Heat-sensitive composition and planographic printing plate

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

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C430S171000, C430S281100, C430S286100, C430S287100, C430S944000, C430S945000

Reexamination Certificate

active

06660446

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a heat-sensitive composition which can be applied widely as a heat-sensitive recording material, and a planographic printing plate having a negative recording layer obtained by using the above-mentioned composition, the plate being writable by infrared laser and being highly sensitive, and image portions of the recording layer being excellent in alkali developing-resistance and printing-endurance.
2. Description of the Related Art
Recent development of laser is remarkable, and particularly, in solid laser and semiconductor layer having light-emitting ranges in a range from near infrared ray to infrared ray, output is increasing and size is decreasing. Therefore, these lasers are very useful as an exposure light source in producing a printing plate directly from digital data of computers and the like.
The above-mentioned negative planographic printing plate material for infrared laser using, as an exposure light source, infrared laser having an emitting range in an infrared range is a planographic printing material having a photosensitive layer containing a light-heat converting agent, a polymerization initiator generating a radical by light or heat, and a polymerizable compound.
Usually, such a negative image recording material utilizes a recording method in which a polymerization reaction is caused by using a radical generated by light or heat as an initiator, and where in exposed portions of a recording layer are hardened to form image portions. Such a negative image forming material has lower image forming property as compared with a positive material in which a recording layer is solubilized by energy of infrared laser irradiation, and forms strong image portions by promoting a hardening reaction by polymerization, therefore, heating treatment is usually conducted before a developing process when the negative image forming material is used. Examples of the negative image recording material which is subjected to such post heating treatment include, recording materials composed of a resol resin and novolak resin descried in U.S. Pat. No. 5,340,699 and the like, as well as other materials.
Particularly when an aluminum substrate is used, there is a problem that energy by infrared laser irradiation is diffused in the substrate having high heat conductivity, and is not used for promotion and initiation of a polymerization reaction to form images, consequently, sufficient sensitivity is not obtained.
SUMMARY OF THE INVENTION
The present invention has been accomplished in view of the above-mentioned problems, and an object of the present invention is to provide a heat-sensitive composition in which highly sensitive substance can be changed irreversibly by heating, and a negative planographic printing plate which is obtained by using the above-mentioned composition which has high sensitivity, requires no heating treatment before development or in which the heating treatment can be simplified, has image portions excellent in alkali development-resistance and printing-endurance, and can be written by heat mode.
The present inventors have done intensive research, and found that a composition having excellent hardening property and color developing property due to exposure to heat is obtained by including an acid/radical generator having the following general formula (A), general formula (B), general formula (C), general formula (D) or general formula (E), and a whose physical properties are irreversible by an acid or radical, and further that increase in sensitivity of recording and improvement of printing endurance of a planographic printing plate can be attained by providing a recording layer containing such a composition. This discovery led to the present invention.
Namely, a heat-sensitive composition comprising (I) a compound which generates an acid or a radical when heated and which has the following general formula (A), general formula (B), general formula (C), general formula (D) or general formula (E), and (II) a compound whose physical and chemical properties are changed irreversibly by an acid or radical

a
X—COO
−a
M
+
  General formula (A)

d
R—COO
−d
M
+
  General formula (D)
e
X
−e
M
+
  General formula (E)
wherein, in general formula (A),
a
M
+
represents a monovalent cation;
a
X represents one of the groups shown below or a halogen atom;
and in the formula, R
1
and R
2
may be the same or different and represent a monovalent non-metal atom,
in the general formula (B),
b
Y has the same definition as for
a
X in the general formula (A) or represents —OH, —CN, —NO
2
, —Si(R
5
) (R
6
) (R
7
); R
3
to R
7
may be the same or different and represent a monovalent non-metal atom; and
b
M
+
represents a monovalent cation,
in the general formula (C), R
8
represents a monovalent non-metal atom; Ar
1
and Ar
2
may be the same or different and represent an aryl group; and
c
M
+
represents a monovalent cation,
in the general formula (D),
d
R represents an alkyl group or aryl group; and
d
M
+
represents a counter cation selected from the group consisting of sulfonium, iodonium, diazonium, ammonium and azinium,
in the general formula (E),
e
X

is an anion of a compound having a structure of the following general formula (F);
in the formula,
F
Y represents a single bond, —CO— or —SO
2
—; each of R
a
and R
b
independently represents a linear, branched or cyclic alkyl group, aryl group, aralkyl group or camphor group; R
a
and R
b
may be connected via an alkylene group, arylene group or aralkyl group to form a ring; when
F
Y is a —CO— group, R
b
may be a hydroxyl group or alkoxy group;
and,
e
M
+
represents a counter cation selected from the group consisting of sulfonium, iodonium, diazonium, ammonium and azinium.
When this composition further contains the heat-sensitive composition according to Claim 1 wherein, the composition further comprises (III) a light-heat converting agent, and by exposure in the absorption wavelength of said (III) a light-heat converting agent, an acid or radical of a compound (I) generating an acid or radical by being heated which is represented by at least one of the above-mentioned general formulae (A) to general formula (E) is generated, and there are changed in physical or chemical properties of compound (II) whose physical or chemical properties are changed irreversibly by an acid or radical leading to possibility of recording by exposure.
Further, the planographic printing plate disclosed by the present invention can realize recording by heat mode exposure, and comprises a substrate having disposed thereon a photosensitive layer containing (I) an acid/radical polymerization initiator represented by at least one of the above-mentioned general formula (A) to general formula (E), (III) a light-heat converting agent, (II-a) a radical-polymerizable compound having an unsaturated bond, and (IV) a binder polymer.
In the present invention, “heat mode applicable” means that recording by heat mode exposure is possible. The definition of the heat mode exposure in the present invention will be explained in detail. As described in Hans-Joachim Timpe, IS&Ts NIP 15: 1999 International Conference on Digital Printing Technologies. P. 209, it is known that process which starts with the light-excitation of a light-excitation of a light absorbing substance (for example, a colorant) in a photosensitive material and the resulting chemical or physical change, and is followed by image formation which is caused by said light excitation and resulting chemical or physical changes, is of mainly two modes. One is a so-called photon mode in which a light absorbing substance which has been light-excited is de-activated by certain photochemical mutual action (for example, energy transfer, electron movement) with other reactive substance in a photosensitive material, and a consequently deactivated reactive substance causes chemical or physical change necessary for the abo

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