Fabrication of light absorbing dye-doped hybrimer optical filter film

Abstract

In recent years, as demand for smart devices such as smartphones, wearable devices, autonomous vehicles and the like has increased, demand for optical sensors mounted on smart devices also has increased. In particular, there is an increasing demand for image sensors required for digital cameras and infrared sensors required for security sensors such as fingerprint recognition, iris recognition, and biometrics, and for position sensors such as autonomous navigation sensors. Generally, the optical sensor detects light and converts it into a digital signal. However, it also detects the light of undesired wavelengths in addition to the wavelengths of light necessary for sensing. So, it is very important to have an optical filter that effectively removes light of undesired wavelengths in order to obtain an accurate signal. Therefore, the optical filter with fine performance is necessary for the optical sensor with a fine performance. There are two types of optical filters, an absorptive optical filter, and a dichroic optical filter, but nowadays a hybrid optical filter, the absorptive optical filter with interference layer coated, is widely used for fine performance. Until now, the glass is widely used as substrate of the absorptive optical filter for the hybrid optical filter but, as demand for thin and flexible smart devices has increased, it is necessary to replace the glass with a plastic film as the substrate of the absorptive optical filter for the hybrid optical filter. In this work, we fabricated light absorbing dye-doped siloxane resin by sol-gel process and light absorbing dye-doped hybrimer optical filter film for replacing the absorptive optical filter with the glass substrate. We fabricated two types of the light absorbing dye-doped hybrimer optical filter film, one is near-infrared cut off hybrimer optical filter film for digital cameras and the other is visible cut off hybrimer optical filter film for IR sensors. We coated near-infrared absorbing dye-doped siloxane resin on COP film to fabricate the near-infrared cut off hybrimer optical filter film and it shows a high transmittance in a visible area with low transmittance in a near-infrared area and low haze value. It also has a high thermal and optical stability, so the near-infrared cut off hybrimer optical filter film is proper for replacing the glass. In case of visible cut off hybrimer optical filter film, we impregnated visible light absorbing dye-doped siloxane resin into glass-fabric and cured it together to fabricate glass-fabric reinforced optical filter film. It shows a high transmittance in the infrared area with low transmittance in the visible area and high mechanical properties. It also has a high thermal and optical stability, so the visible cut off hybrimer optical filter film is proper for replacing the glass