1. Technical Field
The present invention relates to a printing device used for a facsimile device, a copy machine, an office automation (OA) device, or the like, a program for controlling a printing device, and a method of controlling a printing device. More particularly, the present invention relates to a printing device suitable for a so-called inkjet type printing process for ejecting minute particles of a plurality of colors of liquid ink onto printing paper (recording material) so as to draw a predetermined character or image, a program for controlling a printing device, a method of controlling a printing device, a printing data creating device, a program for creating printing data, and a method of creating printing data.
2. Related Art
Hereinafter, a printing device, particularly, an inkjet type of printer (hereinafter, referred to as ‘inkjet printer’) will be described.
Generally, since the inkjet printer has merits in that it is inexpensive and a color printing material of a high quality can be easily obtained, it has widely spread for office and general use as personal computers and digital cameras have widely spread.
This inkjet printer generally has the following structure. According to this structure, a movable body called a carriage, in which an ink cartridge and a printing head are integrally formed, ejects particles of liquid ink in a dot shape through nozzles of the printing head on a printing medium (paper) while reciprocally moving on the recording medium in a direction vertical to a paper transporting direction, and a predetermined character or image is drawn on the printing medium so as to create a desired printing material. In addition, the carriage includes ink cartridges of four colors (black, yellow, magenta, and cyan) including black and printing heads for the respective four colors, so that not only black-and-white printing but also full color printing having combined the respective colors are easily performed (In addition, ink cartridges of six colors including the above-mentioned four colors, light cyan, and light magenta or seven or eight colors has been practically used).
As such, in the inkjet printer in which the printing is performed while reciprocally moving the printing head of the carriage on the recording medium in a direction vertical to a paper transporting direction, the printing head needs to perform a reciprocal motion several tens of times to several hundred times or more so as to clearly perform printing corresponding to one page. Therefore, it takes a lot of time for the inkjet printer to perform printing, as compared with another type of printing device, for example, a laser printer using the electrophotographic technology of a copy machine or the like.
In the meantime, in an inkjet printer in which a printing head having a length corresponding to the same size (or a larger size) as a width of printing paper is arranged and a carriage is not used, since it is unnecessary for the printing head to move in a width direction of the printing paper and the printing can be made through so-called one scan (one pass), high speed printing can be performed in the same manner as the laser printer. In addition, since there is no need to provide the carriage mounting the printing heads thereon and a driving system moving it, a printer case becomes small-sized and light, and noise can be further reduced. The inkjet printer of the former is generally called a ‘multipass-type printer’ and the inkjet printer of the latter is generally called a ‘line-head-type printer’.
In the meantime, in the printing head necessary for the inkjet printer, minute nozzles each having a very small diameter within a range of 10 to 70 μm are disposed in one row or a plurality of rows in a printing direction at predetermined intervals. As a result, an ink ejection direction of some nozzles may be inclined or the nozzle position may deviate from an ideal position due to a manufacturing error, so that a landing position of each dot formed by the nozzles may deviate from an ideal position, thereby causing a so-called ‘flying curve phenomenon’ to occur. In addition, the nozzles may have a large variation, each of which having an ink amount that increases or decreases extremely compared with an ideal ink amount, due to the variation characteristics of the nozzle.
As a result, a printing failure known as a so-called ‘banding (stripe) phenomenon’ occurs in a portion having been printed by using the defective nozzles, so that a printing quality may be extremely lowered. Specifically, if the ‘flying curve’ phenomenon occurs, the distance between dots ejected by adjacent nozzles does not become uniform. At this time, ‘white stripes (in a case in which the printing paper is white)’ occur in a portion where the distance between adjacent dots is larger than the normal distance, and ‘thick stripes’ occur in a portion where the distance between adjacent dots is smaller than the normal distance. In addition, even in a case in which an ink amount is different from an ideal ink amount, thick stripes occur in dots formed by the nozzles ejecting a large amount of ink, and white stripes occur in dots formed by the nozzles ejecting a small amount of ink.
Specifically, it is likely for the banding phenomenon to occur more in ‘a line-head-type printer’ where the printing head or the printing medium is fixed (one pass printing) than in the above-mentioned ‘multipass-type printer’ (in the multipass-type printer, there is a technology in which the printing head performs a reciprocal motion many times to prevent the banding from occurring).
For this reason, in order to prevent the printing failure caused by ‘the banding phenomenon’, research and development have been performed for hardware, such as improving a manufacturing technology of the printing head and design improving thereof. However, it is not possible to provide a printing head capable of preventing the ‘banding phenomenon’ perfectly because of the limits imposed by manufacturing cost or technology.
Accordingly, in addition to the improvement in the hardware, a technology which reduces the ‘banding phenomenon’ by using printing control, that is, a software-like method, which will be described in detail below, has been used.
For example, in JP-A-2002-19101 or JP-A-2003-136702, which will be described below, in order to resolve problems of the nozzle variation or non-ejection of the ink, the problem of the head variation is resolved by using a shading correction technology in a portion having the low printing density, and the problem of the banding or variation is resolved by using another color (for example, when being printed with black, cyan or magenta is alternatively used) in a portion having the high printing density.
Further, in JP-A-2003-63043, which will be described below, a method has been suggested in which for a solid image (that is, a base is covered such that the base is not seen), an ink ejection amount of each nozzle adjacent to the non-ejection nozzle is increased and a solid image is formed using all of nozzles.
Furthermore, in JP-A-05-30361, a method is used in which a variation amount of each nozzle is fed back to an error spreader, so that the variation of the ink ejection amount of the nozzle is absorbed, thereby preventing a banding phenomenon from occurring.
However, according to the methods disclosed in JP-A-2002-19101, JP-A-2003-136702, JP-A-2003-63043, and JP-A-5-30361, since the process, which reduces an image quality from being deteriorated due to the banding phenomenon, is controlled so as to be performed at all portions which become the process subject (locations where the banding occurs), a correction process is performed with respect to locations where deterioration of an image quality (banding phenomenon) is not observed even when the correction process is not performed. As a result, deterioration of another image quality may be observed at these locations due to the correction process.