It is known that commonly referred to as light generally refers to visible light, ie, electromagnetic radiation having a wavelength of between 380 nm and 780 nm, which can cause vision to human eyes and present colors of blue (400-500 nm) and green (500-600 nm). ) and red (600-700nm), if subdivided, that is, red, orange, yellow, green, blue, and purple. These visible light is only a part of the wavelength of electromagnetic radiation is very narrow, and the rest is only visually invisible to people, as shown in Figure 1.
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Normal align=center> Figure 1 Electromagnetic wave radiation area
The discovery of laser light makes the light source have the characteristics of single wavelength and energy concentration. In some photophysical and photochemical reactions, it plays a role that continuous wavelength light cannot achieve. From the perspective of the progress of lasers, from gas to solids, from long to short wavelengths, from large to small, the field of application is more and more extensive. CTP technology is the crystallization of laser technology and digital technology. From the perspective of the lasers it uses, it is a short wavelength transition from long wavelengths. Specifically, YAG (1064nm) infrared laser 830nm near-infrared diode → 650nm red laser diode 532 nm frequency-doubled YAG green laser and 488 nm argon ion gas laser→405 nm violet laser diode. The 400-410nm wavelength region is the violet laser region with the shortest visible light range, so lasers emitting 400, 405, and 410nm wavelengths are called violet lasers.
The shorter the wavelength, the more difficult it is to develop a laser. Until 1996, the 410nm InGaN crystal violet laser diode was developed by Nichio Corporation in Japan. Since then, Nichia's violet laser diode lifespan exceeded 10,000 hours in 1999. On DVD and DVR devices. In recent years, due to the further improvement of the performance of the violet laser diode and the reduction of the price, a new path has been opened up for the new generation of CTP technology, becoming the highly anticipated violet laser CTP technology.
Violet Laser CTP Technology Purple Laser CTP technology was first exposed at the Drupa 2000 expo. Once exhibited, it was favored by visitors because of its attractive features:
1 The dry violet laser has a short wavelength, small scattering, and fast imaging speed. It uses a smaller rotating mirror and motor in the CTP platesetter to increase the speed of the mirror and shorten the exposure time. It can be quickly exposed on large-format plates. Increase productivity. In addition, because of its short wavelength, it can focus on smaller laser beams, improve scanning accuracy, improve line sharpness and resolution, and improve print quality.
2 The violet laser can be used to switch the laser directly without the use of an electronic modulator. It only works when scanning the image on the plate. The YAG and other lasers are synchronized with the platemaker to open and close, and the modulator controls the passage or blocking of the laser when imaging. This is also the main reason why the violet laser has a long life. The 5mw diode produced by Japan's Nichia Corporation has a lifetime of 10,000 hours.
3 The stability of the violet laser diode is good. After 3 minutes, the laser diode can reach a stable state for exposure and platemaking. However, the plate-making machine using the YAG laser needs to be warmed up for more than 20 minutes after the power is turned on. The output energy of the laser light source can reach a stable state. In addition:
a. The violet laser plate can be used under a bright yellow safety light, which is similar to the environment used by conventional PS plates or thermal CTP plates.
b. Violet laser diodes are simpler and cheaper than other solid-state lasers and gas lasers. In addition, it can also be used on DVD and DVR equipments. It has great market potential. This is also the rapid mass production of the violet laser diodes and its great cost. The reason for the decrease.
Thanks to the advantages of violet laser, it has promoted the rapid development of violet laser CTP technology and has received much attention from the industry. In recent years, many equipment manufacturers have invested in the development and promotion of violet laser CTP technology, such as Agfa, Barco, ECRM, Esther-Grod, Highwater, Krause, Fuji, Lighotech-Sack, Purup Eskofot, Prepress Technologles, Heidelberg, etc. the company. Already hundreds of violet laser CTP devices have been sold worldwide. The Institute of Physical and Chemical Technology of the Chinese Academy of Sciences arrived in July 2002 and installed two PLATINUM 2218 lithographic scanning 4 platesetters from Krouse, using violet lasers (405urn) and green lasers (532nm), with a resolution of 1270dPi and 2540dPi. The current operation is normal, which has created favorable conditions for us to study new types of violet laser plates.
The violet laser diode power provided by Nichia, TuiOPtics and other companies currently engaged in laser production is 5mW, and will gradually introduce 10 to 30mw laser diodes. Since the power is not as large as other lasers, the sensitivity of the corresponding plate is proposed. higher requirement.
In recent years, many manufacturers of plate materials have invested in the research and development of CTP plates suitable for violet lasers, such as Agfa, Fuji, Mitsubishi Chemical, and others. It can be said that the silver-diffusion type CTP plate is a plate that is currently suitable for low-power violet lasers, as is the Agfa Lithostar Ultra LAP-V silver salt version. Because its sensitivity is in the μJ/cm2 class, only 5% to 10% of the 5mw laser diode energy is needed. This is not possible with other non-silver salt CTP plates, because other types of plate materials must be energy-efficient. Higher platemaking conditions.
The structure and principle of the silver salt diffusion plate are described by the author and are only briefly described here. As shown in Figure 2, the plate was coated with an ultra-thin layer physical development kernel as an image receiving layer and a laser-sensitive silver halide photosensitive layer on a grained aluminum base plate. After the laser scanning exposure, the non-graphic area was partially washed away by 30 seconds of development and washing to reveal the hydrophilic aluminum group, and the diffusion-transferred silver particles in the graphic area were closely packed into the lipophilic image area. There is a clear line between ink and hydrophilic areas.
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Normal align=center> Figure 2 Silver salt CTP plate structure and processing diagram
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Normal align=center> Figure 5 AFM photograph of nano physical imaging core
Due to its high sensitivity, high quality, and high fidelity, silver salt photosensitive materials have a wide range of applications. A history of more than a hundred years Figure 5 proves its vitality. Although the development of digital technology and other various chemical materials has brought challenges to the silver halide system, there is still no material or technology that can completely replace it. In the future for a long time, with the combination of digital technology, silver salt photosensitive materials will still show strong vitality.
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