On UV curable ink and printing

2022-08-04
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Talking about UV curing ink and printing

in recent years, with the improvement of the quality of flexographic printing materials, many printing materials that used to use other printing processes have turned to flexographic printing technology. Flexographic printing technology has continuously won more market share from the traditional territory of offset printing and embossing printing. On the whole, the requirements for printed matter are becoming more and more complex. At the same time, many new processing technologies have emerged. Therefore, printing manufacturers are looking for a printing method that can obtain multiple printing process effects on the same product. Usually, a printed matter is rarely processed by more than two printing processes. In order to achieve the above purpose, it is the best solution to complete the processing of multiple printing processes at the same time in one printing process. Therefore, in recent years, the combination of various printing processes (hereinafter referred to as combination printing) has become very common. Because people regard printing and post press processing as a holistic solution, combined printing is becoming more and more popular. The development of many related technologies makes combined printing not only a reality, but also a good economy. This paper will discuss the technical progress in this field, focusing on the background and future development trend of the combination printing machine using UV curing ink technology in the narrow web printing market. 1、 What is combinatorial printing

combinatorial printing refers to a flow production line composed of various types of printing and post press processing units. In combination printing, processes such as flexo printing, silk screen printing, embossing, offset printing, gravure printing, hot stamping, cold stamping and indentation can be mixed. The most common combination printing units usually include screen printing, flexo printing, embossing and hot stamping

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will coordinate and communicate with the staff of the farmers' market, so the reason for adopting various printing and post printing processes in the same printing process is very simple, because various printing processes have their own inherent strengths and weaknesses. For example, silk screen printing can accumulate a thick ink layer, which is good for its excellent hiding power. It is mainly used to print a layer of opaque white on the substrate, such as "no look" signs. The color of silk screen printing is suitable for printing strong and thick patterns and words. On the other hand, compared with other printing processes to obtain the required data information, the printing speed of silk screen printing is the slowest. Offset printing and embossing printing both have good picture and text clarity and high printing speed, but their purchase cost is high, and they lack sufficient hiding power compared with silk screen printing. The covering power of flexo printing is worse than that of silk screen printing, but higher than that of offset printing and embossing printing; Flexographic printing has higher printing speed and sharpness than silk screen printing, but slightly worse than offset printing and embossing. From the perspective of purchase cost, it is just between low-end silk screen printing and high-end embossing and offset printing. These processes have their inherent limitations when used alone. If their best characteristics are selected and combined to form a narrow web production line, users can have a variety of choices to obtain the best image definition under the best output efficiency

the number of signs printed by combined printing process is rising rapidly. There are two fundamental reasons. First, end users are always looking for a printing and decoration method that can make their products more competitive on the shelves of supermarkets, and difference is the first demand in the field of products with consumption and brand effect. The innovative concept of packaging decoration promotes the continuous innovation of technology. Driven by this innovative concept, the market is optimistic about the combination printing process, especially the flexo printing and silk screen printing processes using UV curing ink. Secondly, due to the improvement of the performance of printing press, ink, printing materials and other auxiliary materials, the combined printing process has been rapidly promoted and trusted. This has also promoted the post press processing of high-grade label products to enter various medium and small-scale enterprises in the printing industry. If the accuracy of the strain gauge is not high, or the anti-aging ability of the glue used to fix the strain gauge is not good, or the material of the sensor is not good, the accuracy and service life of the sensor will be affected. It is no longer limited to a few large printing plants for processing, thus opening up a broader application field

II. Advantages of UV curing ink

now, the development of ink, especially UV curing ink technology, has become one of the main factors to promote the development of printing technology. It promotes the growth of market demand for combined printing process. UV curing ink has made remarkable progress since it entered the market 20 years ago. It has played a leading role in the screen printing industry. In some cases, it has become an ink curing process that people are willing to adopt. So far, the quality and stability of UV curing ink have reached a very high level and it is easy to use, so its application in other printing processes has also achieved significant growth. In fact, at present, 8 of every 10 newly added printing machines in the flexo printing industry are equipped with at least one UV curing printing unit. Compared with other ink curing methods, the advantage of UV curing ink lies not only in the processing process, but also in the quality level of printed matter. It can achieve the effect that other processes can not achieve. From the processing point of view, the advantage is that the curing process of UV ink is very stable. The whole process only needs to pass under the UV lamp. This technology enables printing, hot stamping, die cutting and any other post press processing technology to be put on one machine for continuous production, so that the maximum production efficiency can be achieved with the minimum workload in the processing process. In addition, UV ink is suitable for a variety of printing materials, including plastic films that were difficult to deal with in the past, such as BOPP, pet, polyethylene, polystyrene and coextrusion composite films. Due to the excellent adhesion of UV ink, the pre press auxiliary working time is significantly reduced

uv inks do not contain volatile components, such as solvents or water, which will not change the color and printing characteristics. In printing, UV ink is easy to maintain the stability of color and viscosity. Once the ink color is adjusted before printing, the adjustment workload on the printing machine is very small, and there is no need to add other additives. When the printing stops halfway, the ink on the smooth roller and the embossing roller will not dry. The surface of UV ink layer has extremely high abrasion resistance and chemical stability, which is also the main reason why label products use combination printing. UV ink has very high hiding power and gloss, and the print is also very clear, which can fully reflect the end-user's demand for product quality - so that the user's products can stand out in the market

III. challenges of combination printing

obviously, once this combination printing process with excellent quality and convenient use is successful, anyone will follow suit, and the market will be full of a large number of similar products. Although this process has become very reliable, in fact, it is still difficult to master. For printing operators, there are still a series of controversial points, and there are quite a number of variable factors that need to be effectively controlled, such as:

1 When purchasing a combined printer, the printer must ensure that the sequence between printing units has enough variability to adapt to the combination of printing processes required for various printed materials. Generally speaking, the hot stamping unit is always placed at the terminal of the printing unit. When printing color plates with silk, whether the silk printing unit is placed in front of or behind the flexo printing unit or even in the middle involves the decision of whether each unit should be fixed or variable when configuring the printer

2. The components of inks used in different printing processes are different, and different inks are not always compatible with each other, because different technologies are supported by different chemical principles. In this way, there will be problems of overprint rate and adhesion between the inks used in two different systems. For example: silicon free UV flexo printing ink often produces poor overprint performance on silk screen printing ink containing silicon; Incompatibility often occurs between inks produced by different manufacturers, and even between different product lines of the same manufacturer. In case of such incompatibility, the operator can usually adjust the ink on the printing machine. But the best way is to test the ink compatibility before printing and obtain technical support from the ink supplier

3. Ink is sometimes incompatible with other post press finishing processes, such as hot stamping, inkjet and laser printing. The key to overcoming such failures is to conduct correct testing in advance or obtain technical support from the ink supplier

4. When the same color is matched with inks of different printing processes, manufacturers often use pigments of different substrates, which means that problems often occur when matching inks of different processes, such as silk screen ink and flexo ink. The error of color matching is quite large when outstanding personnel of Jinan assaying service who have not received formal color matching training from the factory or lack of spectrophotometer and other instruments for advanced color matching

5. The printing speed on the combined press is always controlled by the slowest unit, such as hot stamping unit or round wire printing unit. For example, the speed of flexo printing machine can reach 300 feet/min when using UV ink. If the speed of the hot stamping machine connected to the machine is only 100 feet/min, when the printing piece needs hot stamping, it cannot run at the speed of 300 feet/min

6. It is very important for the factory to train operators in various printing processes, because different processes require different types of operating skills. Various skills training is necessary to ensure that operators master various process operations and fully understand the technical parameters of various processes

7. When the printing factory first stepped into the combined printing process, another training target was the factory's sales personnel, which was not only to enable them to deal with the customer's supply department, but also to learn to interact with the customer's creative designers and work closely together in the final product design process

IV. future development trend

the newly developed ink varieties have shown outstanding improvements, especially in UV screen printing and UV flexo printing ink products. In terms of UV flexo printing inks, water-based inks with high color density and low viscosity have been introduced. They are suitable for high hole capacity roller, so as to obtain excellent printing reproduction effect, lower ink consumption and higher printing speed. Now, the unadjusted flexo ink can even be directly taken from the ink barrel in round wire printing. This new pioneering development makes the combination printing manufacturers have greater variability and diversity, and makes the printing process more stable and reliable

digital printing will begin to show a positive support for combined printing on the printing pieces with a relatively short number of prints. Digital printing has already entered the short version label market, and has become an ideal tool for a large number of personalized printed materials. However, in the near future, it is likely to use silk screen or flexo printing units

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