Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2000-06-22
2002-12-31
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S302000
Reexamination Certificate
active
06500599
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lithographic printing plate precursor, and particularly to a novel lithographic printing plate precursor from which a printing plate can be easily prepared and a plate-making method of a lithographic printing plate using the same. More particularly, the invention relates to a lithographic printing plate precursor that can record images by laser beam scanning exposure based on digital signals and can be printed by easy development processing or development processing on a printing machine (i.e., a printing press), and a plate-making method of a lithographic printing plates using the same.
BACKGROUND OF THE INVENTION
In general, lithographic printing plate precursors comprise lipophilic image areas receiving ink in the printing process and hydrophilic non-image areas receiving fountain solution. As such lithographic printing plate precursors, presensitized plates have hitherto been widely used in which lipophilic light-sensitive resin layers are formed on hydrophilic supports. In plate-making methods thereof, after exposure through images of lithographic films, the non-image areas are usually removed by dissolving them in developing solutions, thereby obtaining desired printing plates.
The process for making the conventional presensitized plates requires the operation of removing the non-image areas by dissolution after exposure, and it is one problem that has been desired to be improved with respect to the prior art to make unnecessary or simplify such additional wet treatment. In particular, the disposal of waste liquid discharged by the wet treatment has recently become a matter of concern in the whole industry from the consideration to the earth circumstances, so that a request for an improvement in this respect has become stronger.
As one of easy plate making methods meeting this request, a method is proposed in which such image recording layers that the non-image areas of the printing plate precursors can be removed in the usual printing process are used and developed on a printing machine after exposure to obtain final printing plates. The plate-making system of the lithographic printing plates by such a method is called an “on-machine (i.e., on-press) development system”. Specific examples thereof include the use of image recording layers soluble in fountain solutions or ink solvents and mechanical removal of image recording layers by contact with an impression cylinder or a blanket cylinder in the printing machine. However, a large problem of the on-machine development system is that it is necessary to employ, for example, a troublesome method of keeping the printing plate precursors in a completely light-shielded state or under constant-temperature conditions until the precursors are mounted on the printing machine, because the image recording layers of the precursors are not fixed even after exposure.
On the other hand, as another recent trend in this field, digitizing techniques of electronically processing, accumulating and outputting image information by the use of computers have been widely applied, and various new image output systems corresponding to such digitizing techniques have come in practice. Associated therewith, computer-to-plate techniques have been noted in which high convergent radiations such as laser beams bear digitized image information, and printing plate precursors are subjected to scanning exposure to the radiations, thereby directly produce printing plates through no lithographic films. Resulting therefrom, it becomes an important technical problem to obtain printing plate precursors adapted to this object.
Accordingly, simplification, conversion to a dry system and dispensing with treatment of the plate-making operation have been desired more strongly than before, from both the above-mentioned circumstance problem and adaption to digitizing.
Recently, solid lasers such as semiconductor lasers and YAG lasers, which are high in output, have become available at low cost. Accordingly, the prospects for the plate-making methods using these lasers as image recording means have become particularly encouraging, as another one of the methods for producing the printing plates by scanning exposure that can be easily incorporated in the digitizing technique. In the conventional plate-making methods, low- to medium-illuminance imagewise exposure is given to light-sensitive printing plate precursors to carry out image recording according to imagewise physical property changes of precursor faces by the photochemical reaction. However, in the methods using high power density exposure using high output lasers, exposure regions are intensively irradiated with a large amount of light energy during momentary exposure time to efficiently convert light energy to heat energy, and chemical changes, phase changes and physical changes such as changes in shape or structure are allowed to occur by that heat to utilize those changes for image recording. That is to say, although image information is inputted by light energy of laser light, image recording is conducted by the reaction due to heat energy. Usually, the recording system utilizing heat generation caused by such high power density exposure is called heat-mode recording, and conversion of light energy to heat energy is called light-heat conversion.
The great advantage of the plate-making methods using heat-mode recording means is that the precursors are not sensitive to light of the usual illuminance level such as room illumination, and that fixing is not indispensable to images recorded by high illuminance exposure. That is to say, when heat-mode light-sensitive materials are used in image recording, they are safe to room light before exposure, and the fixing of images is not indispensable also after exposure. Accordingly, when the plate-making process of using, for example, image recording layers insolubilized or solubilized by heat-mode exposure, and removing the exposed image recording layers imagewise to form printing plates is carried out by the on-machine development system, such printing systems that images are not influenced by development (removal of non-image areas) for a certain period of time after image exposure, for example, even if exposed to room environmental light, become possible.
It is therefore expected that the use of the heat-mode recording will make it possible to obtain lithographic printing plate precursors desirable for the on-machine development system.
WO94/18005 discloses lithographic printing plate precursors comprising supports having provided thereon hydrophilic cross-linked layers and recording layers and the plate making of which can be similarly carried out without development. In these printing plate precursors, it is necessary to scrape away substantially all of the hydrophilic layers and recording layers of laser-exposed areas to expose surfaces of the ink-receptive supports or ink-receptive layers under the recording layers, which is considered to raise problems with regard to simplicity of processing and ink consumption in printing.
The plate-making and printing methods utilizing the heat-mode image recording have advantages that printing plates can be directly produced from camera-ready copies through no films, so that the plate making on the machine is also possible and the development operation is also dispensable. However, they have weak points such as the above-mentioned insufficient heat-mode sensitivity, the difference in sensitivity between the surfaces and bottom portions of the image recording layers, the complexity of multiple constituting layers and the insufficient discrimination between the image areas and the non-image areas. Accordingly, the requests of the market requiring lithographic printing plate precursors in which the advantages of the plate-making and printing methods of the heat-mode image recording system are utilized and both the print quality and the printing durability are improved, are not sufficiently satisfied yet in the present circumstances.
SUMMARY OF THE INVENTION
It is theref
Inno Toshifumi
Tachikawa Hiromichi
Burns Doane , Swecker, Mathis LLP
Gilliam Barbara
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