Researchers at the National Taiwan University of Science and Technology have developed an ultra-thin, double-sided optical film designed to overcome light control problems in LCD-based resin 3D printers, according to a paper published in the journal Optical Materials Express.

The study, led by optical engineer Ding-Zheng Lin, centered on a double-sided structure collimation film (DSSCF) that works by arranging micro-lenticule arrays and trapezoidal microstructures on both faces of the film. 

These microscopic elements redirect light rays to travel in tighter, more parallel paths — a property known as collimation — rather than scattering at wide angles as they pass through the printer’s LCD backlight module.

Vat photopolymerization, the process underpinning resin 3D printing, relies on UV light patterns to cure liquid photosensitive resin layer by layer. In lower-cost LCD printers, backlights often produce poorly distributed and insufficiently directed light, which contributes to surface roughness and dimensional inaccuracies in finished parts. Existing remedies, such as lens arrays or collimating assemblies, tend to add bulk and cost.

The DSSCF approaches this by incorporating trapezoidal microstructures that contain stray high-angle light, reducing non-uniform illumination across the print surface. The film also recycles light that would otherwise be lost through reflection back into the backlight module, improving energy use without increasing the physical footprint of the system.

Performance and applications

Testing with an angle-dependent photometer showed the film restricted beam divergence to below 10 degrees full width at half maximum (FWHM), with intensity uniformity across the illuminated area exceeding 81%. The team built a prototype LCD backlight system using two layers of the film combined with a diffuser module, validating the optical performance in a working 3D printer configuration.

The researchers indicated the technology could serve applications requiring high-dimensional accuracy and surface quality, including dental restoration models, jewelry fabrication, and engineering prototypes.

Work is continuing to improve light utilization efficiency and broaden compatibility across UV wavelengths and resin types.