Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-11-30
2004-04-13
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S016000
Reexamination Certificate
active
06719403
ABSTRACT:
This application is based on Patent Application No. 2000-366291 filed Nov. 30, 2000 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink-jet printing method and an ink-jet printing apparatus and specifically to a configuration for reducing bleeding at a boundary between black and color image areas printed when black ink and other kinds of color ink are used for printing.
2. Description of the Related Art
A printing apparatus having a function of a printer, a copy machine, a facsimile or the like, or a printing apparatus used as an output device of information processed in a composite electronic device including a computer and a word processor, a work station and so on, is structured so that images (including characters and so on) are printed on a printing medium such as a printing sheet and a plastic thin plate based on image information (including character information). Such a printing apparatus is, by a printing method, classified into an ink-jet system, a wire dot system, a thermal transfer system, a laser beam system and the like. Among them, a printing apparatus using the ink-jet system (hereinafter, referred to as an ink-jet printing apparatus) performs printing by ejecting ink to a printing medium from a printing head, and has many advantages such that high resolution printing can be achieved more easily than other printing systems, high-speed and high quiet printing can be performed, and a device is available at relatively low cost.
Such ink-jet printing apparatus on the other hand has been much requested to be able to perform color printing, and a number of color ink-jet printing apparatuses have been provided. In general, in order to improve a printing speed and so on, as a printing head having a plurality of printing elements arranged integrally, the ink jet printing apparatus uses a printing head, in which a plurality of ink ejection openings and ink paths, that compose ink ejection portions, are integrated, and further includes a plurality of printing heads for respective colors of ink to be adapted to color printing.
FIG. 1
is a perspective view mainly showing an example of a schematic configuration of a printing section in an ink-jet printing apparatus.
In
FIG. 1
, printing heads
102
and ink cartridges
101
are detachably mounted on a carriage
106
and are used for printing. More specifically, the printing heads and the ink cartridges are used correspondingly to color inks of black (Bk), cyan (C), magenta (M), and yellow (Y), respectively and the printing heads for the respective inks are scanned for printing by the move of the carriage
106
. Hereinafter, the above mentioned scanning is referred to as main scanning and its direction is referred to as a main scanning direction. The carriage
106
is engaged to a guide shaft
107
so as to slide thereon. The carriage
106
can be moved thus along the guide shaft
107
by driving of a driving mechanism such as a motor and a belt (not shown).
FIG. 2
shows ejection openings disposed on each of the printing heads
102
, taken along direction “z” (FIG.
1
). In
FIG. 2
, reference numeral
201
denotes n ejection openings arranged on the printing head
102
, and the ejection openings are arranged at a density of N dpi. A variety of ejection systems may be adopted for such a printing head. For example, a method may be applicable in which a bubble is produced in ink by using thermal energy generated by an electro-thermal converter and ink is ejected by pressure of the bubble.
Referring to
FIG. 1
again, reference numeral
103
denotes a paper feeding roller, which rotates in a direction shown by an arrow in
FIG. 1
while pressing a printing sheet P in cooperation with an auxiliary roller
104
to on necessary move the printing sheet P as a printing medium in y direction (hereinafter, referred to as a “sub-scanning direction”). Further, reference numeral
105
denotes a paper feeding roller, which feeds printing sheets and also functions as applying constant tension to the printing sheet P similarly to the rollers
103
and
104
.
During a non-printing operation, the carriage
106
is shifted to a home position h and waits for a printing command. During a printing operation, the carriage
106
moves in x direction to scan the printing heads
102
of respective inks. During this scanning operation, ejecting ink from the respective n ejection openings
201
in accordance with image information can perform printing. When the above main scanning completes printing of image information on the end of a printing sheet P, the carriage returns to a printing start position while the printing sheet P is moved at a predetermined amount. Thereafter, scanning and printing in x direction are repeated.
When an image and the like are printed, a variety of image-quality elements are demanded including coloring, gradation, and a uniform density of a printed image. Particularly, it has been known that regarding the uniform density, due to slight unevenness of ejection openings on manufacturing that occurs in a process of manufacturing a printing head, an amount of ejected ink and an ejecting direction may vary among the ejection openings, resulting in uneven density of the printed image.
A specific example of such occurrence of uneven density will be explained referring to
FIGS. 3A
to
3
C and
4
A to
4
C. In
FIG. 3A
, reference numeral
31
denotes a printing head, which is composed of eight ejection openings
32
. Reference numeral
33
denotes ink drops (ink droplets) ejected from the eight ejection openings
32
. Ink is ideally ejected with substantially an equal amount and substantially in the same direction as shown in FIG.
3
A. Such ideal ejection would form ink dots substantially equal in size on a printing sheet as shown in
FIG. 3B
, and entirely obtain a uniform image without variation in density (FIG.
3
C).
However, as described above, ejection openings actually have unevenness to some extent. In this case, when printing is performed in the above manner, as shown in
FIG. 4A
, ink drops ejected from the ejection openings vary in size and direction, resulting in ink dots of
FIG. 4B
that are varied in size and printing position on a printing sheet.
Consequently, for example, a part on a printing sheet, which do not satisfy 100% of an area factor and come out as a ground of the printing sheet, appears periodically in a direction of aligning the ejection openings, resulting in white bands. Or conversely, an image including a part, in which dots formed overlap each other more than necessary, resulting in a black band, is printed. In other words, such an image has a density distribution shown in
FIG. 4C
in a direction of aligning the ejection openings. The density distribution is visually recognized as an uneven density. Moreover, bands may appear due to variations in an amount of feeding printing sheets.
As a solution for such uneven density, for example, Japanese Patent Laid-Open No. 06-143618 discloses the following method. Referring to
FIGS. 4A
to
4
C and
FIGS. 5A
to
5
C, the method will be explained briefly.
As shown in
FIG. 5A
, this method completes printing for the same printing area as that shown in
FIG. 4B
by three times of scanning of the printing head
31
, between which the printing sheet is moved at an amount corresponding to four pitches of ejection openings. More specifically, a scanning area, which is equivalent to a half of the above mentioned printing area and corresponds to four ejection openings, is completed by two times of scanning. At this moment, for the scanning area, in the first scanning lower four of the eight ejection openings of the printing head is used. In the second scanning after feeding at an amount corresponding to four ejection openings, upper four ejection openings are used for printing. And, in the first scanning for each of the ejection openings, printing is performed on image data which is thinned out to about a half according to a predetermined thinning
Kanda Hidehiko
Moriyama Jiro
Nakagawa Yoshinori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
LandOfFree
Ink-jet printing apparatus and ink-jet printing method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink-jet printing apparatus and ink-jet printing method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink-jet printing apparatus and ink-jet printing method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3234592