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
2000-02-14
2003-01-21
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, C101S453000
Reexamination Certificate
active
06509132
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lithographic printing plate precursor comprising a support having a hydrophilic surface, and an ink-receptive image-forming layer (recording layer). More specifically, this invention relates to a lithographic printing plate precursor capable of plate-making a plate by scan exposure based on digital signals, ensuring high sensitivity and long press life, and providing a printed matter free of residual color or staining. The lithographic printing plate precursor is suitable for the development with water or an aqueous solution or can be mounted and subjected to printing in a printing machine without passing through development.
BACKGROUND OF THE INVENTION
In general, the printing plate comprises an ink-receptive image area for receiving ink during the printing process and a hydrophilic non-image area for receiving fountain solution. For the plate precursor of such a lithographic printing plate, a PS plate comprising a hydrophilic support having provided thereon an ink-receptive photosensitive resin layer (recording layer) has heretofore been widely used. According to the typical plate-making process, a plate is subjected to mask exposure through a lith film and then the non-image area is dissolved and removed with a developer to obtain a desired printing plate.
In recent years, digitization technology of electrically processing, storing and outputting image information using a computer has been popularized. To cope with the digitization technology, various new methods for outputting an image have been proposed and are actually used. In pace with this tendency, demands are increasing for a computer-to-plate technique where a printing plate can be directly produced by scanning a ray having high directivity, such as laser ray, according to digitized image information and a lithographic film can be dispensed with. Thus, it is an important technical problem to obtain a printing plate precursor suitable therefor.
In the plate-making process of conventional PS plates, the step of dissolving and removing the non-image area after the exposure is indispensable. This additional wet processing as an indispensable step is another problem requested for conventional techniques to overcome. Particularly in recent years, discretion to the global environment is a great concern in industry as a whole. From both of the environmental aspect and the process rationalization aspect to keep up with the digitization, demands for the simple processing, dry processing or no processing are more keenly increasing.
From this standpoint, an on-press developing system has been proposed, where a photosensitive layer capable of allowing the non-image area of the printing plate precursor to be removed in the usual printing process is used, the plate is developed after the exposure on a printing press without passing through a development step to obtain a final printing plate. However, if a conventional PS plate is applied to a printing plate in the on-press developing system, the printing plate precursor must be stored under completely light-shielding and/or constant temperature conditions until it is mounted on a printing press because the photosensitive layer of the printing plate precursor is not fixed after the exposure.
On the other hand, in a high power density exposure system using a high output solid laser such as semiconductor laser and YAG laser, development different from the photoreaction being used in photosensitive materials for the low to medium power density exposure is available. More specifically, various developments using the structural change such as chemical change, phase change or morphology change can be performed. This recording system by high power density exposure is called “heat-mode recording”.
Conventional printing plate precursors of heat-mode positive system have a problem in that the change in solubility in the image-forming layer upon exposure is small near the support as compared with the change near the surface of the image-forming layer. In the printing plate precursor of heat-mode system, heat generation at the heat-mode exposure is attributable to light absorption of a light absorbent in the recording layer. Therefore, the quantity of heat generated is large on the surface of recording layer and small near the support. As a result, the degree of chance in solubility of the recording layer is relatively low near the support. In addition, when a metal support having high thermal conductivity preferred in view of suitability for printing, such as Al, is used, the increase of temperature is more prevented near the support due to thermal diffusion (i.e., heat diffusion).
For solving the problems due to thermal diffusion to the support upon exposure in the heat-mode printing plate, for example, JP-A-52-37104 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-52-118427 propose a method of providing an aluminum oxide layer having a predetermined thickness or more on the support surface so as to reduce the heat diffusion. This method certainly has an effect but the effect is still insufficient and cannot eliminate the residual film of heat-mode positive printing plate.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a lithographic printing plate precursor capable of plate-making by scan exposure, having high sensitivity and good press life, and free of generation of stains.
Another object of the present invention is to provide a lithographic printing plate precursor developable with water or an aqueous solution or capable of being mounted in a printing press as it is without passing through development and subjected to printing.
As a result of extensive investigations, the present inventors have found the above-described objects can be attained by using the following lithographic printing plate precursor (sometimes, called the lithographic printing original plate). The present invention has been accomplished based on this finding.
That is, the present invention provides:
(1) a lithographic printing plate precursor comprising a support having sequentially formed thereon a layer containing a polymer complex (Layer A) and a recording layer thermally variable in the solubility in at least one of water and an aqueous solution (Layer B), the support having a hydrophilic surface and at least one of Layer a and Layer B containing a light-heat converting agent;
(2) the lithographic printing plate precursor as described in (1) above, wherein the amount of polymer complex-containing layer (Layer A) coated is from 0.1 to 1.0 g/m
2
and the absorbency at the wavelength of laser for drawing an image is 0.3 or more; and
(3) the lithographic printing plate precursor as described in (1) above, wherein the recording layer (Layer B) contains a polymer compound having a hydrophobic functional group thermally variable in the hydrophilicity.
The term “water and an aqueous solution” as used for the lithographic printing plate precursor (hereinafter, called the lithographic printing original plate) of the present invention is described below. When the recording layer of the lithographic printing original plate contains a polar conversion polymer compound (irrespective of positive or negative), the “water” may be pure water, may contain other components, or may be a fountain solution supplied together with ink at the printing, as long as it can dissolve the non-image area.
The “aqueous solution” includes the above-described fountain solution and when the recording layer contains an aqueous alkali solution-soluble resin (irrespective of positive or negative), additionally includes conventionally well-known alkali developers. As such, the fountain solution may be “water” or “aqueous solution”.
In the lithographic printing original plate of the present invention, Layer B of the exposed area is imagewise solubilized (rendered positive) or insolubilized (rendered negative) by the heat generated due to light-heat conversion after the exposure. At this time, when a lig
Kawamura Koichi
Oohashi Hidekazu
Sorori Tadahiro
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
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