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Introduction to Inkjet Printing Technology

Ingredient Selection for Inkjet Ink Formulation

Ingredient Selection for Inkjet Ink Formulation

The formulation and chemistry of the ink determine:

  • The printing quality, and 
  • The jetting characteristics

In digital textile printing, the ink remains the single most important component of the system besides the fabric pre-treatment. This is because, unlike printing on paper or other substrates, the textile material will be subjected to repeated washing using various detergents, and the color ought to be fast to washing, rubbing, and sunlight.

These factors make ink formulation for digital textile printing quite complicated. Therefore, here we will provide an ideal inkjet ink formulation for various types of inks that can be used for digital textile printing. The formulation may vary based on the inkjet machine manufacturer, and also, the effect desired by the printer; however, the items listed for each category of ink are quite exhaustive.

Inkjet Ink Preparation
Vehicle
Additives
Polymers 
Function Act as a carrier Impact special functions Enable the binding of the functional molecules to the substrate after printing
Example
  • Solvents (organic or inorganic)
  • Cross-linkable monomers

  • Colorants (pigments or dyes)
  • Surfactants
  • Preservatives
  • Photoinitiators
  • Binders
  • Conductive Particles

Ordinarily, inkjet inks are described in terms of their carrier fluids, but in others, the naming is based on their properties. Some of the commonly found inkjet ink types in the digital inkjet market and their suggested composition are mentioned below.


Water-based Inks


In water-based inks, the carrier fluid is water.

The table below gives a typical composition of water-based ink that can be used in a wide variety of inkjet printers purposely for graphics and digital textile printing. These inks are used in printing onto coated substrates and the water is absorbed quickly into the coating and the dye or pigment is fixed to the surface of the coating to give a sharply defined image.


Component Function Concentration (%)
Deionized water Aqueous carrier medium 60 - 90
Water soluble solvents Humectants, viscosity controller 5 - 30
Dyes or pigments Provides color (Chromophore) 1 - 10
Surfactants Wetting agent, penetrating agent 0.1 - 10
Biocides Prevents growth of biological organisms 0.05 - 1
Buffers pH controller 0.1 - 0.5
Other additives Chelating agent, binder, defoamer, etc. > 1

Aqueous Inkjet Inks: Accelerate Formulation with Best Practices

Specifically, for digital textiles printing, the components, and more importantly, the concentrations above may vary depending on:

  • The type of base (water, oil, organic medium)
  • The printing machine manufacturer, and
  • The mode of after-treatment such as curing (for pigmented inks) or steaming

Aqueous Inkjet Inks Formulation Best Practices


Solvent-based Inks


As the name implies, these inks use solvent as their carrier fluid.

The composition can be similar to the components in table above. Solvent inks are cheap, durable, and give good coverage on non-porous vinyl and other graphic arts substrates but their use on the textile substrate is not encouraged.

Also, they are not environmentally friendly and sometimes give off strong, often toxic, odors as they dry; thus, requiring special ventilation systems. Their durability on a product still makes them a viable option for the printing of posters and signage for outdoor use. Their corrosive nature requires special print heads and affiliate devices.

Solvent-based Inks

» View All Raw Materials for Solvent-based Inkjet Inks


Latex Inks


Latex refers to microscopic polymer particles suspended in an ink.

Latex ink is composed of approximately 70% water and 30% additives. All other components in water-based inks can be included in this system, but the latex component is usually higher than the other ingredients besides water. These inks give:

  • Good durability and
  • Good environmental health

Latex inks require no drying mechanism because as the liquid evaporates, the latex polymers coalesce and fuse together, encapsulating the colorant leaving a continuous layer of latex polymer, encapsulating, and protecting the pigment.

Latex Inks by HP
Third Generation Latex Inks by HP


Oil-based Inks


Primarily, oil-based inks are composed of: a binder, a varnish and a pigment.

Other additives in table above may be added based on the expected results and the type of printer to be used. The varnish is usually vegetable oil, which increases the glossiness when the substrate dries.

Oil-based inks are suitable for printing on porous substrates such as plain paper, coated paper, and cardboard but not on textiles. These inks are most commonly used in:

  • Coding,
  • Markings, and
  • Some paper-based wide-format graphic applications


UV-cured Inks


UV inks are composed of: photoinitiators, colorants (pigment), water, surfactants, preservatives, and functional additives.

This type of ink represents the fastest-growing segment of the industrial printing ink market. These inks are cured when photoinitiators interact with high-intensity ultraviolet light.

UV inks are environmentally friendly. They and are used for printing onto non-porous substrates and are used mainly in graphics and digital textile printing. Their versatility makes them user-friendly in most print heads.


Design High Performance UV Inkjet Inks to Meet Customer Needs


Take the course by our Industry expert Terence Kenneth who will guide you to select raw materials (monomer, pigment, photoinitiators…) for UV inkjet inks and troubleshoot problems (banding, misting, poor ink transfer…) with practical examples.

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Other Varieties of ‘Ink’


Hot melt, or phase change inks are composed primarily of colorants and polymers that undergo a rapid phase change when heated. The heating in the printhead keeps them liquid and once jetted, solidify on the substrate. These inks are used in the coding and marking and packaging segments but not on textiles.

Conductive Inks on PCB Other Functional Fluid (‘inks’) that can be printed by specially designed printers such that when laid on a substrate, performs a special function such as in the case of metallic or conductive functional fluids printed on circuits. In this case, the functional fluid consists of nanometer-size particles of conductive metals such as silver and copper held in suspension in a carrier fluid. Once printed these inks are then sintered (heated until the tiny particles adhere to each other).

Other functional fluids include:

  • Optical polymers
  • Conductive and semi-conductive polymers
  • Transparent conductors
  • Dielectric and resistor materials, solders, and epoxies


Conventional Emerging Trends in Inkjet Printing

Standard Test Methods for Pigmented Systems

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