Effect pigment having near-infrared reflecting function, paint using the same, and panel

Abstract

Disclosed are a near-infrared reflective functional pigment, a paint, and a panel, particularly for a vehicle, etc. The pigment according to the present invention includes: a flaky substrate; a first metal oxide layer coated on at least a portion of the upper part of the substrate and having a refractive index of 1.8 or more; and a second metal oxide layer coated on at least a portion of the upper part of the first metal oxide layer and including an absorptive material. Also, the pigment reflects an IR electron beam of 850 nm to 950 nm by an average of 30% or more.

Description

Technical Field

[0001] This invention relates to an effect pigment with near-infrared reflective properties, specifically to said pigment, coatings using the same, and panels applied to vehicles, etc. Background Technology

[0002] Effect pigments are used in many industrial sectors, especially in automotive, decorative coatings, plastics, paints, printing inks, and cosmetic compounds.

[0003] In the aforementioned fields, effect pigments are used, especially in automotive coatings. In addition to bright pigments such as pearl, dark pigments such as black are also used in automotive coatings.

[0004] Recently, the automotive industry has been actively researching autonomous vehicles. These autonomous vehicles use sensors such as cameras, ultrasonic sensors, radar, and LiDAR to identify surrounding elements, and the expansion of autonomous driving is driven by the information identified through these systems. Among these sensing technologies, LiDAR systems have a relatively shorter recognition distance compared to Radar systems, but as a 3D recognition system with improved resolution for the surrounding environment at appropriate distances, it characteristically uses a laser with a frequency of approximately 905 nm as its light source.

[0005] However, the dark pigments used in paints applied to ordinary dark-colored vehicles have the following characteristics: based on ordinary optical properties, they absorb light in the visible light region perceptible to the naked eye, as well as light in the near-infrared region, including the 905nm wavelength, which is used as a LiDAR light source. Due to these light absorption characteristics, the recognition efficiency of vehicles with conventionally dark paint by LiDAR sensors is significantly reduced, which has become a major obstacle to the realization of autonomous driving. Summary of the Invention

[0006] Technical problems to be solved

[0007] The purpose of this invention is to provide a novel dark pigment for LiDAR systems, wherein the pigment achieves its dark color by having low reflectivity in the visible light region and by effectively reflecting LiDAR light sources in the near-infrared region, thereby enabling even dark pigments to effectively reflect LiDAR light sources.

[0008] means for solving problems

[0009] The near-infrared reflective functional pigment according to an embodiment of the present invention, which achieves the above-mentioned objective, is characterized by comprising: a sheet-like substrate; a first metal oxide layer coated on at least a portion of the substrate and having a refractive index of 1.8 or higher; and a second metal oxide layer coated on at least a portion of the first metal oxide layer and comprising an absorbing material. Furthermore, the near-infrared reflective functional pigment reflects an average of 30% or more of the IR electron beam from 850 nm to 950 nm.

[0010] Preferably, the first metal oxide layer contains Fe2O3, the second metal oxide layer contains Co3O4, and the ratio of the content of Fe in the first metal oxide layer to the content of Co in the second metal oxide layer can be in the range of 1:0.5 to 1:1.

[0011] Furthermore, preferably, the first metal oxide layer comprises TiO2 and SnO2, the second metal oxide layer comprises CuO, and the ratio of the content of Ti and Sn in the first metal oxide layer to the content of Cu in the second metal oxide layer can be in the range of 1:4 to 1:6.

[0012] More specifically, the pigment has a blackness (L*) of 35 or less and can reflect less than 15% of visible electron beams from 400 nm to 700 nm on average.

[0013] Furthermore, a coating according to another embodiment of the present invention, for achieving the above-mentioned objective, comprises: an adhesive; and a near-infrared reflective functional pigment, wherein the pigment comprises: a flake-like substrate; a first metal oxide layer coated on at least a portion of the substrate and having a refractive index of 1.8 or higher; and a second metal oxide layer coated on at least a portion of the first metal oxide layer and comprising an absorbing material. Furthermore, the pigment reflects an average of 30% or more of the IR electron beam from 850 nm to 950 nm.

[0014] As described above, the pigments applied to the coating have a blackness (L*) of 35 or less and can reflect less than 15% of visible electron beams from 400 nm to 700 nm on average.

[0015] Furthermore, the sheet-like substrate may be one or more sheet-like materials selected from synthetic mica, natural mica, glass flake, plate-like glass, plate-like iron oxide, plate-like alumina, plate-like silicon dioxide, plate-like aluminum, and plate-like TiO2.

[0016] Furthermore, to achieve the above-mentioned objective, another embodiment of the panel according to the present invention is a panel coated with a near-infrared reflective functional coating. Its structural feature is that the coating comprises an adhesive and a near-infrared reflective functional pigment, wherein the pigment comprises: a sheet-like substrate; a first metal oxide layer coated on at least a portion of the substrate and having a refractive index of 1.8 or higher; and a second metal oxide layer coated on at least a portion of the first metal oxide layer and containing an absorbing material. Furthermore, the pigment reflects an average of 30% or more of the 850 nm to 950 nm IR electron beam, and the panel can be detected by Light Detection and Ranging (LiDAR).

[0017] The effects of the invention

[0018] The near-infrared reflective functional pigment of the present invention reflects an average of more than 30% of an IR electron beam of 850 nm to 950 nm, preferably more than 30% at 905 nm (the frequency of a LiDAR sensor), thereby achieving the effect of detection based on light detection and ranging (LiDAR).

[0019] In particular, even in dark conditions where the blackness (L*) is below 35, the pigment according to the present invention can reflect more than 30% of the IR electron beam from 850 nm to 950 nm on average, and reflect less than 15% of the visible electron beam from 400 nm to 700 nm on average, thereby achieving the effect of detection by light detection and ranging (LiDAR). Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view illustrating the structure of the pigment according to the present invention.

[0021] Figures 2 to 4 These are SEM images of pigments according to embodiments of the present invention.

[0022] Figure 5 This is a graph showing the reflective properties of a pigment according to an embodiment of the present invention. Specific Implementation

[0023] The advantages and features of the present invention, as well as the methods of implementing them, will become clear with reference to the following detailed embodiments and accompanying drawings.

[0024] However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. The following description is only intended to make the disclosure of the invention complete and to clearly and fully inform those skilled in the art of the scope of the invention, which is defined only by the scope of the claims.

[0025] The following will describe in detail the functional pigments, coatings, and panels according to embodiments of the present invention.

[0026] Near-infrared reflective functional pigments

[0027] Reference Figure 1 The near-infrared reflective functional pigment 100 of the present invention comprises: a sheet-like substrate 10; a first metal oxide layer 20 coated on at least a portion of the substrate 10 and having a refractive index of 1.8 or higher; and a second metal oxide layer 30 coated on at least a portion of the first metal oxide layer 20 and comprising an absorbing material. Furthermore, the near-infrared reflective functional pigment 100 reflects an average of 30% or more of IR electron beams from 850 nm to 950 nm.

[0028] In this invention, near-infrared radiation refers to IR electron beams with wavelengths between 850 nm and 950 nm. Furthermore, average reflectivity refers to the arithmetic mean of the reflectivity of IR electron beams within a certain range.

[0029] The present invention relates to a pigment 100, which reflects more than 30% of near-infrared light on average, and most preferably, has a reflectivity of more than 30% at 905 nm (the frequency of a LiDAR sensor).

[0030] The type of flake substrate 10 used in the pigment 100 of the present invention is not particularly limited, and one or more of the following plate-shaped materials may be used: synthetic mica, natural mica, glass flake, plate glass, plate iron oxide, plate alumina, plate silicon dioxide, plate aluminum, and plate TiO2.

[0031] Then, for the pigment 100 of the present invention, a first metal oxide layer 20 is coated on at least a portion of the upper part of the sheet substrate 10, and the first metal oxide layer 20 has a refractive index of 1.8 or higher.

[0032] Wherein, the first metal oxide layer 20 being coated on at least a portion of the upper part of the sheet substrate 10 means that the first metal oxide layer 20 can be coated on the entire upper part of the sheet substrate 10, or the first metal oxide layer 20 can be coated on only at least a portion of the upper part of the sheet substrate 10, or the first metal oxide layer 20 can be coated on the upper part of the sheet substrate 10 in the shape of islands.

[0033] The first metal oxide layer 20 functions as follows: compared with the sheet substrate 10, the first metal oxide layer 20 improves the light reflection efficiency of visible light and near-infrared light, and imparts stability to the pigment 100 in the preparation process.

[0034] For the metal oxide contained in the first metal oxide layer 20, any material with a high refractive index of 1.8 or higher can be used without restriction. However, preferably, the first metal oxide layer may contain one or more of Fe2O3, SnO2, and TiO2. More specifically, the first metal oxide layer 20 may contain one or more of Fe2O3, SnO2, and TiO2 individually, or may contain a mixture of two or more of them.

[0035] Then, for the pigment 100 of the present invention, a second metal oxide layer 30 is coated on the upper part of the first metal oxide layer 20, and the second metal oxide layer 30 contains an absorbent material.

[0036] Wherein, the second metal oxide layer 30 being coated on at least a portion of the upper part of the first metal oxide layer 20 means that the second metal oxide layer 30 can be coated on the entire upper part of the first metal oxide layer 20, or the second metal oxide layer 30 can be coated on only at least a portion of the upper part of the first metal oxide layer 20, or the second metal oxide layer 30 can be coated on the upper part of the first metal oxide layer 20 in the shape of an island.

[0037] The absorbent material refers to a material that absorbs visible light, and in this invention, it refers to a material that gives the pigment a dark color.

[0038] In this invention, dark color refers to a dark color with a blackness (L*) of 35 or less. Therefore, the pigment according to the invention has a dark color due to the inclusion of absorbent materials.

[0039] The absorbent material used in this invention is not limited to any material that gives the pigment the dark color described above, but preferably, the absorbent material may include one or more of Co3O4 and CuO.

[0040] According to an embodiment of the present invention, preferably, the first metal oxide layer contains Fe2O3, the second metal oxide layer contains Co3O4, and the ratio of the content of Fe in the first metal oxide layer to the content of Co in the second metal oxide layer can be in the range of 1:0.5 to 1:1.

[0041] When the content of Fe in the first metal oxide layer 20 is considered to be 1 in the content ratio of the components, and the content of Co in the second metal oxide layer 30 is less than 0.5, the pigment will appear red or dark red due to the decrease in the blackness (L*) of the pigment.

[0042] Conversely, when the Fe content in the first metal oxide layer 20 is considered to be 1 in the composition ratio, if the Co content in the second metal oxide layer 30 exceeds 1, there is a problem that the pigment does not exhibit LiDAR reflective properties due to the reduction in near-infrared reflective properties.

[0043] In other words, when the first metal oxide layer 20 contains Fe2O3 and the second metal oxide layer 30 contains Co3O4, considering the characteristics of Fe and Co, the ratio of the content of Fe in the first metal oxide layer 20 to the content of Co in the second metal oxide layer 30 preferably satisfies the range of 1:0.5 to 1:1.

[0044] According to another embodiment of the present invention, preferably, the first metal oxide layer 20 comprises TiO2 and SnO2, the second metal oxide layer 30 comprises CuO, and the ratio of the content of Ti and Sn in the first metal oxide layer 20 to the content of Cu in the second metal oxide layer 30 can be in the range of 1:4 to 1:6.

[0045] When the content of Ti and Sn contained in the first metal oxide layer 20 is considered to be 1 in the content ratio of the components, and the content of Cu contained in the second metal oxide layer 30 is less than 4, there is a problem that it is difficult to represent the dark color of the pigment due to the increase in blackness (L*).

[0046] Conversely, when the content of Ti and Sn contained in the first metal oxide layer 20 is considered to be 1 in the composition ratio, if the content of Cu contained in the second metal oxide layer 30 exceeds 6, there is a problem that the pigment does not exhibit LiDAR reflective properties due to the reduction of near-infrared reflective properties.

[0047] In summary, when the first metal oxide layer 20 contains TiO2 and SnO2, and the second metal oxide layer 30 contains CuO, considering the characteristics of Ti, Sn and Cu, the ratio of the content of Ti and Sn in the first metal oxide layer 20 to the content of Cu in the second metal oxide layer 30 preferably satisfies the range of 1:4 to 1:6.

[0048] Furthermore, preferably, the near-infrared reflective functional pigment 100 of the present invention can have a blackness (L*) of 35 or less and can reflect less than 15% of visible electron beams on average.

[0049] The average reflectance refers to the arithmetic mean of the reflectance of visible electron beams within a certain range.

[0050] As described above, the pigment of the present invention has a relatively low blackness (L*) while exhibiting the effect of highly reflecting near-infrared light.

[0051] As described above, the pigment 100 of the present invention is dark in color while reflecting an average of 30% or more of the IR electron beam from 850 nm to 950 nm. Preferably, the reflectivity at 905 nm (the frequency of the LiDAR sensor) is 30% or more, thereby enabling detection based on Light Detection and Ranging (LiDAR).

[0052] Near-infrared reflective functional coatings

[0053] Next, the near-infrared reflective functional coating according to the present invention, which uses the above-mentioned pigments, will be described.

[0054] The coating according to the present invention comprises: a binder; and a near-infrared reflective functional pigment. The pigment comprises: a flake-like substrate; a first metal oxide layer coated on at least a portion of the substrate and having a refractive index of 1.8 or higher; and a second metal oxide layer coated on at least a portion of the first metal oxide layer and containing an absorbing material. Furthermore, the pigment reflects an average of 30% or more of the 850 nm to 950 nm IR electron beam.

[0055] The adhesive may be a known coating adhesive, and examples include enamel coating adhesives, polyurethane coating adhesives, and enamel-polyurethane composite coating adhesives.

[0056] Furthermore, the near-infrared reflective functional pigment has the dark color described above, while reflecting an average of more than 30% of the IR electron beam from 850nm to 950nm. Preferably, the reflectivity at 905nm (the frequency of the LiDAR sensor) is more than 30%, thereby enabling detection based on LiDAR.

[0057] panel

[0058] Next, the panel according to the present invention, to which the above-described coating has been applied, will be described.

[0059] The panel according to the present invention is a panel coated with a near-infrared reflective functional coating, the coating comprising: an adhesive; and a near-infrared reflective functional pigment. The pigment comprises: a flake-like substrate; a first metal oxide layer coated on at least a portion of the substrate and having a refractive index of 1.8 or higher; and a second metal oxide layer coated on at least a portion of the first metal oxide layer and containing an absorbing material. The pigment reflects an average of 30% or more of the 850 nm to 950 nm IR electron beam, and the panel is capable of detection via Light Detection and Ranging (LiDAR).

[0060] As described above, the near-infrared reflective functional pigment, while being dark in color, reflects an average of over 30% of the IR electron beam from 850 nm to 950 nm, preferably with a reflectivity of over 30% at 905 nm (the frequency of a LiDAR sensor). Because a coating using this pigment is applied, even when the surface of the panel of this invention is coated with a dark color, the panel can still be detected by Light Detection and Ranging (LiDAR).

[0061] In particular, the panel of the present invention can be applied to the exterior of a vehicle. Therefore, the pigments, coatings, and panels of the present invention can be applied to autonomous driving systems.

[0062] Example

[0063] The structure and function of the present invention will now be described in more detail through preferred embodiments. However, this is merely presented as a preferred example of the present invention and should not be construed in any way as limiting the present invention to the following embodiments.

[0064] For any content not described in the following embodiments, since those skilled in the art can fully infer the corresponding content from a technical perspective, the description of such content has been omitted.

[0065] 1. Example 1

[0066] 100g of flake substrate (synthetic mica) is dispersed in water at approximately 9%, and the temperature is raised to between 70°C and 80°C. A diluted iron salt solution, along with a counter ion to maintain the pH at 2.5 to 3.5, is added dropwise to the heated dispersion substrate. At this point, the iron salt coating amount is approximately 33% to 43% based on iron oxide, and coating is carried out within this range until the desired color is achieved. Subsequently, a diluted cobalt salt solution, along with a counter ion, is added dropwise to maintain the pH at 8.0 to 9.5 (alkaline conditions). The amount of cobalt coated is adjusted to approximately 25% to 35% based on oxides, thereby obtaining a pigment of the desired color. To obtain the pigment from the reaction solution, the reaction solution is washed with water, dehydrated, and then heat-treated at 800°C.

[0067] For the pigment of Example 1 prepared according to the method described above, Fe2O3 is coated on the upper part of the sheet-like substrate (synthetic mica), and Co3O4 is coated on the upper part of the Fe2O3.

[0068] Furthermore, in the pigment according to Example 1, the content of Fe is 30.70% and the content of Co is 24.20% relative to the total amount of pigment.

[0069] 2. Example 2

[0070] 100g of sheet-like substrate (plate-like alumina) is dispersed in water at approximately 9%, and the temperature is raised to between 70°C and 80°C. A diluted solution of tin and titanium salts, along with counterions, is added dropwise to the heated dispersed substrate to maintain a pH between 1.0 and 2.0. At this point, the added tin oxide accounts for approximately 0% to 3% of the oxide, and the titanium dioxide accounts for approximately 5% to 10% of the oxide, thus allowing the pigment to exhibit the desired color. Subsequently, a diluted copper salt solution is added dropwise with counterions to maintain a pH between 7.0 and 9.0 (between neutral and alkaline conditions), thereby coating. The amount of copper oxide being coated is adjusted to approximately 20% to 40% based on copper oxide, and coating is performed to the degree that allows the pigment to exhibit the desired color. To obtain the pigment from the reaction solution, the reaction solution is washed with water, dehydrated, and then heat-treated at 800°C.

[0071] For the pigment of Example 1 prepared according to the method described above, a mixture of TiO2 and SnO2 is coated on the upper part of a sheet-like substrate (plate-like alumina), and CuO is coated on the upper part of the mixture layer.

[0072] Furthermore, in the pigment according to Example 2, the content of Ti is 5.46%, the content of Sn is 0.64%, and the content of Cu is 28.60% relative to the total amount of pigment.

[0073] 3. Example 3

[0074] 100g of flake substrate (synthetic mica) is dispersed in water at approximately 9%, and the temperature is raised to between 70°C and 80°C. A diluted solution of tin and titanium salts, along with counterions, is added dropwise to the heated dispersed substrate to maintain a pH between 2.5 and 3.5. At this point, the coating amount of iron salt, based on iron oxide, is approximately 25% to 35%, and coating is carried out within this range until the desired color is achieved. Subsequently, a diluted solution of cobalt salt, along with counterions, is added dropwise to maintain a pH between 8.0 and 9.5 (alkaline conditions). The amount of cobalt being coated is adjusted to approximately 15% to 25% based on oxides, and coating is carried out to achieve the desired color in the pigment. Further, to form copper oxide as an NIR reflective layer, a diluted solution of copper salt, along with counterions, is added dropwise to maintain a pH between neutral and alkaline conditions (7.0 to 9.0) and coated, so that the amount of copper oxide in the final pigment is approximately 20% to 30%. The reaction solution was washed with water and dehydrated, and then heat-treated at 800°C.

[0075] For the pigment of Example 3 prepared according to the method described above, Fe2O3 is coated on the upper part of the sheet-like substrate (synthetic mica), Co3O4 is coated on the upper part of the Fe2O3, and CuO is coated on the upper part of the Co3O4.

[0076] Physical property evaluation of the embodiments

[0077] 1. Observe the surface of the pigment.

[0078] The surface of the near-infrared reflective functional pigments prepared by the above method was observed using a scanning electron microscope. The surfaces of the pigments according to Examples 1 to 3 are illustrated in [illustration]. Figures 2 to 4 middle.

[0079] Reference Figure 2 The illustration shows a SEM image of the pigment according to Example 1.

[0080] In addition, refer to Figure 3 The illustration shows a SEM image of the pigment according to Example 2, and it can be confirmed that the CuO is coated in the shape of islands.

[0081] Furthermore, referring to Figure 4 The illustration shows a SEM image of the pigment according to Example 2.

[0082] Therefore, referring to Figures 2 to 4 This confirms that the metal oxide coating is applied to the upper part of the sheet-like substrate.

[0083] 2. Analyze reflectance, brightness, and chroma.

[0084] The reflectance, lightness, and chroma of the pigments according to the embodiments were analyzed.

[0085] The reflectance of different pigments at various wavelengths was measured as follows: the pigments were mixed with transparent acrylic resin at a concentration of 12%, and a coating was formed on an OHP film with a wet thickness of 150 μm. The coating was then dried thoroughly at room temperature, and the measurements were performed using a UV-Vis spectrometer with barium sulfate as the reference material.

[0086] Lightness and chroma were measured as follows: pigments were mixed with transparent acrylic resin at a concentration of 6%, and a coating was formed on opacity chart with a thickness of 100 μm. The coating was then allowed to dry fully at room temperature, and the measurements were taken using a colorimeter at 25°C.

[0087] The reflectance of the pigments at various wavelengths according to each embodiment is as follows: Figure 5 As shown. Furthermore, the resulting values ​​of 905nm reflectance, lightness, and chroma of the pigments according to each embodiment are recorded in Table 1 below.

[0088] [Table 1]

[0089]

[0090] Reference Figure 5 As shown in Table 1, the pigments of Examples 1 and 2 both exhibit an average reflectance of over 30% for near-infrared wavelengths from 850 nm to 950 nm.

[0091] In particular, at a wavelength of 905 nm, the reflectance of Example 1 is 35% and that of Example 2 is 43%, thus confirming that it can be used as a pigment detectable by LiDAR.

[0092] Furthermore, the pigments of Examples 1 and 2 have an average reflectance of less than 15% in the visible light wavelength region (400 nm to 700 nm).

[0093] Furthermore, referring to Table 1 and Figure 4 Based on the brightness measurement results, the L* values ​​of both Example 1 and Example 2 are below 35.

[0094] However, in Example 3, although both Co and Cu were used for coating, the near-infrared reflectance at a wavelength of 905 nm was less than 30%.

[0095] In summary, it can be confirmed that even if pigments are prepared using components that produce dark colors and reflect near-infrared light, they may not necessarily exhibit a reflectivity of more than 30% for near-infrared light at 905nm.

[0096] It can be confirmed that in order to present a dark color and reflect a certain proportion of near-infrared light at 905nm, the number of coatings applied to the sheet substrate, the selection of components, and the ratio of components constituting each coating all play very important roles.

[0097] Therefore, the pigment according to the present invention is dark in color and has a reflectivity of more than 30% for near-infrared light, and can therefore be used as a pigment that can be detected by LiDAR.

[0098] Although embodiments of the invention have been described with reference to the accompanying drawings, the invention is not limited to these embodiments, but can be modified in various different forms. Those skilled in the art will understand that it can be implemented in other specific forms without altering the technical concept or essential features of the invention. Therefore, the above embodiments should be understood as exemplary in all respects, and not restrictive.

Claims

1. A near-infrared reflective functional pigment, wherein, include: Sheet substrate; A first metal oxide layer is coated on at least a portion of the substrate and has a refractive index of 1.8 or higher. as well as A second metal oxide layer, which is coated on at least a portion of the first metal oxide layer, and includes an absorbent material. Furthermore, the pigment reflects an average of over 30% of the IR electron beam from 850nm to 950nm. The first metal oxide layer is composed of Fe2O3. The second metal oxide layer is composed of Co3O4. Furthermore, the ratio of Fe content in the first metal oxide layer to Co content in the second metal oxide layer is in the range of 1:0.5 to 1:

1. The pigment has a blackness of 35 or less.

2. The near-infrared reflective functional pigment according to claim 1, wherein, The pigment reflects less than 15% of visible electron beams on average.

3. The near-infrared reflective functional pigment according to claim 1, wherein, The sheet-like substrate is one or more of the following sheet-like materials: synthetic mica, natural mica, glass flakes, plate-like glass, plate-like iron oxide, plate-like aluminum oxide, plate-like silicon dioxide, plate-like aluminum, and plate-like TiO2.

4. A near-infrared reflective functional coating, wherein, include: Adhesives; as well as The near-infrared reflective functional pigment as described in claim 1.

5. The near-infrared reflective functional coating according to claim 4, wherein, The pigment has a blackness of 35 or less. Furthermore, the pigment reflects less than 1% of visible electron beams in the 400nm to 700nm range on average.

6. The near-infrared reflective functional coating according to claim 4, wherein, The sheet-like substrate is one or more of the following sheet-like materials: synthetic mica, natural mica, glass flakes, plate-like glass, plate-like iron oxide, plate-like aluminum oxide, plate-like silicon dioxide, plate-like aluminum, and plate-like TiO2.

7. A panel, said panel being coated with a near-infrared reflective functional coating, wherein, The coating comprises an adhesive and the near-infrared reflective functional pigment as described in claim 1.

8. The panel according to claim 7, wherein, The panel is applied to the exterior of the vehicle.

Images