JP2921853B2 - Method for producing silver member having protective layer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a silver member coated with a protective layer using a vapor phase synthesis method and a method for producing the same.

[Conventional technology and its problems]

Silver has been prized as a decorative material alongside gold since ancient times. Especially in Europe, the unique color tone and soft texture of silver are preferred, and many silver products are favored.

However, silver originally has a defect that can be said to be fatal to sulfuration resistance, and even if it is left alone in the air, the silver surface gradually discolors and its color tone and texture are lost, so silver In order to maintain the appearance, it was necessary to periodically remove the sulfide on the silver surface.

Silver alloying, organic coating on silver surface, inorganic coating cord on silver surface, etc. have been considered as means for overcoming this drawback and preserving the original color tone and texture of silver for a long period of time, but none of them have been considered unacceptable. Is enough. Specifically, when sterling silver and magnesium and nickel are added by adding copper, silver is hardened, but sulfidation resistance is not improved at all. Although the sulfidation resistance is improved by silver alloying by adding palladium, the difference in color tone from pure silver is increased, causing a sense of incongruity. Although the improvement of the sulfuration resistance is observed in the application of an organic coating on a silver surface typified by a lacquer coat, the change in color tone and texture due to the thick coating layer is large. In the case of inorganic film coating on the silver surface such as rhodium flash plating, each problem remains, such as insufficient sulfuration resistance due to the pinholes of the inorganic film. In fact, satisfactory characteristics have not been obtained.

An object of the present invention is to provide a silver member having a structure capable of improving sulfidation resistance while maintaining the original color tone of silver in view of the related art.

[Means for solving the problem]

The silver member here means that the color difference from the appearance color tone of pure silver is L ^* a ^* b ^* color system evaluation, Includes everything that satisfies. Therefore, a silver alloy obtained by adding a base metal or a noble metal to pure silver, or a silver film formed on an arbitrary substrate by plating or vapor deposition is also included in the category of a silver member as long as the above characteristics are satisfied.

For this reason, in the present invention, when forming the protective layer on the surface of the silver member, a gas containing a hydrocarbon gas as a main component was introduced under such a condition that the silver member has a negative potential relationship with the plasma potential. It is characterized by using a plasma polymerization method. The protective layer formed in the above-described potential relationship has improved transmittance characteristics in the visible short wavelength region as compared with the conventional one, and no significant difference is recognized even in comparison with the silver member alone in appearance. In addition, since a film without pinholes is formed by using the plasma polymerization method, it is possible to provide a silver member having an original color tone of silver and excellent in sulfuration resistance.

Further, after forming the protective layer on the silver member surface as described above, IIa, IIIa, IVa, Va, IIb, IIIb, IVb
By laminating an oxide or nitride of at least one element selected from group III elements, or a diamond film or a hard carbon film, it has the original color tone of silver, has excellent sulfuration resistance, and has abrasion resistance It is possible to provide a silver member having the following. Hereinafter, the details will be described using embodiments.

Example 1 FIG. 1 shows the structure of the apparatus used in the present invention. In a vacuum chamber 1 evacuated to a reduced pressure, a cathode electrode 2 connected to a high-frequency power supply and an anode electrode 3 are disposed relative to each other, and a gas introduction pipe 4 is introduced therebetween. The silver member 5 as a substrate is held on the anode electrode 3 and is subjected to a film forming process according to the following steps. First, after evacuation to a predetermined degree of vacuum, an argon gas is introduced through a small hole (not shown) provided in the gas introduction pipe, and high-frequency power is supplied to the cathode electrode to generate glow discharge. At this time,
By applying a DC voltage to the anode electrode so that the anode electrode potential takes a negative set value with respect to the plasma potential, the silver member held on the anode electrode becomes electrically negative with respect to the plasma potential. And bombarded with argon ions. Then, the introduced gas type is switched from argon gas to hydrocarbon gas, and discharge is performed for a set time, whereby a protective film made of a target hydrocarbon polymer is formed on the silver member. Specific forming conditions and characteristics of the obtained protective film are described below.

(Formation conditions) Gas type and gas flow rate: Ethylene gas 80 standard cubic centimeters per minute Substrate: Pure silver plate High frequency power: 100 Watt Deposition of vacuum: 0.5 Torr Substrate temperature: 80 ° C Anode potential to plasma potential: -30 V Rate: 100 angstroms per minute Sample created under the above conditions (A)
And A sample in which a film was formed on a pure silver plate in the same manner as described above was used as a sample (B) except that the anode electrode potential was set to a plasma potential (the anode electrode was set in a floating state in the plasma). The characteristics were compared. Table 1 and the results of the color difference measurement and the sulfurization resistance test in the visible region are shown in Table 1, FIG. 2 and FIG.

First, in order to make comparison and evaluation of the reflectance characteristics in the visible region more clear, the results when the thickness of the protective film in the samples (A) and (B) are set to 3,000 Å are shown in FIG. Thus, by forming a protective film on a pure silver plate, the reflectivity in the visible region and in the short wavelength region is reduced, and by setting the anode electrode potential to the plasma potential to be negative, It can be seen that the reflectance characteristics are improved. This is probably because the direction of ion bombardment on the substrate surface during film formation affects the film formation rate of the protective film, absorption characteristics in the short wavelength region, etc., but details of the mechanism are unknown. .

Next, Table 1 shows the results of color difference measurement of the samples (A) and (B) in which the thickness of the protective film was set to 1,000 angstroms. Here, the change in appearance due to the formation of the protective film on the surface of the pure silver plate was evaluated using the color difference ΔE ^* of the L ^* a ^* b ^* color system.

It is generally considered that it is very difficult to determine the color difference for ΔE ^* 3.
It can be seen that the sample has an appearance very similar to a pure silver plate as compared with the sample (B).

Further, FIG. 3 shows the results of the sulfuration resistance test of the samples (A) and (B) in which the thickness of the protective film was set to 1,000 Å in the same manner as above. The sulfuration resistance test conditions at this time are as follows.

(Sulfuration resistance test conditions) (NH ₄ ) ₂ S ・ 2H ₂ O: H ₂ O = 1: 1 Temperature: 25 ℃ Relative temperature: 100% Leaving for a set time Appearance of pure silver plate before test and each sample after test The difference was evaluated as the color difference ΔE ^* . As is clear from the figure,
In a pure silver plate, a large change in ΔE ^* was observed after leaving for a short time, indicating that there was no sulfidation resistance at all. On the other hand, by forming the protective film on the pure silver plate, the sulfidation resistance was greatly improved. In particular, in the sample (A) of this example, the appearance quality almost the same as that of the pure silver plate was maintained even after standing for 60 minutes. The effect is very large.

In addition, when the correlation between the thickness of the protective film formed on a pure silver plate and the effect of improving sulfidation resistance was examined, the effect was confirmed at a film thickness of 200 Å or more. Therefore, the thickness is desirably about 500 to 10,000 angstroms.

In addition to the above, adhesion evaluation by a tape test, corrosion resistance evaluation by an artificial sweat test, and the like were performed, and it was confirmed that the protective film formed on the pure silver plate of this example was sufficiently effective at a practical level.

In this embodiment, as a means for setting the anode electrode potential with respect to the plasma potential, a method in which a DC voltage is externally applied to the anode electrode has been described. However, the same applies when a DC voltage is superimposed on the cathode electrode. The situation can be set, and also in this case, the characteristics can be improved as in the present embodiment.

As for the gas type, hydrocarbon gases such as titanium, acetylene, and benzene can be used in addition to ethylene used in this embodiment.

Example 2 A protective film having a thickness of 500 Å was formed on a silver member in the same manner as in the preparation of the sample (A) of Example 1, and then monosilane gas and oxygen gas were introduced. By reacting, a transparent silicon oxide film having a thickness of 10,000 Å was laminated.

(Silicon oxide film formation conditions) Gas type and gas flow rate: Monosilane gas 20 standard cubic centimeters per minute Oxygen gas 60 standard cubic centimeters per minute High frequency power: 100 watts Deposition vacuum: 0.5 Torr Substrate temperature: 80 ° C Deposition rate : 200 angstroms per minute The sample created under the above conditions is referred to as sample (C).
Table 2 shows the results of a comparison of the wear resistance of the pure silver plate alone with a Suga abrasion tester.

The pure silver plate alone has a very soft Vickers hardness of 50 to 90 Hv and is inferior in abrasion resistance. It can be seen that by coating the silicon oxide film having hardness, the abrasion resistance was significantly improved in addition to the improvement in the sulfidation resistance. Here, the silicon oxide film thickness is set to 10,000 angstroms,
Up to 0,000 angstroms, there was almost no change in appearance.

Further, in this embodiment, silicon oxide was used as an upper protective film for improving abrasion resistance, but other materials such as titanium, zinc, tantalum, aluminum and the like II
oxides of a, IIIa, IVa, Va, IIb, IIIb elements,
As long as the film is harder and more transparent than a pure silver plate, such as a silicon nitride film, a diamond film or a hard carbon film, the present invention can be applied.

Also, the forming method is not limited to the plasma CVD method (chemical vapor deposition method) described in the present embodiment.
A PVD method (physical vapor phase evaporation method) such as a sputtering method and an ion plating method, and a solgen method can be applied.

〔The invention's effect〕

As described above, according to the present embodiment, the sulfuration resistance and the abrasion resistance can be improved while maintaining the original color tone of the conventional silver. Alternatively, by applying the present invention to decorative articles such as medals and broaches, a silver member whose color tone does not change for a long time can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the structure of an apparatus used when forming a protective film on a silver member according to the present invention. FIGS. 5 is a graph showing reflectance characteristics and sulfuration resistance characteristics. 1 ... vacuum chamber, 2 ... cathode electrode, 3 ... anode electrode, 4 ... gas introduction tube, 5 ... silver member.

Claims (1)

(57) [Claims] 1. A method in which a gas containing hydrocarbon as a main component is introduced into a decompression vessel in which a silver member is disposed, and the silver member is set to have a negative potential with respect to a plasma potential. A method for producing a silver member having a protective layer, characterized in that a protective film is formed on a surface of a substrate by plasma polymerization of a hydrocarbon gas using a plasma polymerization method.