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
1999-11-19
2002-07-23
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
C430S019000, C430S348000, C430S944000, C430S945000, C101S458000, C101S465000
Reexamination Certificate
active
06423468
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a novel lithographic printing plate precursor from which a printing plate for general printing, especially for lithography, can be produced with great ease, and to a printing process using the printing plate precursor. The present invention further relates to a lithographic printing plate precursor capable of image deletion/correction and of repeated regeneration and use, and to a printing process using the printing plate precursor.
BACKGROUND OF THE INVENTION
Lithography has especially been generally used because printing plates therefor can be easily produced as compared with other many printing processes, and is one off the current main printing means. This printing process is based on oil/water immiscibility. An oily material, i.e., an ink, is held selectively by the image areas, while a dampening water is held selectively by the nonimage areas. The inked printing plate is brought into contact with the surface to be printed, either directly or indirectly through an intermediate called a blanket, whereby the ink held on the image areas is transferred to the surface to accomplish printing.
A major technique of lithography employs a presensitized plate comprising an aluminum plate as a base and a diazo-sensitized layer formed thereon. In producing the presensitized plate, a surface of the aluminum plate serving as a base is subjected to graining, anodization, and other various steps to enhance ink-receiving ability and the ink repellency of nonimage areas, improve printing durability, and heighten the image fineness of the printing surface. An image to be printed is then formed on the thus-treated surface. Consequently, lithography has become satisfactory in printing durability, the image fineness of the printing surface, and other properties, besides having the advantage of ease of printing plate production.
However, with the spread of printed matter, there has been a desire for further simplification of lithography and many simplified printing techniques have been proposed.
A representative example thereof is a printing technique in which a printing plate is produced by the silver salt diffusion transfer process. This technique is disclosed, e.g., in U.S. Pat. No. 3,511,656 and JP-A-7-56351. (The term “JP-A” as used herein means an “unexamined published Japanese patent application”.) An example of the lithographic printing plate based on this technique is Copyrapid, marketed by Agfa-Gevaert. This technique is in practical use as a simple printing process because an image to be transferred can be obtained through one step and the imaged plate as it is can be used as a printing plate since the image is oleophilic. However, this technique also necessitates the step of diffusion transfer development with an alkaline developing solution, although it is simple. There is hence a desire for a simpler printing process which does not necessitate the step of development with a developing solution.
Under these circumstances, processes for producing a simplified printing plate have been developed in which the step of development with an alkaline developing solution is not conducted after image-wise exposure to light. This simplified printing plate is also called “untreated printing plate” because the development step can be omitted. In this technical field, means based on various principles have been proposed so far, and most of these are based on, e.g., (1) image formation by image-wise exposing an image recording surface and thermally destroying the irradiated areas in the surface, (2) image formation by image-wise exposing a recording surface to make the irradiated areas oleophilic (heat-mode curing), (3) image formation by image-wise exposing a recording surface to make the irradiated areas oleophilic by light-mode curing, (4) to change surface properties by the photodecomposition of a diazo compound, and (5) heat-mode melt transfer in image areas.
Examples of such simplified lithographic techniques are disclosed in, e.g., U.S. Pat. Nos. 3,506,779, 3,549,733, 3,574,657, 3,739,033, 3,832,948, 3,945,318, 3,962,513, 3,964,389, 4,034,183, 4,081,572, 4,693,958, 4,731,317, 5,238,778, 5,353,705, 5,385,092, and 5,395,729 and European Patent 1,068.
Although these devices do not necessitate a developing solution in platemaking, they have one or more of the following drawbacks: the difference between oleophilic areas and hydrophilic areas is insufficient; the quality of printed images is hence poor; resolution is poor and a printing surface having excellent sharpness is difficult to obtain, the imaged printing surface has insufficient mechanical strength and is susceptible to marring; the insufficient mechanical strength necessitates formation of a protective film or another measure and this impairs the advantage of simplicity; and the printing plate has insufficient durability and cannot withstand long-term use. Namely, the mere omission of the step of alkali development impairs suitability for practical use. The strong desire for a method for easily producing a printing plate having the various is properties required for printing remains unsatisfied.
One method for producing the untreated ed printing plate is disclosed in JP-A-9-169098, which utilizes the phenomenon in which a zirconia ceramic becomes hydrophilic upon irradiation with light. However, the printing plate obtained by this method has insufficient discriminability between image areas and nonimage areas because zirconia has low light sensitivity and the photoconversion from hydrophobicity to hydrophilicity is insufficient.
If there is a means for easily regenerating a spent printing plate precursor, besides the above-described simplified printing methods which do not necessitate a developing solution, the means is advantageous from the two standpoints of cost reduction and the diminution of wastes. Although the practical value of the regeneration and reuse of spent printing plate precursors is influenced by the simplicity of regeneration operation, to simplify a regeneration operation is a subject which is highly difficult to accomplish and almost no investigations have so far been made thereon. The only investigation is disclosed in JP-A-9-169098, cited above, in which use is made of a zirconia ceramic which is a special material for printing plate precursors.
Titanium oxide also has been found to come to have a hydrophilic surface upon irradiation with light, and an application of this phenomenon to a simplified printing plate precursor has been proposed. In general, techniques for titanium film deposition are roughly divided into three groups, i.e., vapor-phase processes, liquid-phase processes, and solid-phase processes. Examples of the vapor-phase processes include vapor deposition, sputtering, and CVD. Examples of the liquid-phase processes include spin coating and dipping. Examples of the solid-phase processes include thermal spraying and a film deposition method based on a solid-phase reaction. Although the titanium oxide films obtained by these conventionally known methods show better image-forming properties than the printing plate precursors obtained by the prior art methods described hereinabove, a further improvement in discriminability between image areas and nonimage areas has been desired. Furthermore, improvements in the evenness of a titanium oxide film and in the rate of titanium oxide film deposition have also been desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a lithographic printing plate precursor from which a printing plate having sufficiently intact discriminability between image areas and nonimage areas and attaining excellent image quality can be obtained through a simple platemaking process not necessitating an alkaline developing solution, and which can be used repeatedly. Another object of the present invention is to provide a process for printing.
The present inventors thought that a means was necessary for enhancing the above-described surface property of titanium oxide which changes with light and heat, i.e
Hotta Hisashi
Teraoka Katsuyuki
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilmore Barbara
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