Overview of flexographic printing

Murata Laser Roll (Shanghai) Co., Ltd. Provided by Wang Weizhong

I. Introduction

At the end of the 19th century, the British used a rotary rubber plate printing machine to print simple trademarks, paper bags and printing on packaging paper. Because aniline dyes were used to make ink, they were called flexographic printing. Soon, it spread to Europe and spread to the United States in the early twentieth century. Through the improvement of inks, printing machines, and dryers, we began to print simple patterns and text on cellophane, which was quickly recognized by the society. Around 1940, the United States invented the anilox roller, which greatly improved the quality of printing.

In 1952, at the printing conference held in Stockholm, Sweden, the title of flexographic printing was completely rejected, and the participants unanimously agreed to change to Flexography. The meaning of the discussion on it at the time was that because photosensitive resin had sprouted and the emergence of polyethylene and polyester, the carrier for printing was greatly increased, so the application path of Flexography is flexible and can be suitable for printing for various purposes. Because of this name, domestic translators literally translated it into flexographic printing without knowing its background, which has been passed on and is still in use today. In the first half of the twentieth century, after being used to print transparent non-absorbent packaging material cellophane, its application expanded rapidly, involving polyethylene and various synthetic resin films. As a printing method for packaging materials, it laid the foundation in Europe and the United States.

2. The status quo of flexible printing in Europe, America and Japan

The market share of water-based printing in the United States is approximately 65%. The proportion in Europe is about 36%. Japan is only 3%. Although Japan does not have as many flexible printing equipment as Europe and America, why is there such a big gap? The first is because of different values ​​for packaging. The so-called flexo printing is a type of letterpress printing, using a soft version. Simply put, it is a roller-shaped stamp. Although this is less accurate than gravure printing, it is cheap and easy to operate. But in Japan, what people demand is a pretty exquisite packaging print without any stains and color differences. In Europe and the United States, a slight flaw is not a problem, and it can still be displayed with confidence. It is this difference in values ​​that has created a very different status quo in the two places.

Secondly, the use of chemicals in Europe and the United States is very strict, and the amount of industry control is implemented. The total limit does not refer to a single enterprise, but refers to the entire industry. For printing, not only gravure printing, but all types of printing companies are included. For example, after a new printing company is completed, it cannot start production without obtaining the right to use it. It must be transferred or purchased from other companies that have the right to use before it can be produced, so a large number of environmentally friendly flexible printing companies have appeared in Europe and the United States. In addition, because Japanese printing plants have not yet adopted independent restrictions on the use of chemicals such as p-toluene and MEK, it is difficult for them to enter the strictly regulated European and American markets.

3. Development of Japanese Flexible Printing

Japan introduced this technology from the beginning of the twentieth century to print corrugated paper, paper bags, etc. Unlike Europe and the United States, it has not been used in the field of flexible packaging materials and cartons at the beginning. Gravure and offset printing technologies have met the needs of the country, and flexo printing has not been widely popularized in Japan, and has almost stagnated in the past 20 years. With the continuous improvement of flexographic printing technology, it has caught up with gravure and offset printing in environmental protection and printing quality, which has increasingly attracted the attention of the Japanese printing industry. Therefore, in recent years, flexographic printing has developed by leaps and bounds.

In the past 10 years, flexible printing has become the mainstream printing method in Europe and America. In the European flexo market, the printing of cardboard boxes is growing at a rapid rate of 4-8% per year. At the same time, in the field of flexible packaging printing, there is also a clear tendency to shift from gravure printing to flexible printing. Japan has also gradually recognized the advantages of flexible printing in terms of environmental protection and production efficiency, but its enthusiasm for use is far less than that in Europe. Especially for those customers who pay attention to the reduction effect of printing, many people still think that the effect of flexible printing is not as good as offset printing and gravure printing. But in fact, with the advancement of CTP for flexible printing and the emergence of flexible printing machines with toothless transmission structure, substantial progress has been made in improving accuracy. With the arrival of a new round of printing equipment update cycle, a large number of newly introduced flexible printing equipment provides hardware guarantee for the future development of flexible printing technology applications in Japan.

Fourth, the scope of application of flexible printing

More and more companies try to achieve the differentiation of commodities through the colors of packaging, so that people have higher and higher requirements on the degree of exquisite printing. Regardless of the uneven, elastic and thick print carrier, flexible printing can exert its good advantages in terms of color reproduction.

Flexible printing is made by printing an aqueous ink or UV ink on a high elastic resin relief plate with a certain thickness through an anilox roller, and then printing directly on a printing carrier. Therefore, flexible printing has strong adaptability to materials with poor surface smoothness (such as corrugated paper, etc.) and film, cloth, and non-woven fabrics. And the multi-color (such as 8-color) printing of stretchable film and film has a good performance in color reduction. At the same time, flexible printing is very suitable for thin and uniform coating printing. By overlapping various resins and drugs, it has become possible to further improve accuracy. In recent years, with the advancement of materials and printing processes used for flexible printing, it is possible to produce exquisite color printed products through high line count printing. Needless to say, the stable display of fine print, even the expressiveness of the sense of hierarchy has been significantly improved. For example, a gradation level of 2 to 98% can be expressed with the number of printed lines of 150 lines.

Fifth, what kind of material can flexible printing be printed on

Corrugated cardboard should be the most suitable for flexible printing. It is generally believed that about 80% of the corrugated cardboard on the market is printed by flexible printing. A major feature of flexo printing is that it uses soft plates. Until now, 7 mm thick rubber (resin) plates are generally used for flexible printing, which can avoid the influence of uneven surface materials like corrugated cardboard on printing. In addition to corrugated cardboard, it can be said that flexible printing is most suitable for materials with poor smoothness such as nonwoven fabrics and paper napkins.

Because the aforementioned prints require mostly printing accuracy of only about 65 lines, many people have the feeling that flexible printed products can be seen as long as they can be seen clearly, not to mention any requirements for print quality. However, recently, flexible printing is not only limited to those rough and difficult-to-print printing materials. Like offset printing and gravure printing, this emerging printing method is increasingly accepted by traditional prints.

At present, it is not only packaging materials such as corrugated paper, paper bags, shopping backpacks, and packaging paper, but also paper containers such as cosmetics and snack boxes, and liquid beverage paper containers such as milk bags. Flexible packaging materials for fast food noodles and snacks, diapers and rice bags are all using flexible printing. Packaging materials, paper bags widely used in the commercial and medical fields, as well as labels that have been used for a long time, paper napkins, non-woven fabrics, magnetic tapes, bellows, etc. also use flexible printing. In fact, not only the corrugated board, but also the flexible printing method is gradually being favored in the field of flexible packaging.

For flexographic printing, for printing materials with high smoothness (printed materials that do not require high degree of softness of the plate), you can use a relatively thin plate, such as 1.14 mm to 1.70 mm, which can also print products with more than 150 lines. Some can even achieve a printing accuracy of 200 lines.

Sixth, flexible printing is "mother's choice"

From destroying and polluting the environment to caring for "people" and "Earth", with the enhancement of people's environmental awareness, flexible printing can fully comply with the requirements of laws and regulations in this regard.

Although flexible printing can use a variety of printing inks such as water-based inks, UV inks, solvent inks, flexible printing in Europe and the United States has been highly recognized for its use of environmentally friendly water-based inks. In some printed materials that directly contact the human body, especially food and pharmaceutical packaging, flexible printing has gained an overwhelming market share. At the same time, because the amount of ink used is small, the amount of residual solvent is also small, which is also particularly suitable for the printing requirements of food packaging. In addition, water-based inks use alcohol-based solvents, so there is no problem with product safety.

In 2002, Japan ’s Saitama Prefecture promulgated environmental regulations, and various types of printing plates were controlled. Chiba Prefecture, Tokyo and other places are also preparing to issue corresponding regulations. With the recent enhancement of national environmental awareness, the environmentally friendly flexo printing method is more worthy of our expectations.

5. Unparalleled high production efficiency

Another advantage of flexible printing is its high production efficiency. The flexible printing machine can complete the integrated production from roll paper to post-processing at an unprecedented high speed. By virtue of this, the flexible printing machine can achieve uninterrupted continuous processing including post-print processing, thereby greatly improving production efficiency. Recently, multi-variety and small-batch printing has gradually become a trend, and flexible printing just conforms to this trend. At the same time, because of its integrated production, it has an advantage in quality control.

When we see the printed product, we often hear the exclamation, "Is this really a flexo product?"

In recent years, the thickness of corrugated cardboard has become thinner and thinner. Fine corrugated paper that is slightly thicker than ordinary paper appears. Direct printing on corrugated cardboard makes the advantage of flexible printing more and more people's attention. Those who are engaged in the production of cartons (folding boxes) and flexible packaging related to food, as well as those who try to differentiate the products through the colors of the outer packaging, please be sure to try flexible printing.

A French press, also known as a cafetière, сafetière à piston, Cafeteria, press pot, coffee press, or coffee plunger, is a coffee brewing device patented by Italian designer Attilio Calimani in 1929.
A French press works best with coffee of a coarser grind than does a drip brew coffee filter, about the consistency of kosher salt. Finer grounds, when immersed in water, have lower permeability, requiring an excessive amount of force to be applied by hand to lower the plunger and are more likely to seep through or around the perimeter of the press filter and into the coffee. Additionally, finer grounds will tend to over-extract and cause the coffee to taste bitter. Coffee is brewed by placing the ground coffee in the empty beaker and adding hot-between 93–96 °C (199–205 °F)-water, in proportions of about 30 g (1.1 oz) of coffee grounds to 500 ml (17 US fl oz) of water, more or less to taste. The brewing time is about two to four minutes. The plunger is pressed to separate the grounds and hold them at the bottom of the beaker. The mesh piston normally does not compress the coffee grounds, as most designs leave a generous space-about 30 mm (1.2 in)-below the piston in its lowest position. If the brewed coffee is allowed to remain in the beaker with the used grounds, the coffee may become astringent and bitter, though this is an effect that some users of the French press consider desirable. It is believed that the optimum time for brewing the coffee is around four minutes, and some consider the coffee spoiled after about 20 minutes. Other approaches, such as cold-brewing, require several hours of contact between the water and the grounds to achieve the desired extraction.

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