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
1999-01-26
2000-06-20
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
4302701, 4302801, 430303, G03C 172, G03C 176, G03F 726, G03F 720
Patent
active
060776455
DESCRIPTION:
BRIEF SUMMARY
Lithographic plates may be divided into two classes. Those which require dampening water which is fed to the non-image areas of the plate, forms a water film and acts as an ink-repellant layer; this is the so-called fount solution. Those plates which require no fount solution are called driographs or water-less lithographic plates. Most lithographic plates at present in use are of the first type and require a fount-solution during printing. However, lithographic plates of this type suffer from a number of disadvantages. Some of these are: difficult and requires great experience. If the correct ink-water balance is not achieved scumming is occasioned when the printed ink image extends into the non-image areas ruining the printed image. particularly difficult and can not be stabilised until a large number of sheets have been printed, thus incurring waste, ink on to the plate which causes problems in colour reproduction and in dot reproduction, increasing its size and complexity. selection. Further plate cleaners contain significant levels of solvent which is not desirable.
However, with water-less plates in which the ink-releasing layer is, for example, a cured silicone layer or a fluoroalkyl compound there is no scumming and clearer images can be produced. Very often water-less plates comprise a base material, for example aluminium plate, on which a photosensitive layer is coated, on this photosensitive layer there is coated a silicone layer or a fluoroalkyl compound. After imagewise exposure and development in which selected areas of the photosensitive composition are altered, the overlying silicone or fluoroalkyl compound layer is removed and the plate is inked up. The ink adheres only to those areas of the plate not covered by the silicone or fluoroalkyl compound remaining after development. Thus the plate can be used without a fount solution.
However, in practice it has proved difficult to get the silicone or fluoroalkyl compound layer composition to adhere to the photosensitive layer. In spite of the idea of water-less plates having been described in patent specifications for at least fifteen years very little has been done to commercialise the idea and water-less plates which have been and are being sold are more expensive than the conventional plates which require a fount solution.
In E.P. 349 157 a water-less presensitised lithographic printing plate is disclosed. The plate comprises a support having thereon a light sensitive layer and a silicone rubber layer in this order, wherein said silicone rubber layer contains a copolymer having a silicone monomer and fluorine-containing monomer in its molecular structure. In JP A 5717 6044 there is disclosed a lithographic plate comprising a hydrophobic film consisting of a silanol oligomer and an organic high polytmer.
We have developed a water-less lithographic plate which is different in concept to the hereinbefore proposed water-less lithographic plates and furthermore a plate which requires no wet processing.
Therefore according to the present invention there is provided a water-less lithographic plate precursor which comprises on a base material having in one or two layers a light-sensitive composition which comprises a polymer with hydroxy functional groups, an acid generator which when light exposed yields an acid together with a silyl ether of the general formula I: ##STR2## where Rf is a fluoroaliphatic group having 3 to 10 carbon atoms, Y is selected from --O--, --SO.sub.2 --, --CO-- and a direct link, X is selected from --N--R.sub.4 where R.sub.4 is hydrogen or lower alkyl having up to six carbon atoms and a direct link, each of R.sub.1, R.sub.2 and R.sub.3 are lower alkyl groups having up to six carbon atoms and R.sub.5 is a lower alkyl group having up to six carbon atoms.
Preferably each of R.sub.1, R.sub.2 and R.sub.3 are the same.
The light-sensitive composition of the present invention may be U-V light sensitive, visible light sensitive or infra-red radiation sensitive. When the composition is infra-red light sensitive there should be presen
REFERENCES:
patent: 5849369 (1998-12-01), Ogawa
International Search Report for PCT/GB97/00758.
Bayes Stuart
Bennett Peter Andrew Reath
Smith Carole-Anne
Baxter Janet
Kodak Polychrome Graphics LLC
Lee Sin J.
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