Since the development of printing technology, a pattern of coexistence of various printing processes such as screen printing, rotary screen printing, roller printing, and digital printing has been formed. The scope of application of various printing processes is different, the process characteristics are different, and the printing equipment and consumables used are also different. As a traditional classic printing process, screen printing has a wide range of applications and occupies a relatively high proportion in the printing industry. In recent years, digital printing has developed rapidly, and many people think that there will be a trend to replace screen printing. What are the differences between these two printing processes? The differences between digital printing and screen printing are analyzed here.
The types of printing materials are not much different
Digital printing is divided into five categories: acid digital printing, reactive digital printing, pigment digital printing, dispersed thermal transfer printing and dispersed direct-injection digital printing. Digital printing acid ink is suitable for wool, silk and other protein fibers and nylon fibers and other fabrics. Digital printing reactive dye ink is mainly suitable for digital printing of cotton, linen, viscose fiber and silk and other fabrics, and can be applied to digital printing of cotton fabrics, silk fabrics, wool fabrics and other natural fiber fabrics. Digital printing paint ink is suitable for digital inkjet paint printing of cotton fabrics, silk fabrics, chemical fiber and blended fabrics, knitted fabrics, sweaters, towels, blankets. Digital printing thermal transfer ink is suitable for transfer printing of polyester, non-woven fabrics, ceramics and other materials. Digital printing direct-injection dispersion ink is suitable for digital printing of polyester fabrics, such as decorative cloth, flag cloth, banners, etc.
Compared with digital printing, traditional screen printing does not have much advantage in the types of printing materials. First, the printing format of traditional printing is limited. The inkjet width of large-scale industrial digital inkjet printing machines can reach up to 3~4 meters. It can be printed continuously, and the length is not limited. They can even form a whole production line; On some materials, traditional water-based ink printing cannot achieve good performance. For this reason, only solvent-based inks can be used for printing, while digital printing can use water-based ink for inkjet printing on any material, which avoids a lot of use. Flammable and explosive non-environmentally friendly solvent.
Digital printing is more colorful
The biggest advantage of digital printing is mainly concentrated in the fineness of color and pattern. First of all, in terms of color, digital printing inks are divided into dye-based inks and pigment-based inks. The color of dyes is brighter than that of pigments. Acid digital printing, reactive digital printing, dispersion thermal transfer printing and dispersion direct-injection digital printing all use dye-based inks. Although pigment digital printing uses pigments as colorants, they all use nano-scale pigment pastes. For a specific ink, as long as a dedicated ICC curve is prepared, the color display can reach the extreme. The color of traditional screen printing is based on the contrast of four-color dots, and the second is controlled by pre-printing ink toning, and the color presentation is not as good as digital printing. In addition, in digital printing, the pigment ink uses nano-scale pigment paste, and the dye in the dye ink is water-soluble. Even in the dispersion-type sublimation transfer ink, the pigment is also nano-scale.
The fineness of the digital printing pattern is related to the characteristics of the inkjet print head and the printing speed. The smaller the ink droplets of the inkjet print head, the higher the printing accuracy. Among them, the ink droplets of the Epson micro piezoelectric print head are the smallest. Although the ink droplets of the industrial head are larger than that, they can also print images with an accuracy of 1440 dpi. In addition, the same printer, the faster the printing speed, the smaller the printing accuracy. Screen printing requires negative plate making first. The error in the plate making process and the mesh number of the screen will affect the fineness of the pattern. Theoretically speaking, the smaller the screen aperture, the better, but 100~150 mesh screen is mostly used in ordinary printing, and the mesh number of four-color dots is 200 mesh. The higher the mesh number, the greater the probability of water-based ink blocking the network, which is a common problem. In addition, the accuracy of the plate during scratch printing has a great influence on the fineness of the printing pattern. Machine printing is relatively good, but manual printing is more difficult to control.
Obviously, color and fine graphics are not the advantages of screen printing, but the advantages of special printing pastes, such as gold, silver, pearlescent color, crack effect, bronzing flocking effect, suede foaming effect and so on. In addition, screen printing can print 3D three-dimensional effects, which are difficult to achieve with current digital printing. In addition, it is more difficult to make white ink for digital printing. At present, white ink mainly relies on imported ink to maintain, but printing on dark fabrics is impossible without white. This is the difficulty that needs to be broken through to popularize digital printing in China.
Digital printing is soft to the touch, and screen printing has high color fastness
The main properties of printing products include surface properties, that is, feel (softness), tackiness, resistance, color fastness to rubbing, color fastness to soaping; environmental protection, that is, whether it contains formaldehyde, azo, pH, carcinogenicity Aromatic amines, phthalates, etc. GB/T 18401-2003 "National Basic Safety Technical Specifications for Textile Products" makes clear provisions for some of the items listed above.
In traditional screen printing, in addition to water sizing and discharge, other types of printing have a stronger coating feel. This is because the resin content as a binder in the printing ink formulation is relatively high, and the amount of ink is relatively large. However, digital printing basically has no coating feeling, and the printing is light, soft, and has good stickiness. Even if it is digital printing with paint, because the resin content in the formula is very small, it will basically not affect the hand feel. Acid digital printing, reactive digital printing, dispersive thermal transfer printing and dispersive direct-injection digital printing, these are uncoated and do not affect the original fabric feel.
Whether in traditional water-based printing ink or pigment printing ink, resin is used as a binder to increase the adhesion between the coating and the fabric on the one hand, so that it is not easy to crack and fall off after washing; on the other hand, the resin can encapsulate the pigment particles, so that it is not easy to decolorize by friction. The resin content of traditional water-based printing inks and pastes is 20 percent ~90 percent , usually 70 percent ~80 percent , while the resin content of pigment printing inks in digital printing inks is only 10 percent . Obviously, theoretically, the color fastness to rubbing and soaping of digital printing will be worse than that of traditional printing. In fact, the color fastness to rubbing of digital printing without certain post-treatment is really poor, especially the color fastness to wet rubbing. Although the color fastness to soaping of digital printing can sometimes pass the test according to GB/T 3921-2008 "Color fastness to textiles color fastness test", it is still a long way from the washing fastness of traditional printing. . At present, digital printing needs further exploration and breakthrough in color fastness to rubbing and color fastness to soaping.
High cost of digital printing equipment
There are three main types of printers used in digital printing. One is the tablet machine modified from Epson desktop, such as EPSON T50 modified tablet. These models are mainly used for small-format digital printing of paint and ink. The purchase cost of these models is much cheaper than other models. The second is printers equipped with Epson DX4/DX5/DX6/DX7 series inkjet print heads, of which DX5 and DX7 are the most common, such as MIMAKI JV3-160, MUTOH 1604, MUTOH 1624, EPSONF 7080, EPSON S30680, etc. The purchase cost of a printer is about 100,000 yuan. At present, the market price of DX4 print heads is 4,000 yuan each, the market price of DX5 print heads is more than 7,000 yuan each, and the market price of DX7 print heads is 12,000 yuan each. The third is industrial inkjet digital printing machines, among which the representative machines include Kyocera industrial nozzle digital printing machine, Seiko SPT digital printing machine, Konica industrial nozzle digital printing machine, SPECTRA industrial nozzle digital printing machine, etc. The purchase cost of printers is generally higher than high. The market price of each brand of print head is more than 10,000 yuan, and one print head can only print one color. That is to say, in order to print four colors, one machine has to install four print heads, which is extremely expensive.
Therefore, the cost of digital printing equipment is extremely high, and inkjet print heads, as the main consumables of digital inkjet printers, are also extremely expensive. The market price of digital printing ink is indeed much higher than that of traditional printing materials, but the printing area of 1 kg of ink output is incomparable with the printing area of 1 kg of ink. Therefore, the cost comparison in this regard depends on factors such as the type of ink used, specific printing requirements and printing process.
In traditional screen printing, screen plates and squeegees are consumables during manual printing, and labor costs are more significant at this time. Among the traditional printing machines, imported octopus printing machines and elliptical machines are more expensive than domestic ones, but domestic models have become more and more mature and can also meet the requirements of production and use. If you compare it with an inkjet printer, its purchase cost and maintenance cost are much lower.
Screen printing needs to improve environmental protection
In terms of environmental protection, the environmental pollution caused by traditional screen printing is mainly reflected in the following aspects: the amount of waste water and waste ink generated in the production process is quite large; in the printing production process, it is more or less necessary to use some bad ink. The solvent, even plasticizer (thermosetting ink may add unenvironmental plasticizer), such as printing water, decontamination oil, white oil, etc.; printing workers will inevitably come into contact with chemical solvents, Glue, toxic cross-linking agents (catalysts), chemical dust, etc., have an impact on the health of workers.
In the production process of digital printing, only a certain amount of waste liquid is generated in the pre-treatment sizing and post-treatment washing process, and waste ink is rarely produced in the entire inkjet printing process. The whole source of pollution is less than that of traditional printing, and it has less impact on the environment and the health of contacts.
In short, digital printing has a wide range of printing materials, bright colors, fine patterns, good hand feel and strong environmental protection of printed products, which are its typical characteristics. However, inkjet printers are expensive, with high consumables and maintenance costs, which are its drawbacks. It is difficult to improve the washing fastness and rubbing fastness of digitally printed products; it is difficult to develop stable white ink, resulting in better printing on black and dark fabrics; due to the constraints of inkjet print heads, it is difficult to develop Ink printing with special effects sometimes requires pre-processing and post-processing, which is more complicated than traditional printing. These are the disadvantages of current digital printing.
In order to develop steadily in the current printing industry, traditional screen printing must grasp the following points: improve the environmental protection of printing inks, control environmental pollution in printing production; improve the existing special printing effect printing, and develop new printing special effects , leading the printing trend; keeping up with the 3D craze, developed a variety of 3D printing effects; while maintaining the washing and rubbing color fastness properties of the printed products, the conventional printing developed imitation digital non-touch, light and thin printing effects; developed wide-format printing It is best to develop a printing assembly line platform; simplify printing equipment, reduce the input of consumables, improve the input-output ratio of printing, and enhance the competitive advantage with digital printing.