Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making printing plates
Reexamination Certificate
1999-01-19
2002-06-04
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making printing plates
C430S270100, C430S434000
Reexamination Certificate
active
06399279
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming an image by means of a positive photosensitive material made of a photosensitive composition containing a photo-thermal conversion material sensitive mainly to light in a near infrared region, which is useful e.g. for a copper etching resist for a lithographic printing plate, a proof for offpress proof printing, a printed wiring board or gravure, for a color filter resist useful for the production of a flat display, or for a photoresist useful for the production of LSI. Particularly, it relates to a method for forming an image by means of a positive photosensitive material, which is useful for direct plate making by e.g. a semiconductor laser or a YAG laser.
2. Discussion of Background
Heretofore, a printing plate having a photosensitive layer containing an alkali-soluble resin and a quinonediazide compound on a substrate, has been known as a positive photosensitive lithographic printing plate capable of forming a positive image by irradiation of ultraviolet light through a silver salt masking film original, followed by development by means of an aqueous alkali solution.
With the photosensitive layer containing the quinonediazide compound, the solubility of the alkali-soluble resin in the alkali developer is suppressed by the presence of the quinonediazide compound. On the other hand, by the irradiation of ultraviolet light, the quinonediazide compound will be photochemically decomposed to form indenecarboxylic acid, whereby the above solubility-suppressing effect will be lost, and the solubility of the above photosensitive layer in the alkali developer will rather be improved. Namely, the positive image-forming mechanisms of the photosensitive layer containing the quinonediazide compound is attributable to the difference in solubility as between the exposed portion and the non-exposed portion due to the chemical change as described above.
However, the conventional positive photosensitive lithographic printing plate having a photosensitive layer containing a quinonediazide compound has had a drawback that it must be handled under yellow light, as it has sensitivity to ultraviolet light.
Further, it is known that an aqueous alkaline solution containing alkali metal ions of e.g. sodium silicate, sodium carbonate or sodium hydroxide, is used as a developer for the positive photosensitive lithographic printing plate, that a surfactant can be used as one of various additives for the developer, and that use of an amphoteric surfactant is effective to improve the development latitude. However, in the case of a positive photosensitive lithographic printing plate of this type, the solubility of the exposed portion is accelerated by the presence of the amphoteric surfactant in the developer, while the solubility of the non-exposed portion is lowered by the action of the quinonediazide compound as described above, whereby the above-mentioned effect can be accomplished. Accordingly, the action of the surfactant is nothing more than the disclosure about the photosensitive layer which involves a chemical change for the formation of an image.
On the other hand, along with the progress in the image treating technology by computers, an attention has been drawn to a photosensitive or heat sensitive direct plate making system wherein a resist image is formed directly from digital image information by a laser beam or a thermal head without using a silver salt masking film. Especially, it has been strongly desired to realize a high resolution laser photosensitive direct plate making system employing a high power semiconductor laser or YAG laser, from the viewpoint of downsizing, the environmental light during the plate making operation and plate making costs.
As image-forming methods wherein laser photosensitivity or heat sensitivity is utilized, there have heretofore been known a method of forming a color image by means of a sublimable transfer dye and a method of preparing a lithographic printing plate. Known as the latter is, for example, a method of preparing a lithographic printing plate by means of the curing reaction of a diazo compound (e.g. JP-A-50-15603, JP-A-52-151024, JP-B-60-12939, JP-B-61-21831, JP-B-2-51732, JP-B-3-34051 and U.S. Pat. No. 3,664,737), or a method of preparing a lithographic printing plate by means of the decomposition reaction of nitrocellulose (e.g. JP-A-50-102401 and JP-A-50-102403).
In recent years, a technique in which a chemical amplification type photoresist is combined with a long wavelength light ray absorbing dye, has been proposed. For example, JP-A-6-43633 discloses a negative photosensitive material wherein a certain specific squarilium dye is combined with a photo-acid-generator and a binder. Further, as a technique of this type, JP-A-7-20629 discloses a method for preparing a positive or negative lithographic printing plate by exposing a photosensitive layer containing an infrared ray absorbing dye, latent Brønsted acid, a resol resin and a novolak resin, in an image pattern by e.g. a semiconductor laser, and JP-A-7-271029 discloses a similar method wherein a s-triazine compound is used instead of the above latent Brønsted acid. However, according to a study by the present inventors, these conventional techniques had a drawback that with negative photosensitive compositions which require heat treatment after exposure, the stability in the quality of the image thereby obtainable was not necessarily adequate dependent on the heat treatment conditions.
On the other hand, as a positive photosensitive material, JP-A-7-285275 discloses a positive photosensitive printing plate provided with a photosensitive layer containing a binder, a material which absorbs light and generates heat, and a material which is thermally decomposable and substantially lowers the solubility of the binder in a non-decomposed state (hereinafter referred to as a thermally decomposable material). It is disclosed that the printing plate is developed with an alkali developer to form an image, and to the developer, a surfactant such as an anionic, nonionic or amphoteric surfactant, an organic solvent, a reducing agent, an organic carboxylic acid, a defoaming agent and a hard water-softening agent, may be added as the case requires. However, the thermally decomposable compound containing in the photosensitive layer of the printing plate disclosed in the publication is an onium salt, a diazonium salt or a quinonediazide compound, which is well known as a compound having sensitivity to light in an ultraviolet region and thus has a drawback that it is inferior in the handling property under white light (hereinafter referred to as the safelight safety characteristics). The printing plate of this publication is one whereby an image is formed by a chemical change (a chemical change due to thermal decomposition) at the exposed portion.
Further, JP-A-10-3165 discloses an invention relating to a photosensitive composition comprising a certain acrylic resin or a polyurethane, polyester or polyamide resin having hydrophilic groups, a compound which lowers the solubility of said resin in an alkali solution, and an infrared-absorbing dye, and as additive components which may be added to the alkali developer as the case requires, an organic solvent, a water-soluble sulfite, a solubilizing agent, an anionic surfactant, an amphoteric surfactant, etc., are disclosed. However, nothing is disclosed about an additive for the developer in a case where the resin is a novolak resin. Further, the photosensitive composition disclosed in this publication contains specifically a diphenyl iodonium salt in the photosensitive composition and is considered to be one whereby an image is formed by a chemical change of a thermally decomposable material like the invention disclosed in the above-mentioned JP-A-7-285275.
Further, JP-A-9-43847 discloses a positive resist material wherein the crystallizability of the photosensitive material is changed by heating by irradiation with infrared rays, and a method for forming
Hino Etsuko
Sasaki Mitsuru
Urano Toshiyuki
Baxter Janet
Gilmore Barbara
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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