Brightening materials, electromagnetic wave permeable coatings and painted products

Abstract

This invention provides an electromagnetic wave-transmitting coating that achieves both electromagnetic wave transmittance and aesthetic appeal by enabling the arrangement of glossy materials as densely and highly oriented as possible within the coating film. [Solution] A luminous material 31 to be dispersed in a coating film having electromagnetic wave permeability, comprising a conductive luminous pigment 32 and a coating portion 33 consisting of a non-conductive resin component and nanoparticles 34 dispersed in the resin component, which covers the surface of the luminous pigment 32 to a thickness of 0.7 μm or more and 3.0 μm or less.

Description

[Technical Field]

[0001] This disclosure relates to a glossy material, an electromagnetic wave-transmitting coating, and a painted product. [Background technology]

[0002] On the surface of a vehicle body or other automotive parts, multiple coatings are applied in layers to form a surface coating, which protects the vehicle body and improves its aesthetic appearance. These coatings sometimes contain gloss-enhancing agents to enhance their appearance.

[0003] Incidentally, in ADAS (Advanced Driver-Assistance Systems) and autonomous driving technologies in automobiles, sensor units that use electromagnetic waves to sense distance, speed, and obstacles are installed on the bumper and other parts of the vehicle body. However, if the paint film contains a glossy material, the glossy material may hinder the transmission of electromagnetic waves, potentially degrading the performance of the sensor unit.

[0004] Therefore, proposals have been made to improve electromagnetic wave transmission in coating films containing reflective materials. For example, Patent Document 1 discloses that in a coating film containing a reflective material and a flat, non-conductive pigment, electromagnetic wave transmission can be imparted by satisfying a predetermined relationship between the number of overlapping reflective materials in the film thickness direction and the distance between reflective materials in the film thickness direction.

[0005] Patent Document 2 discloses that in a coating film containing a glossy material, the amount of millimeter-wave transmission attenuation in both directions of the coating film is reduced by setting the area occupancy rate of the glossy material to 60% or more and 75% or less when the coating film is observed under a microscope from a direction perpendicular to it.

[0006] Furthermore, Patent Document 3 discloses a method for transmitting radio waves through gaps between multiple island phases by using a paint in which flakes having a sea-island structure, which includes multiple island phases made of metal and a sea phase made of resin or DLC (Diamond-Like Carbon) that binds the multiple island phases together. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5237713 [Patent Document 2] Patent No. 6933587 [Patent Document 3] Patent No. 7099240 [Overview of the project] [Problems that the invention aims to solve]

[0008] In coatings containing glossy materials, there is a need to improve both electromagnetic wave transmittance and aesthetic appeal. In particular, to achieve high aesthetic appeal in glossy color coatings, it is necessary to include a large amount of conductive glossy material in the coating. However, as the content of glossy material increases, the reflection of electromagnetic waves on the surface of the glossy material and the absorption of electromagnetic waves within the coating due to conductivity when the glossy material comes into contact with each other increase, resulting in a decrease in electromagnetic wave transmittance.

[0009] Therefore, the objective of this disclosure is to enable the arrangement of reflective materials as densely and highly oriented as possible in reflective materials, electromagnetic wave-transmitting coatings, and coated products, thereby suppressing the reflection and absorption of electromagnetic waves within the coating. [Means for solving the problem]

[0010] To solve the above problems, one embodiment of the lustrous material disclosed herein is: A luminescent material dispersed within a coating film having electromagnetic wave permeability, A conductive, lustrous pigment, The invention is characterized by comprising a non-conductive resin component and nanoparticles dispersed in the resin component, and a coating portion that covers the surface of the lustrous pigment to a thickness of 0.7 μm to 3.0 μm.

[0011] As a result of diligent research, the inventors of this application have found that by coating the surface of a conductive lustrous pigment with a non-conductive resin component to create a lustrous material, and dispersing this within a coating film, it is possible to arrange the lustrous material as densely and highly oriented as possible within the coating film, thereby ensuring both aesthetic appeal and excellent electromagnetic wave transmission. Even when the lustrous material is blended at a high concentration and comes into contact with other lustrous material particles, the coating suppresses the formation of conduction paths between the lustrous pigment particles, thereby reducing electromagnetic wave absorption loss, and also reduces the reflection of electromagnetic waves on the surface of the lustrous material pigments. The thinner the thickness of the coating, the closer the lustrous material particles come together, making it easier for electromagnetic wave reflection on the surface of the lustrous material pigments and the formation of conduction paths between the lustrous pigments to occur, thus reducing electromagnetic wave transmission. However, good electromagnetic wave transmission can be achieved if the thickness is 0.7 μm or more. Furthermore, if the coating is too thick, problems arise with the durability (chipping resistance) of the coating film. However, by dispersing nanoparticles in the resin component, it is possible to increase the thickness of the coating compared to cases where nanoparticles are not included in the resin component, thereby further improving electromagnetic wave transmission. Good durability can be maintained with a coating thickness of 3.0 μm or less.

[0012] Preferably, the amount of nanoparticles in the coating portion is 20 wt% or more and 60 wt% or less.

[0013] By incorporating 20 wt% or more of nanoparticles dispersed in the coating, it is possible to improve the durability (chipping resistance) of the coating film. Furthermore, while excessive nanoparticle incorporation reduces dispersibility in the resin, making it difficult to use as a paint, by limiting the nanoparticle incorporation to 60 wt% or less, dispersibility can be maintained, allowing for the use of an easy-to-handle paint.

[0014] Preferably, the luminous pigment is in flake form.

[0015] By using flake-shaped luminous pigments, it becomes possible to arrange the luminous materials in a more highly oriented manner within the coating film.

[0016] Preferably, the phosphorescent pigment is a metal particle. Preferably, the thickness of the metal particle is 0.6 μm or less.

[0017] If the thickness of the metal particle is too thick, the electromagnetic wave permeability is reduced. However, if the thickness is 0.6 μm or less, it is possible to have good electromagnetic wave permeability.

[0018] Preferably, the particle size of the metal particle is 5 μm or more and 20 μm or less.

[0019] If the particle size of the metal particle is too small, the orientation is reduced, resulting in a decrease in reflection intensity and thus deterioration of the design. However, if the particle size is 5 μm or more, it is possible to enhance the design by good orientation. If the particle size of the metal particle is too large, the appearance becomes shiny and the design deteriorates. However, if the particle size is 20 μm or less, it is possible to have a good design with reduced glitter.

[0020] Moreover, one aspect of the electromagnetic wave transmissive coating film disclosed herein is a coating film having electromagnetic wave permeability, characterized by containing a phosphorescent material according to any one of claims 1 to 4.

[0021] According to the above configuration, it is possible to provide a coating film in which the phosphorescent material is arranged as densely and highly oriented as possible. Moreover, the coating film having such a configuration achieves both electromagnetic wave permeability and design, and has good durability.

[0022] The concentration of the phosphorescent pigment in the coating film (PWC: weight of phosphorescent pigment / (weight of phosphorescent pigment + weight of resin component + weight of base resin + weight of nanoparticles) × 100) is 1 wt% or more and 20 wt% or less, and when the phosphorescent pigment is projected onto the bottom surface of the coating film, the ratio of the projected area of the phosphorescent pigment occupying the bottom surface is preferably 70% or more and 99% or less per unit area.

[0023] If the PWC of a lustrous pigment is too low, sufficient luster cannot be imparted, and the aesthetic appeal cannot be guaranteed. However, if it is 1 wt% or higher, good aesthetic appeal can be guaranteed. Also, if the PWC of a lustrous pigment is too high, electromagnetic wave transmittance will decrease, but if it is 20 wt% or lower, good electromagnetic wave transmittance can be maintained.

[0024] The electromagnetic wave-transmitting coating film is preferably 1 μm or more and 20 μm or less in thickness.

[0025] If the coating is too thin, the reflectivity will decrease due to insufficient layering of the reflective material, and there will be concerns about durability. However, if the thickness is 1 μm or more, good reflectivity and durability can be achieved. Also, if the coating is too thick, it will lead to a decrease in electromagnetic wave transmittance, but if the thickness is 20 μm or less, good electromagnetic wave transmittance can be achieved.

[0026] Furthermore, one aspect of the painted product disclosed herein is: A coated material having electromagnetic wave permeability, The object to be coated is characterized by having the above-mentioned electromagnetic wave permeable coating film. [Effects of the Invention]

[0027] As described above, this disclosure makes it possible to arrange the glossy material as densely and highly oriented as possible within the coating film. Furthermore, it is possible to achieve both electromagnetic wave transmittance and aesthetic appeal in the coating film. [Brief explanation of the drawing]

[0028] [Figure 1] This is a schematic cross-sectional view of the electromagnetic wave permeable coating related to this disclosure. [Figure 2] This is a schematic cross-sectional view of the lustrous material related to this disclosure. [Figure 3] This is a schematic diagram illustrating the reflection and attenuation of electromagnetic waves in conventional coatings. [Modes for carrying out the invention]

[0029] Embodiments of the present disclosure will be described in detail below with reference to the drawings. The following description of preferred embodiments is illustrative in nature and is not intended to limit the present disclosure, its applications or uses in any way.

[0030] <Electromagnetic wave transparent coating> The electromagnetic wave permeable coating film of this disclosure is a coating film used, for example, for surface coating of automobiles and other vehicles. Below, as an example of the electromagnetic wave permeable coating film of this disclosure, a case in which an automobile bumper (steel plate) is used as the workpiece 10 and a laminated coating film is formed on its surface will be described. As shown in Figure 1, the laminated coating film provided on the surface of the workpiece 10 has, in order from the surface side, a clear coating film 20 and an electromagnetic wave permeable coating film 30. An electrodeposited coating film 40 is formed on the surface of the workpiece 10 by cationic electrodeposition coating, and the electromagnetic wave permeable coating film 30 is provided on the electrodeposited coating film 40. The clear coating film 20 is a colorless and transparent coating film made of, for example, acrylic resin or polyester resin, and preferably has a film thickness of 25 μm or more and 35 μm or less. The film thickness of the electrodeposited coating film 40 is preferably 5 μm or more and 10 μm or less. A colored clear coating film, which is a colored transparent coating film, may be included between the clear coating film 20 and the electromagnetic wave permeable coating film 30.

[0031] The electromagnetic wave permeable coating 30 is a coating film that has electromagnetic wave permeability and is formed by drying a paint containing a glossy material 31, a solvent, and a resin (base resin). In the following description, the resin, which is one of the main components of the coating film, will be referred to as the "base resin" to distinguish it from the "resin component" contained in the glossy material as a covering. The thickness of the electromagnetic wave permeable coating 30 is preferably 1 μm or more from the viewpoint of ensuring the number of layers of glossy material to ensure reflectivity and ensuring the durability of the coating film. Furthermore, the thickness of the electromagnetic wave permeable coating 30 is preferably 20 μm or less from the viewpoint of preventing a decrease in electromagnetic wave permeability.

[0032] The base resin is not particularly limited as long as it can form a coating film, but for example, acrylic resin, polyester resin, urethane resin, melamine resin, isocyanate resin, etc. can be used individually or in combination of several types.

[0033] As the solvent, various organic solvents capable of dissolving the base resin can be used. One solvent may be used alone, or two or more may be used in mixture form. Examples of solvents include hydrocarbon solvents such as xylene, toluene, ethylbenzene, hexane, and heptane; ester solvents such as ethyl acetate, butyl acetate, and ethylene glycol monomethyl ether acetate; ether solvents such as ethylene glycol monomethyl ether and ethylene glycol diethyl ether; alcohol solvents such as butanol, propanol, pentanol, cyclohexanol, and diethylene glycol; and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone.

[0034] The paint may contain additives such as leveling agents, anti-sagging agents, stabilizers, conductivity enhancers, and other pigments, as needed.

[0035] <Shining material> As shown in Figure 2, the luminous material 31 dispersed in the electromagnetic wave-transmitting coating 30 comprises a conductive luminous pigment 32 and a coating portion 33 containing a non-conductive resin component and nanoparticles 34 dispersed in the resin component. The surface of the luminous pigment 32 is covered by the coating portion 33.

[0036] The lustrous pigment 32 is a general lustrous material that is added to a coating film, for example, to improve its aesthetic appeal, and is preferably a metal particle. The lustrous pigment 32 is non-spherical, and its type, shape, and particle size can be appropriately selected depending on the application of the coating film. Non-spherical means, for example, a shape with an aspect ratio greater than 1. The aspect ratio is the ratio of the length of the major axis to the length of the minor axis of the particle (length of major axis / length of minor axis). Examples of the shape of the lustrous pigment 32 include flake-like (scaly), plate-like, disc-like, elliptical, rod-like, columnar, needle-like, and fibrous shapes, and is preferably flake-like or plate-like, more preferably flake-like. When measuring the particle size, the length along the major axis of each particle should be measured. When considering a coating for an object such as an automobile bumper and a metallic luster is desired, it is preferable to use, for example, aluminum flakes or vapor-deposited aluminum as the lustrous pigment 32, and is more preferably aluminum flakes. When using aluminum flakes, their thickness is preferably 0.6 μm or less from the viewpoint of preventing a decrease in electromagnetic wave transmittance. Furthermore, when using aluminum flakes, their particle size is preferably 5 μm or more from the viewpoint of preventing deterioration of design due to a decrease in orientation, and preferably 20 μm or less from the viewpoint of achieving good design with reduced glare. The particle size can be obtained, for example, by determining D50, which is the 50th percentile value of the particle size distribution measured by a laser diffraction particle size distribution analyzer. The particle size is preferably the number-average particle size. The thickness can be obtained, for example, by observing with a scanning electron microscope, measuring the thickness of multiple (e.g., 50) particulate components, and calculating the average value.

[0037] The concentration of the lustrous pigment in the coating film (PWC: weight of lustrous pigment / (weight of lustrous pigment + weight of resin component + weight of base resin + weight of nanoparticles) × 100) is preferably 1 wt% or more from the viewpoint of providing sufficient lustrousness and ensuring aesthetic appeal, and preferably 20 wt% or less from the viewpoint of ensuring sufficient electromagnetic wave transmission. When aluminum flakes are used as the lustrous pigment, PWC is preferably 5 wt% to 20 wt%, and when vapor-deposited aluminum is used as the lustrous pigment, PWC is preferably 1 wt% to 5 wt%.

[0038] Figure 3 is a schematic diagram illustrating the reflection and attenuation of electromagnetic waves in a coating film. As shown in Figure 3, in a coating film X containing a conductive luminous pigment 32, the transmittance of incident light R is greatly reduced due to attenuation by absorption into the luminous pigment 32 within the coating film X (R1), attenuation by multiple reflections within the coating film X (R2), reflection at the surface of the luminous pigment 32 (R3), and absorption due to the creation of electrical paths between multiple luminous pigments 32 (R4). However, as shown in Figure 2, in this disclosure, the conductive luminous pigment 32 is covered by a coating portion 33 whose surface contains a non-conductive resin component and nanoparticles 34. Therefore, even if the luminous materials 31 come into contact with each other, the luminous pigments do not come into contact with each other, and conductivity is unlikely to occur. Therefore, by using the luminous material of this disclosure, it is possible to maintain the reflection intensity of visible light while suppressing the reflection and absorption of electromagnetic waves within the coating film by arranging the luminous pigments densely and with high orientation.

[0039] The coating portion 33 covering the surface of the lustrous pigment 32 is preferably made of a transparent resin component. The type of resin included in the resin component is not particularly limited as long as it is non-conductive, but for example, a silicone-based resin is preferred. The thickness of the coating portion 33 is preferably 0.7 μm or more from the viewpoint of maintaining an appropriate distance between the lustrous materials and improving electromagnetic wave permeability, and is preferably 3.0 μm or less from the viewpoint of ensuring the durability (chipping resistance) of the coating film. If the thickness of the coating portion 33 is increased, the proportion of the resin component in the electromagnetic wave permeable coating film increases, which may reduce the proportion of the base resin constituting the electromagnetic wave permeable coating film, potentially reducing the durability of the electromagnetic wave permeable coating film. Any known method can be used to form the coating portion 33 on the lustrous pigment 32.

[0040] In the coating portion 33, nanoparticles 34 are dispersed in the resin component. The nanoparticles 34 are inorganic nanoparticles made of inorganic oxides. For example, the nanoparticles 34 are silica, zirconia, alumina, titania, etc., and silica nanoparticles are preferred. The nanoparticles may be hollow or solid. Furthermore, the nanoparticles 34 may be subjected to various known surface treatments to improve their dispersibility in the resin component. The surface of the nanoparticles may be hydrophobic or hydrophilic, and hydrophobic treatment is preferred. The hydrophobic or hydrophilic treatment is not particularly limited, and known methods such as chemical modification treatment with organic compounds and surface modification treatment with fluorine plasma can be used. When a silicone resin is used as the resin component and silica nanoparticles are used as the nanoparticles 34, it is preferable that the nanoparticles 34 are modified silica nanoparticles whose surface is modified with organic groups. This increases the hydrophobicity of the silica nanoparticles, thereby improving the dispersibility of the silica nanoparticles in the silicone resin component. Furthermore, when silica nanoparticles are used as nanoparticles, their average particle size is preferably 50 nm to 300 nm from the viewpoint of improving the durability of the electromagnetic wave permeable coating. In addition, the amount of nanoparticles blended in the coating is preferably 20 wt% or more from the viewpoint of improving the durability of the electromagnetic wave permeable coating, and preferably 60 wt% or less from the viewpoint of ensuring the dispersibility of nanoparticles in the coating.

[0041] When an electromagnetic wave-permeable coating applied to an object is observed in plan view, the luminous pigments contained in the electromagnetic wave-permeable coating can be visually observed. Because the thickness of the electromagnetic wave-permeable coating is thin (1 μm to 20 μm), all of the luminous pigments, including those located at the bottom of the electromagnetic wave-permeable coating, can be visually observed. The electromagnetic wave-permeable coating can be photographed from its surface side, with or without a clear coating, and the ratio of the projected area (overlap rate) can be determined from the obtained image using the following formula.

[0042] Overlapping rate (%) = [(ΣReflection area - Projected area) / ΣReflection area]×100 When a lustrous pigment is projected onto the bottom surface of a coating film, it is preferable that the ratio of the projected area of ​​the lustrous pigment to the bottom surface (overlap rate) is 70% or more and 99% or less. When aluminum flakes are used as the lustrous pigment, the overlap rate is preferably 70% or more and 95% or less, and when vapor-deposited aluminum is used as the lustrous pigment, the overlap rate is preferably 70% or more and 99% or less.

[0043] As described above, by forming an electromagnetic wave-transmitting coating using the luminous material of this disclosure, it is possible to ensure aesthetic appeal by arranging the luminous material as densely and highly oriented as possible within the coating, while also ensuring excellent electromagnetic wave transmittance. Even when the luminous material of this disclosure is blended at a high concentration and comes into contact with other luminous material particles, the coating suppresses the formation of conduction paths between the luminous pigments, thereby reducing electromagnetic wave absorption loss, and also reduces the reflection of electromagnetic waves on the surface of the luminous material pigments. Furthermore, by setting the thickness of the coating to 0.7 μm or more and 3.0 μm or less, it is possible to have good electromagnetic wave transmittance and durability (chipping resistance). Increasing the thickness of the coating increases the proportion of resin components in the electromagnetic wave-transmitting coating, which in turn reduces the proportion of the base resin constituting the electromagnetic wave-transmitting coating, potentially reducing the durability of the electromagnetic wave-transmitting coating. In the luminous material of this disclosure, by dispersing nanoparticles in the resin component of the coating, it is possible to maintain the durability of the electromagnetic wave-transmitting coating even when the thickness of the coating is increased compared to when nanoparticles are not included in the resin component. By dispersing nanoparticles in the resin component of the coating, the thickness of the coating can be increased, ensuring sufficient distance between the luminous pigments and further enhancing the electromagnetic wave permeability of the electromagnetic wave-transmitting coating.

[0044] <Examples> As a paint for forming an electromagnetic wave-transmitting coating, a paint with the formulation shown in Table 1 was used. The formulation in Table 1 was used in common for both the examples and comparative examples. As a lustrous pigment, aluminum flakes with an average particle size of 10 μm and an average thickness of 0.02 μm were used, and the surface of these aluminum flakes was coated with a silicone resin containing dispersed nanoparticles to form a coating portion, which was used as the lustrous material. As nanoparticles, silica nanoparticles that had been hydrophobized by surface modification of organic groups were used. The lustrous material was prepared with coating portion thicknesses of 0.7 μm, 2.0 μm, 3.0 μm, and 3.5 μm.

[0045] [Table 1]

[0046] On the surface of a polypropylene substrate, an electrodeposited coating, an electromagnetic wave-permeable coating, and a clear coating were applied in that order, so that the coating thickness after curing was 7 μm for the electrodeposited coating, 15 μm for the electromagnetic wave-permeable coating, and 30 μm for the clear coating. The coatings were then baked at 90°C for 35 minutes to obtain test specimens with the coatings.

[0047] The dispersibility of nanoparticles in the resin component was evaluated, and the electromagnetic wave transmittance, optical properties, and durability of the obtained coating film were evaluated. The evaluation results for Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 2. In Examples 1 to 4 and Comparative Examples 1 to 4, the amount of aluminum flakes in the electromagnetic wave transmittance coating film was 2 wt%, but different gloss materials were used, differing in the thickness of the coating and the amount of nanoparticles in the coating. Example 1 used a gloss material with a coating containing 20 wt% nanoparticles and a thickness of 0.7 μm, Example 2 used a gloss material with a coating containing 60 wt% nanoparticles and a thickness of 0.7 μm, Example 3 used a gloss material with a coating containing 20 wt% nanoparticles and a thickness of 3.0 μm, and Example 4 used a gloss material with a coating containing 60 wt% nanoparticles and a thickness of 3.0 μm. Furthermore, Comparative Example 1 used a glossy material (untreated aluminum flakes) with a coating thickness of 0 μm, Comparative Example 2 used a glossy material having a coating thickness of 2.0 μm that did not contain nanoparticles, Comparative Example 3 used a glossy material having a coating thickness of 0.7 μm that contained 15 wt% nanoparticles, and Comparative Example 5 used a glossy material having a coating thickness of 3.5 μm that contained 20 wt% nanoparticles. In Comparative Example 4, an attempt was made to form a coating containing 70 wt% nanoparticles, but the nanoparticles and resin components did not mix during the paint preparation stage, and it was not possible to create the paint.

[0048] [Table 2]

[0049] (Evaluation of nanoparticle dispersibility) The dispersibility of nanoparticles in the resin component was evaluated by adding nanoparticles to a paint containing the resin component and visually checking whether they mixed uniformly. Specifically, silica nanoparticles in each proportion were added to a paint mixture of 72 wt% silicone resin and 28 wt% solvent. After roughly mixing by hand, the mixture was mixed using a rotary-orbit mixer (Shinky Co., Ltd., ARV310), and the state of the mixture was visually checked. If all nanoparticles were uniformly mixed in the paint and it was determined that the mixture was paintable, it was evaluated as having good dispersibility with a "○" in Table 2. If the nanoparticles were not uniformly mixed and it was determined that the mixture was not paintable, it was evaluated as not having good dispersibility with a "×".

[0050] (Evaluation of electromagnetic wave permeability) The electromagnetic wave permeability of the coating film was evaluated by placing a test specimen between an electromagnetic wave transmitter and receiver and measuring the transmitted or reflected electromagnetic waves. A KEYSIGHT N5290A network analyzer was used as the electromagnetic wave measurement instrument, an EM Lab FS-Eband was used as the free-space method measurement jig, and the KEYSIGHT N1500A material measurement suite was used as the measurement software to measure the S-parameters. S21 of the S-parameter at a frequency of 76 GHz was determined as the transmission attenuation, and in Table 2, if the transmission attenuation S21 satisfies |S21| ≤ 1.5 dB, it was evaluated as having acceptable electromagnetic wave permeability and marked with "○", and if the transmission attenuation S21 did not satisfy |S21| ≤ 1.5 dB, it was evaluated as not having acceptable electromagnetic wave permeability and marked with "×".

[0051] (Evaluation of optical properties) The optical properties of the coating film were evaluated by determining its brightness using a variable-angle spectrophotometer. A GSP-2B spectrophotometer manufactured by Murakami Color Technology Laboratory was used, with a D65 light source as the incident light. The incident angle of light was fixed at 45°, and the reception angle θ was measured at 5° intervals within the range of -80°≦θ≦80°, according to CIE1976L. * a * b * Lightness index L in color space *The value was obtained. Luminance L in regular reflection (45° incidence, 45° light reception) * 45° was used as the evaluation criterion. In Table 2, for L * 45° when L ≥ 400 is satisfied, it was evaluated as "○", indicating acceptable luminance with good designability. When L * 45° does not satisfy L ≥ 400, it was evaluated as "×", indicating that it does not have acceptable luminance.

[0052] (Evaluation of durability) The evaluation of the durability of the coating film was carried out by a chipping resistance test in which small stones were projected onto the coating film, regarded as flying stones hitting the vehicle body during vehicle driving, and the peeling area of the coating film was evaluated. Specifically, the test piece was attached to the test plate of a flying stone tester (manufactured by Suga Test Instruments Co., Ltd., JA - 400L), the fixed table was made angle - variable, and small stones were made to collide perpendicularly to the test plate under the following test conditions. Then, the areas of 5 locations of the peeled part in the coating film were measured. In Table 2, if the maximum area of the measured peeled part is 5 mm 2 or less, it was evaluated as "○", indicating good durability. If the maximum area of the peeled part does not satisfy 5 mm 2 or less, it was evaluated as "×", indicating that it does not show good durability.

[0053] In Comparative Example 1 using untreated aluminum flakes without a coating part, the electromagnetic wave permeability was poor. In Comparative Example 2 using a bright material with a coating part thickness of 2.0 μm, the durability was poor. In Comparative Example 3 using a bright material with a coating part containing 15 wt% of nanoparticles and a thickness of 0.7 μm, the durability was poor. In Comparative Example 5 using a bright material with a coating part containing 20 wt% of nanoparticles and a thickness of 3.5 μm, the optical properties were poor. Examples 1 to 4 used bright materials with a coating part having a thickness of 0.7 μm to 3.0 μm and containing 20 wt% to 60 wt% of nanoparticles. However, the dispersibility, electromagnetic wave permeability, optical properties, and durability of the nanoparticles were all good, and it was a coating film that achieved both electromagnetic wave permeability and designability. . [Industrial Applicability]

[0054] This disclosure is extremely useful because it makes it possible to arrange the glossy material as densely and highly orientedly as possible within the coating film, thereby providing a coating film that achieves both electromagnetic wave transmittance and aesthetic appeal. [Explanation of symbols]

[0055] 10 Object to be coated 30 Electromagnetic wave transparent coating 31 Bright material 32. Luminous Pigments 33 Covering part 34 nanoparticles

Claims

1. A luminescent material dispersed within a coating film having electromagnetic wave permeability, A conductive, lustrous pigment, A luminous material comprising a non-conductive resin component and nanoparticles dispersed in the resin component, and a coating portion that covers the surface of the luminous pigment to a thickness of 0.7 μm or more and 3.0 μm or less.

2. In claim 1, The amount of nanoparticles in the coating portion is 20 wt% or more and 60 wt% or less, in this glossy material.

3. In claim 2, The aforementioned luminous pigment is in flake form, and is a luminous material.

4. In claim 3, The aforementioned luminous pigment is a metallic particle, a luminous material.

5. In claim 4, A bright material in which the thickness of the metal particles is 0.6 μm or less.

6. In claim 5, A bright material in which the particle size of the metal particles is 5 μm or more and 20 μm or less.

7. A coating film having electromagnetic wave permeability, An electromagnetic wave-transmitting coating film comprising the luminous material described in any one of claims 1 to 6.

8. In claim 7, An electromagnetic wave-transmitting coating film in which the concentration (PWC) of the luminous pigment in the coating film is 1 wt% or more and 20 wt% or less, and when the luminous pigment is projected onto the bottom surface of the coating film, the ratio of the projected area of ​​the luminous pigment to the bottom surface is 70% or more and 99% or less per unit area.

9. In claim 7, An electromagnetic wave-permeable coating film with a thickness of 1 μm or more and 20 μm or less.

10. A coated material having electromagnetic wave permeability, A painted article comprising the electromagnetic wave permeable coating film described in claim 7.

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