Effect of Ultrasonic Vibration on Increasing Embossing Speed during Hot Glass Embossing Process

Abstract

Nowadays, microstructures have an important role in optical products as well as in optical systems. Beside machining methods, hot glass embossing is recently a novel technology to manufacture microstructures in optical components with high quality and low cost. Especially, this technology has been assisted efficiently by ultrasonic vibration. Previous studies showed that high energy of ultrasonic vibration would lead to the temperature rise inside the glass so that the material was easily embossed into the microcavities on the mold. Thus, micro-formability of glass material has been especially improved efficiently. However, there were no studies focusing on effect of ultrasonic vibration on embossing speed in this process. Therefore, this work is aimed to utilize ultrasonic vibration to improve the embossing speed of hot glass embossing process. K-PSK100 optical glass was used as the material for all experiments. Pyramid array with size of 30 × 30 × 20 μm and period of 150 μm was created on the mold. Microstructure hot embossing experiments were conducted for both conventional process (without ultrasonic vibration) and ultrasonic vibration-assisted process (frequency of 35 kHz and amplitude of 3 μm). By fixing the embossing temperature of 430 °C, the embossing speeds of 0.05 mm/min, 0.10 mm/min and 0.15 mm/min were applied, respectively. Experimental results showed that in case of conventional process, the faster embossing speed, the smaller final height of pyramid structures. Nevertheless, this obstacle was resolved by ultrasonic vibration. Under heating effect of ultrasonic vibration, the glass still filled well into the pyramid cavities on the mold even when the high embossing speed was applied. Measurements indicated that in the same experimental conditions (temperature and speed), ultrasonic vibration could improve the filling ability of the glass to 18 %. This finding could be used to optimize the experimental conditions to increase the productivity of the microstructure hot glass embossing process.