Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-04-23
2003-12-30
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S015000, C347S019000
Reexamination Certificate
active
06669331
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet print apparatus, and an ink jet printing method. More particularly, the present invention relates to an ink jet print apparatus, an ink jet printing method, program controlling the apparatus, and a storage medium storing the program that allow a reduction in uneven colors due to the difference in recording time between recording black inks and color inks, the time difference being caused by performing printing by bidirectional scanning of recording heads.
2. Description of the Related Art
In ink jet type print apparatuses, when performing color printing on a commonly-used print medium such as plain paper, it has been difficult to achieve an improvement in recording speed and an enhancement of image quality.
Methods for improving the recording speed that have been used include a method where the size of the region recordable by one scan is increased by lengthening the recording head; a method where the recording (driving) frequency of recording heads is increased; and a method where the printing is performed by bidirectional scanning of the recording heads. Among these methods, the “bidirectional printing” method is a cost-effective method as a total system, since the energy required for obtaining a given throughput is dispersed over time, as compared to the case where printing is performed by unidirectional scanning, i.e., unidirectional printing.
When performing such bidirectional printing, the discharge order of black ink and color inks constituting a pixel differs between the advance and return scanning directions of the recording heads. This is because the discharge ports (hereinafter referred to as nozzles) for the black ink and color inks are arranged in the scanning direction, and the discharging order for the black ink and color inks determined by this arranging manner is different between the advance direction and the return direction. When the discharge order of black ink and color inks is different, a difference in the hue can occur between the region recorded in the advance direction scanning and the region recorded by the return direction scanning, thereby causing degradation in the image quality. For example, band-like uneven colors may occur over an entire printed color image, which causes the poor image quality. As coutermeasures against this, for example, Japanese Patent Application Publication No. 11-313790 proposes a method for eliminating the above-described uneven colors by configuring a head where rows of nozzles of black ink and color inks are disposed symmetrically with respect to the scanning direction thereof.
On the other hand, the present invention uses a high image quality when printing a text and the like on plain paper, an ink jet print device using a pigment-based black ink is being provided. This arrangement especially allows black letters to be improved in quality and density.
In this arrangement, such a pigment-based black ink is frequently provided with a composition that is relatively impermeable with respect to paper in order to prevent ink from permeating along fabrics of paper. Such an arrangement is referred to as feathering. Also, recording heads are frequently used that have a configuration where black ink nozzles and color ink nozzles are arranged in a direction substantially perpendicular to the scanning direction of the recording heads. In the case of the configuration where the nozzles discharging a black ink, which has a low permeability, and the nozzles discharging color inks, which have a high permeability such as to exhibit a permeability value higher than a predetermined value (hereinafter, ink with a high permeability is referred to as a “super-permeable ink”) are arranged along the scanning direction (such an arrangement is referred to as a lateral nozzle-arrangement), an imparting time difference between a black ink and color inks is small since the black ink and color inks are imparted to the same scanning region during one scan when printing is performed on a predetermined region. As a result, for example, when printing a black shade pattern on a print region with a yellow color, bleeding occurs at a boundary portion of the region where printing is performed with a black ink and the region where printing is performed with color inks, or when printing a pattern where a high-density black patch is fringed with a yellow color, a so-called white haze phenomenon can occur, which indicates a reduction in the density due to the retreat of the ink with a low permeability. In order to reduce the above-described bleeding and white haze, recording heads where black nozzles and color nozzles are arranged to be offset along a direction perpendicular to the scanning direction (such an arrangement is referred to as a longitudinal nozzle-arrangement) are frequently used.
However, when colors where a black ink dot and color ink dots are intermingled, such as a gray color, are to be printed by bidirectional printing using the recording heads with the above-described longitudinal nozzle-arrangement, the discharge times between the black ink and the color inks are different, at the right and left ends in each scanning region. This raises a problem that, particularly at the above-described two ends, even if the color is a given gray, a difference in the hue will occur in each scanning region (hereinafter referred to as band). Consequently, a streak-like uneven color can occur for each band over the entire paper on which the printing is performed.
In the above-described longitudinal nozzle-arrangement, during scanning of the recording head, respective scanning regions to which black ink nozzles and color ink nozzles correspond, are different from each other. Therefore, the black ink nozzle corresponds to a predetermined scanning region during an earlier scanning (a first scanning), and the color ink nozzle corresponds to the predetermined scanning region during a later scanning (a second scanning), or conversely, the color ink nozzle corresponds to the predetermined scanning region during an earlier scanning (the first scanning), and the black ink nozzle corresponds to the predetermined scanning region during a later scanning (the second scanning). Consider, for example, a case where the black ink nozzle corresponds to the predetermined scanning region during the first scanning in the advance direction (e.g., a scanning from the left to the right), and the color ink nozzle corresponds to the predetermined scanning region during the second scanning in the return direction (e.g., a scanning from the right to the left). In this case, with respect to the right end of the above-described predetermined scanning region, the black ink is discharged at the end of the first scanning in the advance direction, and the color ink is discharged at the beginning of the second scanning in the return direction, the second scanning being performed immediately after the first scanning. As a consequence, the discharge time difference between the black ink and each of the color inks becomes small. On the other hand, with respect to the left end of the above-described predetermined scanning region, the black ink is discharged at the beginning of the first scanning in the advance direction, and the color ink is discharged at the end of the second scanning in the return direction, the second scanning being performed immediately after the first scanning. As a result, the discharge time difference between black and color inks becomes large. That is, when performing bidirectional printing using the head with the above-described longitudinal nozzle-arrangement, there occur a portion where the black ink is discharged by the black ink nozzle at the end of the scanning and where, upon the change of scanning direction immediately after the above-described discharging, the color ink is discharged from the color ink nozzle, and a portion where the black ink is discharged by the black ink nozzle at the beginning of the scanning and where, after about one round trip of the above-de
Iwasaki Osamu
Otsuka Naoji
Takahashi Kiichiro
Teshigawara Minoru
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