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
2000-12-27
2003-12-09
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
C430S303000, C430S944000, C430S945000
Reexamination Certificate
active
06660453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a waterless planographic printing plate precursor (hereinafter, referred to as a waterless plate precursor) which enables a printing, without the need for dampening water, by means of a heat mode recording process using laser light. More specifically the present invention relates to a waterless plate precursor, which does not generate toxic gas at the time of image formation as well as printing plate preparation.
2. Description of the Related Art
In a conventional printing system using a planographic printing plate precursor which requires dampening water, it is difficult to control the fine balance between dampening water and ink. For this reason, there have been serious problems such as the ink being emulsified or the ink being mixed into dampening water, causing insufficient ink densities and surface stains, and subsequent waste of paper. In contrast, a waterless plate precursor, which requires no dampening water, has many advantages. Various types of such waterless plate precursors have been proposed, for example, in Japanese Patent Application Publication (JP-B) No. 44-23042, JP-B No. 46-16044, JP-B No. 54-26923, JP-B No. 56-14976, JP-B No. 56-23150, JP-B No. 61-54222, Japanese Patent Application Laid-Open (JP-A) No. 58-215411, JP-A No. 2-16561 and JP-A No. 2-236550.
In recent years, along with the rapid development in output systems such as pre-press systems, image setters and laser printers, many methods for providing printing plates have been proposed in which a print image is converted into digital data and new plate-making methods such as a computer-to-plate method or a computer-to-cylinder method are used. Accordingly, there have been increasing demands for new types of printing materials for use in these printing systems, and the development thereof has progressed.
Methods for forming waterless planographic printing plate precursors by utilizing a writing process using laser light are disclosed, for example, in JP-B No. 42-21879, JP-A No. 50-158405, JP-A No. 6-55723, JP-A No. 6-186750, U.S. Pat. No. 5,353,705, and International Publication (WO) No. 9401280. In these methods, on a support member are successively formed a light-to-heat conversion layer containing a light-to-heat conversion agent such as carbon black and a self-oxidizing binder such as nitrocellulose, and a silicone rubber layer which is ink-repellant. Portions of the silicon rubber layer are removed by laser irradiation such that these portions are made to have an ink-adhering property, thereby making it possible to carry out a waterless printing process. However, the light-to-heat conversion layer contains self-oxidizing nitrogen-containing compounds such as nitrocellulose, ammonium nitride or the like as a thermal decomposing compound. For this reason, when the carbon black in the light-to-heat conversion layer absorbs laser light, generates heat and causes the light-to-heat conversion layer to be destroyed, the nitrocellulose is decomposed to generate toxic gases such as nitrogen oxides. Thus, such methods are not preferable from an environmental standpoint.
In order to overcome such environment-related problems due to thermal decomposing nitrogen-containing compounds such as nitrocellulose, JP-A No. 10-319579 has proposed a waterless printing plate which is writable by using a laser and which has a light-to-heat conversion layer containing a light-to-heat conversion agent and a hydroxyl-group-containing compound other than nitrocellulose. In this printing plate, between the light-to-heat conversion layer and the silicone rubber layer, a bond which is dissociated by heat is formed by utilizing a reactant or the like of an epoxy compound. However, this plate has the problem of insufficient sensitivity to lasers used for recording images.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a waterless planographic printing plate precursor which is writable by laser and which does not generate toxic gases such as nitrogen oxides at the time of recording an image. Moreover, another object of the present invention is to provide a waterless planographic printing plate precursor which has a recording layer that exhibits high sensitivity to lasers used for writing.
The inventors of the present invention have studied how to achieve the above-mentioned object, and achieved the present invention by discovering that it is possible to achieve the above-mentioned object by using a specific polyurethane in the light-to-heat layer.
A first aspect of the present invention is a waterless planographic printing plate precursor comprising a support member, a light-to-heat conversion layer for converting laser light to heat and a silicone rubber layer. The light-to-heat conversion layer contains at least one polyurethane having at least one carboxyl group, and at least one light-to-heat conversion substance.
A second aspect of the present invention is a method of producing a waterless planographic printing plate precursor comprising the steps of providing a light-to-heat conversion layer on a support member and forming a silicone rubber layer on the light-to-heat conversion layer. The light-to-heat conversion layer includes at least one of polyurethane having at least one carboxyl group, and at least one light-to-heat conversion substance.
This light-to-heat conversion layer is preferably formed so as not to contain a self-oxidizing nitrogen-containing compound such as nitrocellulose, from the standpoint of prevention of environmental problems.
Since the planographic printing plate precursor of the present invention contains no self-oxidizing compound such as nitrocellulose in its light-to-heat conversion layer, neither violent combustion nor destruction occurs due to irradiation with laser light, and no toxic gases such as nitrogen oxides are generated. Moreover, since polyurethane, which contains at least one carboxyl group, is used in the light-to-heat conversion layer, the decomposition temperature of the light-to-heat conversion layer becomes lower. Therefore, the inventors have concluded that the adhesive strength between the silicone rubber layer and the light-to-heat conversion layer in a laser irradiation section is effectively reduced, with the result that it becomes possible to provide a waterless printing plate with high sensitivity.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be described in detail hereinafter.
In the present invention, the light-to-heat conversion layer is placed closer to the support member than the silicone rubber layer. Namely, the waterless planographic printing plate precursor of the present invention is provided with a light-to-heat conversion layer and a silicone rubber layer that are laminated on a support member in that order. The layer structure is not particularly limited as long as these two layers are laminated in this order, that is, as long as the light-to-heat conversion layer is placed closer to the support member than the silicone rubber layer. Moreover, as long as the effects of the present invention are not impaired, an intermediate layer, an overcoat layer, a back coat layer or the like may be added thereto as needed. Here, the planographic printing plate precursor refers to the structure prior to formation of an image pattern formed by ink receiving portions and ink non-receiving portions.
Light-to-Heat Conversion Layer
The feature of the waterless planographic printing plate precursor is its light-to-heat conversion layer. In other words, the light-to-heat conversion layer contains (A) polyurethane having at least one carboxyl group and (B) a light-to-heat conversion agent as essential components, and may also contain other compounds, if necessary. First, an explanation will be given of this light-to-heat conversion layer.
(A) Polyurethane Having at Least One Carboxyl Group
The polyurethane used in the present invention is polyurethane which has a structural unit as a basic skeleton obtained by a reaction between at least one kind of
Hirano Tsumoru
Sonokawa Koji
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Walke Amanda C.
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