JP2016107610A - Decorative coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decorative coating film which, when fine particles of silver or a silver alloy are used in a decorative coating film formed on a surface of a resin substrate located in a radar device path, can successively improving glossiness of the decorative coating film.SOLUTION: A decorative coating film is formed on a surface of a resin substrate located in a radar device path. The decorative coating film at least comprises fine particles of silver or a silver alloy dispersed in the decorative coating film, and a binding resin having optical transparency and binding the fine particles of silver or a silver alloy to each other. In a color system (L,a,b) specified in the CIE1976 color system, the chromaticness index aand chromaticness index bof the decorative coating film satisfy a relation of 6.7≤((a)+(b))≤23.4.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a decorative coating formed on the surface of a resin substrate, and particularly relates to a decorative coating excellent in gloss.

  2. Description of the Related Art Conventionally, a vehicle such as an automobile is equipped with a radar device such as a millimeter wave radar at the center position in front of the vehicle so as to measure an obstacle ahead of the vehicle or a distance from the vehicle. Radio waves such as millimeter waves emitted from the radar device are radiated forward via the front grill and the vehicle manufacturer's emblem and reflected by an object such as a front vehicle or a front obstacle, and this reflected wave is reflected on the front grill or the like. It returns to a radar apparatus via.

  Therefore, materials and paints that have a low radio wave transmission loss and can give a desired aesthetic appearance are often used at locations arranged in the beam path of radar devices such as the front grille and emblem. It is common practice to form a decorative coating.

  On the other hand, silver coatings are conventionally used in various applications because they have high visible light reflectivity and excellent infrared shielding properties. In addition, the silver coating is also excellent in radio wave shielding. For example, electronic devices that malfunction due to radio waves are protected from external radio waves, or radio waves generated from electronic devices are suppressed. Therefore, it may be used as a radio wave shielding film.

  For example, Patent Document 1 discloses a silver alloy film for radio wave shielding containing 0.01 to 10 at% of bismuth (Bi) and / or antimony (Sb). This silver alloy film for radio wave shielding has a transparent dielectric film formed on it, and defects such as pinholes and scratches are formed on this film, which is directly exposed to the silver alloy film. However, it is said that silver aggregation hardly occurs.

JP 2004-263290 A

  However, for example, when silver is used on the surface of a resin base material such as an emblem located in the radar apparatus path in order to improve design, if the resin base material is covered with a silver coating as in Patent Document 1, for example. Therefore, it is difficult for radio waves such as millimeter waves from the radar device to pass through.

  From this, it is conceivable that the surface of the base material is coated as a decorative film together with fine particles of silver or silver alloy and a binding resin for binding the fine particles. However, when such a decorative coating is used over time, the decorative coating is exposed to light (receives light energy), but the glossiness of the decorative coating is hardly changed.

  The present invention has been made in view of the above points, and the object of the present invention is to form silver or silver alloy fine particles on a decorative film formed on the surface of a resin substrate located in a radar apparatus path. In the case where is used, the object is to provide a decorative coating that can improve the gloss of the decorative coating over time.

  As a result of intensive studies, the inventor obtained knowledge that the gloss of the decorative coating is improved due to surface plasmon resonance absorption on the surface of silver or silver alloy fine particles and the binding resin that binds these. . That is, as shown in FIG. 7A, when the decorative coating is irradiated with light, not only the silver or silver alloy fine particles (metal fine particles) but also the binding resin that binds them vibrates due to the light energy. As a result, it was considered that free electrons inside the fine particles of silver and silver alloy move, and the fine particles of silver or silver alloy are easily polarized.

  In this way, as shown in FIG. 7B, surface electromagnetic waves called surface plasmon polariton are generated on the surface of the silver or silver alloy fine particles or the binding resin, and light of a specific wavelength is absorbed. In particular, the energy of fine particles of silver or silver alloy is easily amplified (surface plasmon resonance absorption).

  As a result, in the case of fine particles of silver or silver alloy, the constituent material around the fine particles is easily subjected to amplification energy, and new knowledge has been obtained that the gloss of the decorative coating is improved by this energy. The reason for this is that the constituent materials around the fine particles are altered, and the fine particles are more dense. Therefore, in order to improve the gloss of the decorative coating, it is important to select a combination of silver or a silver alloy fine particle and a binding resin, which are likely to cause surface plasmon resonance absorption. We thought that the color of the decorative film was caused by resonance absorption.

The present invention has been made in view of the above points, and a decorative coating according to the present invention is a decorative coating formed on the surface of a resin substrate located in a radar apparatus path, and the decorative coating is provided. Comprises at least a fine particle of silver or a silver alloy dispersed in the decorative coating and a light-transmitting binding resin that binds the fine particle of the silver or silver alloy, and is defined in the CIE 1976 color system. In the color system (L ^* , a ^* , b ^* ), the chromaticness index a ^* and the chromaticness index b ^{* of the} decorative coating are 6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) It is characterized by satisfying the relationship of ^1/2 ≦ 23.4.

  The decorative coating has a structure including at least silver or silver alloy fine particles dispersed in the decorative coating and a light-transmitting binding resin that binds the fine particles, and thus has a metallic luster in appearance. It becomes a film having radio wave permeability (electrical insulating property).

Here, in the color system (L ^* , a ^* , b ^* ) defined in the CIE 1976 color system, the closer the chromaticness index a ^* , b ^* is to 0, the closer to achromatic color. On the other hand, according to chromaticness indices a ^* value increases from 0, the color of the enamel coating approaches red, according to chromaticness indices a ^* value becomes smaller from 0, the color of the enamel coating approaches green. Further, according to chromaticness index b ^* value increases from 0, the color of the enamel coating approaches yellow, according chromaticness index b ^* value becomes smaller from 0, the color of the enamel coating approaches blue.

In this embodiment, the chromaticness index a ^* and the chromaticness index b ^{* of the} decorative coating satisfy the relationship of 6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23.4. Therefore, the decorative coating exhibits a color (chromatic color) that is easy to absorb surface plasmon resonance characteristic of silver or silver alloy fine particles, and as a result, the metallic gloss of the decorative coating increases in an environment where light is irradiated. The degree increases over time.

On the other hand, when the chromaticness index a ^* and the chromaticness index b ^{* of} the decorative film satisfy the relationship of ((a ^* ) ² + (b ^* ) ² ) ^1/2 <6.7, ((a ^* ) ² + (B ^* ) ² ) The value of ^1/2 is small, and the decorative film approaches an achromatic color. Thereby, surface plasmon resonance absorption peculiar to fine particles made of silver or a silver alloy is suppressed (light energy is hardly absorbed), so that the glossiness of the decorative coating hardly changes. As will be apparent from the examples described later, at present, the chromaticness index a ^* and the chromaticness index b ^* of the decorative coating are ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23.4. It is possible to produce a decorative coating that satisfies the above relationship.

  In a more preferred embodiment, the average particle diameter of the silver or silver alloy fine particles is 2 to 200 nm. It has been found that when the average particle diameter of the silver or silver alloy fine particles is larger than 200 nm, the silver or silver alloy fine particles are likely to aggregate, and as a result, the silver gloss is likely to be lowered. From this, 200 nm or less is prescribed | regulated as a desirable range of the average particle diameter of silver or a silver alloy. Moreover, when the average particle diameter of the silver or silver alloy fine particles is less than 2 nm, the light incident on the decorative coating is difficult to be reflected. In addition, since the silver or silver alloy fine particles are nano-sized, in this embodiment, light is easily absorbed by a phenomenon called localized surface plasmon resonance absorption.

  Furthermore, as a preferred embodiment, the crystallite diameter of silver or a silver alloy constituting the fine particles is in the range of 2 nm to 98 nm. Here, when the crystallite diameter is less than 2 nm, the light incident on the decorative coating is difficult to be reflected. On the other hand, when the crystallite diameter exceeds 98 nm, it is difficult for radio waves (electromagnetic waves) to pass through the decorative coating.

  According to the present invention, when silver or silver alloy fine particles are used for the decorative coating formed on the surface of the resin substrate located in the radar apparatus path, the gloss of the decorative coating is continuously improved. Can do.

It is the schematic diagram explaining the decorative film which concerns on embodiment of this invention. It is a schematic diagram for demonstrating the structure of the decorative film shown in FIG. 1 is a schematic diagram of the entire vehicle showing a relationship between a front grille (resin base material) in front of the vehicle, an emblem on the surface thereof, and a radar device disposed inside the vehicle behind the resin base material. It is sectional drawing which showed the relationship between the front grille (resin base material) of the vehicle front, the emblem of the surface, and the radar apparatus distribute | arranged inside the vehicle of the resin base back. ^{((A *) 2 + (} b *) 2) is a graph showing a relationship between a ^half and gloss increasing degree. It is the figure which showed the relationship between the wavelength of the light which injects into the decorative coating which concerns on Example 2 and Comparative Example 1, and the reflectance of a decorative coating. (A) is a figure for demonstrating the state until the fine particles of a silver alloy are polarized by light, (b) is a figure for demonstrating surface plasmon resonance absorption.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram illustrating an embodiment of a decorative coating 1 of the present invention. FIG. 2 is a schematic diagram for explaining the configuration of the decorative coating 1 shown in FIG. FIG. 3 is a schematic diagram of the entire vehicle showing the relationship between the front grille F (resin base material 20) in front of the vehicle, the emblem 10 on the surface thereof, and the radar device D disposed inside the vehicle behind the front grille F. FIG. 4 is a cross-sectional view showing the relationship between the front grill F (resin base material 20) in front of the vehicle, the emblem 10 on the surface thereof, and the radar device D disposed in the vehicle behind the front grill F.

  A decorative coating 1 shown in FIG. 1 constitutes a part of an emblem 10 attached to the surface of a resin base material 20 that is a front grille F. As shown in FIG. 3, the radar device D installed in front of the vehicle body A is disposed behind the front grille F.

  As shown in FIG. 4, the millimeter wave L1 emitted from the radar device D is radiated forward through the front grill F and the emblem 10 on the surface thereof. The emitted millimeter wave L1 is reflected by an object such as a forward vehicle or a front obstacle. The reflected millimeter wave L2 returns to the radar device D through the emblem 10 and the front grill F. Therefore, the emblem 10 including the decorative coating 1 is formed on the surface of the resin base material 20 located in the radar apparatus path.

  The decorative coating 1 is applied to the surface of the resin base material 20 (front grille F) located in the radar apparatus path, so that it has a metallic luster and has a radio wave transmission (electrical insulation). It is a film which has.

  Specifically, as shown in FIG. 1, a colorless transparent resin coating layer 2 is laminated in the viewing direction (X direction) on the decorative coating 1 to form an emblem 10. Note that an adhesive seal or the like may be attached to the decorative coating 1 and the adhesive seal may be bonded to the resin substrate 20.

  As shown in FIG. 2, the decorative coating 1 includes at least a silver or silver alloy fine particle 1a dispersed in the decorative coating and a light-transmitting binding resin 1b that binds the silver or silver alloy fine particle 1a. I have. It is preferable that a dispersant (protective agent) 1c is further added to the decorative coating 1 in order to improve the dispersibility of the silver or silver alloy fine particles 1a.

  Thus, since the silver or silver alloy fine particles 1a are discontinuously dispersed within the layer in the decorative coating 1, the distance between the particles is extremely short because of the silver or silver alloy fine particles 1a. Are densely assembled. Thus, while providing a metallic luster for human vision, when the radio wave passes through each nanoparticle, the millimeter wave attenuation of the radio wave is extremely small, resulting in a metallic luster in appearance. However, it can be a film having electrical insulation.

  The “millimeter wave” referred to in the present specification refers to a radio wave having a frequency band of about 30 GHz to 300 GHz among radio waves. For example, about 76 GHz of the frequency band can be specified. Further, the “decorative coating” as used in the present specification is a component constituting the emblem of the vehicle manufacturing company described above or a decorative product peculiar to the vehicle, and is composed of this decorative coating or a part of the decorative coating. The emblem and the like included in the above are formed on the surface of the front grill which is a resin base material.

In the decorative coating 1 according to the present embodiment, the chromaticness index a ^* and the chromaticness index b ^* of the decorative coating 1 in the color system (L ^* , a ^* , b ^* ) defined in the CIE 1976 color system are The relationship of 6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23.4 is satisfied.

As a result, the decorative coating 1 exhibits a color (chromatic color) that is likely to cause surface plasmon resonance absorption peculiar to the silver or silver alloy fine particles 1a, and as a result, the metal of the decorative coating 1 is irradiated by the light irradiated continuously. The degree of increase in gloss increases.
The above-mentioned ((a ^* ) ² + (b ^* ) ² ) ^1/2 becomes larger as the particle diameter of the silver or silver alloy fine particles 1a is smaller, and the particle density (that is, the content) of the silver alloy fine particles 1a. ) Is larger, the larger the value. Furthermore, in the case of the silver alloy fine particles 1a, since silver contributes to surface plasmon resonance absorption, the larger the silver content in the fine particles 1a, the more ((a ^* ) ² + (b ^* ) ² ) ^1/2. Is a large value. Therefore, in order to obtain the decorative coating 1 of 6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23.4, these values may be adjusted.

Here, when the chromaticness index a ^* and the chromaticness index b ^* of the decorative film satisfy the relationship of ((a ^* ) ² + (b ^* ) ² ) ^1/2 <6.7, ((a ^* ) ^{The value of 2} + (b ^* ) ² ) ^1/2 is small, and the decorative film approaches an achromatic color. As a result, surface plasmon resonance absorption peculiar to fine particles made of silver or a silver alloy is suppressed (light energy is hardly absorbed), so that the glossiness of the decorative coating hardly changes regardless of the irradiation time of light energy. On the other hand, it is difficult to produce a coating film in which the chromaticness index a ^* and the chromaticness index b ^{* of} the decorative coating satisfy the relationship of ((a ^* ) ² + (b ^* ) ² ) ^1/2 > 23.4.

Here, the value of ((a ^* ) ² + (b ^* ) ² ) ^1/2 of the decorative coating 1 is, for example, (1) the content of fine particles made of silver or a silver alloy is dispersed in the decorative coating 1 (2) When silver alloy fine particles are used, adjust the metal to be alloyed and its amount, (3) Select the type of binder resin and heat treatment temperature to be described later Can be set experimentally.

When made of silver or a silver alloy, by increasing the amount of the dispersing agent, the adhesion between the fine particles made of silver or the silver alloy is suppressed, the dispersibility of the fine particles in the decorative coating 1 is increased, and the constituent materials around the fine particles are reduced. It becomes easy to receive amplified energy, and the glossiness of the decorative coating 1 can be enhanced by this energy. In the present embodiment, the amount of the dispersant is preferably 7.2% by mass or more with respect to the content of the fine particles, and by using such a composition, the above-described (shown in the present embodiment) The range of (a ^* ) ² + (b ^* ) ² ) is likely to be ^1/2 , and the glossiness of the decorative coating 1 can be improved. The change in glossiness of the decorative coating 1 is highly dependent on the value of ((a ^* ) ² + (b ^* ) ² ) ^1/2 . This is because surface plasmon resonance absorption contributes to a change in glossiness. The change in glossiness of the decorative coating 1 does not depend on the lightness index L ^* , but preferably the range of L ^{* is in} the range of 98-20.

  Here, in the present embodiment, “fine particles” of the silver alloy indicate “nanoparticles”, and “nanoparticles” are particles having an average particle diameter of nano-order, Examples of the particle diameter measuring method include a method of extracting fine particles within a certain range of an SEM image or a TEM image on an image and obtaining an average value thereof to obtain an average particle diameter. Since the silver or silver alloy fine particles 1a are nano-sized, light energy is easily absorbed by the decorative coating by surface plasmon resonance absorption.

  In this embodiment, it is desirable that the average particle diameter of the silver or silver alloy fine particles 1a is 2 to 200 nm. When the average particle diameter of the silver or silver alloy fine particles is larger than 200 nm, the silver alloy fine particles are likely to be irregularly reflected, and as a result, the silver luster tends to be lowered. Moreover, when the average particle diameter of the silver alloy fine particles is less than 2 nm, the light incident on the decorative coating is difficult to be reflected.

  Furthermore, it is preferable that the crystallite diameter of the silver or silver alloy constituting the fine particles is in the range of 2 nm to 98 nm. Here, when the crystallite diameter is less than 2 nm, the light incident on the decorative coating is difficult to be reflected. On the other hand, when the crystallite diameter exceeds 98 nm, it is difficult for radio waves (electromagnetic waves) to pass through the decorative coating.

  For example, fine particles of a silver alloy can be produced by introducing a reducing agent into a metal solution in which silver and a metal that forms an alloy with silver are in an ionic state. The fine particles obtained by such a production method become nano-order particles.

  Moreover, the composition ratio of the alloy of silver and the metal to be alloyed can be adjusted by changing the content of each metal contained in the metal solution. In addition, by adding the reducing agent and the dispersing agent to the metal solution, and adjusting the concentration of the dispersing agent or the stirring time and the heating temperature at that time, the average particle diameter of the silver or silver alloy particles and the crystal of the silver alloy The child diameter can be adjusted.

  The resin coating layer 2 and the binding resin 1b are light-transmitting polymer resins such as acrylic resin, polycarbonate resin, polyethylene terephthalate resin, epoxy resin, and polystyrene resin.

  When the dispersant (protective agent) 1c is added, the dispersant (protective agent) 1c is preferably a resin that has good adhesion to the fine particles 1a of silver or silver alloy and good affinity to the binding resin 1b. When the type of binding resin exemplified above is selected, a resin having a carbonyl group in the resin is preferred. For example, when an acrylic resin is selected as the binding resin 1b, it is preferable to select an acrylic resin having a carbonyl group as the dispersant (protective agent) 1c.

  Thus, by having a carbonyl group in the dispersant (protective agent), it is possible to improve the adhesion of the silver or silver alloy to the fine particles 1a, and further, by selecting the same resin as the binding resin 1b, the binding resin Affinity with 1b can be increased.

  Here, the silver or silver alloy fine particles 1a contained in the entire decorative coating 1 are preferably 85 to 99% by mass. Here, when the content of the fine particles 1a is less than 85% by mass, the metallic luster due to the silver or silver alloy fine particles 1a may not be sufficient, and when the content exceeds 99% by mass, it depends on the binding resin 1b. Bonding with the substrate may not be sufficient.

  The present invention will be described below based on examples.

<Example 1: Ag-Bi alloy fine particles>
220 g of silver nitrate and 3.3 g of bismuth nitrate are mixed. To this, 597 g of amino alcohol (reducing agent) and 80 g of disperse 190 (dispersing agent: manufactured by Big Chemie Japan) are added and heated at 60 ° C. for 120 minutes. Mixed. Thereby, Ag-Bi alloy fine particles were precipitated, and this was UF filtered with a UF membrane (ultrafiltration membrane) under conditions of room temperature and 3 hours. The average particle diameter of the obtained Ag—Bi alloy fine particles was 16 nm, the crystallite diameter of the Ag—Bi alloy was 14 nm, and contained 2.4 mass% of bismuth with respect to the Ag—Bi alloy.

  Next, as a compounding agent, 40 g of propylene glycol monoethyl ether, 8.86 g of styrene, 8.27 g of ethylhexyl acrylate, 15 g of lauryl methacrylate, 34.8 g of 2-hydroxyethyl methacrylate, 3.07 g of methacrylic acid, acid phosphooxyhexamonomethacrylate The compounding agent 1 which mixed 30g, the polymerization initiator 43g of propylene glycol monoethyl ether, and the tertiary butyl peroctoate 0.3g was produced.

  To this compounding agent 1, 0.465 g, 0.38 g of Dispapic 190 (manufactured by Big Chemie Japan), 0.23 g of Epochros WS-300 (manufactured by Nippon Shokubai Co., Ltd.), BYK-330 (manufactured by Big Chemie Japan) 0. 09 g and 150 g of 1-ethoxy-2-propanol were mixed, and this was used as a binder resin. Using this as a binder resin, Ag-Bi alloy was added to the binder resin so that the Ag-Bi alloy fine particles would be 5% by mass with respect to the entire coating. Fine particles were mixed. Next, the obtained mixture was applied by spin coating and then heat-treated at 80 ° C. for 30 minutes to form a decorative film. Ag-Bi alloy fine particles were mixed with the binding resin so that the Ag-Bi alloy fine particles contained 95% by mass with respect to the entire decorative coating.

<Example 2: Ag fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that bismuth nitrate was not added, Ag fine particles made of silver were produced, and the amount of the dispersant was reduced. Specifically, when preparing Ag fine particles, 597 g of amino alcohol (reducing agent) and 27 g of disperse 190 (dispersing agent: manufactured by Big Chemie Japan) are added to 220 g of silver nitrate, and conditions of 60 ° C. and 120 minutes are added. The mixture was heated and mixed to precipitate Ag fine particles, which were filtered through a UF membrane at room temperature for 3 hours. The average particle diameter of the obtained Ag fine particles was 19 nm, and the crystallite diameter of Ag was 16 nm. In addition, Ag fine particles were mixed with the binding resin so that the Ag fine particles contained 95% by mass with respect to the entire decorative coating.

<Example 3: Ag fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that Ag fine particles made of silver were prepared without adding bismuth nitrate, the amount of the dispersant was reduced, the composition of the binding resin was changed, and spin coating And the heat treatment conditions after forming the decorative coating.

  Specifically, in the same manner as in Example 2, when preparing Ag fine particles, 597 g of amino alcohol (reducing agent) and 27 g of disperse 190 (dispersant: manufactured by Big Chemie Japan) were added to 220 g of silver nitrate, Heat mixing was performed at 60 ° C. for 120 minutes to precipitate Ag fine particles, which were filtered through a UF membrane at room temperature for 3 hours. This is the same as in the second embodiment.

  Furthermore, 3.16 g of Plamy's WY (manufactured by Origin Electric Co., Ltd.) as the main agent, 0.72 g of Plamy's WY (manufactured by Origin Electric Co., Ltd.) as the curing agent, 0.03 g of BYK-330 (manufactured by Big Chemie Japan Co., Ltd.), 1-ethoxy-2 -13.97 g of propanol was mixed to prepare a paint, and this was mixed with Ag fine particles as a binding resin. Specifically, Ag fine particles were mixed with the binding resin so that the Ag fine particles contained 95% by mass with respect to the entire decorative coating. The obtained mixture was applied by spin coating and then heat-treated at 80 ° C. for 30 minutes to form a decorative film.

<Example 4: Ag-Pd alloy fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that palladium nitrate was used instead of bismuth nitrate to produce Ag-Pd alloy fine particles made of an alloy of silver and palladium, and the amount of the dispersant was reduced.

  Specifically, 220 g of silver nitrate and 4.0 g of palladium nitrate were mixed, and 597 g of amino alcohol (reducing agent) and 27 g of disperse 190 (dispersing agent: manufactured by Big Chemie Japan) were added to this, It is the point which heat-mixed on the conditions for 120 minutes, and precipitated Ag-Pd alloy microparticles | fine-particles, and filtered this with the UF membrane on the conditions for 3 hours at room temperature.

  The obtained Ag—Pd alloy fine particles had an average particle diameter of 21 nm, an Ag—Pd crystallite diameter of 18 nm, and contained 1.0% by mass of palladium with respect to the Ag—Pd alloy. The Ag—Pd alloy fine particles were mixed with the binding resin so that the Ag—Pd alloy fine particles contained 95% by mass with respect to the entire decorative coating.

<Example 5: Ag fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that bismuth nitrate was not added, Ag fine particles made of silver were produced, and the amount of the dispersant was increased. Specifically, when preparing Ag fine particles, 597 g of amino alcohol (reducing agent) and 108 g of disperse 190 (dispersing agent: manufactured by Big Chemie Japan) are added to 220 g of silver nitrate, and conditions of 60 ° C. and 120 minutes are added. The mixture was heated and mixed to precipitate Ag fine particles, which were filtered through a UF membrane at room temperature for 3 hours. The average particle diameter of the obtained Ag fine particles was 19 nm, and the crystallite diameter of Ag was 16 nm. The Ag fine particles were mixed with the binding resin so that the Ag alloy fine particles contained 95% by mass with respect to the entire decorative coating.

<Comparative Example 1: Ag-Ni alloy fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that nickel nitrate is used instead of bismuth nitrate to produce Ag-Ni alloy fine particles made of an alloy of silver and nickel, and the amount of the dispersant is reduced.

  Specifically, 220 g of silver nitrate and 16 g of nickel nitrate are mixed, and this is added to 597 g of amino alcohol (reducing agent) and 27 g of disperse 190 (dispersing agent: manufactured by Big Chemie Japan Co., Ltd.) at 60 ° C. for 120 minutes. The mixture was heated and mixed under conditions to precipitate Ag-Ni alloy fine particles, which were filtered through a UF membrane at room temperature for 3 hours.

  The average particle diameter of the obtained Ag—Ni alloy fine particles was 35 nm, the Ag—Ni crystallite diameter was 30 nm, and the nickel content relative to the Ag—Ni alloy was 5.1% by mass. In addition, Ag-Ni alloy fine particles were mixed with the binding resin so that the Ag-Ni alloy fine particles contained 95% by mass with respect to the entire decorative coating.

<Comparative Example 2: Ag-Ni alloy fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that nickel nitrate is used instead of bismuth nitrate to produce Ag-Ni alloy fine particles made of an alloy of silver and nickel, and the amount of the dispersant is reduced.

  Specifically, 220 g of silver nitrate and 64 g of nickel nitrate are mixed, and this is added to 597 g of amino alcohol (reducing agent) and 27 g of disperse 190 (dispersing agent: manufactured by Big Chemie Japan Co., Ltd.) at 60 ° C. for 120 minutes. The mixture was heated and mixed under conditions to precipitate Ag-Ni alloy fine particles, which were filtered through a UF membrane at room temperature for 3 hours. The average particle diameter of the obtained Ag—Ni alloy fine particles was 25 nm, the Ag—Ni crystallite diameter was 20 nm, and the nickel content relative to the Ag—Ni alloy was 20.4% by mass. In addition, Ag-Ni alloy fine particles were mixed with the binding resin so that the Ag-Ni alloy fine particles contained 95% by mass with respect to the entire decorative coating.

<Comparative Example 3: Ag-Ni alloy fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 was that nickel nitrate was used in place of bismuth nitrate to produce Ag-Ni alloy fine particles made of an alloy of silver and nickel, the amount of the dispersant was reduced, The composition of the binding resin is changed. Comparative Example 3 is also an example in which Ag fine particles are changed to Ag—Ni alloy fine particles with respect to Example 3.

  Specifically, 220 g of silver nitrate and 16 g of nickel nitrate are mixed, and 597 g of amino alcohol (reducing agent) and 27 g of disperse 190 (dispersant: manufactured by Big Chemie Japan Co., Ltd.) are added thereto, and the conditions are 60 ° C. and 120 minutes. The mixture was heated and mixed to precipitate Ag-Ni alloy fine particles, which were filtered through a UF membrane at room temperature for 3 hours.

  Furthermore, 3.16 g of Plamy's WY (manufactured by Origin Electric Co., Ltd.) as the main agent, 0.72 g of Plamy's WY (manufactured by Origin Electric Co., Ltd.) as the curing agent, 0.03 g of BYK-330 (manufactured by Big Chemie Japan Co., Ltd.), 1-ethoxy-2 -13.97 g of propanol was mixed to prepare a paint, and this was mixed with Ag-Ni alloy fine particles as a binding resin. In addition, Ag-Ni alloy fine particles were mixed with the binding resin so that the Ag-Ni alloy fine particles contained 95% by mass with respect to the entire decorative coating.

<Comparative Example 4: Ag fine particles>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that Ag fine particles made of silver were prepared without adding bismuth nitrate, the amount of the dispersant was reduced, the composition of the binding resin was changed, and the spin Heat treatment conditions after forming a decorative film with a coat. The difference between Comparative Example 4 and Example 3 is the heat treatment temperature after coating by spin coating.

  Specifically, 597 g of amino alcohol (reducing agent) and 27 g of dispersic 190 (dispersing agent: manufactured by Big Chemie Japan) are added to 220 g of silver nitrate, and the mixture is heated and mixed under the conditions of 60 ° C. and 120 minutes to obtain fine Ag particles. This was precipitated and filtered through a UF membrane under the conditions of room temperature and 3 hours.

  Furthermore, 3.16 g of Plamy's WY (manufactured by Origin Electric Co., Ltd.) as the main agent, 0.72 g of Plamy's WY (manufactured by Origin Electric Co., Ltd.) as the curing agent, 0.03 g of BYK-330 (manufactured by Big Chemie Japan Co., Ltd.), 1-ethoxy-2 -13.97 g of propanol was mixed to prepare a paint, and this was mixed with Ag fine particles as a binding resin. Ag fine particles were mixed with the binding resin so that the Ag fine particles contained 95% by mass with respect to the entire decorative coating. The obtained mixture was applied by spin coating and then heat-treated at 120 ° C. for 30 minutes to form a decorative film.

[Weather resistance test (xenon test)]
Before the weather resistance test shown below, the color systems (L ^* , a ^* , b ^* ) defined in the CIE 1976 color system (JIS Z 8729) of the decorative coatings according to Examples 1 to 4 and Comparative Examples 1 to 4 are used ^. chromaticness index ^{a *} of), the chromaticness index ^{b *,} color difference meter (manufactured by Murakami color Research Laboratory: was measured in the CMS-35SP). Further, the value of ((a ^* ) ² + (b ^* ) ² ) ^1/2 was calculated from the measurement result. These results are shown in Table 1.

Next, in accordance with JIS Z 8741, the gloss values of the decorative coatings according to Examples 1 to 4 and Comparative Examples 1 to 4 were measured under the condition of a measurement angle of 60 ° (manufactured by Murakami Color Research Laboratory: GM-). 26PRO-AUTO). A weather resistance test (xenon test) was performed on the decorative coatings according to Examples 1 to 4 and Comparative Examples 1 to 4 (100 W × 125 MJ). The gloss values of the decorative coatings according to Examples 1 to 4 and Comparative Examples 1 to 4 after the weather resistance test were measured. For each of Examples 1 to 4 and Comparative Examples 1 to 4, a value obtained by subtracting the gloss value before the weather resistance test from the gloss value after the weather resistance test was calculated as the gloss increase degree. The results are shown in Table 1. FIG. 5 shows the relationship between ((a ^* ) ² + (b ^* ) ² ) ^1/2 and the degree of increase in gloss.

[Measurement of reflectance]
Before the weather resistance test, the decorative coatings according to Example 2 and Comparative Example 1 were irradiated with light, and the reflectance of the decorative coating for each wavelength was measured from the spectral spectrum of these decorative coatings. FIG. 6 is a diagram showing the relationship between the wavelength of light incident on the decorative coating according to Example 2 and Comparative Example 1 and the reflectance of the decorative coating.

(Result 1)
As shown in FIG. 5 and Table 1, the decorative films according to Examples 1 to 5 satisfy the relationship of 6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23.4. Yes. If it is this range, the gloss increase degree of the decorative coating after a weather resistance test will exceed 60, and the glossiness of a decorative coating will improve. On the other hand, the enamel coating according to Comparative Examples 1 to 4 ^is a ^{1/2 <6.7 ((a *)} 2 + (b *) 2). If it is this range, it can be said that the glossiness of a decorative coating has hardly changed irrespective of a weather resistance test.

  Further, as shown in FIG. 6, the decorative coating according to Example 2 had a large change in reflectance according to the change in wavelength as compared with that of Comparative Example 1. From this, it is considered that when the Ag fine particles according to Example 2 are irradiated with light, the light is absorbed at a specific wavelength of light, and the light energy absorbed by the Ag fine particles is easily amplified (surface plasmon resonance absorption). Thereby, in Example 2, the constituent material around the silver fine particles easily receives amplification energy, and it is considered that the gloss of the decorative coating according to Example 2 after the weather resistance test is improved by this energy. This phenomenon can be considered to occur in the cases of Examples 1, 3, 4, and 5.

From the above, the chromaticness index a ^* and the chromaticness index b ^{* of the} decorative films according to Examples 1 to 5 are 6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23. By satisfying the relationship (4), it is considered that a color (chromatic color) that is likely to cause surface plasmon resonance absorption peculiar to fine particles of Ag or an Ag alloy is exhibited. As a result, in Examples 1 to 4, it is considered that the degree of increase in the metallic luster of the decorative coating after the weather resistance test is increased (the increase in gloss is increased).

On the other hand, in the decorative coatings according to Comparative Examples 1 to 4, the value of ((a ^* ) ² + (b ^* ) ² ) ^1/2 is too small and exhibits a near-achromatic color. For this reason, surface plasmon resonance absorption peculiar to Ag or Ag alloy fine particles will be suppressed. As a result, in Comparative Examples 1 to 4, it is considered that the glossiness of the decorative coating after the weather resistance test almost changed (the degree of increase in gloss is small).

<Example 6>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that the average particle diameter of the fine particles of the silver alloy (Ag-Bi alloy) is changed by changing the heating temperature and mixing time when mixing silver nitrate and bismuth nitrate, amino alcohol, and the dispersant, and the dispersant concentration. Is 200 nm. In addition, the silver alloy fine particles within a certain range of the TEM image were extracted on the image, the average value was obtained, and the average particle size of the silver alloy fine particles was measured.

<Comparative Example 5>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that the average particle size of silver alloy (Ag-Bi alloy) fine particles is changed by changing the heating temperature and mixing time when mixing silver nitrate and bismuth nitrate, amino alcohol, and dispersing agent, and dispersing agent concentration. , 500 nm.

(Result 2)
As a result of observing the decorative coating of Example 6 and Comparative Example 5, in the case of Comparative Example 5 (when the average particle size of the fine particles is larger than 200 nm), the silver alloy fine particles are irregularly reflected. Compared to silver gloss, it tends to decrease. From this result, it is preferable that the average particle diameter of the silver or silver alloy fine particles is 200 nm or less. In addition, from the result 3 mentioned later, it is preferable that an average particle diameter is 2 nm or more.

<Example 7>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that the crystallite diameter of the silver alloy (Ag-Bi alloy) is changed by changing the heating temperature and mixing time when mixing silver nitrate and bismuth nitrate, amino alcohol, and the dispersant, and the dispersant concentration. The range is 2 nm to 98 nm (specifically, the crystallite diameter is 2 nm, 36 nm, 98 nm). The crystallite diameter of the silver alloy is measured by the X-ray diffraction method specified in JIS H 7805.

<Comparative Example 6>
A decorative coating was formed in the same manner as in Example 1. The difference from Example 1 is that the crystallite diameter of the silver alloy (Ag-Bi alloy) is less than 2 nm or more than 98 nm by changing the heating temperature and mixing time of silver nitrate, bismuth nitrate and amino alcohol (specifically, Are crystallite diameters of 1 nm and 99 nm).

(Result 3)
As a result of observing the decorative coating of Example 7 and Comparative Example 6, in Comparative Example 6, when the crystallite diameter was less than 2 nm, the light incident on the decorative coating was difficult to be reflected. On the other hand, when the crystallite diameter exceeded 98 nm in Comparative Example 6, it was found that radio waves (electromagnetic waves) were hardly transmitted through the decorative coating. Note that the decorative coating of Example 7 had metallic luster and good radio wave permeability. From this result, it is considered that the crystallite diameter of silver or silver alloy is preferably in the range of 2 to 98 nm.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Decorative coating, 1a ... Fine particle, 1b ... Binding resin, 1c ... Protective agent (dispersing agent), 2 ... Resin coating layer, 10 ... Emblem, 20 ... Resin base material, F ... Front grille, D ... Radar device

Claims (3)

A decorative coating formed on the surface of a resin substrate located in the radar apparatus path,
The decorative coating comprises at least silver or silver alloy fine particles dispersed in the decorative coating and a light-transmitting binding resin that binds the silver or silver alloy fine particles.
In the color system (L ^* , a ^* , b ^* ) defined in the CIE 1976 color system, the chromaticness index a ^* and the chromaticness index b ^* of the decorative coating are:
6.7 ≦ ((a ^* ) ² + (b ^* ) ² ) ^1/2 ≦ 23.4
A decorative film characterized by satisfying the above relationship.   2. The decorative coating according to claim 1, wherein an average particle diameter of the silver or silver alloy fine particles is 2 to 200 nm.   The decorative coating according to claim 1 or 2, wherein a crystallite diameter of the silver or the silver alloy constituting the fine particles is in a range of 2 to 98 nm.

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