TOWARDS THE SURVIVAL OF THE FITTEST FORMULATION
The 6 evolutionary steps from design to fit for use optical lenses:
Concepts (screening of building blocks)
Candidate inks (optimized rheology, cure speed, jetting performance…)
Prototype inks printed as 3D objects (process optimization, fine tuning)
Final ink (test sales and scale up)
Over the past decade, ChemStream has developed a multitude of dedicated DOD inkjet printing inks for 2D and 3D printing applications. UV Inkjet 3D printing is a unique technology for the digital manufacturing of lenses with optically flat surfaces without the need of a of a post-processing step such as polishing.
Example of 3D printed ophthalmic lenses
The lenses are produced by printing a few hundred layers of UV-curable ink on top of each other.
The development of such inks is very challenging since different properties have to be combined. Firstly, a high transparency and low yellowing must be obtained. Secondly, different concepts must be identified to reach desired physical properties of the printed object such as high hardness, good impact resistance and high refractive index.
In parallel, an advanced process development study is needed in order to identify the most optimal 3D inkjet printing strategy. In this context, optimizing and fine-tuning the rheology, jetting performance and photosensitivity of the ink is key. Furthermore, the inks require a high “overprintability” and a fine-tuned wetting behaviour in order to enable a smooth and homogeneous surface.
Balancing all these requirements, different generations of prototype inks were developed leading to a final ink composition that has been scaled up by ChemStream up to a few hundred kilograms. Lenses which have been digitally printed with this ink are currently commercialized.
Modular printing system @ ChemStream for finetuning the inkjet ink development
More about this subject can be found in our brochure