In printing, water, and ink are the most closely related to the printing plate. The ink-loving performance of the printing plate and the wetting performance of the printing plate will directly affect the balance of water and ink in printing, and then affect the quality of printing. Therefore, CTP plates are indispensable in the printing process. An important part of, and its printability is also a very critical attribute
Ink affinity of CTP plates
We all know that offset printing is a process of forming imprints by controlling ink and ink. The graphic part is ink-friendly, so it can accept the ink on the ink transfer roller, then transfer it to the blanket, and finally transfer it to the paper through the blanket.
Obviously, the thickness of the ink on the printing plate directly affects the thickness of the ink on the blanket and paper. To control the density and color of printed matter, the thickness of the ink layer is a very important factor. The larger the range of the controllable ink layer thickness means the greater the room for adjusting the printing quality in printing, which is more conducive to the control of product quality.
When a certain thickness of ink film has been attached to the surface of the ink transfer roller, the amount of ink transferred on the printing plate will depend on the ink affinity of the printing plate. If the ink affinity of the graphic part of the printing plate is low, the range of controlling the amount of ink in the entire printing will be smaller, which is more detrimental to product quality.
Moreover, if the pre-press process of the printing plate with poor ink affinity is used, the remaining ink will accumulate on the ink transfer roller, which will thicken the ink film of the ink transfer roller, and there will be too much ink at both ends, resulting in ink splashing and reducing Ink hiding power. Therefore, a CTP plate with good ink affinity is very important. In order to improve the ink affinity performance of the CTP plate, the photosensitive material with the chemical characteristics closer to the pigment, resin, and solvent ratio in the ink should be used in the development of the plate. The ink-loving performance of the test printing plate can be concluded by measuring the density of each color block by adjusting the ink volume of the ink transfer roller for trial printing.
Wetting properties of CTP plates
If the amount of water in the printing process is too small, the parts without imprints will easily get dirty. If the amount of water in the printing process is too large, the imprints will be dull, the paper will be uneven, and the paper will be deformed and the registration will not be accurate. Since the surface of the CTP plate is very smooth, it has higher requirements for wetting, and its surface requires a thicker dampening solution film than ordinary plates. The ideal thickness of the fountain solution film layer is 0.6 μm to 1.5 μm. Because after this thickness is exceeded, the ink will be over-emulsified, and the imprint will have no luster. At the same time, if the water volume is too large, in order to achieve the balance of water and ink, the required ink volume will also increase. At this time, the controllable ink volume range will be reduced, and Bad for quality control. Therefore, it is very important to adjust the hydrophilic property of the printing plate to ensure that the film thickness of the fountain solution is between 0.6 μm and 1.5 μm when the water and ink balance is reached.
It is obvious that the wetting performance of the printing plate is directly related to the grain size of the printing plate. Traditional printing plates believe that the denser the grain, the better the wetting performance. However, for CTP plates, due to the fine grain size, of the printing plate Instead, the surface of the stencil blank becomes smooth and difficult to wet. The resolution and dot stability of the printing plate and the wetting characteristics of the printing plate have become a pair of opposite contradictions under the special conditions of CTP plate manufacturing. Resolution and dot stability require a finer sand mesh color sequence, but the wetting conditions require that the sand mesh should not be too fine.
The hydrophilicity of the printing plate can be accomplished by adjusting the water-ink balance through actual printing tests, and the wetting characteristics of the printing plate can be measured by testing the tolerance of the printed water-ink balance. At the same time, the daily maintenance of CTP is also very important.
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/.