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
2001-04-04
2003-06-24
Ashton, Rosemary (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
C430S270100, C430S273100, C430S325000, C430S302000, C430S330000, C430S331000, C430S328000, C430S905000, C430S906000, C430S907000, C430S910000, C430S944000, C430S945000
Reexamination Certificate
active
06582882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an imageable element comprising a graft copolymer having hydrophilic and hydrophobic segments. More particularly, the present invention relates to a graft copolymer, which upon imagewise exposure to thermal energy, produces exposed regions that are less soluble in a developer than the unexposed regions.
2. Description of the Prior Art
Thermally imageable compositions employing hydrophobic heat sensitive polymer particles dispersed in hydrophilic binders are generally known in the art.
JP 60/68992 and EP 514 145 disclose the use of core-shell particles in a thermally imageable composition that can undergo at least partial thermal coalescence.
EP 599 510 and equivalent U.S. Pat. No. 5,948,599 disclose a method of forming an image using a radiation sensitive plate, which comprises a layer which includes (1) a reactive group that undergoes insolubilization at elevated temperature and/or exposure to radiation, and (2) a substance capable of strongly absorbing radiation to produce heat. The layer contains a disperse phase, which has a heat softenable component and a binder or continuous phase that has a component that is soluble or swellable in an aqueous medium. Radiation causes at least partial coalescence in the exposed regions. Following development, the plate is heated or irradiated to effect insolubilization of the image areas by reaction of the reactive groups.
EP 816 070 discloses hydrophobic thermoplastic particles, photothermal converter and a covering layer.
U.S. Pat. No. 6,071,369 and EP 839 647 disclose a method for imagewise exposing an image forming layer that has thermoplastic hydrophobic polymer particles in a hydrophilic binder. Laser exposure is limited to a pixel dwell time of 0.1 to 50 microseconds.
U.S. Pat. No. 6,022,667 and EP 881 096 disclose an imageable layer comprising a hydrophobic thermoplastic polymer latex and a photothermal converter. These references require the use of an alkali soluble intermediate layer between the substrate and the imageable layer.
None of the prior art discloses heat sensitive graft copolymers of the present invention.
SUMMARY OF THE INVENTION
In broad concept, the present invention includes an imageable element comprising a substrate and a thermally imageable composition coated on a surface of the substrate, wherein the thermally imageable composition comprises a graft polymer having hydrophilic and hydrophobic segments. The imageable element according to the present invention is thermally imageable.
The present invention includes an imageable element comprising: a substrate; and a thermally imageable composition coated on a surface of the substrate; wherein the thermally imageable composition comprises a graft copolymer having a hydrophobic polymer backbone and a plurality of pendant groups represented by the formula:
—Q—W—Y
wherein Q is a difunctional connecting group; W is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment; Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment; with the proviso that when W is a hydrophilic segment, Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment, with the further proviso that when W is hydrophobic, Y is a hydrophilic segment.
The present invention also includes a method of producing an imaged element. The method comprises the steps of:
providing an imageable element comprising: a substrate; and a thermally imageable composition coated on a surface of the substrate; the thermally imageable composition comprising a graft copolymer having a hydrophobic polymer backbone and a plurality of pendant groups represented by the formula:
—Q—W—Y
wherein Q is a difunctional connecting group; W is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment; Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment; with the proviso that when W is a hydrophilic segment, Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment, with the further proviso that when W is hydrophobic, Y is a hydrophilic segment;
imagewise exposing the imageable element to thermal radiation to produce exposed and unexposed regions; and
contacting the imagewise exposed imageable element and a developer to remove the unexposed regions and thereby produce the imaged element.
The present invention also includes a thermally imageable composition comprising a graft copolymer having a hydrophobic polymer backbone and a plurality of pendant groups represented by the formula:
—Q—W—Y
wherein Q is a difunctional connecting group; W is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment; Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment; with the proviso that when W is a hydrophilic segment, Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment, with the further proviso that when W is hydrophobic, Y is a hydrophilic segment.
The graft copolymers of present invention can be imaged without a binder. Furthermore, the thermally imageable compositions can be imaged and developed without the need of an intermediate pre-heat step. In addition, the present invention does not require the use of an intermediate barrier or a covering layer.
The present invention provides a thermally imageable composition that is useful in thermal imaging of, for example, lithographic plates and printed circuit boards.
DETAILED DESCRIPTION OF THE INVENTION
Lithographic printing is based on the immiscibility of oil and water. Ink receptive areas are generated on the surface of a hydrophilic surface. When the surface is moistened with water and then ink is applied, the hydrophilic background areas retain the water and repel the ink. The ink receptive areas 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 thereafter reproduced.
Lithographic printing plate precursors, i.e., imageable elements, typically include a radiation-sensitive coating applied over the hydrophilic surface of a support material. If after imagewise exposure to radiation, the exposed regions of the coating become the ink-receptive image regions, the plate is called a negative-working printing plate. Conversely, if the unexposed regions of the coating become the ink-receptive image regions, the plate is called a positive-working plate. In the present invention, the imagewise exposed regions are rendered less soluble or dispersible in a developer and become the ink-receptive image areas. The unexposed regions, being more readily soluble or dispersible in the developer, are removed in the development process, thereby revealing a hydrophilic surface, which readily accepts water and becomes the ink-repellant non-image area.
The present invention includes a thermally imageable composition comprising a graft copolymer, preferably a thermally sensitive graft copolymer, having hydrophobic and hydrophilic segments. The thermally imageable composition comprises a graft copolymer having, preferably, a hydrophobic polymer backbone and a plurality of pendant groups represented by the formula:
—Q—W—Y
wherein Q is a difunctional connecting group;
W is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment;
Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment;
with the proviso that when W is a hydrophilic segment, Y is selected from the group consisting of: a hydrophilic segment and a hydrophobic segment, with the further proviso that when W is hydrophobic, Y is a hydrophilic segment.
The term “graft” polymer or copolymer in the context of the present invention refers to a polymer which has as a side chain a gro
Pappas S. Peter
Saraiya Shashikant
Ashton Rosemary
Faegre & Benson LLP
Kodak Polychrome Graphics LLC
Lee Sin J.
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