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
1999-04-09
2004-04-27
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
C430S281100, C430S286100, C430S300000, C430S302000
Reexamination Certificate
active
06727044
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a lithographic printing original plate, more specifically, a lithographic printing original plate for the plate-making process by scan exposure based on digital signals. Furthermore, the present invention relates to a method for producing a lithographic printing plate using the original plate and relates to a photopolymerizable composition for use in the photosensitive layer of the lithographic printing original plate.
BACKGROUND OF THE INVENTION
Heretofore, a PS plate comprising a hydrophilic support having thereon a lipophilic photosensitive resin has been widely used as a lithographic printing plate. According to the production method thereof in usual, a plate is subjected to mask exposure (plane exposure) through a lithographic film and then the non-image area is dissolved and removed to obtain a desired printing plate.
In recent years, digitization technology of electrically processing, storing and outputting an image information using a computer has been popularized. To cope with the digitization technology, various new methods for outputting an image have been proposed and are actually used. This tendency has yielded the demand for a computer-to-plate (CTP) technique where a printing plate can be directly produced by scanning a highly directive light such as laser light according to a digitized image information and a lithographic film can be dispensed with. As a result, it has become an important technical concern to obtain a printing original plate suitable for the CTP production.
As one of the systems for obtaining a lithographic printing plate capable of scan exposure, a constitution such that a photopolymerizable composition layer having a very excellent photosensitive speed is provided as the photosensitive resin layer formed on a hydrophilic support and an oxygen-impermeable protective layer is further provided thereon, is used in many proposals heretofore made. Some of these proposals are available on the market. The photopolymerizable composition used fundamentally comprises an ethylenically unsaturated compound, a photopolymerization initiator system and a binder resin, and the image formation proceeds as follows. The photopolymerization initiation system absorbs light to generate active radicals and thereby cause addition polymerization of the ethylenically unsaturated compound, and then the photosensitive layer is insolubilized.
In most of conventional proposals on the scan exposure-type lithographic printing plate using a photopolymerization system photosensitive layer, use of a specific photopolymerization initiation system having excellent photosensitivity is disclosed. A large number of high-sensitivity initiation systems are described, for example, in Bruce M. Monroe et al.,
Chemical Revue
., 93, 435 (1993) and R. S. Davidson,
Journal of Photochemistry and Biology A: Chemistry
, 73, 81 (1993).
Some of the initiation systems disclosed have very excellent photosensitivity and by using a photopolymerization photosensitive layer containing such an initiation system, a lithographic printing original plate capable of forming an image with an economical scan exposure light source of approximately from 30 to 200 mW, such as Ar laser (488 nm) or FD-YAG laser (532 nm), can be obtained. However, the lithographic printing original plate obtained is by no means satisfied with respect to the practical performance.
More specifically, the scan exposure-type lithographic printing plate according to conventional techniques has a serious problem that the exposure latitude is narrow. For example, if the laser scanning rate is increased to reduce the plate-making time, a sufficiently long press life cannot be obtained or the dot area ratio decreases in the printing process. On the other hand, if the exposure energy is increased, fogging occurs due to light scattering inherent in the scan exposure optical system.
The technique for obtaining the above-described photopolymerizable composition is important over a wide range even in the industrial field other than CTP, for example, in the field of laser imaging such as photoformation, holography and color hard copy, in the field of manufacture of electronic materials such as photoresist, and in the field of photocurable resin materials such as ink, coating material and adhesive, and demands therefor are more and more increasing.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide a method for producing a lithographic printing plate using a laser scanning lithographic printing original plate which can provide a printing plate having a sufficiently long press life even by high-speed scan exposure and causes little fluctuation in the printing performance of the printing plate depending on the exposure conditions.
A second object of the present invention is to provide a method for producing a lithographic printing plate using the above-described lithographic printing original plate which additionally has excellent developability with an aqueous developer.
A third object of the present invention is to provide a method for producing a lithographic printing plate using the above-described lithographic printing original plate which additionally has good storage stability.
A fourth object of the present invention is to provide a lithographic printing original plate which can simplify the exposure system.
A fifth object of the present invention is to provide a lithographic printing original plate which has high photosensitization rate and excellent storage stability.
A sixth object of the present invention is to provide a photopolymerizable composition suitable for the photosensitive layer of a lithographic printing plate having those superior properties.
As a result of extensive investigations to obtain the above-described objects, the present inventors have found that when a photosensitive layer containing i) at least one polyurethane resin binder, ii) at least one compound having an addition polymerizable ethylenically unsaturated bond, and iii) at least one photopolymerization initiation system is used, the lithographic printing original plate obtained can have a sufficiently long press life even in the conditions of high-speed scan exposure and be reduced in the exposure condition dependency of the printing performance such as fluctuation in the dot area ratio.
More specifically, the present invention is characterized in that a lithographic printing plate is produced using a lithographic printing original plate comprising a hydrophilic support having provided thereon a photosensitive layer containing i) at least one polyurethane resin binder, ii) at least one compound having an addition polymerizable ethylenically unsaturated bond, and iii) at least one photopolymerization initiation system, and processed by scan exposure.
The polyurethane resin is particularly preferably a polyurethane resin having a structural unit derived from a compound selected from the group consisting of a polyether diol compound, a polyester diol compound and a polycarbonate diol compound.
When a urethane resin containing such a component is used, the printing original plate obtained can have good storage stability in particular. This is considered because the urethane resin has good compatibility with other components in the photosensitive layer.
An original plate obtained using a polyurethane resin binder having a carboxyl group in an amount of 0.4 meq/g or more has excellent developability with an aqueous developer and is advantageous in that an organic solvent not preferred in view of labor or environmental conservation can be dispensed with in the development step.
By further providing a protective layer containing a water-soluble oxygen-impermeable substance on the photosensitive layer, the original plate can be prevented from inhibition of the exposure image formation by oxygen in the outside air.
Out of the compounds having an addition polymerizable ethylenically unsaturated bond, when a compound having a urethane structure is used, a photocured product having excell
Fujimaki Kazuhiro
Higashi Tatsuji
Okamoto Yasuo
Sorori Tadahiro
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Thornton Yvette C.
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