An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

An electrorheological fluid which comprises a dispersion medium containing fluorine atoms in an amount larger than 0 wt % but not larger than 50.0 wt % and particles for electrorheological fluid use that are contained in the dispersion medium in an amount of 10-50 vol % of the total volume of the dispersion medium and the particles, the particles comprising a sulfonic-acid-group-containing polymer having a sulfonic acid group content of 30-70 wt %.

Provided is a coated steel sheet having excellent press formability. The coated steel sheet includes a base steel sheet and, on at least one side of the base steel sheet, a film containing organic resin and wax. The organic resin is at least one selected from the group consisting of acrylic resins, epoxy resins, urethane resins, phenolic resins, vinyl acetate resins, and polyester resins. The wax is polyolefin wax having a melting point that is 100 C. or more and 145 C. or less and an average particle size that is 3.0 m or less. The proportion of the wax in the film is 5 mass % or more and 70 mass % or less. Coating weight variation is 0.300 or less. Coating weight .sub.W of the film is 0.3 g/m.sup.2 or more.

Provided is a coated steel sheet having excellent press formability. The coated steel sheet includes a base steel sheet and, on at least one side of the base steel sheet, a film containing organic resin and wax. The organic resin is at least one selected from the group consisting of acrylic resins, epoxy resins, urethane resins, phenolic resins, vinyl acetate resins, and polyester resins. The wax is polyolefin wax having a melting point that is 100 C. or more and 145 C. or less and an average particle size that is 3.0 m or less. The proportion of the wax in the film is 5 mass % or more and 70 mass % or less. Coating weight variation is 0.300 or less. Coating weight .sub.W of the film is 0.3 g/m.sup.2 or more.