Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1998-09-08
2002-02-19
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
Reexamination Certificate
active
06347855
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus utilizing a liquid discharge head for discharging liquid such as ink, and more particularly to a printing apparatus for executing printing on a recording medium such as a paper, a cloth, a non-woven cloth, an OHP sheet or the like.
In particular, the present invention is effective for a printing apparatus for executing a continuous printing operation over a prolonged period, or a printing apparatus for executing a continuous printing operation on a cloth of width of 1 meter or larger. More specifically, the present invention is applicable to an office equipment such as a printer, a copying apparatus, an ink jet printer or a facsimile machine, or a large production equipment such as a cloth printing apparatus.
2. Related Background Art
As conventional liquid discharging apparatus, there have been known an apparatus for forming an image by discharging ink droplets onto a recording medium, and an apparatus utilizing discharge of special liquid. An ink jet recording apparatus (the former) is to form an image by discharging ink droplets onto a recording medium. This apparatus is featured by providing a desired result in a stable manner because intervening factors in the image formation are less in comparison with an electrophotographic process.
Since, in general, a discharging unit for discharging liquid has very small structures, there may result adhesion of dye or pigment contained in the liquid or defective discharge by adhesion of contaminant particles. These phenomena result in defective recording in such liquid discharging apparatus as an ink jet recording apparatus. For avoiding these phenomena, there has been adopted forced discharge of liquid, cleaning of the liquid discharging area containing the discharging unit or discharge of gas or liquid to such discharging area by suction or pressurizing with so-called recovery means at a suitable interval.
In the ink jet recording apparatus, image formation is made with fine nozzles in order to achieve recording of higher quality and finer resolution. However, the use of such fine nozzles leads to unstable recording and deterioration of the recorded image because of the above-mentioned drawbacks. The recorded image may be deteriorated for example by skew in recording, caused by a delicate difference in the landing position of ink droplet resulting instability in the ink discharging direction, failed discharge (non-ejection) resulting from clogging of the discharge opening (nozzle) with dusts or viscosified ink, failed discharge resulting from breakage of an electrothermal converting element (heater) in a bubble jet method employing the heater for generating a bubble in the ink for discharge thereof, or failed discharge resulting from deposition of an ink droplet on a surface of a discharge opening to thereby cover the opening with the ink droplet.
Such failed discharge generates an unrecorded line along the scanning direction in a serial printer, creating a white streak in a recorded image and significantly deteriorating the quality of the recorded image.
In case the number of nozzles is increased to hundreds or thousands in order to increase the throughput of printing, the probability of such abnormality in the nozzles increases proportionally, so that it becomes more difficult to obtain a defect-free image.
Also, in manufacturing the recording head, there has been required a defect-free head in which all the nozzles are normal. However, with the increase of the number of nozzles as mentioned above, the probability of generation of defects in the course of manufacture increases proportionally to deteriorate the production yield, thereby elevating the manufacturing cost and eventually the price in the market.
Also, in the conventional configuration, even a defect-free head becomes unusable for recording if the failure is generated in one of many nozzles in the course of recording. For this reason, in a printing apparatus utilizing a multi-nozzle head with 6 to 8 nozzles, abnormality in the nozzle is often encountered, thus generating a defective print each time. Also, as the head has to be replaced for each generation of abnormal nozzle, there is involved the cost for such replacement and the operation of the apparatus has to be interrupted.
Furthermore, in the recording apparatus not only of the ink jet recording method but also of various recording methods employing varied recording elements for image formation on the recording medium, in case the recording element becomes incapable of recording for example by a damage, it is necessary either to continue the recording operation in a state in which a part of the recording dots is lacking in the recorded image or to interrupt the recording operation and restore the recording state for example by replacing the recording head.
In order to overcome the drawbacks as mentioned above, the present applicant discloses, in the Japanese Patent Application Laid-open No. 6-79956, a method of complementary recording for a recording position by a nozzle which generates failure in discharge (or non-ejection). In this method, a multi-nozzle head is used to execute serial scanning. A predetermined area is divided into plural scans, which are complementarily recorded as a multi-scan recording. Thus, the recording position corresponding to a defective nozzle is complementarily recorded in another scan, thereby preventing deterioration of the image resulting from the failed discharge.
Also, the above-mentioned Japanese Patent Application Laid-open No. 6-79956 discloses a configuration in which the image data of a defective nozzle are recorded in complementary manner by a separately provided head.
As explained in the foregoing, the invention proposed in the Japanese Patent Application Laid-open No. 6-79956 achieves complementary recording for the defective nozzle by reducing the image defect (white streak, skew) caused by an abnormality in the nozzle such as failed discharge. However, in the multi-scanning method disclosed therein, the nozzle effecting the complementary recording prints the overlapping data, and such complementary recording is switched to a speed allowing to record such overlapping data. Therefore, in the multi-scanning recording method in which the sub-scanning is executed by a half of the recordable width, the printing speed is lowered to about a half. In a practical case in which all the nozzles are not completely functions, but a defect exists such as to cause a failed discharge being generated in a certain number of nozzles, the printing speed of the proposed recording apparatus has to be substantially lowered.
The above-mentioned laid-open publication also discloses a configuration in which the image data of a defective nozzle are recorded in complementary manner by a separately provided head. Such configuration allows the recording without decrease in the recording speed, but there is required an exclusive head for complementary recording, which is unnecessary in the absence of abnormality in the nozzle such as failed discharge and which has to be maintained in the complete discharging state. The head becomes expensive particularly in case high-speed recording is intended with an increased number of nozzles in the head. In a color recording apparatus, there are required exclusive complementary heads corresponding to plural colors, so that the apparatus becomes not only expensive but also complex in structure. Furthermore, the apparatus becomes inevitably bulky.
Also, the Japanese Patent Application Laid-open No. 5-301427 of the present applicant discloses a configuration of detecting a state immediately after recording with a sensor, identifying a failed discharge state by calculating the difference between data to be recorded and the detected state, and executing a complementary recording in a subsequent scan or with an ensuing complementary head. However, such configuration does not resolve all the drawbacks mentioned in the foregoing.
Furthermore, the U.S. Pa
Barlow John
Fitzpatrick ,Cella, Harper & Scinto
Huffman Julian D.
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