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
2000-02-16
2003-06-10
Hamilton, Cynthia (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
C430S303000
Reexamination Certificate
active
06576399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording material which is digitally imagable with IR radiation. The recording material includes an aluminum substrate, a primer layer, a layer absorbing infrared radiation and a silicone layer. The present invention further relates to a process for producing a printing plate for waterless offset printing from the recording material.
2. Description of the Related Art
The recording materials from which waterless offset printing plates can be produced are known in the art. German Patent Publication No. 25 12 038-B describes a negative-working material having a substrate for accepting a printing ink, a layer containing particles absorbing laser energy, nitrocellulose, a crosslinkable resin and a crosslinking agent, and a silicone layer repelling printing ink. In the case of exposure to laser radiation, the absorbing layer is destroyed in the exposed parts so that the silicone layer present on top loses its adhesion and can be removed, together with the residues of the absorbing layer, by means of an organic solvent. To develop the plate, it is then heated to about 200° C. to cure the crosslinkable resin and improve the adhesion of the silicone layer in the unexposed parts. The German Patent Publication also mentions an insulating layer which includes an oleophilic or ink-accepting resin. The insulating layer can be arranged between a highly heat-conducting metallic substrate and the IR-absorbing layer. According to the German Patent Publication, the type of resin is not critical. It is possible to use any oleophilic resins which are usual in the area of lithographic printing. Phenol- and cresol-formaldehyde resins, vinyl resins, alkyd resins, polyester resins, polyamides, polyvinyl acetate, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polystyrene and polyethylene are mentioned. However the stability of the plate during printing without a fountain solution and the print run achievable thereby are insufficient in spite of the heat-curing of the IR-absorbing layer.
European Patent Publication No. 802 067-A describes a recording material for the production of waterless offset printing plates which includes a substrate, a heat-insulating layer, a heat-sensitive layer and a top layer for repelling printing ink. The recording material is distinguished by the fact that the heat-insulating layer, the heat-sensitive layer and the laminate formed from the two layers each have an initial modulus of elasticity of from 5 to 100 kgf/mm
2
and a 5% tensile stress of from 0.05 to 5 kgf/mm
2
(kgf=kg force=kp). The substrate is, for example, a degreased 0.24 mm thick aluminum foil. The heat-insulating layer can be produced by applying a mixture of polyurethane resin, blocked isocyanate, epoxy-phenol-urea resin, dibutyltin diacetate, Victoria Purple BOH naphthalenesulfonic acid in dimethylformamide to the substrate and then carrying out drying. The weight of the insulating layer is then 5 g/m
2
. A mixture of nitrocellulose, carbon black, polyurethane, modified epoxy resin, epoxyacrylate and diethylenetriamine in methyl isobutyl ketone can then be applied to the dried layer, and drying can then be carried out for 1 min (layer weight: 2 g/mm
2
). The top layer consists of an RTV-2 silicone rubber of the addition type.
European Patent Publication No. 763 424-A discloses a process for the production of an offset printing plate for printing in the absence of water. In the process, a material is used which comprises a substrate, a layer which converts laser beams into heat and a layer which repels printing ink. A further layer which, for example, improves the acceptance of the printing ink can be arranged between the substrate and the layer which absorbs laser beams. This further layer includes particular organic polymers, such as, acrylic, methacrylic, styrene or vinyl ester polymers, polyesters or polyurethanes.
The recording material for waterless offset printing plates according to European Patent Publication 764 522-A, which recording material is digitally imagable with IR laser beams, includes a substrate, an IR-absorbing layer and a silicone layer on top. A primer layer may also be present between substrate and IR-absorbing layer. The primer layer contains no IR-absorbing carbon black particles, but may include other pigments or dyes which impart greater contrast to the image produced by exposure to laser radiation. In addition, the primer layer reduces the flow of heat away from the IR-absorbing layer and into the substrate.
European Patent Publication No. 755 781-A relates to a recording material for waterless offset printing plates which includes a thin metal layer which absorbs IR laser beams and is ablated thereby.
WO 97/00175 discloses a recording material for offset plates printing in the absence of water, which material contains an oleophilic substrate, a layer which absorbs IR radiation and is preferably oleophilic and a preferably oleophobic top layer which is ablated by IR radiation.
SUMMARY OF THE INVENTION
One object of the invention is to overcome the disadvantages of the known art. Accordingly, there has been provided according to one aspect of the present invention a recording material sensitive to IR radiation which includes a substrate, a primer layer formed over the substrate, an IR-absorbing layer formed over the primer layer, and a silicone layer formed over the IR-absorbing layer, wherein the primer layer includes a mixture of (i) an unmodified epoxy resin, (ii) an organic polymer having functional groups, and (iii) a crosslinking agent which reacts with the unmodified epoxy resin and the functional groups of the organic polymer. In one aspect of the invention, the functional groups of the organic polymer are selected from hydroxyl and carboxyl groups. In another aspect of the invention, the organic polymer having functional groups is a fatty acid-modified, oven-drying or air-drying epoxy resin, a partially acetalated polyvinyl alcohol or an acrylic resin containing hydroxyl groups.
In a preferred aspect, the unmodified epoxy resin is present from about 2 to about 94.0% by weight, preferably form about 2.5 to about 80% by weight, most preferably from 2.5 to about 49% by weight, based on the total weight of the nonvolatile components of the primer layer. In another aspect of the invention, the weight ratio of unmodified epoxy resin to the organic polymer having functional groups is from about 1:36 to 89:1, preferably from about 1:8 to 8:1.
In another aspect of the invention, the crosslinking agent is present from about 5 to about 35% by weight, preferably from about 10 to 30% by weight, based on the total weight of the nonvolatile components of the primer layer.
In another aspect of the invention, the primer layer further includes at least one finely divided pigment. The pigment may include inorganic pigments, such as SiO
2
, Al
2
O
3
, ZrO
2
and TiO
2
pigments. In a preferred aspect, the pigment is present from about 1 to 40% by weight, more preferably from about 5 to 30% by weight, based on the total weight of the nonvolatile components of the primer layer.
In another aspect of the invention, the substrate may be a degreased sheet or foil or aluminum or of an aluminum alloy, which has been bright rolled or pretreated in simple processes.
In another aspect of the invention, the IR-absorbing layer includes (a) a component which converts IR radiant energy into heat, (b) a polymeric binder which undergoes thermal degradation or decomposition under the action of the heat generated from the IR radiation; and (c) a crosslinking resin and/or a crosslinking agent. The weight of the IR absorbing layer is preferably from about 0.1 to about 4 g/m
2
, more preferably from about 0.2 to about 3.0 g/m
2
, and most preferably from about 0.5 to about 1.5 g/m
2
.
In another aspect of the invention, the silicone layer includes an unvulcanized condensation silicone rubber, and the weight of the silicone layer is from about 1 to about 5 g/m
2
, more preferably from about 1.2 to
Gries Willi-Kurt
Schlosser Hans-Joachim
AGFA-Gevaert N.V.
Foley & Lardner
Hamilton Cynthia
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