Plate imaging technology (1)

The CTP technology for direct imaging on plates is classified into off-line direct platemaking and on-machine direct platemaking, the so-called CTPlate and CTPress. The term "machine" as used herein refers to a printer. The former is a direct plate-making system that is independent of the printing press. It converts digital pages directly into plates by an independent plateetter, and then prints on ordinary printers. It has great versatility and flexibility. , suitable for all types of printing. The latter is a direct plate-making system that integrates the printing press and the plate making machine. It directly scans the digital pages on the plate cylinder of the printing press, showing the specificity of the equipment. The feature of on-machine platemaking is that during the scanning and imaging process, the computer completes the registration and ink setting at the same time. Therefore, it has extremely high platemaking efficiency and shorter preparation time before starting up. It is very suitable for short delivery time and variety. Short-run printing market.
Off-line plate making technology (1) Scanning and imaging equipment From the perspective of equipment and plates, off-line plate making is still diversified and serialized. The scanning mechanism of the platesetter is still divided into three types: inner drum, outer drum and platform, but the scanning light source is the original infrared laser IR-LD (830nM), YAG (1064nM), visible light laser source HeNe (635nM), FD A UV source was added on the basis of -YAG (532nM) and AR+ (488nM).
In the ultraviolet light source, there are two basic choices at present, one adopts the ultraviolet laser diode UV-LD (390-410nM) ,The other adopts the conventional high pressure mercury lamp series (250-400nM). UV-LD was successfully developed by a Japanese company. It is said that the life of this solid-state laser light source has been able to reach thousands of hours, but the current power is still very small, limited to several MW/CM2. This is also a solid-state laser light source. Similar to IR-LD, there is still a large space for further improvement in power. The power of the IR-LD light source has increased from several MW/cm2 to several W/cm2, which is an increase of 1,000 times. It has taken less than a decade and it is estimated that the increase in the power of the UV-LD light source will not take longer.
Compared with IR-LD, UV-LD light source is most attractive in its (1) high optical resolution, (2) light-emitting wavelength at the photosensitive wavelength range of conventional photochemical light-sensitive materials, and (3) low price. The characteristics of items (1) and (2) come from the short wavelength of the UV-LD light source, which not only reduces the accuracy and difficulty requirements of the supporting optical system, but also eases the development of the plate material. The sensitivity range of traditional high-sensitivity photochemical systems (eg, photopolymerization) can be easily adjusted to the 390-410nM wavelength range, but it is very difficult to red-shift further to 532nM (YAG laser) and 635nM (HeNe laser). It is unlikely to extend to 780nM (IR-LD laser). Due to these advantages of UV-LD lasers, although this light source was introduced to the market in the late 1990s, it immediately received a huge response. Many well-known platesetters, such as Agfa, Barco, Escher-Grad, Krause, Purup-EskofoT, and others, have these light sources on their devices.
The platesetters using conventional mercury lamp light sources are critical in scanning optical systems. There are currently DICOn systems (Purup-Eskofot) using optical fibers and so-called "light-valuve technology" and using digital micromirror microchips. Technology (DMmC: Digital Micromirror Chip) UV-Setter System (BasysPrint). The light valve technology guides the ultraviolet light beam emitted by a conventional mercury lamp into a light valve. The light valve modulates the ultraviolet light beam, controls the working state of the light beam (On/Off state), and then guides the modulated light beam through the optical fiber. The surface of the plate exposes the plate. The optical fibers are arranged in a line array, covering the entire width of the printing plate, so the main scanning does not involve any optical components for mechanical movement, which greatly improves the speed of exposure scanning. (To be continued)