Printing – Planographic – Lithographic printing plates
Reexamination Certificate
2001-03-22
2003-01-21
Funk, Stephen R. (Department: 2854)
Printing
Planographic
Lithographic printing plates
C101S457000, C101S462000, C101S465000
Reexamination Certificate
active
06508170
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lithographic plate material with an image-receptive layer capable of providing water retention characteristics suitable for a lithographic fountain solution without desensitizing. In particular, it relates to a lithographic plate material capable of forming lipophilic images using an ink-jet printer with hot-melt type solid ink.
2. Related Art
Lithographic printing using a lithographic printing plate is widely used for printing a small number of printed items, e.g., less than ten thousand. Conventionally, the lithographic printing plates are made by forming an image-receptive layer on a substrate such as a waterproof paper and printing a lipophilic image on the image-receptive layer using a typewriter or making a copy of an original block copy using a dry elecrophotography copier to form lipophilic images of toner on the image-receptive layer.
With the recent development of computers and peripheral devices, plate making processes using various kinds of digital printers have been proposed. For example, Japanese patent application laid-open Nos. 6-138719 (94), 6-250424 (94) and 7-1847 (95) disclose methods for making a lithographic printing plate by forming toner images on an image-receptive layer using a dry-type electrophotography laser printer.
The inventions disclosed in the aforementioned patent applications are directed to reduction of scumming in non-image portions of a print, which is likely to occur when dry-type electrophotography laser printers are used, and to obtain a lithographic plate having excellent plate wear.
Japanese patent application laid-open No.9-58144 (97) discloses a method of making a lithographic plate which does not use the dry-type electrophotography laser printer having such a drawback but, rather, forms lipophilic images on an image-receptive layer using an ink-jet printer with a hot-melt type solid ink.
However, the image-receptive layer of the lithographic plate disclosed in the above-mentioned patent application contains zinc oxide and a polymer binder as main components and, therefore, it is necessary to sufficiently desensitize the zinc oxide at the surface of the image-receptive layer in order to impart sufficient water retention to enable application of lithography to the image-receptive layer by means of an etching process using a cyan-system etching solution containing phosphoric acid/potassium ferricyanide as a main component or a non-cyan system etching solution containing phytic acid as a main component.
Despite efforts to improve image-receptive layers or printing methods using digital printers to reduce generation of scumming in non-image portions of a print, insufficient desensitization is achieved in the plate making process due to degradation of the aforementioned etching solution and lowering of the liquid temperature and, as a result, scumming occurs.
In addition, a printing process using the lithographic plate disclosed in the above-mentioned application requires a special fountain solution containing components similar to those of the etching solution. As a result, when the plate is used together with another lithographic plate such as an aluminum graining presensitized (PS) plate and/or lithographic plate made by a silver salt diffusion transfer process, the fountain solution in the lithographic press has to be changed. This makes printing more problematic.
The present invention aims at solving the abovementioned problems. Specifically, an object of the present invention is to provide a lithographic plate material which can be desensitized with distilled water or a fountain solution used for other lithographic plates, without using an etching solution, and to reduce scumming in non-image portions of the printed product. Another object of the present invention is to provide a method of making a lithographic plate using the novel lithographic plate material.
SUMMARY OF THE INVENTION
The lithographic plate material of the present invention comprises a support and an image-receptive layer formed on the support, wherein the surface of the image-receptive layer has an arithmetic mean roughness defined by JIS (Japanese Industrial Standard)-B0601 of not less than 0.40 &mgr;m and less than 1.20 &mgr;m, a contact angle with distilled water at room temperature of less than 50 degrees, and the image-receptive layer has ink-receptiveness for hot-melt and lipophilic ink.
The lithographic plate material of the present invention has an image-receptive layer, a hydrophilic polymer binder and inorganic microparticles.
Preferably, the lithographic plate material of the present invention has an image-receptive layer comprising polyvinyl alcohol cross-linked by hydroxylate of tetra-alkoxy silane, titanium oxide microparticles, and silica having an average primary particle size of from 1 nm to 100 nm and/or alumina having an average primary particle size of from 1 nm to 100 nm.
The lithographic plate material of the present invention may further include an undercoat layer between the support and the image-receptive layer. In this lithographic plate material, the undercoat layer may contain inorganic microparticles or synthetic resin microparticles.
The method of making a lithographic plate of the present invention comprises forming lipophilic images on the image-receptive layer of the lithographic plate material using hot-melt and lipophilic ink.
The method of making a lithographic plate of the present invention may further include imparting water retention characteristics for a lithographic fountain solution to the surface of the image-receptive layer without a desensitizing process.
The method of making a lithographic plate of the present invention may form lipophilic images on the image-receptive layer using an ink-jet printer with hot-melt solid ink.
PREFERRED EMBODIMENT OF THE INVENTION
Preferred embodiments of the present invention will be explained in detail hereinafter. In the following explanation, “part” and “%” are used on a weight basis unless otherwise indicated.
The lithographic plate material of the present invention comprises a support and an image-receptive layer formed on the support.
As the support, a plastic film composed of a resin such as polyethylene, polypropylene, polyvinylchloride, polystyrene, polyethylene-terephthalate, waterproof paper having such a plastic film laminated thereon or waterproof paper coated with such a resin can be used.
A polyethylene-terephthalate film is particularly preferred in view of its mechanical strength, dimensional stability, resistance to chemicals, and waterproof property. The support may include a light-shielding pigment such as carbon black or titanium oxide in order to make it light-shielding. The thickness of the support may be not less than 50 &mgr;m and less than 300 &mgr;m.
In order to improve adhesiveness to the image-receptive layer, the support is preferably exposed to far ultraviolet rays, or subjected to a plasma process, a corona discharge process or, preferably, an undercoating process.
Materials of the undercoat depend on the type of support employed. When polyethylene-terephthalate film is employed, it may be formed by applying a coating solution containing isocyanate prepolymer dissolved in a resin selected from acetal resins such as polyvinylbutyral, polyester resins having a terminal hydroxyl group and acrylic copolymers having side chain with a terminal hydroxyl group, to the support so that the undercoat has a dry thickness of not less than 0.5 &mgr;m and less than 10 &mgr;m.
To improve adhesiveness between the support and the image-receptive layer and to adjust the surface roughness of the image-receptive layer to be laminated thereon, the undercoat may contain inorganic microparticles such as calcium carbonate, barium sulfate, silica, zinc oxide, titanium oxide, clay, alumina or synthetic resin microparticles such as acrylic resin, epoxy resin, nylon resin, polyethylene resin, fluorine resin, or benzoguanamine, in an amount of not less than 5 parts and less than 200 parts based
Katsuoka Toshimichi
Nouda Junichi
Sato Hironori
Funk Stephen R.
Kimoto & Co., Ltd.
Lorusso & Loud
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