Surface-treated steel sheet for organic resin coating and method of producing same, and organic resin coated steel sheet and method of producing same

A method of producing a surface-treated steel sheet for organic resin coating, the method comprising:

• applying, to a surface of a zinc or zinc alloy coated or plated steel sheet, a surface-treatment solution containing:
• a resin compound (A) having a bisphenol skeleton represented by general formula (I) below;
• a cationic urethane resin emulsion (B) having at least one cationic functional group selected from the group consisting of primary to tertiary amino groups and a quaternary ammonium base;
• a silane coupling agent (C) having at least one reactive functional group selected from the group consisting of an active hydrogen-containing amino group, an epoxy group, a mercapto group, and a methacryloxy group;
• an organic titanium chelate compound (D);
• a tetravalent vanadium compound (E);
• a molybdate compound (F);
• a fluorine compound (G) which is at least one selected from the group consisting of fluorosilicic acid, fluoroboric acid, fluorotitanic acid, acid ammonium fluoride, sodium fluoride, and fluorozirconic acid;
• and
• water (H),
• within a range satisfying conditions (1) to (6) below and with a pH of 4 to 5 to form a surface-treatment layer such that a coating weight of the surface-treatment layer per surface is 0.005 g/m2 to 0.18 g/m2 after drying of the surface-treatment solution,
• (1) a ratio of a solid mass (BS) of the cationic urethane resin emulsion (B) to a total of a solid mass (AS) of the resin compound (A), the solid mass (BS) of the cationic urethane resin emulsion (B), and a solid mass (CS) of the silane coupling agent (C), represented by [(BS)/{(AS)+(BS)+(CS)}], is from 0.10 to 0.30,
• (2) a ratio of the solid mass (CS) of the silane coupling agent (C) to a total of the solid mass (AS) of the resin compound (A), the solid mass (BS) of the cationic urethane resin emulsion (B), and the solid mass (CS) of the silane coupling agent (C), represented by [(CS)/{(AS)+(BS)+(CS)}], is from 0.60 to 0.85,
• (3) a ratio of the solid mass (CS) of the silane coupling agent (C) to a titanium equivalent mass (DTi) of the organic titanium chelate compound (D), represented by {(CS)/(DTi)}, is from 50 to 70,
• (4) a ratio of a vanadium equivalent mass (EV) of the tetravalent vanadium compound (E) to the titanium equivalent mass (DTi) of the organic titanium chelate compound (D), represented by {(EV)/(DTi)}, is from 0.30 to 0.50,
• (5) a ratio of a molybdenum equivalent mass (FMo) of the molybdate compound (F) to a total of the solid mass (AS) of the resin compound (A), the solid mass (BS) of the cationic urethane resin emulsion (B), and the solid mass (CS) of the silane coupling agent (C), represented by [(FMo)/{(AS)+(BS)+(CS)}], is from 0.003 to 0.030, and
• (6) a ratio of a fluorine equivalent mass (GF) of the fluorine compound (G) to a total of the solid mass (AS) of the resin compound (A), the solid mass (BS) of the cationic urethane resin emulsion (B), and the solid mass (CS) of the silane coupling agent (C), represented by [(GF)/{(AS)+(BS)+(CS)}], is from 0.101 to 0.200,
• where Y1 and Y2 bonded to benzene rings each independently represent a hydrogen atom or a Z group represented by general formula (II) or (III) below, where an average number of substituent Z groups per benzene ring is from 0.2 to 1.0, and n represents an integer from 2 to 50,
• where R1, R2, R3, R4, and R5 each independently represent a hydrogen atom, a C1-C10 alkyl group, or a C1-C10 hydroxyalkyl group, and A represents a hydroxide ion or an acid ion.