Window film

Abstract

To provide a window film that can suppress metal oxidation caused by the composition of the adhesive layer. [Solution] The window film comprises a first resin film, a second resin film, a layer containing metal, and a first adhesive layer containing a first acrylic polymer, wherein one main surface of the metal layer and one main surface of the first adhesive layer are in contact with each other between one main surface of the first resin film and one main surface of the second resin film, and the total proportion of units derived from monomers containing carboxyl groups and units derived from monomers having a carboxylic acid anhydride structure is 0.025% by mass or less when the mass of the first acrylic polymer is 100% by mass.

Description

[Technical Field]

[0001] This invention relates to window films. [Background technology]

[0002] Window film is a film applied to the windows of moving objects such as automobiles, and windows of buildings, etc., in order to impart a specific function to those windows, and is widely used.

[0003] One type of window film known for providing aesthetic appeal, heat insulation, and privacy (making it difficult to see inside the window) is a window film containing a metal layer. Patent Document 1 discloses a window film having a configuration in which a metal layer and an intermediate layer composed of an adhesive layer or tack layer are in contact between a first substrate and a second substrate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-47598 [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the window film described in Patent Document 1, corrosion of the metal layer caused by the application liquid used during the installation of the window film is less likely to occur.

[0006] However, window films, such as those used for window coverings, are exposed to various types of light, including sunlight, after being applied to a substrate. When window films are exposed to such light, depending on the composition of the adhesive layer, the constituent components may decompose due to the light energy, generating acid. When acid is generated, the metal in the metal layer in contact with the adhesive layer oxidizes, causing problems such as changes in the properties and color of the window film.

[0007] This invention has been made in view of the above circumstances and aims to provide a window film that can suppress metal oxidation caused by the composition of the adhesive layer. [Means for solving the problem]

[0008] The embodiments of the present invention are as follows.

[0009] [1] comprising a first resin film, a second resin film, a layer containing metal, and a first adhesive layer containing a first acrylic polymer, Between one main surface of the first resin film and one main surface of the second resin film, one main surface of the metal-containing layer and one main surface of the first adhesive layer are laminated in contact. The window film is such that, when the mass of the first acrylic polymer is taken as 100% by mass, the total proportion of units derived from monomers containing carboxyl groups and units derived from monomers having a carboxylic acid anhydride structure is 0.025% by mass or less.

[0010] [2] The window film according to [1] wherein the interlayer adhesion between one main surface of the metal-containing layer and one main surface of the first adhesive layer is 5 N / 25 mm or more.

[0011] [3] The window film according to [1] or [2], wherein when the mass of the first acrylic polymer is 100% by mass, the content of units derived from monomers containing hydroxyl groups is 11% by mass or more.

[0012] [4] A second adhesive layer containing a second acrylic polymer is disposed on the other main surface of the first resin film, or on the other main surface of the second resin film. The window film according to any one of [1] to [3], wherein, when the mass of the second acrylic polymer is taken as 100% by mass, the total proportion of units derived from monomers containing a carboxyl group or units derived from monomers having a carboxylic acid anhydride structure is 0.025% by mass or less.

[0013] The window film according to [4], wherein the structural unit of the first acrylic polymer and the structural unit of the second acrylic polymer are the same.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a window film capable of suppressing oxidation of a metal due to the composition of an adhesive layer.

Brief Description of the Drawings

[0015] [Figure 1A] FIG. 1A is a schematic cross-sectional view showing an example of the configuration of the window film according to the present embodiment. [Figure 1B] FIG. 1B is a schematic cross-sectional view showing an example of the configuration of the window film according to the present embodiment. [Figure 1C] FIG. 1C is a schematic cross-sectional view showing an example of the configuration of the window film according to the present embodiment. [Figure 2A] FIG. 2A is a schematic cross-sectional view showing an example of another configuration of the window film according to the present embodiment. [Figure 2B] FIG. 2B is a schematic cross-sectional view showing an example of another configuration of the window film according to the present embodiment.

Modes for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail based on specific embodiments.

[0017] (1. Window Film) A layer containing a metal is formed on the window film. Thereby, by utilizing the luster of the metal, it becomes possible to impart a design property to the window film, control the light transmittance, suppress an increase in the internal temperature of the window, make it difficult to visually recognize the inside of the window, and the like.

[0018] The application of window film to a window, which is the substrate, is usually done by fixing the window film to the window using an application solution, and then removing the application solution. However, if the application solution comes into contact with metal, corrosion such as oxidation of the metal may occur. Therefore, in the window film of the present invention, a configuration is adopted in which a layer containing metal is sandwiched between two layers of resin film to prevent contact between metal and the application solution. In this configuration, an adhesive layer is used to bond the layer containing metal to the two layers of resin film. For example, one resin film on which the metal vapor deposition layer is formed is bonded to the other resin film by the adhesive layer. Therefore, in the window film, the metal and the adhesive layer come into contact.

[0019] Window films applied to windows are exposed to various types of light, such as sunlight, and light also enters the components that make up the window film. If the incident light includes high-energy light such as ultraviolet light, the components that make up the adhesive layer may decompose, generating acid. For example, if the adhesive layer contains polyester resin, the ester bonds of the polyester resin may partially decompose due to light, generating acid. The generated acid may come into contact with metals in contact with the adhesive layer, causing the metal to oxidize. When metal oxidation occurs, the appearance and properties of the metal-containing layer change, which can affect the properties of the window film.

[0020] Therefore, in this embodiment, by controlling the composition of the adhesive layer, a window film is realized that can suppress the photodegradation of the components constituting the adhesive layer (having light resistance). As a result, even when light is incident on the adhesive layer of the window film, the oxidation of the metal is suppressed, and the resulting changes in the properties of the window film can be suppressed.

[0021] As shown in Figure 1A, the window film 1 according to this embodiment comprises a first resin film 11 and a second resin film 12 as a base material, a first adhesive layer 21, and a metal-containing layer 30. The first adhesive layer 21 and the metal-containing layer 30 are laminated so that their main surfaces 21b and 30a are in contact between the main surface 11a of the first resin film 11 and the main surface 12b of the second resin film 12. The metal-containing layer 30 is formed on the first resin film 11.

[0022] The window film 1 may have a configuration other than that shown in Figure 1A, as long as the main surface of the first adhesive layer 21 and the main surface of the metal-containing layer 30 are in contact. For example, as shown in Figure 1B, the metal-containing layer 30 may be formed on the second resin film 12. As shown in Figure 1C, the first adhesive layer 21 may be formed on the first resin film 11 and the second resin film 12, respectively, and the two layers of the first adhesive layer 21 may sandwich the metal-containing layer 30.

[0023] The window film may have other components as long as the effects of the present invention are obtained. For example, in order to easily fix the window film to an adherend, a second adhesive layer may be formed on a main surface of the first or second resin film that is opposite to the main surface on which the metal-containing layer or the first adhesive layer is formed. Figure 2A shows a window film 1 having a configuration in which a second adhesive layer 22 is formed on a main surface 11b of the first resin film 11 that is opposite to the main surface 11a on which the metal-containing layer 30 is formed.

[0024] Furthermore, in order to impart weather resistance, scratch resistance, etc., to the window film, a hard coat layer may be formed on the main surface of the first resin film or the second resin film that is opposite to the main surface on which the metal-containing layer or the first adhesive layer is formed. Figure 2B shows a window film 1 having a configuration in which a hard coat layer 40 is formed on the main surface 12a of the second resin film 12 that is opposite to the main surface 12b on which the first adhesive layer 21 is formed.

[0025] Furthermore, a release sheet may be placed on the main surface 22b of the second adhesive layer 22 to protect the second adhesive layer 22 until it is attached to the substrate. When the window film 1 is used, the release sheet is peeled off from the second adhesive layer 22, and the main surface 22b of the second adhesive layer 22 is attached to the substrate (window).

[0026] The first adhesive layer and the second adhesive layer are formed by creating a predetermined adhesive in layers. In this embodiment, the adhesives constituting the first adhesive layer and the second adhesive layer may be thermosetting adhesives, moisture-sensitive adhesives, thermoplastic resins, etc., but it is preferable that they be pressure-sensitive adhesives. A pressure-sensitive adhesive is an adhesive that has a predetermined elasticity and has tack on its surface, and is a substance that exhibits adhesion to an adherend when pressed against the adherend. A pressure-sensitive adhesive is also called an adhesive. That is, the adhesive layer (first adhesive layer or second adhesive layer) may also be an adhesive layer (first adhesive layer or second adhesive layer). The following describes the case where the first adhesive layer and the second adhesive layer are the first adhesive layer and the second adhesive layer.

[0027] (1.1. Optical properties of window films) The window film according to this embodiment preferably has the following optical properties.

[0028] (1.1.1. Total light transmittance of window film) In this embodiment, it is preferable that the total light transmittance of the window film is 90% or less. This makes it difficult to see inside the window from the outside of the window to which the window film is attached (high visibility protection), providing excellent privacy protection as well as excellent heat insulation.

[0029] The total light transmittance can be set according to the degree of opacity, etc. In this embodiment, the total light transmittance is more preferably 80% or less, and even more preferably 75% or less. In this embodiment, from the viewpoint of visibility, the lower limit of the total light transmittance is preferably 30%, and more preferably 40%. The total light transmittance in this specification can be measured in accordance with JIS K7361-1:1997. Detailed measurement methods will be described in the examples.

[0030] (1.1.2. Haze value of window film) In this embodiment, it is preferable that the haze value of the window film is 10% or less. This ensures good visibility of objects seen through the window film, even when the window film is applied to a window. In particular, even when viewing a light source through the window film, the light from the light source is less likely to diffuse, resulting in good visibility of the light source.

[0031] The above haze value is more preferably 5% or less, and even more preferably 3% or less. The lower limit of the haze value is 0%. The haze value in this specification can be measured in accordance with JIS K7136:2000. Detailed measurement methods will be described in the examples.

[0032] (1.1.3. Chromaticity of window film) CIE1976L of the window film according to this embodiment * a * b * Chromaticity a defined by the color system * This can be -30 to 30, -20 to 20, or -10 to 10. On the other hand, chromaticity b * This can be -30 to 30, -20 to 20, or -10 to 10. Chromaticity a * and chromaticity b * As long as the above range is maintained, the visibility of objects seen through the window film will be good, even when the window film is applied to the window.

[0033] Next, we will explain the components of window film.

[0034] (1.2. Resin film) The resin film according to this embodiment is a material responsible for the rigidity of the window film and functions as a substrate that supports the metal-containing layer and the first adhesive layer (first tack layer).

[0035] Examples of such resin films include films made of 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, or laminated films made of these materials.

[0036] Among these, films made of polyolefin resins and polyester resins, or laminated films thereof, which have excellent mechanical strength and cost-effectiveness, are preferred, and films made of polyester resins or laminated films thereof are particularly preferred.

[0037] The first resin film and the second resin film may have the same configuration or different configurations. In the window film shown in Figure 2A, when applied to a substrate using an application liquid, the first resin film in contact with the second adhesive layer (second tack layer) for application to the substrate preferably has a degree of waterproofing that substantially prevents the application liquid from passing through, and preferably has a degree of waterproofing that substantially prevents water from passing through. A degree of substantially preventing penetration means that the application liquid does not cause corrosion of the metal by passing through the first resin film.

[0038] To improve adhesion to the layer provided on the resin film, one or both sides of the resin film 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.

[0039] The thickness of the resin film 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 installation, the thickness of the resin film may be 5 to 200 μm or 10 to 100 μm.

[0040] (1.3. Layer containing metal) The metal-containing layer may be formed on a resin film or on an anchor coat layer formed on a resin film, as long as it is in contact with the first adhesive layer (first tack layer). The metal-containing layer may consist solely of metal. The metal-containing layer can be formed, for example, by vapor deposition, sputtering, etc. Examples of metals contained in the metal-containing layer include aluminum, gold, silver, copper, nickel, cobalt, chromium, tin, indium, and alloys thereof.

[0041] The thickness of the metal-containing layer can be set appropriately according to the intended use, within a range that allows visible light to pass through. In this embodiment, it may be 1 to 1000 nm or 1 to 500 nm.

[0042] (1.4. First adhesive layer) The first adhesive layer in this embodiment is a first adhesive layer. The first adhesive layer adheres and fixes the first resin film, the second resin film, and the metal-containing layer to each other. The first adhesive layer is formed by the adhesive described later being arranged in layers.

[0043] The first adhesive layer may be a single layer or two or more layers. If the first adhesive layer has multiple layers, their compositions may differ.

[0044] The thickness of the first adhesive layer is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 5 to 30 μm. This facilitates the development of desirable adhesiveness and optical properties.

[0045] (1.4.1. Composition of the adhesive) The adhesive constituting the first adhesive layer is an adhesive containing a first acrylic polymer. This adhesive may be an emulsion type, a solvent type, or a solvent-free type, but is preferable to a solvent type or solvent-free type considering moisture resistance and optical properties. Furthermore, this adhesive may or may not have a crosslinked structure. In this embodiment, from the viewpoint of strengthening the cohesive force of the first adhesive layer and its optical properties, the adhesive containing the acrylic polymer is preferably crosslinked.

[0046] Specifically, the first acrylic polymer is preferably a (meth)acrylic acid ester polymer (A). Therefore, the adhesive containing the acrylic polymer is preferably an adhesive obtained from an adhesive composition containing (meth)acrylic acid ester polymer (A) (hereinafter sometimes referred to as "adhesive composition P"), and more preferably an adhesive obtained by crosslinking an adhesive composition containing (meth)acrylic acid ester polymer (A) and a crosslinking agent (B), i.e., an adhesive having a crosslinked structure of (meth)acrylic acid ester polymer (A) and crosslinking agent (B). Such an adhesive exhibits excellent adhesion between the resin film and the metal-containing layer. In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the concept of "polymer" is also included in "polymer".

[0047] (1.4.2. (Meth)acrylic acid ester polymer (A)) The first acrylic polymer, (meth)acrylic acid ester polymer (A), has a total proportion of units derived from monomers containing carboxyl groups and units derived from monomers having a carboxylic acid anhydride structure of 0.025% by mass or less per 100% by mass of the (meth)acrylic acid ester polymer. That is, the first acrylic polymer, (meth)acrylic acid ester polymer (A), contains units derived from monomers containing carboxyl groups and units derived from monomers having a carboxylic acid anhydride structure, and the total proportion of these units per 100% by mass is greater than 0% by mass and 0.025% by mass or less, or the first acrylic polymer, (meth)acrylic acid ester polymer (A), does not contain units derived from monomers containing carboxyl groups and units derived from monomers having a carboxylic acid anhydride structure (the total proportion of such units is 0% by mass). If the (meth)acrylic acid ester polymer contains a large amount of units derived from such monomers, it is likely to generate acid when the polymer bonds are decomposed by light. As a result, metal oxidation is likely to occur. Therefore, by having (meth)acrylic acid ester polymers that do not have the above units, or that have them but within the above range, the generation of acid can be suppressed even when the window film is exposed to light.

[0048] Examples of monomers containing a carboxyl group include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Examples of monomers having a carboxylic acid anhydride structure include acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, and benzoic anhydride.

[0049] The total of these proportions is preferably 0.001% by mass or less, more preferably 0.0005% by mass or less, and even more preferably 0% by mass (excluding units derived from the above monomers).

[0050] In this embodiment, the (meth)acrylic acid ester polymer (A) preferably has units derived from an alkyl (meth)acrylic acid ester. By containing units derived from an alkyl (meth)acrylic acid ester copolymer, the adhesive can exhibit desirable tackiness. As the alkyl (meth)acrylic acid ester, an alkyl (meth)acrylic acid ester having 1 to 20 carbon atoms in the alkyl group is preferred. The alkyl group may be linear or branched, but for convenience, those having a cyclic structure are excluded in order to distinguish them from alicyclic structure-containing monomers described later.

[0051] 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.

[0052] Among these, alkyl (meth)acrylates with 4 to 8 carbon atoms in the alkyl group are preferred. Specifically, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred. Furthermore, from the viewpoint of obtaining an adhesive with the desired cohesive force, alkyl (meth)acrylates with 1 to 2 carbon atoms in the alkyl group may be used as the alkyl (meth)acrylate, and specifically, methyl (meth)acrylate is preferred.

[0053] The (meth)acrylic acid ester polymer preferably contains 30 to 80% by mass, more preferably 40 to 75% by mass, and even more preferably 45 to 70% by mass, of units derived from alkyl (meth)acrylic acid esters having 4 to 8 carbon atoms in the alkyl group, as units derived from monomers that constitute the polymer. By setting the content ratio 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.

[0054] Furthermore, if the (meth)acrylic acid ester polymer has units derived from monomers that constitute the polymer, specifically units derived from alkyl (meth)acrylic acid esters having 1 to 2 carbon atoms in the alkyl group, the content of these units is preferably 5 to 40% by mass, and more preferably 10 to 30% by mass.

[0055] In this embodiment, it is preferable that the (meth)acrylic acid ester polymer (A) has units derived from monomers containing hydroxyl groups. By containing units derived from monomers containing hydroxyl groups, the (meth)acrylic acid ester polymer reacts with the crosslinking agent (B), described later, via these hydroxyl groups, facilitating the formation of a crosslinked structure (three-dimensional network structure). As a result, an adhesive with the desired cohesive force is obtained, and the adhesive strength of the first adhesive layer is improved. Therefore, the possibility of delamination occurring at the interface between the first adhesive layer and the resin film or metal-containing layer can be reduced. Note that monomers containing hydroxyl groups may be used solely to change the properties of the (meth)acrylic acid ester polymer (A). Therefore, these hydroxyl groups do not necessarily have to react with the crosslinking agent (B).

[0056] Examples of monomers containing a hydroxyl group 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 or 4-hydroxybutyl (meth)acrylate are preferred, with 2-hydroxyethyl (meth)acrylate being more preferred. These may be used individually or in combination of two or more.

[0058] When the (meth)acrylic acid ester polymer (A) contains units derived from monomers containing hydroxyl groups, it is preferable that the (meth)acrylic acid ester polymer contains 11% by mass or more of units derived from monomers containing hydroxyl groups in 100% by mass. The content of units derived from monomers containing hydroxyl groups is more preferably 15% by mass or more and 35% by mass or less, and even more preferably 17% by mass or more and 30% by mass or less.

[0059] The above (meth)acrylic acid ester polymer (A) may contain units derived from monomers having an alicyclic structure within the molecule (alicyclic structure-containing monomers) as units that constitute the polymer. Because alicyclic structure-containing monomers have low polarity, they can improve adhesion to the first resin film or the second resin film even when the first resin film or the second resin film is a low-polarity film such as a film made of polyester resin.

[0060] In monomers containing an alicyclic structure, the carbon ring of the alicyclic structure may be a saturated structure or may have some unsaturated bonds. Furthermore, the alicyclic structure may be a monocyclic alicyclic structure or a polycyclic alicyclic structure such as a bicyclic or tricyclic structure. The above alicyclic structure is preferably a polycyclic alicyclic structure (polycyclic structure). Moreover, considering the compatibility between the (meth)acrylic acid ester polymer (A) and other components, the above polycyclic structure is particularly preferably bicyclic to tetracyclic. In addition, the number of carbon atoms in the alicyclic structure (referring to the total number of carbon atoms in the ring-forming portion, and the total number of carbon atoms if multiple rings exist independently) is usually preferably 5 or more, and more preferably 7 or more. On the other hand, there is no particular upper limit to the number of carbon atoms in the alicyclic structure, but similar to the above, from the viewpoint of compatibility, it is preferably 15 or less, and particularly preferably 10 or less.

[0061] Examples of monomers containing the above-mentioned alicyclic structure include cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate.

[0062] Among these, dicyclopentanyl (meth)acrylate (10 carbon atoms in the alicyclic structure), adamantyl (meth)acrylate (10 carbon atoms in the alicyclic structure), or isobornyl (meth)acrylate (7 carbon atoms in the alicyclic structure) are preferred, with isobornyl (meth)acrylate being particularly preferred, and isobornyl acrylate being even more preferred. These may be used individually or in combination of two or more.

[0063] If the (meth)acrylic acid ester polymer contains units derived from alicyclic structure-containing monomers as units derived from monomers that constitute the polymer, the content of the units derived from alicyclic structure-containing monomers may be 5 to 25% by mass, 8 to 20% by mass, or 9 to 18% by mass.

[0064] The above (meth)acrylic acid ester polymer (A) may contain units derived from nitrogen atom-containing monomers as units derived from monomers that constitute the polymer. This imparts a predetermined polarity to the adhesive, and the adhesive layer exhibits excellent affinity even to adherends that have a certain degree of polarity. As the nitrogen atom-containing monomer, monomers having nitrogen-containing heterocycles are preferred from the viewpoint of giving the (meth)acrylic acid ester polymer (A) appropriate rigidity.

[0065] Examples of monomers having nitrogen-containing heterocycles include N-(meth)acryloylmorpholine, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylaziridine, aziridinylethyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyrazine, 1-vinylimidazole, N-vinylcarbazole, and N-vinylphthalimide.

[0066] Among these, N-(meth)acryloylmorpholine is preferred because it exhibits superior adhesive strength. These may be used individually or in combination of two or more.

[0067] If the (meth)acrylic acid ester polymer (A) contains units derived from nitrogen atom-containing monomers as units derived from monomers that constitute the polymer, the content of the units derived from nitrogen atom-containing monomers may be 1 to 20% by mass, 2 to 15% by mass, or 3 to 12% by mass.

[0068] In this embodiment, the (meth)acrylic acid ester polymer (A) 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.

[0069] When the (meth)acrylic acid ester polymer (A) is a copolymer, the polymerization method may be a random copolymer or a block copolymer.

[0070] The weight-average molecular weight (Mw) of the (meth)acrylic acid ester polymer (A) is preferably 10 to 1.5 million, more preferably 20 to 1.2 million, and even more preferably 30 to 900,000. This makes it easier to obtain the desired adhesive strength. The weight-average molecular weights used herein are values ​​on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0071] The glass transition temperature (Tg) of the (meth)acrylic acid ester polymer (A) may be -60°C to 0°C, -55°C to -10°C, -50°C to -20°C, or -45°C to -30°C. This makes it easier to obtain an adhesive with good tackiness.

[0072] In the adhesive composition P, the (meth)acrylic acid ester polymer (A) may be used alone or in combination of two or more types.

[0073] (1.4.3. 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.

[0074] 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.

[0075] 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, aromatic polyisocyanates and aliphatic polyisocyanates are preferred, and tolylene diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate are more preferred.

[0076] The amount of crosslinking agent (B) in the adhesive composition P may be 0.05 to 10 parts by mass, 0.1 to 5 parts by mass, or 0.12 to 3 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.

[0077] (1.4.4. Silane coupling agents (C)) The adhesive composition P according to this embodiment may contain a silane coupling agent (C). This improves adhesion to the adherend (window).

[0078] The silane coupling agent (C) is preferably an organosilicon compound having at least one alkoxysilyl group in its molecule, which has good compatibility with the (meth)acrylic acid ester polymer (A) and is light-transmitting. As a result, the resulting adhesive tends to have desirable physical properties such as adhesive strength while maintaining good optical properties.

[0079] Specifically, examples include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; silicon compounds having an epoxy structure such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; chloropropyltrimethoxysilane and 3-isocyanatetopropyltriethoxysilane; or condensates of at least one of these with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These may be used individually or in combination of two or more types.

[0080] The content of the silane coupling agent (C) in the adhesive composition P may be 0.05 to 5 parts by mass, 0.1 to 3 parts by mass, or 0.15 to 2 parts by mass per 100 parts by mass of the (meth)acrylic acid ester polymer (A). This improves adhesion to the adherend and makes it easier to satisfy the aforementioned physical properties such as adhesive strength.

[0081] (1.4.5. Other Additives) The adhesive composition P may optionally contain additives commonly used in adhesives containing acrylic polymers. Examples of such additives include tackifiers, fillers, ultraviolet absorbers, 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.

[0082] (1.4.6. Physical properties of the first adhesive) In this embodiment, it is preferable that the adhesive has the following physical properties.

[0083] (1.4.7. Gel fraction of the first adhesive) The gel fraction of the first adhesive is preferably 20% to 100%. This gel fraction may also be 25% to 95% or 30% to 90%. The gel fraction of the first adhesive can be measured by the method shown in the examples described later. While the gel fraction can serve as an indicator for estimating the formation of the cross-linked structure of the adhesive, a high gel fraction alone does not necessarily increase the cohesive force of the adhesive and reduce the possibility of delamination at the interface between the first adhesive layer and the resin film or metal-containing layer. Therefore, to obtain such an effect, it is preferable that the amount of units derived from the monomer containing hydroxyl groups in the (meth)acrylic acid polymer (A) is within the above-mentioned range.

[0084] (1.4.8. Interlayer adhesion of the first adhesive layer to the metal-containing layer) In this embodiment, it is preferable that the interlayer adhesion strength is 5 N / 25 mm or more when the first adhesive layer is peeled off from the metal-containing layer at a peeling angle of 180° and a peeling speed of 0.3 m / min. This makes it easier to reduce the possibility of delamination occurring at the interface between the first adhesive layer and the metal-containing layer.

[0085] The interlayer adhesion strength may be 5-50 N / 25 mm, 6-30 N / 25 mm, or 7-20 N / 25 mm. The specific measurement conditions for the adhesion strength of the first adhesive layer to the metal-containing layer will be described later in the examples.

[0086] (1.4.9. Adhesion strength of the first adhesive layer to the PET film) In this embodiment, the adhesive force when the first adhesive layer is peeled off the PET film at a peeling angle of 180° and a peeling speed of 0.3 m / min may be 5 N / 25 mm or more. This makes it easier to reduce the possibility of delamination occurring at the interface between the first adhesive layer and the main surface 12b of the second resin film.

[0087] The adhesive strength may be 5-50 N / 25 mm, 6-30 N / 25 mm, or 7-20 N / 25 mm. The specific measurement conditions for the adhesive strength of the first adhesive layer to the PET film will be described later in the examples.

[0088] (1.5. Second adhesive layer) In this embodiment, as shown in Figure 2A, it is preferable that the window film 1 has a second adhesive layer 22. The second adhesive layer in this embodiment is a second adhesive layer. The second adhesive layer can be used to facilitate fixing and attaching the window film to the adherend (window). The second adhesive layer is formed by a layer of adhesive, which will be described later.

[0089] The second adhesive layer may be a single layer or two or more layers. If the second adhesive layer has multiple layers, their compositions may differ.

[0090] The thickness of the second adhesive layer may be 3 to 100 μm, 5 to 80 μm, or 10 to 50 μm. This makes it easier to attach and fix the window film to the substrate (window).

[0091] (1.5.1. Composition of the adhesive) The adhesive constituting the second adhesive layer is an adhesive containing a second acrylic polymer. Similar to the adhesive constituting the first adhesive layer, the adhesive constituting the second adhesive layer may be an emulsion type, a solvent type, or a solvent-free type, and is preferably a solvent type or solvent-free type considering moisture resistance and optical properties. Furthermore, the adhesive may or may not have a crosslinked structure. In this embodiment, from the viewpoint of adhesion of the window film to the window, optical properties, and productivity of the window film due to the commonality of raw materials, it is preferable that the adhesive containing the second acrylic polymer has a crosslinked structure, similar to the adhesive constituting the first adhesive layer.

[0092] Specifically, similar to the first acrylic polymer, the second acrylic polymer is preferably a (meth)acrylic acid ester polymer (A). Therefore, the adhesive containing the second acrylic polymer is preferably an adhesive obtained from an adhesive composition P containing a (meth)acrylic acid ester polymer (A), and more preferably an adhesive obtained by crosslinking an adhesive composition containing a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B), i.e., an adhesive having a crosslinked structure of a (meth)acrylic acid ester polymer (A) and a crosslinking agent (B). Such an adhesive has excellent adhesion to the adherend, which is a window.

[0093] The constituent units of the second acrylic polymer may be the same as or different from those of the first acrylic polymer. In this embodiment, from the viewpoint of window film productivity, it is preferable that the constituent units of the second acrylic polymer are the same as those of the first acrylic polymer. Examples of constituent units of the second acrylic polymer include monomer-derived units as exemplified in the description of the constituent units of the first acrylic polymer.

[0094] Furthermore, the proportion of each constituent unit in the second acrylic polymer may be within the range of the proportion of each constituent unit in the first acrylic polymer described above. Also, the proportion of each constituent unit in the second acrylic polymer may be the same as the proportion of each constituent unit in the first acrylic polymer. Moreover, the adhesive constituting the second adhesive layer may be the same as the adhesive constituting the first adhesive layer.

[0095] In this embodiment, the second adhesive layer is not in contact with the layer containing metal. Therefore, the total proportion of units derived from monomers containing carboxyl groups and units derived from monomers having a carboxylic acid anhydride structure in 100% by mass of the second acrylic polymer ((meth)acrylic acid ester polymer (A)) may exceed 0.025% by mass.

[0096] In this case, the proportion of units derived from monomers containing hydroxyl groups in 100% by mass of the second acrylic polymer ((meth)acrylic acid ester polymer (A)) may be less than 11% by mass. A lower proportion of units derived from monomers containing hydroxyl groups in the second acrylic polymer improves the moisture resistance of the second adhesive layer to the application liquid. The proportion of units derived from monomers containing hydroxyl groups in 100% by mass of the second acrylic polymer is preferably 10% by mass or less, more preferably 8% by mass or less.

[0097] (1.6. Hard coat layer) The window film according to this embodiment may have a hard coat layer in addition to the resin film and adhesive layer. In this case, as shown in Figure 2B, in the window film 1 shown in Figure 2A, the hard coat layer 40 may be placed on the main surface 12a of the second resin film 12 opposite to the main surface 12b on which the first adhesive layer 21 is placed.

[0098] The hard coat layer is made of a material that is superior to the resin film in terms of hardness, scratch resistance, and weather resistance. When the window film 1 shown in Figure 2B is attached to the substrate (window) via the second adhesive layer 22, the hard coat layer 40 of the window film 1 is exposed to the outside. Therefore, even if some force is applied from the outside after installation, the resin film is less likely to be damaged. In addition, because external forces are less likely to be transmitted directly to the adhesive layer and the substrate (windows of automobiles or buildings, etc.), it can exhibit excellent impact resistance. Furthermore, even if the substrate breaks, the scattering of fragments can be suppressed, so it can exhibit excellent shatterproof properties. Therefore, safety can be enhanced while maintaining the appearance of moving objects such as automobiles and buildings.

[0099] The thickness of the hard coat layer is preferably 0.3 to 20 μm, more preferably 0.5 to 15 μm, and even more preferably 0.8 to 6 μm, from the viewpoint of surface hardness, scratch resistance, and weather resistance of the window film.

[0100] The constituent materials of the hard coat layer are not particularly limited, as long as they are materials that have superior hardness, scratch resistance, weather resistance, etc., compared to the resin film. For example, the hard coat layer may be a cured product of a composition containing an active energy ray curable resin.

[0101] (2. 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 a silane coupling agent (C) may be added at any stage.

[0102] (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.

[0103] 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.

[0104] 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).

[0105] 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.

[0106] 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.

[0107] 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.

[0108] (3. 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.

[0109] 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.

[0110] 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.

[0111] (4. Window film manufacturing) The method for manufacturing the window film is not particularly limited and may be manufactured by known methods. For example, a coating solution of an adhesive composition P for forming a first adhesive layer is applied to one main surface of a second resin film as a substrate, and a heat treatment is performed to crosslink the adhesive composition P to form a first coating layer having a predetermined thickness. Subsequently, the main surface of the first resin film on which a metal vapor deposition layer, as a layer containing metal, is formed on one main surface, and the exposed surface of the first coating layer are superimposed to form a first laminate.

[0112] Furthermore, if the window film has a second adhesive layer, a coating solution of the adhesive composition P for forming the second adhesive layer is applied to the release surface of the release sheet, and a heat treatment is performed to crosslink the adhesive composition P, thereby forming a second coating layer having a predetermined thickness. The exposed surface of the second coating layer and the main surface of the first laminate on the side of the first resin film where the metal vapor deposition layer is not formed are superimposed to form a second laminate.

[0113] Examples of methods for applying the adhesive composition P include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0114] If curing is required, the coating layer becomes an adhesive layer after a predetermined curing period. If curing is not required, the coating layer becomes the adhesive layer directly. This results in a window film.

[0115] If the window film has a hard coat layer, it is preferable to form the hard coat layer on the other main surface of the second resin film before forming the first adhesive layer on one main surface of the second resin film. For example, a coating solution of a composition containing an active energy ray curable resin is applied to the other main surface of the second resin film and dried to form a coating layer. The formed coating layer is cured by irradiating it with active energy rays such as ultraviolet rays or electron beams, thereby forming a hard coat layer on the resin film.

[0116] 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."

[0117] 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]

[0118] The invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0119] (Example 1) 1. Preparation of (meth)acrylic acid ester polymer (A) A (meth)acrylic acid ester polymer (A) was prepared by copolymerizing 60 parts by mass of 2-ethylhexyl acrylate, 20 parts by mass of methyl methacrylate, and 20 parts by mass of 2-hydroxyethyl acrylate. 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 700,000.

[0120] 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℃

[0121] 2. Preparation of adhesive composition P1 100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth)acrylic acid ester polymer (A) obtained above, 0.25 parts by mass of a tolylene diisocyanate-based crosslinking agent (B1) manufactured by Toyo Chem Co., Ltd., product name "BHS-8515") as a crosslinking agent (B), and 0.25 parts by mass of 3-glycidyloxypropyltrimethoxysilane (KBM403) manufactured by Shin-Etsu Silicone Co., Ltd. as a silane coupling agent (C) were mixed and thoroughly stirred, and then diluted with methyl ethyl ketone to obtain a coating solution of adhesive composition P1 containing the polymerization solvent and dilution solvent.

[0122] 3. Manufacturing of window films As a second resin film, a polyethylene terephthalate (PET) film with a thickness of 38 μm (manufactured by Mitsubishi Chemical Corporation, product name "Diafoil T600E38") was prepared. The coating solution of the prepared adhesive composition P1 was applied to one main surface of the second resin film using a die coat. After coating, the film was heated at 90°C for 1 minute to thoroughly remove the diluting solvent, forming a first adhesive layer with a thickness of 10 μm on the second resin film.

[0123] A resin film with a metal layer was prepared as the first resin film and the layer containing metal. The resin film with a metal layer had nichrome, silver, and nichrome deposited in that order on one main surface of a 23 μm thick polyethylene terephthalate (PET) film, with a total thickness of 150 nm. The main surface of the metal layer of the resin film with a metal layer was laminated to the main surface of the first adhesive layer formed on the second resin film, with the main surface exposed (the main surface not in contact with the second resin film) being bonded to it.

[0124] Next, the prepared adhesive composition P1 coating solution was applied to the release-treated surface of a release sheet, which was obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent, using a die coat. After coating, the sheet was heated at 90°C for 1 minute to thoroughly remove the dilution solvent, forming a second adhesive layer with a thickness of 20 μm on the first resin film.

[0125] The main surface of the resin film with a metal layer, where the metal layer is not formed (the main surface of the resin film), and the main surface exposed in the second adhesive layer formed on the release sheet (the main surface not in contact with the release sheet) were laminated together. Subsequently, by curing for 7 days under conditions of 23°C and 50% RH, a window film having the structure of release sheet / second adhesive layer / first resin film / metal layer / first adhesive layer / second resin film was obtained.

[0126] (Examples 2 to 4, Comparative Example 1) A window film was manufactured in the same manner as in Example 1, except that the first and second adhesive layers were formed using adhesive compositions P1 to P5, which contained (meth)acrylic acid ester polymer (A) with the mass ratio of monomers used in copolymerization and weight-average molecular weight as shown in Table 1, and other additives in the amounts shown in Table 1. The composition of the manufactured window film is shown in Table 2.

[0127] [Table 1]

[0128] Details of the abbreviations and other terms listed in Table 1 are as follows: ((meth)acrylic acid ester polymer (A)) 2EHA: 2-ethylhexyl acrylate MMA: Methyl methacrylate HEA: 2-hydroxyethyl acrylate BA: n-butyl acrylate ACMO:N-Acryloylmorpholine IBXA: Isobornyl Acrylate MA: Methyl acrylate Vac: vinyl acetate AA: Acrylic acid 4HBA: 4-hydroxybutyl acrylate i-BA: Isobutyl Acrylate MAA: Methacrylic acid HEMA: 2-hydroxyethyl methacrylate (Crosslinking agent (B)) B1: Tolylene diisocyanate-based crosslinking agent (manufactured by Toyo Chem Co., Ltd., product name "BHS-8515") B2: Hexamethylene diisocyanate crosslinking agent (manufactured by Toyo Chem Co., Ltd., product name "BXX6105") B3: Xylylene diisocyanate crosslinking agent (manufactured by Soken Chemical Co., Ltd., product name "TD-75") (Silane coupling agent (C)) C1:3-Glycidyloxypropyltrimethoxysilane (Shin-Etsu Silicone Co., Ltd., KBM403)

[0129] [Table 2]

[0130] The following evaluations were performed using the adhesive layers and window films prepared in the examples and comparative examples.

[0131] (Evaluation of the gel fraction of the adhesive) A coating solution of Adhesive Compositions 1 to 5 was applied onto a release sheet, and the diluting solvent was removed by drying to form an adhesive. The prepared adhesive was cut into a size of 50 mm × 50 mm. Next, the release sheet was removed, the adhesive was wrapped with a polyester mesh (product name: Tetoron Mesh #200), and its mass was weighed using an analytical balance. The mass of only the adhesive was calculated by subtracting the mass of the above mesh alone from the weighing value. The mass at this time was designated as M1.

[0132] Next, the adhesive wrapped with the above polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. Then, the mesh was taken out, air-dried for 24 hours in an environment of 23°C and 50% relative humidity, and further dried in an oven at 80°C for 12 hours. After drying, its mass was weighed using an analytical balance. The mass of only the adhesive was calculated by subtracting the mass of the above mesh alone from the weighing value. The mass at this time was designated as M_{2}. Using the obtained M1 and M2, the gel fraction was calculated from the following formula. The results are shown in Table 1. Gel fraction (%) = (M_{2} / M_{1}) × 100

[0133] (Total light transmittance, haze value, and chromaticity of the window film) The release sheet was peeled off from the window films obtained in the examples and comparative examples, and in an environment of 23°C and 50% RH (relative humidity), the exposed adhesive layer was attached to a float glass plate with a thickness of 3 mm, and this was used as a measurement sample. After performing background measurement with the float glass plate, for the above measurement sample, in accordance with JIS K736-1:1997, the total light transmittance of the window film was measured using a spectrophotometric haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., SH7000). Also, for the above measurement sample, in accordance with JIS K7136:2000, the haze value of the window film was measured using a spectrophotometric haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., SH7000). Furthermore, for the above measurement sample, using a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., COH300A), in transmitted light, CIE1976L * a * b * The chromaticity a defined by the color system* and chromaticity b * The following measurements were taken. The results are shown in Table 2.

[0134] (Evaluation of lightfastness of window film and color after lightfastness test) For the measurement samples in which chromaticity was measured, a lightfastness tester (manufactured by Suga Test Instruments Co., Ltd., product name "Ultraviolet Fade Meter U48") was used to apply ultraviolet light with a spectral irradiance peak at a wavelength of 380 nm from the float glass plate side, and an irradiance of 500 W / m² at wavelengths of 300-700 nm. 2 The samples were irradiated for 1000 hours. The lightfastness of the first adhesive layer of the irradiated sample was evaluated according to the following criteria. In addition, the chromaticity a of the irradiated sample was evaluated using the same method as above. * and chromaticity b * The following measurements were taken. The results are shown in Table 2. 〇:a * and b * In all cases, no change of 1 or more occurred before and after UV irradiation. ×:a * and b * At least one of these values ​​showed a change of 1 or more before and after UV irradiation.

[0135] (Interlayer adhesion between the metal layer and the first adhesive layer) From the obtained window film, the release sheet was peeled off, and a laminate sample was prepared by heat laminating (70°C, 1 m / min) the good-adhesion side of a 25 μm thick good-adhesion PET (Toyobo Co., Ltd., PET25A-4100) onto the exposed second adhesive layer surface. The obtained laminate sample was cut into 25 mm wide strips to prepare a sample for measurement. Next, the back side of the good-adhesion PET of the measurement sample (the main surface opposite to the main surface to which the adhesive layer was bonded) was fixed to a rigid support plate with double-sided tape, and a laminate consisting of a rigid support, double-sided tape, good-adhesion PET, second adhesive layer, first resin film, metal layer, first adhesive layer, and second resin film was prepared.

[0136] For the laminate in question, a universal tensile testing machine (Shimadzu Corporation Autograph® AG-IS) was used to peel the second resin film and the first adhesive layer from the metal layer at a measurement distance of 100 mm, a peeling angle of 180°, and a peeling speed of 0.3 m / min. The load at which this occurred was measured. The average load over a 80 mm period, excluding the loads at the first 10 mm and the last 10 mm of the measurement distance, was defined as the interlayer adhesion strength between the metal layer and the first adhesive layer. The results are shown in Table 2.

[0137] (Adhesion strength between the second resin film and the first adhesive layer) A laminated sample was prepared by forming an adhesive layer with the same thickness as the first adhesive layer (10 μm) on the same PET film as the second resin film used in the example, and then attaching the same PET film as the second resin film used in the example to the exposed surface of the first adhesive layer. The obtained laminated sample was cut into 25 mm widths to prepare a sample for measurement. Next, the back side of the PET film that was later attached to the measurement sample (the main surface opposite to the main surface to which the adhesive layer was attached) was fixed to a rigid support plate with double-sided tape, and a laminate consisting of a rigid support, double-sided tape, PET film, an adhesive layer corresponding to the first adhesive layer, and PET film was prepared.

[0138] For the laminate in question, a universal tensile testing machine (Shimadzu Corporation Autograph® AG-IS) was used to peel off the PET film and the portion of the adhesive layer corresponding to the first adhesive layer at a measurement distance of 100 mm, a peeling angle of 180°, and a peeling speed of 0.3 m / min. The load at which this occurred was measured. The average value of the load over 80 mm, excluding the load at the first 10 mm and the load at the last 10 mm of the measurement distance, was defined as the adhesive strength of the first adhesive layer to the PET film. The results are shown in Table 2.

[0139] Table 2 confirms that the window film in the example exhibits excellent light resistance. [Industrial applicability]

[0140] The window film of the present invention can be suitably used, for example, as an adhesive film having a layer containing metal while exhibiting excellent light resistance. [Explanation of Symbols]

[0141] 1… Window film 11…First resin film 12…Second resin film 21...First adhesive layer (first tack layer) 22...Second adhesive layer (second tack layer) 30…Layer containing metal

Claims

1. It comprises a first resin film, a second resin film, a layer containing metal, and a first adhesive layer containing a first acrylic polymer. Between one main surface of the first resin film and one main surface of the second resin film, one main surface of the metal-containing layer and one main surface of the first adhesive layer are laminated in contact. A window film in which, when the mass of the first acrylic polymer is taken as 100% by mass, the total proportion of units derived from monomers containing a carboxyl group and units derived from monomers having a carboxylic acid anhydride structure is 0.025% by mass or less.

2. The window film according to claim 1, wherein the interlayer adhesive strength between one main surface of the metal-containing layer and one main surface of the first adhesive layer is 5 N / 25 mm or more.

3. The window film according to claim 1 or 2, wherein when the mass of the first acrylic polymer is 100% by mass, the content of units derived from monomers containing hydroxyl groups is 11% by mass or more.

4. A second adhesive layer containing a second acrylic polymer is disposed on the other main surface of the first resin film, or on the other main surface of the second resin film. The window film according to claim 1 or 2, wherein when the mass of the second acrylic polymer is 100% by mass, the total proportion of units derived from monomers containing carboxyl groups or monomers having a carboxylic acid anhydride structure is 0.025% by mass or less.

5. The window film according to claim 4, wherein the constituent units of the first acrylic polymer and the constituent units of the second acrylic polymer are the same.

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