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Method of processing laser sensitive lithographic printing plate

a technology of laser imaging and laser printing, applied in thermography, instruments, photosensitive materials, etc., can solve the problems of limited room light stability, cumbersome methods, and laborious methods, and achieve the effects of reducing the cost of laser imaging, improving the accuracy of laser imaging, and improving the quality of laser imaging

Active Publication Date: 2007-05-10
TENG GARY GANGHUI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides methods for lithographically printing images on a receiving medium using a lithographic plate. The methods involve exposing the plate with a laser to cause hardening of the photosensitive layer in the exposed areas, and then applying a deactivating agent, heat, or a different wavelength of radiation to deactivate the photosensitive layer. The deactivated plate is then contacted with ink or fountain solution on a lithographic press to remove the non-hardened areas and print the images. The methods can be performed with the plate under lightings that will not cause hardening of the photosensitive layer, such as in the dark. The technical effects of the invention include improved image quality and efficiency in the printing process.

Problems solved by technology

While capable of providing plate with superior lithographic quality, such a method is cumbersome and labor intensive.
Accordingly, photosensitive plates designed for laser imaging generally have limited room light stability.
For example, before being developed to remove the non-hardened areas, frequency-doubled NdYAG laser sensitive plates usually require red room light for handling, violet laser sensitive plates usually require orange or yellow room light for handling, and infrared laser sensitive photopolymer plates usually require yellow room light for handling and have only limited white light stability (due to the use of certain initiator which has spectral sensitivity in the ultraviolet region).
Such limited room light stability is an inherent barrier for the design and use of laser sensitive lithographic plates.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples 1-3

[0079] An electrochemically grained, anodized, and polyvinylphosphonic acid treated aluminum sheet was first coated with a 0.1% aqueous solution of polyvinyl alcohol (Airvol 540, from Air Products) with a #6 Meyer rod, followed by drying in an oven at 100° C. for 2 min. The polyvinyl alcohol coated substrate was further coated with the photosensitive layer formulation PS-1 with a #8 Meyer rod, followed by drying in an oven at 90° C. for 2 min.

PS-1ComponentWeight ratiosNeocryl B-728 (Polymer from Zeneca)2.75DPHA (Acrylic monomer from UCB Chemicals)6.56Pluronic L43 (Nonionic surfactant from BASF)0.562,2-Bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,1′-1.21biimidazole4,4′-Bis(diethylamino)benzophenone0.772-Mercaptobenzoxazole0.152-Butanone88.00

[0080] The photosensitive layer coated plate was further coated with a water-soluble overcoat OC-1 using a #6 Meyer rod, followed by drying in an oven at 100° C. for 2 min. All the coatings were performed under a red light and the plate was then ...

example 4

[0084] An electrochemically grained, anodized, and silicate treated aluminum sheet was coated with the photosensitive layer formulation PS-1 with a #6 Meyer rod, followed by drying in an oven at 90° C. for 2 min. The photosensitive layer coated plate was further coated with a water-soluble overcoat OC-1 using a #6 Meyer rod, followed by drying in an oven at 100° C. for 2 min. The plate was prepared under a red light and then stored in a light tight box.

[0085] The plate was exposed with a violet plate imager equipped with a 60 mw violet laser diode emitting at about 405 nm (MAKO-8 from ECRM) for a dosage of about 90 μJ / cm2. The plate was imaged in an orange light room, and was kept in a light tight box before and after imaging.

[0086] While under a red light, the laser-exposed plate was rubbed for 10 times for all areas with a cloth soaked with both ink and fountain solution. The exposed areas were well inked, and the non-exposed areas were free of ink.

[0087] The developed plate wa...

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Abstract

A method of developing a laser sensitive lithographic printing plate with ink and / or fountain solution is described. The printing member comprises on a substrate a photosensitive layer soluble or dispersible in ink and / or fountain solution and capable of hardening upon exposure to a laser. The plate is exposed with a laser and deactivated under a safe light or in the dark, and then on-press developed with ink and / or fountain solution preferably under white light. Alternatively, the plate is developed with ink and / or fountain solution or the likes off press, and then mounted on press for lithographic printing.

Description

FIELD OF THE INVENTION [0001] This invention relates to lithographic printing plates. More particularly, it relates to a method of deactivating or developing a laser sensitive lithographic plate after imagewise exposure and before printing on press. BACKGROUND OF THE INVENTION [0002] Lithographic printing plates (after process) generally consist of ink-receptive areas (image areas) and ink-repelling areas (non-image areas). During printing operation, an ink is preferentially received in the image areas, not in the non-image areas, and then transferred to the surface of a material upon which the image is to be produced. Commonly the ink is transferred to an intermediate material called printing blanket, which in turn transfers the ink to the surface of the material upon which the image is to be produced. [0003] At the present time, lithographic printing plates (processed) are generally prepared from lithographic printing plate precursors (also commonly called lithographic printing pl...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B41F1/18
CPCB41C1/1008G03F7/033G03F7/38B41C1/1016B41C2201/02B41C2201/14B41C2210/04B41C2210/08B41C2210/22B41C2210/24
Inventor TENG, GARY GANGHUI
Owner TENG GARY GANGHUI