Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1998-12-31
2002-04-16
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S019000, C347S040000, C347S041000
Reexamination Certificate
active
06371609
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a recording apparatus and a recording method and more particularly to a recording apparatus and a recording method that eject ink droplets towards a recording medium to perform recording.
An ink-jet printer has been available which shoots droplets of recording liquids from orifices formed at the front ends of liquid-flow-paths of nozzles to perform recording.
When the ink-jet printer prints(records) on normal plain paper, the recording liquids (inks) spread or wick, a problem caused by fibers of paper. In recent years, to make a high-quality recorded image, a method has been adopted which ejects a processing liquid for recording(hereinafter referred to simply as a processing liquid) onto the recording medium immediately before or after the recording liquid is ejected. The processing liquid ejected immediately before the printing operation is also called a “pre-ejection” liquid. The processing liquid is transparent and colorless. The processing liquid and the recording liquid are ejected onto the same dot position on the recording medium to overlie each other. The two liquids are mixed on the recording medium and react with each other to be stabilized on the recording medium before they can spread into the recording medium.
Performing the above described recording method can improve the recording liquid's ability to develop color on the recording medium and resist water, and can reduce spreading (or bleeding) thus enhancing the recording performance. The improvement in the recording performance through the use of the processing liquid is significant particularly when normal plain paper without any coating over an ink accepting layer is used as a recording medium.
Referring to
FIG. 1
, the outline of how the processing liquid is ejected in the prior art will be described.
In
FIG. 1
, recording is performed by scanning of a recording head
2
over a recording paper
6
in the direction of arrow. The recording head
2
has two lines of nozzle
1
a
,
1
b
spaced from each other by a distance d in the scanning direction, with the line of nozzle
1
a
ejecting an ink and the line of nozzle
1
b
ejecting a processing liquid. In each of the lines of nozzle
1
a
,
1
b
the orifices are arranged with intervals p (nozzle pitch).
When the recording head
2
starts scanning, the line of nozzle
1
b
ejects the processing liquid to form dots
4
b
on the paper
6
. Next, the line of nozzle
1
a
ejects an ink to form dots
4
a
. When the scanning direction is opposite to the arrow, the above ejection sequence is reversed. The processing liquid is transparent and colorless and the dots of the processing liquid formed cannot actually be seen as illustrated in FIG.
1
.
With the above operation performed, the processing liquid prevents the ink from spreading at a boundary
3
between a recorded region
5
and an unrecorded region
5
a
and at the same time improves the water-resisting and color development capabilities.
According to the results of experiments conducted by using the recording head
2
that the applicant of the invention has developed for ejecting an ink and a processing liquid, it is confirmed that the processing liquid does not need to be delivered for all ink dots, but needs only to be used for about 50% of the ink dots to produce a sufficient effect of the processing liquid. To prevent a waste of the processing liquid, a method is currently employed which sets the ejection ratio of the processing liquid dots to all of the ink dots at, for example, 50% during recording. This ejection ratio of the processing liquid (or a thinning ratio) should preferably be changed according to the volume of each droplet of ink and processing liquid ejected, the kind of ink (black ink and color inks), and the composition of the ink and the processing liquid.
To offer a capability of recording color images and photographic images, ink-jet printers are being developed which eject inks of a plurality of colors from a plurality of lines of nozzle. This type of printer also has provisions to precisely align the landing points of various color inks ejected from a plurality of lines of nozzle. To ensure that the landing points of different color inks agree correctly, a very high precision is required for the installation positions of the lines of nozzle, for the ink ejection speed, and for the paper-nozzle distance (distance between the nozzle surface and the surface of the recording medium), and these stringent requirements in turn cause a great deal of difficulty.
Even if the above high precision cannot be realized, recent printers employ an adjusting method (called a user head position adjusting method) which records a registration test pattern and allows the user to select an appropriate head adjusting position that has resulted in aligned landing points.
However, if an attempt is made to precisely match the landing points of ink and processing liquid with each other, this makes the problem even more difficult than when the above mentioned printer that aligns the landing points of different inks (the ink-jet printer that ejects a plurality of color inks from a plurality of lines of nozzle) is used. In addition to the very high precision required for the positions of the lines of nozzle, the ejection speed and the paper-nozzle distance, as described above, it is also necessary to eject the processing liquid immediately before or after the ink ejection. This makes it impossible to incorporate the ink nozzles and the processing liquid nozzles in the same line of nozzle. Further, because the ink and the processing liquid immediately solidify upon mixing, it is preferred that the line of nozzle for ink and the line of nozzle for processing liquid be spaced with a predetermined distance d in the scanning direction to prevent the ink and the processing liquid from mixing and solidifying and to differentiate the landing times of the ink and the processing liquid by a predetermined length of time.
While in recent years there is a trend toward a reduced nozzle pitch p, below approximately 50 &mgr;m, to meet demands for higher quality, the space d between lines of nozzle is large at around 10 mm. It is, however, difficult to increase the precision of the line of nozzle interval d to the level of nozzle pitch p because of the adopted manufacturing method, and any improvement in the line of nozzle interval precision will lead to increased cost. Although there is a method of fabricating two lines of nozzle separately and then assembling them together, improving the precision is all the more difficult with this method.
As described above, the user head position adjusting method cannot be used with plain paper because the processing liquid is transparent and colorless. With the head position adjusting method, one is required to use a transparent sheet of film and hold it up to light to see the dots. Because of its nuisance and expensive film, this method is not commonly used.
In improving the precision, it is a conventional practice to form the line of nozzle for processing liquid in the same head that has the line of nozzle for ejecting at least one kind of ink, and to minimize the interval d between the two lines of nozzle as practically as possible. The precision improvement, however, leads to increased cost because of the difficulty inherent in the above described manufacturing method.
Arranging the line of nozzle for the ink and the line of nozzle for processing liquid closer together, gives rise to a problem that when the ink and the processing liquid land on the recording medium, rebounding splashes adhere to the orifices and forming mist. This problem may be dealt with by the use of a wiping means for wiping the orifices, however, which increases the cost. Reducing the nozzle pitch p to realize a higher print quality requires a further improvement in precision, which has reached the limit in the manufacturing method. The method of making individual lines of nozzle separately, is very difficult to implement and a
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Shah Manish S.
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