What are the breakthrough directions for digital printing in improving the printing quality of the label industry?

Almost all digital printing manufacturers acknowledge that there is still a gap between the quality of digital printing and traditional printing. This seems a bit like self modesty, but in fact, it is to reserve a way to judge the quality of digital printing and traditional printing, and the confidence is not enough.

I believe that there is no need for self humility. Good is good, bad is bad, and self humility is not beneficial for competing in the market. We should rigorously and systematically compare and make judgments on the two major imaging modes of digital printing, namely electrostatic imaging and inkjet imaging.

(1) Electrostatic imaging uses amplitude modulation mesh, and both electronic ink and carbon powder electrostatic imaging processes have their shortcomings. The uneven edge of carbon powder electrostatic imaging dots is a unique defect, similar to ink emulsification caused by excessive water in offset printing dots. Electronic ink is essentially a solvent based ink, and its quality can be evaluated by transferring it through a rubber blanket and utilizing the deformation of the geometric structure of the dot. Compared with traditional printing, digital printing using electronic ink electrostatic imaging has reached and partially exceeded the level of traditional printing. In terms of dot structure, it is not only similar in shape, but also in spirit. Only in color saturation, it has a big gap with traditional printing, especially compared with gravure printing.

Usually, digital printing uses adding a layer of black screen for color tracing, but the effect is not ideal. Because the difference in saturation cannot be concealed by adding a layer of black mesh, darkening the hue and saturation are actually two different ways to adjust. At this point, digital printing must give up.

(2) UV inkjet printing uses a frequency modulation screen, and the minimum ink dot diameter is an effective method to evaluate the quality, with the key being the difference between 1200dpi and 600dpi. The saturation of inkjet printing can already catch up with screen printing, especially in the combination printing of labels. The original use of screen printing as a base or surface polishing, or even local polishing, has been replaced by inkjet printing in actual production. Inkjet printing uses a frequency modulation screen, without the Moor interference generated by multi-color overprinting, making the image appear very delicate and soft. However, due to the inability to achieve clear and sharp segmentation lines at the edges of the pattern formed by multi-color overprinting, blurred segmentation lines are a unique defect of this printing process.

The inkjet digital printing using frequency modulation network is suitable for image printing of Impressionist paintings, but not for fine brushstroke printing. In recent Asian Label Awards, many of the winning digital printing works and pattern printing utilize changes in light and shadow. In my impression, there is a series of cultural and creative labels that use inkjet printing to interpret the style of well-known foreign oil paintings, indicating that the designer of this label is well versed in the essence of inkjet digital printing for pattern selection. UV inkjet printing has adaptability to images, which is a characteristic but also a limitation.

In fact, FM networks have also encountered considerable embarrassment in the field of packaging and printing. One is that traditional printing, especially packaging printing, does not use an FM screen. This is because it is difficult to control the network expansion during repeated orders, which affects the stability of colors. FM network is generally only used in the traditional printing field for one-time printing of book editions, such as pictorials and picture albums, and there are few additional printed materials. Because different batches of book editions have a greater tolerance for color differences. However, in the field of packaging and printing, it is difficult to withstand this color difference. For example, the spot color on product packaging, especially the color of the logo, is the first element of product packaging, and no one dares to take such a risk.

The second is the connection between short orders and long orders. If an amplitude modulation network is used, there is basically no technical difficulty. It should be noted that using electronic ink digital printing to track traditional printing has certain difficulties. As mentioned earlier, electronic ink electrostatic imaging tracks traditional gravure printing, but traditional printing tracks digital printing. As long as the ink volume is controlled properly during the printing process, the success rate will be extremely high.

Thirdly, inkjet printing uses frequency modulation network, and color saturation is not a problem. However, the connection between digital printing of frequency modulation network and traditional printing of amplitude modulation network will be very difficult, and prepress processing requires experience and skills. If seamless connection cannot be achieved, The tragedy of the huge gap between the Cromalin proofing in flexographic printing more than 20 years ago and the actual printing sample may be repeated (the situation at that time was that the quality of the FM screen proofing was comparable to photography technology and very beautiful, but the actual printing sample in flexographic printing was only 133 lines, and the minimum dot size could not reach 2%, which is completely different from the same level. The final result of the flexographic printing product was not the same as the Cromalin proofing, no matter what method was used). In the end, flexographic printers can only mock themselves. Proofing can only be seen, not counted. Proofing that conforms to reality can only be done on the printing press, laborious and self seeking.
Here, we will introduce a case of traditional printing pursuing digital printing. At the 7th Asian Label Awards in 2020, the overall printing award was based on the high and low scores. Originally, a shrink sleeve label using UV inkjet digital printing won the championship. However, due to the pandemic, the label's launch time was delayed, making the previously submitted work that was on the spot an unlisted work for evaluation. According to the evaluation rules, it was pulled down and missed the highest award. Later on, after the product was launched, sales were booming and orders were added in large quantities. The original process of UV inkjet digital printing was no longer able to complete large-scale orders in a timely manner. Therefore, the printing company adopted flexographic printing to pursue digital printing and replaced the frequency modulation screen of inkjet digital printing with flexographic printing amplitude modulation screen. Due to its exquisite technology, the quality of large-scale flexographic printing products was almost as good as the original process of digital printing. Later, the flexographic printing work participated in the national flexographic printing quality evaluation by the flexographic printing branch of the China Printing Technology Association and won the Excellent Product Award from the Label Group. This work reflects the active cooperation between flexographic printing and digital printing, opening up the market with plateless digital printing, and completing orders with high-capacity flexographic printing, creating a new business growth point in the flexographic printing industry.

It should be noted that there are conditions for pursuing digital printing in flexographic printing: firstly, using amplitude modulation mesh to pursue frequency modulation mesh, the key lies in the prepress of flexographic printing; Secondly, successful printing requires exquisite skills; Thirdly, this technology is difficult to replicate in large quantities and has limitations.

So, can traditional printing catch up with digital printing, and can digital printing successfully catch up with traditional printing? Here, two questions need to be considered first: firstly, flexographic printing can actively cooperate with digital printing, and whether inkjet digital printing can seamlessly connect with traditional printing by imaging with amplitude modulation mesh from the beginning; Secondly, when the network structure tends to be the same or consistent, digital printing and traditional printing can achieve spiritual similarity from appearance. When the two types of printing achieve the same printing quality, is it still necessary for digital printing to be humble about the quality gap?

In fact, for digital printing, using traditional amplitude modulation networks in inkjet digital printing is not a new technology, as some Montai software had this function before the epidemic. Therefore, inkjet digital printing should not be satisfied with following the pace of foreign countries, that is, as long as inkjet printing is used, frequency modulation network should be used. The author has always been unclear about the original intention of foreign peers' preference for frequency modulation networks. During a market research in Wenzhou in June, Wenzhou users did not hesitate to choose the traditional dot structure of electronic ink electrostatic imaging mode when choosing digital printing machines, because customers who place orders liked it. This reason is very real and deserves a thorough study by the industry on the psychology and needs of customers.

According to the customer's needs, the improvement of inkjet digital printing machines is not difficult in the author's opinion. The following aspects can be considered: (1) The improvement and upgrade of RIP for digital printing machines is an effective method for inkjet printing to use amplitude modulation nets. (2) Compared to electronic ink electrostatic imaging, UV inkjet imaging has a thicker ink color and is more environmentally friendly. (3) UV ink-jet digital printing using amplitude modulation screen will be accomplished in one move with the cooperation of traditional printing. Therefore, this solution will be replicable in large quantities and relatively stable and reliable.

It is necessary to remind friends of prepress technology that currently, prepress technology is mainly focused on color management. If we can allocate some of our energy to upgrading the RIP software for inkjet printing, it will greatly benefit the entire printing industry chain, especially the label industry chain. In fact, there are also ready-made software abroad, which is relatively expensive. However, for the label digital printing industry, the improvement and upgrade of RIP, even if it accounts for 10% of the equipment price, is not impossible in this field. The key is not in price, but in listening attentively to the voices of users, including potential users. Labels actually reflect culture, and the aesthetic concepts of the Chinese market, the printing quality standards of Chinese enterprises, and the practical needs of Chinese users are all worthy of attention. The user clearly needs a basic consistency between the dot structure and color saturation, but the supplier insists on the user accepting the color rendering of the frequency modulation dot, emphasizing that the traditional printing AM network and inkjet digital printing FM network are consistent in color, which is a bit ironic.


Finally, as an experienced printer, two suggestions are proposed: firstly, traditional printing should actively embrace digital printing and use the automation of digital printing to drive the automation of traditional printing, moving towards the goal of intelligent traditional printing at full speed; The second reason is that flexographic printing has found a way to break through characteristic defects, and traditional flexographic printing has taken a favorable position in terms of greening and automation. Among the three traditional printing processes, the distance between green and intelligent printing is the shortest. Therefore, as long as we seize the opportunity to compete with digital printing, the difficulties will be minimal.