Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-06-20
2002-11-19
Gordon, Raquel Yvette (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
Reexamination Certificate
active
06481830
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a plate-making method and a plate-making apparatus, which perform digital plate-making, and also relates to a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which perform the digital plate-making on a press and subsequently perform printing. More specifically, the present invention relates to an ink jet plate-making/printing method and an ink jet plate-making/printing apparatus, where in the manufacture of a printing plate, an image is directly formed by an ink jet method of ejecting an oil ink using the electrostatic field and thereby, good image quality can be attained in the plate-making and in the printing.
BACKGROUND OF THE INVENTION
In the lithographic printing, the printing is performed by forming a printing ink-receptive region and a printing 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 recording of an image on a printing original plate (plate-making) is 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 (printing original plate) through the film and then, dissolving and removing the non-image area using an alkaline solution.
In recent years, the lithographic printing process is demanded to meet requirements for more improvement in the digital drawing technique and higher efficiency in the process thereof and in order to satisfy these requirements, a large number of systems for directly drawing digital image information on a printing original plate 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, 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 and therefore, an alkaline waste solution is discharged. This is not preferred in view of the environmental conservation.
As means for realizing an efficient printing process, a system of performing the image drawing on a press is known. Although the above-described method of using a laser may be used, an expensive and large-scale apparatus is necessary. Therefore, a system applying an ink jet method where an inexpensive and compact recording device is used has been proposed.
JP-A-4-97848 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) discloses a method of providing a plate drum having a hydrophilic or lipophilic surface part in place of the conventional plate cylinder, forming thereon a lipophilic or hydrophilic image by an ink jet method, and removing and cleaning the image after the completion of printing. In this method, however, it is difficult to attain removal (namely, easy cleaning) of the printing image and a sufficiently long press life at the same time. In the case of forming a printing image having a sufficiently long press life on a plate cylinder, 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.
JP-A-64-27953 discloses a method of drawing an image on a hydrophilic plate material by an ink jet method using a lipophilic wax ink, thereby performing the 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.
In the ink jet method of ejecting an oil ink using electrostatic field, ink stirring means is provided in the ink tank so as to prevent the precipitation and coagulation of the ink. The stirring means used is a circulation pump, a stirring blade, an undulator or the like. In the case of a circulation pump, a pump for exclusive use of stirring is generally provided. Since a liquid feed pump for feeding an ink to the ejection head is provided, at least 2 pumps are provided and this is one obstacle to the simplification, miniaturization and reduction in the cost of the apparatus as a whole.
The present invention has been made by taking account of the above-described problems.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a plate-making method and a plate-making apparatus, which can adopt the digital technique not requiring a development processing.
A second object of the present invention is to provide a plate-making method and a plate-making apparatus, where a lithographic printing plate capable of creating a large number of clear and high-quality printed matters can be manufactured inexpensively by a simple and easy method.
A third object of the present invention is to provide a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which can adopt the digital technique not requiring a development processing.
A fourth object of the present invention is to provide a computer-to-cylinder type lithographic printing process and a computer-to-cylinder type lithographic printing apparatus, which can print a large number of clear and high-quality printed matters using an inexpensive apparatus by a simple and easy method.
The present invention also provides a method capable of feeding an ink to the ejection head and at the same time, preventing the precipitation and coagulation of the ink by a construction simpler than that in conventional techniques.
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 followings.
1) An ink jet plate-making method comprising:
forming an image directly on a plate material by an electrostatic ink jet method comprising ejecting an oil ink using electrostatic field based on signals of image data; and
fixing said image to manufacture a printing plate,
wherein said process uses:
an ink tank for storing said oil ink,
an ink circulation line for stirring the oil ink stored in said ink tank, and
an ink feed line for feeding said oil ink to an ink jet ejection head, branched from said ink circulation line, and
wherein the ink is circulated to said ink circulation line and thereby stirring of the ink stored in said ink tank and feeding of the ink to said ink jet ejection head are simultaneously performed.
2) The ink jet plate-making method according to item 1) above, wherein an ink recovery line for recovering said oil ink from said ink jet ejection head is provided to connect with said ink circulation line and the ink is recovered from said ink jet ejection head by circulating the ink to said ink circulation line.
3) The ink jet plate-making method according to item 1) or 2) above, wherein said oil ink 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
resin particles dispersed in said nonaqueous solvent, said resin particles being solid and hydrophobic at least at an ordinary temperature.
4) An ink jet 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 i
Nakazawa Yusuke
Ohsawa Sadao
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