Analysis of the characteristics of photosensitive plate and thermal plate
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Classification of thermal plates
To date, at least six thermal plates have entered the market, and it is necessary to find a way to classify them.
(1) negative thermal plate
A cross-linked type optically active polymer plate is included. Kodak Polyphoto's thermal 830 plate and Fujifilm's Brillia LH-NI fall into this category, and this plate is only imaged on an external drum-type platesetter. The printing performance of the negative plate is amazing, and the plate can be guaranteed without printing. It is reported that a printing factory has printed 700,000 copies without baking, and after printing, the printing volume can exceed 2 million.
(2) positive thermal plate
It is a cross-linked type optically active polymer plate. It requires less laser beam power and is suitable for internal drum type platesetters. It does not require preheating, but it needs to be processed. The baking can increase the printing volume. Horsell's Electra DC is one of them, in addition to Agfa's ThermalStar 830 and 1064, Fuji's Brillia LH-PG (1064nm), Lastra Extreme 830, Plurimetal Cygnus and Toray CTP Waterless 830, these plates print 150,000 to 200,000 copies, Electra DC can be more than 1 million after baking.
(3) No processing thermal plate
It consists of an aluminum plate base, a hydrophilic layer and a protective layer coated with an ink-receptive layer, and can be printed without development processing. In addition to the production of Presstek, Kodak Polychrome will also have products this year. There are two deficiencies in the untreated plate. One is that the hydrophilic layer must be strong enough to achieve high print volume. This requires that the layer be as thick as possible, but it also increases the difficulty of removing the fusible impurities. Second, these plates cannot be baked to increase the amount of printing, because the baking plate will completely burn off the hydrophilic layer and lose the printed message.
Photosensitive CTP technology features
(1) faster
The violet laser is a laser with a wavelength of 400 nm. It is known to people with physics that the shorter the wavelength, the greater the energy of the light. The purple light source is of course higher energy than other commonly used CTP light sources such as green light (532 nm) and red light (830 or 1064 nm). The use of a violet laser source, which stays on the plate for a short period of time, also provides sufficient energy to stimulate the reaction of the film on the plate, and thus the imaging speed is higher. With this feature, equipment manufacturers can increase the speed of scanning. At present, the scanning speed of the infrared laser is 20000l/min, the green laser is 37500l/min, and the violet laser can be as high as 55000l/min, which is equivalent to 1024mm at 2400dpi in 1 minute and 46 seconds. Scanning of the x 800mm folio (other operating hours are not included).
(2) Higher precision
Also from a physics point of view, the shorter the spectrum, the smaller the laser spot, so that finer dots can be scanned on the plate. With the conventional light source, it is generally only possible to display 200 lpi (1 to 99%) dots on a photosensitive plate, and the use of a violet laser can increase the accuracy to 250 lpi.
(3) The operating environment is more convenient
Because the digital plate used with the violet laser does not react under red and green light, the violet laser CTP device can use the yellow light (red light + green light = yellow light) as the safety light, providing the operator with more The bright operating environment makes operation easier.
(4) Longer life and cheaper cost
The laser manufacturer's maintenance period for the violet laser source is the same as the previous green laser, which is also 3000 hours. However, because the operating characteristics of the violet laser are: the laser only needs to be activated when it is actually imaged, instead of starting the laser at the same time as other lasers, the lifetime loss is lower than other laser generators, which is why The actual life of violet laser products is longer than other CTP laser sources.
The thermal CTP version and other CTP versions have been in a synchronous growth trend. By May 2000, after the CTP products of the violet laser light source were officially introduced to the market, it was always considered that the most advanced thermal light source CTP products in CTP equipment were severely affected. challenge.