Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1997-04-01
2003-04-01
Nguyen, Lamson (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S043000, C347S015000
Reexamination Certificate
active
06540326
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus and an ink jet recording method.
2. Related Background Art
As information processing apparatuses such as copying apparatuses, word processors, computers, and the like, and communication apparatuses have become popular, an apparatus for performing digital image recording using an ink jet recording head has become increasingly popular as one of image forming (recording) apparatuses of the above-mentioned apparatuses. Furthermore, with the advent of color, low-cost information processing apparatuses and communication apparatuses, a demand has arisen for a color recording apparatus, which can perform a print operation using normal paper sheets. Such a recording apparatus normally comprises, as a recording head (to be referred to as a multi head hereinafter) obtained by integrating and aligning a plurality of recording elements to improve the recording speed, a plurality of multi heads in each of which a plurality of ink ejection orifices and nozzles are integrated in correspondence with colors.
FIG. 1
shows an arrangement of a printer unit when a print operation is performed on a paper sheet using the multi heads. In
FIG. 1
, each of ink cartridges
701
is constituted by an ink tank filled with one of four color inks (black, cyan, magenta, and yellow), and a multi head
702
.
FIG. 2
shows a state of multi nozzles aligned on the multi head from the z-direction. In
FIG. 2
, multi nozzles
801
are aligned on the multi head
702
.
Referring back to
FIG. 1
, a paper feed roller
703
is rotated in a direction of an arrow in
FIG. 1
together with an auxiliary roller
704
while pressing a print sheet
707
, thereby feeding the print sheet
707
in the y-direction. Paper supply rollers
705
supply the print paper, and also serve to press the print paper
707
like the rollers
703
and
704
. A carriage
706
supports the four ink cartridges, and moves these cartridges according to a print operation. The carriage
706
stands by at a home position (h) indicated by a dotted line in
FIG. 1
when no print operation is performed or when the multi heads are subjected to recovery operations.
Before a print operation is started, the carriage
706
is located at the illustrated position (home position), and when a print start command is input, the carriage
706
performs a print operation by a width D on the sheet surface using the n multi nozzles
801
on the multi heads
702
while moving in the x-direction. Upon completion of the data print operation to the end portion of the sheet surface, the carriage is returned to the home position, and then performs a print operation in the x-direction. During an interval after the first print operation is ended until the second print operation is started, the paper feed roller
703
is rotated in the direction of the arrow, thereby feeding the sheet in the y-direction by the width D. In this manner, the print operation and the paper feed operation are repetitively performed per scan of the carriage by the width D of the multi head, thus completing the data print operations on the sheet surface.
When the above-mentioned normal print operation is performed on a coating or coating paper sheet, which is prepared in consideration of ink absorption, no problem is posed. However, a normal paper sheet is prepared without taking a special countermeasure against absorption of a liquid, i.e., an ink, and suffers from a problem of a low black density as compared to the coating paper sheet, which is prepared in consideration of ink absorption. This problem is caused since the normal paper sheet has a considerably low blurring rate of an ink and a low absorption speed to a sheet as compared to the coating paper sheet.
In association with this problem, the most general dot landing state on a coating paper sheet in the above-mentioned ink jet recording apparatus will be described below with reference to
FIGS. 3A and 3B
. In this case, one pixel is constituted by one dot with respect to a pixel density inherent to a printer. The dot central points are aligned at an interval of one pixel unit, and an ejection amount is designed, so that when dots land, they partially overlap each other, as shown in
FIG. 3A
, to satisfy an area factor of 100%. Such an ejection amount design is determined by an ink used in recording, and the blurring rate of the ink on a paper sheet. For example, when a dot diameter of 100 &mgr;m for sufficiently satisfying an area factor of 100% at a pixel density of 360 dpi is realized on a paper sheet having a blurring rate of 2.7 times, at least an ejection amount given by the following equation is required:
4&pgr;(100/2.7/2)
3
/3≅26.6 pl/dot
In this manner, satisfactory images are obtained using suitable ejection amount designs according to the relationship between the ink and the blurring rate of the ink on the paper sheet.
FIGS. 3A and 3B
show a printed dot landing state when a print operation is performed using the above-mentioned method at a duty of 100% with respect to a predetermined pixel density.
FIG. 3A
shows a state wherein a print operation is performed on a coating paper sheet (blurring rate=2.7) with an ejection amount satisfying an area factor of 100%, as described above, and
FIG. 3B
shows a state wherein a print operation is performed on a normal paper sheet (blurring rate=2.0) with the same ejection amount as in FIG.
3
A.
FIGS. 3A and 3B
illustrate states viewed from the horizontal and vertical directions. In the print state on the coating paper sheet shown in
FIG. 3A
, individual landing ink dots widely spread on the sheet surface, and adjacent dots in the diagonal directions also overlap each other. However, in the print state on the normal paper sheet shown in
FIG. 3B
, individual dots do not spread so largely on the sheet surface, and the amount of the ink penetrated in the vertical direction is increased. Therefore, a gap is formed between two adjacent dots in the diagonal direction on the sheet surface. The presence of such a gap largely contributes to a low density of the normal paper sheet.
As a simple method of increasing the density, a method of increasing the ejection amount to a state wherein an area factor of 100% is satisfied on a normal paper sheet is known. However, when a large amount of ink lands on the sheet surface at a time, a time required for causing an ink to penetrate into the sheet surface is further prolonged, and boundary blurring among different colors as another serious problem of the normal paper sheet is further worsened. The boundary blurring is a mixed flow phenomenon of the inks on the paper sheet caused since the normal paper sheet has a low ink absorption speed as compared to the coating sheet, as described above. When the ink ejection amount is increased, the ink penetration speed is further lowered, and different color inks tend to become easily blurred.
In order to solve the above-mentioned problem, a method of landing ink dots twice at identical landing points is proposed. In this method, in
FIG. 1
, the carriage
706
scans twice in the x-direction without rotating the paper feed roller. At this time, the second print operation is performed at the same position as the first print operation. When such print operations are performed, each ink dot area can be slightly increased, and the gap between adjacent dots in
FIG. 3B
can be decreased, thus obtaining a landing state shown in FIG.
3
C. Therefore, the density can be increased as compared to the one-dot print operation. In addition, since the print operations of a single area is completed in a longer period of time than in a case wherein a large ejection amount of ink is printed at a time, blurring can be easily prevented to some extent.
However, in this case, the gaps cannot be completely eliminated unlike in the printed state on the coating paper sheet. When relatively small dots are printed adjacent to each other, a blank stripe still remains. In addition, the normal paper sheet
Akiyama Yuji
Arai Atsushi
Hirabayashi Hiromitsu
Matsubara Miyuki
Nagoshi Shigeyasu
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