Precious metal plating film and method of producing the same, and coating film member and method of producing the same

Abstract

To further enhancing the hardness of a plating film of precious metal such as gold.SOLUTION: There is disclosed a method of producing a precious metal plating film, including forming a precious metal plating film in a plating liquid comprising a precious metal ion source and nano-cellulose. A precious metal plating film may be formed by electrolytic plating.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a precious metal plating film and a method for producing the same, and a coated member and a method for producing the same. [Background technology]

[0002] Films containing precious metals such as gold are often formed by plating using a plating solution (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-023324 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure relates to increasing the hardness of a precious metal plating film that contains a precious metal such as gold. [Means for solving the problem]

[0005] The present disclosure includes the following. [1] A method for producing a precious metal plating film, comprising forming a precious metal plating film in a plating solution containing a precious metal ion source and nanocellulose. [2] The method according to [1], wherein the noble metal plating film is formed by electrolytic plating in the plating solution. [3] forming a coating on a substrate; A method for producing a coated member, wherein the coating is formed by a method including forming a precious metal plating film by the method according to [1] or [2]. [4] A precious metal plating film that contains precious metals and exhibits a Vickers hardness of 150HV or more. [5] A precious metal plating film comprising a precious metal and nanocellulose. [6] The precious metal plating film according to [4] or [5], which contains an amorphous portion. [7] A coated member comprising a substrate and a coating comprising the precious metal plating film according to any one of [4] to [6]. Effect of the Invention

[0006] A precious metal plating film having high hardness can be easily formed. [Brief description of the drawings]

[0007] [Figure 1] 1 is an electron microscope photograph of a gold plating film. [Diagram 2] 1 is an electron microscope photograph of a gold plating film. [Diagram 3] 1 is an electron microscope photograph of a gold plating film. [Figure 4] 1 is an electron microscope photograph of a gold plating film. [Diagram 5] 1 is an electron microscope photograph of a gold plating film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention is not limited to the following examples.

[0009] An example of a method for producing a noble metal plating film includes forming a noble metal plating film in a plating solution containing a noble metal ion source and nanocellulose. The noble metal plating film may be formed by electrolytic plating.

[0010] The noble metal plating film can be formed on the surface of any substrate. The substrate may be a metal molded body (e.g., a stainless steel member). A base metal film (e.g., a nickel plating film) may be provided on the surface of the substrate, and the noble metal plating film may be formed on the base metal film.

[0011] The noble metal plating film formed in a plating solution containing nanocellulose can have a higher hardness than the noble metal plating film formed in a plating solution not containing nanocellulose. The inventor presumes that one of the factors is that the crystal grains in the noble metal plating film are refined by the action of nanocellulose, and in some cases, a noble metal plating film containing an amorphous portion is formed. Nanocellulose may be incorporated into the noble metal plating film, and the hardness of the noble metal plating film can also be increased by the action of the incorporated nanocellulose.

[0012] The nanocellulose contained in the plating solution is a fine fiber material containing cellulose, and may include, for example, cellulose nanofibers, cellulose nanocrystals, bacterial nanocellulose, or a combination thereof. The width (minor axis diameter) of the nanocellulose may be 1 nm or more and 100 nm or less, or 3 nm or more and 100 nm or less. The length of the nanocellulose may be 10 nm or more and 100 μm or less. The aspect ratio of the nanocellulose may be 10 or more.

[0013] Nanocellulose (particularly cellulose nanofibers) may be obtained by a method including an oxidation treatment of cellulose. Nanocellulose obtained by a method including an oxidation treatment often has carboxyl groups converted from hydroxyl groups.

[0014] In the plating solution, nanocellulose is usually dissolved or dispersed in the solvent (particularly water) of the plating solution. The concentration of nanocellulose in the plating solution may be, for example, 10 g / L or more and 1000 g / L, calculated as the concentration of a solution containing 2 mass% nanocellulose. In other words, the concentration of nanocellulose may be 0.2 g / L or more and 20 g / L or less, based on the volume of the plating solution.

[0015] The precious metal ion source contained in the plating solution contains ions of one or more precious metals selected from gold, silver, platinum, palladium, rhodium, iridium, ruthenium, and osmium. The precious metal ion source may contain gold ions, in which case a gold plating film containing gold is formed. The precious metal ion source may be selected from those commonly used to form precious metal plating films, and may be, for example, a precious metal complex. The gold ion source may be, for example, a gold sulfite complex.

[0016] Other components constituting the plating solution can be selected from those typically used in plating solutions for forming precious metal plating films. When the precious metal plating film is formed by electrolytic plating, the electrolytic plating conditions can be the same as those when using a plating solution that does not contain nanocellulose.

[0017] The formed noble metal plating film may contain nanocellulose (e.g., cellulose nanofibers) or may be substantially free of nanocellulose. The noble metal plating film may have high hardness. For example, the Vickers hardness of the noble metal plating film may be 150HV or more, 200HV or more, or 250HV or more, or may be 1000HV or less. When a base metal film is formed under the noble metal plating film, the Vickers hardness of the coating including the base metal film and the noble metal plating film may be within the above range. The Vickers hardness here may be a value converted from the nanoindenter hardness obtained by an ultra-microindentation hardness test under the conditions described in the examples below.

[0018] The thickness of the precious metal plating film may be, for example, 0.01 μm or more and 100 μm or less. The thickness of the precious metal plating film may be 0.2 μm or more, or 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less.

[0019] The noble metal plating film formed by the plating solution containing nanocellulose may contain amorphous parts. The presence of amorphous parts in the noble metal plating film can be confirmed, for example, by the absence of grain boundaries in an electron microscope image of the noble metal plating film at a magnification of 3000.

[0020] By forming a coating including a precious metal plating film on a substrate, a coated member having a substrate and a coating can be obtained. The coating is formed so as to cover a part or all of the outer surface of the substrate. The coating may be a precious metal plating film alone, or may further include other films such as the above-mentioned base metal layer. The thickness of the base metal layer may be, for example, 0.01 μm or more and 10 μm or less. The coating may further include a precious metal plating film formed in a plating solution that does not contain nanocellulose. EXAMPLES

[0021] The present invention is not limited to the following examples.

[0022] Test 1 Plating Solution Cellulose nanofibers (CNF) (2% by mass aqueous dispersion) manufactured by a method including oxidation treatment with TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical) were prepared. CNF was added to pure water to a concentration of 500 g / L, and the mixture was stirred for 30 minutes or more to dissolve the CNF in water. The obtained CNF solution was added little by little to a gold plating solution heated to 60°C. The gold plating solution was a non-cyanide pure gold plating solution containing alkali gold sulfite, water-soluble amine, crystal regulator, and surfactant. The gold plating solution to which CNF had been added was stirred at 600 rpm while evaporating water, and the concentration of CNF in the gold plating solution was adjusted to 10 g / L.

[0023] Plating Test A stainless steel sheet (SUS304) was degreased by immersing it in the solvent for 5 minutes. After being removed from the solvent, the stainless steel sheet was washed with water, treated with activated acid (hydrochloric acid:water = 1:2) at 50°C for 2 minutes, and then washed with water again. Next, the stainless steel sheet was immersed in a nickel plating solution containing nickel chloride (150g / L) and hydrochloric acid (100g / L) and electrolytic plating (room temperature, current density 5A / dm 2 A nickel plating film (thickness: 0.05 μm) was formed on the stainless steel plate by a method similar to that described above.

[0024] The stainless steel sheet on which the nickel plating film was formed was immersed in ion-exchanged water. The stainless steel sheet removed from the ion-exchanged water was immersed in the above gold plating solution containing CNF, and electrolytic plating (60°C, current density 0.5 A / dm 2 A gold plating film was formed on the nickel plating film by a 0.25 μm thick solution (1 min). The stainless steel sheet on which the gold plating film (0.25 μm thick) was formed was washed with water and dried to obtain a coated member having a gold plating film with metallic luster. For comparison, a coated member having a gold plating film (0.25 μm thick) was produced in the same manner, except that the gold plating solution to which the CNF had not been added was used.

[0025] Observation of gold plating film Figures 1 to 6 are electron microscope photographs of gold plating films. Figure 1 is a photograph of the gold plating film surface at a magnification of 3000, and Figure 2 is a photograph of the metal plating film surface at a magnification of 10000. Figure 3 is a photograph of the metal plating film surface at a magnification of 10000, Figure 4 is a photograph of the metal plating film surface at a magnification of 30000, and Figure 5 is a photograph of the metal plating film surface at a magnification of 100000.

[0026] In the photographs of Figures 1 and 2, in the case of the gold plating film formed using the gold plating solution (Au) that does not contain CNF, the crystal grain boundaries were clearly observed, which suggests that a crystalline gold plating film was formed mainly by epitaxial growth. In the case of the metal plating film formed using the gold plating solution that contains CNF (Au / CNF), the crystal grain boundaries were not clearly observed, which suggests that a gold plating film containing amorphous parts was formed.

[0027] In the photographs of Figures 3 and 4, no pinholes were observed on the surface of the gold plating film formed with the gold plating solution (Au) that did not contain CNF, whereas no pinholes were observed on the surface of the metal plating film formed with the gold plating solution containing CNF (Au / CNF).The photograph of Figure 5 shows that, whereas crystal grains with corners were observed in the gold plating film formed with the gold plating solution (Au) that did not contain CNF, the crystal grains in the metal plating film formed with the gold plating solution containing CNF (Au / CNF) were smaller and had almost no corners.

[0028] Test 2 Formation of gold plating film #1 (Comparative Example) The surface of a 10 mm square stainless steel plate (SUS304) was polished to form a smooth surface with a surface roughness Ra of 0.1. A nickel plating film (thickness: 0.05 μm) was formed on the smooth surface in the same manner as in Test 1. A gold plating film with a thickness of 1 μm was formed on the nickel plating film using the gold plating solution in Test 1 before the CNF was added.

[0029] #2 On the nickel plating film formed in the same manner as in #1, a lower gold plating film with a thickness of 0.75 μm was formed using a gold plating solution to which CNF had not yet been added. Then, an upper gold plating film with a thickness of 0.25 μm was formed on the lower gold plating film using a plating solution containing CNF.

[0030] #3 On the nickel plating film formed in the same manner as in #1, a gold plating film having a thickness of 1 μm was formed using a gold plating solution containing CNF.

[0031] Ultra-microindentation hardness test The gold plating films of #1, #2 and #3 were evaluated by a microindentation hardness test using the following equipment and conditions. Equipment: G200 (Agilent Technologies) Maximum pressing load: 1.0mN Indenter: Berkovich indenter (diamond, apex angle 115°) Load time: 30 seconds Holding time: 10 seconds

[0032] From the test results, the Vickers hardness and Young's modulus of the metal plating film were obtained. The Vickers hardness was obtained by converting the nanoindenter hardness obtained from the microindentation hardness test.

[0033] [Table 1]

[0034] The Vickers hardness and Young's modulus of each gold plating film are shown in Table 1. The gold plating films #2 and #3, which include a portion formed with a gold plating solution containing CNF, showed a Young's modulus equal to or greater than that of the gold plating film #1 formed with a gold plating solution not containing CNF, and also showed significantly higher hardness.

Claims

1. A method for producing a precious metal plating film, comprising forming a precious metal plating film in a plating solution containing a precious metal ion source and nanocellulose.

2. The method according to claim 1 , wherein the noble metal plating film is formed by electrolytic plating in the plating solution.

3. forming a coating on a substrate; A method for producing a coated member, the coating being formed by a method comprising forming a precious metal plating film by the method according to claim 1 or 2.

4. A precious metal plating film that contains a precious metal and exhibits a Vickers hardness of 150 HV or more.

5. A precious metal plating film comprising a precious metal and nanocellulose.

6. The precious metal plating film according to claim 4 or 5, which contains an amorphous portion.

7. A coated member comprising a substrate and a coating comprising the precious metal plating film according to claim 4 or 5.

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