Heat-shielding pigments, heat-shielding paints, and coating films

Abstract

To provide a heat-shielding pigment with high visible light transmittance and high solar reflectance. [Solution] A plate-shaped 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 composed of an alloy containing 50% by mass or more of silver or silver, and has a physical film thickness of 5.0 nm to 35 nm, and the dielectric layer is composed of a dielectric having an average refractive index of 1.70 or more at wavelengths of 300 nm to 800 nm, and the optical film thickness of the dielectric layer is 0.50D to 20D, where D [nm] is the physical film thickness of the conductive layer.

Description

[Technical Field]

[0001] This invention relates to heat-shielding pigments, heat-shielding paints, and coating films. [Background technology]

[0002] Heat-reflective paints are sometimes used as coatings for the exteriors and parts of automobiles and buildings. Heat-reflective paints use heat-reflective pigments that reflect or absorb infrared light. By using heat-reflective paints for the exteriors and parts of automobiles and buildings, it is possible to reduce the rise in internal temperature of automobiles and buildings, as well as the temperature of individual parts, caused by sunlight irradiation.

[0003] In particular, heat-shielding pigments that reflect infrared light with high reflectivity have excellent heat-shielding properties. Examples of pigments that reflect infrared light include metals such as silver and aluminum, as well as conductive materials such as alloys containing metals such as silver and aluminum. Furthermore, in the case of painted objects, pigments that reflect infrared light while transmitting visible light are required to minimize the impact on the color development of the paint film.

[0004] Patent Document 1 discloses a thin flake containing aluminum as a reflective layer and used as a pigment. Patent Document 2 discloses a pigment comprising a laminate having a metal thin film layer and a transparent dielectric layer. Patent Document 3 discloses a multilayer coherent pigment having alternating layers consisting of a layer of transparent material with a low refractive index and a layer of metal. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2002-500258 [Patent Document 2] International Publication No. 2016-006664 [Patent Document 3] Special Publication No. 2000-511968 [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0007] Therefore, an object of the present invention is to provide a heat-shielding paint that has high visible light transmittance and high solar reflectance. Another object of the present invention is to provide a heat-shielding paint that has high visible light transmittance and high solar reflectance. Another object of the present invention is to provide a coating film that has high visible light transmittance and high solar reflectance, as well as buildings and mobile bodies having the coating film. [Means for solving the problem]

[0008] The above objective is achieved by the present invention as follows. Specifically, the present invention provides a plate-shaped 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 composed of an alloy containing 50% by mass or more of silver or silver, and has a physical film thickness of 5.0 nm to 35 nm, and the dielectric layer is composed of a dielectric having an average refractive index of 1.70 or more at wavelengths of 300 nm to 800 nm, and the optical film thickness of the dielectric layer is 0.50D to 20D, where D [nm] is the physical film thickness of the conductive layer.

[0009] Furthermore, the present invention provides a plate-shaped heat-shielding pigment having a laminated structure formed by at least three optical functional layers, wherein the first optical functional layer, which is the outermost layer of the laminated structure, is composed of an alloy containing 50% by mass or more silver or silver, and has a physical film thickness of 5.0 nm to 35 nm; the second optical functional layer adjacent to the first optical functional layer is composed of a dielectric having an average refractive index of 1.70 or more at wavelengths of 300 nm to 800 nm; the third optical functional layer adjacent to the second optical functional layer is composed of an alloy containing 50% by mass or more silver or silver, and has a physical film thickness of 5.0 nm to 35 nm; and the optical film thickness of the second optical functional layer is 4.0D to 12D, when the sum of the physical film thicknesses of the first optical functional layer and the third optical functional layer is D [nm].

[0010] Furthermore, the present invention provides a plate-shaped 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 composed of an alloy containing 50% by mass or more silver or silver, and has a physical film thickness of 5.0 nm to 35 nm, 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 to 500 nm.

[0011] Furthermore, the present invention provides a plate-shaped heat-shielding pigment having a laminated structure formed by at least three optical functional layers, wherein the first optical functional layer, which is the outermost layer of the laminated structure, is composed of an alloy containing 50% by mass or more silver or silver, and has a physical film thickness of 5.0 nm to 25 nm; the 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 to 180 nm; and the third optical functional layer adjacent to the second optical functional layer is composed of an alloy containing 50% by mass or more silver or silver, and has a physical film thickness of 5.0 nm to 25 nm. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a heat-shielding paint with high visible light transmittance and high solar reflectance. Furthermore, according to the present invention, it is possible to provide a heat-shielding paint with high visible light transmittance and high solar reflectance. According to the present invention, it is possible to provide a coating film with high visible light transmittance and high solar reflectance, as well as buildings and mobile bodies having the coating film. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view of the heat-shielding pigment according to Embodiment 1. [Figure 2] This is a schematic cross-sectional view of the heat-shielding pigment according to Embodiment 1. [Figure 3] This is a schematic cross-sectional view of the heat-shielding pigment according to Embodiment 1. [Figure 4] This is a schematic diagram showing the manufacturing process of a heat-shielding pigment, paint, and coating film according to an embodiment. [Modes for carrying out the invention]

[0014] Hereinafter, the present invention will be described in more detail by giving preferred embodiments. In this specification, a region where the wavelength is 300 nm or more and less than 800 nm is expressed as the "visible light region". A region where the wavelength is 800 nm or more is expressed as the "infrared light region". A region where the wavelength is less than 300 nm is expressed as the "ultraviolet light region". In this specification, the physical film thickness may be simply described as the "film thickness".

[0015] The inventors of the present invention studied a heat insulating pigment having high solar reflectivity and high visible light transmittance. As a result, it was found that high visible light transmittance and solar reflectivity can be obtained in a multilayer coating having a conductor layer containing silver as the outermost layer and a transparent dielectric layer having a high refractive index adjacent to the conductor layer.

[0016] Furthermore, further studies were conducted, and a laminated structure was studied in which a dielectric layer having an optical film thickness within a specific range was adjacent to a conductor layer using a conductor layer containing silver or a silver alloy that easily reflects infrared light as the outermost layer. It was found that high visible light transmittance and solar reflectivity can be obtained in a pigment having such a structure. The reason for this is considered to be that the reflection of visible light by the heat insulating paint is reduced by the interference effect between the light in the visible light region reflected on the surface of the conductor layer and the light reflected on the surface of the dielectric layer.

[0017] Here, it is known that the reduction of reflected light due to the interference of light from the surface of a thin layer easily occurs in light near a wavelength that is 4n times (n is an integer) the optical film thickness, which is the product of the refractive index and the physical film thickness of the thin layer. Also, from the study by the inventors of the present invention, it was found that the influence of the conductor layer is greater in a configuration where the conductor layer is adjacent to both sides of the dielectric layer than in a configuration where the conductor layer is adjacent to only one side of the dielectric layer.

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

[0019] The embodiments of the present invention will be described below 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 optical functional layers. In this specification, the pigment of this embodiment may be simply referred to as a heat-shielding pigment. The pigment can be incorporated into a medium such as a paint or coating to obtain heat-shielding properties. The pigment may have a substrate in addition to the optical functional layers, 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. An optical functional layer refers to a layer of solid material 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 consists of two types: 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] Furthermore, in this specification, a layer means a layer that exists on the surface of a substrate or other layer, is made of the same material, has continuity in the planar direction including the long axis of the pigment, and extends planarly to the edges. If a layer is fragmented by other protruding layers or air layers and loses its continuity, and is scattered on the surface of the substrate or other layer, it cannot be called a layer, and the desired optical properties cannot be obtained. To prevent the aforementioned fragmentation, 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. Furthermore, the material of each optical functional layer can be analyzed by obtaining a cross-section using a similar method and performing elemental and compositional analysis using energy-dispersive X-ray spectroscopy (SEM-EDX), etc.

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

[0025] The relative permittivity is measured by an impedance analyzer. For example, the 4990EDMS (manufactured by Toyo Technica) can be used to measure the relative permittivity. The refractive index is measured by an ellipsometer. For example, the VASE (manufactured by JAWoollam Japan) can be used to measure the refractive index.

[0026] Figure 1 shows a perspective view of an example of a heat-shielding pigment according to Embodiment 1. Figures 2 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 comprises a conductive layer 2 and a dielectric layer 3 as optical functional layers.

[0027] The number of layers in the pigment and the number of optical functional layers are arbitrary, but a first preferred embodiment is shown in Figure 2(a), in which the optical functional layers consist of two layers: a first optical functional layer which is a conductor and a second optical functional layer which is a dielectric adjacent to it. That is, the conductive layer may be part of one of the outermost layers, and the dielectric layer may be part of the outermost layer of the other. A second preferred embodiment is shown in Figure 2(b), in which the outermost layer has a first optical functional layer which is a conductor, a second optical functional layer which is a dielectric, and a third optical functional layer which is a conductor, in that order. More preferably as a second embodiment, the first optical functional layer, the second optical functional layer, and the third optical functional layer are adjacent to each other in that order, and the conductive layer which is the first optical functional layer may be part of one of the outermost layers, and the conductive layer which is the third optical functional layer may be part of the outermost layer of the other.

[0028] As another example of the heat-shielding pigment according to this embodiment, a pigment having four or five optical functional layers may be used, as shown in Figures 2(c) and 2(d). In the case of a pigment with four optical functional layers, one outermost layer is a conductive layer and the other outermost layer is a dielectric layer. In the case of a pigment with 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 a heat-shielding pigment according to this embodiment is a pigment that includes a substrate, as shown in Figures 3(a) and 3(b). For example, the pigment shown in Figure 3(a) is a pigment in which a conductive layer 2, a dielectric layer 3, and a substrate 4 are adjacent in this order. A portion of the surface of the conductive layer 2 opposite to the portion in contact with the dielectric layer 3 is the outermost layer, and a portion of the surface of the substrate 4 opposite to the portion in contact with 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 layer. The first optical functional layer is a conductive layer, which is an alloy or silver containing 50% by mass or more of silver. Conductors such as metals reflect light in a wide wavelength range, but among them, alloys or silver containing 50% by mass or more of silver are preferred in terms of visible light transmittance because their reflectivity is low for light in the visible light range. Examples of metals that can be used in alloys with silver include gold, copper, platinum, iron, magnesium, aluminum, titanium, chromium, nickel, zinc, palladium, indium, tin, antimony, tantalum, tungsten, thallium, and lead.

[0031] The 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, it will reflect light across all wavelengths, which is disadvantageous from the viewpoint of visible light transmittance. In order to achieve both solar reflectance and visible light transmittance, the thickness of the first optical functional layer is preferably 5.0 nm or more and 35 nm or less.

[0032] The alloys that can be used in the conductive layer are described in detail below. Alloys can be used to suppress the aggregation that may occur over time when silver is used alone, and to suppress the reaction between silver and sulfur atoms in the air. When using a silver alloy containing Cu, Nd, or Zn, it is preferable that the content of each metal is 0.1 atomic percent or more relative to silver. At this content, the aggregation suppression effect and reaction suppression effect of silver will occur.

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

[0034] When the first optical functional layer is completely covered, 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. That is, it is preferable that the refractive index difference between the medium and the coating material be 0.2 or less, and more preferably 0.1 or less. Furthermore, it is preferable that the thickness of the coating layer is within a range that does not optically affect the properties of the pigment. That is, the thickness of the coating layer is preferably 5 nm or less, and more preferably 2 nm or less.

[0035] (Conductive layer) The heat-shielding pigment of this embodiment may have any additional optical functional layer besides the first and second optical functional layers, and may also have a conductive layer. The material and film thickness of the additional optical functional layer are not particularly specified. 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 in or similar to those used in the first or third optical functional layer, and more preferably the same as that of the first optical functional layer.

[0036] In other preferred configurations, a completely different metal 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, etc. It may also be zinc, palladium, indium, tin, antimony, tantalum, tungsten, thallium, lead, etc. It may also be an alloy containing at least one of these metals.

[0037] (Second optical functional layer) The heat-shielding pigment of this embodiment has a first optical functional layer, which is a conductive layer, and a second optical functional layer, which is a dielectric layer, adjacent to it. The second optical functional layer is a dielectric layer that suppresses the reflection of light in the visible light region of the adjacent conductive layer through interference effects. The second optical functional layer (dielectric layer) is a dielectric material with an average refractive index of 1.70 or more for light with wavelengths of 300 nm to 800 nm. Furthermore, it is preferable that the second optical functional layer is transparent.

[0038] Generally, the effect of suppressing reflected light due to interference acts around wavelengths obtained by multiplying the optical film thickness (the product of refractive index and film thickness) by 4n (where n is an integer). If the refractive index of the dielectric is high, the optical film thickness can be adjusted while keeping the dielectric layer thickness thin, thus allowing for a thinner film thickness of the heat-shielding pigment itself. This suppresses the reduction in visible light transmittance due to light scattering, and when forming a coating film, it becomes easier for the pigment to orient in the medium, resulting in the advantage of efficient light reflection.

[0039] From the above viewpoint, the refractive index of the dielectric layer is preferably 1.7 or higher, and more preferably 2.0 or higher. Furthermore, 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 appear for coherent light, causing interference fringing and negatively affecting the visible light transmittance.

[0040] Furthermore, in order for the dielectric layer to transmit light in the visible light region, it is necessary to correct it according to the wavelength range of the reflected light from the adjacent conductive layer. After thorough investigation, it was found that in order to transmit light in an arbitrary wavelength range, it is necessary to correct it according to the wavelength range of the reflected light from 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 conductive layers are adjacent to only one side of the dielectric layer.

[0041] In a coating film, the reflectance of light incident on the conductive layer from the medium increases monotonically as the wavelength increases. Furthermore, the thicker the film, the higher the reflectance for short-wavelength light. In other words, the thicker the film, the shorter the onset of the reflection spectrum. For example, an Ag film with a thickness of 10 nm shows a reflectance of 27% for light with a wavelength of 600 nm, but an Ag film with a thickness of 20 nm shows a reflectance of 58%, with the onset of the reflection spectrum shifting to the shorter wavelength side.

[0042] In other words, even if the total thickness of the conductive layers adjacent to the dielectric layer is the same, the shape of the spectrum differs depending on whether the layers are adjacent on one side or on both sides. In the case of one-sided adjacent layers, the peak wavelength of the reflected light shifts to the shorter wavelength side compared to the case of both sides. The dielectric layer needs to cancel out and transmit the reflected light that has shifted to the shorter wavelength side, so its optical thickness needs to be thinner than in the case of both sides.

[0043] This configuration allows for interference correction at wavelengths corresponding to 4n times the optical film thickness (where n is an integer), resulting in high visible light transmittance. Furthermore, when conductive layers are adjacent to both sides of the dielectric layer, the superposition of reflected light tends to sharpen the peak, requiring a more rigorous application of film thickness correction than in the case of a single-sided layer.

[0044] Therefore, in the first embodiment of this model, as shown in Figure 2(a), where the conductor is adjacent to one side of the dielectric layer, 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. Furthermore, it is more preferably 2.0D or more and 10D or less. The optical thickness of the dielectric layer is more preferably 2.0D or more and 8.0D or less, where D is the sum of the physical thicknesses of the adjacent conductor layers.

[0045] Furthermore, in the second embodiment of this design, as shown in Figure 2(b), where the conductors are adjacent to both sides of the dielectric layer, the optical film thickness of the second optical functional layer is preferably 4.0D or more and 12D or less, where D is the sum of the film thicknesses of the adjacent conductor layers. More preferably, it is 4.0D or more and 10D or less. This allows for an interference effect that corrects wavelengths corresponding to 4n times the optical film thickness (where n is an integer) according to the wavelength dependence of the reflected light from the conductor layer, thereby achieving high visible light transmittance.

[0046] Furthermore, in the third and fourth embodiments of this embodiment, the film thickness of the first to third optical functional layers, which are conductive layers, is 5.0 nm to 25 nm, and a metal oxide or metal sulfide with a high refractive index is used as the second optical functional layer, which is a dielectric layer. Since the film thickness of the conductive layer is fixed, the film thickness of the dielectric can be adjusted without correction. Specifically, in the third embodiment of this embodiment, the film 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 embodiment of this embodiment, the film thickness of the second optical functional layer is adjusted to a range of 30 nm to 180 nm. By doing so, only light in the visible light region can be suppressed by interference, and the same effects as in the first and second embodiments of this embodiment can be obtained.

[0047] The material used in the dielectric layer is not particularly specified in the first or second form, and may be an organic compound or polymer compound as long as it has a high refractive index, but the material used in the third or fourth form is preferred. In the third or fourth form, it 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, it 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] Specifically, examples include titanium dioxide, titanium monoxide, dititanium 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 preferably, examples include titanium dioxide, titanium monoxide, dititanium trioxide, niobium pentoxide, tantalum pentoxide, zirconium oxide, and cerium oxide.

[0049] (Dielectric layer) The heat-shielding pigment of this embodiment may have any optical functional layer in addition to the first and second optical functional layers, and may also be a dielectric layer. The material and film thickness are not particularly specified, but since the dielectric layer cancels out the reflection of the conductive layer and enhances visible light transmittance, it is preferable to use one similar to or exemplified in the second optical functional layer, and more preferably the same as the second optical functional layer.

[0050] (base material) The optical functional layer of this embodiment may be formed on the substrate 4 as shown in Figure 3. 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 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 that can be used as the substrate include glass, polyethylene terephthalate (PET), mica, gelatin, collagen, fibroin, polyester, polyurethane, and polyolefin. Other examples include polystyrene, acrylic resin, polyvinyl chloride, polyvinyl acetate, polyamide, polyimide, polycarbonate, epoxy resin, acrylonitrile / butadiene / styrene copolymer (ABS resin), and silica. More preferably, the materials used as the substrate include glass, polyethylene terephthalate (PET), mica, and silica.

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

[0053] Furthermore, a support layer may be provided on the surface of the release layer or the substrate. The support layer may be, for example, a material that mechanically reinforces the optical multilayer film, and the material of the support layer is not limited. The support layer is also contained in the pigment after the substrate has been 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, and more preferably 100 nm or less.

[0054] The support layer can be formed by any of the known chemical vapor deposition (CVD) method, the vapor phase synthesis method of physical substrate deposition (PVD), the solution coating method, or the liquid phase synthesis method of sol-gel. After forming a transparent layer, which is a precursor material for the support layer, on the substrate surface in advance, plate-like crystals mainly composed of alumina, silica, or silica oxides may be provided on the substrate surface, or they may be formed directly without a precursor. For example, by providing a silica support layer below the optical functional layer, the mechanical strength of the pigment is reinforced, which has the advantage of making it less prone to bending and fracturing.

[0055] (organic compound) The heat-shielding pigment of this embodiment may be coated with an organic compound. Coating with an organic compound can be effective in ensuring uniform dispersion of the heat-shielding pigment in a medium such as a paint or coating film. The type of organic compound may be selected depending on the medium. In paints containing organic solvents or coating films containing resin components, known oily 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 in this embodiment is not particularly defined, but is preferably 0.50 μm to 100 μm. More preferably, it is 1.0 μm to 30 μm, and even more preferably, 2.0 μm to 20 μm. If the particle size is too small, local plasmon resonance may occur at the edges of the conductive layer, causing light absorption, which is disadvantageous in terms of both solar reflectance and visible light transmittance. On the other hand, if the particle size is too large, it is disadvantageous in terms of paint settling and dispersibility in the medium.

[0057] The particle size of a pigment can be quantified as the ferret diameter of the particle projection image. The ferret diameter is the length of the perpendicular line formed by sandwiching the 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, scattering it on a glass plate, drying it, and observing it with a common optical microscope. Alternatively, the particle size and its distribution can be measured by image analysis using the injection-type image analysis particle size distribution analyzer "IF-3200" (manufactured by JUSCO International) while the pigment is dispersed in a common solvent. Common solvents here include, for example, acetone and hexafluoroisopropanol.

[0058] (Pigment thickness) The thickness of the heat-shielding pigment in this embodiment is not particularly specified, but is preferably 100 nm or less, and more preferably 60 nm or less. Thinning the pigment has the advantage of suppressing the reduction in visible light transmittance due to light scattering, and also has the advantage of being easier to orient in the medium, allowing for efficient reflection of light. The thickness of the pigment can be measured, for example, by cutting 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 in this embodiment is flat. While it is not a problem if the plate-like particles are curved, a small curvature is preferable, and a rigid flat plate with zero curvature is most preferable. When the curvature is zero, the incident sunlight can be uniformly reflected across the entire surface, which is most advantageous from the viewpoint of solar reflectance. 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 of manufacturing pigments) The method for manufacturing the heat-shielding pigment of this embodiment is not particularly defined, but one example is a method of peeling 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] Figure 4(a) shows an example of a pigment manufacturing process using the sputtering method. Specifically, a target material for forming the TiO2 layer is sputtered onto a flat PET film substrate to form the TiO2 layer. Subsequently, a target material for forming the Ag layer is sputtered to further laminate the Ag layer onto the TiO2 layer, thereby manufacturing a laminate of optical functional layers.

[0062] Methods of delamination include dissolving the substrate and, if a delamination layer is provided on the substrate, removing the delamination layer. For example, if an acrylic resin has a delamination layer, the delamination layer can be removed by using an organic solvent such as methyl ethyl ketone (MEK). Methods of grinding include ultrasonic grinding, high-speed agitator grinding, vibration milling, ball milling, roll milling, jet milling, etc. The grinding method may be wet or dry. The substrate may also be ground without delamination. Examples of grinding methods include freeze grinding.

[0063] [Embodiment 2] <Heat-reflective paint> The heat-shielding paint of this embodiment is a multilayer pigment having at least two or more optical functional layers, similar to the first to fourth forms of the heat-shielding pigment of Embodiment 1, and contains an organic solvent and a resin component which is a resin or resin composition. That is, the heat-shielding paint may contain a heat-shielding pigment as illustrated in Figure 2 or Figure 3 as a pigment that has a heat-shielding function. Furthermore, the heat-shielding paint may contain other components.

[0064] The manufacturing method for heat-shielding paint is shown in Figure 4(b) as an example of the paint manufacturing process for a heat-shielding pigment. Specifically, the laminate of optical functional layers formed on a PET substrate is dissolved and peeled off, ultrasonic pulverization is performed as needed, and the obtained heat-shielding pigment is dispersed in a dispersion liquid. Then, the dispersion liquid containing the dispersed heat-shielding pigment is washed and the solvent of the dispersion liquid is removed, and a solvent suitable for the paint is added to manufacture the heat-shielding paint.

[0065] (Organic solvents) The heat-shielding paint of this embodiment contains an organic solvent. The organic solvent is added to dissolve the resin component and to adjust the viscosity to suit the painting method, such as spraying. Most of it evaporates when the paint film dries after painting. The organic solvent may be one that is commonly used in paints, for example, 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 (tetrohydrofuran (THF), butyl ether, dioxane, etc.), aromatics (benzene, xylene, toluene, etc.), and amides (N,N-dimethylformamide, dimethylacetamide). A mixture of these solvents may also be used.

[0066] (Resin components) The resin component in the heat-shielding paint of this embodiment, which includes a resin or resin composition, may be one that is commonly used in paints. Examples of resin components include acrylic resin, polyester resin, alkyd resin, fluororesin, epoxy resin, polyurethane resin, and polyether resin. Resin components can be either one-component curing type or two-component curing type, and either may be used.

[0067] (Amount of heat-shielding pigment used) The amount of heat-shielding pigment in the heat-shielding paint of this embodiment is not particularly specified, but it is preferably 0.50% to 10% by mass relative to the resin component. More preferably, it is preferably 1.0% to 5.0% by mass. Light incident on the paint film obtained when the solvent in the paint dries is reflected by the surface of the heat-shielding pigment. If the amount of heat-shielding pigment relative to the resin component contained in the paint is small, the amount of light reaching the pigment surface will be small, which is unfavorable from the viewpoint of solar reflectivity. On the other hand, if the content is large, the amount of light reaching the pigment surface will be large, but the visible light transmittance will decrease.

[0068] Furthermore, a favorable balance between reflectance and visible light transmittance is achieved when the heat-shielding pigments completely cover the film surface on a plane parallel to it, without overlapping. If the ratio of pigment weight to resin component weight at this time is defined as the coating PB ratio, the coating PB ratio can be calculated using the following formula.

[0069]

number

[0070] In contrast, 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 surface density using the following formula.

[0071]

number

[0072] In reality, due to overlapping and tilting of pigment particles, even if the mixing ratio is adjusted to achieve a surface density of 100%, the coverage rate will never be 100%. However, this formula can be used as a guideline to determine the approximate mixing ratio. The pigment coverage rate of a heat-shielding film can be measured by image analysis of an optical microscope image taken at an angle perpendicular to the film surface. The amount of pigment in the paint can be calculated by washing away all components other than the pigment in the paint to obtain a pigment-only state.

[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 paint of this embodiment are the same as those of the heat-shielding pigment according to Embodiment 1. By washing away components other than the pigment in the paint, the pigment can be isolated and analyzed using the same method as for analyzing the heat-shielding pigment. Organic solvents in the paint can be suitably used for washing, and the washing may be heated or dried during the washing process.

[0074] [Embodiment 3] <Paint film> The coating film of this embodiment is a heat-shielding film containing a multilayer pigment having at least two or more optical functional layers, similar to the heat-shielding pigment of Embodiment 1, and a resin component which is a resin or resin composition. It may also contain other components. The coating film of this embodiment may be simply described as a heat-shielding film or coating film. Figure 4(c) shows an example of the manufacturing process of the coating film. The paint described above is prepared, and the painting process is carried out to form a coating film on the surface of the object to be coated. The coating film contains a resin component and the heat-shielding pigment described above. The formed coating film exhibits a heat-shielding function when light incident from the surface of the coating film is received by the heat-shielding pigment.

[0075] (Inclination of heat-shielding pigment) In this embodiment, if the tilt of the pigment relative to the air-side surface of the coating film, with respect to the surface of the optical functional layer, is small, the solar radiation incident on the surface of the heat-shielding film can be more easily received by the optical functional layer. By configuring it in this way, the solar reflectance can be enhanced. When a paint 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 incident into the coating film from the air strikes the pigment within the coating film, and the reflected light returns to the air as reflected light only when total internal reflection does not occur at the interface between the coating film and the air.

[0076] If there is no inclination between the surface layer of the heat-shielding film and the optical functional layer of the pigment, for example, total internal reflection does not occur because the angle of sunlight incident perpendicular to the surface layer of the heat-shielding film is the same as the angle of light reflected by the pigment, which then enters the air through the surface layer of the heat-shielding film. On the other hand, as the inclination of the pigment increases, the angle of incidence when the light enters the air becomes larger, making total internal reflection more likely, and the reflected light is attenuated. For this reason, a small inclination of the pigment is desirable.

[0077] The heat-shielding pigment of this embodiment has a conductive layer made of silver exposed on its surface, and because of its high affinity for air, it easily orients 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 with respect 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 by the average number of tilts calculated by image analysis.

[0078] (resin) The resin used in the heat-shielding coating of this embodiment may be one commonly used in paints, such as acrylic resin, polyester resin, alkyd resin, fluororesin, epoxy resin, polyurethane resin, or polyether resin. In addition, a resin composition containing additives or solvents may be used. The resin or resin composition may be either a one-component curing type or a two-component curing type.

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

[0080] If the amount of heat-shielding pigment in the paint is low relative to the resin component, the amount of light reaching the pigment surface will be reduced, which is disadvantageous in terms of solar reflectance. On the other hand, if the amount is high, the amount of light reaching the pigment surface will increase, but the visible light transmittance will decrease.

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

[0082] The amount of 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). A 10 mg sample of the heat-shielding film is placed in an aluminum pan, and the weight loss is measured in the range of 250°C to 400°C. Since organic compounds decompose and vaporize in the 250°C to 400°C temperature range, 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 pigments) 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 epoxy resin and observing the cross-section of the resin with a transmission electron microscope. Furthermore, the material of each optical functional layer can be analyzed by obtaining a cross-section using the same method and performing elemental and compositional analysis using energy-dispersive X-ray spectroscopy (SEM-EDX), etc.

[0084] <Multi-layer coating> The coating film of this embodiment may be a multi-layer coating having different coating layers in the upper and lower layers. For example, the lower layer preferably has a base coat for construction or a base coat for automobiles, and may be either a water-based or oil-based coating. Also, for example, the upper layer preferably has a clear coat for construction or a clear coat for automobiles. The base coating film mainly has the function of imparting and maintaining aesthetics and design to the object on which the multi-layer 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] <Object to be coated> The heat-shielding film of this embodiment has a high reflectivity at wavelengths other than visible light, thereby preventing the housing from overheating due to sunlight and the deterioration of the performance and quality of the equipment and other contents of the housing due to the overheating.

[0086] It is primarily suitable for applications where installation or use outdoors is anticipated, and where aesthetic appeal and transparency are required in addition to heat-shielding performance. For example, it is suitable for painting on mobile objects and buildings. It may be used on the exterior or at least part of the 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 the body, mounted equipment, and various windows. It may also be used on the exterior or at least part of the parts of a building. Examples of buildings include electronic devices and equipment equipped with sensors such as ETC gates, solar panels, residential windows, and vending machines. Alternatively, it may be directly painted on metal or plastic materials used in automobiles, for example. It can also be used in applications where aesthetic appeal and transparency are not necessarily required, such as roofs and walls of buildings, storage tanks, and outdoor units of air conditioners, where heat-shielding performance is required.

[0087] The heat-shielding film of this embodiment is preferably applied to a coating film that has been painted with a primer such as cationic electrodeposition paint, or in some cases, an intermediate coat. The building may be a residence, a warehouse, or a container. In both automobiles and buildings, the longer the time exposed to the solar environment, the greater the heat-shielding and temperature-suppressing effect. For this reason, it is preferably used in trucks, warehouses, containers, etc., that store precision equipment, food, etc.

[0088] <Method for measuring heat shielding properties and solar reflectance> The heat shielding performance 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, the 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 the reflection spectrum at wavelengths from 200 nm to 2300 nm at an incident angle of 5° and multiplying it by the weights described in JIS.

[0089] <Method for measuring visible light transmittance> The visible light transmittance of the heat-shielding film in this embodiment can be evaluated by visible light transmittance. Visible light transmittance can be measured by the method described in JIS K A5759:2008. Specifically, the same spectrophotometer used for measuring solar reflectance can be used to obtain transmission spectra at wavelengths from 200 nm to 2300 nm at an incident angle of 5°, and the transmittance can be calculated by applying 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 in any way by the following examples unless it exceeds the gist of the invention. Unless otherwise specified, amounts of components indicated in "parts" and "%" are based on mass.

[0091] <Preparation of base material> (Preparation of base material 1) An 85 x 85 mm, 188 μm thick PET film (product name "Lumirror® T60", manufactured by Toray) was coated with acrylic resin (product name "Acrydic A-405", manufactured by DIC) using a bar coater to a dry film thickness of 1 μm. The PET film was then dried in an 80°C oven for 1 hour to form a release layer, which was used as substrate 1.

[0092] (Preparation of base material 2) As base material 2, a base material was prepared in which a silica layer was provided as a support layer on top of base material 1. Specifically, it is as follows:

[0093] A SiO2 sol solution was prepared by mixing tetraethoxysilane (TEOS), isopropyl alcohol (IPA), and 0.01 M [HCl aq.] and stirring at room temperature for approximately 3 hours. The molar ratio of the mixture was TEOS:IPA = 1:20, and the amount of HCl aq. added was twice the molar amount of TEOS.

[0094] Substrate 1 was immersed in an SiO2 sol solution, and then a coating film was formed on the surface of substrate 1 by dipping (with a pulling speed of 3 mm / second, at 20°C and 56% RH). After drying the coating film, it was heat-treated at 100°C for 1 hour to obtain a transparent SiO2-based gel film. Next, the SiO2-based gel film was immersed in hot water at 100°C for 30 minutes, and then dried at 100°C for 10 minutes to obtain substrate 2. The silica film thickness formed on substrate 2 was 160 nm. As will be described later, this layered silica also functions as an optically functional layer.

[0095] (Preparation of base material 3) Mica (product name "PDM-20L," manufactured by Topy Industries) was scattered onto a PET film, another PET film was placed on top, and the two films were rubbed together to charge the mica, causing it to adhere to the PET film. The thickness of the mica adsorbed on the PET film was 300 nm. As will be described later, this layered mica also functions as an optical functional layer.

[0096] <Formation of optical functional layer> (Preparation of laminates (1) to (17) and comparative laminates (1) to (8)) Next, optical functional layers containing dielectric layers or metal layers were formed on one or both sides of the prepared substrates 1 to 3 to obtain laminates. The configurations of the substrates and optical functional layers used in each laminate are shown in Tables 1-1 and 1-2. The dielectric layers and metal layers were formed by electron beam deposition using a vacuum deposition apparatus (EX-200, ULVAC).

[0097] Laminates (9) to (11) were fabricated using substrate 3 as the base material. Laminates (9) to (11) were released from the PET film using acetone to remove the base material and recovered. Laminate (11), in which optical functional layers were formed on both sides of substrate 3, was fabricated by repeating the formation and release of the optical functional layer in two stages.

[0098] Specifically, an adhesive film (transparent X12-SN, manufactured by Nichiei Shinka) was used to prepare the laminate (11). The laminate, with an optical functional layer formed on one side, was bonded to the adhesive side of the adhesive film, released from the PET plate, and recovered. The same optical functional layer was formed again using the recovered laminate, and the adhesive was dissolved and released using acetone to create the laminate (11).

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

[0100] Furthermore, the refractive index of the dielectric layer, which is the second optical functional layer, was measured using an ellipsometer (VASE, JAWoollam Japan). The average refractive index n, film thickness d, and their product, optical film thickness nd, of the measured 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 (the sum of the film thicknesses of the first and third optical functional layers), and the value obtained by dividing the optical film thickness by D are also shown in Tables 1-1 and 1-2.

[0101] The deposition materials used for each optical functional layer shown in Tables 1-1 and 1-2 are as follows. Ag: Silver (made by ULVAC) TiO2: Titanium dioxide (manufactured by ULVAC) Ag / Cu: Silver / copper alloy (silver content 80% by weight, copper content 20% by weight, manufactured by Oike Kogyo) Nb2O5: Niobium pentoxide (manufactured by Astron) Y2O3: Yttrium oxide (manufactured by Astron) Fe2O3: Iron oxide (manufactured by Astron) Al2O3: Aluminum oxide (manufactured by Astron) Al: Aluminum (manufactured by ULVAC)

[0102] [Table 1-1]

[0103] [Table 1-2]

[0104] <Examples 1-21, Comparative Examples 1-8> (Preparation of pigments (1) to (21) and comparative pigments (1) to (8)) (Removal of substrate) Next, the laminates using substrate 1 and substrate 2 were immersed in methyl ethyl ketone (manufactured by Kishida Chemical) for 30 minutes to dissolve and remove 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] (Pigment grinding) Subsequently, the laminates (1) to (17) and the comparative laminates (1) to (8) were crushed in acetone (manufactured by Kishida Chemical) using an ultrasonic grinder for 2 minutes to obtain 12 mg each of pigments (1) to (17) and comparative pigments (1) to (8).

[0106] Furthermore, using the laminate (1), the same process as for the preparation of pigment (1) was performed except that the ultrasonic grinding time was changed to 10 seconds, and 12 mg of pigment (18) was obtained. Also, using the laminate (1), the same process as for the preparation of pigment (1) was performed except that the ultrasonic grinding time was changed to 20 minutes, and 12 mg of pigment (19) was obtained.

[0107] Furthermore, using the laminate (2), the same process as for the preparation of pigment (2) was performed except that the ultrasonic grinding time was changed to 10 seconds, and 12 mg of pigment (20) was obtained. Also, using the laminate (2), the same process as for the preparation of pigment (2) was performed except that the ultrasonic grinding time was changed to 20 minutes, and 12 mg of pigment (21) was obtained.

[0108] The particle sizes of the obtained pigments (1) to (21) and comparative pigments (1) to (8) were measured using an image analysis method with an injection-type image analysis particle size distribution analyzer (IF-3200, manufactured by JUSCO 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 structure of the heat-shielding pigments, and the film thickness, particle size, specific gravity of the material in each layer, and the pigment specific gravity calculated from the film thickness, as measured by cross-sectional observation.

[0109] The specific gravities of the materials used in calculating the specific gravity of the pigments in Tables 2-1 and 2-2 are as follows: Ag: 10.5 g / cm³ 3 TiO2: 4.1 g / cm³ 3 Ag / Cu: 10.2 g / cm³ 3 Nb2O5: 4.6 g / cm³ 3 Y2O3: 5.0 g / cm³ 3 Fe2O3: 5.2 g / cm³ 3 Al2O3: 4.0 g / cm³ 3 Al: 2.7 g / cm³ 3 <Examples 22-44, Comparative Examples 9-16> (Coating of pigments with organic matter) Next, pigments (1) to (21) and comparative pigments (1) to (8) were filtered by suction to remove acetone. Then, each pigment was placed in 10 mL of distilled water, and sodium aluminate (manufactured by Kishida Chemical Co., Ltd.) was added to a concentration of 4% by mass relative to the pigment. The pH of the slurry was then adjusted to 6-9 using sulfuric acid. The mixture was then stirred at 60°C for 1 hour, filtered, washed, and dried to obtain 12 mg of heat-shielding pigment with a portion of its surface coated with aluminum oxide.

[0110] The obtained heat-shielding pigment was immersed in 3 mL of ethyl acetate (manufactured by Kishida Chemical Co., Ltd.) to which stearic acid was added at a concentration of 5% by mass relative to the pigment. The mixture was stirred at room temperature, and the aluminum oxide was replaced with stearic acid. This mixture was filtered and dried to obtain a heat-shielding pigment in which a portion of the surface was coated with stearic acid.

[0111] (Preparation of paints (1) to (23) and comparative paints (1) to (8)) 12 mg each of pigments (1) to (21) and comparative pigments (1) to (8) were prepared, with a portion of the surface coated with stearic acid. Acrylic resin solution (product 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. The mixed materials were kneaded for 3 minutes using a rotary-orbit mixer (Awatori Rentaro ARE-310, manufactured by Shinki). 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. An EMS viscometer (EMS-1000S, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) was used to measure the viscosity. Paints (1) to (23) and comparative paints (1) to (8) were obtained.

[0112] Tables 2-1 and 2-2 show the pigments and paint PB ratios used in the preparation of the obtained paints (1) to (23) and comparative paints (1) to (8).

[0113] [Table 2-1]

[0114] [Table 2-2]

[0115] <Examples 45-69, Comparative Examples 17-24> (Preparation of coating films (1) to (25) and comparative coating films (1) to (8)) Using a spray gun (WIDER1, manufactured by Anest Iwata), paints (1) to (23) and comparative paints (1) to (8) were spray-coated onto PET film (product name "Lumirror (registered trademark) T60," manufactured by Toray) at a pressure of 1.0 MPa. The coated PET film was dried for one day at room temperature and pressure to obtain coated films (1) to (23) and comparative coated films (1) to (8) with a film thickness of 20 μm.

[0116] Furthermore, a coating film (24) with a thickness of 50 μm was obtained in the same manner as the method for producing coating film (1), except that the spray painting pressure was changed to 1.5 MPa. A coating film (25) with a thickness of 10 μm was obtained in the same manner as the method for producing coating film (1), except that the spray painting pressure was changed to 0.5 MPa.

[0117] (Evaluation of paint film) The paint film was observed from above using an optical microscope at 20x magnification, and the coverage rate was calculated from the obtained images using image analysis. Furthermore, the paint film was fractured using a cross-section polisher (SM-09010, JEOL) and cross-sectional observation was performed using a scanning electron microscope (SEM, SU-70, Hitachi High-Tech). In the cross-sectional images, 100 pigment particles were counted, and the average value of the pigment's inclination relative to the air-side surface of the paint film was calculated.

[0118] The reflectance and transmission spectra of the obtained coating film in the wavelength range of 200 nm to 2300 nm were acquired using a spectrometer (V-670, manufactured by JUSCO International) with an integrating sphere unit (ISN-923, manufactured by JUSCO International). The solar reflectance was calculated by multiplying the obtained reflectance spectra by the weights specified in JIS K A5602:2008.

[0119] Furthermore, the visible light transmittance was calculated by multiplying the obtained transmission spectrum by the weights 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 conditions for preparing the coating film and the evaluation results. <Evaluation Criteria for Solar Reflectance> Rank A: Solar reflectance is 40% or higher, indicating excellent solar reflectance. Rank B: Solar reflectance is between 30% and 40%, which is within an acceptable range. Rank C: Solar reflectance is less than 30%, making it unsuitable for use as a heat-shielding film due to its low solar reflectance. <Evaluation Criteria for Visible Light Transmittance> Rank A: Visible light transmittance is 65% or higher, indicating excellent visible light transmittance. Rank B: Visible light transmittance is between 60% and 65%, which is within an acceptable range. Rank C: Visible light transmittance is less than 60%, and does not transmit visible light.

[0120] [Table 3-1]

[0121] [Table 3-2]

[0122] <Use of silver alloy and weather resistance evaluation> In this invention, in addition to using a silver / copper alloy (Ag / Cu: 80 / 20 [wt%], manufactured by Oike Kogyo) as in the coating film (6), it is also possible to use a silver alloy as long as the silver content is maintained at 50 wt%. Specific embodiments are shown below.

[0123] [Form, composition, and content of silver alloys] Table 4 shows specific examples of the form, composition, and content of silver alloys, but the present invention is not limited thereto. All of the silver alloys were purchased and used from sputtering targets manufactured by Furuya Metal Co., Ltd.

[0124] <Examples 70 to 95> [Production of the coating film (1)] The coating film (1) was obtained by the production procedure described above.

[0125] [Production of the coating films (26) to (50)] The laminate was produced in accordance with the production procedure of the laminate (1), except that silver alone was changed to the silver alloy described in Table 1. Also, the pigment or paint was produced in accordance with the production procedure of the pigment (1) or paint (1), except that silver alone was changed to the silver alloy described in Table 1. Finally, the coating film was produced in accordance with the production procedure of the coating film (1), except that silver alone was changed to the silver alloy described in Table 1, and the coating films (26) to (50) were obtained.

[0126] Also, the average refractive index n, film thickness d, and the optical film thickness nd which is their product, in the wavelength range of 300 nm to 800 nm of TiO₂ which is the second optical functional layer, and the film thickness D of the silver alloy which is the first optical functional layer were determined, and the value obtained by dividing the optical film thickness by D is shown in Table 4.

[0127] [Weather resistance evaluation] The obtained coating film was placed in a super xenon weather meter Sx75 (manufactured by Iwata Denki Co., Ltd.), and a xenon exposure test was conducted for 472 hours at a temperature of 50 °C and a humidity of 55% RH with an irradiance of 180 W / m²@350 nm.

[0128] Incidentally, from the annual ultraviolet dose of 360 x 10 6 (J / m 2 ) ÷ the irradiance of the light source 180 (W / m 2 ) ÷ 3600 seconds / hour ≈ 472 hours, this exposure test corresponds to the outdoor exposure time for one year.

[0129] The measured results of the solar reflectance of the heat-insulating coating film after exposure are shown in the table. From the results, the solar reflectance of the silver single film decreased by about 5%, but in the case of the silver alloy, no decrease in the solar reflectance was observed before and after exposure. The reason is unknown, but there were some coating films in which the solar reflectance slightly increased after exposure.

[0130] From these results, it was found that using a silver alloy containing 90% or more, more preferably 97% or more, of Ag by weight percentage of the metal species results in superior light resistance compared to silver alone.

[0131] [Table 4]

[0132] <Fabrication and evaluation of multi-layer coatings> (Example 70) A base coat (product name "nax Admira (registered trademark) Alpha 611 Chinching Black NP", manufactured by Nippon Paint) was spray-coated onto an aluminum sheet metal, and then paint (1) was applied as a topcoat and dried to obtain a multi-layer coating (1). It was confirmed that a heat-shielding coating could be applied to the multi-layer coating (1) without impairing the aesthetic appearance of the colored paint.

[0133] (Example 71) A topcoat agent (product name "nax Aegis® RS Clear", manufactured by Nippon Paint) was spray-coated onto the multi-layer coating (1) to obtain a multi-layer coating (2). The multi-layer coating (2) did not abrade even when scratched with a fingernail, confirming that it had sufficiently high mechanical strength.

[0134] <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 in a sunny environment with a temperature of 30°C and humidity of 30%, from midnight to 11:00 AM. At 11:00 AM, the ceiling temperature and interior temperature were measured to be 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 temperature rise suppression effect of the heat-shielding paint.

[0135] (Example 73) Paint (1) was spray-painted onto the entire surface of a logistics container (manufactured by China International Container Systems) and allowed to dry. 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 AM. At 11:00 AM, the ceiling temperature and interior temperature were measured 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 59°C and 42°C, respectively, confirming the temperature rise suppression effect of the heat-shielding paint.

[0136] This embodiment includes the following configurations and methods.

[0137] (Composition 1) A flat plate-shaped heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, The conductive layer is composed of an alloy containing 50% by mass or more of silver, or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. The dielectric layer is composed of a dielectric material having an average refractive index of 1.70 or more at wavelengths between 300 nm and 800 nm. A heat-shielding pigment characterized in that the optical thickness of the dielectric layer is 0.50D or more and 20D or less, when the physical thickness of the conductive layer is D [nm].

[0138] (Configuration 2) The heat-shielding pigment according to configuration 1, characterized in that the optical thickness of the dielectric layer is 2.0D or more and 10D or less, when the physical thickness of the dielectric layer is D [nm].

[0139] (Composition 3) The heat-shielding pigment according to configuration 1 or 2, characterized in that the particle size of the heat-shielding pigment is 0.50 μm or more and 100 μm or less.

[0140] (Composition 4) The heat-shielding pigment according to any one of configurations 1 to 3, characterized in that the thickness of the heat-shielding pigment is 100 nm or less.

[0141] (Composition 5) A 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 at wavelengths of 300 nm to 800 nm, wherein the laminated structure is adjacent to one side of the substrate.

[0142] (Composition 6) A 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 at wavelengths of 300 nm to 800 nm, and two sets of the laminated structures, wherein the laminated structures are adjacent to each of the two sides of the substrate and the conductive layer is the outermost layer.

[0143] (Composition 7) A flat plate-shaped heat-shielding pigment having a laminated structure formed by at least three optical functional layers, The first optical functional layer, which is the outermost layer of the laminated structure, is composed of an alloy containing 50% or more by mass of silver or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. The 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 higher at wavelengths between 300 nm and 800 nm. The third optical functional layer adjacent to the second optical functional layer is composed of an alloy containing 50% or more by mass of silver or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. A heat-shielding pigment characterized in that the optical film thickness of the second optical functional layer is 4.0D or more and 12D or less, when the sum of the physical film thickness of the first optical functional layer and the physical film thickness of the third optical functional layer is D [nm].

[0144] (Composition 8) The heat-shielding pigment according to configuration 7, characterized in that the particle size of the heat-shielding pigment is 0.50 μm or more and 100 μm or less.

[0145] (Composition 9) The heat-shielding pigment according to configuration 7 or 8, characterized in that the thickness of the heat-shielding pigment is 100 nm or less.

[0146] (Composition 10) The heat-shielding pigment according to any one of the configurations 7 to 9, characterized in that the laminated structure comprises the first optical functional layer, the second optical functional layer, and the third optical functional layer.

[0147] (Composition 11) A heat-shielding pigment according to any one of the configurations 7 to 10, comprising a substrate having an average refractive index of 1.65 or less at wavelengths of 300 nm to 800 nm, wherein the laminated structure is adjacent to one side of the substrate.

[0148] (Composition 12) A 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 at wavelengths of 300 nm to 800 nm, and two sets of the laminated structures, wherein the laminated structures are adjacent to each of the two sides of the substrate.

[0149] (Composition 13) A flat plate-shaped heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, The conductive layer is composed of an alloy containing 50% by mass or more of silver, or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. The dielectric layer is characterized by containing 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 having a physical film thickness of 5.0 nm or more and 500 nm or less.

[0150] (Composition 14) A flat plate-shaped heat-shielding pigment having a laminated structure formed by at least three optical functional layers, The first optical functional layer, which is the outermost layer of the laminated structure, is composed of an alloy containing 50% or more by mass of silver or silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less. The 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 to 180 nm. A heat-shielding pigment characterized in that the third optical functional layer adjacent to the second optical functional layer is composed of an alloy containing 50% by mass or more of silver, or silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less.

[0151] (Composition 15) A heat-shielding paint characterized by comprising a heat-shielding pigment, an organic solvent, and a resin as described in any one of items 1 to 14.

[0152] (Composition 16) A coating film characterized by containing the heat-shielding pigment and resin described in any one of the items 1 to 14.

[0153] (Composition 17) A coating film comprising a heat-shielding pigment and resin as described in any one of items 1 to 14, A coating film characterized in that the average inclination of the heat-shielding pigment with respect to the air-side surface of the coating film is 20° or less.

[0154] (Composition 18) A mobile body characterized by comprising a coating film containing a heat-shielding pigment and resin as described in any one of the configurations 1 to 14.

[0155] (Composition 19) A building characterized by comprising a paint film containing a heat-shielding pigment and resin as described in any one of items 1 to 14.

[0156] (Composition 20) A method for manufacturing a heat-shielding pigment having a laminated structure including a conductive layer and a dielectric layer, A process of depositing a dielectric material containing 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 onto a substrate 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 an alloy containing 50% or more by mass of silver or a conductor composed of silver onto the dielectric layer to form a conductive layer having a physical film thickness of 5.0 nm or more and 35 nm or less, A method for producing a heat-shielding pigment, characterized by comprising the step of pulverizing a laminate including the dielectric layer and the conductive layer. [Explanation of Symbols]

[0157] 1. Heat-shielding pigment 2. Conductive layer 3. Dielectric layer 4 Base material

Claims

1. A flat plate-shaped heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, The conductive layer is composed of an alloy containing 50% by mass or more of silver, or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. The dielectric layer is composed of a dielectric material having an average refractive index of 1.70 or more at wavelengths of 300 nm to 800 nm. A heat-shielding pigment characterized in that the optical thickness of the dielectric layer is 0.50D or more and 20D or less, when the physical thickness of the conductive layer is D [nm].

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

3. The heat-shielding pigment according to claim 1, characterized in that the particle size 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, characterized in that 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 at wavelengths of 300 nm to 800 nm, wherein the laminated structure is adjacent to one side 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 at wavelengths of 300 nm to 800 nm, and two sets of the laminated structures, wherein the laminated structures are adjacent to each of the two sides of the substrate and the conductive layer is the outermost layer.

7. A flat plate-shaped heat-shielding pigment having a laminated structure formed by at least three optical functional layers, The first optical functional layer, which is the outermost layer of the laminated structure, is composed of an alloy containing 50% or more by mass of silver or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. The 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 at wavelengths of 300 nm to 800 nm. The third optical functional layer adjacent to the second optical functional layer is composed of an alloy containing 50% or more by mass of silver or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. A heat-shielding pigment characterized in that the optical film thickness of the second optical functional layer is 4.0D or more and 12D or less, when the sum of the physical film thickness of the first optical functional layer and the physical film thickness of the third optical functional layer is D [nm].

8. The heat-shielding pigment according to claim 7, characterized in that the particle size 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, characterized in that the thickness of the heat-shielding pigment is 100 nm or less.

10. The heat-shielding pigment according to claim 7, characterized in that 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, comprising a substrate having an average refractive index of 1.65 or less at wavelengths of 300 nm to 800 nm, wherein the laminated structure is adjacent to one side of the substrate.

12. The heat-shielding pigment according to claim 7, comprising a substrate having an average refractive index of 1.65 or less at wavelengths of 300 nm to 800 nm, and two sets of the laminated structures, wherein the laminated structures are adjacent to each of the two sides of the substrate.

13. A flat plate-shaped heat-shielding pigment having a laminated structure formed by one conductive layer and one dielectric layer adjacent to each other, The conductive layer is composed of an alloy containing 50% by mass or more of silver, or silver, and has a physical film thickness of 5.0 nm or more and 35 nm or less. The dielectric layer is characterized by containing 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 having a physical film thickness of 5.0 nm or more and 500 nm or less.

14. A flat plate-shaped heat-shielding pigment having a laminated structure formed by at least three optical functional layers, The first optical functional layer, which is the outermost layer of the laminated structure, is composed of an alloy containing 50% or more by mass of silver or silver, and has a physical film thickness of 5.0 nm or more and 25 nm or less. The 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 to 180 nm. A heat-shielding pigment characterized in that the third optical functional layer adjacent to the second optical functional layer is composed of 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 characterized by comprising a heat-shielding pigment, an organic solvent, and a resin according to any one of claims 1 to 14.

16. A coating film characterized by comprising the heat-shielding pigment and resin described in any one of claims 1 to 14.

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

18. A mobile body characterized by comprising a coating film containing a heat-shielding pigment and resin according to any one of claims 1 to 14.

19. A building characterized by comprising a coating film containing a heat-shielding pigment and resin as described in any one of claims 1 to 14.

20. A method for manufacturing a heat-shielding pigment having a laminated structure including a conductive layer and a dielectric layer, A step of depositing a dielectric material containing 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 onto a substrate 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 an alloy containing 50% or more by mass of silver or a conductor made of silver onto the dielectric layer to form a conductive layer having a physical film thickness of 5.0 nm or more and 35 nm or less, A method for producing a heat-shielding pigment, characterized by comprising the step of pulverizing a laminate including the dielectric layer and the conductive layer.

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