Application of Soft Gravure Printing Technology in Plastic Soft Packaging Printing (I)

Plastic flexible packaging printing mainly adopts two printing methods: gravure printing and flexo printing. Gravure printing is the earliest and most widely used printing method in the field of plastic flexible packaging. Due to the high efficiency of gravure printing, it can print more elaborate patterns and conform to the oriental aesthetics, so it is very popular among users in the field of packaging and printing. However, gravure printing ink using toluene, butanone, ethyl ester, etc. as the solvent is relatively polluted to the environment, and is not environmentally friendly, which restricts the development of gravure printing. Flexo printing is a new printing method. It has emerged in the field of plastic flexible packaging printing with the advantages of fast printing speed, short plate-making cycle, small tension, and environmental protection. It is the trend of plastic flexible packaging printing in the future. China has introduced a number of wide-width, narrow flexographic printing production lines and achieved good results. Flexo printing has never been accepted by the market and matured into technology. It has been generally accepted as a fashionable stage. This article discusses in detail the respective characteristics of gravure printing and flexographic printing in plastic flexible packaging printing and the differences between the two, for the use of the industry for reference.

The gravure plastic flexible packaging has the advantages of exquisite printing, good barrier property, light weight, softness, small space occupation, low cost and cost effectiveness (volume and area per unit weight packaging), and it fully exerts the three functions of the packaging. The progress of the gravure plastic flexible packaging industry has greatly promoted the development of the food industry and other industries. The development of these industries has in turn further stimulated the market's demand for plastic flexible packaging and enabled the gravure plastic flexible packaging industry to gain tremendous market momentum.

Gravure printing is characterized by rich layers, thick ink layers, bright colors, and rich three-dimensional. Its ink layer is more than 5 times thicker than plain printing products, more than 2 times thicker than embossing, and is about O. O1 mm.

Because gravure printing has the advantages of being able to print on various large-format substrates such as high-grade paper, rough paper, plastic film, and metal foil, and can achieve high quality, it has been adopted by packaging and decorating industries at home and abroad. Gravure printing plates are resistant to printing forces, and the greater the number of packaging prints, the more suitable gravure printing is used. In a word, gravure printing is mainly suitable for commercial promotion and printing of commodity packaging and decoration materials, such as various shapes of trademarks, folding cartons, flexible packaging materials (cellophane, vinyl film, polyethylene film, polypropylene film, polyester, nylon, etc.) , gift packaging materials, various types of packaging paper and other commodity packaging, decoration materials.

Gravure is divided into three types: engraving gravure, gravure gravure and gravure gravure. The gravure used in packaging printing generally adopts the traditional photogravure, also known as the shadow edition, and some use the more advanced photo dot gravure or electronic engraving gravure, laser engraving gravure.

1. The principle of plate-making of electronic engraving gravure is as follows: on the electronic engraving machine, using the photoelectric principle, according to different layers of the manuscript in the manuscript, the different light quantity reflected by the light source, the lifting and lifting distance of the engraving tool is controlled, and the preprocessed metal plate engraving is carried out , get the text. The degree of darkness of the printing plate layout changes according to the shade of the original document, and the copied printing image is similar to the original image.

Electronic engraving operation method: a thick manuscript with a continuous tone image and text is placed on an electronic engraving machine, and a signal is stored in a computer through a scanning head, and then the computer reflects the shades of the manuscript in different shades of light. The strength becomes current, and the diamond engrave needles according to the size of current draw different shades of the dots to form a gravure plate.

2. The laser engraving gravure engraving system is a comprehensive utilization of laser technology and electrochemical technology. The laser and electron beam engraving systems are a series of processes in which a low-power, high-speed laser is used to control diamond knives in a series of processes, which are inscribed on a pre-processed plate.

3. Photogravure is a traditional way of making gravure. At present, many factories in China still use this method to produce gravure cylinders. It differs from dot-dot printing in that it relies on the size of the dots to achieve the shades of the picture. The indefiniteness of the picture on the gravure is directly related to the level of the copy. The formation of photogravure depth must be achieved through the transfer of graphic and text on carbon paper and the corrosion of acidic solution.

Flexo printing

Flexo printing is a type of letterpress printing. The printing plate structure of flexographic printing is the same as the copper and zinc relief plates, that is, the graphic part is higher than the non-graphic part, and the printing method is also direct imprinting. The basic features of the printing process are:

1 Wide applicability. Suitable for printing on any substrate, either on rough-surfaced cardboard or absorbent sanitary paper, or on smooth paper surfaces, or even plastic films, metal foils and all types that are not absorbed on the surface. The composite material is printed in exquisite color graphics.

2. high productivity. Flexible printing plates have evolved from the original poor-quality rubber plates into today's flexible, photosensitive synthetic rubber plates with stable quality and high resistance to printing. The ink used was also developed from a volatile liquid color ink made of aniline dye into a water-based ink and an ultraviolet drying ink. Due to technological improvements, the production efficiency of today's flexographic printing is indeed higher than ordinary embossing, plain printing and even gravure printing. The reason is that the plate making is simple, the cost is low, and the plate loading is also convenient. The flexo printing press has high speed, simple mechanical structure and easy operation. It can print multiple colors at a time, and can also complete several color printing at the same time. Printing inks are bright, clear, short in printing cycle, and printing plates are resistant to printing forces. All these have created favorable conditions for increasing production efficiency and reducing production costs.

3. Many specifications of the press. Printers can be selected based on the purpose and size of the substrate, from small strips that can print a few centimeters, to substrates that are several meters wide. Flexographic printing with these characteristics can play a decisive role in the printing of packaging and decorating products today. First of all, it has a wide range of applications. Printed materials with different properties are suitable for flexographic printing. For example, various types of paper, paperboard, plastic films, plastic sheets, pressure-sensitive adhesive tapes, aluminum foils, and various types of composite materials used in trademarks, merchandise, packaging, and decorating can be printed by flexo printing. In addition, flexographic printing is more flexible than other types of printing, and has a short printing cycle, high speed, and relatively low cost, and is suitable for printing various kinds of packaging and decorating materials that are also suitable for large-volume batch printing.

The comparison and competition between gravure and flexo have been going on for more than 20 years. In the past 10 to 15 years, the application of new technologies (such as ceramic anilox, closed squeegee, sleeve type plate cylinder, electron beam engraving technology and computer technology) in flexo printing has improved the flexibility Printing quality at the same time also increases the cost of flexo printing. Today, the fact that both flexographic and gravure technologies coexist and begin to merge with each other tells us that they all have the rationality of existence and their respective market demands. Especially in recent years, with the deepening of the concept of environmental protection and the global financial crisis, packaging producers and end users have begun to pay attention to flexographic printing. Because of simple graphics, low hiding power requirements, low order volume, and non-recurring orders, especially those with shorter lead times, the advantages of flexo printing are obvious. As long as flexo printing continues to maintain its advantages of “short (short version of live), flat (low cost), and fast (delivery of delivery)”, flexographic printing will still have a healthy development in China.

Gravure printing and flexo printing are two completely different printing methods. Each has its own advantages and disadvantages, and each has its own adaptation field. The performance of the two is shown in the following table. In general, the gravure print has a high degree of fineness and a strong sense of hierarchy, while the flexographic print has an accurate overlay and a good three-dimensional effect. In particular, flexo and gravure mainly differ in the following points.

(to be continued)