The principle and process of digital inkjet printing

Digital inkjet printing, also known as color inkjet printing, uses a scanner or digital camera as an input device to input the desired text into a computer, edited by an electronic color separation system, and then directly controlled by the computer's inkjet system. Dyestuffs or pigments are sprayed on fabrics for printing. Inkjet printing can be classified into continuous ink-jet and drop-on-demand according to the ink jet principle.

1. Continuous jet CIJ (ContinuouslnkJet)

The continuous jet principle is to apply a high frequency oscillating pressure to the ink, so that the ink is ejected from the nozzle to form a uniform continuous droplet flow. At the nozzle there is an electric field that changes in synchronization with the graphic photoelectric conversion signal. The ejected droplets are selectively charged in the charging electric field. When the droplet stream continues to pass through the deflection electric field, the charged droplets are deflected by the electric field, and the uncharged droplets continue to maintain the straight flight state. Straight flying droplets

Can not reach the substrate and be collected by the liquid trap. The charged droplets are ejected onto the substrate to complete the printing.

2. Drop On Demand

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 it forms tiny droplets to be ejected from the nozzle and is controlled by a computer to eject the ink. The pattern is set. The most widely used on-demand spray type is thermal ink jet technology, which relies on thermal pulsation to generate ink droplets. A computer controls a heated resistance wire to a specified temperature, causing ink gas (fog) to be ejected from the nozzle. Another DOD technique is a voltage-type injection system, in which a computer controls the application of a potential to a conductive material to cause the conductive material to compress in the direction of the electric field and expand in the vertical direction to eject the ink.

Inkjet printing not only requires high-precision nozzle technology, high-precision control technology, but also requires the use of 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 an ink jet printing process using reactive dye inks for cotton fabrics.

Fabric pretreatment → prepress drying → inkjet printing → postpress drying → steaming (100-102°C, 8min) → washing → drying.

The pretreatment of fabrics is mainly due to the wettability of the fabrics and the capillary effect between the fibers. Appropriate printed fillers must be used in conventional fabric printing pastes to prevent bleedout. The general inkjet printer can only use low-viscosity water-based ink. If it is directly printed on the fabric, the dye liquor will be permeated in all directions, so the printed fabric must be properly pretreated. Use special software for inkjet printing at appropriate resolution

Lines, pattern printing, printing fabric post-processing is mainly to improve its fastness.