JP2014145678A - Decorative film - Google Patents

Abstract

The present invention relates to a decorative coating formed by dispersing fine particles of silver alloy in an organic substance, and provides a decorative coating that can effectively solve the problem that the fine particles of silver alloy aggregate, coarsen and easily discolor. To do.
A decorative coating 10 is formed on a surface of a resin substrate located in a radar apparatus path, and the decorative coating 10 is a layer 1 formed by dispersing silver alloy fine particles 1a in an organic substance 1b. The silver alloy has bismuth as an alloy composition ratio (Bi / Ag) in the range of 2% by mass to 10% by mass.
[Selection] Figure 1

Description

  The present invention relates to a decorative coating formed on the surface of a resin base material and in a radar apparatus path.

  Antennas that transmit and receive radio waves, such as communication equipment and radar, are given priority over their functions, so the antenna body and surrounding structure are less likely to be restricted in terms of design. A rod antenna with a bare shape is used. By the way, depending on the mounting position of the antenna, there may be a case where it is desired to make the antenna invisible. For example, in a radar that measures the distance to an obstacle in front of the vehicle or the distance between the front vehicle and the like, the performance is demonstrated. In order to do so, it is preferably provided at the center position of the front portion of the vehicle. In such a case, for example, an antenna is attached in the vicinity of the front grille of the vehicle, but it is desirable that the antenna is not visible from the outside as much as possible from the design surface.

  By the way, the auto cruise system measures the inter-vehicle distance and relative speed between the vehicle ahead and the host vehicle using sensors mounted in front of the vehicle, and controls the throttle and brake based on this information to accelerate and decelerate the host vehicle. However, it is a technology that controls the distance between vehicles, and is attracting attention as one of the technologies of the Intelligent Transport System (ITS) that aims to alleviate traffic congestion and reduce accidents in recent years. In general, a radio wave transmission / reception device such as a millimeter wave radar is used as a sensor used in the auto cruise system.

  A radar device installed in front of a vehicle body is generally disposed behind a front grille, and an emblem of a vehicle manufacturing company or a decoration unique to the vehicle is mounted on the surface of the front grille. It is common. The millimeter wave emitted from the radar device is radiated forward through the front grille or emblem, reflected by an object such as a forward vehicle or a front obstacle, and the reflected wave returns to the radar device through the front grille or the like. It has become. Therefore, it is desirable to use a material or paint that has a small loss of radio wave transmission and can give a desired aesthetic appearance at a place arranged in the beam path of the radar device such as a front grill or an emblem.

  For the above reasons, it is common to provide a window part through which radio waves can be transmitted at the front grille part corresponding to the place where the radio wave transmission / reception device is arranged, and radio waves can enter and exit through this window part. On the other hand, the appearance of the front grille loses continuity due to the provision of the window, and the radio transmission / reception device and engine room inside the vehicle can be visually recognized from this window. The risk of damage is increased. For this reason, conventionally, for example, a radio wave transmission cover (decorative coating) as disclosed in Patent Document 1 is inserted into the window portion of the front grill so that the window portion and the front grill body have a sense of unity. Yes.

  This will be described with reference to FIGS. As shown in FIG. 4, the radar device D installed in front of the vehicle body A is disposed behind the front grille F, and the millimeter waves irradiated from the radar device D are separated from the front grille F as shown in FIG. 5. It is emitted forward through the emblem E on the surface (millimeter wave L1) and reflected by an object such as a forward vehicle or a front obstacle, and this reflected wave (millimeter wave L2) passes through the emblem E and the front grille F. It returns to the radar apparatus D.

  Here, the emblem E is composed of decorative coatings M and M 'as shown in FIGS. 6a and 6b. The decorative coating M shown in FIG. 6 a is formed by, for example, silver nanoparticles P being dispersed inside the organic layer Y. On the other hand, the decorative coating M ′ shown in FIG. 6B simulates the form disclosed in Patent Document 1, and, for example, silver nanoparticles P ′ are deposited discontinuously on the surface of the front grille F, and organic matter is deposited thereon. The layer Y is covered. Thus, although the dispersion | distribution form of a metal nanoparticle differs, in any form, the metal nanoparticle disperse | distributed discontinuously so that a millimeter wave can permeate | transmit.

  By the way, when silver fine particles are applied as metal nanoparticles in these decorative coatings, silver fine particles with an average particle diameter of about several nm are aggregated and coarsened and discolored by a weather resistance test such as a xenon accelerated weathering test. It has the problem of being easy to do. Silver fine particles with an average particle size of several nanometers have high activity and are unstable, so that the metal nanoparticles are excited by heat and light during the weather resistance test, and ionized to move within the layer (the film The reason is that the metal color tone is likely to change (or the color is likely to change) due to the change in state.

  Here, Patent Document 2 discloses an electrochromic film that is colored by a reduction reaction, a conductive reflective film that is formed on one side in the thickness direction of the electrochromic film and contains silver, and a conductive reflective film. An electrochromic mirror is disclosed which is provided on one side in the thickness direction on the opposite side of the electrochromic film and formed of a protective layer containing bismuth. According to this electrochromic mirror, it is said that such a layer configuration suppresses the diffusion of silver into the electrochromic film and can suppress yellowing of the electrochromic film. However, even when this electrochromic mirror is applied, the problem that silver fine particles aggregate due to light energy and coarsen to show a color tone change cannot be effectively solved.

  Patent Document 3 discloses a silver alloy film for electromagnetic wave shielding containing, for example, 0.01 to 10 at% of bismuth. According to this silver alloy film for electromagnetic wave shielding, silver aggregation is unlikely to occur, and as a result, deterioration of electromagnetic wave shielding characteristics due to loss of conductivity due to silver aggregation and occurrence of white spots are unlikely to occur. However, even in the case of a silver alloy film containing bismuth in such a numerical range, the metal color tone is changed by exciting the metal nanoparticles with heat or light during ionization and moving in the layer. It is unclear whether the problem of being easily changed can be solved.

Japanese Unexamined Patent Publication No. 2000-159039 JP 2011-095406 A JP 2004-263290 A

  The present invention has been made in view of the problems described above, and relates to a decorative coating formed by dispersing fine particles of silver alloy in an organic matter, and the problem that the fine particles of silver alloy are aggregated and coarsened and easily discolored. An object is to provide a decorative coating which can be effectively eliminated.

  In order to achieve the above object, a decorative coating according to the present invention is a decorative coating formed on the surface of a resin substrate located in a radar device path, and the decorative coating includes silver alloy particles dispersed in an organic matter. The silver alloy has bismuth as an alloy composition ratio (Bi / Ag) in the range of 2% by mass to 10% by mass.

  The decorative coating of the present invention is applied to the surface of a resin base material (for example, front grille) located in the radar apparatus path, so that it has a metallic luster in appearance and has radio wave permeability (electrical insulation). ). Since this decorative coating has a metallic luster, it can inherently be a current-carrying coating, but since the metal nanoparticles are discontinuously dispersed in the layer and are metal nanoparticles, the distance between the particles is extremely short. In addition to providing a metallic luster for human vision, the radio wave passes through each nanoparticle, so the millimeter wave attenuation is extremely small. In addition, it has a metallic luster in appearance and can be a film having electrical insulation. Here, “millimeter wave” refers to a radio wave having a frequency band of about 30 GHz to 300 GHz among electromagnetic waves, and for example, about 76 GHz of the frequency band can be specified.

  Further, the “decorative coating” referred to here 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 includes the decorative coating as a part. An emblem or the like is formed on the surface of the front grill, which is a resin base material.

  The decorative coating of the present invention is formed by dispersing fine particles of a silver alloy in an organic substance. The silver alloy has a bismuth content of 2 to 10% by mass as an alloy composition ratio (Bi / Ag). By providing the silver alloy fine particles containing bismuth in the numerical range in such a numerical range, aggregation and coarsening of the silver fine particles due to light energy can be suppressed, and color change can be suppressed. it can.

  The silver fine particles themselves exhibit a blue color, but the silver alloy containing bismuth exhibits a yellow color or a color close to yellow. Therefore, even if the silver alloy is agglomerated and coarsened and the color tone changes to yellow, the color tone change amount is much smaller than when the color tone changes from blue to yellow.

  Here, “fine particles” of silver alloy indicate “nanoparticles”, and “nanoparticles” are particles whose average particle size is nano-order, and the particle size measurement of nanoparticles. Examples of the method include a method of extracting metal particles within a certain range of SEM images and TEM images of fine particles of silver alloy on the image, obtaining an average value thereof, and obtaining an average particle size.

  According to the verification by the present inventors that the color difference change was obtained by variously changing the alloy composition ratio of bismuth in the silver alloy, the curve of the color difference change was changed when the alloy composition ratio (Bi / Ag) of bismuth was 2% by mass. It has been found that the color difference changes to a constant value at 2% by mass or more, reaching the inflection point. On the other hand, according to the present inventors, it has been found that when the alloy composition ratio of bismuth is 10% by mass or less, a decrease in silver gloss can be suppressed. From these verification results, 2% by mass was defined as the lower limit value of the alloy composition ratio of bismuth in the silver alloy, and 10% by mass was defined as the upper limit value.

  The dispersion form of the silver alloy fine particles in the layer constituting the decorative coating is as shown in FIG. 6a in which the fine particles are dispersed in the organic substance (binder resin) constituting the layer, or the other layer as shown in FIG. 6b. And a dispersion form in which fine particles of silver alloy are deposited and dispersed discontinuously. In the former form, the silver alloy fine particles are formed by applying a dispersion of silver alloy fine particles using ethanol or the like as a solvent to the surface of the resin substrate (spray coating or bar coating method and subsequent drying). A decorative coating dispersed in an organic layer can be formed.

  On the other hand, in the latter form, fine particles of silver alloy are applied to the surface of the resin substrate by vacuum deposition, sputtering, ion plating included in the PVD method, thermal CVD, plasma CVD, laser CVD, etc. included in the CVD method. By discontinuously adhering and coating the solvent on this, silver alloy fine particles are deposited on the surface of the resin substrate discontinuously, etc., forming a decorative film on which an organic layer is formed can do.

  A preferred embodiment of the decorative coating according to the present invention includes an embodiment in which the average particle diameter of the silver alloy fine particles is 200 nm or less.

  According to the present inventors, it has been found that when the average particle diameter of the silver alloy fine particles is larger than 200 nm, the silver alloy fine particles are likely to aggregate, and the silver gloss is likely to be lowered due to this. From this verification result, a decorative film in which the average particle size of the silver alloy fine particles is 200 nm or less is used as a preferred embodiment.

  It has also been found that by making the average particle diameter of silver alloy fine particles 200 nm or less, fine particles of silver alloy containing bismuth can be synthesized with a yield of almost 100%.

  As can be understood from the above description, according to the decorative coating of the present invention, the silver alloy fine particles are formed in a dispersed manner in the organic matter with respect to the decorative coating formed on the surface of the resin base material located in the radar device path. In the case where the silver alloy has bismuth in an alloy composition ratio (Bi / Ag) in the range of 2% to 10% by mass, aggregation and coarsening of silver fine particles due to light energy can be suppressed, Color tone change can be suppressed.

It is the schematic diagram explaining embodiment of the decorative film of this invention. It is the figure which showed the experimental result which specifies the optimal range of the alloy composition ratio of bismuth in a silver alloy, (a) is the alloy composition ratio of Bismuth in a silver alloy: Bi / Ag (mass%) and the relationship between initial b value (B) is a figure which shows the alloy composition ratio: Bi / Ag (mass%) of a bismuth in a silver alloy, and the relationship of a color difference change ((DELTA) E). FIG. 3 is a diagram showing a TEM image in which the alloy composition ratio of bismuth in a silver alloy is 0% by mass, 1.0% by mass, and 2.0% by mass. It is the schematic 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. The millimeter wave emitted from the radar device is radiated forward through the front grille and emblem, which is a resin base material, and the reflected light reflected by the front object returns to the radar device through the emblem and front grille. FIG. (A), (b) is the schematic diagram explaining embodiment of the internal structure of the decorative coating film which comprises the conventional emblem.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment of decorative coating)
FIG. 1 is a schematic diagram illustrating an embodiment of a decorative coating of the present invention. The decorative coating 10 shown in FIG. 1 constitutes an emblem that is attached to the front surface of the resin base material K, which is a front grille, and is a millimeter wave irradiated from a radar device (not shown) on the back surface of the resin base material K. Is radiated forward through the resin base material K and the decorative coating 10 (emblem) and reflected by an object such as a forward vehicle or a front obstacle, and the reflected millimeter wave passes through the decorative coating 10 and the resin base material K. Through the radar device.

  The decorative coating 10 shown in the figure is configured by laminating the layer 1 and the transparent substrate 2 in the viewing direction (X direction). Note that an adhesive seal or the like may be attached to the layer 1 and the adhesive seal may be bonded to the resin substrate K.

  The layer 1 is obtained by dispersing silver alloy fine particles 1a in an organic substance 1b made of a binder resin.

  In addition to the silver alloy, gold or an alloy thereof can be applied to the metal, but fine particles made of a silver alloy are applied from the viewpoint of material cost and good metallic luster. In addition, the metal other than silver constituting the silver alloy uses any one of aluminum, titanium, indium, manganese, iron, copper, tin, lead, bismuth, etc., which are more easily ionized than silver. In the decorative coating 10 shown in the drawing, bismuth nanoparticles, which is a metal that is relatively easy to form nanoparticles among metals having a large ionization tendency, are applied.

  Here, the silver alloy 1a has bismuth as an alloy composition ratio (Bi / Ag) in the range of 2% by mass to 10% by mass. As will be described below, when the alloy composition ratio of bismuth is 2 mass%, the inflection point of the curve regarding the color difference change and the initial b value is reached, and when the mass ratio is 2 mass% or more, the color difference change reaches a constant value and the initial b value is reached. Is known to reach a high constant value. On the other hand, it is known that when the alloy composition ratio of bismuth is 10% by mass or less, it is possible to suppress a decrease in silver luster. From these results, the lower limit of the alloy composition ratio of bismuth in the silver alloy 1a is 2% by mass, The upper limit is defined as 10% by mass.

  Further, it is desirable that the average particle diameter of the silver alloy is 200 nm or less. It has been found that when the average particle diameter of the silver alloy fine particles is larger than 200 nm, the silver alloy fine particles are likely to aggregate, and the silver luster is likely to be lowered due to this. As a desirable range of the average particle diameter, 200 nm or less is specified.

  According to the decorative coating 10 shown in the figure, the silver alloy fine particles 1a are dispersed in the organic substance 1b, and the silver alloy 1a has bismuth as an alloy composition ratio in the range of 2 to 10% by mass. Thus, aggregation and coarsening of silver fine particles due to light energy can be suppressed, and a change in color tone can be suppressed.

[Experiment and results to determine the optimal range of bismuth alloy composition in silver alloys]
The present inventors conducted an experiment to identify the optimum range of the alloy composition ratio of bismuth in the silver alloy in the layer constituting the decorative coating shown in FIG. Specifically, a mixture of silver nitrate and bismuth nitrate, added to aminoalcohol (reducing agent) and heated and mixed, UF filtered, mixed with a compounding agent, prepared a paint, and applied by spin coating. After the work, a decorative coating was formed by heat treatment at 80 ° C. for 30 minutes. At this time, various decorative coatings are formed by changing Bi / Ag variously. A weather resistance test (xenon test) was performed on each decorative coating (100 W × 500 MJ).

  FIG. 2a is a graph showing the relationship between the alloy composition ratio of bismuth in a silver alloy: Bi / Ag (mass%) and the initial b value, and FIG. 2b is the alloy composition ratio of bismuth in a silver alloy: Bi / Ag (mass%). FIG. 6 is a diagram showing a relationship between color difference change (ΔE) and color difference. The degree of hue change was measured based on Lab color difference. Each figure shows a plurality of actually measured plot values and an approximate curve passing through them.

  From the curve graph showing the relation between the alloy composition ratio of bismuth in the silver alloy: Bi / Ag (mass%) and the initial b value shown in FIG. 2a, the inflection point is reached when Bi / Ag is 2 mass%, and 2 mass%. The initial b value is suddenly lowered at a temperature less than that, and the silver alloy exhibits a blue color. In the range of 2% by mass or more, the initial b value is saturated within the range of 10 to 12, and the silver alloy exhibits a yellow color.

  On the other hand, from the curve graph showing the relationship between the alloy composition ratio of Bis / Ag (mass%) and the color difference change (ΔE) in the silver alloy shown in FIG. 2b, the inflection point is similarly obtained when Bi / Ag is 2 mass%. The color difference change suddenly increases at less than 2% by mass and shows ΔE = 14, and in the range of 2% by mass or more, the color difference change is saturated in a low range of about 2 to 4.

  From this experimental result, the alloy composition ratio of bismuth in the silver alloy: Bi / Ag (mass%) is specified to be in the range of 2 mass% or more, so that the silver alloy has a yellow color and the change in color difference is low. I understood.

  On the other hand, according to the present inventors, it has been found that when the alloy composition ratio of bismuth is 10% by mass or less, a decrease in silver gloss can be suppressed.

  From the above, the alloy composition ratio of bismuth in the silver alloy: 2% by mass as the lower limit of Bi / Ag (% by mass) and 10% by mass as the upper limit are specified.

  FIG. 3 is a diagram showing TEM images of an alloy composition ratio of Bi / Ag (mass%) of 0 mass%, 1.0 mass%, and 2.0 mass% in the silver alloy. In each mass% of silver alloy, the upper figure shows the case where the silver alloy has an average particle diameter of 500 nm, and the lower figure shows the case where the silver alloy has an average particle diameter of 200 nm. . In the figure, black dots indicate silver alloy fine particles (nanoparticles).

  From the figure, it can be confirmed that the aggregation of the silver alloy is suppressed in the case of 2.0% by mass compared to the case of Bi / Ag of 0% by mass and 1.0% by mass.

  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 ... Layer, 1a ... Silver alloy fine particle, 1b ... Organic substance (binder resin), 2 ... Transparent base material, 10 ... Decorative coating, K ... Resin base material, F ... Front grille (resin base material), E ... Emblem, D ... Radar device, L1 ... Irradiated millimeter wave, L2 ... Reflected millimeter wave

Claims (2)

A decorative coating formed on the surface of a resin substrate located in the radar apparatus path,
The decorative coating is formed by dispersing fine particles of silver alloy in an organic substance,
The silver alloy is a decorative coating having bismuth in an alloy composition ratio (Bi / Ag) in the range of 2% by mass to 10% by mass.   The decorative coating according to claim 1, wherein the silver alloy fine particles have an average particle size of 200 nm or less.

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