Traditional inkjet printing nozzles use two methods, and there are still certain differences compared with UV flat-panel printing nozzles.
1. Continuous jet
The principle of the continuous jet is to apply high-frequency oscillating pressure to the nozzle to form a uniform and continuous stream of droplets. An electric field that changes synchronously with the pattern photoelectric conversion signal is provided at the nozzle. The ejected droplets are selectively charged in the charging electric field. When the flow of droplets continues to pass through the deflection electric field, the charged droplets are deflected under the action of the electric field, and the uncharged droplets continue to maintain a straight flight state. The droplets flying in a straight line cannot reach the substrate and are recovered by the liquid collector. The charged droplets are ejected onto the substrate to complete printing.
2. On-demand jetting
The working principle of the on-demand jet printing system is that when printing is needed, the system applies high-frequency mechanical force and electromagnetic thermal shock to the nozzle to form tiny droplets that are ejected from the nozzle, and the computer controls the jet to the device. Set the pattern. The most widely used jet-on-demand technology is thermal inkjet technology, which relies on heat pulsation to produce ink droplets. A computer controls a heating resistance wire to a specified temperature, resulting in a pneumatic pressure jet system, which is controlled by the computer on the conductive material. Imposing electric potential causes the conductive material to compress in the direction of the electric field and expand in the vertical direction, thereby causing ejection.
3. The process of digital inkjet printing
Inkjet printing not only requires high-precision nozzle technology, high-precision control technology, but also requires ink with high purity, high concentration, high fastness, and high stability. The process of inkjet printing depends on the process 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 the inkjet printing process of reactive dyes used on cotton fabrics.
Textile pretreatment → pre-press drying → inkjet printing → post-press drying → steaming.
The pretreatment of textiles is mainly due to the wettability of the textiles and the capillary effect between the fibers. In conventional textile printing pastes, appropriate printing fillers must be used to prevent permeation. Generally, inkjet printers can only use low-viscosity water-based inks. If they are directly printed on the fabric, the dye liquor will permeate in all directions. Therefore, the printed fabric must be properly pretreated. In jet printing, special software is used to print lines and patterns with appropriate resolution. The post-processing of printed fabrics is mainly to improve the colorfastness.
It can be seen from the above that there is still a certain gap between traditional inkjet printing and UV flatbed printers. Micolorprint’s UV flatbed printer uses micro-piezoelectric technology, printing is not interfered with by external factors, the ink does not need to be heated, and the color is guaranteed to be pure, that is, it dries immediately, and it does not need to go through the second process. It has high printing accuracy and printing speed. Soon, it has been sought after by customers.