Talking about waterless offset printing technology

Waterless offset printing, as its name suggests, does not involve water during the printing process, and does not rely on the principle of ink-and-wash balance, and can accomplish higher-quality printing jobs. The printing process is very similar to offset printing. Nowadays, it is being paid more and more attention by superb printing quality, simple operation technology, and perfect environmental protection.

Process principle:

Waterless offset printing is the coating of photosensitive liquid and silicone rubber on the plate. During printing, the photo-crosslinking reaction occurs in the silicone rubber in the light-transmitting portion of the positive plate. When developing, no visible light is washed away, thus forming an image; the negative plate version is just the opposite. Since the surface energy of silicone rubber is very low, the surface energy of the graphic part is high, and the surface energy of the waterless offset ink is between the two. Therefore, only the graphic energy part with high surface energy is used for printing but the graphic part is not inked. There is no need for water to participate in the entire printing process.

Printing supplies:

Waterless offset printing requires special plates and inks. Traditional PS plates and offset inks cannot meet the needs of the waterless offset process.

Waterless offset printing plate

The non-graphic part of the water offset printing plate sees that the light is dissolved after being developed, and the graphic part is convex, which is also called flat relief. Unlike water offset printing plates, waterless offset printing plates consist of aluminum plates, coatings, photosensitive layers and silicone rubber. Since the final printing plate graphic part is lower than the non-graphical picture part, we also call it the flat intaglio printing plate. The composition and structure of this special printing plate exactly reflects the biggest features and advantages of the waterless printing technology: Silicone rubber can well bear the ink repellent layer, the printing process does not require the participation of water, and the emulsification of the ink is avoided; The structure of gravure can restrict the dot gain to a certain extent and strive for a better copying effect.

2. Waterless offset ink

Waterless offset inks consist of high molecular weight resins, low molecular weight resins, pigments, and silicone oils (which help reduce the surface tension of the ink). In order to reduce the printed imprinting burr, talc was added.

The special process conditions of waterless offset printing also make special requirements for the inks used:

1 to have a higher viscosity and lower viscosity;
2 The transferability of the ink is better and the thixotropy is greater;
3 high gloss, ink particles can not be too large;
4 does not require water resistance.

Your own advantages:

Water offset printing uses the principle of water-ink balance. However, due to the participation of water in printing, the complexity of the process has been greatly improved, and this has led to a series of problems. First, the ink color saturation is not high, the ink emulsification phenomenon is serious, it is easy to cause prints blotting, affect the printing quality; Second, before the official printing, in order to adjust the appropriate ink balance and register, the amount of overprinting paper relative Larger, third, the increase in dot size is not easy to control; fourth, certain chemical components in the fountain solution can cause environmental pollution.

It is precisely because of these drawbacks that it has promoted the research and promotion of the waterless offset printing technology. The use of the ink resistance of silicone rubber to replace the role of the fountain solution in water offset printing has fundamentally solved various obstacles caused by water. The confusion of printing production shows the strong advantage of waterless offset printing.

1. Excellent printing quality

1 The density of the ink in the field is higher, the saturation of the color is increased, and the printing screen is more vivid;
2 The network is lighter in size, clearer in copying, and rich in tone levels;
3 increase the number of screens, water-free offset printing products can reach 300 lines / inch, up to 500 lines / inch;
4 The hue of prints is uniform, which is particularly important in the field of packaging and printing.

2. Simple process operation

The water-ink offset is difficult to control, and the amount of water supply is less likely to cause dirty plates and stencils. The amount of water supplied is more prone to problems such as ink emulsification, prints, and paper deformation. Waterless offset printing is completely free of these annoyances. In addition, the fountain solution is removed, and the accuracy of color matching and registration at the time of printing becomes easy to grasp.

3. The actual economic benefits

1 save the amount of overprinted paper, can save about 30% to 40% of overprinted paper;
2 The printing process is easy to control, working hours are shortened, and work efficiency is improved;
3 The printing quality is high, the company reputation is good, and the livelihood is relatively stable.

4. Excellent environmental protection concept

With the advancement of science and technology and the improvement of ecological environment requirements, the printing industry is paying more and more attention to improving the environment. Waterless offset printing unifies the contradiction between the polluting industry and environmental protection, and it embodies the concept of environmental protection. The whole process of waterless offset printing does not use fountain solution, does not contain alcohol and other components, and plays an environmental role; it does not require three waste treatment problems and saves costs; it can reduce paper waste, protect trees, and to a certain extent, it also plays an environmentally friendly role. effect.

Process Control:

In general, waterless offset printing is simple and easy to control, but in order to get a fine print, some process parameters still need to be taken care of.

1. Roller temperature

The key to printing exquisite prints using waterless offset technology is the tight control of temperature. Since the printing speed of waterless offset printing is fast and there is no water involved in the printing process, the surface temperatures of the tandem roller and the plate cylinder will be very high. After the temperature rises, the viscosity of the ink will decrease and the dirty version will be prone to failure. Therefore, we need to add a cooling device to the waterless offset press to control the temperature of the transferred ink. Usually the temperature should be controlled at 27 to 30°C and it can be monitored by a non-contact far-infrared thermometer.

2. Workshop temperature and humidity

Waterless offset printing is demanding on the operating environment. Since the temperature of the printing press will change with the temperature of the environment, the printing shop must control the temperature and humidity of the workshop within a reasonable range. Shop temperature should be controlled at (23 ± 2) °C and humidity should be controlled at 50% to 60%.

3. Plate protection

Due to the special nature of the waterless offset printing plate structure, that is, the printing plate graphic part is resistant to printing force, and the graphic part is composed of silicone rubber, the resistance to printing force is low, and the surface is easily scratched. Therefore, the printing should be performed as far as possible. Reducing plate friction; particles of waterless offset ink should not be too large. The cleaning of the plate must be done carefully and carefully. Use a soft material to clean the surface and avoid damage to the plate.

Constraints:

Although waterless offset printing can provide high-quality printed products and is better than water offset printing in many aspects, its promotion and application in China is not high, and it is optimistic that its market share is not as good as that of the entire water offset market. 1%. The primary factor affecting its promotion at present is that the price of special plates and inks is higher than that of water offsets. Second, due to the higher viscosity of waterless offset inks, higher demands are placed on the printability of paper. If the surface strength of the paper is not enough, it will cause the paper to lose powder and lose hair, affecting the quality of the printed product and printing. However, as more manufacturers take part in the competition in the field of waterless offset printing, the monopoly situation will gradually collapse, the prices of waterless offset printing supplies will continue to decline, and the outlook for waterless offset printing is still promising.

Market positioning:

Waterless offset printing has the advantages of high printing speed, short printing preparation time, and high printing quality. It is the best printing method for printing small batches, multiple varieties, high quality, and short-term printing. Its market position is in the use of sheet-fed offset and web offset presses, high-fidelity commercial printing with high quality requirements, reproduction of fine art works, and artwork printing, as well as substrates for film printing, plastic printing, and metal printing. In the printing field with poor absorptivity and high surface strength, waterless offset printing is popular in the field of packaging and printing due to its features such as good printing, high color saturation, and bright colors.

In recent years, waterless offset printing technology is very popular in European and American countries, but in China, the promotion of waterless offset printing technology is still difficult. However, it can be predicted that with the rising popularity of environmental protection, waterless offset printing will certainly have its own broad space for development with its unique advantages.

Author: Zhang Meng Tong

Reprinted from: Printing Technology