Heat-shielding pigment, heat-shielding coating material, and coating film

Abstract

Provided is a tabular heat-shielding pigment having a laminated structure formed by one conductor layer and one dielectric layer adjacent to each other, the heat-shielding pigment being characterized in that: the conductor layer is configured from silver or an alloy that contains 50 mass% or more of silver, the conductor layer having a physical film thickness of 5.0-35 nm; the dielectric layer is configured from a dielectric having an average refractive index of 1.70 or greater at a wavelength of 300-800 nm; and the optical film thickness of the dielectric layer is 0.50D-20D, where D [nm] is the physical film thickness of the conductor layer.

Description

Heat-shielding pigments, heat-shielding paints and coatings

[0001] The present invention relates to a heat-shielding pigment, a heat-shielding paint, and a coating film.

[0002] Heat-shielding paints with heat-shielding properties are sometimes used to paint the exteriors and parts of automobiles and buildings. Heat-shielding paints contain heat-shielding pigments that reflect or absorb infrared light. By using heat-shielding paints to paint the exteriors and parts of automobiles and buildings, it is possible to reduce the rise in the internal temperature of the automobile or building and the temperature of each part due to exposure to sunlight.

[0003] In particular, heat-shielding pigments that reflect infrared light with a high reflectance have high heat-shielding properties. Examples of pigments that reflect infrared light include metals such as silver and aluminum, and conductive materials such as alloys containing metals such as silver and aluminum. Furthermore, in order to reduce the impact on the color development of color-coated objects, pigments that reflect infrared light and transmit visible light are required.

[0004] Patent Document 1 discloses flakes containing aluminum as a reflective layer and used as pigments. Patent Document 2 discloses pigments having a laminate with a metal thin film layer and a transparent dielectric layer. Patent Document 3 discloses multilayer interference pigments having alternating layers of a transparent material with a low refractive index and a metal layer.

[0005] JP 2002-500258 A, International Publication No. 2016-006664, JP 2000-511968 A

[0006] In heat-shielding pigments, solar reflectivity and visible light transmittance tend to be in a trade-off relationship. Therefore, it has been difficult to obtain a pigment that achieves both high solar reflectivity and high visible light transmittance. For example, to improve visible light transmittance, a transparent dielectric material can be used as a material constituting the outermost layer of a multi-layer pigment, but this can sometimes result in a decrease in infrared light reflectance.

[0007] Therefore, an object of the present invention is to provide a heat-shielding coating material that has high visible light transmittance and high solar radiation reflectance. Another object of the present invention is to provide a heat-shielding coating material that has high visible light transmittance and high solar radiation reflectance. Another object of the present invention is to provide a coating film that has high visible light transmittance and high solar radiation reflectance, and a building or a mobile object that has a coating film.

[0008] The above object can be achieved by the present invention, which provides a heat-shielding pigment having a plate-like structure formed by one conductive layer and one dielectric layer adjacent to each other, wherein the conductive layer is made of silver or an alloy containing 50 mass % or more of silver and has a physical film thickness of 5.0 nm or more and 35 nm or less, the dielectric layer is made of a dielectric having an average refractive index of 1.70 or more in the wavelength range of 300 nm or more and 800 nm or less, and the optical film thickness of the dielectric layer is 0.50 D or more and 20 D or less, where D [nm] is the physical film thickness of the conductive layer.

[0009] The present invention also provides a flat heat-shielding pigment having a layered structure formed by at least three optical functional layers, wherein a first optical functional layer that is the outermost layer of the layered structure is composed of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less; a second optical functional layer adjacent to the first optical functional layer is composed of a dielectric material having an average refractive index of 1.70 or more in the wavelength range of 300 nm or more and 800 nm or less; a third optical functional layer adjacent to the second optical functional layer is composed of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less; and the optical film thickness of the second optical functional layer is 4.0D or more and 12D or less, where D [nm] is the sum of the physical film thicknesses of the first optical functional layer and the third optical functional layer.

[0010] The present invention also provides a heat-shielding coating material, which is a flat-plate heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, wherein the conductive layer is made of silver or an alloy containing 50 mass % or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less, and the dielectric layer contains 50 mass % or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, and has a physical film thickness of 5.0 nm or more and 500 nm or less.

[0011] The present invention also provides a heat-shielding pigment having a flat plate-like structure formed by at least three optical functional layers, wherein a first optical functional layer that is the outermost layer of the laminate structure is composed of silver or an alloy containing 50 mass % or more of silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less; a second optical functional layer that is adjacent to the first optical functional layer contains 50 mass % or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, and has a physical film thickness of 30 nm or more and 180 nm or less; and a third optical functional layer that is adjacent to the second optical functional layer is composed of silver or an alloy containing 50 mass % or more of silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less.

[0012] According to the present invention, it is possible to provide a heat-shielding coating material having high visible light transmittance and high solar radiation reflectance. Furthermore, according to the present invention, it is possible to provide a heat-shielding coating material having high visible light transmittance and high solar radiation reflectance. According to the present invention, it is possible to provide a coating film having high visible light transmittance and high solar radiation reflectance, and a building and a mobile body having a coating film.

[0013] FIG. 1 is a perspective view of a heat-shielding pigment according to embodiment 1. FIG. 2 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 3 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 4 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 5 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 6 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 7 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 8 is a schematic cross-sectional view of a heat-shielding pigment according to embodiment 1. FIG. 9 is a schematic view showing a manufacturing process for a heat-shielding pigment according to an embodiment. FIG. 10 is a schematic view showing a manufacturing process for a paint according to an embodiment. FIG. 11 is a schematic view showing a manufacturing process for a paint film according to an embodiment.

[0014] The present invention will be described in further detail below with reference to preferred embodiments. In this specification, the region with a wavelength of 300 nm or more and less than 800 nm is referred to as the "visible light region." The region with a wavelength of 800 nm or more is referred to as the "infrared light region." The region with a wavelength of less than 300 nm is referred to as the "ultraviolet light region." In this specification, the physical film thickness may be simply referred to as the "film thickness."

[0015] The present inventors have investigated heat-shielding pigments that have high solar radiation reflectivity and high visible light transmittance, and as a result, have found that high visible light transmittance and solar radiation reflectivity can be achieved in a multilayer coating material that has a silver-containing conductor layer as an outermost layer and a high-refractive-index transparent dielectric layer adjacent to the conductor layer.

[0016] Further research led to the development of a laminated structure in which a conductive layer containing silver or a silver alloy, which is highly reflective of infrared light, is used as the outermost layer, and a dielectric layer having an optical film thickness within a specific range is placed adjacent to the conductive layer. It was found that a pigment with such a structure can achieve high visible light transmittance and solar reflectivity. The reason for this is thought to be that the visible light reflection by the heat-shielding coating material is reduced due to the interference effect between light in the visible light range reflected by the surface of the conductive layer and light reflected by the surface of the dielectric layer.

[0017] It is known that the reduction of reflected light due to the interference of light from the surface of the thin layer is likely to be effective for light having a wavelength near 4n times (n is an integer) the optical thickness, which is the product of the refractive index and physical thickness of the thin layer. Furthermore, the inventors have found through their studies that the influence of the conductor layers is greater in a configuration in which the conductor layers are adjacent to both sides of the dielectric layer than in a configuration in which the conductor layers are adjacent to only one side of the dielectric layer.

[0018] From the above investigations, it was found that, in a heat-shielding pigment having a laminated structure formed of one conductor layer and one dielectric layer, high visible light transmittance and solar radiation reflectance can be obtained when the optical film thickness of the dielectric layer is 0.50 D or more and 20 D or less. Here, the physical film thickness of the conductor layer is defined as D [nm]. Furthermore, it was found that, in a heat-shielding pigment having a laminated structure of three or more layers including a conductor layer and a dielectric layer, when the total physical film thickness of the conductor layers is D [nm], high visible light transmittance and solar radiation reflectance can be obtained when the optical film thickness of the dielectric layer is 4.0 D or more and 12 D or less.

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

[0020] [Embodiment 1] <Heat-shielding pigment> The pigment of this embodiment is a multilayer pigment having at least two or more optically functional layers. In this specification, the pigment of this embodiment may be simply referred to as a heat-shielding pigment. The pigment can obtain heat-shielding properties by being contained in a medium such as a paint or a coating film. The pigment may have a substrate in addition to the optically functional layer, and may have an organic compound on its surface.

[0021] (Optical Functional Layer) The heat-shielding pigment of this embodiment is a multilayer pigment having at least two or more optical functional layers. The optical functional layer refers to a layer of a solid substance that reflects or diffuses visible light or infrared light. The optical functional layer in the heat-shielding pigment is a layer that controls the reflection and transmission of light, and includes two types of layers: a conductive layer that reflects light in the infrared region, and a dielectric layer that suppresses the reflection of light in the visible region through interference.

[0022] In this specification, a layer means a layer that exists on the surface of a substrate or another layer, is made of the same material, has continuity in the plane direction including the major axis of the pigment, and extends planarly to the edges. If a layer loses continuity due to being separated by other protruding layers or air spaces and is scattered on the surface of the substrate or another layer, it cannot be called a layer, and the desired optical properties cannot be obtained. To prevent the aforementioned separation, the film thickness of each layer is preferably 5 nm or more, more preferably 10 nm or more.

[0023] The film thickness and continuity of the optical functional layer can be measured by embedding the pigment in epoxy resin and observing the cross section of the resin with a transmission electron microscope. The material of each optical functional layer can also be analyzed by elemental analysis and composition analysis using energy dispersive X-ray spectroscopy (SEM-EDX) or the like after cross sectioning in a similar manner.

[0024] Generally, a conductor refers to a material having a resistivity of 1 Ωcm or less at room temperature. A dielectric refers to a material having a relative dielectric constant greater than 1. Generally, the refractive index of a dielectric is higher than that of a conductor. The conductor according to this embodiment is preferably a metal. The dielectric according to this embodiment preferably has an average refractive index of 1.70 or more, more preferably 2.00 or more, in the visible light wavelength range of 300 nm or more and 800 nm or less.

[0025] The dielectric constant is measured by an impedance analyzer. The dielectric constant can be measured, for example, by a 4990EDMS (manufactured by Toyo Corporation). The refractive index is measured by an ellipsometer. The refractive index can be measured, for example, by a VASE (manufactured by J.A. Woollam Japan).

[0026] Fig. 1 shows a perspective view of an example of a heat-shielding pigment according to embodiment 1. 2A to 2D and 3 show schematic cross-sectional views of an example of a heat-shielding pigment 1 according to embodiment 1. The heat-shielding pigment 1 includes a conductor layer 2 and a dielectric layer 3 as optically functional layers.

[0027] The number of layers in the pigment and the number of optical functional layers are arbitrary. However, as shown in FIG. 2A , a first preferred embodiment includes two optical functional layers: a first optical functional layer that is an electrical conductor and a second optical functional layer that is a dielectric layer adjacent to the first optical functional layer. That is, the electrical conductor layer may be part of one outermost layer, and the dielectric layer may be part of the other outermost layer. As shown in FIG. 2B , a second preferred embodiment includes a first optical functional layer that is an electrical conductor, a second optical functional layer that is a dielectric, and a third optical functional layer that is an electrical conductor, which are the outermost layers, in this order. More preferably, as the second embodiment, the first optical functional layer, the second optical functional layer, and the third optical functional layer may be adjacent to each other in this order, and the electrical conductor layer that is the first optical functional layer may be part of one outermost layer, and the electrical conductor layer that is the third optical functional layer may be part of the other outermost layer.

[0028] Another example of the heat-shielding pigment according to this embodiment may be a pigment having four or five optical functional layers, as shown in Figures 2C and 2D. In the case of a pigment having four optical functional layers, one outermost layer may be a conductive layer, and the other outermost layer may be a dielectric layer. In the case of a pigment having five optical functional layers, a portion of one outermost layer may be a conductive layer, and a portion of the other outermost layer may also be a conductive layer.

[0029] Another example of the heat-shielding pigment according to this embodiment may be a pigment that includes a substrate, as shown in Figures 3A and 3B. For example, the pigment shown in Figure 3A is a pigment that is configured by adjacently arranging a conductor layer 2, a dielectric layer 3, and a substrate 4 in this order. A portion of the surface of the conductor layer 2 opposite to the portion that contacts the dielectric layer 3 may be the outermost layer, and a portion of the surface of the substrate 4 opposite to the portion that contacts the dielectric layer 3 may also be the outermost layer.

[0030] (First Optical Functional Layer) The heat-shielding pigment of this embodiment has a first optical functional layer on the outermost surface of the optical functional layers. The first optical functional layer is a conductor layer and is made of silver or an alloy containing 50% by mass or more of silver. Conductors such as metals reflect light over a wide wavelength range, and among these, an alloy containing 50% by mass or more of silver has low reflectance for light in the visible light range and is therefore preferred in terms of visible light transmittance. Examples of metals that can be used in the alloy with silver include gold, copper, platinum, iron, magnesium, aluminum, titanium, chromium, nickel, zinc, palladium, indium, tin, antimony, tantalum, tungsten, thallium, and lead.

[0031] The film thickness of the first optical functional layer (conductor layer) according to this embodiment must be 35 nm or less. If it is thicker than this, light will be reflected across all wavelengths, which is disadvantageous in terms of visible light transmittance. In order to achieve both solar reflectance and visible light transmittance, the film thickness of the first optical functional layer is preferably 5.0 nm or more and 35 nm or less.

[0032] Alloys that can be used for the conductive layer are described in detail below. The alloys can be used to suppress the aggregation that may occur over time when silver is used alone, and to suppress the reaction between sulfur atoms in the air and silver. When using a silver alloy containing any of Cu, Nd, and Zn, the content of each metal relative to silver is preferably 0.1 atomic % or more. This content provides the effect of suppressing the aggregation and reaction of silver.

[0033] In the heat-shielding pigment of this embodiment, the first optical functional layer, which is a conductive layer, is located on the outermost surface of the optical functional layers. This is preferable from the viewpoint of solar reflectivity because it can directly reflect light incident on the pigment. The surface of the first optical functional layer may contain an organic or inorganic compound such as a dispersant. The organic or inorganic compound may completely cover the first optical functional layer to form a covering layer, but it is preferable that a portion of the first optical functional layer is exposed.

[0034] When the first optical functional layer is completely coated, it is desirable that the coating layer be optically negligible. Optically negligible means that when the heat-shielding pigment is present in a medium such as air or resin, it has the same refractive index as the medium. In other words, the difference in refractive index between the medium and the coating material is preferably 0.2 or less, and more preferably 0.1 or less. Furthermore, it is desirable that the thickness of the coating layer be within a range that does not optically affect the properties of the pigment. In other words, the thickness of the coating layer is preferably 5 nm or less, and more preferably 2 nm or less.

[0035] (Conductor Layer) The heat-shielding pigment of this embodiment may have an optional optical functional layer in addition to the first and second optical functional layers, or may have a conductive layer. The material and film thickness of the additional optical functional layer are not particularly limited. From the viewpoint of reflecting infrared light and transmitting visible light, the material and film thickness of the additional optical functional layer are preferably those used for the first or third optical functional layer or similar, and more preferably the same as those for the first optical functional layer.

[0036] In another preferred embodiment, a metal completely different from the above may be used to limit the reflected light to a specific wavelength. The metal may be, for example, gold, silver, copper, platinum, iron, magnesium, aluminum, titanium, chromium, nickel, or zinc, palladium, indium, tin, antimony, tantalum, tungsten, thallium, lead, or the like. An alloy containing at least one of these metals may also be used.

[0037] (Second Optical Functional Layer) The heat-shielding pigment of this embodiment has a second optical functional layer, which is a dielectric layer, adjacent to the first optical functional layer, which is a conductor layer. The second optical functional layer is a dielectric layer that suppresses reflection of light in the visible light range of the adjacent conductor layer through an interference effect. The second optical functional layer (dielectric layer) is a dielectric having an average refractive index of 1.70 or more for light with a wavelength of 300 nm or more and 800 nm or less. Furthermore, the second optical functional layer is preferably transparent.

[0038] In general, the effect of suppressing reflected light due to interference works around a wavelength that is 4n times (n is an integer) the optical film thickness, which is the product of the refractive index and the film thickness. If the refractive index of the dielectric is high, the optical film thickness can be adjusted while keeping the film thickness of the dielectric layer thin, and therefore the film thickness of the heat-shielding pigment itself can be made thin. This has the advantages of suppressing a decrease in visible light transmittance due to light scattering, and making it easier for the pigment to be oriented in the medium when forming a coating film, thereby enabling efficient reflection of light.

[0039] From the above viewpoints, the refractive index of the dielectric layer is preferably 1.7 or more, and more preferably 2.0 or more. The optical film thickness of the dielectric layer is preferably 500 nm or less, and more preferably 180 nm or less. This is because if the dielectric layer is thicker than 500 nm, multiple interference effects will appear for coherent light, causing interference fringes and adversely affecting the visible light transmittance.

[0040] Furthermore, in order for a dielectric layer to transmit light in the visible light range, it is necessary to make corrections according to the wavelength range of the reflected light of the adjacent conductive layer. After careful consideration, it was found that in order to transmit a desired wavelength range, it is necessary to make corrections according to the wavelength range of the reflected light of the adjacent conductive layer. It was also found that the influence of the conductive layer is greater when conductive layers are adjacent to both sides of the dielectric layer than when a conductive layer is adjacent to one side of the dielectric layer.

[0041] In the coating film, the reflectance of light incident on the conductive layer from the medium increases monotonically as the wavelength becomes longer. Furthermore, the thicker the film, the higher the reflectance for light with a shorter wavelength. In other words, the thicker the film, the more the rise in the reflection spectrum shifts toward shorter wavelengths. For example, a 10-nm-thick Ag film exhibits a reflectance of 27% for light with a wavelength of 600 nm, while a 20-nm-thick Ag film exhibits a reflectance of 58%, with the rise shifting toward shorter wavelengths.

[0042] That is, even if the total thickness of the conductive layers adjacent to the dielectric layer is the same, the shape of the spectrum differs when the dielectric layer is adjacent to one side (one side) compared to when two sets of stacked structures are adjacent to both sides (both sides), and the peak wavelength of the reflected light is shifted to the shorter wavelength side when the dielectric layer is adjacent to one side compared to when the two sets of stacked structures are adjacent to each other. Since the dielectric layer needs to cancel out the reflected light shifted to the shorter wavelength side and transmit it, the optical thickness needs to be thinner than when the dielectric layer is adjacent to both sides.

[0043] This configuration makes it possible to obtain the effect of interference correction at a wavelength equivalent to 4n times the optical thickness (n is an integer), resulting in high visible light transmittance. Furthermore, when conductive layers are adjacent to both sides of the dielectric layer, the peak tends to become sharper due to the overlap of reflected light, so it is necessary to apply thickness correction more strictly than when there is only one side.

[0044] Therefore, in a first aspect of this embodiment in which a conductor is adjacent to one side of a dielectric layer as depicted in Figure 2A, the optical thickness of the dielectric layer is preferably 0.50D or more and 20D or less, where D is the sum of the physical thicknesses of the adjacent conductor layers. It is even more preferable that it is 2.0D or more and 10D or less. It is even more preferable that the optical thickness of the dielectric layer is 2.0D or more and 8.0D or less, where D is the sum of the physical thicknesses of the adjacent conductor layers.

[0045] 2B , in a second aspect of the present embodiment in which conductors are adjacent to both sides of the dielectric layer, the optical film thickness of the second optical function layer is preferably 4.0D or more and 12D or less, where D is the total film thickness of the adjacent conductor layers. It is even more preferably 4.0D or more and 10D or less. This makes it possible to obtain an interference effect that corrects the wavelength corresponding to 4n times the optical film thickness (n is an integer) in accordance with the wavelength dependency of the light reflected by the conductor layer, thereby achieving high visible light transmittance.

[0046] In addition, in the third and fourth aspects of this embodiment, the first to third optical functional layers, which are conductive layers, have a thickness of 5.0 nm to 25 nm, and the second optical functional layer, which is a dielectric layer, uses a metal oxide or metal sulfide with a high refractive index. Because the thickness of the conductive layer is fixed, the thickness of the dielectric can be adjusted without correction. That is, in the third aspect of this embodiment, the thickness of the second optical functional layer is adjusted to a range of 5.0 nm to 500 nm, preferably 5 nm to 120 nm. In the third aspect of this embodiment, the thickness of the second optical functional layer is adjusted to a range of 30 nm to 180 nm. This allows only light in the visible light range to be suppressed by interference, achieving the same effects as the first and second aspects of this embodiment.

[0047] The material used in the dielectric layer is not particularly specified in the first or second embodiment, and may be an organic compound or a polymer compound as long as it has a high refractive index, but is preferably one used in the third or fourth embodiment. In the third or fourth embodiment, the dielectric layer contains 50 parts by weight or more of an oxide or sulfide of a metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium. More preferably, the dielectric layer contains 50 parts by weight or more of an oxide of a metal selected from the group consisting of titanium, niobium, tantalum, zirconium, and cerium.

[0048] Specific examples include titanium dioxide, titanium monoxide, titanium trioxide, niobium pentoxide, tantalum pentoxide, zirconium oxide, cerium oxide, and MU3. Other examples include zinc sulfide, silicon, MU2-C, GL2, MU2, hafnium oxide, silicon monoxide, yttrium oxide, magnesium oxide, and indium tin oxide (ITO). More preferred examples include titanium dioxide, titanium monoxide, titanium trioxide, niobium pentoxide, tantalum pentoxide, zirconium oxide, and cerium oxide.

[0049] (Dielectric Layer) The heat-shielding pigment of this embodiment may have an optional optical functional layer in addition to the first and second optical functional layers, and may be a dielectric layer. The material and film thickness are not particularly limited, but the dielectric layer has the role of canceling out the reflection of the conductor layer and increasing visible light transmittance, and therefore is preferably one of the examples of the second optical functional layer or a similar material, and more preferably the same as the second optical functional layer.

[0050] (Substrate) The optical functional layer of this embodiment may be formed on a substrate 4 as depicted in Figures 3A and 3B. The optical functional layer may be formed on one or both sides of the substrate. The substrate may be a conductive layer, a dielectric layer, or neither. From the viewpoint of reducing the influence on reflected light in the infrared light region, the refractive index of the substrate is preferably 1.65 or less.

[0051] Furthermore, from the viewpoint of visible light transmittance, the substrate is preferably transparent. Examples of materials used for the substrate include glass, polyethylene terephthalate (PET), mica, gelatin, collagen, fibroin, polyester, polyurethane, and polyolefin. Examples of materials used for the substrate also include polystyrene, acrylic resin, polyvinyl chloride, polyvinyl acetate, polyamide, polyimide, polycarbonate, epoxy resin, acrylonitrile / butadiene / styrene copolymer (ABS resin), and silica. More preferably, the substrate is made of glass, polyethylene terephthalate (PET), mica, or silica.

[0052] A release layer may be provided on the surface of the substrate. The release layer is preferably made of an acrylic resin. A known method can be used to form the release layer. The material constituting the release layer is applied to the surface of the substrate by, for example, a bar coater method, a spin coater method, a spray method, or the like. By providing a release layer on the surface of the substrate, the laminate of the optical functional layer, which is the raw material for the multilayer pigment, can be peeled from the substrate and used.

[0053] A support layer may also be provided on the surface of the release layer or the substrate. The support layer may be made of any material that mechanically reinforces the optical multilayer film, and the material is not limited. The support layer is also included in the pigment after the substrate is removed. Therefore, from the viewpoint of reducing the influence on reflection and transmission, the support layer is preferably transparent, and the refractive index of the support layer is preferably 1.65 or less. The thickness of the support layer is preferably 200 nm or less, more preferably 100 nm or less.

[0054] The support layer can be formed by any of the well-known gas-phase synthesis methods, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), as well as solution coating and sol-gel liquid-phase synthesis. A transparent layer, which is a precursor material for the support layer, may be formed on the surface of the substrate in advance, and then alumina, silica, or tabular crystals primarily composed of an oxide such as silica may be provided on the surface of the substrate, or the support layer may be formed directly without a precursor. For example, providing a silica support layer below the optical functional layer has the advantage of reinforcing the mechanical strength of the pigment, making it less susceptible to bending or shattering.

[0055] (Organic Compound) The heat-shielding pigment of this embodiment may be coated with an organic compound. Coating with an organic compound may be effective in dispersing the heat-shielding pigment uniformly in a medium such as a paint or coating film. The type of organic compound may be selected appropriately depending on the medium. In paints containing organic solvents or coating films containing resin components, known oil-based dispersants may be used, such as stearic acid, oleic acid, phosphonic acid, and phosphate esters. In paints containing aqueous emulsions or water in addition to organic solvents, known aqueous dispersants may be used.

[0056] (Particle Size) The particle size of the heat-shielding pigment of this embodiment is not particularly limited, but is preferably 0.50 μm or more and 100 μm or less. It is more preferably 1.0 μm or more and 30 μm or less, and even more preferably 2.0 μm or more and 20 μm or less. If the particle size is too small, local plasmon resonance may occur at the edge of the conductive layer, resulting in light absorption, which is disadvantageous in terms of both solar reflectivity and visible light transmittance. On the other hand, if the particle size is too large, it is disadvantageous in terms of the sedimentation properties of the coating material and dispersibility in the medium.

[0057] The particle size of a pigment can be quantified as the Feret diameter of a projected particle image. The Feret diameter is the length of the perpendicular line formed by sandwiching a projected particle between two parallel lines in a fixed direction. The particle size of a pigment can be quantified, for example, by dispersing the pigment in a common solvent, spraying it on a glass plate, and then observing the resulting solution under a common optical microscope. Furthermore, the particle size and its distribution can be measured by image analysis using an injection-type image analysis particle size distribution analyzer "IF-3200" (manufactured by Jasco International) when the pigment is dispersed in a common solvent. Examples of common solvents include acetone and hexafluoroisopropanol.

[0058] (Thickness of Pigment) The thickness of the heat-shielding pigment of this embodiment is not particularly limited, but is preferably 100 nm or less, and more preferably 60 nm or less. A thinner pigment has the advantages of being able to suppress a decrease in visible light transmittance due to light scattering, and of being more easily oriented in a medium, thereby enabling efficient reflection of light. The thickness of the pigment can be measured, for example, by cutting out a cross section of the pigment embedded in a resin such as epoxy and using a scanning electron microscope or a transmission electron microscope.

[0059] (Pigment Shape) The heat-shielding pigment of this embodiment has a plate-like shape. Although there is no particular problem if the plate-like particles are warped, a small curvature is preferable, and a rigid plate with a curvature of 0 is most preferable. A curvature of 0 is most advantageous in terms of solar reflectivity, because incident sunlight can be reflected uniformly across the entire surface. The shape of the pigment can be measured, for example, by cutting out a cross section of the pigment embedded in a resin such as epoxy and using a scanning electron microscope or a transmission electron microscope.

[0060] (Method for Producing Pigment) The method for producing the heat-shielding pigment of this embodiment is not particularly limited, but examples thereof include a method of peeling off and pulverizing a laminate of optical functional layers formed on a substrate. Methods for forming a laminate of optical functional layers on a substrate include chemical vapor deposition (CVD), sputtering, solution coating, electron beam deposition, and ion plating. Among these, chemical vapor deposition (CVD), sputtering, and solution coating are preferred.

[0061] 4A shows an example of a pigment manufacturing process using a sputtering method. Specifically, a target material for forming a TiO layer is sputtered onto a flat PET film substrate to form a TiO layer. Then, a target material for forming an Ag layer is sputtered to laminate an Ag layer on the TiO layer, producing a laminate of optically functional layers.

[0062] Examples of the peeling method include dissolving the substrate, and removing the peeling layer if one is provided on the substrate. For example, if an acrylic resin peeling layer is provided, the peeling layer can be removed by using an organic solvent such as methyl ethyl ketone (MEK). Examples of the pulverization method include ultrasonic pulverization, high-speed agitator pulverization, pulverization using a vibration mill, ball mill, roll mill, jet mill, etc. The pulverization method may be wet or dry. The substrate may be pulverized as is without being peeled from the substrate. Examples of the pulverization method include freeze pulverization, etc.

[0063] [Embodiment 2] <Heat-shielding paint> The heat-shielding paint of this embodiment is a heat-shielding paint containing a multilayer pigment having at least two or more optically functional layers, which corresponds to the first to fourth aspects of the heat-shielding pigment of Embodiment 1, and a resin component that is an organic solvent and a resin or a resin composition. That is, the heat-shielding paint may contain, as a pigment having a heat-shielding function, a heat-shielding pigment exemplified in Figures 2A to 2D or Figures 3A and 3B. The heat-shielding paint may further contain other components.

[0064] 4B shows an example of a method for producing a heat-shielding paint, with the steps of producing a paint as an example of a heat-shielding pigment. Specifically, a laminate of optical functional layers formed on a PET substrate is dissolved and peeled off, and ultrasonic pulverization is performed as necessary, and the resulting heat-shielding pigment is dispersed in a dispersion. Thereafter, the dispersion in which the heat-shielding pigment is dispersed is washed, and the dispersion solvent is removed, and a suitable solvent is added to the paint to produce the heat-shielding paint.

[0065] (Organic Solvent) The heat-shielding coating of this embodiment contains an organic solvent. The organic solvent is added to dissolve the resin components or to adjust the viscosity to suit the coating form, such as spraying. Most of the organic solvent volatilizes and disappears when the coating film is dried after coating. The organic solvent may be one used in general coatings, such as alcohols (methanol, ethanol, isopropanol, n-butyl alcohol, ethylene glycol, etc.). Other examples include ketones (acetone, methyl ethyl ketone, etc.) and esters (ethyl acetate, butyl acetate, etc.). Other examples include halides (chloroform, methylene chloride, etc.), olefins (butane, hexane, etc.), ethers (tetrahydrofuran (THF), etc., butyl ether, dioxane, etc.), aromatics (benzene, xylene, toluene, etc.), and amides (N,N-dimethylformamide, dimethylacetamide). Mixtures of these solvents may also be used.

[0066] (Resin Component) The resin component containing the resin or resin composition in the heat-shielding coating material of this embodiment may be a resin used in a general coating material. Examples of the resin component include acrylic resin, polyester resin, alkyd resin, fluororesin, epoxy resin, polyurethane resin, and polyether resin. The resin component may be one-component curing or two-component curing, and either may be used.

[0067] (Amount of Heat-Shielding Pigment) The amount of heat-shielding pigment in the heat-shielding coating material of this embodiment is not particularly limited, but is preferably 0.50 mass % or more and 10 mass % or less relative to the resin component. More preferably, it is 1.0 mass % or more and 5.0 mass % or less. Light incident on the coating film obtained when the solvent in the coating material has dried is reflected by the surface of the heat-shielding pigment. If the amount of heat-shielding pigment in the coating material is too small relative to the resin component contained in the coating material, the amount of light that reaches the pigment surface will be small, which is disadvantageous in terms of solar reflectivity. On the other hand, if the content is too large, the amount of light that reaches the pigment surface will increase, resulting in a corresponding decrease in visible light transmittance.

[0068] Furthermore, when the heat-shielding pigments completely cover a surface parallel to the film surface without overlapping each other, a favorable balance between reflectance and visible light transmittance is achieved. If the ratio of the pigment weight to the resin component weight in this case is taken as the coated PB ratio, the coated PB ratio can be calculated using the following formula:

[0069]

[0070] On the other hand, if the ratio of the weight of the heat-shielding pigment to the weight of the resin component in the paint is defined as the paint PB ratio, the amount of paint relative to the ideal amount can be calculated as the surface density using the following formula.

[0071]

[0072] In reality, because pigment particles overlap and tilt, adjusting the blending amount so that the surface density is 100% will not result in a 100% coverage, but this formula can be used as a guide to determine the approximate blending amount. The pigment coverage of a heat-shielding film can be measured by image analysis of an optical microscope image taken at a perpendicular angle to the film surface. The blending amount of pigment in the paint can be calculated by washing away all components other than the pigment from the paint, leaving only the pigment.

[0073] (Particle size, thickness, and shape of the heat-shielding pigment) The particle size, thickness, and shape of the heat-shielding pigment in the heat-shielding coating material of this embodiment are similar to those of the heat-shielding pigment in embodiment 1. By washing away components other than the pigment in the coating material, it is possible to leave only the pigment, which can be analyzed using a method similar to the analysis method for the heat-shielding pigment. The organic solvent in the coating material can be suitably used for washing, and heating or drying may be performed during washing.

[0074] [Embodiment 3] <Coating Film> The coating film of this embodiment is a heat-shielding film containing a multilayer pigment having at least two or more optically functional layers, similar to the heat-shielding pigment of embodiment 1, and a resin component that is a resin or a resin composition. Other components may also be contained. The coating film of this embodiment may be simply referred to as a heat-shielding film or a coating film. Figure 4C shows an example of the manufacturing process for a coating film. The paint described above is prepared, and a coating process is carried out to form a coating film on the surface of the substrate. The coating film contains a resin component and the heat-shielding pigment described above. The formed coating film exhibits a heat-shielding function when the heat-shielding pigment receives light that is incident on the surface of the coating film.

[0075] (Tilt of the heat-shielding pigment) In the heat-shielding film of this embodiment, if the tilt of the pigment relative to the surface of the optical functional layer relative to the air-side surface of the coating film is small, solar radiation incident on the surface layer of the heat-shielding film can be more easily received by the optical functional layer, and therefore, by configuring it in this way, solar reflectivity can be improved. When a coating material using the heat-shielding pigment of this embodiment is applied to any substrate and dried, a coating film with a small tilt can be obtained. Light that enters the coating film from the air hits the pigment in the coating film, and only when the reflected light does not undergo total reflection at the interface between the coating film and the air does it return to the air as reflected light.

[0076] If there is no inclination between the surface layer of the heat-shielding film and the optically functional pigment layer, for example, the angle of sunlight incident perpendicularly on the surface layer of the heat-shielding film and the light reflected by the pigment enters the air at the same angle, so total reflection does not occur. On the other hand, as the inclination of the pigment increases, the angle of incidence when entering the air becomes larger, making total reflection more likely and resulting in attenuation of the reflected light. For this reason, a small inclination of the pigment is desirable.

[0077] The heat-shielding pigment of this embodiment has an exposed conductive layer made of silver on its surface, and because of its high affinity with air, it is likely to be oriented on the surface of the coating film, resulting in a small tilt. The average tilt of the surface of the optical functional layer of the pigment relative to the air-side surface of the coating film is preferably 20° or less, and more preferably 10° or less. The tilt of the pigment can be calculated by observing the cross section of the coating film with a transmission electron microscope and performing image analysis. The average tilt is calculated as the number average of the tilts calculated by image analysis.

[0078] (Resin) The resin used in the heat-shielding coating material of this embodiment may be one that is used in general coating materials, such as acrylic resin, polyester resin, alkyd resin, fluororesin, epoxy resin, polyurethane resin, polyether resin, etc. Note that a resin composition containing additives and solvents in addition to the resin may also be used. Resins or resin compositions are available in one-component curing types and two-component curing types, and either may be used.

[0079] (Amount of Heat-Shielding Pigment) The amount of heat-shielding pigment in the heat-shielding film of this embodiment is not particularly limited, but is preferably 0.50 mass % or more and 10 mass % or less relative to the resin component. More preferably, it is 1.0 mass % or more and 5.0 mass % or less. Light incident on the heat-shielding film obtained by drying the solvent in the paint is reflected by the surface of the heat-shielding pigment.

[0080] If the amount of heat-shielding pigment blended relative to the resin component contained in the paint is small, the amount of light reaching the pigment surface will be small, which is disadvantageous in terms of solar reflectivity.On the other hand, if the content is large, the amount of light reaching the pigment surface will increase, resulting in a corresponding decrease in visible light transmittance.

[0081] Furthermore, when the heat-shielding pigments completely cover a plane parallel to the film surface without overlapping with each other, a favorable balance between reflectance and visible light transmittance is achieved. The blending amount of the heat-shielding pigment in the film can be determined by mass analysis or thermal analysis.

[0082] The blending amount of the heat-shielding pigment in the film can be determined, for example, using a thermogravimetric differential thermal analyzer (TG / DTA STA7200, manufactured by Hitachi High-Tech Science). 10 mg of a heat-shielding film sample is placed in an aluminum pan, and the weight loss in the temperature range of 250°C to 400°C is measured. Because organic compounds decompose and vaporize in the temperature range of 250°C to 400°C, the weight of the resin component in the heat-shielding film can be quantified by measuring the weight loss. The weight of the heat-shielding pigment in the heat-shielding film can be quantified by measuring the remaining weight.

[0083] (Analysis of Heat-Shielding Pigment) The heat-shielding film of this embodiment contains a heat-shielding pigment. The film thickness and continuity of the optical functional layer in the heat-shielding pigment can be measured by embedding the pigment in an epoxy resin and observing a cross-section of the resin using a transmission electron microscope. Furthermore, the material of each optical functional layer can be analyzed by elemental analysis and composition analysis using energy dispersive X-ray spectroscopy (SEM-EDX) or the like after a cross-section is taken using a similar method.

[0084] <Multilayer Coating Film> The coating film of this embodiment may be a multilayer coating film having different coating layers in the upper and lower layers. For example, the lower layer preferably has an architectural base coat or an automotive base coat, and may be a water-based or oil-based coat. Furthermore, for example, the upper layer preferably has an architectural clear coat or an automotive clear coat. The base coating film primarily functions to impart and maintain aesthetic appeal and design to the substrate on which the multilayer coating film is formed. The base coating film is formed by applying a base paint. The base paint may be either a solvent-based or water-based paint.

[0085] <Substrate> The heat shielding film of the present embodiment has high reflectance at wavelengths other than visible light, and thus prevents temperature rise of the housing due to sunlight and deterioration of the performance and quality of the contents of the housing, such as equipment, due to the temperature rise.

[0086] It is primarily intended for outdoor installation or use, and is suitable for applications requiring design and transparency in addition to heat-shielding performance. For example, it is suitable for use as a coating on mobile objects or buildings. It may be used on at least a portion of the exterior or parts of an automobile, which is an example of a mobile object. Examples of mobile objects include automobiles, aircraft, drones, and ships. Examples of exteriors or parts include bodies, mounted equipment, and various windows. It may also be used on at least a portion of the exterior or parts of a building. Examples of buildings include electronic devices and devices equipped with sensors, such as ETC gates, solar panels, residential windows, and vending machines. Alternatively, it may be directly applied to, for example, metal or plastic materials for automobiles. It may also be used in applications that do not necessarily require high design and transparency, such as building roofs and walls, storage tanks, and air conditioner outdoor units, where heat-shielding performance is required.

[0087] The heat-shielding film of this embodiment is preferably applied on a coating film coated with a primer paint such as a cationic electrodeposition paint, and in some cases, an intermediate paint. The building may be a residence, a warehouse, or a container. In both automobiles and buildings, the longer the exposure time to a solar radiation environment, the higher the heat-shielding and temperature-suppressing effects. For this reason, the film is preferably used in trucks, warehouses, containers, and the like that store precision instruments, food, etc.

[0088] <Method of Measuring Heat Shielding Property and Solar Reflectance> The heat shielding property of the heat shielding film of this embodiment can be evaluated by solar reflectance. Solar reflectance can be measured by the method described in JIS K A5602:2008. Specifically, an integrating sphere unit (ISN-923, manufactured by Jasco International) of a spectrometer (V-670, manufactured by Jasco International) is used to measure solar reflectance. Solar reflectance can be calculated by obtaining a reflection spectrum of wavelengths from 200 nm to 2300 nm at an incident angle of 5° and multiplying it by the weighting specified in JIS.

[0089] <Method for Measuring Visible Light Transmittance> The visible light transmittance of the heat shielding film of this embodiment can be evaluated by visible light transmittance. The visible light transmittance can be measured by the method described in JIS K A5759:2008. Specifically, using the same spectrophotometer as used to measure the solar reflectance, a transmission spectrum of wavelengths from 200 nm to 2300 nm is obtained at an incident angle of 5°, and the transmittance can be calculated by multiplying it by the weights described in JIS.

[0090] [Examples] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples in any way as long as the gist of the invention is not exceeded. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0091] <Preparation of Substrate> (Production of Substrate 1) An acrylic resin (trade name "Acrydic A-405", manufactured by DIC) was applied to a PET film (trade name "Lumirror (registered trademark) T60", manufactured by Toray Industries, Inc.) measuring 85 x 85 mm and 188 μm in thickness using a bar coater so that the dry film thickness was 1 μm. The PET film was then dried in an oven at 80°C for 1 hour to form a release layer, and substrate 1 was obtained.

[0092] (Preparation of Substrate 2) A substrate having a silica layer provided as a support layer on the substrate 1 was prepared as the substrate 2. Specifically, the process is as follows.

[0093] Tetraethoxysilane (TEOS), isopropyl alcohol (IPA), and 0.01M HCl aq. were mixed and stirred at room temperature for about 3 hours to obtain SiO ２ A sol solution was prepared by mixing TEOS and IPA in a molar ratio of 1:20, and adding HCl aq. in a total amount twice that of TEOS in molar ratio.

[0094] The substrate 1 is made of SiO ２ After immersion in the sol solution, a coating film was formed on the surface of the substrate 1 by a dipping method (with a withdrawal speed of 3 mm / sec, at 20°C and 56% RH). After drying the coating film, it was heat-treated at 100°C for 1 hour to form a transparent SiO ２ A SiO-based gel film was obtained. ２ The silica gel film was immersed in hot water at 100°C for 30 minutes and then dried at 100°C for 10 minutes to obtain a substrate 2. The thickness of the silica film formed on the substrate 2 was 160 nm. As will be described later, this layered silica also functions as an optically functional layer.

[0095] (Preparation of Substrate 3) Mica (trade name "PDM-20L", manufactured by Topy Industries) was spread on a PET film, and another PET film was sandwiched between them and rubbed together to charge the mica, which was then adsorbed onto the PET film. The film thickness of the mica adsorbed onto the PET film was 300 nm. As will be described later, this layer of mica also functions as an optically functional layer.

[0096] <Formation of Optical Functional Layer> (Preparation of Laminates (1) to (17) and Comparative Laminates (1) to (8)) Subsequently, an optical functional layer including a dielectric layer or a metal layer was formed on one or both sides of the prepared substrates 1 to 3 to obtain laminates. The structures of the substrates and optical functional layers used in each laminate are shown in Tables 1-1 and 1-2. The dielectric layer and metal layer were formed by an electron beam method using a vacuum deposition apparatus (EX-200, manufactured by ULVAC).

[0097] Laminates (9) to (11) were produced using substrate 3 as the substrate. Laminates (9) to (11) were recovered by releasing them from the PET film with acetone in order to remove the substrate. Laminate (11), in which optical functional layers were formed on both sides of substrate 3, was produced by repeatedly forming and releasing the optical functional layers in two stages.

[0098] Specifically, a film with adhesive (transparent X12-SN, manufactured by Nichiei Shinka) was used to prepare the laminate (11). A laminate having an optical function layer formed on one side was attached to the adhesive surface of the film with adhesive, and then the laminate was removed from the PET plate and recovered. The same optical function layer was formed again using the recovered laminate, and the adhesive was dissolved and removed using acetone to prepare the laminate (11).

[0099] The obtained laminate was fractured using a cross-section polisher (SM-09010, manufactured by JEOL). The cross section of the laminate was observed using an SEM (SU-70, manufactured by Hitachi High-Technologies), and the film thickness of each optical functional layer was measured. Tables 1-1 and 1-2 show the configuration of the optical functional layer of the laminate, the substrate, the surface on which the optical functional layer was formed, and the number of optical functional layers.

[0100] The refractive index of the material of the dielectric layer, which is the second optical functional layer, was measured using an ellipsometer (VASE, manufactured by J.A. Woollam Japan). The average refractive index n, film thickness d, and optical film thickness nd, which are the product of the measured average refractive index n and film thickness d, of the second optical functional layer in the wavelength range of 300 nm to 800 nm, are shown in Tables 1-1 and 1-2. The film thickness of the first optical functional layer, the film thickness of the third optical functional layer, D, which is the total film thickness of the first and third optical functional layers, and the value obtained by dividing the optical film thickness by D, are shown in Tables 1-1 and 1-2.

[0101] The deposition materials used for the optical functional layers shown in Tables 1-1 and 1-2 are as follows: Ag: silver (manufactured by ULVAC) TiO ２ : Titanium dioxide (manufactured by ULVAC) Ag / Cu: Silver / copper alloy (silver content 80% by weight, copper content 20% by weight, manufactured by Oike Kogyo) Nb ２ O ５ : Niobium pentoxide (manufactured by Astron) Y ２ O ３ : Yttrium oxide (manufactured by Astron) Fe ２ O ３ : Iron oxide (manufactured by Astron) Al ２ O ３ : Aluminum oxide (manufactured by Astron) Al: Aluminum (manufactured by Ulvac)

[0102]

[0103]

[0104] Examples 1 to 21, Comparative Examples 1 to 8 (Preparation of Pigments (1) to (21), Comparative Pigments (1) to (8)) (Removal of Substrate) Next, the laminates using Substrate 1 and Substrate 2 were immersed in methyl ethyl ketone (Kishida Chemical Co., Ltd.) for 30 minutes to dissolve and peel the release layer, and the substrate and release layer were washed away. For the laminate using Substrate 3, the substrate was not washed away.

[0105] (Pulverization of Pigments) Thereafter, the laminates (1) to (17) and the comparative laminates (1) to (8) were crushed in acetone (Kishida Chemical Co., Ltd.) for 2 minutes using an ultrasonic crusher to obtain 12 mg of each of the pigments (1) to (17) and the comparative pigments (1) to (8).

[0106] Furthermore, using laminate (1), the same process as in the preparation of pigment (1) was carried out except that the ultrasonic pulverization time was changed to 10 seconds, thereby obtaining 12 mg of pigment (18). Furthermore, using laminate (1), the same process as in the preparation of pigment (1) was carried out except that the ultrasonic pulverization time was changed to 20 minutes, thereby obtaining 12 mg of pigment (19).

[0107] Furthermore, using laminate (2), the same process as in the preparation of pigment (2) was carried out except that the ultrasonic pulverization time was changed to 10 seconds, thereby obtaining 12 mg of pigment (20). Furthermore, using laminate (2), the same process as in the preparation of pigment (2) was carried out except that the ultrasonic pulverization time was changed to 20 minutes, thereby obtaining 12 mg of pigment (21).

[0108] The particle sizes of the obtained pigments (1) to (21) and comparative pigments (1) to (8) were measured by image analysis using an injection-type image analysis particle size distribution meter (IF-3200, manufactured by Jasco International). Tables 2-1 and 2-2 show the laminates from which pigments (1) to (21) and comparative pigments (1) to (8) were derived, the layer structures of the heat-shielding pigments, and the film thickness and particle size of each layer measured by cross-sectional observation, as well as the specific gravity of the material of each layer and the specific gravity of the pigment calculated from the film thickness.

[0109] The specific gravities of the materials used to calculate the pigment specific gravities in Tables 2-1 and 2-2 are as follows: Ag: 10.5 g / cm ３ TiO ２ : 4.1 g / cm ３ Ag / Cu: 10.2g / cm ３ Nb ２ O ５ : 4.6 g / cm ３ Y ２ O ３ : 5.0 g / cm ３ Fe ２ O ３ : 5.2 g / cm ３ Al ２ O ３ : 4.0 g / cm ３ Al: 2.7g / cm ３

[0110] Examples 22 to 44, Comparative Examples 9 to 16 (Coating of Pigments with Organic Substances) Next, pigments (1) to (21) and comparative pigments (1) to (8) were subjected to suction filtration to remove acetone. Thereafter, each pigment was placed in 10 mL of distilled water, and sodium aluminate (manufactured by Kishida Chemical Co., Ltd.) was added so that the concentration was 4% by mass relative to the pigment, and the pH of the slurry was adjusted to 6 to 9 using sulfuric acid. The mixture was further stirred at 60°C for 1 hour, filtered, washed, and dried to obtain 12 mg of heat-shielding pigments whose surfaces were partially coated with aluminum oxide.

[0111] The obtained heat-shielding pigment was immersed in 3 mL of ethyl acetate (Kishida Chemical Co., Ltd.) to which stearic acid had been added so that the amount was 5% by mass based on the pigment, and the mixture was stirred at room temperature to replace the aluminum oxide with stearic acid. The resulting mixture was filtered and dried to obtain a heat-shielding pigment whose surface was partially coated with stearic acid.

[0112] (Preparation of Paints (1) to (23) and Comparative Paints (1) to (8)) 12 mg of each of Pigments (1) to (21) and Comparative Paints (1) to (8), each partially coated with stearic acid, was prepared. An acrylic resin solution (trade name "Acrydic A405" manufactured by DIC) was added to each pigment to achieve the paint PB ratio shown in Tables 2-1 and 2-2, respectively. The mixed material was kneaded for 3 minutes using a planetary centrifugal mixer (Thinky Mixer ARE-310). Furthermore, 200 parts by weight of xylene (manufactured by Kishida Chemical) was added to 100 parts by weight of the mixed material and stirred for 2 minutes to adjust the viscosity to 10 mPa·s to 50 mPa·s, which is suitable for spray coating. Viscosity was measured using an EMS viscometer (EMS-1000S manufactured by Kyoto Electronics Manufacturing Co., Ltd.). Paints (1) to (23) and Comparative Paints (1) to (8) were obtained.

[0113] The pigments and paint PB ratios used in preparing the resulting paints (1) to (23) and comparative paints (1) to (8) are shown in Tables 2-1 and 2-2.

[0114]

[0115]

[0116] Examples 45 to 69, Comparative Examples 17 to 24 (Preparation of Coating Films (1) to (25) and Comparative Coating Films (1) to (8)) Using a spray gun (WIDER1, manufactured by Anest Iwata), coating materials (1) to (23) and comparative coating materials (1) to (8) were spray-coated onto PET films (trade name "Lumirror (registered trademark) T60", manufactured by Toray Industries) at a pressure of 1.0 MPa. The coated PET films were dried at room temperature and normal pressure for one day to obtain coating films (1) to (23) and comparative coating films (1) to (8) with a film thickness of 20 μm.

[0117] In addition, a coating film (24) having a film thickness of 50 μm was obtained in the same manner as the coating film (1), except that the spray coating pressure was changed to 1.5 MPa. A coating film (25) having a film thickness of 10 μm was obtained in the same manner as the coating film (1), except that the spray coating pressure was changed to 0.5 MPa.

[0118] (Evaluation of coating film) The coating film was observed from above using an optical microscope at 20x magnification, and the coverage was calculated from the obtained images using image analysis. In addition, the coating film was fractured using a cross-section polisher (SM-09010, manufactured by JEOL) and the cross-section was observed using an SEM (SU-70, manufactured by Hitachi High-Tech). In the cross-sectional image, 100 pigment particles were counted, and the average inclination of the pigment relative to the air-side surface of the coating film was calculated.

[0119] The reflection and transmission spectra of the resulting coating film in the wavelength range of 200 nm to 2300 nm were measured using an integrating sphere unit (ISN-923, manufactured by Jasco International) of a spectrometer (V-670, manufactured by Jasco International). The solar reflectance was calculated by multiplying the obtained reflection spectrum by the weighting specified in JIS K A5602:2008.

[0120] The visible light transmittance was calculated by multiplying the obtained transmission spectrum by the weighting factor specified in JIS K A5759: 2008, and the solar reflectance and visible light transmittance were evaluated according to the following criteria. Tables 3-1 and 3-2 show the preparation conditions and evaluation results of the coating film.

[0121] <Evaluation criteria for solar reflectivity> Rank A: Solar reflectivity is 40% or more, and is excellent in solar reflectivity. Rank B: Solar reflectivity is 30% or more and less than 40%, which is within the acceptable range. Rank C: Solar reflectivity is less than 30%, and is low in solar reflectivity, and cannot be used as a heat-shielding film.

[0122] <Evaluation criteria for visible light transmittance> Rank A: Visible light transmittance is 65% or more, and is excellent in visible light transmittance. Rank B: Visible light transmittance is 60% or more and less than 65%, and is within the acceptable range. Rank C: Visible light transmittance is less than 60%, and no visible light is transmitted.

[0123]

[0124]

[0125] <Use of silver alloy and weather resistance evaluation> In the present invention, in addition to using a silver / copper alloy (Ag / Cu: 80 / 20 [wt %], manufactured by Oike Kogyo Co., Ltd.) as in the coating film (6), it is also possible to use a silver alloy within a range in which the silver content is maintained at 50 wt %. Specific embodiments are shown below.

[0126] [Form, composition, and content of silver alloy] As specific examples, the form, composition, and content of the silver alloy are shown in Table 4, but the present invention is not limited thereto. All of the silver alloys were purchased and used as sputtering targets manufactured by Furuya Metal Co., Ltd.

[0127] Examples 70 to 95 [Production of Coating Film (1)] Coating film (1) was obtained according to the above-described production procedure.

[0128] [Production of Coating Films (26) to (50)] The production of the laminate was carried out in accordance with the production procedure for the laminate (1), except that the silver alone was changed to a silver alloy shown in Table 1. Furthermore, the production of the pigment or paint was carried out in accordance with the production procedure for the pigment (1) or paint (1), except that the silver alone was changed to a silver alloy shown in Table 1. Finally, the production of the coating film was carried out in accordance with the production procedure for the coating film (1), except that the silver alone was changed to a silver alloy shown in Table 1, to obtain coating films (26) to (50).

[0129] In addition, the average refractive index n, film thickness d, and optical film thickness nd, which is the product of these, of TiO2, which is the second optical functional layer, in the wavelength range of 300 nm to 800 nm, and the film thickness D of the silver alloy, which is the first optical functional layer, were calculated, and the value obtained by dividing the optical film thickness by D is shown in Table 4.

[0130] [Weather Resistance Evaluation] The resulting coating film was placed in a Super Xenon Weather Meter Sx75 (Ibiden Co., Ltd.) and subjected to a xenon exposure test at an irradiance of 180 W / m@2 @ 350 nm for 472 hours at a temperature of 50°C and a humidity of 55% RH.

[0131] In addition, the annual UV dose is 360x10 ６ (J / m ２ ) ÷ irradiance of light source 180 (W / m ２) ÷ 3600 seconds / hour = 472 hours, so this exposure test is equivalent to one year of outdoor exposure time.

[0132] The results of measuring the solar reflectance of the heat-shielding coating film after exposure are shown in the table. The results show that the solar reflectance of the silver-only film decreased by about 5%, but in the case of the silver alloy, no decrease in solar reflectance was observed before and after exposure. The reason for this is unknown, but there were some coatings whose solar reflectance increased slightly after exposure.

[0133] From the above results, it was found that the use of a silver alloy containing 90% or more, more preferably 97% or more, of Ag by weight of the metal species provides better light resistance than silver alone.

[0134]

[0135] <Preparation and evaluation of multilayer coating film> (Example 70) A base coating agent (trade name "nax Admira (registered trademark) Alpha 611 Chinching Black NP", manufactured by Nippon Paint) was spray-coated on an aluminum sheet metal, and the paint (1) was then applied on top and dried to obtain a multilayer coating film (1). It was confirmed that the multilayer coating film (1) can be used as a heat-shielding coating on top of a colored paint without impairing the design.

[0136] (Example 71) A top coating agent (trade name "nax Aegis (registered trademark) RS Clear", manufactured by Nippon Paint) was further spray-coated onto the multilayer coating film (1) to obtain a multilayer coating film (2). It was confirmed that the multilayer coating film (2) was not scraped even when scratched with a fingernail, and had sufficiently high mechanical strength.

[0137] <Painting and evaluation of vehicles and buildings> (Example 72) Paint (1) was spray-painted onto the roof of a 4-ton truck (Giga (silver), manufactured by Isuzu) and allowed to dry. The painted truck was left standing from midnight to 11:00 a.m. in a sunny environment with a temperature of 30°C and humidity of 30%, and the ceiling temperature and interior temperature were measured at 11:00 a.m., finding that they were 42°C and 39°C, respectively. When the ceiling temperature and interior temperature were measured under the same conditions without spray painting, they were 60°C and 45°C, respectively, confirming the effect of the heat-shielding paint in suppressing temperature rise.

[0138] (Example 73) Paint (1) was spray-painted onto the entire surface of a logistics container (manufactured by China International Containers) and dried. The painted logistics container was left in a sunny environment with a temperature of 30°C and humidity of 30% from midnight to 11:00 a.m., and the ceiling temperature and interior temperature were measured at 11:00 a.m., finding them to be 38°C and 37°C, respectively. When the ceiling temperature and interior temperature were measured under the same conditions without spray painting, they were found to be 59°C and 42°C, respectively, confirming the effect of the heat-shielding paint in suppressing temperature rise.

[0139] The disclosure of this embodiment includes the following configurations and methods.

[0140] (Configuration 1) A flat-plate heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, wherein the conductive layer is made of silver or an alloy containing 50 mass % or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less, the dielectric layer is made of a dielectric having an average refractive index of 1.70 or more in the wavelength range of 300 nm or more and 800 nm or less, and the optical film thickness of the dielectric layer is 0.50 D or more and 20 D or less, where D [nm] is the physical film thickness of the conductive layer.

[0141] (Configuration 2) The heat-shielding pigment according to Configuration 1, wherein the optical film thickness of the dielectric layer is 2.0D or more and 10D or less, where D [nm] is the physical film thickness of the dielectric layer.

[0142] (Configuration 3) The heat-shielding pigment according to configuration 1 or 2, wherein the particle diameter of the heat-shielding pigment is 0.50 μm or more and 100 μm or less.

[0143] (Configuration 4) The heat-shielding pigment according to any one of Configurations 1 to 3, wherein the thickness of the heat-shielding pigment is 100 nm or less.

[0144] (Configuration 5) The heat-shielding pigment according to any one of Configurations 1 to 4, comprising a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less, and the layered structure is adjacent to one surface of the substrate.

[0145] (Configuration 6) The heat-shielding pigment according to any one of Configurations 1 to 4, comprising: a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less; and two sets of the laminate structures, wherein the laminate structures are adjacent to both surfaces of the substrate, and the conductor layer is an outermost layer.

[0146] (Configuration 7) A flat heat-shielding pigment having a laminated structure formed by at least three optical functional layers, wherein a first optical functional layer that is the outermost layer of the laminated structure is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less; a second optical functional layer adjacent to the first optical functional layer is made of a dielectric material having an average refractive index of 1.70 or more in the wavelength range of 300 nm to 800 nm; a third optical functional layer adjacent to the second optical functional layer is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less; and the optical film thickness of the second optical functional layer is 4.0 D or more and 12 D or less, where D [nm] is the sum of the physical film thicknesses of the first optical functional layer and the third optical functional layer.

[0147] (Configuration 8) The heat-shielding pigment according to Configuration 7, wherein the particle diameter of the heat-shielding pigment is 0.50 μm or more and 100 μm or less.

[0148] (Configuration 9) The heat-shielding pigment according to configuration 7 or 8, wherein the thickness of the heat-shielding pigment is 100 nm or less.

[0149] (Configuration 10) The heat-shielding pigment according to any one of Configurations 7 to 9, wherein the layered structure includes the first optical functional layer, the second optical functional layer, and the third optical functional layer.

[0150] (Configuration 11) The heat-shielding pigment according to any one of Configurations 7 to 10, further comprising a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less, and the layered structure is adjacent to one surface of the substrate.

[0151] (Configuration 12) The heat-shielding pigment according to any one of Configurations 7 to 10, comprising: a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less; and two sets of the laminate structures, wherein the laminate structures are adjacent to each of both surfaces of the substrate.

[0152] (Configuration 13) A flat-plate heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, wherein the conductive layer is made of silver or an alloy containing 50 mass % or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less, and the dielectric layer contains 50 mass % or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, and has a physical film thickness of 5.0 nm or more and 500 nm or less.

[0153] (Configuration 14) A flat heat-shielding pigment having a laminated structure formed by at least three optical functional layers, wherein a first optical functional layer that is the outermost layer of the laminated structure is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less; a second optical functional layer adjacent to the first optical functional layer contains 50% by mass or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, and has a physical film thickness of 30 nm or more and 180 nm or less; and a third optical functional layer adjacent to the second optical functional layer is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less.

[0154] (Configuration 15) A heat-shielding coating material comprising the heat-shielding pigment according to any one of Configurations 1 to 14, an organic solvent, and a resin.

[0155] (Configuration 16) A coating film comprising the heat-shielding pigment according to any one of Configurations 1 to 14 and a resin.

[0156] (Configuration 17) A coating film comprising the heat-shielding pigment according to any one of Configurations 1 to 14 and a resin, wherein an average inclination of the heat-shielding pigment with respect to the air-side surface of the coating film is 20° or less.

[0157] (Configuration 18) A mobile object, comprising a coating film containing the heat-shielding pigment according to any one of Configurations 1 to 14 and a resin.

[0158] (Configuration 19) A building comprising a coating film containing the heat-shielding pigment according to any one of Configurations 1 to 14 and a resin.

[0159] (Configuration 20) A method for producing a heat-shielding pigment having a laminated structure including a conductor layer and a dielectric layer, the method comprising: a step of depositing, on a substrate, a dielectric material including 50 mass % or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, to form a dielectric layer having a physical film thickness of 5.0 nm or more and 500 nm or less; a step of depositing, on the dielectric layer, a conductor made of silver or an alloy including 50 mass % or more of silver, to form a conductor layer having a physical film thickness of 5.0 nm or more and 35 nm or less; and a step of pulverizing the laminated body including the dielectric layer and the conductor layer.

[0160] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0161] This application claims priority based on Japanese Patent Application No. 2024-146725 filed on August 28, 2024 and Japanese Patent Application No. 2025-131576 filed on August 6, 2025, the entire contents of which are incorporated herein by reference.

[0162] 1 heat-shielding pigment 2 conductive layer 3 dielectric layer 4 substrate

Claims

1. A heat-shielding pigment having a flat plate-like structure formed by one conductive layer and one dielectric layer adjacent to each other, wherein the conductive layer is made of silver or an alloy containing 50 mass% or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less, the dielectric layer is made of a dielectric material having an average refractive index of 1.70 or more in the wavelength range of 300 nm or more and 800 nm or less, and the optical film thickness of the dielectric layer is 0.50 D or more and 20 D or less, where D [nm] is the physical film thickness of the conductive layer.

2. The heat-shielding pigment according to claim 1, wherein the optical film thickness of the dielectric layer is 2.0D or more and 10D or less, where D [nm] is the physical film thickness of the dielectric layer.

3. The heat-shielding pigment according to claim 1, characterized in that the particle diameter of the heat-shielding pigment is 0.50 μm or more and 100 μm or less.

4. The heat-shielding pigment according to claim 1, wherein the thickness of the heat-shielding pigment is 100 nm or less.

5. The heat-shielding pigment according to claim 1, comprising a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less, and the laminated structure is adjacent to one surface of the substrate.

6. The heat-shielding pigment according to claim 1, comprising a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less, and two sets of the laminated structures, wherein the laminated structures are adjacent to both sides of the substrate, and the conductive layer is the outermost layer.

7. A flat heat-shielding pigment having a laminated structure formed by at least three optical functional layers, wherein a first optical functional layer that is the outermost layer of the laminated structure is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less; a second optical functional layer adjacent to the first optical functional layer is made of a dielectric material having an average refractive index of 1.70 or more in the wavelength range of 300 nm to 800 nm; a third optical functional layer adjacent to the second optical functional layer is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less; and the optical film thickness of the second optical functional layer is 4.0 D or more and 12 D or less, where D [nm] is the sum of the physical film thicknesses of the first optical functional layer and the third optical functional layer.

8. The heat-shielding pigment according to claim 7, characterized in that the particle diameter of the heat-shielding pigment is 0.50 μm or more and 100 μm or less.

9. The heat-shielding pigment according to claim 7, wherein the thickness of the heat-shielding pigment is 100 nm or less.

10. The heat-shielding pigment according to claim 7, wherein the laminated structure comprises the first optical functional layer, the second optical functional layer, and the third optical functional layer.

11. The heat-shielding pigment according to claim 7, characterized in that it comprises a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less, and the laminated structure is adjacent to one surface of the substrate.

12. The heat-shielding pigment according to claim 7, characterized in that it comprises a substrate having an average refractive index of 1.65 or less in the wavelength range of 300 nm or more and 800 nm or less, and two sets of the laminated structures, the laminated structures being adjacent to each of both surfaces of the substrate.

13. A flat-plate heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, wherein the conductive layer is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less, and the dielectric layer contains 50% by mass or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, and has a physical film thickness of 5.0 nm or more and 500 nm or less.

14. A flat-plate heat-shielding pigment having a laminated structure formed by at least three optical functional layers, wherein a first optical functional layer that is the outermost layer of the laminated structure is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less; a second optical functional layer adjacent to the first optical functional layer contains 50% by mass or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium, and has a physical film thickness of 30 nm or more and 180 nm or less; and a third optical functional layer adjacent to the second optical functional layer is made of silver or an alloy containing 50% by mass or more of silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less.

15. A heat-shielding paint comprising the heat-shielding pigment according to any one of claims 1 to 14, an organic solvent, and a resin.

16. A coating film comprising the heat-shielding pigment according to any one of claims 1 to 14 and a resin.

17. A coating film comprising the heat-shielding pigment and a resin according to any one of claims 1 to 14, wherein the average inclination of the heat-shielding pigment relative to the air-side surface of the coating film is 20° or less.

18. A mobile object characterized by being provided with a coating film containing the heat-shielding pigment according to any one of claims 1 to 14 and a resin.

19. A building characterized by being provided with a coating film containing the heat-shielding pigment according to any one of claims 1 to 14 and a resin.

20. A method for producing a heat-shielding pigment having a laminated structure including a conductive layer and a dielectric layer, the method comprising the steps of: depositing a dielectric material containing 50 mass% or more of an oxide or sulfide of at least one metal selected from the group consisting of titanium, niobium, tantalum, zirconium, cerium, zinc, copper, silicon, hafnium, yttrium, magnesium, and indium on a substrate to form a dielectric layer having a physical film thickness of 5.0 nm or more and 500 nm or less; depositing a conductive material composed of silver or an alloy containing 50 mass% or more of silver on the dielectric layer to form a conductive layer having a physical film thickness of 5.0 nm or more and 35 nm or less; and pulverizing the laminated body including the dielectric layer and the conductive layer.

Images