Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2002-05-20
2004-10-26
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S176000, C430S270100, C430S302000
Reexamination Certificate
active
06808857
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority from Japanese patent application number JP2001-150669, which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a negative-working photosensitive lithographic printing plate used in the offset printing field and, more particularly, to a negative-working photosensitive lithographic printing plate used as a so-called computer-to-plate (CTP) capable of directly making plates based on a digital signal from a computer, and a negative-working photosensitive composition suited for use in a photosensitive layer of such a lithographic original printing plate. 2. Background Information
With the progress of computer image processing techniques, a method of directly writing an image by light irradiation corresponding to a digital signal has recently been developed. An intense interest has been shown towards a computer-to-plate (CTP) system of directly forming an image on a photosensitive lithographic printing plate without outputting to a silver salt mask film by utilizing this system in lithographic printing plates. A CTP system using a high-output laser having a maximum intensity within a near infrared or infrared range as a light source of light irradiation has advantages such that a high-resolution image can be obtained by exposure in a short time and a photosensitive lithographic printing plate used in the system can be handled in a lighted room. Particularly, high-output and small-sized lasers are easily available as solid lasers and semiconductor lasers, which emit infrared rays having a wavelength within a range from 760 to 1200 nm.
As the negative-working photosensitive composition which can form an image using a solid laser or semiconductor laser which is capable of emitting infrared rays, those comprising an alkali-soluble resin (novolak resin, etc.), a compound capable of being crosslinked by an acid (acid-crosslinking agent such as a resol resin), a compound capable of generating an acid by heat (acid-generating agent), and a photothermal converting agent (infrared absorber such as a dye or pigment) are proposed in Japanese Unexamined Patent Application, First Publication No. Hei 7-20629.
In this negative-working photosensitive composition, it is found that a negative-working image is formed in the following manner. First, infrared rays emitted from the solid laser or semiconductor laser are converted into heat by the photothermal converting agent. An acid is generated from the acid-generating agent by the heat. When preheated (heating) prior to development, catalytic action of the acid causes crosslinking. Consequently, a negative-working image is formed.
This photothermal converting agent incorporated into the negative-working photosensitive composition has an action of suppressing dissolution of the alkali-soluble resin, in addition to an action of converting light into heat. Therefore, it has an effect of suppressing the alkali-soluble resin from excessively dissolving upon development, thereby to improving (widening) “preheat latitude” (tolerance of heat treating conditions). Thus, even if a slight variation in treating time or heating temperature of preheating occurs among photosensitive lithographic printing plates to be preheated, the solubility of the alkali-soluble resin upon development is not drastically influenced by the variation and does not vary too much itself.
As described above, widening of the preheat latitude has an advantage such that it becomes unnecessary to strictly control the preheating conditions, and the operability is improved. Also, a further improvement in the preheat latitude is desired.
However, the photothermal converting agent has a problem such that it increases ablation (scattering phenomenon of the photosensitive composition) upon exposure. It is necessary to suppress the ablation because it can cause a stain in the light source such as a solid laser or semiconductor laser.
Therefore, presently, the amount of the photothermal converting agent cannot be increased for the object of widening the preheat latitude.
SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide a negative-working photosensitive composition which can widen the preheat latitude without increasing ablation upon exposure, and a negative-working photosensitive lithographic printing plate.
To achieve the object described above, the present inventors have made intensive studies and discovered that a specific sulfone compound has an excellent dissolution suppressing effect and does not cause ablation upon exposure, and thus the present invention has been completed.
That is, the negative-working photosensitive composition of the present invention comprises (a) an alkali-soluble resin, (b) a compound capable of being crosslinked by an acid, (c) a compound capable of generating an acid by heat, (d) a photothermal converting agent, and (e) a sulfone compound represented by the following general formula (I):
R—SO
2
—R′ (I)
wherein R and R′ may be the same or different and represent a substituted or non-substituted alkyl, alkenyl, aryl, or heterocyclic group.
The negative-working photosensitive lithographic printing plate of the present invention comprises a substrate and a photosensitive layer comprising the negative-working photosensitive composition of the present invention formed on the surface of the substrate.
The negative-working photosensitive composition of the present invention can widen the preheat latitude upon exposure without increasing ablation.
The negative-working photosensitive lithographic printing plate of the present invention suppresses ablation upon exposure to the same level as that of a conventional printing plate and achieves a wide preheat latitude.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
Negative-working Photosensitive Composition
The alkali-soluble resin (a) refers to a binder resin which is insoluble in water and is soluble in an aqueous alkali solution.
Examples of the alkali-soluble resin (a) include: novolak resins or resol resins, such as phenol-formaldehyde resins, cresol-formaldehyde resins, phenol-cresol-formaldehyde co-condensed resins; polyhydroxystyrene; polyhalogenated hydroxystyrene; acrylic resins containing one or more kinds of monomers having an acidic group, such as N-(4-hydroxyphenyl)methacrylamide, hydroquinone monomethacrylate, N-(sulfamoylphenyl) methacrylamide, N-phenylsulfonylmethacrylamide, N-phenylsulfonylmaleimide, acrylic acid, or methacrylic acid; active methylene group-containing resins as described in Japanese Unexamined Patent Application, First Publication No. Sho 63-127237; vinyl polymer resins such as urea bond-containing resins as described in Japanese Unexamined Patent Application, First Publication No. Hei 8-339082; polyurethane resins having a sulfonylamide group, N-sulfonylureido group or N-aminosulfonylamide group as described in Japanese Unexamined Patent Application, First Publication No. Sho 63-261350; polyurethane resins such as active imide group-containing polyurethane resins as described in Japanese Unexamined Patent Application, First Publication No. Hei 2-77748; polyamide resins such as polyhydroxypolyamide as described in Japanese Unexamined Patent Application, First Publication No. Hei 1-6947; and polyester resins such as polyester resins having a phenolic hydroxyl group as described in Japanese Unexamined Patent Application, First Publication No. Hei 6-236029.
Among these resins, a novolak resin is preferably used because a wide developing tolerance can be obtained.
The amount of the alkali-soluble resin (a) is preferably within a range from 40 to 95% by weight based on the solid content of the negative-working photosensitive composition. If necessary, two or more kinds of alkali-soluble resins (a) may be used in combination.
The compound (b) capable of being crosslinked by an acid is not specifically limited as far as it is crosslinked and
Hayakawa Eiji
Miyamoto Yasushi
Chu John S.
Faegre & Benson LLP
Kodak Polychrome Graphics LLC
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