Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-05-11
2002-11-26
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06485127
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a plate-making method and a plate-making apparatus, which perform digital plate-making by an electrostatic ink jet process using an oil-based ink, and also relates to a computer-to-cylinder type lithographic printing method and a computer-to-cylinder type lithographic printing apparatus, which perform the above-described digital plate-making on the printing apparatus and subsequently performing printing. More specifically, the present invention relates to a plate-making method, a plate-making apparatus, a computer-to-cylinder type lithographic printing method and a computer-to-cylinder type lithographic printing apparatus, where the oil is filtered before use and thereby, the image on the printing plate and the printed image are improved in the quality.
BACKGROUND OF THE INVENTION
In the lithographic printing, the printing is performed by forming an ink-receptive region and an ink-repulsive region on the surface of a printing plate in correspondence to an image original and adhering a printing ink to the ink-receptive region. Usually, hydrophilic and lipophilic (ink-receptive) regions are imagewise formed on the surface of a printing plate and the hydrophilic region is rendered ink-repulsive using a fountain solution.
In general, the formation of an image (plate-making) on a printing original plate (plate material) is heretofore performed by a method of once outputting an image original on a silver salt photographic film in an analog or digital manner, exposing a diazo resin or photopolymerizable photopolymer light-sensitive material (plate material) through the film and then, dissolving and removing the non-image area using an alkaline developer.
In recent years, the lithographic printing method is demanded to meet requirements for more improvement in the digital drawing technique and higher efficiency in the process thereof and in view of these recent requirements, a large number of systems for directly recording digital image information have been proposed. These techniques are called CTP (computer-to-plate) or DDPP (digital direct printing plate), With respect to the plate-making method, for example, a system of recording an image in the light or heat mode using a laser has been proposed and this system is partially put into practical use.
However, even in this plate-making method, irrespective of light mode or heat mode, the plate-making generally involves a treatment with an alkaline developer after the laser recording to dissolve and remove the non-image area, therefore, an alkaline waste solution is discharged and this is not preferred in view of the environmental conservation.
In the method of using a laser, an expensive and large-scale apparatus is necessary. In this respect, a system applying an ink jet process which is an inexpensive and compact recording device, has been proposed.
JP-A-64-27953 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a method of forming an image on a hydrophilic plate material by an ink jet process using a lipophilic wax ink, thereby performing plate-making. In this method, the image is formed by a wax and therefore, the image area is weak in the mechanical strength and deficient in the adhesive property to the hydrophilic surface of the plate material, which gives rise to poor press life.
As means for realizing an efficient printing process, a system of performing the image formation on a printing apparatus is known. JP-A-4-97848 discloses a method of providing a plate drum having a hydrophilic or lipophilic surface area in place of a conventional plate cylinder, forming thereon a lipophilic or hydrophilic image by an ink jet process, and removing and cleaning the image after the completion of printing. In this method, however, it is difficult to attain easy removing (namely, cleaning) of the printed image and a sufficiently long press life at the same time. Furthermore, in the case of forming an image having high press life on the plate drum, an ink containing a resin in a relatively high concentration must be used and accompanying the evaporation of solvent at the nozzle part, the resin readily fixes to the ink jet means of forming a printing image, as a result, the ink ejection stability decreases and a good image cannot be obtained.
In the case of forming an image by an ink jet process, aggregates in the ink or foreign matters such as dust fed to the ejection head cause clogging of the head and this gives rise to unstable ejection of ink and in turn deterioration in the image quality or stopping of the ejection. The present invention has been made to overcome these problems.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a plate-making method for manufacturing a lithographic printing plate which ensures printing of a large number of printed matters having a clear and high-quality image by an inexpensive and simple process, where a development processing is not necessary and a digital technique can be adopted.
Another object of the present invention is to provide a plate-making apparatus for realizing this plate-making method.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing method capable of blocking flowing of aggregates or foreign matters such as dust and always feeding an ink kept in a normal state to an ejection head, where a development processing is not necessary and a digital technique can be adopted.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing apparatus for realizing this computer-to-cylinder type lithographic printing method.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing method capable of printing a large number of printed matters having a clear and high-quality image by an inexpensive apparatus and a simple and easy method.
A still other object of the present invention is to provide a computer-to-cylinder type lithographic printing apparatus for realizing this computer-to-cylinder type lithographic printing method.
Other objects and effects of the present invention will become apparent from the following description.
The above-described objects of the present invention have been achieved by providing the following methods and apparatuses.
1) A plate-making method comprising:
filtering an oil-based ink;
forming an image directly on a plate material by an ink jet process comprising ejecting said filtered oil-based ink using electrostatic field based on signals of image data; and
fixing said formed image to prepare a printing plate.
2) The plate-making method according to item 1) above, wherein said oil-based comprises:
a nonaqueous solvent having an electric resistivity of 10
9
&OHgr;cm or more and a dielectric constant of 3.5 or less; and
a component dispersed in the nonaqueous solvent, comprising at least resin particles which are solid and are hydrophobic at least at ordinary temperatures.
3) A plate-making apparatus comprising:
an image-forming unit which forms an image directly on a plate material based on signals of image data; and
an image-fixing unit which fixes the image formed by said image-forming unit to prepare a printing plate,
wherein said image-forming unit comprises an ink jet drawing device having an ejection head which ejects an oil-based ink using electrostatic field and having at least one ink-filtering member provided in a passage of said oil-based ink.
4) The plate-making apparatus according to item 3) above, wherein said filtering member is provided at a portion immediately preceding an ink ejection part of said ejection head.
5) The plate-making apparatus according to item 3) or 4) above, wherein said filtering member comprises a filter material which blocks coarse aggregates of said oil-based ink and foreign matters including dust mingled during the image formation.
6) The plate-making apparatus according to item 5) above, wherein said filter material has pores having various
Nakazawa Yusuke
Naniwa Mutsumi
Ohsawa Sadao
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