Pressure-sensitive adhesive sheet, optical member, and touch panel

Abstract

The purpose of this invention is to provide an adhesive sheet, optical component, or touch panel that can form an adhesive layer that does not easily reduce the appearance of the display device or input device even under low pressure conditions. The adhesive sheet of the present invention has an adhesive layer, and in the following low-pressure test, the number of voids with a diameter of 300 μm or more is less than 10, and the number of voids with a diameter of 50 μm or more but less than 300 μm is less than 20. Low-pressure test A 5 cm × 10 cm display panel with a laminated structure of glass plate / polarizing plate / adhesive layer / glass plate was prepared as a sample. The thickness of the glass plate was 700 μm, the thickness of the polarizing plate was 115 μm (95 μm for the polarizing plate + 20 μm for the polarizing plate adhesive), and the thickness of the adhesive layer was 150 μm. The display panel was subjected to a heating and decompression condition of 23800 Pa and 65°C, and then left to stand for 8 hours. After being placed at room temperature and atmospheric pressure for 30 minutes, the diameter and number of gaps were visually measured.

Description

Technical Field

[0001] This invention relates to an adhesive sheet, an optical component, and a touch panel. Prior Technology

[0002] In recent years, display devices such as liquid crystal displays (LCDs) and input devices such as touch panels used in conjunction with such display devices have become widely used in various fields. In these display devices or input devices, adhesive sheets with an adhesive layer are used for bonding optical components. For example, transparent adhesive sheets are used for bonding touch panels to various display components or optical components (see, for example, Patent Documents 1-3).

[0003] In applications such as the manufacture of touch panels using electrostatic capacitive methods, adhesive sheets are sometimes directly attached to metal thin films or metal oxide thin films such as ITO (indium tin oxide) film (hereinafter, metal thin films and metal oxide thin films are sometimes collectively referred to as "metal thin films").

[0004] In recent years, in applications such as the manufacture of capacitive touch panels, the use of films with metal mesh wiring formed by processing metals such as silver or copper into a mesh (metal mesh film) or films with a silver nanowire layer (AgNW layer) (silver nanowire film) as metal films has been increasing, replacing the previous ITO films. Capacitive touch panels using metal mesh films or silver nanowire films are input devices that effectively utilize the characteristics of low-resistance metal wiring, providing high sensitivity and broad applicability to displays ranging from small to large sizes.

[0005] If optical components with metal wiring, such as metal mesh films or silver nanowire films, are bonded to an adhesive sheet, the following problem arises: the stress and strain applied to the adhesive around the metal wiring can easily cause uneven display at the periphery of the image display panel. Therefore, to prevent uneven display, the adhesive layer of the adhesive sheet used to bond the optical components with metal wiring must be flexible enough to mitigate the stress on the metal wiring. [Previous Technical Documents] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2003-238915 [Patent Document 2] Japanese Patent Application Publication No. 2003-342542 [Patent Document 3] Japanese Patent Application Publication No. 2004-231723 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] However, display devices or input devices that use highly flexible adhesive sheets for bonding to prevent uneven display have the following problems: their appearance will be reduced under low-pressure conditions such as manufacturing processes, cargo holds of passenger aircraft, or high-altitude areas.

[0009] Therefore, the object of the present invention is to provide an adhesive sheet suitable for bonding metal mesh films, etc., which do not easily reduce the appearance of display devices or input devices even under low pressure conditions. Furthermore, another object of the present invention is to provide a high-performance optical component and touch panel having the adhesive sheet, and whose appearance is not easily reduced even under low pressure conditions. [Technical means to solve the problem]

[0010] The first embodiment of the present invention provides an adhesive sheet having an adhesive layer. In the adhesive sheet of the first embodiment of the present invention, the number of voids with a diameter of 300 μm or more in the low-pressure test is less than 10, and the number of voids with a diameter of 50 μm or more but less than 300 μm is less than 20. Low-pressure test A 5 cm × 10 cm display panel with a laminated structure of glass plate / polarizing plate / adhesive layer / glass plate was prepared as a sample. The thickness of the glass plate was 700 μm, the thickness of the polarizing plate was 115 μm (95 μm for the polarizing plate + 20 μm for the polarizing plate adhesive), and the thickness of the adhesive layer was 150 μm. The display panel was subjected to a heating and decompression condition of 23800 Pa and 65°C, and then left to stand for 8 hours. After being placed at room temperature and atmospheric pressure for 30 minutes, the diameter and number of gaps were visually measured.

[0011] Furthermore, in this specification, the adhesive sheet of the first embodiment of the present invention is sometimes referred to as "the adhesive sheet of the present invention", and the adhesive layer constituting "the adhesive sheet of the present invention" is sometimes referred to as "the adhesive layer of the present invention".

[0012] In the adhesive sheet of the present invention, from the viewpoint that the appearance of the display device or input device is not easily reduced under low pressure conditions, it is more suitable to have a configuration in which the number of gaps with a diameter of 300 μm or more is less than 10 and the number of gaps with a diameter of 50 μm or more but less than 300 μm is less than 20.

[0013] In the adhesive sheet of the present invention, the maximum diameter of the void portion during the aforementioned low-pressure test is preferably 600 μm or less. From the viewpoint that the appearance of the display device or input device is not easily degraded under low-pressure conditions, this configuration is more suitable.

[0014] In the adhesive sheet of the present invention, the gel content of the adhesive layer is preferably 50% or more. This configuration is more suitable in that the appearance of the display device or input device is not easily degraded even under low pressure conditions.

[0015] In the adhesive sheet of the present invention, the 300% tensile residual stress of the adhesive layer is preferably below 5 N / cm². This configuration is more suitable for applications requiring high flexibility, such as laminating films with metal wiring, such as metal mesh films or silver nanowire films, to adequately alleviate stress on the metal wiring and prevent uneven display.

[0016] In the adhesive sheet of the present invention, the adhesive layer is preferably formed of an adhesive composition containing an acrylic polymer (A) and a hydrogenated polyolefin resin (B). Furthermore, the adhesive layer of the present invention is also preferably formed of an adhesive composition containing a mixture of monomer components constituting the acrylic polymer (A) or a portion of a mixture of monomer components constituting the acrylic polymer (A) and a hydrogenated polyolefin resin (B). Furthermore, in this specification, the adhesive composition constituting the adhesive layer of the present invention is sometimes referred to as "the adhesive composition of the present invention". Furthermore, in this specification, the term "acrylic polymer (A)" unless otherwise specified includes both "acrylic polymer (A)" and "a mixture of monomeric components constituting acrylic polymer (A) or a portion of a mixture of monomeric components constituting acrylic polymer (A)".

[0017] The adhesive composition of the present invention comprising an acrylic polymer (A) is preferred in that it can achieve an adhesive layer with high flexibility, and when laminating films with metal wiring such as metal mesh films or silver nanowire films, it can also adequately alleviate the stress of the metal wiring and prevent uneven display.

[0018] Furthermore, in terms of achieving an adhesive layer that does not easily degrade the appearance of the display device or input device even under low-pressure conditions, the adhesive composition of the present invention is more suitable in which hydrogenated polyolefin resin (B) is included.

[0019] In the adhesive sheet of the present invention, the aforementioned acrylic polymer (A) is preferably a monomer component comprising an alkyl (meth)acrylate having an alkyl group having 8 or more carbon atoms. In this specification, the "alkyl (meth)acrylate having an alkyl group having 8 or more carbon atoms" is sometimes referred to as "(meth)acrylate (A)".

[0020] In the adhesive composition of the present invention, the acrylic polymer (A) comprising (meth)acrylate alkyl ester (A) as a constituent monomer component is preferred in the following aspects: it can achieve an adhesive layer with high flexibility, and when laminating films with metal wiring such as metal mesh films or silver nanowire films, it can also adequately alleviate the stress of the metal wiring and prevent uneven display.

[0021] In the adhesive sheet of the present invention, the hydrogenated polyolefin resin (B) preferably contains hydrogenated polyolefin. The adhesive composition of the present invention comprising the hydrogenated polyolefin resin (B) is suitable as a component of the hydrogenated polyolefin in the following ways: it enables the achievement of an adhesive layer whose appearance of the display device or input device is not easily degraded even under low-pressure conditions.

[0022] In the adhesive sheet of the present invention, the hydrogenated polyolefin resin (B) preferably further contains a hydrogenated polyolefin polyol. This configuration is more suitable in terms of achieving an adhesive layer that does not easily degrade the appearance of the display device or input device even under low pressure conditions.

[0023] From the viewpoint of effectively mitigating stress on the metal wiring, preventing uneven display, and easily maintaining an excellent appearance, the thickness of the adhesive sheet of the present invention is preferably 12~350 μm.

[0024] The second embodiment of the present invention provides an optical component having at least the adhesive sheet and substrate of the present invention, wherein the substrate has metal wiring on at least one side, and the adhesive sheet is attached to the side of the substrate having the metal wiring. In this specification, the optical component of the fifth embodiment of the present invention is sometimes referred to as "the optical component of the present invention".

[0025] Furthermore, a third embodiment of the present invention provides a touch panel that has at least the adhesive sheet and substrate of the present invention, wherein the substrate has metal wiring on at least one side, and the adhesive sheet is attached to the side of the substrate having the metal wiring. In this specification, the touch panel of the third embodiment of the present invention is sometimes referred to as "the touch panel of the present invention".

[0026] In the optical components and touch panels of the present invention, the aforementioned metal wiring is preferably a metal mesh wiring or silver nanowires.

[0027] The optical components and touch panel of the present invention do not easily degrade the appearance of the display device or input device even under low pressure conditions. Furthermore, by using a flexible adhesive sheet to bond metal mesh wiring or silver nanowires and other metal wiring, uneven display is less likely to occur. [Effects of the Invention]

[0028] The adhesive sheet of this invention provides a display device or input device whose appearance is not easily degraded even under low-pressure conditions. Furthermore, when bonding films with metal wiring, such as metal mesh films or silver nanowire films, it can effectively alleviate the stress on the metal wiring and prevent uneven display. Therefore, by using the adhesive sheet of this invention to bond metal mesh films or silver nanowire films, high-performance touch panels and other optical components that do not easily degrade in appearance and are less prone to uneven display, even under low-pressure conditions, can be efficiently manufactured. Therefore, the adhesive sheet of the present invention can be preferably used for attaching to optical components having metal mesh wiring or silver nanowire layers, especially for transparent conductive films such as metal mesh films or silver nanowire films having metal wiring layers. Simple Explanation of the Diagram

[0029] Figure 1 is a schematic diagram showing a preferred embodiment of the optical component of the present invention. Figures 2(A) to (D) are schematic diagrams illustrating specific examples of preferred embodiments of the touch panel of the present invention. Implementation

[0030] [1. Adhesive sheet, adhesive layer, and adhesive composition] The adhesive sheet of the present invention has an adhesive layer, and in the following low-pressure test, the number of voids with a diameter of 300 μm or more is less than 10, and the number of voids with a diameter of 50 μm or more but less than 300 μm is less than 20. Low-pressure test A 5 cm × 10 cm display panel with a laminated structure of glass plate / polarizing plate / adhesive layer / glass plate was prepared as a sample. The thickness of the glass plate was 700 μm, the thickness of the polarizing plate was 115 μm (95 μm for the polarizing plate + 20 μm for the polarizing plate adhesive), and the thickness of the adhesive layer was 150 μm. The display panel was subjected to a heating and decompression condition of 23800 Pa and 65°C, and then left to stand for 8 hours. After being placed at room temperature and atmospheric pressure for 30 minutes, the diameter and number of gaps were visually measured.

[0031] The reason for the reduced appearance of display or input devices under low-pressure conditions is believed to be the formation of microbubbles in the adhesive layer. Therefore, regarding the adhesive layer that ensures minimal reduction in the appearance of display or input devices even under low-pressure conditions, a configuration in the aforementioned low-pressure test is preferable where the number of voids with a diameter of 300 μm or more is less than 10, and the number of voids with a diameter of 50 μm or more but less than 300 μm is less than 20. From the viewpoint that the appearance of the display device or input device is not easily degraded under low-pressure conditions, the adhesive sheet of the present invention preferably has 9 or fewer gaps with a diameter of 300 μm or more in the aforementioned low-pressure test, more preferably 8 or fewer, and even more preferably 6 or fewer, or 5 or fewer, or 4 or fewer. There is no particular limitation on the lower limit of the number of gaps with a diameter of 300 μm or more in the aforementioned low-pressure test, but preferably 0.

[0032] From the viewpoint that the appearance of the display device or input device is not easily degraded under low-pressure conditions, the adhesive sheet of the present invention preferably has 15 or fewer gaps with a diameter of 50 or more but less than 300 μm in the aforementioned low-pressure test, and more preferably 10 or fewer. There is no particular limitation on the lower limit of the number of gaps with a diameter of 50 or more but less than 300 μm in the aforementioned low-pressure test; preferably 0, but also about 1 is possible.

[0033] From the viewpoint that the appearance of the display device or input device is not easily degraded under low-pressure conditions, the maximum diameter of the gap portion of the adhesive sheet of the present invention during the aforementioned low-pressure test is preferably 600 μm or less. From the viewpoint that the appearance of the display device or input device is not easily degraded under low-pressure conditions, the maximum diameter of the gap portion during the aforementioned low-pressure test is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less, and may also be 150 μm or less, or 100 μm or less.

[0034] From the viewpoint that the appearance of the display device or input device is not easily degraded under low-pressure conditions, the number of voids with a diameter of 50 μm or less in the adhesive sheet of the present invention during the aforementioned low-pressure test is not particularly limited. That is, voids with a diameter of 50 μm or less have a smaller impact on appearance, but can also be 100 or less.

[0035] In the adhesive sheet of the present invention, specifically, the diameter or number of voids in the low-pressure test is determined by the low-pressure test in the embodiments disclosed below. For example, it can be adjusted by adjusting the monomer composition of the acrylic polymer (A), the type or amount of crosslinking agent, the type of hydrogenated polyolefin resin (B), and the mixing ratio of acrylic polymer (A) and hydrogenated polyolefin resin (B).

[0036] In the adhesive sheet of the present invention, from the viewpoint that the appearance of the display device or input device is not easily degraded under low pressure conditions, the gel content (ratio of solvent-insoluble components) of the adhesive layer of the present invention is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more, and may also be 65% or more. Furthermore, from the viewpoint that the adhesive layer can be given flexibility to prevent uneven display, the gel content of the adhesive layer of the present invention is preferably 90% or less, more preferably 85% or less, and may also be 80% or less.

[0037] Specifically, the gel fraction (the ratio of solvent-insoluble components) mentioned above is, for example, a value calculated by the following "Method for Determining Gel Fraction".

[0038] Approximately 0.1 g of the self-adhesive sheet adhesive layer was wrapped within a porous tetrafluoroethylene sheet (trade name "NTF1122", manufactured by Nitto Denko Corporation) with an average pore size of 0.2 μm. The sheet was then secured with kite string, and the weight at this point was measured. This weight was designated as the weight before impregnation. Furthermore, this weight before impregnation was the total weight of the adhesive layer (the adhesive layer mentioned above), the tetrafluoroethylene sheet, and the kite string. Additionally, the combined weight of the tetrafluoroethylene sheet and the kite string was also measured beforehand, and this weight was designated as the packaging weight. Next, the sample (referred to as the "sample"), which was wrapped with a tetrafluoroethylene sheet and secured with kite string, was placed in a 50 ml container filled with ethyl acetate and left to stand at 23°C for 7 days. Afterward, the sample (after ethyl acetate treatment) was removed from the container, transferred to an aluminum cup, and dried in a desiccator at 130°C for 2 hours to remove the ethyl acetate. The weight was then measured and recorded as the weight after impregnation. Furthermore, the gel fraction is calculated according to the following formula. Gel fraction [% (weight %)] = (XY) / (ZY) × 100

[0039] The gel fraction can be controlled, for example, by the monomer composition, weight average molecular weight, type or amount of crosslinking agent used (addition amount) of the acrylic polymer (A). Furthermore, when the adhesive composition of the present invention is hardened by ultraviolet irradiation, for example, the carbon-carbon double bonds in the hydrogenated polyolefin resin (B) decrease, thus reducing polymerization inhibition and preventing a decrease in gel fraction.

[0040] The 300% tensile residual stress of the adhesive layer of the present invention is not particularly limited. For applications with excellent flexibility and capable of sufficiently mitigating stress from metal wiring when bonding to films with metal mesh films or silver nanowire films, thus preventing unevenness, a residual stress of 5 N / cm² or less is preferred, more preferably 4.5 N / cm² or less, and even more preferably 4 N / cm² or less. A residual stress of 3.5 N / cm² or less, or 3 N / cm² or less, is also permissible. Furthermore, the 300% tensile residual stress of the adhesive layer of the present invention is not particularly limited. From the viewpoint of adhesion reliability, a residual stress of 0.5 N / cm² or more, or 1 N / cm² or more, is also permissible.

[0041] The aforementioned 300% tensile residual stress was determined by stretching the adhesive layer along its length to an elongation (strain) of 300% at 23°C, maintaining this elongation, and calculating the tensile stress (N) applied to the adhesive layer 300 seconds after the end of the stretching. This tensile stress was then divided by the initial cross-sectional area of ​​the adhesive layer (the cross-sectional area before stretching) to obtain the value (N / cm²). Furthermore, the initial elongation of the adhesive layer was 100%.

[0042] Specifically, the 300% tensile residual stress of the adhesive layer of the present invention is measured by the method described in the examples disclosed below. For example, it can be adjusted by adjusting the monomer composition of the acrylic polymer (A), the type or amount of crosslinking agent, the type of hydrogenated polyolefin resin (B), and the mixing ratio of acrylic polymer (A) and hydrogenated polyolefin resin (B).

[0043] The adhesive layer of this invention is not particularly limited. However, from the viewpoint of preventing malfunctions of optical components such as touch panels having this adhesive layer, it is preferable to control the dielectric constant to be low. The dielectric constant of the adhesive layer of this invention at a frequency of 1 MHz is preferably 3.5 or less, more preferably 3.4 or less, and even more preferably 3.3 or less. The lower limit of the dielectric constant at a frequency of 1 MHz is not particularly limited, but it is preferably 2.3 or more, more preferably 2.4 or more, and even more preferably 2.5 or more. Furthermore, the dielectric constant at a frequency of 100 kHz is preferably 4.0 or less, more preferably 3.9 or less, and even more preferably 3.8 or less. There is no particular limitation on the lower limit of the dielectric constant at a frequency of 100 kHz, but it is preferably 2.3 or more, more preferably 2.4 or more, and even more preferably 2.5 or more.

[0044] The dielectric constant of the adhesive layer of the present invention can be adjusted, for example, by adjusting the monomer composition of the acrylic polymer (A), the type of hydrogenated polyolefin resin (B), and the mixing ratio of acrylic polymer (A) and hydrogenated polyolefin resin (B).

[0045] The adhesive layer of the present invention has excellent transparency. Therefore, the visibility and appearance of the adhesive layer are excellent. Thus, the adhesive layer of the present invention can be suitably used for optical applications.

[0046] The haze of the adhesive layer of the present invention (according to JIS K7136) is not particularly limited, but is preferably 1.0% or less, more preferably 0.8% or less. If the haze is 1.0% or less, excellent transparency or excellent appearance can be obtained, which is preferable. The lower limit of haze is not particularly limited, theoretically it is 0%, and practically it can exceed 0.01%. Furthermore, the above-mentioned haze can be measured, for example, by preparing an adhesive layer (thickness: 100 μm), letting it stand at normal temperature (23°C, 50%RH) for at least 24 hours, and then attaching it to a glass slide (e.g., with a total light transmittance of 92% and a haze of 0.2%) as a sample, and using a haze meter (manufactured by Murakami Color Technology Research Institute Co., Ltd., trade name "HM-150N") or its equivalent.

[0047] The total light transmittance (according to JIS K7361-1) of the adhesive layer of the present invention in the visible light wavelength region is not particularly limited, but preferably 90% or more, more preferably 91% or more, and even more preferably 92% or more. If the total light transmittance is 90% or more, excellent transparency or excellent appearance can be obtained, which is preferable. The upper limit of the total light transmittance is not particularly limited, and theoretically it is the value obtained by subtracting the light loss (Fresnel loss) caused by reflection generated at the air interface from 100%, but in practice it can also be 95% or less. Furthermore, the aforementioned total light transmittance can be obtained, for example, by preparing an adhesive layer (thickness: 100 μm), allowing it to stand at normal temperature (23°C, 50%RH) for at least 24 hours, peeling it off with a release liner, and attaching it to a glass slide (e.g., with a total light transmittance of 92% and a haze of 0.2%) as a sample, and measuring it using a haze meter (manufactured by Murakami Color Technology Research Institute Co., Ltd., trade name "HM-150N") or an equivalent.

[0048] There is no particular limitation on the method for producing the adhesive layer of the present invention. For example, it can be produced by preparing the adhesive composition (precursor composition) of the present invention and subjecting it to active energy line irradiation, heating and drying, etc., as needed. Specifically, examples include the following methods: producing the adhesive layer by adding hydrogenated polyolefin resin (B), other additives, etc., as needed to a mixture of monomer components or a portion thereof, and mixing them together.

[0049] The adhesive layer of the present invention is preferably formed of an adhesive composition containing an acrylic polymer (A) and a hydrogenated polyolefin resin (B). Furthermore, the adhesive layer of the present invention is preferably formed of an adhesive composition containing a mixture of monomer components constituting acrylic polymer (A) or a portion of a mixture of monomer components constituting acrylic polymer (A), and a hydrogenated polyolefin resin (B).

[0050] In addition to the above, the adhesive composition of the present invention may also contain the following polyfunctional (meth)acrylates, silane coupling agents, or other additives. Furthermore, in this specification, the term "mixture of monomeric components" includes cases containing a single monomeric component and cases containing two or more monomeric components. Also, the term "partial polymer of a mixture of monomeric components" refers to a composition in which one or more of the constituent monomeric components of the aforementioned "mixture of monomeric components" are partially polymerized.

[0051] In this specification, for example, when "the adhesive layer of the present invention contains an acrylic polymer (A) and a hydrogenated polyolefin resin (B)," it also includes the case where the adhesive composition forming the adhesive layer of the present invention (the adhesive composition of the present invention) contains an acrylic polymer (A) and a hydrogenated polyolefin resin (B). The same applies when the adhesive layer of the present invention contains components other than the acrylic polymer (A) and the hydrogenated polyolefin resin (B), including but not limited to those components.

[0052] The adhesive composition of the present invention can have any form, such as emulsion type, hot melt type, solvent-free type (active energy line curing type, such as monomer mixture, or monomer mixture and some polymer, etc.). Preferably, the adhesive composition of the present invention is not solvent-based. This is because when using a solvent-based adhesive composition to obtain an adhesive layer, undesirable appearances such as orange peel are easily produced. Furthermore, "orange peel" refers to the unevenness of the peel of a fruit like a grapefruit. Also, from the perspective of obtaining an adhesive layer with excellent appearance, the adhesive composition of the present invention is preferably active energy line curing type. In this specification, "adhesive composition" means a composition used to form an adhesive layer, and includes the meaning of a composition used to form an adhesive.

[0053] As described above, it is preferable that the adhesive composition of the present invention is not solvent-based, that is, preferably free of or substantially free of organic solvents. As for the aforementioned organic solvents, there are no particular limitations as long as they are organic compounds that can be used as solvents. 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 isopropanol. Furthermore, the aforementioned organic solvents can also be mixtures containing two or more organic solvents.

[0054] In the adhesive composition of the present invention, "substantially free" of organic solvents means that, except in cases where organic solvents are unavoidably mixed in, no organic solvents are actively formulated. Specifically, "substantially free" can be defined as follows: the content of organic solvents in the adhesive composition is 1.0% by weight or less (preferably 0.5% by weight or less, and more preferably 0.2% by weight or less) relative to the total amount of the adhesive composition (total weight, 100% by weight).

[0055] As the base polymer constituting the adhesive composition of the present invention, considering factors such as transparency, weather resistance, adhesion reliability, and ease of functional design of the adhesive layer due to the wide variety of monomers, it is preferably an acrylic polymer. That is, the adhesive composition of the present invention is preferably an acrylic adhesive composition containing the following acrylic polymer (A) as the base polymer. Furthermore, acrylic polymer (A) can be used alone or in combination of two or more.

[0056] The content of the acrylic polymer (A) as the base polymer in the adhesive composition of the present invention is not particularly limited, but is preferably 74% by weight or more (e.g., 74 to 99.9% by weight), and more preferably 80% by weight or more (e.g., 80 to 99.9% by weight).

[0057] The adhesive composition of the present invention is preferably free of or substantially free of carboxyl-containing monomers as monomeric components constituting the acrylic polymer (A). Therefore, the adhesive layer described above can achieve corrosion protection for metal wiring such as metal mesh wiring and silver nanowires. "Substantially free" means that, relative to the total amount of the adhesive composition, the content of carboxyl-containing monomers is preferably 0.05% by weight or less (e.g., 0 to 0.05% by weight), more preferably 0.01% by weight or less (e.g., 0 to 0.01% by weight), and even more preferably 0.001% by weight or less (e.g., 0 to 0.001% by weight).

[0058] [1-1. Acrylic polymers (A)] The adhesive composition of the present invention is preferably an acrylic adhesive composition with acrylic polymer (A) as the main component. The specific content of acrylic polymer (A) is not particularly limited, but relative to the total amount (total weight, 100% by weight) of the adhesive composition of the present invention, it is preferably 74% by weight or more (e.g., 74 to 99.9% by weight), more preferably 80% by weight or more (e.g., 80 to 99.9% by weight).

[0059] The adhesive composition of the present invention, which forms an adhesive layer containing an acrylic polymer (A) as the main component, is not particularly limited. Examples include compositions in which the acrylic polymer (A) is an essential component; compositions in which a mixture of monomer components constituting the acrylic polymer (A) (sometimes referred to as a "monomer mixture") or a portion thereof is an essential component. There are no particular limitations; for the former, examples include water-dispersible compositions (emulsion compositions), and for the latter, examples include active energy line curing compositions. Furthermore, the above-mentioned adhesive compositions may contain other additives as needed.

[0060] The aforementioned "monomer mixture" includes cases containing a single monomer component and cases containing two or more monomer components. Furthermore, the aforementioned "partial polymer" refers to a composition in which one or more components of the aforementioned monomer mixture are partially polymerized. Preferably, the aforementioned adhesive composition is a composition in which the monomer mixture or its partial polymer is an essential component.

[0061] Acrylic polymer (A) is a polymer that contains acrylic monomers as essential monomer units (monomeric units). In other words, acrylic polymer (A) is a polymer that contains structural units derived from acrylic monomers as structural units. That is, acrylic polymer (A) is a polymer that constitutes (forms) acrylic monomers as essential monomer components. Furthermore, in this specification, "(meth)acrylic acid" means either or both of "acrylic acid" and "methacrylic acid," and so on. The weight-average molecular weight of acrylic polymer (A) is not particularly limited, but is preferably 100,000 to 5,000,000.

[0062] The acrylic polymer (A) preferably contains an alkyl methacrylate (A) (an alkyl methacrylate having 8 or more carbon atoms) as an essential monomer unit. That is, the acrylic polymer (A) of the present invention is preferably obtained by polymerizing a monomer component containing an alkyl methacrylate having a medium- to long-chain alkyl group, such as alkyl methacrylate (A). The acrylic polymer (A) is preferred in that, through the action of the aforementioned medium- to long-chain alkyl group, a highly flexible adhesive layer can be achieved, and when laminating films with metal wiring, such as metal mesh films or silver nanowire films, it can adequately alleviate the stress of the metal wiring and prevent uneven display.

[0063] Examples of the aforementioned alkyl methacrylates (A) include: octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, isostearyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, and other alkyl methacrylates in which the alkyl group has 8 or more carbon atoms (preferably 8 to 24 carbon atoms). Furthermore, alkyl methacrylates (A) can be used alone or in combination with two or more other alkyl groups.

[0064] As an alkyl acrylate (A), alkyl acrylate is superior to alkyl methacrylate in terms of shortening the polymerization time of acrylic polymer (A) and improving productivity. Especially when the acrylic polymer (A) of the present invention is hardened by radiation polymerization, alkyl acrylate is more suitable.

[0065] Among these, the alkyl (meth)acrylate (A) is preferably a (meth)acrylate containing branched alkyl groups having 8 or more carbon atoms, which is preferred for achieving a highly flexible adhesive layer and for effectively mitigating stress from metal wiring when laminating films with metal mesh films or silver nanowire films, thus preventing uneven display. This is especially true for alkyl (meth)acrylate containing branched alkyl groups having 8 or 9 carbon atoms, and more preferably 2-ethylhexyl (meth)acrylate, particularly 2-ethylhexyl acrylate (2EHA). The number of carbon atoms in the side chain alkyl groups of the aforementioned branched alkyl groups is not particularly limited, but is preferably alkyl groups having 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl). "Side chain alkyl" refers to an alkyl group in which the side chain of the longest carbon chain is substituted.

[0066] The content (ratio) of the aforementioned (meth)acrylate alkyl ester (A) in all monomer units (total monomer components constituting acrylic polymer (A)) of the acrylic polymer (A) is not particularly limited. In order to achieve a more flexible adhesive layer and to adequately alleviate the stress of the metal wires when laminating films with metal wires, such as metal mesh films or silver nanowire films, and to prevent display, the content is preferably 30 to 95 parts by weight, more preferably 35 to 90 parts by weight, and even more preferably 40 to 85 parts by weight relative to the total monomer components constituting acrylic polymer (A) (100 parts by weight).

[0067] When the (meth)acrylate (A) comprises a branched alkyl group having 8 or 9 carbon atoms (hereinafter, in this specification, it is sometimes referred to as (meth)acrylate (A1)), it is preferable to further comprise a branched alkyl group having 10 to 24 carbon atoms (hereinafter, in this specification, it is sometimes referred to as (meth)acrylate (A2)).

[0068] When (meth)alkyl acrylate (A) is included in addition to (meth)alkyl acrylate (A1) and (meth)alkyl acrylate (A2), it is preferable that, by means of the long-chain branched alkyl group, the dielectric constant of the adhesive layer of the present invention can be reduced, and when it is attached to a transparent conductive film on which metal wiring layers such as metal mesh wiring or silver nanowires are formed, malfunction can be prevented because the adhesive layer has a low dielectric constant.

[0069] The Tg of the homopolymer of (meth)acrylate (A2) is preferably -80 to 0°C, and more preferably -70 to -10°C. If the Tg of the homopolymer is below -80°C, the elastic modulus of the adhesive layer at room temperature is too low, which is undesirable; and if it is above 0°C, the adhesion strength is reduced, which is also undesirable. The Tg of the homopolymer is measured using a differential scanning calorimeter (DSC). Furthermore, as a branched alkyl group with 10 to 24 carbon atoms, the carbon number is 10 to 24, which satisfies the requirement of a moderately low dielectric constant and elastic modulus. However, the (meth)acrylate alkyl group with a preferred alkyl group can be appropriately selected according to the manufacturing method of the (meth)acrylate polymer. For example, when manufacturing (meth)acrylate polymers by solution polymerization, the aforementioned alkyl group is preferably 10 to 18 carbon atoms, more preferably 10 to 16 carbon atoms, and more preferably 10 to 14 carbon atoms. When manufacturing acrylic polymers (A) by means of radiation polymerization, the alkyl group is preferably 12 to 18 carbon atoms, and more preferably 14 to 18 carbon atoms.

[0070] Examples of (meth)acrylate alkyl esters (A2) include, for example: isodecanyl acrylate (10 carbons, Tg = -60°C for homopolymer, hereinafter simply referred to as Tg), isodecanyl methacrylate (10 carbons, Tg = -41°C), isomymyristyl acrylate (14 carbons, Tg = -56°C), isostearyl acrylate (18 carbons, Tg = -18°C), 2-propylheptyl acrylate, isoundecyl acrylate, isododecyl acrylate, isotridecyl acrylate, isopentadecanyl acrylate, isohexadecyl acrylate, isoheptadecyl acrylate, and the methacrylate monomers exemplified above. Alkyl (meth)acrylate (A2) can be used alone or in combination of two or more.

[0071] Furthermore, among the aforementioned branched alkyl groups having 10 to 24 carbon atoms, those having a third butyl or other branched alkyl group at the end of the ester group are particularly preferred in that they are considered to provide an adhesive layer that balances both an increase in molar volume and a decrease in dipole moment. Additionally, they are also preferred in terms of excellent compatibility between the acrylic polymer (A) of the present invention and the hydrogenated polyolefin resin (B). As for the branched alkyl group at the end of the ester group, branched alkyl groups having 4 to 6 carbon atoms, such as third butyl, neopentyl, or third pentyl, are preferred, with third butyl being particularly preferred. As a preferred example of an alkyl (meth)acrylate (A2) having a third butyl group at the end of the ester group, isostearyl acrylate represented by the following formula can be cited. [Chemistry 1]

[0072] The content (ratio) of the aforementioned (meth)acrylate alkyl ester (A1) in all monomer units (the total monomer components constituting acrylic polymer (A)) of the acrylic polymer (A) is not particularly limited. However, to achieve a more flexible adhesive layer and to adequately alleviate stress on the metal wiring when laminating films with metal wiring, such as metal mesh films or silver nanowire films, and to prevent malfunctions, the content is preferably 30 parts by weight or more, more preferably 45 parts by weight or more, and even more preferably 50 parts by weight or more, relative to the total monomer components constituting the acrylic polymer (A) (100 parts by weight). Furthermore, from the viewpoint of reducing the dielectric constant of the adhesive layer to prevent malfunctions, the aforementioned content is preferably 70 parts by weight or less, more preferably 65 parts by weight or less, and even more preferably 60 parts by weight or less.

[0073] The content (ratio) of the aforementioned (meth)acrylate alkyl ester (A2) in all monomer units of the acrylic polymer (A) (total monomer components constituting 100 parts by weight of acrylic polymer (A)) is not particularly limited. However, from the viewpoint of reducing the dielectric constant of the adhesive layer to prevent malfunctions, it is preferably 10 parts by weight or more, more preferably 15 parts by weight or more, and even more preferably 20 parts by weight or more. Furthermore, in order to achieve an adhesive layer with high flexibility and to adequately alleviate the stress of the metal wiring when bonding films with metal wiring, such as metal mesh films or silver nanowire films, and to prevent display issues, the aforementioned content is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, even more preferably 35 parts by weight or less, and particularly preferably 30 parts by weight or less.

[0074] The ratio of the content of alkyl methacrylate (A2) to the content of alkyl methacrylate (A1) in all monomer units (the total amount of monomer components constituting the acrylic polymer (A)) of the acrylic polymer (A) is not particularly limited. However, for the purpose of achieving a more flexible adhesive layer and sufficiently mitigating stress on the metal wiring when laminating films with metal wiring, such as metal mesh films or silver nanowire films, and preventing malfunctions, the ratio is preferably 1.1 or less, more preferably 0.6 or less, further preferably 0.55 or less, especially preferably 0.5 or less, and also 0.45 or less. Furthermore, from the viewpoint of reducing the dielectric constant of the adhesive layer to prevent malfunctions, the above ratio is preferably 0.2 or more, more preferably 0.25 or more, further preferably 0.3 or more, and also 0.35 or more.

[0075] The acrylic polymer (A) of the present invention may also include alkyl methacrylates (hereinafter, sometimes referred to as "alkyl methacrylates (B)") other than alkyl methacrylates (A) as monomer components. Examples of the aforementioned alkyl methacrylates (B) include straight-chain or branched alkyl esters having 1 to 7 carbon atoms, such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate (n-butyl methacrylate), isobutyl methacrylate, dibutyl methacrylate, tributyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, etc. Alkyl methacrylates (B) may be used alone or in combination of two or more.

[0076] The content (ratio) of the aforementioned (meth)acrylate alkyl ester (B) in all monomer units (total monomer components constituting acrylic polymer (A)) is not particularly limited. In order to achieve a more flexible adhesive layer and to adequately alleviate the stress of the metal wires when laminating films with metal wires such as metal mesh films or silver nanowire films, and to prevent display issues, it is preferable to be 10 parts by weight or less, and more preferably 5 parts by weight or less, relative to the total monomer components constituting acrylic polymer (A) (100 parts by weight).

[0077] In addition to the aforementioned alkyl methacrylate (A) and alkyl methacrylate (B), acrylic polymer (A) may also contain copolymerizable monomers (copolymerizable monomers) as monomer units. That is, acrylic polymer (A) may also contain copolymerizable monomers as constituent monomer components. Furthermore, copolymerizable monomers may be used alone or in combination of two or more.

[0078] Hydroxyl-containing monomers are preferred examples of the aforementioned copolymerizable monomers. If the acrylic polymer (A) contains hydroxyl-containing monomers as monomer units, polymerization is readily achieved when the constituent monomer components are polymerized, and good cohesiveness is easily obtained. Therefore, strong adhesion is easily obtained, and the gel fraction can be increased, resulting in an adhesive layer whose appearance of the display or input device is not easily degraded even under low-pressure conditions. Furthermore, excellent resistance to foaming and peeling is easily achieved. Moreover, it is easy to suppress the whitening of adhesive sheets that sometimes occurs in high-humidity environments.

[0079] The content (ratio) of the hydroxyl-containing monomers is not particularly limited relative to the total amount (100 parts by weight) of the monomer components constituting the acrylic polymer (A). If the amount of hydroxyl-containing monomers is certain or higher, adhesion reliability, such as cohesiveness and foam peel resistance, is easily obtained. The lower limit of the content of the hydroxyl-containing monomers is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 3 parts by weight or more. Furthermore, considering the ease of obtaining compatibility with hydrogenated polyolefin resins (B), the upper limit of the content of the hydroxyl-containing monomers is preferably 25 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 15 parts by weight or less.

[0080] Furthermore, nitrogen-containing monomers are preferably used as copolymerizing monomers. If the acrylic polymer (A) contains nitrogen-containing monomers as monomer units, moderate cohesive strength is easily obtained. Therefore, increasing the 180° peel adhesion to the glass plate and the 180° peel adhesion to the acrylic plate easily yields strong adhesion. Furthermore, the gel fraction can be increased, resulting in an adhesive layer whose appearance is not easily compromised even under low-pressure conditions. Excellent foaming peel resistance is also easily obtained. Moreover, moderate flexibility is easily achieved in the adhesive layer, allowing the 300% tensile residual stress to be adjusted to a specific range. This effectively mitigates stress from the metal wiring when bonding films with metal wiring, such as metal mesh films or silver nanowire films, preventing uneven display.

[0081] When the aforementioned acrylic polymer (A) contains the aforementioned nitrogen-containing monomer as a monomer component constituting the polymer, the ratio of the aforementioned nitrogen-containing monomer in all monomer components (100 parts by weight) constituting the acrylic polymer (A) is not particularly limited, but is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more. If the above ratio is 1 part by weight or more, it is preferable from the viewpoint of easily obtaining good cohesion and easy obtaining adhesion reliability at high temperatures. Furthermore, the suppression of turbidity and durability in high humidity environments are further improved, and higher adhesion reliability for metal mesh wiring or silver nanowire layers can be obtained. Moreover, from the viewpoint of obtaining an adhesive layer with moderate flexibility to prevent uneven display and obtaining an adhesive layer with excellent transparency, the upper limit of the ratio of the aforementioned nitrogen-containing monomer is preferably 30 parts by weight or less, more preferably 25 parts by weight or less, and even more preferably 20 parts by weight or less.

[0082] The ratio of hydroxyl-containing monomers to nitrogen-containing monomers in the acrylic polymer (A) is not particularly limited, and can be appropriately selected from the range of 95 / 5 to 5 / 95, more preferably 90 / 10 to 10 / 90, even more preferably 70 / 30 to 30 / 70, further preferably 60 / 40 to 40 / 60, and even more preferably 50 / 50 to 35 / 65.

[0083] Furthermore, monomers containing alicyclic structures are preferably exemplified as the aforementioned copolymerizable monomers. If the acrylic polymer (A) contains nitrogen-containing monomers as monomer units, it is easy to obtain moderate cohesive strength. Therefore, by increasing the 180° peel adhesion to the glass plate and the 180° peel adhesion to the acrylic plate, strong adhesion can be easily obtained. Furthermore, the gel fraction can be increased, resulting in an adhesive layer that does not easily degrade the appearance of the display device or input device even under low pressure conditions. Also, excellent foaming peel resistance can be easily obtained. Furthermore, moderate flexibility can be easily obtained in the adhesive layer, and the 300% tensile residual stress can be adjusted to a specific range. When bonding films with metal wiring, such as metal mesh films or silver nanowire films, the stress of the metal wiring can be sufficiently mitigated, preventing uneven display.

[0084] When the aforementioned acrylic polymer (A) contains the aforementioned alicyclic monomer as a monomeric component of the polymer, the ratio of the alicyclic monomer in all monomeric components (100 parts by weight) constituting the acrylic polymer (A) is not particularly limited. However, considering the improvement of durability and obtaining higher bonding reliability for metal mesh wiring and silver nanowire layers, it is preferable to have 3 parts by weight or more, more preferably 10 parts by weight or more. Furthermore, considering the obtaining of an adhesive layer with appropriate flexibility and preventing unevenness, the upper limit of the ratio of the alicyclic monomer is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and even more preferably 30 parts by weight or less.

[0085] The aforementioned acrylic polymer (A) can be obtained by polymerizing the aforementioned monomer units (monomer components) using a known or conventional polymerization method. Examples of polymerization methods for the aforementioned acrylic polymer (A) include solution polymerization, emulsion polymerization, bulk polymerization, and polymerization using active energy line irradiation (active energy line polymerization). Among these, considering the transparency, water resistance, and cost of the adhesive layer, solution polymerization and active energy line polymerization are preferred, with active energy line polymerization being even more preferred.

[0086] The active energy rays used for polymerization (photopolymerization) can be, for example, ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, electron beams, or ultraviolet rays, with ultraviolet rays being particularly preferred. Furthermore, there are no particular limitations on the irradiation energy, irradiation time, or irradiation method of the active energy rays, as long as they can activate the photopolymerization initiator and produce monomer components.

[0087] During the polymerization of the aforementioned acrylic polymer (A), various common solvents can also be used. Examples of such solvents include: esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. Furthermore, solvents can be used alone or in combination of two or more.

[0088] Furthermore, during the polymerization of the aforementioned acrylic polymer (A), polymerization initiators such as thermal polymerization initiators or photopolymerization initiators (photoinitiators) can be used, depending on the type of polymerization reaction. Moreover, polymerization initiators can be used alone or in combination of two or more.

[0089] There are no particular limitations on the aforementioned photopolymerization initiators. Examples include: benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and 9-oxosulfuron-methyl-2-ethylhexylene ... These include photopolymerization initiators, etc. Furthermore, photopolymerization initiators can be used alone or in combination of two or more.

[0090] Examples of 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 acetophenone-based photopolymerization initiators include: 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone. Examples of α-ketool-based photopolymerization initiators include: 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include: 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzophenone-based photopolymerization initiators include benzoin. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, etc. Examples of ketal-based photopolymerization initiators include benzophenone dimethyl ketal. As for the above-mentioned 9-oxosulfur... Photopolymerization initiators, such as 9-oxosulfuron-methyl. 2-Chloro-9-oxosulfur 2-Methyl-9-oxosulfur 2,4-Dimethyl-9-oxosulfur Isopropyl-9-oxosulfur 2,4-Diisopropyl-9-oxosulfur Dodecyl-9-oxosulfur wait.

[0091] There is no particular limitation on the amount of the above-mentioned photopolymerization initiator used. For example, it is preferably 0.001 to 1 part by weight, and more preferably 0.01 to 0.50 parts by weight, relative to 100 parts by weight of all monomer units of acrylic polymer (A) (the total amount of monomer components constituting acrylic polymer (A)).

[0092] Furthermore, there are no particular limitations on the aforementioned thermal polymerization initiators. Examples include azo polymerization initiators, peroxide polymerization initiators (such as benzoyl peroxide, tributyl maleate peroxide, 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 aforementioned 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 ester, and 4,4'-azobis-4-cyanopentanoic acid.

[0093] There is no particular limitation on the amount of the above-mentioned thermal polymerization initiator used. For example, in the case of the above-mentioned azo polymerization initiator, it is preferably 0.05 to 0.5 parts by weight, and more preferably 0.1 to 0.3 parts by weight, relative to 100 parts by weight of all monomer units of acrylic polymer (A) (the total amount of monomer components constituting acrylic polymer (A)).

[0094] [1-2. Monomers containing carboxyl groups, etc.] The adhesive composition of the present invention is preferably substantially free of carboxyl-containing monomers as monomeric components constituting the acrylic polymer (A). Furthermore, "substantially free" means that it is not actively formulated except in cases where it is unavoidably mixed in. Also, carboxyl-containing monomers refer to monomers having at least one carboxyl group within their molecule. From the viewpoint of obtaining superior anti-corrosion effects, specifically, it can be considered substantially free if the content of carboxyl-containing monomers is preferably 0.05 parts by weight or less (e.g., 0 to 0.05 parts by weight), more preferably 0.01 parts by weight or less (e.g., 0 to 0.01 parts by weight), and even more preferably 0.001 parts by weight or less (e.g., 0 to 0.001 parts by weight), relative to the total amount (100 parts by weight) of monomeric components constituting the acrylic polymer (A). Furthermore, examples of the aforementioned carboxyl-containing monomers include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, butenoic acid, isobutenoic acid, etc. Also, the aforementioned carboxyl-containing monomers also include anhydride-containing monomers such as maleic anhydride and itaconic anhydride.

[0095] Furthermore, from the viewpoint of obtaining superior anti-corrosion effects, the adhesive composition of the present invention preferably does not only substantially contain carboxyl-containing monomers as monomeric components constituting the acrylic polymer (A), but also substantially does not contain monomers having acidic groups other than carboxyl groups (sulfonyl, phosphoric acid, etc.) as monomeric components constituting the acrylic polymer (A). That is, the acrylic polymer (A) preferably does not substantially contain either carboxyl-containing monomers or monomers having other acidic groups as monomeric components. Specifically, the following can be considered as substantially non-existent: relative to the total amount (100 parts by weight) of monomeric components constituting the acrylic polymer (A), the total amount of carboxyl-containing monomers and monomers having other acidic groups constituting the acrylic polymer (A) is preferably 0.05 parts by weight or less (e.g., 0 to 0.05 parts by weight), more preferably 0.01 parts by weight or less (e.g., 0 to 0.01 parts by weight), and even more preferably 0.001 parts by weight or less (e.g., 0 to 0.001 parts by weight).

[0096] Furthermore, from the same perspective, the adhesive composition of the present invention preferably does not contain or substantially does not contain acidic monomers as monomeric components constituting polymers other than acrylic polymers (A). For example, it is preferable that it substantially does not contain carboxyl monomers. Moreover, the meaning of "substantially does not contain," the preferred degree, and monomers having acidic groups other than carboxyl groups are assumed to be the same as the monomeric components constituting acrylic polymers (A).

[0097] [1-3. Monomers containing basic groups] Furthermore, the adhesive composition of the present invention preferably does not contain or substantially does not contain basic monomers as monomeric components constituting the acrylic polymer (A). Also preferably, as monomeric components constituting polymers other than acrylic polymer (A), it also substantially does not contain basic monomers, and even when not a monomeric component constituting various polymers, it also substantially does not contain basic monomers in the aforementioned adhesive layer; this aspect is the same as in the case of carboxyl monomers. Furthermore, the meaning of "substantially does not contain," the degree of preference, etc., are also the same.

[0098] [1-4. Hydroxyl-containing monomers] Hydroxyl-containing monomers refer to monomers that have at least one hydroxyl group within their molecule. Furthermore, monomers that have at least one hydroxyl group and at least one carboxyl group within their molecule are carboxyl-containing monomers, but not hydroxyl-containing monomers. There are no particular limitations on the types of hydroxyl-containing monomers mentioned above; specifically, examples include: 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) methacrylate, etc., which are hydroxyl-containing (meth)acrylates; vinyl alcohol, allyl alcohol, etc. Among these, considering the ease of obtaining good cohesiveness and reliable adhesion at high temperatures, hydroxyl-containing (meth)acrylates are preferred as monomers, and more preferably 2-hydroxyethyl acrylate (HEA), 2-hydroxypropyl acrylate (HPA), and 4-hydroxybutyl acrylate (4HBA). Furthermore, hydroxyl-containing monomers can be used alone or in combination of two or more.

[0099] [1-5. Nitrogen-containing monomers] A nitrogen-containing monomer refers to a monomer having at least one nitrogen atom within a molecule. However, the aforementioned hydroxyl-containing monomers do not include the aforementioned nitrogen-containing monomers. That is, in this specification, monomer systems having both hydroxyl and nitrogen atoms within a molecule are included in nitrogen-containing monomers. Furthermore, a monomer having at least one nitrogen atom and at least one carboxyl group within a molecule is a carboxyl-containing monomer, not a nitrogen-containing monomer.

[0100] From the viewpoint of improving foaming and peel resistance, N-vinylcyclic amides and (meth)acrylamides are preferred as the aforementioned nitrogen-containing monomers. Furthermore, nitrogen-containing monomers can be used alone or in combination of two or more.

[0101] From the viewpoint of easily obtaining good cohesiveness and easy obtaining high-temperature adhesion reliability, the N-vinylcyclic amide represented by the following formula (1) is preferred as the above-mentioned N-vinylcyclic amide. [Chemistry 2] (In formula (1), R1 represents a divalent organic group)

[0102] In the above formula (1), R1 is a divalent organic group, preferably a divalent saturated hydrocarbon group or an unsaturated hydrocarbon group, and more preferably a divalent saturated hydrocarbon group (e.g., an alkyl group with 3 to 5 carbon atoms).

[0103] From the viewpoint of further improving foaming peel resistance, the N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactone, N-vinyl-3-pyrrolidone, N-vinyl-1,3-vinyl-2-one, N-vinyl-3,5-pyrrolidone, etc., are preferred as the N-vinyl-2-pyrrolidone or N-vinyl-2-caprolactone, and even more preferably N-vinyl-2-pyrrolidone.

[0104] Examples of the aforementioned (meth)acrylamides include (meth)acrylamide, N-alkyl (meth)acrylamide, and N,N-dialkyl (meth)acrylamide. Examples of the aforementioned N-alkyl (meth)acrylamides include N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-n-butyl (meth)acrylamide, and N-octylacrylamide. Furthermore, the aforementioned N-alkyl (meth)acrylamides also include (meth)acrylamides having an amino group, such as dimethylaminoethyl (meth)acrylamide, diethylaminoethyl (meth)acrylamide, and dimethylaminopropyl (meth)acrylamide. Examples of the aforementioned N,N-dialkyl(meth)acrylamides 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(tert-butyl)(meth)acrylamide.

[0105] Furthermore, the aforementioned (meth)acrylamides also include various N-hydroxyalkyl (meth)acrylamides. Examples of the aforementioned N-hydroxyalkyl (meth)acrylamides include: N-hydroxymethyl (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.

[0106] Furthermore, the aforementioned (meth)acrylamides also include various N-alkoxyalkyl (meth)acrylamides. Examples of the aforementioned N-alkoxyalkyl (meth)acrylamides include N-methoxymethyl (meth)acrylamide and N-butoxymethyl (meth)acrylamide.

[0107] Furthermore, examples of nitrogen-containing monomers other than the aforementioned N-vinylcyclic amides and (meth)acrylamides include: aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, tributylaminoethyl (meth)acrylate, etc., which contain amino groups; acrylonitrile, methacrylonitrile, etc., which contain cyano groups; (meth)acrylamide, N-vinylpiperidine, N-vinylpyrrole, N-vinylimidazolium, N-vinylpyridine, N-vinylpyridine, vinylpyridine, vinylpyridine, vinylisopyridine, vinylthiazole, vinylisothiazole, vinylpyridine, (meth)acrylamide, (meth)acrylamide, (meth)acrylamide, N-... -Methylvinylpyrrolidone and other heterocyclic monomers; N-cyclohexylcis-butenyldiimidine, N-isopropylcis-butenyldiimidine, N-laurylcis-butenyldiimidine, N-phenylcis-butenyldiimidine and other cis-butenyldiimidine monomers; N-methyldiimidine, N-ethyldiimidine, N-butyldiimidine, N-octyldiimidine, N-2-ethylhexyldiimidine, N-lauryldiimidine Acrylimide monomers such as amines and N-cyclohexyl acetimines; succinimide monomers such as N-(meth)propenylidene acetimine, N-(meth)propenylidene-6-oxyhexamethylene acetimine, and N-(meth)propenylidene-8-oxyoctamethylene acetimine; and isocyanate monomers such as 2-(meth)propenylidene acetimine ethyl ester.

[0108] [1-6. Monomers containing alicyclic structures] Alicyclic monomers refer to monomers that have polymerizable functional groups with unsaturated double bonds, such as (meth)acrylic or vinyl groups, and possess an alicyclic structure. For example, alkyl (meth)acrylates with cycloalkyl groups are included among the aforementioned alicyclic monomers. Monomers having at least one alicyclic structure and at least one carboxyl group within their molecule are carboxyl-containing monomers, not alicyclic monomers. Furthermore, alicyclic monomers can be used alone or in combination of two or more.

[0109] The alicyclic structure in the above-mentioned monomers containing alicyclic structures is a cyclic hydrocarbon structure, preferably with 5 or more carbon atoms, more preferably with 6 to 24 carbon atoms, further preferably with 6 to 15 carbon atoms, and even more preferably with 6 to 10 carbon atoms.

[0110] Examples of the aforementioned alicyclic monomers include: cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, 3,3,5-trimethylcyclohexyl methacrylate, cycloheptyl methacrylate, cyclooctyl methacrylate, isopropyl methacrylate, dicyclopentyl methacrylate, HPMPA as represented by formula (2), TMA-2 as represented by formula (3), and HCPA as represented by formula (4). Furthermore, in formula (4), the bonding site between the cyclohexyl ring connected by the line and the structural formula within parentheses is not particularly limited. Among these, isopropyl methacrylate, cyclohexyl methacrylate, and 3,3,5-trimethylcyclohexyl methacrylate are preferred. [Chemistry 3] [Chemistry 4] [Chemistry 5]

[0111] [1-7. Other comonomers] In addition to the nitrogen-containing monomers, hydroxyl-containing monomers, and alicyclic monomers mentioned above, other examples of comonomers in acrylic polymers (A) include: alkoxyalkyl esters of (meth)acrylate [e.g., 2-methoxyethyl ester, 2-ethoxyethyl ester, methoxytriethylene glycol ester, 3-methoxypropyl ester, 3-ethoxypropyl ester, 4-methoxybutyl ester, 4-ethoxybutyl ester, etc.]; epoxy-containing monomers [e.g., glycidyl methacrylate]. Glyceryl esters, methyl glycidyl acrylate, etc.; monomers containing sulfonic acid groups [e.g., sodium vinyl sulfonate, etc.]; monomers containing phosphate groups; meth acrylates with aromatic hydrocarbon groups [e.g., phenyl methacrylate, phenoxyethyl methacrylate, benzyl methacrylate, 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 ethers, etc.]; vinyl chloride, etc.

[0112] [1-8. Hydrogenated polyolefin resins (B)] The adhesive composition of the present invention is preferably an acrylic adhesive composition with an acrylic polymer (A) as the main component and a hydrogenated polyolefin resin (B) as a formulation. The adhesive composition of the present invention is preferred in that, by including the hydrogenated polyolefin resin (B) in addition to the acrylic polymer (A), the appearance of the display device or input device is less likely to deteriorate under low-pressure conditions. Furthermore, the hydrogenated polyolefin resin (B) is a material with a low dielectric constant, which is advantageous in that, by incorporating it into the acrylic polymer (A) of the present invention, the dielectric constant does not increase, and a more flexible adhesive layer is achieved without the need for low-molecular-weight polymerization of the acrylic polymer (A). Moreover, when laminating films with metal wiring, such as metal mesh films or silver nanowire films, it can adequately alleviate the stress of the metal wiring and prevent uneven display. Furthermore, the hydrogenated polyolefin resin (B) exhibits excellent compatibility with the acrylic polymer (A), thus providing superior performance in maintaining the transparency of the adhesive composition of the present invention. The hydrogenated polyolefin resin (B) can be used alone or in combination with two or more other resins.

[0113] In terms of achieving a highly flexible adhesive layer and effectively mitigating stress on the metal wiring when laminating films with metal mesh films or silver nanowire films, thus preventing defects, the hydrogenated polyolefin resin (B) preferably exhibits liquid flowability at 25°C. Liquid flowability of the hydrogenated polyolefin resin (B) at 25°C refers to a viscosity of 10,000 mPa·s or less, measured at 25°C using a type B viscometer.

[0114] Hydrogenated polyolefin resin (B) is obtained by reducing the carbon-carbon double bonds contained in polyolefin resin through a hydrogenation reaction. Because hydrogenated polyolefin resin (B) has fewer carbon-carbon double bonds within its molecule, it is less prone to polymerization inhibition, reduction in polymerization rate, or molecular weight degradation when the adhesive composition of the present invention is hardened, for example, by ultraviolet irradiation. Therefore, it can highly maintain the adhesion reliability of the adhesive composition of the present invention at high temperatures.

[0115] From the perspective of minimizing polymerization inhibition and ensuring reliable bonding at high temperatures, the hydrogenation rate of hydrogenated polyolefin resin (B) is preferably 90% or higher, more preferably 95% or higher, and even more preferably 97% or higher. There is no particular upper limit to the hydrogenation rate; theoretically it is 100%, but practically it can be below 99.9% or even below 99.8%. Furthermore, the hydrogenation rate of hydrogenated polyolefin resin (B) can be determined by 1H-NMR (Nuclear Magnetic Resonance) to quantify the amount of residual double bonds in the hydrogenated polyolefin resin (B).

[0116] From the perspective of minimizing polymerization inhibition and ensuring reliable adhesion at high temperatures, the iodine value (Ig / 100 g) of hydrogenated polyolefin resin (B) is preferably 30 or lower, more preferably 25 or lower, and even more preferably 20 or lower. There is no particular limitation on the lower limit of the iodine value; it can be 0.1 or higher, or 0.2 or higher. Furthermore, the iodine value is determined according to JIS K 0070-1992.

[0117] For imparting appropriate stress relief and flowability to the adhesive layer and improving compatibility with the acrylic polymer (A), the number average molecular weight (Mn) of the hydrogenated polyolefin resin (B) is preferably 1000 to 5000. For imparting appropriate stress relief and flowability to the adhesive composition, the number average molecular weight (Mn) is preferably 1000 or more, more preferably 1500 or more, and even more preferably 1800 or more. For improving compatibility with the acrylic polymer (A) and maintaining the transparency of the adhesive composition of the present invention more effectively, the number average molecular weight (Mn) is preferably 5000 or less, more preferably 4800 or less, and even more preferably 4600 or less.

[0118] In terms of imparting appropriate stress relief and flowability to the adhesive layer, improving compatibility with acrylic polymers (A), maintaining high transparency, and suppressing haze, the polydispersity (Mw / Mn) of the hydrogenated polyolefin resin (B) is preferably 2.0 or less, and more preferably 1.8 or less. There is no particular limitation on the lower limit of polydispersity; practically, it can be 1.0 or more.

[0119] The number average molecular weight (Mn) and polydispersity (Mw / Mn) of hydrogenated polyolefin resin (B) were determined by gel permeation chromatography (GPC) and obtained from polystyrene standards.

[0120] The aforementioned hydrogenated polyolefin resin (B) comprises hydrogenated polyolefin. The adhesive composition of the present invention is more suitable in that, by comprising hydrogenated polyolefin as the hydrogenated polyolefin resin (B), an adhesive layer that does not easily degrade in appearance of the display device or input device even under low pressure conditions can be achieved.

[0121] The aforementioned hydrogenated polyolefins are hydrides of polymers (polyolefins) having structural units derived from olefins. Hydrogenated polyolefins include hydrides of 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. Preferably, hydrogenated polyolefins are hydrides of 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.

[0122] Regarding the adhesive layer that can achieve an appearance that is not easily reduced even under low-pressure conditions, the hydrogenated polyolefin resin (B) is preferably, in addition to hydrogenated polyolefin, to include hydrogenated polyolefin polyol.

[0123] The aforementioned hydrogenated polyolefin polyols are compounds obtained by modifying the terminal hydroxyl groups of the aforementioned hydrogenated polyolefins. Preferably, the hydrogenated polyolefin polyol is a hydroxyl-modified homopolymer or copolymer of a diene compound, such as hydrogenated polybutadiene polyol or hydrogenated polyisoprene polyol. The hydrogenated polyolefin polyol can be used alone or in combination of two or more.

[0124] From the viewpoint that the appearance of the display device or input device is not easily reduced under low pressure conditions, hydrogenated polyolefin and hydrogenated polyolefin polyol are preferred as described above, in terms of imparting appropriate stress relief and fluidity to the adhesive layer and improving compatibility with acrylic polymer (A).

[0125] The hydrogenated polybutadiene is preferably represented by the following formula (5), and the hydrogenated polybutadiene polyol is preferably represented by the following formula (6). [Chemistry 6] In the above formula, m represents the degree of polymerization of hydrogenated polybutadiene.

[0126] Commercially available products can be used as hydrogenated polyolefins and hydrogenated polyolefin polyols. Examples of commercially available hydrogenated polyolefins include "BI-2000" and "BI-3000" (manufactured by Nippon Soda Co., Ltd.). Examples of commercially available hydrogenated polyolefin polyols include "GI-1000," "GI-2000," and "GI-3000" (manufactured by Nippon Soda Co., Ltd.), and "EPOL" (manufactured by Idemitsu Kosan Co., Ltd.).

[0127] The content of hydrogenated polyolefin resin (B) in the above-mentioned adhesive composition is not particularly limited. From the viewpoint that the appearance of the display device or input device is not easily reduced under low pressure conditions, it is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and even more preferably 5 parts by weight or more, and may also be 8 parts by weight or more, relative to 100 parts by weight of acrylic polymer (A). On the other hand, from the viewpoint of suppressing the increase of haze and ensuring higher transparency, and considering the viewpoint of maintaining adhesion and adhesion reliability at high temperatures, the content of hydrogenated polyolefin resin (B) is preferably 35 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 25 parts by weight or less.

[0128] The content of hydrogenated polyolefin in the above-mentioned adhesive composition is not particularly limited. From the viewpoint that the appearance of the display device or input device is not easily reduced under low pressure conditions, it is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 1.5 parts by weight or more, and particularly preferably 2 parts by weight or more, relative to 100 parts by weight of acrylic polymer (A). On the other hand, from the viewpoint of suppressing the increase of haze and ensuring higher transparency, and from the viewpoint of maintaining adhesion and adhesion reliability at high temperatures, the content of hydrogenated polyolefin is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and even more preferably 12 parts by weight or less, or 10 parts by weight or less, or 5 parts by weight or less.

[0129] The content of hydrogenated polyolefin polyol in the above-mentioned adhesive composition is not particularly limited. From the viewpoint that the appearance of the display device or input device is not easily reduced under low pressure conditions, it is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 3 parts by weight or more, or 5 parts by weight or more, or 10 parts by weight or more, relative to 100 parts by weight of acrylic polymer (A). On the other hand, from the viewpoint of suppressing the increase of haze and ensuring higher transparency, and from the viewpoint of maintaining adhesion and adhesion reliability at high temperatures, the content of hydrogenated polyolefin polyol is preferably 30 parts by weight or less, more preferably 25 parts by weight or less, even more preferably 20 parts by weight or less, and particularly preferably 15 parts by weight or less.

[0130] The ratio of hydrogenated polyolefin content to hydrogenated polyolefin polyol content (hydrogenated polyolefin / hydrogenated polyolefin polyol) in the above-mentioned adhesive composition is not particularly limited. From the viewpoint that the appearance of the display device or input device is not easily reduced under low pressure conditions, it is preferably 5 / 95 or more, more preferably 12 / 88 or more, and may also be 15 / 85 or more, or 18 / 88 or more. Furthermore, from the viewpoint of suppressing the increase of haze and ensuring higher transparency, and considering that the appearance of the display device or input device is not easily reduced under low pressure conditions and that transparency is ensured, the above ratio is preferably 90 / 10 or less, more preferably 80 / 20 or less, and more preferably 70 / 30 or less, and may also be 55 / 45 or less, 45 / 55 or less, or 30 / 70 or less.

[0131] [1-9. Polyfunctional (meth)acrylates] The adhesive composition of the present invention preferably further comprises a polyfunctional (meth)acrylate. The polyfunctional (meth)acrylate acts as a crosslinking component, and the adhesive composition has moderate cohesiveness, so that the appearance of the display device or input device is not easily reduced under low pressure conditions.

[0132] Examples of multifunctional (meth)acrylates include: hexanediol dimethacrylate, butanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, trimethylolpropane trimethacrylate, tetramethylolmethane trimethacrylate, allyl methacrylate, ethylene methacrylate, divinylbenzene, epoxy acrylates, polyester acrylates, and urethane acrylates. Furthermore, multifunctional (meth)acrylates can be used alone or in combination of two or more.

[0133] The content (ratio) of polyfunctional (meth)acrylate is not particularly limited. Regarding the adhesive layer having appropriate cohesive strength, ensuring that the appearance of the display device or input device is not easily degraded even under low-pressure conditions, the content is preferably 0.001 parts by weight or more, more preferably 0.002 parts by weight or more, and even more preferably 0.005 parts by weight or more, or even 0.01 parts by weight or more, relative to 100 parts by weight of acrylic polymer (A). Furthermore, regarding the content (ratio) of polyfunctional (meth)acrylate, in order to achieve an adhesive layer with high flexibility and to adequately alleviate stress on the metal wiring and prevent display issues, the content is preferably 0.5 parts by weight or less, more preferably 0.35 parts by weight or less, and even more preferably 0.2 parts by weight or less, or even 0.1 parts by weight or less, relative to 100 parts by weight of acrylic polymer (A).

[0134] [1-10. Silicon coupling agents] The adhesive composition of the present invention preferably further contains a silane coupling agent. The inclusion of a silane coupling agent in the adhesive composition is advantageous in readily achieving excellent adhesion to glass (especially excellent adhesion reliability to glass under high temperature and humidity).

[0135] There are no particular limitations on the aforementioned silane coupling agents, and examples include: γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and N-phenylaminopropyltrimethoxysilane. Among these, γ-glycidoxypropyltrimethoxysilane is preferred. Furthermore, commercially available products such as "KBM-403" (manufactured by Shin-Etsu Chemical Co., Ltd.) can also be used as examples of the aforementioned silane coupling agents. Moreover, the silane coupling agent can be used alone or in combination of two or more.

[0136] The content of the silane coupling agent is not particularly limited. Considering the improvement of the bonding reliability of glass, it is preferably 0.01 to 1 part by weight, and more preferably 0.03 to 0.5 parts by weight, relative to 100 parts by weight of acrylic polymer (A).

[0137] [1-11. Crosslinking agent] The adhesive composition of the present invention, as described above, is preferably non-solvent-based, that is, preferably free of or substantially free of crosslinking agents. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. The adhesive composition of the present invention is preferably free of or substantially free of isocyanate-based crosslinking agents and / or epoxy-based crosslinking agents, and more preferably free of or substantially free of isocyanate-based crosslinking agents.

[0138] Examples of the aforementioned isocyanate-based crosslinking agents (polyfunctional isocyanate compounds) include: lower aliphatic polyisocyanates such as 1,2-epoxyethyl diisocyanate, 1,4-epoxybutyl diisocyanate, and 1,6-hexamethylene diisocyanate; alicyclic polyisocyanates such as epoxycyclopentyl diisocyanate, epoxycyclohexyl diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated xylene diisocyanate; and aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenyl dimethyl diisocyanate. Furthermore, examples of the aforementioned isocyanate-based crosslinking agents include: trimethylolpropane / toluene diisocyanate adduct [manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate L"], trimethylolpropane / hexamethylene diisocyanate adduct [manufactured by Nippon Polyurethane Industries, Ltd., trade name "Coronate HL"], and trimethylolpropane / phenylenedimethyl diisocyanate adduct [manufactured by Mitsui Chemicals, Ltd., trade name "Takenate D-110N"], etc.

[0139] Examples of epoxy-based crosslinking agents (multifunctional epoxy compounds) include: N,N,N',N'-tetraglycidyl-m-phenylenediamine, diglycidyl-aniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. Sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan anhydride polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tri(2-hydroxyethyl)isocyanurate triglycidyl ether, resorcinol diglycidyl ether, bisphenol-S-d-diglycidyl ether, and other epoxy resins having two or more epoxy groups within their molecules. Furthermore, as an example of the aforementioned epoxy crosslinking agent, commercially available products such as "Tetrad C" manufactured by Mitsubishi Gas Chemical Co., Ltd. can also be cited.

[0140] In the adhesive composition of the present invention, "substantially free" of crosslinking agent means that, except in cases where crosslinking agent is unavoidably mixed in, no crosslinking agent is actively formulated. Specifically, "substantially free" can be considered as follows: the content of crosslinking agent in the adhesive composition is 1.0% by weight or less (preferably 0.5% by weight or less, and more preferably 0.2% by weight or less) relative to the total amount of the adhesive composition (total weight, 100 parts by weight). Furthermore, "substantially free" can also be considered as follows: relative to the total amount (100 parts by weight) of the monomer components constituting the acrylic polymer (A), it is preferably 0.05 parts by weight or less (e.g., 0 to 0.05 parts by weight), more preferably 0.01 parts by weight or less (e.g., 0 to 0.01 parts by weight), and more preferably 0.001 parts by weight or less (e.g., 0 to 0.001 parts by weight).

[0141] [1-12. Additives] The adhesive composition of the present invention may, as needed and without impairing the characteristics of the present invention, include crosslinking accelerators, adhesion-improving resins (rosin derivatives, polyterpene resins, oil-soluble phenols, etc.), anti-aging agents, fillers, colorants (pigments or dyes, etc.), ultraviolet absorbers, chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, rust inhibitors, antioxidants, and other known additives. From the viewpoint of suppressing the increase of haze in the adhesive layer of the present invention, the adhesive composition of the present invention is preferably substantially free of rust inhibitors and antioxidants. Furthermore, such additives may be used alone or in combination of two or more.

[0142] From the viewpoint of suppressing the increase in haze of the adhesive layer of the present invention, the adhesive composition of the present invention is preferably substantially free of rust inhibitors and antioxidants. "Substantially free of" rust inhibitors and antioxidants means that, except in cases where rust inhibitors and antioxidants are unavoidably mixed in, rust inhibitors and antioxidants are not actively formulated. Specifically, "substantially free" can be considered as follows: the content of rust inhibitors and / or antioxidants in the adhesive composition is 1.0% by weight or less relative to the total amount of the adhesive composition (total weight, 100% by weight) (preferably 0.5% by weight or less, and more preferably 0.2% by weight or less). Furthermore, the following can also be considered substantially absent: relative to the total amount (100 parts by weight) of monomer components constituting the acrylic polymer (A), for example, preferably less than 0.5 parts by weight (e.g., 0 to 0.5 parts by weight), less than 0.05 parts by weight (e.g., 0 to 0.05 parts by weight), more preferably less than 0.01 parts by weight (e.g., 0 to 0.01 parts by weight), and even more preferably less than 0.001 parts by weight (e.g., 0 to 0.001 parts by weight).

[0143] [1-13. Preparation of Adhesive Compositions] The adhesive composition of the present invention can be prepared by mixing an acrylic polymer (A), a hydrogenated polyolefin resin (B), a polyfunctional (meth)acrylate as needed, a silane coupling agent, and other additives, and stirring uniformly. From the viewpoint of uniform preparation, the monomer components constituting the acrylic polymer (A) can also be formulated as diluents. For example, the hydrogenated polyolefin resin (B) can be diluted and added using the monomer components. When using the monomer components constituting the acrylic polymer (A) as diluents, in order to maintain the aforementioned properties of the adhesive layer, it is preferable to prepare the acrylic polymer (A) using a mixture of monomers other than the monomer components used as diluents. There are no particular limitations on the monomer components used as diluents; for example, alkyl (meth)acrylate (A1) (alkyl (meth)acrylates having a branched alkyl group having 8 or 9 carbon atoms) is preferred. The amount of monomer components used as diluents is not particularly limited, as long as it is appropriately set in a way that allows the adhesive composition to be uniformly mixed.

[0144] [2. Adhesive sheet] The adhesive sheet of the present invention only needs to have the adhesive layer of the present invention (an adhesive layer formed by the adhesive composition of the present invention), and there are no other particular limitations.

[0145] The adhesive sheet of this invention can 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. From the viewpoint of bonding two components together, a double-sided adhesive sheet is preferred. Furthermore, in this specification, the term "adhesive sheet" also includes strip-shaped materials, i.e., "adhesive tape." Also, in this specification, the adhesive layer surface is sometimes referred to as the "adhesive surface."

[0146] The adhesive sheet of the present invention may also have a release liner provided on the adhesive surface before use.

[0147] The adhesive sheet of the present invention can be a so-called "substrate-free" adhesive sheet that does not have a substrate (substrate layer) (hereinafter, sometimes referred to as "substrate-free adhesive sheet"), or it can be an adhesive sheet with a substrate (hereinafter, sometimes referred to as "substrate-attached adhesive sheet"). Examples of the aforementioned substrate-free adhesive sheet include, for example, a double-sided adhesive sheet containing only the aforementioned adhesive layer, or a double-sided adhesive sheet containing the aforementioned adhesive layer and an adhesive layer other than the aforementioned adhesive layer (sometimes referred to as "other adhesive layers"). On the other hand, examples of a substrate-attached adhesive sheet include adhesive sheets having the aforementioned adhesive layer on at least one side of the substrate. Preferably, it is a substrate-free adhesive sheet (substrate-free double-sided adhesive sheet), and more preferably, a substrate-free double-sided adhesive sheet containing only the aforementioned adhesive layer. Furthermore, the aforementioned "substrate (substrate layer)" does not include a release liner that is peeled off when using (attaching) the adhesive sheet.

[0148] [2-1. Other physical properties of adhesive sheets] The 180° peel adhesion force of the adhesive sheet of the present invention to a glass plate at a tensile speed of 300 mm / min at 25°C (especially the 180° peel adhesion force of the adhesive surface provided by the adhesive layer (the adhesive layer of the present invention) to the glass plate at a tensile speed of 300 mm / min at 25°C) is not particularly limited. If the adhesion force is high, from the viewpoint of obtaining sufficient adhesion to metal surfaces such as metal mesh wiring and silver nanowires, and improving the corrosion resistance, it is preferably 10 N / 20 mm or more, more preferably 12 N / 20 mm or more, more preferably 14 N / 20 mm or more, and more preferably 16 N / 20 mm or more. If the 180° peel adhesion force of the adhesive sheet of the present invention to a glass plate at a tensile speed of 300 mm / min at 25°C is a certain value or more, the adhesion to the glass and the suppression of bulges in the step are more excellent. Furthermore, the upper limit of the 180° peel adhesion force of the adhesive sheet of the present invention to the glass plate at a tensile speed of 300 mm / min at 25°C is not particularly limited. For example, it is preferably 60 N / 20 mm or less, and more preferably 40 N / 20 mm or less.

[0149] The 180° peel adhesion force of the adhesive sheet of the present invention to a glass plate at a tensile speed of 300 mm / min at 65°C (especially the 180° peel adhesion force of the adhesive surface provided by the adhesive layer (the adhesive layer of the present invention) to the glass plate at a tensile speed of 300 mm / min at 65°C) is not particularly limited. From the viewpoint of improving the adhesion reliability at high temperatures, it is preferably 6 N / 20 mm or more, more preferably 6.5 N / 20 mm or more, and even more preferably 7 N / 20 mm or more. If the 180° peel adhesion force of the adhesive sheet of the present invention to a glass plate at a tensile speed of 300 mm / min at 65°C is a certain value or more, the adhesion to the glass at high temperatures and the suppression of bulging in the step are more excellent. Furthermore, the upper limit of the 180° peel adhesion force of the adhesive sheet of the present invention to the glass plate at a tensile speed of 300 mm / min at 65°C is not particularly limited. For example, it is preferably 60 N / 20 mm or less, and more preferably 40 N / 20 mm or less.

[0150] The ratio of the 180° peel adhesion force of the adhesive sheet of the present invention at a tensile speed of 300 mm / min to a glass plate at 65°C to the 180° peel adhesion force at a tensile speed of 300 mm / min to a glass plate at 25°C (180° peel adhesion force at a tensile speed of 300 mm / min to a glass plate at 65°C / 180° peel adhesion force at a tensile speed of 300 mm / min to a glass plate at 25°C × 100) is not particularly limited. From the viewpoint of improving adhesion force and adhesion reliability at high temperatures, it is preferably 30 or more, more preferably 35 or more, and even more preferably 40 or more, and even more preferably 45 or more. Since the elastic modulus of the adhesive layer decreases at high temperatures, the above ratio usually decreases. However, if the above ratio of the adhesive sheet of the present invention is a certain value or more, the adhesion force, adhesion reliability, and suppression of bulging in the step difference of the glass at high temperatures are more excellent. There is no particular upper limit to the above ratio; in practice, it can be below 100 or below 90.

[0151] The 180° peel adhesion force of the glass plate at a tensile speed of 300 mm / min at 25°C and 65°C was determined by the following method for measuring 180° peel adhesion force. There are no particular limitations on the glass plate mentioned above; for example, the trade name "Soda Lime Glass #0050" (manufactured by Matsunami Glass Industry Co., Ltd.) can be cited. Alkali-free glass or chemically strengthened glass can also be cited as examples.

[0152] The 180° peel adhesion force of the adhesive sheet of the present invention to an acrylic sheet at a tensile speed of 300 mm / min at 25°C (especially the 180° peel adhesion force of the adhesive surface provided by the adhesive layer (the adhesive layer formed by the adhesive composition of the present invention) to the acrylic sheet at a tensile speed of 300 mm / min at 25°C) is not particularly limited. However, from the viewpoint of obtaining sufficient adhesion to the metal surface and improving corrosion resistance, a higher adhesion force is preferred, preferably 10 N / 20 mm or more, more preferably 12 N / 20 mm or more, and even more preferably 14 N / 20 mm or more. If the 180° peel adhesion force of the adhesive sheet of the present invention to an acrylic sheet at a tensile speed of 300 mm / min at 25°C is 10 N / 20 mm, it is easier to obtain good adhesion to the acrylic sheet or good suppression of bulges in the gradient, which is preferable. Furthermore, the upper limit of the 180° peel adhesion force of the adhesive sheet of the present invention to an acrylic sheet at a tensile speed of 300 mm / min at 25°C is not particularly limited, for example, it is 40 N / 20 mm, more preferably 60 N / 20 mm. The 180° peel adhesion force to the acrylic sheet at a tensile speed of 300 mm / min at 25°C is determined according to the following method for measuring 180° peel adhesion force.

[0153] There are no particular limitations on the acrylic sheet mentioned above. For example, PMMA (Polymethyl methacrylate) sheets (trade name "Acrylite", manufactured by Mitsubishi Rayon Co., Ltd.) can be cited.

[0154] The adhesion force and adhesion ratio of the adhesive sheet of the present invention can be adjusted by adjusting the monomer composition of the acrylic polymer (A), the type of hydrogenated polyolefin resin (B), and the mixing ratio of acrylic polymer (A) and hydrogenated polyolefin resin (B).

[0155] (A-1. Method for determining 180° peel adhesion) The adhesive side of the adhesive sheet is attached to the substrate and pressed under the condition of one round trip with a 2 kg roller. It is then aged for 30 minutes at 23°C and 50%RH. After aging, according to JIS Z 0237, the adhesive sheet is peeled from the substrate at 25°C or 65°C and 50%RH, with a tensile speed of 300 mm / min and a peel angle of 180°. The 180° peel adhesion force (N / 20 mm) is then measured.

[0156] (B. Thickness) The thickness (total thickness) of the adhesive sheet of this invention is not particularly limited, but is preferably 12-350 μm, more preferably 12-300 μm. A thickness of a certain value or higher can adequately alleviate stress on the metal wiring, preventing uneven display. Furthermore, a thickness of a certain value or lower facilitates maintaining an excellent appearance during manufacturing or roller storage, and is less prone to adhesive residue buildup during cutting. Moreover, the thickness of the adhesive sheet of this invention does not include the thickness of the release liner.

[0157] (C. Haze) The haze of the adhesive sheet of this invention (according to JIS K7136) is not particularly limited, but is preferably 1.0% or less, more preferably 0.8% or less. If the haze is 1.0% or less, excellent transparency or excellent appearance can be obtained, which is preferable. The lower limit of haze is not particularly limited; theoretically it is 0%, but practically it can exceed 0.01%. Furthermore, the aforementioned haze can be measured, for example, by allowing the adhesive sheet to stand at normal temperature (23°C, 50%RH) for at least 24 hours, then peeling it off with a release liner, attaching it to a glass slide (e.g., with 92% total light transmittance and 0.2% haze), using the resulting sample, and measuring it using a haze meter (manufactured by Murakami Color Technology Research Institute Co., Ltd., trade name "HM-150N") or an equivalent.

[0158] (D. Total light transmittance) The total light transmittance (according to JIS K7361-1) of the adhesive sheet of the present invention in the visible light wavelength region is not particularly limited, but preferably 90% or more, more preferably 91% or more, and even more preferably 92% or more. If the total light transmittance is 90% or more, excellent transparency or excellent appearance can be obtained, which is preferable. There is no particular upper limit to the total light transmittance. Theoretically, it is the value obtained by subtracting the light loss (Fresnel loss) caused by reflection generated at the air interface from 100%, and practically it can also be 95% or less. Furthermore, the above-mentioned total light transmittance can be obtained, for example, by letting the adhesive sheet stand at normal temperature (23°C, 50%RH) for at least 24 hours, peeling it off with a release liner, and attaching it to a glass slide (e.g., with a total light transmittance of 92% and a haze of 0.2%). The resulting sample is then measured using a haze meter (manufactured by Murakami Color Technology Research Institute Co., Ltd., trade name "HM-150N") or its equivalent.

[0159] [2-2. Manufacturing method of adhesive sheet] The adhesive sheet of the present invention is not particularly limited, but it is preferably manufactured according to a known or conventional manufacturing method. For example, when the adhesive sheet of the present invention is a substrate-free adhesive sheet, it can be obtained by forming the adhesive layer on the release liner using the above method. Furthermore, when the adhesive sheet of the present invention is a substrate-attached adhesive sheet, it can be obtained by directly forming the adhesive layer on the surface of the substrate (direct printing method), or by temporarily forming the adhesive layer on the release liner and then transferring (adhering) it to the substrate, thereby depositing the adhesive layer on the substrate (transfer printing method).

[0160] [2-3. Adhesive layer of adhesive sheet] (Storage modulus at 25°C) The storage modulus of the adhesive layer (the adhesive layer formed from the adhesive composition of the present invention) at 25°C is not particularly limited, but is preferably 0.01 MPa or more, more preferably 0.05 MPa or more, and even more preferably 0.1 MPa or more. If the storage modulus is 0.01 MPa or more, good adhesion reliability is easily obtained, which is preferable. Furthermore, in terms of achieving a more flexible adhesive layer and adequately mitigating stress on the metal wiring to prevent display issues, the storage modulus of the adhesive layer at 25°C is preferably 0.5 MPa or less, more preferably 0.4 MPa or less. The storage modulus of the adhesive layer is measured by dynamic viscoelasticity.

[0161] The storage modulus of the adhesive layer of the present invention can be adjusted by adjusting the monomer composition of the acrylic polymer (A), the type of hydrogenated polyolefin resin (B), and the mixing ratio of acrylic polymer (A) and hydrogenated polyolefin resin (B).

[0162] (thickness) The thickness of the aforementioned adhesive layer (especially the adhesive layer formed by the adhesive composition of the present invention) is not particularly limited, but is preferably 12 to 350 μm, more preferably 12 to 300 μm. A thickness of a certain value or higher is preferable in that it can adequately alleviate stress on the metal wiring and prevent uneven display. Furthermore, a thickness of a certain value or lower is particularly preferable in terms of operability and manufacturability.

[0163] (Manufacturing method) There are no particular limitations on the manufacturing method of the adhesive layer described above. For example, the following method can be used: applying the adhesive composition to a substrate or release liner and drying, hardening, or drying and hardening as needed.

[0164] Furthermore, the coating (application) of the above-mentioned adhesive composition can also be performed using known coating methods. For example, gravure roller coating machines, reverse roller coating machines, contact roller coating machines, dip roller coating machines, rod coating machines, doctor blade coating machines, spray coating machines, corner wheel coating machines, direct coating machines, and other coating machines can be used.

[0165] [2-4. Other layers of the adhesive sheet] In addition to the adhesive layer described above, the adhesive sheet of the present invention may also have other layers. Examples of other layers include: other adhesive layers (adhesive layers other than the adhesive layers described above, and adhesive layers other than those formed by the adhesive composition of the present invention)), intermediate layers, and primer layers. Furthermore, the adhesive sheet of the present invention may also have two or more other layers.

[0166] [2-5. Substrate for Adhesive Sheets] The substrate used as the adhesive sheet in this invention is not particularly limited, and examples include various optical films such as plastic films, anti-reflective (AR) films, polarizing plates, and retardation plates. Examples of raw materials for the aforementioned plastic films include polyester resins such as polyethylene terephthalate (PET); acrylic resins such as polymethyl methacrylate (PMMA); and cyclic olefin polymers such as polycarbonate, triacetin (TAC), polyurethane, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, and cyclic olefin polymers such as Arton (a cyclic olefin polymer manufactured by JSR Corporation) and Zeonor (a cyclic olefin polymer manufactured by Zeon Corporation of Japan). Furthermore, these plastic materials can be used alone or in combination of two or more. Furthermore, the aforementioned "substrate" refers to the portion of the adhesive sheet that is attached to the substrate along with the adhesive layer when the adhesive sheet is applied. Release pads that are peeled off during the use of the adhesive sheet (application) are not included in the "substrate".

[0167] The aforementioned substrate is preferably transparent. The total light transmittance (according to JIS K7361-1) of the aforementioned substrate in the visible light wavelength region is not particularly limited, but is preferably 85% or higher, more preferably 88% or higher. Furthermore, the haze (according to JIS K7136) of the aforementioned substrate is not particularly limited, but is preferably 1.0% or less, more preferably 0.8% or less. Examples of such transparent substrates include PET films, or non-alignment films such as those marketed under the names "Arton" or "Zeonor".

[0168] The thickness of the aforementioned substrate is not particularly limited; for example, it is preferably 12 to 500 μm. Furthermore, the aforementioned substrate can have either a single layer or multiple layers. Also, the surface of the aforementioned substrate can be appropriately subjected to physical treatments such as corona discharge treatment and plasma treatment, and chemical treatments such as primer treatment, or other commonly known surface treatments.

[0169] [2-6. Release gasket for adhesive sheet] The adhesive sheet of the present invention may also have a release liner provided on the adhesive surface before use. Furthermore, when the adhesive sheet of the present invention is a double-sided adhesive sheet, each adhesive surface can be protected by two release liners, or by a single release liner with release surfaces on both sides, wound into a roll for protection. The release liner serves as a protective material for the adhesive layer and is peeled off when attached to the substrate. Also, when the adhesive sheet of the present invention is a substrate-free adhesive sheet, the release liner also serves as a support for the adhesive layer. Furthermore, the release liner may not necessarily be provided.

[0170] The release liner described above is not particularly limited, and examples include: release liners having a release layer (release treatment layer) on at least one surface of the release liner substrate, low-adhesion release liners containing fluoropolymers, and low-adhesion release liners containing non-polar polymers. The fluoropolymers described above are not particularly limited, and examples include: polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Similarly, the non-polar polymers described above are not particularly limited, and examples include: olefin resins such as polyethylene (PE) and polypropylene (PP). Preferably, a release liner having a release layer on at least one surface of the release liner substrate is used.

[0171] There are no particular limitations on the substrate for the aforementioned release liner, and examples include plastic films. Examples of such plastic films include those containing the following components: polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polybutylene terephthalate (PBT); olefin resins with α-olefins as monomers, such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), ethylene-propylene copolymer, and ethylene-vinyl acetate copolymer (EVA); polyvinyl chloride (PVC); vinyl acetate resins; polycarbonate (PC); polyphenylene sulfide (PPS); amide resins such as polyamide (nylon) and fully aromatic polyamide (aromatic polyamide); polyimide resins; and polyetheretherketone (PEEK). From the perspectives of processability, availability, workability, dust protection, and cost, plastic films formed from polyester resins are preferred, and PET films are even more preferred.

[0172] There are no particular limitations on the release agent constituting the aforementioned release layer. Examples include polysiloxane-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, and molybdenum sulfide release agents. Among these, polysiloxane-based release agents are preferred from the viewpoint of release control and stability over time. Furthermore, the release agent can be used alone or in combination of two or more.

[0173] Furthermore, the aforementioned peeling layer can be a single layer, or, within the scope of not impairing the characteristics of the present invention, a laminated structure consisting of two or more layers.

[0174] One preferred embodiment of the release liner described above can be exemplified by the following configuration: a PET film is used as the release liner substrate, and a release layer formed by a polysiloxane-based release agent is provided on at least one surface of the release liner substrate. Furthermore, the surface on which the release layer is not provided on the side opposite to the side in contact with the adhesive layer is sometimes referred to as the "back side" of the release liner.

[0175] From the viewpoint of ensuring die-cutting workability, processability, or maintaining flexibility and thickness, the aforementioned release liner may also have a carrier material laminated on its back side. This carrier material is not particularly limited; examples include a structure consisting of two layers of PET film substrate laminated with an adhesive, or a structure consisting of two layers of COP (Cyclo Olefin Polymer) film substrate and PET film substrate laminated with an adhesive. Furthermore, the aforementioned release liner may also not have a carrier material.

[0176] Furthermore, from the viewpoint of suppressing the charging generated during transport or peeling off the release liner, and reducing the adhesion and contamination of foreign matter, the aforementioned release liner may have a release layer and / or a conductive treatment layer on the back side. This conductive treatment layer is not particularly limited; for example, a coating treatment layer with a composite of poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, and polystyrene sulfonic acid (PSS) as the main component can be cited. Alternatively, the aforementioned release liner may not have a conductive treatment layer.

[0177] The aforementioned release liner can be manufactured using known and conventional methods. The aforementioned carrier material and conductive treatment layer can be prepared by depositing them onto the release layer and / or the back side of the release liner using known methods. Furthermore, without impairing the effects of the present invention, the aforementioned release liner of the present invention may also have other layers (e.g., intermediate layer, primer layer, etc.).

[0178] The thickness of the aforementioned release liner is not particularly limited. However, from the perspective of cost or the rationality of adhesive sheet placement in bonding operations, it is preferably 12~200 μm, more preferably 25~150 μm, and even more preferably 38~125 μm.

[0179] Furthermore, when the adhesive sheet of the present invention is a double-sided adhesive sheet of the double-release pad type, a release pad is provided on one adhesive surface and a release pad is also provided on the other adhesive surface. In this case, it is preferable that the two release pads are release pads with only one surface as a release layer (especially release pads having a release layer containing a polysiloxane-based release agent on one surface of a plastic substrate). Also, the release pads are provided in such a way that the release layer contacts the adhesive surface.

[0180] Furthermore, when the adhesive sheet of the present invention is a double-release pad type double-sided adhesive sheet, it is preferable to have a difference in the peel force of the two release pads. For example, when the adhesive sheet of the present invention is a double-release pad type double-sided adhesive sheet, it is preferable to use one release pad on the adhesive surface used (attached) first (also referred to as "side 1"), and to use another release pad on the adhesive surface used (attached) later (also referred to as "side 2"). Therefore, it is preferable to use one release pad as the release pad for the "light peel side" that can be peeled with a smaller force (peel force), and to use the other release pad as the release pad for the "heavy peel side" that requires a larger force (peel force). Furthermore, in this specification, the release pad on the light peel side is sometimes referred to as the "light peel pad," and the release pad on the heavy peel side is sometimes referred to as the "heavy peel pad."

[0181] Furthermore, when the adhesive sheet of the present invention is a double-sided adhesive sheet of the single-release pad type, a release pad is provided on one adhesive surface, and by winding it, the other adhesive surface of the adhesive body is also protected by the release pad. When the adhesive sheet of the present invention is of the single-release pad type, it is preferable that the surface of the release pad is a release layer (release treatment layer). Also, sometimes the release layer on the side that contacts the adhesive surface by winding is referred to as the "back release layer". Usually, the back release layer side of the release pad is used on the "one side" of the double-sided adhesive sheet.

[0182] The adhesive sheet of this invention provides stress relief without reducing the molecular weight of the acrylic polymer, thus suppressing roughness, deformation, and slippage of the adhesive layer on the peeling surface during the peeling of the release liner, resulting in more stable use of the adhesive sheet. Furthermore, slippage is a vibration phenomenon generated on the peeling surface, which can damage the bonded object, causing breakage, or leaving adhesive residue on the bonded object.

[0183] When the adhesive sheet of the present invention is a double-sided adhesive sheet, from the perspective of suppressing the roughness or deformation and slippage of the adhesive layer on the adhesive surface during the peeling of the release liner, and using the adhesive sheet stably, the peel force (release liner peel force) of the release liner on one side (light peeling side) to the adhesive layer is 0.01~0.5 N / 50 mm, preferably 0.05~0.25 N / 50 mm, and the peel force (release liner peel force) of the release liner on the other side (heavy peeling side) to the adhesive layer (e.g., the acrylic adhesive layer, the rubber adhesive layer, etc.) is 0.1~1.00 N / 50 mm, preferably 0.2~0.85 N / 50 mm. Preferably, the peel force of the release liner on the heavy peeling side is always greater than that on the light peeling side, and there is a peel difference of about 1.1 to 10.0 times.

[0184] Especially when the adhesive sheet of the present invention is a double-sided adhesive sheet, from the perspective of suppressing the so-called adhesion separation phenomenon, the roughness or deformation of the adhesive surface of the adhesive layer during the peeling of the release liner, the generation of slippage, and the stable use of the adhesive sheet, the difference between the peeling force of the heavy release liner on the adhesive layer (release liner peeling force) and the peeling force of the light release liner on the adhesive layer (release liner peeling force) is preferably 0.01 N / 50 mm or more, more preferably 0.02 N / 50 mm or more, further preferably 0.05 N / 50 mm or more, and even more preferably 0.06 N / 50 mm or more.

[0185] Furthermore, the peel strength of the aforementioned release liner refers to the adhesion of the release liner to the adhesive layer after a 180° peel test, as determined by the 180° peel test. Additionally, the tensile speed is 300 mm / min.

[0186] [2-7. Applications of adhesive sheets, etc.] The adhesive sheet of this invention has the adhesive layer of this invention (an adhesive layer formed by the adhesive composition of this invention), thus the appearance of the display device or input device is not easily degraded under low pressure conditions. Furthermore, it has excellent flexibility, preventing uneven display of the display device or input device when bonding films with metal wiring, such as metal mesh films or silver nanowire films. Moreover, it exhibits excellent adhesion, foaming peel resistance, and step tracking. Therefore, optical components with the adhesive sheet of this invention do not easily degrade in appearance under low pressure conditions, have high flexibility, can effectively mitigate stress from metal wiring, prevent uneven display, and have excellent adhesion reliability, especially at high temperatures.

[0187] Therefore, the adhesive sheet of the present invention can be usefully used for bonding films with metal wiring, such as metal mesh films or silver nanowire films. Furthermore, the adhesive sheet of the present invention can also be usefully used for substrates that are prone to foaming at the interface at high temperatures. For example, polymethyl methacrylate (PMMA) resin sometimes contains unreacted monomers, which are prone to foaming due to foreign matter at high temperatures. Also, polycarbonate (PC) is prone to releasing water and carbon dioxide at high temperatures. Because the adhesive sheet of the present invention has excellent resistance to foaming and peeling, it can also be usefully used for plastic substrates containing such resins.

[0188] Furthermore, the adhesive sheet of the present invention can be usefully used not only for substrates with a small coefficient of linear expansion, but also for substrates with a large coefficient of linear expansion. Moreover, there is no particular limitation on the substrate with a small coefficient of linear expansion; examples include glass plates (coefficient of linear expansion: 0.3×10⁻⁵~0.8×10⁻⁵ / ℃) and polyethylene terephthalate substrates (PET film, coefficient of linear expansion: 1.5×10⁻⁵~2×10⁻⁵ / ℃). Furthermore, there is no particular limitation on the substrate with a relatively large coefficient of linear expansion. For example, resin substrates with a relatively large coefficient of linear expansion can be cited. More specifically, examples include: polycarbonate resin substrates (PC, coefficient of linear expansion: 7×10⁻⁵~8×10⁻⁵ / ℃), polymethyl methacrylate resin substrates (PMMA, coefficient of linear expansion: 7×10⁻⁵~8×10⁻⁵ / ℃), cycloolefin polymer substrates (COP, coefficient of linear expansion: 6×10⁻⁵~7×10⁻⁵ / ℃), trade name "Zeonor" (manufactured by Zeon Corporation of Japan), trade name "Arton" (manufactured by JSR Corporation), etc.

[0189] The adhesive sheet of the present invention can be usefully used for bonding an adhesive with a small coefficient of linear expansion to an adhesive with a large coefficient of linear expansion. Specifically, the adhesive sheet of the present invention is preferably used for bonding a glass adhesive (e.g., a glass plate, chemically strengthened glass, a glass lens, etc.) to the aforementioned resin substrate with a large coefficient of linear expansion.

[0190] Thus, the adhesive sheet of the present invention can be used to bond various raw materials to each other, and is particularly useful for bonding glass substrates and plastic substrates. Furthermore, the plastic substrate can also be an optical film such as a plastic film with metal mesh wiring or silver nanowires on its surface.

[0191] Furthermore, the adhesive sheet of the present invention can be usefully used not only for substrates with smooth surfaces, but also for substrates with surface gradients, such as metal mesh films or silver nanowire films with metal wiring. In particular, even if at least one of the glass substrate and the aforementioned resin substrate with a large coefficient of linear expansion has surface gradients, the adhesive sheet of the present invention can still be usefully used to bond the glass substrate and the aforementioned resin substrate with a large coefficient of linear expansion.

[0192] The adhesive sheet of this invention is preferably used in the manufacture of portable electronic devices. Examples of such portable electronic devices include: mobile phones, PHS (Personal Handyphone System), smartphones, tablets (tablet computers), mobile computers (mobile PCs), portable information terminals (PDAs), electronic notebooks, portable televisions or portable radios and other portable broadcast receivers, portable game consoles, Walkmans, portable (Digital Versatile Disc) players, digital cameras and other cameras, camcorders, etc.

[0193] The adhesive sheet of this invention is preferably used, for example, for attaching components or modules of portable electronic devices to each other, or for fixing components or modules of portable electronic devices to a housing. More specifically, examples include: bonding a cover glass or lens (especially a glass lens) to a touch panel or touch sensor (especially a film with metal wiring, such as a metal mesh film or a silver nanowire film); bonding a polarizing plate to a touch panel or touch sensor; bonding a display panel to a touch panel or touch sensor; fixing a cover glass or lens (especially a glass lens) to a housing; fixing a display panel to a housing; fixing an input device such as a sheet keyboard or touch panel to a housing; bonding a protective panel of an information display unit to a housing; bonding housings to each other; bonding a housing to a decorative sheet; and fixing or bonding various components or modules of portable electronic devices. Furthermore, in this specification, a display panel refers to a structure that includes at least a lens (especially a glass lens) and a touch panel. Furthermore, the lens in this specification includes both transparent bodies that refract light and transparent bodies that do not refract light. That is, the lens in this specification also includes simple window panels that do not refract light.

[0194] Furthermore, the adhesive sheet of the present invention is preferably used for optical applications. That is, the adhesive sheet of the present invention is preferably an optical adhesive sheet for optical applications. More specifically, for example, it is preferably used for bonding optical components (for bonding optical components) or for manufacturing articles using the above-mentioned optical components (optical articles), etc.

[0195] [3. Optical Components] The optical component of the present invention comprises at least the aforementioned adhesive sheet and substrate, wherein the substrate has metal wiring (e.g., metal mesh wiring, silver nanowires, etc.) on at least one side. It is sufficient that the adhesive layer of the present invention (an adhesive layer formed from the adhesive composition of the present invention) is adhered to the side of the substrate having the aforementioned metal wiring; there are no other particular limitations. Furthermore, the adhesive sheet of the present invention may have a release liner provided on the adhesive surface before use, but the adhesive sheet in the optical component of the present invention is the adhesive sheet for use, therefore it does not have a release liner.

[0196] From the viewpoint of obtaining excellent corrosion resistance, the optical component preferably has the adhesive layer on the side of the substrate opposite to the side having the metal wiring, and more preferably the adhesive layer is attached to the surface of the substrate opposite to the side having the metal wiring.

[0197] There are no particular limitations on the materials used to constitute the aforementioned metal wiring. Examples include: titanium, silicon, niobium, indium, zinc, tin, gold, silver, copper, aluminum, cobalt, chromium, nickel, lead, iron, palladium, platinum, tungsten, zirconium, tantalum, hafnium, etc. Furthermore, examples include those containing two or more of these metals, or alloys with these metals as the main component. From a conductivity perspective, gold, silver, and copper are preferred; from a conductivity and cost perspective, silver and copper are more preferred. That is, the aforementioned metal wiring is preferably silver wiring and / or copper wiring, especially copper mesh wiring, silver mesh wiring, and silver nanowires. Furthermore, for higher rust resistance, an oxide film or metal coating can be applied to the metal wiring. The same applies to the materials used to constitute the metal wiring of the touch panel described below.

[0198] Optical components refer to components that have optical properties (such as polarization, refraction, scattering, reflection, transmittance, absorption, diffraction, rotation, and visibility). The substrates constituting the aforementioned optical components are not particularly limited. Examples include substrates constituting display devices (image display devices), input devices, and other equipment (optical equipment), or substrates used in such equipment. Examples include polarizing plates, waveplates, phase retardation plates, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflective films, hard-coated films (films on at least one side of plastic films such as PET films with hard coating treatment), transparent conductive films (e.g., plastic films with an ITO layer on the surface (preferably PET-ITO, polycarbonate, cyclic olefin polymers, etc. ITO films)), design films, decorative films, surface protection plates, prisms, lenses, color filters, transparent substrates (glass sensors, glass display panels (LCDs, etc.), glass substrates with transparent electrodes, etc.), or substrates on which such layers are deposited (sometimes collectively referred to as "functional films"). Furthermore, these films may have metal nanowire layers or conductive polymer layers. Furthermore, fine metal lines can be screen-printed on these films. Moreover, the aforementioned "plate" and "film" are respectively provided to include plate-like, film-like, and sheet-like forms; for example, "polarizing film" includes "polarizing plate" and "polarizing sheet," etc. Also, "film" includes film sensors, etc.

[0199] In particular, the adhesive sheet of the present invention is suitable for use in transparent conductive films (metal mesh films, silver nanowire films) where the metal wiring is metal mesh wiring or silver nanowires, especially optical components with metal mesh films. If optical components with metal wiring, such as metal mesh films or silver nanowire films, are bonded using an adhesive sheet, the following problem arises: due to the stress and strain applied to the adhesive around the metal wiring, uneven display can easily occur at the periphery of the image display panel. Therefore, to prevent uneven display, the adhesive layer of the adhesive sheet used to bond optical components with metal wiring needs to be flexible enough to mitigate the stress of the metal wiring. However, to prevent uneven display, display devices or input devices that use adhesive sheets with higher flexibility to bond optical components have the following problems: the appearance deteriorates under low-pressure conditions such as manufacturing processes, aircraft cargo holds, or high-altitude areas.

[0200] In the adhesive sheet of this invention, the adhesive layer has high flexibility, which can effectively alleviate the stress of the metal wiring when bonding films with metal wiring, such as metal mesh films or silver nanowire films, and prevent uneven display. Furthermore, the appearance of display devices or input devices using the adhesive sheet of this invention is not easily degraded even under low-pressure conditions. Similarly, the same applies to the metal mesh film and silver nanowire film constituting the touch panel described below.

[0201] Examples of display devices include liquid crystal displays, organic EL (electroluminescent) displays, PDP (plasma display panels), and electronic paper. Examples of input devices include touch panels.

[0202] The substrate constituting the aforementioned optical component is not particularly limited, and examples include substrates such as glass, acrylic resin, polycarbonate, polyethylene terephthalate, cyclic olefin polymers, and metal thin films (e.g., sheet-like, film-like, or plate-like substrates). Furthermore, the "optical component" in this invention, as described above, also includes components (design films, decorative films, or surface protective films, etc.) that maintain the visibility of the display device or input device and are responsible for decoration or protection.

[0203] If the adhesive sheet of the present invention is an adhesive sheet attached to a substrate, and the adhesive sheet constitutes a component with optical properties, then the substrate can be regarded in the same way as the substrate, and the adhesive sheet can also be considered as an optical component of the present invention.

[0204] When the adhesive sheet of the present invention is an adhesive sheet with a substrate, and the above-mentioned functional film is used as the substrate, the adhesive sheet of the present invention can also be used as an "adhesive functional film", which has the above-mentioned adhesive layer on at least one side of the functional film.

[0205] Next, a preferred embodiment of the optical component of the present invention will be described with reference to the schematic diagram in FIG1.

[0206] Figure 1 shows an optical component 1, which is an optical component having at least an adhesive sheet 10 and a substrate as a metal mesh film 11, and the metal mesh film 11 has metal mesh wiring 3 on one side, and the adhesive sheet 10 is attached to the side of the metal mesh film 11 with metal mesh wiring 3.

[0207] [4. Touch Panel] The touch panel of the present invention comprises at least the aforementioned adhesive sheet and substrate, wherein the substrate has metal wiring (e.g., metal mesh wiring, silver nanowires, etc.) on one side. It is sufficient that the adhesive layer is adhered to the side of the substrate having the metal wiring; there are no other particular limitations. Furthermore, since the adhesive sheet in the touch panel of the present invention is an adhesive sheet used in application, it does not have a release liner.

[0208] The aforementioned touch panel is preferably constructed by bonding the optical components of the present invention with other optical components (which may or may not have the aforementioned adhesive sheet, but from the viewpoint of obtaining excellent anti-corrosion effect, it is preferable to have the aforementioned adhesive sheet). Furthermore, the aforementioned other optical components may be singular or plural.

[0209] The bonding configuration of the optical component of the present invention with the other optical components described above is not particularly limited. Examples include: (1) bonding the optical component of the present invention with the other optical components via the adhesive sheet of the present invention; (2) bonding the adhesive sheet of the present invention, which includes or constitutes an optical component, to the other optical components; (3) bonding the optical component to a component other than an optical component via the adhesive tape of the present invention; and (4) bonding the adhesive tape of the present invention, which includes or constitutes an optical component, to a component other than an optical component. Furthermore, in configuration (2) above, the adhesive sheet of the present invention is preferably a double-sided adhesive sheet whose substrate is an optical component (e.g., an optical film).

[0210] Next, a preferred embodiment of the touch panel of the present invention will be described with reference to the schematic diagram in FIG2.

[0211] Figure 2(A) shows a touch panel 2A, which sequentially comprises a transparent substrate 12a, an adhesive sheet 10a, a metal mesh film 11a, an adhesive sheet 10b, and a transparent substrate 12b in contact with each other. The metal mesh film 11a has metal mesh wiring 3 on the side of the adhesive sheet 10b, and the adhesive sheet 10b is attached to the side of the metal mesh film 11a with the metal mesh wiring 3. The transparent substrates 12a and 12b are preferably glass, and the substrate of the metal mesh film 11a is preferably PET. The adhesive sheet 10a may be the adhesive sheet of the present invention, or it may not be the adhesive sheet of the present invention, but it is preferred to be the adhesive sheet of the present invention.

[0212] Figure 2(B) shows a touch panel 2B, which sequentially comprises a transparent substrate 12a, an adhesive sheet 10a, a metal mesh film 13a, an adhesive sheet 10b, a polarizing plate 14, and the transparent substrate 12b in contact with each other. The metal mesh film 13a has metal mesh wiring 3 on the side of the adhesive sheet 10b, and the adhesive sheet 10b is attached to the side of the metal mesh film 13a with the metal mesh wiring 3. The transparent substrate 12a is preferably glass, and the transparent substrate 12b is preferably a glass display panel such as an LCD. The adhesive sheet 10a may or may not include the adhesive layer (an adhesive layer formed by the adhesive composition of the present invention), but it is preferred to include the adhesive layer (an adhesive layer formed by the adhesive composition of the present invention).

[0213] Figure 2(C) shows a touch panel 2C, which sequentially comprises a transparent substrate 12a, an adhesive sheet 10a, a metal mesh film 11b, and the transparent substrate 12b in contact with each other. The metal mesh film 11b has metal mesh lines 3a and 3b on both sides respectively. The adhesive sheet 10a is attached to the side of the metal mesh film 11b with the metal mesh lines 3a, and the adhesive sheet 10b is attached to the side of the metal mesh film 11b with the metal mesh lines 3b. The transparent substrate 12a and transparent substrate 12b are preferably glass, and the substrate of the metal mesh film 11b is preferably PET. It is permissible as long as at least one of the adhesive sheet 10a and adhesive sheet 10b is the adhesive sheet of the present invention, but it is preferred that both adhesive sheets 10a and adhesive sheet 10b are the adhesive sheets of the present invention.

[0214] Figure 2(D) shows a touch panel 2D, which sequentially comprises a transparent substrate 12a, an adhesive sheet 10a, a metal mesh film 13b, a polarizing plate 14, and the transparent substrate 12b in contact with each other. The metal mesh film 13b has metal mesh lines 3a and 3b on both sides respectively. The adhesive sheet 10a is attached to the side of the metal mesh film 13b with the metal mesh lines 3a, and the adhesive sheet 10b is attached to the side of the metal mesh film 13b with the metal mesh lines 3b. The transparent substrate 12a is preferably glass, and the transparent substrate 12b is preferably a glass display panel such as an LCD. It is permissible as long as at least one of the adhesive sheet 10a and the adhesive sheet 10b includes the aforementioned adhesive layer (an adhesive layer formed by the adhesive composition of the present invention), but it is preferred that both the adhesive sheet 10a and the adhesive sheet 10b include the aforementioned adhesive layer (an adhesive layer formed by the adhesive composition of the present invention).

[0215] There are no particular limitations on the method of forming the metal mesh wiring on the metal mesh film. Examples include methods such as removing the pre-set metal layer by etching or printing. [Example]

[0216] The present invention will now be described in more detail with reference to embodiments, but the present invention is not limited to these embodiments. Furthermore, the quantities (parts by weight) refer to the quantities of each of the described ingredients.

[0217] [Manufacturing Example 1: Preparation of Prepolymer Composition A] In a monomer mixture comprising 40.5 parts by weight of 2-ethylhexyl acrylate (2EHA), 40.5 parts by weight of isostearate acrylate (ISTA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 1 part by weight of 4-hydroxybutyl acrylate (4-HBA), 0.05 parts by weight of photopolymerization initiator (trade name "Omnirad184", manufactured by IGM Resins BV) and 0.05 parts by weight of photopolymerization initiator (trade name "Omnirad651", manufactured by IGM Resins BV) were added, and then the mixture was irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measuring temperature 30°C) became approximately 20 Pa·s, thereby obtaining a prepolymer composition A formed by the partial polymerization of one of the above monomer components.

[0218] [Manufacturing Example 2: Preparation of Prepolymer Composition B] In a monomer mixture comprising 56 parts by weight of 2-ethylhexyl acrylate (2EHA), 24 parts by weight of isostearate acrylate (ISTA), 14 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 6 parts by weight of 4-hydroxybutyl acrylate (4-HBA), 0.035 parts by weight of photopolymerization initiator (trade name "Omnirad184", manufactured by IGM Resins BV) and 0.035 parts by weight of photopolymerization initiator (trade name "Omnirad651", manufactured by IGM Resins BV) were added, and then the mixture was irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measuring temperature 30°C) became approximately 20 Pa·s, thereby obtaining a prepolymer composition B formed by partial polymerization of one of the above monomer components.

[0219] [Manufacturing Example 3: Preparation of Prepolymer Composition C] In a monomer mixture comprising 56 parts by weight of 2-ethylhexyl acrylate (2EHA), 24 parts by weight of isostearate acrylate (ISTA), 19 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 1 part by weight of 4-hydroxybutyl acrylate (4-HBA), 0.035 parts by weight of photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM Resins BV) and 0.035 parts by weight of photopolymerization initiator (trade name "Omnirad 651", manufactured by IGM Resins BV) were added, and then the mixture was irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measuring temperature 30°C) became approximately 20 Pa·s, thereby obtaining a prepolymer composition C formed by partial polymerization of one of the above monomer components.

[0220] [Example 1] To the prepolymer composition A100 parts by weight obtained in Manufacturing Example 1, 3 parts by weight of hydrogenated 1,2-polybutadiene (trade name "BI-3000", quantity average molecular weight (Mn): 4750 (measured value), weight average molecular weight (Mw): 6150 (measured value), polydispersity (Mw / Mn): 1.30 (measured value), hydrogenation rate: ≥97% (catalog value), iodine value: ≤21 (catalog value), manufactured by Nippon Soda Co., Ltd.), and 3 parts by weight of hydrogenated 1,2-polybutadiene glycol (trade name "GI-2000", quantity average molecular weight (Mn): ≥97% (catalog value), weight average molecular weight (Mw / Mn): ≥21 (catalog value), were added. Mn): 3110 (measured value), weight average molecular weight (Mw): 5090 (measured value), polydispersity (Mw / Mn): 1.64 (measured value), hydrogenation rate: ≥93% (list value), iodine value: ≤21 (list value), manufactured by Nippon Soda Co., Ltd. 12 parts by weight, 0.040 parts by weight of trimethylolpropane triacrylate (TMPTA), and 0.3 parts by weight of silane coupling agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed to obtain an adhesive composition (pre-curing composition).

[0221] The adhesive composition described above is applied to a polyethylene terephthalate (PET) release liner (heavy release liner, trade name "MRF75", manufactured by Mitsubishi Resin Co., Ltd.) with a final thickness (adhesive layer thickness) of 150 μm to form a coating layer (adhesive composition layer). Then, a PET release liner (light release liner, trade name "MRE75", manufactured by Mitsubishi Resin Co., Ltd.) is placed on the coating layer to block oxygen. A laminate of MRF75 / coating layer (adhesive composition layer) / MRE75 is obtained. Next, the laminate was irradiated with ultraviolet light (5 mW / cm²) for 300 seconds from its upper surface (MRF38 side) using a black light lamp (manufactured by Toshiba Corporation). Then, it was dried in a 90°C dryer for 2 minutes to evaporate any residual monomers. This resulted in a substrate-free double-sided adhesive sheet containing only the adhesive layer, with both sides of the adhesive layer protected by a release liner.

[0222] [Examples 2-10, Comparative Examples 1-3] Except for the composition of the adhesive composition and the thickness of the adhesive layer as shown in Table 1, a substrate-free double-sided adhesive sheet was obtained in the same manner as in Example 1.

[0223] [Table 1] (Table 1) composition Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 Prepolymer Composition A 100 - - - - - - - - - 100 100 100 B - 100 100 100 100 100 - - - - - - - C - - - - - - 100 100 100 100 - - - Hydrogenated polyolefins BI-3000 3 3 5 5 10 12 3 3 1.5 1.5 - - - GI-2000 12 12 5 5 10 3 12 18 twenty one twenty four - - 18 Multifunctional acrylates TMPTA 0.040 0.050 0.035 0.050 0.050 0.050 0.050 0.050 0.070 0.070 0.020 0.15 0.04 Chain transfer agent α-Thioglycerol - - - - - - - - - - - 0.15 - Silane coupling agent KBM-403 0.300 0.300 0.300 0.300 0.300 0.300 0.300 0.300 0.300 0.300 0.300 0.300 0.300 Adhesive thickness (μm) 150 150 150 150 150 150 150 150 150 150 150 150 150

[0224] The detailed information about the components shown in Table 1 is as follows. (Prepolymer Composition) A: Prepolymer composition A manufactured in Example 1 B: The prepolymer composition manufactured in Example 2 C: The prepolymer composition manufactured in Example 3

[0225] (Hydrogenated polyolefin) BI-2000: Trade name "BI-2000", hydrogenated 1,2-polybutadiene, quantity average molecular weight (Mn): 2930 (measured), weight average molecular weight (Mw): 4050 (measured), polydispersity (Mw / Mn): 1.38 (measured), hydrogenation rate: ≥97% (catalog value), iodine value: ≤21 (catalog value), manufactured by Nippon Soda Co., Ltd. GI-2000: Trade name "GI-2000", hydrogenated 1,2-polybutadiene glycol, quantity average molecular weight (Mn): 3110 (measured), weight average molecular weight (Mw): 5090 (measured), polydispersity (Mw / Mn): 1.64 (measured), hydrogenation rate: ≥97% (catalog value), iodine value: ≤21 (catalog value), manufactured by Nippon Soda Co., Ltd.

[0226] (Multifunctional acrylates) TMPTA: Trimethylolpropane triacrylate (Chain transfer agent) α-Thioglycerol (Silane coupling agent) KBM-403: Trade name "KBM-403", 3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0227] The measured values ​​of the number average molecular weight (Mn), weight average molecular weight (Mw), and polydispersity (Mw / Mn) of the above-mentioned hydrogenated polyolefins and non-hydrogenated polyolefins were determined by GPC (gel permeation chromatography) under the following conditions and were calculated based on the values ​​converted from polystyrene. Analysis apparatus: GPC: HLC-8320GPC (Tosoh) Measurement conditions: Column: TSKgel SuperHZM-H / HZ4000 / HZ3000 / HZ2000 String dimensions: 6.0 mm I.D. × 150 mm Dissolution solution: THF (tetrahydrofuran) Flow rate: 0.6 mL / min Detector: Differential refractometer (RI) Column temperature: 40℃ Injection volume: 20 μL The molecular weight was calculated using polystyrene.

[0228] [Feature Evaluation] The substrate-free double-sided adhesive sheets of the Examples and Comparative Examples were subjected to the following measurements or evaluations. The evaluation results are shown in Table 2.

[0229] (1) 300% tensile residual stress The substrate-free double-sided adhesive sheets of the examples and comparative examples were cut into 4 cm × 4 cm sizes and folded twice in the center without trapping air bubbles to obtain a sample (adhesive layer) with a width of 1 cm, a length of 4 cm and a thickness of 600 μm. At 23°C, the obtained sample was stretched along its length to an elongation (strain) of 300% (60 mm) with a clamping gap of 20 mm and a stretching speed of 200 mm / min (the clamping gap after stretching was 80 mm). Maintaining this elongation, the tensile stress (N) applied to the sample 300 seconds after the end of stretching was calculated. The value (N / cm²) obtained by dividing this tensile stress by the initial cross-sectional area of ​​the sample (the cross-sectional area before stretching) was set as the 300% tensile residual stress. Furthermore, the initial elongation of the sample was 100%.

[0230] (2) Gel fraction Approximately 0.1 g of adhesive layer was taken from the double-sided adhesive sheet and wrapped inside a porous tetrafluoroethylene sheet (trade name "NTF1122", manufactured by Nitto Denko Corporation) with an average pore size of 0.2 μm. The sheet was then secured with kite string, and the weight at this point was measured. This weight was designated as the weight before impregnation. Furthermore, this weight before impregnation was the total weight of the adhesive layer (the adhesive layer taken above), the tetrafluoroethylene sheet, and the kite string. Also, the combined weight of the tetrafluoroethylene sheet and the kite string was measured beforehand, and this weight was designated as the packaging weight. Next, the sample (referred to as the "sample"), which was wrapped with a tetrafluoroethylene sheet and secured with kite string, was placed in a 50 ml container filled with ethyl acetate and left to stand at 23°C for 7 days. Afterward, the sample (after ethyl acetate treatment) was removed from the container, transferred to an aluminum cup, and dried in a desiccator at 130°C for 2 hours to remove the ethyl acetate. The weight was then measured and recorded as the weight after impregnation. Furthermore, the gel fraction is calculated according to the following formula. Gel fraction [% (weight %)] = (XY) / (ZY) × 100

[0231] (3) Low-pressure test A 5 cm × 10 cm display panel sample was prepared by pressing and bonding the glass plate / polarizing plate / adhesive layer / glass plate laminated under vacuum pressure below 100 Pa and pressure of 0.2~0.5 MPa for 5 seconds, followed by autoclaving at 50℃ × 0.5 MPa × 15 min. The glass plate thickness was 700 μm, the polarizing plate thickness was 115 μm (polarizing plate 95 + polarizing plate adhesive 20) μm, and the adhesive layer thickness was 150 μm. The display panel was placed in a thermostatic bath at 23800 Pa and 65℃ for 8 hours. After removing the display panel from the thermostatic bath, it was placed at room temperature and atmospheric pressure for 30 minutes. The diameter and number of gaps were visually measured, and the panel was evaluated according to the following criteria. The number of voids with a diameter of 300 μm or more is 0, and the number of voids with a diameter of 50 μm or more but less than 300 μm is also 0. The number of voids with a diameter of 300 μm or more is 0, and the number of voids with a diameter of 50 μm or more but less than 300 μm is 1 or more but less than 10. △···The number of voids with a diameter of 300 μm or more is 1 or more but less than 10, or the number of voids with a diameter of 50 μm or more but less than 300 μm is 10 or more but less than 20. The number of voids with a diameter of 300 μm or more is 10 or more, or the number of voids with a diameter of 50 μm or more but less than 300 μm is 20 or more.

[0232] [Table 2] (Table 2) evaluate Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 300% tensile residual stress (N / cm²) 3.4 2.8 3.2 3.7 2.8 2.9 3.5 3.0 2.8 2.6 6 1.3 2.6 Gel fraction (%) 62 70 72 76 71 74 67 62 67 65 65 42 58 Low pressure test Maximum diameter of the void portion (μm) 100 - - - - - - 200 - - 200 500 500 Number of voids with a diameter of 300 μm or more 0 0 0 0 0 0 0 0 0 0 0 18 10 Number of pores with a diameter of 50 μm or more but less than 300 μm 2 0 0 0 0 0 0 3 0 0 twenty four 2 0 evaluate ○ ◎ ◎ ◎ ◎ ◎ ◎ ○ ◎ ◎ × × ×

[0233] Variations of the present invention are described below. [Note 1] An adhesive sheet having an adhesive layer, and In the following low-pressure tests, the number of voids with a diameter of 300 μm or more is less than 10, and the number of voids with a diameter of 50 μm or more but less than 300 μm is less than 20. Low-pressure test A 5 cm × 10 cm display panel with a laminated structure of glass plate / polarizing plate / adhesive layer / glass plate was prepared as a sample. The thickness of the glass plate was 700 μm, the thickness of the polarizing plate was 115 μm (95 μm for the polarizing plate + 20 μm for the polarizing plate adhesive), and the thickness of the adhesive layer was 150 μm. The display panel was subjected to a heating and decompression condition of 23800 Pa and 65°C, and then left to stand for 8 hours. After being placed at room temperature and atmospheric pressure for 30 minutes, the diameter and number of gaps were visually measured. [Note 2] As described in Note 1, the maximum diameter of the void portion in the above-mentioned low-pressure test is less than 600 μm. [Note 3] As described in Note 1 or 2, the adhesive sheet has a gel content of 50% or more in the adhesive layer. [Note 4] The adhesive sheet described in any of Notes 1 to 3, wherein the 300% tensile residual stress of the adhesive layer is less than 5 N / cm 2. [Note 5] The adhesive sheet described in any of Notes 1 to 4, wherein the adhesive layer is formed of an adhesive composition containing an acrylic polymer (A) and a hydrogenated polyolefin resin (B). [Note 6] The adhesive sheet described in any of Notes 1 to 4, wherein the adhesive layer is formed of an adhesive composition comprising a mixture of monomeric components constituting acrylic polymer (A) or a portion thereof constituting a mixture of monomeric components constituting acrylic polymer (A) and hydrogenated polyolefin resin (B). [Note 7] As in Note 5 or 6, the adhesive sheet wherein the acrylic polymer (A) comprises an alkyl (meth)acrylate having an alkyl group having 8 or more carbon atoms as a monomer component. [Note 8] The adhesive sheet described in any of Notes 5 to 7, wherein the above-mentioned hydrogenated polyolefin resin (B) contains hydrogenated polyolefin. [Note 9] As described in Note 8, the adhesive sheet wherein the above-mentioned hydrogenated polyolefin resin (B) further contains hydrogenated polyolefin polyol. [Note 10] The adhesive sheet described in any of Notes 1 to 9 has a thickness of 12 to 350 μm. [Appendix 11] An optical component having at least an adhesive sheet and a substrate as described in any one of Appendices 1 to 10, wherein the substrate has metal wiring on at least one side, and the adhesive sheet is attached to the side of the substrate having the metal wiring. [Note 12] As described in Note 11, the aforementioned metal wiring is a metal mesh wiring or silver nanowires. [Appendix 13] A touch panel having at least an adhesive sheet and a substrate as described in any one of Appendices 1 to 10, wherein the substrate has metal wiring on at least one side, and the adhesive sheet is attached to the side of the substrate having the metal wiring. [Note 14] The touch panel described in Note 13, wherein the metal wiring is metal mesh wiring or silver nanowires.

[0234] 1: Optical components 2A: Touch panel 2B: Touch panel 2C: Touch panel 2D: Touch panel 3: Metal mesh wiring 3a: Metal mesh wiring 3b: Metal mesh wiring 10: Adhesive sheet 10a: Adhesive sheet 10b: Adhesive sheet 11: Metal mesh film 11a: Metal mesh film 11b: Metal mesh film 12a:Transparent substrate 12b:Transparent substrate 13a: Metal mesh film 13b: Metal mesh film 14:Polarizing plate

Claims

1. An adhesive sheet having an adhesive layer, wherein the 300% tensile residual stress of the adhesive layer is less than 5 N / cm², wherein the adhesive layer is formed of an adhesive composition containing an acrylic polymer (A), or a mixture containing monomer components constituting the acrylic polymer (A), or a mixture of monomer components constituting the acrylic polymer (A), and a hydrogenated polyolefin resin (B) that is liquid at 25°C, wherein in the following low-pressure test, the number of voids with a diameter of 300 μm or more is less than 10, and the number of voids with a diameter of 50 μm or more but less than 300 μm is less than 20. <Low-pressure test> A 5 ​​cm × 10 cm display panel having a laminated structure of glass plate / polarizing plate / adhesive layer / glass plate is prepared as a sample; the thickness of the glass plate is 700 μm, and the thickness of the polarizing plate is 115 (polarizing plate 95 + polarizing plate adhesive 20). μm, the adhesive layer thickness is 150 μm; the display panel is placed under heating and decompression conditions of 23800 Pa and 65℃ for 8 hours, and then placed at room temperature under normal pressure for 30 minutes. The diameter and number of the gaps are measured by visual inspection.

2. The adhesive sheet as requested in item 1, wherein the maximum diameter of the void portion in the aforementioned low-pressure test is 600 μm or less.

3. The adhesive sheet as requested in item 1 or 2, wherein the gel content of the adhesive layer is 50% or more.

4. The adhesive sheet as claimed in claim 1, wherein the acrylic polymer (A) comprises an alkyl (meth)acrylate having an alkyl group having 8 or more carbon atoms as a monomer component.

5. The adhesive sheet as claimed in claim 1, wherein the hydrogenated polyolefin resin (B) contains hydrogenated polyolefin.

6. The adhesive sheet as claimed in claim 5, wherein the aforementioned hydrogenated polyolefin resin (B) further contains hydrogenated polyolefin polyol.

7. The adhesive sheet, as requested in item 1 or 2, has a thickness of 12 to 350 μm.

8. An optical component having at least an adhesive sheet and a substrate as described in any one of claims 1 to 7, wherein the substrate has metal wiring on at least one side, and the adhesive sheet is attached to the side of the substrate having the metal wiring.

9. The optical component of claim 8, wherein the aforementioned metal wiring is a metal mesh wiring or silver nanowires.

10. A touch panel having at least an adhesive sheet and a substrate as described in any one of claims 1 to 7, wherein the substrate has metal wiring on at least one side, and the adhesive sheet is attached to the side of the substrate having the metal wiring.

11. The touch panel of claim 10, wherein the aforementioned metal wiring is a metal mesh wiring or silver nanowires.

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