Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
1998-02-09
2002-04-16
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
Reexamination Certificate
active
06371608
ABSTRACT:
This application is based on patent application Nos. 026,534/1997 filed Feb. 10, 1997 and 018,937/1998 filed Jan. 30, 1998 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 apparatus, and particularly, to an ink-jet printing method and an apparatus in which an ink and a printing quality improving liquid that makes the ink insoluble or coagulate are ejected onto a printing medium. A definite device to which the present invention is applicable includes office equipment such as printers, copy machines and facsimile machines which use the ink-jet printing apparatus as an output device, industrial production machines and the like.
2. Description of the Prior Art
The ink-jet printing method is widely used for printers, copy machines the like because the method has various advantages such as its low noise, low running costs, and abilities to enable the apparatus to be compact and to easily realize the apparatus printing color images.
When, however, such a printing apparatus to which the ink jet printing method is applied performs printing of an image on a printing medium called plain paper, it may occur that a printing image has insufficient water-resistance. In addition, when printing color images, a high density image that does not cause feathering may be incompatible with an image having bleeding between colors. Thereby a durable image or a high-quality color image may not be achieved.
To improve the water-resistance of the image, an ink containing coloring materials having water-resistance has recently been put to practical use. The water-resistance of the ink, however, is still insufficient and the ink is unlikely to be dissolved into water after drying. As a result of this, an ejection opening and the like of a print head is likely to be clogged. In addition, to prevent this clogging, the apparatus must have a complicated configuration.
There has been disclosed a large number of techniques that improve image durability of a printed product by applying a processing liquid that reacts with a print ink to provide water-resistance, to the same position as an ink on a printing medium.
For example, Japanese Patent Application Laying-open No. 58-128862 discloses an ink-jet printing method in which a position to be printed in an image is preliminary identified and then the print ink and the processing liquid are applied in an overlaying manner to the identified position for printing. More specifically, the method allows following various printing manners. The processing liquid is applied to draw an image before the print ink is applied, the processing liquid is deposited on the image drawn the print ink or the processing liquid is further applied on the image which is drawn by depositing the processing liquid and then depositing the print ink. In addition, Japanese Patent Application Laying-open No. 8-7223 discloses a method which has a means for controlling whether the ejection of the processing liquid is performed or not, and whether or not the processing liquid is ejected in set depending on a user's selection or a medium used for printing. Furthermore, Japanese Patent Application Laying-open No. 7-195823 discloses a method for applying a colorless precursor that causes two- or three-component chemical reaction, to a surface of a printing medium so as to adjust its conditions of the surface. In this method, when the remaining amount of the colorless liquid becomes small, a conventional method for printing an image with a plurality of scanning operations is employed.
None of these publications, however, discloses a method for avoiding making an ink ejection portion dirty to increase reliability of the ink-jet printing apparatus. More specifically, when the processing liquid is used to improve the water-resistance of the inks as in the prior art, it is difficult to remove dirt on the ejection portion, as described below. Thus, this is a relatively important technical problem, but none of the above publications describe the method for avoiding making the ink ejection portion dirty.
On the other hand, this problem of making the ink ejection portion dirty has been known in conventional ink-jet printing methods that do not use the processing liquid as described above.
More specifically, when the print head ejects ink droplets onto the print medium to perform printing, the ink is deposited on an ink ejection opening surface of the print head due to the splashing of fine ink droplets (mist) or rebounding of ejected ink droplets from the printing medium. If a large amount of such droplets are gathered near the ejection opening or a foreign matter such as paper powder or the like are deposited to the ink droplets, there may be caused a harmful influence such that an ejection direction of the ink is varied (deflection), or the ink droplets can not be ejected (non ejection).
FIGS. 1A and 1B
schematically show a process in which the ink ejection opening surface is made dirty due to the rebounding of the ink and the mist.
FIG. 1A
shows the rebounding of the ink. In an example shown in the figure, a print head has respective ink ejection portions for ejecting liquids A and B, respectively, and eject the liquids with a relatively high printing duty.
As the print head moves, the liquid A is firstly ejected on a sheet, thereby spreading like an ocean. The liquid B is subsequently ejected on the ocean of the liquid A at a certain speed. As a result, there is caused a rebounding of the liquids A and B or their mixture and thereby, they are deposited on the respective ejection opening surfaces for the liquids A and B.
FIG. 1B
shows a deposition process of mist. Droplets of the liquid A ejected from the ejection portion of liquid A are composed of a main ink droplet and fine ink droplets (mist). The main ink droplet reaches the printing medium and the mist spreads around by the flow of air generated as a carriage moves. The mist of the liquid A, which has spread in such manner, may be deposited on the surface of the ejection portion of liquid B.
Dirt on the ejection opening surface caused by the rebounding of the ink described above can be reduced by increasing a distance between the sheet and the ejection opening surface (hereafter referred to as a “distance to paper”). However, as the distance to paper increases, a flying distance of an ejected ink and time for flying increases and accuracy in depositing the ink on the sheet may be reduced, thereby degrading a printed image.
In addition, a configuration that wipes the ejection opening surface using a blade formed of an elastic member such as rubber is generally used as means for cleaning and removing the dirt once deposited on the ejection section opening surface. Such a configuration, however, has various problems. For example, it cannot totally remove the dirt. In particular, in the case that a processing liquid that makes the inks insoluble is used, it is likely to be mixed in the mist or the rebounded liquid. When the mixed liquid in deposited near the ink or processing-liquid ejection openings, it often becomes a highly viscous deposit and cannot be removed by a normal wiping means. Consequently, deflection or non ejection are often caused, and further, when the deposit becomes significant, the ink ejection may even be totally prevented from being ejected.
With respect to a general problem caused by the mist or the rebounded ink, the inventors of the present invention have found that such mist and rebounded ink are closely related to the printing duty. That is, in the example shown in
FIGS. 1A and 1B
, the inventors have found that the dirt on the ink ejection opening surface can be reduced by reducing the printing duty of the respective liquids A and B. It is thought be achieved by reducing an an amount of liquids simultaneously ejected from a plurality of ejection openings to reduce the mist, by reducing an ejection duty of the liquid A so that the liquid A is prevented from becoming like an ocean
Kato Minako
Moriyama Jiro
Barlow John
Brooke Michael S.
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