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
2001-12-12
2004-03-02
Chu, John S. (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
C430S165000, C430S166000, C430S302000
Reexamination Certificate
active
06699636
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to imageable elements useful in lithographic printing. More particularly, this invention relates to imageable elements with improved run length in which the element comprises a thermally activated crosslinking agent and to methods for their use to form lithographic printing plates.
BACKGROUND OF THE INVENTION
In lithographic printing, ink receptive regions, known as image areas, are generated on a hydrophilic surface. When the surface is moistened with water and ink is applied, the hydrophilic regions retain the water and repel the ink, and the ink receptive regions accept the ink and repel the water. The ink is transferred to the surface of a material upon which the image is to be reproduced. Typically, the ink is first transferred to an intermediate blanket, which in turn transfers the ink to the surface of the material upon which the image is to be reproduced.
Imageable elements useful as lithographic printing plates, also called printing plate precursors, typically comprise a radiation sensitive imageable layer applied over a hydrophilic surface of a substrate. The imageable layer includes one or more radiation-sensitive components, which may be dispersed in a suitable binder. Alternatively, the radiation-sensitive component can also be the binder material. If after imaging the exposed regions of the imageable layer are removed in the developing process, revealing the underlying hydrophilic surface, the plate is called as a positive-working printing plate. Conversely, if the unexposed regions are removed by the developing process and the exposed regions remain, the plate is called a negative-working plate. In each instance, the regions of the imageable layer that remain are ink-receptive and the regions of the hydrophilic surface revealed by developing process accept water, typically a fountain solution, and repel ink.
In use, a lithographic printing plate comes in contact with fountain solution and may subjected to aggressive blanket washes, such as a “UV wash” to remove ultraviolet curable inks. However, many imageable layers have limited resistance to either fountain solution and/or aggressive blanket washes.
Attempts have been made to improve the resistance of lithographic printing plates to fountain solution and to blanket washes. Kawauchi, U.S. Pat. No. 6,143,464 (EP 0 894 622), for example, discloses single-layer lithographic printing plates in which the photosensitive composition comprises a phenolic resin and a copolymer comprising 10 mol % or more of at least one acrylic polymer having a sulfonamide group. However, even when these plates are baked for extremely high run lengths, often no significant increase in run length is achieved due to poor abrasive resistance of the printing surface. Thus, a need exists for improved imageable elements that do not suffer from these disadvantages.
SUMMARY OF THE INVENTION
In one aspect, the invention is an imageable element suitable for use as a lithographic printing plate precursor. The element comprises, in order:
(a) a substrate comprising a hydrophilic surface; and
(b) an imageable layer over the hydrophilic surface;
in which:
the imageable layer is ink receptive;
the element comprises a compound that comprises a multiplicity of oxazoline groups;
the element comprises a polymeric material that comprises one or more functional groups selected from the group consisting of carboxyl, carboxylic acid anhydride, phenolic hydroxyl, and sulphonamide; and
the compound that comprises the multiplicity of oxazoline groups and the polymeric material that comprises one or more functional groups selected from the group consisting of carboxyl, carboxylic acid anhydride, phenolic hydroxyl, and sulphonamide are in the same layer.
In another aspect, the invention is a positive-working imageable element suitable for use as a lithographic printing plate precursor. The element comprises, in order:
(a) a substrate comprising a hydrophilic surface; and
(b) an imageable layer over the hydrophilic surface;
in which:
the imageable layer is ink receptive;
the element comprises a compound that comprises a multiplicity of oxazoline groups;
the element comprises a polymeric material that comprises one or more functional groups selected from the group consisting of carboxyl, carboxylic acid anhydride, phenolic hydroxyl, and sulphonamide; and
the compound that comprises the multiplicity of oxazoline groups and the polymeric material that comprises one or more functional groups selected from the group consisting of carboxyl, carboxylic acid anhydride, phenolic hydroxyl, and sulphonamide are in the same layer.
In another aspect, the invention is a method for forming a lithographic printing plate. The method comprises the steps of (a) imaging an imageable element of the invention to form a imaged element, (b) developing the imaged element with a developer to form a developed element, and (c) forming the lithographic printing plate by baking the developed element and crosslinking the polymeric material that comprises one or more functional groups selected from the group consisting of carboxyl, carboxylic acid anhydride, phenolic hydroxyl, and sulphonamide, in which the thermally activated crosslinking groups do not substantially crosslink the polymeric material prior to step (c).
DETAILED DESCRIPTION OF THE INVENTION
Unless the context indicates otherwise, in the specification and claims, the terms “first polymeric material,” “second polymeric material,” “photothermal conversion material,” “dissolution inhibitor,” monomer”, “crosslinking agent,” and similar terms also refer to mixtures of such materials.
In one aspect, the invention is an imageable element. The imageable element comprises an imageable layer over a hydrophilic substrate.
Hydrophilic Substrate
Substrates for lithographic printing are well known. The hydrophilic substrate, i.e., the substrate that comprises at least one hydrophilic surface, comprises a support, which may be any material conventionally used to prepare imageable elements useful as lithographic printing plates. The support is preferably strong, stable and flexible. It should resist dimensional change under conditions of use so that color records will register in a full-color image. Typically, it can be any self-supporting material, including, for example, polymeric films such as polyethylene terephthalate film, ceramics, metals, or stiff papers, or a lamination of any of these materials. Metal supports include aluminum, zinc, titanium, and alloys thereof.
The surface of an aluminum support may be treated by techniques known in the art, including physical graining, electrochemical graining, chemical graining, and anodizing. The substrate should be of sufficient thickness to sustain the wear from printing and be thin enough to wrap around a printing form, typically from about 100 to about 600 &mgr;m. Typically, the substrate comprises an interayer between the aluminum support and the imageable layer. The interlayer may be formed by treatment of the support with, for example, silicate, dextrine, hexafluorosilicic acid, phosphate/fluoride, polyvinyl phosphonic acid (PVPA) or polyvinyl phosphonic acid copolymers.
Single Layer Imageable Elements
The imageable element may be a single layer imageable element, comprising an imageable layer over a hydrophilic substrate, in which the imageable layer comprises the compound that comprises a multiplicity of oxazoline groups. As used herein, a single layer imageable element is an element that does not comprise a developer soluble or removable underlayer between the imageable layer and the substrate. Although an absorber layer may be present between the imageable layer and the substrate, preferably no layers are present between the imageable layer and the substrate. The imageable layer may be either positive working or negative working. The imageable layer may be photoimageable (i.e., imageable by ultraviolet and/or visible radiation) or thermally imageable.
Positive Working Photoimageable Elements
Positive working photoimageable elements are well kno
Chu John S.
Kodak Polychrome Graphics LLC
RatnerPrestia
LandOfFree
Imaging element comprising a thermally activated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Imaging element comprising a thermally activated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Imaging element comprising a thermally activated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3244557