Vehicle exterior parts

Abstract

To provide an exterior component for vehicles that is enhanced in both structural durability and aesthetic qualities.SOLUTION: An exterior component 10 for vehicles includes a substrate 11 and a multilayer coating film 12 covering a surface of the substrate 11. The multilayer coating film 12 includes a base coating film 13 closest to the substrate 11, a decorative coating film 14 that is in contact with the base coating film 13 and covers a part of the surface of the base coating film 13, and a protective coating film 15 that is transparent and covers the base coating film 13 and the decorative coating film 14 so as to be in contact with the decorative coating film 14 and a portion of the base coating film 13 that is not covered with the decorative coating film 14, and the protective coating film 15 has a refractive index of 1.5210 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to exterior parts for vehicles.

Background Art

[0002] Conventionally, exterior parts for vehicles include parts with an emblem displaying a manufacturer name, a vehicle model name, etc., attached thereto, and parts with a seal or the like pasted thereon. Such exterior parts for vehicles are required to have a high aesthetic appearance in order to give the vehicle a luxurious feel. In addition, such exterior parts for vehicles are required to have high durability because they may be exposed to sunlight, wind, rain, and chemicals (such as detergents when washing the car).

[0003] Patent Document 1 discloses a configuration in which characters, symbols, etc. are printed on an exterior case of a hot water unit by inkjet printing and the surface thereof is covered with a clear paint layer. Further, Patent Document 2 discloses a configuration in which a design is applied to a building material by inkjet printing and the surface of the building material is covered with a clear layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 1

Summary of the Invention

[0005] (Problems to be Solved by the Invention) Incidentally, if there are minute irregularities on the surface of the coating film that forms letters or other shapes, light is more easily scattered on that surface, which reduces the clarity of the letters or other shapes (i.e., the letters or other shapes appear blurred). For this reason, in order to improve the aesthetic appearance of exterior parts, it is desirable to improve the clarity of letters or other shapes. In particular, inkjet coating devices spray minute amounts of ink towards the object to be coated, so minute irregularities tend to occur on the surface of the printed letters or other shapes (i.e., the surface of the formed coating film).

[0006] This invention has been made in view of the above circumstances, and one of its objectives is to improve the aesthetic appearance (looks) of exterior parts of a vehicle while ensuring the durability of the coating film on those parts.

[0007] (Means for solving the problem) To achieve the above objective, the exterior parts of a vehicle according to the present invention are A vehicle exterior part comprising a base material and a multi-layer coating film covering the surface of the base material, The aforementioned multi-layer coating film is The first coating film closest to the substrate, A second coating film is in contact with the first coating film and covers a portion of the surface of the first coating film, A third coating film that is transparent and covers the first coating film and the second coating film so as to be in contact with the second coating film and the portion of the first coating film that is not covered by the second coating film, Equipped with, The refractive index of the third coating film is 1.5210 or higher. the law of nature , The substrate comprises a thermoplastic resin material that softens at temperatures above 80°C. The glass transition temperatures of the first coating film and the second coating film are 80°C or lower.

[0008] According to the present invention, by setting the refractive index of the third coating film to 1.5210 or higher, the amount of light reflected from the surface of the third coating film can be increased, and the amount of light incident from outside the multi-layer coating film to the interface between the third coating film and the second coating film (the surface of the second coating film) can be reduced. Therefore, even if minute irregularities exist on the surface of the second coating film, the amount of light diffusely reflected from that surface can be reduced, and as a result, the second coating film can be made to appear clearer. In this way, by covering the first and second coating films with the third coating film, the durability, weather resistance, and chemical resistance of the first and second coating films can be ensured while improving the aesthetic appearance of the exterior parts.

[0009] The substrate comprises a thermoplastic resin material that softens at temperatures above 80°C. The glass transition temperatures of the first coating film and the second coating film are 80°C or lower. This configuration can be applied.

[0010] With this configuration, by heating the vehicle's exterior parts to approximately 80°C to soften the first and second coatings, it is possible to prevent or suppress deformation of the substrate while improving the adhesion between the first and second coatings and the third coating.

[0011] The glass transition temperature of the second coating is lower than that of the third coating. This configuration can be applied.

[0012] With this configuration, by heating the vehicle's exterior parts to a temperature higher than the glass transition temperature of the second coating, the adhesion (bonding strength) between the second and third coatings can be improved. Therefore, peeling of the second coating from the third coating can be prevented or suppressed, thereby improving the durability of the second coating while preventing or suppressing deformation of the third coating.

[0013] The glass transition temperature of the second coating film is 40°C or lower. The glass transition temperature of the third coating is 80°C or higher and below the softening temperature of the substrate. Such a configuration can be applied.

[0014] When the glass transition temperature of the second coating film is 40°C or lower, it becomes easy to heat the second coating film to a temperature above the glass transition temperature to improve the adhesion between the second coating film and the third coating film. On the other hand, when the glass transition temperature of the third coating film is 80°C or higher, the third coating film is prevented or suppressed from reaching a temperature above the glass transition temperature in the normal use environment of the vehicle, so the deformation of the third coating film is prevented or suppressed.

[0015] The refractive index of the third coating film is 1.5300 or less. Such a configuration can be applied.

[0016] According to such a configuration, since it is not necessary to increase the content rate of additives or the like for increasing the refractive index of the third coating film, an increase in the material cost of the third coating film can be prevented or suppressed.

[0017] The second coating film is a colored film colored in a predetermined color, and is laminated on the side of the colored film toward the third coating film, and is a transparent film that is transparent and has a glass transition temperature lower than that of the third coating film, and includes the transparent film is in direct contact with the third coating film. Such a configuration can be applied.

[0018] According to such a configuration, since the restrictions on the material and properties of the colored layer of the second coating film are reduced, an increase in the material cost of the second coating film can be prevented or suppressed.

[0019] The first coating film is a colored film colored in a predetermined color, and is laminated on the side of the colored film toward the second coating film, and is a transparent film that is transparent and has a glass transition temperature lower than that of the third coating film, and includes the transparent film is in direct contact with the second coating film. Such a configuration can be applied.

[0020] With this configuration, the limitations on the material and properties of the colored layer of the first coating are reduced, thus preventing or suppressing an increase in the material cost of the first coating. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 is a schematic diagram showing the configuration of exterior parts of a vehicle according to the first embodiment. [Figure 2A] Figure 2A is a graph showing the relationship between the refractive index of the protective coating and the wave scan value. [Figure 2B] Figure 2B is a graph showing the relationship between the refractive index of the protective coating and the wave scan value. [Figure 3A] Figure 3A is a graph showing the relationship between the thickness of the protective coating and the wave scan value. [Figure 3B] Figure 3B is a graph showing the relationship between the thickness of the protective coating and the wave scan value. [Figure 4] Figure 4 is a graph showing the relationship between the glass transition temperature of the base coating and decorative coating and the adhesion of the protective coating. [Figure 5] Figure 5 is a schematic diagram showing the configuration of the exterior components of a vehicle according to the first embodiment. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will now be described with reference to the drawings. The exterior parts of a vehicle according to each embodiment of the present invention are parts that are attached to the exterior of a vehicle such that at least a portion of them is exposed to the outside of the vehicle. The exterior parts of a vehicle according to this embodiment may be functional parts or decorative parts (sometimes called garnishes). Examples of exterior parts of a vehicle according to each embodiment include outside door handles, emblems indicating the manufacturer or model, or parts to which such emblems are attached, and center pillar garnishes, rear garnishes, front garnishes, frame moldings, fuel lid covers, spoilers, roof panels, side mirrors, etc. Hereinafter, exterior parts of a vehicle may be simply referred to as exterior parts.

[0023] <First Embodiment> Figure 1 is a schematic diagram showing the cross-sectional structure of the exterior component 10 according to the first embodiment. As shown in Figure 1, the exterior component 10 comprises a base material 11 and a multi-layer coating 12 provided on the surface of the base material 11.

[0024] The base material 11 is a component that constitutes the portion of the exterior part 10 to which the multi-layer coating 12 is applied. If the exterior part 10 consists only of the base material 11 and the multi-layer coating 12, then the base material 11 can be said to be the exterior part 10 before painting (unpainted). If the exterior part 10 consists of components other than the base material 11, then the base material 11 can be said to be a component that constitutes the main part (the part visible from the outside of the vehicle) of the exterior part 10 before painting. The material of the base material 11 is not limited and is set appropriately according to the type of exterior part 10, etc. For example, if the exterior part 10 is an outside door handle, emblem, or center pillar as described above, then a thermoplastic resin material such as a mixed material of polycarbonate and polybutylene terephthalate can be applied to the material of the base material 11. Furthermore, when a thermoplastic resin material is applied to the substrate 11, the substrate must be made of a resin material having a softening temperature (heat resistance temperature) higher than the glass transition temperatures of the base coating 13, decorative coating 14, and protective coating 15 of the multi-layer coating 12 described later. In addition, a metal material may be applied as the material of the substrate 11.

[0025] The multilayer coating 12 is provided on the outer surface of the substrate 11. The multilayer coating 12 comprises three coatings that are laminated together: a base coating 13, a decorative coating 14, and a protective coating 15. The base coating 13 is an example of the first coating of the present invention, the decorative coating 14 is an example of the second coating of the present invention, and the protective coating 15 is an example of the third coating of the present invention. The multilayer coating 12 may be provided on the entire surface of the substrate 11, or on a part of the surface of the substrate 11 (for example, a part that is visible from the outside of the vehicle when the exterior part 10 is attached to the vehicle).

[0026] The base coating 13 is located on the side closest to the surface of the substrate 11 and, in this embodiment, is in direct contact with the surface of the substrate 11. By providing the base coating 13 on the surface of the substrate 11 (covering the surface of the substrate 11), the color of the base coating 13 becomes the basic color of the exterior part 10. In other words, it can be said that "the color of the base coating 13 is the base color of the exterior part 10." The base coating 13 can be a paint made of a resin material whose glass transition temperature is lower than that of the protective coating 15 described later, or a paint that mainly contains a resin material whose glass transition temperature is lower than that of the protective coating 15 described later. For example, the base coating 13 can be a paint that mainly contains an ultraviolet-curable acrylic resin material. If the substrate 11 is metal, the base coating 13 may contain a silane coupling agent to increase the bonding strength between the substrate 11 and the base coating 13. The glass transition temperature of the base coating 13 will be described later.

[0027] The color and texture of the base coating 13 are not limited, but for example, if the exterior parts 10 are to have a metallic texture, a glossy silver color is applied as the color of the base coating 13. In this case, the base coating 13 can be made of a resin material in which a filler made of a metallic material or a filler made of a material having metallic luster is dispersed. In this embodiment, the base coating 13 is opaque.

[0028] The decorative coating 14 is a coating film for representing at least one of letters, symbols, patterns, and figures (hereinafter sometimes referred to as "letters, etc.") on the surface of the exterior part 10. It can also be said that "the decorative coating 14 is a coating film that decorates the exterior part 10." The decorative coating 14 is laminated on a part of the surface of the base coating 13 and is in direct contact with the surface of the base coating 13 opposite to the substrate 11. Similar to the base coating 13, the decorative coating 14 can be made of a resin material whose glass transition temperature is lower than that of the protective coating 15 described later, or a paint that mainly contains a resin material whose glass transition temperature is lower than that of the protective coating 15 described later. For example, the decorative coating 14 can be made of an ultraviolet-curing acrylic paint mainly containing isobornyl acrylate. In this embodiment, the decorative coating 14 is opaque. However, the color of the decorative coating 14 is not limited. Furthermore, the decorative coating 14 may be a single color or multiple colors. The glass transition temperature of the decorative coating 14 will be described later.

[0029] The protective coating 15 is a coating film laminated on the base coating 13 and the decorative coating 14, and is the outermost coating film of the multi-layer coating 12 (in other words, the coating film furthest from the substrate 11). The protective coating 15 has the function of protecting the base coating 13 and the decorative coating 14, and the function of improving the aesthetic appearance of the exterior parts 10. The protective coating 15 is transparent, and the base coating 13 and the decorative coating 14 can be seen through the protective coating 15 from the outside of the vehicle. A transparent material with a refractive index within the range described later is applied to the protective coating 15. In addition, a paint with a higher glass transition temperature than the base coating 13 and the decorative coating 14 is applied to the protective coating 15. For example, a paint containing a two-component acrylic resin material as the main component is applied to the protective coating 15. The protective coating 15 may also contain additives to obtain a predetermined refractive index. For example, urethane can be used as an additive to obtain a predetermined refractive index. In this case, the refractive index of the protective coating 15 increases as the urethane content increases.

[0030] The protective coating 15 may contain light stabilizers such as ultraviolet absorbers to improve weather resistance. In addition, the protective coating 15 may appropriately contain defoamers, fungicides, and preservatives.

[0031] Inkjet-type coating equipment (printing equipment) can be used to form the base coating 13, decorative coating 14, and protective coating 15, respectively. Using an inkjet-type coating equipment eliminates the need for a drying oven after coating (after the formation of each coating), thus reducing CO2 emissions. Furthermore, since the nozzles that dispense the paint, which is the material for each coating, can be brought close to the substrate 11, paint waste (paint that does not reach the substrate 11) can be reduced. Also, coatings can be formed even if there are irregularities on the surface of the substrate 11. Additionally, if UV-curable paints are applied to the base coating 13, decorative coating 14, and protective coating 15, the paint can be cured immediately by irradiating it with ultraviolet light after application, thereby forming the coating.

[0032] After all coatings have been formed, a baking process is performed to increase the strength of each coating. The heating temperature in this baking process is above the temperature required to improve the strength of each coating (crosslinking temperature), is higher than the glass transition temperature of the base coating 13 and protective coating 15, and is lower than the heat resistance temperature of the substrate 11 (the temperature at which the substrate 11 softens). Further details will be described later.

[0033] (Refractive index of protective coating) The refractive index of the protective coating 15 is 1.5210 or higher. The reason for this is as follows: If there are fine irregularities at the interface between the decorative coating 14 and the protective coating 15 (this interface can also be said to be the surface of the decorative coating 14), light incident on this interface from outside the multilayer coating 12 through the protective coating 15 may be diffusely reflected at the interface. In particular, when the protective coating 15 is formed by an inkjet coating device, irregularities are more likely to be formed on the surface of the decorative coating 14, making it easier for diffuse reflection to occur at this interface. If the amount of light diffusely reflected at this interface is large, the image of characters, etc., represented by the decorative coating 14 may appear blurred.

[0034] In order to make the images of characters, etc., represented by the decorative coating 14 appear clear, it is preferable to reduce the amount of light diffusely reflected at the interface. When the refractive index of the protective coating 15 increases, the reflectivity of the surface of the protective coating 15 increases, so the amount of light incident on the interface decreases, and as a result, the amount of light diffusely reflected at the interface decreases. Therefore, the images of characters, etc., represented by the decorative coating 14 become clearer, and the aesthetic appearance (look) of the exterior part 10 can be improved.

[0035] Figures 2A and 2B are graphs showing the relationship between the refractive index of the protective coating 15 and the wave scan value. Figure 2A quantifies the degree of orange peel texture on the exterior part 10, and Figure 2B quantifies the clarity. The wave scan value, which indicates the degree of orange peel texture, indicates that a smaller value means the surface of the object being measured appears smoother. The wave scan value, which indicates clarity, indicates that a smaller value means the surface of the object being measured appears clearer (i.e., the characters etc. represented by the decorative coating 14 appear clearer (higher clarity)). A mixed material of polycarbonate and polybutylene terephthalate was used for the substrate 11, an acrylic resin-based paint was used for the base coating 13, a UV-curing acrylic resin-based ink was used for the decorative coating 14, and an acrylic resin-based paint was used for the protective coating 15. As shown in Figures 2A and 2B, when the refractive index of the protective coating 15 is 1.5210 or higher, the wave scan value becomes 40.0 or lower, and the clarity of the characters etc. represented by the decorative coating 14 increases. Furthermore, within the range where the refractive index of the protective coating 15 is 1.5210 or higher, the fluctuation in the wave scan value is small. Therefore, from the viewpoint of the aesthetic appearance of the exterior part 10 (from the viewpoint of the clarity of characters etc. represented by the decorative coating 14), the refractive index of the protective coating 15 is set to 1.5210 or higher.

[0036] On the other hand, as is clear from Figures 2A and 2B, even if the refractive index of the protective coating 15 exceeds 1.5300, the wave scan value hardly decreases. Therefore, from the viewpoint of the aesthetic appearance of the exterior part 10, there is no upper limit to the refractive index of the third coating. Conversely, even if the refractive index of the protective coating 15 exceeds 1.5300, the clarity of the letters, etc., represented by the decorative coating 14 does not increase. As mentioned above, in a configuration where the paint material of the decorative coating 14 contains additives to increase the refractive index, the material cost of the protective coating 15 increases as the additive content increases. Therefore, from the viewpoint of the material cost of the protective coating 15 (in other words, the product price), it is preferable that the refractive index of the protective coating 15 is 1.5300 or less.

[0037] With a configuration in which the multilayer coating 12 includes such a protective coating 15, the durability, weather resistance, and chemical resistance of the base coating 13 and the decorative coating 14 can be improved by protecting the decorative coating 14, while the aesthetic appearance of the exterior parts 10 can be improved by increasing the clarity of the letters and other elements represented by the decorative coating 14. In particular, the exterior parts 10 of a vehicle are exposed to direct sunlight and wind and rain, and chemicals such as detergents may adhere to them when the vehicle is washed. According to this embodiment, the aesthetic appearance of the exterior parts 10 can be improved while ensuring the durability, weather resistance, and chemical resistance required for the exterior parts 10 of a vehicle.

[0038] Figures 3A and 3B are graphs showing the relationship between the film thickness of the protective coating 15 and the wave scan value. As shown in Figures 3A and 3B, within the evaluated film thickness range (specifically, the range of 3.13 to 58.05 μm), no strong correlation was observed between the film thickness of the protective coating 15 and the wave scan value. Therefore, the film thickness of the protective coating 15 is not particularly limited. At least, if the film thickness of the protective coating 15 is in the range of 3.13 to 58.05 μm, the protective coating 15 can achieve the effect of "enhancing the clarity of characters, etc., represented by the decorative coating 14."

[0039] (Softening temperature of the substrate and glass transition temperature of each coating film) Next, the softening temperature of the substrate 11 and the glass transition temperature of each coating film (it can also be said that the glass transition temperature of each coating film is the glass transition temperature of the resin material that is the main component of each coating film) will be explained. In this embodiment, the substrate 11 is made of a thermoplastic resin material that softens at temperatures above 80°C. As described above, if the substrate 11 is made of a mixed material of polycarbonate and polybutylene terephthalate, the softening temperature (heat resistance temperature) is 102°C. The substrate 11 may be molded from a thermoplastic resin material that mainly contains a resin material that softens at temperatures above 80°C. In short, the substrate 11 just needs to soften at a predetermined temperature.

[0040] If the substrate 11 is made of a thermoplastic material, or if the substrate 11 contains a thermoplastic material, the glass transition temperatures of the base coating 13, decorative coating 14, and protective coating 15 are lower than the softening temperature (heat resistance temperature) of the substrate 11. If the substrate 11 is made of a resin material that softens at temperatures above 80°C as described above, the glass transition temperatures of the base coating 13, decorative coating 14, and protective coating 15 are 80°C or lower.

[0041] With this configuration, in the baking process after molding each coating film, the exterior part 10 is heated to a temperature (80°C in this embodiment) that is above the glass transition temperature of the base coating film 13 and the decorative coating film 14 and below the softening temperature of the substrate 11, thereby preventing or suppressing deformation of the substrate 11 while improving the adhesion between the base coating film 13 and the decorative coating film 14 and the protective coating film 15. Specifically, the base coating film 13 and the decorative coating film 14 can be softened to relieve stress between the base coating film 13 and the decorative coating film 14 and the protective coating film 15. Furthermore, by softening the base coating film 13, a multiphase of the base coating film 13 and the protective coating film 15 can be formed at and near the interface between the base coating film 13 and the protective coating film 15. As a result, the adhesion (bonding strength) between the base coating film 13 and the protective coating film 15 can be improved. Similarly, by softening the decorative coating 14, a multiphase of the decorative coating 14 and the protective coating 15 can be formed at and near the interface between the decorative coating 14 and the protective coating 15. This increases the adhesion (bonding strength) between the decorative coating 14 and the protective coating 15. In other words, the anchoring effect increases the bonding strength between the base coating 13 and the decorative coating 14 and the protective coating 15. Therefore, the durability of the multilayer coating 12 can be increased, and in particular, peeling of the protective coating 15 can be prevented or suppressed.

[0042] Furthermore, it is preferable that the glass transition temperatures of the base coating 13 and the decorative coating 14 are lower than the glass transition temperature of the protective coating 15. For example, if the glass transition temperature of the protective coating 15 is set to approximately 80°C, which is lower than the softening temperature of the substrate 11, it is preferable that the glass transition temperatures of the base coating 13 and the decorative coating 14 be 40°C or lower. With such a configuration, in the baking process after molding each coating, the exterior part 10 is heated to a temperature higher than the glass transition temperatures of the base coating 13 and the decorative coating 14 and near the glass transition temperature of the protective coating 15 (for example, approximately 80°C), thereby preventing or suppressing deformation due to softening of the protective coating 15, while softening the base coating 13 and the decorative coating 14 to improve the adhesion between the base coating 13 and the decorative coating 14 and the protective coating 15.

[0043] Furthermore, if the glass transition temperature of the protective coating 15 is higher than that of the base coating 13 and the decorative coating 14, even if the temperature of the vehicle's operating environment rises above the glass transition temperature of the base coating 13 and the decorative coating 14, softening of the protective coating 15 is prevented or suppressed, thereby preventing or suppressing deformation of the base coating 13 and the decorative coating 14. In this way, by making the glass transition temperature of the protective coating 15 higher than that of the base coating 13 and the decorative coating 14, the adhesion between the base coating 13 and the decorative coating 14 and the protective coating 15 can be improved while preventing or suppressing deformation of the base coating 13 and the decorative coating 14.

[0044] Furthermore, from the viewpoint of durability, weather resistance, and chemical resistance, the lower limit of the glass transition temperature of the base coating 13 and the decorative coating 14 is not limited. However, if the glass transition temperature of the base coating 13 and the decorative coating 14 is below the temperature of the vehicle's normal operating environment (so-called room temperature), the base coating 13 and the decorative coating 14 may soften during vehicle use. If the base coating 13 and the decorative coating 14 are softened and come into contact with the exterior parts 10 by the user's body or an object, the base coating 13 and the decorative coating 14 may deform. Therefore, it is preferable that the glass transition temperature of the base coating 13 and the decorative coating 14 be higher than room temperature (for example, above 20°C), and preferably higher than the maximum temperature expected in the vehicle's operating environment.

[0045] Next, the results of the adhesion evaluation between the base coating 13 and decorative coating 14 and the protective coating 15 will be described. Figure 4 is a graph showing the relationship between the glass transition temperatures of the base coating 13 and decorative coating 14 and the adhesion between the base coating 13 and decorative coating 14 and the protective coating 15. A cross-cut test (grid test) was applied to evaluate the adhesion. A mixed material of polycarbonate and polybutylene terephthalate was used for the substrate 11. The softening temperature of the substrate 11 was 102°C. An acrylic resin-based paint was used for the base coating 13, a UV-curable acrylic resin-based ink was used for the decorative coating 14, and an acrylic resin-based paint was used for the protective coating 15. The heating temperature in the baking process was set to 80°C.

[0046] In the cross-cut test, adhesion was judged as good if no peeling occurred on any of the grids, and as poor if peeling occurred on any of the grids. In the graph, "○ (white circle)" indicates good adhesion, and "× (cross)" indicates poor adhesion. As shown in Figure 4, adhesion was good when the glass transition temperature of the base coating 13 was 80°C or lower, and poor when it was above 80°C. Therefore, it was confirmed that it is preferable for the glass transition temperature of the base coating 13 to be 80°C or lower.

[0047] <Second Embodiment> Next, a second embodiment will be described. Figure 5 is a schematic diagram showing the cross-sectional structure of the exterior part 10 according to the second embodiment. In the second embodiment, the base coating 13 and the decorative coating 14 each have a laminated structure of multiple coating films.

[0048] As shown in Figure 5, the base coating 13 comprises a first sub-base coating 131 closer to the substrate 11 and a second sub-base coating 132 closer to the decorative coating 14, and has a laminated structure of the first sub-base coating 131 and the second sub-base coating 132. The first sub-base coating 131 is a coating that defines the basic color of the exterior part 10. It can also be said that "the color of the first sub-base coating 131 is the base color of the exterior part 10." The second sub-base coating 132 is a layer provided to improve adhesion (improve bonding strength) with the decorative coating 14 and the protective coating 15. The second sub-base coating 132 is transparent so that the color of the first sub-base coating 131 can be seen from outside the multi-layer coating 12. The second sub-base coating 132 can be a film made of a transparent resin material with a glass transition temperature lower than that of the protective coating 15, or a film mainly composed of such a resin material. Specifically, the glass transition temperature of the second sub-base coating 132 can be the same as the glass transition temperature of the base coating 13 of the multi-layer coating 12 according to the first embodiment. The glass transition temperature of the first sub-base coating 131 is not particularly limited.

[0049] The decorative coating 14 comprises a first secondary decorative coating 141 that is in direct contact with the second secondary base coating 132, a second secondary decorative coating 142 that is in direct contact with the protective coating 15, and a third secondary decorative coating 143 located between the first secondary decorative coating 141 and the second secondary decorative coating 142. The first secondary decorative coating 141 and the third secondary decorative coating 143 are in direct contact, and the second secondary decorative coating 142 and the third secondary decorative coating 143 are in direct contact. The first secondary decorative coating 141 is a layer (coating) provided to improve adhesion with the base coating 13. The second secondary decorative coating 142 is a layer provided to improve adhesion with the protective coating 15. The second secondary decorative coating 142 is transparent. The third secondary decorative coating 143 is a coating for decoration. The third secondary decorative coating 143 is a layer colored with a predetermined color, and the color of the third secondary decorative coating 143 defines the color of the letters, etc., represented by the decorative coating 14. As described above, since the second secondary decorative coating 142 is transparent, the color of the third secondary decorative coating 143 can be seen through the protective coating 15 and the second secondary decorative coating 142.

[0050] The first secondary decorative coating 141 and the second secondary decorative coating 142 can be made of a resin material having a glass transition temperature lower than that of the protective coating 15, or a resin material containing such a resin material as a main component. For example, the first secondary decorative coating 141 and the second secondary decorative coating 142 can be made of an ultraviolet-curable acrylic resin material mainly composed of isobornyl acrylate. The glass transition temperatures of the first secondary decorative coating 141 and the second secondary decorative coating 142 can be the same as the glass transition temperature of the decorative coating 14 of the multilayer coating 12 according to the first embodiment. The glass transition temperature of the third secondary decorative coating 143 is not particularly limited.

[0051] The protective coating 15 of the second embodiment has the same configuration as the protective coating 15 of the first embodiment. That is, the protective coating 15 of the second embodiment is a transparent film with a refractive index of 1.5210 or higher.

[0052] The second embodiment can achieve the same effects as the first embodiment. Furthermore, the second embodiment reduces the restrictions on the materials used for the first sub-base coating 131 (i.e., the coating that defines the basic color of the exterior part 10) and the third sub-decorative coating 143 (i.e., the coating that defines the color of letters, etc.). Therefore, by applying inexpensive paints to the first sub-base coating 131 and the third sub-decorative coating 143, it is possible to reduce material costs or prevent or suppress increases in material costs.

[0053] <Variation> Next, a brief description will be given of modifications of each embodiment. If the opacity of the decorative coating 14 in the first embodiment is low, a film of a highly opacity material may be provided in the portion between the base coating 13 and the decorative coating 14 that is covered by the decorative coating 14. Similarly, if the opacity of the third secondary decorative coating 143 in the second embodiment is low, a film of highly opacity may be provided between the first secondary decorative coating 141 and the third secondary decorative coating 143. That is, the decorative coating 14 may have a four-layer laminated structure. Such films can be made of UV-curable acrylic resin colored white or gray.

[0054] If the substrate 11 is a metal such as steel, a film to improve the corrosion resistance of the substrate 11 may be provided on the surface of the substrate 11. Such a film can be made of epoxy resin. In this case, the multilayer coating 12 does not directly contact the surface of the substrate 11, but contacts the film to improve corrosion resistance. Furthermore, in this case, a film to prevent or suppress light transmission may be provided between the film to improve the corrosion resistance of the substrate 11 and the multilayer coating 12. As such a film to prevent or suppress light transmission, for example, a two-component acrylic resin material containing a filler made of a material with low light transmittance, or a resin material mainly composed of such a two-component acrylic resin material, can be applied.

[0055] Although embodiments and modifications of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the formation of each coating film is not limited to a method using an inkjet coating apparatus. [Explanation of Symbols]

[0056] 10...Vehicle exterior parts, 11...Base material, 12...Multi-layer coating, 13...Base coating, 14...Decorative coating, 15...Protective coating

Claims

1. A vehicle exterior part comprising a base material and a multi-layer coating film covering the surface of the base material, The aforementioned multi-layer coating film is The first coating film closest to the substrate, A second coating film is in contact with the first coating film and covers a portion of the surface of the first coating film, A third coating film that is transparent and covers the first coating film and the second coating film so as to be in contact with the second coating film and the portion of the first coating film that is not covered by the second coating film, Equipped with, The refractive index of the third coating film is 1.5210 or higher. The substrate comprises a thermoplastic resin material that softens at temperatures exceeding 80°C. The glass transition temperatures of the first coating film and the second coating film are 80°C or lower. Vehicle exterior parts.

2. A vehicle exterior part comprising a base material and a multi-layer coating film covering the surface of the base material, The aforementioned multi-layer coating film is The first coating film closest to the substrate, A second coating film is in contact with the first coating film and covers a portion of the surface of the first coating film, A third coating film that is transparent and covers the first coating film and the second coating film so as to be in contact with the second coating film and the portion of the first coating film that is not covered by the second coating film, Equipped with, The refractive index of the third coating film is 1.5210 or higher. The glass transition temperature of the second coating is lower than that of the third coating. Vehicle exterior parts.

3. An exterior part of a vehicle according to Claim 2, The glass transition temperature of the second coating film is 40°C or lower. The glass transition temperature of the third coating film is 80°C or higher and below the softening temperature of the substrate. Vehicle exterior parts.

4. A vehicle exterior part comprising a base material and a multi-layer coating film covering the surface of the base material, The aforementioned multi-layer coating film is The first coating film closest to the substrate, A second coating film is in contact with the first coating film and covers a portion of the surface of the first coating film, A third coating film that is transparent and covers the first coating film and the second coating film so as to be in contact with the second coating film and the portion of the first coating film that is not covered by the second coating film, Equipped with, The refractive index of the third coating film is 1.5210 or higher. The second coating film is A colored film that has been colored to a predetermined color, A transparent film is laminated on the side of the third coating film of the colored film, and is transparent with a glass transition temperature lower than that of the third coating film. Equipped with, The transparent film is in direct contact with the third coating film. Vehicle exterior parts.

5. A vehicle exterior part comprising a base material and a multi-layer coating film covering the surface of the base material, The aforementioned multi-layer coating film is The first coating film closest to the substrate, A second coating film is in contact with the first coating film and covers a portion of the surface of the first coating film, A third coating film that is transparent and covers the first coating film and the second coating film so as to be in contact with the second coating film and the portion of the first coating film that is not covered by the second coating film, Equipped with, The refractive index of the third coating film is 1.5210 or higher. The first coating film is A colored film that has been colored to a predetermined color, A transparent film is laminated on the side of the second coating film of the colored film, and is transparent with a glass transition temperature lower than that of the third coating film. Equipped with, The transparent film is in direct contact with the second coating film. Vehicle exterior parts.

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