JP2013024727A - Decorative film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decorative film which is formed in a radar device path on a surface of a resin substrate and which can effectively suppress color tone change of the decorative film when having undergone a weathering test.SOLUTION: A decorative film 10 is formed on a surface of a resin substrate K located in a radar device path and includes: a first layer 1 composed of first metal nanoparticles 1a scattered in organic material 1b; and a second layer 2 being in contact with the first layer 1 and composed of second metal nanoparticles 2a which are less noble than the first metal nanoparticles 1a, and are scattered in organic material 2b.

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 structures are less likely to be restricted in terms of design. For example, antennas for vehicle radios, etc. 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, the performance of these decorative coatings is generally evaluated by a weather resistance test such as a xenon accelerated weathering light test. According to the present inventors, the metal color tone is likely to change due to the metal nanoparticles being excited by heat and light during the weather resistance test, ionizing and moving in the layer (the state of the film changes). The occurrence of the problem that the color is easy to change has been identified.

Japanese Unexamined Patent Publication No. 2000-159039

  The present invention has been made in view of the above-mentioned problems, and relates to a decorative coating formed on the surface of a resin base material and in a radar apparatus path, and effectively suppresses a change in color tone when subjected to a weather resistance test. An object of the present invention is to provide a decorative coating that can be applied.

  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 apparatus path, and the decorative coating includes first metal nanoparticles in an organic substance. And a second layer in which second metal nanoparticles that are in contact with the first layer and are lower than the first metal nanoparticles are dispersed in an organic substance. It is what.

  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 includes a first layer in which first metal nanoparticles are dispersed in an organic substance, and second metal nanoparticles in contact with the first layer and lower than the first metal nanoparticles. Is formed from the second layer dispersed in the organic matter, and the second layer in which the relatively base second metal nanoparticles are dispersed is in contact with the first layer, The ionization of the first metal nanoparticles dispersed in the first layer is suppressed, so that the color tone change of the first layer is effectively suppressed.

  Here, the “base” metal generally refers to a metal that has a higher ionization tendency than hydrogen and is easily ionized. In this specification, in addition to this general concept, the second metal nanoparticles are used. Includes the concept that the metal has a relatively large ionization tendency as compared with the first metal nanoparticles.

  In the present invention, for example, a second metal which is lower than the first metal dispersed in the first layer is dispersed with respect to the first layer which has an appearance design surface and wants to suppress the color change. The second layer is brought into contact with each other, and so-called dissimilar metal contact corrosion technology that suppresses ionization of the first metal by promoting ionization of the second metal is applied.

  Here, examples of the first metal nanoparticles include metal nanoparticles such as gold and alloys thereof and silver and alloys thereof. In addition, “nanoparticles” are particles whose average particle diameter is nano-order. As a method for measuring the particle diameter of nanoparticles, metal particles within a certain range of SEM images and TEM images of metal particles are used. For example, a method of extracting on an image and obtaining an average value thereof to obtain an average particle diameter can be used.

  In addition, as the second metal nanoparticles that are lower than the first metal nanoparticles, metal ions having a higher ionization tendency than that applied in relation to the applied first metal nanoparticles, for example, , Aluminum, titanium, indium, manganese, iron, copper, tin, lead, bismuth, and the like. Since the second metal nanoparticle is a metal that is easily ionized, it is generally difficult to form a nanoparticle, but bismuth is a suitable metal material because it is a metal that easily forms a nanoparticle. is there.

  The dispersion form of the first metal nanoparticles in the first layer and the second metal nanoparticles in the second layer is the form shown in FIG. 6a in which the dispersion is densely dispersed in the organic substance (binder resin) constituting the layer. Alternatively, as shown in FIG. 6b, a dispersion form in which metal nanoparticles are discontinuously deposited and dispersed on the other layer can be mentioned.

  In the former form, a dispersion of metal nanoparticles using ethanol or the like as a solvent is applied to the surface of the resin substrate or the surface of the other layer (spray coating or bar coating method and subsequent drying). A first layer and a second layer in which the first and second metal nanoparticles are dispersed in a layer made of an organic substance can be formed.

  On the other hand, in the latter form, the surface of the resin substrate or the other side is formed by vacuum deposition, sputtering, ion plating included in the PVD method, thermal CVD, plasma CVD, laser CVD included in the CVD method. By discontinuously adhering to the surface of the layer, and applying a solvent thereon, the metal nanoparticles are discontinuously deposited on the surface of the resin substrate, and the layer made of organic matter is formed thereon. The first layer and the second layer can be formed.

  In addition, examples of the configuration form in which the first layer and the second layer are in contact with each other include the following two configuration forms.

  One of the configuration forms is a form in which the first layer is disposed on the side where the first layer is visually recognized and is in contact with the second layer stacked in the viewing direction.

  In the case where the decorative coating forms the entire configuration of the emblem, the second layer and the first layer are directed from the front grille side where the decorative coating (emblem) is mounted toward the outside (the visually recognized design surface side). Furthermore, a transparent base material that protects the first layer is laminated to form a decorative film.

  By the way, an altered portion whose color tone has changed due to a reaction caused by a potential difference between both layers (metal nanoparticles constituting the layer) can be formed at the interface between the first layer and the second layer. In the case of the configuration in which the first layer is laminated on the second layer as described above, when the thickness of the first layer is too thin, the altered portion is visible from the outside of the decorative coating. End up.

  According to the present inventors, a thickness of 300 nm or more is specified as the thickness of the first layer in which the altered portion is invisible from the outside of the decorative coating.

  On the other hand, in another configuration, the first layer and the second layer are stacked and contacted in a direction orthogonal to the viewing direction, and a black layer is disposed in front of the contact interface so that the contact interface of both is not visible. Is the form in which is formed.

  In this embodiment, the stacking direction of the first and second layers differs from that described above by 90 degrees. And in this form, there is also a region where the interface between the first and second layers is close to the outer peripheral surface (design surface) of the decorative coating, and in order to make the altered portion invisible from the outside, the layer thickness of the first layer Since it is not sufficient to adjust only, a black layer is provided on the surface of the first layer.

  Moreover, it is preferable that the amount of the second metal nanoparticles in the second layer is adjusted to a range of 3% by mass to 98% by mass.

  When the concentration of the second metal nanoparticles in the second layer is less than 3% by mass, it is difficult to expect the ionization suppression effect of the first metal nanoparticles in the second layer, and the first layer in the first layer Since the change in color tone becomes obvious by ionization of metal nanoparticles (for example, silver nanoparticles), 3% by mass is defined as the lower limit.

  On the other hand, when the concentration of the second metal nanoparticles in the second layer exceeds 98% by mass (that is, the concentration of the organic substance that is the binder resin is less than 2% by mass), the amount of the binder resin is too small and the layer is formed. Since it cannot be formed, 98% by mass is defined as the upper limit.

  As can be understood from the above description, according to the decorative coating of the present invention, the decorative coating formed on the surface of the resin substrate located in the radar apparatus path is visually recognized by applying the technique of contact with different metals. The decorative coating is such that the second layer in which the second metal nanoparticles dispersed in the first metal nanoparticles dispersed in the first layer located on the side of the first layer are in contact with the first layer By forming, the ionization of the first metal nanoparticles can be suppressed, and thus the color tone change of the decorative coating can be effectively suppressed when a weather resistance test is performed.

It is a schematic diagram explaining one embodiment of the decorative coating of the present invention. It is the schematic diagram explaining other embodiment of the decorative film of this invention. It is a graph which shows the experimental result which prescribes | regulates the layer thickness of a 1st layer. 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. The decorative coating shown in the figure is one in which the first and second metal nanoparticles are dispersed in an organic substance (corresponding to FIG. 6a of the conventional structure). It may be a layer in which metal nanoparticles are deposited in a discontinuous manner (corresponding to FIG. 6b of the conventional structure).

(Embodiment 1 of decorative coating)
FIG. 1 is a schematic diagram illustrating an embodiment of the decorative coating of the present invention. A decorative coating 10 shown in FIG. 1 constitutes an emblem that is attached to the front surface of a resin base material K that 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.

  In the illustrated decorative coating 10, the first layer 1 and the second layer 2 are laminated and in contact with each other in a direction perpendicular to the viewing direction (X direction), and both contact interfaces (interface region A in the figure). The black layer 3 is formed in front of the contact interface (in the figure, the front surface of the second layer 2), and the transparent base material 4 is laminated on the outer peripheral side of the first layer 1 so that the entire surface is not visible. Is configured. The first layer 1 may be a decorative coating laminated on a base material (not shown), and the surface of the base material (the surface opposite to the side where the first layer 1 is laminated) may be used. A form in which an adhesive seal or the like is attached and the adhesive seal of the base material constituting the decorative coating is bonded to the resin base material K may be used.

  The first layer 1 is obtained by dispersing the first metal nanoparticles 1a in an organic substance 1b made of a binder resin, and the second layer 2 is similarly formed by a second metal in an organic substance 2b made of a binder resin. Although the nanoparticles 2a are dispersed, the second metal nanoparticles 2a are made of a base metal that is more easily ionized than the first metal nanoparticles 1a.

  As the first metal nanoparticle 1a, any one of gold, an alloy thereof, silver, an alloy thereof, and the like can be used. Above all, silver nanoparticles are used from the viewpoint of material cost and good metallic luster. Is preferred. As the second metal nanoparticles 2a, any one of aluminum, titanium, indium, manganese, iron, copper, tin, lead, bismuth and the like can be used. Here, since the second metal nanoparticle is a metal that is easily ionized, it is generally difficult to form a nanoparticle that is a fine particle. It is preferable to use nanoparticles of bismuth, which is a metal that is easy to form.

  The outline of the method for forming the decorative coating 10 is as follows. The transparent substrate 4 having the shape shown in the figure is manufactured, the black layer 3 is formed in the peripheral depression, and the second layer is masked in the center on the surface of the black layer 3. 2, the central masking is removed, and the first layer 1 is formed here to produce the decorative coating 10. Here, when forming the 2nd layer 2 on the surface of the black layer 3, or forming the 1st layer 1 on the surface of the transparent base material 4, the 2nd metal nanoparticle which uses ethanol etc. as a solvent The dispersion liquid of 2a or the first metal nanoparticles 1a is applied to the surface of the black layer 3 or the surface of the transparent substrate 4 (spray coating or bar coating method and subsequent drying). In addition, it is preferable to use the organic material (binder resin) of both the 1st layer 1 and the 2nd layer 2 from a viewpoint of favorable adhesiveness.

  In the interface region A between the first layer 1 and the second layer 2, an altered portion whose color tone has changed due to a reaction caused by a potential difference between the two layers (the metal nanoparticles 1 a and 2 a constituting the layer) can be formed. The altered portion cannot be visually recognized by the black layer 3 from the outside.

  The decorative coating 10 shown in the figure has a very short inter-particle distance because the first metal nanoparticles 1a are dispersed in the organic material 1b constituting the first layer 1, so that the particles are densely assembled and human. The film can provide a good metallic luster for visual perception, and further, when radio waves pass through each nanoparticle, the millimeter wave attenuation of radio waves is extremely small, and the film has good radio wave permeability. It has become. Furthermore, since the second layer 2 in which the relatively second base metal nanoparticles 2a are dispersed is in contact with the first layer 1, the first metal nanoparticles dispersed in the first layer 1 The ionization of 1a is suppressed, so that the color tone change of the first layer 1 can be effectively suppressed. This is particularly effective when the decorative coating 10 is placed in an environment where the metal nanoparticles are easily excited by heat or light as in the xenon accelerated weathering test.

(Embodiment 2 of decorative coating)
FIG. 2 is a schematic diagram illustrating another embodiment of the decorative coating of the present invention. The decorative coating 10A shown in FIG. 2 is in a form in which the first layer 1 is disposed on the side where the first layer 1 is visually recognized and is laminated and in contact with the second layer 2 in the viewing direction (X direction). The transparent base material 4 is laminated on the further outer peripheral side of 1 to constitute the whole.

  Also in the decorative coating 10 </ b> A, an altered portion whose color tone has changed due to a reaction caused by a potential difference between the two layers may be formed in the interface region A between the first layer 1 and the second layer 2 </ b> A. And since there is no black layer 3 which makes this altered portion invisible from the outside like the decorative coating 10, if the layer thickness t of the first layer 1 is too thin, this can be seen from the outside. There is a risk that.

  The inventors of the present invention have specified 300 nm or more as the layer thickness t of the first layer 1 in the decorative coating 10A by an experiment described later, and by forming the first layer 1 to satisfy this condition, The altered portion is difficult to visually recognize from the outside, and the color tone change of the first layer 1 can be effectively suppressed by the ionization of the second metal nanoparticles 2a dispersed in the second layer 2A.

[Xenon test for determining the concentration of the second metal nanoparticles in the second layer constituting the decorative coating and its results]
The inventors have used the decorative coating of the embodiment shown in FIG. 1 (an example in which the content of bismuth in the second layer is 3% by mass) and the decorative coating of the conventional structure in which the second layer does not exist (comparison). Example) was made as a prototype, both sides were subjected to a xenon test, and the degree of hue change after the implementation was measured based on the Lab color difference. Table 1 shows the Lab values and hue change results before and after the xenon test.

  From Table 1, the degree of hue change in the examples is reduced to about 20% of the comparative example, and it is proved that the ionization of silver is effectively suppressed and the hue change by the xenon test can be remarkably suppressed.

  Here, when the concentration of bismuth in the second layer is less than 3% by mass, it is difficult to expect the silver ionization suppressing effect of the second layer, and the hue change is caused by ionization of the silver nanoparticles in the first layer. In order to be manifested, the concentration of bismuth is preferably 3% by mass or more.

  On the other hand, when the concentration of bismuth in the second layer exceeds 98% by mass, that is, when the concentration of the organic substance that is the binder resin is less than 2% by mass, the amount of the binder resin is too small to form a layer. The concentration is preferably 98% by mass or less. Therefore, it can be specified that the concentration of bismuth should be adjusted to 3% by mass or more and 98% by mass or less in the second layer.

[Xenon test to define the thickness of the first layer constituting the decorative coating and its results]
The present inventors further changed the thickness of the first layer in the decorative coating according to the embodiment shown in FIG. 2 to variously change the thickness of the first layer so as to specify the thickness of the first layer. The xenon test was performed on each test piece to identify the hue change. The results are shown in Table 2 and FIG.

  From FIG. 3, it is demonstrated that the test piece with the thickness of the first layer of 300 nm has the inflection point, and the test piece with the thickness of the first layer thicker than that has a hue change of 2 or less and almost no change. Therefore, in the decorative coating of the form shown in FIG. 2, the thickness of the first layer can be specified to be 300 nm or more.

  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 ... 1st layer, 1a ... 1st metal nanoparticle, 1b ... Organic substance (binder resin), 2,2A ... 2nd layer, 2a ... 2nd metal nanoparticle, 2b ... Organic substance (binder resin), 3 ... black layer, 4 ... transparent substrate, 10, 10A ... decorative coating, A ... interface region, F ... front grill (resin substrate), E ... emblem, D ... radar device, L1 ... irradiated millimeter wave, L2 Millimeter wave reflected

Claims (6)

A decorative coating formed on the surface of a resin substrate located in the radar apparatus path,
The decorative coating is composed of a first layer in which first metal nanoparticles are dispersed in an organic substance, and second metal nanoparticles in contact with the first layer and lower than the first metal nanoparticles are organic substances. A decorative coating formed from a second layer dispersed therein.   The decorative coating according to claim 1, wherein the first layer is disposed on a side where the first layer is visually recognized, and is laminated and in contact with the second layer in the viewing direction.   The decorative coating according to claim 2, wherein the first layer has a thickness of 300 nm or more.   2. The first layer and the second layer are stacked and contacted in a direction perpendicular to the viewing direction, and a black layer is formed in front of the contact interface so that the contact interface of both is not visible. The decorative coating according to 1.   The decorative coating according to any one of claims 1 to 4, wherein the amount of the second metal nanoparticles in the second layer is adjusted to a range of 3% by mass to 98% by mass.   The decorative coating according to any one of claims 1 to 5, wherein the first metal nanoparticles are made of silver, and the second metal nanoparticles are made of bismuth.

Images