Section outline

  • One of the largest problems with digital ink-jet printing on textiles is obtaining the desired colour, as there exists a strong interaction between the relationship between texture of the substrate and the ink. Fundamental research is being conducted to model the relationship between the texture, colour of the textile material, dye and the resulting colour. The relationship between fabric, inks and the resulting colour is complex. The number of textile substrates being used in the industry is very large. It is, therefore, not realistic to suppose that a strictly mathematical model will be found to describe these relationships. Moreover, optical effects have to be taken into account.

    Digital InkJet technology is a graphical multicolor image reproduction technology, originally developed for homogeneous, uniform surface structures such as paper. However, textiles as a unique, heterogeneous, three-dimensional form is having its own surface regularities, completely different from homogeneous paper or plastic structures. Previous research on similar topics has confirmed that it is precisely the fundamental mechanisms that define print quality that have not been fully clarified, and the role of the surface structure of textile material has only recently been recognized as one of the fundamental factors for print quality and the achievement of an optimal color gamut. Therefore, any study of the influence of surface structural characteristics of textile materials on the formed shape, degree of deformation and spreading of the droplets on the surface of textile materials and penetration of printing ink droplets into the structure of textiles, contributes to the understanding of these fundamental mechanisms.

    • A specific problem is the porosity of the textile material, which causes a certain loss of information in the reproduction, since the penetration of printing ink into the deeper layers of the textile substrate as well as the loss of printing ink on porous parts cannot be prevented. 
    • Also, the issue of providing an active surface and the specific relationship of chemical constitutions of dyes and functional groups of textiles also defines the platform of the still unresolved issues in digital printing technology.
    • Problems of modification and adaptation of inks and components of printing pastes for application in ink jet technology, as well as problems of technical requirements of devices for InkJet printing, additionally complicate the optimization of printing pastes or printing inks.
    • Also, a significant problem is the optimization of pre-processing and post-processing methods of textiles as key stages in the application of digital technology.


    The picture shows three motifs printed with digital inkjet technology and clearly shows the impact of the background. Motifs and prints were made by the author Ivana Ravlic, a student at the University of Zagreb, Faculty of Textile Technology, graduate study Industrial Design of Textiles and Clothing, generation of graduates in 2016.    


     

    The motif, originally created by Ivana Ravlic, was printed using the digital technique of textile InkJet printing on various substrates, with pronounced surface structures (for example, velvet, velvet, jute, linen). The impact of the substrate is immediately visible. Therefore, knowledge of the relationship between the structure and color of the substrate with the printed motif is necessary. It is necessary to be able to predict in which direction and which color parameters will be affected by a certain structure and color of the substrate in order to carry out timely color correction and color matching. 

    • TEXTILE-INK DROPLET Relationship Lesson

      The spreading of an ink drop on a substrate mainly includes two processes. First one is the drop impacting on the substrate. In this case, according to different impacting conditions, six different phenomena have been observed including deposition, prompt splash, corona splash, receding breakup, partial rebound and complete rebound. The other process is the liquid wetting the substrate. Both the two stages are closely related with the nature of the substrate, such as the surface texture, chemically homogeneous or heterogeneous, hydrophobic or hydrophilic and planar or nonplanar.


      When a drop of ink comes out of the nozzle of the print head, during a free fall towards the printing surface, it forms into a regular ball shape. All droplet formation technologies are designed so that when a droplet of the regular shape comes to the printing surface it forms a regular circle. In this way, proper positioning of the droplets and proper mixing of colors is ensured for optimal reproduction of each pixel of the image.

      But this is only possible on homogenic surfaces like paper. Such homogenic surface is shown in the right side of the figure, showing a correct circular print of process colors. However, the enlarged photograph of the digitally printed knit (left side of the figure) clearly shows the interaction of the printed image with the structure of the material. Due to the deep penetration of inkjet ink into the structure of the material, the image becomes an integral part of the structure of the material and in addition to the colors defined by the design, it also has a characteristic three-dimensionality consistent with the construction of textile material.

    • Additional literature - THE EFFECT OF INK DROP SPREADING and COALESCING on the IMAGE QUALITY of PRINTED COTTON FABRIC File

      Cotton fabric has been extensively used as the substrate of inkjet printing to manufacture traditional garments as well as emerging e-textiles due to its comfort, renewability, good dyeability, biodegradability and relatively low cost. In present work, the spreading and coalescence of ink drops on a cotton fabric as well as their effects on the image quality were investigated. A reactive orange 13 dye was selected as the colorant to make it convenient to observe the depositing morphologies of ink drops. The impacting and wetting processes of an ink drop on a cotton fiber were observed through a high-speed camera. Depositing morphologies of an ink drop, coalescing structures of ink drops and patterns printed with different drop spacings were observed through a microscope

    • Additional literature - INKJET PRINTING OF FUNCTIONAL OXIDE NANOSTRUCTURES FROM SOLUTION BASED INKS File

      The inkjet printing of functional oxide nanostructures from solutions provides many advantages when compared to conventionally used top-down patterning methods. It does not require masks and—as the material is deposited only where and when needed—any material-removal steps are not needed. This contributes to reduced waste, cost, and time required to fabricate the device. Despite its apparent simplicity, the inkjet printing process offers many challenges, including the ink chemistry, ink-substrate interaction, and drying; these are discussed in the present review. The ink should have suitable values of viscosity, surface tension, density, and vapor pressure to fulfil the requirements for stable drop formation and pattern formation. The substrate properties are discussed from the points of view of wetting and stability of the printed patterns. Drying of wet deposits without build-up of the material at the edges via the coffee-stain effect is a critical step and strategies to overcome it are discussed. Finally, the potential of inkjet printing technology in many different applications is discussed