Waterless offset printing plates have been published in Driography from 3M in the United States, and have been introduced to the Toray Corporation in Japan for a period of 25 years.

First, the development of anhydrous glue ink

Compared with the first and second generations, the third generation of waterless offset printing has used low viscosity waterless offset printing inks. In addition, the printed matter is no longer a thick ink film printing, but the same thin ink film printing as ordinary offset printing, and other printing workability and stackability are also basically the same as ordinary offset printing. The improvements in sheet-fed and web-fed presses to improve printing speed and automation are endless, but the impact of printing speed on printability far exceeds the expectations of printer designers, especially for ink transferability. Has a significant impact.

1. Sheet-fed offset printing ink "Dry-O-Color Artis"

In the past five years, "Dry-O-Color Artis" has improved the ink transferability, ink receptivity, fixation, and post processing suitability, and has been adapted to high-speed, on the basis of maintaining product gloss and anti-scuffing properties. Requirements for multicolor sheetfed waterless offset presses.

(1) Design ideas. After achieving the low viscosity and low viscosity required for high-speed printing, special additives must be used to further control the anti-dirt properties. To maintain the viscosity and viscosity, only the fluidity of the ink can be further improved to improve the ink's performance. Transferability. The specific approach is:

1 To improve the dispersibility of the pigment, use a high-soluble resin binder.

2 In order to maintain the resistance to scumming, new non-aromatic hydrocarbon solvents that allow rapid diffusion of the printing plate oleophilic resin and the non-image part of the silicon layer were developed.

(2) Ink characteristics. Under the condition that the viscosity and viscosity of the ink are almost the same as those of the original product, the fluidity of the ink is improved by about 15%, and the ink transferability is improved by about 10%.

(3) Market evaluation. Gloss is good, fast fixing; close to the quality of water offset printing; has the same printability as ordinary offset printing ink; ink hiding power is also improved. A few users have suggested that the overprintability of ink is about 5% lower; the color reproducibility is not exactly the same as with water printing; the density in the field is slightly worse than the offset with water.

2. High-speed web offset press thermosetting type waterless offset printing ink

Compared with sheetfed printing, Web offset printing has increased the printing speed by about 2 times. It requires higher ink flowability and lower viscosity requirements. Using the same resin design as Dry-O-Color Artis, it is also suitable for rotary waterless offset printing inks, that is, under the premise of not reducing the cT (index of occurrence of pasting), using a link material that improves the ink flowability to make the ink at high speed Get good transferability when printing.

Second, the study of anhydrous offset ink

Waterless offset printing plates are composed of an oleophilic resin layer and an oil repellent silicone layer. For waterless offset inks, the most important properties are anti-dirt resistance, ink transferability, and ink/ink properties.

1. Development points of waterless offset inks

(1) Development towards low viscosity and high mobility

Due to the improvement of paperless paper and recycled paper, and the increase in the amount of paper, in order to increase production efficiency, the printing speed has been continuously improved, and the occurrence of paper picking and printing plate stacking has subsequently occurred. Waterless offset printing Because the fountain solution is not used, the viscosity of the ink on the paper surface is higher than that of the offset printing with water and is more prone to pick-up and stack failure. Therefore, the low viscosity and high fluidity of the ink is an innovation of the ink technology. The essential.

The use of a polymer and a highly soluble new resin is effective for obtaining a low-viscosity, high-fluidity ink, and can be used to cross-link low-viscosity resins without impairing the flowability. In the cross-linking process of the resin, a network structure is formed between the macromolecules, the internal cohesive force is increased, and the viscosity is increased. If the aluminum chelate compound gelator, the fluidity of the ink may be lost. Thus, a heat-polymerized resin composed of a rosin-modified phenolic resin and a molecular chain-length oligomer was proposed to make the resin quantified with high plasticity, thereby obtaining a low-viscosity resin binder.

(2) Improve anti-dirt

Resistance to scumming is expressed in terms of cT, which is related to ink viscosity, viscosity, and fluidity, and is proportional to viscosity and viscosity, and inversely proportional to fluidity. Therefore, it is not easy to design high cT inks with low viscosity, low viscosity, and good flow (high speed printing) ink technology. Waterless offset printing should have anti-dirt resistance while achieving low viscosity. Therefore, the key issue in formula design of waterless offset inks is how to suppress the dirtiness of the printing plate. In general, there is a close relationship between the resistance to dinging and the viscosity of the ink, the solvent used and the density of the printing field, the structure of the printing press, and the printing speed.

(3) improve ink receptivity

Soybean oil ink is an environmentally friendly ink that replaces organic solvent inks. Compared with high-curing inks or waterless offset inks, the curing speed is slower. However, from the perspective of practical results, the transferability of the ink is good, and the ink repellency in the field is good, and the highlights of the dots are evenly distributed.

After the ordinary offset printing ink reaches the paper, the solvent penetrates quickly. In the part near the paper surface, the ink film will break off, while the soy ink is slow to penetrate, and the ink break surface is closer to the side of the blanket, which is equal to The thicker ink film is transferred to the paper surface, so the ink transfer amount increases.

(4) Improve ink transferability

There is a certain relationship between ink characteristics and color development, that is, the higher the ink viscosity and viscosity, the lower the color development; the smaller the fluidity, the lower the color development. In order to obtain high color developability, it is necessary to improve the transferability of the ink, and thus it is required that the ink must have low viscosity, low viscosity, and high flowability.

Both offset resistance and ink transferability cannot be balanced. How to balance it is the key to waterless offset ink design.

2. New products and features that have been developed

In response to these problems, ink manufacturers have conducted research based on actual printing conditions and have developed a series of products.

(1) Since the ambient temperature of waterless offset printing is to be as low as possible, it should be kept at a constant temperature. Therefore, ink manufacturers are fully committed to the development of low-viscosity and non-stick version of the ink series.

(2) Due to the business features of waterless offset printing, many types of inks are required. Therefore, spot inks, specialty inks, synthetic paper inks, and special inks have been developed.

Sheet-fed waterless offset inks have the characteristics of good fluidity, low viscosity, soft body, etc., while maintaining the same anti-dirt properties as the original products. They have passed trials by many companies and Heidelberg is also on the Quickmaster D146. The printing was carried out to prove that it has greatly improved in terms of ink repellency, fluidity, stain resistance, glossiness and abrasion resistance of the ink film.

3. Web printing anhydrous ink

In the past, the popularity of waterless offset printing on webs has been slow due to the lack of print force and printing ink hiding power of waterless offset printing plates. However, recently, due to the increase in the strength of the non-image portion of the silicone layer, in Japan, more than 20 web offset presses have been converted to waterless offset presses.

In order to cope with the high-speed production of web offset printing presses, inks need to have low viscosity and high fluidity that are resistant to high speed printing, in order to obtain good ink transferability, ink receptivity, and dryness, and to prevent ink stains. One of the most notable technologies is the self-adhesive resin technology led by Japan.

Since the self-adhesive resin has a large molecular weight and a large number of cross-linking points between molecules, it is not necessary to use a metal chelate gelator to obtain a binder having a strong gelling elasticity. The ink using such a binder has lower viscosity than the ink using a resin binder, and thus can maintain high speed while avoiding paper fluffing. In addition, its viscoelasticity is less affected by the temperature, which can reduce the dirt problem caused by the rise in the temperature of the printing press during the long live printing, and shows the superiority of high-speed printing. The aromatic-free inks using these resins have been used in production and will undoubtedly promote the development of web-free offset printing.

4. UV waterless offset ink develops to low viscosity

UV waterless offset inks are characterized by a fast drying and strong dry ink film. Similarly, UV-curing inks have also been improved from high-viscosity type to low-viscosity type, and they are expanding into the field of film printing (PP, PC, PVC, PS, synthetic paper, telephone cards, etc.) after satisfying paper printing.

Third, full development of aromatic-free ink

The composition of the waterless offset ink is the same as that of a water-based offset ink, which is produced by dispersing rosin-modified phenol resin, dry oil, petroleum solvents, pigments, etc. into a binder. After satisfying various printability requirements for waterless offset printing, environmental protection safety has been an important issue in the manufacture of waterless offset inks for the sake of environmental protection.

After more than 20 years of development, waterless offset printing has been widely recognized by the industry for its advancement in inks, plates, printing presses and peripheral materials. In the 21st century, many industrially advanced countries have promoted it as an environmentally friendly technology and have made more remarkable progress.

Some users have indicated that waterless offset printing, though with high labor prices, can be compensated for in terms of increasing production efficiency. Therefore, in order to expand this process technology, waterless offset printing plates, inks and equipment providers should work together to further increase productivity, promote unattended and centralized management of printing, and build a new technology development environment.

Although the number of waterless offset presses in Japan, the United States, Europe, and other countries and regions is not as large as that of ordinary offset presses, the environmental protection calls have become increasingly high. Many regions in the United States have actively recommended waterless offset printing. This is It is noteworthy.

At the same time, in order to obtain the same printing quality as offset printing, the improvement of waterless offset inks and related equipment is inevitable: reduce the amount of waste ink due to the crust (sheetfed ink); reduce the VOC in the ink (Volatile organic compounds); Reduces the content of aromatics in solvents; Improves offset resistance, ink repellency, and hiding power of printing plates.

Keywords: Waterless Offset/Ink