The present and future of flexo printing

Flexo printing has become the main force in the field of packaging and printing. The origin of flexographic printing is inconclusive. China introduced the flexographic printing process in the early 1970s. After many technological innovations, it has established its status in the field of packaging and printing. This article analyzes the status quo and prospects of the popular flexographic printing technology and presents it to the packaging and printing industry.
History
It is said that around 1890, in the United Kingdom, the use of rotary rubber-plate printing presses was seen. At the time, only simple labels and paper bags could be printed and printed on the wrapping paper. Due to the use of aniline dyes to make inks, it is called flexographic printing. Soon, the popularization spread to the European continent and it was only transmitted to the United States after the First World War. After the improvement of inks, printing machines and dryers, cellophane printing began. It was quickly recognized by the society. Then around 1940, an aniloxroller was invented by the United States, which improved the printing quality.
At the printing conference held in Stockholm, Sweden, in 1952, the designation of aniline printing was denied and participants agreed to change to Flexography. The meaning of the discussion at that time was that since the photosensitive resin had sprouted, the emergence of polyethylene and polyester, and the substrate for printing materials had been greatly increased, the application of Flexography was flexible and could be adapted to printing for various purposes. For this reason, the domestic translators literally transliterated the flexographic prints without knowing its background, and they agreed to become popular today.
In the first half of the 20th century, after being used to print clear, non-absorbable packaging materials, cellophane, its application rapidly expanded. It involved polyethylene and various synthetic resin films. As a printing method for packaging materials, it laid the foundation for European and American countries.
Japan imported this technology from the beginning of the 20th century. It is used in India, India, and paper bags. Unlike Europe and the United States, it has not been used in the fields of flexible packaging materials and carton boxes for two reasons. One is that the quality of flexographic printing is not Very satisfied, and secondly, gravure and offset printing technology has already been introduced to meet the demand. Recently, as the environment of flexographic printing technology has caught up with gravure and offset printing, the speed of expansion has accelerated.
Technical status
In the past five or six years, the progress of flexographic printing technology is indeed enviable. The reason why it is appreciated is that the printing press, 2 anilox roll, 3 plate material, 4 plate making, 5 ink and other aspects have all been innovated. The following is directed to an in-line type flexographic printing machine suitable for narrow webs. Introduce the center.

(1). Flexo printing machine
According to the unit arrangement of a flexographic printing press, there are three types (see Figure 1). In the past, in particular, in the case of printing thin films such as flexible packaging, in terms of overlay accuracy in terms of quality, Flexopak machines manufactured by COMCO Inc. in the United States have adopted soft tension adjustments for the delivery positions. The device was equipped with an S-shaped lap joint mechanism on the part of the unit, equipped with a chill roller on the drying part, and achieved the registration accuracy comparable to the gravure printing. Comparing the Flexopak machines produced by COMCO with those of past printing machines, as shown in Figure 2

In addition, a standard:Drying device is installed on the COMCO machine, which is combined with the development of the ink to realize the printing that can protect the environment. In order to shorten the preparation time and improve the operating performance, rapid change of plate cylinder, anilox roller, ink fountain tank, etc., is equipped with a standard COMCO programming system, which is more conducive to the production activities of many varieties and small batches. According to the latest information, a variable and repeatable system has been completed that can be continuously changed, and the structure is closer to gravure.
(2). Anilox roll
In the past, the core of the anilox roll was chemically etched, or was hard chrome-plated on the surface after mechanical engraving. The number of lines was at most 400-500 lpi, so the number of printing lines was limited to 100-120 lpi. Due to restrictions on print resolution and factors such as poor quality, Japan has not been promoted in the fields of flexible packaging and carton printing. Afterwards, an anilox roller with laser engraving on the iron core was used. The maximum number of lines reached 1200 lpi. The degree of randomness of its ink hole shape has also been expanded. So the number of printing lines can reach 300lpi. At present, the number of gravure printing lines used in packaging printing in Japan is 1200 lpi, and the life of the rollers has also been greatly improved. Therefore, printing for flexible packaging is not a problem at all.
(3). Plates for flexographic printing
Currently used media, rubber, and photosensitive trees (liquids, solids) are the mainstream, and in particular, a photosensitive resin solid plate is used for high-quality printing for packaging printing. The photosensitive resin plate was born from the early 1970s, and since then the printing process has been rationalized, and thin printing plates can be made, and the printing quality is also improved.
The plates used today vary depending on the application. The thickness used for packaging printing is 1.14-1.70 mm, and the hardness is generally 50-60 degrees. The surface state of the plate and its resin composition have a certain influence on the transfer of the ink to the substrate, which is important for the quality. Since the relationship with the ink is relatively close, it is also very important to develop inks conforming to the plate. In view of this, in order to further improve the printing quality, there is a need for close cooperation between the plate material manufacturers and ink manufacturers. In recent times, overseas has gradually adopted the water development version, which is beneficial to environmental protection.
(4). Plates and plates
In the past, through the negative images made in the photographic process, the parts of the image were hardened by ultraviolet light exposure and developed, and non-hardened non-image portions were removed to make printing plates. Recently, this process has been introduced by gravure printing and offset printing. Various types of CIPs that have been developed in the United States and Europe by the use of lasers to image images directly onto the plates by the computer system are listed in the table below. Japan has also introduced them. The comparison between the past process and the CIP process is shown in Figure 3 - see later. Using CIP's direct platemaking, compared with the past method, no film output is required, so that the delivery time is short and the working price is reduced, because the smaller ideas can be reproduced, the reproducibility of bright tuning is improved, and the performance of thin lines and characters is also improved. With greater improvements, the layout of the layout has greatly improved.

(5). Printing ink
The various types of inks currently used are based on synthetic resins, but UV-curable inks (UV inks) without solvent flexographic inks have been widely used as countermeasures against solvents in Europe and the United States. Japanese ink manufacturing The factory also followed up on the development. Compared with water-based inks, UV inks are highly viscous (1000-3000 cps). After hardening, the ink film is durable. The adhesion to various plastic materials and the surface smoothness are also good. It is expected that it will have better development in the future. The UV ink composition is shown in Table 2. At present, free radical UV inks are the mainstream. In the future, from a safety point of view, cationic: inks will become the mainstream in packaging and printing.
In addition, a variety of flexographic printing presses equipped with UV curing devices have been introduced. Here, photos of the Flexopak machines manufactured by COMCO Co., Ltd., which is exclusively used for packaging printing, are introduced (see FIG. 4).
Outlook
After entering the 21st century, in addition to the market environment of the printing industry, that is, multi-species, small-batch, individuation, and low price, in addition to being represented by legalized container packaging recycling and chemical substance excretion management laws, etc. Environmental regulations will become more stringent and become a major issue that must be resolved in the early 21st century.
If we want to solve these problems, we must not, as in the past, make small reforms to production projects or simply change the contents of business operations. We must, however, look to change the mode of production and adopt comprehensive reforms to activate corporate organizations. Let’s start by saying that The problems of gravure printing and offset printing in the period of prosperity, and finally the prospect of flexographic printing.
Gravure printing
The need to deal with the market environment is not a problem in terms of printing speed, but there are limits to adapting to small-volume production. Productivity cannot be improved, and there are still problems with the delivery period.
As for the response to laws and regulations, solvent inks, equipment that requires exhaust (burning, recycling), due to the initial investment, working capital and other problems, plus the need to consider improving the operating environment. It is also necessary to consider the water-based ink, which leads to a decrease in the speed and a drop in productivity. In addition, there are many problems that require drainage treatment devices.
Offset printing
There is no problem in dealing with laws and regulations at present. However, in the printing of films for flexible packaging, new inks and drying methods need to be developed. There are still many unknown areas and it is not easy to solve them immediately. In addition, carbon dioxide from the high-boiling point solvent treatment is also a problem that must be solved from the perspective of global environmental protection.
3. Flexo printing
Water-based, solvent-free (UV-based) and other easy to do, especially UV inks fully meet the needs of environmental protection. In addition, the use of narrow web applications, the time required to replace the work is very small, in the COMCO 16-inch press, each unit only needs 90 seconds to complete the replacement, and rarely go wrong, to deal with small batches and more varieties Compared with the above two methods, it has an absolute advantage, especially when the volume of printed matter is less than 10,000 meters.
At present, the problem encountered is to comprehensively innovate gravure printing for packaging, and it is necessary to solve the problem of high investment and excessive operating load. It is still impossible to do so at the same time. At the same time, subtle quality exists between the flexographic printing and the above two methods. The difference is also a resistance. However, considering the constraints of environmental protection, priority should be given to it. Therefore, it is necessary for the packaging and printing industry to introduce as soon as possible a narrow flexographic printing press that can cope with small batches and short delivery times in order to innovate packaging printing. industry.
If the flexible version of the CIP is further improved, a seamless printing plate in the middle of development will be introduced. When the quality of the other types of layout is not much different, it is not only a small batch.