Printing – Planographic – Lithographic plate making – and processes of making or using...
Reexamination Certificate
2001-11-30
2004-12-28
Funk, Stephen R. (Department: 2854)
Printing
Planographic
Lithographic plate making, and processes of making or using...
C347S041000
Reexamination Certificate
active
06834586
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ink jet recording method which provides an image having a good quality using a multiple channel head recording device. The invention further relates to an lithographic printing method and apparatus which carries out digital-plate making on a press using the ink jet recording method, a plate making method and apparatus which carries out the digital-plate making, and an ink jet printing method and apparatus.
BACKGROUND ART
As a method for applying an ink jet recording method to a printing system, a method for additionally printing variable numbers, marks, etc., on the same sheets of paper with the ink jet system by additionally attaching an ink jet printing apparatus to a rotary press has been disclosed in, for example, Japanese Patent Unexamined Publication No. Hei-10-286939.
It is preferable that high quality image information such as photographic images can be printed. However, since a great deal of liquid drops including much solvent is ejected in an ink technology for jetting aqueous or organic solvent-based ink, which includes conventional dyes or pigments as coloring agents, under pressure, there is a problem in that ink blurs out onto a printed image unless expensive specialty sheets of paper are used.
Therefore, where printing images on normal sheets of paper or plastic sheets of a non-absorbing type, no high quality printed image can be obtained.
In addition, as one of the ink jet technologies, there is a method in which ink that is solid in a normal temperature is heated and melted, and an image is formed by jetting the liquefied ink. The blurring of printed images may be reduced by using the ink. However, since the viscosity of the ink is high when ejecting the same, it is difficult to jet minute drops of ink, and individual dot images thus obtained become large in area and thick, wherein it is difficult to form highly fine images.
In the ink jet recording method using the conventional multiple channel head, when image recording is effected with an image resolution of 600 dpi, the various electrodes of the head each have a size of about 126 &mgr;m, which corresponds to about 200 dpi, under restrictions in working. Accordingly, explaining 4-channel head as an example as shown in
FIG. 11
, the various ejection electrodes
56
-(
1
) to
56
-(
4
) each move by two steps each being about 42 &mgr;m, which corresponds to 600 dpi, and skipped by 10 steps to continue image recording.
In this case, however, a so-called cross talk phenomenon occurs, causing ink particles to be exhausted in the head and hence reducing the diameter of dots thus formed or disabling ejection.
Further, adjacent ink droplets which have been ejected are off the course which they should follow during flying due to electrostatic repulsion, occasionally deteriorating the precision in the hitting position.
On the other hand, in the field of lithographic printing, ink receptive areas and ink repellent areas are formed on a surface of a printing plate in accordance with an original image. Printing ink adheres to the ink receptive areas to effect printing. Ordinarily, hydrophilic areas and oleophilic (ink receptive) areas are formed imagewise on the surface of a printing plate, and the hydrophilic areas are converted to oil-based ink repellent areas by applying dampening water thereto.
Conventional image recording (plate-making) on a printing original plate is carried out by exposing a silver salt photographic film with the desired image in an analog or digital manner, exposing a photopolymer material (printing original plate) containing a diazo resin or a photopolymerizable polymer to light through the silver halide photographic film, and then dissolving out the non-image areas mostly with an alkaline solution.
With recent improvements in digital recording technology and the demand for more efficient printing processes, various methods where digital image information is directly recorded on a printing original plate have been proposed in the field of lithographic printing method. These methods include technologies referred to a CTP (computer-to-plate) and a DDPP (digital direct printing plate) method. As the plate making method, there is provided a system where the image is recorded in a photon mode or heating mode using a laser beam. Some of these methods have been put to practical use.
However, after the image is recorded on a plate using either the photon mode or the heating mode, the non-image areas are dissolved out by treating the plate with an alkaline developer, resulting in the discharge of an alkaline waste liquid, which is environmentally undesirable.
As a means of carrying out the printing process at an enhanced efficiency there is proposed a system in which image recording is carried out on the press. The foregoing method involving the use of laser may be employed. However, this method requires an expensive and large-sized apparatus. Thus, a system utilizing an ink jet method which employs an inexpensive and compact image recording apparatus has been attempted.
Japanese Patent Unexamined Publication No. Hei. 4-97848 discloses a method which comprises forming an oleophilic or hydrophilic image on a plate drum, which is hydrophilic or oleophilic on the surface thereof instead of the conventional plate cylinder, by an ink jet process, and then removing the image after printing to clean the plate drum. However, this method is disadvantageous in that the desired removability of printed image (i.e., cleanability) and press life cannot be accomplished at the same time. In order to form a printed image having a prolonged press life on the plate cylinder, it is necessary that an ink containing a resin in a relatively high concentration be used. Thus, in the ink jet recording means for forming a printed image, the resin can be easily solidified due to the evaporation of solvent at the nozzle, deteriorating the stability in the ejection of ink. As a result, a good image can hardly be obtained.
Further, Japanese Patent Unexamined Publication No. sho. 64-27953 discloses a plate-making method which comprises recording an image of an oleophilic wax ink on a hydrophilic plate material by an ink jet process. In this method, since the image is formed of a wax, the resulting image area has a reduced mechanical strength and the adhesion of the image area to the hydrophilic surface of the plate material is insufficient, reducing the press life.
It is an object of the present invention to provide an ink jet recording method using a multiple channel head which can give an image having an extremely high and stable quality. Further, it is an object of the present invention to provide a lithographic printing method and apparatus for use with a digital recording system requiring no development process. It is another object of the present invention to provide a lithographic printing method and apparatus capable of providing a large number of prints having sharp images of high quality by an inexpensive apparatus and a simplified method. Further, it is still another object of the invention to provide a plate making method and a plate making apparatus for use with a digital recording system requiring no development process. In addition, it is still another object of the invention to further provide an ink jet printing method capable of providing a print having sharp images of high quality by an inexpensive apparatus and a simplified method.
DISCLOSURE OF THE INVENTION
(1) An on-press recording type lithographic printing method comprising mounting a plate material on a plate cylinder of a press, ejecting an oil-based ink onto the plate material from a recording head having a plurality of ejection channels utilizing an electrostatic field according to signals of image data to directly form an image on the surface of the plate material and prepare a printing plate, and then effecting the lithographic printing using the printing plate as it is,
wherein the distance of the ejection channels is 170 &mgr;m or more {150 dpi (150 dots per inch) or less as calculated in terms
Ishii Kazuo
Kato Eiichi
Nakazawa Yusuke
Ohsawa Sadao
Fuji Photo Film Co. , Ltd.
Funk Stephen R.
Sughrue & Mion, PLLC
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