Printing ink and printing conditions for the most

Printing plate, ink and printing conditions of high-precision and high-density printing

as for high-precision printing, it can increase the amount of information per unit area and reduce the rose spots and moire patterns that usually exist in plate making. In addition to increasing the workload and reducing the scope of image reproduction, it is far better than conventional printing in terms of printing quality. In other words, through the study of high-grade printing technology, it has become the standard of printing quality in the all digital era

1 high-precision printing

1) characteristics of high-precision printing

generally, printing with a resolution of more than 300lpi is called high-precision printing

the biggest difference between high-precision printing and ordinary printing lies in the difference of dot enlargement rate. For example, under the accuracy of 175lpi, the point enlargement rate of 50% is about 15%; At 600lpi accuracy, the expansion rate of 50% points is close to 30%. Therefore, it is natural to adjust the conditions of plate making and color separation for high-precision printing. How to control the expansion of printing points is also an important link to determine the printing quality. In addition, compared with the side length of 20 m of 175 LPI highlights, the side length of 600 LPI highlights is only 6 m. How to maintain the reproduction of 6 m dots, plate making, color separation, printing and other conditions are important

2) printing plates for high-precision printing

the commonly used printing plates can be divided into two types: aqueous PS version and anhydrous silicone rubber version. In terms of dot enlargement, since the waterless printing plate is a flat intaglio plate, there is less mechanical dot enlargement between the printing plate and the blanket, and the gradient reproduction performance is excellent, which is suitable for high-precision printing. However, there is still room for improvement in the development of small dots due to the solvent expansion method of removing the silica gel layer of the unexposed part (positive pattern)

this is not quite the right way to emphasize the sustainability development at present. Because it is a flat relief plate, the mechanical dot expansion is more prominent, and under the joint action of the influence factors of the fountain solution on the emulsifying characteristics of the ink, it will have an adverse impact on the tone reproduction. However, the recent 4-layer sand mesh PS version has improved its water storage performance, which can inhibit the expansion of points. Compared with the previous PS version, the reproduction performance has been improved

in terms of plate exposure, we must pay attention to the reproduction of the highlight and reset the exposure. Compared with the usual situation, the exposure will be greatly reduced. It is also easy to cause quality problems due to dust during exposure, which requires careful operation

3) ink for high-precision printing

the importance of controlling the dot enlargement rate of high-precision printing has been described above. The expansion of high-precision printing points is also related to the ink used. Especially for water offset printing, the following points are very important

① improvement of emulsifying performance

when the ink emulsification is serious, the dot deformation is serious, the dot enlargement rate increases, and the printing quality decreases significantly. In terms of ink, we should properly absorb the fountain solution, and do not produce ink water intrusion (easy for Lianhe communication; blead) fault, and try to reduce the excess water. Such ink is what we expect. It is important to choose the binder and pigment that have the greatest impact on the emulsifying properties of ink

② expand the control point by increasing the ink concentration and viscosity

in order to expand the control point from the ink composition, it is necessary to increase the proportion of pigments and maintain the required ink concentration with a thinner ink layer. It is also an effective method to improve the viscosity of ink without affecting the transferability of ink

③ improve printing gloss

the thinner the ink layer is, the worse the flatness is, and the printing gloss is correspondingly reduced, which is just the opposite of the above effect of increasing the ink concentration. Therefore, in order to improve the gloss of printing, it is important to choose resins with good pigment wettability and pigments with good dispersion

④ printing conditions of high-precision prints

in order to stably carry out high-precision printing production, it is necessary to minimize the dot expansion caused by the printing machine and control the ink emulsification. Among them, the important problem is to adjust the printing press, the temperature and humidity of the equipment and the fountain solution

① stamping control

dot enlargement mainly occurs in the process of transferring ink from printing plate to blanket. Therefore, the pressure between the printing plate and the blanket is too large, which will cause the point enlargement rate to increase. It is best to minimize the pressure between the printing plate and the blanket without affecting the ink transfer. In addition, choose rubber blanket with good compression performance

② temperature control

when the temperature of the equipment is too high, the viscosity of the ink decreases, resulting in an increase in the dot expansion rate and poor emulsifying suitability. Therefore, the temperature of the equipment should be maintained at a certain level through the adjustment of the cooling water. Water free offset press is particularly prone to sticky dirt after temperature rise, which has become an important factor affecting quality

③ control of fountain solution

when the amount of ink remains constant and the fountain solution increases, the water content of the ink will increase, resulting in the decrease of ink viscosity and ink transferability (concentration)

when printing with too much fountain solution, in order to maintain a certain ink concentration, check whether the power supply voltage connected to the experimental machine is normal; It is necessary to increase the ink thickness, resulting in an increase in the dot enlargement rate

therefore, in order to control the excessive expansion of points, the water volume should be minimized as far as possible. In addition, in order to improve the emulsifying suitability of the ink, it is also important to choose the fountain solution that matches the ink used