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
2000-05-30
2002-05-07
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, C430S921000, C101S462000
Reexamination Certificate
active
06383714
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a negative-type image recording material, and more particularly to a negative-type image recording material ideal for a plate material for use in planographic printing which enables so-called direct plate-making, which can be written with heat from an infrared laser or thermal head or the like, and which enables a plate to be made directly from digital signals from a computer or the like.
2. Description of the Related Art
In recent years, with the development of solid lasers and semiconductor lasers having light emission spectrums from near infrared to infrared, attention is being focused on systems for making plates directly from computer digital data which employ such infrared lasers.
One negative-type image recording material capable of recording by infrared laser is a recording material comprising an onium salt, resol resin, novolac resin, and infrared absorbing agent, as described in Japanese Patent Application Laid-Open (JP-A) No. 7-20629.
This is a material wherewith, in a plate material used for planographic printing and using the image recording material, energy provided by a solid laser or semiconductor laser emitting infrared radiation is converted to thermal energy by the infrared absorbing agent, and that heat causes the onium salt to decompose, whereby the image is formed. That is, the acid produced by the decomposition of the onium salt promotes a crosslinking reaction between a binder and a crosslinking agent that effects crosslinking in the presence of an acid, whereby the image recording, that is, the making of the plate from the recording material, is conducted.
However, the only infrared absorbing agents used in this case are cationic dyes. Because the amount of heat generated by exposure to light is low, there is a problem in that good images cannot be obtained (low sensitivity and narrow developing latitude). What is meant here by developing latitude is the allowable range wherein good images can be formed when changing the alkali concentration of an alkali developing fluid. There is another problem, moreover, involving changes in sensitivity before and after storage in high-temperature, high-humidity environments, that is, a problem of poor storage stability.
SUMMERY OF THE INVENTION
The purpose of the present invention is to resolve the problems noted above with the prior art and achieve the object stated below. That is, an object of the present invention is to provide a negative-type image recording material wherewith direct plate-making is possible by recording digital data from a computer or the like using a solid laser or semiconductor laser that emits infrared radiation, which material is not easily contaminated and exhibits good developing latitude and storage stability.
The inventors performed much exacting research with the objective of improving image formation characteristics (sensitivity and developing latitude) and storage stability and, as a result, discovered that high-sensitivity images can be formed using an infrared absorbing agent exhibiting certain properties, and thus perfected the present invention.
The means for resolving the problems noted earlier are as follows. The present invention is an image recording material characterized in that it at least contains the substances (a) to (d) noted below.
(a) a compound decomposable by light or heat, and which produces an acid when decomposed thereby;
(b) a crosslinking agent that crosslinks in the presence of an acid;
(c) a high-polymer compound substantially insoluble in water and-substantially soluble in an alkali aqueous solution; and
(d) an infrared absorbing agent selected from the group of general formulas consisting of general formula (I) or general formula (II) as follows:
wherein in general formula (I), M represents a conjugated chain; G
a
−
represents an anionic substituent; G
b
represents a neutral substituent; and X
m+
represents a hydrogen ion or a cation of valence m, where m represents an integer from 1 to 6; and in general formula (II), R
1
to R
4
each independently represent a hydrogen atom, alkyl group, or aryl group; R
5
and R
6
each independently represent an alkyl group, substituted oxy group, or halogen atom; n and m each independently represent an integer from 0 to 4; either R
1
and R
2
, or R
3
and R
4
, may bond to form a ring, or R
1
and/or R
2
may bond with R
5
, or R
3
and/or R
4
may bond with R
6
to form a ring, and, furthermore, either R
5
's may bond to form a ring or R
6
's may bond to form a ring; Z
1
and Z
2
are each independently a hydrogen atom, alkyl group, or aryl group, and at least one of Z
1
and Z
2
represents either a hydrogen atom or an alkyl group; Q is a trimethine group or pentamethine group that may have a substituent, and may form a ring structure together with a bivalent organic group; and X
−
represents a counter-anion.
The reason why a prescribed effect is obtained in using the infrared absorbing agent expressed by the general formula (I) is believed to be that the use of an anionic infrared absorbing agent makes it possible to control the interaction with the binder in the counter-cation part. More specifically, the current situation is that, in the case of a cationic infrared absorbing agent known in the prior art, the structure thereof naturally becomes limited in order to impart absorption in the infrared region, the structure responsible for the interaction with the binder is limited to a range wherein the absorbing ability in the infrared region is not impaired, and the desired interaction cannot be controlled given the molecular structure. When an anionic infrared absorbing agent like that of the present invention is employed, however, free selection of the counter-cation becomes possible, and the interaction with the binder can be freely changed without restriction, wherefore, it is believed, it becomes possible to make the desired improvement in image forming characteristics, which is a benefit of the present invention.
Moreover, with compounds that generate acids when heated (hereinafter called “acid generating compounds”) that are cationic, in particular, due to ionic bonding, the distance between the anionic infrared absorbing agent and the cationic acid generating compound in the film is small, and heat can be efficiently propagated from the infrared absorbing agent to the acid generating compound. That is also thought to be a reason.
The reason why the prescribed effect is obtained when using the infrared absorbing agent of general formula (II) is thought to be as follows. The molecular weight of the infrared absorbing agent relating to the present invention is comparatively small, and the number of molecules of the infrared absorbing agent itself relative to the quantity added becomes large. Therefore the absorbency becomes high, the sensitivity rises, and, together therewith, a dense interaction is formed in the interior of the photosensitive layer film. For that reason, it is thought, even when stored in high humidity, the penetration of moisture that impairs the crosslinking reaction into the film of the photosensitive layer can be effectively prevented, and degradation in sensitivity during storage can be suppressed.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The image recording material of the present invention contains at least (a) a compound (acid generating compound) that is decomposed by light or heat and produces an acid, (b) a crosslinking agent that crosslinks in the presence of an acid (hereinafter called “crosslinking agent”), (c) a high-polymer compound that is insoluble in water but soluble in an alkali aqueous solution (hereinafter called “alkali-soluble polymer”), and (d) either an anionic infrared absorbing agent expressed by the general formula (I) given above or an anionic infrared absorbing agent expressed by the general formula (II) given above, and also contains other components as necessary.
The infrared absorbing agents expressed by the general formulas (I) and (
Kunita Kazuto
Nakamura Ippei
Nakamura Kunio
Nakamura Tatsuo
Ashton Rosemary
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
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