Laminate

Abstract

The present invention provides a laminate that exhibits high adhesion to alkali-free glass or chemically strengthened glass and is resistant to dents even when subjected to impact. [Solution] The laminate 1 comprises an adhesive layer 2 and an adhesive layer 3 laminated on at least one surface of the adhesive layer 2. The total light transmittance of the laminate 1 is 85% or more. The gel fraction of the adhesive layer 2 is 85 to 99.9% by mass. Preferably, the stress retention rate of the adhesive layer 2 after 60 seconds when stretched to 100% is 70 to 99.9%.

Description

[Technical Field]

[0001] This invention relates to a laminate. [Background technology]

[0002] OLED (Organic Light Emitting Diode) displays offer several advantages over liquid crystal displays, including higher visibility, less dependence on viewing angle, and faster response times. Furthermore, because OLED displays do not use backlights, they are more suitable for thinner designs and can be used as flexible, curved, or foldable devices.

[0003] In OLED display devices, layers of various optical elements, such as a substrate (plastic or thin glass) and a hard coat layer, are laminated on the viewing side of the OLED element via an adhesive layer to provide functions such as surface protection and flexibility.

[0004] In recent years, with the spread of foldable devices, optical products such as OLED display devices are sometimes required to have properties that prevent peeling or lifting even when repeatedly bent and folded. For this reason, highly flexible adhesive sheets that can withstand bending at multiple points have been proposed (see Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-083201 [Overview of the project] [Problems that the invention aims to solve]

[0006] In particular, in the case of a foldable device, even more thinning is required so that it can be easily folded. As such thin glass in a foldable device, alkali-free glass or chemically strengthened glass with high bending resistance may be used. However, since the conventional adhesive layer has low adhesion to alkali-free glass and chemically strengthened glass, when it is laminated to and folded with alkali-free glass or chemically strengthened glass, the adhesive layer cannot hold the alkali-free glass or chemically strengthened glass, and there is a problem that peeling is likely to occur.

[0007] In order to improve the adhesion to alkali-free glass and chemically strengthened glass, it is conceivable to use an adhesive layer with relatively high flexibility. However, the adhesive layer with high flexibility has a problem that it is likely to be indented when receiving an impact such as a touch by a touch pen when used in a foldable device.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a laminate having high adhesion to alkali-free glass or chemically strengthened glass and being less likely to be indented even when receiving an impact.

Means for Solving the Problems

[0009] As a result of intensive studies to achieve the above object, the present inventors have found that a specific laminate has high adhesion to alkali-free glass or chemically strengthened glass and is less likely to be indented even when receiving an impact.

[0010] The present invention is a laminate including an adhesive layer and an adhesive layer laminated on at least one surface of the adhesive layer, the total light transmittance of the laminate is 85% or more, and the gel fraction of the adhesive layer is 85 to 99.9% by mass.

[0011] It is preferable that the stress residual ratio of the adhesive layer after 60 seconds at 100% elongation is 70 to 99.9%.

[0012] Preferably, the adhesive layer and the bonding layer each contain an acrylic polymer.

[0013] The thickness of the adhesive layer is preferably 200 nm to 10 μm.

[0014] The ratio of the thickness of the adhesive layer to the thickness of the adhesive layer [thickness of adhesive layer:thickness of adhesive layer] is preferably 1:0.0001 to 1:1. [Effects of the Invention]

[0015] The laminate of the present invention exhibits high adhesion to alkali-free glass or chemically strengthened glass, and is resistant to dents even when subjected to impact. Therefore, even when used laminated in a foldable device (particularly a foldable OLED display device), it is less likely to detach from the alkali-free glass or chemically strengthened glass in a wide range of environments, providing an aesthetically pleasing foldable device. [Brief explanation of the drawing]

[0016] [Figure 1] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 2] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 3] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 4] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 5] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 6] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 7] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 8] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 9] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Figure 10] This is a cross-sectional view showing one embodiment of the laminate of the present invention. [Modes for carrying out the invention]

[0017] In this specification, "adhesion" refers to the property of two surfaces adhering tightly to each other based on cohesive forces derived from the chemical structure of the composition in response to external pressure (e.g., minute pressure), and being able to be separated if necessary. In contrast, "bonding" refers to the property of two surfaces being firmly joined by fluidization due to heating and subsequent solidification, curing, heating, pressurization, or two or more of these operations.

[0018] Furthermore, in this specification, the form of the "adhesive" is not particularly limited and may be liquid at room temperature (for example, a fluid solid (paste), an adhesive composition, etc.), or a solid at room temperature. Also, the form of the "adhesive" is not particularly limited and may be in the form of a sheet. In this specification, the "adhesive layer" is a non-fluid sheet-like (layered) adhesive layer.

[0019] [Laminated structure] The laminate of the present invention comprises at least an adhesive layer and an adhesive layer laminated on at least one surface of the adhesive layer. Furthermore, the total light transmittance of the laminate of the present invention is 85% or more.

[0020] Figures 1 and 2 show cross-sectional views of one embodiment of the laminate of the present invention. The laminate 1 shown in Figure 1 comprises an adhesive layer 2 and an adhesive layer 3. The adhesive layer 3 is formed on one surface of the adhesive layer 2 so as to be in contact with the adhesive layer 2. Note that even if a compatible layer, described later, is formed between the adhesive layer 2 and the adhesive layer 3, the adhesive layer 2 and the adhesive layer 3 are considered to be in contact. The shape of the adhesive layer 3 is not particularly limited, but for example, it may be in the form of a sheet, similar to the adhesive layer 2, or it may be formed over the entire surface of one surface of the adhesive layer 2, or it may be in a shape (annular, frame-like) that covers a part of one surface of the adhesive layer 2.

[0021] In the laminate of the present invention, the adhesive layer only needs to be laminated on at least one surface of the adhesive layer. In this case, as shown in Figure 1, the adhesive layer 3 may be laminated over the entire surface of one surface of the adhesive layer 2, or it may be laminated over a part of one surface.

[0022] The laminate of the present invention may comprise multiple adhesive layers. For example, the laminate of the present invention comprises at least one adhesive layer on one side of the adhesive layer, but may also comprise an adhesive layer on the side of the adhesive layer opposite to the aforementioned side (the other side). The multiple adhesive layers may have the same thickness, composition, shape, or physical properties, or they may be different layers.

[0023] The laminate 1 shown in Figure 2 comprises a plurality of adhesive layers 3, with adhesive layers 3 comprising adhesive layer 31 and adhesive layer 32. In the laminate 1 shown in Figure 2, adhesive layer 31 is formed over the entire surface of one side of the adhesive layer 2, and adhesive layer 32 is also formed on the other side of the adhesive layer 2. Although adhesive layer 32 is formed over the entire surface of the other side of the adhesive layer 2, it may also be formed on a part of the other side of the adhesive layer 2. Furthermore, in Figure 2, adhesive layer 31 may also be formed on a part of one side of the adhesive layer 2.

[0024] Furthermore, the laminate of the present invention may comprise multiple adhesive layers. For example, the laminate of the present invention may have a thick adhesive layer formed by laminating multiple adhesive layers. The multiple adhesive layers may have the same thickness, composition, shape, or physical properties, or they may be different.

[0025] The laminate of the present invention comprises at least an adhesive layer having a gel fraction of 85 to 99.9% by mass. In this specification, the above adhesive layer may be referred to as the "adhesive layer of the present invention." If the laminate of the present invention comprises a plurality of adhesive layers, at least one adhesive layer may be the adhesive layer of the present invention, and it is preferable that all adhesive layers are the adhesive layer of the present invention.

[0026] (Adhesive layer) As described above, the adhesive layer of the present invention has a gel fraction of 85 to 99.9% by mass. The adhesive layer of the present invention, when having a gel fraction of 85% by mass or more, is less susceptible to stress relaxation when subjected to impact, less prone to dents, and less prone to creases even when subjected to repeated bending. When the gel fraction is 99.9% by mass or less, it exhibits excellent adhesion when bonded to an adhesive layer, and is less prone to peeling even when bonded to alkali-free glass or chemically strengthened glass and bent. The gel fraction is preferably 87% by mass or more, and may be 89% by mass or more or 91% by mass or more. Furthermore, the gel fraction may be 99% by mass or less, 97% by mass or less, 95% by mass or less, or 93% by mass or less. The gel fraction can be adjusted by designing the degree of crosslinking in the adhesive layer.

[0027] The gel fractions mentioned above are calculated according to the "Method for Measuring Gel Fractions" described below. <Method for measuring gel fraction> Approximately 0.1 g of the adhesive layer to be measured is taken, wrapped in a porous tetrafluoroethylene sheet with an average pore size of 0.2 μm (product name "NTF1122", manufactured by Nitto Denko Corporation), tied with kite string, and its weight is measured. This weight is defined as the weight before immersion A. This weight before immersion is the total weight of the adhesive layer (the adhesive layer taken above), the tetrafluoroethylene sheet, and the kite string. The total weight of the tetrafluoroethylene sheet and the kite string is also measured and defined as the weight of the package B. Next, the adhesive layer wrapped in the tetrafluoroethylene sheet and tied with kite string (referred to as the "sample") is placed in a 50 mL container filled with ethyl acetate and left to stand at 23°C for one week. After that, the sample (after ethyl acetate treatment) is removed from the container and transferred to an aluminum cup. The ethyl acetate is then removed by drying in a dryer at 130°C for 2 hours, and the weight of the sample is measured. This weight is defined as the weight after immersion C. Then, the gel fraction is calculated using the following formula. Gel fraction [% (mass %)] = (CB) / (AB) × 100

[0028] The adhesive layer of the present invention preferably has a stress retention rate (60s) of 70% or more after 60 seconds of 100% elongation, more preferably 75% or more, and even more preferably 80% or more. When the stress retention rate (60s) is 70% or more, stress relaxation is less likely to occur when subjected to impact, dents are less likely to form, and creases are less likely to form even when subjected to repeated bending. The stress retention rate (60s) is preferably 99.9% or less, may be 99% or less, 97% or less, 95% or less, 93% or less, or 91% or less. When the stress retention rate (60s) is 99.9% or less, adhesion is excellent when bonded to the adhesive layer, and peeling is less likely even when bonded to alkali-free glass or chemically strengthened glass and bent.

[0029] The adhesive layer of the present invention preferably has a stress retention rate (600s) of 65% or more after 600 seconds of 100% elongation, more preferably 72% or more, and even more preferably 75% or more. When the above stress retention rate (600s) is 65% or more, stress relaxation is less likely to occur even after a long time has passed since impact, making it less likely to be dented, and less likely to be creased even after repeated bending. The above stress retention rate (600s) is preferably 99.9% or less, may be 98% or less, 96% or less, 94% or less, 92% or less, or 90% or less. When the above stress retention rate (600s) is 99.9% or less, it has excellent adhesion when bonded to the adhesive layer, and is less likely to peel off even when bonded to alkali-free glass or chemically strengthened glass and bent.

[0030] The adhesive layer of the present invention preferably has a ratio of the stress retention rate (600s) to the stress retention rate (60s) [value of stress retention rate (600s) / stress retention rate (60s) × 100] of 88% or more, more preferably 89% or more, and even more preferably 90% or more. When the above ratio is 88% or more, the decrease in stress retention rate is small both immediately after impact and over time, making it even less prone to dents and less prone to creases even when subjected to repeated bending. The above stress retention rate can be adjusted by the molecular weight and crosslinking density of the base polymer, and the higher these values ​​tend to result in a higher stress retention rate.

[0031] The above stress retention rates (60s) and (600s) are calculated by rolling an adhesive layer measuring 40mm in width and 30mm in length into a cylindrical shape with the longer side being the longer side. The upper and lower bottoms of the cylinder are gripped by gripping jigs of a universal tensile and compression testing machine so that the distance between the gripping jigs is 10mm. The cylindrical adhesive layer is stretched at a tensile speed of 50mm / min until the distance between the gripping jigs becomes 20mm. The stress at the moment the distance between the gripping jigs reaches 20mm (0 seconds) is defined as σ0, and the stress after 60 seconds is defined as σ 60 and stress σ after 600 seconds 600 It is measured and calculated using the following formula. Stress retention rate (60s) [%] = σ 60 / σ0×100 Stress residual rate (600s)[%]=σ 600 / σ0×100

[0032] The adhesive layer of the present invention can be a known or conventional adhesive layer. Preferably, the adhesive layer is a solvent-free adhesive layer containing a photopolymerized polymer as the base polymer. Such an adhesive layer can be manufactured from a solvent-free adhesive composition. In the process of manufacturing the adhesive layer from a solvent-free adhesive composition, there is no need to volatilize and remove the solvent from the coating film of the composition. Therefore, a laminate comprising the adhesive layer is suitable for reducing environmental impact.

[0033] The adhesive layer is preferably a sheet-like pressure-sensitive adhesive (solvent-free adhesive layer) formed from a solvent-free adhesive composition. Therefore, the adhesive layer (solvent-free adhesive composition) preferably contains at least a photopolymerizable polymer as a base polymer. A photopolymerizable polymer is a polymer formed by a polymerization method in which the polymerization reaction of polymerizable components is advanced by irradiation with active energy rays such as ultraviolet light. Depending on the type of polymerization reaction, a thermal polymerization initiator or a photopolymerization initiator (photoradical generator, photoinitiator) can be used as the polymerization initiator used in the polymerization reaction. Only one type of polymerization initiator may be used, or two or more types may be used.

[0034] The base polymer is an adhesive component that exhibits tackiness in the adhesive layer. The base polymer is not particularly limited, but examples include acrylic polymers, rubber polymers (such as natural rubber polymers and synthetic rubber polymers), silicone polymers, polyester polymers, urethane polymers, polyamide polymers, epoxy polymers, vinyl alkyl ether polymers, and fluorine polymers. Among these, acrylic polymers are preferred because of their transparency, weather resistance, adhesive reliability, and the ease with which the adhesive layer can be functionally designed due to the wide variety of monomers available. The base polymer may be used by one type or by using two or more types.

[0035] The content of the base polymer in the adhesive layer is not particularly limited, but is preferably 75% by mass or more (for example, 75 to 99.9% by mass) and more preferably 85% by mass or more (for example, 85 to 99.9% by mass) based on the total amount (100% by mass) of the adhesive layer.

[0036] Acrylic polymers are polymers (polymers) that contain acrylic monomers (acrylic monomers) as essential monomer units (monomer units, monomer constituent units). In other words, acrylic polymers are polymers that contain constituent units derived from acrylic monomers as constituent units. That is, acrylic polymers are polymers that are composed (formed) with acrylic monomers as essential monomer components. In this specification, "(meth)acrylic" refers to either or both of "acrylic" and "methacrylic," and the same applies to other terms. The weight-average molecular weight of the acrylic polymer in the adhesive layer is not particularly limited, but is preferably between 100,000 and 5,000,000.

[0037] The above acrylic polymer is preferably a polymer containing an alkyl (meth)acrylate which may have an alkoxy group as a monomer unit. Examples of the alkyl (meth)acrylate which may have an alkoxy group include alkyl (meth)acrylate which has a linear or branched alkyl group, and alkyl (meth)acrylate which has an alicyclic alkyl group such as cycloalkyl (meth)acrylate. The number of carbon atoms in the ester portion of the alkyl (meth)acrylate which may have an alkoxy group is preferably 1 to 24. Only one or more of the hydrocarbon group-containing alkyl (meth)acrylate which may have an alkoxy group may be used.

[0038] Examples of the alkyl (meth)acrylate esters having linear or branched alkyl groups include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate (n-butyl (meth)acrylate), isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate (n-octyl (meth)acrylate), and 2-ethylhexyl (meth)acrylate. Examples include alkyl esters of (meth)acrylates having 1 to 24 carbon atoms in the alkyl group, such as 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.

[0039] Alkyl (meth)acrylate esters having an alkoxy group may have only one alkoxy group or two or more, and these two or more alkoxy groups may be bonded in series. Furthermore, the two or more alkoxy groups may be the same or different. Examples of the above-mentioned alkyl (meth)acrylate esters having an alkoxy group include (poly)oxyalkylene-modified (meth)acrylates such as 2-ethylhexyl carbitol (meth)acrylate (2EHCA), ethyl carbitol acrylate (CBA), methoxydipropylene glycol acrylate, methoxy-polyethylene glycol acrylate, and phenoxy-polyethylene glycol acrylate (especially (poly)oxyethylene-modified (meth)acrylates).

[0040] Of the alkyl (meth)acrylate esters mentioned above, alkyl acrylates are preferred over alkyl methacrylates because they can shorten the polymerization time of the acrylic polymer and improve productivity. In particular, alkyl acrylates are preferred when the acrylic polymer is cured by active energy ray polymerization.

[0041] As for alkyl (meth)acrylates which may have alkoxy groups, in the adhesive layer, from the viewpoint of balancing the flexibility and tackiness required for adhesive layers in flexible device applications with the low moisture permeability of the adhesive layer, alkyl (meth)acrylates which may have alkoxy groups with 6 to 14 carbon atoms in the ester portion are preferred, and alkyl (meth)acrylates which may have alkoxy groups with 8 to 12 carbon atoms in the ester portion are more preferred. As alkyl (meth)acrylates which may have alkoxy groups with 6 to 14 carbon atoms in the ester portion, 2-ethylhexyl acrylate (2EHA), n-octyl acrylate (NOAA), lauryl acrylate (LA), and 2-ethylhexyl carbitol acrylate (2EHCA) are preferred.

[0042] The content of the alkyl (meth)acrylate which may have an alkoxy group in the total monomer units of the above acrylic polymer (total amount of monomer components constituting the acrylic polymer) is not particularly limited, but in order to exhibit a low dielectric constant and drop impact resistance, it is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, based on the total amount of monomer components constituting the acrylic polymer (100% by mass), and may also be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. Furthermore, the above content is preferably 99% by mass or less.

[0043] In this specification, when referring to "the total amount of monomer components constituting the acrylic polymer," it includes not only the monomer components constituting the prepolymer, but also monomer components that are separately added to the prepolymer and the adhesive layer that forms the base after formation, as described later. Furthermore, in this specification, "monomer component" refers to a compound having only one polymerizable functional group (monofunctional monomer), and does not include compounds having two or more polymerizable functional groups, such as polyfunctional (meth)acrylates.

[0044] The monomer component preferably includes an alkyl (meth)acrylate (sometimes referred to as "alkyl (meth)acrylate (A)") which may have an alkoxy group with 8 or more carbon atoms in the ester portion. Using alkyl (meth)acrylate (A) makes it easier to adjust the glass transition temperature of the adhesive layer to a relatively low level. Examples of alkyl (meth)acrylate (A) include alkyl (meth)acrylates which may have an alkoxy group with 8 to 24 carbon atoms in the ester portion.

[0045] Of the above alkyl (meth)acrylate (A), alkyl acrylate is preferred over alkyl methacrylate because it can shorten the polymerization time of the acrylic polymer and improve productivity. In particular, alkyl acrylate is preferred from the viewpoint of superior UV curability.

[0046] Among the above alkyl (meth)acrylate (A), it is preferable to include alkyl (meth)acrylates that have an alkoxy group having a linear or branched ester portion with 8 or more carbon atoms, in order to easily achieve a low modulus of elasticity while exhibiting high tackiness, more preferably alkyl (meth)acrylates that have an alkoxy group having a linear or branched ester portion with 8 or 9 carbon atoms, even more preferably n-octyl (meth)acrylate and / or 2-ethylhexylcarbitol (meth)acrylate, and particularly preferably n-octyl acrylate (NOAA) and / or 2-ethylhexylcarbitol acrylate (2EHCA). The number of carbon atoms in the side chain alkyl group of the branched ester portion is not particularly limited, but alkyl groups with 1 to 3 carbon atoms (e.g., methyl group, ethyl group, n-propyl group, isopropyl group) are preferred. The "side chain alkyl group" is an alkyl group that is substituted on the side chain of the carbon chain with the longest number of carbon atoms.

[0047] The content of the above alkyl (meth)acrylate (A) is not particularly limited, but from the viewpoint of easily achieving a low modulus of elasticity while exhibiting high tackiness, it is preferably 30 to 99% by mass, more preferably 40 to 98% by mass, and even more preferably 50 to 97% by mass, based on the total amount (100% by mass) of monomer components constituting the above acrylic polymer.

[0048] The above monomer component may include an alkyl (meth)acrylate (A) other than alkyl (meth)acrylate (A), which may have an alkoxy group (hereinafter sometimes referred to as "alkyl (meth)acrylate (B)"). Examples of alkyl (meth)acrylate (B) include alkyl (meth)acrylates which may have an alkoxy group having a linear or branched ester portion with 1 to 7 carbon atoms.

[0049] The content of the above alkyl (meth)acrylate (B) is not particularly limited, but from the viewpoint of easily achieving a low modulus of elasticity while exhibiting high tackiness, it is preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total amount (100% by mass) of monomer components constituting the above acrylic polymer. The above content may be 1% by mass or more, 3% by mass or more, 8% by mass or more, or 13% by mass or more.

[0050] The above-mentioned acrylic polymer may contain, in addition to the alkyl (meth)acrylate ester which may have the above-mentioned alkoxy group as a monomer component constituting the acrylic polymer, copolymerizable functional group-containing monomers (copolymerizable functional group-containing monomers). Note that only one type of functional group-containing monomer may be used, or two or more types may be used.

[0051] As the above-mentioned functional group-containing monomers, hydroxyl group-containing monomers are preferred. When an acrylic polymer contains a hydroxyl group-containing monomer as a monomer unit, polymerization of the constituent monomer components becomes easier, and the cohesive force can be increased. Furthermore, the interaction with the adherend interface can be enhanced. As a result, strong adhesion can be easily obtained.

[0052] The above-mentioned hydroxyl group-containing monomers refer to monomers that have at least one hydroxyl group in their molecule. Furthermore, monomers that have at least one hydroxyl group and at least one carboxyl group in their molecule are carboxyl group-containing monomers and not hydroxyl group-containing monomers. The above-mentioned hydroxyl group-containing monomers are not particularly limited, but specifically include, for example, hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl) (meth)acrylate; vinyl alcohol, allyl alcohol, etc. In particular, as the above-mentioned hydroxyl group-containing monomer, hydroxyl group-containing (meth)acrylic acid esters are preferred from the viewpoint of easily obtaining good cohesive force and improving adhesive reliability at high temperatures, and more preferably 2-hydroxyethyl acrylate (HEA), 2-hydroxypropyl (meth)acrylate (HPA), and 4-hydroxybutyl acrylate (4HBA). Note that one type of hydroxyl group-containing monomer may be used, or two or more types may be used.

[0053] Furthermore, nitrogen atom-containing monomers are preferred as the functional group-containing monomers. When an acrylic polymer contains nitrogen atom-containing monomers as monomer units, it becomes easier to obtain appropriate cohesive force, which in turn makes it easier to obtain strong adhesion and excellent foaming resistance.

[0054] Examples of monomers containing a carboxyl group include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0055] The content of the carboxyl group-containing monomer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, relative to the total amount of monomer components constituting the acrylic polymer (100% by mass), from the viewpoint of introducing a crosslinked structure into the acrylic polymer, ensuring cohesive force in the adhesive layer, and ensuring adhesion to the substrate in the adhesive layer of the present invention. The above content is preferably 3% by mass or less, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the substrate by acid.

[0056] The content ratio of the functional group-containing monomer relative to the total amount (100% by mass) of monomer components constituting the acrylic polymer is not particularly limited, but is preferably 0.1 to 20% by mass, more preferably 0.5 to 15% by mass, and even more preferably 1 to 10% by mass, in order to exhibit appropriate tackiness. Furthermore, it is preferable that the total content ratio of hydroxyl group-containing monomers and nitrogen atom-containing monomers (especially the content ratio of hydroxyl group-containing monomers) be within the above range.

[0057] The above acrylic polymer may contain a crosslinked structure derived from a crosslinking agent. By using the above crosslinking agent in the polymerization of the above acrylic polymer, the acrylic polymer will have a crosslinked structure. Examples of the above crosslinking agent include photopolymerizable polyfunctional compounds having multiple groups that can react with polymerizable functional groups in the monomer component. Examples of the above photopolymerizable polyfunctional compounds include polyfunctional monomers and polyfunctional oligomers containing two or more ethylenically unsaturated double bonds in one molecule. Examples of polyfunctional monomers include polyfunctional (meth)acrylates. Only one type of crosslinking agent may be used, or two or more types may be used.

[0058] Examples of polyfunctional (meth)acrylates include difunctional (meth)acrylates, trifunctional (meth)acrylates, and polyfunctional (meth)acrylates with four or more functions.

[0059] Examples of difunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, ethoxylated bisphenol A diacrylate (BPAEODE), and neopentyl glycol di(meth)acrylate. Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl) isocyanurate. Examples of polyfunctional (meth)acrylates with four or more functions include ditrimethylolpropanetetra(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Examples of polyfunctional oligomers include urethane(meth)acrylate oligomers, polyester(meth)acrylate oligomers, polyether(meth)acrylate oligomers, polyol(meth)acrylate oligomers, epoxy(meth)acrylate oligomers, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

[0060] The weight-average molecular weight (Mw) of the polyfunctional oligomer is preferably 5000 or more, preferably 20000 or less, and more preferably 15000 or less, from the viewpoint of compatibility between the polyfunctional oligomer and the partially polymerized or monomer mixture constituting the base polymer. The weight-average molecular weight is measured by gel permeation chromatography (GPC) and calculated on a polystyrene basis.

[0061] From the viewpoint of ensuring the cohesive force of the adhesive layer, the content of the structural components derived from the above-mentioned crosslinking agent is preferably 0.001 parts by mass or more, more preferably 0.002 parts by mass or more, and even more preferably 0.005 parts by mass or more, and may be 0.01 parts by mass or more, per 100 parts by mass of the total amount of monomer components constituting the acrylic polymer. The above content is preferably 0.5 parts by mass or less, more preferably 0.35 parts by mass or less, and even more preferably 0.2 parts by mass or less, and may be 0.1 parts by mass or less, per 100 parts by mass of the acrylic polymer, in order to realize a highly flexible adhesive layer and sufficiently relieve stress with metal wiring to prevent uneven display.

[0062] The adhesive layer of the present invention may contain other components besides those described above, as long as they do not impair the effects of the present invention. Examples of these other components include curing agents, curing catalysts, crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents, fillers (metal powders, organic fillers, inorganic fillers, etc.), colorants (pigments, dyes, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, rust inhibitors, granular materials, foil-like materials, flame retardants, silane coupling agents, ion trapping agents, and the like. Each of these other components may be used individually or in combination of two or more.

[0063] The thickness of the adhesive layer of the present invention is preferably 5 to 2500 μm, more preferably 10 to 1000 μm, and even more preferably 15 to 500 μm. When the thickness of the adhesive layer is 5 μm or more, the adhesion to the substrate and the decorative layer is superior. When the thickness of the adhesive layer is 2500 μm or less, when the substrate is bent, the formation of creases due to deformation of the adhesive layer is less likely to occur. In the case where the adhesive layer is composed of multiple layers (a single layer formed by the contact of multiple layers), the above thickness is the total thickness of the multiple layers.

[0064] The elastic modulus of the adhesive layer of the present invention at 25°C is 10 3 ~10 6Pa is preferable, more preferably 2×10 3 ~5×10 5 Pa, even more preferably 5×10 3 ~10 5 Pa. When the elastic modulus of the adhesive layer at 25°C is 10 3 Pa or more, it has appropriate cohesive force and excellent adhesion to the adhesive layer. When the elastic modulus of the adhesive layer at 25°C is 10 6 Pa or less, it is excellent in flexibility and flex resistance. When the adhesive layer has curability, the elastic modulus may be the elastic modulus of the adhesive layer before curing or the elastic modulus of the adhesive layer after curing.

[0065] The elastic modulus of the adhesive layer of the present invention at -20°C is 10 3 ~10 9 Pa is preferable, more preferably 2×10 3 ~5×10 7 Pa, even more preferably 5×10 3 ~10 6 Pa. When the elastic modulus of the adhesive layer at -20°C is 10 3 Pa or more, it has appropriate cohesive force and excellent adhesion to the adhesive layer. When the elastic modulus of the adhesive layer at -20°C is 10 9 Pa or less, it is excellent in flexibility and flex resistance. When the adhesive layer has curability, the elastic modulus may be the elastic modulus of the adhesive layer before curing or the elastic modulus of the adhesive layer after curing.

[0066] The elastic modulus of the adhesive layer of the present invention at 60°C is 5×10 2 ~10 6 [[ID=4O]]Pa is preferable, more preferably 10 3 ~5×10 5 Pa, even more preferably 2×10 3 ~10 5 Pa. When the elastic modulus of the adhesive layer at 60°C is 5×10 2 [[ID=5OD]]Pa or more, it has appropriate cohesive force and excellent adhesion to the adhesive layer. When the elastic modulus of the adhesive layer at 60°C is 10 6If the elastic modulus is Pa or less, it provides superior flexibility and bending resistance. If the adhesive layer is curable, the elastic modulus may be the elastic modulus of the adhesive layer before curing, or the elastic modulus of the adhesive layer after curing.

[0067] The above modulus of elasticity is the storage modulus, which is a value measured by dynamic viscoelasticity. The above storage modulus may be the shear modulus or the tensile modulus, but it is preferably the shear modulus. The above storage modulus can be controlled by the type of base polymer constituting the adhesive layer, the monomer composition, the weight-average molecular weight, the amount of crosslinking agent used (amount added), and the type and content of other additives.

[0068] The glass transition temperature Tg1 of the adhesive layer of the present invention (or the lowest glass transition temperature if the adhesive layer of the present invention has two or more glass transition temperatures) is preferably -120°C or higher, more preferably -100°C or higher, even more preferably -80°C or higher, and particularly preferably -70°C or higher. When Tg1 is -120°C or higher, it is easier to improve the adhesive strength. Tg1 is preferably -10°C or lower, more preferably -20°C or lower, and even more preferably -30°C or lower. When Tg1 is -10°C or lower, it is easier to exhibit tack, making it easier to bond with the adhesive layer and the adherend.

[0069] In this specification, the glass transition temperature of the adhesive layer may be determined using the peak temperature value of tanδ obtained by dynamic mechanical analysis (DMA), or the median temperature value of the baseline shift obtained by differential scanning calorimetry (DSC). The glass transition temperature can be controlled by the type, number, monomer composition, molecular weight, and content of the polymers constituting the adhesive layer.

[0070] The adhesive layer of the present invention may or may not have curability, but it is preferable that it does not. Examples of curability include active energy ray curability, thermosetting, and moisture curability. Examples of active energy rays include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays.

[0071] (adhesive layer) The adhesive layer described above may contain a heat-transferable resin. When the adhesive layer contains a heat-transferable resin, the adhesive layer, which is prepared on a temporary substrate separate from the alkali-free glass or chemically strengthened glass, can be transferred onto the alkali-free glass or chemically strengthened glass by heating, resulting in superior adhesion to the alkali-free glass and chemically strengthened glass. In this specification, "heat-transferable resin" refers to a resin in which a single layer of resin formed using the heat-transferable resin can be transferred to a substrate at a heating temperature (for example, at least one temperature between 40 and 150°C). The adhesive layer may contain only one type of heat-transferable resin, or it may contain two or more types.

[0072] The above-mentioned heat-transferable resin preferably satisfies at least one of the following conditions: (1) the ratio of the elastic modulus at the heating temperature (for example, at least one temperature between 40 and 150°C) to the elastic modulus at 25°C [elastic modulus at heating temperature / elastic modulus at 25°C] is 1 / 2 or less, or (2) the softening point is between 0 and 150°C.

[0073] The ratio of the elastic moduli is more preferably 1 / 5 or less, and even more preferably 1 / 10 or less. When the ratio of the elastic moduli is 1 / 2 or less, the adhesive layer is not sticky at room temperature and is easy to handle, and when heated, it becomes sticky and can be transferred to the substrate.

[0074] The above softening point is more preferably 20 to 150°C, and even more preferably 40 to 150°C. If the above softening point is 0°C or higher, the adhesive layer is less sticky at room temperature and easier to handle, resulting in superior handling properties. If the above softening point is 150°C or lower, stickiness can be generated by heating with less energy, allowing for energy-saving transfer to the substrate. If the above adhesive layer is curable, the above softening point of the adhesive layer may be the softening point of the adhesive layer before curing, or the softening point of the adhesive layer after curing. Furthermore, it is preferable that the above softening point of the adhesive layer is the softening point before heat transfer.

[0075] The above softening point can be measured by any of the methods specified in JIS K7234 (Environmental Method), JIS K7234 (Mercury Replacement Method), or JIS K7206 (Vicat Softening Temperature). The above softening point can be controlled by the type of base polymer constituting the above heat transferable resin, the monomer composition, the weight-average molecular weight, the amount of crosslinking agent used (amount added), and the type and content of other additives.

[0076] As the above-mentioned heat-transferable resin, polymers (A) and polymers (B) described later that correspond to the above-mentioned heat-transferable resin can be used.

[0077] The adhesive layer described above preferably contains a polymer with a molecular weight of 2,000 to 60,000. In this specification, the adhesive layer described above may be referred to as "the adhesive layer of the present invention." The polymer with a molecular weight of 2,000 to 60,000 may also be referred to as "polymer (A)." By containing polymer (A), the adhesive layer of the present invention exhibits higher adhesion to alkali-free glass or chemically strengthened glass of the laminate of the present invention, and is less prone to peeling, both at room temperature and under humid heat conditions.

[0078] The molecular weight of polymer (A) is 2000 or more, and may be 3000 or more, 5000 or more, 10000 or more, or 20000 or more. Having a molecular weight of 2000 or more suppresses the migration of components from the adhesive layer to the adhesive layer of the present invention, which can cause changes in adhesion over time when the adhesive layer and the adhesive layer are joined. The molecular weight is 60000 or less, and may be 50000 or less, or 40000 or less.

[0079] The molecular weight of polymer (A) can be determined by the weight-average molecular weight in polystyrene terms, measured by gel permeation chromatography (GPC), or, in the case of commercially available products, by the catalog value.

[0080] The adhesive layer of the present invention may contain only one polymer (A), or it may contain two or more polymers (A). Examples of two or more polymers (A) include a polymer (A1) with a molecular weight of 2,000 to 10,000 and a polymer (A2) with a molecular weight of more than 10,000 and 60,000 or less. The adhesive layer of the present invention preferably contains polymer (A1) as polymer (A), and more preferably contains both polymer (A1) and polymer (A2).

[0081] The molecular weight of polymer (A1) is preferably 2000 to 8000, more preferably 2000 to 7000, and even more preferably 2000 to 6000. When polymer (A1) is included, the adhesive layer of the present invention exhibits even greater adhesion to alkali-free glass or chemically strengthened glass, especially under humid and thermal environments.

[0082] The molecular weight of polymer (A2) is preferably 15,000 to 55,000, and more preferably 20,000 to 54,000. When polymer (A2) is included in addition to polymer (A1), the adhesive layer of the present invention is more likely to form a phase-separated structure.

[0083] The polymer (A) is not particularly limited, but examples include acrylic oligomers, rubber oligomers, silicone oligomers, polyester oligomers, urethane oligomers, polyamide oligomers, epoxy oligomers, vinyl alkyl ether oligomers, and fluorine oligomers. Among the above polymers (A), acrylic oligomers and epoxy oligomers are preferred.

[0084] The above-mentioned acrylic oligomer is composed of an acrylic monomer as an essential monomer component. Examples of acrylic monomers constituting the above-mentioned acrylic oligomer include those exemplified and described as acrylic monomers constituting the above-mentioned acrylic polymer. As the above-mentioned acrylic monomer, a monofunctional (meth)acrylate having only one polymerizable functional group is preferred.

[0085] The above monofunctional (meth)acrylate preferably includes an alkyl (meth)acrylate having an alicyclic alkyl group. The above constituent unit may consist of only one monofunctional (meth)acrylate or two or more.

[0086] The content of alkyl (meth)acrylate having an alicyclic alkyl group in 100% by mass of the total amount of all monomer components constituting the above acrylic oligomer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. The above content is preferably 99% by mass or less, and may be 97% by mass or less.

[0087] The above monofunctional (meth)acrylate preferably contains an alkyl (meth)acrylate. Methyl methacrylate (MMA) is preferred as the alkyl (meth)acrylate. The content of the alkyl (meth)acrylate in the total monomer components constituting the above acrylic oligomer is preferably 10% by mass or more, more preferably 20% by mass or more. The above content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less.

[0088] The epoxy oligomer described above is an oligomer having one or more epoxy groups. Examples of the epoxy oligomer include aromatic epoxy resins such as bisphenol-type epoxy resins (e.g., bisphenol A-type epoxy resin), novolac-type epoxy resins, and naphthalene-type epoxy resins; nitrogen-containing cyclic epoxy resins such as triepoxypropyl isocyanurate (triglycidyl isocyanurate) and hydantoin epoxy resins; aliphatic epoxy resins; alicyclic epoxy resins (e.g., dicyclocyclic epoxy resins); glycidyl ether-type epoxy resins; and glycidylamine-type epoxy resins. Among these, alicyclic epoxy resins are preferred.

[0089] Examples of the epoxy oligomers mentioned above include the product names "EHPE-3150" (manufactured by Daicel Corporation), "jER-1256B40", and "jER-1010" (all manufactured by Mitsubishi Chemical Corporation).

[0090] Polymer (A) is obtained by polymerizing a composition containing the monomer components that constitute the polymer. Preferred polymerization methods include bulk polymerization, thermal polymerization, and active energy ray polymerization. Various general solvents may be used during the polymerization of the monomer components. One solvent may be used, or two or more may be used. Polymerization initiators, chain transfer agents, emulsifiers, etc., used in the radical polymerization of the monomer components are not particularly limited and can be appropriately selected and used.

[0091] The content of polymer (A) in the adhesive layer of the present invention is preferably 10% by mass or more, and more preferably 20% by mass or more, based on 100% by mass of the total amount of the adhesive layer of the present invention. The above content may be 100% by mass or less, and may be 90% by mass or less, 80% by mass or less, 70% by mass or less, 60% by mass or less, or 50% by mass or less.

[0092] When the adhesive layer of the present invention contains polymer (A1), the ratio of polymer (A1) to 100% by mass of the total amount of polymer (A) in the adhesive layer of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The above ratio is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0093] When the adhesive layer of the present invention contains polymer (A2), the ratio of polymer (A2) to the total amount of polymer (A) in the adhesive layer of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more. The above ratio is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and particularly preferably 60% by mass or less.

[0094] The adhesive layer of the present invention may further contain a polymer with a molecular weight of 100,000 to 3,000,000. In this specification, the polymer with a molecular weight of 100,000 to 3,000,000 may be referred to as "polymer (B)". When the adhesive layer of the present invention contains polymer (B) in addition to polymer (A), its adhesion to alkali-free glass or chemically strengthened glass is further improved under humid and thermal conditions.

[0095] The molecular weight of polymer (B) is 100,000 or more, preferably 200,000 or more, more preferably 300,000 or more, even more preferably 400,000 or more, even more preferably 500,000 or more, even more preferably 600,000 or more, even more preferably 700,000 or more, and particularly preferably 800,000 or more. When the molecular weight is 100,000 or more, the adhesive layer of the present invention can maintain sufficient cohesive force even when softened by heat or the like, and is less likely to peel off from the adherend. The molecular weight is 3,000,000 or less, preferably 2,500,000 or less, more preferably 2,000,000 or less, even more preferably 1,500,000 or less, and particularly preferably 1,000,000 or less. When the molecular weight is 3,000,000 or less, the adhesive layer of the present invention has appropriate flexibility and superior adhesion to the adherend.

[0096] The molecular weight of polymer (B) can be determined by the weight-average molecular weight in polystyrene terms, measured by gel permeation chromatography (GPC), or, in the case of commercially available products, by the catalog value.

[0097] When the adhesive layer of the present invention contains polymer (B), the content of polymer (B) in the adhesive layer of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 40% by mass or more, and may be 50% by mass or more or 60% by mass or more, based on 100% by mass of the total amount of the adhesive layer of the present invention. The above content is preferably 90% by mass or less, and more preferably 80% by mass or less.

[0098] The adhesive layer of the present invention preferably comprises polymer (A1), polymer (A2), and / or polymer (B). In this case, the adhesive layer of the present invention exhibits even greater adhesion to alkali-free glass or chemically strengthened glass, particularly under humid and thermal conditions.

[0099] The adhesive layer described above may contain other components besides those listed above, as long as they do not impair the effects of the present invention. Examples of these other components include crosslinking agents, curing agents, curing catalysts, crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents, fillers (metal powders, organic fillers, inorganic fillers, etc.), colorants (pigments, dyes, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, rust inhibitors, granular materials, foil-like materials, flame retardants, silane coupling agents, ion trapping agents, photoacid generators, thermal polymerization initiators, and photopolymerization initiators (photoradical generators, photoinitiators). Each of these other components may be used individually or in combination of two or more.

[0100] The glass transition temperature Tg2 of the adhesive layer (or the lowest glass transition temperature if the adhesive layer has two or more glass transition temperatures) is preferably -20°C or higher, more preferably -15°C or higher, even more preferably -10°C or higher, and particularly preferably -5°C or higher. When Tg2 is -20°C or higher, the adhesive layer exhibits even greater adhesion to alkali-free glass or chemically strengthened glass, especially in a humid heat environment. Tg2 is preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower. When Tg2 is 150°C or lower, the adhesive layer exhibits tack and superior adhesion to the adherend in a room temperature environment.

[0101] The adhesive layer described above may have two or more glass transition temperatures. In this case, any glass transition temperature other than Tg2, Tg3, is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 110°C or higher. Tg3 is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower.

[0102] The adhesive layer described above may or may not have curability. Examples of curability include active energy ray curability, thermosetting, and moisture curing. Examples of active energy rays include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays.

[0103] The adhesive layer may contain a curable resin. Examples of curable resins include active energy ray curable resins, thermosetting resins, and moisture-curable resins. The adhesive layer may contain only one type of curable resin, or two or more types. In addition, one or more selected from the group consisting of the heat-transferable resin, polymer (A), and polymer (B) may have curable properties.

[0104] The adhesive layer described above preferably has a phase separation structure. In this case, the adhesive layer can achieve higher adhesion to alkali-free glass or chemically strengthened glass in both room temperature and humid heat environments. The presence or absence of the phase separation structure can be confirmed by transmission electron microscopy. Furthermore, the phase separation structure tends to be formed by using two or more different types of polymers (for example, acrylic polymers and epoxy polymers).

[0105] The thickness of the adhesive layer is preferably 200 nm to 10 μm, more preferably 500 nm to 8 μm, and even more preferably 800 nm to 5 μm. When the thickness is 200 nm or more, adhesion to alkali-free glass and chemically strengthened glass is superior. When the thickness of the adhesive layer is 10 μm or less, stress can be reduced when the laminate of the present invention is bonded to an adherend and used in a bent state. If the adhesive layer is composed of multiple layers (a single layer formed by the contact of multiple layers), the thickness is the total thickness of the multiple layers. Furthermore, if the laminate of the present invention includes a decorative layer (details described later), and there is a portion comprising adhesive layer A, decorative layer, adhesive layer B, and adhesive layer in this order, the thickness of the adhesive layer is the thickness of adhesive layer A, that is, the thickness of the adhesive layer located on the side opposite to the side where the adhesive layer of the decorative layer is located.

[0106] The elastic modulus of the above adhesive layer at 25°C is 10 4 ~10 10 Pa is preferred, more preferably 3 × 10 4 ~1 × 10 9 Pa, more preferably 5 × 10 4 ~5×10 8 The elastic modulus of the above adhesive layer at 25°C is 10 4 When the elastic modulus of the adhesive layer is Pa or higher, it has appropriate cohesive force and superior adhesion to the adhesive layer and substrate. 10 If the elastic modulus is Pa or less, it is possible to maintain appropriate flexibility and bending resistance. If the adhesive layer has curability, the elastic modulus may be the elastic modulus of the adhesive layer before curing or the elastic modulus of the adhesive layer after curing, but it is preferable to use the elastic modulus of the adhesive layer before curing.

[0107] The above modulus of elasticity is the storage modulus, which is a value measured by dynamic viscoelasticity. The above storage modulus may also be the shear modulus or the tensile modulus. However, if the adhesive layer is curable, the modulus of elasticity after curing will be high, and when measuring the shear modulus, slippage may occur between the adhesive layer and the measuring jig, making it impossible to perform the measurement properly. For this reason, if the shear modulus cannot be measured properly (for example, if the modulus of elasticity is 10 8 If it exceeds [a certain value], the storage modulus is preferably the tensile modulus. The storage modulus can be controlled by the type of polymer and monomer composition that may be contained in each layer, the weight-average molecular weight, the amount of crosslinking agent used (amount added), and the type and content of other additives.

[0108] (compatible layer) The laminate of the present invention may have a compatible layer at the interface between the adhesive layer and the adhesive layer of the present invention. The compatible layer is a layer formed by compatibility near the boundary between the adhesive layer and the adhesive layer. The mechanism by which the compatible layer is formed is not particularly limited, but for example, when the adhesive layer and the adhesive layer are bonded together by lamination or the like, at least a portion of the adhesive layer mixes with at least a portion of the adhesive layer. Alternatively, when the adhesive composition is directly applied (coated) onto the adhesive layer, at least a portion of the adhesive composition mixes with at least a portion of the adhesive layer. Furthermore, the formation of the compatible layer can be promoted by heating or the like at the time of bonding, the time of direct application, or at any point after the adhesive layer and the adhesive layer have been laminated. Because the adhesion between the adhesive layer and the adhesive layer is improved by the formation of the compatible layer, peeling that may occur between the adhesive layer and the adhesive layer when bending and folding operations are repeated is suppressed, and as a result, the occurrence of peeling and creases is further suppressed.

[0109] The thickness of the compatible layer is preferably 10 nm to 20 μm, more preferably 20 nm to 10 μm, and even more preferably 30 nm to 5 μm. When the thickness of the compatible layer is 10 nm or more, the adhesion between the adhesive layer and the tack layer is improved. When the thickness of the compatible layer is 20 μm or less, the influence on the elastic modulus of the tack layer can be further suppressed, resulting in improved flexibility and bending resistance.

[0110] The thickness ratio R of the compatible layer, defined by the following formula (3), is not particularly limited, but is preferably 0.01 to 0.99, more preferably 0.02 to 0.95, and even more preferably 0.05 to 0.9. When R is 0.01 or higher, the adhesion between the adhesive layer and the tack layer is superior. When R is 0.99 or lower, the influence on the elastic modulus of the adhesive layer can be further suppressed, resulting in superior flexibility and bending resistance. The compatible layer can be confirmed, for example, by observing the cross-section of an optical element using spectroscopic analysis such as infrared absorption spectroscopy (IR method) or by observation with a transmission electron microscope (TEM), and its thickness can be measured. R = [DC / (DC + DB)] (3)

[0111] In equation (3) above, DB is the thickness of the adhesive layer and DC is the thickness of the compatible layer.

[0112] (Removable liner) The laminate of the present invention may have a release liner bonded to at least one surface (for example, the surface of the adhesive layer or the tack layer) until use. When both sides of the laminate of the present invention are protected with a release liner, each side may be protected by two release liners, or it may be protected by a single release liner with both sides being release surfaces, wound in a roll shape (winding body). The release liner is used as a protective material for the laminate and is peeled off when it is attached to the substrate. Note that the release liner is not necessarily required.

[0113] The above-mentioned release liner can be conventional release paper or the like, and is not particularly limited, but examples include a substrate having a release treatment layer, a low-adhesion substrate made of a fluoropolymer, or a low-adhesion substrate made of a nonpolar polymer. Examples of the substrate having the release treatment layer include plastic films and paper surface-treated with release agents such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide. Examples of fluorine-based polymers in the low-adhesion substrate made of a fluoropolymer include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, and chlorofluoroethylene-vinylidene fluoride copolymer. Examples of the above-mentioned nonpolar polymer include olefin resins (e.g., polyethylene, polypropylene, etc.). The release liner can be formed by known or conventional methods. The thickness of the release liner is also not particularly limited.

[0114] (base material) The laminate of the present invention may have a substrate on one of its surfaces (the surface of the adhesive layer or the tack layer). When the laminate of the present invention has a substrate, it is preferable that the adhesive layer is in contact with the substrate from the viewpoint of excellent adhesion to the substrate. The substrate can be a known or conventional substrate. The substrate is preferably an optically transparent substrate. The substrate is not particularly limited, but is preferably glass. The glass is not particularly limited, but may be alkali-free glass or chemically strengthened glass. Furthermore, the substrate can be thin. For example, ultra-thin glass can be used.

[0115] Alkali-free glass refers to glass that contains less alkali components (e.g., alkali metal oxides such as Na2O and K2O) than conventional alkali glass. However, alkali-free glass also includes glass that contains only trace amounts of alkali components. In this specification, the alkali component (alkali metal oxide) content in alkali-free glass may be, for example, 1% by mass or less, 0.1% by mass or less, or 0.05% by mass or less, or it may be substantially free of alkali components. Here, "substantially free" means that it is not contained except for unavoidable impurities.

[0116] Chemically strengthened glass offers superior bending resistance and impact resistance compared to unstrengthened glass. Furthermore, chemically strengthened glass possesses excellent mechanical strength, allowing for the use of thinner glass.

[0117] Chemically strengthened glass is glass whose mechanical properties have been enhanced by chemical means through ion exchange near the glass surface, and it has a compressive stress layer on its surface. Chemically strengthened glass has a high potassium content on its surface, resulting in compressive stress on the surface. For example, by performing ion exchange at a temperature below the glass transition temperature, alkali metal ions with small ionic radii (e.g., lithium ions, sodium ions) on the glass surface are replaced with other alkali ions with larger ionic radii (e.g., sodium ions, potassium ions). This leaves compressive stress on the glass surface, improving the strength of the glass.

[0118] Chemically strengthened glass typically has a rectangular parallelepiped shape, or a hexahedron. Chemically strengthened glass has two faces (first and second principal faces) and four sides. Typically, chemically strengthened glass is hexahedral glass, where all faces are chemically strengthened. Hexahedral glass can be obtained, for example, by chemically strengthening a glass plate. Alternatively, chemically strengthened glass may be 2-sided glass, obtained by cutting hexahedral glass to a desired size.

[0119] Examples of glass materials that make up chemically strengthened glass include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborsilicate glass.

[0120] Chemically strengthened glass has a higher potassium ion concentration on its surface than near the center in the thickness direction. Therefore, the glass can be identified as chemically strengthened glass by the following method. For example, if the glass is divided into 10 sections in the thickness direction, and the potassium ion concentrations in each section are labeled d1, d2, d3, ..., d10 from the outermost surface, the glass can be identified as chemically strengthened glass if the potassium ion concentrations satisfy both d1 > d5 and d10 > d5. The potassium concentration distribution in the thickness direction can be measured, for example, by energy-dispersive X-ray analysis (EDX). Specifically, EDX mapping can be performed on the side surface of the glass substrate in the thickness direction using Oxford Instruments' "X-MaxN" at an acceleration voltage of 10 kV, and the potassium concentration can be quantified.

[0121] As chemically strengthened glass, ultra-thin glass can be used. Commercially available chemically strengthened glass can be used as appropriate, for example, Corning's "Gorilla Glass," and as ultra-thin glass, examples include SCHOTT's "SCHOTT UTG," Corning's "Willow Glass," and Nippon Electric Glass's "Dinorex UTG."

[0122] The thickness of the substrate (thickness of alkali-free glass or chemically strengthened glass) is preferably 10 to 2000 μm, more preferably 15 to 1000 μm, and even more preferably 20 to 500 μm, from the viewpoint of excellent flexibility and impact resistance.

[0123] (Decorative layer) The laminate of the present invention may include a decorative layer. The decorative layer is a layer in OLED display devices and the like that is intended to prevent external light from penetrating the OLED element, and is a layer that has reflectivity and light-shielding properties. Since such decorative layers generally do not adhere well to thin glass, they are often formed by bonding them to a plastic substrate, and then incorporated into OLED display devices and the like by laminating the plastic substrate onto thin glass. In recent years, there has been a demand for thinner optical products such as OLED display devices. Therefore, attempts have been made to form the decorative layer directly onto thin glass without using a plastic substrate. Such laminates contribute to thinner designs because they do not require the use of a plastic substrate for forming the decorative layer. In particular, foldable devices require even thinner designs so that they can be easily folded. As thin glass in such foldable devices, alkali-free glass or chemically strengthened glass with high flexibility resistance may be used. However, conventional decorative layers have low adhesion to alkali-free glass and chemically strengthened glass, making it difficult to form the decorative layer on alkali-free glass or chemically strengthened glass using conventional methods such as screen printing. Furthermore, even if it were possible to form the decorative layer, there were problems such as the decorative layer easily detaching from the alkali-free or chemically strengthened glass when subjected to impact or repeated bending.

[0124] Here, when the laminate of the present invention includes a decorative layer, the decorative layer exhibits high adhesion to alkali-free glass and chemically strengthened glass, and a laminate is provided in which the decorative layer is less likely to fall off. One embodiment of the laminate of the present invention, in which the laminate includes a base material and a decorative layer, will be described with reference to Figures 3 to 7.

[0125] When the laminate of the present invention comprises a substrate and a decorative layer, the adhesive layer is preferably formed to be in contact with at least one of the adhesive layer and the decorative layer, and is preferably formed to be in contact with at least the adhesive layer from the viewpoint of superior adhesion of the adhesive layer to the substrate. In particular, it is more preferable that the adhesive layer is formed to cover both the adhesive layer and the decorative layer from the viewpoint of more reliably preventing the decorative layer from falling off. Furthermore, the adhesive layer is preferably provided on at least a part of the substrate, and may be provided on the entire surface of the substrate.

[0126] In the laminate of the present invention, the decorative layer may be a single layer or multiple layers. By forming multiple layers, a thicker decorative layer can be formed, and if the decorative layer has light-shielding properties, the light-shielding properties can be made even higher. When the decorative layer is multiple layers, the thickness and formation areas of the multiple decorative layers may be the same or different.

[0127] In the laminate of the present invention, the adhesive layer may be laminated on at least a part of the substrate or on the entire surface.

[0128] Figures 3 to 7 show cross-sectional views of one embodiment of the laminate of the present invention. The laminate 1 shown in Figure 3 comprises a base material 5, an adhesive layer (the adhesive layer of the present invention) 3, a decorative layer 6, and an adhesive layer (the adhesive layer of the present invention) 2. The adhesive layer 3 is formed to be in contact with a part of the base material 5. The shape of the adhesive layer 3 is not particularly limited, but for example, in the view of preventing light from entering the interior when the decorative layer 6 has light-shielding properties, it is formed in a frame shape (annular, picture frame shape, etc.) along the edge of the base material 5. The adhesive layer 3 only needs to be formed on at least a part of the side of the base material 5 where the decorative layer 6 is located, and may be formed on the entire surface of the side of the base material 5 where the decorative layer 6 is located. The decorative layer 6 is laminated via the adhesive layer 3. In other words, the decorative layer 6 is laminated on the adhesive layer 3. The formation region of the decorative layer 6 is preferably a region that coincides with the formation region of the adhesive layer 3, or inside the formation region of the adhesive layer 3. From the viewpoint of improving the adhesion of the decorative layer 6 to the substrate 5 and more reliably preventing the decorative layer 6 from falling off, it is preferable that the area where the decorative layer 6 is formed is inside the area where the adhesive layer 3 is formed. The shape of the decorative layer 6 is not particularly limited, but for example, from the viewpoint of preventing light from entering the interior when the decorative layer 6 has light-shielding properties, it is formed in a frame shape (ring-shaped, picture frame shape, etc.) along the edge of the substrate 5. The adhesive layer 2 is formed so as to cover the entire surface of one side of the substrate 5 (the side with the adhesive layer 3 and the decorative layer 6) with the adhesive layer 3 and the decorative layer 6. The adhesive layer 2 is in contact with both the adhesive layer 3 and the decorative layer 6.

[0129] The laminate 1 shown in Figure 4 is the same as the laminate 1 shown in Figure 3, except that the adhesive layer 3 is formed over the entire surface of one of the surfaces of the base material 5. As shown in Figure 4, the adhesive layer 3 is provided over the entire surface of the base material 5, which further increases the adhesion of the adhesive layer 2 to the base material 5.

[0130] The laminate 1 shown in Figure 5 is the same as the laminate 1 shown in Figure 4, except that the adhesive layer 3 is formed over the entire surface of one side of the substrate 5 and covers the decorative layer 6. As shown in Figure 5, when the adhesive layer 3 covers the decorative layer 6, there is no area where the adhesive layer 2 and the decorative layer 6 come into contact, and the adhesion of the adhesive layer 2 to the substrate 5 becomes even higher.

[0131] The laminate 1 shown in Figure 6 comprises a plurality of adhesive layers 2 and a plurality of adhesive layers 3. The adhesive layers 2 include adhesive layer 21 and adhesive layer 22, and the adhesive layers 3 include adhesive layer 31 and adhesive layer 32. The adhesive layer 22 is provided via an adhesive layer 32 formed on the entire surface of the other side of the base material 5. Other aspects are the same as the laminate shown in Figure 4. In the laminate 1 shown in Figure 6, the adhesive layer 32 is formed on the entire surface of the other side of the base material 5, but it may also be formed on a part of the other side of the base material 5. Also, in Figure 6, the adhesive layer 31 may be formed on a part of one side of the base material 5.

[0132] In the laminate 1 shown in Figure 7, the adhesive layer 31 is formed over the entire surface of one side of the substrate 5 and is also formed to cover the decorative layer 6. Other aspects are the same as those of the laminate 1 shown in Figure 6.

[0133] Furthermore, the laminate of the present invention may not have a base material but may have a decorative layer. As an embodiment in which the laminate of the present invention does not have a base material but has a decorative layer, Figures 8 to 10 show a cross-sectional view of one embodiment of the laminate of the present invention.

[0134] The laminate 1 shown in Figure 8 is the same as the laminate 1 shown in Figure 3, except that it does not have a base material 5. Similarly, the laminate 1 shown in Figure 9 is the same as the laminate 1 shown in Figure 4, except that it does not have a base material 5. Furthermore, the laminate 1 shown in Figure 10 is the same as the laminate 1 shown in Figure 5, except that it does not have a base material 5.

[0135] The decorative layer preferably contains at least a heat-transferable resin. When the decorative layer contains a heat-transferable resin, it can be formed by transferring a decorative layer, which has been prepared on a temporary substrate separate from the base material, to the adhesive layer by heating. Furthermore, when both the adhesive layer and the decorative layer contain a heat-transferable resin, when the adhesive layer is heat-transferred onto the decorative layer, or when the laminate of the adhesive layer and the decorative layer is transferred onto the base material, the area near the boundary between the decorative layer and the adhesive layer becomes compatible, resulting in excellent adhesion between the adhesive layer and the decorative layer, and consequently, excellent adhesion of the decorative layer to the base material (particularly alkali-free glass and chemically strengthened glass). The decorative layer may contain only one type of heat-transferable resin, or it may contain two or more types.

[0136] Examples of the heat-transferable resin in the decorative layer include those exemplified and described as heat-transferable resins that may be included in the adhesive layer described above. The preferred embodiment of the heat-transferable resin in the decorative layer is the same as the preferred embodiment of the heat-transferable resin in the adhesive layer.

[0137] The heat-transferable resin in the decorative layer may be the same type as the heat-transferable resin that can be contained in the adhesive layer (for example, acrylic polymer and acrylic polymer), or it may be a different type (for example, acrylic polymer and rubber polymer). If they are the same type, when the decorative layer is heat-transferred onto the adhesive layer, the area near the boundary between the decorative layer and the adhesive layer becomes compatible, resulting in excellent adhesion between the adhesive layer and the decorative layer, and consequently, excellent adhesion of the decorative layer to the substrate (especially alkali-free glass and chemically strengthened glass).

[0138] The decorative layer preferably contains the heat-transferable resin as a base polymer. The content of the base polymer in the decorative layer is not particularly limited, but is preferably 10% by mass or more (for example, 10 to 99.9% by mass) and more preferably 25% by mass or more (for example, 25 to 99.9% by mass) based on the total amount (100% by mass) of the decorative layer.

[0139] The decorative layer may contain a coloring agent. The coloring agent may be a dye or a pigment, as long as it is soluble or dispersible in the decorative layer. Pigments are preferred from the viewpoint of superior weather resistance and durability. One coloring agent may be used alone, or two or more may be used.

[0140] Examples of the above-mentioned colorants include black colorants, cyan colorants, magenta colorants, and yellow colorants.

[0141] As the above-mentioned coloring agent, from the viewpoint of excellent light-shielding properties of the decorative layer, a coloring agent that produces black is preferred, that is, it is preferable to include a coloring agent so that the decorative layer produces black. As the above-mentioned coloring agent that produces black, a black-based coloring agent may be used, which is a combination of the above-mentioned black-based coloring agent or a coloring agent that produces a color other than black and functions as a black-based coloring agent.

[0142] The decorative layer described above may contain other components besides those listed above, as long as they do not impair the effects of the present invention. Examples of these other components include crosslinking agents, curing agents, curing catalysts, crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents, fillers (metal powders, organic fillers, inorganic fillers, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, rust inhibitors, granular materials, foil-like materials, flame retardants, silane coupling agents, and ion trapping agents. Each of these other components may be used individually or in combination of two or more.

[0143] The thickness of the decorative layer is preferably 0.01 to 50 μm, more preferably 0.05 to 35 μm, and even more preferably 0.1 to 20 μm. If the thickness of the decorative layer is 0.01 μm or more, the light-shielding properties are superior when light-shielding properties are present. If the thickness of the decorative layer is 50 μm or less, the difference in height between the adhesive layer and the decorative layer is small, resulting in a good appearance. If the decorative layer is composed of multiple layers (a single layer formed by the contact of multiple layers), the above thickness is the total thickness of the multiple layers.

[0144] (Laminated structure) In the laminate of the present invention, the adhesive layer and the bonding layer of the present invention preferably contain the same type of polymer, and it is particularly preferable that each contains an acrylic polymer. When the adhesive layer and the bonding layer of the present invention contain the same type of polymer (especially an acrylic polymer), the affinity between the adhesive layer and the bonding layer of the present invention is high, and the interlayer adhesion is further improved during bonding. Examples of the acrylic polymer include the acrylic polymers and acrylic oligomers mentioned above.

[0145] In the laminate of the present invention, it is preferable that the glass transition temperature Tg1 of the adhesive layer and the glass transition temperature Tg2 of the adhesive layer satisfy the following formula (1). By satisfying the following formula (1) in the laminate of the present invention, the adhesive layer and the adhesive layer of the present invention can be firmly bonded, and delamination is unlikely to occur in both room temperature and humid heat environments. If Tg2 is sufficiently high compared to Tg1, the polymer chains of the adhesive layer are less likely to move, and cohesive failure is unlikely to occur. In particular, in a humid heat environment, it is possible to suppress the softening of the adhesive layer and the peeling caused by cohesive failure. If Tg1 is sufficiently low compared to Tg2, the adhesive layer is soft, and the stress on the adhesive layer does not become too strong during deformation such as bending, and it is possible to suppress peeling due to stress and failure of the adherend due to increased load on the adherend. Tg2-Tg1≧20℃ (1)

[0146] If the adhesive layer of the present invention has two or more glass transition temperatures, it is sufficient that at least one of the glass transition temperatures Tg satisfies formula (1) above.

[0147] As mentioned above, the Tg2-Tg1 temperature is 20°C or higher, preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher. Furthermore, the Tg2-Tg1 temperature is preferably 200°C or lower, more preferably 190°C or lower, even more preferably 180°C or lower, and particularly preferably 170°C or lower.

[0148] When the adhesive layer has a glass transition temperature Tg3, it is preferable that the glass transition temperature Tg1 of the adhesive layer of the present invention and the glass transition temperature Tg3 of the adhesive layer satisfy the following formula (2). When the laminate of the present invention satisfies the following formula (2), the adhesive layer and the adhesive layer of the present invention can be bonded more firmly, and delamination is less likely to occur in both room temperature and humid heat environments. Tg3-Tg1≧40℃ (2)

[0149] The Tg3-Tg1 temperature is preferably 60°C or higher, more preferably 80°C or higher, and even more preferably 100°C or higher. Furthermore, the Tg3-Tg1 temperature is preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower.

[0150] In the laminate of the present invention, the ratio of the thickness of the adhesive layer to the thickness of the adhesive layer [thickness of the adhesive layer:thickness of the adhesive layer] is preferably 1:0.0001 to 1:1, more preferably 1:0.0025 to 1:0.75, and even more preferably 1:0.005 to 1:0.5. When the thickness of the adhesive layer of the present invention is greater than 1:1, the thickness of the adhesive layer is sufficient relative to the thickness of the adhesive layer, resulting in superior resistance to bending. Furthermore, when the thickness of the adhesive layer is less than 1:1, superior step-following ability is achieved. When the thickness of the adhesive layer is greater than 1:0.0001, the thickness of the adhesive layer is sufficient relative to the thickness of the adhesive layer, resulting in superior adhesion to alkali-free glass and chemically strengthened glass. Furthermore, when the thickness of the adhesive layer of the present invention is less than 1:0.0001, adhesive overflow from the adhesive layer and blocking between laminates can be further suppressed. Furthermore, if the adhesive layer and the bonding layer are each composed of multiple layers (a single layer formed by the contact of multiple layers), the above thickness is the total thickness of the multiple layers. Also, if bonding layers are provided on both sides of the adhesive layer, one side and the other side, the bonding layer in the above ratio refers to the layer provided on the same side as the adhesive layer. That is, the bonding layer in the above ratio is the bonding layer formed on the one side (for example, bonding layer 31 in Figure 2) or the bonding layer formed on the other side (for example, bonding layer 32 in Figure 2). Here, if bonding layers are provided on both sides of the adhesive layer, the ratio of the thickness of the adhesive layer to the thickness of the bonding layer formed on the one side (for example, [thickness of adhesive layer 2:thickness of bonding layer 31] in Figure 2), and the ratio of the thickness of the adhesive layer to the thickness of the bonding layer formed on the other side (for example, [thickness of adhesive layer 2:thickness of bonding layer 32] in Figure 2), may be the same or different.

[0151] The laminate of the present invention preferably has a peel force of 1.5 N / 10 mm or more, and more preferably 2 N / 10 mm or more, on the surface of the adhesive layer opposite the tin side of the alkali glass, measured under the conditions of a temperature of 23°C, a relative humidity of 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180°. When the above peel force is 1.5 N / 10 mm or more, it is difficult to peel from the adherend at room temperature. The above peel force is, for example, 10 N / 10 mm or less. The above peel force is specifically measured by the method described in the examples.

[0152] The laminate of the present invention preferably has a peel force of 1 N / 10 mm or more, more preferably 1.2 N / 10 mm or more, and even more preferably 1.5 N / 10 mm or more, on the side opposite to the tin side of the alkali glass, measured under the conditions of a temperature of 60°C, a relative humidity of 90% RH, a tensile speed of 300 mm / min, and a peel angle of 180° on the surface of the adhesive layer. When the above peel force is 1 N / 10 mm or more, it is difficult to peel from the adherend even in a humid and hot environment. The above peel force is, for example, 10 N / 10 mm or less. The above peel force is specifically measured by the method described in the examples.

[0153] The laminate of the present invention may include layers other than those described above. When the laminate of the present invention includes a substrate, it is preferable that the substrate and the adhesive layer are in contact in at least a portion (preferably the entire surface of one side of the substrate) (if a compatible layer is formed, it is considered to be in contact). Furthermore, when the laminate of the present invention includes a decorative layer, it is preferable that the adhesive layer and the decorative layer are in contact in at least a portion (preferably the entire surface of one side of the decorative layer).

[0154] The total light transmittance of the laminate of the present invention is 85% or more, as described above, and is preferably 90% or more from the viewpoint of ensuring the brightness of the OLED display device. Furthermore, the upper limit of the total light transmittance is not particularly limited, but may be less than 100%, 99.9% or less, or 99% or less. It is preferable that the total light transmittance of the laminate in which one end face is an adhesive layer and the other end face is a tack layer is within the above range, and it is also preferable that the total light transmittance of the laminate in which both end faces are adhesive layers is within the above range. In addition, when alkali-free glass or chemically strengthened glass is used as the substrate and a decorative layer is provided, it is preferable that the total light transmittance of the laminate in which one end face (for example, the end face of the one surface) is an adhesive layer or tack layer provided on one surface of the substrate, and the other end face (for example, the end face of the other surface) is the substrate, or an adhesive layer or tack layer provided on the other surface of the substrate is within the above range. Furthermore, if the laminate of the present invention includes a decorative layer, it is preferable that the total light transmittance in the region where the decorative layer is not laminated is within the above range.

[0155] The haze value (H) of the laminate of the present invention is not particularly limited, but from the viewpoint of suppressing image blurring in the OLED display device and displaying high-definition images, it is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. Furthermore, although not defining a lower limit, the haze value may be 0.01% or more, or 0.05% or more. It is preferable that the haze value of the laminate in which one end face is an adhesive layer and the other end face is a tack layer is within the above range, and it is also preferable that the haze value of the laminate in which both end faces are adhesive layers is within the above range. In addition, when alkali-free glass or chemically strengthened glass is used as the substrate and a decorative layer is provided, it is preferable that the haze value of the laminate in which one end face (for example, the end face of the one surface) is an adhesive layer or tack layer provided on one surface of the substrate, and the other end face (for example, the end face of the other surface) is the substrate, or an adhesive layer or tack layer provided on the other surface of the substrate, is within the above range. Furthermore, if the laminate of the present invention includes a decorative layer, it is preferable that the haze in the region where the decorative layer is not laminated is within the above range.

[0156] When the laminate of the present invention includes a decorative layer, the total light transmittance of the region of the laminate where the decorative layer is laminated is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less, from the viewpoint of ensuring the concealment provided by the decorative layer. Furthermore, the above total light transmittance is not particularly limited, but may be, for example, 0.00001% or more, or 0.0001% or more. It is preferable that the above total light transmittance of the laminate in which one end face is an adhesive layer and the other end face is a tack layer is within the above range, and it is also preferable that the above total light transmittance of the laminate in which both end faces are adhesive layers is within the above range. Furthermore, when alkali-free glass or chemically strengthened glass is used as the substrate and a decorative layer is provided, it is preferable that the above total light transmittance of the laminate in which one end face (for example, the end face of the one surface) is an adhesive layer or tack layer provided on one surface of the substrate, and the other end face (for example, the end face of the other surface) is the substrate, or an adhesive layer or tack layer provided on the other surface of the substrate, is within the above range.

[0157] The haze value and total light transmittance of the laminate of the present invention can be measured by the methods specified in JIS K7136 and JIS K7361, respectively, and can be controlled by the type and thickness of each layer constituting the laminate.

[0158] The laminate of the present invention has a structure in which an adhesive layer and an adhesive layer of the present invention, with a gel fraction of 85 to 99.9% by mass, are laminated together. Due to this structure, the adhesive layer has high adhesion to alkali-free glass or chemically strengthened glass, and the adhesive layer of the present invention makes it resistant to dents even when subjected to impact. Furthermore, since the laminate of the present invention has a total light transmittance of 85% or more, when used in optical products such as OLED display devices, it does not obstruct the light emitted from the display device and can ensure brightness. For this reason, it can be preferably used for bonding alkali-free glass or chemically strengthened glass to each other, or to alkali-free glass or chemically strengthened glass to other substrates.

[0159] The applications of the laminate of the present invention are not particularly limited and can be used for any application. Preferably, the laminate of the present invention is a laminate that can be used for optical applications, that is, for lamination on optical members (optical laminate). Examples of the optical members include electrical and electronic equipment. Note that "electrical and electronic equipment" refers to equipment that falls under at least one of electrical equipment or electronic equipment. Examples of the electrical and electronic equipment include image display devices such as liquid crystal displays, electroluminescent displays, and plasma displays, and portable electronic devices. Examples of the image display devices include image display devices in portable electronic devices, and displays (roll displays) inside and outside vehicles such as trains and buses.

[0160] Examples of the above-mentioned image display devices include liquid crystal displays, organic / inorganic electroluminescent displays, plasma displays, and OLED display panels. Examples of the above-mentioned image display devices include image display devices in portable electronic devices, in-vehicle displays, and digital signage (electronic billboards). The above-mentioned image display devices may be in a form (structure) such as a so-called "flexible type," or they may be in a form (structure) that can be bent or folded, such as a so-called "foldable type" or "rollable type."

[0161] Examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear-type devices worn on the wrist like watches, modular devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular types, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, and portable modems. In this specification, "portable" means not merely being able to carry something, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

[0162] The optical components mentioned above specifically include, for example, components and modules that make up portable electronic devices, and housings for components and modules that make up portable electronic devices. More specifically, they include cover glass, lenses (especially glass lenses), touch panels, touch sensors such as touch sensor films (especially touch sensor films with metal wiring such as metal mesh films and silver nanowire films), polarizing films, display panels, sheet keyboards, protective panels for information display sections, housings, and decorative sheets. In this specification, a display panel refers to a structure that consists of at least a lens (especially a glass lens) and a touch panel. Furthermore, the term "lens" in this specification is a concept that includes both transparent materials that exhibit light refraction and transparent materials that do not exhibit light refraction. In other words, the term "lens" in this specification also includes simple window panels that do not exhibit light refraction.

[0163] The laminate of the present invention may include alkali-free glass or chemically strengthened glass with high flexibility as a substrate. Therefore, the laminate of the present invention is preferably used for lamination onto components in electrical and electronic equipment that is used in a bendable manner, such as a bendable substrate, such as a bendable image display device (flexible display) (especially a foldable image display device (foldable display)).

[0164] The laminate of the present invention is preferably used by being laminated onto an OLED display panel. The OLED display panel comprises at least an OLED element in which an anode, an OLED layer including an emissive layer, and a cathode are laminated in that order. The laminate of the present invention is laminated on the viewing side of the OLED element in the OLED display panel. An OLED display device in which the laminate of the present invention and the OLED display panel are laminated may be referred to as "the OLED display device of the present invention".

[0165] The laminate of the present invention is preferably a laminate used in an OLED display device in which only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element (laminated for OLED display device). That is, the OLED display device of the present invention preferably has an OLED display panel in which only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element. "Only optical elements with a polarization degree of 95% or less are laminated on the viewing side of the OLED element" means that the optical elements on the viewing side of the OLED element do not include optical elements with a polarization degree exceeding 95%. "Optical elements with a polarization degree exceeding 95%" are not particularly limited, but include polarizers such as linear polarizers, quarter phase difference plates, half phase difference plates, circular polarizers, and reflective polarizers. That is, the OLED display device of the present invention is preferably an OLED display device that does not include polarizers on the viewing side of the OLED element.

[0166] The degree of polarization is determined by the following formula, based on the parallel transmittance Tp and orthogonal transmittance Tc, which are measured using a UV-Vis spectrophotometer and corrected for luminous sensitivity. Polarization degree (%)={(Tp-Tc) / (Tp+Tc)}1 / 2×100

[0167] The OLED display device of the present invention, by not including a polarizing plate on the viewing side of the OLED element, suppresses the absorption of light emitted from the OLED element by the polarizing plate, improving light collection efficiency, saving power consumption, and extending the lifespan of the OLED element. Furthermore, the absence of a polarizing plate allows for a thinner design and reduces manufacturing costs.

[0168] [Method for manufacturing the laminated material of the present invention] The laminate of the present invention can be manufactured by a manufacturing method (manufacturing method (i)) comprising at least a step of forming an adhesive layer (adhesive layer forming step) and a step of directly forming an adhesive layer on the adhesive layer (direct adhesive layer forming step). The laminate of the present invention can also be manufactured by a manufacturing method (manufacturing method (ii)) comprising at least a step of forming an adhesive layer (adhesive layer forming step), forming an adhesive layer (adhesive layer forming step), and bonding the adhesive layer and the adhesive layer together (bonding step). The above manufacturing method may include a step of bonding a release liner to at least one surface of the laminate of the present invention. The above manufacturing method may also include a step of bonding a release liner to at least one surface of the adhesive layer and the adhesive layer.

[0169] Regarding the above manufacturing method (i), a specific method for manufacturing the laminate 1 shown in Figure 1 will be described. Note that the manufacturing method described below is a preferred embodiment, and the manufacturing method for the laminate of the present invention is not limited to the above method.

[0170] (Adhesive layer formation process) In the above adhesive layer formation step, an adhesive layer 2 is formed on the release liner. The adhesive layer 2 can be manufactured, for example, by applying an adhesive composition for forming the adhesive layer 2 onto the release liner and drying and curing the resulting adhesive composition layer, or by applying the adhesive composition onto the release liner and curing the resulting adhesive composition layer by irradiating it with active energy rays. If necessary, it may also be further heated and dried. If necessary, the release liner may be bonded to the side of the adhesive layer 2 opposite to the side to which the release liner is bonded, and then cured. Furthermore, if necessary, at least one release liner may be peeled off, and another release liner may be bonded to the exposed adhesive surface.

[0171] Known coating methods may be used for applying (coating) the above adhesive composition. For example, coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, direct coaters, and die coaters may be used.

[0172] (Adhesive layer direct formation process) In the adhesive layer formation step described above, the adhesive layer 3 is directly formed on one surface of the adhesive layer 2. The adhesive layer can be formed on the adhesive layer 2 by known or conventional methods. The adhesive layer 3 can be manufactured, for example, by applying (coating) a composition for forming the adhesive layer 3 (adhesive composition) onto the adhesive layer 2 and drying and curing the resulting adhesive composition layer, or by applying (coating) the adhesive composition onto the adhesive layer 2 and curing the resulting adhesive composition layer by irradiating it with active energy rays. If a release liner is bonded to the surface of the adhesive layer 2, the release liner can be peeled off and the adhesive layer 3 can be formed on the exposed adhesive surface. In this way, the laminate 1 shown in Figure 1 can be manufactured. Furthermore, if necessary, heating and drying may be performed. The heating temperature at this time is not particularly limited, but for example, 50 to 150°C is preferred. When the adhesive layer 3 contains a heat-transferable resin or the same type of resin as the adhesive layer 2 (for example, acrylic polymer and acrylic polymer), heating the curing process allows a portion of the adhesive layer 3 to become compatible with a portion of the adhesive layer 2, thereby forming a compatible layer more efficiently.

[0173] A known coating method may be used for applying (coating) the above adhesive composition. For example, coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, comma coaters, and direct coaters may be used.

[0174] (Release liner application process) A release liner may be attached to the laminate of the present invention obtained as described above (release liner attachment step). The release liner may be attached to one side of the laminate of the present invention, or to both sides, or one release liner with both sides being release surfaces may be attached to one side.

[0175] The adhesive layer formation step in manufacturing method (ii) above can be carried out in the same manner as the adhesive layer formation step in manufacturing method (i) above. Furthermore, the adhesive layer formation step in manufacturing method (ii) above can be carried out in the same manner as the direct adhesive layer formation step in manufacturing method (i) above, except that the adhesive layer is formed on the release liner instead of directly on the adhesive layer. Furthermore, the bonding step in manufacturing method (ii) above can be performed by bonding the adhesive layer and the adhesive layer by a known or conventional method. In the bonding step above, if a release liner is bonded to the surfaces of the adhesive layer and the adhesive layer, the release liner can be peeled off and the exposed adhesive surface and the bonding surface can be bonded together. Heating (e.g., heat lamination, heat pressing) may be performed in the bonding step above if necessary. Furthermore, manufacturing method (ii) above may include the release liner application step in manufacturing method (i) above.

[0176] While alkali glass is commonly used for glass sheets, its hydrophilic surface allows for high adhesion of conventional adhesive layers to the glass. However, alkali-free glass and chemically strengthened glass, despite their high strength and flexibility even at thinness, have smooth and highly hydrophobic surfaces, making it difficult to adhere conventional adhesive layers to them with high flexibility. In contrast, the laminate of the present invention, by comprising adhesive layers and bonding layers with different elastic moduli, exhibits excellent adhesion even when the adherend is alkali-free glass or chemically strengthened glass, and is less likely to detach from alkali-free glass or chemically strengthened glass. Furthermore, it can follow bending and folding movements with high flexibility, is less prone to delamination or creases between layers, and exhibits excellent flexibility.

[0177] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. [Examples]

[0178] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0179] Example 1 (Preparation of acrylic prepolymer A solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 24 parts by mass of lauryl acrylate (LA), 16 parts by mass of butyl acrylate (BA), 57 parts by mass of n-octyl acrylate (NOAA), 3 parts by mass of 4-hydroxybutyl acrylate (4HBA), 0.05 parts by mass of photoradical generator (trade name "Omnirad 127D", manufactured by IGM Resins Italia Srl), and 0.05 parts by mass of photoradical generator (trade name "Omnirad 2959", manufactured by IGM Resins Italia Srl) were added. Then, nitrogen gas was introduced, and nitrogen purging was performed for approximately 20 minutes while stirring. After that, 5 mW / cm² was added. 2 Polymerization was carried out by irradiating with ultraviolet light, and the reaction rate was adjusted to 5-15% to obtain acrylic prepolymer solution A.

[0180] (Preparation of Acrylic Oligomer C) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 60 parts by mass of dicyclopentanyl methacrylate (DCPMA), 40 parts by mass of methyl methacrylate (MMA), 3 parts by mass of a chain transfer agent (α-thioglycerol), 0.3 parts by mass of a thermal polymerization initiator (azobisisobutyronitrile), and a solvent (ethyl acetate) (solid content concentration 26% by mass) was added. Then, nitrogen gas was introduced, and the mixture was purged with nitrogen for about 20 minutes while stirring. The reaction was then carried out at 72°C to 74°C for 6 hours (polymerization reaction). Next, the reaction solution was heated at 90°C for 12 hours to volatilize and remove ethyl acetate, the chain transfer agent, and unreacted monomers, thereby obtaining acrylic oligomer C.

[0181] (Preparation of adhesive composition) To the above acrylic prepolymer A solution, 15 parts by mass of lauryl acrylate (LA) as an acrylic monomer, 0.3 parts by mass of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 0.5 parts by mass of acrylic oligomer C, and 0.3 parts by mass of 3-glycidyloxypropyltrimethoxysilane as a silane coupling agent were added and stirred to prepare an adhesive composition.

[0182] (Formation of the adhesive layer) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38," manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with a release treatment on one side, 38 μm thick) to form an adhesive composition layer, and the release-treated surface of a release liner (product name "MRF38," manufactured by Mitsubishi Chemical Corporation) was bonded onto this adhesive composition layer. Next, a black light was used to measure 2.5 mW / cm². 2 The ultraviolet light at an illuminance of 2400 mJ / cm² is measured by the cumulative light intensity of 2400 mJ / cm². 2 Polymerization was carried out by irradiation until the desired result was obtained, yielding an adhesive layer (optically transparent adhesive sheet) with a thickness of 40 μm.

[0183] (Preparation of adhesive composition) As the first oligomer, 50 parts by mass of 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol (trade name "Celoxide EHPE3150", manufactured by Daicel Corporation) and 50 parts by mass of ethyl acetate were mixed and stirred to prepare the first oligomer solution. Subsequently, as the second oligomer, 50 parts by mass of acrylic oligomer (trade name "Dianal BR-83", manufactured by Mitsubishi Chemical Corporation) and 850 parts by mass of ethyl acetate were mixed and stirred to prepare the second oligomer solution. The first oligomer solution and the second oligomer solution were mixed in equal amounts and stirred to obtain an adhesive composition.

[0184] (Preparation of adhesive sheets) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with release treatment on one side, thickness 38 μm) to form an adhesive composition layer, and dried at 80°C for 1 minute to form an adhesive layer with a thickness of 2 μm. Next, one side of the release liner of the adhesive layer obtained above was peeled off, and the exposed adhesive surface of the adhesive layer was subjected to corona treatment (0.3 kV, 10 mm / min), and then the adhesive layer was bonded together to obtain a sheet (adhesive sheet) in which one side was the adhesive layer surface and the other side was the adhesive layer surface.

[0185] Example 2 An adhesive sheet was prepared in the same manner as in Example 1, except that an acrylic oligomer (product name "Dianal BR-105", manufactured by Mitsubishi Chemical Corporation) was used as the second oligomer in the preparation of the adhesive composition.

[0186] Example 3 (Preparation of Acrylic Polymer G Solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture (solid content 40% by mass) containing 90 parts by mass of butyl acrylate, 3 parts by mass of acrylic acid, 7 parts by mass of acryloyl morpholine, 0.2 parts by mass of thermal polymerization initiator (azobisisobutyronitrile), and solvent (ethyl acetate) was added. Then, nitrogen gas was introduced, and the mixture was purged with nitrogen while stirring for about 20 minutes. The reaction was then carried out at 60°C for 3 hours. Next, the reaction solution was heated at 72°C for 3 hours to obtain acrylic polymer G solution.

[0187] (Preparation of adhesive composition) As the first oligomer, 50 parts by mass of 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol (trade name "Celoxide EHPE3150", manufactured by Daicel Corporation) and 50 parts by mass of ethyl acetate were mixed and stirred to prepare the first oligomer solution. Subsequently, as the second oligomer, 40 parts by mass of acrylic oligomer (trade name "Hi-pearl M4006", manufactured by Negami Kogyo Co., Ltd.) and 680 parts by mass of ethyl acetate were mixed and stirred to prepare the second oligomer solution. Subsequently, as the polymer, the above acrylic polymer G solution and 735 parts by mass of ethyl acetate were mixed and stirred to prepare the polymer solution. The two oligomer solutions and the polymer solution were mixed and stirred so that the first oligomer was 40 parts by mass, the second oligomer was 40 parts by mass, and the polymer was 20 parts by mass to obtain an adhesive composition.

[0188] (Preparation of adhesive sheets) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with release treatment on one side, thickness 38 μm) to form an adhesive composition layer, and dried at 80°C for 1 minute to form an adhesive layer with a thickness of 2 μm. Next, one side of the release liner of the adhesive layer obtained above was peeled off, and the exposed adhesive surface of the adhesive layer was subjected to corona treatment (0.3 kV, 10 mm / min), and then the adhesive layer was bonded together to obtain a sheet (adhesive sheet) in which one side was the adhesive layer surface and the other side was the adhesive layer surface.

[0189] Comparative Example 1 (Preparation of acrylic prepolymer B solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 40 parts by mass of lauryl acrylate (LA), 57 parts by mass of 2-ethylhexyl acrylate (2EHA), 3 parts by mass of 4-hydroxybutyl acrylate (4HBA), 0.25 parts by mass of photoradical generator (trade name "Omnirad 819", manufactured by IGM Resins Italia Srl), and 0.05 parts by mass of photoradical generator (trade name "Omnirad 184", manufactured by IGM Resins Italia Srl) were added. Then, nitrogen gas was introduced, and nitrogen purging was performed for approximately 20 minutes while stirring. After that, 5 mW / cm² was added. 2 Polymerization was carried out by irradiating with ultraviolet light, and the reaction rate was adjusted to 5-15% to obtain acrylic prepolymer solution B.

[0190] (Preparation of adhesive composition) To the above acrylic prepolymer B solution, 0.1 parts by mass of dipentaerythritol penta and hexaacrylate (DPHA) as crosslinking agents, and 0.3 parts by mass of 3-glycidyloxypropyltrimethoxysilane as a silane coupling agent were added and stirred to prepare an adhesive composition.

[0191] (Formation of the adhesive layer) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38," manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with a release treatment on one side, 38 μm thick) to form an adhesive composition layer, and the release-treated surface of a release liner (product name "MRF38," manufactured by Mitsubishi Chemical Corporation) was bonded onto this adhesive composition layer. Next, a black light was used to measure 2.5 mW / cm². 2 The ultraviolet light at an illuminance of 2400 mJ / cm² is measured by the cumulative light intensity of 2400 mJ / cm². 2 Polymerization was carried out by irradiation until the desired result was reached, forming an adhesive layer with a thickness of 40 μm, and obtaining the adhesive sheet of Comparative Example 1 (optically transparent adhesive sheet).

[0192] Comparative Example 2 A comparative adhesive sheet was prepared in the same manner as in Example 1, except that an adhesive layer was not formed.

[0193] Example 4 (Preparation of adhesive composition) To the acrylic prepolymer A solution prepared in Example 1, 10 parts by mass of lauryl acrylate (LA) as an acrylic monomer, 0.1 parts by mass of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 0.5 parts by mass of acrylic oligomer C, and 0.3 parts by mass of 3-glycidyloxypropyltrimethoxysilane as a silane coupling agent were added and stirred to prepare an adhesive composition.

[0194] (Formation of the adhesive layer) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38," manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with a release treatment on one side, 38 μm thick) to form an adhesive composition layer, and the release-treated surface of a release liner (product name "MRF38," manufactured by Mitsubishi Chemical Corporation) was bonded onto this adhesive composition layer. Next, a black light was used to measure 2.5 mW / cm². 2 The ultraviolet light at an illuminance of 2400 mJ / cm² is measured by the cumulative light intensity of 2400 mJ / cm². 2 Polymerization was carried out by irradiation until the desired result was obtained, yielding an adhesive layer (optically transparent adhesive sheet) with a thickness of 40 μm.

[0195] (Preparation of adhesive composition) As the first oligomer, 50 parts by mass of 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol (trade name "Celoxide EHPE3150", manufactured by Daicel Corporation) and 50 parts by mass of ethyl acetate were mixed and stirred to prepare the first oligomer solution. Subsequently, as the second oligomer, 850 parts by mass of acrylic oligomer (trade name "Hi-pearl M4006", manufactured by Negami Kogyo Co., Ltd.) and 50 parts by mass of ethyl acetate were mixed and stirred to prepare the second oligomer solution. The first oligomer solution and the second oligomer solution were mixed in equal amounts and stirred to obtain an adhesive composition.

[0196] (Preparation of adhesive sheets) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with release treatment on one side, thickness 38 μm) to form an adhesive composition layer, and dried at 80°C for 1 minute to form an adhesive layer with a thickness of 2 μm. Next, one side of the release liner of the adhesive layer obtained above was peeled off, and the exposed adhesive surface of the adhesive layer was subjected to corona treatment (0.3 kV, 10 mm / min), and then the adhesive layer was bonded together to obtain a sheet (adhesive sheet) in which one side was the adhesive layer surface and the other side was the adhesive layer surface.

[0197] Example 5 An adhesive sheet was prepared in the same manner as in Example 4, except that an acrylic oligomer (product name "Hi-pearl M6400", manufactured by Negami Kogyo Co., Ltd.) was used as the second oligomer in the preparation of the adhesive composition.

[0198] Example 6 An adhesive sheet was prepared in the same manner as in Example 4, except that an acrylic oligomer (product name "Hi-pearl M4003", manufactured by Negami Kogyo Co., Ltd.) was used as the second oligomer in the preparation of the adhesive composition.

[0199] Example 7 (Preparation of adhesive composition) As an oligomer, 30 parts by mass of acrylic oligomer (trade name "Hi-pearl M4006", manufactured by Negami Kogyo Co., Ltd.) and 60 parts by mass of ethyl acetate were mixed and stirred to prepare an oligomer solution. Subsequently, as a polymer, the above acrylic polymer G solution prepared in Example 3 and 735 parts by mass of ethyl acetate were mixed and stirred to prepare a polymer solution. The oligomer solution and the polymer solution were mixed and stirred so that the oligomer was 30 parts by mass and the polymer was 70 parts by mass to obtain an adhesive composition.

[0200] Comparative Example 3 A comparative adhesive sheet was prepared in the same manner as in Example 4, except that an adhesive layer was not formed.

[0201] Example 8 (Preparation of adhesive composition) To the acrylic prepolymer A solution prepared in Example 1, 10 parts by mass of lauryl acrylate (LA) as an acrylic monomer, 125 parts by mass of 2-ethylhexyl EO modified acrylate (trade name "M-120", manufactured by Toagosei Co., Ltd.), 0.1 parts by mass of 1,9-nonanediol diacrylate (NDDA) as a crosslinking agent, 0.2 parts by mass of a hexamethylene diisocyanate derivative (trade name "Duranate D101", manufactured by Asahi Kasei Corporation), 0.5 parts by mass of acrylic oligomer C, and 0.3 parts by mass of 3-glycidyloxypropyltrimethoxysilane as a silane coupling agent were added and stirred to prepare an adhesive composition.

[0202] (Formation of the adhesive layer) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38," manufactured by Mitsubishi Chemical Corporation, a polyethylene terephthalate film with a release treatment on one side, 38 μm thick) to form an adhesive composition layer, and the release-treated surface of a release liner (product name "MRF38," manufactured by Mitsubishi Chemical Corporation) was bonded onto this adhesive composition layer. Next, a black light was used to measure 2.5 mW / cm². 2 The ultraviolet light at an illuminance of 2400 mJ / cm² is measured by the cumulative light intensity of 2400 mJ / cm². 2 Polymerization was carried out by irradiation until the desired result was obtained, yielding an adhesive layer (optically transparent adhesive sheet) with a thickness of 40 μm.

[0203] (Preparation of Acrylic Polymer D Solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 95 parts by mass of butyl acrylate, 5 parts by mass of acrylic acid, 0.2 parts by mass of a thermal polymerization initiator (azobisisobutyronitrile), and solvent (ethyl acetate) (solid content concentration 30% by mass) was added. Then, nitrogen gas was introduced, and the mixture was purged with nitrogen while stirring for about 20 minutes. The reaction was then carried out at 60°C for 3 hours. Next, the reaction solution was heated at 72°C for 3 hours to obtain acrylic polymer D solution.

[0204] (Preparation of adhesive composition) As an oligomer, 30 parts by mass of acrylic oligomer C prepared in Example 1 and 150 parts by mass of ethyl acetate were mixed and stirred to prepare an oligomer solution. Subsequently, as a polymer, the above acrylic polymer D solution and 620 parts by mass of ethyl acetate were mixed and stirred to prepare a polymer solution. The oligomer solution and the polymer solution were mixed and stirred so that the oligomer was 30 parts by mass and the polymer was 70 parts by mass to obtain an adhesive composition.

[0205] (Preparation of adhesive sheets) The above adhesive composition was applied to the release-treated surface of a release liner (product name "MRE38", manufactured by Mitsubishi Chemical Corporation, polyethylene terephthalate film with release treatment on one side, thickness 38 μm) to form an adhesive composition layer, and dried at 80°C for 1 minute to form an adhesive layer with a thickness of 2 μm. Next, one side of the release liner of the adhesive layer obtained above was peeled off, and the exposed adhesive surface of the adhesive layer was subjected to corona treatment (0.3 kV, 10 mm / min), and then the adhesive layer was bonded together to obtain a sheet (adhesive sheet) in which one side was the adhesive layer surface and the other side was the adhesive layer surface.

[0206] Example 9 (Preparation of Acrylic Polymer E Solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 90 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 0.2 parts by mass of a thermal polymerization initiator (azobisisobutyronitrile), and solvent (ethyl acetate) (solid content concentration 30% by mass) was added. Then, nitrogen gas was introduced, and the mixture was purged with nitrogen while stirring for about 20 minutes. After that, the reaction was carried out at 60°C for 3 hours. Next, the reaction solution was heated at 72°C for 3 hours to obtain acrylic polymer solution E.

[0207] (Preparation of adhesive sheets) An adhesive sheet was prepared in the same manner as in Example 8, except that acrylic polymer solution E was used instead of acrylic polymer solution D in the preparation of the adhesive composition.

[0208] Example 10 (Preparation of acrylic polymer F solution) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 95 parts by mass of butyl acrylate, 5 parts by mass of acryloyl morpholine, 0.2 parts by mass of a thermal polymerization initiator (azobisisobutyronitrile), and solvent (ethyl acetate) (solid content concentration 30% by mass) was added. Then, nitrogen gas was introduced, and the mixture was purged with nitrogen while stirring for about 20 minutes. After that, the reaction was carried out at 60°C for 3 hours. Next, the reaction solution was heated at 72°C for 3 hours to obtain acrylic polymer F solution.

[0209] (Preparation of adhesive sheets) An adhesive sheet was prepared in the same manner as in Example 8, except that acrylic polymer F solution was used instead of acrylic polymer D solution in the preparation of the adhesive composition.

[0210] Comparative Example 4 A comparative adhesive sheet was prepared in the same manner as in Example 8, except that an adhesive layer was not formed.

[0211] The components shown in Tables 1-3 are as follows: <Additives> M-120: 2-Ethylhexyl EO-modified acrylate, trade name "Arronix M-120", manufactured by Toagosei Co., Ltd., acrylic monomer. DPHA: Dipentaerythritol penta and hexaacrylate, crosslinking agent NDDA: 1,9-nonanediol diacrylate, crosslinking agent D-101: Product name "Duranate D-101", manufactured by Asahi Kasei Corporation, crosslinking agent <Polymer (A)> EHPE3150: Product name "Celoxide EHPE3150", manufactured by Daicel Corporation, curable epoxy resin (epoxy oligomer, heat transfer resin) BR-83: Product name "BR-83", manufactured by Mitsubishi Chemical Corporation, methacrylic resin (acrylic oligomer) BR-105: Product name "BR-105", manufactured by Mitsubishi Chemical Corporation, methacrylic resin (acrylic oligomer, heat transfer resin) Hi-pearl M4006: Product name "Hi-pearl M4006", manufactured by Negami Kogyo Co., Ltd., methacrylic resin (acrylic oligomer, heat transfer resin) Hi-pearl M6400: Product name "Hi-pearl M6400", manufactured by Negami Kogyo Co., Ltd., methacrylic resin (acrylic oligomer, heat transfer resin) <Polymer (B)> Hi-pearl M4003: Product name "Hi-pearl M4003", manufactured by Negami Kogyo Co., Ltd., made of methacrylic resin (acrylic polymer).

[0212] [evaluation] The following evaluations were performed on the adhesive layers, adhesive sheets, and adhesive sheets obtained in the examples and comparative examples. Furthermore, the following molecular weight measurements were performed on the acrylic polymers used or prepared in the examples and comparative examples. The results are shown in Tables 1-3.

[0213] (1) Total light transmittance The release liner was peeled off the adhesive layer surface of the adhesive sheet (or the adhesive layer surface of the adhesive sheet in the case of an adhesive sheet) and bonded to alkali-free glass (product name "Eagle XG", 40 mm long, 50 mm wide, 0.7 mm thick, manufactured by Corning). This was then subjected to heating and pressurizing treatment at 50°C, 0.5 MPa for 15 minutes to ensure adhesion. Next, the remaining release liner was peeled off to obtain a test specimen. The total light transmittance of the test specimen was measured from the alkali-free glass side using a haze meter (product name "HM-150", manufactured by Murakami Color Technology Laboratory Co., Ltd.).

[0214] (2) Glass transition temperature The adhesive or bonding layer to be measured was laminated to a thickness of 1.0 to 2.0 mm, and then punched out into an 8 mm diameter disc to be used as the measurement sample. During lamination, the adhesive or bonding layer was heated to 50°C as needed. The shear modulus was measured using a rheometer (product name "ARES-G2", manufactured by TA Instruments) in torsion mode, under the conditions of a measurement frequency of 1 Hz, a measurement temperature of -50 to 150°C, and a heating rate of 5°C / min. Furthermore, even below 150°C, the shear modulus was measured to be 10 3 If the temperature fell below Pa, the measurement was terminated at that point. The loss tangent tanδ of the adhesive layer and the tack layer were measured in the manner described above. The peak temperature of the loss tangent tanδ when temperature and loss tangent tanδ were plotted was defined as the glass transition temperature Tg. The glass transition temperature of the tack layer was defined as Tg1. The glass transition temperature of the adhesive layer was defined as Tg2. If the adhesive layer had two glass transition temperatures, the lower temperature was defined as Tg2 and the higher temperature as Tg3.

[0215] (3-1) 180° peel strength (room temperature) Under a measurement environment of 23°C and 50% RH, a corona-treated 25 μm thick PET film was bonded to the exposed adhesive surface of the adhesive sheet prepared in the example, by peeling off the release liner (adhesive layer side) opposite the adhesive layer. For the adhesive sheet prepared in the comparative example, a corona-treated PET film was bonded to the exposed adhesive surface. This was then subjected to heating and pressurizing treatment at 50°C, 0.5 MPa for 15 minutes to ensure adhesion. Next, the backed adhesive sheet or adhesive sheet was cut to a size of 10 mm wide and 100 mm long to serve as test specimens. For the test specimens in the example, the release liner on the adhesive layer side was peeled off and bonded to the side opposite the tin side of an alkali glass substrate (100 mm long, 100 mm wide, 0.1 mm thick), and pressed down by passing a 2 kg roller back and forth once. In addition, for the comparative example, the release liner on the adhesive layer of the test specimen was peeled off and bonded to the side of the alkali glass (100 mm long, 100 mm wide, 0.1 mm thick) opposite to the tin side, and pressed with a 2 kg roller for one back-and-forth motion. This was then subjected to heating and pressurizing treatment at 50°C, 0.5 MPa, and 15 minutes to ensure adhesion. After being left in the same environment for 24 hours, the 180° peel force (adhesion force) [N / 10 mm] was measured using a universal tensile and compression tester in accordance with JIS Z 0237:2000, at a tensile speed of 300 mm / min and a peel angle of 180 degrees. A universal tensile and compression tester (device name "AGX-V2", manufactured by Shimadzu Corporation) was used.

[0216] (3-2) 180° peeling force (humidified heat environment) The measurement was performed under the same conditions as the 180° peel strength test (room temperature), except that the environment using the universal tensile and compression testing machine was changed from 23°C and 50%RH to 60°C and 90%RH.

[0217] (4) Molecular weight Mw The molecular weight was determined by gel permeation chromatography (GPC) and expressed in polystyrene equivalent. A GPC analyzer (Waters) was used for the measurement. The sample solution was prepared as follows: First, an acrylic oligomer or acrylic polymer to be measured was used as the sample, and a tetrahydrofuran (THF) solution with a sample concentration of 0.10% by mass was prepared. This THF solution was then left to stand for 20 hours. Next, the THF solution was filtered through a membrane filter with an average pore size of 0.45 μm, and the filtrate was obtained as the sample solution for molecular weight measurement. [GPC measurement conditions] Column: TSKgel SuperHZM x 2 (manufactured by Tosoh) Column temperature: 40℃ Eluent: THF solution Flow rate: 0.2mL / min Sample injection volume: 30 μL Standard sample: Polystyrene (manufactured by Agilent) Detector: Differential refractometer (RI)

[0218] (5) Gel fraction The release liner was peeled off from the adhesive layer prepared in the examples and comparative examples, and approximately 0.2 g was scraped off to obtain a small piece. Next, the obtained small piece was wrapped in a stretched porous polytetrafluoroethylene membrane (product name "NTF1122", average pore size 0.2 μm, manufactured by Nitto Denko Corporation) and tied with kite string to obtain a test specimen. Next, the weight A of the obtained test specimen was measured. Weight A is the sum of the weight of the adhesive layer piece, the stretched porous membrane, and the kite string. The total weight B of the stretched porous membrane and kite string used was measured in advance. Next, the test specimen was immersed in a 50 mL container filled with ethyl acetate and left to stand at 23°C for one week. After standing, the test specimen was removed from the container and dried in a dryer set to 130°C for two hours, and then the weight C of the test specimen was measured. Then, from the measured weights A, B, and C, the gel fraction of the adhesive layer was calculated using the formula: Gel fraction (mass [%]) = (CB) / (AB) × 100 (%).

[0219] (6) Stress retention rate The adhesive layers prepared in the examples and comparative examples were cut to a size of 40 mm in width and 30 mm in length. The release liners on both sides of the adhesive layer were peeled off, and the adhesive layer was rolled into a cylindrical shape with the longer side being the length direction. The upper and lower bottoms of the cylinder were then gripped with gripping jigs on a universal tensile and compression testing machine so that the distance between the gripping jigs was 10 mm, and the cylinder was set in place. Subsequently, the cylindrical adhesive layer was stretched at a tensile speed of 50 mm / min until the distance between the gripping jigs became 20 mm. The stress at the moment the distance between the gripping jigs reached 20 mm (0 seconds) was defined as σ0, and the stress after 60 seconds was defined as σ 60 and stress σ after 600 seconds 600 The following was measured. The stress retention rate was calculated using the formula below. Stress retention rate after 60 seconds [%] = σ 60 / σ0×100 Stress retention rate after 600 seconds [%] = σ 600 / σ0×100

[0220] (7) Impact marks In the example, a 25 μm thick corona-treated PET film was laminated to the exposed adhesive surface of the adhesive sheet prepared in the example, by peeling off the release liner (adhesive layer side) opposite the adhesive layer. Similarly, a 25 μm thick corona-treated PET film was laminated to the exposed adhesive surface of the adhesive sheet prepared in the comparative example. This was then subjected to heating and pressurizing treatment at 50°C, 0.5 MPa, and 15 minutes to ensure adhesion. Next, the laminated adhesive sheet or adhesive sheet was cut to a size of 30 mm wide and 40 mm long to serve as a test specimen. For the example, the release liner on the adhesive layer side of the test specimen was peeled off and laminated to alkali-free glass (product name "Eagle XG", 40 mm long, 50 mm wide, 0.7 mm thick, manufactured by Corning) as the substrate, and pressed down by passing a 2 kg roller back and forth once. In addition, for the comparative example, the release liner on the adhesive layer surface of the test specimen was peeled off and bonded to alkali-free glass (product name "Eagle XG", 40 mm length, 50 mm width, 0.7 mm thickness, manufactured by Corning) as the substrate, and pressed down by rolling a 2 kg roller back and forth once. This was left in the same environment for 24 hours to be used as the measurement sample. From the PET film side of the measurement sample, a jig for indentation testing (radius of curvature of the tip R: 2 mm) was pressed using a universal tensile and compression tester under the following pressing conditions. After pressing for the specified time, the load was removed, and the specimen was observed using an optical microscope (product name "VHX-7000", manufactured by Keyence Corporation) in reflection mode, at a magnification of 20x, and at a 30° angle to the test specimen to check for the presence or absence of indentation marks. From the observation, "◎" was recorded if no indentation marks were observed, "○" if a slight indentation mark was observed, and "×" if a clear indentation mark was observed. A tensile and compression testing machine (device name "AGX-V2", manufactured by Shimadzu Corporation) was used as a universal tensile and compression testing machine. <Imposed conditions> Speed: 0.9mm / min Test force: 0.05 kgf Pressing time: 10 seconds

[0221] [Table 1]

[0222] As shown in Table 1, the adhesive sheets of Examples 1-3 were confirmed to have high 180° peel strength against alkali-free glass, and were evaluated as having high adhesion to alkali-free glass and being resistant to peeling. Furthermore, they were evaluated as being resistant to dents even when subjected to impact, and resistant to creases even when subjected to bending. On the other hand, the adhesive sheet of Comparative Example 2, which did not have an adhesive layer, was resistant to dents, but had low 180° peel strength and was evaluated as having poor adhesion to alkali-free glass. In addition, the adhesive sheet of Comparative Example 1 was evaluated as being easily dented.

[0223] [Table 2]

[0224] As shown in Table 2, the adhesive sheets of Examples 4-7 were confirmed to have high 180° peel strength against alkali-free glass, and were evaluated as having high adhesion to alkali-free glass and being resistant to peeling. Furthermore, they were evaluated as being resistant to dents even when subjected to impact, and resistant to creases even when subjected to repeated bending. On the other hand, the adhesive sheet of Comparative Example 3, which did not have an adhesive layer, was evaluated as having low 180° peel strength and poor adhesion to alkali-free glass.

[0225] [Table 3]

[0226] As shown in Table 3, the adhesive sheets of Examples 8-10 were confirmed to have high 180° peel strength against alkali-free glass, and were evaluated as having high adhesion to alkali-free glass and being resistant to peeling. Furthermore, they were evaluated as being resistant to dents even when subjected to impact, and resistant to creases even when subjected to repeated bending. On the other hand, the adhesive sheet of Comparative Example 4, which did not have an adhesive layer, was evaluated as having low 180° peel strength and poor adhesion to alkali-free glass.

[0227] Hereinafter, variations of the invention according to the present disclosure will be described. [Appendix 1] A laminate comprising an adhesive layer and an adhesive layer laminated on at least one surface of the adhesive layer, The total light transmittance of the laminate is 85% or more, A laminate in which the gel fraction of the adhesive layer is 85 to 99.9% by mass. [Appendix 2] The laminate according to Appendix 1, wherein the adhesive layer has a stress retention rate of 70 to 99.9% 60 seconds after 100% elongation. [Appendix 3] The laminate according to Appendix 1 or 2, wherein the adhesive layer and the adhesive layer each contain an acrylic polymer. [Appendix 4] The laminate according to any one of Appendices 1 to 3, wherein the thickness of the adhesive layer is 200 nm to 10 μm. [Appendix 5] The laminate according to any one of Appendices 1 to 4, wherein the ratio of the thickness of the adhesive layer to the thickness of the adhesive layer [thickness of the adhesive layer: thickness of the adhesive layer] is 1:0.0001 to 1:1.

Explanation of reference numerals

[0228] 1 Laminate 2, 21, 22 Adhesive layer 3, 31, 32 Adhesive layer 5 Base material 6 Decorative layer

Claims

1. A laminate comprising an adhesive layer and an adhesive layer laminated on at least one surface of the adhesive layer, The total light transmittance of the laminate is 85% or more. A laminate in which the gel fraction of the adhesive layer is 85 to 99.9% by mass.

2. The laminate according to claim 1, wherein the adhesive layer has a stress retention rate of 70 to 99.9% after 60 seconds when fully extended.

3. The laminate according to claim 1 or 2, wherein the adhesive layer and the bonding layer each contain an acrylic polymer.

4. The laminate according to claim 1 or 2, wherein the thickness of the adhesive layer is 200 nm to 10 μm.

5. The laminate according to claim 1 or 2, wherein the ratio of the thickness of the adhesive layer to the thickness of the bonding layer [thickness of adhesive layer:thickness of bonding layer] is 1:0.0001 to 1:1.

Images