Window film

Abstract

The invention provides a window film which has high visible light transmittance and heat ray shielding rate and also has improved constructability. A window film in which a low-refractive-index layer, a hard coat layer, a substrate, a heat-ray shielding layer, and an adhesive layer are laminated in this order, the low-refractive-index layer being formed from a composition for forming a low-refractive-index layer containing hollow silica particles and an active-energy-ray-curable component, the heat ray shielding layer is formed from a heat ray shielding layer-forming composition containing an infrared shielding metal oxide and an active energy ray-curable component.

Description

Technical Field

[0001] The present invention relates to a window film. Background Art

[0002] In recent years, window films applied to building and vehicle windows have become widely used. These films have infrared shielding properties, for example, that inhibit the intrusion of infrared rays, preventing excessive temperature rises inside buildings and vehicles, thereby reducing the use of air conditioners and achieving energy savings.

[0003] On the other hand, window films used for vehicle windows, particularly windshields and front side glasses, require high visibility, and therefore require high visible light transmittance.

[0004] Patent Document 1 discloses a heat-shielding window film comprising a metal particle layer that reflects heat rays. When the window film is provided on window glass, a low-refractive-index layer having a refractive index within a specific range is provided on the outermost surface of one side indoors. This reduces the refractive index difference at the interface between air and the film, thereby reducing light reflection. Furthermore, the low-refractive-index layer is sometimes preferably hard-coated. Furthermore, Patent Document 1 describes a hard-coat layer that may contain a heat-ray absorber and may be provided between the low-refractive-index layer and the substrate.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-118281 Summary of the Invention

[0008] As described in Patent Document 1, there are cases where the low-refractive-index layer on the outermost surface has a hard-coat property, where the film has a heat-shielding hard-coat layer between the substrate and the low-refractive-index layer, and where the window film curls with the low-refractive-index layer facing inward. Curling can make it difficult to install the film on the window, leading to reduced work efficiency. This problem is particularly problematic with window films used on vehicle windshields and front side windows, which are large in area and have curved glass surfaces, making installation difficult.

[0009] Therefore, an object of the present invention is to provide a window film having high visible light transmittance and heat ray shielding rate and improved workability.

[0010] In order to achieve at least one of the above-mentioned objects, a window film reflecting one aspect of the present invention has the following configuration.

[0011] (1) A window film comprising a low refractive index layer, a hard coat layer, a substrate, a heat ray shielding layer, and an adhesive layer laminated in this order, wherein the low refractive index layer is formed from a low refractive index layer-forming composition comprising hollow silica particles and an active energy ray-curable component, and the heat ray shielding layer is formed from a heat ray shielding layer-forming composition comprising an infrared shielding metal oxide and an active energy ray-curable component.

[0012] (2) The window film according to (1), wherein the thickness of the substrate is 100 μm or less.

[0013] (3) The window film according to (1) or (2), wherein the low refractive index layer is an outermost layer.

[0014] (4) The window film according to any one of (1) to (3), wherein the infrared shielding metal oxide is at least one selected from the group consisting of indium-doped tin oxide, antimony-doped tin oxide, and cesium-doped tungsten oxide.

[0015] (5) The window film according to any one of (1) to (4), wherein the hard coat layer and the heat ray shielding layer are arranged adjacent to the substrate.

[0016] (6) The window film according to any one of (1) to (5), wherein the low refractive index layer and the hard coat layer are arranged adjacent to each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a cross-sectional view of a window film according to one embodiment of the present invention. DETAILED DESCRIPTION

[0018] The present invention provides a window film comprising a low-refractive-index layer, a hard coat layer, a substrate, a heat-ray-shielding layer, and an adhesive layer laminated in this order. The low-refractive-index layer is formed from a low-refractive-index layer-forming composition containing hollow silica particles and an active-energy-ray-curable component, and the heat-ray-shielding layer is formed from a heat-ray-shielding layer-forming composition containing an infrared-shielding metal oxide and an active-energy-ray-curable component. The window film of the present invention provides a window film having high visible light transmittance and heat-ray shielding rate, while also improving workability.

[0019] Window films (hereinafter referred to simply as films) are often attached using water stickers. Water stickers are a method in which a construction liquid (e.g., an aqueous surfactant solution) is sprayed onto the adhesive layer of the film and / or the surface of the window glass to temporarily attach the window film to the window glass. The film surface is then evenly wiped with a scraper called a scraper, squeezing out the construction liquid to remove it while the film is adhered to the window glass. The film becomes sticky due to water evaporation. In order to prevent scratches caused by the scraper treatment, the surface of the film is sometimes hard-coated. The inventors of the present application have discovered that when a hard-coated low-refractive index layer is provided on the surface, the window film curls up with the low-refractive index layer facing inward (e.g., the comparative example described later). The inventors of the present application speculate that this may be because, after the low-refractive index layer-forming composition is applied, ultraviolet curing is performed, which causes curing shrinkage. Based on this assumption, the present invention was completed by discovering a window film that suppresses curling of the window film and has high visible light transmittance and heat ray shielding rate by forming a UV-curable heat ray shielding layer that causes cure shrinkage on the opposite side of the substrate of the low refractive index layer.

[0020] In this specification, "X to Y" in a range means "X or greater and Y or less." Unless otherwise specified, operations and property measurements were performed at room temperature (20-25°C) and a relative humidity of 45-55% RH. Furthermore, in this specification, "(meth)acrylic acid" means "acrylic acid or methacrylic acid," and "(meth)acrylate" means "acrylate or methacrylate."

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the accompanying drawings, identical elements are denoted by identical reference numerals, and duplicate descriptions are omitted. Furthermore, for ease of description, the dimensional ratios in the drawings may be exaggerated and may differ from the actual ratios.

[0022] Figure 1 1 is a cross-sectional view of a window film according to an embodiment of the present invention. For convenience of explanation, the drawings are sometimes exaggerated, and the dimensional ratios of the components in the drawings are different from the actual ones. Figure 1In the embodiment, the window film 10 is composed of a low-refractive index layer 11, a hard coat layer 12, a substrate 13, a heat ray shielding layer 14, an adhesive layer 15, and a release liner 16. The adhesive layer 15 is provided to bond the window glass, which is the adherend, to the window film. The low-refractive index layer 11 is the outermost layer. Since the low-refractive index layer 11 contains an active energy ray-curable resin, even if it is placed on the outermost layer, it can prevent scratches caused by scraping. At the same time, by being placed on the outermost layer, the visible light transmittance can be further improved. In addition, the hard coat layer 12 and the heat ray shielding layer 14 are placed adjacent to the substrate 13. This arrangement is preferred because the curing shrinkage of both sides of the substrate is the same, which suppresses curling of the window film. The release liner 16 is a component that protects the adhesive layer 15 and has the function of preventing a decrease in adhesion. In addition, the release liner 16 peels off from the window film when attached to the adherend. Therefore, a window film without a release liner 16 is also within the technical scope of the present invention. Window film can be attached to either the indoor (inside the vehicle) or outdoor (outside the vehicle) side of the window glass. However, it is preferably attached to the indoor (inside the vehicle) side of the window glass for durability reasons. When the window film is attached to the indoor (inside the vehicle) side of the window glass, the side with the adhesive layer is the side where (sun)light enters.

[0023] Figure 1 In the form of, the window film 10 is composed of a low refractive index layer 11, a hard coating layer 12, a substrate 13, a heat ray shielding layer 14, an adhesive layer 15, and a release liner 16. As long as the low refractive index layer 11, the hard coating layer 12, the substrate 13, the heat ray shielding layer 14, the adhesive layer 15, and the release liner 16 are arranged in this order, other functional layers (such as a printing layer, an antistatic layer, a adhesion improvement layer, a light shielding layer, a stress relaxation layer, an antifog layer, an antifouling layer, and an ultraviolet reflection layer, etc.) may be present between the layers. In addition, as Figure 1 The low refractive index layer 11 and the hard coating layer 12 are arranged in a manner adjacent to each other, which is also a suitable form. This configuration is preferred from the perspectives of improving visible light transmittance, ensuring scratch resistance, and thinning the film.

[0024] Hereinafter, components constituting the window film of the present invention will be described.

[0025] (Low refractive index layer)

[0026] The low refractive index layer is formed from a low refractive index layer-forming composition containing hollow silica particles and an active energy ray-curable component. The inclusion of hollow silica particles can exhibit antireflection properties by utilizing the refractive index difference between air and the particles.

[0027] Hollow silica particles have microscopic voids in the particle in an open state or a closed state. Since the hollow silica particles are filled with gas (air) in the above-mentioned voids, the refractive index is low and the reflection of light can be reduced. The shape of the hollow silica particles is not particularly limited, but preferably spherical, spindle-shaped, egg-shaped, flat, cubic, amorphous, etc. Among them, spherical, flat, cubic, etc. are particularly preferred. The hollow silica particles can have independent bubbles or continuous bubbles. In addition, they can also have both independent bubbles and continuous bubbles. For purposes such as improving dispersibility, the hollow silica particles can be modified by organic matter. In addition, the hollow silica particles are also preferably in the form of an organosol (colloidal) (hollow silica sol).

[0028] In the hollow silica particles, the proportion of voids is preferably 5% or more of the volume, preferably 10 to 80%, and more preferably 20 to 60%.

[0029] The average particle size of the hollow silica particles is preferably from 5 nm to 100 nm. It is more preferably from 20 nm to 80 nm, and even more preferably from 40 nm to 70 nm. When the average particle size of the hollow silica particles is within this preferred range, excellent antireflection effects and transparency of the low refractive index layer can be achieved. The average particle size is a volume-based arithmetic average value obtained using a laser diffraction / scattering method.

[0030] The refractive index of the hollow silica particles is preferably in the range of 1.01 to 1.45. It is more preferably in the range of 1.15 to 1.38, and even more preferably in the range of 1.15 to 1.35. Within this range, an excellent anti-reflection effect can be achieved. The refractive index of the hollow silica particles herein is measured using the minimum deviation angle method.

[0031] From the viewpoint of excellent antireflection effect, the content of the hollow silica particles in the low refractive index layer is preferably 20 to 80% by mass, more preferably 30 to 60% by mass.

[0032] Examples of active energy ray-curable components include multifunctional (meth)acrylate monomers, (meth)acrylate prepolymers, and active energy ray-curable polymers. One of these compounds may be used alone, or two or more thereof may be used simultaneously. Among these, the active energy ray-curable component used in the low-refractive index layer-forming composition is preferably a multifunctional (meth)acrylate monomer and / or a (meth)acrylate prepolymer.

[0033] Examples of the multifunctional (meth)acrylate monomer include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, dicyclopentyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, di(acryloyloxyethyl) isocyanurate, allyl cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1,2-diol-1

[0014] Bifunctional monomers include trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloyloxyethyl)isocyanurate, and ε-caprolactone-modified tris(2-(meth)acryloyloxyethyl)isocyanurate; tetrafunctional monomers include diglycerol tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional monomers include propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional monomers include dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. These multifunctional (meth)acrylate monomers may be used alone or in combination of two or more. Among them, from the viewpoint of the hardness of the low refractive index layer to be formed, the polyfunctional (meth)acrylate monomer is preferably trifunctional or higher, and particularly preferably tetrafunctional or higher.

[0034] Examples of the (meth)acrylate prepolymer include polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, and polyol (meth)acrylate prepolymers. Among these, urethane (meth)acrylate prepolymers are preferred from the perspectives of the hardness and curved surface adhesion of the resulting low-refractive-index layer.

[0035] The polyester (meth)acrylate prepolymer can be obtained, for example, by esterifying the hydroxyl groups of a polyester oligomer having hydroxyl groups at both terminals obtained by condensation of a polycarboxylic acid and a polyol with (meth)acrylic acid, or by esterifying the terminal hydroxyl groups of an oligomer obtained by adding an alkylene oxide to a polycarboxylic acid with (meth)acrylic acid.

[0036] The epoxy (meth)acrylate-based prepolymer can be obtained by, for example, reacting and esterifying an oxirane ring of a relatively low-molecular-weight bisphenol-type epoxy resin or a novolac-type epoxy resin with (meth)acrylic acid.

[0037] The urethane (meth)acrylate-based prepolymer can be obtained by esterifying a polyurethane oligomer obtained by a reaction between a polyether polyol or a polyester polyol and a polyisocyanate with (meth)acrylic acid, for example.

[0038] The polyol acrylate-based prepolymer can be obtained, for example, by esterifying the hydroxyl group of polyether polyol with (meth)acrylic acid.

[0039] The above-mentioned prepolymers may be used alone or in combination of two or more.

[0040] In consideration of hard coating properties, the content of the active energy ray-curable component in the low refractive index layer-forming composition is preferably 20 to 80% by mass, more preferably 40 to 70% by mass, based on solid content.

[0041] In addition to the above-mentioned components, the low refractive index layer forming composition can also contain various additives. As various additives, for example, photopolymerization initiator, surface conditioning agent, leveling agent, antifouling agent, dispersant, ultraviolet absorber, antioxidant, light stabilizer, antistatic agent, silane coupling agent, anti-aging agent, thermal polymerization inhibitor, colorant, refractive index adjuster, surfactant, storage stabilizer, plasticizer, lubricant, defoamer, organic filling material, wettability improver, coating modifier etc. can be listed. In addition, the low refractive index layer forming composition optionally includes the following infrared shielding metal oxide. Specifically, the low refractive index layer forming composition optionally includes zinc oxide, tungsten oxide, antimony-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide, tin oxide, antimony-doped tin oxide (ATO), indium-doped tin oxide (ITO), cesium-doped tungsten oxide (CWO (registered trademark)) etc. As a scheme, the low refractive index layer forming composition preferably does not contain the following infrared shielding metal oxide substantially. Specifically, the low refractive index layer forming composition is preferably substantially free of any one of zinc oxide, tungsten oxide, antimony-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide, tin oxide, antimony-doped tin oxide (ATO), indium-doped tin oxide (ITO), and cesium-doped tungsten oxide (CWO (registered trademark)). Here, substantially free of means that the content in the layer is 0.1% by mass or less (lower limit 0% by mass), preferably 0.01% by mass or less (lower limit 0% by mass), and more preferably 0.001% by mass or less (lower limit 0% by mass).

[0042] Examples of the photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propane-1-one, 4-(methylthio)phenyl)-2-morpholino-propane-1-one, and 4-(methylthio)phenyl)-2-morpholino-propane-1-one. -(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, etc. These photopolymerization initiators may be used alone or in combination of two or more.

[0043] The content of the photopolymerization initiator in the low-refractive-index layer-forming composition is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, relative to 100 parts by mass of the active-energy-ray-curable component.

[0044] Taking the refractive index into consideration, the thickness of the low refractive index layer is preferably 20 to 300 nm, more preferably 40 to 200 nm, and even more preferably 60 to 150 nm.

[0045] The pencil hardness of the low refractive index surface of the window film when the low refractive index layer is arranged on the outermost layer is preferably F or more, preferably H or more, and more preferably 2H or more. By making the low refractive index layer have such a pencil hardness, the surface of the window film has sufficient hardness and can exert excellent scratch resistance. The upper limit of the above pencil hardness is not particularly limited, but is preferably 9H or less. In addition, the method for measuring the pencil hardness uses an electric pencil scratch hardness tester (manufactured by YASUDA SEIKISEISAKUSHO, LTD., product name "No.553-M1") and is based on JIS K5600-5-4:1999.

[0046] (Hard Coating)

[0047] A hard coat layer is provided to improve scratch resistance. Since the low refractive index layer is generally thin to the order of nanometers by controlling the refractive index, scratch resistance can be ensured by further providing a hard coat layer.

[0048] The hard coat layer is, for example, a cured product of a hard coat agent (composition for forming a hard coat layer). The hard coat agent generally contains an active energy ray-curable component.

[0049] As active energy ray curing components, polyfunctional (meth) acrylate monomers, (meth) acrylate prepolymers, active energy ray curing polymers, etc. can be listed. One of these compounds can be used alone, or two or more can be used simultaneously. Among them, as active energy ray curing components for hard coat layer forming compositions, polyfunctional (meth) acrylate monomers and / or (meth) acrylate prepolymers are preferably used. Polyfunctional (meth) acrylate monomers and (meth) acrylate prepolymers can be used alone, or both can be used simultaneously. For its specific examples and preferred embodiments, they are the same as those described in the above-mentioned low refractive index layer section. In addition, the active energy ray curing component for the hard coat layer forming composition can be the same material as the active energy ray curing component for the low refractive index layer forming composition, or it can be a different material.

[0050] In consideration of hard coating properties, the content of the active energy ray-curable component in the hard coating agent is preferably 70 to 100% by mass, more preferably 75 to 99% by mass, in terms of solid content.

[0051] In addition to the above components, hard coat layer can also contain various additives. As various additives, for example, it can also be made to contain photopolymerization initiator, stabilizer, surfactant, ultraviolet absorber, flame retardant, antistatic agent, antioxidant, heat stabilizer, lubricant, filler, colorant, pigment, adhesion regulator etc. In the present invention, due to the presence of heat ray shielding layer, therefore on hard coat layer, not necessarily further need infrared shielding agents such as infrared shielding metal oxide or infrared absorber, can include infrared shielding agent, also can be substantially free of infrared shielding agent. Specifically, hard coat layer formation composition optionally includes zinc oxide, tungsten oxide, antimony-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide, tin oxide, antimony-doped tin oxide (ATO), indium-doped tin oxide (ITO), cesium-doped tungsten oxide (CWO (registered trademark)) etc. Here, “substantially free” means that the content in the layer is 0.1% by mass or less (lower limit 0% by mass), preferably 0.01% by mass or less (lower limit 0% by mass), and more preferably 0.001% by mass or less (lower limit 0% by mass).

[0052] Specific examples of the photopolymerization initiator that can be used in the hard coat agent include the photopolymerization initiators described in the section on the low refractive index layer.

[0053] The content of the photopolymerization initiator in the hard coating agent is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, relative to 100 parts by mass of the active energy ray-curable component.

[0054] From the viewpoint of scratch resistance and film hardness, the thickness of the hard coat layer is preferably 0.1 to 20 μm, more preferably 0.5 to 10 μm, and even more preferably 1 to 5 μm.

[0055] The pencil hardness of the hard coat layer is preferably F or higher, preferably H or higher, and more preferably 2H or higher. By ensuring that the hard coat layer has this pencil hardness, a balance can be achieved with the hardness of the laminate of the low refractive index layer and the hard coat layer, effectively suppressing curling. The pencil hardness of the hard coat layer can be determined by exposing the hard coat layer and measuring the pencil hardness of the hard coat surface.

[0056] (Base material)

[0057] The material forming the substrate is not particularly limited, but a resin substrate is preferably used. The substrate may be a single layer or a laminated film of two or more layers.

[0058] The resin substrate may be a stretched film such as a uniaxially stretched film or a biaxially stretched film, or may be a non-stretched film, or may be formed using an engineering material by a casting method or the like.

[0059] From the perspective of visibility, the substrate is preferably transparent. Transparency here means a total light transmittance of 80% or greater, preferably 90% or greater (with an upper limit of 100%). The substrate transmittance can be measured in accordance with JIS K7361-1:1997 (Test method for total light transmittance of plastic transparent materials).

[0060] As the material constituting the resin substrate, there is no particular limitation, for example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate can be listed; polyolefin resins such as polyethylene, polypropylene, poly (4-methyl-1-pentene), and poly-1-butene; cellulose resins such as cellophane, diacetyl cellulose, triacetyl cellulose, and acetyl cellulose butyrate; polyvinyl chloride resin; polyvinylidene chloride resin; polyvinyl alcohol resin; polystyrene resin; polycarbonate resin; polysulfone resin; fluorine resin; acrylic resin; cyclic olefin resins such as norbornene resin; polyamide resin; styrene resin, etc. These materials constituting the resin substrate can be used alone or in combination of two or more. Among them, from the perspective of transparency, the material constituting the resin substrate is preferably a polyester resin or a polyolefin resin, more preferably polyethylene terephthalate, polyethylene, and polypropylene, and further preferably polyethylene terephthalate.

[0061] The substrate may be in the form of a resin substrate with a primer layer provided thereon. The primer layer may be formed on one or both sides of the resin substrate. For example, acrylic, polyester, polyurethane, or rubber-based primer layers may be suitably used as the primer layer. The thickness of the primer layer may be, for example, 0.1 to 10 μm, or 0.5 to 5 μm.

[0062] The base material may contain stabilizers, lubricants, fillers, colorants, processing aids, softeners, metal powders, antifogging agents, ultraviolet absorbers, antioxidants, antistatic agents, flame retardants, and the like as needed.

[0063] The thickness of the substrate is, for example, 5 to 150 μm. In order to facilitate the follow-up of the window glass as the adherend (curved surface followability), the thickness of the substrate is preferably 100 μm or less. From the perspective of curved surface followability, the thinner the substrate thickness, the better, but the thinner the substrate, the more serious the curling problem. However, according to this embodiment, even when the substrate is thin, for example, 100 μm or less, curling can be fully suppressed. The thickness of the substrate is preferably 10 to 100 μm, more preferably 10 to 50 μm, and even more preferably 10 to 30 μm.

[0064] (Heat ray shielding layer)

[0065] The heat ray shielding layer contains an infrared shielding metal oxide and an active energy ray-curable component.

[0066] From the perspective of visible light transmittance, infrared shielding metal oxide is preferably infrared absorptive. As infrared absorptive metal oxide, specifically zinc oxide, tungsten oxide, antimony-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), gallium-doped zinc oxide (GZO), aluminum-doped zinc oxide, tin oxide, antimony-doped tin oxide (ATO), indium-doped tin oxide (ITO), cesium-doped tungsten oxide (CWO (registered trademark)) etc. can be listed. These infrared shielding metal compounds can be used alone or in combination. Wherein, due to the high visible light transmittance, the infrared shielding metal compound is more preferably at least one selected from the group consisting of indium-doped tin oxide (ITO), antimony-doped tin oxide (ATO) and cesium-doped tungsten oxide (CWO (registered trademark)).

[0067] The content of the infrared shielding metal compound in the heat ray shielding layer can be appropriately set in consideration of the heat ray shielding effect and visible light transmittance, and is preferably 20 to 80 mass %, more preferably 40 to 75 mass %, and even more preferably 50 to 70 mass % in the heat ray shielding layer.

[0068] The heat ray shielding layer is formed from a heat ray shielding layer-forming composition containing an active energy ray-curable component.

[0069] As active energy ray curable components, polyfunctional (meth) acrylate monomers, (meth) acrylate prepolymers, active energy ray curable polymers, etc. can be listed. One of these compounds can be used alone, or two or more can be used at the same time. Among them, as active energy ray curable components for the heat ray shielding layer forming composition, polyfunctional (meth) acrylate monomers and / or (meth) acrylate prepolymers are preferred. Polyfunctional (meth) acrylate monomers and (meth) acrylate prepolymers can be used alone or both can be used at the same time. Its specific examples and preferred embodiments are the same as those described in the low refractive index layer section. The active energy ray curable component for the heat ray shielding layer forming composition can be the same material as the active energy ray curable component for the low refractive index layer forming composition and the active energy ray curable component for the hard coat layer forming composition, or it can be a different material.

[0070] Considering the balance with the hardness of the low refractive index layer and the hard coat layer, the content of the active energy ray-curable component in the heat ray shielding layer-forming composition is preferably 20 to 80% by mass, more preferably 30 to 50% by mass, based on solid content.

[0071] Taking into account the balance with the heat ray shielding effect and the low refractive index layer (curling suppression effect), the thickness of the heat ray shielding layer is preferably 1 to 10 μm.

[0072] The pencil hardness of the heat ray shielding layer is preferably F or higher, preferably H or higher, and more preferably 2H or higher. By ensuring that the heat ray shielding layer has this pencil hardness, a balance can be achieved with the hardness of the laminated body of the low refractive index layer and the hard coat layer, effectively suppressing curling. The pencil hardness of the heat ray shielding layer can be determined by exposing the heat ray shielding layer and measuring the pencil hardness of the heat ray shielding layer surface.

[0073] In consideration of curling suppression, the thicknesses of the hard coat layer and the heat ray shielding layer are preferably such that the thickness of the hard coat layer / the thickness of the heat ray shielding layer = 0.5 to 1.5, and more preferably 0.8 to 1.2.

[0074] In addition to the above components, the heat ray shielding layer may also contain various additives such as photopolymerization initiators, stabilizers, surfactants, ultraviolet absorbers, antistatic agents, antioxidants, heat stabilizers, lubricants, fillers, colorants, pigments, adhesion regulators, and the like.

[0075] Specific examples of the photopolymerization initiator that can be used in the heat ray shielding layer include the photopolymerization initiators described in the section on the low refractive index layer.

[0076] The content of the photopolymerization initiator in the heat ray shielding layer is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, relative to 100 parts by mass of the active energy ray-curable component.

[0077] (adhesive layer)

[0078] The adhesive layer may be used on the heat ray shielding layer side of the substrate.

[0079] The adhesive used for the adhesive layer is not particularly limited, and acrylic adhesives, rubber adhesives, silicone adhesives, urethane adhesives, polyester adhesives, styrene-diene block copolymer adhesives, vinyl alkyl ether adhesives, polyamide adhesives, fluorine-based adhesives, etc. can be used. These adhesives can be used alone or in combination of two or more.

[0080] From the viewpoint of reliability of adhesion, acrylic adhesives are particularly preferably used as the adhesive.

[0081] By using an alkyl (meth)acrylate as the main monomer component and optionally using a monomer copolymerizable with the alkyl (meth)acrylate (copolymerizable monomer), an acrylic copolymer constituting an acrylic adhesive can be formed. Here, the main component refers to a monomer comprising 50% by mass or more (upper limit 100% by mass), and the preferred proportions of the alkyl (meth)acrylate relative to the total monomer content are, in that order, 65% by mass or more, 85% by mass or more, and 90% by mass or more.

[0082] Examples of alkyl (meth)acrylates include 2-ethylhexyl (meth)acrylate, n-butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, and the like. These alkyl (meth)acrylates may be used alone or in combination of two or more. From the perspective of adhesive performance, the alkyl (meth)acrylate is preferably at least one selected from the group consisting of 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, and n-butyl (meth)acrylate, more preferably n-butyl (meth)acrylate, and even more preferably n-butyl acrylate.

[0083] When a cross-linking agent is used, it is preferred to further use a vinyl monomer containing a functional group reactive with the cross-linking agent (hereinafter also referred to as a cross-linkable functional group-containing vinyl monomer).

[0084] The functional group in the cross-linkable functional group-containing vinyl monomer varies depending on the cross-linking agent selected, and examples thereof include a carboxyl group, anhydride group, hydroxyl group, glycidyl group, amino group, amide group, and nitrile group. Among these, the cross-linkable functional group-containing vinyl monomer is preferably at least one selected from a carboxyl group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer, because it can ensure high cohesive force.

[0085] The crosslinkable functional group-containing vinyl monomer may be used alone or in combination of two or more.

[0086] Examples of the carboxyl group- or acid anhydride group-containing vinyl monomer include (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, itaconic anhydride, myristic acid, palmitoleic acid, and oleic acid. Among these, (meth)acrylic acid is preferred from the viewpoint of polymerizability.

[0087] As long as the hydroxyl-containing vinyl monomer has a polymerizable functional group with an unsaturated double bond such as (meth) acryloyl or vinyl and has a hydroxyl group, it is not particularly limited. From the perspective of copolymerizability with (meth) alkyl acrylate, the hydroxyl-containing vinyl monomer is preferably (meth) hydroxyalkyl acrylate. As (meth) hydroxyalkyl acrylate, 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 etc. can be listed. Wherein, from the perspective of crosslinking, it is preferred to use at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and 2-hydroxybutyl (meth) acrylate, more preferably 2-hydroxyethyl (meth) acrylate.

[0088] The content of the crosslinkable functional group-containing vinyl monomer in all monomers is preferably 0.1 to 20% by mass. When the content of the crosslinkable functional group-containing vinyl monomer is within the above range, the crosslinking density is appropriate and the adhesiveness is maintained.

[0089] The molecular weight of the acrylic copolymer is not particularly limited, and the weight average molecular weight (Mw) can be, for example, 100,000 to 2,000,000, or 200,000 to 1,000,000. In this specification, the weight average molecular weight (Mw) is the value measured by gel permeation chromatography (GPC) using a standard polystyrene-equivalent molecular weight.

[0090] The method for preparing the acrylic copolymer is not particularly limited, and conventionally known methods such as solution polymerization, emulsion polymerization, suspension polymerization, reverse phase suspension polymerization, thin film polymerization, and spray polymerization using a polymerization initiator can be employed. Furthermore, in addition to methods initiating polymerization using a polymerization initiator, methods initiating polymerization by irradiation with radiation, electron beams, ultraviolet rays, and the like can also be employed.

[0091] The adhesive may be formed from an adhesive composition. The content (solid content) of the acrylic copolymer in the adhesive composition is preferably 50 to 100% by mass, more preferably 60 to 100% by mass.

[0092] In addition to the acrylic copolymer, the adhesive composition may further include a cross-linking agent. Examples of the cross-linking agent include isocyanate cross-linking agents, epoxy cross-linking agents, and metal chelate cross-linking agents. The amount of the cross-linking agent added is preferably 0.001 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the acrylic copolymer. The cross-linking agent may be used alone or in the form of a mixture of two or more.

[0093] The adhesive composition may further contain other conventionally known additives. Examples of such additives include fillers, pigments, ultraviolet absorbers, and thickeners. Examples of fillers include zinc oxide, silicon dioxide, and calcium carbonate.

[0094] The thickness of the adhesive layer may generally be 5 to 100 μm, or may be 5 to 50 μm.

[0095] (Release liner)

[0096] The release liner is a component that protects the adhesive layer and has the function of preventing the adhesiveness from decreasing. In addition, the release liner peels off from the adhesive sheet when attached to the adherend. Therefore, the window film in the present invention also includes the case where it does not have a release liner.

[0097] The release liner is not particularly limited, and examples thereof include plastic films such as polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polypropylene and polyethylene; and papers such as high-quality paper, glassine paper, kaolin-coated paper, and polyethylene-laminated paper.

[0098] The thickness of the release liner is generally about 10 to 400 μm. Furthermore, a layer of a release agent such as silicone may be provided on the surface of the release liner to enhance the releasability of the adhesive layer. When such a layer is provided, the thickness is generally about 0.01 to 5 μm.

[0099] <Manufacturing method>

[0100] As a method for manufacturing a window film, for example, it is preferred to form a hard coating layer 12 and a low refractive index layer 11 in this order on one side of a substrate 13, and then form a heat ray shielding layer 14 on the side of the substrate 13 opposite to the low refractive index layer 11. Alternatively, it is preferred to form the heat ray shielding layer 14 on one side of the substrate 13, and then form a hard coating layer 12 and a low refractive index layer 11 in this order on the side of the substrate 13 opposite to the heat ray shielding layer 14.

[0101] Specifically, for example, a hard coating agent may be applied to the substrate 13 and then cured by, for example, ultraviolet light to form the hard coating layer 12. Subsequently, a low-refractive index layer-forming composition may be applied to the hard coating layer 12 and then cured by, for example, ultraviolet light to form the low-refractive index layer 11. Furthermore, a heat-ray shielding layer 14 may be formed by applying, for example, a heat-ray shielding layer-forming composition to the surface of the substrate 13 opposite to the low-refractive index layer 11 and curing it by, for example, ultraviolet light.

[0102] The low-refractive-index layer-forming composition, hard coat agent, and heat-ray-shielding-layer-forming composition may contain a solvent as needed. Examples of the solvent include esters such as ethyl acetate and butyl acetate; ketones such as methyl isobutyl ketone, methyl ethyl ketone, and cyclohexanone; and aromatic hydrocarbons such as toluene and xylene. These solvents may be used alone or in combination of two or more.

[0103] The coating method of the low refractive index layer-forming composition, the hard coating agent, and the heat ray shielding layer-forming composition is not particularly limited. For example, coating can be performed using a known coating apparatus such as a roll coater, a knife coater, an air knife coater, a rod coater, a blade coater, a slit coater, a lip coater, or a gravure coater.

[0104] Each composition may be dried after application. Drying conditions are not particularly limited, and may be performed at 80 to 120° C. for 30 seconds to 2 minutes, for example.

[0105] Examples of ultraviolet irradiation sources include mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, metal halide lamps, and LEDs. Furthermore, the amount of ultraviolet irradiation is not particularly limited as long as a cured product can be formed. Typically, the cumulative amount of light is between 10 and 2000 mJ / cm 2 within the range.

[0106] The method for forming the adhesive layer is not particularly limited. The adhesive layer may be formed by directly coating the adhesive composition on the heat ray shielding layer. Alternatively, the adhesive layer may be formed on a release liner and then bonded to the heat ray shielding layer surface of a laminate of a low refractive index layer-hard coat layer-substrate-heat ray shielding layer.

[0107] The method for applying the adhesive composition to the substrate or release liner is not particularly limited, and can be applied using, for example, a roll coater, knife coater, air knife coater, rod coater, blade coater, slot coater, lip coater, gravure coater, or other known coating apparatus. Drying conditions are not particularly limited, but are generally performed at 60 to 150° C. for 10 to 60 seconds.

[0108] The thickness of the adhesive layer (film thickness after drying) is usually 5 to 100 μm, preferably 10 to 50 μm.

[0109] (Visible light transmittance)

[0110] The visible light transmittance of the window film is preferably 60% or higher (upper limit 100%), more preferably 70% or higher, and even more preferably 80% or higher. By ensuring that the visible light transmittance is above this lower limit, high visibility can be ensured even when attached to a vehicle's windshield or front side glass. Visible light transmittance can be measured using the method described in the Examples.

[0111] (Infrared reflectivity)

[0112] From the perspective of heat shielding performance, the infrared reflectivity of the window film is preferably 30% or less, more preferably 20% or less. In addition, the infrared reflectivity can be measured by the method described in the Examples.

[0113] (use)

[0114] The window film of the present invention can be attached to the windows of buildings, vehicles (such as vehicles), etc. As vehicles, for example, cars, trams, streetcars, etc. can be listed. When the window film is attached to the window of an automobile, as the window glass of the automobile to be attached, the front windshield, rear windshield, front triangular window glass, front door glass, rear door glass, rear triangular window glass, rear side window glass, etc. can be listed. Wherein, due to the requirement of transparency, the window glass of the automobile to be attached is preferably the front windshield, front triangular window glass, front door glass. In addition, as the material constituting the window, for example, it is suitable for glass, glass substitutes for resin, etc. As glass substitutes for resin, there is no particular limitation, and polycarbonate resin, polysulfone resin, acrylic resin, polyolefin resin, polyether resin, polyester resin, polyamide resin, polysulfide resin, unsaturated polyester resin, epoxy resin, melamine resin, phenolic resin, diallyl phthalate resin, polyimide resin, styrene resin, vinyl chloride resin, etc. can be listed.

[0115] The method of attaching the window film can be, for example, by using a so-called water sticker. Specifically, the water sticker is to impart an aqueous medium to at least one of the contact surfaces of the film, so that the adhesive layer contacts the adherend, and the aqueous medium is removed as needed. The aqueous medium is a medium used as a construction fluid. The aqueous medium refers to a medium containing 50% by mass or more (the upper limit is 100% by mass), preferably 70% by mass or more, and more preferably 85% by mass or more of water. The most preferred aqueous medium is water. In addition, in order to improve the lubricity between the adherend and the film, a surfactant is usually contained in the construction fluid of the water sticker.

[0116] Next, bring the adhesive layer of the film into contact with the adherend. That is, place the adhesive layer of the film on the adherend. At this point, remove the release liner. Using the aqueous medium (applying liquid), slide the adhesive film over the adherend while adjusting the window film application position.

[0117] Then, the aqueous medium is removed and the window film is attached to the adherend.

[0118] One method for removing (discharging) the aqueous medium between the adherend and the window film is to evenly wipe the film surface with a scraper to squeeze out the aqueous medium. This process squeezes out bubbles formed between the window film and the adherend and smoothes out any wrinkles on the window film.

[0119] Example

[0120] The effects of the present invention are illustrated using the following examples and comparative examples. In the examples, where "parts" or "%" are used, these values ​​represent "parts by mass" or "mass %" unless otherwise specified. All operations were performed at room temperature (25°C) unless otherwise specified.

[0121] (Example 1)

[0122] 1. Formation of hard coating

[0123] 100 parts by mass of a urethane acrylate prepolymer (manufactured by Arakawa Chemical Industries, Ltd., product name "BEAMSET 575CB") as an active energy ray-curable component and 3 parts by mass of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone as a photopolymerization initiator were mixed in a 1:1 (mass ratio) mixed solvent of cyclohexanone and methyl isobutyl ketone to obtain a coating liquid of a hard coat layer-forming composition.

[0124] The resulting coating liquid of the hard coat layer-forming composition was applied to a transparent PET film (25 μm thick, Cosmo Shine (registered trademark) A4360 (manufactured by TOYOBO CO., LTD.)) using a Meyer bar and dried at 90°C for 1 minute. Subsequently, under a nitrogen atmosphere, ultraviolet light was irradiated using an ultraviolet irradiation device (manufactured by EYE GRAPHICS CO., LTD., product name "EyeGrandage ECS-401GX") under the following conditions to form a hard coat layer having a thickness of 3 μm.

[0125] [Ultraviolet irradiation conditions]

[0126] Light source: high pressure mercury lamp

[0127] Lamp power: 2kW

[0128] Conveyor belt speed: 4.23m / min

[0129] Illumination: 300mW / cm 2

[0130] Light intensity: 250mJ / cm 2

[0131] 2. Formation of a low refractive index layer

[0132] 100 parts by mass of a urethane acrylate prepolymer (manufactured by Arakawa Chemical Industries, Ltd., product name "BEAMSET 575CB") as an active energy ray-curable component, 100 parts by mass (solid content) of a silica sol containing hollow silica particles (manufactured by JGC C&C., product name "THRULYA 4320", solid content 20.5%, solvent: methyl isobutyl ketone, average particle size of the hollow silica particles: 60 nm, refractive index 1.25), and 3 parts by mass of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone as a photopolymerization initiator were mixed in a 1:1 (mass ratio) mixed solvent of cyclohexanone and methyl isobutyl ketone to obtain a coating liquid of a composition for forming a low refractive index layer.

[0133] The resulting coating liquid of the low-refractive-index layer-forming composition was applied to the hard coat layer of the PET film-hard coat layer obtained in step 1 using a Meyer bar and dried at 90°C for 1 minute. Subsequently, under a nitrogen atmosphere, ultraviolet light was irradiated using an ultraviolet irradiation device (manufactured by EYEGRAPHICS CO., LTD., product name "Eye Grandage ECS-401GX") under the following conditions to form a low-refractive-index layer having a thickness of 100 nm.

[0134] [Ultraviolet irradiation conditions]

[0135] Light source: high pressure mercury lamp

[0136] Lamp power: 2kW

[0137] Conveyor belt speed: 4.23m / min

[0138] Illumination: 300mW / cm 2

[0139] Light intensity: 250mJ / cm 2

[0140] 3. Formation of heat ray shielding layer

[0141] 100 parts by mass of a urethane acrylate prepolymer (manufactured by Arakawa Chemical Industries, Ltd., product name "BEAMSET 575CB") as an active energy ray-curable component, 150 parts by mass of indium tin oxide (ITO) as an infrared shielding material, and 3 parts by mass of 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone as a photopolymerization initiator were mixed in a 1:1 (mass ratio) mixed solvent of cyclohexanone and methyl isobutyl ketone to obtain a coating liquid of a composition for forming a heat ray shielding layer.

[0142] The resulting coating liquid of the heat-ray shielding layer-forming composition was applied to the PET film opposite the low-refractive index layer of the film prepared in 1. using a Meyer bar and dried at 90°C for 1 minute. Subsequently, under a nitrogen atmosphere, ultraviolet light was irradiated using an ultraviolet irradiation device (manufactured by EYE GRAPHICS CO., LTD., product name "Eye Grandage ECS-401GX") under the following conditions to form a heat-ray shielding layer having a thickness of 3.0 μm.

[0143] [Ultraviolet irradiation conditions]

[0144] Light source: high-pressure mercury lamp

[0145] Lamp power: 2kW

[0146] Conveyor belt speed: 4.23m / min

[0147] Illumination: 300mW / cm 2

[0148] Light intensity: 250mJ / cm 2

[0149] 4. Formation of adhesive layer

[0150] To 100 parts by mass of a toluene solution (solid content: 40% by mass) of an acrylic copolymer (weight average molecular weight: 400,000) having a monomer composition of n-butyl acrylate (n-BA) / 2-hydroxyethyl methacrylate (2-HEMA) / methacrylic acid (MAAc) = 93.76 / 6.2 / 0.04 (mass ratio), 1 part by mass (solid content) of CORONATE (registered trademark) HL (manufactured by TOSOH CORPORATION) as an isocyanate crosslinking agent was added to obtain an adhesive composition.

[0151] The adhesive composition was applied to a release liner using a knife coater to a dry film thickness of 20 μm and dried to form an adhesive layer. This adhesive layer was then attached to the heat-shielding layer to produce a window film comprising a low-refractive-index layer-hard-coat layer-substrate-heat-shielding layer-adhesive layer-release liner.

[0152] (Example 2)

[0153] A window film was obtained in the same manner as in Example 1 except that a PET film (thickness: 125 μm, Cosmo Shine (registered trademark) A4360 (manufactured by TOYOBO CO., LTD.)) was used as the transparent substrate.

[0154] (Comparative Example 1)

[0155] A window film was obtained in the same manner as in Example 1 except that each layer was formed in the same manner as the laminated structure of low refractive index layer-heat ray shielding layer-base material-adhesive layer-release liner.

[0156] [Evaluation method 1: Visible light transmittance]

[0157] The window film after peeling off the release liner was measured using the test method described in JIS A5759:2016 (Film for Architectural Window Glass - Visible Light Transmittance Test). The measurement was performed with the glass surface of the test piece facing the light source.

[0158] [Evaluation method 2: Infrared reflectivity]

[0159] The window film after peeling off the release liner was measured for infrared reflectivity using a spectrophotometer (UV-3600 manufactured by Shimadzu Corporation), and the average infrared reflectivity at 780 to 2500 nm was defined as the infrared reflectivity.

[0160] [Evaluation method 3: curling]

[0161] (Evaluation of the Effect of Suppressing Curling of Adhesive Sheets)

[0162] The produced window film was cut into 10 cm×10 cm pieces and placed on a flat table with the release liner. The warping of the four corners of the window film from the table was observed and evaluated according to the following evaluation criteria.

[0163] ○: No change

[0164] △: Edge lifting occurs

[0165] ×: Curling occurs to the extent of forming a tube

[0166] The results are shown in Table 1 below.

[0167] [Table 1]

[0168]

[0169] The above results show that the window films of the examples have high visible light transmittance, excellent infrared reflectivity, and excellent curling suppression. Furthermore, compared to the window film of Example 2, the window film of Example 1 has a thinner substrate thickness and excellent curve-following properties. While thin substrates can easily cause film curling, the configuration of the present invention, as shown in Example 1, suppresses curling and reduces the risk of film lifting during application.

[0170] This application is based on Japanese Patent Application No. 2023-54863 filed in Japan on March 30, 2023, and the disclosed contents are referred to and incorporated into the present invention in their entirety.

[0171] Description of Reference Numerals

[0172] 10: Window film; 11: Low refractive index layer; 12: Hard coat layer; 13: Base material; 14: Heat ray shielding layer; 15: Adhesive layer; 16: Release liner.

Claims

1. A window film comprising a low refractive index layer, a hard coat layer, a substrate, a heat ray shielding layer, and an adhesive layer laminated in this order, The low-refractive-index layer is formed of a low-refractive-index layer-forming composition containing hollow silica particles and an active energy ray-curable component. The heat ray shielding layer is formed from a heat ray shielding layer-forming composition containing an infrared shielding metal oxide and an active energy ray-curable component.

2. The window film according to claim 1, wherein The thickness of the substrate is 100 μm or less.

3. The window film according to claim 1 or 2, wherein: The low refractive index layer is the outermost layer.

4. The window film according to claim 1 or 2, wherein: The infrared shielding metal oxide is at least one selected from the group consisting of indium-doped tin oxide, antimony-doped tin oxide, and cesium-doped tungsten oxide.

5. The window film according to claim 1 or 2, wherein: The hard coat layer and the heat ray shielding layer are arranged adjacent to the substrate.

6. The window film according to claim 1 or 2, wherein: The low refractive index layer is arranged adjacent to the hard coat layer.

Images