Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
1999-06-29
2001-08-14
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S014000, C347S021000
Reexamination Certificate
active
06273536
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink jet recording apparatus in which recording is performed by ejecting a recording liquid (referred to as ink hereinafter) from ink ejection orifices to fly in the form of droplets, and causing the ink to adhere onto a recording medium.
2. Description of the Related Art
In an ink jet recording system, an image is recorded by ejecting ink droplets from an ink jet recording head to a recording medium such as paper, a high image-quality recording medium (e.g., specific coated paper, calendered paper, or a calendered film), and an OHP film. Therefore, mists may occur due to fine ink droplets generated in addition to the ejected ink droplets, and a rebounding of the ink droplets ejected to impinge against the recording medium. Such mists may deposit on an ejection surface of the ink jet recording head. If a large amount of those ink droplets deposit around ejection orifices, or if foreign matters such as paper dust adhere to the deposited ink droplets, there arise problems of impairing the ink ejection and causing troubles including an undesirable deflection (a deviation of the ink droplets from the desired direction) and an ejection failure.
Particularly, when a gap between the ink jet recording head and the recording medium (referred to a head-to-paper gap hereinafter) is as narrow as not more than 1 mm, a large amount of the rebounding mist deposits around the ejection orifices.
In the ink jet recording system, the above problems are generally coped with by widening the head-to-paper gap to reduce the amount of the ink mists deposited, or wiping the ejection surface with a blade, which is formed of a rubber-like elastic member, to clean and remove the contaminations caused by the ink mists on the ejection surface.
Further, a recording medium which is extensible upon absorbing a large amount of ink, such as ordinary paper, accompanies a problem below. If the gap between the ink jet recording head and the recording medium is narrow, the head scratches the recording medium because the recording medium sags during high-duty recording due to a cockling thereof.
The above problem is also generally coped with by widening the head-to-paper gap. Widening the head-to-paper gap however increases the undesired deflection proportionally, thus resulting in a degradation of recording quality. Moreover, in an ink jet recording apparatus having a plurality of ink jet recording heads for color recording, registration of the heads (head alignment) is more apt to lose accuracy, which degrades recording quality and impairs color balance.
Meanwhile, recording is often made by using not only ink but also a treatment liquid for making a color material in the ink insoluble from the standpoints of improving water resistance and image quality. Although such a method is effective in improving water resistance and image quality, the ink made insoluble is gradually deposited at the orifices and thereabout in the ejection surface due to the aforesaid rebounding mist. Those deposits are hard to remove by the above-described wiping, preliminary ejection, or restoration by suction, and a serious ejection failure may occur.
Deposition of the ink made insoluble at the ejection orifices, etc. occurs primarily based on a phenomenon below. Ink droplets and a treatment liquid both ejected from an ink jet recording head rebound from a recording medium and are then deposited onto the ink jet recording head after being mixed together. Especially, if the ink droplets are ejected to an area to which the treatment liquid has been already ejected, the treatment liquid and the ink droplets may rebound and deposit onto the head in the form of an insoluble resulting from reaction between them.
Japanese Patent Laid-Open No. 9-216354 discloses an invention wherein a cover plate is provided to protect the ejection surface of an ink jet recording head in consideration of the nature and behavior of the rebounding mist generated upon ink and a treatment liquid impinging against a recording medium in an superimposed relation.
With the above related art, however, because the cover plate is provided between the ink jet recording head and the recording medium, the head-to-paper gap must be increased by an amount corresponding to a thickness of the cover plate, and recording quality degrades for the reasons mentioned above.
SUMMARY OF THE INVENTION
Objects of the present invention are therefore to achieve the following points:
1) To reduce deposition of an insoluble to ejection orifices caused by the rebounding mist when recording is made by using an ink jet recording head which ejects ink and a treatment liquid for making a color material in the ink insoluble.
2) To avoid the ink jet recording head from scratching the recording medium which sags due to cockling.
3) To suppress a degradation of image quality when a high image-quality recording medium is used.
To achieve the above objects, the present invention provides an ink jet recording apparatus in which recording is performed by ejecting ink from an ink ejection portion of a recording head, and causing the ink to adhere onto a recording medium, the recording apparatus comprising a control unit for changing a distance between the ink ejection portion and the recording medium depending on how the recording medium is apt to elongate in nature thereof upon application of the ink to the recording medium.
Also, the present invention provides an ink jet recording apparatus in which an ink ejection portion for ejecting ink and a processing liquid ejection portion for ejecting a processing liquid having an action to make a color material in the ink insoluble are employed to perform recording by selecting one of a first recording mode to make recording by ejecting the ink and the processing liquid onto a recording medium in an superimposed relation and a second recording mode to eject the ink but not the processing liquid onto the recording medium, the recording apparatus comprising a control unit for increasing a distance between the ink ejection portion and the recording medium to a larger value when recording is performed in the first recording mode than when recording is performed in the second recording mode.
With the above features, the distance between the ink ejection portion and the recording medium can be maintained at an appropriate value depending on the recording medium or the recording mode. Therefore, when recording is made by using the ink jet recording head which ejects the ink and the processing liquid for making the color material in the ink insoluble, deposition of an insoluble to ejection orifices caused by the rebounding mist can be reduced.
Also, the ink jet recording head can be kept from scratching the recording medium which sags due to cockling.
Further, in the case of using a high image-quality recording medium, the distance between the ink ejection portion and the recording medium can be set to be very narrow and better image quality than conventionally achieved can be ensured.
In the present invention, the processing liquid is a liquid having an action to improve printing properties. Here, an improvement of printing properties includes it to improve image quality such as represented by density, saturation, edge sharpness and dot size, to improve fixation of ink, to improve image preservation, i.e., weatherability such as resistance against water and light, and to suppress the occurrence of blur and white fog. Also, the processing liquid is a liquid that contributes to improving the printing properties, and is a liquid that contains a substance for making a color material in ink insoluble or agglomerated. Thus the treatment liquid includes a liquid for making a dye in the ink insoluble, a liquid capable of causing dispersion and disruption of a pigment in the ink, etc. The term “making a material insoluble” means such a phenomenon that an anionic group contained in the dye in the ink and a cationic group of a cationic substance contained in the liquid for improving the printi
Barlow John
Canon Kabushiki Kaisha
Dudding Alfred
Fitzpatrick ,Cella, Harper & Scinto
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