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
1998-01-15
2000-04-11
Baxter, Janet
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
430138, 430923, 522 35, 428403, 428407, G03C 1725, B32B 516, C08F 246
Patent
active
060486678
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a substrate material in microparticle form with covalently bonded, identical or different photoinitiators; to a composition of at least one photopolymerizable or photocrosslinkable monomer and the substrate material; to polymers formed from these compositions; to a substrate coated with the composition; to a substrate having a protective coat or a relief image formed from the polymerized composition; to a process for photopolymerizing monomers; and to the use of the substrate material as photoinitiators.
N. Sasa et al. describe, in Polymers for Advanced Technologies, Volume 5, pages 98 to 104 (1994), UV-sensitive photopolymerizable systems which in addition to the photopolymerizable monomer and the photoinitiator dissolved therein include an ionogenic, crosslinked microgel. The photosensitivity of these systems is said to be higher in comparison to homogeneous systems without microgel. The systems can be used for the lithographic production of printing plates.
In Polymers for Advanced Technologies, Volume 5, pages 297 to 308 (1994) N. Sasa et al. mention that the photosensitivity of these systems can be increased further if the microgels contain ethylenically unsaturated groups bonded ionogenically or covalently.
These compositions in the course of coating, in comparison to pure solutions, have the advantage that their flowability is reduced, so that they are easier to handle from an applications standpoint and can be masked off with plastic films formed, for example, from polyvinyl alcohol in order to protect against instances of contamination prior to exposure to light. It is generally perceived to be a disadvantage that the photoinitiator must be dissolved in the monomers, as is also the case with macromolecular photoinitiators. Such photoinitiators are described, for example, by K. K. Dietliker in Chemistry & Technology of UV & EB Formulation for Coatings, Inks and Paints, Volume 3: Photoinitiators for Free Radical and Cationic Polymerisation, 1991 (Published by SITA Technology Ltd, London).
M. Kohler et al. describe, in Radiation Curing of Polymeric Materials; Hoyle, C. E., Kinstle J. F., Editors; American Chemical Society: Washington, D.C., pages 106 to 124 (1990), that functionalized .alpha.-hydroxyacetophenones can be immobilized on commercial silica gel. This silica gel has particle sizes in the millimetre range. In photopolymerization studies it was found that polymers are formed exclusively on the surface of the modified silica gel and that mass polymerization of an ethylenically unsaturated monomer presentis not possible.
It has now surprisingly been found that the dissolving of the photoinitiators can be avoided completely and that it is possible to use photoinitiators in heterogeneous form if they are employed as microparticles with covalently bonded photoinitiators. It has additionally been surprisingly found that these heterogeneous photoinitiators have an excellent sensitivity to light, which is generally even higher than in the systems described by N. Sasa, or systems with dissolved photoinitiators. These heterogeneous photoinitiators also have advantages from the standpoints of operational hygiene and use, since they are storage-stable, non-dusting and free-flowing products which can be processed without problems to form photopolymerizable compositions, often even without the use of a surfactant. The sensitivity to light can, surprisingly, be increased still further if the microparticles additionally comprise ionogenically or covalently bonded, ethylenically unsaturated groups.
A first subject of the invention is therefore a heterogeneous photoinitiator in microparticle form, which consists of a finely divided substrate material to which identical or different photoinitiators are covalently bonded.
Heterogeneous in the context of the invention means that the photoinitiators are insoluble or only swellable in the photopolymerizable or photocrosslinkable compositions. Swellable finely divided substrate materials are also referred to as microgels or emulsion
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Polymers for Advanced Technologies, vol. 5, pp. 98-104, (1994).
Polymers for Advanced Technologies, vol. 5, pp. 297-308 (1994).
Radiation Curing of Polymeric Materials, (1990) pp. 106-124.
Koehler et al., "Coreactive Photoinitiators for Surface Polymerization", pp. 106-124, 1990.
VIII Macromolecular UV Photoinitiators, pp. 204-226, pp. 147-148 & p.311.
Dietliker Kurt
Eldin Sameer Hosam
Grieshaber Peter
Rime Fran.cedilla.ois
Ashton Rosemary
Baxter Janet
Ciba Specialty Chemicals Corp.
Kovaleski Michele A.
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