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UV-curable inkjet printing is one of the main imaging platforms for making wide-format images. Compared with solvent-based ink, UV curing inkjet more health and safety advantages, and high production efficiency, almost instantaneous curing, super-strong, widely used in a variety of printing media. Some of the properties of UV-curable inkjet are attractive, but they also impose limitations on the technical capabilities of inkjet printing. After carefully modifying the recipe used, UV-curable inkjet can be used for a variety of potential applications. In industrial thermal blistering applications, UV-curable inkjet can replace very time-consuming artificial decals and lacquers.
While the market potential for translating such applications into digital printing is attractive, the development of UV inks is that it relies heavily on a dual-function, highly cross-linked acrylate that does not tolerate the thermoforming process Temperature, pressure and ductility.
Through careful study of the role of monofunctional acrylates, the printing industry can develop a potentially important market segment that uses the ink that can withstand ultra-high ductility during high-temperature thermoforming processes to customize the printing industry and packaging products The The monofunctional acrylate allows the UV inkjet ink to be sufficiently flexible to reach or exceed the possible elongation by means of the substrate. After rethinking the dyeing process, increase the ink so that it produces four primary colors that will not discolor when heated and will not fade in tension, ultimately helping to achieve this important technological innovation.
This new high-toughness ink was acquired by EFI in 2014 and applied to its VUTEk GS Pro-TF product. This article will focus on the basic development philosophy behind this ink.
Flexible forming temperature
Thermoforming is a manufacturing process in which the plastic substrate is first heated to a flexible molding temperature and then molded into a specific shape using a mold and finally trimmed into a product or package. The substrate can be thin (disposable cups, containers, covers, pallets, blister packs, hard plastic wraps and other packaging products for food, medical and general retail) or thick (doors and dashboards, , Multi-purpose vehicle compartment and plastic tray and other products).
Thermoforming is also a vacuum forming process that requires heating and pressurization. The standard temperature used in the thermoforming process is between 137.8 and 238+ degrees Celsius (280 and 460+ degrees Fahrenheit). The mold or tool configuration used depends on the specific product or label needs or application.
Each of us deals with thermoforming products almost every day. E.g:
Aviation industry: interior, cover, fairing.
Agriculture: pallets, barrels, transparent plastic greenhouses, lawn mower covers.
Automotive: Wheels and wheel covers, automotive interiors, spoilers, dashboards, sports and sport utility vehicle fairing.
Maritime industry: hull, canoe and rubber boats, cabin and dashboard.
Electronic industry: handheld devices, household appliances, computers, instrumentation equipment.
Entertainment: stage background, costume, animation model, simulation, game kiosk.
Medical industry: scanners, masks, prosthetic parts.
Construction: bucket and shower shell, jacuzzi, custom counter.
Retail: packaging, blister packaging, signs, vending machines.
This technology is increasingly attracting brands, retailers and other businesses that can produce products such as 3D retail terminal signs, kiosks and roof racks, which are comparable to traditional production processes. In the typical example of a conventional thermoforming process, it may take up to 7.5 man-hours to produce two 13.5 x 4ft vacuum forming signs using the current printing and painting process. What happens when you imagine how much time and cost are drastically reduced?
Into the wide inkjet printing era. As with any digital printing process, wide inkjet printing can drastically reduce working hours, just as fast as the highly customizable raw materials, and both the sample and the final product. Using digital printing thermoforming technology, we can produce 34 of the same signposts in 7.5 hours - 93% reduction in labor costs and 95% increase in productivity. While the use of traditional technology will take 3.5 weeks to produce 34 signs.
As a result, digital printing technology is very attractive for thermoformed products. But the digital wide inkjet ink used is not suitable for such applications.
UV inkjet ink: status quo
Thermoforming requires not only heating and pressing, but also the extension of the molding substrate. The development of inkjet ink is highly dependent on single-function high cross-linked acrylate, but this material can not withstand the temperature and pressure required for the thermoforming process. In addition, this ink can not withstand the extension type required for most thermoforming applications.
During the heating of the thermoforming process, both the ink and the plastic substrate become ductile. This phenomenon is known in the industry as thermal depression, vitrification or foaming. Dye color or hue will change during heating or molding. The extension of the molding process can cause the final product to crack or mosaic, resulting in unacceptable quality defects.
This is because in the UV inkjet formulations commonly used in the bifunctional acrylate, the two molecules are very active, fast curing speed, high hardness, which improves the durability of ink and productivity, but the flexibility of the restrictions.
The advantages of UV inkjet formulations for bifunctional high cross-linked acrylates include fast curing, good chemical resistance, and good surface hardness. However, for thermoforming applications, there are limitations such as limited bonding range, brittle fracture, and easy shrinkage and curling.
Explore single-function acrylates for thermoforming applications
Through a careful study of the effects of monofunctional acrylates, the printing industry can develop a potentially important market segment that uses custom ink that can withstand ultra-high ductility during high-temperature thermoforming processes to customize printed industrial products. This technology is not only for traditional industrial thermoforming operators, but also with its enhanced printing function for the printing company to open up new sources of income and expand the product range, so that it can be carried out in the internal imaging and decoration operations.
What are the results? With high-stretch 3D graphics with lifelike colors and highly appealing design capabilities.
Digital Thermoformed Inkjet Ink: Background information
Since the 1970s, Don Sloan has been working on the development of UV printing inks. In 1993, he set up Polymeric Imaging (PI) to develop UV ink formulations for the replacement of solvent-borne chemicals. By 2010, PI has developed a patented formulation for deep-drawing thermoformed UV inkjet inks and coatings. In October 2014, PI's patent and digital thermoforming technology-related intellectual property rights were acquired by EFI.
Less is more: single function low cross-linked acrylate
The custom ink formulation, which was initially used for digital thermoformed UV inkjet inks and coatings, performed well in the PI lab test, but it would take years to optimize before putting it into the actual production environment. This ink can be deeply thermoformed but does not crack or mosaic like conventional dual-function, highly crosslinked UV inkjet inks. In this paper, the use of EFI VUTEk GS Pro-TF and other wide UV inkjet printer digital thermoforming printing, developed a perfect solution.
The effect of using single-function low-crosslinked acrylates is significantly different from traditional single-function, highly crosslinked UV inkjet inks. We have developed a functional solution for digital printing thermoforming products, as shown in the drawings. These include:
Dyes or dispersants are not easily stained in a hot state; i.e., their color or color tone does not change during heating or molding.
This ink can achieve unlimited ductility, can meet or exceed the plastic substrate extension characteristics. At present, more than 24 inches of stretch length and over 1000% elongation have been successfully achieved, with an aspect ratio of more than 30: 1.
Ink bonding range is very large, and the application is very wide, which are the traditional vacuum forming technology can not be achieved.
Ink development is only one of the steps needed to bring this technology to market. In order to develop the application shown in the figure, we need to use the deformation software, so that the image correctly aligned mold. Deformed printing keeps the color intact and prevents chromaticity loss when the substrate is extended. Through the deformation software, we can in the design of all the deformation factors into account. Quadraxis developed Thermo 3D Suite (distributed by R & R Graphix in the United States) is such a deformation software.
Obviously, we need to use special color management techniques to ensure the final product color accuracy. In most cases, the printer does not need to adjust the color after the correct color calibration. The print ink density is larger, but the hue / chroma value remains the same. As long as the correct operation, you can produce consistent with the design intent of the final product.
However, the success of the thermoforming application gives the ink another burden: the ink must have the characteristics of the free film; in other words, the cured ink film can exist almost alone, like a layer of cellophane. Free film properties, coupled with a higher ink density, you can maintain the same color in the molding process.
Important Characteristics of Single Function Low Crosslinking Inkjet Ink
Laboratory tests and field operations have demonstrated that several important features of this new ink have revolutionized the thermoforming process using UV inkjet printing. These include:
Simplify the production steps of parts or decorative signs, greatly shorten the production time.
Without the need for screen printing production preparation costs, or eliminates the need for traditional thermoforming used in hand-painted and vinyl lettering process.
Has excellent ductility, support deep drawing thermoforming, while maintaining PETG, acrylic, polycarbonate, polystyrene and PVC and other plastic substances opacity.
The ink can withstand thermoforming and cutting operations without cracking, peeling or loss of adhesion.
The ink has moisture resistance, and the printed image does not fade for a long time.
LED curing: a new cutting edge technology
As with most technologies, there is room for improvement in single-function low cross-linked UV inkjet ink for better thermoforming performance. A project currently underway is the use of LED-based photoinitiators to develop LED cold state curing ink formulations, which use 365-400 nm wavelength, while the traditional UV ink is 320-365 nm wavelength. This formula uses EFI's LED inkjet expertise for thermoforming high-stretch-rate ink technology and enhanced coating.
Conventional UV curing techniques employ high temperature UV light, which limits the use of lightweight, thermally or dimensionally unstable substrates. LED curing temperature of 81 degrees Fahrenheit, can improve material stability, reduce the deformation coefficient, reduce the degree of material degradation. Another benefit of LED curing is that LED lamps have long lifespan and low energy consumption.
Through the LED curing process, the film deep drawing characteristics can be used to direct packaging and other packaging applications such as film packaging ultra-high flexibility and color consistency, creating new business opportunities for vacuum modeling.
In addition, whether it is LED curing or traditional curing methods, through the extension of the thermoforming process, can increase profits and reduce production costs. For reasons of cost reduction and environmental sustainability, measures to simplify the packaging process, the thermoforming package does not have to use cardboard box packing, in addition to the packaging assembly process can reduce the time and cost. Another advantage of printing directly on thermoformed packaging is that there is no need to print labels. In this way, we have the opportunity to use 3D plastic packaging available data, the bar code, serial number and even personalization and other information included.
Bright market prospects
As shown in the example above, the development of single-function, low-crosslinked UV inkjet inks for thermoforming products has led to technological advances that have created a bright future for thermoforming applications in all walks of life. This technology is suitable for a wide range of:
Speed up the market.
Provide higher quality, produce more related thermoformed products. Reduce the amount of packaging materials.
As long as the full play to imagine, there is infinite possibilities. This is just the beginning.
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