The principle and process of digital inkjet printing
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Digital inkjet printing, also known as color inkjet printing, is to input the required graphics into the computer through an input device such as a scanner or a digital camera. After editing and processing by the electronic color separation system, the inkjet system is directly controlled by the computer. Printing dyes or pigments onto fabrics for printing, inkjet printing can be divided into continuous inkjet and drop-on-demand inkjet according to the inkjet principle.
1. Continuous jet type CIJ (ContinuouslnkJet)
The principle of continuous jetting is to apply a high-frequency oscillating pressure to the ink to eject the ink from the nozzle to form a uniform continuous flow of droplets. An electric field that changes in synchronism with the pattern photoelectric conversion signal is provided at the nozzle. The ejected droplets are selectively charged in the charging electric field. When the droplet stream continues to pass through the deflecting electric field, the charged droplets are deflected by the electric field, and the uncharged droplets continue to maintain a straight flight state. Straight flight of droplets
Can not reach the substrate and be recovered by the liquid collector. The charged droplets are ejected onto the substrate to complete the printing.
2. Drop-on-demand DOD (DropOnDemand)
The working principle of the on-demand jet printing system is that when printing is required, the system applies high-frequency mechanical force and electromagnetic thermal shock to the ink in the nozzle, so that tiny droplets are formed to be ejected from the nozzle, and the jet is controlled by the computer. Set the pattern. The most popular application of the on-demand jet type is thermal inkjet technology, which relies on thermal pulsation to generate ink droplets, and a heating resistor wire is controlled by a computer to a predetermined temperature, so that the ink gas (fog) is ejected from the nozzle. Another DOD technology is a voltage injection system in which a potential is imposed on a conductive material by a computer to cause the conductive material to compress in the direction of the electric field and to expand in the vertical direction, thereby causing the ink to be ejected.
Inkjet printing not only requires high-precision nozzle technology, high-precision control technology, but also requires high purity, high concentration, high fastness, high stability ink (ink) to match it.
3. Digital inkjet printing process
The process of inkjet printing depends on the ink used. Generally, acid dyes are mainly used for carpet printing, disperse dyes are mainly used for polyester fabrics, and reactive dyes are mainly used for cotton fabrics. The following is an example of a reactive dye ink used in an inkjet printing process for cotton fabrics.
Fabric pretreatment → prepress printing → inkjet printing → postpress drying → steaming (100 ~ 102 ° C, 8 min) → water washing → drying.
The pretreatment of the fabric is mainly due to the wettability of the fabric and the capillary effect between the fibers. In the conventional fabric printing paste, a suitable printing filler must be used to prevent seepage. The general inkjet printer can only use low-viscosity water-based ink. If it is directly printed on the fabric, the dye solution will permeate in all directions, so the printed fabric must be properly pretreated. Spray printing with special software at the right resolution
Line, pattern printing, post-processing of printed fabrics is mainly to improve their fastness to color.