UV curing ink is a specialized type of ink that dries and cures instantly upon exposure to ultraviolet (UV) light with a wavelength of 315 to 405 nanometers (nm). The most common LED-UV curing systems typically use wavelengths around 365 nm, 385 nm, 395 nm, and 405 nm. The process of exposing the ink to UV light is known as UV curing, which enables the ink film to form a hard and durable finish.

Changing consumer demands, safety considerations, and environmental concerns have all driven advancements in inkjet technology. These evolving requirements have influenced wide-format, grand-format, and cylindrical graphic applications. As the printing industry and technologies have developed, so too have the printing inks.

These advancements have led to the creation of more sustainable inks that enhance print quality and minimize environmental impact. In addition, the integration of digital solutions has enabled faster production times and greater customization, meeting the diverse needs of today’s consumers.

History of UV printing process

The early 1970s saw the introduction of UV inkjet printing for use on barcodes, labels, and generally flat surfaces. At that time, UV printing was considered slow and expensive.

While there is limited information regarding the development of UV inkjet printers in the 1970s and 1980s, the concept of a UV inkjet printer was theorized by Michel Caza to NUR in the mid-1990s. At that time, NUR did not perceive market or technological viability.

According to wide-format-printers.org, a representative from NUR stated, “It was impossible to build such a printer.” In the mid-1990s, a company named Data Mate developed one of the first flatbed wide-format inkjet printers ever created—the Rembrant, which utilized printheads from Sharp.

It is important to note that the initial inkjet machines relied on solvent inkjet inks.

In the late 1990s to mid-2000s, the emergence of UV-curing gel nail polish technology provided valuable insights into the potential benefits of UV ink curing. These benefits ultimately led to the development of UV inkjet printers that utilized UV ink for printing on various surfaces, including plastic, glass, and metals.

Fast forward to today, UV inkjet printers continue to evolve and have become a popular graphics printing technology. Utilizing UV LED curable inks, this technology can deliver full-color graphics, serialize materials, print on cylinders, and create braille or even one-off high-quality images.

UV Curing Process Explained

UV curing is a photochemical process that utilizes ultraviolet (UV) light to rapidly dry UV inks. Elements found in the UV curing ink include monomers, oligomers, sensitizers, photoinitiators, colorants, and other additives that adjust the ink bonding characteristics, surface tension and viscosity.

Photoinitiators act as catalysts that trigger the ink drying and curing process (polymerization) when exposed to radiation (UV).

The photoinitiators absorb UV light, triggering the crosslinking of the liquid monomers and oligomers. This chemical reaction leads to the formation of polymeric structures that encapsulate the colorants and bond the ink to the material.

Advantages and Disadvantages of UV-Cure Inks

Although there are various types of inkjet inks and printheads available, at Boston Industrial Solutions, Inc., we specialize in manufacturing inks specifically for industrial piezo printheads. Let’s review some of the pros and cons of these digital printing inks.

UV-cure inks are thicker and have a higher viscosity than water-based or solvent-based inkjet inks. For the printheads to jet effectively and efficiently, they must operate at an optimum temperature. This temperature is internally raised to ensure the ink is jetted effectively.

While there are only three major categories of inkjet inks—hard, neutral, and flexible—these inks are not substrate-specific when compared to traditional pad printing or screen printing inks. With neutral or flexible inks, it is possible to print virtually on any material. These inks can adhere to nearly any surface with the aid of UV adhesion promoters.

Solvent inks have VOCs, which tend to clog the nozzles of the printheads once the solvents evaporate. Unlike solvent-based inks, UV/LED inks have an advantage because they do not dry on the printhead. This feature makes it easy to manage and clean the capping station on the machines.

One of the major vulnerabilities of the inks is the presence of stray UV light, which can cause clogs in the nozzles. Although stray light poses a challenge, we design our UV printers with features that protect the nozzles from UV light and ambient light.

Another challenge with UV ink is that oxygen in the air competes with the monomers and oligomers for the free radicals generated during UV exposure. We solve this problem by increasing the amount of photoinitiation agents in the ink. This practice helps prevent ink degradation by oxygen.

Lastly, it is crucial to utilize powerful UV/LED lights to completely cure the inks. For these inks to dry effectively, the UV light must penetrate all the way down to the material layer. Any ink that does not receive UV light will not dry, leading to adhesion failure.

Benefits for Packaging Industries

There is a wide range of inkjet printing applications, encompassing promotional products, industrial uses, and packaging.

The packaging industry utilizes inkjet inks for a diverse array of applications, including product identification, variable data printing, promotional messages, and regulatory compliance. These inks are especially suited for label printing, flexible packaging, folding cartons, and corrugated packaging, thanks to their non-contact printing process and capability to print on various materials.

How Safe are These Inks?

Once cured, UV inkjet inks pose very few safety problems. However, in their raw form, users of these inks should exercise caution when handling them; after all, they are chemicals.

Like any other chemical, before handling UV cure inks, users must obtain a copy of the safety data sheet for the materials and read it thoroughly.

It is important to note that inkjet inks contain chemicals that can be harmful to humans. Some of these chemicals may react with skin upon contact. Therefore, it is essential to wear protective equipment, such as gloves and goggles. Additionally, it is crucial to always work in a well-ventilated environment, even when handling low-VOC chemicals like inkjet inks.

Lastly, safety training is crucial for maintaining a secure working environment. It serves as the foundation for awareness and understanding. This training equips employees with the knowledge necessary to protect themselves and their colleagues from potential hazards associated with UV light and the chemicals involved in the curing process, as well as the maintenance of the equipment.

Future Trends in UV Curing Inkjet Ink

Digital printing is quickly evolving, and with it so are the inks. Some of the future trends in the UV ink industry include a shift toward more sustainable inks and increased use of UV LED curing technology. Check out the article advantages of digital printing.

With an increase in LED printing, customers are demanding a more detailed and accurate representation of colors. While most UV printing has relied on a limited color palette—CMYKWLcLm—we are likely to see an expanded range of colors that includes oranges, reds, greens, and grays. Digital equipment manufacturers will need to develop machines that incorporate these additional colors to meet customer demands.

Additionally, the manufacturing and graphics industries are demanding higher printing speeds and smart inks. The next generation of inks must evolve to meet these needs.

To learn more about UV-curable inkjet inks, reach out to us or visit our support hub or YouTube channel.