Overview of the hottest digital inkjet printing

Comprehensive description of digital ink-jet printing

digital ink-jet printing began in the 1970s. It applies computer ink-jet printing technology to textile printing, uses scanners, digital cameras, digital cameras and other input means to digitally input the required patterns into the computer, uses the printing color separation system (CAD) designed with computer assistance to quickly generate color separation patterns, and then uses the digital ink-jet printing machine, The printing ink is directly sprayed onto various fiber fabrics to print various patterns required

I. technical characteristics of digital ink-jet printing

to sum up, digital ink-jet printing technology has the following characteristics

1. Digital ink-jet printing is a new high-tech, which greatly simplifies the printing process, eliminates the complicated production processes of traditional printing, such as color separation, pattern design, sizing, printing, post-treatment, and saves a lot of auxiliary equipment and related costs. In addition, flexible production can be carried out on demand, and the production batch is flexible. It can be made separately or in large quantities. The design and production of printing products can not only quickly meet their order needs, but also have great randomness, fast and flexible, adapt to small batch, multi variety and personalized production, have strong market adaptability, and the printing cost of small batch production (within 200 m) is lower than that of traditional printing. The whole equipment covers a small area and can be printed in offices and homes. In addition, it has unique advantages in personalized production

2. The printing accuracy of digital ink-jet printing can reach 720 lines, while the traditional screen printing can only reach 200 lines. The overprint accuracy of digital ink-jet printing machine is high (alignment accuracy, repetition accuracy ± 0.1 mm), and there is almost no problem of inaccurate alignment and chromaticity. No matter what kind of pattern and how many kinds of chromaticity, it can be directly printed. In addition, it can be printed on any surface without considering the porous structure of the fabric. It avoids the pollution of a large number of reducing agents and the waste of dyes in the "engraving and printing" process of the traditional process, and also ensures the bright color light and fastness. Digital ink-jet printing pattern precise control, easy operation, high efficiency, can make full use of fabric area, do not waste grey cloth. On the basis of several basic colors, 16.7 million colors can be generated by computer mixing. High printing accuracy provides designers with rich imagination space, making the production of high-definition printed textiles possible, which are unmatched by traditional printing

3. Design modification is flexible

the design sample can design patterns arbitrarily on the computer, modify colors, patterns, etc., and fully display the designer's design concept and aesthetic concept. It is not limited by the number of color sets in the pattern, and can print high-quality tonal effects. In traditional printing, the pattern of color separation is usually designed. Once the sample is determined, it is difficult to create and modify again, and it is unable to flexibly and quickly adapt to market changes. In addition, the digital printing machine realizes personalized e-commerce consumption through Internet. Consumers can transmit their own patterns, personal data and requirements to manufacturers through the Internet. Based on this, manufacturers can immediately arrange production and send products to consumers

4 . Data storage is convenient to ensure that different batches of colors are consistent

all the data and process plans required in the production process of digital ink-jet printing are stored in the computer, and the computer automatically remembers the data of various colors, which can ensure the reproducibility of printing, and solve the problem of file preservation in the process of traditional printing, which is significantly accelerated with the pace of capacity reduction in the industry. Ensure that the color data remains unchanged in batch production and the consistency between small samples and large samples. And because the pattern and color data are processed by digital technology, it is not easy to copy and counterfeit. In addition, because the pattern data is stored in the computer, it is easy to update the pattern and color. As long as the digital information of the new pattern and color sequence is input into the machine, it can be completed, which not only improves the ability to meet the market demand, but also has no worries about inventory

5. No flower return problem

the process of digital printing is not constrained by flower return. After being processed by intelligent RIP software, it can spray print patterns up to tens of meters without any splicing. In addition, digital ink-jet printing has strong adaptability. It can print exquisite patterns directly on natural fiber fabrics such as cotton, hemp, silk, etc., and it can also print on chemical fiber fabrics such as polyester through a transfer machine. Internationally, digital ink-jet printing has been successful in the field of high-end clothing and personalized home textiles

6. In line with green environmental protection

digital printing is a green production method. There is no water in the spray printing process, no preparation of color paste, no pollution of waste liquid, waste water, waste pulp, no waste and waste of dyes and additives. The utilization rate of printing dyes is up to 90%, no pollution in the production process, and low noise in the printing process. It also does not produce any waste, which is fast and slow (such as residual color paste, sewage, etc.), and does not pollute the environment

II. Digital ink-jet printing process and the use of inks

the process flow of digital ink-jet 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. In digital ink-jet printing, attention should be paid to the pretreatment and post-treatment of fabrics. Although the sprayed ink already contains a large number of colorants and some necessary surfactants and additives, there are still many materials that can only be applied in fabric pretreatment, such as darkening agent, leveling agent, color fixing agent and necessary thickener. After fabric pretreatment, the quality of pigments sprayed on fabrics cannot be affected. In ink-jet printing, different pretreatment processes must be applied for different fabrics, fibers and pigments. Due to the wettability of fabric and the capillary effect between fibers, appropriate printing paste must be used in conventional fabric printing paste to prevent seepage. The general inkjet printer can only use low viscosity water-based ink. If it is directly sprayed on the fabric, the ink will seep in all directions, so the printed fabric must be properly pretreated. After printing, the fabric also needs to adopt appropriate post-treatment processes according to different requirements, such as color fixation, washing, drying, etc., in order to improve the color fastness of the fabric

digital ink-jet printing is fine, accurate in color and light, fast in printing, excellent in printing quality, not prone to printing defects, and suitable for printing of all kinds of fabrics. However, because different fabrics such as cotton, wool, hemp and chemical fiber have their own characteristics, different special inks should be used. In digital ink-jet printing, by exerting external force on the ink, it is sprayed onto the fabric through the nozzle to form color dots. Digital technology controls the ink-jet volume of the nozzle and the movement in the X and Y directions, which can form a corresponding and accurate image on the printed medium. Because the whole image is composed of small color dots, a higher resolution is required, but limited by the warp and weft density of printed fabric, the resolution should not be too high, and the improvement of resolution requires higher requirements for the spray frequency and positioning accuracy of the nozzle. Generally speaking, 360 ~ 720 DPI can achieve the effect of high definition, while 1440 DPI has been regarded as a pointless state. Digital ink-jet printing is characterized by dot circles, high dot density and low through printing, high affinity for the backing cloth and good firmness. Therefore, it requires high-precision nozzle and mechanical control technology, high stability and high-quality printing ink. In digital ink-jet printing, there are two ways: Y M C K ink-jet printing with high-precision nozzle (i.e. dot matrix) and pre mixing (i.e. the dye is pre mixed into a certain color and sprayed on the fabric). YMCK ink-jet printing is a widely used printing method at present. When using YMCK method for printing, in order to obtain high fineness and smooth light color transition, high resolution must be required, which requires that the diameter of the nozzle is very small. As Wang Wei said, the requirements for ink are also very high, and it is difficult to improve the ink-jet speed, but the number of dyes used is relatively small, and the basic color is four colors. The pre mixing method does not require high fineness of the nozzle. 180 DPI can meet the general requirements, and 360 DPI can obtain a very fine printing effect. The printing product is close to the printed style. Due to the large diameter of the nozzle, the requirement for dyes is not high

the world's major dye companies and companies producing ink-jet printing machines have carried out research on ink-jet printing inks. For example, Ciba Specialty applied for the patent of reactive dye ink for ink-jet printing. Reactive dyes containing reactive groups are used in digital ink-jet printing inks. First, inorganic salts in the dyes are removed by membrane separation methods such as ultrafiltration and reverse osmosis, and solubilizing solvents, methyl cellulose, ethyl cellulose or alginate are added as thickeners, Then add p h buffer and anti mildew agent to form inkjet ink, and print with micro piezoelectric inkjet printing machine, the effect is ideal. Canon applied for a patent for the preparation of disperse dye inkjet ink, which can be used for fabric printing with a hot foaming inkjet printing machine. The processing method of the ink is: add the dye into deionized water, add organic solvents such as diethylene glycol, stir for 2 hours and then filter to obtain the ink. Viscosity regulator, surface tension regulator and fluorescent brightener can be added when necessary, and the importance of fabric pretreatment is emphasized. In addition, pigment inkjet printing ink is also the focus of recent development. This kind of ink can be used for all kinds of fibers and their blended fabrics, and satisfactory color fastness can be obtained without fabric pretreatment

III. problems needing attention in digital ink-jet printing

ink-jet printing is developed on the basis of paper ink-jet printing. Therefore, some operating points and problems needing attention in the use of ink-jet printers can also be used for reference in ink-jet printing. Compared with paper ink-jet, due to the diversity of fabric varieties and raw material types, especially the particularity of color fastness and hand feel required by printed fabrics, There are differences between paper inkjet printing and fabric printing, and there will be more problems in fabric inkjet printing

1. Standard operation and good environment

to operate reasonably and be diligent in maintenance, we must complete the whole operation in strict accordance with the instructions, especially to develop the correct habit of turning on and off, which is of great importance to the maintenance of inkjet printing machine. Generally, when turning on and off, the printing machine should carry out system initialization detection, preparation, automatic cleaning of the print head, etc., so as to ensure normal operation, eliminate hidden troubles, ensure the normal use of ink, reduce the loss of machine materials, etc. When the printer is powered on, do not forcibly unplug the power plug and shut down abnormally, which is very easy to cause the positioning failure of the print head. In order to ensure the good operation of ink-jet printing, it is generally required that the product oil market is wide, the working environment temperature is 15 ~ 35 ℃, and the humidity is 20 ~ 80%, and the environment should be free of dust, static electricity and other interference as far as possible. Countless tiny nozzles are distributed on the nozzle of the inkjet printing machine, which is exposed to the air when it is not working

2. Choose high-quality inks

inkjet printing consumables are mainly inks. The original inks have quality assurance, but the price is relatively expensive. When using compatible (filling) inks, we must choose inks with quality assurance. If you use unqualified ink, it will not only seriously affect the quality, but also easily cause damage to the machine. Ink jet printing requires the following inks: