Resin composition

Abstract

The resin composition has a matrix resin and a filler added to the matrix resin, and has electromagnetic wave permeability. The filler has a higher dielectric constant or conductivity than the matrix resin, and is non-uniformly present in the resin composition.

Description

Technical Field

[0001] The present invention relates to a resin composition. Background Art

[0002] Japanese Patent Application Laid-Open No. 2004-244516 describes a bright coating film applied to a coated product for covering an electromagnetic wave radar. The bright coating film is formed from a coating composition containing a bright material.

[0003] The coating composition is a coating material having a resin material as a main component.

[0004] According to such a bright coating film, a coated product having both bright properties and electromagnetic wave transmittance can be obtained.

[0005] However, if the content of the glitter material in the glitter coating is increased in order to improve the appearance, the electromagnetic wave transmittance may be reduced. In addition, this problem is not limited to the glitter coating, and may also occur in any resin composition in which a filler having a higher dielectric constant than that of the matrix resin or a conductive filler is added to the matrix resin serving as the main component of the coating composition. Summary of the invention

[0006] A resin composition according to one embodiment of the present invention is a resin composition having a matrix resin and a filler added to the matrix resin and having electromagnetic wave permeability, wherein the filler has a higher dielectric constant or conductivity than the matrix resin and is unevenly present in the resin composition. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a cross-sectional view showing a vehicle exterior part.

[0008] Figure 2 This is an enlarged representation of one embodiment of the resin composition. Figure 1 Cross-sectional view of a bright coating film on a vehicle exterior part.

[0009] Figure 3A to Figure 3C This is a diagram schematically showing the state of the portion other than the filler in the bright coating film.

[0010] Figure 4 This is a graph showing the frequency distribution of the distance between fillers in a bright coating film.

[0011] Figure 5 This is a diagram for explaining the method of analyzing the distribution of the distance between fillers. DETAILED DESCRIPTION

[0012] Below, refer to Figure 1 to Figure 5One embodiment of the resin composition will be described. In this embodiment, the present invention is embodied as a resin composition applied to a vehicle exterior part.

[0013] like Figure 1 As shown, a radar device 90 for transmitting and receiving electromagnetic waves is mounted on the front of the vehicle. The radar device 90 transmits electromagnetic waves having a wavelength of 1 mm to 10 mm and a frequency of 30 GHz to 300 GHz, namely, so-called millimeter waves 91. In addition, the front and rear of the transmission direction of the millimeter waves 91 from the radar device 90 will be described as simply the front and rear.

[0014] <Basic Structure of Cover 10>

[0015] A cover 10 as a vehicle exterior part covering the radar device 90 from the front is provided at the front of the vehicle. The cover 10 has millimeter wave transmittance. The cover 10 includes a base material 11, a primer layer 12, a clear coating film 13, and a clear coating layer 14.

[0016] The substrate 11 is formed of a synthetic resin material and has millimeter wave permeability. As the resin material, for example, thermoplastic resins such as polypropylene (PP), vinyl chloride (PVC), polymethyl methacrylate resin (PMMA), acrylonitrile-butadiene-styrene copolymer (ABS) resin, acrylonitrile-ethylene propylene diene monomer-styrene (AES) resin, acrylonitrile-styrene-acrylate copolymer (ASA) resin, and polycarbonate (PC) can be used. In the present embodiment, the substrate 11 is formed of PP.

[0017] The primer layer 12 can improve the adhesion of the bright coating film 13 to the substrate 11, and is provided on the front surface 11a of the substrate 11. The primer layer 12 is formed of a known resin coating material for primers.

[0018] The bright coating film 13 is arranged in front of the front surface 12a of the primer layer 12. In addition, the bright coating film 13 in this embodiment corresponds to the resin composition according to the present invention.

[0019] The clear coating layer 14 provides durability to the cover 10, for example, and is provided on the front surface 13a of the clear coating film 13. The clear coating layer 14 is formed of a known resin paint for a clear coating layer.

[0020] <Bright coating 13>

[0021] Next, the structure of the bright coating film 13 will be described in detail.

[0022] like Figure 2 As shown, the bright coating film 13 includes a matrix resin 21 and a filler 22 added to the matrix resin 21 .

[0023] The bright coating film 13 is formed by applying a coating material including a matrix resin 21 and a filler 22 to the front surface 12a of the primer layer 12. As the coating method, a known coating method such as spraying, dipping, shower coating, flow coating, and roll coating can be used.

[0024] The thickness of the bright coating film 13 is greater than or equal to 1 μm and less than or equal to 10 mm, more preferably greater than or equal to 3 μm and less than or equal to 150 μm, and further preferably greater than or equal to 5 μm and less than or equal to 100 μm.

[0025] The bright coating 13 has millimeter wave transmittance. From the viewpoint of improving the millimeter wave transmittance, the round-trip millimeter wave transmission attenuation of the bright coating 13 is preferably set to 5.0 dB or less. More preferably, it is set to 3.0 dB or less.

[0026] The lightness L* value (hereinafter referred to as L value) of the front surface 13a of the bright coating film 13 in the L*a*b* color system (hereinafter referred to as the Lab color system) is greater than or equal to 40. From the viewpoint of improving the aesthetic appearance, it is more preferable to set the L value to be greater than or equal to 60. It is further preferable to set the L value to be greater than or equal to 80. In addition, the larger the L value, the more shiny the appearance of a metallic tone can be obtained.

[0027] <Matrix resin 21>

[0028] The matrix resin 21 is a resin material contained in a known resin coating such as acrylic resin, polyurethane resin, polyester resin, epoxy resin, melamine resin, alkyd resin, phenol resin, etc. In the present embodiment, the matrix resin 21 is a urethane resin.

[0029] <Padding 22>

[0030] The filler 22 may be a material having a higher dielectric constant or conductivity than the matrix resin 21. Examples of fillers having a higher dielectric constant than the matrix resin 21 include bright materials such as mica, pearl mica, and glass flakes. Examples of conductive fillers include conductive fillers made of metals such as aluminum flakes, conductive fillers of metal oxides such as zinc oxide, and conductive fillers of metal coatings in which the surface of mica or glass flakes is coated with metals such as aluminum and nickel.

[0031] In this embodiment, the filler 22 is an aluminum sheet.

[0032] The average particle size of the aluminum flakes is greater than or equal to 3 μm and less than or equal to 30 μm. More preferably, the average particle size of the aluminum flakes is greater than or equal to 4 μm and less than or equal to 25 μm.

[0033] The content of aluminum flakes in the bright coating film 13 is 2.0% or more and 20.0% or less. From the viewpoint of improving the appearance, the content is more preferably 2.5% or more and 18% or less.

[0034] The area occupancy of the aluminum flakes in the bright coating film 13 is greater than or equal to 30% and less than or equal to 100%. From the viewpoint of improving the appearance, it is more preferably greater than or equal to 50% and less than or equal to 100%. It is further preferably greater than or equal to 70% and less than or equal to 100%.

[0035] The bright coating film 13 is configured so that the distribution of the distance between the adjacent fillers 22, that is, the distance between the fillers, has a peak.

[0036] The distance between fillers at the peak is greater than or equal to 3.0 μm and less than or equal to 6.0 μm.

[0037] like Figure 2 to Figure 3C As shown in FIG. 1 , the fillers 22 are unevenly present in the bright coating film 13. Specifically, a region (hereinafter referred to as a separation region A) in which the fillers 22 in the bright coating film 13 are adjacent to each other at a filler inter-distance D1 greater than the filler inter-distance at the peak is located in the thickness direction ( Figure 2 ), and the surface direction along the virtual plane P orthogonal to the thickness direction (refer to Figure 3A to Figure 3C ) are dispersed in the bright coating film 13 over the entire range. That is, in the bright coating film 13, the separation region A and the region where the fillers 22 are adjacent to each other at a filler distance D2 that is less than or equal to the filler distance at the peak (hereinafter referred to as the proximity region B) exist alternately in both the thickness direction and the surface direction of the bright coating film 13. In the present embodiment, the thickness direction coincides with the transmission direction of the millimeter wave 91.

[0038] <Example>

[0039] Next, the above-mentioned embodiment will be described in more detail with reference to examples.

[0040] [Adjustment of sample]

[0041] The paints for forming the bright coating films of Examples 1 to 3 were prepared as follows. In the preparation, the acrylic urethane resin paint was diluted with a diluent and used. Aluminum flakes were used as fillers.

[0042] The acrylic polyurethane resin coating material and aluminum flakes having a particle size of 5 to 25 μm were mixed and stirred sufficiently to obtain a coating material for forming a bright coating film of Example 1.

[0043] The acrylic polyurethane resin coating material and aluminum flakes having a particle size of 3 to 25 μm were mixed and stirred sufficiently to obtain a coating material for forming a bright coating film of Example 2.

[0044] The acrylic polyurethane resin coating material and aluminum flakes having a particle size of 5 to 25 μm were mixed and stirred sufficiently to obtain a coating material for forming a bright coating film of Example 3.

[0045] The coating material of each example was spray-coated on a plate (2.3 mm thick) made of the same material (PP) as the base material 11 of the cover 10 to form a coating film of a predetermined thickness (1 μm or more and 10 mm or less), thereby obtaining a sample.

[0046] [Measurement of sample]

[0047] The thickness of the bright coating film (film thickness), the content of aluminum flakes, the area occupancy of aluminum flakes, the dielectric constant, the round-trip millimeter wave transmission attenuation, and the L value of each sample of Examples 1 to 3 were measured. In addition, the distribution of the distance between fillers was analyzed. Figure 3A to Figure 4 The results are shown in .

[0048] The content of aluminum flakes was measured in the following manner.

[0049] Each sample was photographed using a 3D X-ray microscope, and based on the obtained 3D images, the volume of aluminum flakes present in a range of 10 μm or less from the surface of the bright coating in the thickness direction of the bright coating was measured. The ratio of the volume of the aluminum flakes in the above range to the volume of the bright coating was calculated as the content of the aluminum flakes.

[0050] The area occupancy of the aluminum sheet was measured in the following manner.

[0051] Each sample was photographed using an optical microscope, and the area of ​​the aluminum flakes within a specified range was analyzed using image analysis software based on the obtained microscope photographs. The ratio of the area of ​​the aluminum flakes within the above range to the area of ​​the bright coating film was calculated as the area occupancy of the aluminum flakes.

[0052] The round-trip millimeter wave transmission attenuation is measured in the following manner.

[0053] Using an electromagnetic wave absorption measuring device, after a millimeter wave with a frequency of 76.5 GHz is incident on each sample at an incident angle of 0°, the millimeter wave transmitted from each sample is incident on each sample again at an incident angle of 0°, and the millimeter wave transmitted from each sample is received, and the millimeter wave transmission attenuation of each sample is measured. The round-trip millimeter wave transmission attenuation of the plate is subtracted from the obtained transmission attenuation to calculate the round-trip millimeter wave transmission attenuation of only the bright coating. In addition, if the round-trip millimeter wave transmission attenuation is less than or equal to 5.0 dB, it can be evaluated that the millimeter wave is fully transmitted.

[0054] The L value is measured in the following manner.

[0055] The bright coating film was irradiated with light at an angle of 25° using a multi-angle spectrophotometer, and the spectral reflectance at a light receiving angle of 25° was measured with respect to the regular reflected light. Next, the L value of the Lab colorimetric system calculated from the spectral reflectance was calculated. If the L value is greater than or equal to 40, the appearance of the bright coating film can be evaluated as showing sufficient brightness.

[0056] Using a three-dimensional image obtained by a three-dimensional X-ray microscope, the distribution of the distance between fillers was analyzed in the following manner.

[0057] like Figure 5 As shown, by filling the bright coating with a substance having a maximum diameter D that can exist in a virtual sphere C between adjacent aluminum flakes 22a, the state of the portion other than the aluminum flakes 22a in the bright coating of each sample is evaluated. The maximum diameter D is regarded as the "distance between fillers (aluminum flakes)", and the separation area A, the proximity area B, and the middle area N are set in the following manner. The separation area A is an area where aluminum flakes are adjacent to each other with a distance between fillers greater than 6.0μm. The proximity area B is an area where aluminum flakes are adjacent to each other with a distance between fillers less than or equal to 3.0μm. The middle area N is an area where aluminum flakes are adjacent to each other with a distance between fillers greater than 3.0μm and less than or equal to 6.0μm. In Figure 3A to Figure 3C In FIG. 1 , each region is schematically shown by lightness and darkness. Figure 3A Example 1 is schematically shown in Figure 3B Example 2 is schematically shown in Figure 3C In addition, a frequency distribution graph of the distance between fillers in the bright coating film is plotted based on the maximum diameter D of each of the plurality of virtual spheres C that have been filled (see Figure 4 ).

[0058] [result]

[0059] [Table 1]

[0060]

[0061] As shown in Table 1, for Examples 1 to 3, the film thickness was greater than or equal to 1 μm and less than or equal to 10 mm, the content of aluminum flakes was greater than or equal to 2.0% and less than or equal to 20.0%, and the area occupancy of aluminum flakes was greater than or equal to 30%. In addition, the L value at this time was greater than or equal to 40. It can be confirmed that in Examples 1 to 3, a bright coating film showing sufficient brightness was realized. In addition, in each Example, the content of aluminum flakes showed different values, and it can be confirmed that the difference in the content of aluminum flakes was to a degree that did not affect the brightness (L value).

[0062] As shown in Table 1, the round-trip millimeter wave transmission attenuation is less than or equal to 5.0 dB for each of Examples 1 to 3. This confirms that each of Examples 1 to 3 has sufficient millimeter wave transmittance.

[0063] On the other hand, the round-trip millimeter wave transmission attenuation of each embodiment is the largest in embodiment 1 and the smallest in embodiment 3. Generally, the larger the dielectric constant, the lower the millimeter wave transmittance, so the result is not inconsistent with the result of the dielectric constant. It can be confirmed that the millimeter wave transmittance of embodiment 2 is better than that of embodiment 1. In addition, it can be confirmed that the millimeter wave transmittance of embodiment 3 is better than that of embodiment 2.

[0064] From the above results, it can be confirmed that in Example 2, the content of aluminum flakes is maintained at a level that does not change with respect to Example 1, and the millimeter wave transmittance is improved. In addition, it can be confirmed that in Example 3, the content of aluminum flakes is maintained at a level that does not change with respect to Examples 1 and 2, and the millimeter wave transmittance is improved.

[0065] like Figure 3A to Figure 3C As shown, it can be confirmed that in Examples 1 to 3, the separation area A and the proximity area B are dispersed in the bright coating film over the entire range of both the thickness direction of the bright coating film and the surface direction along the virtual plane P orthogonal to the thickness direction. In other words, it can be confirmed that in Examples 1 to 3, the aluminum flakes are unevenly present in the bright coating film.

[0066] On the other hand, Figure 3A to Figure 4 As shown, when comparing Examples 1 to 3 with respect to the proportion of the separation region A in the entire bright coating film, the proportion of the separation region A is the largest in Example 3 and the smallest in Example 1. It can be confirmed that in Example 2, the aluminum flakes are more unevenly present in the bright coating film than in Example 1. In addition, it can be confirmed that in Example 3, the aluminum flakes are more unevenly present in the bright coating film than in Examples 1 and 2.

[0067] From the above results, it was confirmed that the aluminum flakes were unevenly present in the bright coating film, thereby maintaining the beautiful appearance and improving the millimeter wave transmittance.

[0068] Next, the effects of this embodiment will be described.

[0069] (1) The filler 22 is unevenly present in the bright coating film 13 .

[0070] According to this structure, the filler 22 is unevenly present in the bright coating 13, so that a portion where the intervals between adjacent fillers 22 are larger is generated compared to the case where the filler 22 is uniformly dispersed in the bright coating 13. As a result, the millimeter wave 91 easily passes through the bright coating 13 through the above portion. As a result, the millimeter wave transmission attenuation in the bright coating 13 is reduced. On the other hand, by maintaining the content of the filler 22 in the bright coating 13, the appearance of the bright coating 13 is not easily changed. Therefore, the appearance of the bright coating 13 can be maintained and the millimeter wave transmittance can be improved.

[0071] (2) The thickness of the bright coating film 13 is greater than or equal to 1 μm and less than or equal to 10 mm. The round-trip millimeter wave transmission attenuation of the bright coating film 13 is less than or equal to 5.0 dB.

[0072] According to this structure, by making the thickness of the bright coating 13 greater than or equal to 1 μm and less than or equal to 10 mm, the millimeter wave transmittance can be improved while maintaining the aesthetic appearance of the bright coating 13. As a result, the round-trip millimeter wave transmission attenuation of the bright coating 13 can be set to less than or equal to 5.0 dB. Therefore, the beautiful appearance of the bright coating 13 can be maintained while improving the millimeter wave transmittance.

[0073] (3) The bright coating film 13 is configured such that the distribution of the distance between adjacent fillers 22, i.e., the distance between fillers, has a peak. The separation regions A are dispersed throughout the bright coating film 13 in both the thickness direction of the bright coating film 13 and the surface direction along the virtual plane P orthogonal to the thickness direction.

[0074] According to such a structure, the separation regions A where the fillers 22 exist separately from each other are three-dimensionally dispersed in the bright coating film 13. Therefore, the millimeter wave 91 easily passes through the bright coating film 13 through the separation regions A. Therefore, the millimeter wave transmittance can be further improved.

[0075] (4) The proximity regions B are dispersed in the bright coating film 13 over the entire range of both the thickness direction of the bright coating film 13 and the surface direction along the virtual plane P perpendicular to the thickness direction.

[0076] According to this structure, the close region B and the separated region A are dispersed in the bright coating film 13 in a three-dimensional manner. That is, in the bright coating film 13, the close region B and the separated region A exist alternately in both the thickness direction and the surface direction of the bright coating film 13. Therefore, when the bright coating film 13 is observed from the front, the close region B where the fillers 22 exist close to each other exists in a wide range of the bright coating film 13, so that the appearance of the bright coating film 13 can be improved. In addition, the separated region A where the fillers 22 exist separately from each other exists between the close regions B in both the thickness direction and the surface direction, so that the millimeter wave 91 easily passes through the separated region A and passes through the bright coating film 13. Therefore, the appearance of the bright coating film 13 can be maintained, and the millimeter wave transmittance can be further improved.

[0077] (5) The filler 22 is a conductive metal filler.

[0078] According to such a configuration, the bright coating film 13 having high brilliance can be realized. Therefore, the bright coating film 13 having high millimeter wave transmittance while maintaining excellent appearance can be realized.

[0079] (6) The filler 22 is aluminum flakes 22a. The average particle size of the aluminum flakes 22a is greater than or equal to 3 μm and less than or equal to 30 μm. The content of the aluminum flakes 22a in the bright coating film 13 is greater than or equal to 2.0% and less than or equal to 20.0%. The area occupancy rate of the aluminum flakes 22a in the bright coating film 13 is greater than or equal to 30% and less than or equal to 100%.

[0080] According to this structure, the aluminum flakes 22a are selected as the filler 22, so that the bright coating 13 with high brightness can be easily realized. On the other hand, the aluminum flakes 22a have the property of not allowing electromagnetic waves such as the millimeter wave 91 to pass through. In this regard, according to the above structure, the effect of maintaining the appearance of the bright coating 13 and improving the millimeter wave transmittance can be more appropriately exerted. Therefore, the bright coating 13 with excellent appearance and improved millimeter wave transmittance can be easily realized.

[0081] (7) The L value of the Lab colorimetric system of the front surface 13a of the bright coating film 13 is 40 or more.

[0082] According to such a configuration, the bright coating film 13 having high brilliance can be reliably realized. Therefore, the bright coating film 13 having improved millimeter wave transmittance while maintaining excellent appearance can be reliably realized.

[0083] <Change Example>

[0084] This embodiment can be implemented in the following modified forms. This embodiment and the following modified examples can be implemented in combination with each other within the scope of no technical contradiction.

[0085] The resin composition of the present invention is not limited to the bright coating film 13 having excellent glossiness and aesthetic appearance. For example, the resin composition can be realized as a color coating film having excellent aesthetic appearance by replacing the filler 22 with a known coloring pigment such as titanium oxide. In this case, the dielectric constant of the filler only needs to be higher than that of the matrix resin 21.

[0086] The resin composition of the present invention is not limited to the bright coating film 13 formed by coating the front surface 12a of the primer layer 12 as shown in the present embodiment. The resin composition may be a film-like structure formed by printing a coating containing the filler 22 on a film substrate made of a transparent resin material.

[0087] According to such a structure, the clear coating film 13 can be directly attached to the base material 11 in the cover 10. Therefore, the primer layer 12 and the clear coating layer 14 can be omitted.

[0088] The resin composition according to the present invention may be, for example, a resin molded product obtained by injection molding a resin material in which the filler 22 is dispersed in a resin matrix.

[0089] The cover 10 only needs to be arranged in front of the radar device 90, and the position of the cover 10 mounted on the vehicle as a vehicle exterior accessory can be appropriately selected. For example, when the radar device 90 transmits the millimeter wave 91 toward the rear of the vehicle, the cover 10 can be arranged in front of the radar device 90 in the transmission direction of the millimeter wave 91 and at a position behind the vehicle relative to the radar device 90. The same is true when the radar device 90 is mounted obliquely in front of or obliquely behind the vehicle.

Claims

1. A resin composition comprising a matrix resin and a filler added to the matrix resin, and having electromagnetic wave permeability, wherein: The filler has a higher dielectric constant or electrical conductivity than the matrix resin, and is unevenly present in the resin composition.

2. The resin composition according to claim 1, wherein The resin composition has millimeter wave transmittance, The thickness of the resin composition is greater than or equal to 1 μm and less than or equal to 10 mm, The resin composition has a round-trip millimeter wave transmission attenuation of less than or equal to 5.0 dB.

3. The resin composition according to claim 2, wherein The resin composition is configured so that the distance between the adjacent fillers, that is, the distribution of the distance between fillers has a peak value, When a region in which the fillers in the resin composition are adjacent to each other at a filler inter-distance greater than the filler inter-distance at the peak is set as a separation region, The separation regions are dispersed in the resin composition over the entire range of both the thickness direction of the resin composition and the surface direction along a virtual plane perpendicular to the thickness direction.

4. The resin composition according to claim 3, wherein When a region in which the fillers in the resin composition are adjacent to each other at an inter-filler distance that is less than or equal to the inter-filler distance at the peak is defined as a proximity region, The proximity regions are dispersed in the resin composition over the entire range of both the thickness direction and the surface direction along the virtual plane orthogonal to the thickness direction.

5. The resin composition according to any one of claims 1 to 4, wherein The filler is a conductive metal filler.

6. The resin composition according to claim 5, wherein The filler is aluminum flakes, The average particle size of the aluminum flakes is greater than or equal to 3 μm and less than or equal to 30 μm, The content of the aluminum flakes in the resin composition is greater than or equal to 2.0% and less than or equal to 20.0%, The area occupancy rate of the aluminum sheet in the resin composition is greater than or equal to 30% and less than or equal to 100%.

7. The resin composition according to claim 6, wherein The surface of the resin composition has an L* value of 40 or more in an L*a*b* colorimetric system.

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