Roll-to-roll pilot nanoimprinting process for backlight devices

A pilot scale roll-to-roll manufacturing process for backlight devices was demonstrated using Poly(methyl methacrylate) (PMMA) film. Backlight device (28 × 28) mm² consist more than 78,000 binary elements with different orientation. Each element has 40 trenches with 5 μm width and 1.3 μm thick, totally 3.1 million trenches in one device. These devices can be used for display illumination in various applications when three LED is connected on the other end of the device. More than 1000 device was printed on 50 mm wide 375 μm thick PMMA web using custom made nanoimprinting equipment. These devices demonstrate a high throughput and a low cost production possibility for micron- and submicron optical structures.

The printed patterns were analysed by using optical microscopy, atomic force microscopy (AFM) and confocal microscopy. The backlight device after LED integration was characterized using luminescence measurements. The three surface mounted LED is connect to the upper side of printed PMMA device to give light in the polymer film. To collect statistics, every 50th sample was analysed. The pattern replication is good and the depth of the imprinted structure is typically in the range of 1.2–1.4 μm when limits for working device is ca. 1.0 μm. The optical properties of the analysed devices show good homogeneity inside one device. The standard deviation for the measured luminescence values for all devices was within 17% which is still acceptable for final production. No drastic wearing of the stamp can be seen after pilot manufacturing.