Radio wave transparent metal-like component and its manufacturing method

Abstract

An object of the present invention is to provide a radio wave-transmissive metal-like component having an excellent metallic luster. The present invention relates to a metal-like component comprising a substrate, an ion exchange resin layer formed on the substrate, and a metal particle layer formed on the ion exchange resin layer, wherein gaps exist between metal particles in the metal particle layer, and in a cross section of the metal-like component, the maximum horizontal length a (nm) of the metal particles, the maximum vertical length b (nm) of the metal particles, and the vertical length c (nm) of the portion of the metal particles embedded in the ion exchange resin layer satisfy the following conditions: 1.5 nm ≤ a ≤ 200 nm, b / a ≥ 1.25, and c ≥ 0, and the inclination angle θ of the metal particles relative to the bottom surface of the ion exchange resin layer satisfies the following conditions: 60° ≤ θ ≤ 90°.

Description

Technical Field

[0001] The present invention relates to a radio wave transparent metal-like component and a method for manufacturing the same. Background Art

[0002] Metal-like components are used in various products because they can give the surface of the product a high-brightness metallic luster and give it a sense of luxury. In addition to having an excellent metallic luster, metal-like components are also required to have various characteristics depending on the product they are used in. One of such characteristics is radio wave transmittance. For example, a millimeter-wave radar mounted on a car or the like is a device that measures the time it takes for radio waves in the millimeter wave band (radio waves with a wavelength of 1 to 10 mm) to be reflected from an obstacle and measures the distance to the obstacle. When a metal-like component is used in this millimeter-wave radar, the metal-like component is required to have excellent metallic luster and millimeter wave transmittance.

[0003] As a metal-like member having radio wave transparency, for example, Patent Document 1 discloses an electromagnetic wave transparent metallic luster member produced by sputtering a metal onto a substrate to form a discontinuous film. However, sputtering is a vacuum batch process, which increases the cost.

[0004] Patent Document 2 discloses a method for producing an electromagnetically transparent metal composite material, comprising forming a metal coating on a resin substrate and removing a portion of the formed metal coating to form regular island-shaped metal regions. Patent Document 2 discloses forming the metal coating by sputtering or vacuum deposition, and then removing a portion of the metal coating by masking the portion of the metal coating corresponding to the metal region and etching. However, this method involves numerous and complex steps, and etching is difficult to manage, making it difficult to achieve the desired structure.

[0005] In addition, Patent Document 3 discloses a metal-like film produced by a method different from sputtering or vapor deposition.

[0006] However, in metal-like components manufactured by conventional manufacturing methods, surface plasmon resonance occurs, causing the metal film to strongly absorb light of a specific wavelength in the visible light region, sometimes impairing the original color and gloss of the metal.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-69462

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2010-251899

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2021-155844 Summary of the Invention

[0012] Problems to be solved by the invention

[0013] As described above, conventional radio wave transparent metal-like components may sometimes lose the original color and gloss of the metal. Therefore, an object of the present invention is to provide a radio wave transparent metal-like component having excellent metallic gloss.

[0014] Means of solving problems

[0015] The inventors of the present invention have conducted various studies on methods for solving the above-mentioned problems and found that by making metal particles with a high aspect ratio stand upright relative to a substrate, a metal-like component can be obtained that has no special absorption in the visible light region and has excellent metallic luster and radio wave transmittance, thereby completing the present invention.

[0016] That is, the main idea of ​​the present invention is as follows.

[0017] [1] A metal-like component comprising a substrate, an ion exchange resin layer formed on the substrate, and a metal particle layer formed on the ion exchange resin layer,

[0018] There are gaps between the metal particles in the metal particle layer.

[0019] In the cross section of the metal-like member, the maximum length a of the metal particles in the horizontal direction, the maximum length b of the metal particles in the vertical direction, and the length c of the portion of the metal particles buried in the ion exchange resin layer in the vertical direction satisfy:

[0020] 1.5nm≤a≤200nm, b / a≥1.25, and c≥0

[0021] The units of length a, length b and length c are all nm.

[0022] An inclination angle θ of the metal particles relative to the bottom surface of the ion exchange resin layer satisfies the following: 60°≤θ≤90°.

[0023] [2] In the metal-like component as described in [1] above, the metal of the metal particles is one or more metals selected from Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co and Sn.

[0024] [3] In the metal-like component as described in [2] above, the metal of the metal particles is Ag.

[0025] [4] The metal-like member according to any one of [1] to [3] above, wherein the ion exchange resin of the ion exchange resin layer is a resin having a carboxyl group and / or a sulfonic group.

[0026] [5] As the metal-like component described in [4] above, the ion exchange resin of the ion exchange resin layer is polyamic acid.

[0027] [6] The metal-like component as described in any one of [1] to [5] above, wherein at least a portion of the surface of the metal particles is covered with a polymer adsorbed on the metal surface.

[0028] [7] In the metal-like component described in [6] above, the weight average molecular weight of the polymer adsorbed on the metal surface is 10,000 to 360,000.

[0029] [8] In the metal-like component described in [6] or [7] above, the polymer adsorbed on the metal surface is at least one selected from polyethylene polymers, polyethylene glycol polymers and polyacrylic acid polymers.

[0030] [9] A method for manufacturing a metal-like component according to any one of [1] to [8], comprising:

[0031] An ion exchange resin layer is formed on the surface of the substrate.

[0032] The metal ions are introduced into the ion exchange resin layer by treating the ion exchange resin layer with a solution containing metal ions.

[0033] The ion exchange resin layer into which the metal ions have been introduced is treated with a solution containing 0.1 mM to 500 mM of a polymer capable of adsorbing on a metal surface and 0.01 mM to 10 mM of a reducing agent to reduce the metal ions and precipitate metal particles on the surface of the ion exchange resin layer.

[0034] Effects of the Invention

[0035] According to the present invention, a radio wave transparent metal-like member having excellent metallic luster can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A is a schematic cross-sectional view showing one embodiment of the metal-like member of the present invention. Figure 1 B is a partially enlarged schematic cross-sectional view of an embodiment of the metal-like component of the present invention.

[0037] Figure 2 A represents a TEM image of a cross section of the metal-like component of Example 3. Figure 2 B shows a TEM image of a cross section of the metal sample member of Comparative Example 1.

[0038] Figure 3 3D-TEM image of the metal-like component of Example 3.

[0039] Figure 4 The absorption spectra of the metal-like components of Examples 2 and 3 and Comparative Example 1 are shown.

[0040] Description of the accompanying drawings

[0041] 10: Metal-like member, 11: Matrix, 12: Ion exchange resin layer, 13: Metal particle, 14: Polymer adsorbed on the metal surface, a: Maximum horizontal length of the metal particle (nm), b: Maximum vertical length of the metal particle (nm), c: Vertical length of the portion of the metal particle buried in the ion exchange resin layer (nm), θ: Inclination angle of the metal particle relative to the bottom surface of the ion exchange resin layer (°) DETAILED DESCRIPTION

[0042] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0043] The present invention relates to a metal-like component comprising a substrate having an ion exchange resin layer on its surface and a metal particle layer formed on the ion exchange resin layer side of the substrate. Specifically, the metal-like component of the present invention comprises a substrate, an ion exchange resin layer formed on the substrate, and a metal particle layer formed on the ion exchange resin layer.

[0044] Figure 1 A is a schematic cross-sectional view showing an embodiment of a metal-like member of the present invention. Figure 1 As shown in Figure A, the metal-like component 10 includes a substrate 11, an ion exchange resin layer 12 formed on the substrate 11, and a layer of metal particles 13 formed on the ion exchange resin layer 12. That is, the metal-like component 10 is composed of layers of the substrate 11, the ion exchange resin layer 12, and the metal particles 13 stacked in this order from bottom to top. In a preferred embodiment, the metal-like component 10 is composed of the substrate 11, the ion exchange resin layer 12 directly stacked on the substrate 11, and the metal particles 13 directly stacked on the ion exchange resin layer 12. In the metal particle layer, gaps exist between the metal particles. The metal-like component may also have an ion exchange resin layer and a metal particle layer on both sides of the substrate.

[0045] The substrate is not particularly limited, and a base film, a resin molded product base, a glass base, and an article to be imparted with metallic luster can be used.

[0046] As the substrate film, for example, a resin film can be used. Transparent films are preferred, and examples thereof include polyethylene terephthalate, polycarbonate, polymethyl methacrylate, and polyacrylic acids, with polycarbonate and polyacrylic acids being preferred. Furthermore, resins containing groups such as carboxyl and / or sulfonic groups that can be converted into ion-exchange groups can also be used as the resin film. Examples of such resins include polycarbonate, polyacrylic acids, polyimide, and polystyrene, with polyimide having a high functional group density being preferred.

[0047] Examples of resin molded article substrates include resins for automobile logos, etc. Examples of articles to be imparted with metallic luster include door handles of automobiles equipped with smart keys, mobile phone housings, computer housings, refrigerators, and the like.

[0048] The thickness of the substrate is usually 10 μm to 10 mm, preferably 10 μm to 5 mm.

[0049] The ion exchange resin layer is formed on the surface of the substrate. As long as the ion exchange resin has an ion exchange group capable of performing ion exchange with metal ions, for example, a resin having a carboxyl group and / or a sulfonic group can be used. As the ion exchange resin, polyamic acid and styrene-divinylbenzene copolymer are preferred, and polyamic acid is more preferred. The ion exchange resin can also be a form in which the ion exchange group is converted into an arbitrary form by heat treatment or the like. For example, polyamic acid is converted into polyimide by heat treatment dehydration.

[0050] The thickness of the ion exchange resin layer is usually 0.5 to 10 μm, preferably 0.7 to 1.5 μm.

[0051] The metal particle layer is formed on the surface of the ion exchange resin layer. The metal of the metal particles is preferably Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co, and Sn. From the perspective of high brightness, Ag, Al, and Cr are more preferred, and Ag is particularly preferred.

[0052] In the metal particle layer, the metal particles are formed into an island shape, for example, and there are gaps between the metal particles. That is, the metal particle layer is a discontinuous film of metal particles. The gaps between the metal particles only need to exist between at least a part of the metal particles, and preferably there are gaps between each metal particle. The gaps between the metal particles are generally 1nm to 1000nm, preferably 1nm to 100nm. The gaps between the metal particles refer to the average length of the linear gaps measured by connecting straight lines between the central parts of the adjacent particles, for example, 100 randomly selected from the surface image of the metal-like component obtained by a field emission scanning electron microscope (FE-SEM) (50,000 times), and using image analysis software Image J. By having gaps between the metal particles, the metal-like component has excellent radio wave transmittance.

[0053] The metal-like structure of the present invention is characterized by aligning metal particles with a high aspect ratio in an upright orientation relative to the ion exchange resin layer and substrate. This shifts the absorption peak due to surface plasmon resonance, resulting in a metal film with no specific absorption in the visible light region and possessing the inherent color and luster of the metal.

[0054] Figure 1 B is a partially enlarged schematic cross-sectional view of an embodiment of the metal-like component of the present invention. Figure 1 As shown in FIG. B, in one embodiment, metal particles 13 are embedded in the ion exchange resin layer 12. The metal particles 13 have a high aspect ratio and are oriented upright relative to the ion exchange resin layer 12 and the substrate (not shown). In one embodiment, a portion of the surface of the metal particles 13 is covered by a polymer 14 adsorbed on the metal surface. Figure 1 In B, a represents the maximum length of the metal particle in the horizontal direction (nm), b represents the maximum length of the metal particle in the vertical direction (nm), and c represents the length of the portion of the metal particle embedded in the ion exchange resin layer in the vertical direction (nm). Figure 1 In B, θ represents the tilt angle (°) of the metal particles relative to the bottom surface of the ion exchange resin layer.

[0055] In the metal-like component of the present invention, metal particles with a high aspect ratio are oriented upright relative to the ion exchange resin layer and the substrate, which is expressed by the ratio b / a of the maximum length b (nm) in the vertical direction of the metal particles to the maximum length a (nm) in the horizontal direction and the inclination angle θ (°) of the metal particles.

[0056] The maximum horizontal length a of the metal particles refers to their maximum length in the horizontal direction relative to the surfaces of the ion exchange resin layer and substrate. The maximum vertical length b of the metal particles refers to their maximum length in the direction perpendicular to the surfaces of the ion exchange resin layer and substrate. Furthermore, the metal particles may be inclined at an angle θ (°) relative to the bottom surface of the ion exchange resin layer. Therefore, the vertical direction does not necessarily mean a 90° angle relative to the surfaces of the ion exchange resin layer and substrate; it may be an angle between 60° and 90°, depending on the angle θ (°).

[0057] The maximum length a of the metal particles in the horizontal direction and the maximum length b in the vertical direction can be determined by obtaining a cross-sectional image of the metal-like component by a scanning transmission electron microscope (STEM), randomly extracting, for example, 100 particles from the particles present in a 50,000-fold field of view, calculating the length using image analysis software Image J, and finding the average value (number average). In addition, the maximum length a of the metal particles in the horizontal direction can also be determined by obtaining a surface image of the metal-like component using a field emission scanning electron microscope (FE-SEM) (50,000 times) and finding the average value (number average) of the maximum diameter of the particles. In addition, it can be considered that the maximum length a of the metal particles in the horizontal direction is the same value regardless of which one is measured using STEM and FE-SEM.

[0058] The maximum horizontal length a (nm) of the metal particles is 1.5 nm ≤ a ≤ 200 nm. When the length a is within this range, the metal particles reflect visible light and transmit millimeter waves, exhibiting radio wave transparency. The length a (nm) is preferably 5 nm ≤ a ≤ 150 nm, more preferably 5 nm ≤ a ≤ 100 nm, and particularly preferably 5 nm ≤ a < 50 nm.

[0059] The maximum length b (nm) of the metal particles in the vertical direction is preferably 1.9 nm ≤ b ≤ 500 nm, more preferably 10 nm ≤ b ≤ 100 nm. If the length b is within this range, a metal film having the original color and luster of the metal can be obtained.

[0060] The ratio b / a (also referred to as the aspect ratio) of the maximum vertical length b of the metal particles to the maximum horizontal length a is b / a ≥ 1.25, preferably b / a ≥ 1.5, and more preferably b / a ≥ 2.0. When the aspect ratio b / a of the metal particles is 1.25 or greater, the absorption peak due to surface plasmon resonance is shifted, thereby suppressing absorption of specific wavelengths in the visible light region. This allows for the production of a metal film having the inherent color and luster of the metal without any specific absorption in the visible light region.

[0061] The vertical length c (nm) of the portion of the metal particles embedded in the ion exchange resin layer satisfies c ≥ 0. That is, the metal particles are in contact with the surface of the ion exchange resin layer (c = 0), or a part of them is embedded in the ion exchange resin layer (c > 0). From the perspective of high durability, the length c (nm) is preferably c > 0. The length c (nm) is less than the maximum vertical length b (nm) of the metal particles (c < b), preferably c < 50 nm, more preferably c < 25 nm, and particularly preferably c < 10 nm. Similar to the lengths a and b, the length c of the metal particles can be obtained by acquiring a cross-sectional image of the metal-like member using a scanning transmission electron microscope (STEM), randomly extracting the particles present in the 50,000-fold field of view, and using the image analysis software Image J to determine. As Figure 1 shown in B, the metal particles are in contact with the surface of the ion exchange resin layer at both ends. The length c of the metal particles is calculated by calculating the vertical (90°) length from the straight line passing through the bottom surface of the particles in the ion exchange resin layer to the two ends of the particles in contact with the surface of the ion exchange resin layer in the cross-sectional image. For example, this length is calculated for 25 to 50 particles respectively, and the average value (number average) of these lengths is obtained.

[0062] The inclination angle θ (°) of the metal particles with respect to the bottom surface of the ion exchange resin layer (i.e., the surface on the substrate side) is 60° ≤ θ ≤ 90°, preferably 75° ≤ θ ≤ 90°, and more preferably 80° ≤ θ ≤ 90°. By making the inclination angle θ of the metal particles within this range, the metal film can have the natural color and luster of the metal.

[0063] Similar to the measurement of the length of the metal particles, the inclination angle θ of the metal particles can be obtained by analyzing the TEM image obtained by STEM using Image J. Randomly extract, for example, 100 particles from the particles present in the 50,000-fold field of view, and calculate the angle formed by the central axis in the vertical direction of the metal particles and the bottom surface of the ion exchange resin layer. The central axis in the vertical direction of the metal particles corresponds to the maximum vertical length b of the metal particles.

[0064] A structure in which metal particles with a high aspect ratio are vertically oriented can be obtained by using a polymer that can adsorb on the metal surface in the manufacturing method of the metal-like member described below. Therefore, it is preferred that at least a part of the surface of the metal particles is covered with a polymer that adsorbs on the metal surface. Since the polymer adsorbed on the metal surface adsorbs on a specific crystal plane of the metal, usually a part of the surface of the metal particles is covered with this polymer.

[0065] From the perspective of high adsorption to the metal surface, the weight-average molecular weight of the polymer adsorbed on the metal surface is preferably 10,000 to 360,000, and more preferably 10,000 to 100,000.

[0066] As polymers that adsorb onto metal surfaces, polymers containing nitrogen (N), sulfur (S), or oxygen (O) lone pairs of electrons within their molecular chain structures can be used, preferably those containing oxygen lone pairs. Due to the varying atomic filling rates on each crystal face of a metal, the electronic states on the crystal surface vary. In the manufacture of metal-like components, polymers containing N, S, or O lone pairs of electrons can be used to control the aspect ratio and tilt angle of the metal particles by allowing the lone pairs of electrons to adsorb onto specific crystal faces of the metal.

[0067] The polymer adsorbed on the metal surface is not particularly limited, and examples thereof include polyethylene polymers such as polyvinyl acetate, polyvinyl alcohol, poly-N-vinylacetamide, and polyvinyl pyrrolidone, polyethylene glycol polymers such as polyethylene glycol, polyepichlorohydrin, and polybromohydrin, polyacrylic acid polymers such as polyacrylic acid, polymethacrylic acid, sodium polyacrylate, and sodium polymethacrylate, and poly(amide amine) dendrimers synthesized by alternating addition of ethylenediamine and methyl acrylate, etc. Preferred are polyethylene polymers, polyethylene glycol polymers, and polyacrylic acid polymers, preferred are polyvinyl alcohol and polyvinyl pyrrolidone, more preferred are polyethylene glycol and sodium polyacrylate, and particularly preferred is polyvinyl pyrrolidone.

[0068] The metal-like component preferably has an L* value of 75 or higher, indicating high brightness. The L* value of the metal-like component can be measured, for example, using a spectrocolorimeter using the SCI method (including regular reflection light). The spectral reflectance R(λ) is calculated from the ratio of the spectral radiant flux at a wavelength λ reflected from the object to the spectral radiant flux at a wavelength λ reflected from a completely diffuse reflecting surface (JIS Z 8722). The spectral reflectance R(λ) is then used to calculate the index value L* of the CIE1976 (L*, a*, b*) color system specified by the International Commission on Illumination (CIE).

[0069] The a* value of the metal-like member is preferably -2 to 2, and the color tone change with respect to red and green hues is small. The a* value of the metal-like member can be measured in the same manner as the L* value.

[0070] The b* value of the metal-like member is preferably -5 to 6, and the color tone change with respect to the yellow and blue hues is small. The b* value of the metal-like member can be measured in the same manner as the L* value.

[0071] The metal-like member preferably has an a* value of -2 to 2, and a b* value of -5 to 6. When the metal-like member has an a* value and a b* value within this range, the metal film has the original color or luster of the metal and has excellent metallic luster.

[0072] The present invention also relates to a method for manufacturing the aforementioned metal-like component. The method comprises: forming an ion exchange resin layer on the surface of a substrate (step 1); treating the ion exchange resin layer with a solution containing metal ions to introduce metal ions into the ion exchange resin layer (step 2); and treating the ion exchange resin layer into which the metal ions have been introduced with a solution containing a polymer capable of adsorbing on a metal surface and a reducing agent to reduce the metal ions and precipitate metal particles on the surface of the ion exchange resin layer (step 3).

[0073] In step 1, an ion exchange resin layer is formed on the surface of a substrate. As the substrate, the above-mentioned metal-like member can be used.

[0074] In step 1, the ion exchange resin layer can be formed by, for example, applying a solution containing an ion exchange resin (hereinafter also referred to as an ion exchange resin solution) to the substrate surface and drying to remove the solvent. The ion exchange resin solution is not particularly limited to the coating method on the substrate surface and can be applied by a known coating method, such as a nozzle flow method, a spray method, an immersion method, a roller method, and a rotary method. In one embodiment, when a roller method is used, a micro-gravure coater or a knife coater can be used.

[0075] The application of the ion exchange resin solution to the substrate surface can be performed under conditions that allow the formation of an ion exchange resin layer having a desired thickness.

[0076] The ion exchange resin solution applied on the substrate surface may be dried under conditions that sufficiently remove the solvent, and is usually dried at 10° C. to 120° C. for 0.5 to 4 hours.

[0077] In another embodiment, the ion exchange resin layer can also be formed by modifying the surface of the matrix. In this embodiment, as the matrix, a resin film with a group that can be converted into an ion exchange group can be used. As such a resin film, a functional group that can be hydrolyzed can be used, and by hydrolysis, the ion exchange group can be imported into the resin film. As such a resin film, a resin with a group that can be converted into a carboxyl and / or sulfo group by hydrolysis can be used, and for example polycarbonate, polyacrylic acid, polyimide etc. can be listed, preferably a polyimide with a high functional group density. When using polyimide, by hydrolysis, a polyamic acid layer with a carboxyl group as an ion exchange group is formed on the surface. In addition, polystyrene can also be used as a resin film, for example, by sulfonating the surface with concentrated sulfuric acid, a layer with a sulfo group can be formed on the surface.

[0078] In step 2, the ion exchange resin layer is treated with a solution containing metal ions (hereinafter referred to as the metal ion solution). This treatment replaces the ion exchange groups of the ion exchange resin layer with metal ions through ion exchange, thereby introducing metal ions into the ion exchange resin layer. The ion exchange groups may not be completely replaced by the metal ions, and some may remain as ion exchange groups.

[0079] There is no special limitation on the metal ions. For metal-like components, the ions are the ions of the above-mentioned metals, such as Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co and Sn. From the perspective of high brightness, the ions are preferably Ag, Al and Cr, and the Ag ions are more preferred.

[0080] The metal ion solution may be any solution containing the metal ions. The metal ion solution is not particularly limited, and a salt solution of the metal ions may be used. Examples of the salt include nitrates, sulfates, chlorides, carbonates, acetates, and phosphates.

[0081] The concentration of the metal ion solution is usually 1 mM (mmol / l) to 500 mM, preferably 50 mM to 150 mM.

[0082] Treatment with a metal ion solution can be performed, for example, by immersing the substrate having an ion exchange resin layer formed on its surface in the metal ion solution. Regarding the conditions for treatment with the metal ion solution, the treatment temperature is preferably 10°C to 50°C, more preferably 20°C to 30°C, and the treatment time is preferably 1 minute to 60 minutes, more preferably 15 minutes to 45 minutes.

[0083] In step 3, the ion exchange resin layer, into which the metal ions have been introduced, is treated with a solution containing a polymer capable of adsorbing on metal surfaces and a reducing agent. This treatment reduces the metal ions to metal, and metal particles precipitate on the surface of the ion exchange resin layer. Since the metal ions diffuse onto the surface of the ion exchange resin layer in the presence of the reducing agent and are reduced to metal, the resulting metal-like structure comprises a substrate, an ion exchange resin layer formed thereon, and a layer of metal particles formed on the ion exchange resin layer. In one embodiment, at least a portion of the surface of the metal particles is covered by the polymer adsorbed on the metal surface.

[0084] In step 3, by using a polymer capable of adsorbing onto the metal surface together with a reducing agent, metal particles with a high aspect ratio can be oriented upright relative to the ion exchange resin layer and substrate. Furthermore, by using a polymer capable of adsorbing onto the metal surface, the polymer covers at least a portion of the surface of the metal particles, thereby protecting the metal particles. Therefore, when, for example, a resin layer is provided to protect the metal particles, pretreatment is unnecessary, reducing the number of steps.

[0085] Regarding the polymer adsorbed on the metal surface, the metal-like components are as described above.

[0086] The concentration of the polymer in the solution containing the polymer capable of adsorbing on metal surfaces and the reducing agent is 0.1 mM to 500 mM, preferably 0.1 mM to 30 mM. When the concentration of the polymer capable of adsorbing on metal surfaces is 0.1 mM or greater, the aspect ratio of the metal particles can be controlled within the specified range of the present invention, resulting in an excellent metallic luster of the metal film. When the concentration is 500 mM or less, metal ions can be reliably reduced to metal particles.

[0087] The reducing agent is not particularly limited, and examples thereof include phosphoric acid compounds, boron hydride compounds, and hydrazine derivatives. Examples of phosphoric acid compounds include hypophosphorous acid, phosphorous acid, pyrophosphoric acid, and polyphosphoric acid. Furthermore, examples of boron hydride compounds include methyl hexaborane, dimethylamine borane, diethylamine borane, morpholine borane, pyridylamine borane, piperidine borane, ethylenediamine borane, ethylenediamine diborane, tert-butylamine borane, imidazole borane, methoxyethylamine borane, and sodium borohydride. Furthermore, examples of hydrazine derivatives include hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, and hydrazine derivatives such as pyrazoles, triazoles, and hydrazine derivatives. In addition to pyrazole, examples of pyrazole derivatives include 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone. Furthermore, examples of triazoles include 4-amino-1,2,4-triazole and 1,2,3-triazole. As hydrazides, adipic acid hydrazide, maleic acid hydrazide, carbohydrazide, etc. can be used. The reducing agent is preferably dimethylamine borane (DMAB).

[0088] The reducing agent concentration in the solution containing the polymer capable of adsorbing on the metal surface and the reducing agent is 0.01 mM to 10 mM, preferably 0.1 mM to 5 mM. When the reducing agent concentration is 0.01 mM or higher, the adhesion between the metal particles and the ion exchange resin layer is enhanced, resulting in improved durability and wear resistance. When the reducing agent concentration is 10 mM or lower, the metal particle layer is converted into a discontinuous film with gaps between the metal particles, resulting in excellent radio wave transparency.

[0089] The molar concentration ratio of the reducing agent to the polymer (reducing agent:polymer) in the solution containing the polymer capable of adsorbing on the metal surface is usually 1:0.01 to 1:50,000, preferably 1:0.05 to 1:500.

[0090] Treatment using a solution containing a polymer capable of adsorbing on the metal surface and a reducing agent can be performed, for example, by immersing a substrate having an ion exchange resin layer on its surface in the solution. The treatment conditions are: a temperature of typically 10°C to 60°C, preferably 25°C to 50°C, and a time of typically 10 seconds to 60 minutes, preferably 30 seconds to 30 minutes. By adjusting the treatment time and temperature according to the reducing power of the reducing agent, a metal film can be obtained in which gaps exist between the precipitated metal particles and the metal particles have a predetermined length.

[0091] The treatment is carried out using a solution containing a polymer and a reducing agent that can be adsorbed on the metal surface, preferably while stirring the solution. In this treatment, the tilt angle θ of the metal particles can be adjusted by changing the solution stirring speed. Specifically, when the solution stirring speed is fast, the particles grow along the flow direction, and the tilt angle θ of the metal particles tends to become smaller. Therefore, the treatment is carried out using a solution containing a polymer and a reducing agent that can be adsorbed on the metal surface, and the solution can be stirred while the tilt angle θ of the metal particles is 60°≤θ≤90°. In one embodiment, when a stirrer is used to stir a solution containing a polymer and a reducing agent, when the rotation speed is 0rpm~1250rpm (preferably 0rpm~500rpm), the tilt angle θ of the metal particles can be made to be: 60°≤θ≤90°. In a preferred embodiment, when a stirrer is used to stir a solution containing a polymer and a reducing agent, when the rotation speed is 0rpm~300rpm, the tilt angle θ of the metal particles can be made to be: 80°≤θ≤90°. The stirring conditions of the solution are appropriately selected in consideration of other processing conditions so as to achieve the desired tilt angle θ of the metal particles.

[0092] The method for manufacturing a metal-like component of the present invention may further include a step 4 of heat treatment after step 3. This treatment can transform the ion exchange resin layer into any desired form. In one embodiment, when the ion exchange resin contains carboxyl groups and / or sulfonic groups, these groups are dehydrated by heat treatment. For example, polyamic acid is converted into polyimide by heat treatment. The heat treatment temperature is generally 100°C to 300°C.

[0093] Since the metal-like component of the present invention has radio wave transmittance and excellent metallic luster, it can be suitably used as a metal-like component for products requiring radio wave transmittance.

[0094] Example

[0095] Hereinafter, the present invention will be described in more detail using examples, but the technical scope of the present invention is not limited to these examples.

[0096] Example 1

[0097] 250 μL of a polyamic acid solution (Pyre-ML (registered trademark) RC-5019, manufactured by IST Co., Ltd.) was spin-coated on the surface of a polycarbonate (PC) film (thickness 400 μm, manufactured by Sumika Akrill Sales Co., Ltd., Tecnoloy (registered trademark) C000) at 1000 rpm for 15 seconds and then at 3000 rpm for 60 seconds, and the mixture was vacuum-dried at 40° C. for 1 hour to form a polyamic acid layer on the surface of the polycarbonate film.

[0098] Silver nitrate (AgNO3) (manufactured by Nakalai Tesku, 31018-14) was dissolved in pure water to prepare a 100 mM AgNO3 solution. After washing the membrane surface with water, the membrane was immersed in the AgNO3 solution at room temperature for 30 minutes to introduce Ag ions into the polyamic acid layer through ion exchange.

[0099] Dimethylamine borane (DMAB) (Wako, 028-08401) was dissolved in pure water, and polyvinyl pyrrolidone (PVP) with a weight-average molecular weight of 10,000 was added to this solution and mixed to prepare a mixed solution of 1.5 mM DMAB and 0.1 mM PVP. A stirrer was added to the mixed solution of DMAB and PVP, and while the mixed solution was stirred at 200 rpm, a film was immersed in the mixed solution at 30°C for 10 minutes to reduce Ag ions and precipitate Ag particles on the surface of the polyamic acid layer. The film was then washed with water and dried to obtain a metal-like component.

[0100] Example 2

[0101] The metal-like component of Example 2 was obtained in the same manner as in Example 1, except that the PVP concentration in the mixed solution of DMAB and PVP was changed to 1.0 mM.

[0102] Example 3

[0103] The metal-like component of Example 3 was obtained in the same manner as in Example 1, except that the PVP concentration in the mixed solution of DMAB and PVP was changed to 5.0 mM.

[0104] Example 4

[0105] The metal-like component of Example 4 was obtained in the same manner as in Example 1, except that the PVP concentration in the mixed solution of DMAB and PVP was changed to 500 mM.

[0106] Example 5

[0107] The metal-like component of Example 5 was obtained in the same manner as in Example 3 except that the DMAB concentration in the mixed solution of DMAB and PVP was changed to 0.01 mM.

[0108] Example 6

[0109] The metal-like component of Example 6 was obtained in the same manner as in Example 3 except that the DMAB concentration in the mixed solution of DMAB and PVP was changed to 0.05 mM.

[0110] Example 7

[0111] The metal-like component of Example 7 was obtained in the same manner as in Example 3 except that the DMAB concentration in the mixed solution of DMAB and PVP was changed to 10 mM.

[0112] Example 8

[0113] The metal-like component of Example 8 was obtained in the same manner as in Example 3 except that the weight-average molecular weight of PVP was changed to 40,000.

[0114] Example 9

[0115] The metal-like component of Example 9 was obtained in the same manner as in Example 3 except that the weight-average molecular weight of PVP was changed to 360,000.

[0116] Example 10

[0117] The metal sample component of Example 10 was obtained in the same manner as in Example 3 except that the rotation speed of the mixed solution when the film was immersed in the mixed solution of DMAB and PVP was changed to 1000 rpm and the tilt angle θ of the metal particles was changed to 75°.

[0118] Example 11

[0119] The metal-like component of Example 11 was obtained in the same manner as in Example 3 except that the rotation speed of the mixed solution when the film was immersed in the mixed solution of DMAB and PVP was changed to 1250 rpm and the tilt angle θ of the metal particles was changed to 60°.

[0120] Comparative Example 1

[0121] A metal sample component of Comparative Example 1 was obtained in the same manner as in Example 1 except that the mixed solution of DMAB and PVP was replaced with a DMAB solution.

[0122] Comparative Example 2

[0123] A metal sample member of Comparative Example 2 was obtained in the same manner as in Example 1 except that the PVP concentration in the mixed solution of DMAB and PVP was changed to 5000 mM.

[0124] Comparative Example 3

[0125] A metal sample member of Comparative Example 3 was obtained in the same manner as in Example 3 except that the DMAB concentration in the mixed solution of DMAB and PVP was changed to 100 mM.

[0126] Comparative Example 4

[0127] A metal sample member of Comparative Example 4 was obtained in the same manner as in Example 3 except that the rotation speed of the mixed solution when the film was immersed in the DMAB and PVP mixed solution was changed to 1500 rpm and the tilt angle θ of the metal particles was changed to 55°.

[0128] The following measurements were performed on the metal sample members of Examples 1 to 11 and Comparative Examples 1 to 4.

[0129] Color difference measurement

[0130] L*, a*, and b* were measured as follows. Spectral reflectance R(λ) was calculated as the ratio of the spectral radiant flux at wavelength λ reflected from an object to the spectral radiant flux at wavelength λ reflected from a perfectly diffuse reflecting surface (JIS Z8722). A CMS-35SP spectrophotometer manufactured by Murakami Color Research Laboratory was used for measurement using the SCI method (including specular reflection).

[0131] Using the calculated spectral reflectance R(λ), calculate the index values ​​L*, a*, and b* of the CIE1976 (L*, a*, b*) color system specified by the International Commission on Illumination (CIE). Here, the L* value is an index that describes the brightness of the color. The larger the L* value, the brighter the color. The a* value is an index that describes the intensity relative to red and green hues. A larger a* value (positive value) indicates a more reddish hue, and a smaller a* value (negative value) indicates a more greenish hue. The b* value is an index that describes the intensity relative to yellow and blue hues. A larger b* value (positive value) indicates a more yellowish hue, and a smaller b* value (negative value) indicates a more bluish hue.

[0132] Absorption spectrum determination

[0133] Absorption spectra were measured in the visible light range of 380 nm to 780 nm using the formula: Absorbance (%) = 100% - (Transmittance (%) + Reflectance (%)). Absorption spectra were measured using a spectrophotometer (UV-3600i Plus (positive), manufactured by Shimadzu Corporation) with a spectral bandwidth of 2 nm and a wavelength scan rate of 1000 nm / min. Transmittance was measured with the spectrophotometer positioned opposite the light source (across the sample), while reflectance was measured with the spectrophotometer positioned on the light source side.

[0134] Lengths a and b of metal particles

[0135] The maximum length a (nm) in the horizontal direction and the maximum length b (nm) in the vertical direction of the Ag particles were measured using a scanning transmission electron microscope (STEM). Specifically, a cross-section of a metal-like component was photographed using a scanning transmission electron microscope (JEOL, JEM-ARM300F). 100 particles were randomly selected from the particles present in the 50,000-fold field of view. The outer edge of each particle was encircled with an ellipse. The maximum length a (nm) in the horizontal direction and the maximum length b (nm) in the vertical direction were calculated using the image analysis software Image J, and their average values ​​were obtained.

[0136] Length c of partially embedded metal particles

[0137] The length c of the vertical direction of the part where the Ag particles are embedded in the polyamic acid layer is measured as follows using a scanning transmission electron microscope (STEM). The surface of the polyamic acid layer is confirmed from the TEM image of the cross section of the metal-like component, and a straight line is drawn through the two ends of the particle in contact with the surface of the polyamic acid layer. In addition, although the surface of the polyamic acid layer can be visually confirmed in the TEM image due to the different contrasts between the polyamic acid layer and the Ag particles, when it is difficult to find the surface, the boundary can be clearly determined by adjusting the contrast through image processing or detecting N atoms through EDX. Next, a straight line is drawn through the bottom surface of the Ag particles in the polyamic acid layer, and a line is pulled perpendicularly (90°) from the straight line relative to one end of the particle in contact with the surface of the polyamic acid layer to measure its length (length c). The length is also measured in the same way for the other end of the particle. This process is performed randomly at 50 to 100 locations to calculate the average value.

[0138] The tilt angle θ of the metal particles

[0139] The angle formed by the bottom surface of metal particles (Ag particles) and ion exchange resin layer (polyamic acid layer) is set to the inclination angle θ of metal particles for measurement. Similarly to the length a and b of metal particles, the TEM image of the cross section of the metal sample component obtained by STEM is analyzed with Image J, 100 are randomly selected from the particles existing in 50,000 times the visual field, and the angle formed by the central axis of the bottom surface of polyamic acid layer and the vertical direction of the particle is calculated. Here, the central axis of the particle refers to the axis drawn in the form of the center of the top and the center of the bottom of the particle, which is equivalent to the maximum length b of the vertical direction of the metal particles.

[0140] 3D-TEM

[0141] The cross section of the metal sample was rotated multiple times by 1 degree using a scanning transmission electron microscope (Talos F200X manufactured by Thermo Fisher Scientific) to obtain images, which were then synthesized to obtain an image.

[0142] Millimeter wave attenuation

[0143] The millimeter wave attenuation of the metal-like component is measured to evaluate the millimeter wave transmission. The millimeter wave attenuation is determined by measuring the unidirectional attenuation using a millimeter wave characteristic measuring device with a horn antenna, and doubling the measured value. Specifically, the millimeter wave is irradiated from the horn antenna on the transmitting signal side to the measuring sample, and the intensity of the millimeter wave passing through the sample and incident on the horn antenna on the receiving signal side is measured to determine the attenuation in one direction. The distance between the horn antennas on the transmitting signal side and the receiving signal side is 95 cm. The sample is set to an elevation angle of 17° relative to the horn antenna on the transmitting signal side, and the distance between the sample and the horn antenna on the transmitting signal side is set to approximately 40 mm. The measurement is performed at 77 GHz, an applicable frequency for vehicle-mounted millimeter wave radar.

[0144] Figure 2 A represents a TEM image of a cross section of the metal-like component of Example 3, Figure 2 B represents a TEM image of a cross section of the metal sample member of Comparative Example 1. Figure 3 3D-TEM image of the metal-like component of Example 3. Figure 2 A. Figure 2 B and Figure 3 As shown, in the metal-like component of Example 3, compared with the metal-like component of Comparative Example 1, the Ag particles with a high aspect ratio are oriented upright relative to the polyamic acid layer and the PC film thereunder, and gaps exist between the Ag particles.

[0145] For the metal-like members of Examples 1 to 11 and Comparative Examples 1 to 4, the manufacturing conditions and evaluation results are shown in Table 1. In Table 1, for millimeter-wave transmissivity, a millimeter-wave attenuation of 0.2 dB or less for the round trip is judged as good (〇), and a round-trip exceeding 0.2 dB is judged as bad (×). In addition, in Table 1, when the millimeter-wave transmissivity is good (〇), all of 75 ≤ L*, -2 < a* < 2, and -5 < b* ≤ 6 are satisfied, and the change in hue is sufficiently small, it is judged as good (〇), and when at least one of these conditions is not satisfied, it is judged as bad (×). In addition, in Comparative Example 2, since the Ag particle layer was not formed, it was judged as bad.

[0146]

Table 1

[0147]

[0148] As shown in Table ۱, in Comparative Example ۱ where PVP was not used, b / a < ۱.۲۵, the a* value of the metal film was 6.5, and the b* value was 8, resulting in a hue with red and yellow, and the metal film did not have the original color and luster of the metal. On the other hand, in Examples 1 to 11 where PVP was used, b / a ≥ 1.25, the hue change of the metal film was small, the metal film had the original color and luster of the metal, and had excellent metallic luster. From Comparative Example 1 and Examples 1 to 11, it can be seen that in order to obtain a metal film with little hue change, it is necessary to use PVP that can adsorb on the metal surface in the reduction process, and the metal particles have a high aspect ratio satisfying b / a ≥ 1.25.

[0149] From Examples 1 to 4 and Comparative Example 2, it can be known that if the PVP concentration in the mixed solution of DMAB and PVP is 0.1 mM to 500 mM (Examples 1 to 4), Ag ions can be reliably reduced to Ag particles, but if the PVP concentration is 5000 mM (Comparative Example 2), Ag ions are not reduced to Ag particles, indicating that no Ag particle layer is formed. According to Examples 3, 8, and 9, within the range of the weight-average molecular weight of PVP from 10,000 to 360,000, the Ag particles have a high aspect ratio, and the metal film has excellent metallic luster.

[0150] From Examples 3, 5 to 7 and Comparative Example 3, it can be seen that when the DMAB concentration in the mixed solution of DMAB and PVP is 0.01 mM to 10 mM (Examples 3, 5 to 7), since the reducing power of the reducing agent is within an appropriate range, the Ag particle layer becomes a discontinuous film, and the metal-like member has excellent millimeter-wave transmissivity. However, if the DMAB concentration is 100 mM (Comparative Example 3), the reducing power of the reducing agent is too strong, so the Ag particle layer becomes a continuous film, and the millimeter-wave transmissivity of the metal-like member deteriorates.

[0151] According to Examples 3, 10, 11 and Comparative Example 4, when the metal particle tilt angle θ is in the range of 60° to 90°, the b* value of the metal film is 6 or less, and the color tone becomes less yellow, showing the original color and luster of the metal.

[0152] Figure 4 is the absorption spectrum of the metal-like components of Examples 2, 3 and Comparative Example 1. Figure 4 As shown, in Comparative Example 1, the metal film strongly absorbs light of a specific wavelength (380nm to 480nm) in the visible light region, and the color of the metal film changes, but the metal-like components of Examples 2 and 3 have no special absorption in the visible light region, the color of the metal film changes little, and has the original color or luster of the metal.

Claims

1. A metal-like member comprising a substrate, an ion exchange resin layer formed on the substrate, and a metal particle layer formed on the ion exchange resin layer, There are gaps between the metal particles in the metal particle layer. In the cross section of the metal-like member, the maximum length a of the metal particles in the horizontal direction, the maximum length b of the metal particles in the vertical direction, and the length c of the portion of the metal particles buried in the ion exchange resin layer in the vertical direction satisfy: 1.5nm≤a≤200nm, b / a≥1.25, and c≥0 The units of length a, length b and length c are all nm. The inclination angle θ of the metal particles relative to the bottom surface of the ion exchange resin layer satisfies: 60°≤θ≤90°.

2. The metal-like component as described in claim 1, wherein the metal of the metal particles is one or more metals selected from Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co and Sn.

3. The metal-like component according to claim 2, wherein the metal of the metal particles is Ag.

4. The metal-like member according to claim 1, wherein the ion exchange resin of the ion exchange resin layer is a resin having a carboxyl group and / or a sulfonic group.

5. The metal-like component according to claim 4, wherein the ion exchange resin of the ion exchange resin layer is polyamic acid.

6. The metal-like component according to claim 1, wherein at least a portion of the surface of the metal particles is covered with a polymer adsorbed on the metal surface.

7. The metal-like component according to claim 6, wherein the weight average molecular weight of the polymer adsorbed on the metal surface is 10,000 to 360,000.

8. The metal-like component according to claim 6 or 7, wherein the polymer adsorbed on the metal surface is at least one selected from polyethylene polymers, polyethylene glycol polymers and polyacrylic acid polymers.

9. The method for manufacturing the metal-like component according to claim 1, comprising: An ion exchange resin layer is formed on the surface of the substrate. The metal ions are introduced into the ion exchange resin layer by treating the ion exchange resin layer with a solution containing metal ions. The ion exchange resin layer into which the metal ions have been introduced is treated with a solution containing 0.1 mM to 500 mM of a polymer capable of adsorbing on a metal surface and 0.01 mM to 10 mM of a reducing agent to reduce the metal ions and precipitate metal particles on the surface of the ion exchange resin layer.

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