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New Epson White Ink Reduces the Environmental Impacts of Proofing

Epson has developed white ink for proofing, another example of how it is creating industry-leading and innovative new products while mitigating environmental impacts.

The Secrets of White Ink

White plays a vital role in printing on transparent films, such as those used for labels on plastic bottles and bags for snack foods. A layer of white ink has to be laid down first on these films before other colors are added so that background colors are not visible and so that the printed colors look good. Epson entered the package printing industry and made a big splash by developing a ground-breaking product: a water-based white ink that can conveniently and inexpensively be used for printing proofs on transparent films. Here we unearth the secrets of this water-based white ink, which solved a long-standing and difficult problem while also sharply reducing environmental impacts associated with proofing and offering enhanced usability.

What is proof printing?

Printshops print in huge volumes, with print runs ranging from many thousands to many millions of prints, so mistakes are not an option. For this reason test prints are taken to check and correct color to ensure that they are accurate before production printing takes place. These test prints are called "proofs." Proofs can be printed on the same printing machine as that used for actual production runs or they can be made more simply and conveniently using a special proofing printer. Proofing on the actual printing machine has the advantage of allowing you to check a print that is very close to the actual finished product. However, it also requires special skills and knowledge. Moreover, using the actual printing machine to produce proofs not only is extremely time-consuming, it requires that production printing be halted. This makes it prohibitively costly, both in monetary terms and time. Given this, simple proofing that can be performed relatively easily and affordably on a special proofing printer has become the norm. However, a number of problems had to be solved before simple proofing could be used for proof printing on transparent films.

Hard-to-Handle Inks

Transparent films have a smooth, slippery surface that, unlike paper, does not absorb ink. A special ink that adheres well to film thus has to be used in proof printing. Broadly speaking, there are two main types of ink for this purpose. One is solvent ink, which contains an organic solvent, and the other is UV-cured ink, which is has to be hardened with ultraviolet light. Both types were troublesome to use and came at a comparatively high environmental cost, so proof printing on transparent film a highly problematic proposition.

Solvent Ink

This ink uses an organic solvent that allows it to deeply penetrate transparent films and that gives it exhibit excellent lightfastness and water resistance. However, organic solvents have a strong, unpleasant odor. Ventilation systems normally need to be installed to capture and discharge exhaust from the printer. An energy-consuming heating system is needed to improve ink adhesion to media during printing.

UV-Cured Ink

This ink is cured by exposure to ultraviolet light. Curing speeds up the process time and allows the ink to be printed on nonabsorbent media such as plastic. However, people need to be careful around this type of ink because uncured ink can cause skin inflammation on contact. It also has a distinctive smell and, like solvent ink, requires ventilation. Process time is also constrained to some extent. Furthermore, the mercury lamp that is used to cure the ink becomes dangerously hot and uses a great deal of energy. In addition, safety precautions have to be taken when UV light is used.

The Industry's First Water-Based White Ink

Epson solved the problem of printing proofs on transparent film by developing a water-based white ink. Unlike solvent and UV-cured inks, water-based inks produce very little odor and present no risk of adverse health effects during ordinary use. Water-based ink on film dries as quickly after printing as ordinary ink on paper, without the need for heat. This type of proofing thus uses only slight more energy than an ordinary inkjet printer, so environmental impacts are mitigated. And a closer look reveals that these are not the only benefits of Epson white ink.

No Need for Frequent Shaking?

The white color of white solvent ink and white UV-cured ink comes from titanium dioxide. Titanium dioxide is a very heavy substance and quickly settles to the bottom of an ink cartridge. In practice, this has meant that cartridges containing white ink had to be taken out and shaken frequently.
That is, before Epson developed its white ink. Pigment is not used in Epson white ink. Then why does it appear white? The explanation can be found in the conformation of particles in the ink. The particles have a hollow center and diffusely reflect light so that the ink looks white (see the above diagram). Since these particles are lighter than particles of titanium dioxide, they don't sink and settle as easily, so the cartridges don't have to be shaken up as often. Moreover, solvent ink and UV-cured ink required frequent nozzle checks and head cleanings, processes that generate a large volume of waste ink. With Epson's new white ink, however, the waste is negligible.

Transparent Film That Supports White Ink

Essential to the realization of this ground-breaking white ink was the development of transparent film capable of simultaneously printing both the white ink and other colors of ink. Clear, vivid prints could not be obtained on existing transparent films because these inks neither stuck adequately to them nor were sufficiently absorbed. To solve this problem, Epson developed a new type of transparent film that can support water-based ink. The new film has double the absorbency of ordinary films.

From the Printing Plant to the Office - A New Work Flow.

The printers in which the water-based white ink is used do not require ventilation and do not require a lot of space. Moreover, the printer hardware costs and running costs are so much smaller than those for traditional proofing systems, Epson's proofing printers are well within the reach of almost anyone who needs to quickly and easily produce proofs. Proofing equipment, which was once found exclusively in printing plants, has evolved into an ordinary-looking printer that readily fits in any office. The effect is a whole host of possibilities for changing the traditional work flow.

Water-based white ink brings a host of benefits, including a
smaller environmental footprint. Eco-technology that itself creates
customer value makes these printers very promising.