Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Patent
1997-04-14
1998-08-18
Baxter, Janet C.
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
4302881, 430302, 101456, G03C 11725, B41N 100
Patent
active
057956987
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates generally to photoresist compositions suitable for on-press development, and more particularly, to the incorporation of amphoteric hydrogen bond-forming developability stabilizers in the photoresists of lithographic printing plates for the purpose of promoting their on-press developability.
BACKGROUND
At the present time, virtually all printed copy is produced through the use of three basic types of printing plates. One type is a relief plate which prints from a raised surface. Another type is an intaglio plate which prints from a depressed surface. The third type is a lithographic plate which prints from a substantially flat surface which is neither appreciably raised above nor appreciably depressed below the adjacent and surrounding non-printing areas. Printing is occasioned by an ink's respective affinity and/or aversion to areas of different chemical properties. Lithographic printing plates are commonly processed to have water-repellent (hydrophobic), oil-receptive (oleophilic) image areas and water-receptive (hydrophilic) non-image areas.
Prior to processing for use, conventional lithographic plates will typically have a hydrophobic, photoreactive polymeric photoresist (i.e., photoresist) coated or otherwise deposited atop a hydrophilic substrate.
In preparing a conventional lithographic plate for use on a printing press, the plate is first exposed to actinic radiation. Specific chemical reactions are caused to occur in the plate's photoresist by expo sure to actinic radiation. Such photoinduced chemical reactions may either reduce or enhance the solubility of the photoresist, depending on whether the resist is negative-working or positive-working. In negative-working plates, exposure to actinic radiation will generally cause a "hardening" of the photoresist. In positive-working plates, exposure to actinic radiation will generally cause a softening or solubilization of the photoresist.
After photoexposure, a wet development step is normally conducted. The objective of such wet development is to remove those areas of the photoresist which have undergone photoinduced chemical change or those which have not been photoexposed. Solvation under conventional development techniques will typically involve treating the exposed plate with organic solvents in a developing bath. For negative-working resists, the solvent will swell and dissolve the unexposed portions of the resist. The solvent should not swell the exposed portions or distortion of the developed image may result. For positive-working resists, the response of the unexposed and exposed coatings are reversed, but the same general principles apply.
As a result of the preferential solvation and washing away of portions of the photoresist, corresponding portions of the underlying hydrophilic substrate are uncovered. For negative-working plates, the aforementioned hydrophobic image areas correspond to the portions of the photoresist remaining after solvation and washing. The aforementioned hydrophilic non-image areas correspond to uncovered portions of the substrate. The image and non-image areas thus differentiated, the processed plate may then be mounted onto a printing press and run.
Encumbered by required wet development, the processing of conventional lithographic plates prior to their use on a printing press is both time and labor consuming and involves considerable use of organic chemicals. It will be appreciated that there is a considerable desire for means that would satisfactorily eliminate or reduce conventional lithography's long-felt dependency upon the conduct of wet development and thereby permit use of lithographic plates on a printing press immediately after exposure without required post-exposure prepress processing.
In the past, dry developable lithographic printing plates have been suggested which enable the wet processing steps of lithographic printing plates after exposure to be omitted and printing to be conducted by directly mounting the exposed plates on a printing press. Amo
REFERENCES:
patent: 5607816 (1997-03-01), Fitzgerald et al.
patent: 5677110 (1997-10-01), Chia et al.
PCT International Search Report for PCT/US96/14611 (Form PCT/ISA/210) (mailed Mar. 10, 1997).
Fitzgerald Maurice J.
Jurek Michael J.
Liang Rong-Chang
Sugrue Richard J.
Ashton Rosemary
Baxter Janet C.
de Luna Renato M.
Polaroid Corporation
LandOfFree
On-press developable printing plate with amphoteric hydrogen bon does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with On-press developable printing plate with amphoteric hydrogen bon, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On-press developable printing plate with amphoteric hydrogen bon will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1113460