Direct drawing type lithographic printing plate precursor

Details Direct drawing type lithographic printing plate precursor Direct drawing type lithographic printing plate precursor

2002-03-12

2004-07-13

Nutter, Nathan M. (Department: 1711)

Stock material or miscellaneous articles

Composite

C428S423100, C428S424200, C428S425100, C428S425800, C428S474400, C428S476300, C428S479300, C428S479600, C428S480000, C428S481000, C428S483000, C428S500000, C428S507000, C428S515000, C428S524000, C428S526000

Reexamination Certificate

active

06761972

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a direct drawing type lithographic printing plate precursor and, more particularly, to a direct drawing type lithographic printing plate precursor capable of providing a lithographic printing plate which enables to print a great number of printed matters having clear images free from background stain.
BACKGROUND OF THE INVENTION
Lithographic printing plate precursors which are mainly used at present in the filed of small-scale commercial printing include (1) a direct drawing type lithographic printing plate precursor comprising a water-resistant support having provided thereon a hydrophilic image-receiving layer, (2) a printing plate precursor comprising a water-resistant support having provided thereon a lipophilic image-receiving layer comprising zinc oxide, which is converted into a printing plate by undergoing direct drawing image formation and then oil-desensitizing treatment with an oil-desensitizing solution to render the non-image area hydrophilic, (3) a printing plate precursor of an electrophotographic light-sensitive material comprising a water-resistant support having provided thereon a photoconductive layer comprising photoconductive zinc oxide, which is converted into a printing plate by undergoing image formation and then oil-desensitizing treatment with an oil-desensitizing solution to render the non-image area hydrophilic, and (4) a printing plate precursor of a silver-halide photographic material comprising a water-resistant support having provided thereon a silver halide emulsion layer.
With the development of office appliances and the expansion of office automation in recent years, it has been desired in the field of printing to adopt an offset printing system wherein a lithographic printing plate is directly prepared from the direct drawing type printing plate precursor (1) described above utilizing various image forming means, e.g., an electrophotographic printer, a thermal transfer printer or an ink jet printer without undergoing any other special treatment for conversion into the printing plate.
A conventional direct drawing type lithographic printing plate precursor comprises a support such as paper, having on one surface side thereof an image-receiving layer which is a surface layer provided via an interlayer and on the other surface side thereof a back layer. The interlayer and the back layer are each composed of a water-soluble resin such as PVA or starch, a water-dispersible resin such as a synthetic resin emulsion, and a pigment. The image-receiving layer ordinarily comprises an inorganic pigment, a water-soluble resin and a water resisting agent.
Examples of the inorganic pigment used include kaolin, clay, talc, calcium carbonate, silica, titanium oxide, zinc oxide, barium sulfate and alumina.
Examples of the water-soluble resin used include polyvinyl alcohol (PVA), a modified PVA such as a carboxylated PVA, starch and a derivative thereof, a cellulose derivative such as carboxymethyl cellulose or hydroxyethyl cellulose, casein, gelatin, polyvinyl pyrrolidone, a vinyl acetate-crotonic acid copolymer and a styrene-maleic acid copolymer.
Examples of the water resisting agent used include glyoxal, an initial condensate of aminoplast such as a melamine-formaldehyde resin or a urea-formaldehyde resin, a modified polyamide resin such as a methylolated polyamide resin, a polyamide-polyamine-epichlorohydrin adduct, a polyamide-epichlorohydrin resin and a modified polyamide-polyimide resin.
It is also known that a cross-linking catalyst such as ammonium chloride or a silane coupling agent can be used in addition to the above described components.
Further, it is proposed that as a binder resin used in an image-receiving layer of a direct drawing type lithographic printing plate precursor, a resin having a functional group capable of forming a carboxy group, a hydroxy group, a thiol group, an amino group, a sulfo group or a phosphono group upon decomposition and being previously crosslinked with heat-curing or light-curing groups included therein is used as described in JP-A-1-226394, JP-A-1-269593 and JP-A-1-288488 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), a resin having the above-described functional group is used together with a heat-curing or light-curing resin as described in JP-A-1-266546, JP-A-1-275191 and JP-A-1-309068, or a resin having the above-described functional group is used together with a curing agent as described in JP-A-1-267093, JP-A-1-271292 and JP-A-1-309067, for the purpose of improving hydrophilicity of the non-image area, film strength of the image-receiving layer and printing durability.
For improving hydrophilicity of the non-image area, it is also proposed that resin particles having a minute particle size of one &mgr;m or less and containing a hydrophilic group, for example, a carboxy group, a sulfo group or a phosphono group as described in JP-A-4-201387 and JP-A-4-223196, or resin particles having a minute particle size and containing a functional group capable of forming the hydrophilic group as described above upon decomposition as described in JP-A-4-319491, JP-A-4-353495, JP-A-5-119545, JP-A-5-58071 and JP-A-5-69684 are incorporated into the image-receiving layer together with the inorganic pigment and the binder resin.
However, in order to improve printing durability of a printing plate obtained by a conventional manner as described above, if the hydrophobicity of the printing plate is enhanced by adding a large amount of the water resisting agent or by using a hydrophobic resin, printing stain due to the decrease in hydrophilicity occurs although the printing durability is improved. On the contrary, the enhancement of hydrophilicity results in lowering of the water resistance to cause deterioration of the printing durability.
In particular, when the printing plate is used under a high temperature condition of 30° C. or more, it has a defect that the surface layer thereof is dissolved in dampening water used for offset printing to result in deterioration of the printing durability and occurrence of printing stain. Moreover, in case of a direct drawing type lithographic printing plate precursor, since images are directly drawn on an image-receiving layer of the printing plate precursor with oil-based ink, poor adhesion of the oil-based ink to the image receiving layer causes falling off of the oil-based ink in the image area during printing, thereby deteriorating the printing durability even if the occurrence of printing stain in the non-image area is prevented because of sufficient hydrophilicity. This problem has not yet come to a satisfactory solution.
On the other hand, a printing plate precursor having a hydrophilic layer containing titanium oxide, polyvinyl alcohol and hydrolyzed tetramethoxysilane or tetraethoxysilane as an image-receiving layer has been proposed as described, for example, in JP-A-3-42679 and JP-A-10-268583. As a result of plate-making using such a printing plate precursor to prepare a printing plate and printing using the printing plate, however, it has been practically found that printing durability of the image is insufficient.
SUMMARY OF THE INVENTION
The present invention aims to solve these problems which conventional direct drawing type lithographic printing plate precursors have been encountered.
Therefore, an object of the present invention is to provide a direct drawing type lithographic printing plate precursor providing a printing plate free from not only background stain over an entire surface but also dot-like stain.
Another object of the present invention is to provide a direct drawing type lithographic printing plate precursor capable of forming a printing plate which can provide a great number of printed matters having clear images free from background stain and disappearance or distortion of images.
Other objects of the present invention will become apparent from the following description.
It has been found that these objects of the present invention are accomplished with th

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