Patent ID: 8167425

Claim:
A method of printing an indication of defective printing, comprising: printing one page of print data on a print medium using an inkjet head that moves in a main scanning direction perpendicular to a transportation direction by driving a carriage motor and a paper transportation motor to convey the print medium in the transportation direction; executing an interrupt process after completing printing one page of print data but before executing a control command indicating a page break, the interrupt process including: interrupting an operation of printing the print data that drives the carriage motor and the paper transportation motor, moving the inkjet head to a standby position by driving the carriage motor, detecting whether or not ink droplets are being discharged normally from each ink nozzle of the inkjet head, and when it is detected that ink droplets are not being discharged normally from an ink nozzle in the standby position, then conveying the print medium a predetermined distance in a reverse direction that is opposite to the transportation direction in which the print medium is conveyed when printing the one page of print data by driving the paper transportation motor, and printing previously stored print data representing a defective printing mark on the print medium; wherein detecting whether or not ink droplets are being discharged normally from each ink nozzle of the inkjet head comprises detecting a current change produced by charged ink landing on an absorbent member; and wherein the print data representing a defective printing mark is data for an image that can be printed in a band on the print medium in a single pass while the inkjet head moves in the main scanning direction; when it is detected that ink droplets are being discharged normally from an ink nozzle in the standby position, then executing a control command indicating a page break that conveys the print medium in the transportation direction and that discharges the print medium; and printing a next page of print data on the print medium if the print data for the next page is received.