Metal-tone film and method for producing the same

Abstract

To provide a metallic tone film having both of a high brightness and an excellent electric wave permeability.SOLUTION: The invention relates to a metallic tone film having a resin base material and a metal particle layer formed on the resin base material, and a manufacturing method thereof. In the metal particle layer, there is a gap between metal particles, the metal particle contains Pd and at least another type of metal other than Pd, and a Pd content in the metal particle is 1.6 mole% to 34.4 mole%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a metallic film and a method for manufacturing the same.

Background Art

[0002] Metallic films are used in various products because they can impart a high-luminance metallic luster to the surface of products and give a high-class feeling. Metallic films require various characteristics depending on the products to be used, and one of such characteristics is radio wave transmissivity. For example, a millimeter-wave radar mounted on an automobile or the like is a device that irradiates radio waves in the millimeter-wave band (radio waves with a wavelength of 1 to 10 mm), measures the time it takes for the radio waves to be reflected by an obstacle and return, and measures the distance to the obstacle. When using a metallic film for this millimeter-wave radar, the metallic film is required to have high luminance and excellent radio wave transmissivity.

[0003] As a metallic film having radio wave transmissivity, for example, a film formed by depositing or sputtering indium (In), tin (Sn), or chromium (Cr) on the surface of a substrate is widely known (Patent Documents 1 to 3). Also known are those using other metals instead of In, Sn, or Cr. For example, Patent Document 4 discloses a radio wave transmissive metallic luster member including a substrate having radio wave transmissivity and an aluminum layer having discontinuous regions directly formed on the continuous surface of the substrate, and the metallic luster member is produced by sputtering. Further, Patent Document 5 discloses a metal film composed of more than 10,000 fine metal regions per unit area (1 mm 2 ) for electromagnetic wave transmission in which adjacent fine metal regions are electrically isolated, and a metal film made of palladium or a palladium alloy is disclosed. Patent Document 6 also discloses a metallic film produced by a method different from deposition, sputtering, or plating. Patent Document 7 also discloses a composition containing palladium-coated anisotropic gold nanoparticles, and it is disclosed that this is used as a black colorant.

[0004] Metal-tone films using In, Sn, Cr, etc., as disclosed in Patent Documents 1 to 3, have limitations in brightness. Also, sputtering treatment, which is widely used in the production of metal-tone films using In, Sn, Cr, etc., and is also used in the production of metal-tone films using aluminum in Patent Document 4, is a vacuum batch process, so the cost is high. Further, when the metal film is thickened to increase the brightness, it becomes a continuous film partially, so the radio wave permeability decreases. Also, in the metal-tone films as disclosed in Patent Documents 5 or 6, depending on the use of the metal-tone film, it may be desired to further increase the brightness of the metal film in some cases.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0006] As described above, the manufacturing cost of conventional metallic films may be high. Further, in conventional metallic films, depending on the use of the metallic film, it may be desirable to further increase the luminance of the metal film. Therefore, an object of the present invention is to provide a metallic film that achieves both high luminance and excellent radio wave transmissivity.

Means for Solving the Problems

[0007] As a result of various studies on means for solving the above problems, the present inventors have found that by adding a minute amount of palladium to metal particles, the luminance of the metal film can be remarkably improved, and completed the present invention.

[0008] That is, the gist of the present invention is as follows. (1) A metallic film having a resin substrate and a metal particle layer formed on the resin substrate, wherein in the metal particle layer, there are gaps between the metal particles, the metal particles contain Pd and at least one other metal other than Pd, and the Pd content in the metal particles is 1.6 mol% to 34.4 mol%. (2) The metallic film according to (1) above, wherein the other metal is selected from Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co, and Sn. (3) The metallic film according to (1) or (2) above, wherein the other metal is Ag. (4) The metallic film according to any one of (1) to (3) above, wherein the resin substrate is polyimide. (5) A method for manufacturing the metallic film according to any one of (1) to (4) above, Step 1 of preparing a resin substrate having a layer having a functional group capable of ion-exchanging with metal ions on the surface; Step 2 of treating the resin substrate having a layer having a functional group capable of ion-exchanging with metal ions on the surface with a solution containing Pd ions and ions of at least one other metal other than Pd, and introducing Pd ions and the ions of the other metal into the layer by ion exchange; Step 3 of treating a resin substrate having a layer with Pd ions and ions of the other metal introduced thereon with a reducing agent to deposit metal particles containing Pd and the other metal on the surface A method for manufacturing a metallic film, comprising the above. (6) The method for manufacturing a metallic film according to (5) above, further comprising Step 4 of performing heat treatment after Step 3. (7) The method for manufacturing a metallic film according to (5) or (6) above, wherein in Step 1, by modifying the surface of the resin substrate, a layer having a functional group capable of ion-exchanging with the metal ions is formed on the surface of the resin substrate.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a metallic film that combines high brightness and excellent radio wave transparency.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0012] The present invention relates to a metallic film having a resin substrate and a metal particle layer formed thereon. In the metal particle layer, there are gaps between the metal particles, that is, the metal particle layer is a discontinuous film of metal particles.

[0013] FIG. 1 shows a schematic cross-sectional view of an embodiment of the metallic film of the present invention. The metallic film 10 has a resin substrate 11 and a metal particle layer 12 formed on the surface of the resin substrate 11. In the metal particle layer 12, there are gaps between the metal particles. Further, the metallic film may have metal particle layers on both sides of the resin substrate.

[0014] The resin substrate is preferably made of an insulating material. As the resin substrate, for example, a resin having a group convertible to a carboxyl group and / or a sulfo group can be used. The resin substrate is not particularly limited, and for example, polycarbonate, acrylic, polystyrene, polyimide, polyethylene terephthalate, polymethyl methacrylate, and ABS can be used. Polycarbonate, acrylic, and polyimide are preferred, and polyimide is more preferred.

[0015] As the resin substrate, a resin film can be used without particular limitation. The thickness of the resin substrate is usually 10 μm to 5 mm, preferably 20 μm to 800 μm.

[0016] The resin substrate may have a film layer on its surface. The metallic film having a film layer can be obtained, for example, by the second embodiment of the manufacturing method of the present invention described below.

[0017] FIG. 2 shows a schematic cross-sectional view of an embodiment of the metallic film having a film layer. As shown in FIG. 2, the metallic film 20 has a resin substrate 21 having a film layer 22 on its surface and a metal particle layer 23 formed thereon. In the metallic film 20, the resin substrate 21, the film layer 22, and the metal particle layer 23 are laminated in this order from the bottom. In the metal particle layer 23, there are gaps between the metal particles. Note that the film layer and the metal particle layer may be formed on both sides of the resin substrate.

[0018] The film layer is preferably a resin film layer. As the resin constituting the resin film layer, those having a functional group capable of ion-exchanging with metal ions can be used. Resins having a carboxyl group and / or a sulfo group are preferred, polyamic acid and styrene-divinylbenzene copolymer are more preferred, and polyamic acid is particularly preferred. In one embodiment, when the resin constituting the film layer is polyamic acid, the film layer may be in a form in which polyamic acid is dehydrated and cyclized to be converted into polyimide.

[0019] In one embodiment, it is preferable that the resin substrate is polycarbonate or acrylic, and the film layer is polyamic acid or polyimide.

[0020] The thickness of the film layer is usually smaller than the thickness of the resin substrate, for example, 0.5 μm to 10 μm, preferably 0.5 μm to 9.0 μm, and more preferably 0.7 μm to 1.5 μm.

[0021] The metal particle layer is formed on the resin substrate. In the metal particle layer, the metal particles are formed, for example, in an island shape, that is, the metal particles are independent of each other, and there are gaps between the metal particles. Due to the gaps between the metal particles, the film exhibits radio wave permeability. Preferably, a part of the metal particles is in a state of being buried in the resin substrate or the surface of the film layer on its surface. Therefore, the metal particles are not easily peeled off, have high stability, and the metallic film has high corrosion resistance and high weather resistance.

[0022] The metal particles contain Pd and at least one other metal other than Pd, that is, alloy particles of Pd and at least one other metal other than Pd. The other metal is not particularly limited and is, for example, Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co, and Sn. From the viewpoint of having high brightness, Ag, Al, and Cr are preferred, and Ag is more preferred.

[0023] The Pd content in the metal particles is 1.6 mol% to 34.4 mol% with respect to the metal particles. When the Pd content in the metal particles is within this range, the L value of the metallic film becomes larger and the brightness becomes higher as compared with the case where the metal particles do not contain Pd. From the viewpoint of obtaining a metallic film with higher brightness, the Pd content in the metal particles is preferably 1.6 mol% to 22.0 mol%, more preferably 1.6 mol% to 9.6 mol%. The Pd content in the metal particles can be determined, for example, by dissolving the metal particle layer in a solvent, mass-analyzing the solution in which the metal constituting the metal particles is dissolved, quantifying the amount of metal ions, and calculating it as mol%. In the metallic film of the present invention, it is considered that Pd is contained almost uniformly in each metal particle.

[0024] The shape of the metal particles is not particularly limited and may be, for example, spherical, ellipsoidal, plate-like, flake-like, scaly, dendritic, rod-like, wire-like, and irregular.

[0025] The metal particles usually have an average particle size of 5 nm to 200 nm, preferably 10 nm to 200 nm, more preferably 10 nm to 150 nm. When the average particle size of the metal particles is 5 nm to 200 nm, the metal particles can reflect visible light and transmit millimeter waves, and have excellent radio wave permeability. In the present invention, the average particle size of the metal particles refers to the number average particle size of the major axis (maximum diameter) of the particles measured from the FE-SEM (50,000 times) observation image on the film surface. When the metal particles are spherical, the average particle size refers to the number average particle size of the diameters of the metal particles.

[0026] The thickness of the metal particle layer is usually 5 nm to 200 nm, preferably 10 nm to 150 nm.

[0027] The metallic tone film has an L value that is usually over 75, preferably over 80, and more preferably over 85. The L value of the metallic tone film can be measured, for example, by using a spectrocolorimeter in the SCI mode (including regular reflection light), obtaining the spectral reflectance R(λ) as the ratio of the spectral radiant flux of wavelength λ reflected from the object to the spectral radiant flux of wavelength λ reflected from a perfect diffusing reflector (JIS Z 8722), and calculating the index value L* of the CIE1976 (L*, a*, b*) color system defined by the International Commission on Illumination (CIE) using the spectral reflectance R(λ).

[0028] The present invention also relates to a method for manufacturing the above-mentioned metallic tone film. The method for manufacturing the metallic tone film of the present invention includes: preparing a resin substrate having a layer with functional groups capable of ion-exchanging with metal ions on the surface (step 1); treating the resin substrate having a layer with functional groups capable of ion-exchanging with metal ions on the surface with a solution containing Pd ions and ions of at least one other metal other than Pd, and introducing Pd ions and the ions of the other metal into the layer by ion exchange (step 2); and treating the resin substrate having a layer with Pd ions and the ions of the other metal introduced thereon with a reducing agent to deposit metal particles containing Pd and the other metal on the surface (step 3). The method for manufacturing the metallic tone film of the present invention may further include step 4 of heat-treating the resin substrate on which metal particles containing Pd and the other metal are deposited after step 3.

[0029] In step 1, a resin substrate having a layer with functional groups capable of ion-exchanging with metal ions on the surface is prepared. As the resin substrate, those described above for the metallic tone film can be used.

[0030] In Step 1, a resin substrate having a layer with metal ions and ion-exchangeable functional groups on its surface can be prepared by forming this layer on the surface of the resin substrate. The formation of the layer having metal ions and ion-exchangeable functional groups may be performed, for example, by modifying the surface of the resin substrate (First Embodiment), or by forming a film layer having metal ions and ion-exchangeable functional groups on the surface of the resin substrate (Second Embodiment). That is, the layer having metal ions and ion-exchangeable functional groups may be a layer derived from the resin substrate, or may be a new layer not derived from the resin substrate. Hereinafter, the first embodiment and the second embodiment of the method for manufacturing the metallic film of the present invention will be described.

[0031] <First Embodiment> The method of the first embodiment includes forming a layer (modified layer) having metal ions and ion-exchangeable functional groups on the surface of the resin substrate by modifying the surface of the resin substrate (Step 1), treating the resin substrate having the modified layer on its surface with a solution containing Pd ions and ions of at least one other metal other than Pd (hereinafter also referred to as a metal ion solution) to introduce Pd ions and the ions of the other metal into the modified layer by ion exchange (Step 2), and treating the resin substrate having the modified layer into which Pd ions and the ions of the other metal have been introduced with a reducing agent to deposit metal particles containing Pd and the other metal on the surface to form a metal particle layer (Step 3).

[0032] In Step 1, a modified layer having metal ions and ion-exchangeable functional groups is formed on the surface of the resin substrate by modifying the surface of the resin substrate.

[0033] The resin substrate only needs to be one that can modify its surface, preferably having a hydrolyzable functional group and being able to introduce a functional group exchangeable with metal ions by hydrolysis. As the resin substrate, for example, a resin having a group convertible to a carboxyl group and / or a sulfo group by hydrolysis can be used. Examples of such resin substrates include polycarbonate, acrylic, polyimide, etc., and polyimide with a high functional group density is preferred. When polyimide is used as the resin substrate, a polyamic acid layer is formed on the substrate surface by hydrolysis, and a carboxyl group is generated as a functional group exchangeable with metal ions. Also, as the resin substrate, a resin capable of modifying the surface and introducing a sulfo group can be used. Examples of such a resin include polystyrene, and for example, a sulfo group can be introduced by sulfonating the surface with concentrated sulfuric acid.

[0034] In Step 1, for example, the surface of the resin substrate can be treated with an alkaline solution to form a modified layer having a functional group exchangeable with metal ions by hydrolysis.

[0035] The alkaline solution is not particularly limited, and examples include NaOH, KOH, LiOH, CaO, and Ca(OH)2, etc., and KOH is preferred.

[0036] The concentration of the alkaline solution is usually 1 M (mol / l) to 100 M, preferably 1 M to 10 M.

[0037] The treatment conditions with the alkaline solution are that the treatment temperature is usually 15°C to 60°C, preferably 25°C to 50°C, and the treatment time is usually 10 seconds to 10 minutes, preferably 30 seconds to 5 minutes.

[0038] In Step 1, the density of the functional groups exchangeable with metal ions in the formed modified layer is preferably 1 mol / l to 10 mol / l, more preferably 5 mol / l to 8 mol / l.

[0039] In Step 1, the thickness of the modified layer is preferably 0.5 μm to 10 μm, more preferably 0.7 μm to 1.5 μm.

[0040] In Step 2, the resin substrate having the modified layer on its surface is treated with a solution containing Pd ions and ions of at least one other metal other than Pd. By this treatment, through ion exchange, the functional groups in the modified layer are replaced with Pd ions and ions of other metals, and these metal ions are introduced into the modified layer.

[0041] The ions of the other metal are the ions of the other metal for the metal-tone film and are not particularly limited. For example, they are ions of Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co, and Sn. From the viewpoint of having high brightness, they are preferably ions of Ag, Al, and Cr, and more preferably Ag ions.

[0042] The solution containing Pd ions and ions of other metals can be prepared, for example, by mixing a solution of a compound containing Pd ions and a solution of a compound containing ions of other metals, adding a compound (solid) containing ions of other metals to a solution of a compound containing Pd ions, or adding a compound (solid) containing Pd ions to a solution of a compound containing ions of other metals.

[0043] As the compound containing Pd ions, for example, salts and complexes of Pd ions can be used and are not particularly limited. For example, nitrates, sulfates, chlorides, carbonates, acetates, and phosphates of Pd ions, and bis(triphenylphosphine)palladium(II) diacetate, bis(benzonitrile)dichloropalladium(II), bis(acetonitrile)dichloropalladium(II), dichloro(ethylenediamine)palladium(II), dichloro(1,10-phenanthroline)palladium(II), dichlorobis(triphenylphosphine)palladium(II), tetraamminepalladium(II) nitrate, etc. can be mentioned, and tetraamminepalladium nitrate is preferred.

[0044] The concentration of Pd ions in the solution is usually 0.002 mM to 50 mM, preferably 0.02 mM to 20 mM.

[0045] As the compound containing ions of other metals, for example, salts and complexes of ions of other metals can be used. Examples of the salts include nitrates, sulfates, chlorides, carbonates, acetates, phosphates and the like. When the ions of other metals are Ag ions, silver nitrate is preferably used.

[0046] The concentration of ions of other metals in the solution is usually 1 mM to 500 mM, preferably 50 mM to 150 mM.

[0047] The molar ratio of Pd ions to ions of other metals in the solution (Pd ions: ions of other metals) may be selected so as to satisfy a predetermined Pd content in the obtained metal-like film, and is usually 1:5 to 1:500, preferably 1:15 to 1:500, more preferably 1:90 to 1:500.

[0048] The mass ratio of the compound containing Pd ions in the solution to the compound containing ions of other metals may be selected so as to satisfy a predetermined Pd content in the obtained metal-like film. For example, in one embodiment, when tetraamminepalladium nitrate is used as the compound containing Pd ions and silver nitrate is used as the compound containing ions of other metals, the mass ratio of tetraamminepalladium nitrate to silver nitrate in the solution is usually 1:5 to 1:300, preferably 1:8 to 1:300, more preferably 1:50 to 1:300.

[0049] The treatment with the metal ion solution can be carried out, for example, by immersing the resin substrate in the metal ion solution. The treatment conditions with the metal ion solution are as follows: the treatment temperature is preferably 10°C to 50°C, more preferably 20°C to 30°C, and the treatment time is preferably 10 seconds to 30 minutes, more preferably 1 minute to 10 minutes.

[0050] In Step 3, a resin substrate having a modified layer introduced with Pd ions and ions of other metals on its surface is treated with a reducing agent. By this treatment, metal particles containing Pd and other metals are deposited on the surface, and a metallic film with a metal particle layer formed is obtained. Since the metal ions diffuse to the surface where the reducing agent exists and are reduced to metal particles, the resulting metallic film has a resin substrate, a modified layer formed thereon, and a metal particle layer formed thereon. In the present invention, since a part of each of the deposited metal particles is buried in the modified layer (the surface of the resin substrate), they do not easily peel off.

[0051] The reducing agent is not particularly limited, and examples thereof include phosphoric acid compounds, borohydride compounds, and hydrazine derivatives. Examples of the phosphoric acid compounds include hypophosphorous acid, phosphorous acid, pyrophosphoric acid, and polyphosphoric acid. Examples of the borohydride compounds include methylhexaborane, dimethylamine borane, diethylamine borane, morpholine borane, pyridineamine borane, piperidine borane, ethylenediamine borane, ethylenediamine bisborane, t-butylamine borane, imidazole borane, methoxyethylamine borane, and sodium borohydride. Examples of the hydrazine derivatives that can be used include hydrazine salts such as hydrazine sulfate and hydrazine hydrochloride, and hydrazine derivatives such as pyrazoles, triazoles, and hydrazides. Among these, as pyrazoles, in addition to pyrazole, pyrazole derivatives such as 3,5-dimethylpyrazole and 3-methyl-5-pyrazolone can be used. As triazoles, 4-amino-1,2,4-triazole, 1,2,3-triazole, etc. can be used. As hydrazides, adipic acid hydrazide, maleic acid hydrazide, carbohydrazide, etc. can be used. The reducing agent is preferably dimethylamine borane (DMAB).

[0052] The treatment with the reducing agent can be carried out, for example, by immersing the resin substrate in a reducing agent solution. The concentration of the reducing agent solution is usually from 0.01 mM to 100 mM, preferably from 0.01 mM to 10 mM, more preferably from 0.01 mM to 1 mM, and particularly preferably from 0.01 mM to 0.5 mM. The treatment conditions with the reducing agent are such that the treatment temperature is preferably from 10°C to 60°C, more preferably from 20°C to 50°C, and the treatment time is preferably from 10 seconds to 60 minutes, more preferably from 30 seconds to 30 minutes. By applying such reduction conditions, it is possible to improve the adhesion, durability, and abrasion resistance of the metal particles while reducing the amount of the reducing agent used.

[0053] The method of the first embodiment may further include step 4 of heat-treating the resin substrate having metal particles containing Pd and other metals deposited on the surface after step 3 to convert the modified layer. In one embodiment, when the modified layer contains carboxyl groups and / or sulfonic groups, these groups are dehydrated by the heat treatment. In this embodiment, the heat treatment temperature is usually from 100°C to 300°C.

[0054] The metal-tone film obtained by the method of the first embodiment includes a resin substrate, a modified layer formed thereon, and a metal particle layer formed thereon. Also, when step 4 is performed, since the modified layer is converted into the resin substrate, the obtained metal-tone film includes a resin substrate and a metal particle layer formed thereon. The metal-tone film shown in FIG. 1 is obtained by performing steps 1 to 4 in the method of the first embodiment. As described above, the metal-tone film 10 shown in FIG. 1 has a resin substrate 11 and a metal particle layer 12 formed on the surface of the resin substrate 11.

[0055] In a preferred embodiment of the method of the first embodiment, the resin substrate is polyimide and the other metal is Ag. In this embodiment, the manufacturing method of the present invention hydrolyzes polyimide by modifying the surface of the polyimide resin substrate with an alkaline solution (for example, KOH) to form a polyamic acid layer having carboxyl groups on the surface of the resin substrate (step 1); treating the polyimide resin substrate having the polyamic acid layer on the surface with a solution containing Pd ions and Ag ions, and substituting H of the carboxyl group with Pd ions and Ag ions by ion exchange to introduce Pd ions and Ag ions into the polyamic acid layer (step 2); and treating the polyimide resin substrate having the polyamic acid layer into which Pd ions and Ag ions are introduced with a reducing agent (for example, dimethylamine borane) to precipitate alloy particles of Pd and Ag on the surface of the polyamic acid layer (step 3). In this embodiment, after step 3, step 4 of converting the polyamic acid layer into polyimide by heat treatment may be performed.

[0056] <Second Embodiment> The method of the second embodiment includes: forming a film layer having a functional group capable of ion exchange with metal ions on the surface of a resin substrate (step 1); treating the resin substrate having the film layer on the surface with a solution containing Pd ions and ions of at least one other metal other than Pd, and introducing Pd ions and the ions of the other metal into the film layer by ion exchange (step 2); and treating the resin substrate having the film layer into which Pd ions and the ions of the other metal are introduced with a reducing agent to precipitate metal particles containing Pd and the other metal on the surface to form a metal particle layer (step 3).

[0057] As the resin substrate, a resin film can be used without particular limitation. As the resin film, a transparent film is preferable, and examples thereof include polyethylene terephthalate, polycarbonate, polymethyl methacrylate, and acrylic, and polycarbonate and acrylic are preferable. In the method of the second embodiment, since a film layer having a functional group capable of ion-exchanging with metal ions is formed on the resin substrate, the resin substrate does not necessarily have a group convertible into a functional group capable of ion-exchanging with metal ions as in the method of the first embodiment.

[0058] The film layer only needs to have a functional group capable of ion-exchanging with metal ions. For example, a resin having a carboxyl group and / or a sulfo group can be used. As the film layer, a polyamic acid and a styrene-divinylbenzene copolymer are preferable, and a polyamic acid is more preferable.

[0059] The film layer can be formed, for example, by applying a solution of the resin for forming the film layer onto the resin substrate and drying to remove the solvent.

[0060] The thickness of the film layer is usually 0.5 μm to 10 μm, preferably 0.7 μm to 1.5 μm.

[0061] The density of the functional group capable of ion-exchanging with metal ions in the film layer is preferably 1 mol / l to 10 mol / l, more preferably 5 mol / l to 8 mol / l.

[0062] The metal ions are not particularly limited and are, for example, ions of Ag, Al, Au, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Zr, Nb, Mo, In, Co, and Sn. From the viewpoint of having high brightness, ions of Ag, Al, and Cr are preferable, and Ag ions are more preferable.

[0063] In Step 2, a resin substrate having a film layer on its surface is treated with a solution containing Pd ions and ions of at least one other metal other than Pd. By this treatment, functional groups exchangeable with metal ions are replaced with Pd ions and the ions of the other metal by ion exchange, and these metal ions are introduced into the film layer.

[0064] Regarding the metal ion solution and its concentration used in Step 2, it is as described above for the method of the first embodiment.

[0065] The treatment with the metal ion solution can be carried out, for example, by immersing a resin substrate having a film layer on its surface in a solution containing Pd ions and ions of at least one other metal other than Pd. The treatment conditions with this solution are that 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.

[0066] In Step 3, a resin substrate having a film layer into which Pd ions and ions of other metals are introduced is treated with a reducing agent. By this treatment, metal particles containing Pd and other metals are deposited on the surface, and a metallic film having a metal particle layer is obtained. Since Pd ions and ions of other metals diffuse to the surface where the reducing agent exists and are reduced to metal particles, the obtained metallic film has a resin substrate, a film layer formed thereon, and a metal particle layer formed thereon. In the present invention, since a part of each metal particle is embedded in the film layer, the deposited metal particles do not easily peel off.

[0067] Regarding the reducing agent used in Step 3, it is as described above for the method of the first embodiment.

[0068] The treatment with the reducing agent can be carried out, for example, by immersing the resin substrate in a reducing agent solution. The concentration of the reducing agent is preferably from 0.01 mM to 100 mM, more preferably from 0.01 mM to 50 mM. The treatment conditions with the reducing agent are such that the treatment temperature is preferably from 25°C to 60°C, more preferably from 40°C to 60°C, and the treatment time is preferably from 1 minute to 60 minutes, more preferably from 5 minutes to 30 minutes.

[0069] The method of the second embodiment may further include step 4 of heat-treating the resin substrate on which metal particles containing Pd and other metals are deposited on the surface of the film layer after step 3 to convert the film layer. In one embodiment, when the film layer contains carboxyl groups and / or sulfonic groups, these groups are dehydrated by the heat treatment. In this embodiment, the heat treatment temperature is usually from 100°C to 300°C.

[0070] The metal-tone film obtained by the method of the second embodiment includes a resin substrate, a film layer formed thereon, and a metal particle layer formed thereon. The metal-tone film shown in FIG. 2 is obtained by the method of the second embodiment. As described above, the metal-tone film 20 shown in FIG. 2 has a resin substrate 21 having a film layer 22 on the surface and a metal particle layer 23 formed thereon.

[0071] In a preferred embodiment of the method of the second embodiment, the resin substrate is polycarbonate or acrylic, the film layer is polyamic acid, and the other metal is Ag. In this embodiment, the manufacturing method of the present invention includes forming a film layer made of polyamic acid on the surface of a polycarbonate or acrylic resin substrate (step 1); treating the resin substrate having the film layer on its surface with a solution containing Pd ions and Ag ions, and by ion exchange, substituting H of the carboxyl group with Pd ions and Ag ions to introduce Pd ions and Ag ions into the film layer (step 2); and treating the resin substrate having the film layer into which Pd ions and Ag ions have been introduced with a reducing agent (for example, dimethylamine borane) to deposit alloy particles containing Pd and Ag on the surface of the film layer (step 3). In this embodiment, after step 3, step 4 of converting the polyamic acid of the film layer into polyimide by heat treatment may be performed.

[0072] Since the metal-tone film of the present invention can achieve both high brightness and radio wave transparency, it can be suitably used as a metal-tone film for products that require radio wave transparency.

Examples

[0073] Hereinafter, the present invention will be described more specifically using examples. However, the technical scope of the present invention is not limited to these examples.

[0074] Example 1 As the resin substrate, a 50-μm-thick polyimide film (manufactured by Toray DuPont, Kapton 200H) was used. The size of the polyimide film was 5 cm × 5 cm.

[0075] The polyimide film was immersed in a 5M KOH solution at 40°C for 1 minute to hydrolyze the surface of the polyimide film and form a polyamic acid layer.

[0076] Silver nitrate (AgNO3) (manufactured by Nacalai Tesque, 31018-14) was dissolved in pure water to prepare a 100 mM silver nitrate solution. An aqueous solution of tetraamminepalladium nitrate was added to the prepared silver nitrate solution so that the molar ratio of Pd to Ag (Pd:Ag) was 1:10, and a mixed solution of tetraamminepalladium nitrate and silver nitrate was prepared. After washing the film with water, the film was immersed in the prepared mixed solution at room temperature for 5 minutes, and Ag ions and Pd ions were introduced into the polyamic acid layer by ion exchange.

[0077] Dimethylamine borane (DMAB) (manufactured by Wako, 028-08401) was dissolved in pure water to prepare a 0.1 mM DMAB solution. After washing the film with water, the film was immersed in the DMAB solution at 30 °C for 10 minutes to reduce Ag ions and Pd ions, and alloy particles of Ag and Pd were deposited on the surface of the polyimide film. The film was washed with water and heat-treated at 200 °C to convert the polyamic acid to polyimide, and a metallic film was obtained. When the surface of this metallic film was observed by SEM (scanning electron microscope) and the cross-section of the metallic film was observed by TEM (transmission electron microscope), alloy particles of Ag and Pd were deposited in an island shape on the surface of the polyimide film, and there were gaps between the particles.

[0078] Examples 2 to 5 Except for using a mixed solution of tetraamminepalladium nitrate and silver nitrate having the molar ratio of Pd to Ag shown in Table 1, metallic films of Examples 2 to 5 were obtained in the same manner as in Example 1.

[0079] Comparative Example 1 Except for changing the mixed solution of tetraamminepalladium nitrate and silver nitrate to a 100 mM silver nitrate solution, a metallic film of Comparative Example 1 was obtained in the same manner as in Example 1. In Comparative Example 1, a metallic film having a layer of Ag particles on the surface of the polyimide film was obtained.

[0080] The following measurements were performed on the metallic films of Examples 1 to 5 and Comparative Example 1.

[0081] Pd content The Pd content in the metal particles was measured as follows. First, the metal-tone film was immersed in nitric acid to dissolve Ag and Pd in the nitric acid. The nitric acid solution in which Ag and Pd were dissolved was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) for Ag + and Pd 2+ and the amounts of these were quantified, and the Pd content (mol%) in the metal particles was calculated from these results.

[0082] Color difference The initial color L (i.e., L*) of the metal-tone film was measured as follows. The spectral reflectance R(λ) was determined by the ratio of the spectral radiant flux of wavelength λ reflected from the object to the spectral radiant flux of wavelength λ reflected from a perfect diffuser (JIS Z 8722). As the spectral colorimeter, CMS-35SP manufactured by Murakami Color Research Laboratory was used, and the measurement was performed in the SCI mode (including regular reflection light). Using the calculated spectral reflectance R(λ), the respective index values L*, a*, b* of the CIE1976 (L*, a*, b*) color system defined by the International Commission on Illumination (CIE) were calculated. Here, the L value is an index describing the lightness of the color, and the larger the L value, the brighter the color.

[0083] Millimeter-wave attenuation amount The millimeter-wave attenuation amount of the metal-tone film was measured to evaluate the millimeter-wave permeability. The millimeter-wave attenuation amount was determined by performing one-way attenuation measurement using a millimeter-wave characteristic measuring device having a horn antenna and doubling the obtained measurement value. Specifically, millimeter waves were irradiated from the horn antenna on the transmission side to the measurement sample, and the intensity of the millimeter waves incident on the horn antenna on the reception side after passing through the sample was measured to determine the one-way attenuation amount. The distance between the horn antennas on the transmission side and the reception side was set to 95 cm. The sample was installed with an elevation angle of 17° with respect to the horn antenna on the transmission side and a distance of approximately 40 mm between the sample and the horn antenna on the transmission side. The measurement was performed at 77 GHz, which is the applicable frequency of an in-vehicle millimeter-wave radar.

[0084] Table 1 shows the measurement results (Pd content, L value, millimeter wave attenuation) of the metallic tone films of Examples 1 to 5 and Comparative Example 1. Further, Fig. 3 shows the relationship between the Pd content of the metal particles and the L value of the metallic tone film.

[0085]

Table 1

[0086] As shown in Table 1, the metallic tone films of Examples 1 to 5 in which the metal particles contain Pd have equivalent excellent radio wave permeability compared to the metallic tone film of Comparative Example 1 in which the metal particles do not contain Pd, while having a larger L value and higher brightness. In the metallic tone films of Examples 1 to 5, by making the alloy particles of Ag and Pd, the crystallinity of the particles became high, total reflection of light easily occurred on the particle surface, and it is considered that high brightness was achieved. Further, as shown in Table 1 and Fig. 3, by adding a minute amount of Pd, the L value of the metallic tone film could be remarkably improved. Furthermore, as shown in Fig. 3, there was a linear correlation between the Pd content in the metal particles and the L value of the metallic tone film, and the L value of the metallic tone film tended to decrease as the Pd content increased. As shown in Fig. 3, when the Pd content in the metal particles was 34.4 mol% or less, the L value of the metallic tone film exceeded 75, exceeding the L value of Comparative Example 1 without Pd. Also, when the Pd content in the metal particles was 22 mol% or less, the L value of the metallic tone film exceeded 80, and when the Pd content in the metal particles was 9.6 mol% or less, the L value of the metallic tone film exceeded 85, and a metallic tone film with higher brightness was obtained.

Explanation of Symbols

[0087] 10: Metallic tone film, 11: Resin substrate, 12: Metal particle layer 20: Metallic tone film, 21: Resin substrate, 22: Film layer, 23: Metal particle layer

Claims

1. A metallic film having a resin substrate and a metal particle layer formed on the resin substrate, wherein in the metal particle layer, there are gaps between the metal particles, the metal particles are composed of Pd and Ag, and the Pd content in the metal particles is 1.6 mol% to 34.4 mol%.

2. The metallic film according to Claim 1, wherein the resin substrate is polyimide.

3. A method for manufacturing the metallic film according to Claim 1 or 2, comprising: Step 1 of preparing a resin substrate having a layer with functional groups capable of ion-exchanging with metal ions on the surface; Step 2 of treating the resin substrate having a layer with functional groups capable of ion-exchanging with metal ions on the surface with a solution containing Pd ions and Ag ions, and introducing Pd ions and Ag ions into the layer by ion exchange; Step 3 of treating the resin substrate having a layer with Pd ions and Ag ions introduced on the surface with a reducing agent to deposit metal particles composed of Pd and Ag on the surface A method for manufacturing a metallic film.

4. The method for manufacturing a metallic film according to Claim 3, further comprising Step 4 of performing a heat treatment after Step 3.

5. The method for manufacturing a metallic film according to Claim 3 or 4, wherein in Step 1, a layer having functional groups capable of ion-exchanging with the metal ions is formed on the surface of the resin substrate by modifying the surface of the resin substrate.

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