UV printer ink overview
Apr 03, 2024
Leave a message
For the vast majority of users who hope to benefit from digital printing technology, the emergence of UV-curable ink chemistries has turned their wishes into reality. Although well established in simulation environments, these formulations have several challenges to overcome before truly practical engines can enter the mainstream inkjet market. These began around 2000 with the introduction of UV potential into the rapidly expanding wide-format sector, beginning a general sea change in how rigid materials were used directly to produce display and point-of-purchase applications. In subsequent years, this important technology has diversified, and the utility of UV curing is no longer limited to ink products, but is widely used in a wide range of industries where the deposition of different fluids plays an important role.
These challenges faced by UV-cure engine manufacturers are diverse and continue to expand as production needs become more diverse and time-sensitive. There are, of course, alternative ink technologies suitable for specific applications, such as the textile and apparel sectors, the photography and fine art markets, and jobs where solvent or latex chemicals provide adequate results. However, for the most part, the use of UV energy and its incorporation into today's printing equipment in the form of inks and curing has led to a shift in printing presses that handle not only decorative but also functional and industrial processes. .
In the early iterations of UV digital printing, bonding the ink to the material surface was not easy because, unlike solvent-based chemistry, UV curable inks do not bond to the media itself, which inevitably meant adhesion and loss of finished prints. Rupture is usually inevitable. Most scientific successes do not happen overnight but are continual developments, some based on trial and error, that have resulted in the flexibility of today's print engines and the behavior of their inks and curing systems.
There are two crucial considerations when introducing UV curing chemicals into the print engine. The first is the ink itself, which must have the correct rheology and viscosity for use with the selected printhead and nozzle density; the second is the efficacy of the curing method, which is ultimately responsible for delivering the correct finished product appearance, including adhesion and Color accuracy. The main reason why UV-curable formulations have been so quickly embraced by the digital printing community is that they offer a practical panacea that can be used on a variety of different substrates, whether thick or thin, rigid or flexible. The limitations lie in the type of press and expectations for the final product.
Typically, UV-curable ink formulations contain monomers, oligomers, photoinitiators and pigments as well as additives so that when exposed to the correct wavelength of UV light, the monomers polymerize to form a cured or dried finish. These ink formulations have been used for many years in many traditional analog environments, including screen printing, flexographic printing, gravure printing, and offset offset printing, while improved printhead technology and material coatings bring greater versatility. These ink formulations have become popular in the digital realm as the application options available have increased. Printing company.
Advantages of UV-curable inks include no VOCs and significantly reduced air pollution, as well as the advantage of faster operation due to immediate curing after spraying; unlike alternative chemical methods, drying each print does not rely on traditional , often time-consuming heat sources that need to follow the actual laying of the ink. Because the ink remains liquid until it solidifies, press maintenance is reduced as there are no longer issues with solvent evaporation in the printhead that can cause clogging and nozzle damage. In addition, the chemical's high viscosity also simplifies the quality of droplet formation and maintains a fixed accuracy as it cures, which allows the print engine to run at high speeds without compromising quality.
The disadvantages of UV curing technology have now been largely overcome, as the viscosity of the ink also makes it less likely to produce a very smooth surface. Again, since the cured ink does not bond to the material surface, the process requires ensuring that the correct level of UV light is applied to ensure correct adhesion. Too much can result in a hard, brittle surface that may peel and chip, while too little can give the print a tacky feel, which is undesirable even with free-radical chemicals. For this type of curing, polymerization stops once the light source is removed, and free radical systems represent the majority of commercial UV systems in use today. Instead, cationic technology continues curing in a daisy-chain approach even after the light source is terminated, and although this principle is adopted by one or two print engine manufacturers, it is not considered a viable option for practical reasons.
In today's market, another option has also emerged and, after a relatively slow start, is now increasingly used in print engines, covering a wide range of areas using UV-curable inks. Previously, mercury arc lamps were most commonly used for all applications, however, although their curing properties are satisfactory, they also suffer from various disadvantages, one of which is the inclusion of mercury, which is now being phased out as a substance containing hazardous properties disuse. Additionally, these lamps generate high heat via infrared rays, require careful handling, and may not be suitable when working with thin and sensitive materials. Lamps tend to have a limited service life of around 1000 hours, during which time efficacy gradually decreases and this can lead to inconsistent curing as the lamp approaches the end of its cycle.
Alternatives to traditional UV curing include the adoption of LED lamps, but initial challenges to overcome focus on their narrow spectral output, which in turn means that the formulation of inks and coatings and other dispersing liquids needs to be modified to operate within the basic emission range. Nonetheless, UV LEDs have gained momentum over the past few years and are gaining traction as a practical option for the display industry, allowing the use of a wider range of materials, saving on energy costs, and eliminating the need to replace curing lamps on short notice. A relatively short period of time.
LED curing is also becoming valuable in functional and industrial areas, where UV printed components may need to be part of an integrated production line or as an integral autonomous unit in the manufacturing process. Under the conditions expected, there is no room for bulky and hot equipment due to its drying requirements, and in these cases mercury arc curing is not a viable option. This is particularly important for single-pass applications employing printhead arrays and for high-speed operations such as product encoding, marking and labeling environments.
In summary, the principles behind UV-cured production now cover a variety of printing requirements, from wide-format graphics, web and sheet-fed commercial printing to packaging and label converting. Specialty applications outside of traditional printing, such as industrial coatings, are also turning to UV deposition and, increasingly, LED curing capabilities. The technology is fully aligned with today's trend of reducing batch size, customization and version control, and improving turnaround times with the help of efficient digital front-end and workflow practices. These standards are important components in any inkjet process, but are especially important as the drive continues to increase production speed and versatility from desktop to finished product.
As the advantages of UV curing replace alternative inks and methods, manufacturers are now able to develop high-quality equipment that prints on a variety of media without compromise. The use of common technology simplifies the design of custom machines that require specialized deposition, as well as those that rely on reliable and consistently high-quality results in many areas of the printing industry.