DIGITAL PLATES -- Covering the Spectrum
Thermal ablative imaging is the most common technology used in processless plates, but Agfa currently also offers a phase-change product and other options are being explored in labs around the world. By definition, the ablative process involves removing material from the surface of the plate through the application of energy by the laser. As a result, a platesetter must be fitted with a vacuum/evacuation system to capture loosened particles, if it is to be used for imaging ablative plates.
Whether or not this system can be added as a retrofit depends on the manufacturer and model. In addition to the capital cost of the extra unit, vacuum systems have a filter that must be changed regularly.
Hot and Hotter
The term thermal has become a generic reference, but it actually encompasses imaging systems with two different sensitivities—830nm and 1,064nm. The majority of thermal plates are sensitive to 830nm, but some are dual range. One implication of the different sensitivities is an external—versus internal—drum design in the platesetter.
Photopolymer is another term that tends to be used imprecisely as the designation for a special category of plates. Non-ablative thermal plates typically also use a cross-linking polymer coating, just one that has a different spectral sensitivity. Aside from processing requirements, what sets polymer plates apart is the ability to post-bake them for increased durability. This enables the plates to produce longer runs and better withstand applications such as using UV inks.
Opinions vary widely on the significance of a plate's imaging resolution. A potential wrinkle in the debate is the apparent re-emergence of stochastic/FM screening and other related technologies, which require high-resolution imaging. CTP is considered to be an enabling technology for specialty screening, but it remains to be seen if that will be enough of a boost to get potential users to buy into the process this time around.