Positive-working imageable elements
AssigneeEastman Kodak Company
InventorsJames L. Mulligan, Eric Clark
Life of this patent
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Abstract
Positive-working imageable elements have a substrate and an imageable layer that can be used to prepare lithographic printing plates. The imageable elements also include a radiation absorbing compound, and a mixture of first and second polymers in the same imageable layer. The first polymer has two or more centered H-bonds (hydrogen bonds) within a non-covalently bonded unit, and the second polymer is a polyvinyl acetal. This mixture of polymers in the same imageable layer provides improved solvent resistance and processing latitude without a loss in imaging speed.
Claims15
A positive-working imageable element comprising a substrate having thereon a single, outermost thermally imageable layer, said element further comprising an infrared radiation absorbing compound that absorbs at a wavelength of from about 700 to about 1200 nm,
- wherein said single outermost thermally imageable layer comprises first and second polymers,
- said first polymer is an alkaline soluble polymer that comprises:
- (1) at least one covalently bonded unit that is derived from a polyfunctional material that is soluble or dispersible in an aqueous developer, and (2) at least one thermally reversible non-covalently bonded unit that includes a two or more centered H-bonds within that unit, and
- said second polymer is a polyvinyl acetal in which at least 50% of the recurring units are acetal units,
- wherein the weight ratio of said first polymer to said second polymer is from about 1:1 to about 15:1.
A method for forming an image comprising:
- A) thermally imaging a positive-working imageable element using radiation having a maximum absorbance of from about 700 to about 1200 nm, thereby forming an imaged element with exposed and non-exposed regions, and
- B) contacting said imaged element with an alkaline developer to remove only said exposed regions,
- said imageable element comprising a substrate having thereon a single, outermost thermally imageable layer, said element further comprising an infrared radiation absorbing compound that absorbs at a wavelength of from about 700 to about 1200 nm,
- wherein said single outermost thermally imageable layer comprises first and second polymers,
- said first polymer is an alkaline soluble polymer that comprises:
- (1) at least one covalently bonded unit that is derived from a polyfunctional material that is soluble or dispersible in an aqueous developer, and (2) at least one thermally reversible non-covalently bonded unit that includes a two or more centered H-bonds within that unit, and
- said second polymer is a polyvinyl acetal in which at least 50% of the recurring units are acetal units,
- wherein the weight ratio of said first polymer to said second polymer is from about 1:1 to about 15:1, and
- said imageable element having been prepared by applying said imageable layer to said substrate followed by a heat treatment at from about 50 to about 70° C. for at least 24 hours while said imageable element is wrapped in a water-impermeable sheet material.
Dependencies are inferred from the claim text.