Light-absorbing and heat-shielding film, light-absorbing and heat-shielding member, article, and manufacturing method thereof

Abstract

To provide a light-absorption heat-shielding film that absorbs a visible ray and a near-infrared ray but has reduced radiation of a far-infrared ray, which are generally incompatible.SOLUTION: A light-absorption heat-shielding film includes a metal layer with a fine rugged-shape matter, where an average height of the fine rugged-shape matter is 100 nm or more and 1000 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a light absorbing and heat shielding film, a light absorbing and heat shielding member, an article, and a method for manufacturing the same. [Background technology]

[0002] In recent years, the use of heat-shielding materials that suppress temperature rise has been expanding in the interior and exterior parts of optical equipment, space equipment, and transportation products. In addition, heat-shielding materials that also have light-absorbing properties can reduce noise caused by stray light when used in the lens barrel of an infrared camera or in aperture films, and are less likely to increase in temperature and have high dimensional stability, so materials that have both light-absorbing and heat-shielding properties are in demand. Conventionally, light-absorbing materials that have been subjected to black electroless nickel plating have been known (for example, Non-Patent Document 1). This is a light-absorbing material that is made by blackening the surface by forming a fine uneven shape by oxidizing the nickel plating on the surface of an object. In addition, a technology has been shown in which a resin with a fine structure on the surface is produced by injection molding using a metal mold with a fine uneven shape on the surface (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-261910 A [Non-patent literature]

[0004] [Non-Patent Document 1] "Black Electroless Nickel Plating", Surface Technology, Vol. 66, No. 11, 503-506, 2015 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the black material shown in Non-Patent Document 1 has a problem that it does not show excellent heat shielding properties because it has a large radiation even in the far infrared region. Also, the invention described in Patent Document 1 is based on injection molding of resin using a mold, and it is not possible to mold a metal film in a versatile form, so it is difficult to apply it to various products as a light absorbing and heat shielding material, and there is a problem with its practicality. [Means for solving the problem]

[0006] The present invention has been made in view of the above problems, and has the characteristics of absorbing visible light and near infrared rays (i.e., low reflectance) and emitting little far infrared rays (i.e., high reflectance), which are usually incompatible. Light absorption and heat shielding Membrane and Light absorption and heat shielding The purpose is to provide components.

[0007] The present invention Light absorption and heat shielding The film is characterized in that it comprises a metal layer having a fine concave-convex shape containing a metal, the average difference in height between the apexes of the convex portions and the bottoms of the concave portions of the fine concave-convex shape is 100 nm or more and 1000 nm or less, the average surface roughness Ra' of the surface including the fine concave-convex shape is 1 nm or more and 50 nm or less, and the specific surface area Sr of the surface including the fine concave-convex shape is 1.0 or more and 3.0 or less. Effect of the Invention

[0008] According to the present invention, Light absorption and heat shielding By using the film, it is possible to realize light absorption and heat shielding properties that are usually not compatible. Light absorption and heat shielding By providing a film on the surface, the detection temperature can be reduced by approximately 3°C or more. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an embodiment of a light absorbing and heat shielding film of the present invention. [Diagram 2] 1 is a schematic diagram showing an embodiment of a light absorbing and heat shielding member of the present invention. [Diagram 3] 1 is a process diagram showing one embodiment of a method for producing a light absorbing and heat shielding member of the present invention. [Figure 4] 2 is an electron microscope image of a cross section of the light absorbing and heat shielding member obtained in Example 1. FIG. [Diagram 5] 1 shows the results of measuring the reflectance spectra in the visible light region of the light absorbing and heat shielding members obtained in Examples 1 and 3 and the light absorbing member obtained in Comparative Example 1. [Figure 6] 1 shows the results of measuring the reflectance spectra in the infrared region of the light absorbing and heat shielding members obtained in Examples 1 and 3 and the light absorbing member obtained in Comparative Example 1. [Figure 7] FIG. 11 is an electron microscope image of a cross section of the light absorbing and heat shielding member obtained in Example 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail. The light absorbing and heat shielding film according to the present invention is Contains metal uneven shape Prepare a letter With a metal layer 、 before Record convex shape Shape It is characterized by having a height of 100 nm or more and 1000 nm or less.

[0011] Metals with high electrical conductivity, such as aluminum and nickel, have low far-infrared radiation and heat shielding properties, but do not absorb light. On the other hand, fine unevenness due to a subwavelength structure smaller than the wavelength of visible light is known to have an anti-reflection effect, and it is known that by continuously changing the spatial occupancy rate of the structure, excellent wavelength band characteristics and incident angle characteristics are exhibited. Therefore, when a metal surface is made finely uneven, reflection on the metal surface is suppressed in a wide wavelength range of visible light, the reflectance in the entire visible light range decreases, it appears black, and absorbency is exhibited. Therefore, it is considered that a metal member whose surface has a fine uneven structure can have both light absorption and heat shielding properties. However, the light-absorbing material shown in Non-Patent Document 1 has a fine uneven shape obtained by oxidizing the nickel surface on its surface, but has high radiation (low reflectance) even in the far-infrared range and does not exhibit heat shielding properties. From this, the inventors have found that in addition to the heat shielding properties of the metal itself that forms the light-absorbing and heat-shielding film, a specific shape of the fine unevenness of the metal surface is important for exhibiting heat shielding properties, and have completed the present invention.

[0012] That is, the light absorbing and heat shielding film of the present invention has a specific fine uneven shape provided on the metal layer, and therefore can exhibit both light absorbing and heat shielding properties. In particular, the light absorbing and heat shielding film of the present invention preferably has a reflectance of 10% or less in the visible light region (550 nm) and a reflectance of 70% or more in the far infrared light region (10 μm).

[0013] <Light absorption heat shield film> The light-absorbing and heat-shielding film of the present invention will be described with reference to FIG. 1. As shown in FIG. 1(a), one embodiment of the light-absorbing and heat-shielding film of the present invention is a light-absorbing and heat-shielding film having a metal layer 1 including fine irregularities 2 on its surface. The material of the metal layer 1 is preferably a metal having high electrical conductivity. Examples of metals having high electrical conductivity include silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, and chromium, among which nickel, zinc, and chromium are preferred, and nickel is particularly preferred. The fine irregularities 2 provided on the surface of the metal layer 1 are also preferably made of the above-mentioned metal having high electrical conductivity, and more preferably made of the same metal as the metal layer 1. A transparent metal oxide may be attached to the surface of the fine irregularities 2.

[0014] The fine unevenness 2 is a fine unevenness provided on one surface of the metal layer 1, and the height of the fine unevenness 2 refers to the difference in height between the top of the convex portion and the bottom of the concave portion formed on the metal layer surface. The average height of the fine unevenness 2 is 100 nm or more and 1000 nm or less, preferably 100 nm or more and 500 nm or less. A transparent metal oxide may be attached to the surface of the fine unevenness 2. The average height of the fine unevenness 2 containing a transparent metal oxide is preferably 150 nm or more and 600 nm or less. Here, the height of the fine unevenness 2 or the height of the fine unevenness 2 containing a transparent metal oxide means the difference in height between the peak and the valley bottom as specified in "Definition and Display of Surface Roughness" of JIS-B-061, and corresponds to the maximum roughness (Rmax). In addition, the light-absorbing and heat-shielding film of the present invention preferably has an average surface roughness Ra', which is obtained by surface-expanding the centerline average roughness Ra, of 1 nm or more and 50 nm or less on its surface. Here, the average surface roughness Ra' value (nm) is the center line average roughness Ra defined in JIS B 0601, which is applied to the measurement surface and expanded three-dimensionally. It is expressed as "the average of the absolute values ​​of the deviation from the reference surface to the specified surface" and is calculated by the following formula (1).

number

[0015] Furthermore, the light-absorbing and heat-shielding film of the present invention preferably has a specific surface area Sr of 1.0 or more and 3.0 or less. The specific surface area Sr is calculated by the following formula (2). Sr=S / S0 formula (2) In equation (2), S0 is the surface area when the measurement surface is ideally flat, and S is the surface area of ​​the actual measurement surface.

[0016] In addition, the actual surface area of ​​the measurement surface is calculated by dividing the surface into infinitesimal triangles ΔABC consisting of the three closest data points (A, B, C), and then calculating the area ΔS of each infinitesimal triangle using a vector product as shown in the following equation (3). The sum of these ΔS is the desired surface area S. [ΔS(ΔABC)] 2 =[s(s-AB)(s-BC)(s-CA)] Equation (3) In equation (3), AB, BC, and CA are the lengths of each side, and 2s = AB + BC + CA.

[0017] The height of the fine unevenness 2 can be determined by observing the cross section of the light absorbing and heat shielding film of the present invention with a scanning electron microscope, etc. Also, the average surface roughness Ra' and specific surface area of ​​the surface of the light absorbing and heat shielding film of the present invention can be determined by observing the surface of the metal layer having the fine unevenness with a scanning probe microscope, etc.

[0018] In another embodiment of the light absorbing and heat shielding film of the present invention, as shown in FIG. 1(b), the light absorbing and heat shielding film may be provided with a transparent metal oxide fine unevenness 3 in close contact with the fine unevenness 2. In another embodiment of the light absorbing and heat shielding film of the present invention, as shown in FIG. 1(c), the light absorbing and heat shielding film may be provided with a transparent metal oxide layer 4 covering the surface of the metal oxide fine unevenness 3 that is not in contact with the fine unevenness 2. Here, "closely contacted" means that the metal oxide constituting the metal oxide fine unevenness 3 fills the space surrounded by the fine unevenness 2 and reaches the metal layer 1. When the light absorbing and heat shielding film is provided with the fine unevenness 3 and the metal oxide layer 4, it is preferable that the average surface roughness Ra' obtained by surface-expanding the center line average roughness Ra on the surface of the metal oxide layer 4 that is the surface of the light absorbing and heat shielding film is 1 nm or more and 4 nm or less, and the specific surface area Sr of the surface of the light absorbing and heat shielding film is 1.0 to 1.1.

[0019] The material of the metal oxide micro-irregular shape 3 is not particularly limited, but is preferably alumina-based, and more preferably contains alumina-based plate crystals. The alumina-based plate crystals are formed of alumina-based plate crystals containing aluminum oxide or hydroxide or hydrates thereof as the main component, and boehmite is a particularly preferred crystal. Here, the alumina-based plate crystals may be alumina-based plate crystals or alumina-based plate crystals containing trace amounts of zirconium, silicon, titanium, zinc, etc.

[0020] The metal oxide fine unevenness 3 can protect the fine unevenness 2. When the metal oxide fine unevenness 3 is a plate-like structure of plate-like crystals mainly composed of alumina, it is preferable that the plate-like crystals mainly composed of alumina are arranged in a direction perpendicular to the surface direction of the metal layer 1, and that their spatial occupancy rate changes continuously.

[0021] The material of the metal oxide layer 4 is not particularly limited, but preferably contains amorphous gel of alumina. The metal oxide layer 4 increases the hardness of the surface of the light absorbing and heat shielding film of the present invention while decreasing the light absorbency. Therefore, the thickness of the metal oxide layer 4 may be appropriately determined so as to satisfy the required hardness and light absorbency.

[0022] The aluminum element, silicon element, etc. in the fine unevenness 2, the fine unevenness 3, and the metal oxide layer 4, and the metal elements, such as silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, and chromium, in the metal layer 1 can be detected by energy dispersive X-ray analysis (EDX) or X-ray photoelectron spectroscopy (XPS) measurements during surface or cross-sectional observation with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). When the fine unevenness 2, the fine unevenness 3, or the metal oxide layer 4 is provided, the proportion of metal oxides, such as aluminum element, decreases relatively from the surface (metal oxide layer 4) to the inside (metal layer 1) in the direction perpendicular to the surface direction of the metal layer 1, and the proportion of the metal elements constituting the metal layer 1 and the fine unevenness 2 increases, and finally only the metal elements are detected.

[0023] <Light absorbing and heat shielding material> As shown in FIG. 2(a), an embodiment of the light absorbing and heat shielding member of the present invention is a light absorbing and heat shielding member in which a substrate 5 is provided on the surface of the metal layer 1 of the light absorbing and heat shielding film of the present invention opposite to the fine unevenness 2. The shape of the substrate 5 may be any shape that can be formed according to the purpose of use, and includes, but is not limited to, a flat plate shape, a film shape, a sheet shape, and the like. Materials for the substrate 5 include, but are not limited to, metal, glass, ceramics, wood, paper, resin, and the like. Examples of resins include films and molded products of thermoplastic resins such as polyester, triacetyl cellulose, cellulose acetate, polyethylene terephthalate, polypropylene, polystyrene, polycarbonate, polymethyl methacrylate, ABS resin, polyphenylene oxide, polyurethane, polyethylene, and polyvinyl chloride; and thermosetting resins such as unsaturated polyester resin, phenolic resin, crosslinked polyurethane, crosslinked acrylic resin, and crosslinked saturated polyester resin.

[0024] 2(b), in another embodiment of the present invention, the light absorbing and heat shielding film and the substrate 5 may be adhered to each other by an adhesive layer 6. The adhesive layer 6 may be any layer capable of adhering the light absorbing and heat shielding film to the substrate 5, and examples of the adhesive layer 6 include a layer made of a cured product of an adhesive resin (e.g., an epoxy resin), a double-sided tape, and the like.

[0025] Although Figures 2(a) and (b) show a light-absorbing and heat-shielding member having a light-absorbing and heat-shielding film shown in Figure 1(c), the light-absorbing and heat-shielding member may have a light-absorbing and heat-shielding film shown in Figure 1(a) or (b) instead of the light-absorbing and heat-shielding film shown in Figure 1(c).

[0026] <Method of Manufacturing Light Absorbing and Heat Shielding Film and Light Absorbing and Heat Shielding Member> Hereinafter, a method for producing the light absorbing and heat shielding film and the light absorbing and heat shielding member of the present invention will be described with reference to FIG. The method for producing a light absorbing and heat shielding film of the present invention includes a first step of forming a fine uneven shape of metal oxide, and a second step of forming a metal layer on the fine uneven shape of metal oxide. The light absorbing and heat shielding member of the present invention further includes a step of adhering a substrate to the surface of the metal layer of the light absorbing and heat shielding film opposite to the surface in contact with the fine uneven shape of metal oxide.

[0027] (First step: Fabricating a fine uneven surface of metal oxide) In the first step, a fine concave-convex shape is formed from metal oxide to serve as a mold.

[0028] The material of the metal oxide fine unevenness is not particularly limited, but it is preferable that the main component is alumina. The fine unevenness can be formed by known gas phase methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), and liquid phase methods such as sol-gel. By these methods, it is possible to provide a fine unevenness of a metal oxide containing plate crystals mainly composed of alumina. Among them, a method of treating a film containing aluminum with hot water to grow alumina plate crystals is preferable.

[0029] Examples of the aluminum-containing film include an alumina gel film formed by applying a sol-gel coating liquid containing an aluminum compound, and a film containing metallic aluminum formed by dry film formation such as vacuum deposition or sputtering. From the viewpoints of reactivity and ease of adjusting the height of the fine concave-convex shape of the metal oxide, it is preferable to form the fine concave-convex shape of the metal oxide using an alumina gel film.

[0030] As the raw material of the alumina gel film, aluminum compounds such as aluminum alkoxides, aluminum halides, aluminum salts, etc. From the viewpoint of film formability, it is preferable to use aluminum alkoxides.

[0031] Examples of the aluminum compound include aluminum alkoxides such as aluminum ethoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum sec-butoxide, and aluminum tert-butoxide, and oligomers thereof, aluminum halides such as aluminum chloride, aluminum salts such as aluminum nitrate, aluminum acetate, aluminum phosphate, and aluminum sulfate, aluminum acetylacetonate, and aluminum hydroxide.

[0032] The alumina gel film may also contain other compounds. Examples of the other compounds include alkoxides, halides, and salts of zirconium, silicon, titanium, and zinc, and combinations thereof. By including other compounds in the alumina gel film, the height of the fine unevenness of the metal oxide formed can be increased compared to when the alumina gel film does not include these compounds.

[0033] The alumina gel film is formed on a base substrate by applying a sol-gel coating solution containing an aluminum compound as shown below. The sol-gel coating solution is prepared by dissolving an aluminum compound in an organic solvent. The amount of organic solvent relative to the aluminum compound is preferably about 20 times by molar ratio.

[0034] Examples of the organic solvent that can be used include alcohols, carboxylic acids, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, esters, ketones, ethers, and mixtures thereof. Examples of the alcohol include methanol, ethanol, 2-propanol, butanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol, 4-methyl-2-pentanol, 2-ethylbutanol, 3-methoxy-3-methylbutanol, ethylene glycol, diethylene glycol, and glycerin. Examples of carboxylic acids include n-butyric acid, α-methylbutyric acid, iso-valeric acid, 2-ethylbutyric acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,3-dimethylbutyric acid, 3-methylpentanoic acid, 4-methylpentanoic acid, 2-ethylpentanoic acid, 3-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 3,3-dimethylpentanoic acid, 2,3-dimethylpentanoic acid, 2-ethylhexanoic acid, and 3-ethylhexanoic acid. Examples of aliphatic or alicyclic hydrocarbons include n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane. Examples of aromatic hydrocarbons include toluene, xylene, and ethylbenzene. Examples of esters include ethyl formate, ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Examples of ethers include dimethoxyethane, tetrahydrofuran, dioxane, diisopropyl ether, etc. Among them, it is preferable to use alcohol from the viewpoint of the stability of the sol-gel coating liquid.

[0035] When aluminum alkoxide is used as the aluminum compound, it is highly reactive to water, and therefore the aluminum alkoxide may be rapidly hydrolyzed by the addition of moisture in the air or water, causing the sol-gel coating liquid to become cloudy and precipitate. In order to prevent these, it is preferable to add a stabilizer to the sol-gel coating liquid to stabilize it. As the stabilizer, β-diketone compounds, β-ketoester compounds, alkanolamines, etc. can be used. Examples of β-diketone compounds include acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, benzoylacetone, 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, etc. Examples of β-ketoester compounds include methyl acetoacetate, ethyl acetoacetate, butyl acetoacetate, hexyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, iso-propyl acetoacetate, 2-methoxyethyl acetoacetate, sec-butyl acetoacetate, tert-butyl acetoacetate, and iso-butyl acetoacetate. Examples of alkanolamines include monoethanolamine, diethanolamine, triethanolamine, etc. The amount of the stabilizer relative to the aluminum alkoxide is preferably about 1:1 in molar ratio.

[0036] A catalyst may be used to promote the hydrolysis reaction of the aluminum alkoxide, and examples of the catalyst include nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and ammonia.

[0037] In addition, a water-soluble organic polymer compound can be added to the alumina gel film as necessary. The water-soluble organic polymer compound is easily dissolved from the alumina gel film by immersion in hot water, which increases the reaction surface area between the aluminum compound and hot water, making it possible to form a fine uneven shape at a low temperature and in a short time. In addition, by changing the type and molecular weight of the organic polymer to be added, it becomes possible to control the height of the fine uneven shape to be formed. As the organic polymer, polyether glycols such as polyethylene glycol and polypropylene glycol are preferable because they are easily dissolved from the alumina gel film by immersion in hot water. The amount of polyether glycols relative to the weight of the aluminum compound in the alumina gel film is preferably in the range of 0.1 to 10 times by weight.

[0038] A method for producing a fine uneven shape of a metal oxide is described with reference to Figs. 3(a) and (b). An aluminum compound, and if necessary, other compounds, a stabilizer, and a water-soluble organic polymer compound are dissolved or suspended in an organic solvent to prepare a sol-gel coating liquid. This sol-gel coating liquid is applied to a base substrate 8 and dried to form an alumina gel film as the aluminum-containing film 7. Alternatively, a film containing metallic aluminum as the aluminum-containing film 7 is formed on the base substrate 8 by dry film formation such as vacuum deposition or sputtering. There is no particular limitation on the material of the base substrate 8, and various materials such as glass, plastic, and metal can be used. When forming an alumina gel film using a sol-gel coating liquid that does not contain a stabilizer, it is preferable to use an inert gas atmosphere such as dry air or dry nitrogen as the atmosphere in which the coating is performed. The relative humidity of the dry atmosphere is preferably 30% or less. As a solution coating method for forming an alumina gel film, a known coating means such as a dipping method, a spin coating method, a spray method, a printing method, a flow coating method, and a combination of these methods can be appropriately adopted. The film thickness can be controlled by changing the pulling speed in the dipping method, the substrate rotation speed in the spin coating method, and the concentration of the sol-gel coating liquid. Drying can be performed at room temperature for about 30 minutes. If necessary, drying or heat treatment can be performed at a higher temperature. The higher the heat treatment temperature, the more stable the metal oxide fine unevenness 3 can be formed by the immersion treatment described below. The suitable film thickness of the aluminum-containing film 7 is 100 nm or more and 600 nm or less, preferably 100 nm or more and 300 nm or less, and more preferably 100 nm or more and 200 nm or less.

[0039] Next, the aluminum-containing film 7 is immersed in hot water to form a fine uneven shape of alumina. By immersing the alumina gel film in hot water, the surface layer of the alumina gel film is subjected to peptization, etc., and some components are dissolved, but due to the difference in solubility of various hydroxides in hot water, plate-like crystals mainly composed of alumina are precipitated and grown on the surface layer of the alumina gel film, forming a fine uneven shape of metal oxide 3. In addition, when a film containing metallic aluminum is used instead of the alumina gel film, after aluminum reacts with hot water and is oxidized to alumina, the fine uneven shape of metal oxide 3 is formed in the same manner as when the alumina gel film is used. Therefore, when the material of the base substrate 8 mainly contains aluminum or alumina, the formation of the aluminum-containing film 7 on the base substrate 8 can be omitted. The temperature of the hot water is preferably 40°C or higher and lower than 100°C. The immersion treatment time is preferably about 5 minutes to about 24 hours. In the immersion treatment of an alumina gel film containing compounds other than the alumina component, the difference in solubility of each component in hot water is used to crystallize the plate-like crystals of alumina. Therefore, unlike the immersion treatment of an alumina gel film containing only alumina, the size of the plate-like crystals can be controlled over a wide range by changing the composition of the inorganic components. In addition, the height of the fine unevenness 3 of alumina can be adjusted by adjusting the film thickness of the aluminum-containing film 7. The average height of the fine unevenness 3 of the metal oxide is preferably 100 nm or more and 1000 nm or less, more preferably 100 nm or more and 500 nm or less. As a result, it is possible to control the fine unevenness formed by the plate-like crystals over the above-mentioned wide range.

[0040] (Second step: forming a metal layer) In the second step, a metal layer is formed on the fine unevenness of the metal oxide, and a fine unevenness to which the fine unevenness is transferred is formed on the metal layer. With reference to FIG. 3(c), the step of forming the metal layer 1 on the fine unevenness of the metal oxide 3 will be described below. As a method for forming the metal layer 1, a metal plating process is preferable, and an electroless plating process is more preferable. In the electroless plating process, an aqueous solution in which a palladium compound such as palladium chloride, a gold compound such as gold chloride, a silver compound such as silver chloride, a tin compound such as tin chloride, etc. is dissolved is applied to the fine unevenness of the metal oxide 3 to perform activation. The activation may be performed by immersing the fine unevenness of the metal oxide 3 together with the base substrate 8 in an aqueous solution in which a palladium compound is dissolved. Thereafter, the metal layer 1 is deposited on the fine unevenness of the metal oxide 3 using an electroless plating solution. The metal ions in the electroless plating solution correspond to the metal layer of the light absorbing and heat shielding film of the present invention, and an electroless plating solution containing nickel ions, chromium ions, and zinc ions is preferable, and a nickel plating solution containing nickel ions is particularly preferable. The nickel plating solution may contain phosphorus and boron components in addition to the nickel component. Examples of commercially available nickel plating solutions include the Top Nicoron series from Okuno Chemical Industries. The temperature of the plating solution in the electroless plating process is preferably 30°C to 98°C, more preferably 50°C to 90°C. The time for electroless plating can be adjusted according to the thickness of the metal layer to be formed, and is usually 30 seconds to 1 hour. In this way, the metal layer 1 is formed so as to fill the gaps of the fine unevenness, and the metal layer 1 including the fine unevenness 2 to which the fine unevenness 3 of the metal oxide is transferred is formed.

[0041] It is preferable to perform electroless plating so that the thickness of the metal layer 1 including the fine unevenness 2 is 200 nm or more and 15,000 nm or less. The average height of the fine unevenness 2 corresponds to the average height of the fine unevenness 3 of the metal oxide, and is 100 nm or more and 1,000 nm or less. When the thickness of the metal layer 1 including the fine unevenness 2 is 200 nm or more, the light absorbing and heat shielding film of the present invention exhibits excellent light absorbing and heat shielding properties.

[0042] After the electroless plating process described above, in order to increase the thickness of the metal layer 1, an electroplating process may be performed on the opposite side of the surface of the metal layer 1 on which the fine unevenness 2 is provided. A known electroplating solution may be used for the electroplating process, and for example, an electroplating solution containing nickel ions, iron ions, copper ions, etc. may be used as metal ions. When the electroplating process is performed using the same metal as the metal layer 1, the thickness of the metal layer can be increased by the electroplating process. When the electroplating process is performed using a metal different from the metal layer 1, the metal layer provided by the electroplating process becomes the base material 5. In addition to inorganic salts that are raw materials for metal ions, conductive salts, salts for adjusting counter ions, carboxylic acid additives for increasing the homogeneity of the plating film, gloss agents, etc. may be added to the electroplating solution as necessary. In addition, in the electroplating process, the temperature, current density, and plating time of the electroplating solution may be adjusted to make the metal layer 1 have a desired thickness. If necessary, prior to the electroplating step, the surface of the metal layer 1 opposite to the surface on which the fine concave-convex structure 2 is formed may be activated with an aqueous solution containing an acid or the like. Furthermore, in order to improve the quality of the film formed by the electroplating step, a step of removing foreign matter from the electroplating solution may be provided in addition to stirring the electroplating solution during the electroplating step.

[0043] (Third process: Adhesion of substrate) In the manufacture of the light absorbing and heat shielding member of the present invention, as shown in FIG. 3(d), the substrate 5 is adhered to the surface opposite to the surface on which the fine unevenness 2 of the metal layer 1 obtained above is provided. The shape and material of the substrate 5 may be the same as those described above. When the substrate 5 is made of a metal, the metal that will become the substrate 5 may be laminated on the surface opposite to the surface on which the fine unevenness 2 of the metal layer 1 is provided. The metal may be laminated by the above-mentioned electroplating process or by physical vapor deposition such as sputtering. When the substrate 5 is made of a resin, the substrate 5 may be provided by depositing the resin that will become the substrate 5 on the surface opposite to the surface on which the fine unevenness 3 of the metal oxide of the metal layer 1 is provided and then curing the resin. The substrate 5 may be adhered to the metal layer 1 by an adhesive layer 6. The adhesive used for the adhesive layer 6 is not particularly limited, and may be a material that can firmly adhere the substrate 5 and the metal layer 1.

[0044] (4th process: Etching process) 3(e) to (h), the etching step will be described in detail using an example of a light absorbing and heat shielding member having a base material 5 and an adhesive layer 6, but the same applies to a light absorbing and heat shielding member having only a base material 5 without an adhesive layer 6, and a light absorbing and heat shielding film having no base material 5 and no adhesive layer 6. Note that Fig. 3(e) is the light absorbing and heat shielding member shown in Fig. 3(d) turned upside down.

[0045] First, in order to obtain the light-absorbing and heat-shielding member of the present invention, the base substrate 8 is removed as shown in FIG. 3(f). The light-absorbing and heat-shielding member after removing the base substrate 8 has a film 7 containing aluminum on its surface. When the film 7 containing aluminum is a film containing metallic aluminum, visible light is reflected by metallic aluminum, so that the film containing metallic aluminum must be further removed by etching as shown in FIG. 3(g). When the film 7 containing aluminum is an alumina gel film, the alumina gel film is the metal oxide layer 4 of the light-absorbing and heat-shielding member. Therefore, the alumina gel film may be removed by etching so as to satisfy the required surface hardness and light absorption. As an etching method, wet etching in which the film 7 containing aluminum is dissolved using an acid or an alkaline solution is preferable. Examples of acids include hydrochloric acid, nitric acid, and sulfuric acid. Examples of alkalis include sodium hydroxide and potassium hydroxide. From the viewpoint of work efficiency, an etching method using an alkaline solution is more preferable. It is preferable that the etching concentration is in the range of several % to several tens of %, and the etching time is in the range of several hours to several days. 3(h), the metal oxide fine unevenness 3 may also be removed by etching. A light absorbing and heat shielding member in which a metal layer 1 having a fine unevenness 2 on its outermost surface is bonded to a substrate 5 via an adhesive layer 6 realizes particularly excellent light absorption.

[0046] The remaining metal oxide such as alumina after etching can be detected by EDX or XPS measurement during surface or cross-sectional observation using SEM or TEM.

[0047] As described above, the degree of etching may be adjusted according to the balance between the light absorbing and heat shielding material or film's desired light absorbing performance and surface hardness. Also, the etching step may be performed before the substrate bonding step, which is the third step, and then the substrate may be bonded.

[0048] The light-absorbing and heat-shielding member and light-absorbing and heat-shielding film of the present invention obtained in this manner have a metal layer 1 containing fine unevenness 2, and therefore absorb visible light, resulting in a low reflectance in the visible light region, and because they emit little far-infrared light, they have a high reflectance in the far-infrared region, thereby achieving excellent light-absorbing and heat-shielding properties.

[0049] The light-absorbing heat-shielding film of the present invention can be provided on the surface of various members or articles to form a light-absorbing heat-shielding member. The light-absorbing heat-shielding film of the present invention is preferably used for a heat-generating body as a member or article. Examples of articles equipped with such a heat-generating body include batteries, engines, motors, and vehicles. In addition, the light-absorbing heat-shielding film of the present invention can be used for clothing and the like. The light-absorbing heat-shielding film of the present invention may also be used as a heat-shielding decorative film. For example, the light-absorbing heat-shielding film of the present invention can be provided as a heat-shielding decorative film on the surface of the interior of a vehicle, a mobile device, a home appliance, a parasol, or a tent. When providing the light-absorbing heat-shielding film of the present invention on the surface of a member or article, various adhesives can be used. Therefore, the light-absorbing heat-shielding film of the present invention can be provided on the surface of a member or article according to the purpose of use, and the surface of the member or article is not limited to being smooth, and may have a two-dimensional or three-dimensional curved surface.

[0050] Conventionally, when various members or objects are present within the viewing angle, it has been difficult for an infrared thermal imaging camera to identify a member or object to be detected. Since a member or object having the light-absorbing heat-shielding film of the present invention on its outermost surface has a difference in detected temperature compared to a member or object not having the light-absorbing heat-shielding film, it is possible to clearly identify the member or object by using the light-absorbing heat-shielding film of the present invention. Usually, the error range of the detected temperature of an infrared thermal imaging camera is 2°C, so it is sufficient that the detected temperature on the surface opposite to the surface of the light-absorbing heat-shielding film that contacts the member or object is 3°C or more lower than the detected temperature on the part of the member or object that does not have the light-absorbing heat-shielding film. In this case, if the member or object is a heat generating body, it is possible to more clearly identify it. EXAMPLES

[0051] The present invention will now be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In the examples, the reflectance spectrum in the visible light region was measured using a lens reflectance measuring instrument (product name: USPM-RU III, manufactured by Olympus Corporation). In the examples, the reflectance spectrum in the infrared region was measured using a Fourier transform infrared spectrophotometer (FT / IR-6600, manufactured by JASCO Corporation).

[0052] Example 1 (Manufacture of light absorbing and heat shielding materials) Aluminum sec-butoxide (hereinafter also referred to as "Al(O-sec-Bu)3") and ethyl acetoacetate (hereinafter also referred to as "EtOAcAc") were dissolved in 2-propanol (hereinafter also referred to as "IPA") and stirred at room temperature for about 3 hours to prepare an alumina sol solution. The molar ratio of each component in the alumina sol solution was Al(O-sec-Bu)3: EtOAcAc: IPA = 1: 1: 20. A 0.01M dilute hydrochloric acid solution was added to the alumina sol solution so that the amount of hydrochloric acid added was twice that of Al(O-sec-Bu)3 in terms of molar ratio, and the mixture was refluxed for about 6 hours to prepare a sol-gel coating solution. The sol-gel coating solution was applied to a quartz glass substrate, which is a base material, by spin coating to form a coating film. The coating film was then heat-treated at 100 °C for 1 hour to obtain a transparent alumina gel film. Next, the alumina gel film was immersed in warm water at 80° C. for 30 minutes, and then dried at 100° C. for 10 minutes to form an alumina layer having a fine concave-convex shape.

[0053] A palladium chloride aqueous solution was applied by spin coating onto the alumina layer with the fine concave-convex shape, and then dried at 100° C. The alumina layer was then immersed for 1 minute in a nickel-phosphorus plating solution (phosphorus content: approximately 10 wt%) set at 80° C. to form the fine concave-convex shape and a nickel layer as a metal layer.

[0054] An epoxy resin was applied to the surface of the metal layer opposite to the alumina layer having the fine concave-convex shape, which served as an adhesive layer, and cured, and a PET film was attached to the substrate via the adhesive layer. After that, the light-absorbing and heat-shielding member was peeled off together with the substrate from the quartz glass substrate to produce a light-absorbing and heat-shielding member.

[0055] (Observation of cross-sectional shape) In the manufacturing of the light absorbing and heat shielding member, the nickel layer formed on the alumina layer having the fine unevenness was cut out with a dicing saw, then sliced ​​in the cross-sectional direction by the focused ion beam (FIB) method, and the cross-section was observed with an SEM. The cross-sectional observation was performed with a scanning transmission electron microscope (product name: HD-2300, manufactured by Hitachi High-Technologies Corporation). From the observation image shown in FIG. 4, nickel fine unevenness 2 is formed so as to fill the inside of the alumina plate crystals, which are the metal oxide fine unevenness 3 formed from the alumina gel film on the base material 8, and a nickel layer, which is the metal layer 1, is present on the fine unevenness 2.

[0056] The average height of the fine unevenness 2 of the obtained light absorbing and heat shielding member was 323 nm, the average height of the fine unevenness 3 was 255 nm, and the thickness of the aluminum-containing film 7 was 68 nm. The average surface roughness Ra' of the surface of the light absorbing and heat shielding member was 1.0 nm, and the specific surface area was 1.0.

[0057] (Evaluation of light absorbing and heat shielding materials) The reflectance spectrum in the visible light region and the reflectance spectrum in the infrared region of the light-absorbing and heat-shielding member obtained in Example 1 were measured. The reflectance spectrum was measured using a lens reflectance measuring instrument (product name: USPM-RU III, manufactured by Olympus Corporation), and the reflectance spectrum in the infrared region was measured using a Fourier transform infrared spectrophotometer (product name: FT / IR-6600, manufactured by JASCO Corporation). The results of the reflectance spectrum measurement in the visible light region are shown in FIG. 5, and the results of the reflectance spectrum measurement in the infrared region are shown in FIG. 6. Table 1 shows the reflectance in the visible light region and the infrared region obtained by measuring the reflectance spectrum in the visible light region and the infrared region of the light-absorbing and heat-shielding member. From FIG. 5, it can be said that the light-absorbing and heat-shielding member of the present invention has excellent light absorption because of its low reflectance in the visible light region. As can be seen from FIG. 6, the light absorbing and heat shielding member of the present invention has an excellent heat shielding property since the reflectance increases toward the longer wavelength side in the mid-infrared and far-infrared regions.

[0058] Comparative Example 1 For a light-absorbing material produced by the same method as that described in Non-Patent Document 1, the reflectance spectrum in the visible light region and the reflectance spectrum in the infrared region were measured under the same conditions as for the light-absorbing and heat-shielding member of Example 1. The results are shown in Figures 5 and 6, and Table 1.

[0059] As shown in FIG. 5, the light absorbing material of Comparative Example 1 is inferior to the light absorbing and heat shielding member of Example 1, but has low reflectance in the visible to near infrared region and is excellent in light absorption. On the other hand, as shown in FIG. 6, the light absorbing material of Comparative Example 1 has a reflectance in the mid-infrared region and the far-infrared region inferior to the light absorbing and heat shielding member of the present invention, and cannot be said to have heat shielding properties.

[0060] Example 2 (Manufacture of light-absorbing and heat-shielding films) As in Example 1, an alumina sol solution was prepared and applied to a quartz glass substrate, which is a base material, by spin coating to form a coating film. The coating film was then heat-treated at 100°C for 1 hour to obtain a transparent alumina gel film. The alumina gel film was then immersed in 80°C warm water for 30 minutes and then dried at 100°C for 10 minutes to form an alumina layer with a fine concave-convex shape.

[0061] A palladium chloride solution was applied to the alumina layer with the fine irregularities by spin coating, and then dried at room temperature.Then, the layer was immersed in a nickel-phosphorus plating solution (phosphorus content: approx. 10 wt%) at 80°C for 20 minutes to form the fine irregularities and a nickel layer as the metal layer.

[0062] The light-absorbing and heat-shielding film was then peeled off from the quartz glass substrate. The overall film thickness of the obtained light-absorbing and heat-shielding film was approximately 10 μm. The average height of the fine unevenness of the light-absorbing and heat-shielding film was 303 nm, the average height of the fine unevenness was 233 nm, and the film thickness of the aluminum-containing film was 70 nm. Furthermore, the average surface roughness Ra' of the light-absorbing and heat-shielding film was 1.0 nm, and the specific surface area was 1.0.

[0063] In the following Examples 3 to 11, light absorbing and heat shielding films were manufactured by changing the number of gel film layers and the etching conditions.

[0064] Example 3 A light-absorbing heat-shielding film was produced in the same manner as in Example 2, and the light-absorbing heat-shielding film peeled off from the quartz glass substrate was etched at room temperature for 50 hours using a 3M aqueous sodium hydroxide solution as an etching process to produce a light-absorbing heat-shielding film. A small amount of transparent metal oxide was attached to the fine unevenness after etching. The average height of the fine unevenness containing transparent metal oxide in the obtained light-absorbing heat-shielding film was 251 nm, the average height of the fine unevenness was 213 nm, the average surface roughness Ra' of the surface of the light-absorbing heat-shielding film was 5.0 nm, and the specific surface area was 1.1. The results of the reflectance spectrum measurement in the visible light region are shown in FIG. 5, and the results of the reflectance spectrum measurement in the infrared region are shown in FIG. 6. In addition, a cross section was extracted by the FIB method, and the cross section was observed by SEM. The cross section was observed using a scanning electron microscope (product name: ULTRA55, manufactured by Carl Zeiss). The observation image shown in Figure 7 shows that nickel fine irregularities 2 were formed on the nickel layer, which is the metal layer 1, and a small amount of alumina remained on the fine irregularities 2. The alumina layer detected by SEM-EDX analysis and XPS measurement had a relatively low proportion of Al element from the surface to the inside in the film thickness direction of the cross section, while the proportion of Ni element was high.

[0065] Example 4 A light-absorbing and heat-shielding film was produced in the same manner as in Example 3, except that the etching step was performed at room temperature for 47 hours using a 7.5 M aqueous sodium hydroxide solution. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 235 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 18 nm, and the specific surface area was 1.4.

[0066] Example 5 A light-absorbing and heat-shielding film was produced in the same manner as in Example 3, except that a nickel-phosphorus plating solution (phosphorus content: approximately 1 to 2 wt%) was used as the plating solution. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 272 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 3.8 nm, and the specific surface area was 1.1.

[0067] Example 6 The alumina sol solution shown in Example 2 was prepared and applied to a quartz glass substrate, which is a base material, by spin coating to form a coating film. The coating film was then heat-treated at 100°C for 1 hour, and the film application and drying processes were repeated to obtain a transparent alumina gel film as an aluminum-containing film with two lamination layers. Thereafter, a light-absorbing and heat-shielding film was manufactured in the same manner as in Example 2. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 306 nm, the average height of the fine unevenness was 371 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 1.1 nm, and the specific surface area was 1.0.

[0068] Example 7 A light-absorbing and heat-shielding film was produced in the same manner as in Example 6, except that after the metal film with the alumina layer was peeled off from the quartz glass substrate, an etching treatment was performed at room temperature for 50 hours using a 3M aqueous sodium hydroxide solution as an etching step. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 315 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 10 nm, and the specific surface area was 1.2.

[0069] Example 8 A light-absorbing and heat-shielding film was produced in the same manner as in Example 7, except that the etching step was performed at room temperature for 50 hours using a 7.5 M aqueous sodium hydroxide solution. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 303 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 27 nm, and the specific surface area was 1.7.

[0070] Example 9 A light-absorbing and heat-shielding film was produced in the same manner as in Example 2, except that the number of laminated alumina gel films was 3. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 374 nm, the average height of the fine unevenness was 419 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 1.2 nm, and the specific surface area was 1.0.

[0071] Example 10 A light-absorbing and heat-shielding film was produced in the same manner as in Example 9, except that after the metal film with the alumina layer was peeled off from the quartz glass substrate, an etching treatment was performed at room temperature for 50 hours using a 3M aqueous sodium hydroxide solution in the etching step. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 354 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 16 nm, and the specific surface area was 1.3.

[0072] Example 11 A light-absorbing and heat-shielding film was produced in the same manner as in Example 10, except that the etching step was performed at room temperature for 45 hours using a 6 M aqueous sodium hydroxide solution. The average height of the fine unevenness of the obtained light-absorbing and heat-shielding film was 346 nm, the average surface roughness Ra' of the surface of the light-absorbing and heat-shielding film was 35 nm, and the specific surface area was 2.1.

[0073] Table 1 shows the reflectance in the visible light region and the infrared light region obtained by measuring the reflectance spectrum in the visible light region and the infrared light region of the light absorbing and heat shielding films or light absorbing and heat shielding members produced in Examples 1 to 11 and Comparative Example 1. [Table 1]

[0074] Example 12 An article (hereinafter referred to as "article with light-absorbing heat-shielding film") was produced by attaching the light-absorbing heat-shielding film produced in Example 3 to the surface of plate-shaped stainless steel (SUS). An article with a light-absorbing heat-shielding film and an article that is the same as the article with a light-absorbing heat-shielding film on its surface except that it does not have a light-absorbing heat-shielding film (hereinafter referred to as "article without light-absorbing heat-shielding film") were placed on a heater, and when the surface temperature of the article without the light-absorbing heat-shielding film reached 40°C, the surface temperatures of the article with the light-absorbing heat-shielding film and the article without the light-absorbing heat-shielding film were measured using an infrared thermography device (model: H2640, manufactured by Nippon Avionics Co., Ltd.). The surface temperature was measured at room temperature, and the distance between the article and the measuring device was about 40 cm. The surface temperature of the article with the light-absorbing heat-shielding film was about 28°C, which was about 12°C lower than the surface temperature of the article without the light-absorbing heat-shielding film. In addition, when the surface temperature of an article without a light-absorbing and heat-shielding film was set to about 60°C, the surface temperature of the article with the light-absorbing and heat-shielding film was about 37°C, which was about 23°C lower. From the above, it was found that the light-absorbing and heat-shielding film of the present invention has excellent heat shielding properties. A clear temperature difference was observed between the detected temperature of the article and the actual temperature, and it was found that the article can be identified using an infrared thermal imaging camera.

[0075] (Example 13) An article with a light-absorbing heat-shielding film was produced by attaching the light-absorbing heat-shielding film produced in Example 5 to the surface of a plate-shaped stainless steel, and the surface temperatures of the article with the light-absorbing heat-shielding film and the article without the light-absorbing heat-shielding film were measured in the same manner as in Example 12. When the surface temperature of the article without the light-absorbing heat-shielding film was about 40°C, the surface temperature of the article with the light-absorbing heat-shielding film was about 28°C, which was about 12°C lower than the surface temperature of the article without the light-absorbing heat-shielding film. When the surface temperature of the article without the light-absorbing heat-shielding film was about 60°C, the surface temperature of the article with the light-absorbing heat-shielding film was about 33°C, which was about 27°C lower.

[0076] From the above, it was found that the parts of the present invention have excellent light absorption and heat shielding properties. [Industrial Applicability]

[0077] The present invention can provide a light-absorbing and heat-shielding film and a light-absorbing and heat-shielding member that absorb visible light and near infrared rays (low reflectance) and emit little far infrared rays (high reflectance), which are normally incompatible. The light-absorbing and heat-shielding film and the light-absorbing and heat-shielding member of the present invention can be used as a stray light prevention and heat-shielding member inside optical equipment, as an interior and exterior member for space-related equipment such as artificial satellites, and can also be used as an exterior film, a solar collector, etc. [Explanation of symbols]

[0078] 1 metal layer 2 Finely textured objects 3. Micro-irregular shapes of metal oxides 4 Metal oxide layer 5 Base material 6 Adhesive layer 7. Aluminum-containing films 8 Base Material

Claims

1. A metal layer having a fine concave-convex shape containing a metal is provided, the average height difference between the apex of the convex portion and the bottom of the concave portion of the fine concave-convex shape is 100 nm or more and 1000 nm or less; the average surface roughness Ra' of the surface including the fine irregularities is 1 nm or more and 50 nm or less, and the specific surface area Sr of the surface including the fine irregularities is 1.0 or more and 3.0 or less, A light-absorbing and heat-shielding film characterized in that the reflectance in the visible light region (550 nm) is 10% or less and the reflectance in the far-infrared light region (10 μm) is 70% or more.

2. 2. The light absorbing and heat shielding film according to claim 1, wherein the thickness of the metal layer including the fine unevenness is 200 nm or more and 15,000 nm or less.

3. 3. The light-absorbing and heat-shielding film according to claim 1, further comprising a fine concave-convex shape of a metal oxide in close contact with the fine concave-convex shape.

4. 4. The light-absorbing and heat-shielding film according to claim 3, wherein the fine irregularities of the metal oxide include plate-like crystals mainly composed of alumina.

5. 5. The light-absorbing and heat-shielding film according to claim 3, wherein the surface including the fine unevenness has an average surface roughness Ra' of 1 nm or more and 4 nm or less, and the surface including the fine unevenness has a specific surface area Sr of 1.0 or more and 1.1 or less.

6. 6. The light-absorbing and heat-shielding film according to claim 1, wherein a material of the metal layer contains at least one selected from the group consisting of nickel, chromium, and zinc.

7. A light absorbing and heat shielding member comprising a base material and a light absorbing and heat shielding film provided on the base material, A light-absorbing and heat-shielding member, wherein the light-absorbing and heat-shielding film is the light-absorbing and heat-shielding film according to any one of claims 1 to 6.

8. 8. The light absorbing and heat shielding member according to claim 7, wherein the light absorbing and heat shielding film and the base material are bonded to each other by an adhesive layer.

9. An article comprising the light-absorbing and heat-shielding film according to any one of claims 1 to 6 on its outermost surface.

10. A first step of forming a fine uneven shape of a metal oxide; A second step of forming a metal layer on the fine unevenness of the metal oxide; Including, the average height difference between the apex of the convex portion and the bottom of the concave portion of the fine concave-convex shape is 100 nm or more and 1000 nm or less; the average surface roughness Ra' of the surface including the fine irregularities is 1 nm or more and 50 nm or less, and the specific surface area Sr of the surface including the fine irregularities is 1.0 or more and 3.0 or less, A method for producing a light-absorbing and heat-shielding film, characterized in that the reflectance in the visible light region (550 nm) is 10% or less and the reflectance in the far-infrared light region (10 μm) is 70% or more.

11. The method for producing a light absorbing and heat shielding film according to claim 10 , wherein the first step includes immersing the aluminum-containing film in warm water.

12. 12. The method for producing a light absorbing and heat shielding film according to claim 10, further comprising a step of removing fine irregularities of the metal oxide.

13. 10. The article according to claim 9, wherein a detected temperature of the light absorbing and heat shielding film is at least 3° C. lower than a detected temperature of a portion of the article not provided with the light absorbing and heat shielding film.

14. 14. The article of claim 13, wherein the article is a heating element.

15. Use of the light absorbing and heat shielding film according to any one of claims 1 to 6, The use of the present invention, characterized in that by providing the light-absorbing heat-shielding film on the outermost surface of an article, the detected temperature of the light-absorbing heat-shielding film is 3°C or more lower than the detected temperature of a portion of the article on which the light-absorbing heat-shielding film is not provided.

16. 16. The use according to claim 15, characterized in that the article is a heating element.

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