JP2021155817A - Method of manufacturing silver plating coated body - Google Patents

Abstract

To provide a method of manufacturing a silver plating coated body in which the silver plating coated body can be obtained which has adhesive strength improved between a silver plating layer and a top coat layer.SOLUTION: A method of manufacturing a silver plating coated body which has at least a silver plating layer and a top coat layer on a base material in this order comprises: treating the silver plating layer with surface treatment liquid containing urea or an urea derivative represented by formula (1) after forming the silver plating layer; and further forming the top coat layer. In formula, R1 and R2 represent a hydrogen atom, or a 4C or less alkyl group or alkenyl group, and R1 and R2 may be linked to form a circle.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a silver-plated coated body having at least a silver-plated layer and a topcoat layer on a base material. More specifically, the present invention relates to a method for producing a silver-plated coated body capable of obtaining a silver-plated coated body having an improved adhesive force between the silver-plated layer and the top coat layer.

A silver-plated coated body having a silver-plated layer on a base material such as metal or plastic is used as a design material, a reflective material, or the like because silver has the highest reflective luster among metals. Further, it is a material that can be effectively used as, for example, an electromagnetic wave shielding material by utilizing the high conductivity of silver.

The silver-plated layer is a useful material that exhibits high reflective luster and high conductivity even if it is a thin film, but its mechanical strength is weak because it is thin and soft. In order to make up for such a defect, a method of providing a top coat layer on the surface by using various hard coat materials is known. For example, Japanese Patent Application Laid-Open No. 2000-129448 (Patent Document 1) describes that various resins such as liquid epoxy resin and unsaturated polyester resin can be used for the top coat layer. However, even if the top coat layer is provided on the silver plating layer, there is a problem that sufficient adhesive force between the silver plating layer and the top coat layer cannot be obtained, especially in a high temperature and high humidity environment or in an atmosphere containing salt water. This problem becomes even more pronounced in harsh environments.

Various topcoat layers have been proposed in order to solve the problem of adhesive strength between the silver plating layer and the topcoat layer. For example, Japanese Patent Application Laid-Open No. 2003-155580 (Patent Document 2), Japanese Patent Application Laid-Open No. 2004-203014, etc. describe that a silicone acrylic paint having a specific glass transition temperature is used, and Japanese Patent Application Laid-Open No. 2008-106081 The publication describes that a specific ultraviolet curable resin is used for the top coat layer. Further, Japanese Patent Application Laid-Open No. 2012-206326 (Patent Document 3) discloses a top coat layer containing a thiol organic acid derivative. However, even in these methods, the adhesive strength between the silver plating layer and the top coat layer is not sufficient, and further improvement in the adhesive strength has been desired.

As another method for improving the adhesive strength between the silver-plated layer and the topcoat layer, a method of applying some treatment to the silver-plated layer before applying the topcoat layer has also been proposed. Japanese Patent Application Laid-Open No. 2003-293146 describes that the adhesion between the silver-plated layer and the topcoat layer is improved by treating the silver-plated layer with a liquid containing a sulfite, and Japanese Patent Application Laid-Open No. 2004-169157. Japanese Patent Application Laid-Open No. 4 (Patent Document 4) and Japanese Patent Application Laid-Open No. 2020-33616 (Patent Document 5) disclose a method for treating a silver-plated layer with a compound having a thion group or a mercapto group. However, even with these methods, the adhesive strength between the silver plating layer and the top coat layer was not yet sufficient.

Japanese Unexamined Patent Publication No. 2000-129448 Japanese Unexamined Patent Publication No. 2003-155580 Japanese Unexamined Patent Publication No. 2012-206326 Japanese Unexamined Patent Publication No. 2004-169157 Japanese Unexamined Patent Publication No. 2020-33616

An object of the present invention is to provide a manufacturing method for obtaining a silver-plated coated body having improved adhesive strength between a silver-plated layer and a topcoat layer, and silver capable of obtaining sufficient adhesive strength even in a harsh environment. An object of the present invention is to provide a manufacturing method for obtaining a plated coated body.

The above object of the present invention is achieved by the invention described below.
In the method for producing a silver-plated coating body having at least a silver-plated layer and a top coat layer on the base material in this order, a urea or a urea derivative represented by the following general formula (1) is contained after the silver-plated layer is formed. A method for producing a silver-plated coating body, which comprises treating the plating layer with a surface treatment liquid to further form a top coat layer.

In the formula, R ₁ and R ₂ represent a hydrogen atom or an alkyl group or an alkenyl group having 4 or less carbon atoms, and R ₁ and R ₂ may be linked to form a ring.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a manufacturing method capable of improving the adhesiveness between the silver-plated layer and the topcoat layer and obtaining a silver-plated coated body having sufficient adhesive strength even in a harsh environment.

Hereinafter, the present invention will be described in detail.

The silver-plated coated body obtained by the present invention is a silver-plated coated body having at least a silver-plated layer and a top coat layer on the base material in this order, and is represented by the general formula (1) after the silver-plated layer is formed. The plating layer is treated with a surface treatment liquid containing the urea or a urea derivative.

In the general formula (1), R ₁ and R ₂ represent a hydrogen atom or an alkyl group or an alkenyl group having 4 or less carbon atoms, and R ₁ and R ₂ may be linked to form a ring. Specific examples of the compound represented by the general formula (1) used in the present invention include urea, 1-methylurea, 1,3-dimethylurea, 1-ethylurea, 1,3-diethylurea and 1-. Examples thereof include propylurea, 1-butylurea, 1-allylurea, 2-imidazolidinone, tetrahydro-2-pyrimidinone, and the like, but the present invention is not limited thereto.

The amount of the compound represented by the general formula (1) added to the surface treatment liquid used in the present invention depends on the treatment time and the treatment temperature. If the treatment time is long or the treatment temperature is high, the effect can be obtained by adding a small amount. When treated within 1 minute at around room temperature, the preferable addition amount is 0.05 to 1 mol / L. If the amount added is too small, a sufficient effect cannot be obtained, while if the amount added is too large, there is no particular adverse effect, but the effect reaches a plateau.

The surface treatment liquid used in the present invention may contain a compound having a mercapto group and a carboxyl group in addition to the compound represented by the general formula (1). Specific examples of the above-mentioned compounds having a mercapto group and a carboxyl group include mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 3-mercapto-2-methylpropionic acid, mercaptosuccinic acid and the like, and these compounds. Examples thereof include sodium salt, potassium salt, ammonium salt, and salt with amines. Further, amino acids having a mercapto group such as cysteine, N-acetylcysteine, penicillamine and glutathione, salts with sodium salts, potassium salts, ammonium salts and amines of these compounds, or salts with acids such as hydrochloric acid and sulfuric acid. And so on.

The surface treatment liquid used in the present invention may contain a nitrogen-containing heterocyclic compound having a mercapto group or a thioon group in addition to the compound represented by the general formula (1). Examples of the nitrogen-containing heterocycle in the above compound include an imidazole ring, a triazole ring, a tetrazole ring, a triazine ring, an oxazole ring, a thiazole ring, a thiadiazole ring, and an oxadiazole ring. Specific examples include 2-mercapto-1-methylimidazole, 5-amino-2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 3-mercapto-4-methyl-4H-1,2,4- Triazole, 5-mercapto-1-phenyl-1H-tetrazole, 1- (4-hydroxyphenyl) -5-mercapto-1H-tetrazole, 2-dibutylamino-4,6-dimercapto-1,3,5-triazine, 2-Anilino-4,6-dimercapto-1,3,5-triazole, 2-mercaptobenzoxazole, 2-mercaptobenzthiazole, 2-mercapto-5-methylthio-1,3,4-thiazazole, 2-mercapto- Examples thereof include 5-phenyl-1,3,4-oxadiazole.

The surface treatment liquid used in the present invention may further contain an antioxidant. Specific examples of the antioxidant include ascorbic acid, elsorbic acid, hydroquinone, catechol, resorcinol, hydroquinone sulfonic acid, gallic acid, sulfite, barous sulfate, and salts thereof.

The solvent of the surface treatment liquid used in the present invention is preferably water or a mixed liquid of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and isobutyl alcohol, dimethylformamide and dimethyl. Amids such as acetamido, ketones and ketone alcohols such as acetone and diacetone alcohols, ethers such as tetrahydrofuran and dioxane, ethylene glycol, propylene glycol, ethylene glycol methyl ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl Examples thereof include polyhydric alcohols such as ethers and lower alkyl ethers of polyhydric alcohols. Further, the pH is not particularly limited, but can be appropriately determined from the viewpoint of the solubility of the added component and the stability over time. Generally, from the viewpoint of handleability, the pH is preferably in the range of 4 to 10.

As a method for performing the surface treatment of the present invention, a silver plating layer is applied to the surface treatment liquid by a gravure roll method, a reverse roll method, a dip roll method, a bar coater method, a knife coater method, an air spray method, an airless spray method, a dip method, or the like. Examples thereof include a method of supplying to the surface for treatment. These can be arbitrarily selected according to the situation.

The silver-plated coated body obtained by the present invention has a silver-plated layer on a base material. The method for forming the silver plating layer may be either dry plating such as a vapor deposition method or a sputtering method, or wet plating such as electrolytic plating or electroless plating, but the silver plating layer is formed by electroless plating. The method is simple and preferable.

In the method of forming a silver plating layer on a base material by electroless plating, a method in which an undercoat layer is provided on the base material and a silver plating layer is provided on the undercoat layer is common. Such an undercoat layer preferably has high adhesion to silver plating. For example, in addition to the undercoat layer described in JP-A-10-309774 and JP-A-2002-256455, polymers or oligomers having terminal hydroxyl groups such as alkyd polyols, polyester polyols, and acrylic polyols and isocyanates as curing agents. An undercoat layer obtained by applying a urethane-based coating composition mixed with a nald compound, an epoxy-based coating composition obtained by mixing an amine compound as a curing agent with an epoxy resin, or the like can be used. These can be appropriately selected and used based on the characteristics required as a coated body.

A preferred method for forming an electroless silver plating layer on the undercoat layer is to treat the surface of the undercoat layer on which the electroless silver plating layer is formed with an active treatment liquid containing tin (II) chloride to tin (II). ) Ions are supported on the surface of the undercoat layer, and an electroless silver plating layer is formed on the activated undercoat layer by a silver mirror reaction.

Examples of the treatment method for treating with an active treatment liquid containing tin (II) chloride include a method of immersing the surface of the undercoat layer in the active treatment liquid and an active treatment containing tin (II) chloride on the surface of the undercoat layer. There is a method of applying a liquid and the like. As a coating method, spray coating regardless of the shape of the base material is preferable. Further, it is preferable to wash the active treatment liquid excessively attached to the surface with deionized water.

After the step of treating with the activation treatment liquid for silver mirror, it is preferable to provide a step of performing activation treatment with silver ions. Examples of the activation treatment with silver ions include treatment with an aqueous silver nitrate solution. The concentration of the silver nitrate aqueous solution used here is preferably a dilute solution of 0.1 mol or less per liter, and this solution is brought into contact with the tin (II) chloride-treated undercoat layer. Examples of the method of this activation treatment include a method of immersing the undercoat layer treated with tin (II) chloride in the above-mentioned treatment liquid or a method of spray coating.

The electroless silver plating layer is formed by the silver mirror reaction by subjecting two solutions, an ammoniacal silver nitrate solution containing silver nitrate and ammonia, and a reducing agent solution containing a reducing agent and a strong alkaline component, to the surface of the undercoat layer. Apply to mix above. As a result, a redox reaction occurs to precipitate metallic silver, form a silver film, and form an electroless silver plating layer.

Examples of the reducing agent solution include an aqueous solution containing an aldehyde compound such as glucose and glyoxal, and an aqueous solution containing a hydrazine compound such as hydrazine sulfate, hydrazine carbonate or hydrazine hydrate.

Some additives can also be added to the aqueous ammoniacal silver nitrate solution to produce good silver. For example, monoethanolamine, tris (hydroxymethyl) aminomethane, 2-amino-2-hydroxymethyl-1,3-propanediol, 1-amino-2-propanol, 2-amino-1-propanol, diethanolamine, diisopropanol. Examples thereof include amino alcohol compounds such as amines, triethanolamines and triisopropanolamines, amino acids such as glycine, alanine and sodium glycine or salts thereof, but are not particularly limited.

As a method of applying the two solutions of the ammoniacal silver nitrate solution and the reducing agent solution so as to be mixed on the surface forming the electroless silver plating layer, the two aqueous solutions are mixed in advance and the mixed solution is sprayed. A method of spraying on the surface of the undercoat layer using a gun or the like, a method of spraying using a concentric spray gun having a structure in which two types of aqueous solutions are mixed in the head of the spray gun and immediately discharged, and two types of aqueous solutions are sprayed. There is a method of discharging and spraying each from a double-headed spray gun having a spray nozzle, a method of spraying two kinds of aqueous solutions at the same time using two separate spray guns, and the like. These can be arbitrarily selected according to the situation.

Subsequently, it is preferable to wash the surface of the electroless silver plating layer with deionized water to remove the solution or the like remaining on the surface after the silver mirror reaction. After that, it is preferable to subsequently perform the surface treatment of the present invention. After the treatment is completed, it is preferable to wash the silver surface with deionized water and dry it.

Since the metallic silver formed as described above is easily damaged, in the present invention, a top coat layer is further provided on the surface of the silver plating layer. The top coat layer is preferably formed by applying a paint made of a heat or photocurable resin.

As the paint used for forming the top coat layer used in the present invention (hereinafter referred to as the paint for the top coat layer), a paint containing a thermosetting resin is generally used. Examples of the thermosetting resin include epoxy resins, unsaturated polyester resins, melamine resins, silicon resins, and acrylics described in JP-A-2000-129448, JP-A-2003-155580, and JP-A-2006-111857. Examples thereof include silicon resin and urethane resin. Among these, a paint containing a melamine resin, a urethane resin, and an acrylic silicon resin is preferably used because of its high transparency and easy application.

As the coating material containing a urethane resin, a two-component curable urethane-based coating material in which a polyol resin such as an alkyd polyol, a polyester polyol, or an acrylic polyol and a polyisocyanate compound as a curing agent is mixed is preferable. As the paint containing the acrylic silicone resin, an acrylic silicone-based paint in which an acrylic resin and an alkoxysilane compound (silicon-based curing agent) are mixed as a curing agent is preferable.

Examples of commercially available thermosetting paints include Origin Tuk (registered trademark) # 100 (acrylic silicone paint) manufactured by Origin Co., Ltd. and Neopolynal (registered trademark) No. 100 manufactured by Ohashi Chemical Industries, Ltd. 800S (acrylic silicone paint), Omac (registered trademark) No. 100 (E) Clear FV (Acrylic Silicone Paint), Polynal (Registered Trademark) 800 (Acrylic Urethane Paint), Neohard (Registered Trademark) Clear H (Acrylic Melamine Paint) and the like are preferably used.

The thermosetting type coating material for a top coat layer used in the present invention can be obtained by dissolving or diluting the above-mentioned coating composition in an organic solvent. Examples of such an organic solvent include hydrocarbons such as toluene, xylene, cyclohexane and T-SOL (registered trademark) 100FLUID (trade name, manufactured by JXTG Energy Co., Ltd.), and alcohols such as methanol, ethanol, isopropyl alcohol and butyl alcohol. Examples include ethers such as butyl cellosolve, tetrahydrofuran and methyl cellosolve acetate, esters such as ethyl acetate, n-butyl acetate, isobutyl acetate and isobutyl isobutyrate, and ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. It is not limited. These organic solvents are appropriately selected depending on the solubility of the coating composition, the drying time and temperature, the surface quality improvement of the coated surface, and the like, and may be used alone or in combination of two or more.

The coating method for the top coat layer may be a conventionally known coating method, for example, a gravure roll method, a reverse roll method, a dip roll method, a bar coater method, a knife coater method, an air spray method, an airless spray method, or a dip. The method and the like can be mentioned. Of these, the air spray method, which can be applied to complicated surface shapes, is particularly preferable.

The thermosetting type paint for the top coat layer is dried after application and crosslinked to form the top coat layer. Although it can be naturally dried at room temperature, it is preferable to heat it to promote the cross-linking reaction. A higher heating temperature is preferable because the cross-linking reaction can be promoted, but if the temperature is too high, the base material may be deformed, so it is necessary to heat within a temperature range in which the base material is not deformed. Usually, heating is performed at 60 to 160 ° C. for about 20 to 120 minutes.

The thickness of the top coat layer formed from the thermosetting paint is preferably in the range of 10 to 50 μm. If the layer is too thin, the function of protecting the silver plating layer cannot be obtained, and a uniform coating film cannot be formed. On the contrary, if it is too thick, the peripheral portion tends to be thicker locally, and it is difficult to obtain a uniform coating film. Further, if the top coat layer is too thick, the optical path passing through the layer becomes long and the light loss increases, which is not preferable because the reflectance of the silver-plated layer is lowered.

Coloring materials such as pigments and dyes may be added to the paint for the top coat layer in order to improve the design. Pigments include organic pigments such as carbon black, quinacridone, naphthol red, cyanine blue, cyanine green, and Hansa yellow, and inorganic pigments such as titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, mica, petals, and composite metal oxides. Pigments can be mentioned, and one or a combination of two or more selected from these pigments can be used. The dispersion of the pigment is not particularly limited, and a method of directly dispersing the pigment powder by a usual method, for example, a dyno mill, a paint shaker, a sand mill, a ball mill, a kneader, a roll, a dissolver, a homogenizer, ultrasonic vibration, a stirrer, etc. Is used. At that time, a dispersant, a dispersion aid, a thickener, a coupling agent and the like can be used. The amount of the pigment added is not particularly limited because the hiding power differs depending on the type of pigment, but is usually 0.1 to 5% by mass with respect to the total solid content of the coating material.

Examples of dyes include azo-based, anthraquinone-based, indicoid-based, sulfide-based, triphenylmethane-based, xanthene-based, alizarin-based, acridine-based, quinoneimine-based, thiazole-based, methine-based, nitro-based, and nitroso-based dyes. It can be mentioned, and one kind or a combination of two or more kinds selected from these dyes can be used. The amount of the dye added is not particularly limited because the hiding power differs depending on the type of dye, but is usually 0.1 to 5% by mass with respect to the total solid content of the paint for the top coat layer.

The top coat layer may further contain a leveling agent, a metal powder, a glass powder, an antibacterial agent, an antioxidant, an ultraviolet absorber, a light stabilizer and the like as additives.

As the base material of the silver-plated coated body obtained by the present invention, various plastics, metals, glasses, rubbers and the like are used. Examples of plastics include polycarbonate resin, acrylic resin, ABS resin, vinyl chloride resin, epoxy resin, phenol resin, polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin and other polyester resins, fluororesin, polypropylene ( Examples thereof include a PP) resin, a resin obtained by combining these, and a fiber-reinforced plastic (FRP) reinforced with organic fibers such as nylon fiber and pulp fiber, but the present invention is not particularly limited. Examples of the metal include iron, aluminum, stainless steel, copper, brass and the like, but the metal is not particularly limited. The glass is also not particularly limited, such as inorganic glass or plastic glass.

Hereinafter, the present invention will be described with reference to examples, but this description does not limit the present invention. In addition,% as a unit in the following description is based on mass unless otherwise specified.

(Example 1)
Acrylic polyol resin (Mirror Shine Undercoat Clear D-1 manufactured by Ohashi Chemical Industries, Ltd.), polyisocyanate compound (hardener N for mirror shine undercoat manufactured by Ohashi Chemical Industries, Ltd.) and thinner (methyl ethyl ketone and butyl cell solve) in mass ratio (Mixed at a ratio of 1: 1) was mixed at a mass ratio of 10: 2:10. Further, 2% of 3-mercaptopropyltrimethoxysilane and 2% of 3-isocyanatepropyltrimethoxysilane were added to this coating composition to obtain an undercoat coating composition. This coating composition was spray-coated on an ABS resin plate whose surface was washed and dried with isopropyl alcohol, and then heat-dried at 80 ° C. for 1 hour to form an undercoat layer having a thickness of 20 μm.

0.1 mol of hydrochloric acid and 0.1 mol of stannous chloride were added to water to prepare 1000 g of a silver mirror activation treatment solution, which was sprayed onto the undercoat layer with a spray gun for activation treatment, and then into deionized water. And washed. Subsequently, 0.05 mol of silver nitrate was dissolved in water to make 1000 g, and this liquid was sprayed with a spray gun to perform activation treatment with silver ions, and then washed with deionized water.

The silver mirror plating solution was prepared as follows. A silver nitrate solution prepared by dissolving 20 g of silver nitrate in deionized water to make 1000 g and another ammonia solution prepared by dissolving 100 g of a 28% aqueous ammonia solution and 5 g of monoethanolamine in deionized water to make 1000 g were prepared. Prior to use, these silver nitrate solutions and ammonia solutions were mixed 1: 1 to obtain an ammoniacal silver nitrate solution. Next, a reducing agent solution prepared by dissolving 10 g of hydrazine sulfate, 5 g of monoethanolamine, and 10 g of sodium hydroxide in deionized water to make 1000 g was prepared. The ammoniacal silver nitrate solution and the reducing agent solution thus obtained were simultaneously sprayed using a double-headed spray gun to form a silver-plated layer, and washed with deionized water.

Subsequently, the surface treatment liquid was sprayed onto the silver plating layer at 25 ° C. for 20 seconds, washed with deionized water, sufficiently removed from the surface water, and then dried at 45 ° C. for 30 minutes to obtain a silver plating sample. And said. The following surface treatment liquids (0) to (12) were used as the surface treatment liquid.

<Surface treatment liquid (0)>
Deionized water only.

<Surface treatment liquid (1)>
Deionized water was added to 0.1 mol of urea to make 1 liter.

<Surface treatment liquid (2)>
Deionized water was added to 0.2 mol of urea to make 1 liter.

<Surface treatment liquid (3)>
Deionized water was added to 0.5 mol of urea to make 1 liter.

<Surface treatment liquid (4)>
Deionized water was added to 0.2 mol of 1-methylurea to make 1 liter.

<Surface treatment liquid (5)>
Deionized water was added to 0.2 mol of 1,3-diethylurea to make 1 liter.

<Surface treatment liquid (6)>
Deionized water was added to 0.2 mol of 1-butyl urea to make 1 liter.

<Surface treatment liquid (7)>
Deionized water was added to 0.2 mol of 1-allyl urea to make 1 liter.

<Surface treatment liquid (8)>
Deionized water was added to 0.2 mol of 2-imidazolidinone to make 1 liter.

<Surface treatment liquid (9)>
Deionized water was added to 10 mmol of potassium sulfite and 5 mmol of 2-mercaptopropionic acid to make 1 liter. The pH was adjusted to 7.0 with sulfuric acid.

<Surface treatment liquid (10)>
0.2 mol of urea was added to 1 liter of the surface treatment liquid (9).

<Surface treatment liquid (11)>
Deionized water was added to 10 mmol of potassium sulfite and 1 mmol of 5-mercapto-1-phenyl-1H-tetrazole to make 1 liter. The pH was adjusted to 7.0 with sulfuric acid.

<Surface treatment liquid (12)>
0.2 mol of urea was added to 1 liter of the surface treatment liquid (11).

A top coat layer was provided on the prepared silver-plated sample as follows. Acrylic silicon-based top coat paint (Ohashi Chemical Industries, Ltd. Omac No. 100 (E) Clear FV), silicone-based curing agent (Ohashi Chemical Industries, Ltd. curing agent W), thinner (methyl ethyl ketone and butyl cell solve, mass ratio 1: 1) (Mixed at a ratio) was mixed at a mass ratio of 6: 1: 6 to obtain a top coat paint. This topcoat paint is spray-applied on the surface-treated silver-plated layer using a spray gun, and then heated and dried at 80 ° C. for 30 minutes to form a topcoat layer with a thickness of 20 μm, and a sample of the silver-plated body is prepared. Obtained.

The adhesion of the silver-plated sample was evaluated under the following conditions. After scratching the silver-plated sample with a cutter knife so that it reaches the ABS base material from the top coat layer surface, these samples are subjected to a salt spray tester (model STP-) of Suga Test Instruments Co., Ltd. In 90), 5% saline solution was sprayed in an environment of 35 ° C. for 20 days. The sample after spraying with salt water is washed with water, dried, and the cellophane tape is strongly attached from the part where the cross is scratched, and then the tape is peeled off. bottom. The results are shown in Table 1.
〇: The peeling of the top coat layer cannot be confirmed with the naked eye.
Δ: The width of the widest part of the peeling of the top coat layer is less than 2 mm from the center of the cut line.
X: The width of the widest part of the peeling of the top coat layer is 2 mm or more from the center of the cut line.

(Example 2)
A sample of the silver-plated body was prepared in exactly the same manner as in Example 1 except that the top coat layer was replaced with the one shown below. The evaluation was also performed in the same manner as in Example 1. The evaluation results of Example 2 are shown in Table 2.

Acrylic urethane-based top coat paint (Polynal No. 800HN-INP manufactured by Ohashi Chemical Industries, Ltd.), isocyanate-based curing agent (hardener IP60 manufactured by Ohashi Chemical Industries, Ltd.), thinner (thinner No. 6820 manufactured by Ohashi Chemical Industries, Ltd.) by mass ratio A top coat paint was obtained by mixing at a ratio of 6: 1: 5. This topcoat paint is spray-applied on the surface-treated silver-plated layer using a spray gun, and then heated and dried at 80 ° C. for 60 minutes to form a topcoat layer with a thickness of 20 μm, and a sample of the silver-plated body is prepared. Obtained.

(Example 3)
A sample of the silver-plated coated body was prepared in the same manner as in Example 2 except that the following surface treatment liquids (13) to (19) were used as the surface treatment liquid.

<Surface treatment liquid (13)>
Deionized water was added to 10 mmol of potassium sulfite and 5 mmol of 2-mercaptopropionic acid to make 1 liter. The pH was adjusted to 7.0 with sulfuric acid.

<Surface treatment liquid (14)>
0.2 mol of urea was added to 1 liter of the surface treatment liquid (13).

<Surface treatment liquid (15)>
0.2 mol of 1-methylurea was added to 1 liter of the surface treatment liquid (13).

<Surface treatment liquid (16)>
0.2 mol of 1,3-diethylurea was added to 1 liter of the surface treatment liquid (13).

<Surface treatment liquid (17)>
Deionized water was added to 10 mmol of potassium sulfite and 5 mmol of cysteine to make 1 liter. The pH was adjusted to 7.0 with sulfuric acid.

<Surface treatment liquid (18)>
0.2 mol of urea was added to 1 liter of the surface treatment liquid (17).

<Surface treatment liquid (19)>
Deionized water was added to 10 mmol of potassium sulfite and 5 mmol of mercaptosuccinic acid to make 1 liter. The pH was adjusted to 7.0 with sulfuric acid.

<Surface treatment liquid (20)>
0.2 mol of urea was added to 1 liter of the surface treatment liquid (19).

The adhesion of the silver-plated sample was evaluated under the following high-temperature and high-humidity environment. The silver-plated samples were cross-scratched with a utility knife so as to reach the ABS substrate from the topcoat layer surface, and then these samples were stored in an environment of 65 ° C. and 95% RH for 20 days. Then, the sample was washed with water and dried, and after the cellophane tape was strongly attached on the portion where the cross was scratched, the tape was peeled off, and the judgment was made based on the peeling condition of the top coat layer based on the following criteria. The results are shown in Table 1.
〇: The peeling of the top coat layer cannot be confirmed with the naked eye.
Δ: The width of the widest part of the peeling of the top coat layer is less than 2 mm from the center of the cut line.
X: The width of the widest part of the peeling of the top coat layer is 2 mm or more from the center of the cut line.

The evaluation results of Example 3 are shown in Table 3.

As is clear from the results of Tables 1, 2 and 3, according to the present invention, the adhesive strength between the silver plating layer and the top coat layer is improved, and the silver plating coating has sufficient adhesive strength even in a harsh environment. It is possible to provide a method for producing a silver-plated coated body capable of obtaining a body.

Claims (1)

In the method for producing a silver-plated coating body having at least a silver-plated layer and a top coat layer on the base material in this order, a urea or a urea derivative represented by the following general formula (1) is contained after the silver-plated layer is formed. A method for producing a silver-plated coating body, which comprises treating the plating layer with a surface treatment liquid to further form a top coat layer.

In the formula, R ₁ and R ₂ represent a hydrogen atom or an alkyl group or an alkenyl group having 4 or less carbon atoms, and R ₁ and R ₂ may be linked to form a ring.