Inkjet printer and image recording method

摘要

In a head part of inkjet printer, a leading droplet and a following droplet are ejected from an outlet by inputting one driving signal, and the leading droplet and the following droplet land onto a recording paper. At this time, a waveform of the driving signal is set such that an average of distance from the center of a main dot element formed by the leading droplet to the farthest point in a group of dot elements formed by the leading droplet and the following droplet is equal to or more than 1.1 times an average of radius of the main dot element and equal to or less than 3.0 times the average. Therefore, the dot shape can be made noncircular, and as the result, it is possible to suppress jaggies on edges of an image on the recording paper and lowering of density in a solid area.

主权项

1. An inkjet printer, comprising:
a head part for ejecting droplets of ink from a plurality of outlets toward an object and including piezoelectric elements provided for respective outlets of the plurality of outlets; a scanning mechanism for moving said object in a predetermined scanning direction relative to said head part; and a controller for repeatedly inputting an output value and a driving signal to said head part to form a solid area having an edge on said object, said output value and said driving signal being input in parallel with relative movement of said object to said head part, said output value indicating whether to form a dot or not, and said driving signal being applied for ejection of droplet; wherein the driving signal includes a plurality of ejection pulses each operative to make a respective one of the piezoelectric elements perform a series of operations, a leading droplet and a following droplet are ejected from an outlet by inputting said output value indicating to form a dot and said driving signal, wherein said leading droplet is a main droplet ejected by an ejection pulse included in said driving signal and said following droplet is a main droplet ejected by the next ejection pulse in said driving signal, and said leading droplet and said following droplet land onto said object, an average distance from the center of a leading dot element formed on said object by said leading droplet to the farthest point in a group of dot elements formed on said object by said leading droplet and said following droplet to form the solid area is equal to or more than 1.1 times an average radius of said leading dot element and equal to or less than 3.0 times said average radius, said leading dot element and a dot element formed by said following droplet partially overlap with each other, and said leading dot element and said dot element formed by said following droplet are included in a dot corresponding to a pixel, another type of driving signal having a waveform different from said driving signal can be selectively inputted to said head part, said another type of driving signal including a plurality of ejection pulses, and in the case where said another type of driving signal is inputted to said head part:
said leading droplet and said following droplet are ejected from said outlet so that an average distance from the center of said leading dot element by said leading droplet to the farthest point in said group of dot elements by said leading droplet and said following droplet is less than 1.1 times an average radius of said leading dot element, orsaid average distance in the case of said another type of driving signal is different from said average distance in the case of said driving signal, while staying within a range which is equal to or more than 1.1 times an average radius of said leading dot element and equal to or less than 3.0 times said average radius.