Fujifilm Business Innovations used this week’s Japan Inkjet Technology Forum in Tokyo to showcase a new type of ink, known as structural colour, for industrial inkjet.
Takashi Fukui, supervisory group head for Fujifilm Business Innovation, explained: “Usually we express colour by pigment or dye that absorbs specific light rays. But in structural colour the ink itself has no colour.”
The ink appears to be clear and instead of pigments it uses micro structures – hence the name – which are arranged to physically change the way that the light waves are refracted through the ink. Fukui adds: “We have three types of ink and each one has a specific structure. By changing the size and structure we show particular colours.”
Consequently, the substrate itself plays a large role in the final appearance of the image, meaning that the same image can look dramatically different according to the background, with clear colours when against a black background that absorbs the transmitted light, and pale pearl-like colours with a white background where the transmitted light mixes with the structural colours. The colour also changes dramatically according to the viewing angle.
The main advantage of the structured ink is that it produces very vivid iridescent or pearl-like effects, which can be used for decoration in a number of fields from jewellery to interior design. A further advantage is that the colour should not fade over time since it relies on physical microstructures that are not affected by ultraviolet light rays. It’s also said to be a more sustainable solution since there’s no water or dyestuff used to produce this ink.
The basis behind structural colours is taken from nature where many creatures such as Morpho butterflies use structural elements rather than pigments in their skin to create a rich palette of colours.
The structural ink is UV-curable and Fukui says that most inkjet printheads designed for use with UV inks should be able to jet it. The inkset currently consists of three colours – red, green and blue. The ink is designed to be jetted to a PET film from 50-150 microns thick though it can also be used for resin and glass decoration.
Fukui says that Fujifilm is keen to talk to customers about exploring different applications, adding: “We have some test machines for this ink up to 1m wide.” He continues: “If a product manufacturer wants to use our structural ink then we can sell to OEMs as well.”
Fujifilm has already worked with Citizen Watch to produce the dial for a wristwatch where the colour tones vary depending on the angle and intensity of the lighting.
You can find further details from fujifilm.com (this page is in Japanese but with a translation to English available.)