Adhesive composition, adhesive layer, adhesive sheet, optical member with adhesive layer, and optical laminate

Abstract

The invention relates to an adhesive composition, an adhesive layer, an adhesive sheet, an optical member with an adhesive layer, and an optical laminate. The present invention provides an adhesive composition capable of forming an adhesive layer that has excellent adhesion to an adherend during use and is easy to peel when intentionally peeled off. The present invention provides an active energy ray-curable adhesive composition for forming an adhesive layer for adhering an optical member. The adhesive composition contains a hydrophilic component other than a monomer having a nitrogen atom-containing ring, and the content ratio of the hydrophilic component with respect to the total amount of non-volatile components in the adhesive composition is less than 10 mass%. The initial adhesive force of the adhesive layer to the glass is 10 N / 25 mm or more, and when the adhesive layer having a width of 25 mm is bonded to the glass, 0.1 mL of water is added to the interface between the longitudinal end of the adhesive layer and the glass, and the adhesive layer is pulled at a load of 1.8 N in a 90-degree direction, the peeling distance after one minute is 3 mm or more.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive layer, an adhesive sheet, an optical member with an adhesive layer, and an optical laminate. More specifically, it relates to an adhesive composition, an adhesive layer, an adhesive sheet, an optical member with an adhesive layer, and an optical laminate that can be preferably used in optical applications. Background Art

[0002] In recent years, image display devices such as liquid crystal displays (LCDs) and organic EL displays (OLEDs), and touch panels in which touch sensors are incorporated into these image display devices, have been widely used in various fields. Such image display devices and touch panels have a structure in which various optical components such as a polarizing film, a phase difference film, an optical compensation film, a touch sensor film, and a cover film are laminated on the image display panel. In the application of bonding these optical components, an adhesive sheet having an adhesive layer is used. For example, a transparent adhesive sheet is used to bond various optical components in an image display device (for example, refer to Patent Documents 1 to 3).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-238915

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2003-342542

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2004-231723 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The bonding of the optical components is typically performed using an optical component with an adhesive layer having an adhesive sheet attached thereto. After use, the adhesive sheet is sometimes peeled off from the optical component and recovered. Therefore, adhesive sheets are sometimes required to be easily peeled off. On the other hand, adhesive sheets are also required to have excellent adhesion to an adherend and to be difficult to peel off from the adherend.

[0010] The present invention is intended to solve such problems, and its object is to provide a pressure-sensitive adhesive layer that has excellent adhesion to an adherend during use and is easily peelable when intentionally peeled off, a pressure-sensitive adhesive composition that can form the pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer, an optical member with a pressure-sensitive adhesive layer, and an optical laminate.

[0011] Means used to solve problems

[0012] The present invention provides an adhesive composition, which is an active energy ray-curable adhesive composition for forming an adhesive layer for bonding optical components, wherein the above-mentioned adhesive composition contains a hydrophilic component other than a monomer having a nitrogen atom ring, the content ratio of the above-mentioned hydrophilic component relative to the total amount of non-volatile components in the above-mentioned adhesive composition is less than 10% by mass, the initial adhesion of the above-mentioned adhesive layer to glass is 10N / 25mm or more, and when the above-mentioned adhesive layer with a width of 25mm is attached to the glass, 0.1mL of water is added to the interface between the longitudinal end of the above-mentioned adhesive layer and the above-mentioned glass, and the adhesive layer is pulled in the 90° direction with a load of 1.8N, the peeling distance after 1 minute is 3mm or more.

[0013] For the above-mentioned adhesive composition, it is preferred that: the above-mentioned adhesive layer is adhered to glass, 0.1 mL of water is added to the interface between the longitudinal end of the above-mentioned adhesive layer and the above-mentioned glass, and when it is peeled off in the 90° direction at a peeling speed of 300 mm / min, the initial adhesive force is greater than 5 N / 25 mm.

[0014] For the above-mentioned adhesive composition, it is preferred that: the above-mentioned adhesive composition contains a monomer having a nitrogen atom ring as a monomer component constituting the polymer, and the content ratio of the above-mentioned monomer having a nitrogen atom ring is 5% by mass or more relative to 100% by mass of the total monomer components in the above-mentioned adhesive composition.

[0015] It is preferred that the pressure-sensitive adhesive layer have a water absorption of 1.00% by mass or less when stored under conditions of 85° C. and 85% RH for 240 minutes.

[0016] Preferably, the peeling distance of the pressure-sensitive adhesive layer after storage at 50° C. for 4 weeks is 3 mm or more.

[0017] It is preferred that the degree of swelling of the adhesive layer when immersed in ethyl acetate at 23° C. for 120 minutes is 50% or less.

[0018] Preferably, when the adhesive layer is adhered to glass, 0.1 mL of water is added to the interface between the longitudinal end of the adhesive layer and the glass and the adhesive layer is peeled off in a 90° direction, the ratio of the peeling force (X) when peeling off at at least one peeling speed of 6 mm / min or less to the peeling force (Y) when peeling off at at least one peeling speed of 120 mm / min to 300 mm / min [Y / X] (wherein Y>X) is 5 or more.

[0019] The present invention also provides a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition.

[0020] The thickness of the adhesive layer is preferably 50 μm or less.

[0021] The present invention also provides a pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.

[0022] The present invention also provides a pressure-sensitive adhesive layer-attached optical member comprising: an optical member; and the pressure-sensitive adhesive sheet adhered to at least one surface of the optical member.

[0023] The present invention also provides an optical layered body comprising a touch sensor, the pressure-sensitive adhesive layer, and an image display device in this order.

[0024] Effects of the Invention

[0025] According to the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer can be formed that has excellent adhesiveness to an adherend during use and is easily peelable when intentionally peeled off. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram (cross-sectional view) showing one embodiment of the pressure-sensitive adhesive sheet of the present invention.

[0027] Figure 2 It is a schematic diagram (cross-sectional view) showing one embodiment of the optical layered body of the present invention.

[0028] Figure 3 It is a schematic diagram (cross-sectional view) showing another embodiment of the optical layered body of the present invention.

[0029] Figure 4 It is a schematic diagram (cross-sectional view) showing still another embodiment of the optical layered body of the present invention.

[0030] Label Description

[0031] 1. Optical laminate

[0032] 2 adhesive layers

[0033] 21, 22, 23 adhesive layer (adhesive sheet)

[0034] 3 Protective components

[0035] 41, 42, 43 touch sensors

[0036] 44 noise reduction layers

[0037] 5 Image display device

[0038] 6 polarizing film

[0039] 10 adhesive sheets

[0040] 11a, 11b release liner DETAILED DESCRIPTION

[0041] [Adhesive composition]

[0042] The adhesive composition of the present invention is an adhesive composition for forming an adhesive layer for bonding optical members. The adhesive composition is an active energy ray-curable adhesive composition.

[0043] The adhesive composition contains a hydrophilic component other than the nitrogen-containing ring monomer. In this specification, the hydrophilic component other than the nitrogen-containing ring monomer may be simply referred to as the "hydrophilic component." The adhesive composition containing the hydrophilic component facilitates the adhesive layer's removal when intentionally removed in the presence of water.

[0044] Examples of the hydrophilic component include the hydrophilic monomers described below. The hydrophilic component may be used alone or in combination of two or more.

[0045] Relative to the total amount of 100 mass % of the non-volatile components in the above-mentioned adhesive composition, the content of the above-mentioned hydrophilic component in the above-mentioned adhesive composition is less than 10 mass %, preferably less than 7 mass %, more preferably less than 5 mass %. By the above-mentioned content being less than 10 mass %, when in use (i.e., when not wanting to intentionally peel off), the adhesion to the adherend is excellent. The above-mentioned content is greater than 0 mass %, preferably more than 0.5 mass %.

[0046] The initial adhesion of the adhesive layer formed using the above-mentioned adhesive composition to the glass is 10N / 25mm or more, preferably 12N / 25mm or more, more preferably 14N / 25mm or more, and further preferably 16N / 25mm or more. By having the above-mentioned initial adhesion of 10N / 25mm or more, the adhesion when attached to the optical component is excellent. The above-mentioned initial adhesion is, for example, 50N / 25mm or less, and can be 45N / 25mm or less, 40N / 25mm or less, or 35N / 25mm or less. The above-mentioned initial adhesion is a value measured under the conditions of a temperature of 23°C, a peeling angle of 90°, and a peeling speed of 300mm / min with the adherend being glass, and can be measured, for example, using the method described in the examples. It should be noted that in this specification, the adhesion measured within 12 hours after the film formation of the adhesive layer is included in the "initial adhesion".

[0047] Regarding the above-mentioned adhesive layer, a 25mm wide adhesive layer is attached to glass, 0.1mL of water is added to the interface between the longitudinal end of the above-mentioned adhesive layer and the glass, and when it is pulled in a 90° direction with a load of 1.8N, the peeling distance after 1 minute is 3mm or more, preferably 4mm or more, and more preferably 5mm or more. By having the above-mentioned peeling distance of 3mm or more, the adhesive layer can be easily peeled off when intentionally peeled off in the presence of water. The above-mentioned peeling distance is, for example, 50mm or less. The above-mentioned peeling distance is a value measured at a temperature of 23°C, and can be measured, for example, by the method described in the examples.

[0048] The adhesive composition of the present invention contains the above-mentioned hydrophilic component in a small amount less than 10% by mass, and the initial adhesion of the adhesive layer to the glass is 10N / 25mm or more, thereby having excellent adhesion when pasting optical components. Moreover, by containing the above-mentioned hydrophilic component in a small amount less than 10% by mass, and the peeling distance after 1 minute when pulling under specific conditions in the presence of water is more than 3mm, it can be easily peeled off when intentionally peeled off in the presence of water. Most conventional adhesive layers that are easily peeled off in the presence of water use a large amount of hydrophilic monomers as monomer components of the base polymer used in the adhesive layer, thereby increasing the water absorption rate of the adhesive layer, so that the adhesive layer absorbs a lot of water and swells when it is desired to peel, thereby peeling off from the adherend. However, such an adhesive layer has the following problem: even if it is not desired to be peeled off from the adherend, it will peel off in the presence of water. In contrast, the adhesive layer formed by the adhesive composition of the present invention does not swell even in the presence of water by containing a small amount of hydrophilic components, and has excellent adhesion to optical components. Furthermore, by reducing the water absorption of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer is less likely to absorb water in the presence of water, and water is continuously present between the pressure-sensitive adhesive layer and the optical member, making it easy to peel the optical member when intentionally peeled.

[0049] The initial adhesion of the adhesive layer to glass in the presence of water is preferably 5N / 25mm or more, more preferably 6N / 25mm or more, and further preferably 7N / 25mm or more. When the initial adhesion is 5N / 25mm or more, the adhesion to the adherend is excellent even in the presence of water during use. The initial adhesion is, for example, 32N / 25mm or less, and may be 28N / 25mm or less, 24N / 25mm or less, or 20N / 25mm or less. The initial adhesion is a value measured under the conditions of a temperature of 23°C, a peeling angle of 90°, and a peeling speed of 300mm / min, with the adherend being glass, 0.1mL of water being added to the interface between the longitudinal end of the adhesive layer and the glass, and the peeling speed being 300mm / min. For example, it can be measured using the method described in the examples.

[0050] Regarding the above-mentioned adhesive layer, a 25 mm wide adhesive layer stored at 50°C for 4 weeks is attached to glass, 0.1 mL of water is added to the interface between the longitudinal end of the above-mentioned adhesive layer and the glass, and the adhesive layer is pulled at a load of 1.8 N in a 90° direction. The peeling distance after 1 minute is preferably 3 mm or more, more preferably 4 mm or more, and further preferably 5 mm or more. When the above-mentioned peeling distance is 3 mm or more, the storage stability is excellent, and the adhesive layer can be easily peeled off even when intentionally peeled off in the presence of water after storage. The above-mentioned peeling distance is, for example, 50 mm or less. The above-mentioned peeling distance is a value measured at a temperature of 23°C, and can be measured, for example, by the method described in the examples.

[0051] Regarding the above-mentioned adhesive layer, when the above-mentioned adhesive layer is attached to glass, 0.1 mL of water is added to the interface between the longitudinal end of the above-mentioned adhesive layer and the glass and peeled in the 90° direction, the ratio [Y / X] (wherein, Y>X) of the peel force (X) when peeling at at least one peeling speed of 6 mm / minute or less to the peel force (Y) when peeling at at least one peeling speed of 120 mm / minute to 300 mm / minute is preferably 5 or more, more preferably 5.5 or more, and further preferably 6 or more. When the above-mentioned ratio is 5 or more, in the presence of water, the adhesiveness is excellent at the peeling speed at the peeling force (Y) and it is not easy to peel, but it is easy to peel at the peeling speed at the peeling force (X). The above-mentioned ratio is, for example, 10 or less.

[0052] The degree of swelling of the adhesive layer when immersed in ethyl acetate at 23°C for 120 minutes is preferably 50% or less, more preferably 48% or less, and further preferably 46% or less. When the above-mentioned swelling degree is 50% or less, it is possible to further suppress the damage of the adhesive layer after lamination in actual use. The above-mentioned swelling degree is preferably 5% or more, more preferably 10% or more, further preferably 12% or more, and particularly preferably 14% or more. When the above-mentioned swelling degree is 5% or more, it is possible to further suppress the peeling after lamination in actual use. When the mass when immersed in ethyl acetate at 23°C for 120 minutes is set as W1 and the mass before immersion is set as W2, the above-mentioned swelling degree is expressed by the following formula.

[0053] Swelling degree [%] = W1 / W2 × 100

[0054] The water absorption of the adhesive layer is preferably 1.00% by mass or less, more preferably 0.95% by mass or less, and even more preferably 0.90% by mass or less. Generally, low water absorption makes it difficult to peel the adhesive layer from the adherend in the presence of water. However, even when the water absorption is as low as 1.00% by mass or less, the adhesive layer can be easily peeled in the presence of water. The water absorption is the water absorption of the adhesive layer after being stored at 85°C and 85% RH for 240 minutes.

[0055] The pressure-sensitive adhesive layer is used for bonding optical components such as image display devices and therefore has excellent transparency, thereby providing excellent visibility and appearance through the pressure-sensitive adhesive layer.

[0056] In the adhesive composition of the present invention, the above-mentioned two initial adhesive forces, the above-mentioned two peel distances, [Y / X], the above-mentioned swelling degree and the above-mentioned water absorption rate can be adjusted, for example, by the amount of the hydrophilic monomer, the monomer having a nitrogen atom ring, the amount of other monomer components, etc.

[0057] The haze of the adhesive layer (according to JIS K7136) is not particularly limited, and is preferably 1.0% or less, and more preferably 0.8% or less. When the haze is 1.0% or less, excellent transparency and excellent appearance are obtained. The haze is not particularly limited, and in theory it can be 0%, and in practice it can be greater than 0.01%. It should be noted that the haze can be measured, for example, by making an adhesive layer (thickness: 100 μm), leaving it to stand at a normal temperature (23°C, 50% RH) for at least 24 hours, and then attaching it to a slide glass (for example, a slide glass with a total transmittance of 92% and a haze of 0.2%), using the object thus obtained as a sample, and using a haze meter (manufactured by Murakami Color Technology Research Institute, trade name "HM-150N") or its equivalent product.

[0058] The total light transmittance of the adhesive layer in the visible light wavelength region (according to JIS K7361-1) is not particularly limited, but is preferably 90% or more, more preferably 91% or more, and further preferably 92% or more. When the total light transmittance is 90% or more, excellent transparency and excellent appearance are obtained. The total light transmittance is not particularly limited. Theoretically, it is the value after removing the light loss (Fresnel loss) caused by reflection at the air interface from 100%. In practice, it can be 95% or less. It should be noted that the total light transmittance can be measured, for example, by preparing an adhesive layer (thickness: 100 μm), leaving it to stand at normal conditions (23°C, 50% RH) for at least 24 hours, then peeling it off with a release liner, attaching the adhesive layer to a slide glass (for example, a slide glass with a total light transmittance of 92% and a haze of 0.2%), and using the resulting object as a sample and using a haze meter (manufactured by Murakami Color Research Institute, trade name "HM-150N") or its equivalent.

[0059] The thickness of the adhesive layer is not particularly limited, but is preferably 50 μm or less, more preferably 46 μm or less, and even more preferably 42 μm or less. When the adhesive layer is 50 μm or less, it absorbs less water in the presence of water, allowing water to remain between the adhesive layer and the adherend, making peeling easier. To achieve superior adhesion to the adherend, the adhesive layer is preferably 10 μm or greater.

[0060] Examples of the adhesive composition of the present invention include a mixture of monomer components that form a polymer when forming an adhesive layer (sometimes referred to as a "monomer mixture") or a composition containing a partial polymer thereof as an essential component.

[0061] Examples of the mixture of monomer components include those composed of a single monomer component and those composed of two or more monomer components. Furthermore, the "partially polymerized product" is sometimes also referred to as a "prepolymer," "syrup," or the like, and refers to a composition obtained by partially polymerizing one or more of the monomer components in the monomer mixture.

[0062] The adhesive composition preferably contains a hydrophilic monomer other than the nitrogen-containing ring monomer as the hydrophilic component. When a hydrophilic monomer is contained as a monomer component, the adhesive layer can be more easily peeled when intentionally peeled in the presence of water.

[0063] Examples of the hydrophilic monomer include (meth)acrylates having a hydrophilic ester residue (sometimes referred to as "hydrophilic (meth)acrylates"), nitrogen-containing hydrophilic monomers, etc. These hydrophilic monomers may be used alone or in combination of two or more.

[0064] Examples of the hydrophilic (meth)acrylate include alkoxyalkyl (meth)acrylates, polyalkylene glycol (meth)acrylates, hydroxyalkyl (meth)acrylates, and hydroxyaralkyl (meth)acrylates.

[0065] Examples of the (meth)acrylate alkoxyalkyl ester include methoxyethyl acrylate (MEA) and ethoxyethoxyethyl acrylate (EEEA). Examples of the polyalkylene glycol (meth)acrylate include the formula: CH2=CR 1 -CO-(O-CH2CHR 2 ) n -OR 3 (Where R 1 and R 2 Each independently represents a hydrogen atom or a methyl group, R 3 represents an alkyl group having 1 to 20 carbon atoms, and n represents an integer of 1 to 12), methoxypolyethylene glycol (meth)acrylate or methoxypolypropylene glycol (meth)acrylate, etc.

[0066] Among the hydrophilic (meth)acrylates, hydroxyalkyl (meth)acrylates are preferred.

[0067] The nitrogen-containing hydrophilic monomer is a monomer containing a nitrogen atom and a hydrophilic group. Examples of the hydrophilic group include carboxyl groups, hydroxyl groups, and amino groups. The nitrogen-containing hydrophilic monomer is preferably a water-soluble monomer, and examples thereof include dialkyl (meth)acrylamides such as (meth)acrylamide and N,N-dimethyl (meth)acrylamide; monoalkyl (meth)acrylamides such as N-isopropyl (meth)acrylamide; alkoxy diacetone acrylamide, hydroxyethyl acrylamide (HEAA), vinyl formamide (NVF), and N-vinylacetamide (NVA).

[0068] Relative to the total amount of monomer components in the above-mentioned adhesive composition (100% by mass), the content of the above-mentioned hydrophilic monomer in the above-mentioned adhesive composition is preferably less than 5% by mass, more preferably less than 3% by mass. When the above-mentioned content is less than 5% by mass, the adhesive composition has excellent adhesion to the adherend during use (i.e., when not wanting to intentionally peel off). The above-mentioned content can be greater than 0% by mass, preferably more than 0.5% by mass.

[0069] The adhesive composition of the present invention preferably includes a monomer having a nitrogen-containing atom ring as a monomer component. When the above-mentioned monomer having a nitrogen-containing atom ring is included, appropriate cohesive force is easily obtained, so the initial adhesive force is more excellent. In addition, appropriate flexibility is easily obtained in the adhesive layer, even when attached to an optical component (touch sensor film) having metal wiring such as a metal mesh film and a silver nanowire film, the stress with the metal wiring is fully relaxed, thereby easily preventing uneven display.

[0070] It should be noted that, in this specification, the term "monomer component" in the adhesive composition is used to include monomer components that constitute a partial polymer. Furthermore, in this specification, "monomer component" refers to a compound having only one polymerizable functional group and does not include compounds having two or more polymerizable functional groups, such as multifunctional (meth)acrylates.

[0071] Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl Oxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine, etc. The above monomers having a nitrogen atom-containing ring may be used alone or in combination of two or more.

[0072] Relative to the monomer component total amount (100% by mass) in the above-mentioned adhesive composition, the above-mentioned monomer with nitrogen-containing atom ring in the above-mentioned adhesive composition preferably contains a ratio of more than 5% by mass, more preferably more than 7% by mass, further preferably more than 9% by mass. When the above-mentioned containing ratio is more than 5% by mass, it is easy to obtain appropriate cohesive force, so initial bonding force is more excellent. In addition, it is easy to obtain appropriate flexibility in the adhesive layer, even when being attached to the optical component (touch sensor film) of the metal wiring such as metal mesh film, silver nanowire film, it is also fully relaxed with the stress of metal wiring, so as to easily prevent uneven display. The above-mentioned containing ratio is, for example, less than 40% by mass.

[0073] Relative to the total amount 100 mass % of the non-volatile component in the above-mentioned adhesive composition, the above-mentioned monomer with nitrogen-containing atom ring in the above-mentioned adhesive composition preferably contains a ratio of more than 5 mass %, more preferably more than 10 mass %, more preferably more than 15 mass %.When the above-mentioned containing ratio is more than 5 mass %, it is easy to obtain appropriate cohesive force, so initial bonding force is more excellent. In addition, it is easy to obtain appropriate flexibility in the adhesive layer, even when being attached to the optical component (touch sensor film) of the metal wiring such as metal mesh film, silver nanowire film, it is also fully relaxed with the stress of metal wiring, so as to easily prevent uneven display. The above-mentioned containing ratio is, for example, less than 40 mass %.

[0074] As the base polymer contained in the adhesive layer formed by the adhesive composition of the present invention, there is no particular limitation, and examples thereof include: acrylic polymers contained as base polymers in acrylic adhesive layers, rubber polymers contained as base polymers in rubber adhesive layers (natural rubber adhesive layers, synthetic rubber adhesive layers, etc.), silicone polymers contained as base polymers in silicone adhesive layers, polyester polymers contained as base polymers in polyester adhesive layers, urethane polymers contained as base polymers in urethane adhesive layers, polyamide polymers contained as base polymers in polyamide adhesive layers, epoxy polymers contained as base polymers in epoxy adhesive layers, vinyl alkyl ether polymers contained as base polymers in vinyl alkyl ether adhesive layers, fluorine-containing polymers contained as base polymers in fluorine-containing adhesive layers, etc. Among them, from the perspectives of transparency, weather resistance, adhesion reliability, and the rich variety of monomers that make it easy to design the functions of the adhesive layer, the above-mentioned base polymer is preferably an acrylic polymer. That is, the adhesive layer formed by the adhesive composition of the present invention is an acrylic adhesive composition containing an acrylic polymer as a base polymer. In addition, the base polymer may be only one kind or two or more kinds.

[0075] The content of the base polymer in the adhesive layer is not particularly limited, but is preferably 75% by mass or more (e.g., 75% to 99.9% by mass), and more preferably 85% by mass or more (e.g., 85% to 99.9% by mass), relative to the total amount of the adhesive layer (100% by mass).

[0076] The acrylic pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition that forms a pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

[0077] The acrylic pressure-sensitive adhesive composition is not particularly limited, and examples thereof include compositions containing a mixture of monomer components constituting an acrylic polymer (monomer mixture) or a partially polymerized component thereof as an essential component.

[0078] The acrylic adhesive composition contains an acrylic monomer (acrylic monomer) as the monomer component. In other words, the acrylic adhesive composition comprises an acrylic monomer or a partially polymerized product of a monomer mixture containing an acrylic monomer. It should be noted that, in this specification, "(meth)acrylic acid" refers to either or both "acrylic acid" and "methacrylic acid," and the same applies to other terms. The weight-average molecular weight of the acrylic polymer is not particularly limited, but is preferably 100,000 to 5,000,000.

[0079] The acrylic monomer preferably includes an alkyl (meth)acrylate having a linear or branched alkyl group (hereinafter sometimes simply referred to as “alkyl (meth)acrylate”).

[0080] Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate (n-butyl (meth)acrylate), isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and tert-butyl (meth)acrylate. Alkyl (meth)acrylates having an alkyl group with 1 to 24 carbon atoms, such as nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0081] As the alkyl (meth)acrylate, alkyl acrylate is more preferred than alkyl methacrylate from the viewpoint of shortening the polymerization time of the acrylic polymer and improving productivity. alkyl acrylate is particularly preferred from the viewpoint of superior active energy ray curability.

[0082] Among the above-mentioned alkyl (meth)acrylates, those having an alkyl group with 1 to 18 carbon atoms are preferred from the viewpoint of better initial adhesion, methyl methacrylate (MMA), butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), and isostearyl acrylate (ISTA) are more preferred, and 2-ethylhexyl acrylate (2EHA) and isostearyl acrylate (ISTA) are even more preferred.

[0083] The content ratio of the above-mentioned alkyl (meth)acrylate in the above-mentioned acrylic adhesive composition is not particularly limited. From the viewpoint of improving durability and obtaining high adhesive reliability, it is preferably 30% to 99% by mass, more preferably 35% to 95% by mass, and even more preferably 40% to 90% by mass, relative to the total amount of monomer components in the above-mentioned acrylic adhesive composition (100% by mass).

[0084] The monomer component preferably includes an alkyl (meth)acrylate having an alkyl group having 8 or more carbon atoms (sometimes referred to as "alkyl (meth)acrylate (A)"). The alkyl (meth)acrylate (A) has a medium- to long-chain alkyl group. The alkyl group provides a highly flexible adhesive layer. Even when bonded to an optical member (touch sensor film) having metal wiring, such as a metal mesh film or a silver nanowire film, the stress from the metal wiring is sufficiently alleviated, thereby preventing display unevenness.

[0085] Examples of the alkyl (meth)acrylate (A) include alkyl (meth)acrylates having an alkyl group with 8 to 24 carbon atoms, such as octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0086] As the alkyl (meth)acrylate (A), alkyl acrylate is more preferred than alkyl methacrylate from the viewpoint of shortening the polymerization time of the acrylic polymer (A) and improving productivity. In particular, alkyl acrylate is preferred from the viewpoint of superior active energy ray curability.

[0087] As the above-mentioned (meth) acrylate alkyl ester (A), from the perspective of being able to achieve a highly flexible adhesive layer and being able to sufficiently relax the stress with the metal wiring even when attached to an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, thereby preventing display unevenness, it is preferred to include a (meth) acrylate alkyl ester having a branched alkyl group with 8 or more carbon atoms, more preferably an (meth) acrylate alkyl ester having a branched alkyl group with 8 or 9 carbon atoms, further preferably 2-ethylhexyl (meth) acrylate, and particularly preferably 2-ethylhexyl acrylate (2EHA). The number of carbon atoms in the side chain alkyl group of the above-mentioned branched alkyl group is not particularly limited, and an alkyl group with 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl) is preferred. A "side chain alkyl group" is an alkyl group substituted with a side chain of the carbon chain with the largest number of carbon atoms.

[0088] The content ratio of the above-mentioned alkyl (meth)acrylate (A) in the above-mentioned acrylic adhesive composition is not particularly limited. From the perspective of being able to achieve a highly flexible adhesive layer and being able to sufficiently relax the stress between the metal wiring and the metal wiring even when bonded to an optical member (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, thereby preventing display unevenness, the content ratio of the above-mentioned alkyl (meth)acrylate (A) is preferably 30% by mass to 99% by mass, more preferably 35% by mass to 95% by mass, and even more preferably 40% by mass to 90% by mass relative to the total amount of monomer components in the above-mentioned acrylic adhesive composition (100% by mass),

[0089] When the alkyl (meth)acrylate (A) contains an alkyl (meth)acrylate having a branched alkyl group having 8 or 9 carbon atoms (hereinafter sometimes referred to as alkyl (meth)acrylate (A1) in this specification), it is further preferred to contain an alkyl (meth)acrylate having a branched alkyl group having 10 to 24 carbon atoms (hereinafter sometimes referred to as alkyl (meth)acrylate (A2) in this specification).

[0090] When the alkyl (meth)acrylate (A) contains an alkyl (meth)acrylate (A2) in addition to the alkyl (meth)acrylate (A1), the dielectric constant of the adhesive layer can be reduced by the action of the long-chain branched alkyl group. Even when the adhesive layer is attached to an optical member (touch sensor film) having a metal wiring layer such as a metal mesh wiring or silver nanowires, the adhesive layer has a low dielectric constant, thereby preventing malfunctions.

[0091] The Tg of the homopolymer of the (meth) alkyl acrylate (A2) is preferably -80°C to 0°C, more preferably -70°C to -10°C. When the Tg of the homopolymer is -80°C or higher, the elastic modulus of the adhesive layer at room temperature will not be too low. In addition, when the Tg of the homopolymer is 0°C or lower, the initial adhesive force is more excellent. The Tg of the homopolymer is a value measured using a differential scanning calorimeter (DSC). In addition, from the viewpoint of being able to satisfy a moderate low dielectric constant and elastic modulus, the number of carbon atoms of the branched alkyl group with 10 to 24 carbon atoms is 10 to 24, but according to the production method of the (meth) acrylic polymer, an alkyl (meth) acrylate having a preferred alkyl group can be appropriately selected. For example, the above-mentioned alkyl group more preferably has 12 to 18 carbon atoms, and further preferably has 14 to 18 carbon atoms.

[0092] Examples of the (meth)acrylic acid alkyl ester (A2) include isodecyl acrylate (10 carbon atoms, Tg of the homopolymer = -60°C, hereinafter referred to as Tg), isodecyl methacrylate (10 carbon atoms, Tg = -41°C), isomyristyl acrylate (14 carbon atoms, Tg = -56°C), isostearyl acrylate (18 carbon atoms, Tg = -18°C), 2-propylheptyl acrylate, isoundecyl acrylate, isododecyl acrylate, isotridecyl acrylate, isopentadecyl acrylate, isohexadecyl acrylate, and isoheptadecyl acrylate.

[0093] Among the branched alkyl groups having 10 to 24 carbon atoms, those having a branched alkyl group such as a tert-butyl group at the end of the ester group are particularly preferred from the perspective of increasing the molar volume, reducing the dipole moment, and obtaining an adhesive layer with a balance between the two. Preferred branched alkyl groups at the end of the ester group are those having 4 to 6 carbon atoms such as tert-butyl, neopentyl, and tert-amyl, with tert-butyl being particularly preferred. Preferred examples of the (meth)acrylate (A2) having a tert-butyl group at the end of the ester group include isostearyl acrylate represented by the following formula.

[0094]

[0095] The content ratio of the (meth) alkyl acrylate (A1) in the acrylic adhesive composition is not particularly limited. From the perspective of being able to achieve a highly flexible adhesive layer, even when attached to an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, the stress on the metal wiring can be sufficiently relaxed, thereby preventing uneven display. The content ratio is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, and can be 30% by mass or more or 40% by mass or more, relative to the total amount of monomer components in the acrylic adhesive composition (100% by mass). In addition, from the perspective of making the adhesive layer low in dielectric constant and preventing malfunction, the content ratio is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and further preferably 60% by mass or less.

[0096] The content of the (meth) acrylate alkyl ester (A2) in the acrylic adhesive composition is not particularly limited. From the perspective of reducing the dielectric constant of the adhesive layer and preventing malfunction, the content is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more, relative to the total amount of monomer components in the acrylic adhesive composition (100% by mass). It can be 30% by mass or more or 40% by mass or more. In addition, from the perspective of being able to achieve a highly flexible adhesive layer that can fully alleviate stress on the metal wiring even when attached to an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, thereby preventing uneven display, the content is preferably 70% by mass or less, more preferably 65% ​​by mass or less, and further preferably 60% by mass or less.

[0097] The mass ratio of the above-mentioned (meth) alkyl acrylate (A1) to the (meth) alkyl acrylate (A2) [(meth) alkyl acrylate (A2) / (meth) alkyl acrylate (A1)] is not particularly limited. From the perspective of being able to achieve an adhesive layer with high flexibility, even when attached to an optical component (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, the stress with the metal wiring can be fully relaxed, thereby preventing uneven display. It is preferably 2 or less, more preferably 1.5 or less, further preferably 1 or less, particularly preferably 0.5 or less, and may also be 0.45 or less. In addition. From the perspective of making the adhesive layer low in dielectric constant and preventing misoperation, the above-mentioned mass ratio is preferably 0.2 or more, more preferably 0.25 or more, further preferably 0.3 or more, and may also be 0.35 or more.

[0098] The monomer component may contain an alkyl (meth)acrylate other than the alkyl (meth)acrylate (A) (hereinafter sometimes referred to as "alkyl (meth)acrylate (B)"). Examples of the alkyl (meth)acrylate (B) include alkyl (meth)acrylates having a linear or branched alkyl group having 1 to 7 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate (n-butyl (meth)acrylate), isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, and heptyl (meth)acrylate.

[0099] The content ratio of the above-mentioned alkyl (meth)acrylate (B) in the above-mentioned acrylic adhesive composition is not particularly limited. From the perspective of achieving a highly flexible adhesive layer and being able to sufficiently relax the stress between the adhesive layer and the metal wiring even when bonded to an optical member (touch sensor film) having metal wiring such as a metal mesh film or a silver nanowire film, thereby preventing display unevenness, the content ratio of the above-mentioned alkyl (meth)acrylate (B) is preferably 10% by mass or less, and more preferably 5% by mass or less, relative to the total amount of monomer components in the above-mentioned acrylic adhesive composition (100% by mass).

[0100] The acrylic pressure-sensitive adhesive composition may contain, as a monomer component, a copolymerizable functional group-containing monomer (copolymerizable functional group-containing monomer) in addition to the aforementioned alkyl (meth)acrylate (including alkyl (meth)acrylate (A) and alkyl (meth)acrylate (B)).

[0101] Examples of the copolymerizable functional group-containing monomer include polar group-containing monomers such as carboxyl group-containing monomers, acid anhydride monomers, hydroxyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, and nitrogen atom-containing monomers. Each of the copolymerizable functional group-containing monomers may be used alone or in combination of two or more.

[0102] The content ratio of the copolymerizable functional group-containing monomer in the acrylic adhesive composition is not particularly limited. However, from the viewpoint of obtaining a highly reliable adhesive layer whose adhesive strength is less susceptible to changes due to environmental changes, having little change in adhesive strength due to the storage environment immediately after film formation, and having excellent productivity, the content ratio is preferably 5% to 40% by mass, more preferably 10% to 30% by mass, and even more preferably 15% to 25% by mass relative to the total amount of monomer components in the acrylic adhesive composition (100% by mass), from the viewpoint of obtaining a highly reliable adhesive layer whose adhesive strength is less susceptible to changes due to environmental changes, having little change in adhesive strength due to the storage environment immediately after film formation, and having excellent productivity.

[0103] There are no particular restrictions on the copolymerizable functional group-containing monomers. However, from the perspective of obtaining a highly reliable adhesive layer in which the various properties of the adhesive layer (especially initial adhesion, peeling distance, water absorption, swelling degree, etc.) are controlled within a prescribed range and the adhesion is not easily changed due to environmental changes, as well as from the perspective of adhesive reliability, compatibility with various additives such as ultraviolet absorbers, and transparency, nitrogen atom-containing monomers and hydroxyl group-containing monomers are preferably listed.

[0104] When a nitrogen-containing monomer is included as the monomer component, appropriate cohesive strength is easily obtained and initial adhesive strength is more excellent. The nitrogen-containing monomer is a monomer (monomer) having at least one nitrogen atom in the molecule (in one molecule).

[0105] Examples of the nitrogen-containing monomers include amide-containing monomers, amino-containing monomers, cyano-containing monomers, and the above-mentioned monomers having nitrogen-containing rings. Examples of the amide-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide. Examples of the amino-containing monomers include aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and tert-butylaminoethyl(meth)acrylate. Examples of the cyano-containing monomers include acrylonitrile and methacrylonitrile.

[0106] In the case where the acrylic adhesive composition contains the nitrogen-containing monomer as the monomer component, the ratio of the nitrogen-containing monomer in the acrylic adhesive composition is not particularly limited. Relative to the total monomer component amount (100% by mass) in the acrylic adhesive composition, it is preferably more than 1% by mass, more preferably more than 3% by mass, further preferably more than 5% by mass, and can be more than 10% by mass or more than 15% by mass. When the ratio is more than 1% by mass, the various properties (particularly initial adhesion, peeling distance, water absorption, swelling, etc.) of the adhesive layer can be easily controlled within the specified range. From the viewpoint of being able to easily control the various properties (particularly initial adhesion, peeling distance, water absorption, swelling, etc.) of the adhesive layer within the specified range, the ratio is preferably less than 30% by mass, more preferably less than 25% by mass, and further preferably less than 20% by mass.

[0107] When the acrylic pressure-sensitive adhesive composition contains the hydroxyl group-containing monomer as the monomer component, polymerization of the monomer component is facilitated, good cohesive strength is easily obtained, and initial adhesive strength is further improved.

[0108] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

[0109] When the acrylic adhesive composition contains the hydroxyl-containing monomer as the monomer component, the content of the hydroxyl-containing monomer in the acrylic adhesive composition is not particularly limited. However, from the perspective of enabling easy peeling of the adhesive layer when intentionally peeled in the presence of water, the content of the hydroxyl-containing monomer is preferably 8% by mass or less, and more preferably 6% by mass or less, relative to the total amount of the monomer component (100% by mass) in the acrylic adhesive composition. The content of the hydroxyl-containing monomer is not particularly limited. However, from the perspective of enabling easy peeling of the adhesive layer when intentionally peeled in the presence of water, the content is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and even more preferably 1% by mass or more.

[0110] The total content of the nitrogen-containing monomer and the hydroxyl-containing monomer in the acrylic adhesive composition is not particularly limited, but is preferably 5% by mass or greater, more preferably 10% by mass or greater, and even more preferably 15% by mass or greater, relative to the total amount of the monomer components in the acrylic adhesive composition (100% by mass). The total content is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 25% by mass or less.

[0111] The mass ratio of the nitrogen-containing monomer to the hydroxyl-containing monomer in the acrylic adhesive composition [nitrogen-containing monomer / hydroxyl-containing monomer] is not particularly limited, but is preferably 1 to 50, more preferably 1.5 to 40, further preferably 2 to 30, and particularly preferably 2 to 25. When the mass ratio is within the above range, the initial adhesive strength is further improved, and the adhesive layer can be easily peeled off when intentionally peeled off in the presence of water.

[0112] The monomer components may further contain other monomers in addition to the various monomer components mentioned above. Examples of the other monomers include: vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrenes (such as α-methylstyrene), and vinyltoluene; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; alkoxy-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether. Each of the other monomer components may be used alone or in combination of two or more.

[0113] The proportion of the other monomers in the total amount of monomer components (100% by mass) in the acrylic adhesive composition can be, for example, 0.05% by mass or more, 0.5% by mass or more, 5% by mass or more, or 10% by mass or more. The proportion can be, for example, 20% by mass or less, 10% by mass or less, or 5% by mass or less, or the acrylic adhesive composition may be substantially free of the other monomers.

[0114] In order to form a cross-linked structure in the polymer backbone, the acrylic adhesive composition may contain a multifunctional monomer such as a multifunctional (meth)acrylate copolymerizable with the monomer components. Examples of the multifunctional (meth)acrylate include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. These multifunctional monomers may be used alone or in combination of two or more.

[0115] In order to appropriately exhibit basic properties such as adhesion brought about by the above-mentioned alkyl (meth)acrylate in the adhesive layer, the content of the above-mentioned multifunctional monomer is preferably 0.001 to 1 part by mass, and more preferably 0.01 to 0.1 part by mass, relative to 100 parts by mass of the total monomer components in the above-mentioned acrylic adhesive composition.

[0116] The adhesive composition of the present invention may contain a polymerization initiator, a chain transfer agent, an emulsifier, etc. for free radical polymerization of the monomer components. It should be noted that the weight-average molecular weight of the polymer can be controlled by the amount of the polymerization initiator and chain transfer agent used and the reaction conditions, and their amounts can be appropriately adjusted depending on their types.

[0117] A photopolymerization initiator (photoinitiator) can be used for polymerization of the monomer components.

[0118] The photopolymerization initiator is not particularly limited, and examples thereof include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators. Furthermore, acylphosphine oxide-based photopolymerization initiators and titanocene-based photopolymerization initiators may also be mentioned. Examples of the benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone. Examples of the α-ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methyl-1-propanone. Examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl)-oxime. Examples of the benzoin-based photopolymerization initiator include benzoin. Examples of the benzyl-based photopolymerization initiator include benzyl. Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, poly(vinylbenzophenone), and α-hydroxycyclohexylphenyl ketone. Examples of the ketal-based photopolymerization initiator include benzyldimethylketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Examples of the titanocene photopolymerization initiator include bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium. The amount of the photopolymerization initiator used may be a conventional amount, for example, 0.01 to 5 parts by mass, preferably 0.05 to 3 parts by mass, relative to 100 parts by mass of the monomer component.

[0119] The adhesive composition of the present invention can include other components in addition to the above-mentioned components within the scope of not damaging the effect of the present invention. As above-mentioned other components, cross-linking agent, curing agent, curing catalyst, cross-linking accelerator, tackifying resin (rosin derivative, polyterpene resin, petroleum resin, oil-soluble phenolic etc.), anti-aging agent, filler (metal powder, organic filler, inorganic filler etc.), colorant (pigment or dye etc.), antioxidant, plasticizer, softener, surfactant, antistatic agent, surface lubricant, leveling agent, light stabilizer, ultraviolet absorber, polymerization inhibitor, rust preventive, granular material, foil-like material, flame retardant, silane coupling agent, ion capture agent etc. can be listed. Above-mentioned other components can be used only one respectively, or two or more can be used.

[0120] The adhesive composition of the present invention is preferably solvent-free. That is, the adhesive composition of the present invention preferably contains no or substantially no organic solvent. The organic solvent is not particularly limited as long as it is an organic compound used as a solvent. 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. It should be noted that the organic solvent may be a mixed solvent containing two or more organic solvents.

[0121] In the adhesive composition of the present invention, "substantially free of" an organic solvent means that no organic solvent is actively incorporated except for unavoidable inclusions. Specifically, the adhesive composition can be said to be substantially free of an organic solvent if the organic solvent content in the adhesive composition is 1.0% by mass or less (preferably 0.5% by mass or less, more preferably 0.2% by mass or less) relative to the total amount of the adhesive composition (total mass, 100% by mass).

[0122] The adhesive composition of the present invention can be prepared by a known or customary method. The active energy ray-curable adhesive composition of the present invention can be prepared, for example, by mixing additives as needed with a mixture of monomer components or a partially polymerized product thereof.

[0123] [Adhesive layer]

[0124] The adhesive composition of the present invention can be used to form an adhesive layer. The adhesive layer formed using the adhesive composition of the present invention is sometimes referred to as the "adhesive layer of the present invention." The adhesive layer can be formed by, for example, applying the adhesive composition to the release-treated surface of a release liner or a substrate to form an adhesive composition layer, and then curing the adhesive composition layer by polymerization using active energy ray irradiation. In addition, as needed, in addition to the irradiation with the active energy ray, heating, drying, etc. can also be performed.

[0125] Examples of the active energy rays include ionizing radiation such as α-rays, β-rays, γ-rays, neutron rays, electron rays, and ultraviolet rays, with ultraviolet rays being particularly preferred. Specifically, the active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition.

[0126] The adhesive composition can be applied (coated) using a known coating method. For example, a coating machine such as a gravure roll coater, a reverse roll coater, a contact roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma knife coater, or a direct coater can be used.

[0127] After the monomer mixture or its partially polymerized product is cured by irradiation with active energy rays to form an adhesive layer, a solution containing an additive can be applied to the adhesive layer, allowing the additive to penetrate through the thickness of the adhesive layer from one surface. This allows the adhesive layer to be imbued with the desired properties based on the additive. Furthermore, the transparency of the adhesive layer is maintained by the penetration of the additive in solution. The adhesive layer is then dried by heating or other means. This process returns the adhesive layer to a state close to that before application. That is, because the adhesive layer is cured first, its physical properties, such as adhesion and elastic modulus, are restored to a state close to that before application of the solution. Since the adhesive layer is cured before the additive is added, if the composition, curing conditions, and physical properties of the adhesive composition are determined first, there is no need to redesign the composition by adding additives, making it easier to adjust the thickness of the adhesive layer. Furthermore, by changing the application conditions of the additive solution, the desired properties of the adhesive layer can be controlled. Thus, since the control of the physical properties of the adhesive layer can be separated from the control of the desired properties based on the additive, changes in the thickness of the adhesive layer, the amount of additive added, and other factors do not require a complete redesign of the adhesive layer, resulting in improved efficiency.

[0128] As the above-mentioned additive, any additive can be used without particular limitation, and additives added in the adhesive field can be used. For example, polymerization initiators, crosslinking agents, ultraviolet light absorbers, rust inhibitors, antistatic agents, crosslinking accelerators, silane coupling agents, tackifying resins, anti-aging agents, colorants such as dyes, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, etc. can be listed. From the viewpoint of easily exerting the desired effect of the present invention, polymerization initiators, crosslinking agents, ultraviolet light absorbers, rust inhibitors, and antistatic agents are preferred.

[0129] [Adhesive sheet]

[0130] Adhesive sheet can be obtained using the adhesive layer of the present invention. Sometimes the adhesive sheet with the adhesive layer of the present invention is referred to as "adhesive sheet of the present invention". The above-mentioned adhesive sheet can be a double-sided adhesive sheet with both sides being the adhesive layer surface, or a single-sided adhesive sheet with only one side being the adhesive layer surface. Wherein, from the viewpoint of laminating two components to each other, a double-sided adhesive sheet is preferably used. It should be noted that, in this specification, when referred to as "adhesive sheet", a tape-shaped adhesive sheet, i.e., "adhesive tape" is also included. In addition, in this specification, the adhesive layer surface is sometimes referred to as "adhesive face".

[0131] The above-mentioned adhesive sheet may be a so-called "substrate-free" adhesive sheet (hereinafter sometimes referred to as a "substrate-free adhesive sheet") that does not have a substrate (substrate layer), or may be an adhesive sheet of a type having a substrate (hereinafter sometimes referred to as a "substrate-free adhesive sheet"). As the above-mentioned substrate-free adhesive sheet, for example, a double-sided adhesive sheet consisting only of the adhesive layer of the present invention, a double-sided adhesive sheet comprising an adhesive layer of the present invention and an adhesive layer other than the adhesive layer of the present invention (sometimes referred to as "other adhesive layers"), etc. can be cited. On the other hand, as an adhesive sheet with a substrate, an adhesive sheet having an adhesive layer of the present invention on at least one side of the substrate can be cited. Among them, a substrate-free adhesive sheet (substrate-free double-sided adhesive sheet) is preferred, and a substrate-free double-sided adhesive sheet consisting only of the adhesive layer of the present invention is more preferred. In addition, an adhesive sheet having an adhesive layer on both sides of a substrate (double-sided adhesive sheet with a substrate) is also preferred. The adhesive layers on both sides of the above-mentioned double-sided adhesive sheet with a substrate may both be adhesive layers of the present invention, or one may be an adhesive layer of the present invention and the other may be other adhesive layers. The “base material (base material layer)” does not include a release liner to be peeled off when the pressure-sensitive adhesive sheet is used (attached).

[0132] Since the aforementioned adhesive sheet may cause millimeter wave radiation loss due to the substrate when the adhesive sheet is provided with a substrate, the aforementioned adhesive sheet is preferably a substrate-less adhesive sheet. However, if the substrate is composed of a material with a low dielectric constant and low dielectric loss, an adhesive sheet with a substrate may also be provided.

[0133] The substrate is a member that functions as a support for the adhesive layer in the adhesive sheet. Examples of substrates include plastic substrates (particularly plastic films). The substrate may be a single layer or a laminate of the same or different substrates.

[0134] As the above-mentioned base material, there is no particular limitation, for example, various optical films such as plastic film, anti-reflection (AR) film, anti-glare (AG) film, polarizing plate, phase difference plate can be listed. As the raw materials of the above-mentioned plastic film etc., for example, polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose (TAC), polysulfone, polyarylate, polyimide, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, ethylene-propylene copolymer, trade name "ARTON" (cyclic olefin polymer, JSR (strain) manufacturing), trade name "ZEONOR" (cyclic olefin polymer, Japan Rui Weng (strain) manufacturing) and other cyclic olefin polymers, fluorine-containing polymers and other plastic materials can be listed. In addition, these plastic materials can be used only one, or two or more.

[0135] To improve adhesion and retention with the adhesive layer, the surface of the substrate on the side having the adhesive layer may be subjected to physical treatments such as corona discharge treatment, plasma treatment, sandblasting, ozone exposure, flame exposure, high voltage electric shock exposure, or ionizing active energy ray treatment; chemical treatments such as chromic acid treatment; and surface treatments such as adhesion-enhancing treatment using a coating agent (primer). The surface treatment for improving adhesion is preferably applied to the entire surface of the substrate on the side facing the adhesive layer.

[0136] The substrate may be a noise reduction film. The noise reduction film is not particularly limited as long as it has noise reduction properties, and examples include films having a noise reduction layer formed on at least one surface of a film substrate. The noise reduction layer may be a single layer or multiple layers, and is not particularly limited as long as it functions to reduce electromagnetic noise. From the perspective of transparency, a transparent conductive layer is preferred. The transparent conductive layer may be a thin film layer formed of a conductive organic or inorganic material, or a conductive layer formed by partial contact of conductive organic or inorganic materials.

[0137] Above-mentioned adhesive sheet can be provided with release liner on the adhesive face until use. Release liner is used to protect the adhesive face that contacts before the use until above-mentioned adhesive layer, is peeled off when using above-mentioned adhesive layer. It should be noted that, when above-mentioned adhesive sheet is a double-sided adhesive sheet, each adhesive face can be protected respectively by two release liners, and also can be protected with the form of being wound into roll-shaped by a piece of release liner that is the release face on both sides. Release liner is used as the protective material of adhesive layer, and is peeled off when being pasted on adherend. In addition, when above-mentioned adhesive sheet is the non-base material adhesive sheet, release liner also bears the effect of the support as adhesive layer. It should be noted that, also can need not be provided with release liner.

[0138] Examples of the substrate of the release liner include polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylic acid copolymer film, ethylene-(meth)acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, and fluorine-containing resin film. Cross-linked films thereof may also be used. Furthermore, laminated films thereof may also be used.

[0139] The release surface of the release liner (particularly the surface in contact with the adhesive layer) is preferably subjected to a release treatment. Examples of release agents used for the release treatment include alkyd, polysiloxane, fluorine-containing, unsaturated polyester, polyolefin, and wax release agents.

[0140] The thickness of the release liner is not particularly limited, and is, for example, about 20 μm to 150 μm.

[0141] Figure 1 This is a schematic cross-sectional view showing one embodiment of the pressure-sensitive adhesive sheet of the present invention. Figure 1 The illustrated PSA sheet 10 is a substrate-less double-sided PSA sheet composed of a single PSA layer 2 serving as the PSA layer of the present invention, and has release liners 11a and 11b provided on both adhesive surfaces, respectively.

[0142] [use]

[0143] The adhesive composition, adhesive layer, and adhesive sheet of the present invention are used for optical applications, i.e., applications for laminating to optical components. More specifically, for example, applications for laminating to optical components (optical component lamination) and for manufacturing products (optical products) using such optical components. By using the adhesive composition, adhesive layer, and adhesive sheet of the present invention for optical applications, excellent reliability is achieved.

[0144] The adhesive composition, adhesive layer, and adhesive sheet of the present invention are useful for laminating adherends having a low linear expansion coefficient to adherends having a high linear expansion coefficient. Specifically, the adhesive composition, adhesive layer, and adhesive sheet of the present invention are preferably used for laminating glass adherends (e.g., glass plates, chemically strengthened glass, glass lenses, etc.) to resin substrates having a high linear expansion coefficient.

[0145] As can be seen, the adhesive composition, adhesive layer, and adhesive sheet of the present invention are useful for laminating adherends made of various materials, and are particularly useful for laminating glass adherends to plastic adherends.

[0146] The adhesive composition of the present invention, the adhesive layer of the present invention, and the adhesive sheet of the present invention are used, for example, when various components or parts are installed (arranged) in a prescribed position (for example, a housing, a front panel, a window, etc.) in an optical component of an electrical or electronic device. In addition, "electrical or electronic equipment" refers to a device belonging to at least any one of an electrical device or an electronic device. As the above-mentioned electrical or electronic equipment, for example, image display devices such as liquid crystal displays, organic / inorganic electroluminescent displays, plasma displays, portable electronic devices, etc. can be listed. As the above-mentioned image display device, the image display device in the above-mentioned portable electronic device, a car-mounted display, a digital signage (electronic billboard / electronic bulletin board), etc. can be listed. It should be noted that, as the above-mentioned image display device, it can be a so-called "rigid type", a so-called "flexible type", etc. form (structure), and it can also be a so-called "foldable type", "curling type", etc. form (structure) that can be bent or folded.

[0147] Examples of the portable electronic devices include mobile phones, smartphones, tablet personal computers, notebook personal computers, various wearable devices (e.g., wrist-worn devices such as watches, modular devices worn on a part of the body with a clip or strap, eyewear devices including glasses (including monocular, binocular, and head-worn devices), clothing devices worn on shirts, socks, hats, etc. in the form of accessories, and ear-worn devices such as headphones), digital cameras, digital video cameras, audio equipment (e.g., portable music players, voice recorders), computers (e.g., desktop calculators), portable gaming devices, electronic dictionaries, electronic organizers, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. It should be noted that, in this specification, the term "portable" is not sufficient to simply mean "portable," but rather refers to a level of portability that allows a person (a standard adult) to carry the device with relative ease.

[0148] As the use of the adhesive layer of the present invention and the adhesive sheet of the present invention, specifically, it is preferably provided for the bonding of a touch sensor and an image display device between the touch sensor and the image display device. The adhesive layer of the present invention is particularly preferably directly laminated with the above-mentioned touch sensor. In addition, the adhesive layer of the present invention can be directly laminated on the image display device or laminated via other layers such as a polarizing film. The adhesive layer of the present invention is not easy to cause noise amplification, and thus it is possible to make it difficult for noise emitted from the image display device to be transmitted to the touch sensor.

[0149] In addition, the adhesive layer of the present invention and the adhesive sheet of the present invention are useful in the purpose of laminating a component constituting an antenna (millimeter wave antenna) for millimeter wave communication. The adhesive layer of the present invention has a low dielectric constant and dielectric loss in high frequency bands such as millimeter waves, and therefore can suppress the radiation loss of millimeter waves. In this specification, "millimeter wave communication" refers to communication in a frequency band of 20 GHz to 300 GHz.

[0150] In addition, the adhesive composition of the present invention, the adhesive layer of the present invention and the adhesive sheet of the present invention can be used for the purpose of peeling and recycling optical components. The adhesive layer can be peeled off, for example, in the presence of water. As the conditions for peeling a 25 mm wide adhesive layer, the peeling angle is 90°, the peeling speed is, for example, 100 mm / min or less (preferably 50 mm / min or less, more preferably 10 mm / min or less, particularly preferably 6 mm / min or less), the peeling load is, for example, 5 N or less (preferably 3 N or less), and the peeling temperature is, for example, room temperature (for example, greater than 0°C and less than or equal to 40°C). In addition, it is preferred that the adhesive layer not be peeled off under the conditions of a peeling speed of 120 mm / min or more (for example, 120 mm / min to 300 mm / min) and / or a peeling load of 10 N or more.

[0151] [Optical member with adhesive layer]

[0152] By laminating the sheet of the present invention to an optical component, an optical component with a pressure-sensitive adhesive layer can be obtained, comprising the optical component and the pressure-sensitive adhesive sheet of the present invention adhered to at least one surface of the optical component. The pressure-sensitive adhesive layer of the optical component with a pressure-sensitive adhesive layer may or may not be provided with a release liner on the pressure-sensitive adhesive surface until use.

[0153] The optical component with an adhesive layer of the present invention may be an optical component (touch sensor film) having metal wiring, such as a metal mesh film or a silver nanowire film, to which the adhesive sheet of the present invention is attached. In this case, the adhesive sheet of the present invention is preferably attached to the surface of the touch sensor film having the metal wiring.

[0154] [Optical laminate]

[0155] By arranging the adhesive layer of the present invention or the adhesive sheet of the present invention between the touch sensor and the image display device, an optical laminate (optical laminate of the present invention) having a touch sensor, an adhesive layer of the present invention and an image display device in sequence is obtained. The above-mentioned optical laminate may have a touch sensor and an adhesive layer in a single layer, respectively, or may have multiple layers. In the case of having a plurality of touch sensors, each touch sensor is preferably stacked with an adhesive layer therebetween. In the case of having a plurality of adhesive layers, the plurality of adhesive layers may be layers with the same composition, thickness, etc., or layers with different composition, thickness, etc. In the case of having a plurality of adhesive layers, at least one layer is an adhesive layer of the present invention. All adhesive layers preferably provided between the touch sensor and the image display device are adhesive layers of the present invention.

[0156] Examples of the image display device include the aforementioned display device. The touch sensor is a capacitive touch sensor, for example, a transparent conductive film having a transparent conductive layer provided on a glass plate or a transparent plastic film (particularly a PET film, a polycarbonate film, or a cyclic olefin polymer film). The adhesive layer of the present invention is preferably bonded to the transparent conductive layer.

[0157] Examples of the transparent conductive layer include ITO (indium tin oxide), ZnO, SnO, and CTO (cadmium tin oxide) films. Furthermore, the transparent conductive layer can be formed from silver, copper, or carbon nanotubes (CNTs). Furthermore, the transparent conductive layer can also be formed from metal mesh sensors such as Ag nanowires or Ag / Cu. Furthermore, the touch sensor can also have routing wiring formed from thin copper or silver paste at its ends.

[0158] The above-mentioned optical laminate may have a protective member. The above-mentioned protective member is arranged on the surface of the side of the touch sensor opposite to the side with the image display device, protecting the touch sensor and the image display device in the above-mentioned optical laminate. As the above-mentioned protective member, protective glass and plastic cover can be listed. The above-mentioned protective member can be attached to the layer constituting the above-mentioned optical laminate such as the touch sensor through an adhesive layer. The above-mentioned adhesive layer can be the adhesive layer of the present invention, but since the function of suppressing the amplification of the noise emitted by the image display device is not required, it can also be other adhesive layers. In addition, the above-mentioned optical laminate can have a polarizing film on the surface of the image display device (the surface on the side with the touch sensor).

[0159] The above-mentioned optical laminate may have a noise reduction layer (noise reduction film, etc.). From the perspective of the function of suppressing the amplification of noise emitted by the image display device, the above-mentioned noise reduction layer is preferably provided between the touch sensor and the image display device. The above-mentioned noise reduction layer and the touch sensor, as well as the above-mentioned noise reduction layer and the image display device are respectively adhered by an adhesive layer (preferably the adhesive layer of the present invention). The above-mentioned noise reduction layer may be a single layer or a multilayer. In the case of having multiple noise reduction layers, the multiple noise reduction layers may be layers of the same composition, thickness, etc., or layers of different composition, thickness, etc.

[0160] Figures 2 to 4 One embodiment of the optical layered body of the present invention is shown. Figure 2 The optical laminate 1 shown includes, in this order, an image display device 5, a polarizing film 6 disposed on the image display device 5, a touch sensor 41, a touch sensor 42, and a protective member 3. The polarizing film 6 and the touch sensor 41 are bonded together by an adhesive layer (adhesive sheet) 21, and the touch sensor 41 and the touch sensor 42 are bonded together by an adhesive layer (adhesive sheet) 22. Adhesive layers 21 and 22 are adhesive layers of the present invention. Furthermore, the touch sensor 42 and the protective member 3 are bonded together by an adhesive layer (adhesive sheet) 23. Adhesive layer 23 is another adhesive layer.

[0161] Figure 3 The optical laminate 1 shown has an image display device 5, a polarizing film 6 provided on the image display device 5, a touch sensor 43, and a protective member 3 in this order. The touch sensor 43 has both Figure 2 The touch sensors 41 and 42 in the polarizing film 6 function as both of them. The polarizing film 6 and the touch sensor 43 are bonded together by an adhesive layer 21. Adhesive layer 21 is the adhesive layer of the present invention. Furthermore, the touch sensor 43 and the protective member 3 are bonded together by an adhesive layer 23. Adhesive layer 23 is another adhesive layer.

[0162] Figure 4 The optical laminate 1 shown includes, in this order, an image display device 5, a polarizing film 6 disposed on the image display device 5, a noise reduction layer 44, a touch sensor 43, and a protective member 3. The polarizing film 6 and the noise reduction layer 44 are bonded together via an adhesive layer 21, and the noise reduction layer 44 and the touch sensor 43 are bonded together via an adhesive layer 22. Adhesive layers 21 and 22 are adhesive layers of the present invention. Furthermore, the touch sensor 43 and the protective member 3 are bonded together via an adhesive layer 23. Adhesive layer 23 is another adhesive layer.

[0163] It should be noted that in Figures 2 to 4 In this case, the image display device 5 and the touch sensor 41, the touch sensor 43 or the noise reduction layer 44 are bonded together via the adhesive layer 21. Alternatively, the image display device 5 and the polarizing film 6 may be bonded together via an adhesive sheet.

[0164] The embodiments described above are described to facilitate understanding of the present invention and are not described to limit the present invention.

[0165] Example

[0166] The present invention will be described in more detail below with reference to the following examples, but the present invention is not limited to these examples. It should be noted that all the blending numbers (parts by mass) represent the blending numbers of the respective components described.

[0167] [Manufacturing Example 1: Preparation of Prepolymer Composition A]

[0168] A monomer mixture consisting of 40 parts by mass of 2-ethylhexyl acrylate (2EHA), 40 parts by mass of isostearyl acrylate (ISTA), 19 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 1 part by mass of 4-hydroxybutyl acrylate (4-HBA) was added with 0.05 parts by mass of a photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM Resins BV) and 0.05 parts by mass of a photopolymerization initiator (trade name "Omnirad 651", manufactured by IGM Resins BV). The mixture was then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s, thereby obtaining a prepolymer composition A in which part of the above monomer components was polymerized.

[0169] [Manufacturing Example 2: Preparation of Prepolymer Composition B]

[0170] A monomer mixture consisting of 80 parts by mass of 2-ethylhexyl acrylate (2EHA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 5 parts by mass of 2-hydroxyethyl acrylate (2-HEA) was added with 0.035 parts by mass of a photopolymerization initiator (trade name "Omnirad 184", manufactured by IGM Resins BV) and 0.035 parts by mass of a photopolymerization initiator (trade name "Omnirad 651", manufactured by IGM Resins BV). The mixture was then irradiated with ultraviolet light until the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s, thereby obtaining a prepolymer composition B in which part of the above monomer components was polymerized.

[0171] [Example 1]

[0172] To 100 parts by mass of the prepolymer composition A obtained in Production Example 1, 0.02 parts by mass of trimethylolpropane triacrylate (TMPTA) was added and mixed, thereby obtaining an adhesive composition (pre-curing composition).

[0173] The adhesive composition was applied to a polyethylene terephthalate (PET) release liner (heavy release liner, trade name "MRF75", manufactured by Mitsubishi Chemical Corporation) to a final thickness (adhesive layer thickness) of 25 μm, thereby forming a coating layer (adhesive composition layer). Next, a PET release liner (light release liner, trade name "MRE75", manufactured by Mitsubishi Chemical Corporation) was placed on the coating layer to cover the coating layer and isolate oxygen. Thus, a laminate of MRF75 / coating layer (adhesive composition layer) / MRE75 was obtained.

[0174] Next, the laminate was irradiated with a black light lamp (manufactured by Toshiba Corporation) from the upper surface (MRF75 side) of the laminate for 300 seconds at an illumination intensity of 5 mW / cm 2 The mixture was then dried in a 90°C dryer for 2 minutes to volatilize any remaining monomers. This resulted in a double-sided adhesive sheet consisting solely of an adhesive layer protected on both sides by release liners.

[0175] [Comparative Examples 1 and 2]

[0176] A substrate-less double-sided PSA sheet was obtained in the same manner as in Example 1, except that the PSA composition and the PSA layer thickness were set as shown in Table 1. In Table 1, "HDDA" stands for 1,6-hexanediol diacrylate.

[0177] [Characteristics evaluation]

[0178] The substrate-less double-sided PSA sheets of Examples and Comparative Examples were subjected to the following measurements or evaluations. The evaluation results are shown in Table 1.

[0179] (1) Initial adhesion

[0180] The light release liner was peeled off from the substrate-free double-sided adhesive sheet of the embodiment and the comparative example, and a PET film (trade name "Lumirror S10", manufactured by Toray Industries, Ltd., with a thickness of 25 μm) was laminated on the exposed surface of the exposed adhesive layer to obtain a laminate. Next, a test piece (width 25 mm × length 150 mm) was cut out from the laminate, the heavy release liner was peeled off, and the laminate was laminated to a glass plate (a green plate edged product, manufactured by Matsunami Glass Co., Ltd.). In this lamination, the test piece was pressed against the adherend by moving a 2 kg roller back and forth once under an environment of 25°C. After the above lamination, the mixture was allowed to stand at 23°C for 2 minutes, and then a peeling test of peeling the test piece from the glass plate was performed, and the peeling strength was measured as the initial adhesive force. In the above measurement, the measuring temperature was set to 23°C, the peeling angle of the test piece relative to the adherend was set to 90°, the pulling speed (peeling speed) of the test piece was set to 300 mm / min, and the peeling length was set to 50 mm.

[0181] (2) Initial adhesion (water added)

[0182] After the test piece was bonded to a glass plate, one end of the test piece was slightly peeled off, and 0.1 mL of water was dropped onto the interface between the test piece and the glass plate to perform a peel test. The initial adhesive strength (water dropping) was measured in the same manner as described above.

[0183] (3) Constant load peel test

[0184] The light release liner was peeled off from the substrate-free double-sided adhesive sheet of the embodiment and the comparative example, and a PET film (trade name "LumirrorS10", manufactured by Toray Industries, Ltd., with a thickness of 25 μm) was laminated on the exposed surface of the exposed adhesive layer to obtain a laminate. Then, a test piece (width 25 mm × length 150 mm) was cut out from the laminate, the heavy release liner was peeled off, and the laminate was laminated to a glass plate (a green plate edging product, manufactured by Matsunami Glass). In this lamination, the test piece was pressed against the adherend by moving a 2 kg roller back and forth once under a 25°C environment. After the above lamination, the test piece was allowed to stand at 23°C for 2 minutes, then laminated to the glass plate, and then one end of the test piece was slightly peeled off, 0.1 mL of water was added dropwise to the interface between the test piece and the glass plate, and a peeling test of peeling the test piece from the glass plate was performed to measure the peel strength. In the above measurement, the measurement temperature was set to 23° C., the peeling angle of the test piece relative to the adherend was set to 90°, the pulling load of the test piece was set to 1.8 N, and the peeling length was set to 50 mm.

[0185] (4) Water absorption

[0186] For the double-sided adhesive sheet without substrate of the embodiment and the comparative example, it was cut into 1 cm squares, and the adhesive layer after peeling off the release liner on both sides was placed in a moisture adsorption and desorption measuring device (IGA-sorp, manufactured by Hiden Company) for moisture adsorption and desorption measurement. The measurement mode was set to sequential mode, and the temperature was set to 150 ° C and the humidity was set to 0% RH for 60 minutes (Program 1), and then the temperature was set to 23 ° C and the humidity was set to 0% RH for 240 minutes (Program 2), and then the temperature was set to 85 ° C and the humidity was set to 85% RH for 240 minutes (Program 3). The etching at the end of Program 2 was regarded as an absolute dry state, and the weight change rate at the end of Program 3 obtained by the following formula according to the absolute dry state was used as the water absorption rate (%).

[0187] Water absorption rate (%) = (weight at the end of program 3 - weight at the end of program 2 (absolutely dry state)) / (weight at the end of program 2 (absolutely dry state)) × 100

[0188] (5) Ratio of initial adhesion (water added)

[0189] The initial adhesive strength (with water added) was measured in the same manner as described above except that the test piece pulling speed (peeling speed) was set to 6 mm / min. The initial adhesive strength (with water added) ratio was then calculated according to the following formula.

[0190] Ratio of initial adhesion (water added) = [(initial adhesion at a peeling speed of 300 mm / min (water added)) / (initial adhesion at a peeling speed of 6 mm / min (water added))]

[0191] (6) Swelling degree

[0192] Samples of the substrate-free double-sided PSA sheets of the Examples and Comparative Examples were cut into 1 cm squares and their pre-immersion mass (W2) was measured. The samples were then immersed in ethyl acetate at 23°C for 120 minutes, removed, and dried at 130°C for 120 minutes, and their mass (W1) was measured. The degree of swelling was then calculated using the following formula.

[0193] Swelling degree [%] = W1 / W2 × 100

[0194]

[0195] As shown in Table 1, the initial adhesive force of the adhesive sheet of the Example was 10 N / 25 mm or greater, indicating excellent adhesion to the adherend during use. Furthermore, the constant load peel test (peel distance) was 3 mm or greater, indicating that the sheet was easily peeled when intentionally peeled. In contrast, the constant load peel test (peel distance) of the adhesive sheet of the Comparative Example was 0 mm or greater, indicating that the sheet was difficult to peel when intentionally peeled.

[0196] Modifications of the disclosed invention will be described below.

[0197] [Note 1] An adhesive composition, which is an active energy ray-curable adhesive composition for forming an adhesive layer for bonding optical components, wherein the adhesive composition contains a hydrophilic component other than a monomer having a nitrogen atom ring, the content ratio of the hydrophilic component in the adhesive composition relative to the total amount of non-volatile components is less than 10% by mass, the initial adhesion of the adhesive layer to glass is 10N / 25mm or more, and when the 25mm wide adhesive layer is attached to the glass, 0.1mL of water is added to the interface between the longitudinal end of the adhesive layer and the glass, and the layer is pulled in the 90° direction with a load of 1.8N, the peeling distance after 1 minute is 3mm or more.

[0198] [Note 2] The adhesive composition according to Note 1, wherein the adhesive layer is adhered to glass, 0.1 mL of water is added to the interface between the longitudinal end of the adhesive layer and the glass, and the adhesive layer is peeled off in a 90° direction at a peeling speed of 300 mm / min, and the initial adhesive force is greater than 5 N / 25 mm.

[0199] [Note 3] The adhesive composition according to Note 1 or 2, wherein the adhesive composition contains a monomer having a nitrogen atom ring as a monomer component constituting a polymer, and the content ratio of the monomer having a nitrogen atom ring is 5% by mass or more relative to 100% by mass of the total amount of monomer components in the adhesive composition.

[0200] [Supplementary Note 4] The adhesive composition according to any one of Supplementary Notes 1 to 3, wherein the adhesive layer has a water absorption of 1.00% by mass or less when stored under conditions of 85° C. and 85% RH for 240 minutes.

[0201] [Supplementary Note 5] The adhesive composition according to any one of Supplementary Notes 1 to 4, wherein the peeling distance of the adhesive layer after storage at 50° C. for 4 weeks is 3 mm or more.

[0202] [Supplementary Note 6] The adhesive composition according to any one of Supplementary Notes 1 to 5, wherein the degree of swelling of the adhesive layer when immersed in ethyl acetate at 23° C. for 120 minutes is 50% or less.

[0203] [Note 7] The adhesive composition according to any one of Notes 1 to 6, wherein the adhesive layer is attached to glass, 0.1 mL of water is added to the interface between the longitudinal end of the adhesive layer and the glass, and the adhesive layer is peeled in a 90° direction, and the ratio [Y / X] (wherein Y>X) of the peeling force (X) when peeling at at least one peeling speed of 6 mm / min or less to the peeling force (Y) when peeling at at least one peeling speed of 120 mm / min to 300 mm / min is 5 or more.

[0204] [Supplementary Note 8] A pressure-sensitive adhesive layer, comprising the pressure-sensitive adhesive composition according to any one of Supplementary Notes 1 to 7.

[0205] [Supplementary Note 9] The adhesive layer according to Supplementary Note 8, wherein the thickness of the adhesive layer is 50 μm or less.

[0206] [Supplementary Note 10] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to Supplementary Note 8 or 9.

[0207] [Supplementary Note 11] An optical member with a pressure-sensitive adhesive layer, comprising: an optical member; and the pressure-sensitive adhesive sheet according to Supplementary Note 10 adhered to at least one surface of the optical member.

[0208] [Supplementary Note 12] An optical layered body comprising a touch sensor, the pressure-sensitive adhesive layer according to Supplementary Note 8 or 9, and an image display device in this order.

Claims

1. An adhesive composition, which is an active energy ray-curable adhesive composition for forming an adhesive layer for bonding optical components, wherein: The adhesive composition contains a hydrophilic component other than a monomer having a nitrogen atom-containing ring, and the content ratio of the hydrophilic component in the adhesive composition relative to the total amount of non-volatile components is less than 10% by mass. The initial adhesion of the adhesive layer to the glass is 10N / 25mm or more. The 25 mm wide adhesive layer was attached to glass, 0.1 mL of water was added to the interface between the longitudinal end of the adhesive layer and the glass, and the layer was pulled at 90° with a load of 1.8 N. The peeling distance after 1 minute was 3 mm or more.

2. The adhesive composition according to claim 1, wherein The adhesive layer was attached to glass, 0.1 mL of water was added to the interface between the longitudinal end of the adhesive layer and the glass, and the adhesive layer was peeled off at a rate of 300 mm / min in a 90° direction, and the initial adhesive strength was 5 N / 25 mm or more.

3. The adhesive composition according to claim 1 or 2, wherein The adhesive composition contains a nitrogen-atom-containing ring monomer as a monomer component constituting a polymer, and the content of the nitrogen-atom-containing ring monomer is 5% by mass or more relative to 100% by mass of the total monomer components in the adhesive composition.

4. The adhesive composition according to claim 1 or 2, wherein The pressure-sensitive adhesive layer had a water absorption of 1.00% by mass or less when stored under conditions of 85° C. and 85% RH for 240 minutes.

5. The adhesive composition according to claim 1 or 2, wherein The peeling distance of the pressure-sensitive adhesive layer after storage at 50° C. for 4 weeks was 3 mm or more.

6. The adhesive composition according to claim 1 or 2, wherein The degree of swelling of the adhesive layer when immersed in ethyl acetate at 23° C. for 120 minutes was 50% or less.

7. The adhesive composition according to claim 1 or 2, wherein The adhesive layer is bonded to glass, 0.1 mL of water is added to the interface between the longitudinal end of the adhesive layer and the glass, and the adhesive layer is peeled off in a 90° direction. The ratio [Y / X] (wherein Y>X) of the peeling force (X) when peeling off at at least one peeling speed of 6 mm / minute or less to the peeling force (Y) when peeling off at at least one peeling speed of 120 mm / minute to 300 mm / minute is 5 or more.

8. An adhesive layer, wherein The adhesive layer is formed from the adhesive composition according to claim 1 or 2.

9. The adhesive layer according to claim 8, wherein The thickness of the adhesive layer is 50 μm or less.

10. An adhesive sheet, wherein: The pressure-sensitive adhesive sheet comprises the pressure-sensitive adhesive layer according to claim 8 .

11. An optical member with an adhesive layer, wherein: The pressure-sensitive adhesive layer-attached optical member includes an optical member and the pressure-sensitive adhesive sheet according to claim 10 adhered to at least one surface of the optical member.

12. An optical layered body, wherein: The optical laminate includes a touch sensor, the pressure-sensitive adhesive layer according to claim 8, and an image display device in this order.

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