Recently, a new type of digital offset printing plate has appeared on the market, which is called thermal version. The photosensitive range of the thermal plate is 830nm ~ 1064nm, or even wider. Its printing plate technology includes melting, ablation, transfer, crosslinking, photoelectron decomposition and so on. No matter which of the above technologies is used, the printing plate can be obtained after imaging and development. Due to plate
Some require wet processing.
1. Chemical insolubility
Through laser heat, the polymer in the active layer is crosslinked to produce chemical insolubility and form a negative image. After IR exposure and heating, acid is generated, which catalyzes the chemical crosslinking of polymer adhesive to selectively crosslink the exposure area. The pre heating procedure can obtain a sufficiently high degree of crosslinking after multi-molecular reaction. Therefore, in order to obtain a high printing process, such a plate can be obtained by using the traditional wet processing and post baking plate after the pre heating process. The tolerance of pre heating shall be small, and the control of heating box shall be good.
2. Physical insolubility
The technology generates physical insoluble substances by heating the active layer. The active layer contains a uniform dispersed thermoplastic flowing polymer latex particle, which can dissolve rapidly. However, after IR laser exposure, the thermal coalescence of thermoplastic polymer particles inhibits the solubility of the polymerization layer. The dual properties of this particle produce high-quality images. The advantages of this technology are bright room, stable quality, and image output of internal and external drum printing plates. It belongs to printing plate. After wet processing, baking plate can obtain high printing process plate. Agfa's rd-9 plate has a photosensitive wavelength range of 830nm ~ 1100nm and has both internal and external drum recording and imaging technology, but it has not been commercialized at present.
3. Chemically soluble
This technology is heated through the active layer to produce chemical dissolved substances. Without heating, a positive plate is obtained, which is completely bright and chambered. After wet processing, the plate is baked, and the printing process is high. The active layer can be based on acid resin, and the solubility of the layer is improved during thermal imaging. If the red line absorbing species is added to the layer as a dissolution inhibitor, the exposure area will be selectively removed.
4. Thermal UV mask
The technology senses visible light and uses IR ray for imaging exposure, so that the ultraviolet absorption layer is no longer dissolved in alkaline developer, so as to act as the ultraviolet mask of the lower layer. The other is to expose and image the ultraviolet photosensitive layer at the bottom through the infrared sensitive ultraviolet absorption layer and thermal etching exposure. However, its disadvantage is that the process is complex and requires two parts of processing to completely or incompletely remove the ultraviolet mask layer.
5. Thermal physical mask
This technology was pioneered by Agfa. It is a new type of thermal positive plate, named thermostar. The physical mask layer is heated by high-energy laser to change its structure. After the carbon or IR dye in the protective layer absorbs IR light, the infrared light energy is converted into heat. The heat energy makes the temperature in the active layer rise sharply to 400 ℃ or higher, so as to complete the exposure. The specific temperature is determined by the thermal diffusion coefficient of the layer, exposure time, layer thickness and the thermal diffusion coefficient of the adjacent layer. At the same time, the thin active layer can withstand the expansion caused by the light pulse, and the volume and thickness of the layer increase. The laser used in the two exposure at the same time can complete the ablation reaction in the layer.
Due to the high IR light absorption capacity on the protective layer of this plate, it can also produce high temperature for relatively low exposure energy level, resulting in physical deformation of the protective layer. This physical deformation can not only effectively make the alkaline developing solution wet the exposed part of the layout, but also quickly penetrate the protective layer, enter the bottom layer, effectively dissolve the bottom layer, and dissolve faster than the non exposed area. Its protective layer acts as a mask for the alkaline protective film. Obviously, its surface and interfacial tension are important parameters for washing and processing.
It is concluded that this technology uses the different effects of physical developers to image. This unique non ablation process has imaged before harmful volatile compounds have been formed in the layer or some components in the layer have not degraded. Because the compound components in the layer will not pollute the environment during treatment. Therefore, by using the above technology, the risk can be reduced, and the dust suction equipment can not be used, while the laser ablation technology needs to be equipped with dust suction facilities in the imaging area.
6. Non ablative characteristics of imaging technology
Ablation includes the evaporation and decomposition of the infrared photosensitive layer. In the meantime, physical and chemical changes have taken place in the layer. When the layer is used as a protective layer, the ablated material evaporates into the air. In most cases, a part is powder and redeposited on the surface of the material. This may further affect the imaging of the material, especially when the ablation degree is too high. When the whole layer is uniformly colored, the powder can be easily wiped off to make the layer thinner and the chemical density smaller. This ablation medium can distinguish the quality with eyes and can also be tested with instruments.
Transferred from: Aimai printing