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DIGITAL PLATES -- Covering the Spectrum

August 2001
BY MARK SMITH


Adopting a computer-to-plate (CTP) workflow is as much about buying into a technology and process as it is purchasing products. Visible laser systems can lay claim to having created the product segment. However, it really took the introduction of thermal technology for CTP to gain mainstream acceptance, at least in the North American market.

Now violet systems are causing a stir and generating a bit of controversy. More on that later.

While product offerings continue to grow, key decisions made by CTP buyers early on still can dictate their subsequent product options. Typically this process begins with the selection of a chosen imaging technology and inexorably leads to a plate. It can work the other way, though, especially in the case of processless plates. If a buyer is sold on this technology, then at least for now thermal imaging is the only option.

Developments in plate sensitivity and platesetter capabilities tend to be so interdependent that if they don't move in lock step, leading-edge products will be of little practical use. Picking which platesetter and plate to buy can almost end up being a single decision. This is particularly true in the violet laser segment due to differences in the energy requirements of silver vs. polymer plates and the output energy of first-, second- and third-generation diodes.

Turning Bluer
First-generation violet laser diodes have a maximum power output of 5mW. The high sensitivity of a silver-based reactive coating is required for plates to respond at that low of a threshold. The downsides to silver-halide plates—controlling processing and disposing of chemicals—are seen as potential barriers to adoption of the process.

These concerns are being answered by the new violet-sensitive polymer plates just coming to market, but they require at least a 30mW violet laser source. Such diodes only recently have become available, so platesetters that image at that power naturally are still a new development. A number of product introductions in this category are expected at PRINT 01. (Since platesetters will be the focus of an article in an upcoming issue of Printing Impressions, they won't be discussed in any depth here.)

In the usual game of high-tech one-upmanship, diode manufacturers now have started announcing 100mW units. As impressive as a 10-fold increase may seem, these diodes likely will have their greatest impact on the speed of platesetters, not the range of materials they can image. The energy output would have to be increased by several orders of magnitude to image conventional ("analog") plates, for example. One exception may be high-speed UV (ultraviolet) plates, since 100mW violet laser diodes may be sufficient to image these plates, if they can support the slightly higher imaging frequency.

 

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