JP6556177B2 - Electromagnetic wave transmitting metal film, method of forming electromagnetic wave transmitting metal film, and on-vehicle radar device - Google Patents

Description

  The present invention relates to an electromagnetic wave transmitting metal film having a metallic luster and having electromagnetic wave permeability, a method of forming an electromagnetic wave transmitting metal film, and an in-vehicle radar device having a cover member provided with the metal film.

  2. Description of the Related Art Conventionally, in order to decorate a member that requires electromagnetic wave transparency, an indium film in which indium is formed in an island shape on a surface of a base material is provided on the member by a vacuum deposition method. The indium film formed in an island shape has a metallic luster, and a gap between the islands can be used as an electromagnetic wave transmission path. For this reason, the indium coating is used as a metal coating for decorating a cover member of a millimeter wave radar device mounted on an automobile such as an emblem (see, for example, “Patent Document 1” and “Patent Document 2”). .

  However, since indium is an expensive metal, there is a need for an electromagnetic wave transmitting metal film that uses less indium or an electromagnetic wave transmitting metal film that uses a metal other than indium.

  Therefore, by providing a first film formed by vacuum vapor deposition of indium on the surface of the resin substrate and providing a second film formed by vacuum vapor deposition of chromium on the upper surface of the first film, the amount of indium used can be reduced. Reduction is performed (for example, refer to “Patent Document 3”).

  On the other hand, at the present time, it is a metal film for electromagnetic wave transmission other than an indium island film formed by vacuum deposition, and has a level of electromagnetic wave transmission that can withstand practical use, and has a sufficient metallic luster in appearance. There is no known metal film for transmitting electromagnetic waves.

Japanese Unexamined Patent Publication No. 2000-159039 JP 2000-049522 A JP 2007-162125 A

  The present invention provides an electromagnetic wave transmitting metal film having a sufficient metallic luster in appearance even when a metal other than indium is used, and formation of an electromagnetic wave transmitting metal film optimal for the formation of the electromagnetic wave transmitting metal film It is an object of the present invention to provide a method and an in-vehicle radar device using the electromagnetic wave transmitting metal coating.

  Therefore, as a result of intensive studies, the present inventors have achieved the above-mentioned problems by adopting the following electromagnetic wave transmitting metal coating, electromagnetic wave transmitting metal coating forming method and on-vehicle radar device. .

The metal film for electromagnetic wave transmission according to the present invention is a metal film capable of transmitting electromagnetic waves provided on the surface of a base material, and the metal film is provided on the surface of the base material via an underlayer, It is an aggregate of fine islands surrounded by fine cracks that become an electromagnetic wave transmission path obtained through a production process by a dry process, and has a metallic luster, and the fine islands are in a unit area (1 mm ² ). There are 2 to 10000, and the linear expansion coefficient of the base layer provided on the surface of the substrate is larger than that of the metal coating, and the linear expansion coefficient on the substrate side is equal to the linear expansion coefficient of the metal coating. On the other hand, it is 1.01 times or more and 100 times or less, and the thickness of the base layer is 0.1 μm or more and 2 μm or less .

  The metal film for electromagnetic wave transmission according to the present invention preferably has an average island diameter of the fine islands provided on the surface of the substrate of 0.01 μm to 500 μm when observed with a scanning electron microscope.

  The metal film for electromagnetic wave transmission according to the present invention preferably has a width of the fine crack of 0.01 μm to 100 μm.

The metal film for electromagnetic wave transmission according to the present invention preferably has a metal film thickness of 0.005 μm to 2 μm.

  The metal film for electromagnetic wave transmission according to the present invention may be a non-conductive film obtained by heat-treating the conductive film formed on the surface of the substrate in the production process by the dry process. preferable.

In the metal film for electromagnetic wave transmission according to the present invention, the metal film preferably has 1 to 10,000 fine cracks in a unit area (1 mm ² ).

  In the metal film for electromagnetic wave transmission according to the present invention, the base material is preferably one type selected from insulating resin, ceramics, paper, glass, and fiber.

  In the metal film for electromagnetic wave transmission according to the present invention, the linear expansion coefficient of the base layer provided on the surface of the substrate is higher than that of the metal film, and the linear expansion coefficient on the substrate side is a line of the metal film. The expansion coefficient is preferably 1.01 times or more.

  In the metal coating for electromagnetic wave transmission according to the present invention, the metal coating is chromium, chromium alloy, stainless alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, copper, copper alloy, tantalum, tantalum alloy, silver , Silver alloy, tin, tin alloy, gold, gold alloy, platinum, platinum alloy, palladium, palladium alloy, silicon, silicon alloy, cobalt, cobalt alloy, niobium, niobium alloy, indium, indium alloy, tungsten, tungsten alloy, carbon And at least one selected from carbon steel.

The method for forming an electromagnetic wave transmitting metal coating according to the present invention is a method for forming an electromagnetic wave transmitting metal coating that is capable of transmitting electromagnetic waves to the surface of a substrate and has a metallic luster, The conductive film forming step of forming a conductive film having a metallic luster on the base layer provided on the surface of the base material, and the conductive film formed in the conductive film forming step is subjected to heat treatment, whereby the conductive layer Forming fine cracks as a transmission path for electromagnetic waves in a film, and transmitting the electromagnetic waves as an aggregate of fine islands in which 2 to 10,000 fine islands surrounded by the fine cracks exist in a unit area (1 mm ² ) A fine island coating forming step of forming a metal coating, and in the fine island coating forming step, the linear expansion coefficient of the underlayer provided on the surface of the base material is Wherein greater than the electromagnetic wave transmissive metal coating, the linear expansion coefficient of the base material side, with respect to the linear expansion coefficient of the metal coating, not more than 100 times 1.01 times, and the thickness of the underlying layer , 0.1 μm or more and 2 μm or less .

The method for forming an electromagnetic wave transmitting metal coating according to the present invention is a method for forming an electromagnetic wave transmitting metal coating that is capable of transmitting electromagnetic waves to the surface of a substrate and has a metallic luster, The conductive film forming step of forming a conductive film having a metallic luster on the base layer provided on the surface of the base material, and the conductive film formed in the conductive film forming step is subjected to heat treatment, whereby the conductive layer 1 to 10,000 fine cracks serving as an electromagnetic wave transmission path are formed in a film in a unit area (1 mm ² ), and the metal coating for electromagnetic wave transmission as an aggregate of fine islands surrounded by the fine cracks. Forming a fine island coating, wherein in the fine island coating step, the linear expansion coefficient of the underlayer provided on the surface of the substrate is the electromagnetic wave transmitting Greater than genus coating, the linear expansion coefficient of the base material side, with respect to the linear expansion coefficient of the metal coating, not more than 100 times 1.01 times, and the thickness of the underlying layer, 0.1 [mu] m It is characterized by being 2 μm or less .

  A vehicle-mounted radar device according to the present invention uses a cover member provided with a metal film for transmitting electromagnetic waves according to any one of the above on a surface of a base material.

In the on-vehicle radar device according to the present invention, the cover member is preferably an emblem attached to the center of the front grille of the automobile in the vehicle width direction.

  According to the present invention, by adopting a dry process, it is possible to select various types of deposited metal instead of expensive indium, and by designing the film thickness appropriately, even if it is an inexpensive metal, It is possible to provide an electromagnetic wave transmitting metal coating that has a sufficient metallic luster in appearance and can transmit electromagnetic waves.

It is the schematic diagram which represented typically the metal film for electromagnetic wave transmission which concerns on this invention. 1 is a schematic diagram of a film forming apparatus according to an embodiment of the present invention. It is a flowchart which shows film-forming operation | movement. It is a front view which shows the emblem which is a cover member of the vehicle-mounted radar apparatus which concerns on this invention. It is a figure for demonstrating the formation method of the other emblem which is a cover member of the vehicle-mounted radar apparatus which concerns on this invention. 2 is a stereomicrograph of the surface of the electromagnetic wave transmitting metal coating obtained in Example 1. FIG.

  Hereinafter, preferred embodiments of a metal coating for electromagnetic wave transmission, a method for forming a metal coating for electromagnetic wave transmission, an in-vehicle radar device, and a radio wave shielding material for light transmission according to the present invention will be described.

<Electromagnetic wave transmission metal coating>
First, with reference to FIG. 1, the metal film 100 for electromagnetic wave transmission which concerns on this invention is demonstrated. An electromagnetic wave transmitting metal coating 100 according to the present invention is a metal coating 20 provided on the surface of a base material 10, which has a metal gloss that is sufficiently metallic in appearance and can transmit electromagnetic waves. is there. The metal film 100 for transmitting electromagnetic waves is obtained through a dry process such as sputtering, and as shown in FIG. 1A, as shown in FIG. 1A, the fine islands 22 surrounded by the fine cracks 21 serving as electromagnetic wave transmission paths. It is configured as an aggregate. The fine cracks 21 are formed so as to be distributed substantially uniformly over the entire surface of the metal coating 20. The metal film 100 for electromagnetic wave transmission according to the present invention appropriately adjusts the number of the fine islands 22 in the unit area, the width of the fine cracks 21, the thickness of the metal film 20, etc. The amount of transmission attenuation can be adjusted, and electromagnetic waves with various wavelengths can be selectively transmitted. In the present embodiment, a description will be given mainly by taking, as an example, a metal film 20 for transmitting millimeter waves that can transmit millimeter waves that enter and exit from a millimeter wave radar device mounted on an automobile or the like.

  The number of the fine islands 22 in the unit area can be adjusted by the interval between the fine cracks 21 formed in the metal film 20. The interval at which the microcracks 21 are formed and the width of the microcracks 21 can be adjusted by a heat treatment performed after forming a film on the surface of the substrate 10 by a dry process such as sputtering. Hereinafter, the metal coating 20 and the substrate 10 will be described in this order. Hereinafter, in the present invention, the heat treatment performed after forming a film on the surface of the base material 10 by a dry process such as sputtering is referred to as “after baking”.

Metal coating 20: The metal coating 20 according to the present invention is configured as an aggregate of fine islands 22 surrounded by fine cracks 21, as described above. Two to 10,000 fine islands 22 exist in a unit area (1 mm ² ). Thus, by covering the surface of the base material 10 discontinuously with the fine islands 22 surrounded by the fine cracks 21, electromagnetic waves can be transmitted through the gaps (fine cracks 21) between the adjacent fine islands 22. In addition, the metal coating 20 can be made to exhibit a sufficient metallic luster in appearance.

  Fine islands 22: Here, the fine islands 22 are fine metal films that are in close contact with the substrate 10 and are adjacent to other fine islands 22 with fine cracks 21 therebetween. The average island diameter of the fine islands 22 is preferably 0.01 μm to 500 μm when observed with a scanning electron microscope (magnification 1000 times). When the average island diameter of the fine islands 22 is in the range of 0.01 μm to 500 μm, it can exhibit a sufficient metallic luster in appearance and the fine cracks as an electromagnetic wave transmission path are uniform on the surface of the substrate 10. It can be in a state of being dispersed. Further, when the average island diameter of the fine islands 22 is within the range, the number of fine islands in the unit area (1 mm 2) can be within the above range.

  On the other hand, when the average island diameter of the fine islands 22 is less than 0.01 μm, the ratio of the area occupied by the fine cracks 21 on the surface of the substrate 10 increases, and the ratio of the area occupied by the fine islands 22 decreases. As a result, the glitter of the metal coating is lowered, and there is a case where a sufficient metallic luster cannot be expressed in appearance. If the average island diameter of the fine islands 22 exceeds 500 μm, the area of each fine island 22 increases, and the possibility that electromagnetic waves will enter the fine islands 22 increases. For this reason, the electromagnetic wave transmission attenuation amount of the metal coating 20 increases, and the function as the metal coating 100 for electromagnetic wave transmission may not be sufficiently exhibited.

  Next, a method for calculating the average island diameter will be described. First, the island diameter of one fine island 22 is obtained. Here, the island diameter refers to the distance between the ends that is the longest distance from one end to the other end of the fine island 22. Alternatively, it is possible to use an approximate diameter obtained by calculating the diameter of a circle equal to the area of the fine island 22 by using an image processing apparatus. For each of the plurality of fine islands 22, an island diameter is obtained and an average value thereof is obtained to obtain an average island diameter. However, when obtaining the average island diameter, for example, the island diameter is obtained for all the fine islands 22 existing in the observation field when observed with a scanning electron microscope (1000 magnifications), and the average value is obtained. Alternatively, the island diameter may be obtained for all the fine islands 22 existing in the unit area (for example, 1 mm 2), and the average value may be obtained.

  Shape of fine island 22: In the present invention, the shape of the fine island 22 is preferably polygonal. In consideration of disposing the electromagnetic wave transmitting metal coating 100 on a path of millimeter waves entering and exiting the in-vehicle radar device, it is preferable that at least one of the corners is an acute angle. By forming the fine island 22 into a polygonal shape having at least one corner as an acute angle, the acute angle portion functions as an antenna that receives electromagnetic waves, and can serve as a relay point that radiates electromagnetic waves incident on the metal coating 20. Considering that the metal coating 20 is provided for decoration of a design member typified by an automobile emblem, it is preferable that the shape and size of each fine island 22 are substantially the same. When the shape and size of each fine island 22 are uniform, the metal coating 20 can exhibit a superior metallic luster with no gloss unevenness.

  Fine crack 21: In the present invention, the width of the fine crack 21 is preferably in the range of 0.01 μm to 100 μm. By setting the width of the fine crack 21 to 0.01 μm or more, the millimeter wave can be transmitted through the fine crack 21 from one side of the metal coating 20 to the other side. Millimeter waves can be satisfactorily transmitted from the other surface side to the one surface side. That is, in the thickness direction of the metal coating 20, the metal coating 20 according to the present invention can pass through when the millimeter wave is incident from any direction. Further, by setting the width of the fine crack 21 to 100 μm or less, the fine crack 21 in the metal coating 20 can be made invisible and the appearance can be kept excellent.

  Furthermore, it is preferable that the fine cracks 21 exist at an interval of 0.1 μm to 10000 μm on an arbitrary straight line on the metal coating 20. However, “arbitrary straight line on the metal coating 20” refers to a straight line virtually drawn on the surface of the metal coating 20 in any direction. By setting the interval in which the fine cracks 21 are present in an arbitrary straight line on the metal coating 20 within the range, the number of the fine islands 22 described above and the average island diameter are adjusted within the above range. In addition, the shape of the fine islands 22 can be made substantially uniform. In addition, by setting the interval at which the microcracks 21 are present within this range, it is possible to eliminate the uneven electromagnetic wave transmission over the entire surface of the metal coating 20.

Moreover, it is preferable that 1-10000 fine cracks 21 exist in a unit area (1 mm < ² >). The number of the fine islands 22 and the size of the island diameter can be within the above-described ranges by the presence of the fine cracks 21 in the range of 1 to 10000 in the unit area (1 mm ² ).

  Film thickness of metal coating 20: In the present invention, the thickness of the metal coating 20 is preferably 0.005 μm to 2 μm. When the film thickness of the metal coating 20 is less than 0.005 μm, the glossiness is lowered, and there is a case where sufficient metal luster cannot be expressed in appearance. On the other hand, when the film thickness of the metal coating exceeds 2 μm, electromagnetic waves incident on the microcracks 21 between the microislands 22 may enter the end surfaces of the microislands 22 depending on the incident angle, and may be attenuated and become undetectable. For this reason, the function as the electromagnetic wave transmitting metal coating 100 may not be sufficiently exhibited.

  The metal coating 20 is made of chromium, chromium alloy, stainless alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, copper, copper alloy, tantalum, tantalum alloy, silver, silver alloy, tin, tin alloy, A kind selected from gold, gold alloy, platinum, platinum alloy, palladium, palladium alloy, silicon, silicon alloy, cobalt, cobalt alloy, niobium, niobium alloy, indium, indium alloy, tungsten, tungsten alloy, carbon, and carbon steel Preferably it consists of. Moreover, when these metals are formed to a film thickness having a sufficient metallic luster in appearance by a vacuum vapor deposition method, a continuous film is formed and electromagnetic wave permeability is lost. On the other hand, in the present invention, by performing a dry process such as sputtering and appropriate after-baking, it is possible to obtain a metal film 20 having an electromagnetic wave permeability while exhibiting a sufficient metallic luster in appearance. Moreover, the design of the member provided with the metal coating 20 can be varied depending on the metal color exhibited by each metal.

  Substrate 10: Next, the substrate 10 according to the present invention will be described. As the base material 10 on which the metal coating 20 is provided, one kind selected from insulating resin, ceramics, paper, glass, and fiber can be used. Further, as the insulating resin, any of a thermoplastic insulating resin and a thermosetting insulating resin may be used, and the material of the resin used as the substrate 10 is not particularly limited.

  In the present invention, the base material 10 made of any of the above materials can be used. However, the linear expansion coefficient on the base material 10 side is 1 with respect to the linear expansion coefficient of the metal constituting the metal coating 20. It is preferably 01 times or more. When the linear expansion coefficient on the substrate 10 side is 1.01 times or more of the linear expansion coefficient of the metal coating 20, the thermal expansion deformation of the metal coating 20 is caused by the thermal expansion deformation on the substrate 10 side after baking. I can't follow you. As a result, appropriate fine cracks suitable for electromagnetic wave transmission can be formed in the metal coating 20. Here, when the linear expansion coefficient on the base material 10 side is less than 1.01, the difference between the linear expansion coefficient on the base material 10 side and the linear expansion coefficient of the metal coating 20 is small, and even after baking is performed. It becomes difficult to form the fine crack 21 in the metal coating 20. Moreover, although the upper limit of the linear expansion coefficient by the side of the base material 10 can be suitably set according to the kind of metal which comprises the metal film 20, it is appropriate to make about 100 times the upper limit. When the linear expansion coefficient on the base material 10 side exceeds 100 times, the linear expansion coefficient on the base material 10 side is larger than the linear expansion coefficient of the metal film 20, so that a large crack is formed in the metal film 20 during after-baking. There is a fear, and it becomes difficult to form fine cracks uniformly dispersed on the entire surface of the metal coating 20.

  Here, when the linear expansion coefficient of the base material 10 itself is low and the linear expansion coefficient of the base material 10 itself is not within the above-described range with respect to the linear expansion coefficient of the metal coating 20, the underlayer 30 described below. By providing this, the linear expansion coefficient on the base material 10 side can be adjusted to be within the above-mentioned range. However, the linear expansion coefficient on the substrate 10 side includes the linear expansion coefficient of the base layer 30 provided on the upper surface of the substrate 10. For example, many of the insulating resins have a linear expansion coefficient in the above range with respect to the linear expansion coefficient of the metal coating 20. On the other hand, the coefficient of linear expansion of ceramics, glass, etc. is low, and may show the same value as the coefficient of linear expansion of the metal constituting the metal coating 20. Accordingly, when a material having a low linear expansion coefficient such as ceramics or glass is used as the base material 10, an underlayer formed using a resin material having a higher linear expansion coefficient than the metal coating 20 on the surface of the base material 10. 30 is preferably adjusted so that the linear expansion coefficient on the substrate 10 side is adjusted within the above range. In addition, even when a material having a linear expansion coefficient of the base material 10 itself within the above-described range, such as an insulating resin, is used as the base material 10, the base layer 30 may be provided. . The underlayer 30 will be described later.

  When an insulating resin is used as the substrate 10, it is preferable to use a material having a linear expansion coefficient of 1.01 times or more with respect to the linear expansion coefficient of the metal coating 20 from the same viewpoint as described above. As such an insulating resin, as described above, both a thermoplastic resin and a thermosetting resin can be used. As an example of the insulating resin that can be used as the base material 10, ABS (acrylonitrile-butadiene-styrene) resin, AES (acrylonitrile-ethylene-styrene) resin, acrylic resin, polyacetal resin, polyamide resin, polyamideimide resin, polyimide resin, Polyurethane resin, polyester resin, polyethylene resin, polyethylene naphthalate resin, polyethersulfone, polyetheretherketone, liquid crystal polymer (LCP), polyvinyl chloride resin, polyolefin resin, polycarbonate resin, polystyrene resin, polysulfone resin, cellulose resin, polyphenylene Examples thereof include sulfide resins. However, these various listed resins are only examples, and in the present invention, various thermoplastic insulating resins and thermosetting insulating resins can be used as the base material.

  Among the insulating resins listed above, in particular, one selected from polyester, ABS (acrylonitrile-butadiene-styrene) resin, AES (acrylonitrile-ethylene-styrene) resin, polycarbonate resin, acrylic resin and polyolefin resin is used. preferable. Since these resins have a linear expansion coefficient several times that of the metal film 20, fine cracks can be satisfactorily formed in the above-described range with respect to the metal film 20 by performing heat treatment. Further, these resins are strong and have good moldability, so that, for example, they can achieve the mechanical strength required when used as automobile parts such as a cover member of an in-vehicle radar device, It can be formed into a desired shape such as an automobile emblem.

  The shape of the base material 10 described above is not particularly limited, and a three-dimensional shape such as a plate material, a sheet material, a film material, or the like, or an automobile emblem described above may be used. Since the electromagnetic wave transmitting metal coating 100 according to the present invention is obtained through an electroless plating process, even if it is a base material 10 having a complicated three-dimensional shape, a metal is accurately applied to the entire surface of the base material 10. A coating 20 can be formed.

  Underlayer 30: The underlayer 30 referred to here is an auxiliary layer that needs to be provided on the surface of the base material 10 when the linear expansion coefficient on the base material 10 side does not satisfy the above requirements. In addition, when the linear expansion coefficient on the substrate 10 side is low and deformation occurs during heat treatment, the underlayer is also used when performing heat treatment (after baking) at a temperature lower than the deformation start temperature (softening point) of the substrate 10. 30 is provided as an auxiliary. Thus, by providing the base layer 30 on the surface of the base material 10 in an auxiliary manner, the fine cracks 21 are formed in the metal coating 20 by after baking at a temperature lower than the softening point of the base material 10. Deformation can be prevented.

  As described above, it is preferable to use a resin material having a linear expansion coefficient higher than that of the metal coating 20 such as a polyester resin as a material for forming the base layer 30. Thus, by forming the base layer 30 using a resin material whose linear expansion coefficient is higher than that of the metal coating 20, it is possible to adjust the linear expansion coefficient on the substrate 10 side within the above-described range. Moreover, as such resin with a high linear expansion coefficient, both hydrophilic resin and water-insoluble resin can be used, but it is preferable to use hydrophilic resin. Furthermore, the underlayer 30 formed using such a resin may be water-insoluble.

  In addition, by providing the base layer 30 and improving the adhesion between the base material 10 and the metal coating 20, fine cracks can be dispersed substantially uniformly over the entire surface of the metal coating 20 by after-baking. . That is, at the time of after baking, the underlayer 30 and the metal coating 20 cause expansion behavior according to the respective linear expansion coefficients. The fine crack 21 of the metal coating 20 is adjusted using the difference in linear expansion coefficient at this time. Therefore, it is possible to uniformly form the fine cracks 21 in the surface of the metal coating 20 at the time of after-baking by eliminating the poor adhesion portion between the base material 10 and the metal coating 20. Further, by distributing the fine cracks substantially uniformly on the entire surface of the metal coating 20, variations in the shape and size of the fine islands 22 and the island diameter can be reduced.

  It should be noted that, as a precaution, even if the linear expansion coefficient on the base material 10 side satisfies the above requirements, it may be provided on the surface of the base material 10 as an auxiliary. There is nothing. For example, even when a material having a linear expansion coefficient within the above-described range, such as an insulating resin, is used as the base material 10, the base layer 30 is provided on the surface of the base material 10, and the linear expansion coefficient on the base material 10 side. Is adjusted to a preferable value or an optimal value, the adhesion between the base material 10 and the metal coating 20 is improved, and the fine cracks 21 formed in the metal coating 20 are uniformly dispersed. It becomes easy to adjust the interval formed and the width of the fine crack 21 within the above-mentioned range.

  The number average molecular weight of the polyester resin is preferably 2000 to 30000. By forming the underlayer 30 using a polyester resin having a number average molecular weight of 2000 or more, the underlayer 30 can be made a strong film. Further, by forming the underlayer 30 using a polyester resin having a number average molecular weight of 30000 or less, it is possible to prevent the occurrence of a curling phenomenon after the formation of the underlayer 30 when using the film-like substrate 10. . Specific examples of such water-insoluble polyester resins include self-crosslinking type water-insoluble polyester resins (Pesresin wac-15x, Pesresin wac-17x) manufactured by Takamatsu Yushi Co., Ltd. Resin (plus coat Z-850, Z-730, RZ-570) or the like can be used.

  The underlayer 30 may be formed of a hydrophilic (meth) acrylic resin, a resin having a hydroxyl group, an isocyanate compound, or the like in addition to the polyester resin.

  The hydrophilic monomer contained in the hydrophilic (meth) acrylic resin has a polymerizable double bond, and has a carboxyl group, a hydroxyl group, a hydroxymethyl group, an amino group, a sulfonic acid group, a polyethylene oxide group, a sulfate ester base, A monomer having a phosphate ester base or the like can be used. For example, “(meth) acrylates having a hydroxyl group such as 2-hydroxylethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate”, “acrylic acid, methacrylic acid, maleic acid or a monoalkyl ester thereof containing a carboxyl group” , Ethylenically unsaturated carboxylic acids such as itaconic acid or its monoalkyl ester, fumaric acid or its monoalkyl ester, "" acrylamide, N-methylol (meth) acrylamide, dimethylol (meth) acrylamide, N-methylolpropane (meth) " (Meth) acrylamides such as acrylamide and N, N-dimethylacrylamide ”,“ N-methylaminoethyl methacrylate, N-methylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethyl Alkylamino esters of acrylic acid or methacrylic acid such as aminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl acrylate "," N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide, N Unsaturated amides having an alkylamino group such as N, dimethylaminopropylacrylamide ”,“ monovinylpyridines such as vinylpyridine ”,“ vinyl ethers having an alkylamino group such as dimethylaminoethyl vinyl ether ”,“ vinylsulfonic acid ” , Styrene sulfonic acid and its salt, 2-acryloylamino-2-methylpropane sulfonic acid and its salt, etc. having a sulfone group, “vinyl pyrrolidone”, “(meth) acrylic” "May be used alone or two or more of such.

  Further, when the underlayer is formed from a resin having a hydroxyl group and an isocyanate compound, since the resin has a hydroxyl group, the hydroxyl group and the isocyanate group of the isocyanate compound in the cured layer are chemically bonded to each other. The formation is hardened. Further, by curing the base layer, it is difficult to absorb moisture in the base layer and the insulating characteristics can be improved, and it can be suitably used for applications such as printed wiring boards and antennas that require insulation.

  Examples of the resin having a hydroxyl group include a polyester resin, polyvinyl butyral, polyvinyl acetal, and an acrylic resin. However, a monomer having a hydroxyl group may be copolymerized with a resin having no hydroxyl group. These hydroxyl group-containing resins are preferably selected according to the type of the non-conductive substrate in order to improve the adhesion to the non-conductive substrate. Specifically, when the non-conductive substrate is made of polyester, polypropylene (polyolefin), polyimide, polycarbonate, or liquid crystal polymer, the resin having a hydroxyl group is preferably a polyester resin. When the non-conductive substrate is made of cellulose or polyphenylene sulfide, the hydroxyl group-containing resin is preferably a (meth) acrylic resin obtained by copolymerizing a hydroxyl group-containing monomer.

  Although the resin having a hydroxyl group depends on the reactivity of the isocyanate compound and the resin constituting the catalyst adhesion layer, the hydroxyl value is preferably in the range of 1 to 30 mgKOH / g. By setting the hydroxyl value to 1 mgKOH / g or more, the underlayer can be sufficiently cured.

  As isocyanate compounds, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tetramethylene diisocyanate, xylylene diisocyanate, lysine diisocyanate , Trimethylhexamethylene diisocyanate, 1,4-cyclohexylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene Examples thereof include diisocyanates and derivatives thereof.

  The amount of the isocyanate compound cannot be generally determined depending on the type of the resin having a hydroxyl group, but the hydroxyl group of the resin having a hydroxyl group and the isocyanate group of the isocyanate compound are in a range of 1: 1 to 1:10 in a molar ratio. It is preferable to do.

  The thickness of the underlayer is preferably 0.1 to 2 μm. By setting the thickness to 0.1 μm or more, it is possible to improve the adhesion with the non-conductive substrate. In addition, by setting the thickness to 2 μm or less, it is possible to easily reflect the surface shape of the base material on the surface of the base layer when the surface of the nonconductive base material is exposed, and when the surface of the nonconductive base material is exposed. be able to.

  Moreover, when forming the base layer 30, you may use the resin composition which mixed the polyester resin and other resin. Specifically, polyvinyl butyral, acrylic resin, polyurethane resin, or the like can be used as the other resin. However, when the base layer 30 is formed of a resin composition using a resin other than the polyester resin together with the polyester resin, the polyester resin contains 50% by weight or more when the resin composition is 100% by weight. Adopting the composition is preferable for obtaining good adhesion between the substrate 10 and the metal coating 20. In order to further stabilize the adhesion between the substrate 10 and the metal coating 20, it is more preferable to employ a composition containing the polyester resin component in an amount of 80% by weight or more. Furthermore, considering the existence of manufacturing variations in industrial production, it is most preferable to employ a composition containing 90% by weight or more of the polyester resin component.

  The underlayer 30 is formed by applying a coating solution obtained by dissolving the above-described polyester resin or the like and other resin added as necessary in an appropriate solvent by a known coating method such as dipping or bar coating. It can be formed by coating on top and drying. Moreover, you may form the base layer 30 by drying after spray application. Alternatively, when the base material 10 is configured using a resin, the base layer is formed by co-extrusion of the resin material that forms the base material 10 and the water-insoluble polyester resin that forms the base layer 30. 30 may be formed.

  Thickness of the underlayer 30: The thickness of the underlayer 30 formed as described above varies depending on the type of monomer constituting the polyester resin, but is preferably in the range of 0.1 μm to 2 μm, preferably 0.1 μm to 1 μm. A range is more preferred. By providing the base layer 30 with the thickness in the range on the surface of the base material 10, by using the difference between the linear expansion coefficient of the resin material and the linear expansion coefficient of the metal constituting the metal coating, after baking, It is possible to easily generate fine cracks uniformly on the entire surface of the metal coating 20.

  When the thickness of the foundation layer 30 is less than 0.1 μm, the role of the foundation layer 30 may not be sufficiently exhibited. On the other hand, if the thickness of the underlayer 30 exceeds 1 μm, the fine crack 21 is hardly generated in the metal coating 20 even after baking.

<Method of forming metal film for electromagnetic wave transmission>
Next, a method for forming the electromagnetic wave transmitting metal coating 100 will be described. The electromagnetic wave transmitting metal film 100 according to the present invention is preferably formed by the following steps. By adopting the following steps, the metal film for electromagnetic wave transmission 100 according to the present invention can be easily manufactured using a metal other than indium.
(1) A conductive film forming step of forming a conductive film having a metallic luster on the surface of the substrate 10 by a dry process.
(2) After conducting baking of the conductive film formed in the conductive film forming step, a fine crack 21 serving as an electromagnetic wave transmission path is formed in the conductive film, and a fine island 22 surrounded by the fine crack 21 is a unit. A fine island coating forming step of forming an electromagnetic wave transmitting metal coating 100 as an aggregate of two to 10000 fine islands 22 present in an area (1 mm 2).

[Conductive film forming process]
Next, the conductive film forming process according to the present invention will be described. In the conductive film forming step, a metal film is formed on the surface of the base material 10 by a dry process such as sputtering to form a conductive film having a metallic luster on the surface of the base material 10. In the present invention, by forming a metal film on the surface of the base material 10 by a dry process such as sputtering, the dense metal film 20 having a uniform film thickness can be accurately formed on the surface of the base material 10. .

  Here, as described above, a substrate made of various materials such as insulating resin, ceramics, paper, glass, fiber, etc. can be used as the substrate 10. However, the linear expansion coefficient on the substrate 10 side is preferably 1.01 times or more than the linear expansion coefficient of the metal constituting the conductive film. Further, the upper limit value of the linear expansion coefficient on the substrate 10 side is preferably about 100 times for the same reason as described above. Furthermore, for the same reason as described above, when a material having a low linear expansion coefficient such as ceramics or glass is used as the base material 10, the base material 10 is made of a resin material having a higher linear expansion coefficient than the metal coating. It is preferable to form the conductive film after forming the base layer 30 on the surface. In addition, even when a material having a linear expansion coefficient within the above-described range, such as an insulating resin, is used as the base material 10, a resin having a linear expansion coefficient of 1.01 times or more for the same reason as described above. More preferably, the base layer 30 is provided on the surface of the base material 10 using a material, and the linear expansion coefficient on the base material 10 side is adjusted to a preferable value or an optimal value.

  When the surface of the substrate 10 is smooth, the surface of the substrate 10 is roughened by mechanical treatment, chemical treatment, optical treatment (UV treatment, plasma treatment, etc.), etc. Processing may be performed. Moreover, you may provide the base layer 30 formed using the resin material mentioned above. By providing the base layer 30, the ability to form fine cracks on the metal coating 20 can be improved.

In general, the skin depth of a metal coating and the radio wave transmission are closely related. The skin depth is a distance at which an electromagnetic field incident on a certain material is attenuated to 1 / e (≈1 / 2.718≈−8.7 dB). The skin depth (D) can be expressed by the following formula (1).

D = {2ρ / (ωμ)} ^0.5 formula (1)

Here, D is the skin depth, ρ is the electrical resistivity of the conductor, ω is the angular frequency of the current, and μ is the absolute permeability of the conductor.
Theoretically, a material having a large electrical resistivity and a small absolute permeability has a large skin depth (D) and a low radio wave attenuation. As shown in Table 1, the depth values of various metal materials at a frequency of 79 GHz vary depending on the type of metal.
If a material having a large skin depth is selected, the amount of radio wave attenuation can be further reduced, so that the thickness of the metal film can be increased. In addition, it is known that a certain degree of film thickness is required to express a color tone with a metallic luster, and that the original reflectance (color tone) of the substance approaches as the thickness increases to 40 nm, 65 nm, 80 nm, and 100 nm. From 100 nm or more, the same reflectance (color tone) continues. Conventionally, since only an indium film has been put into practical use, the metal film thickness that has been set to about 60 nm due to the problem of radio wave attenuation can be further increased by the method using a dry process such as sputtering according to the present invention. There is a possibility, and the effect that the range of the design spreads can be obtained.

  According to the present invention, various film forming metals can be selected by adopting a dry process, and by appropriately designing the film thickness, it has a sufficient metallic luster in appearance and has electromagnetic waves. A permeable metal coating for electromagnetic wave transmission can be provided. In addition, for example, a metal other than indium can be used. Therefore, by selecting a metal having a high resistance value such as chromium, there is a feature that even if the metal film thickness is increased, the radio wave transmission property is easily obtained. . Originally, the skin depth is related to radio wave attenuation, so there is a trade-off relationship between film thickness and metal feeling, and radio wave permeability. Sexual compatibility is possible.

  FIG. 2 is a schematic diagram of the sputtering apparatus according to the present embodiment.

  The sputtering apparatus according to the present embodiment performs film formation by sputtering on a workpiece in which a base layer 30 is formed on a base material 10. This sputtering apparatus includes a film forming chamber 60 composed of a main body 61 and an opening / closing part 62. The opening / closing part 62 is in a state of constituting a film forming chamber 60 sealed between the main body 61 and a loading / unloading position for loading a workpiece in which the base layer 30 is formed on the base material 10 via a packing 64. It can move between closed positions. In the state where the opening / closing part 62 is moved to the loading / unloading position, an opening for loading and unloading the workpiece having the base layer 30 formed on the substrate 10 to and from the film forming chamber 60 is formed on the side surface of the film forming chamber 60. Will be. In addition, a work placement portion 63 for placing a work on which the base layer 30 is formed on the base material 10 is disposed so as to pass through a passage hole formed in the opening / closing portion 62.

  The workpiece placement portion 63 functions as a counter electrode with respect to an electrode portion 71 described later, and moves relative to the opening / closing portion 62 in a state where a workpiece having the base layer 30 formed on the base material 10 is placed. It is possible. The work placement unit 63 is grounded by a grounding unit 69. The workpiece mounting portion 63 is configured by a so-called punching plate in which a large number of pores are formed. As shown in FIG. 2, the workpiece placement unit 63 opens the lower surface of the workpiece on which the base layer 30 is formed on the base material 10 according to the shape of the workpiece on which the base layer 30 is formed on the base material 10, or A hole for inserting a workpiece in which the base layer 30 is formed in the base material 10 is formed.

  Further, this sputtering apparatus includes a sputtering electrode 73 composed of an electrode portion 71 and a target material 72. The sputter electrode 73 is attached to the main body 61 in the film forming chamber 60 via an insulating member (not shown). The main body 61 constituting the film forming chamber 60 is grounded by a grounding portion 69. The sputter electrode 73 is connected to a DC power source 91.

  A main body 61 constituting the film forming chamber 60 is connected to a supply unit 83 for an inert gas such as argon via a pipe 85 via an on-off valve 81 and a flow rate adjusting valve 82. The pipe 85 includes a gas outlet 86 disposed near the sputter electrode 73.

  Further, the main body 61 constituting the film forming chamber 60 is connected to a turbo molecular pump 87 through an on-off valve 89, and this turbo molecular pump 87 is connected to an auxiliary pump 88 through an on-off valve 98. Yes. Further, the auxiliary pump 88 is also connected to a main body 61 constituting the film forming chamber 60 through an on-off valve 99.

  Next, the film forming operation by the sputtering apparatus having the above configuration will be described. FIG. 3 is a flowchart showing the film forming operation.

  When the film forming operation is executed by the sputtering apparatus, the work having the base layer 30 formed on the base material 10 is transferred into the film forming chamber (step S1). At this time, after the opening / closing part 62 is moved to the carry-in / carry-out position, the work in which the base layer 30 is formed on the base material 10 is placed on the work placing part 63.

  Next, the opening / closing part 62 is arranged at the closed position, and the pressure in the film forming chamber 60 is reduced from 0.05 Pascal to a low vacuum of about 1 Pascal (Step S2). Before the depressurization by the turbo molecular pump 87, the depressurization is performed at a high speed to about 100 Pascal using an auxiliary pump 88 such as a rotary pump. Thereafter, using the turbo molecular pump 37, the inside of the film forming chamber 60 is depressurized from 0.05 Pascal to a low vacuum of about 1 Pascal.

  Next, by opening the on-off valve 81, argon as an inert gas is supplied from the inert gas supply unit 83 into the film forming chamber 60, and the degree of vacuum in the film forming chamber 60 is 0.1-10. The inside of the film forming chamber 60 is filled with argon so as to be Pascal (step S3).

  Next, sputtering film formation is performed (step S4). For example, chromium is used as the target material 72, and a DC voltage is applied to the sputtering electrode 73 from the DC power supply 91. As a result, the chromium metal film 20 as the target material 72 is formed on the surface of the workpiece in which the base layer 30 is formed on the base material 10 by a sputtering phenomenon.

  When the sputtering film formation is completed, the film is vented into the film formation chamber 60. And the workpiece | work mounting part 63 is moved after arrange | positioning the opening-closing part 62 in a carrying in / out position, The workpiece | work which formed the base layer 30 in the base material 10 after the film-forming mounted on the workpiece | work mounting part 63 was carried out. Is carried out (step 5).

  Then, it is determined whether or not the processing for all the workpieces has been completed (step S6). When the processing for all the workpieces is completed, the apparatus is stopped. On the other hand, if there is an unprocessed work, the process returns to step S1.

[Fine island coating formation process]
Next, the fine island film forming process will be described. In the fine island film forming step, the conductive film formed in the conductive film forming step is heat-treated to form a fine crack 21 in the conductive film, and the fine island 22 surrounded by the fine crack 21 has a unit area (1 mm 2). ) A metal coating film 100 for transmitting electromagnetic waves is formed as an aggregate of the fine islands 22 existing in the number 2 to 10000. As described above, this heat treatment is referred to as “after baking” in the present invention. Further, in the fine island film forming step, by forming the fine cracks in the unit area (1 mm 2) by 1 to 10000 by the after baking, the number of fine islands is within the above range. Yes.

  After-baking temperature: Here, the heating temperature during the after-baking is preferably within the range of the glass transition temperature of the substrate 10 ± 50 ° C. By heating within the range of the glass transition temperature ± 50 ° C. of the base material 10, the thermal expansion deformation of the base material 10 is improved and the linear expansion coefficient between the base material 10 and the metal constituting the conductive film is increased. By utilizing the difference, the fine cracks 21 can be more uniformly dispersed on the entire surface of the conductive film. Here, the heating temperature during after-baking is more preferably within the range of the glass transition temperature of the substrate 10 ± 30 ° C., and particularly preferably within the range of the glass transition temperature of the substrate 10 ± 10 ° C.

  When the after-baking is performed at a glass transition temperature of the substrate 10 of less than −50 ° C., the thermal expansion deformation of the substrate 10 is small, and the interval at which the fine cracks 21 are formed on the conductive film formed on the surface of the substrate 10 is large. The number of fine islands existing in the unit area (1 mm 2) is reduced and the electromagnetic wave transmission attenuation amount is increased. In addition, when after-baking is performed at a temperature higher than the glass transition temperature + 50 ° C. of the base material 10, the base material 10 undergoes large thermal expansion deformation, and the conductive film that cannot follow the thermal expansion deformation of the base material 10 has a large crack. Is not preferable since a good metallic luster cannot be obtained. Here, from the viewpoint of forming the fine cracks 21 having a width within the above-mentioned range in the conductive film of the base material 10 within the above-mentioned range with an interval described above in an arbitrary straight line on the conductive film, at the time of after baking. The heating temperature is preferably a glass transition temperature of the substrate 10 of −30 ° C. or higher, and more preferably a glass transition temperature of the substrate 10 of −10 ° C. or higher. In addition, when the base material 10 is used as a design member such as an emblem of an automobile or various parts, it is preferable that the base material 10 is less deformed. Therefore, the heating temperature at the time of after baking is the glass transition temperature of the base material +30. The glass transition temperature of the substrate 10 is preferably + 10 ° C. or lower.

  After baking time: After baking is preferably performed for 1 to 60 minutes within the above temperature range. When the after baking time is less than 1 minute, the baking time is short, and it becomes difficult to form the fine cracks 21 in the conductive film formed in the conductive film forming step. Further, by performing after baking for 1 minute to 60 minutes, the fine cracks 21 having a width within the above-described range can be formed at an interval described above in an arbitrary straight line on the conductive film. Although it is possible to carry out after-baking for more than 60 minutes, it is reasonable that the after-baking time is 60 minutes or less from an economic point of view. There is a high possibility that the constituent resin of the material 10 or the base layer 30 is deteriorated.

  As described above, as a method of forming fine cracks in the conductive film, a method of forming fine cracks from the difference in linear expansion coefficient between the substrate and the metal film or between the base layer and the metal film by performing after baking. Although demonstrated, this invention is not limited to this, You may form a fine crack by a cooling process. That is, by cooling, fine cracks can be formed from the difference in shrinkage between the substrate and the metal film, or the difference in shrinkage between the underlayer and the metal film.

<Use Mode of Metal Film for Electromagnetic Wave Transmission According to the Present Invention>
The electromagnetic wave transmitting metal coating 100 according to the present invention described above can be suitably used as the metal coating 20 for decorating the cover member of the millimeter wave radar device. Hereinafter, the on-vehicle radar device and the cover member will be described.

  In-vehicle radar device: The in-vehicle radar device (not shown) according to the present invention receives a transmission means for transmitting millimeter waves as a transmission wave and a radio wave reflected by an object such as a preceding vehicle as a reception wave. The receiving means, the measuring means for measuring the time from when the transmitted wave is transmitted until the received wave is received, the distance from the object based on the time measured by the measuring means, the relative speed with the object, etc. And a calculation means for calculating. Such an on-vehicle radar device is generally disposed on the back side of the exterior member of the vehicle, such as the back side of the front grille of the vehicle. The exterior member of a vehicle is usually subjected to metal plating from the viewpoint of design. For this reason, the exterior member in which these in-vehicle radar devices are arranged is provided with an opening for emitting and receiving millimeter waves. The on-vehicle radar device according to the present invention includes a cover member for covering such an opening. In the present embodiment, the in-vehicle radar device is arranged behind the emblem 40 (or emblem 50) provided in the center of the front grille in the vehicle width direction, and the front grille emblem 40 (or emblem 50) is attached to the position. The following description will be made on the assumption that an opening for entering and exiting a millimeter wave is formed.

  Emblem: Emblems 40 and 50 as cover members according to the present invention are shown in FIGS. The emblem 40 shown in FIG. 4 (a) is related to the present invention, as shown in FIG. 4 (b), the background color coating layer 11 including a masking portion on the back side of a transparent substrate 10 such as polycarbonate resin. It has a layer structure in which 20 metal coating layers are sequentially laminated. In the background color coating layer 11, the design portion 41 representing the emblem 40 shown in FIG. 4A is masked when the background color paint is applied, and the masked design portion 41 (masking portion) has a background. The color paint is not applied. Further, in the example shown in FIG. 4A, the portion represented by the letter “K” is referred to as “design portion 41 representing the emblem 40”. Examples of the background color paint include a black paint that does not shield millimeter waves, but the background color is not limited to black. Since the base material 10 constituting the emblem 40 shown in FIG. 4 is transparent, the metal film 20 provided on the masked design portion 41 can be observed from the surface side of the base material 10. Therefore, when the emblem 40 is observed from the surface side of the base material 10, it appears that the metal film is provided only on the design portion 41 representing the letter “K” in the illustrated example. In order to observe the metal film through the base material 10, when the surface of the base material 10 is roughened, the base material 10 becomes opaque. In such a case, an underlayer 30 may be provided between the background color coating layer 11 and the metal coating 20.

  On the other hand, the emblem 50 shown in FIG. 5A is obtained by providing the metal coating 20 according to the present invention on the surface of the base material 10 formed into a shape representing the emblem 50, as shown in FIG. 5B. Furthermore, the surface of the base material 10 has a layer structure in which the metal coating 20 according to the present invention, the design coating layer 12 and the topcoat layer 13 are sequentially provided. The emblem 50 shown in FIG. 5A differs from the emblem 40 shown in FIG. 4A in that the metal film 20 is provided on the surface of the base material 10 instead of providing the metal film 20 on the back surface side of the base material 10. Since it has a layer structure, an opaque base material 10 can be used. As the base material 10, for example, ABS resin, AES resin, polycarbonate resin, cycloolefin polymer, or the like can be used. Moreover, since the base material 10 may be opaque, the surface of the base material 10 may be roughened. Further, even in the case of the emblem 50 illustrated in FIG. 5A, the base layer 30 may be provided between the base material 10 and the metal coating 20 as in the emblem 40 illustrated in FIG. 4. In this case, it is possible to use the underlayer 30 and the metal coating 20 as an exterior, and the change in the metal luminance (reflectance) is smaller than when the back side is visually observed as shown in FIG. A feeling is hard to be damaged.

  Here, in the emblem 40 shown in FIG. 4 and the emblem 50 shown in FIG. 5, the layer thickness of the metal coating 20 layer is preferably about 0.005 μm to 2 μm. As described above, when the thickness of the metal coating layer 20 is less than 0.005 μm, sufficient metallic luster cannot be expressed in appearance. On the other hand, when the thickness of the metal coating layer 20 exceeds 2 μm, the electromagnetic wave permeability tends to decrease, which is not preferable.

  Further, in the emblem 40 shown in FIG. 4 and the emblem 50 shown in FIG. 5, various film formation parameters (input power, distance between target and substrate, pressure in chamber, gas type and mixing ratio, substrate, substrate by dry process) The brightness can be adjusted by adjusting the reflectance of the metal coating without adjusting the temperature) and changing the metal material (target material).

  In the emblem 50 shown in FIG. 5, an interference optical layer (dielectric film) composed of one or more layers having electromagnetic wave permeability is provided on the metal coating 20, and the reflectance is controlled by the light interference effect. Various color tones with a metallic feel are possible.

  Furthermore, in the emblem 40 shown in FIG. 4, when the back side is in the viewing direction, the reflectance is controlled by the interference effect of light by providing an interference optical layer between the base layer 30 and the metal coating 20, Various color tones with a metallic feel are possible.

  Further, as a method capable of expressing various color tones, for example, in the emblem 40 shown in FIG. 4 and the emblem 50 shown in FIG. 5, a pigment or a dye is added to the base layer 30, the base material 10, and the protective layer 13. It is also possible to control the reflectance (metallic luster brightness and color tone).

  As described above, various film deposition parameters (input power, distance between target and substrate, pressure in chamber, gas type and mixing ratio, substrate temperature), method of providing interference optical layer, pigment or dye added Any of these methods can be used not only independently but also in various combinations to control various color tones.

  Further, in the emblem 40 shown in FIG. 4 and the emblem 50 shown in FIG. 5, a backlight such as an LED is installed at the bottom as viewed from the viewing direction, and the substrate 10, the base layer 30, and the protective layer 13 are materials that transmit light. The thickness of the metal film is set to 80 nm or less and light is transmitted, whereby the emblem 40 or emblem 50 that appears to emit light when viewed from the viewing direction can be provided. In this way, forming a half mirror with the thickness of the metal coating being equal to or less than a certain value can be a color tone of reflection by metallic luster in the daytime and a color tone in which light is transmitted by the backlight at night.

  Furthermore, the emblem in which the metal film is made into a half mirror as described above has various film formation parameters (input power, distance between target and substrate, pressure in the chamber, gas type and mixing ratio, substrate temperature) as described above. Various color tones may be controlled by arbitrarily combining a method of adjusting, a method of providing an interference optical layer, and a method of adding a pigment or a dye.

  Further, when the metal film is half-mirrored as described above, when the interference optical layer is provided, when a pigment or dye is added, or when a combination thereof is performed, light having a wavelength in the ultraviolet region is selectively selected. An electromagnetic wave transmissive metal film having a function of blocking ultraviolet rays can be obtained by absorbing the interference optical layer, pigment, dye, or the like.

  The present embodiment described above is an aspect of the present invention, and it is needless to say that the embodiment can be appropriately changed without departing from the gist of the present invention. For example, in the above-described embodiment, the cover member or the like disposed on the millimeter wave path of the millimeter wave radar device has been mainly described as the electromagnetic wave transmitting metal film. However, the electromagnetic wave transmitting metal film according to the present invention is a millimeter wave. The present invention is not limited to the use for decorating the cover member of the radar device. As described above, the metal film 100 for transmitting electromagnetic waves according to the present invention can be obtained by appropriately adjusting the number of fine islands 22 in a unit area, the width of the fine cracks 21, the thickness of the metal film 20, and the like. The transmission attenuation amount of 20 electromagnetic waves can be adjusted, and electromagnetic waves of various wavelengths can be selectively transmitted. For example, by adjusting the conditions for after baking so that the width of the fine cracks is 0.01 μm to 100 μm, the appearance has a sufficient metallic luster and selectively transmits light, It can be used as a light transmitting radio wave shielding material that blocks unnecessary external radio waves. The light transmitting radio wave shielding material can be used, for example, as a decorative coating for a design panel of a mobile phone or the like, and transmits light for notifying an incoming call, etc., and can transmit light that shields unnecessary radio waves from the outside. It can be used as a simple radio wave shielding material.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

  The metal layer for electromagnetic wave transmission of Example 1 was formed through the following underlayer forming process, conductive film forming process, and fine island film forming process in order.

<Underlayer formation process>
In Example 1, a commercially available polycarbonate resin having a thickness of 1000 μm was used as the base material. An undercoat layer having a thickness of 0.8 μm is formed by dip-coating a coating solution obtained by diluting a water-insoluble polyester resin (Plus Coat Z-850: Kyoyo Chemical Co., Ltd.) with a solvent on one surface of this substrate, and then drying. Formed.

<Conductive film formation process>
The substrate on which the underlayer is formed is placed in the film forming chamber of the sputtering apparatus, the inside of the film forming chamber is reduced to a predetermined pressure by a vacuum pump, and then argon gas is introduced to apply a DC voltage to the chromium target. A chromium conductive film having a thickness of 40 nm was formed on the surface of the underlayer by a sputtering phenomenon.

<Fine island film formation process>
In the fine island coating formation step, the base material on which the conductive film was formed was post-baked at 110 ° C. for 5 minutes to obtain an electromagnetic wave transmitting metal coating of Example 1. However, the linear expansion coefficient on the base material side is 7 × 10 −5, and the linear expansion coefficient of chromium is 6.8 × 10 −6. The glass transition temperature of the substrate is 130 ° C.

<Evaluation>
(1) Number of fine islands present in unit area FIG. 6 shows a stereomicrograph of the surface of the metal film for electromagnetic wave transmission of Example 1 taken. As shown in FIG. 6, the metal film for electromagnetic wave transmission obtained in Example 1 has about 200 fine islands in a unit area (1 mm 2). Moreover, about 200 fine cracks exist in the same unit area. As described above, by performing the fine island film forming step, an infinite number of fine cracks can be formed on the entire surface of the conductive film in the conductive film obtained in the conductive film forming step. As a result, the metal film can be formed as an electromagnetic wave transmitting metal film as an aggregate of fine islands in which countless fine islands are aggregated. However, a stereo microscope of model BX51RF (manufactured by Olympus) was used for taking a stereomicrograph shown in FIG. Further, the number of fine cracks (and the number of cracks) was counted as follows. First, in the present invention, one fine crack refers to one that does not intersect with other fine cracks in the length direction of the fine cracks and that contacts the end portions of the other fine cracks only at both ends of the fine cracks. . That is, in the present invention, in the length direction of the fine crack, the one having no contact with the end of the other fine crack or the intersection with the other fine crack between both ends thereof is regarded as one fine crack. The number of fine cracks present in the unit area was counted. Regarding the cracks, the number of cracks present in the unit area was counted in the same manner as the fine cracks.

(2) Attenuation amount of electromagnetic wave transmission In the fine island coating formation process of Example 1, the base material on which the conductive film was formed was after-baked at 110 ° C. for 5 minutes, thereby generating fine cracks. About the metal film for electromagnetic wave transmission obtained in Example 1, the electromagnetic wave transmission attenuation amount in 76 GHz and 79 GHz of each film was evaluated using the network analyzer by Keysight Technology. The results are shown in Table 2.

  As shown in Table 2, the electromagnetic wave transmission metal coating of Example 1 had a transmission attenuation amount of electromagnetic waves in the 76 GHz band of −0.817 dB and a transmission attenuation amount of electromagnetic waves in the 79 GHz band of −0.89 dB. As described above, the electromagnetic wave transmitting metal coating according to the present invention has a very small transmission attenuation amount of electromagnetic waves at 76 GHz and 79 GHz. For example, the cover member such as an emblem disposed on the millimeter wave path of the millimeter wave radar device is decorated. It can be suitably used as a metal coating.

  The electromagnetic wave transmitting metal coating 20 according to the present invention employs a dry process, and has an appearance that is sufficiently metallic luster using an inexpensive metal such as chromium, and is capable of transmitting electromagnetic waves. Metal coatings can be provided on the surface of various shaped substrates. In addition, various products can be provided with various metal coatings that have a sufficient metallic luster and can transmit electromagnetic waves in various products. Further, according to the present invention, by adjusting the number of fine islands in the unit area, the width of the fine cracks, etc., it is possible to selectively transmit electromagnetic waves of various wavelengths, or to adjust the transmission attenuation of electromagnetic waves. It becomes possible. Therefore, it is possible to provide metal coatings for various new uses such as a light transmitting radio wave shielding member that transmits light and shields radio waves.

DESCRIPTION OF SYMBOLS 10 ... Base material 20 ... Metal coating 21 ... Fine crack 22 ... Fine island 30 ... Underlayer
40, 50 ... Emblem 100 ... Metal coating 60 for electromagnetic wave transmission ... Deposition chamber 61 ... Sputtering device body 62 ... Opening / closing part 63 ... Work placement part 64 ... Packing 69 ... Grounding part 71 ... Electrode part 72 ... Target material 73 ... Sputter electrode 81 ... On-off valve 82 ... Flow rate adjusting valve 83 ... Inert gas supply part 85 ... Pipe 86 ... Gas jet 87 ... Turbo molecular pump 88 ... Auxiliary pump 89 ... Open / close valve 91 ... DC power supply 98 ... Open / close valve 99 ... Open / close valve

Claims (11)

It is a metal film capable of transmitting electromagnetic waves provided on the surface of the substrate,
The metal coating is an aggregate of fine islands surrounded by fine cracks, which are provided on the surface of the base material via a base layer, and are generated through a generation process by a dry process, and serve as an electromagnetic wave transmission path. It has a metallic luster,
2 to 10,000 fine islands exist in a unit area (1 mm ² ),
The linear expansion coefficient of the base layer provided on the surface of the substrate is larger than that of the metal coating, and the linear expansion coefficient on the substrate side is 1.01 or more times the linear expansion coefficient of the metal coating. The metal film for electromagnetic wave transmission , wherein the thickness is 100 times or less and the thickness of the base layer is 0.1 μm or more and 2 μm or less .   The metal film for electromagnetic wave transmission according to claim 1, wherein an average island diameter of the fine islands provided on the surface of the base material is 0.01 μm to 500 μm when observed with a scanning electron microscope.   The metal film for electromagnetic wave transmission according to claim 1 or 2, wherein a width of the fine crack is 0.01 µm to 100 µm.   The metal film for electromagnetic wave transmission according to any one of claims 1 to 3, wherein the metal film has a film thickness of 0.005 m to 2 m.   5. The non-conductive film obtained by heating or cooling the conductive film formed on the surface of the base material in the generation step by the dry process, according to claim 1. The metal film for electromagnetic wave transmission as described. 6. The metal film for electromagnetic wave transmission according to claim 5, wherein in the metal film, 1 to 10,000 fine cracks are present in a unit area (1 mm < ² >).   The metal substrate for electromagnetic wave transmission according to any one of claims 1 to 6, wherein the base material is a kind selected from insulating resin, ceramics, paper, glass, and fiber.   The metal coating is chromium, chromium alloy, stainless alloy, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, copper, copper alloy, tantalum, tantalum alloy, silver, silver alloy, tin, tin alloy, gold, At least one selected from gold alloy, platinum, platinum alloy, palladium, palladium alloy, silicon, silicon alloy, cobalt, cobalt alloy, niobium, niobium alloy, indium, indium alloy, tungsten, tungsten alloy, carbon, and carbon steel The metal film for electromagnetic wave transmission of any one of Claims 1-7 containing. A method of forming an electromagnetic wave transmitting metal coating that is capable of transmitting electromagnetic waves to the surface of a substrate and has a metallic luster,
A conductive film forming step of forming a conductive film having a metallic luster on the base layer provided on the surface of the substrate by a dry process;
By heating the conductive film formed in the conductive film forming step, a fine crack serving as an electromagnetic wave transmission path is formed in the conductive film, and a fine island surrounded by the fine crack has a unit area (1 mm ² ). A fine island coating forming step of forming the electromagnetic wave transmitting metal coating as a collection of 2 to 10000 fine islands therein,
In the fine island coating formation step,
The linear expansion coefficient of the base layer provided on the surface of the base material is larger than that of the metal film for electromagnetic wave transmission, and the linear expansion coefficient on the base material side is 1. The method for forming a metal film for electromagnetic wave transmission , wherein the thickness is from 01 to 100 and the thickness of the underlayer is from 0.1 to 2 μm . A method of forming an electromagnetic wave transmitting metal coating that is capable of transmitting electromagnetic waves to the surface of a substrate and has a metallic luster,
A conductive film forming step of forming a conductive film having a metallic luster on the base layer provided on the surface of the substrate by a dry process;
By heat-treating the conductive film formed in the conductive film forming step, 1 to 10,000 fine cracks serving as electromagnetic wave transmission paths are formed in the conductive film in a unit area (1 mm ² ), and the metal coating film A fine island film forming step of forming the electromagnetic wave transmitting metal film as an aggregate of fine islands surrounded by fine cracks,
In the fine island coating process,
The linear expansion coefficient of the base layer provided on the surface of the base material is larger than that of the metal film for electromagnetic wave transmission, and the linear expansion coefficient on the base material side is 1. The method for forming a metal film for electromagnetic wave transmission , wherein the thickness is from 01 to 100 and the thickness of the underlayer is from 0.1 to 2 μm .   An in-vehicle radar device using a cover member provided with the metal film for transmitting electromagnetic waves according to any one of claims 1 to 8 on a surface of a base material.