Ink Jet Textile Printing

Christina Cie

• Publisher: Woodhead Publishing
• Year: 2015
• Print ISBN: 9780857092304
• eBook ISBN: 9780857099235
• Topic: Technology & Engineering
• Subtopic: Industrial Engineering
• Index: Technology & Engineering

With the rapid expansion of ink jet printing, textile printing and allied industries need to understand the principles underpinning this technology and how it is currently being successfully implemented into textile products.Considering the evolution of new print processes, technological development often involves a balance of research across different disciplines. Translating across the divide between scientific research and real-world engagement with this technology, this comprehensive publication covers the basic principles of ink jet printing and how it can be applied to textiles and textile products.Each step of the ink jet printing process is covered, including textiles as a substrate, colour management, pre-treatments, print heads, inks and fixing processes. This book also considers the range of textile printing processes using ink jet technology, and discusses their subsequent impact on the textile designer, manufacturer, wholesaler, retailer and the environment.- Covers the foundations and development of ink jet textile printing technology- Discusses the steps of ink jet printing from colour management to fixing processes- Analyses how ink jet printing has affected the textile industry

1

Theoretical foundations for ink jet technology

Abstract

Technology is science’s application in the “real” world. The reality of technology is that sometimes it doesn’t quite do what it was expected, or hoped, to do. The users of a technology do not need to understand all of the science that went into the making of that technology; however, it can be useful to have a frame of reference for what to do when it doesn’t work. This chapter will introduce, through history, the scientific principles that influence the movement of dye as “ink,” propelled by a jet, to print on a textile, as ink jet printing. The history of the scientific discoveries that lead to the development of ink jet printing reflect the development of science itself.

Keywords

Ink jet

Inkjet

Digital

Print

Textile

Fabric

Placement print featuring horse silhouette and repeat, inspired by binary code.

1.1 Introduction

Ink jet printing on textiles, also known as inkjet or digital printing, is a generic technology that primarily uses, but is not limited to, dye formulated as “ink.” Ink jet printing is highly adaptable, both within what it can do as a technology as well as the uses to which this generic technology can be applied. Not only can two-dimensional results be achieved, using a colorant ink to print onto a surface, but “structural” fluids can also print layers that harden to form three-dimensional (3D) structures. Ink jet printing can be applied to a wide range of different processes and purposes, from the batch coding of soft drink cans to 3D printing for rapid prototyping in product design. Due to such adaptability, some hail ink jet printing as the future of manufacturing (The Economist, 2011). Ink jet printing is a deceptively simple term but, for the purposes of this book, it will be defined as drops of colorant as ink jetted into specific positions to form a printed design, in this case on a textile substrate. Defining points for this technology can be noted as:

• The noncontact or nonimpact nature of the process

• A wide variety of applications

• A variety of visual information that can be generated

A complex technology, such as an ink jet printer capable of printing on a textile substrate, must necessarily draw on many and diverse fields of scientific study and theory for its invention and development. Theories informing the foundations of the ink jet printing process will be discussed in this chapter, with further theoretical and technological developments related to the specific parts of the process discussed chronologically in later chapters of this book. As drops of ink being jetted into specific positions onto a substrate, the generic technology brings up key fields for scientific investigation:

• Ink: how to form those drops of ink

• Jet: how to generate the fall of that ink

• Printing: how to control that droplet of ink to land in the right place

In the development of the modern discipline of physics, practical experiments in the study of natural physical phenomena were fundamental in gradually shifting the balance of proof from a priority of theory, or philosophy, as in “natural philosophy,” to a more empirical and experimental basis with the inclusion and requirement of accompanying experimental proofs. With hindsight, this may appear to be an obviously necessary requirement, but perspectives shift, and the inclusion of philosophical treatises rather than repeatable experiments as “proofs” may also have offered a form of shield for researchers. Galileo Galilei in the 1600s was judged by the Catholic Church as to have wandered from “natural philosophy” into challenging the tenets of theology. To be seen as developing a formula for calculating how something might happen was probably wiser than developing theories on why something might be happening, especially if it questioned a deity. Another way of considering this shift is the difference between “theories” and “laws.” A law describes something that is happening, often accompanied by repeatable experiments as confirmation, as “if this, then this.” Theory on the other hand, seeks to explain why something might happen, as “if this, then this, because of this.” Theories are derived from descriptions or observations of events, but are particularly useful when they can then be applied to explain other occurrences.

1.2 Hydrodynamics

Firstly, in an ink jet printing process, the ink droplet has to form. Aristotle’s concept of a body of water as a continuum allowed that the continuum was also divisible, so that a flow of water could break into droplets and was divisible, in all amounts and directions to infinity (Johnson, 1998). Once a body can be broken up conceptually into parts, it is a short step to the mathematical processing of these parts, adding them up, or subtracting them. This mathematical processing can be used to predict how things might happen as a result of altering the circumstances of an event or an object. This is part of the origins of the mathematically based branch of experimental physics, returning to the theory from another direction by experimentation with numbers as well as, or even instead of, experimenting with matter.

Aristotle’s other contribution to this field was his concept of resistance acting on a body in motion in either air or fluid, known nowadays as “drag.” This is what slows and eventually stops the movement of that body. Having considered what stops the motion, Anderson lists Archimedes’ idea as to what starts the motion (Anderson, 1998). Archimedes realized that when pressure was exerted in one area of a static body, it created a difference in the otherwise equal pressure across the entire body. This “pressure gradient” starts the fluid moving toward the direction of least pressure. Wijshoff describes da Vinci’s observations on the movement of fluid as recorded in the Codex Leicester of 1508 along with da Vinci’s conclusion that gravity was the principle agent in the formation of drops (Wijshoff, 2010). Edmé Mariotte also assumed that gravity, rather than what we now know as surface tension, was the principal player in the formation of drops (Mariotte, 1686). Surface tension is also significant during the interaction as the ink drop lands on and is absorbed into the textile substrate. Inks are discussed at greater length in Chapter 7 of this book. Mariotte’s other studies included optics, and the discovery of the eye’s blind spot is also attributed to him. Without extrapolating too far, perhaps scholars might refer to this timely caution: that there may always be something more to see, and to understand, as these early texts reveal mistaken assumptions as well as startling discoveries. Judgment in retrospect, although easy, should not be harsh. For established theories that have stood the test of time and are still used today, it is easy to look back and consider a particular deduction to be obvious, given the evidence. In establishing those theories, and challenging others in the process, it was far harder to combat centuries of accepted certainties and to hold fast to the conviction that these were incorrect.

1.3 Elasticity

Elasticity refers to how far something, not only a solid, can be stretched before it breaks or is permanently altered and cannot return to its original form. Water can stream from a tap for a while before breaking into separate drops. Yield is that point at which the matter relinquishes, and it shifts from being elastic, i.e., able to recover its original form, to a state where alterations in its shape are no longer reversible. This can be an important consideration for printed textiles that are likely to encounter strain and respond with some stretch in their service life, yet must still retain the integrity of the printed image. Different forms of bonding between ink and cloth molecules are also significant, these are discussed further in Chapter 8 of this book. Elasticity and friction are also important considerations in engineering the effective movement of cloth, particularly from roll to roll, through an ink jet printer; this is discussed further in Chapter 3 of this book. Wijshoff (2010, p. 79) mentions Robert Hooke’s law of elasticity, reportedly developed in 1660 and finally published in 1678 (’Espinasse, 1956, p. 71; Hooke, 1678), and adds that Navier formed the theory into a mathematical form in 1821 (Navier, 1822, 1823). To further complicate matters, this law refers to “linear” elasticity, implying that the change can be measured in direct proportion to something else (e.g., pressure) and will be represented by a straight line on a graph. Nonlinear elasticity, in which essentially an outcome or output is not directly proportional to the input, shows in graphic representation of measurements as not regular, straight, or linear, as is the case with many natural phenomena studied outside of controlled laboratory conditions.

1.4 Viscosity

Viscosity is the measure of a fluid’s resistance to movement due to internal friction. “Shear” is the action of different parallel layers within the fluid sliding over each other due to the liquid’s internal friction, moving much like scissor blades. Newton (1687, p. 12) states that once the state of inertia is unsettled by an external force, the motion of an object is directly proportional to that external force and should be in a straight line with the resulting shear of the fluid directly proportional to the force applied and inversely proportional to its viscosity. If the flow or viscosity of a liquid continues regardless of external forces like stirring, then a fluid like water is described as Newtonian. If when stirred, for example, a temporary “hole” is left or a liquid such as paint even climbs the stirring rod, it is described as non-Newtonian because of such contradictory behavior. Non-Newtonian behavior becomes an issue when trying to print certain inks, and viscosity is an important factor when matching print head and nozzle size to ink type.

In 1822, the French engineer and physicist Claude Navier published equations to formulate the movement of fluids (Navier, 1822, pp. 389-440). In 1845, George Stokes published his equations on the movement of fluids (Stokes, 1849). Euler’s equations (1757), part of the basis of the Navier-Stokes equations, considered the flow of so-called “ideal” fluids that lack viscosity; in reality, the vast majority of fluids have some internal resistance and thus some viscosity. Wijshoff mentions the refinement in 1822 by Navier, and independently in 1845 by Stokes on Eul...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Woodhead Publishing Series in Textiles
• Preface
• 1: Theoretical foundations for ink jet technology
• 2: The development of ink jet printing on textiles
• 3: Cloth as a substrate for ink jet printing
• 4: Color management in ink jet printing
• 5: Pretreatment for ink jet printing
• 6: Ink jet print heads
• 7: Inks for digital printing
• 8: Fixing ink jet printed textiles
• 9: Washing ink jet printed textiles
• 10: Heat transfer and sublimation printing
• 11: The effect of ink jet on the textile printing industry
• 12: The effect of ink jet printing on design for the textile industry
• 13: Further opportunities with ink jet printed textiles
• Index