Adhesive sheet

Abstract

To provide an adhesive sheet that minimizes the residue of the application liquid between the adhesive sheet and the adherend (good water drainage). [Solution] The adhesive sheet comprises a substrate containing a first resin film and a first adhesive layer formed on the first surface of the substrate and attached to an adherend, wherein the arithmetic mean height Sa of the adhesive surface of the first adhesive layer that is attached to the adherend is 0.020 μm or less.

Description

[Technical Field]

[0001] The present invention relates to an adhesive sheet having an adhesive layer for attachment to a substrate. [Background technology]

[0002] Adhesive sheets are products that are attached to a substrate for purposes such as protection, fixing, and bonding. An example of an adhesive sheet is one which comprises an adhesive layer for attachment to a substrate on a base material having a predetermined rigidity.

[0003] Specific applications of adhesive sheets include window films that are applied to windows of moving objects such as automobiles and buildings to provide impact resistance, shatterproof functionality, and UV and infrared shielding capabilities.

[0004] Patent Document 1 discloses a window film having a film layer and a pressure-sensitive adhesive layer. Furthermore, Patent Document 1 discloses that, according to this window film, when applied using a wet application method, it can be applied to window glass with sufficient adhesive strength with a short curing time. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-012082 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, when such window films are applied to a substrate using the wet application method, there is a problem in that the application liquid present between the window film and the substrate does not easily evaporate even after the curing period. If the application liquid remains between the window film and the substrate, areas where the application liquid has evaporated and areas where it remains will mix, resulting in unevenness and a loss of aesthetic appeal.

[0007] The present invention has been made in view of such a situation, and an object thereof is to provide an adhesive sheet in which a working liquid hardly remains (has good drainage property) between the adhesive sheet and the adherend.

Means for Solving the Problems

[0008] Aspects of the present invention are as follows.

[0009] [1] It has a base material including a first resin film, and a first adhesive layer formed on the first surface of the base material and attached to the adherend. The adhesive sheet is such that, in the first adhesive layer, the arithmetic mean height Sa of the adhesion surface attached to the adherend is 0.020 μm or less.

[0010] [2] The adhesive sheet according to [1], wherein a functional layer is formed on the second surface of the base material facing the first surface.

[0011] [3] The adhesive sheet according to [2], wherein the functional layer is a hard coat layer.

[0012] [4] The adhesive sheet according to any one of [1] to [3], wherein the base material further includes a metal layer.

[0013] [5] The adhesive sheet according to any one of [1] to [4], wherein the first surface of the base material is the surface of the first resin film.

[0014] [6] The adhesive sheet according to any one of [1] to [5], wherein the visible light transmittance of the adhesive sheet is 70% or more.

[0015] [7] The adhesive sheet according to any one of [1] to [6], wherein the visible light reflectance of the adhesive sheet is 20% or less.

[0016] [8] The adhesive sheet according to any one of [1] to [7], wherein the shielding coefficient of the adhesive sheet is 0.72 or less.

[0017] [9] CIE1976L of the adhesive sheet* a * b * The lightness L defined by the color system * is the adhesive sheet according to any one of [1] to [8] and is 80 or more.

[0018]

[10] The adhesive sheet is an adhesive sheet according to any one of [1] to [9] and is a window film. [Advantages of the Invention]

[0019] According to the present invention, it is possible to provide an adhesive sheet in which a construction liquid hardly remains (has good water drainage property) between the adhesive sheet and the adherend. [Brief Description of the Drawings]

[0020] [Figure 1A] FIG. 1A is a schematic cross-sectional view showing an example of the configuration of the adhesive sheet according to the present embodiment. [Figure 1B] FIG. 1B is a schematic cross-sectional view showing an example of the configuration of the adhesive sheet according to the present embodiment. [Figure 2A] FIG. 2A is a schematic cross-sectional view showing an example of another configuration of the adhesive sheet according to the present embodiment. [Figure 2B] FIG. 2B is a schematic cross-sectional view showing an example of another configuration of the adhesive sheet according to the present embodiment. [Figure 2C] FIG. 2C is a schematic cross-sectional view showing an example of another configuration of the adhesive sheet according to the present embodiment. [Modes for Carrying Out the Invention]

[0021] Hereinafter, the present invention will be described in detail based on specific embodiments.

[0022] (1. Adhesive Sheet) As shown in Figure 1A, the adhesive sheet 1 according to this embodiment comprises a base material 10 and a first adhesive layer 21. The first adhesive layer 21 is formed on one main surface (first surface 10a) of the base material. The adhesive sheet may also have other components, as long as the effects of the present invention are obtained. That is, the adhesive sheet may have layers other than the base material and the first adhesive layer, which perform predetermined functions (functional layers). Furthermore, a release sheet may be placed on the main surface 21a of the adhesive layer 21 to protect the adhesive layer 11 until it is attached to an object.

[0023] When using the adhesive sheet 1, the main surface 21a of the first adhesive layer 21 is attached to the object for protection, fixing, and bonding. In other words, the main surface 21a of the first adhesive layer is the adhesive surface.

[0024] The adhesive sheet according to this embodiment can be used depending on the application. For example, the adhesive sheet can be used as a window film, screen protection film, surface protection sheet, shatterproof film, label, process sheet, etc. In this embodiment, the adhesive sheet can be suitably used as a window film. Below, a window film will be described as an example of an adhesive sheet.

[0025] If the adhesive sheet is a window film, the window film is applied to the window, which is the adherend on the adhesive surface 21a of the first adhesive layer 21. The window film is usually applied to the window using a wet application method with an application liquid. The application liquid is present at the interface between the window and the window film and helps to properly adhere the window film to the window. After wet application, the application liquid is removed by extrusion, drying, etc., and the window and window film are bonded together in direct contact.

[0026] After application, the application liquid needs to be removed from the interface as quickly as possible. However, even with a longer curing period, the application liquid may not be completely removed and may remain at the interface. When the application liquid remains at the interface, areas where the liquid has been removed and areas where it remains become mixed, resulting in unevenness and a loss of aesthetic appeal.

[0027] In response to this problem, the inventors have found that residual application liquid is trapped in voids scattered at the interface between the window and the window film, making it difficult for a discharge route to the outside to be formed.

[0028] Therefore, in this embodiment, the physical properties of the first adhesive layer that comes into contact with the adherend (for example, a window) are controlled as follows to suppress the formation of voids at the interface that can easily trap the application liquid. The components of the adhesive sheet will be described in detail below.

[0029] (2. First adhesive layer) The first adhesive layer is formed by a layer of adhesive, which will be described later. The first adhesive layer is used to ensure that the adhesive sheet adheres tightly to the substrate when it is attached, allowing the adhesive sheet to perform its predetermined function. When the adhesive sheet is a window film, the substrate is a window of an automobile, building, etc.

[0030] The window to which the first adhesive layer is attached may be made of glass material or of a glass substitute material such as plastic. In this embodiment, it is preferable that the window be made of glass material. Furthermore, the surface of the window to which the first adhesive layer is attached may be the surface of the window on the side to which sunlight or other light rays enter, or the surface of the window on the opposite side. That is, in the case of an automobile, it may be the surface of the window on the outside of the vehicle or the surface of the window on the inside of the vehicle, and in the case of a building, it may be the surface of the window on the outside or the surface of the window on the inside.

[0031] The first adhesive layer may consist of one layer (single layer) or of two or more layers. If the first adhesive layer has multiple layers, their compositions may differ.

[0032] The thickness of the first adhesive layer 21 is not particularly limited as long as it exhibits a predetermined adhesive strength, and can be set appropriately according to the intended use, but it may be 8 to 50 μm, 15 to 40 μm, or 20 to 30 μm. This makes it easier to exhibit suitable adhesiveness and optical properties.

[0033] (2.1. Surface properties of the first adhesive layer) In this embodiment, the surface properties of the adhesive surface (adhesive surface 21a of the first adhesive layer 21 in Figure 1A) that is attached to the adherend are controlled to a predetermined shape in the first adhesive layer.

[0034] Specifically, if Sa is the arithmetic mean height of the surface to which the first adhesive layer is applied, then Sa is 0.020 μm or less. The arithmetic mean height of the surface is one of the surface roughness parameters defined in ISO 25178, and is the average of the absolute values ​​of the peak height and valley depth on the measured surface. Sa represents the average surface roughness over the entire measured surface, with the influence of local irregularities suppressed.

[0035] Because Sa is within the above range, the surface roughness of the application surface of the first adhesive layer is smooth overall. As a result, the formation of voids at the interface between the adherend and the first adhesive layer is suppressed, and the removal of the application liquid proceeds smoothly (water drainage is improved).

[0036] Sa may be 0.020 μm or less, 0.015 μm or less, or 0.010 μm or less. On the other hand, while the lower limit of Sa is preferably 0 μm, from a manufacturing standpoint, the lower limit of Sa may be 0.001 μm.

[0037] Sa can be controlled by adjusting the smoothness of the first surface of the substrate (described later), the method of applying the composition for forming the first adhesive layer (adhesive composition), the composition of the coating liquid containing the adhesive composition, and so on.

[0038] The surface properties of the first adhesive layer can be measured as follows. When the adhesive surface is represented as an XY plane using mutually orthogonal X and Y axes, the surface properties of the adhesive surface can be represented as a displacement in the Z-axis direction perpendicular to the XY plane. That is, the surface roughness of the adhesive surface is represented as a three-dimensional (X,Y,Z) shape.

[0039] Therefore, the arithmetic mean height Sa, which is a surface roughness parameter, is calculated from the measurement results of the displacement in the Z-axis direction within the measurement area. The size of the measurement area can be, for example, a rectangular area of ​​100-500 μm × 100-500 μm.

[0040] In this embodiment, it is preferable to use a non-contact white light interference microscope for measuring surface properties. In a white light interference microscope, the optical path of light emitted from a white light source is divided into two; one is directed to a reference mirror, and the other to the sample surface, and the light reflected from both is imaged by a camera. In the obtained image, the three-dimensional shape of the sample surface is obtained by converting the information of interference fringes caused by the optical path difference due to the unevenness of the sample surface into height information. The magnification of the white light interference microscope can be appropriately set according to the value of Sa.

[0041] The measurement results of the surface properties of a measurement surface, obtained as 3D shape data, mainly include factors attributable to the shape of the measurement surface, factors attributable to the surface roughness of the measurement surface, and factors attributable to the waviness of the measurement surface. Therefore, the measurement results of the surface properties of a measurement surface are a contour curve obtained by combining these factors. These factors are distinguished by the length of their period (wavelength): factors attributable to surface roughness have short periods (short wavelengths), factors attributable to shape have long periods (long wavelengths), and factors attributable to waviness have periods intermediate between these two.

[0042] From the obtained measurement results, the factors due to shape and the factors due to waviness are removed to obtain a surface roughness curve composed of factors due to surface roughness. Specifically, based on the obtained surface roughness curve, Sa is calculated in accordance with the method specified in ISO 25178. That is, it can be measured using the same method as specified in ISO 25178, but it may also be measured under conditions different from those described in ISO 25178.

[0043] The surface roughness curve can be obtained from the measurement results by known filtering, planarization, etc. For example, analysis software included with a white light interference microscope or commercially available analysis software can be used.

[0044] (2.2. Composition of the adhesive) Examples of adhesive compositions for the first adhesive layer include acrylic adhesives, polyester adhesives, polyurethane adhesives, rubber adhesives, and silicone adhesives. The adhesive may be in emulsion, solvent, or solvent-free form. Furthermore, the adhesive may or may not have a cross-linked structure.

[0045] In this embodiment, from the viewpoint of the adhesive properties, optical properties, and ease of realizing the physical properties described later for the adhesive sheet, an acrylic adhesive is preferred, and an acrylic adhesive having a crosslinked structure is more preferred.

[0046] Specifically, the adhesive is preferably obtained from an adhesive composition containing a (meth)acrylic acid polymer (A) (hereinafter sometimes referred to as "adhesive composition P"). Furthermore, the adhesive is preferably obtained by crosslinking an adhesive composition containing a (meth)acrylic acid polymer (A) and a crosslinking agent (B), that is, an adhesive containing a crosslinked structure of a (meth)acrylic acid polymer (A) and a crosslinking agent (B). Such an adhesive is likely to satisfy the above-mentioned viewpoint. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Also, the concept of "polymer" is included in the concept of "polymer".

[0047] (2.2.1. (Meth)acrylate ester polymer (A)) The (meth)acrylic acid ester polymer (A) preferably contains units derived from monomers, including units derived from alkyl (meth)acrylic acid esters and units derived from monomers having reactive functional groups in the molecule (reactive functional group-containing monomers).

[0048] The (meth)acrylic acid ester copolymer (A) contains units derived from (meth)acrylic acid alkyl ester, thereby enabling the adhesive to exhibit desirable tackiness. As the (meth)acrylic acid alkyl ester, an alkyl ester with 1 to 20 carbon atoms in the alkyl group is preferred. The alkyl group may be linear or branched, but for convenience, those with a cyclic structure are excluded to distinguish them from the alicyclic structure-containing monomers described later.

[0049] Examples of alkyl (meth)acrylate esters having 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0050] Among these, (meth)acrylic acid esters having 1 to 8 carbon atoms in the alkyl group are preferred. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred, and methyl acrylate, methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, and 2-ethylhexyl acrylate are particularly preferred.

[0051] The (meth)acrylic acid ester polymer preferably contains 30 to 50% by mass of units derived from alkyl (meth)acrylic acid esters having 1 to 20 carbon atoms in the alkyl group, as units derived from monomers that constitute the polymer. It may also contain 35 to 45% by mass, 37 to 43% by mass, or 40 to 42% by mass. By setting the content of units derived from alkyl (meth)acrylic acid esters within the above range, suitable tackiness can be imparted to the (meth)acrylic acid ester polymer. In addition, other monomer components can be introduced into the (meth)acrylic acid ester polymer in desired amounts.

[0052] The (meth)acrylic acid ester polymer (A) contains units derived from a monomer containing a reactive functional group. Through these reactive functional groups, the (meth)acrylic acid ester polymer reacts with the crosslinking agent (B), described later, forming a crosslinked structure (three-dimensional network structure) in the adhesive. As a result, an adhesive with the desired cohesive force is obtained. Note that the reactive functional group may be used solely to alter the properties of the adhesive, and it is not necessary for the reactive functional group to react with the crosslinking agent (B).

[0053] Preferred monomers containing reactive functional groups include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers). These reactive functional group-containing monomers may be used individually or in combination of two or more.

[0054] The (meth)acrylic acid ester polymer may contain 1 to 10% by mass or 3 to 8% by mass of units derived from monomers that constitute the polymer, as units derived from monomers that contain reactive functional groups.

[0055] In this embodiment, from the viewpoint of controlling the optical properties of the adhesive sheet, at least one selected from hydroxyl group-containing monomers and carboxyl group-containing monomers is preferred as the reactive functional group-containing monomer. By including at least one unit selected from the hydroxyl group-containing monomer and the carboxyl group-containing monomer in the (meth)acrylic acid ester polymer, the optical properties of the adhesive sheet become less susceptible to the effects of moisture even when the adhesive sheet is applied by the water application method.

[0056] Examples of hydroxyl group-containing monomers include hydroxyalkyl methacrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0057] Among these, hydroxyalkyl (meth)acrylate esters having a hydroxyalkyl group with 1 to 4 carbon atoms are preferred. Specifically, 2-hydroxyethyl (meth)acrylate is preferred. These may be used individually or in combination of two or more.

[0058] If the (meth)acrylic acid ester polymer contains units derived from hydroxyl group-containing monomers as units derived from monomers that constitute the polymer, the (meth)acrylic acid ester polymer may contain 0.01 to 0.1% by mass or 0.05 to 0.08% by mass of units derived from hydroxyl group-containing monomers in 100% by mass.

[0059] Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid and methacrylic acid are preferred from the viewpoint of readily copolymerizing with other monomers. These may be used alone or in combination of two or more.

[0060] If the (meth)acrylic acid ester polymer contains units derived from carboxyl group-containing monomers as units derived from monomers that constitute the polymer, the (meth)acrylic acid ester polymer may contain 1 to 10% by mass or 3 to 8% by mass of units derived from carboxyl group-containing monomers in 100% by mass.

[0061] In this embodiment, the (meth)acrylic acid ester polymer may optionally contain other monomers as monomer units constituting the polymer. As other monomers, monomers that do not contain reactive functional groups are preferred in order not to inhibit the effects of the reactive functional group-containing monomer described above. Examples of such monomers include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, vinyl acetate, and styrene. These may be used individually or in combination of two or more.

[0062] The polymerization mode of the (meth)acrylic acid ester polymer may be a random copolymer or a block copolymer.

[0063] The weight-average molecular weight (Mw) of the (meth)acrylic acid ester polymer is preferably 350,000 to 500,000, and more preferably 400,000 to 450,000. This makes it easier to obtain the desired adhesive strength. The weight-average molecular weight used herein is the value on a standard polystyrene basis, measured by gel permeation chromatography (GPC).

[0064] In adhesive composition P, one (meth)acrylic acid ester polymer may be used alone, or two or more polymers may be used in combination.

[0065] (2.2.2. Crosslinking agent (B)) In this embodiment, the adhesive composition P preferably contains a crosslinking agent (B). The crosslinking agent (B) crosslinks the (meth)acrylic acid ester polymer (A) when the adhesive composition P containing the crosslinking agent is heated, etc., forming a crosslinked structure (three-dimensional network structure). As a result, the cohesive strength of the resulting adhesive is improved.

[0066] The crosslinking agent (B) can be any agent that reacts with the reactive groups of the (meth)acrylic acid ester polymer (A). Examples include isocyanate crosslinking agents, epoxy crosslinking agents, amine crosslinking agents, melamine crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, and ammonium salt crosslinking agents. Among these, isocyanate crosslinking agents are preferred from the viewpoint of reactivity with the functional groups of the (meth)acrylic acid ester polymer (A). Note that crosslinking agent (B) can be used alone or in combination of two or more types.

[0067] The isocyanate crosslinking agent includes at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. These isocyanate compounds also include their biuret form, isocyanurate form, and adduct form which is a reaction product with low molecular weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, hexamethylene diisocyanate is preferred.

[0068] The amount of crosslinking agent (B) in the adhesive composition P may be 0.2 to 1 part by mass or 0.3 to 0.5 parts by mass per 100 parts by mass of (meth)acrylic acid ester polymer (A). This makes it easier to obtain the desired cohesive force.

[0069] (2.2.3. UV absorber (C)) The adhesive composition P may also contain an ultraviolet absorber (C). This allows the adhesive sheet to be given an ultraviolet shielding function.

[0070] Examples of UV absorbers include compounds such as benzophenone, benzotriazole, benzoate, benzoxazinon, methine, triazine, phenyl salicylate, cyanoacrylate, and nickel complex salt compounds. A single UV absorber may be used, or two or more may be used in combination. Among UV absorbers (C), benzophenone, benzotriazole, and triazine compounds are preferred, and triazine compounds are more preferred.

[0071] Examples of triazine compounds include 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, 2,4,6-tris(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4,6-tris[2-hydroxy-4-(3-butoxy-2-hydroxypropyloxy)phenyl]-1,3,5-triazine, and 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0072] Examples of benzophenone compounds include 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-octoxybenzophenone.

[0073] Examples of benzotriazole compounds include 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-amyl-5'-isobutylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-isobutyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-isobutyl-5'-propylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and 2-[2'-hydroxy-5'-(1,1,3,3-tetramethyl)phenyl]benzotriazole.

[0074] The amount of ultraviolet absorber (C) in the adhesive composition P may be 1.0 to 3.0 parts by mass or 1.5 to 2.5 parts by mass per 100 parts by mass of (meth)acrylic acid ester polymer (A). As a result, the resulting adhesive layer exhibits excellent ultraviolet shielding properties.

[0075] (2.2.4. Other Additives) The adhesive composition P may optionally contain additives commonly used in acrylic adhesives. Examples of such additives include tackifiers, fillers, infrared absorbers, softeners, antioxidants, light stabilizers, crosslinking agents, modifiers, rust inhibitors, flame retardants, hydrolysis inhibitors, surface lubricants, corrosion inhibitors, heat stabilizers, lubricants, antistatic agents, colorants, polymerization inhibitors, catalysts, leveling agents, thickeners, dispersants, defoamers, and surfactants. Polymerization solvents and diluent solvents described later are not included in the additives constituting the adhesive composition P.

[0076] (3.Base material) The base material is a layered member responsible for the rigidity of the adhesive sheet and has the function of supporting the first adhesive layer. The base material has at least a first resin film.

[0077] Examples of the first resin film include polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyolefin resins such as polyethylene, polypropylene, poly-methylpentene-1, and polybutene-1; polyurethane resins; polycarbonate resins; polyvinyl chloride resins; polyethersulfone resins; polyethylene sulfide resins; styrene resins; acrylic resins; polyamide resins; and cellulose resins such as cellulose acetate, as well as films made of these materials or laminated films.

[0078] Among these, films made of polyolefin resins and polyester resins or laminated films thereof, which have excellent mechanical strength and cost-effectiveness, are preferred, films made of polyester resins or laminated films thereof are more preferred, and polyethylene terephthalate films or laminated films containing polyethylene terephthalate are even more preferred.

[0079] The substrate may consist only of the first resin film, but in this embodiment, it is preferable that the substrate has layers other than the first resin film. Examples of such layers include a metal layer. The metal layer is formed in a layered manner on the first resin film. This makes it easy to adjust the optical properties of the adhesive sheet (transmittance, reflectance, brightness, etc.), to impart design to the adhesive sheet, and to provide durability (rust prevention, etc.).

[0080] The metal layer may be a layer containing metal, or a layer consisting solely of metal. Examples of metals that may be contained in the metal layer include aluminum, gold, silver, copper, nickel, cobalt, chromium, tin, indium, alloys thereof, or oxides thereof. Methods for forming the metal layer include vacuum deposition and sputtering.

[0081] The metal layer is preferably composed of multiple layers in order to impart multiple functions to the adhesive sheet. Furthermore, the metal layer may have surface properties such as an uneven structure in order for the adhesive sheet to exhibit predetermined optical properties.

[0082] To improve the adhesion between the first resin film and the metal layer, the surface of the first resin film on which the metal layer is formed may be surface-treated by oxidation, embossing, or other methods. Examples of oxidation methods include corona discharge treatment, chromic acid treatment (wet), flame treatment, hot air treatment, and ozone / ultraviolet irradiation treatment. Examples of embossing methods include sandblasting and solvent treatment.

[0083] Therefore, the surface roughness of the metal layer and the surface roughness of the surface on which the metal layer is formed in the first resin film are often relatively large. Consequently, when the first adhesive layer is formed on the metal layer or on the surface on which the metal layer is formed in the substrate, the surface properties of the substrate may affect the surface roughness of the surface to which the first adhesive layer is applied, making it difficult to keep the Sa of the application surface within the above range. In this embodiment, the surface roughness of the surface on which the metal layer is formed in the first resin film is rougher than the surface roughness of the surface on which the metal layer is not formed in the first resin film. For example, the surface roughness of the surface on which the metal layer is formed in the first resin film is 0.06 to 0.08 μm. Also, the surface roughness of the metal layer in the first resin film is rougher than the surface roughness of the surface on which the metal layer is not formed in the first resin film. For example, the surface roughness of the metal layer in the first resin film is 0.01 to 0.03 μm.

[0084] Therefore, in this embodiment, as shown in Figure 1B, it is preferable that the first adhesive layer 21 is formed on the side 11a of the first resin film 11 where the metal layers 12 and 13 are not formed. That is, it is preferable that the first surface of the substrate 10 is the side 11a of the first resin film 11 on which the first adhesive layer is formed. This reduces the influence of the surface roughness of the metal layer on the first adhesive layer, and makes it easier to keep the Sa of the adhesive surface of the first adhesive layer within the range described above.

[0085] Furthermore, it is preferable that the surface 11a on which the first adhesive layer is formed in the first resin film 11 is smoothed. This makes it easier to keep the Sa of the adhesive surface 21a of the first adhesive layer within the range described above.

[0086] Examples of substrates having a first resin film and a metal layer include the Reftel® series manufactured by Teijin Frontier Co., Ltd. In the Reftel series, the surface roughness of the surface on which the metal layer is formed in the first resin film is rougher than the surface roughness of the surface on which the metal layer is not formed in the first resin film. Furthermore, the surface roughness of the metal layer in the first resin film is rougher than the surface roughness of the surface on which the metal layer is not formed in the first resin film.

[0087] The thickness of the base material is not particularly limited as long as it exhibits a predetermined rigidity, and can be set appropriately according to the intended use. In this embodiment, from the viewpoint of ensuring mechanical strength suitable for workability during use and from the viewpoint of easily exhibiting the adhesive properties described above, the thickness of the base material may be 18 to 100 μm, 25 to 75 μm, or 25 to 50 μm.

[0088] (4. Functional Layer) Adhesive sheets may have a functional layer in addition to the base material and adhesive layer. This allows for the provision of various functions to the adhesive sheet. Examples of functions that the functional layer may have include hard coating properties, anti-glare properties, anti-reflective properties, ultraviolet absorption properties, infrared absorption properties, improved writing feel, Newton's ring prevention properties, transparency, semi-permeability, antibacterial properties, antiviral properties, anti-fogging properties, water repellency, hydrophilicity, oil repellency, lipophilicity, sebum resistance (sebum wiping properties, sebum compatibility, sebum absorption, etc.), decorative properties, and stain resistance.

[0089] As shown in Figure 2A, in the adhesive sheet 1, it is preferable that the functional layer 30 is located on the main surface 10b of the base material 10, opposite to the main surface 10a on which the adhesive layer 21 is located. If the base material has a first resin film and a metal layer, as shown in Figure 2B, it is preferable that the functional layer 30 is formed on the surface 11b of the first resin film 11 on the side where the metal layers 12 and 13 are formed. In this case, in order to improve the adhesion between the functional layer 30 and the metal layer 13, the functional layer 30 and the metal layer 13 may be bonded via an adhesive layer (second adhesive layer 22). Alternatively, as shown in Figure 2C, the functional layer 30 may be formed on one main surface of the second resin film 14, and the other main surface of the second resin film 14 (the side on which the functional layer 30 is not formed) and the metal layer 13 may be bonded via an adhesive layer (second adhesive layer 22).

[0090] The functional layer may consist of one layer having one or more of the above functions, or it may consist of multiple layers having one or more of the above functions. In this embodiment, the functional layer is preferably a hard coat layer having hard coat properties, and more preferably a hard coat layer having hard coat properties and at least one of the following functions: anti-glare, anti-reflection, ultraviolet absorption, infrared absorption, improved writing feel, Newton ring prevention, transparency, semi-permeability, antibacterial, antiviral, anti-fogging, water repellency, hydrophilicity, oil repellency, lipophilicity, sebum resistance (sebum wiping ability, sebum compatibility, sebum absorption, etc.), decorative properties, and stain resistance. The case where the functional layer is a hard coat layer will be described below.

[0091] The hard coat layer is made of a material that is superior to the substrate in terms of hardness, scratch resistance, weather resistance, etc. When the adhesive sheet has the configuration shown in Figure 2A, when the first adhesive layer 21 is attached to the adherend, the hard coat layer 30 of the adhesive sheet 1 is exposed to the outside. Therefore, scratches during the application of the adhesive sheet due to external forces, deformation of the first adhesive layer, etc. can be suppressed. In addition, the adhesive sheet can exhibit excellent impact resistance, scratch resistance, and weather resistance even after application. In particular, in combination with the adhesive layer and the substrate, it becomes easier to obtain an adhesive sheet that exhibits scattering prevention and impact resistance (local or overall), thereby enhancing the protection of the adherend.

[0092] The thickness of the hard coat layer can be set according to the application, and in this embodiment, from the viewpoint of surface hardness, scratch resistance, and weather resistance of the adhesive sheet, it may be 1 to 5 μm or 1.5 to 3.0 μm.

[0093] The constituent material of the hard coat layer is not particularly limited as long as it is a material that has superior hardness, scratch resistance, weather resistance, etc., compared to the first resin film constituting the substrate. The hard coat layer according to this embodiment is preferably a cured product of a hard coat layer forming composition containing an active energy ray curable resin.

[0094] (4.1. Composition Q for forming a hard coat layer) In this embodiment, the hard coat layer forming composition Q may be thermosetting or active energy ray curable. In this embodiment, from the viewpoint of productivity and ease of obtaining desired scratch resistance, the hard coat layer forming composition Q is preferably active energy ray curable, and in particular preferably contains an active energy ray curable resin (a) and a photopolymerization initiator (b).

[0095] (4.2. Active energy ray curable resins (a)) The active energy ray-curable resin is not particularly limited and can be selected from those conventionally known. Examples include active energy ray-curable monomers, oligomers, or compositions containing them.

[0096] Examples of active energy ray-curable monomers include polyfunctional (meth)acrylates. Examples of active energy ray-curable oligomers include urethane (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, and silicone (meth)acrylates.

[0097] Examples of polyfunctional (meth)acrylates include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol polyfunctional (meth)acrylates such as pentaerythritol tri(meth)acrylate and pentaerythritol tetra(meth)acrylate, dipentaerythritol polyfunctional (meth)acrylates such as dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate, glycerol tri(meth)acrylate, triallyl(meth)acrylate, and the like.

[0098] Of these, pentaerythritol polyfunctional (meth)acrylate or dipentaerythritol polyfunctional (meth)acrylate is more preferable because it can impart appropriate hardness, scratch resistance, weather resistance, etc., to the hard coat layer.

[0099] (4.3. Photopolymerization initiators (b)) When ultraviolet light is used as the active energy ray for curing the hard coat layer forming composition Q, it is preferable that the hard coat layer forming composition Q contains a photopolymerization initiator (b). A photopolymerization initiator is a compound that generates radical species upon irradiation with active energy rays such as ultraviolet light. By including a photopolymerization initiator (b), a hard coat layer can be efficiently formed when the hard coat layer forming composition is irradiated with ultraviolet light. As the photopolymerization initiator (b), for example, any known compound that generates radicals upon irradiation with active energy rays may be used.

[0100] (4.4. Other Additives) Within the limits that do not impair the effects of the present invention, the hard coat layer forming composition Q may contain other additives. Examples of other additives include antioxidants, ultraviolet absorbers, antistatic agents, colorants, polymerization accelerators, polymerization inhibitors, plasticizers, leveling agents, antiviral agents, antibacterial agents, fillers, and diluent solvents.

[0101] (5. Physical properties of adhesive sheets) The adhesive sheet according to this embodiment preferably has the following physical properties.

[0102] (5.1. Visible light transmittance of adhesive sheets) The adhesive sheet according to this embodiment preferably has a light transmittance (visible light transmittance) of 50% or more in the wavelength range of 380 to 780 nm, more preferably 60% or more, and even more preferably 70% or more. This ensures sufficient transparency of the adhesive sheet. As a result, visibility through the object to which the adhesive sheet is attached (for example, a window) can be improved.

[0103] The visible light transmittance of the adhesive sheet can be measured in accordance with JIS A 5759:2016. The specific measurement method will be explained in the examples described later.

[0104] (5.2. Visible light reflectance of adhesive sheets) The adhesive sheet according to this embodiment preferably has a light reflectance (visible light reflectance) in the wavelength range of 380 to 780 nm of 30% or less, more preferably 20% or less, and even more preferably 10% or less. Thereby, the reflection of the adherend (for example, window) to which the adhesive sheet is attached is reduced.

[0105] The visible light reflectance of the adhesive sheet can be measured in accordance with JIS R 3106:2019. The specific measurement method will be described in the examples described later.

[0106] (5.3. Brightness and chromaticity of the adhesive sheet) CIE1976L of the adhesive sheet according to this embodiment * a * b * The brightness L defined by the color system * is preferably 80.0 or more, and more preferably 90.0 or more, from the viewpoints of transparency and visibility.

[0107] CIE1976L of the adhesive sheet according to this embodiment * a * b * The chromaticity a defined by the color system * is preferably -2.0 to 0.0. Also, CIE1976L of the adhesive sheet according to this embodiment * a * b * The chromaticity b defined by the color system * is preferably 3.0 to 5.0. When the chromaticity a * and the chromaticity b * are within the above ranges, the visibility is good.

[0108] The measurement methods for the brightness and chromaticity of the adhesive sheet will be described in the examples described later.

[0109] (5.4. Shading coefficient of the adhesive sheet) The shielding coefficient of the adhesive sheet according to this embodiment is preferably 0.72 or less, and more preferably 0.69 or less. This improves the heat shielding capacity of the substrate to which the adhesive sheet is attached (for example, a window), resulting in an energy-saving effect.

[0110] The shielding coefficient of the adhesive sheet can be measured in accordance with JIS A 5759:2016. The specific measurement method will be explained in the examples described later.

[0111] (6. Manufacturing of adhesive compositions) The adhesive composition P can be produced, for example, by first producing a (meth)acrylic acid ester polymer (A), and then mixing the obtained (meth)acrylic acid ester polymer (A) with a crosslinking agent (B). Optionally, additives such as an ultraviolet absorber (C) may be added at any stage.

[0112] (Meth)acrylic acid ester polymers can be produced, for example, by polymerizing a mixture of monomers constituting the polymer using a conventional radical polymerization method. Polymerization of (meth)acrylic acid ester polymers can be carried out by solution polymerization using a polymerization initiator as needed.

[0113] Examples of polymerization solvents used in solution polymerization include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone. One type of polymerization solvent may be used, or two or more may be used in combination. Examples of polymerization initiators include azo compounds and organic peroxides, and two or more may be used in combination. Furthermore, the weight-average molecular weight of the resulting polymer can be adjusted by incorporating a chain transfer agent such as 2-mercaptoethanol during polymerization.

[0114] Next, a crosslinking agent (B) and, if necessary, additives are added to the solution of the obtained (meth)acrylic acid polymer (A), and the mixture is thoroughly mixed to obtain a solvent-diluted adhesive composition P (coating solution).

[0115] Furthermore, if any of the above components is a solid component, or if it precipitates when mixed with other components in an undiluted state, that component may be dissolved or diluted in a diluting solvent beforehand before being mixed with the other components.

[0116] Examples of diluent solvents include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

[0117] The concentration and viscosity of the prepared coating solution can be selected as appropriate depending on the situation, as long as they are within the range of coating. For example, the adhesive composition P is diluted to a concentration of 10 to 60% by mass. It is not always necessary to add a diluent to obtain the coating solution; if the adhesive composition P has a viscosity suitable for coating, a diluent may not be added. In this case, the adhesive composition P becomes a coating solution in which the polymerization solvent of the (meth)acrylic acid ester polymer is used directly as the diluent.

[0118] (7. Manufacturing of adhesives) The adhesive is preferably obtained by crosslinking the adhesive composition P described above. Crosslinking of the adhesive composition P can usually be carried out by heat treatment. This heat treatment can also be combined with the drying treatment used to volatilize the diluent solvent, etc., from the coating film of the adhesive composition P applied to the desired object.

[0119] The heating temperature for the heat treatment is preferably 50 to 150°C, and more preferably 70 to 120°C. The heating time is preferably 10 seconds to 10 minutes, and more preferably 50 seconds to 2 minutes.

[0120] After heat treatment, the coating layer obtained by drying the coating film may be allowed to cure for 1 to 2 weeks at room temperature (e.g., 23°C, 50% RH (relative humidity)) as needed. If curing is necessary, an adhesive with a cross-linked structure will be obtained in the coating layer after the curing period has elapsed. If curing is not necessary, an adhesive with a cross-linked structure will be obtained in the coating layer after the heat treatment is completed.

[0121] (8. Manufacturing of adhesive sheets) The method for manufacturing the adhesive sheet is not particularly limited and can be manufactured by known methods. For example, a coating solution of an adhesive composition P for forming a first adhesive layer is applied to the release surface of a known release sheet, and the adhesive composition P is crosslinked by heat treatment to form a first coating layer having a predetermined thickness. If curing is required, after a predetermined curing period, the first coating layer becomes the first adhesive layer. If curing is not required, the first coating layer becomes the first adhesive layer as is. This provides a first adhesive layer formed on the release sheet.

[0122] If the substrate consists only of a first resin film, one side of the first resin film (the first surface) is bonded to the surface exposed in the first adhesive layer formed on the release sheet. If the substrate has a structure in which the first resin film and a metal layer are laminated, the side of the first resin film on which the metal layer is not formed (the first surface) is bonded to the surface exposed in the first adhesive layer formed on the release sheet. This results in the adhesive sheet 1 shown in Figure 1A or Figure 1B.

[0123] If the adhesive sheet has a functional layer such as a hard coat layer, a coating solution of a functional layer-forming composition such as hard coat layer-forming composition Q is applied to one surface of the second resin film and dried to form a coating layer. The formed coating layer is then cured by irradiating it with active energy rays such as ultraviolet light or electron beams as needed, thereby forming a functional layer such as a hard coat layer on the second resin film.

[0124] Next, on the side of the second resin film where the functional layer is not formed, a coating solution of adhesive composition P for forming the second adhesive layer is applied, and heat treatment is performed to crosslink the adhesive composition P, thereby forming a second coating layer having a predetermined thickness. If curing is required, after a predetermined curing period, the second coating layer becomes the second adhesive layer. If curing is not required, the second coating layer remains the second adhesive layer.

[0125] The exposed surface of the second adhesive layer is bonded to the side of the adhesive sheet 1 shown in Figure 1A or Figure 1B where the first adhesive layer is not formed, or the side where the metal layer is formed. This results in the adhesive sheet 1 shown in Figure 2A or Figure 2B.

[0126] Examples of methods for applying the coating solution of the adhesive composition P and the hard coat layer forming composition Q include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0127] In this specification, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Similarly, when "greater than or equal to X" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "less than or equal to Y" (where Y is any number) is written, unless otherwise specified, it includes the meaning of "preferably less than Y."

[0128] Although embodiments of the present invention have been described above, the present invention is not limited in any way to the embodiments described above, and may be modified in various ways within the scope of the present invention. [Examples]

[0129] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0130] (Example 1) 1. Fabrication of a laminate including a hard coat layer The active energy ray curable component (a) is 100 parts by mass of pentaerythritol polyfunctional (meth)acrylate (manufactured by Shin Nakamura Chemical Industry, product name "NK Ester-A-TMM-3L") (expressed as a solid content equivalent; the same applies to other components below), the photopolymerization initiator (b) is 10 parts by mass of α-hydroxyalkylphenone (manufactured by IGM Resins, product name "Omnirad 184") and 3 parts by mass of α-hydroxyacetophenone (manufactured by IGM Resins, product name "Omnirad 127D"), the additive is 0.045 parts by mass of silica filler (manufactured by CIK Nanotech, product name "SIRPGM15WT%-E26") and leveling agent (manufactured by Toray Dow Corning, product name "DOWSIL(registered trademark) 8032) ADDITIVE was mixed with 0.3 parts by mass and diluted with a mixed solvent of toluene and glycol ether (mass ratio 1:1) to prepare a coating solution for the hard coat layer forming composition.

[0131] A polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine® A4360") with a thickness of 25 μm was coated with a solution of the prepared hard coat layer forming composition using a Meyer bar so that the thickness after drying would be 2 μm. The film was then heated at 90°C for 1 minute to thoroughly remove the diluent. Next, under a nitrogen atmosphere, the hard coat layer forming composition was cured by irradiating it with ultraviolet light using an ultraviolet irradiation device (manufactured by I-Graphics Co., Ltd., product name "I-Grantage ECS-401GX") under the following conditions to form a hard coat layer (thickness: 2 μm), and a laminate 1 was obtained in which the second resin film and the hard coat layer were laminated together. [Ultraviolet irradiation conditions] • Light source: High-pressure mercury lamp • Lamp power: 2kW Conveyor speed: 4.23 m / min ·Illuminance: 300mW / cm 2 ·Light amount: 250mJ / cm 2

[0132] 2. Preparation of laminate 2 including the adhesive layer (Preparation of (meth)acrylic acid ester polymer (A)) (Meth)acrylic acid ester polymer (A) was prepared by copolymerizing 44 parts by mass of n-butyl acrylate, 44 parts by mass of isobutyl acrylate, 5 parts by mass of vinyl acetate, 6 parts by mass of 2-hydroxyethyl methacrylate, and 0.04 parts by mass of methacrylic acid. The molecular weight of the obtained (meth)acrylic acid ester polymer (A) was measured by the method shown below, and the weight-average molecular weight (Mw) was 450,000.

[0133] The weight-average molecular weight (Mw) is the weight-average molecular weight on a polystyrene basis, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). (Measurement conditions) • GPC measuring device: Tosoh Corporation, HLC-8020 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Guard Column HXL-H TSK gel GMHXL (x2) TSK gel G2000HXL • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0134] (Formation of the adhesive layer) 100 parts by mass (based on solid content; the same applies hereinafter) of the (meth)acrylic acid ester polymer (A) obtained above, 0.35 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, product name "Takenate D-165N") as a crosslinking agent (B), and 1.5 parts by mass of a benzophenone-based ultraviolet absorber (manufactured by Cytec, product name "Cyasorb UV-24") as an ultraviolet absorber (C) were mixed and thoroughly stirred, and then diluted with methyl ethyl ketone to obtain a coating solution of adhesive composition P containing a polymerization solvent and a diluent.

[0135] Next, a release sheet (38 μm thick) made of polyethylene terephthalate (PET) film, with one side of the sheet released using a silicone-based release agent, was coated with the prepared adhesive composition P using a die coat so that the thickness after drying would be 20 μm. After coating, the sheet was heated at 90°C for 1 minute to thoroughly remove the dilution solvent, forming a first adhesive layer with a thickness of 20 μm on the release sheet.

[0136] (Formation of a laminate) A resin film with a metal layer (Teijin Frontier Co., Ltd., Reftel® WH03, 25 μm) was prepared as the substrate. The resin film with a metal layer was a multilayer film in which two metal layers were formed on one main surface of a 25 μm thick PET film (first resin film). The main surface exposed in the first adhesive layer formed on the release sheet (the main surface not in contact with the release sheet) was bonded to the main surface of the resin film with a metal layer on the side where the metal layer was not formed, thereby obtaining a laminate 2 in which the substrate and the adhesive layer were laminated together.

[0137] 3. Manufacturing of adhesive sheets On the second resin film of laminate 1, the coating solution of the prepared adhesive composition P was applied to the main surface on the side where the hard coat layer was not formed, using a knife coater, so that the thickness after drying was 20 μm. After coating, the surface was heated at 90°C for 1 minute to thoroughly remove the diluting solvent, forming a second adhesive layer with a thickness of 20 μm on the second resin film of laminate 1.

[0138] The exposed main surface of the second adhesive layer of laminate 1 (the main surface not in contact with the second resin film) and the main surface of the substrate of laminate 2 on the side where the metal layer is formed (the main surface not in contact with the first adhesive layer) were bonded together and laminated. Subsequently, by curing for 7 days under conditions of 23°C and 50% RH, an adhesive sheet having the following structure was obtained: "hard coat layer / PET film (second resin film) / second adhesive layer / two metal layers / PET-based film (first resin film) / first adhesive layer / release sheet". The structure of the adhesive sheet is shown in Table 1.

[0139] (Comparative Example 1) An adhesive sheet was manufactured in the same manner as in Example 1, except that the main surface of the first adhesive layer formed on the release sheet, which is exposed, was bonded to the main surface of the metal layer-attached resin film on the side where the metal layer is formed, thereby obtaining a laminate 2 in which the substrate and the first adhesive layer are laminated. The manufactured adhesive sheet had the following structure as shown in Table 1: "hard coat layer / PET film (second resin film) / second adhesive layer / PET-based film (first resin film) / two metal layers / first adhesive layer / release sheet".

[0140] (Comparative Example 2) A resin film with a metal layer (Teijin Frontier Co., Ltd., Reftel® WH03, 50 μm) was prepared as the substrate. The resin film with a metal layer was a multilayer film in which multiple metal layers were formed on one main surface of a 50 μm thick PET film.

[0141] The coating solution of the hard coat layer forming composition described above was applied to the main surface of the metal-layered resin film on the side where the metal layer was not formed, using a Meyer bar so that the thickness after drying would be 2 μm. The film was then heated at 90°C for 1 minute to thoroughly remove the diluent solvent. Next, ultraviolet light was irradiated using the ultraviolet irradiation device described above under the ultraviolet irradiation conditions described above to form a hard coat layer (thickness: 2 μm) on the metal-layered resin film.

[0142] Next, an adhesive sheet was manufactured in the same manner as in Example 1, except that the main surface exposed in the first adhesive layer formed on the release sheet (the main surface not in contact with the release sheet) was bonded to the main surface on the side of the metal layer-attached resin film where the metal layer is formed. The manufactured adhesive sheet had the following structure, as shown in Table 1: "hard coat layer / PET film (first resin film) / two metal layers / first adhesive layer / release sheet".

[0143] The following evaluations were performed using the adhesive sheets prepared in the examples and comparative examples.

[0144] (Sa on the adhesive surface of the first adhesive layer) In each adhesive sheet of the examples and comparative examples, the exposed surface of the first adhesive layer was observed using a scanning white light interference microscope (Hitachi High-Tech Science Corporation, product name "VS-1550") under the following conditions, and Sa was calculated.

[0145] The observation magnification was set to 50x. A square region with a length of 250 μm in the X-axis direction and a length of 250 μm in the Y-axis direction was defined in the observation field. Displacement in the Z-axis direction was obtained within the defined square region, and Sa was calculated. The results are shown in Table 1.

[0146] (Visible light transmittance of adhesive sheet) The release liner was peeled off the adhesive sheets obtained in the examples and comparative examples, and the exposed first adhesive layer was attached to a 3 mm thick float glass plate at 23°C and 50% RH (relative humidity) to serve as the measurement sample. After performing background measurements on the float glass plate, the visible light transmittance of the adhesive sheet was measured using a spectrophotometer (Shimadzu Corporation, product name "UV-3600i Plus") in accordance with JIS A 5759:2016, by irradiating the adhesive sheet with light in the wavelength range of 380 to 780 nm from the float glass plate side. The results are shown in Table 1.

[0147] (Visible light reflectance of adhesive sheet) The release sheets were peeled off from the adhesive sheets obtained in the examples and comparative examples, and the exposed first adhesive layer was attached to a 3 mm thick float glass plate at 23°C and 50% RH (relative humidity) to serve as the measurement sample. After performing background measurements on the float glass plate, the visible light reflectance of the adhesive sheet was measured using a spectrophotometer (Shimadzu Corporation, product name "UV-3600i Plus") in accordance with JIS R 3106:2019, by irradiating the adhesive sheet with light in the wavelength range of 380 to 780 nm from the hard coat layer side. The results are shown in Table 1.

[0148] (Brightness and color of the adhesive sheet) The release sheet was peeled off from the adhesive sheets obtained in the examples and comparative examples, and the exposed first adhesive layer was attached to a 3 mm thick float glass plate at 23°C and 50% RH (relative humidity) to serve as the measurement sample. After performing background measurements on the float glass plate, the above measurement sample was subjected to CIE1976L in transmitted light using a colorimeter (COH300A, manufactured by Nippon Denshoku Industries Co., Ltd.). * a * b * Lightness L as defined by the color system * , chromaticity a * and chromaticity b * The following measurements were taken. The results are shown in Table 1.

[0149] (Shielding coefficient of adhesive sheet) The release sheets were peeled off from the adhesive sheets obtained in the examples and comparative examples, and the exposed first adhesive layer was attached to a 3 mm thick float glass plate under conditions of 23°C and 50% RH (relative humidity) to serve as the measurement sample. After performing background measurements on the float glass plate, the solar transmittance and solar reflectance of the measurement sample were measured using a spectrophotometer (Shimadzu Corporation, product name "UV-3600") in accordance with JIS A 5759:2016. The amount of heat inflow was calculated from the measured values, and the shielding coefficient was calculated using the following formula (1). The results are shown in Table 1. Shielding coefficient = Heat inflow into the measurement sample / Heat inflow into the float glass (1)

[0150] (Evaluation of water drainage of adhesive sheets) The release sheets were peeled off the adhesive sheets obtained in the examples and comparative examples. Under conditions of 23°C and 50% RH (relative humidity), the application solution (0.1% aqueous solution of surfactant) was sprayed onto the entire surface of the exposed first adhesive layer and the entire surface of the glass plate to be adhered using a sprayer, and then the adhesive sheet was wet-applied to the surface of the glass plate. After wet-applied, the application solution was drained off the adhesive sheet using a squeegee, and the sheet was left to stand for 30 days under conditions of 23°C and 50% RH (relative humidity). After 30 days, the interface between the adhesive sheet and the glass plate was visually observed, and the remaining state of the application solution was evaluated according to the following criteria. The results are shown in Table 1. A: No application liquid remains. B: The area where the application solution remains is less than 10%. C: The area where the application liquid remains is 10% or more.

[0151] [Table 1]

[0152] Table 1 confirms that the adhesive sheets in the examples exhibit excellent water drainage properties for the application liquid. [Industrial applicability]

[0153] The adhesive sheet of the present invention is suitable, for example, as a window film to be applied to the windows of moving objects such as automobiles, or to the windows of buildings. [Explanation of symbols]

[0154] 1…Adhesive sheet (window film) 10… Resin film 11…First resin film 12...Metal layer 13...Metal layer 21…First adhesive layer 22...Second adhesive layer 30… Functional layer (hard coat layer)

Claims

1. The material comprises a substrate containing a first resin film, and a first adhesive layer formed on a first surface of the substrate and attached to an object. An adhesive sheet in which the first adhesive layer has an arithmetic mean height Sa of the adhesive surface that is attached to the adherend of 0.020 μm or less.

2. The adhesive sheet according to claim 1, wherein a functional layer is formed on a second surface facing the first surface of the substrate.

3. The adhesive sheet according to claim 2, wherein the functional layer is a hard coat layer.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the base material further comprises a metal layer.

5. The adhesive sheet according to any one of claims 1 to 3, wherein the first surface of the substrate is the surface of the first resin film.

6. The adhesive sheet according to any one of claims 1 to 3, wherein the visible light transmittance of the adhesive sheet is 70% or more.

7. The adhesive sheet according to any one of claims 1 to 3, wherein the visible light reflectance of the adhesive sheet is 20% or less.

8. The adhesive sheet according to any one of claims 1 to 3, wherein the shielding coefficient of the adhesive sheet is 0.72 or less.

9. The aforementioned adhesive sheet CIE1976L * a * b * Lightness L as defined by the color system * An adhesive sheet according to any one of claims 1 to 3, wherein the ratio is 80 or more.

10. The adhesive sheet according to any one of claims 1 to 3, wherein the adhesive sheet is a window film.

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