There are many types of heat-sensitive CTP plates, but there are mainly two mature types at present, namely heat-melting type and heat-crosslinking type.
The hot-melt CTP plate is mainly composed of three parts: an aluminum plate that does not need to be roughened, an ink-receptive layer, and a PVA layer (used in conventional offset printing) or silica gel (used in waterless offset printing). Its imaging principle is to use semiconductor laser diode exposure. The heat-sensitive coating (ie, the ink-receptive layer) on the plate base is ink-friendly and insoluble in alkaline chemicals. After exposure, the coating absorbs energy, improves solubility, and can be dissolved in alkaline potions.
When developing, the exposed part is dissolved in the alkaline solution to form the blank part of the printing plate. The non-exposed parts are not dissolved and form the graphic part of the printing plate. After development, it generally needs to be cleaned and glued before it can be printed on the machine.
Thermally cross-linked CTP plates mainly consist of a roughened aluminum plate and a single-layer PS photosensitive layer. Its imaging principle is through infrared exposure. When exposed, the photothermal conversion material converts the light energy of the infrared laser into heat energy, causing thermal cross-linking reaction of some polymers in the photosensitive layer to form a latent image; reheating, further cross-linking reaction occurs in the molecular compounds of the graphic part , so that the graphic part is not dissolved in the alkaline developer. It should be noted that during preheating, the blank part also partially reacts, so the image of the blank part should be removed during development. If the temperature is too high, heat fog will form on the printing plate; if the temperature is too low, the graphics and text will be diluted or weakened.
Features of Thermal CTP Plates
(1) Thermal CTP plates have low sensitivity to natural light and are exposed by infrared lasers, so they can be operated under bright room conditions.
(2) To generate an image on a heat-sensitive plate, it must reach the initial thermal energy threshold, and thermal energy higher than the initial threshold will not change the dot shape. It is the only technology that can control the predictable results. The printing plate can be extended to 6 months before going to develop, which will not have the slightest impact on the quality of the plate.
(3) The heat-sensitive CTP plate has good dot reproducibility, high resolution, sharp and clear dot edge, easy to achieve water-ink balance during printing, has good printability, and the printing durability of the plate after baking is up to 1 million prints or more.
Huida Print-All Technology company is an advanced and professional manufacturer of producing printing plates, mainly selling CTP, CTCP, and PS plates as well as offering ODM/OEMs, especially for the offset. For more information, please click the official website link here: https://www.huidaoffsetplate.com/.