Indian Journal of Fibre & Textile Research Vol. 26. March-June 2001. pp. 156-161 Inkjet printing-A revolutionary ecofriendly technique for textile printing Sanjay Gupta" National In stitute of Fash ion Technology. Hauz Khas, Ne w Dcl hi 110016, India Some of thc aspects of inkjct or di gital printing, such as com pari son bctwecn conventional and di gita l printing. di git al printing systcms, suitablc inks bascd on dyes and pi gments, colour man agc ment software, application and iuture scope of digit al printing, arc brieny discussed in view of the demand-activated manufac turing architect to satisfy th e chan gin g fa shi on trends and new market requ irements. Keywords: Inkjet printing, Rotary scrcen printing, Textile printing 1 Introduction has been pushing the print production towards th e In ITMA 1999, an array of diffe rent technologies developing countries. As a result, Far East has the fo r di gital printing on fabric was presented. Though major share of 50% with the USA hav ing only II % the idea had been around for nearly IS years, it was and the EU, 15 %. A major reason for thi s shift is th e not until now th at equipment adequate enough for long, polluting and capital intensive nature of production on tex til es was show n. However, th e conventional tex tile printin g. Di gital printing has the 'different competing technologies th at were di splayed potential to reverse this trend. showed a lack of clear-cut direction and served onl y Changing fas hion trend s an d new market to confuse buyers, most of wh om were un exposed and requirements are also pushing th e dri ve for digital un ed ucated about the capabilities of these printing. The most influencing factors are: technologies. Educated buyers were wary of purchasin g a technology th at might be obsol ete by th e • Personalization and quick response: rapid fashion end of the year. However, as we moved through th e change necessitates quicker transposition from year 2000 into 200 I, th e developmen t of bigger, faster des ign to production and shorter print run s as a and better print engines capable of increasing print consequence. speeds is being reported. The commercial availability • Design piracy: original designs are copied very of this technology will redefine th e way the traditional fast and repeat orders are rare. Speed in tex tile producers run their business . The importance transposition and quick potenti al profit rea li zation of understanding the process and building ex peri ence are important. with the current technology cannot be underestimated. • Printing on new and unusua l surfaces: printed Thi s paper briefly di sc usses some of the aspects of made-up products, engineered prints, and digital or inkjet printing, such as comparison between technical tex tiles are demanded by customers. co nventional and di gital printing, di gital printing • Environmental constraints: environment-friendly systems, suitable inks bases on dyes and pig ments, wear properti es and production processes. co lour management software, application and future • Press ure on costs: short fabric len gths mean scope of di gital printing. shorter inventories and sav ing in storage space. 2 Trends Influencing the Emergence of Digital 3 Conventional vs Digital Printing-t,S Printing)-] If one consi ders conventional textile printing, It IS Worldover, 11-1 3% of th e tex til es produced are immediately obvious th at the variabl e with the printed. Thi s amou nts to nearly 27 billion running greatest effect is fabric length . For long lengths, meters of tex ti Ie material. Dynami cs of global trade analog printing technology like rotary prin ting is fast (30m/min on an average), continuous and economical. "Phonc: 6850455; Fax : 009 1-0 11 -685 11 98: The colour ga mut is wide and no special pretreatment E- mail : sg upt a34@ hotmail.com of fabric is required before printing. GUPTA: INKJ ET PRINTING 157 For short runs, however, the process is colourways can be printed. Invento ry and polluti on uneconomical owing to hi gh downtime, hi gh wastage control costs are minimal as all the dye goes onto the of fab ri c and inks, hi gh engraving cost, high labour fab ric, no thickener or paste is used and, water and cost and cost of time spent on colour-matching, paste energy consumptions are low. The technology is making, sa mpling, design, registration, etc. amply suitable for just-in-time del iveries and mass Operations like screen engraving, print washing, and customization. sc reen washin g add signi ficantly to the pollution load. The technology is, however, still limited by low Des ign sampling or proofing is particularl y a very production speed, low avail abi lity of fast and low­ lengthy and expensive process (Fig. 1). viscosity dyes, and small size of colour cartridges. Di gital pnntIng, therefore, offers di stinct Fabric mu st be speciall y prepared to be abl e to run on advantages for short runs, sampling and proofing. these printers in open width condition and absorb There are no screens; consequently, all costs dyes quickly. Many pigments, like pearl, metallic and pertaining to screen engravi ng, paste mak ing, strike­ white, are not yet avail able for printing through these offs, downtime and wastage are eliminated. There are printers yet. Material handling is also limited . Stretch no registration probl ems and unlimited choice in knits and performance fabrics are not printable as yet. terms of repeat size is available. Any number of Durable solutions for post printing operations like print fixation and finishing are yet to emerge. Analog Printing 1 3 4 Digital Printing Systems . ,4.6 A di gital printing system for applicati on on textiles is an integration of four components, namely the inkjet head, ink chemistry, medi a and the colour management software. For each component, various technologies and suppliers exist. Based on th e choice Production of Artwork T of level of technology ava il able today, two major types of system, namely the Drop-on-Demand (DOD) Traditional! Digital 1 Week Methods and the Continuous Ink Jet (CIJ), have emerged (Fig. 2). The most important features of the inkjet printer are the printing head and the nozzles. In case 1 Inkjet Printing i Engrave Designs 6-8 Weeks Color Matching PrmilJr.tion of Artwork - Digital Files T 1 Week - Design Manipulati 2 Weeks 1 Hours . ~ Fi g. I-Conve nt ional vs digital printing 15 8 INDIAN J. FIBRE TEXT. RES ., MARCH-JUNE 2001 Ink Jet Technologies I I I Continuous Ink Jet (CIJ) Drop-on-Demand (DOD) I I r-' I I Multi- Binary Piezo Thermal l)eflection Deflection I J j Jemtex Scitex -Epson HP, Canon Linx Stork Brother Xerox Image Domino Tektronix Lexmark Taxat Toxot Aprion Videajet Spectra Willet Xaar Konika Trident Seiren Fi g. 2- lnkjet technologies in textile printing of both these technologies, numerous nozzles are used crystals can use any type of dye or pigment and are for each colour. These nozzles are 10-100 J.l in more suitable for hi gh volume printing. diameter, providing a resolution of up to 720 dpi (dots Continuous inkjet, on the other hand, generates per inch). Between one thousand and one million ink droplets continuously, but only the required droplets droplets are processed per second. are directed towards the target spot of the fabric by Many digital printing solutions have been made electric charge and deflection. Unneeded droplets are possible through integrat ion of the experien ce of redirected to a gutter. C[J printers are further different companies, speciali zing in their respective classified into two types: binary and multi-deflection. fie ld s. One such group is Ciba Speciality Chemicals, The binary systems are expensive and not adapted to Sophis and Mimaki. Another is Ciba Spec iality process colours. Multi-deflection systems are cheaper, Chemicals and Di gital Printing Systems (A prion). A allow for larger drop size and multiple dye types. third group ha vin g dye heads Zimmer (Austri a) and They are, therefore, well sui ted for textile printing at Jemco (Israel) and ink head DyStar is developing a high speed. new printer which is claimed to be ab le to ac hieve production speeds of 200 m/h. This printer named 4.2 Ink Chcmistry and Mcdia7 "Cromotex" is being designed for fabric widths of 2 m Inks for digital printing require special control on and printing eight pre-mixed colours with a resol uti on parameters like viscosity, conductiv ity, surface of 100 and 125 dpi. tension, chemical stability, physical stability, pH and foam-free properti es. Without the colour chem istry 4.1 Inkjct Hcads In DOD system, the drops are generated and base and in-formulation technology, th e particle size ejected when required. Drops can be generated either distribution required for such inks is not poss ibl e. A by a bubble (thermal) jet or a piezo crystal. These further requirement is ideal combination of ink and print heads are relatively simple and cheap; however, substrate. their life and applications are limited. Only very small BASF and Ciba Specialty Chemicals (Table 1) are droplets are generated. Consequently, a very large the two major manufactures of reactive inks for cotton number of nozz les are required to get acceptable and cotton blends, em ul sion inks for PET, acid inks results. Thermal jets are inexpensive, use water- based for silk, polyamide and woo l, and pigments for all inks and produce a very fine droplet size.