Figure 6 Infrared ablation-free CTP plate development process
Agfa's infrared ablation CTP plate is a positive-type thermal plate that uses metal as a melting layer. The metal melting layer is coated on a hydrophilic aluminum substrate which is oleophilic. The imaging mechanism is that the metal layer in the exposure zone melts into droplets under high-intensity laser irradiation, and the contact angle with the aluminum substrate becomes larger and can be removed without development, exposing the hydrophilic printing plate base. The process is shown in Figure 6.
Fuji's thermal ablation type plate is different from Agfa. It is based on the printing plate first coated with an ink-receptive layer, which has metal particles as the hydrophilic layer of the photothermal conversion agent. Metal particles can embrittle and easily be removed during scanning exposure. Alternatively, the hydrophilic layer may be coated with a metal oxide or metal hydroxide and an acid-containing hydroxy resin on the ink-receptive layer, and sometimes a hydrophilic surface layer.
3.3 Substrate-friendly ink-free CTP plate
Figure 7 Underlying ink-inhibiting treatment CTP plate development process
This is a patent of KPG, which belongs to the waterless offset printing plate. The plate is first coated on the substrate with an ink-receptive interlayer, and then a special silicone copolymer is applied on the ink-receptive layer. This ink-repellent silicone copolymer acts as a heat-sensitive layer and is a thermal decomposition type. The imaging mechanism is that the thermal layer of the exposed area undergoes a thermal decomposition reaction, and these decomposed silicone copolymers are easily removed during the exposure process or the usual procedure after exposure to expose the intermediate ink-receptive layer. The development process is shown in Figure 7.
Source: Bison
3.2 Infrared ablation-free CTP plate