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
2000-05-19
2003-08-05
Ashton, Rosemary (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
C430S302000, C430S964000, C101S467000
Reexamination Certificate
active
06602645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive composition that is favorable as a positive image formation material, and to a planographic printing plate base in which this composition is used, and more particularly relates to a photosensitive composition that forms a positive image through the solubilization of an infrared irradiation portion, which is favorable for a planographic printing plate base that is writable by means of heart from an infrared laser, thermal head, or the like, and particularly one that is used in so-called direct plate making, with which a plate can be produced directly from the digital signals of a computer or the like, and to a planographic printing plate base that makes use of this composition.
2. Description of the Related Art
As advances have been made in recent years in solid state lasers and semiconductor lasers having an emission band ranging from near infrared to infrared, there has been a great deal of interest in systems for direct plate making from the digital data of a computer, in which these infrared lasers are used.
Japanese Patent Application Laid-Open (JP-A) No. H7-285275 discloses a positive-type planographic printing plate material for an infrared laser used in direct plate making. This invention is an image recording material produced by adding a substance that absorbs light and generates heat, and a positive-type photosensitive compound such as a quinone diazide compound to an alkali aqueous solution-soluble resin. In the image portion, the positive-type photosensitive compound serves as a dissolution inhibitor that substantially lowers the solubility of the alkali aqueous solution-soluble resin, and in the non-image portion this photosensitive compound is decomposed by heat and rendered incapable of inhibiting dissolution, and can be removed by developing, thereby forming an image.
Meanwhile, onium salts and alkali-insoluble hydrogen-bondable compounds are also known to have an alkali dissolution inhibiting action on alkali-soluble polymers. It is stated in WO97/39894 that with an image formation material corresponding to this type of infrared laser, a positive action is exhibited by a composition in which a cationic infrared absorbing colorant is used as the dissolution inhibitor for an alkali aqueous solution-soluble polymer. This positive action is such that the infrared absorbing colorant absorbs the laser light, and the heat thus generated eliminates the dissolution inhibiting effect of the polymer film in the irradiated portion, allowing an image to be formed.
In this case, the image formability is adequate on the laser irradiated surface of the photosensitive material, but a satisfactory effect is not obtained in the deep part of the material due to heat diffusion, and it is therefore difficult for the alkali developing to be turned on and off in the exposed and unexposed portions, which is a problem in that a good image is not obtained (low sensitivity and a narrow developing latitude). The term “developing latitude” as used here refers to a tolerance range in which a good image can be formed when the alkali concentration is varied in the alkali developing solution.
A cyanine-based infrared absorbing colorant has usually been used as the substance that absorbs laser light and converts it to heat in these image formation materials that form a positive image, but while these [colorants] do have high sensitivity, they are susceptible to degradation by heat and light, which poses storage stability problems.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide photosensitive composition which has high sensitivity and good developing latitude and storage stability, and a positive-type planographic printing plate base for direct plate making, which makes use of this photosensitive composition and allows an image to be formed at high sensitivity with an infrared laser.
The inventors conducted diligent research aimed at achieving better image formability, that is, sensitivity and storage stability. As a result, they discovered as the first aspect of the present invention that excellent sensitivity and storage stability can be achieved by using an infrared absorbent having a specific phthalocyanine skeleton.
Specifically, the first photosensitive composition of the present invention contains (a) a macromolecular compound having alkali-soluble groups, and (b) a compound that has a phthalocyanine skeleton and has in its molecule at least one group which can form a bond by interaction with an alkali-soluble group in said macromolecular compound (a), wherein [the photosensitive composition] becomes soluble in an alkali aqueous solution upon irradiation with infrared rays.
It is preferable for the compound (b) that has a phthalocyanine skeleton used here to be expressed by the following General Formula 1.
Here, R
11
to R
14
, R
21
to R
24
, R
31
to R
34
and R
41
to R
44
each independently represent substitutable hydrogen atom, halogen atom, cyano group, alkyl group, aryl group, alkenyl group, alkynyl group, hydroxyl group, carbonyl group, thio group, sulfonyl group, sulfinyl group, oxy group, amino group, or onium salt structure, and at least one of these R
11
to R
14
, R
21
to R
24
, R
31
to R
34
and R
41
to R
44
groups is selected from the group consisting of an amino group, hydroxyl group, thio group, carbonyl group, sulfonyl group, sulfinyl group, oxy group, and onium salt structure. Two or more of the R
11
to R
14
, R
21
to R
24
, R
31
to R
34
and R
41
to R
44
groups may be bonded together to form a ring. M represents two hydrogen atoms or a metal atom, halometal group, or oxymetal group.
The action of the present invention is not entirely clear, but it is believed that the presence of the alkali-soluble groups in the (a) macromolecular compound having alkali-soluble groups, and the groups which can form a bond by interaction with these alkali-soluble groups, which are present in the (b) compound having a phthalocyanine skeleton (hereinafter referred to as “phthalocyanine compound”), results in the formation of bonds between the two, preventing the association of the (b) phthalocyanine compound molecules in a coating film composed of this photosensitive composition, suppressing fluctuations in their association with the (a) macromolecular compound, and enhancing storage stability.
It is also believed that a phthalocyanine compound makes it possible through this interaction for the heat converted from light to be transmitted more efficiently to a coating film composed of the macromolecular compound. This probably results in a desirable effect in terms of better sensitivity.
Examples of bonds that can be formed by interaction between these functional groups include ionic bonds (including interaction between acid group and basic group), hydrogen bonds, coordination bonds, electrostatic interaction, and charge transfer interaction. Ionic bonds and hydrogen bonds are particularly favorable.
Most phthalocyanine compounds are prone to association and have low solvent solubility, so they are commonly used as pigments, but due to problems including print soiling attributable to the developing gas, these compounds have usually been considered unsuited to use in photosensitive compositions such as that of the present invention. A phthalocyanine compound has nitrogen atoms in its own skeleton, but it is believed that by additionally introducing substituents capable of forming bonds through interaction into the molecules as in the present invention, bonds are formed and the solubility of the phthalocyanine compound itself is also increased, resulting in the excellent effect characteristic of the present invention.
As a result of diligent research aimed at enhancing image formability (sensitivity and developing latitude) and storage stability, the inventors discovered as the second characteristic of the present invention that image formation with high discrimination (a large difference in dissolution rate between the exposed
Kitatani Katsuji
Kunita Kazuto
Nakamura Kunio
Nakamura Tatsuo
Ashton Rosemary
Fuji Photo Film Co. , Ltd.
Gilliam Barbara
Nakamura Kunio
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