Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/46—Electroplating: Baths therefor from solutions of silver
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/64—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of silver

Definitions

• the present invention relates to an electrolytic silver plating solution. Specifically, the present invention relates to an electrolytic silver plating solution capable of obtaining a plating film with high gloss and high reflectance, and relates to an electrolytic silver plating solution using cyanide as a silver source. Furthermore, the present invention relates to an electrolytic silver plating solution capable of obtaining a plating film having a high hardness, and relates to an electrolytic silver plating solution using cyanide as a silver source.
• Silver has been used extensively in jewelry since ancient times due to its white luster. Since silver is a relatively large amount of precious metal and is inexpensive, silver plating has been applied to decorative applications such as silver accessories and tableware even today. Further, since silver has the highest electrical conductivity at room temperature, silver plating is often used for lead frames and substrates for electronic devices such as ICs and transistors. Furthermore, since silver has the highest visible light reflectance among all metals, silver plating is often applied on lead frames and various substrates for light emitting devices represented by LEDs. In addition, silver plating is also used for bearing parts and uses utilizing the antibacterial property of silver.
• Patent Document 1 and Patent Document 2 describe a method for producing a brightener containing sulfur. However, no consideration is given to the glossiness and reflection characteristics of the resulting plating film.
• Patent Document 3 describes a technique for adjusting the crystal size of silver plating
• Patent Document 4 describes a technique of a silver plating solution that can obtain a silver plating film having a high reflectance.
• the glossiness and reflectance of the silver plating film are greatly affected by the surface roughness and glossiness of the base before plating.
• an object of the present invention is to provide an electrolytic silver plating solution capable of obtaining a silver film having a high gloss and a high reflectance even on a base with a matte appearance. Furthermore, it is providing the electrolytic silver plating solution which can obtain the plating film of high hardness.
• the present inventors have found that a silver film having a high gloss and a high reflectance can be obtained even on a matte appearance by adding a saturated fatty acid and / or a salt thereof to an electrolytic silver plating solution. . Furthermore, it has been found that a plating film with high hardness can be obtained by adding a selenium compound at a predetermined concentration to the electrolytic silver plating solution, and the present invention has been completed.
• the present invention for solving the above problems is described below.
• the saturated fatty acid and / or salt thereof is decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, and salts thereof Electrolytic silver plating solution as described in [1] containing at least 1 sort (s) chosen from.
• the electrolytic silver plating solution of the present invention can stably provide a highly glossy and highly reflective silver coating even on a matte appearance undercoat. This eliminates the need to prepare a smooth base, leading to cost reduction. In addition, since stable performance can be obtained, the production yield can be improved.
• a selenium compound is added at a predetermined concentration, in addition to the above effects, an effect that a plating film with high hardness can be obtained is obtained.
• the electrolytic silver plating solution of the present invention contains a silver cyanide complex, an electrically conductive salt, a selenium salt, and a saturated fatty acid salt as silver salts.
• silver Cyanide Complex In the electrolytic silver plating solution of the present invention, a known silver cyanide complex can be used without limitation as a silver source. Examples of the silver cyanide complex include silver cyanide, silver potassium cyanide, and sodium silver cyanide. These may be used alone or in combination of two or more.
• the compounding amount of the silver cyanide complex is preferably 10 to 100 g / L, more preferably 20 to 70 g / L, as the silver ion concentration.
• the silver ion concentration is less than 10 g / L, the deposition efficiency may be lowered and a desired silver film thickness may not be obtained.
• the silver ion concentration exceeds 100 g / L, the silver salt loss due to taking out of the plating solution by the object to be plated increases, which is not economical.
• the electroconductive salt blended in the electrolytic silver plating solution of the present invention is not particularly limited as long as it has electrical conductivity in an aqueous solution, but it can be used industrially stably or an electrolytic silver plating solution.
• soluble organic acid salts are also preferred. These may be used alone or in combination of two or more.
• cyanate include potassium cyanide and sodium cyanide.
• the phosphate include potassium phosphate, sodium phosphate, ammonium phosphate, and potassium pyrophosphate.
• nitrates include potassium nitrate, sodium nitrate, and ammonium nitrate.
• citrate examples include potassium citrate, sodium citrate, ammonium citrate and the like.
• tartaric acid examples include potassium tartrate, sodium tartrate, potassium sodium tartrate and the like.
• the concentration of the electroconductive salt in the electrolytic silver plating solution of the present invention is preferably 5 to 250 g / L, and more preferably 50 to 150 g / L.
• concentration of the electroconductive salt is less than 5 g / L, the electric resistance of the plating solution becomes too high, and there may be a case where plating production with an appropriate cathode current density cannot be performed.
• the selenium compound blended in the electrolytic silver plating solution of the present invention is a selenium-containing compound, and particularly selenocyanic acid and its salt, selenic acid and its salt, selenious acid and its salt are preferable.
• selenocyanic acid and salts thereof include selenocyanic acid and potassium selenocyanate.
• selenic acid and salts thereof include selenic acid, potassium selenate, and sodium selenate.
• selenious acid and salts thereof include selenious acid, potassium selenite, sodium selenite, selenium dioxide, and the like. These may be used alone or in combination of two or more.
• the concentration of the selenium compound in the electrolytic silver plating solution of the present invention is preferably 0.1 to 200 mg / L as the selenium concentration. If the blending amount of the selenium compound deviates from the above concentration, a shiny silver film may not be obtained or plating production with an appropriate cathode current density may not be possible.
• the selenium concentration for obtaining a silver film having excellent glossiness is preferably 0.1 to 200 mg / L. When a selenium compound is contained in this range, a silver film having excellent gloss can be obtained. If it is less than 0.1 mg / L, the gloss of the silver film may not be sufficiently improved. When it exceeds 200 mg / L, it becomes economically disadvantageous.
• the selenium concentration may be 0.1 to 80 mg / L, and is preferably 1 to 10 mg / L from the economical viewpoint.
• the selenium concentration for obtaining a silver film having a high film hardness is preferably 30 to 200 mg / L.
• the selenium compound is contained within this range, a silver film having excellent gloss and high film hardness can be obtained. If it is less than 80 mg / L, the hardness of the silver film may not be sufficiently improved. When it exceeds 200 mg / L, it becomes economically disadvantageous.
• the selenium concentration is more preferably from 50 to 180 mg / L, and more preferably from 80 to 160 mg / L economically.
• saturated fatty acid (salt) The saturated fatty acid and / or salt thereof (hereinafter abbreviated as “saturated fatty acid (salt)”) blended in the electrolytic silver plating solution of the present invention is a saturated fatty acid having 10 to 20 carbon atoms and / or a salt thereof.
• Specific examples include decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, and salts thereof. These may be used alone or in combination of two or more.
• the concentration of the saturated fatty acid (salt) in the electrolytic silver plating solution of the present invention is preferably 0.01 to 20 g / L, more preferably 0.1 to 5 g / L.
• concentration of the saturated fatty acid (salt) is less than 0.01 g / L, the surface roughness of the base film affects the gloss of the silver plating film. If the concentration of the saturated fatty acid (salt) exceeds 20 g / L, precipitation may occur, and the viscosity of the plating solution may increase excessively, resulting in failure to produce a plating with an appropriate cathode current density. The carry-out amount may increase.
• components such as a surfactant are included in a range that does not impair the purpose of the present invention in order to reduce the viscosity and suppress the occurrence of unevenness of the silver film.
• the surfactant include an anionic surfactant such as polyoxyethylene alkyl ether sodium sulfate and a nonionic surfactant such as a polyoxyethylene alkyl ether condensate.
• the electrolytic silver plating solution of the present invention is preferably used at a pH of 6 to 14, more preferably at a pH of 8 to 13.
• pH is less than 6
• cathode current efficiency falls and the film
• pH exceeds 14 the external appearance of the film obtained is deteriorated.
• the temperature of the electrolytic silver plating solution of the present invention is preferably 10 to 60 ° C, more preferably 20 to 40 ° C. If the temperature of the plating bath is out of the above range, it is not preferable because the cathode current efficiency is lowered or the stability of the plating bath is impaired.
• the current density when using the electrolytic silver plating solution of the present invention is set in consideration of the composition of the plating solution, the solution temperature, and other conditions.
• the current density is preferably set to 3 to 15 A / dm 2 . If the current density is not set appropriately, the appearance of plating and the characteristics of the plating film may be abnormal. In addition, the plating bath may become unstable and decomposition of the plating solution component may occur.
• Examples 1 to 12, Comparative Examples 1 to 5 A 0.1 dm 2 copper plate was used as the object to be plated. First, this was degreased with an alkaline degreasing solution and then neutralized with dilute sulfuric acid. Thereafter, matte copper plating was applied in an amount of about 1 ⁇ m using a cyan bath. Then, about 0.1 ⁇ m of silver plating was applied by a cyan strike bath.
• plating solutions of Examples 1 to 12 and Comparative Examples 1 to 5 were prepared.
• the object to be plated is immersed in 1 L of the prepared plating solution, electrolytic silver plating operation is performed until the silver film thickness reaches 4 ⁇ m under the conditions described in Tables 1 and 2, and after washing with clean pure water, drying is performed. did.
• concentration of the selenium compound of Table 1 is a selenium conversion amount.
• the glossiness and reflectance of the silver films of Examples 1 to 12 and Comparative Examples 1 to 5 obtained as described above were measured.
• the glossiness here is a numerical value measured with a densitometer ND-11 manufactured by Nippon Denshoku Industries Co., Ltd.
• the reflectance here is a 450 nm SCI measurement value measured with a spectrocolorimeter CM-2600d manufactured by Konica Minolta Sensing Co., Ltd.
• the measurement results are shown in Tables 1 and 2.
• the silver films obtained in Examples 1 to 12 all had a glossiness of 2.0 or more and a reflectance of 98% or more.
• the color tone was silver white, and there was no unevenness and the appearance was good.
• the bath stability was also good.
• the silver films obtained in Comparative Examples 1 to 5 all had a glossiness of less than 1.8 and a reflectance of 97% or less.
• the color tone was silver white, and there was no unevenness and the appearance was good.
• the bath stability was also good.
• the silver film obtained in Comparative Example 6 was a brittle plating film with a burnt appearance. The bath stability was good.
• Examples 13 to 24, Comparative Examples 7 to 11, Reference Examples 1 and 2 A 0.1 dm 2 copper plate was used as the object to be plated. First, this was degreased with an alkaline degreasing solution and then neutralized with dilute sulfuric acid. Thereafter, matte copper plating was applied in an amount of about 1 ⁇ m using a cyan bath. Then, about 0.1 ⁇ m of silver plating was applied by a cyan strike bath.
• the plating solutions of Examples 13 to 24, Comparative Examples 7 to 11, and Reference Examples 1 and 2 were prepared with the compositions described in Tables 3 and 4. After immersing the object to be plated in 1 L of the prepared plating solution and performing electrolytic silver plating operation until the silver film thickness reaches 20 ⁇ m under the conditions described in Tables 3 and 4, and washing with clean pure water, Dried.
• Hardness was measured for the silver films of Examples 13 to 24, Comparative Examples 7 to 11, and Reference Examples 1 and 2 obtained as described above. The hardness was measured immediately after plating and 6 months after plating.
• the term “hardness” as used herein refers to micro Vickers hardness obtained by holding for 10 seconds at a test force of 10 g using a Mitutoyo micro hardness tester MVK-H300. The results obtained by removing the three times are averaged.
• the glossiness of the silver films obtained in Reference Examples 1 and 2 was 2.05 and 2.02, respectively.

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• 2018
  • 2018-03-26 CN CN201880017469.2A patent/CN110392751B/zh active Active
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