Radiation imagery chemistry: process – composition – or product th – Diazo reproduction – process – composition – or product – Composition or product which contains radiation sensitive...
Reexamination Certificate
2001-07-17
2003-02-04
Chu, John S. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Diazo reproduction, process, composition, or product
Composition or product which contains radiation sensitive...
C430S175000, C430S176000, C430S281100, C430S288100, C430S275100, C430S278100
Reexamination Certificate
active
06514657
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive composition for a lithographic printing plate and to a photosensitive lithographic printing plate which utilizes the photosensitive composition. In particular, the present invention relates to a photosensitive lithographic printing plate with a long press life, high sensitivity, and excellent storage stability, and to a photosensitive composition for a lithographic printing plate for producing such a photosensitive lithographic printing plate.
2. Description of the Prior Art
Photosensitive lithographic printing plates are typically formed by providing a photosensitive layer including a photosensitive compound on the surface of a support such as aluminum, paper or plastic, which has undergone suitable surface treatment. Such photosensitive lithographic printing plates are manufactured by the application of a photosensitive composition, including a photosensitive compound which has been dissolved or dispersed in an organic solvent, to the surface of the support, followed by subsequent drying.
Photosensitive lithographic printing plates of this type, such as a photopolymerizable photosensitive lithographic printing plate in which a photosensitive composition including a binder resin, a monomer having ethylenically unsaturated double bonds, and a photopolymerization initiator is applied on a support having a hydrophilic surface, are generally used in the manner described below.
First, with a negative film or the like superimposed thereon, the photosensitive layer of a photopolymerizable photosensitive lithographic printing plate is exposed to light, and the exposed areas undergo polymerization and/or crosslinking and become insoluble in the developing solution. The photosensitive lithographic printing plate is then developed, and the unexposed areas are dissolved by the developing solution. Therefore, the area which is insoluble in the developing solution forms the “image area”, which repels water and which is to retain oil-based ink, whereas the area dissolved by the developing solution forms the “non-image area”, which is to retain water and which repels oil-based ink.
Since the photosensitive layer of such a photopolymerizable photosensitive lithographic printing plate is susceptible to inhibition of polymerization by oxygen, an overcoat layer including a polyvinyl alcohol or the like is provided on the photosensitive layer so that a practical press life and sensitivity can be maintained.
A photosensitive lithographic printing plate which does not require an overcoat layer is proposed in, for example, Japanese Unexamined Patent Application, First Publication No. Sho 59-53836, which is a photosensitive lithographic printing plate of a photopolymerizable composition/diazo resin hybrid system in which a photosensitive composition including a binder resin, a diazo resin, a monomer having ethylenically unsaturated double bonds, and a photopolymerization initiator is applied on a support.
Such a photosensitive lithographic printing plate of a photopolymerizable composition/diazo resin hybrid system can have practical levels of press life and sensitivity even without an overcoat layer due to the effect of the diazo resin reducing inhibited polymerization caused by oxygen.
However, the press life and the sensitivity of these photopolymerizable photosensitive lithographic printing plates and photosensitive lithographic printing plates of a photopolymerizable composition/diazo resin hybrid system are still insufficient to satisfy recent demands for extending press life and increasing sensitivity, and further improvements in the press life and the sensitivity have been sought after.
On the other hand, since a photopolymerizable photosensitive composition contains a monomer having ethylenically unsaturated double bonds, there is a problem in that the storage stability of the photosensitive composition and that of a photosensitive lithographic printing plate using the photosensitive composition are inferior.
A photopolymerizable photosensitive composition which has improved storage stability is proposed in Japanese Unexamined Patent Application, First Publication No. Sho 60-2945, which contains a stabilizer including an o-tert-butylphenol derivative and a heterocyclic thiol.
If the photopolymerizable photosensitive composition is used in a photosensitive layer of a photosensitive lithographic printing plate, the storage stability is improved. However, the press life and the storage stability are still insufficient in comparison with those of conventional diazo-type photosensitive lithographic printing plates, which do not have ethylenically unsaturated double bonds, and need to be further improved.
Accordingly, the object of the present invention is to provide a photosensitive lithographic printing plate with a long press life, high sensitivity, and excellent storage stability, and to provide a photosensitive composition for a lithographic printing plate for producing such a photosensitive lithographic printing plate.
The inventors have made diligent studies in order to achieve the above object, and as a result have completed the present invention based on the finding that the addition of a stabilizer including a combination of a specific phenol compound and a specific mercaptoimidazole compound to a photosensitive composition of a photopolymerizable composition/diazo resin hybrid system results in a photosensitive lithographic printing plate with a longer press life and higher sensitivity than those of a conventional photosensitive lithographic printing plate of a photopolymerizable composition/diazo resin hybrid system, and with a storage stability superior to that of a conventional photopolymerizable photosensitive lithographic printing plate in which a photosensitive composition is used which contains a stabilizer including an o-tert-butylphenol derivative and a heterocyclic thiol.
SUMMARY OF THE INVENTION
The present invention provides a photosensitive composition for a lithographic printing plate which includes:
a binder resin;
a diazo resin;
a monomer or oligomer compound having at least two polymerizable ethylenically unsaturated double bonds;
a photopolymerization initiator;
an o-tert-butylphenol derivative; and
a 2-mercaptoimidazole derivative.
The present invention further provides a photosensitive lithographic printing plate which includes:
a support; and
a photosensitive composition according to the present invention for a lithographic printing plate on the support.
As indicated by the comparative examples, printing plates that use the photosensitive composition according to the present invention exhibited superior press life, sensitivity and storage stability relative to those of the conventional photosensitive lithographic printing plates.
The present invention is described in detail in the following section.
DETAILED DESCRIPTION OF THE INVENTION
The photosensitive composition for a lithographic printing plate according to the present invention includes:
(A) a binder resin;
(B) a diazo resin;
(C) a monomer or oligomer, a molecule of which has at least two polymerizable ethylenically unsaturated double bonds;
(D) a photopolymerization initiator;
(E) an o-tert-butylphenol derivative; and
(F) a 2-mercaptoimidazole derivative represented by the following general formula (I):
wherein R is a group which forms an aromatic ring fused to the imidazole ring and may be substituted with a halogen or an alkyl group; R
1
is H, Na, K, or —CH
2
—N(—R
2
)
2
; and R
2
is a C
1
to C
10
alkyl group.
It is preferable that the binder resin (A) have ethylenically unsaturated bonds.
It is preferable that the binder resin (A) have an alkali-soluble group.
A binder resin which has been used in a conventional negative photosensitive lithographic printing plate can be used in the binder resin (A) of the present invention. Examples of such binder resins include (meth)acrylic acid/(meth)acrylic acid ester copolymers, copolymers including a hydroxyalkyl (meth)acrylate having an acid value of 10 to
Hayakawa Eiji
Sakurai Hideo
Kodak Polychrome Graphics L.L.C.
Ohlandt Greeley Ruggiero & Perle LLP
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