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
2000-07-11
2001-12-25
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S273100, C430S906000
Reexamination Certificate
active
06333134
ABSTRACT:
The present invention relates to a multilayered photopolymer element wherein photopolymerizable photosensitive layers are provided on a support which is made of metal or plastic. More particularly, it relates to a multilayered photopolymer element by which it is possible to give a printing plate having a sharp-edged shape at a relief top and providing excellent print quality without a thickening by impression.
It has been already known to prepare printing plates by forming a letterpress using a photosensitive resin and that print quality is greatly dependent upon the hardness of the photosensitive resin layers. When the photosensitive resin layer is hard, deformation at the relief top is small. Therefore, though reproductivity of fine lines, dots and images is excellent, ink transferability is not good and there is a tendency for images with a large area to become blurred. In order to overcome such a disadvantage, printing is conducted with a high impression but another problem of thickening of fine lines and dots results. On the other hand, when the photosensitive resin layer is soft, the ink transferability is good but the relief top is apt to be deformed by printing pressure and, accordingly, there is a problem that the image is apt to become thick.
Accordingly, hardness of the photosensitive resin layers is chosen depending upon the aimed printing field. However, it has been difficult to solve both of the above-mentioned problems caused by hardness of the photosensitive resin layers.
In order to solve the above problems, there has been a proposal to add a sensitivity controlling agent which controls the sensitivity to the upper layer of the photosensitive resin layers whereby the shape of the relief is made sharp-edged. A specific example of such a proposal is that the photosensitive resin is provided in a multilayered manner in which the thermal polymerization inhibitor in the layers is successively made in larger amounts from the lower to the upper layers so that the shape of the shoulder at the relief top has a sharp-edge and a sharp printed image without thickening results (cf. Examined Japanese Publications No. 35/16614 and No. 37/1306). However, in such a method, there is a disadvantage that, when the unexposed photopolymer plate is stored for long time, the thermal polymerization inhibitor with a low molecular weight migrates to the lower layers whereupon the effect of making the shape of the shoulder sharp is lost. On the other hand, there has been another proposal for giving a sharp print of high quality without thickening using a photosensitive resin latterpress in which a relief is composed of a base layer comprising a certain soft photosensitive resin layer and a top layer comprising a hard one (cf. Examined Japanese Publication No. 61/56506). However, the material for such a photosensitive resin letterpress has the defect that, when it is in a form of a solid plate, manufacture of the multilayered structure is difficult and, when unexposed photopolymer plate is stored for long time, a crosslinking agent which is used for making the hardness between the laminated layers different migrates between the layers resulting in a deterioration of quality.
The object of present invention is to solve the problems in the conventional photosensitive resin letterpress and to provide a multilayered photopolymer element whereby the shelf life of unexposed photopolymer plates is extended and a printed image which does not thicken but is sharp can be achieved.
In order to solve the above-mentioned problems, the present inventors have carried out extensive studies and have at last achieved the present invention. Thus the present invention relates to a multilayered photopolymer element comprising at least a support, a photosensitive layer and a cover film which is characterized in that there are at least two photosensitive layers and the uppermost layer of said photosensitive layers contains a sensitivity controlling agent bonded with a polymer.
With regard to the photosensitive resin composition used in the photosensitive resin layer comprising at least two layers in the present invention, it is possible to use known photosensitive resin compositions such as a composition wherein a polyether amide is used as a polymeric binder (e.g. Japanese Laid-Open Publication No. 55/79437); a composition wherein a polyether ester amide is used as a polymeric binder (e.g. Japanese Laid-Open No. 58/117537); a composition wherein a polyamide having a tertiary nitrogen is used as a polymeric binder (e.g. Japanese Laid-Open No. 50/76055); a polyamide containing a quarternary ammonium (e.g. Japanese Laid-Open Publication No. 53/36555); an addition polymer of an amide having one or more amide bond(s) with an organic diisocyanate compound (e.g. Japanese Laid-Open No. 58/140737); an addition polymer of a diamine having no amide bond with an organic diisocyanate compound (e.g. Japanese Laid-Open No. 04/97154); etc.
The photosensitive resin layer in accordance with the present invention is composed of at least two layers and it is sufficient that the uppermost layer thereof contains a sensitivity controlling agent bonded with a polymer. Incidentally, it is not necessary that other components are contained from the initial stage but may migrate from the lower layers. Specific examples of the sensitivity controlling agent are known photopolymerization inhibitors, thermal polymerization inhibitors, ultraviolet absorbers, compounds which improve the sensitivity balance (Japanese Laid-Open Publication No. 55/153945), etc. and it is preferred that they contain functional groups necessary for bonding with the polymer such as an amino group, epoxy group, hydroxy group, isocyanate group, etc. When direct reaction with the polymer is difficult, they may be further compounded with a binder for binding a high-molecular active hydrogen with a sensitivity controlling agent such as a diepoxy compound, a diisocyanate compound, etc.
Specific examples of thermal polymerization inhibitors which may be used as a sensitivity controlling agent are the compounds having a thermal polymerization inhibiting ability and having one or more functional group(s) capable of reacting with the polymer. More specific examples are hydroquinone derivatives, hydroquinone monomethyl ether derivatives, benzoquinone derivatives, derivatives of aromatic amine compounds, catechol derivatives, derivatives of nitro compounds, derivatives of sulfur compounds, etc.
Examples of the ultraviolet absorbers which may be used as sensitivity controlling agents are the compounds having an ultraviolet absorbing ability and having one or more functional group(s) for making the molecular weight higher. Specific examples thereof are azobenzene derivatives (e.g. p-aminoazobenzene, chrysoidine, etc.), benzothiazole derivatives (e.g. 2-(p-aminophenyl)-6-methylbenzothiazole, primulin, etc.), stilbene derivatives (e.g. p-nitroaniline, 4-nitro-o-anisidine, etc.), acridine derivatives (e.g. 9-aminoacridine, etc.) and the like.
The sensitivity balancing agents which may be used as sensitivity controlling agents are the compounds exhibiting an ability of improving the sensitivity balance and having one or more functional group(s) for making molecular weight higher. Specific examples thereof are aminonaphthoquinone derivatives which are disclosed in the Japanese Laid-Open Publication No. 55/153935.
It is essential that the sensitivity controlling agent compounded in accordance with the present invention is bonded with a polymer and, with regard to the polymer which is bonded with the functional group of the sensitivity controlling agent, it is possible to use known soluble polymers having active hydrogens at the terminals thereof. Specific examples are polyether amides, polyether ester amides, polyamides containing tertiary nitrogens, polyamides containing quarternary nitrogen, addition polymers of diamine having an amide bond with an organic diisocyanate, addition polymers of diamine having no amide bond with an organic diisocyanate compound, polyvinyl alcohol, graft
Fujimura Toshiaki
Kouda Hajime
Taguchi Yuji
Chapman Mark
Foley & Lardner
Toyo Boseki Kabushiki Kaisha
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