A printing form precursor comprises a printing surface which comprises an inorganic metal compound, the printing surface being hydrophobic and capable of being made hydrophilic by energy but capable of becoming hydrophobic again, for reuse, if desired. An associated method of printing includes steps
A printing form precursor comprises a printing surface which comprises an inorganic metal compound, the printing surface being hydrophobic and capable of being made hydrophilic by energy but capable of becoming hydrophobic again, for reuse, if desired. An associated method of printing includes steps of subjecting the printing surface imagewise to energy so as to locally increase its hydrophilicity sufficient to make the surface differentiated in its acceptance of an oleophilic a printing ink; applying the ink to the printing surface and printing from the printing surface; causing or allowing the printing surface to undergo a reduction in hydrophilicity sufficient again to make the printing surface uniform in its acceptance of a printing ink; and, if wished, repeating these steps on multiple occasions. Thus the invention achieves the goal of providing a printing form precursor which does not need a chemical developer, and which can be used multiple times, to print different images.
대표청구항▼
1. A method of printing comprising: a) providing a printing form precursor having an aluminium oxide printing surface, uncoated by a developable image layer and uniform in its acceptance of an oleophilic printing ink;b) subjecting the printing surface imagewise to energy in the form of pulses of ele
1. A method of printing comprising: a) providing a printing form precursor having an aluminium oxide printing surface, uncoated by a developable image layer and uniform in its acceptance of an oleophilic printing ink;b) subjecting the printing surface imagewise to energy in the form of pulses of electromagnetic radiation of duration not greater than 1×10−10 second, so as to increase the hydrophilicity of the printing surface, where subjected to energy, sufficient to make the surface differentiated in its acceptance and non-acceptance of the ink; andc) applying the ink to the printing surface and printing from the printing surface. 2. A method as claimed in claim 1, wherein step c) is followed by steps of d) causing or allowing the printing surface to undergo a reduction in hydrophilicity sufficient again to make the printing surface uniform in its acceptance of a printing ink; ande) repeating at least steps b) and c). 3. A method as claimed in claim 1, wherein the printing surface is anodized. 4. A method as claimed in claim 1, wherein the printing form precursor comprises the aluminium oxide printing surface on a metal base layer. 5. A method as claimed in claim 1, wherein the printing form precursor comprises the aluminium oxide printing surface on a plastics base layer. 6. A method as claimed in claim 1, wherein the printing surface is caused to undergo a reduction in hydrophilicity by the passage of time, under ambient conditions. 7. A method as claimed in claim 2, wherein the reduction in hydrophilicity in step d) is controlled wholly or in part by an external agency preferably selected from a surface treatment carried out in step a) or by being subjected to energy and/or a gaseous environment in step d). 8. A method as claimed in claim 1, wherein the printing surface remains sufficiently hydrophilic, after step b), for a printer to be able to use it for printing for a period of at least 4 hours and not greater than 72 hours, measured from the image-forming step b). 9. A method as claimed in claim 2, wherein step d) is repeated, along with steps b) and c); wherein each of steps b), c) and d) are carried out at least 3 times. 10. A method as claimed in claim 1, wherein step b) involves, in a single stage of operation, delivery of sufficient energy to cause said increase in the hydrophilicity of the printing surface. 11. A method as claimed in claim 1, wherein in step b) energy is delivered to the printing surface in two or more discrete stages, with the final stage causing the hydrophilicity of the printing surface to reach a desired level, and the previous stage, or stages, preparing the printing surface for that to happen. 12. A method as claimed in claim 1, wherein the pulses of electromagnetic radiation have a duration of at least 1×10−18 second, and are delivered by a laser. 13. A method as claimed in claim 12, wherein the average frequency of the pulses is at least 100 pulses per second. 14. A method as claimed in claim 12, wherein the fluence is at least 1 mJ/cm2 and does not exceed 20,000 mJ/cm2 and the incubation number N is 1 or a larger number up to 10. 15. A method as claimed in claim 12, including subjecting an area of the printing surface to energy from two successive pulses from a pulsed energy beam. 16. A method as claimed in claim 12 including traversing a pulsed energy beam across the printing surface at a speed (V) determined according to one or more of the pulse repetition frequency (f) and the diameter (D) of the beam. 17. A method as claimed in claim 12, wherein the energy per pulse delivered in the method is between 0.1 μJ and 50 μJ. 18. The method of claim 17, wherein the energy per pulse is at least one of the following: between 0.1 μJ and 20 μJ, between 0.1 μJ and 10 μJ, between 0.1 μJ and 5 μJ, between 0.5 μJ and 50 μJ, between 0.5 μJ and 20 μJ, between 0.5 μJ and 5 μJ, between 1 μJ and 50 μJ, between 1 μJ and 20 μJ, or between 1 μJ and 5 μJ.
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