What is the role of water in offset printing (c)

4. Advantages and disadvantages of horizontal offset printing;

4.1 The main advantages of waterless offset printing:

l) Bright and bright colors with good consistency. Waterless printed products have large contrasts. That is, the dark part is darker and the highlight part is brighter. Can print printing quality that cannot reach traditional printing. In the waterless printing process, the color can be quickly reached, and the color can be immediately registered, and the color change during the printing process is small, and the color consistency can be maintained.

2) The color saturation is good. Waterless printing produces high ink density. Therefore, under the same number of screens, waterless printing products are richer and more real than traditional printing products. The four-color printing density is about 20% higher than the SWOP standard. Color reproduction is more realistic.

3) Smaller dot gain, higher resolution, better detail reproduction, and layered feel. The waterless offset printing plate is a plano-gravure structure, and the non-watermarked plate layout is a non-ink absorbing plane. The layout is an "ink-absorbing hole" structure. These "ink-absorbing holes" provide a supporting net wall when the ink is transferred from the printing plate to the blanket cylinder. It can copy from 2 to 3% of highlights to 97-98% of shadows, with a reproduction range of 95%. Waterless printing not only has a small dot gain, but also greatly increases the number of screen lines. Printing products with printable high-line screens can reproduce the details. Toray's unwatermarked version generally has 175 lines per inch, and some waterless printers use 400 lines per inch.

4) High production efficiency and short print preparation time. Waterless printing simplifies the printing process from a chemical/physical process to a purely mechanical process, so that the finished product is printed at a high speed. The color adjustment method in the printing process is almost the same as the traditional printing, so it also eliminates many factors that cause changes in the process and reduces the downtime due to other reasons, and can be about 40% shorter than the traditional printing preparation time.

4.2 Waterless Printing Inadequacies

1) There is no horizontal printing. The temperature and humidity of the working environment is very demanding. The general environmental temperature zone should be maintained between 23°C and 25°C, and the relative humidity zone should be between 55% and 60%. There are also some inks that require temperature control to remain in the soil at 15°C. Production practice shows that when the temperature is too low, the ink solidifies, the offset system of the offset printing machine is blocked, and printing cannot be performed; when the temperature is too high, “burning” occurs. At the same time, faults caused by static electricity increase and print quality defects are likely to occur.

2) The required ink viscosity is very high. It is easy to adhere dirt (dust, fluff, silk, and ink) on the ink roller, printing plate, and rubber market. After the stain, the decontamination operation is cumbersome and difficult. It is easy to produce quality defects on printed products.

3) The quality of waterless offset printing products is mainly reflected by ink to adjust. Therefore, in addition to the quality of the ink, the pressure between the ink supply system, especially the ink roller, is also very important. The pressure between several ink roller rollers, the pressure between the roller and the printing plate, between the printing plate and the blanket, and the pressure between the blanket and the substrate (disc) must meet the corresponding specification requirements. Large easy to cause ink bars, but also easy to make the layout from dirty, roller pressure is too small to make the poor transmission of ink, ink uneven, reducing product quality, so the pressure adjustment between the roller and the printing roller must be strictly according to the requirements to do .

4) The silicone layer is not resistant to friction, and revision is not easy. The silicone rubber layer on the non-watermark portion of the unwatermarked plate is easily scratched, exposing the photosensitive resin layer under which it absorbs ink. At this time it is necessary to use its special correction fluid (a kind of liquid silicone rubber) to repair the scratched part. However, due to the fine mesh. The operation is difficult.




Source: China Design Printing Network