From the perspective of function and effect, the direct plate-making process can be described as a physical or chemical reaction under the action of the 0n/0ff signal from the physical stimulus source of the imaging material, which ultimately leads to the destruction of graphic parts and non-graphic parts (printed parts and non-printed parts) The material properties change to meet the printability requirements and produce sufficient property differences. Depending on the printing method, material property contrast can be caused by factors such as the selection of the material, changes in the affinity of the material, differences in the physical height of the material, and other factors. If the material cannot produce sufficient physical contrast after scanning and imaging, it will be difficult to establish sufficient physical contrast between graphic and non-graphic parts. Necessary post-processing (such as high-temperature treatment, liquid development, etc.) must be performed after imaging. This type of imaging system is called an imaging system that requires post-processing, otherwise, it is called an imaging system that does not require post-processing.
physical stimulus
Light is the most important form of physical stimulation source. According to the maturity of technology and wavelength, it can be simply divided into several basic types such as infrared light source, red light source, green light source, blue light source, and ultraviolet light source.
Infrared light sources mainly include laser diodes (IR-LD) with a wavelength of 830nm and YAG laser with a wavelength of 1064nm. Both of these light sources are solid-state lasers with mature technology and high power (a few W/cm2 or more). They are the main light sources for thermal imaging. Red light sources mainly include laser diodes (LD) with a wavelength of 780nm, light-emitting diodes (LEDs) with a wavelength of about 650nm, and helium-neon lasers with a wavelength of 635nm. The first two are solid-state lasers with mature technology. They can be made into either a single light source or an integrated light source. Since these light sources all emit light in the red region of visible light, they are generally suitable for direct scanning imaging of electrostatic photography and silver halide photographic materials.
The green light source is currently mainly a frequency-doubled YAG laser (FD-YAG) with a wavelength of 532nm. This is also a high-power solid laser suitable for electrostatic photography, silver salt photography, and direct imaging of sensitized photosensitive polymers and other materials. Scan imaging.
The blue light source is mainly an argon ion laser with a wavelength of 488nm. This laser is very suitable for direct scanning imaging of photosensitive polymers and silver salt photographic materials.
There are currently two basic options for ultraviolet light sources, one is an ultraviolet laser diode (UV-LD) with a wavelength of 390~410nm, and the other is a conventional high-pressure mercury lamp with a wavelength in the range of 250~400nm. UV-LD is a new solid-state laser with a service life of thousands of hours. However, the current power is not high, generally, a few mW/cm2, and devices with tens of mW/cm2 have also appeared. Due to its high optical resolution, emission wavelength within the sensitive wavelength range of traditional photochemical photosensitive materials, and low price, UV-LD light source is very suitable for direct scanning imaging of photosensitive polymer materials. The conventional high-pressure mercury lamp source is a continuous discharge light source and requires a digital scanning optical system.
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