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
1999-10-21
2002-05-21
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
C430S306000, C430S019000, C430S944000, C430S945000
Reexamination Certificate
active
06391522
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to general printing field, in particular, offset printing, and a novel offset printing method in which a printing plate can be easily formed, and an offset printing plate. Specifically the present invention relates to an offset printing method capable of replication reclamation of a printing plate precursor and a printing plate precursor.
BACKGROUND OF THE INVENTION
The offset printing method has been generally used and has become a primary printing means at present because a manufacturing process of a printing plate is simple among various printing methods. This printing technique is based on the incompatibility of oil and water. An oily material, i.e., ink, is retained in an image area and a fountain solution is retained in a non-image area selectively. By bringing an ink carrying-printing plate into contact with a part to be printed directly or indirectly via an intermediate which is called blanket, the ink on the image area is transferred to the part to be printed, thereby printing is performed.
The offset printing method mainly comprises a PS plate comprising an aluminum substrate as a support having coated thereon a diazo photosensitive layer. The aluminum support of a PS plate is surface-grained and anodized to heighten the ink receptivity of the image area and ink repellency of the non-image area through other various processes to thereby improve the press life and contrive accuracy of the printing plate. Accordingly, the offset printing is provided with press life and high accuracy of the printing plate in addition to simplicity.
However, further simplification of the offset printing technique has been required with the prevalence of printed matters and a variety of simple printing methods have been proposed.
Representative examples thereof are copy rapid offset printing plate commercially available from Agfa-Gevaert Co. and a printing method based on printing plate making by means of a silver salt diffusion transfer process as disclosed 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”). This method has been put to practical use as a simple printing method because a lipophilic transfer image can be formed through one step according to this method, hence the image can be used as a printing plate as it is. However, this method also includes diffusion transfer development process with an alkaline developing solution, although it is simple. Therefore, a further simpler printing method which necessitates no development process with a developing solution has been demanded.
From the above background, a simpler printing plate-making method without performing development with an alkaline developing solution after image exposure has been developed. This simpler printing plate is called a non-processing printing plate because a development process is excluded and many improved methods have been proposed. Every sort and kind of means based on various principles, e.g., (1) image formation by thermal destruction of the irradiated part on image recording surface by imagewise exposure, (2) image formation by lipophilization (heat mode hardening) of the irradiated part by imagewise exposure, (3) image formation by lipophilization (light mode hardening) of the irradiated part by imagewise exposure, (4) decomposition of surface property by photolysis of a diazo compound, and (5) heat transfer of the image area by heat mode melting have been suggested.
The above simple offset printing techniques are disclosed in 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, 731,317, 5,238,778, 5,353,705, 5,385,092, 5,395,729 and European Patent 1068.
These techniques do not require a developing solution at plate-making but they have at least one of the drawbacks that the difference between a hydrophilic area and a lipophilic area is insufficient, consequently the image quality of the printed image is inferior, that the resolving power is inferior, consequently a printed image plane having excellent sharpness can hardly be obtained, that the image surface is insufficient in mechanical strength and is liable to be damaged, resulting in the necessity of the provision of a protective film, consequently the simplicity is rather lost, and that the durability capable of enduring long term printing is insufficient. These facts show that only the exclusion of an alkali developing process does not lead to the solution of the problem. Thus, a method for making a printing plate which fulfills requisite characteristics for printing and can easily produce a printing plate has been strongly demanded but such a method has not been realized yet.
On the other hand, along with the simplification of a printing method represented by a non-processing printing plate, reclaiming of used printing plate precursors for recycling is advantageous to the reduction of the costs and wastes and to environmental protection. However, the reclamation and reuse of printing plate precursors are accompanied by various difficulties hence these have been hardly given serious consideration, and only a special material for a printing precursor which is called zirconia ceramic is disclosed in JP-A-9-169098. Zirconia ceramic is, however, insufficient in light sensitivity and light conversion effect from hydrophobicity to hydrophilicity is unsatisfactory, therefore discrimination of an image area from a non-image area is insufficient.
In the above circumstances, the present inventors have proposed a printing plate precursor composed of a thin layer of specific metallic oxides belonging to group II, IV, or V of the Periodic Table, e.g., titanium oxide, and a printing method using the same in JP-A-11-78272, JP-A-11-105234 and Japanese Patent Application Nos. 9-258784, 9-308822, 9-308823, 9-313740, 9-348077, and 9-348078. This is a non-processing printing plate precursor which can be easily reclaimed and is excellent in simplicity, economization and environmental suitability but the present inventors have found that this printing plate precursor is inferior in ink stain of the printed paper when repeatedly used in comparison with the printed paper obtained by using a new printing plate precursor. Therefore, it has been desired to develop a method which generates little ink stain with repeated use of the printing plate precursor and which can maintain the printing quality of the printed paper in the initial printing.
This printing plate precursor has a thin layer the surface of which becomes hydrophilic with the irradiation of active light and becomes lipophilic by absorbing light energy, and the above-described simplicity and environmental suitability of this printing plate precursor are satisfied due to this constitution. However, it is desired to further increase the sensitivity to active light and the sensitiveness of the transformation of the physical properties of the thin layer surface by heat energy absorption to heighten the ink-receptivity and ink-repellency of the printing plate precursor to thereby improve the printing quality of the printed paper.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to improve the above-described non-processing printing plate precursor having a thin layer composed of a specific metallic oxide, specifically an object is to provide a printing plate precursor having high sensitivity to active light, having high sensitiveness of the transformation of the physical properties of the surface by heat energy absorption, hence hydrophilicity and lipophilicity are highly discriminable, and excellent in ink-receptivity and ink-repellency.
Another object of the present invention is to improve the above-described non-processing printing plate precursor having a thin layer composed of a specific metallic oxide which can be reclaimed repeatedly, specifically another object is to provide an offset printing means which generates little ink stain of the printed paper when the
Fukino Kiyotaka
Kamiyama Koji
Mori Nobufumi
Nakamura Takashi
Nakayama Takao
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
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