Looking forward to a more perfect offset printing ink

In order to meet users' diversified requirements for quality and variety of printed matter, printed publications and printed packaging products must be developed in the direction of diversification and gentrification. In order to achieve this goal, printing companies are constantly updating and improving their printing equipment. Updated, better printed materials - printing inks. Offset printing ink has always been in an important position in the printing field and represents the status quo and development direction of ink products. Therefore, for many years, most ink companies have not stopped the technical research and development of offset printing inks, constantly improving old products, and developing new types of marketable products. Offset printing ink, while the variety increases, the quality of the product is gradually approaching the international advanced level. For example, the output and quality of high-grade offset bright fast-drying inks, cardboard offset offset inks, newsprint rotary offset inks, cold-set offset offset inks, and UV-cured offset offset inks have increased year by year.

However, the domestic level of offset printing ink technology is still at a stage of development. Compared with imported inks of the same type, there is still a certain gap. Printing users often have problems in the use of ink. Users often encounter problems and ink requirements are also improved by ink manufacturers. The best guide for the product.

For this reason, the author interviewed the printing houses of books, magazines, packaging, and newspapers to summarize the overall view and requirements of the current offset printing ink in the production of offset printing ink users.

Improve the quality of the direction

In recent years, ink manufacturers have made remarkable achievements in the main technical indicators such as the color density, dryness, water resistance, printability, and on-board stability of offset inks, and have also achieved remarkable results. In spite of this, the development speed of the ink does not seem to be as fast as the printing technology. The lack of quality is always revealed at the time of printing. During the interview, when asked what the user's current offset inks are, their opinions are mainly focused on several important ink indicators.

Color concentration

Color concentration is the saturation of color. Now, newspapers are no longer the same as black and white, and more have been replaced with graphic newspapers. Therefore, the user has higher requirements for the color density of offset printing inks for newspapers. When Mr. Zhu Xiaolin of Nanjing Xinhua Daily Newspaper Printing Center mentioned color concentration, advertisements, pictures, and titles on the color newspaper were more eye-catching. Therefore, the color density of the ink needed to be relatively increased. However, the color concentration of many newspaper inks is not ideal. In order to ensure the printing density, printing companies have to increase the amount of ink or increase the percentage of outlets. However, the result of this is bound to cause stacking of ink and increase the use of ink. Mr. Zhu also said: “Increasing the ink volume will also cause the network to be connected in parallel. The normal increase in web offset printing offsets should be controlled below 25%. If the ink is large, it will result in the loss of levels and the excessive increase of outlets, especially the pictures. The consequences of the increase in outlets are even more pronounced."

In addition, the problem that has arisen in the past few years is that black ink saturation is insufficient and it still exists, but it is no longer a big problem. The reason for the low concentration of black ink is that when the printing plant prints ordinary text, in order to reduce costs, black ink of low price and poor quality is selected. It is because of this demand that some ink factories naturally produce such inferior ink, which affects the overall quality of the ink.

According to the interview, the reasons for the unsatisfactory color density of domestic ink are as follows: First, most of the current ink factories do not produce their own pigments, but instead purchase domestic pigments for grinding. There is still a gap in the quality of domestic pigments and imported pigments. The second is that the ink factory uses less pigment in order to save the cost, resulting in insufficient color saturation of the ink. The key point is that even if the quality and amount of pigments pass, the particle size of the ink cannot exceed 15 μm. The finer the grind, the brighter the color of the ink. If the processing of the pigment is not good enough, if the size of the ground particles is not suitable, the color density of the ink will also be affected.

Feng Youjie, director of the color printing workshop at Weifang Plant of Shandong Xinhua Printing Factory, told us that they had used a German ink with very fine grain size, good color density, and very good printing results. In contrast, domestic inks are still relatively crude.

Of course, the level and color of printed matter is not only related to ink, but also related to the process conditions such as printing plate production, printing equipment, and ink balance, and the quality of ink is also a prerequisite and guarantee for the improvement of printing quality.

2. Overprinting

There are two main requirements for the chromatographic properties of offset printing inks in newspaper printing. One is the color sequence, and the other is the viscosity of the ink. At present, the standard color sequence for printing in the international newspaper is cyan-magenta-yellow-black, and its viscosity should be gradually reduced. Otherwise, ink pull-back phenomenon will occur. During the interview, we learned that some large ink companies have now noticed that the ink viscosity value is pulled according to the printing sequence. Mr. Zhu of Xinhua Daily told us that they often communicated with the ink supplier and adjusted the ink ink in time.

3. Dryness

The drying speed of the ink will usually affect the printing quality, and at the same time it will cause many printing failures, such as causing the back of the printed material to become dirty, and even causing the web printing to fail. During the interview, users generally reported that the dryness of domestic ink has a great influence on the quality of printed matter. Director Feng of Shandong Xinhua Weifang Plant deeply understands the importance of ink drying: “The workshop was printed with promotional materials before the factory celebration. At that time, it was printed with matt coated paper. After printing, it was dry for one week and it was delayed. In addition, the pink ink used for the cover of printed textbooks has not been dried for 3 days after printing. The above problems are caused by poor drying of the ink.” Of course, these are more typical phenomena but they are made of ink. The problem of dry and incomplete printing and defective products, and the influence of seasons and climate on the drying performance cannot be ignored.

4. Printability

In modern printing, the variety of substrates is large, the types of auxiliary consumables are numerous, and the performance difference is also large. Therefore, the requirements for ink are also more complicated. Beijing Guocai Printing Co., Ltd. attaches great importance to the printability of inks. According to Lu Qiquan, the director of the company, in order to ensure the printability of the ink, they ensure the compatibility of ink and various consumables and substrates, often with a fixed number of The ink supplier stays in touch and informs the ink supplier of its own special requirements. The director of Shandong Xinhua’s Feng also believes that the printability of inks and various printing materials is very important. For example, when they use ordinary offset printing inks to print coated paper, the coated papers are printed with bright colors and good gloss; the same inks are used. Printing light coated paper, then through the phenomenon of printing is more serious, and the gloss decreased, but the market does not seem to have specifically applied to light coated paper printing ink, so he hopes that ink factory can be based on different substrates, especially now commonly used New materials, such as light-coated paper, developed the corresponding ink.

In addition, there are differences in the selection of inks among newspaper printing companies. For example, Mr. Zhu of Xinhua Daily told us: “Our press is an ink-jet method, and its performance requirements for inks are relatively high. At present, the performance of domestic inks, such as rheological properties and viscosity, cannot fully meet our requirements. The printing equipment under the ink printing method also has the problems of stencil printing and filthy printing, and newspapers have relatively high requirements for pictures and titles. Therefore, the ink factory needs to adjust the relative performance of the ink according to our actual situation."

It can be seen that the printability of offset printing inks remains to be further adjusted. If each user makes special requests, the ink factory may not be able to cope with it.

5. Stability

For printers, the stability of the ink is also related to the quality of the printed product. When talking about the stability of offset printing inks, Mr. Lu of Beijing Guocai emphasized: “We have used some foreign brand inks produced in China. Although ink formulations are the same as imported products, due to the production conditions and management of domestic ink factories, There is a certain gap between the level and the original ink production plant, resulting in some differences in the ink performance of the same brand and model. If the same red ink is used, the ink is transferred in the same proportion, but there is a clear color difference.”

Domestic inks and imported inks still have large gaps in the coloring, environmental protection, and drying speed of inks, and domestic inks have poor fluidity and high viscosity, and sometimes they have to be removed. The printing factory hopes that the ink viscosity can be improved and gradually replace the import of high-grade, high-priced inks. Mr. Zhu of Xinhua Daily also preached that newspaper printing requires high viscosity and low viscosity in terms of printing effects, and ink with good transfer performance, especially for high-speed printing presses, has higher drying requirements for ink.

The demand for environmental protection has a “wang” potential

At present, environmental protection and non-pollution have become an important prerequisite for more and more printing users to purchase ink. It can be seen that the environmental protection issue of ink has been widely concerned by manufacturers and users. It is understood that some large-scale ink factories have already passed the ISO14000 environment system certification. Of course, this does not completely explain the ink they produce is the true sense of environmental protection ink, but at least that the ink factory has been environmentally aware. For a printing plant, if the use of environmentally friendly ink does not cause the quality of the printed matter to decline and harm the worker's body, why wouldn't it be natural? However, in reality, most environmentally-friendly inks are expensive and the printing quality is unstable. The demand for environmental protection ink is also not great.

Offset printing ink is not environmentally friendly, mainly in its odor, especially ink. Mr. Zhu of Xinhua Daily said: “The excessive ventilation of newspaper printing workshops will cause ink flying phenomenon. Decreasing the air volume will make the ink of the workshop too heavy. In addition, the humidity of the pressroom is relatively large, and many inks are still using mineral oil. Solvents are used to make the inks and solvents in the printing room have a large odor and pose a threat to the operator's health.” Even so, newspaper printing still prefers traditional offset printing inks because the current production of environmentally friendly inks is limited by the ingredients. Poor permeability, affecting the drying speed, is inconsistent with high-speed printing requirements. Therefore, users very much hope that the use of offset printing ink can not only ensure the printing effect, but also have environmental protection. Mr. Zhu believes that the environmental protection of offset printing inks used in newspapers is not ideal, and everyone's environmental awareness is indifferent and the press printing industry is not concerned with environmental protection requirements. I believe that with the introduction of relevant national policies, the printing industry will have more demand for environmental protection inks.

New ink popularity needs to wait

At present, there are more and more varieties of special offset printing inks and new types of offset printing inks. Among them, several UV offset printing inks are most familiar to most printing factories. In the interview, we also investigated its use.

UV offset printing ink is mainly used for printing gold, silver cardboard and plastic film base, so the packaging and printing plants use more, reflecting the problems are also more concentrated. Many users do not use UV offset ink directly, but instead mix it with common ink before printing on the machine because the UV offset ink dries too quickly. If the printer stops or runs slowly, it will cause the ink to crust on the roller.

High-fidelity six-color offset printing is a new process pursued by modern offset printing. The high-precision six-color overprint system needs to be composed of a new and improved CMYK ink, PANTONE Hexachrome green and PANTONE Hexachrome orange ink to create a wider printing color gamut. High-fidelity six-color inks have naturally become a new focus of offset printing inks, however, from several printing houses interviewed,