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
2001-02-26
2003-08-05
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, C430S348000, C430S944000, C430S945000, C430S964000
Reexamination Certificate
active
06602648
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positive-type or negative-type image-forming material in which images can be recorded by exposure to an infrared laser, characterized in that solubility of exposed portions of a recording layer changes or hydrophilicity and hydrophobicity of the exposed portions of the recording layer change, and relates to a planographic printing original plate using the material. Further, the present invention relates to an image-forming material for use with an infrared laser, which is writable by exposure to near-infrared region light from an infrared laser or the like and is suitable for use in a planographic printing original plate that can be prepared by a so-called direct plate-making process, enabling the plate to be imaged directly according to digital signals, particularly from a computer or the like, and relates to a planographic printing original plate using the material.
2. Description of the Related Art
In recent years, owing to progress in technologies related to solid-state lasers and semiconductor lasers that emit rays in regions ranging from the near-infrared region to the infrared region, a system, which uses these infrared lasers in a printing plate-making process so that a printing plate is prepared directly according to digital data from a computer has drawn attention.
Japanese Patent Application Laid-Open (JP-A) No. 7-285275 discloses a material for a positive-type planographic printing plate for use with an infrared laser in direct plate-making. That invention relates to an image-forming material comprising a resin soluble in an aqueous alkaline solution, a substance capable of generating heat by absorbing light, and a positive-type photosensitive compound such as a quinonediazide, wherein at image portions the positive-type photosensitive compound acts as a dissolution inhibiting agent which substantially reduces the solubility of the resin soluble in the aqueous alkaline solution, and at non-image portions the positive-type photosensitive compound is thermally decomposed to thereby lose the dissolution inhibiting capability, and the image-forming material can be removed by a development treatment to form an image.
After studies, the present inventors have found that a positive image can be obtained without the addition of a quinonediazide to an image-recording material. However, mere elimination of the quinonediazide from the image recording material presents a drawback that the stability of sensitivity with respect to concentration of a developing solution, i.e., latitude in development, becomes poor.
Meanwhile, onium salts and compounds capable of forming alkali-insoluble hydrogen bonds are known to act as an agent which inhibits a polymer soluble in an aqueous alkaline solution from being dissolved by the alkali. With regard to an image-forming material for use with an infrared laser, WO 97/39,894 describes that a composition which uses a cationic infrared absorbing dye as an agent for inhibiting the polymer soluble in an aqueous alkaline solution from being dissolved exhibits a positive-working phenomenon. This positive working is that the infrared absorbing dye absorbs the laser light and generates heat which deprives a polymeric film in an irradiated region of dissolution inhibition, to thereby form an image.
However, this invention is associated with a problem that, although image-forming performance of the photosensitive composition at a surface irradiated with a laser is satisfactory, a satisfactory effect cannot be obtained deeper in the photosensitive material, because of diffusion of heat. As a result, an on-off distinction between exposed areas and unexposed areas is insufficient in a developing process with alkali. Consequently, a good image was not obtained (i.e., sensitivity was low and latitude in development was narrow). The term “latitude in development” as used herein means the broadness, when the alkali concentrations varies, of a range of the alkali concentrations of an alkaline developing solution allowable for the creation of a good image.
An increase of exposure amount in order to obtain sufficient latitude in development is associated with the problem that ablation of the infrared absorber or other components in the photosensitive layer occurs and, as a result, smudges are formed on an optical system of an exposing apparatus.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an image-forming material which has high sensitivity and is excellent in image-forming performance and does not produce smudges on an optical system of an exposing apparatus. A further object of the present invention is to provide a planographic printing original plate which uses the material and which can form images by an infrared laser for a direct plate-making process.
After a series of studies for the purpose of raising sensitivity and image-forming performance, the present inventors found that the use of a specific infrared absorber makes it possible to raise both the sensitivity and image-forming performance and to inhibit ablation of the infrared absorber. Based on these findings, the inventors have achieved the present invention.
A first aspect of the present invention is an image-forming material capable of recording an image by infrared exposure, wherein the image-forming material contains an infrared radiation absorber having in a molecule thereof at least two chromophoric groups, each of which can absorb an infrared ray and is bonded to another portion of the molecule by a covalent bond.
A second aspect of the present invention is characterized by, in the image-forming material according to the first aspect of the present invention, wherein one of the chromophoric groups has an absorption peak at a wavelength in the range of 720 to 1200 nm.
A third aspect of the present invention is characterized by, in the image-forming material according to the first aspect of the present invention, further comprising a polymeric compound insoluble in water and soluble in an aqueous alkaline solution, wherein image recording can be effected by utilizing a change of solubility of the polymeric compound in the aqueous alkaline solution.
A fourth aspect of the present invention is characterized by, in the image-forming material according to the first aspect of the present invention, further comprising a radical generator which is caused to generate a radical by at least heat, and a polymerizable compound which reacts with the radical in a radical polymerization reaction, wherein image recording can be effected by utilizing curing caused by the radical polymerization reaction of the polymerizable compound.
A fifth aspect of the present invention is characterized by, in the image-forming material according to the first aspect of the present invention, further comprising an acid-generating agent which is caused to generate an acid by at least heat, and a compound which crosslinks, with the acid acting as a catalyst for a crosslinking reaction, wherein image recording can be effected by utilizing a decrease of alkali-solubility of the image-forming material.
A sixth aspect of the present invention is characterized by, in the image-forming material according to the first aspect of the present invention, further comprising an acid-generating agent which is caused to generate an acid by at least heat, and a compound that severs a chemical bond, with the generated acid acting as a catalyst for a bond cleaving reaction, wherein image recording can be effected by utilizing an increase of alkali-solubility of the image-forming material.
A seventh aspect of the present invention is characterized by, in the image-forming material according to the first aspect of the present invention, further comprising a polarity switchable material whose hydrophilicity and hydrophobicity are changed by at least heat, wherein image recording can be effected by utilizing change of the hydrophilicity and hydrophobicity of the image-forming material.
A eighth aspect of the present i
Baxter Janet
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
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