Laminate, decorative device, millimeter wave radar device, and sensor device

Abstract

Provided is a laminate comprising a clearcoat layer, a base material, and a silver mirror layer in this order. The clearcoat layer contains particles.

Description

Laminate, decorating device, millimeter wave radar device, and sensor device

[0001] The present disclosure relates to a laminate, a decorating device, a millimeter-wave radar device, and a sensor device.

[0002] In recent years, interest in millimeter-wave sensors has been growing. For example, in recent automobiles, the advancement of safety devices has been remarkable, and automatic collision avoidance systems, for example, have become common. Automatic collision avoidance systems automatically apply the brakes using image data from an onboard camera and relative distance information from millimeter-wave radar to an object.

[0003] Furthermore, with growing interest in energy conservation, resource conservation, safety, and health, the use of millimeter wave sensors is also attracting attention inside homes and other buildings. In addition to the conventional function of infrared motion sensors, which detect people, hands, etc. and automatically switch on, millimeter wave sensors can also detect the movement of people and other objects, making it possible to detect falls and monitor health conditions such as pulse and respiratory rate.

[0004] Previously, sensor covers for motion sensors were mainly flat or curved plastic products, lacking in design and aesthetic appeal. However, if a metal plating layer is applied to the sensor cover to create a clean, luxurious metallic look, the sensor behind it will not function because the metal plating layer does not transmit millimeter waves or infrared rays. Known alternatives to metal plating layers that form a metallic surface and transmit millimeter waves include indium vapor deposition films and metallic films.

[0005] Japanese Patent Application Laid-Open No. 2022-082052

[0006] For example, it is desirable to place a millimeter-wave radar that constitutes an automatic collision avoidance system in the center of the front of the vehicle, where the vehicle's emblem is usually located. Therefore, it is desirable to place the millimeter-wave radar behind the vehicle's emblem.

[0007] Automobile emblems generally have a metal film formed on a base material such as resin to create a metallic luster. For example, automobile emblems with a silver mirror film as the metal film are also being considered.

[0008] In laminates such as automobile emblems, millimeter-wave radar devices, sensor devices, and the like, it is desirable to suppress the reflection of millimeter waves and reduce the transmission attenuation of millimeter waves.

[0009] The present disclosure has been made in consideration of the above circumstances, and aims to provide a laminate capable of reducing the transmission attenuation of millimeter waves, as well as a decoration device, a millimeter-wave radar device, and a sensor device that include this laminate.

[0010] Specific means for achieving the above object are as follows. <1> A laminate comprising, in this order, a clear coat layer, a substrate, and a silver mirror layer, wherein the clear coat layer contains particles. <2> The laminate according to <1>, wherein the particles contain organic particles. <3> The laminate according to <2>, wherein the organic particles contain polymethyl methacrylate particles. <4> The laminate according to any one of <1> to <3>, wherein the particles have an average particle size of 2 μm to 50 μm. <5> The laminate according to any one of <1> to <4>, which is a sensor cover or an automobile emblem. <6> A decoration device comprising the laminate according to any one of <1> to <5> and a light source disposed on the silver mirror layer side. <7> A millimeter-wave radar device comprising the laminate according to any one of <1> to <5> and a millimeter-wave radar transceiver disposed on the silver mirror layer side. <8> A sensor device comprising the laminate according to any one of <1> to <5> and a sensor disposed on the silver mirror layer side.

[0011] According to the present disclosure, there are provided a laminate capable of reducing the transmission attenuation of millimeter waves, as well as a decorating device, a millimeter-wave radar device, and a sensor device that include this laminate.

[0012] 1 is a schematic cross-sectional view showing an example of a laminate according to the present disclosure;

[0013] Hereinafter, embodiments for carrying out the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0014] In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, particles corresponding to each component may include multiple types of particles. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified. In the present disclosure, the terms "layer" and "film" include cases where the layer or film is formed over the entire area when the area in which the layer or film is present is observed, as well as cases where the layer or film is formed over only a portion of the area.

[0015] When describing embodiments with reference to the drawings in this disclosure, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of components in each drawing are conceptual, and the relative size relationships between components are not limited to these. In this disclosure, the side on which the clear coat layer is provided is also referred to as the design surface, and the side opposite the design surface is also referred to as the back surface.

[0016] <Laminate> The laminate of the present disclosure includes a clear coat layer, a substrate, and a silver mirror layer in this order, and the clear coat layer contains particles. It is presumed that the presence of particles in the clear coat layer of the laminate of the present disclosure makes it possible to reduce the transmission attenuation of millimeter waves.

[0017] The laminate of the present disclosure can also be used as an automobile emblem with a millimeter-wave radar transceiver mounted on the back side, and as a sensor cover with at least one sensor selected from the group consisting of a millimeter-wave sensor and an infrared sensor mounted on the back side.

[0018] In the present disclosure, millimeter wave transparency refers to the property of transmitting radio waves of frequencies between 20 GHz and 300 GHz that are generally used in millimeter wave radar transceivers or millimeter wave sensors.

[0019] Each member used in this disclosure will be described below.

[0020] - Substrate - The material of the substrate is not particularly limited, and inorganic materials such as glass, organic materials such as resins, etc. Examples of resins include thermosetting resins and thermoplastic resins.

[0021] Examples of thermoplastic resins include polyethylene, polypropylene, polycarbonate, polystyrene, polyvinyl chloride, vinyl polymers, polyester, polyamide, ABS resin (acrylonitrile-butadiene-styrene copolymer resin), polyester, thermoplastic elastomer, and acrylic resin. These resins may be used alone or in combination of two or more. An example of a combination of two or more resins is polycarbonate / ABS resin.

[0022] Examples of the thermosetting resin include silicone resin, polyurethane resin, polyester resin, melamine resin, epoxy resin, phenol resin, urea resin, etc. These resins may be used alone or in combination of two or more.

[0023] When used for sensor covers for motion sensors, etc., preferred substrate materials include polypropylene, polycarbonate, ABS resin, polycarbonate / ABS, and acrylic resin. Polypropylene has a low specific gravity among resins, is easy to process, has high tensile strength, impact strength, and compressive strength, and is also excellent in weather resistance and heat resistance. ABS resin is relatively easy to apply surface treatments to, among plastic materials, and therefore is a resin that is easy to paint after molding the substrate. It also has excellent chemical resistance and rigidity, as well as excellent impact resistance, heat resistance, and cold resistance. Polycarbonate has high impact resistance among plastic materials, excellent weather resistance and heat resistance, and excellent transparency. Polycarbonate is also easy to process, and is a relatively light and durable material among plastic materials.

[0024] The thickness of the substrate can be appropriately designed depending on the application, and the shape of the substrate is not particularly limited.

[0025] In order to improve adhesion between the substrate and the silver mirror layer and to smooth the substrate surface, an undercoat layer may be provided on the side of the substrate on which the silver mirror layer is to be formed. The material for the undercoat layer is not particularly limited and can be selected depending on the purpose of the undercoat layer. For example, fluororesin, polyester resin, epoxy resin, melamine resin, silicone resin, acrylic silicone resin, acrylic urethane resin, etc. may be used. These resins may be in the form of a paint to which a solvent or the like has been added.

[0026] The thickness of the undercoat layer is not particularly limited, but from the viewpoint of ensuring a smooth surface, it is preferably about 5 μm to 25 μm.

[0027] In order to improve the adhesion between the undercoat layer and the substrate, a primer layer may be provided between the undercoat layer and the substrate.

[0028] - Silver Mirror Layer - The silver mirror layer contains silver particles (precipitated silver particles) precipitated by a silver mirror reaction. The silver mirror layer is capable of transmitting millimeter waves. The millimeter wave transmittance can be determined by the surface resistivity of the silver mirror layer, as described below.

[0029] The formation of the silver mirror layer by the silver mirror reaction may be carried out by contacting an aqueous ammoniacal silver nitrate solution with an aqueous reducing agent solution, which causes an oxidation-reduction reaction to produce silver particles and form the silver mirror layer.

[0030] When a silver mirror layer is formed as the metal layer, it is possible to reduce carbon dioxide emissions compared to forming other metal layers, such as an indium layer or a chrome-plated layer, and rare metal-free and chrome-free products can be achieved. Reducing carbon dioxide emissions can contribute to carbon neutrality.

[0031] In one embodiment of the present disclosure, the ammoniacal silver nitrate aqueous solution is obtained by dissolving silver nitrate, ammonia, and at least one amine compound selected from the group consisting of amino alcohol compounds, amino acids, and amino acid salts in water. Specific examples of the amine compound include amino alcohol compounds such as monoethanolamine, diethanolamine, diisopropanolamine, triethanolamine, and triisopropanolamine, and amino acids or salts thereof such as glycine, alanine, and sodium glycinate.

[0032] The contents of silver nitrate, ammonia, and amine compound contained in the aqueous ammoniacal silver nitrate solution are not particularly limited.

[0033] The concentration of silver nitrate contained in the ammoniacal silver nitrate aqueous solution is not particularly limited, but from the viewpoint of controlling the reaction rate, it is preferably adjusted to a range of 0.1% by mass to 10% by mass. The pH of the ammoniacal silver nitrate aqueous solution is preferably adjusted to a range of 10 to 13, more preferably 11 to 12.

[0034] In one embodiment of the present disclosure, the aqueous reducing agent solution is obtained by dissolving a reducing agent containing a phenolic compound and a strong alkaline component in water. Examples of phenolic compounds contained in the reducing agent include benzenediol compounds such as hydroquinone, catechol, and resorcinol, with hydroquinone being preferred. The reducing agent may contain only phenolic compounds or a combination of phenolic compounds and compounds other than phenolic compounds. Examples of compounds other than phenolic compounds include hydrazine compounds such as hydrazine sulfate, hydrazine carbonate, and hydrazine hydrate, sulfite compounds such as sodium sulfite, and thiosulfate compounds such as sodium thiosulfate. When the reducing agent contains a phenolic compound and a compound other than phenolic compounds, the proportion of the phenolic compound in the total reducing agent is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more.

[0035] Specific examples of the strong alkaline component contained in the aqueous reducing agent solution include sodium hydroxide and potassium hydroxide.

[0036] The aqueous reducing agent solution may contain the above-mentioned amine compound as needed. The aqueous reducing agent solution may contain a compound containing a formyl group as needed. Specific examples of the compound containing a formyl group include glucose and glyoxal. The contents of the reducing agent, strong alkaline component, amine compound (if needed), and compound containing a formyl group (if needed) contained in the aqueous reducing agent solution are not particularly limited.

[0037] The concentration of the reducing agent contained in the aqueous reducing agent solution is not particularly limited, but is preferably adjusted to a range of 0.1% by mass to 10% by mass from the viewpoint of controlling the reaction rate. The pH of the aqueous reducing agent solution is preferably adjusted to a range of 10 to 13, more preferably 10.5 to 11.5.

[0038] The average primary particle size of the silver particles in the silver mirror layer is preferably 1 nm to 30 nm, more preferably 5 nm to 25 nm, and even more preferably 10 nm to 20 nm. In particular, when the average primary particle size of the silver particles in the silver mirror layer is 15 nm or more, the uniformity of the silver mirror layer is excellent, and the appearance is improved.

[0039] The silver particles in the silver mirror layer may be aggregated to form secondary particles, and the average secondary particle size is preferably 350 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less.

[0040] The average primary particle size and average secondary particle size of silver particles are determined by measuring the diameters of 50 silver particles (for example, the value at which the distance between two planes circumscribing the silver particles is maximum) using a scanning electron microscope (SEM) image or a transmission electron microscope (TEM) image, and calculating the arithmetic mean.

[0041] The thickness of the silver mirror layer is not particularly limited. From the viewpoint of obtaining a sufficient metallic luster, the thickness of the silver mirror layer is preferably 50 nm or more, and from the viewpoint of obtaining a sufficient millimeter wave transmittance, the thickness of the silver mirror layer is preferably 300 nm or less.

[0042] The surface resistivity of the silver mirror layer is 10 ４ It is preferably 10 Ω / □ or more, ５ It is more preferable that the surface resistivity of the silver mirror layer is Ω / □ or more. When the surface resistivity of the silver mirror layer is within the above range, it can be determined that sufficient millimeter wave transmittance has been achieved. There is no particular upper limit for the surface resistivity of the silver mirror layer. The surface resistivity of the silver mirror layer refers to a value measured in accordance with JIS K6911:2006.

[0043] A protective layer may be provided on the outer surface of the silver mirror layer to protect the silver mirror layer. The material of the protective layer is not particularly limited and can be selected, for example, from the resins described above as the material for the undercoat layer of the substrate. The thickness of the protective layer is not particularly limited and is preferably, for example, about 2 μm to 20 μm.

[0044] - Clear Coat Layer - The clear coat layer is a layer disposed on the opposite side of the substrate from the silver mirror layer, and contains particles. The clear coat layer may be a colored layer or a non-colored layer.

[0045] The particles contained in the clear coat layer may be organic particles, inorganic particles, or a combination of organic particles and inorganic particles. The particles contained in the clear coat layer may be of one type or of two or more types.

[0046] Examples of materials for the organic particles include polymethyl methacrylate (PMMA), polyolefin, polyethylene, polypropylene, polystyrene, polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyimide, melamine resin, phenolic resin, epoxy resin, and urethane resin. The organic particles may be particles in which the above-mentioned materials are crosslinked, such as crosslinked polymethyl methacrylate particles. The organic particles that can be contained in the clear coat layer may be one type or two or more types. Among these, from the viewpoint of electromagnetic wave transmission, it is preferable that the organic particles include polymethyl methacrylate particles.

[0047] When the clear coat layer contains organic particles, the content of polymethyl methacrylate particles in the organic particles may be 50% by mass to 100% by mass, 70% by mass to 100% by mass, or 90% by mass to 100% by mass.

[0048] When organic particles are contained in the clear coat layer, the content of the organic particles may be 50% by mass to 100% by mass, 70% by mass to 100% by mass, or 90% by mass to 100% by mass, based on the total amount of particles.

[0049] Examples of inorganic particle materials include fused silica, crystalline silica, glass, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, beryllia, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, talc, clay, mica, aluminum hydroxide, magnesium hydroxide, and zinc borate. The inorganic particles that can be contained in the clear coat layer may be of one type or two or more types.

[0050] When inorganic particles are contained in the clear coat layer, the content of the inorganic particles may be 50% by mass to 100% by mass, 70% by mass to 100% by mass, or 90% by mass to 100% by mass, based on the total amount of particles.

[0051] When the clear coat layer contains organic particles and inorganic particles, the mass ratio of the organic particles to the inorganic particles (organic particles:inorganic particles) may be 1:9 to 9:1, 2:8 to 8:2, or 3:7 to 7:3.

[0052] The content of the particles may be 0.1% by mass to 5% by mass, 0.5% by mass to 4% by mass, or 1% by mass to 3% by mass, based on the total amount of the clear coat layer.

[0053] The average particle size of the particles may be 2 μm to 50 μm, 2 μm to 20 μm, or 5 μm to 20 μm.

[0054] The average particle size of the particles can be determined by the following measurement method. A portion of the clear coat layer is cut out, embedded in resin, and then cut in the thickness direction of the clear coat layer to prepare a thin section sample. This thin section sample is imaged using a scanning electron microscope (SEM). In the SEM image, 100 particles contained in the clear coat layer are randomly selected, and the major axes of the 100 particles are measured. The arithmetic mean of the major axes of the 100 particles is taken as the average particle size of the particles.

[0055] The material for the clear coat layer is not particularly limited, and can be selected from the resins mentioned above as the material for the undercoat layer, for example.

[0056] When the clear coat layer is a colored layer (also referred to as a colored clear coat layer), the color of the colored clear coat layer is not particularly limited. By changing the color of the colored clear coat layer, the metallic color can be changed, and a laminate with excellent color variation can be easily obtained.

[0057] The colored clear coat layer preferably has a transparency to the extent that it does not significantly impair the metallic luster of the silver mirror layer that is the underlying metallic decorative layer.

[0058] The colored clear coat layer may be a commonly used top coat layer or clear coat layer containing a colorant. Examples of the colorant include pigments. The type of colorant is not particularly limited and can be selected appropriately.

[0059] The thickness of the clear coat layer is not particularly limited and can be appropriately designed depending on the application. The thickness of the clear coat layer may be, for example, 0.001 μm to 900 μm, 0.01 μm to 500 μm, or 0.1 μm to 100 μm.

[0060] A top coat layer may be provided on the outer side of the colored clear coat layer. The top coat layer preferably has a transparency sufficient to not obscure the metallic luster of the silver mirror layer. The material for the top coat layer is not particularly limited, and can be selected from the resins described above as the material for the undercoat layer of the substrate, for example.

[0061] The thickness of the topcoat layer is not particularly limited and can be appropriately designed depending on the application.

[0062] The silver mirror layer has a sea-island structure in which silver particles are scattered like islands. This structure allows infrared light, visible light, and millimeter waves to pass through the gaps between the silver particles. Placing a backlight on the backside makes it possible to emit light. For example, if the backlight is white, the light will be the color of the colored clear coat layer, and if the backlight is colored, the light will be a mixture of the color of the backlight and the color of the colored clear coat layer.

[0063] Fig. 1 shows a cross-sectional schematic diagram illustrating an example of a laminate of the present disclosure. The laminate 100 of Fig. 1 has, in order from the design surface side, a clear coat layer 10, a substrate 20, a silver mirror layer 30, and a protective layer 40. The protective layer 40 is optional. As described above, a primer layer (not shown) and an undercoat layer (not shown) may be provided between the substrate 20 and the silver mirror layer 30.

[0064] <Physical properties of laminate> The laminate preferably has a transmission attenuation of 1.0 dB or less, more preferably 0.75 dB or less, and even more preferably 0.70 dB or less at 76.5 GHz, which is the millimeter wave region. The transmission attenuation of the laminate is measured based on JIS R1679:2007 (Method for measuring radio wave absorption characteristics of radio wave absorbers in the millimeter wave band). The transmission attenuation is calculated from the transmitted wave (transmission coefficient) obtained by the free space method in which a sample is placed between a transmitting antenna and a receiving antenna and electromagnetic waves are irradiated perpendicularly to the sample. The transmission attenuation can be calculated using the transmission coefficient (absolute value) according to the following formula: Transmission attenuation = 20 log １０ | (Permeability coefficient) |

[0065] <Method for producing laminate> The method for producing the laminate is not particularly limited. In forming a silver mirror layer by silver mirror reaction, the method for bringing an aqueous ammoniacal silver nitrate solution and an aqueous reducing agent solution into contact with each other is not particularly limited, and examples thereof include a method in which these aqueous solutions are applied to the surface of a substrate in a mixed state or in an unmixed state.

[0066] The method for applying the ammoniacal silver nitrate aqueous solution and the reducing agent aqueous solution to the silver mirror reaction-treated surface is not particularly limited. Among these, spray coating is preferred, as it can form a uniform silver mirror layer regardless of the shape of the substrate. Spray coating can be carried out using known means such as an airbrush or a spray gun.

[0067] If necessary, the surface of the substrate may be subjected to a surface activation treatment before the silver mirror layer is formed. In one embodiment of the present disclosure, the surface activation treatment involves applying a surface activation treatment liquid containing an inorganic tin compound to the surface of the substrate. This causes tin to be present on the surface of the substrate. The presence of tin between the silver mirror layer and the substrate tends to improve adhesion between the substrate and the silver particles.

[0068] Examples of inorganic tin compounds contained in the surface activation treatment liquid include tin(II) chloride, tin(II) oxide, and tin(II) sulfate. In addition to the inorganic tin compound, the surface activation treatment liquid may contain hydrogen chloride, hydrogen peroxide, polyhydric alcohol, and the like, as needed. The content of these components contained in the surface activation treatment liquid is not particularly limited.

[0069] The pH of the surface activation treatment solution is preferably adjusted to between 0.5 and 3.0, and more preferably between 0.5 and 1.5.

[0070] Methods for applying the surface activation treatment liquid to the surface of a substrate include a method of immersing the substrate in the surface activation treatment liquid, a method of coating the surface of the substrate with the surface activation treatment liquid, etc. Among these, spray coating is preferred because it can be applied uniformly to any substrate regardless of its shape.

[0071] After the surface activation treatment, it is preferable to remove excess surface activation treatment solution from the surface of the substrate, for example, by rinsing the surface of the substrate with deionized water or purified distilled water.

[0072] If necessary, the surface of the substrate may be pretreated before the silver mirror layer is formed. In one embodiment of the present disclosure, as the pretreatment, a pretreatment liquid such as an aqueous silver nitrate solution is applied to the surface of the substrate after the above-described surface activation treatment. This causes silver to be present on the surface of the substrate. The presence of silver between the silver mirror layer and the substrate tends to facilitate the precipitation of silver particles of uniform size.

[0073] The pH of the pretreatment liquid is preferably adjusted to a range of 4.0 to 8.0, and more preferably to a range of 6.0 to 7.0.

[0074] Methods for applying the pretreatment liquid to the surface of a substrate include a method of immersing the substrate in the pretreatment liquid, a method of coating the surface of the substrate with the pretreatment liquid, etc. Among these, spray coating is preferred because it can apply the pretreatment liquid uniformly regardless of the shape of the substrate.

[0075] If necessary, a passivation treatment may be performed after forming a silver mirror layer on the surface of the substrate. In one embodiment of the present disclosure, the passivation treatment involves contacting the silver mirror layer with a passivation treatment solution, which is an aqueous solution containing a strong alkaline component such as potassium hydroxide and a sulfite such as sodium sulfite. This reduces the reactivity of the silver in the silver mirror layer with residual ions such as chloride ions and sulfide ions. The content of the components contained in the passivation treatment solution is not particularly limited.

[0076] The pH of the inactivation treatment solution is preferably adjusted to between 4.0 and 8.0, more preferably between 7.0 and 8.0.

[0077] Methods for bringing the inactivation treatment liquid into contact with the silver mirror layer include immersing the substrate on which the silver mirror layer has been formed in the inactivation treatment liquid, applying the inactivation treatment liquid to the silver mirror layer, etc. Among these, spray application is preferred because it can apply the inactivation treatment liquid uniformly regardless of the shape of the substrate.

[0078] Before and after the passivation treatment, it is preferable to wash the silver mirror layer with deionized water or purified distilled water.

[0079] The clear coat layer may be formed using a clear coat agent containing particles. The clear coat agent may contain, in addition to the resin described above, a solvent, an ultraviolet absorber, a curing agent, etc. The solvent may be water or an organic solvent.

[0080] The colored clear coat layer may be formed using a clear coat agent containing particles and a colorant, or may be formed using a clear coat agent containing the above-mentioned components such as a resin.

[0081] It is preferable that the particle-containing clear coating agent exhibits functions such as scratch prevention and ultraviolet degradation prevention.

[0082] The method for applying the particle-containing clear coating agent to the substrate is not particularly limited, and any known coating method can be used, such as dipping, screen printing, inkjet printing, dispenser coating, spin coating, brush coating, spray coating, doctor blade coating, and roll coating.

[0083] <Physical Properties of Laminate> In the laminate of the present disclosure, Y (reflectance) in the XYZ color system (Yxy color system) may be 70% or less, 50% or less, or 30% or less. When the laminate of the present disclosure includes an uncolored clear coat layer, Y (reflectance) may be 60% to 70%. When the laminate of the present disclosure includes a colored clear coat layer, Y (reflectance) may be 5% to 50%, 5% to 30%, or 5% to 20%. Y (reflectance) in the XYZ color system (Yxy color system) can be measured by the method described in the examples.

[0084] <Uses of Laminate> The silver mirror layer is transparent to infrared rays, visible light, and millimeter waves. Therefore, as an automobile part, it can be suitably used as an automobile emblem to be placed in front of a millimeter-wave radar transceiver. It can also be used for other interior and exterior automobile parts. Examples of other interior and exterior automobile parts include parts for the front of the vehicle body, parts from the sides to the rear of the vehicle body, and interior automobile parts, such as vehicle surrounding sensing modules such as bumpers, grilles, back doors, and garnishes; interior parts for vehicle interior and exterior human detection sensors and vital signs sensing; and sensor modules such as door mirrors, door handles, and rearview mirrors. The laminate of the present disclosure can also be used as various sensor covers.

[0085] Examples of sensors include sensors that detect human movement and monitor health status, and can be used as covers for indoor and outdoor sensors such as vital signs sensors, security motion sensors, automatic faucet sensors, toilet seat / standby sensors, automatic toilet seat opening / closing sensors, automatic flushing sensors, automatic lighting sensors, elderly care sensors, automatic door sensors, sensor-activated escalator sensors, remote controller sensors, non-contact body temperature sensors, sensor-activated traffic lights sensors, and traffic volume measurement sensors. The detection targets may be other than people, and may include bicycles, automobiles, airplanes, and other transportation vehicles, animals, plants, and merchandise (such as precious metals). Because the exterior is reflective, it may be placed in place of an existing mirror, or it may be placed as an interior or exterior fixture.

[0086] <Decoration Device> The decoration device of the present disclosure includes the laminate of the present disclosure and a light source arranged on the silver mirror layer side (rear side). When a backlight serving as a light source is arranged on the rear side opposite the viewing side of the laminate, light emitted from the backlight passes through the laminate and reaches the viewing side, which is the design surface. Therefore, when the laminate is observed from the viewing side, it appears to glow.

[0087] The type of light source is not particularly limited, and conventionally known light sources can be appropriately selected and used. Examples of light sources include lamp light sources and light-emitting elements. Examples include lamp light sources, incandescent lamps, halogen lamps, discharge lamps, and neon lamps. Examples of light-emitting elements include light-emitting diodes (LEDs), laser diodes (LDs), and organic electroluminescence elements. Among the above, LEDs are preferred from the viewpoints of visibility, ease of dimming, power consumption, lifespan, and the like.

[0088] The wavelength of the light emitted from the light source is not particularly limited and can be selected appropriately. For example, two or more light sources emitting light of different wavelengths may be used to create an illumination device in which light of different colors is observed depending on the location.

[0089] The light source may include a point light source, a surface light source, or two or more point light sources. When the light source includes two or more point light sources, the range of designs for the lighting device can be expanded, and the design tends to be further improved.

[0090] When the light source includes two or more point light sources, the point light sources are preferably arranged in the decoration device appropriately according to the shape of the mounting location of the vehicle, etc., and may be arranged regularly or irregularly. For example, the decoration device may have a plurality of point light sources arranged in a straight line, a curved line, or a combination thereof.

[0091] 2 is a schematic cross-sectional view showing an example of a decoration device according to the present disclosure. The decoration device 200 has a light source 110 disposed on the rear surface side opposite the viewing side. The light source 110 may be housed in a housing 120. The housing 120 is preferably light-blocking. The housing 120 may also house a millimeter-wave radar transceiver, a sensor, and the like, which will be described later, together with the light source 110.

[0092] <Millimeter-wave radar device> The millimeter-wave radar device of the present disclosure includes the laminate of the present disclosure and a millimeter-wave radar transceiver disposed on the silver mirror layer side (back side). The millimeter-wave radar transceiver can be a typical one used in automatic collision avoidance systems.

[0093] <Sensor Device> The sensor device of the present disclosure includes a laminate and a sensor disposed on the silver mirror layer side (back side). Examples of the sensor include those described above.

[0094] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to the following examples.

[0095] Example 1 (1) Preparation of Substrate The surface of a polycarbonate substrate having a thickness of 2 mm was washed with alkaline ionized water to remove oil film, dirt, and dust, and then the substrate was dried.

[0096] (2) Surface Activation Step After the substrate was spray-washed with pure water, a surface activation treatment solution (MSPS-Sa1A, manufactured by Mitsubishi Paper Mills, Ltd.) was spray-coated onto the substrate. The substrate was then spray-washed with pure water. The surface activation treatment solution used was an aqueous solution containing tin(II) chloride, hydrogen chloride, hydrogen peroxide, and a polyhydric alcohol, with a pH of 1.0.

[0097] (3) Pretreatment Step A pretreatment liquid (MSPS-Sa2A manufactured by Mitsubishi Paper Mills Co., Ltd.) was sprayed onto the surface of the substrate after the surface activation treatment. The surface was then spray-washed with pure water. The pretreatment liquid used was a silver nitrate aqueous solution with a pH of 6.8.

[0098] (4) Silver Mirror Layer Formation Step An ammoniacal silver nitrate aqueous solution and a reducing agent aqueous solution were prepared. The ammoniacal silver nitrate aqueous solution was an aqueous solution containing silver nitrate, ammonia, and triethanolamine with a pH of 11.5 (silver nitrate concentration: 0.5% by mass). The reducing agent aqueous solution was an aqueous solution containing hydroquinone, triethanolamine, sodium hydroxide, and an amino alcohol with a pH of 10.8 (hydroquinone concentration: 4.5% by mass).

[0099] The ammoniacal silver nitrate aqueous solution and the reducing agent aqueous solution were simultaneously sprayed from separate airbrushes. The discharge rates of the airbrushes were 1.0 g / 10 seconds to 1.5 g / 10 seconds, respectively. During this process, silver particles precipitated on the surface of the substrate due to the silver mirror reaction, forming a silver mirror layer (thickness: 0.2 μm) with a silver luster. The substrate was then spray-washed with pure water.

[0100] (5) Passivation Treatment Step After the silver mirror layer formation step, the surface of the substrate was sprayed with a passivation treatment solution (MSPS-R1A, manufactured by Mitsubishi Paper Mills, Ltd.). The substrate was then spray-washed with pure water. The passivation treatment solution used was an aqueous solution containing potassium hydroxide and sulfite, with a pH of 7.5.

[0101] (6) Clear Coat Layer Formation Step: A clear coat layer composition was prepared by adding organic polymethyl methacrylate particles (average particle size: 2.5 μm) to ORIGIPLATE Z clear coat agent manufactured by ORIGIN Co., Ltd. in an amount of 3 mass% based on the total amount of the composition. This composition was spray-coated onto the substrate on the side opposite the silver mirror layer to form a clear coat layer with a thickness of 18 μm. Through the above operations, a laminate was produced comprising a clear coat layer, a substrate, and a silver mirror layer in this order.

[0102] Example 2 A laminate was produced in the same manner as in Example 1, except that polymethyl methacrylate particles having a larger average particle size (average particle size: 8 μm) were used in (6) clear coat layer forming step.

[0103] Example 3 A laminate was produced in the same manner as in Example 1, except that in the (6) clear coat layer forming step in Example 1, the clear coat agent and a black colorant manufactured by Mitsubishi Paper Mills, Ltd. were blended in a ratio of 100:3 (based on parts by mass).

[0104] Example 4 A laminate was produced in the same manner as in Example 2, except that in the (6) clear coat layer forming step in Example 2, the clear coat agent and a black colorant manufactured by Mitsubishi Paper Mills, Ltd. were blended in a ratio of 100:3 (based on parts by mass).

[0105] Example 5 A laminate was produced in the same manner as in Example 1, except that in the (6) clear coat layer forming step in Example 1, the clear coat agent and a black colorant manufactured by Mitsubishi Paper Mills, Ltd. were blended in a ratio of 100:6 (based on parts by mass).

[0106] Example 6 A laminate was produced in the same manner as in Example 2, except that in the (6) clear coat layer forming step in Example 2, the clear coat agent and a black colorant manufactured by Mitsubishi Paper Mills, Ltd. were blended in a ratio of 100:6 (based on parts by mass).

[0107] Comparative Example 1 A laminate was produced in the same manner as in Example 1, except that the polymethyl methacrylate particles were not added in the (6) clear coat layer forming step.

[0108] Comparative Example 2 A laminate was produced in the same manner as in Example 3, except that the polymethyl methacrylate particles were not added in the (6) clear coat layer forming step in Example 1.

[0109] Comparative Example 3 A laminate was produced in the same manner as in Example 5, except that the polymethyl methacrylate particles were not added in the (6) clear coat layer forming step in Example 1.

[0110] <Evaluation> (1) Measurement of Y Value Y (reflectance) in the XYZ color system (Yxy color system) of the design surface side of each Example and Comparative Example was measured by the following method. The XYZ color system is a color system standardized by the International Commission on Illumination (CIE) in 1931 and adopted in JIS Z 8781-3:2016. The Y value of the silver particle layer in the XYZ color system was measured using a CM-2600d manufactured by Konica Minolta, Inc. The results are shown in Table 1.

[0111] (2) Measurement of millimeter wave transmission attenuation For the laminates of each example and each comparative example, the attenuation (transmission attenuation) when millimeter waves (76.5 Hz) were transmitted was measured by the following method. The transmission attenuation was calculated from the transmitted wave (transmission coefficient) obtained by the free space method specified in JIS R1679:2007 (Method for measuring radio wave absorption characteristics of radio wave absorbers in the millimeter wave band), in which a sample is placed between a transmitting antenna and a receiving antenna and electromagnetic waves are irradiated perpendicularly to the sample. Here, the transmission attenuation (dB) can be calculated using the transmission coefficient (absolute value) from the following formula: Transmission attenuation = 20 log １０ |(Permeability coefficient)| The results are shown in Table 1.

[0112]

[0113] As shown in Table 1, in Comparative Example 1 and Examples 1 and 2, which had an uncolored clear coat layer, the millimeter wave transmission attenuation could be reduced in Examples 1 and 2. Next, in Comparative Example 2 and Examples 3 and 4, in which the clear coat layer had the same degree of coloring, the millimeter wave transmission attenuation could be reduced in Examples 3 and 4. In Comparative Example 3 and Examples 5 and 6, in which the clear coat layer had a darker coloring than Comparative Example 2, Examples 3 and 4, the millimeter wave transmission attenuation could be reduced in Examples 5 and 6.

[0114] The disclosure of Japanese Patent Application No. 2024-113653, filed on July 16, 2024, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual publication, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0115] 10 Colored clear coat layer, 20 Substrate, 30 Silver mirror layer, 40 Protective layer, 100 Laminate, 110 Light source, 120 Housing, 200 Decorating device

Claims

1. A laminate comprising a clear coat layer, a substrate, and a silver mirror layer in this order, wherein the clear coat layer contains particles.

2. The laminate of claim 1, wherein said particles comprise organic particles.

3. The laminate according to claim 2, wherein the organic particles include polymethyl methacrylate particles.

4. The laminate according to claim 1, wherein the particles have an average particle size of 2 μm to 50 μm.

5. The laminate according to any one of claims 1 to 4, which is a sensor cover or an automobile emblem.

6. A decorating device comprising the laminate according to any one of claims 1 to 4 and a light source disposed on the silver mirror layer side.

7. A millimeter wave radar device comprising the laminate according to any one of claims 1 to 4 and a millimeter wave radar transmitter / receiver placed on the silver mirror layer side.

8. A sensor device comprising the laminate according to any one of claims 1 to 4 and a sensor disposed on the silver mirror layer side.

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