US Patent 9028029 Inkjet printing method

A printing method is performed on a plurality of inkjet print heads to which humidified air is supplied to retain the humidity in the print heads. Ink colors for the plurality of heads are arranged in a sequence corresponding to ink characteristics. The plurality of print heads is divided into groups, with one of the groups being subjected to preliminary ejection on a sheet. The other print head group not subjected to preliminary ejection is located in a more upstream area with respect to a conveyance direction of the sheet.