Radiation imagery chemistry: process – composition – or product th – Imaged product – Nonsilver image
Patent
1995-09-11
1998-09-22
Young, Christopher G.
Radiation imagery chemistry: process, composition, or product th
Imaged product
Nonsilver image
430162, 430166, 4302721, 4302731, 430303, G03F 711
Patent
active
058112103
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a water-less lithographic raw plate, in more detail, a water-less lithographic raw plate, in which the area exposed to an image is photo-bonded, and also to a water-less lithographic printing plate obtained from it.
BACKGROUND OF THE INVENTION
Various water-less lithographic printing plates using a silicone rubber layer as an ink repellent layer are proposed. Among them, those which allow practical printing without using dampening water include the water-less lithographic printing plates with a photo-polymerizable adhesive layer and a silicone rubber layer laminated on a substrate as proposed in Japanese Patent Publication (Koho) SHO 54-26923 and 56-23150, etc., water-less lithographic printing plates with a photo-dimerized photosensitive layer and a silicone rubber laminated on a substrate as proposed in Japanese Patent Publication (Koho) HEI 3-56622, Japanese Patent Laid-Open (Kokai) SHO 61-153655, etc., and water-less lithographic printing plates with a photosensitive diazo resin layer and a silicone rubber layer laminated on a substrate as proposed in Japanese Patent Laid-Open (Kokai) HEI 1-150142, etc.
The inventors examined in detail the performance, especially the printing durability, of the water-less lithographic printing plates obtained by these conventional typical techniques, and as a result, found that since they are not high enough in printing durability, they cannot be practically used in the areas requiring high printing durability such as commercial web offset printing area and newspaper web offset printing area.
An object of the present invention is to present a water-less lithographic raw plate which can be processed into a water-less lithographic printing plate which can show high printing durability even when it is used for commercial web offset printing or newspaper web offset printing.
Another object of the present invention is to present a practical water-less lithographic raw plate with high image reproducibility, in addition to a water-less lithographic printing plate with high printing durability.
SUMMARY OF THE INVENTION
The inventors pursued the cause for the low printing durability of the conventional water-less lithographic printing plates, and found that the insufficient bonding strength between the photosensitive layer and the silicone rubber layer, and the high initial elastic modulus of the photosensitive layer after completion of exposure cause rupture at the bonding interface after actual long-time offset printing. Especially when a water-less lithographic printing plate is used for commercial web offset printing, it is required to have a printing durability of 100,000 to 600,000 copies, and the printing is effected at a speed of 600 to 1000 rpm. It was found that, in this case, the repeated stress acts on the water-less lithographic printing plate when the ink is transferred between the printing plate and the blanket cylinder in a tendency to cause rupture at the bonding interface between the photosensitive layer and the silicone rubber layer, thus keeping the printing durability low.
This problem was examined intensively, and as a result, it was found that if the preliminary bonding strength between the photosensitive layer and the silicone rubber in the water-less lithographic raw plate (the peel bonding strength before exposure) is intensified, the lithographic printing plate obtained by exposing the raw plate to an image-can achieve strong photo bonding between the non-image area (exposed area) of the photosensitive layer and the silicone rubber, and that if the photosensitive layer is lower in elastic modulus, the repeated stress acting on the silicone rubber layer and the photosensitive layer at the time of offset printing can be eased, to provide a water-less lithographic printing plate excellent in printing durability and image reproducibility. Thus, in the present invention, since the preliminary bonding strength between the photosensitive layer and the silicone rubber layer in the raw plate not yet expos
Ikeda Norimasa
Kawamura Ken
Tsuda Mikio
Miller Austin R.
Toray Industries Inc.
Young Christopher G.
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