Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2002-06-05
2004-01-27
Nguyen, Thinh (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S016000
Reexamination Certificate
active
06682168
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image printing apparatus, control method therefor, storage medium, and program and, more particularly, to a uniform image printing method in an ink-jet printing apparatus for printing information by discharging ink to a printing member.
BACKGROUND OF THE INVENTION
A printing apparatus used to print an image or the like in a printer, copying machine, facsimile apparatus, or the like, or a printing apparatus used as a print output device in a workstation or a composite electronic device including a computer, word processor, and the like prints an image or the like on a printing member (to be also referred to as a printing medium hereinafter) such as a sheet or plastic thin plate on the basis of image information (including all pieces of output information such as character information).
Printing apparatuses can be classified into an ink-jet type, wire dot type, thermal type, laser beam type, and the like depending on their printing methods.
Of these printing apparatuses, the ink-jet printing apparatus (to be referred to as an ink-jet printer hereinafter) prints information by discharging ink onto a printing medium from a printhead or the like. Compared to other printing types, the ink-jet printer has various advantages such as easy implementation of high resolution, high speed, low noise, and low cost.
In recent years, color outputs such as a color image become more and more important, and a variety of color ink-jet printers with high quality equivalent to a silver halide photograph have been developed.
To increase the printing speed, the ink-jet printer adopts a printhead on which pluralities of ink orifices and liquid channels are integrated as a printhead (to be also referred to as a multihead hereinafter) on which a plurality of printing elements are integrally aligned. To output color images, the ink-jet printer generally comprises a plurality of multiheads.
FIG. 1
is a view showing the main part of a general ink-jet printer for printing information on a sheet surface by using the multihead.
In
FIG. 1
, reference numerals
1101
denote ink-jet cartridges. These ink-jet cartridges are made up of ink tanks which store four color inks, i.e., black, cyan, magenta, and yellow inks, and multiheads
1102
corresponding to the respective inks.
FIG. 2
is a schematic view showing orifices (to be also referred to as nozzles hereinafter) for one color arranged in the multihead
1102
when viewed from a Z direction in FIG.
1
.
In
FIG. 2
, reference numerals
1201
denote D nozzles aligned at a density of D nozzles per inch (D dpi) in the multihead
1102
. Even-numbered nozzles out of d aligned nozzles will be called Even nozzles, and odd-numbered nozzles will be called Odd nozzles.
In
FIG. 1
, reference numeral
1103
denotes a sheet supply roller, which rotates together with an auxiliary roller
1104
in a direction indicated by an arrow in
FIG. 1
while clamping a printing medium P between them, and conveys the printing medium P in the Y direction (subscanning direction, convey direction, and sheet supply direction).
Reference numerals
1105
denote a pair of sheet feed rollers, which feed a printing medium. Similar to the rollers
1103
and
1104
, the pair of rollers
1105
rotate while clamping the printing medium P. The rotational speed of the rollers
1105
is set lower than that of the sheet supply roller
1103
to apply tension to the printing medium.
Reference numeral
1106
denotes a carriage which supports the four ink-jet cartridges
1101
and scans them at the same time as printing. The carriage
1106
stands by at a home position h represented by a broken line in
FIG. 1
during an idle period of printing or in recovery processing of the multihead
1102
.
If the carriage
1106
at the home position h receives a printing start instruction before the start of printing, the carriage
1106
moves in the X direction (main scanning direction). D/D-inch wide printing is done on a; sheet surface by the D nozzles
1201
of the multihead
1102
which are aligned at a density of D nozzles per inch. During an interval between the end of the first printing and the start of the second printing, the sheet supply roller
1103
rotates in the direction indicated by the arrow to supply the sheet in the Y direction by a D/D-inch width.
D/D-inch wide printing by the multiheads
1102
(information is printed on a 1-inch wide portion of a printing medium by using D nozzles) and sheet supply are repeated every main scanning of the carriage
1106
, completing, e.g., printing of one page. This printing mode will be called a 1-pass printing mode.
Another printing mode will be described. If the carriage
1106
at the home position h receives a printing start instruction before the start of printing, the carriage
1106
moves in the X direction (e.g., forward direction of main scanning). D/D-inch wide printing is done on a sheet surface by the D nozzles
1201
of the multihead
1102
which are aligned at a density of D nozzles per inch.
Dots printed by this scanning form an image of specified image data which is interlaced into almost half by a predetermined pattern. During an interval between the end of the first printing and the start of the second printing, the sheet supply roller
1103
rotates in the direction indicated by the arrow to supply the sheet in the Y direction by a D/2D-inch width.
In the second scanning, the carriage
1106
is scanned in a direction (e.g., backward direction of main scanning) opposite to that in the first printing. Images are printed in accordance with respective patterns, completing printing in regions corresponding to respective nozzles. This printing mode will be called a 2-pass printing mode. M (≧2)-pass printing will be generally called a multipass printing mode.
As a color printer, the ink-jet printer can optimally print a photographic image at high quality in the multipass printing mode.
However, a uniform image may not be obtained owing to the discharge direction of ink droplets discharged from nozzles, or ink droplets (to be referred to as satellites) which are separated from main droplets in discharge and are smaller than main droplets.
Especially when the discharge direction changes in the main scanning direction between Even and Odd nozzles of d aligned nozzles, the landing positions of satellites on the sheet surface change, failing to forming a uniform image.
A case in which a uniform image cannot be obtained due to satellites and different discharge directions of Even and Odd nozzles will be explained in detail with reference to the accompanying drawings.
FIGS. 3A
to
3
C are views showing the landing positions of a main droplet and satellite on a sheet surface serving as a printing medium in an ink droplet discharge direction.
FIG. 3A
is a schematic view showing the landing positions of a main droplet and satellite when the ink droplet discharge direction is perpendicular to the sheet surface.
FIG. 3B
is a schematic view showing the landing positions of a main droplet and satellite when the ink droplet discharge direction inclines to the carriage traveling direction.
FIG. 3C
is a schematic view showing the landing positions of a main droplet and satellite when the ink droplet discharge direction inclines to a direction opposite to the carriage traveling direction.
In
FIGS. 3A
to
3
C, reference numeral
1301
denotes a main droplet;
1302
, a satellite;
1303
, a carriage traveling direction; and
1304
, a discharge inclination direction.
The landing positions of the main droplet and satellite when the ink droplet discharge direction is perpendicular to the sheet surface serving as a printing medium, i.e., the ink droplet discharge direction does not incline to the carriage traveling direction will be explained with reference to FIG.
3
A.
In
FIG. 3A
, a comparison between the discharge speeds of the main droplet
1301
and satellite
1302
discharged from a nozzle reveals that the discharge speed of the main droplet
1301
is generally higher than that of the satellite
130
Kanda Hidehiko
Moriyama Jiro
Nakagawa Yoshinori
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Nguyen Thinh
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