JP2008063592A - Discoloration inhibitor for silver-plated product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discoloration inhibitor for a silver-plated product, which can easily inhibit discoloration without causing problems such as a deterioration of the adhesiveness and whitening of the silver-plated layer. <P>SOLUTION: The discoloration inhibitor is formed of a solution containing a chloride ion and a complexing agent. The discoloration-inhibiting method includes applying the treatment solution to the surface of a silver-plated layer or immersing the silver-plated product in the treatment solution. Then, impurities are easily removed from the surface of the silver-plated layer, and the discoloration occurring when a top coating layer is formed later can be easily prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discoloration inhibitor for silver-plated products, and avoids the phenomenon of slight yellowishness due to the presence of impurities on the surface of the silver-plated layer, and is useful for removing impurities and is used for removing discoloration. Is to provide.

In order to form a silver mirror surface on the surface of a substrate such as glass, resin, or metal, a method of laminating an undercoat layer, a silver plating layer, and a topcoat layer in order on the substrate surface is known.
As a method for producing such silver plating, for example, an undercoat agent made of a paint containing at least one of an alkoxytitanium ester, a silane coupling agent having an epoxy group, and an epoxy resin is applied to a substrate and dried. The undercoat layer is then formed, and then a silver plating layer is formed by simultaneously spraying an ammoniacal silver nitrate aqueous solution and a reducing agent such as glyoxal on the surface of the undercoat layer, and then a top coat layer is formed. A method of manufacturing a silver-plated product has been proposed (see, for example, Patent Document 1).

  However, the silver-plated product manufactured by such a method is difficult to sufficiently remove impurities adhering to the silver-plated layer during the silver mirror reaction. There is a problem that the silver mirror surface turns yellow.

As a means for solving such a problem, a method is proposed in which either 3 to 10% acetic acid, 2 to 6% dilute sulfuric acid, or a protein dispersion is applied or immersed on the surface of the silver plating layer after the silver mirror reaction. (For example, refer to Patent Document 2).
However, it is disclosed that, by performing such treatment, impurities on the surface of the silver plating after the silver mirror reaction can be removed and discoloration can be suppressed. The problem of being attacked and whitening occurred. In addition, since protein is a polymer, it is easily adsorbed firmly on the surface of silver plating, and itself becomes an impurity, resulting in a new problem of lowering the adhesion between the silver plating layer and the topcoat layer.

JP 10-309774 A JP 2002-256454 A

The present invention has been made to solve the above-described problems in the prior art.
That is, an object of the present invention is to provide a discoloration inhibitor for silver-plated products that can easily suppress discoloration without causing any problems such as deterioration in adhesion of the silver plating layer and whitening.

  The inventors of the present invention have made extensive studies in order to solve the problems of the prior art as described above. As a result, impurities can be easily removed from the surface of the silver plating layer by applying or dipping a treatment agent containing chloride ions and a complexing agent on the surface of the silver plating layer, and discoloration during top coating can be achieved. The present inventors have found a drug that can be prevented and completed the present invention.

  That is, this invention relates to the discoloration inhibitor for silver plating products which consists of a solution containing a chloride ion and a complexing agent.

  The discoloration inhibitor for silver-plated products of the present invention can easily remove impurities in the silver-plated layer by applying or dipping the silver-plated layer, and exhibits an excellent effect in preventing discoloration of the silver-plated layer. To do.

The discoloration inhibitor for silver-plated products of the present invention contains a chloride ion as the first component and a complexing agent as the second component.
The chloride ion as the first component can remove impurities from the surface of the silver plating, and has an effect of suppressing yellow coloring that occurs during top coating.
The concentration of chloride ions is not particularly limited, but is desirably 0.0001 to 1% by mass. That is, when the amount is less than 0.0001% by mass, the treatment time becomes long, and when it exceeds 1% by mass, chloride ions cause corrosion of the silver plating layer and whitening is likely to occur. The supply source of chloride ions may be any source that releases chloride ions in water, and examples thereof include hydrochloric acid, sodium chloride, potassium chloride, magnesium chloride, and calcium chloride.

The complexing agent as the second component of the present invention has an effect of suppressing whitening caused by corrosion of silver plating caused by chloride ions.
As a kind of complexing agent that can be used, silver and silver ions, or compounds that can mutually stabilize with these compounds may be used. Among them, it is desirable to use amino acids, hydroxycarboxylic acid, ascorbic acid, boric acid, hypophosphorous acid, or a salt thereof, since it is possible to particularly effectively suppress harmful effects such as whitening of silver plating and deterioration of adhesion. .

The concentration of the complexing agent is not particularly limited as long as it is in a concentration range in which the effect of suppressing discoloration can be exhibited without causing adverse effects such as whitening of silver plating and deterioration of adhesion, but is particularly preferably in the range of 0.001 to 10% by mass.
That is, if the amount is less than 0.001% by mass, the corrosion of the silver plating layer due to chloride ions cannot be suppressed. On the other hand, if the amount exceeds 10% by mass, the difference in treatment effect due to the difference in concentration is not seen and is wasteful. This is not preferable because it consumes a drug.

The discoloration inhibitor for silver-plated products of the present invention is a process for removing impurities such as silver ions and silver compounds adhering to the silver-plated layer, so that the method can be applied to general silver plating in general. is there.
Among them, a silver plating product in which an undercoat layer, a silver plating layer formed by a silver mirror reaction, and a top coat layer are laminated on the substrate surface is optimal.

Hereinafter, the discoloration inhibitor for silver-plated products of the present invention will be described based on an example of the processing steps shown in FIG.
First, the base material used for the undercoat is subjected to a cleaning step (S01).
Next, an undercoat process (S02) is performed by coating the compound for undercoat layer formation on a base material.
Subsequently, after being subjected to a surface activation treatment step (S03) with stannous ions, it is subjected to a pure water washing step (S04) in order to remove excess tin compounds. Next, a silver mirror plating step (S05) for depositing a silver plating layer is performed, and then subjected to a pure water cleaning step (S06). Subsequently, the discoloration suppressing step (S07) is performed by applying or immersing an aqueous solution containing a chloride ion and a complexing agent that is the discoloration suppressing agent of the present invention, and further a pure water cleaning step for washing away the chemical solution. (S08) is performed, and then subjected to draining and drying step (S09).
Finally, the top coat step (S10) is performed by coating the silver plating layer using a top coat compound.

These series of steps will be further described in detail. First, as a base material for forming a silver plating layer used in the present invention, any material such as metal, synthetic resin, rubber, glass, ceramics, and wood can be used without any particular limitation on the material, shape, and the like. .
A generally used cleaning method such as degreasing with an alkali or alcohol can be applied to the substrate cleaning step (S01). Further, this step (S01) is performed to remove dirt on the surface of the base material, and this step can be omitted when the base material is not contaminated.

Although the compound used for an undercoat process (S02) is not specifically limited, An acrylic resin, a silicon acrylic resin, a urethane resin, an epoxy resin, an acrylate oligomer, an acrylate monomer, etc. can be used.
As the aqueous solution containing stannous ions used in the surface activation treatment step (S03), treatment chemicals generally used for plating can be used. Examples thereof include an aqueous solution containing 0.1 to 3% by mass of tin (II) chloride and 0.10 to 5% by mass of hydrochloric acid.

  The pure water used in the pure water washing step (S04) is not particularly limited in its purification method and can be used as long as it is general, but for example, one having an electric conductivity of 3 μS / cm or less is recommended. can do.

  The silver mirror plating step (S05) is not particularly limited as long as it is a method for forming a silver plating layer by a silver mirror reaction, and a conventional method can be used. For example, a method in which an ammonia-containing silver salt aqueous solution and a reducing agent are simultaneously sprayed onto a substrate using a concentric spray gun, a double-head spray gun, or the like. Examples of the silver salt to be used include silver oxide, silver chloride, silver sulfate, silver carbonate, silver nitrate, and silver acetate. Among them, silver nitrate is particularly preferable because of its excellent solubility in water and cost. be able to. As the reducing agent, for example, an aqueous solution containing glyoxal, formaldehyde, ascorbic acid, glucose, hydroquinone, hydrazine, sodium sulfite and the like can be used.

  The pure water used in the pure water washing step (S06) is not particularly limited in its purification method and can be used as long as it is a general one. For example, it has an electric conductivity of 3 μS / cm or less. be able to.

  The discoloration suppressing step (S07) is a step of treating the surface of the silver plating with the discoloration suppressing agent of the present invention. The treatment method may be any method as long as the discoloration inhibitor and the silver plating surface are in contact with each other. For example, a spray method, a dipping method, or the like can be preferably used. Moreover, although processing time is not specifically limited, An effect is exhibited in 1-120 seconds.

  The pure water used in the pure water cleaning step (S08) may be the same as that used in the cleaning steps of S04 and S06, which are the previous steps.

  Any method may be used for the draining and drying step (S09) as long as the water on the silver plating layer can be removed. For example, methods such as air blowing and heat drying can be applied.

  Next, a top coat (S10) is performed to protect the silver layer. The coating material used for the top coat is not particularly limited, and acrylic resin, silicon acrylic resin, urethane resin, epoxy resin, acrylate oligomer, acrylate monomer, and the like can be used.

  The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
The ABS resin plate (10 × 10 cm) was washed with isopropanol and dried, and then the coating agent shown below was applied by spraying. Then, after drying at 70 ° C. for 3 minutes, an ultraviolet ray of 2500 mJ / cm ² (integrated light amount) was irradiated and cured to undercoat.
In addition, said coating agent used for undercoat was prepared in accordance with the following method.
90 parts by mass of silicate 40 (manufactured by Tama Chemical Co., Ltd.), 10 parts by mass of 3-mercaptopropyltrimethoxysilane (manufactured by GE Toshiba Silicone Co., Ltd.) and 20 parts by mass of isopropanol are mixed, and 20% by mass of 0.4% by mass hydrochloric acid is mixed. Part was added and stirred at room temperature for 30 minutes. To this, 210 parts by mass of isopropanol was further added, and hydrolysis was carried out by aging at room temperature for 48 hours. Subsequently, an undercoat coating agent was produced by blending 1 part by mass of dipentaerythritol pentaacrylate KAYARAD D-310 (manufactured by Nippon Kayaku Co., Ltd.) with respect to 5 parts by mass of the hydrolyzate.

  Next, a surface activation treatment was performed by spraying an aqueous solution containing 2% by mass of tin (II) chloride and 1% by mass of hydrochloric acid, and then pure water was washed. Further, an aqueous solution containing silver nitrate and ammonia and an aqueous glyoxal solution were simultaneously sprayed on the surface of the base material using a concentric spray gun to form a silver plating layer. Thereafter, the silver plating layer was washed with pure water.

Next, discoloration suppression processing was performed. A treatment chemical compounded with 0.2% by mass of sodium chloride and 5% by mass of ascorbic acid was applied by spraying and contacted with the treatment chemical for 5 seconds, followed by washing with pure water. Subsequently, the silver plating layer was drained by air blowing.
Finally, the same coating agent as the undercoat is spray applied onto the silver plating layer, dried at 70 ° C. for 3 minutes, and then irradiated with ultraviolet rays of 2500 mJ / cm ² (integrated light amount) to be cured. A silver-plated product treated with a discoloration inhibitor was prepared.

[Example 2]
Except for changing the discoloration inhibiting treatment from the method of Example 1 by spraying the treatment agent of the present invention containing 0.005% by mass of sodium chloride and 0.02% by mass of glycine and contacting the treatment agent for 5 seconds, A silver-plated product was prepared in the same manner as in Example 1.

[Example 3]
Silver plating is performed in the same manner as in Example 1 except that the treatment chemical of the present invention containing 0.005 mass% sodium chloride and 0.1 mass% boric acid is spray-coated and the condition is changed to contact with the treatment chemical for 30 seconds. Created a product.

[Example 4]
The same method as in Example 1 except that the treatment chemical of the present invention containing 0.005% by mass of sodium chloride and 0.1% by mass of sodium hypophosphite was sprayed and changed to the condition of contacting with the treatment chemical for 60 seconds. Made a silver-plated product.

[Example 5]
Silver plating is performed in the same manner as in Example 1 except that the treatment chemical of the present invention containing 0.005 mass% sodium chloride and 0.02 mass% ascorbic acid is spray-coated and the condition is changed to contact with the treatment chemical for 5 seconds. Created a product.

[Example 6]
Silver plating is performed in the same manner as in Example 1 except that the treatment chemical of the present invention containing 0.2% by mass of potassium chloride and 5% by mass of ascorbic acid is spray-coated and the condition is changed to contact with the treatment chemical for 5 seconds. Created a product.

[Example 7]
Except for changing to the condition of spraying the treatment agent of the present invention containing 0.005% by mass sodium chloride, 0.02% by mass ascorbic acid and 0.01% by mass sodium hypophosphite and contacting with the treatment agent for 5 seconds, A silver-plated product was prepared in the same manner as in Example 1.

[Comparative Example 1]
A silver-plated product was prepared in the same manner as in Example 1 except that the discoloration suppression treatment was omitted.

[Comparative Example 2]
A silver-plated product was prepared in the same manner as in Example 1 except that the discoloration suppression treatment was changed to a condition in which a 0.2 mass% sodium chloride aqueous solution was spray-coated and contacted with the treatment chemical for 5 seconds.

[Comparative Example 3]
A silver-plated product was prepared in the same manner as in Example 1 except that the discoloration suppressing treatment was changed to a condition in which 5% by mass of an ascorbic acid aqueous solution was spray applied and contacted with the treatment chemical for 120 seconds.

[Comparative Example 4]
A silver-plated product was prepared in the same manner as in Example 1 except that the discoloration suppressing treatment was changed to a condition in which a 3% by mass acetic acid aqueous solution was spray-coated and contacted with the treatment chemical for 120 seconds.

  Using the silver plating products obtained in these examples and comparative examples, the adhesion and the appearance of the silver plating products were evaluated. In addition, each performance evaluation was performed with the following method. The evaluation results are shown in Table 1.

<Evaluation of adhesion of silver-plated products>
Adhesion was evaluated according to JIS K5600-5-6 (Paint General Test Method).
Using a razor on the silver-plated product, eleven cuts were made at 1mm intervals, creating 100 grids. After cellophane tape (made by Nichiban Co., Ltd., width 25 mm) was adhered closely to this, the mass that remained without peeling off the coating when peeled off at an angle of about 60 degrees for 0.5 to 1 second on the plated surface. The number of eyes (X) was expressed as X / 100.

<Appearance evaluation of silver-plated products>
The appearance color of the silver-plated product was visually observed, and the evaluation results were shown in three stages: ◯ (good), Δ (slightly bad), and x (bad). In addition, in the case of evaluations other than ◯, the problem that is the reason is added.

It is process drawing which shows the usage example of the discoloration inhibitor for silver plating products of this invention.

Claims (4)

Discoloration inhibitor for silver plating products comprising a solution containing chloride ions and a complexing agent. The discoloration inhibitor for silver-plated products according to claim 1, which is a solution having a chloride ion concentration of 0.0001 to 1% by mass and a complexing agent concentration of 0.001 to 10% by mass. The discoloration inhibitor for silver-plated products according to claim 1 or 2, wherein the complexing agent is a solution containing at least one amino acid, hydroxycarboxylic acid, ascorbic acid, boric acid, hypophosphorous acid, or a salt thereof. . The silver-plated product is a product obtained by laminating an undercoat layer, a silver-plated layer, and a topcoat layer on a substrate surface, and the silver-plated layer is a product produced by a silver mirror reaction. Discoloration inhibitor for silver plating products.

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