# US 7,407,569 B2 · Gold plating solution and gold plating method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,407,569 B2 - Document ID: US7407569B2 - Status: Granted - Kind: B2 - Application number: 10/937,392 - Filed: 2004-09-10 - Published: 2005-03-17 - Granted: 2008-08-05 - Earliest claimed: 2002-03-13 - Assignees: Mitsubishi Chemical Corporation - Inventors: Fumikazu Mizutani; Hiroshi Takaha; Makoto Ishikawa; Yasuhiro Kawase - Web page: https://patentgrep.com/patent/US7407569B2 ## CPC - C25D 3/48: of gold - C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR ## Abstract A gold plating solution comprising iodide ions, gold iodide complex ions and a non-aqueous solvent, which is less toxic and stable, while having a performance comparable to a cyanide type gold plating solution. The present invention further provides a gold plating solution comprising iodide ions, gold iodide complex ions, a non-aqueous solvent and a water-soluble polymer, which is less toxic and stable, while having a performance comparable to a cyanide type gold plating solution and which is capable of forming a gold plating film in which gold crystal particle sizes are very fine and grain boundaries are dense. The present invention further provides a gold plating method employing such a gold plating solution. ## Claims ### Claim 1 A gold plating solution, comprising: iodine, iodide ions, gold iodide complex ions, at least 10 wt % of a non-aqueous solvent and 1-85 wt % water, based on the weight of the plating solution. ### Claim 2 (depends on 1) The gold plating solution according to claim 1, wherein the content of elemental iodine ranges from 0.5 to 50 wt %. ### Claim 3 (depends on 1) The gold plating solution according to claim 1, wherein the non-aqueous solvent is at least one member selected from the group consisting of a compound having an alcoholic hydroxyl group and/or a phenolic hydroxyl group, and an aprotic organic solvent. ### Claim 4 (depends on 3) The gold plating solution according to claim 3 wherein the compound having an alcoholic hydroxyl group has at least two alcoholic hydroxyl groups. ### Claim 5 (depends on 1) The gold plating solution according to claim 1, which contains substantially no cyanide. ### Claim 6 (depends on 1) A gold plating method, comprising: coating a substrate with the gold plating solution as defined in claim 1. ### Claim 7 (depends on 6) The gold plating method according to claim 6, which is an electrolytic plating method. ### Claim 8 (depends on 7) The gold plating method according to claim 7, wherein the electrolytic plating is conducted in a cell having an anode of gold or a gold alloy. ### Claim 9 A gold plating solution, comprising: iodine, iodide ions, gold iodide complex ions, at least 10 wt % of a non-aqueous solvent and 1-85 wt % water, based on the weight of the plating solution, and a water soluble polymer. ### Claim 10 (depends on 9) The gold plating solution according to claim 9, wherein the content of elemental iodine ranges from 0.5 to 50 wt %. ### Claim 11 (depends on 9) The gold plating solution according to claim 9, wherein the non-aqueous solvent is at least one member selected from the group consisting of a compound having an alcoholic hydroxyl group and/or a phenolic hydroxyl group, and an aprotic organic solvent. ### Claim 12 (depends on 11) The gold plating solution according to claim 11, wherein the compound having an alcoholic hydroxyl group has at least two alcoholic hydroxyl groups. ### Claim 13 (depends on 11) The gold plating solution according to claim 11, wherein the non-aqueous solvent is at least one member selected from the group consisting of ethylene glycol, propylene glycol, glycerol and γ-butyrolactone. ### Claim 14 (depends on 9) The gold plating solution according to claim 9, wherein the water-soluble polymer has at least one group selected from the following substituents and connecting groups consisting of (D1) to (D3) in the main chain or side chain in the repeating unit structure of the polymer: wherein (D1) is at least one acidic substituent selected from the group consisting of —CO2H, —SO3H and PO3H2, (D2) is at least one basic substituent or connecting group selected from the group consisting of —CONR—, —CH2—NR—CH2—, —NR2 and —NR3+ wherein R is a hydrogen atom, a C1-4 alkyl group, a methylene group or a halogen atom, provided that when two or more R groups are present in one substituent, they may be the same or different, and (D3) is —OH, as a non-electrolyte substituent. ### Claim 15 (depends on 14) The gold plating solution according to claim 14, wherein the water-soluble polymer has, as a water-soluble functional group, an alcoholic hydroxyl group and/or —CONR—, wherein R is a hydrogen atom, a C1-4 alkyl group, a methylene group or a halogen atom. ### Claim 16 (depends on 15) The gold plating solution according to claim 15, wherein the water-soluble polymer is at least one member selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, starch and cyclodextrin. ### Claim 17 (depends on 9) The gold plating solution according to claim 9, which contains substantially no cyanide. ### Claim 18 (depends on 9) A gold plating method, comprising: coating a substrate with the gold plating solution as defined in claim 9. ### Claim 19 (depends on 18) The gold plating method according to claim 18, which is an electrolytic plating method. ### Claim 20 (depends on 19) The gold plating method according to claim 19, wherein the electrolytic plating is conducted in a cell having an anode of gold or a gold alloy. ### Claim 21 A gold plating solution, comprising: iodine, iodide ions, gold iodide complex ions, at least 10 wt % of a non-aqueous solvent of ethylene glycol or γ-butylolactone, and 1-85 wt % water, based on the weight of the plating solution.