature (Tg) of the substrate-less double-sided adhesive sheets obtained in the examples and comparative examples was calculated using Fox's formula described above.

[0171] (4) Dielectric loss tangent For the substrate-less double-sided adhesive sheets obtained in the examples and comparative examples, the frequency was set to 10 3 Hz~10 4 The dielectric loss tangent was measured in the same manner as the dielectric constant described above, except that it was set to Hz (dielectric loss tangent (immediately after)). In addition, the dielectric loss tangent of the substrate-less double-sided adhesive sheet, which was stored at room temperature (23°C, 50%RH) for 6 months after fabrication, was also measured in the same manner as the dielectric loss tangent (immediately after) described above (dielectric loss tangent (6 months later)).

[0172] (5) Drop impact resistance (Creation of evaluation samples) As shown in Figure 5, the substrate-less double-sided adhesive sheet 1 obtained in the examples and comparative examples was cut to a length of 75 mm x width of 45 mm, the second release liner was peeled off, and the exposed adhesive surface was bonded to the center of the first glass plate 51 (length 100 mm x width 75 mm, thickness 500 μm) along all four sides. A roll laminator was used for bonding, with a roll pressure of 0.2 MPa and a feed speed of 100 mm / min. Next, the first release liner was peeled off the adhesive sheet 1 on the first glass plate 51, and the exposed adhesive surface was bonded to the center of the second glass plate 52 (length 100 mm x width 50 mm, thickness 500 μm) with a printed layer 53 along all four sides to obtain a bonded body. A ring-shaped printed layer 53 (thickness 30 μm, black ink layer) is formed on the bonded surface of the second glass plate 52. Specifically, the printed layer 53 is formed such that it is 15 mm wide in the direction of the long side from the short side edge of the second glass plate 52, and 5 mm wide in the direction of the short side from the long side edge. The adhesive sheet 1 is attached to the center of the second glass plate 52, and the adhesive sheet 1 is in contact with the printed layer 53 at a width of 2.5 mm along the entire circumference of all four edges. That is, on both the long and short sides, a 2.5 mm area of ​​the printed layer 53 on the second glass plate 52 is sandwiched between the second glass plate 52 and the adhesive sheet 1. An evaluation sample was prepared by heat-treating this joint at 50°C, 0.5 MPa, and for 30 minutes. Figure 5(a) shows a plan view of the evaluation sample, Figure 5(b) shows a cross-sectional view of the evaluation sample in the direction of the short side (cross section b-b' in Figure 5(a)), and Figure 5(c) shows a cross-sectional view of the evaluation sample in the direction of the long side (cross section c-c' in Figure 5(a)).

[0173] The above evaluation samples were stored for one day after preparation, and then the following drop impact resistance tests were conducted. The evaluation sample was placed on a support stand such that the first glass plate was positioned on top, and both ends of the first glass plate in the width direction were supported from below by the support stand, with the lower second glass plate not in contact with the support stand. Next, the evaluation sample on the support stand was fixed to the support stand with adhesive tape. Then, the support stand and evaluation sample were kept in a -5°C environment for 24 hours. After the support stand and evaluation sample were returned to room temperature, a metal ball was dropped onto the evaluation sample on the support stand within 40 seconds, causing the metal ball to collide with the first glass plate of the evaluation sample. The mass of the metal ball was 15g. The position where the metal ball landed on the evaluation sample was 10mm away from the printed layer in both the length and width directions. Two tests (tests with different samples) were performed for each adhesive sheet (n=2). The height from which the metal ball was dropped in the first test was 300mm, and the height from which the metal ball was dropped in the second test was 400mm. Regarding the drop impact resistance of the adhesive sheet, a "Superior" rating was given if no peeling (the phenomenon in which one or more voids of 100 μm or more occur in the bonding area between the substrate-less double-sided adhesive sheet and the glass plate) occurred in the first and second tests, a "Fair" rating was given if no peeling occurred only in the first test, and a "Poor" rating was given if peeling occurred in both the first and second tests (Drop Impact Resistance (Immediately After)). Furthermore, the drop impact resistance of the evaluation samples was measured in the same manner as described above after being stored at 80°C for one week and at room temperature for six months (Drop Impact Resistance (After 1 Week at 80°C), Drop Impact Resistance (After 6 Months)).

[0174] (6) Transmittance The transmittance of the adhesive layer obtained by peeling off the release liner from the substrate-less double-sided adhesive sheets obtained in the examples and comparative examples was evaluated at different wavelengths (wavelength range: 300~800nm) using a spectrophotometer (model "U4100", manufactured by Hitachi High-Tech Corporation). The transmittance at wavelengths of 380nm and 420nm was then obtained.

[0175] [Table 1]

[0176] The substrate-less double-sided adhesive sheet of the example was evaluated to have a sufficiently low dielectric constant, thereby reducing noise generation. Furthermore, it was confirmed to have sufficient glass adhesive strength, easy adhesion to the substrate, and drop impact resistance. Moreover, even after storage at 80°C for one week and six months, it was confirmed to maintain a sufficiently low dielectric constant, sufficient glass adhesive strength, and drop impact resistance. In addition, it was evaluated to have high transmittance at both 380nm and 420nm, a wide wavelength selectivity range, and the ability to cure quickly even at low illumination. On the other hand, when the dielectric constant of the adhesive layer was high (Comparative Example 1), noise generation was evaluated to be insufficient. When the dielectric loss tangent in the high-speed region was small, although low dielectric constant was achieved, drop impact resistance could not be exhibited (Comparative Example 2). Also, when the transmittance was low at 380nm (Comparative Example 3), light did not sufficiently penetrate the adhesive layer at wavelengths other than 420nm, where the transmittance was high, resulting in low wavelength selectivity.

[0177] The following describes variations of the invention relating to this disclosure. [Note 1] Having an adhesive layer, The adhesive layer does not peel off in the following drop impact test, has a dielectric constant of 4 or less at a frequency of 100 kHz, has a glass adhesive strength of 10 N / 20 mm or more under the conditions of a peel angle of 180° on at least one side and a tensile speed of 300 mm / min, and has a transmittance of 80% or more at both a wavelength of 380 nm and a wavelength of 420 nm. Adhesive sheets used in optical components. <Drop Impact Resistance Test> A first glass plate (100 mm long x 75 mm wide, 500 μm thick), the adhesive layer (75 mm long x 45 mm wide), a printed layer (30 μm thick) formed within a 15 mm radius around the edge of the second glass plate, and the second glass plate (100 mm long x 50 mm wide, 500 μm thick) are stacked in that order, and a bonded body is produced by heat treatment at 50°C, 0.5 MPa, and 30 minutes. The bonded body is placed on a support base so that only the protruding portions at both ends in the width direction of the first glass plate are supported by the support base, and the second glass plate is not in contact with the support base, with the first glass plate on the upper side of the bonded body. A metal ball with a mass of 15 g is dropped from a height of 300 mm toward the first glass plate, and it is checked whether or not the adhesive layer and the first glass plate or the printed layer peel off. [Note 2] The adhesive sheet described in Note 1, which does not peel off in the drop impact resistance test after the joint is manufactured and stored at 80°C for one week. [Note 3] The adhesive sheet described in Note 1 or 2, which does not peel off in the drop impact resistance test after the joint has been manufactured and stored at room temperature for 6 months. [Note 4] The adhesive sheet according to any one of Notes 1 to 3, wherein the ratio of the adhesive sheet to the glass adhesive strength after being bonded to a glass plate and stored at room temperature for 6 months, under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min of the adhesive layer, is 1.0 to 2.0. [Note 5] An optical component with an adhesive layer, wherein an adhesive sheet described in any one of Notes 1 to 4 is attached to at least one side of the optical component. [Note 6] An image display device having an optical component with an adhesive layer as described in Note 5. [Note 7] The image display device described in Note 6, which is a touch panel. [Explanation of Symbols]

[0178] 1 Adhesive sheet 10. The adhesive layer of the present invention 11, 12 Peel-off liner 2A Optical component with adhesive layer 2B Touch sensor film with adhesive layer 20 The adhesive layer of the present invention 21 Optical components 22. Peel-off liner 23 Touch Sensor Film 24 Metal wiring 3 Image display device 30, 31 The adhesive layer of the present invention 32 Image display panel 33 Polarizing film 34 Transparent substrate 4 Touch panel 40, 41 The adhesive layer of the present invention 42 Image display panel 43 Touch Sensor Film 44 Transparent substrate 45 Metal wiring

Claims

1. Having an adhesive layer, The adhesive layer does not peel off in the following drop impact test, has a dielectric constant of 4 or less at a frequency of 100 kHz, has a glass adhesive strength of 10 N / 20 mm or more under the conditions of a peel angle of 180° on at least one side and a tensile speed of 300 mm / min, and has a transmittance of 80% or more at both a wavelength of 380 nm and a wavelength of 420 nm. Adhesive sheets used in optical components. <Drop Impact Resistance Test> A first glass plate (100 mm long x 75 mm wide, 500 μm thick), the adhesive layer (75 mm long x 45 mm wide), a printed layer (30 μm thick) formed within a 15 mm radius around the edge of the second glass plate, and the second glass plate (100 mm long x 50 mm wide, 500 μm thick) are stacked in that order, and a bonded body is produced by heat treatment at 50°C, 0.5 MPa, and 30 minutes. The bonded body is placed on a support base so that only the protruding portions at both ends in the width direction of the first glass plate are supported by the support base, and the second glass plate is not in contact with the support base, with the first glass plate on the upper side of the bonded body. A metal ball with a mass of 15 g is dropped from a height of 300 mm toward the first glass plate, and it is checked whether or not the adhesive layer and the first glass plate or the printed layer peel off.

2. The adhesive sheet according to claim 1, wherein no peeling occurs in the drop impact resistance test after the joint is manufactured and stored at 80°C for one week.

3. The adhesive sheet according to claim 1 or 2, wherein the bonded body does not peel off in the drop impact resistance test after being stored at room temperature for 6 months after being manufactured.

4. The adhesive sheet according to claim 1 or 2, wherein the ratio of the glass adhesive strength to the aforementioned glass adhesive strength is 1.0 to 2.0 when the adhesive sheet is bonded to a glass plate and stored at room temperature for 6 months, under the conditions of a peel angle of 180° and a tensile speed of 300 mm / min of the adhesive layer.

5. An optical member with an adhesive layer, wherein the adhesive sheet described in claim 1 or 2 is attached to at least one side of the optical member.

6. An image display device having an optical member with an adhesive layer as described in claim 5.

7. The image display device according to claim 6, wherein it is a touch panel.

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