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
1999-02-04
2001-03-13
Chu, John S. (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
C430S190000, C430S326000, C430S905000
Reexamination Certificate
active
06200727
ABSTRACT:
The present invention relates to a positive photosensitive composition useful for a lithographic printing plate, a color proof for print correction, a color filter resist for liquid crystal display, a resist for integrated circuits for semiconductor elements or a copper etching resist to be used for a printed wiring board or gravure plate making, and further relates to a photosensitive lithographic printing plate and a method for forming a positive image.
Heretofore, as a positive photosensitive composition capable of forming a positive image by irradiation of ultraviolet light through a silver salt masking film, followed by development, a system has been known which comprises an alkali-soluble resin and an o-quinonediazide group-containing compound as a photosensitivity-imparting component. It is considered that in such a system, upon irradiation of ultraviolet light absorbable by the o-quinonediazide group-containing compound, the diazo moiety will be decomposed to finally form a carboxylic acid, whereby the alkali-solubility of the photosensitive composition will increase, i.e. only the exposed portion will be dissolved in an alkali developer to form an image. Namely, this system is one wherein a component of the photosensitive composition undergoes a photochemical change and yet has a sensitivity to ultraviolet light (hereinafter referred to simply as “UV-sensitivity”).
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 a technique relating to an image-forming method wherein laser photosensitivity is utilized, a technique has been proposed in which a chemical amplification type photoresist is combined with a long wavelength light ray absorbing dye. For example, JP-A-6-43633 discloses a positive 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 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, the photosensitive materials used in these conventional techniques have UV-sensitivity and accordingly have a difficulty in handling under white light.
Further, in connection with an image-forming technique involving a chemical change by thermal decomposition, JP-A-7-285275 discloses an image-recording material comprising 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 solubility-suppressing agent). In this publication, it is disclosed to use an onium salt, a diazonium salt or a quinonediazide compound, as the thermally decomposable solubility-suppressing agent. However, it is well known that each of such compounds has UV-sensitivity and thus has a difficulty in handling under white light. Further, this publication discloses a quinonediazide sulfuric acid ester of a certain type of a resin, such as a pyrogallol acetone resin, as a compound falling within a concept of an ester of a resin. However, the ester of a resin disclosed in this publication is nothing more than one disclosed as a type of a quinonediazide compound.
On the other hand, as an image-forming material having no UV-sensitivity and involving substantially no chemical change, the following may, for example, be mentioned.
Firstly, JP-A-9-43847 discloses a resist material wherein the crystallizability of the photosensitive material is changed by heating by irradiation with infrared rays, and a method for forming a pattern utilizing such a resist material.
Further, the present applicants have previously proposed a photosensitive composition comprising a photo-thermal conversion material and an alkali-soluble resin, whereby a positive image can be formed with a very simple system where no chemical change can be expected (U.S. patent application Ser. No. 08/906,258). This image formation is carried out by a change other than a chemical change. This is evident also from a reversible phenomenon observed such that when the photosensitive composition used which was once subjected to irradiation with light, is heated at a temperature of about 50° C. for 24 hours, the alkali solubility at the exposed portion which once increased immediately after the exposure often returns to a state close to the state before the exposure. Further, this is also evident from the relation between the glass transition temperature (or the softening point) of the photosensitive composition used and the likeliness of the reversible phenomenon, such that the lower the glass transition temperature (or the softening temperature), the more likely the reversible phenomenon.
The reason as to why the above-mentioned photosensitive composition forms such a positive image, is not clearly understood. However, it is considered that light energy absorbed by the photo-thermal conversion material is converted to heat, and the alkali-soluble polymer material at the portion receiving the heat undergoes a certain change other than the chemical change, such as a conformation change, whereby the alkali solubility at that portion will increase to facilitate formation of an image by the alkali developer.
In said application, the present applicants have further proposed sulfonic acid esters, etc., as solubility-suppressing agents for said composition.
However, such a composition is required to be further improved with respect to the sensitivity, the development latitude attributable to a difference in solubility between the exposed portion and the non-exposed portion, the strength of the photosensitive layer and the printing resistance.
Further, as a photosensitive composition having no sensitivity to UV, similar to the above, WO97/39894 discloses a lithographic printing plate capable of forming a positive image by irradiation with a laser beam of at least 600 nm, followed by development with an alkali developer. For example, it is disclosed to form a positive image by subjecting a lithographic printing plate having a photosensitive layer containing a novolak resin, a certain IR-absorbing agent and ethyl p-toluenesulfonate, to laser exposure. However, as a result of a study by the present inventors, it has been found that when the sulfonic acid ester disclosed in this publication is used, the film strength tends to be weak, and the printing resistance tends to be inadequate, although a positive image may be formed.
It is an object of the present invention to provide a positive photosensitive composition, a positive photosensitive lithographic printing plate and a method for forming a positive image, whereby the sensitivity is high, the chemical resistance of the image area is high, the film strength of the photosensitive layer is high, and high printing resistance can be obtained. A further object of the present invention is to provide a positive photosensitive composition, a positive photosensitive lithographic printing plate and a method for forming a positive image, which present high sensitivity to a near infrared laser.
Another object of the present invention is to provide a positive photosensitive lithographic printing plate excellent in handling under white light.
A stil
Hino Etsuko
Murata Akihisa
Urano Toshiyuki
Chu John S.
Mitsubishi Chemical Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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