Ultra-High Viscosity Jetting of Optical Materials: a Solution by DELO and Xaar

Most inkjet printheads are capable of jetting materials with viscosities with a range of 10-25 mPa·s (10-25 cP). Thanks to Xaar’s TF Technology, DELO’s advanced optical fluids which have significantly higher viscosities can now be successfully jetted. In this application, fluids with a viscosity of 250 mPa·s at room temperature are heated to 43° C, reducing the viscosity to 63.5 mPa·s and enabling them to be effectively ejected with Xaar’s printheads. Having the capability to jet fluids with viscosities greater than 25 mPa·s provides much more flexibility for manufacturers of optical elements in consumer electronics and automotive applications, offering an alternative or addition to the predominantly used imprint technology for selected applications like micro lenses. For nano-imprint applications, inkjet-printing can also replace spin-coating, reducing material waste by up to 80 percent.

Optical materials based on UV-curing polymers

DELO has worked closely with Xaar to evaluate and develop this application using Xaar’s new 5-step process. It helps with initial fluid evaluation and guidance through to sample production and application development, enabling customers to evaluate the technology with confidence. Continued support, technical advice and application improvements also form part of the process. Optical materials based on UV-curing polymers instead of glass or injection-moulded plastics have become increasingly widespread in recent years. They are used as lenses for applications like flashlights, time-of-flight-sensors or diffractive optical elements (DOEs) for structured light emitters and miniature cameras.

Material waste reduced

DELO provides fast UV curing materials with good optical properties such as a matched refractive index, high transmission and non-yellowing. They are all solvent-free and provide adjusted mechanical functions and stability as well as good adhesion and application on various substrates. The precise placement of tiny droplets, a few picolitres in size, makes inkjet printing ideal for coating and protecting thin layers to achieve optical correction. It is a viable alternative to spin coating and other dispensing methods and has significantly reduced material waste, saving up to 80%.