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
2001-10-15
2004-11-23
Gilliam, Barbara (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
C430S138000, C101S453000
Reexamination Certificate
active
06821704
ABSTRACT:
TECHNICAL FIELD
The present invention relates to heat sensitive type plate materials for use in making lithography and a method for preparing the same, to liquid heat sensitive materials for use in making the above plate materials, and to lithography made by the application of heat to the above plate materials.
BACKGROUND ART OF THE INVENTION
There have been proposed methods for making lithography using a computer. Particularly in the CTP (Computer-to-Plate) system, plate making is performed by printing print image information edited and produced by way of DTP (Desktop Publishing) directly on a plate material without any imaging processing, using a laser or thermal head. Much is expected from the CTP system in the field of commercial printing because it will enable the rationalization of plate making process, the reduction in time needed for plate making, and reduction in material cost.
In regard to plate materials for use in such CTP system, the present applicants propose heat sensitive plate materials on the plate surface (the surface an ink is put on at the time of printing) whose oleophilic area and non-ink-receptive area are formed by writing with heat according to the print image information, the heat sensitive plate materials being characterized in that they require no developing processing and provide lithography with excellent trait in durability of plate wear.
The lithography technology utilized by the plate making process from these plate materials, is used for, for example, printing using an oil-based ink, and plate surface formed at the time of plate making, of an oil-based-ink accepting area (oleophilic area) and an oil-based-ink rejecting area (hydrophilic area). At the time of printing, the ink is retained in the oleophilic area on the plate surface, and in the offset printing, the image corresponding to the oleophilic area on the plate surface is formed on paper by pressing the ink on the paper via a rubber blanket.
For example, Japanese Patent Laid-Open No. 7-1849 discloses a heat sensitive material for use in plate material which contains microcapsules with a component (oleophilic component) used to form an oleophilic area (image area) and a hydrophilic polymer (a hydrophilic binder polymer). The hydrophilic polymer includes a functional group capable of three-dimensionally crosslinking and a functional group reacting and combining with the oleophilic component in the microcapsules after the application of heat fractures the microcapsules.
The same specification also discloses a plate material produced by forming a heat sensitive layer (hydrophilic layer) consisting of the above described heat sensitive material on the surface of a support and then discloses the process of three-dimensionally crosslinking the hydrophilic polymer. According to the specification, this plate material is constructed in such a manner that the oleophilic component in the microcapsules forms a polymer and becomes an oleophilic area (an image area) once the microcapsules are fractured by heat during plate making, and at the same time, the oleophilic component reacts and combines with the hydrophilic polymer.
And according to the specification, with such construction, the plate material allows the plate making operation to eliminate developing process, and the lithography thus obtained is markedly excellent not only in plate wear durability but also in the quality of the hydrophilic area (non-image area). This results in clearly printed articles free from scumming layer.
WO (international publication) 98/29258 specification discloses a method of further enhancing the plate wear durability of the plate materials described in Japanese Patent Laid-Open No. 7-1849 in which the three-dimensional crosslinking of the hydrophilic polymer is formed by Lewis base moieties containing nitrogen, oxygen or sulfur interacting with polyvalent metal ions, such as tin.
The same specification also describes a method of stabilizing the hydrophilic area (non-image area) on the plate surface as well as preventing dirt from adhering to the plate surface by forming a hydrophilic polymer thin film layer, as a protective agent, on the surface of a heat sensitive layer (hydrophilic layer).
Therefore, in the above-mentioned specifications, plate materials utilizing lithography which do not require the developing processing and are excellent in plate wear durability as well as in enhancing the performance of the hydrophilic area (oil-based-ink non-receptive area, non-image area) can be obtained, as described above. These plate materials, however, leave much to be desired in terms of the mechanical strength and plate wear durability (especially preventing dirt from accumulating in the hydrophilic area) of lithography technology utilizing the plate making as described.
If the mechanical strength of a lithography is not satisfactorily high, scratches can easily result on the plate surface, and therefore, much care should be used when handling the plate. Further, when doing printing under such severe conditions that the pressure between the plate of the printing press and the blanket is high, stripping can occur between the plate body (the heat sensitive layer portion of the plate material) and the support. As a result, even at the stage where a relatively small number of prints have been produced, the plate wear may deteriorate.
When dirt accumulates on the hydrophilic area, the ink can easily adhere to the non-image area on the surface of the blanket especially when printing under severe conditions as described above. When this occurs, the blanket needs to be cleaned frequently, in order to prevent the scumming effect on the printed articles. This, in effect, decreases the efficiency of printing operation.
According to the method described in the above WO 98/29258 specification, it is possible to improve the mechanical strength and plate wear of lithography; however, the method is time-consuming and labor-intensive because it requires the refining process or the long-term cleaning process, which means that the production costs become higher when mass-producing the lithography. In this respect, the method still has room for improvement.
WO 99/04974 specification describes a plate material which has a special hydrophilic layer on the support and thereby does not require the developing process and can be manufactured inexpensively and easily.
The hydrophilic layer consists of a crosslinked polymeric matrix which contains a colloid of special metal oxides or hydroxides and a material capable of becoming ink-receptive by the irradiation of highly intensive light and heat. The above special metals include, for example, beryllium, magnesium, aluminum, silicon, gadolinium, germanium, arsenic, indium, tin, antimony, tellurium, lead, bismuth and transition metals.
The same specification describes a need for the hydrophilic layer to be crosslinked in order to print for long periods. It also describes a need for the hydrophilic layer to retain sufficient water in order to make the developing process unnecessary. And it further describes the invention being claimed on the finding that the overcoat of a metal colloid crosslinked with a crosslinker containing ionic groups (for example, colloidal silica) retains water and improves the printing performance.
In the examples described in the specification, the hydrophilic layer of the plate material is formed by coating polyethylene terephthalate with the mixture containing 5% colloidal silica, 1% 3-aminopropyl triethoxy silane (silane coupling agent) and 2% carbon, followed by drying.
In the plate material described in the specification, the hydrophilic layer is considered to be crosslinked by the combination among the metal oxides and the dehydration condensation between the metal oxide and a silane coupling agent. In this method, however, since the crosslinking results from the condensation of hydrophilic groups such as OH groups, increasing the number of crosslinked points results in decreasing the number of hydrophilic groups. Thus, with the plate material described in this sp
Ide Youichiroh
Shirataki Hironobu
Suzuki Taro
Tomeba Kei
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
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