Color tuning characterization and modeling of textile displays made from polymeric optical fibres

Abstract

This research presents a systematical study of fabrication, characterisation, theoretical analysis and applications of polymetyl methacrylate (PMMA) optical fibres and their textile displays. This project not only aims to create a scientific basis for the polymer optical fibres (POF) with respect to its physical properties, optical attenuation and dyeability but also luminescence properties of PMMA POP based textile displays. In the study, polymer optical fibres serve as a basic material in flexible displays as they are easy to handle, flexible and economical. PMMA material systems were examined, including PMMA thin films, POF fabrication and characterisation, POF dyeing by laser dyes and conventional dyes, and POF textile fabric panels. Various characterisation techniques were applied in relation to the mechanical, thermal and optical properties of the systems under investigation. PMMA thin films were fabricated by spin coating technique with various molecular weights, concentration levels, temperatures and spin speeds. Optical properties of the thin films were investigated by using a prism coupler. A coupling pressure of 35 ~ 40psi has been identified as appropriate for measuring the refractive index of the films. PMMA optical fibres were fabricated by using a two-step fabrication technique with a preform-drawing unit. Critical parameters on preform quality, drawing speed and furnace temperature were found to impart significantly the resultant fibre geometry and quality. The resultant PMMA POFs exhibited a break elongation from 140% to 270%, with a maximum load ranging from 1N to 2N. On the other hand, commercial POFs were further drawn to produce finer fibres under various operating conditions of the preform-drawing system. The workable ranges have been identified for both preform and fibre drawing processes. Finally, trials of surface modification of POFs were made, by employing a number of techniques, to achieve side emitting effects. Colouration experiments of PMMA POFs were carried out. PMMA POFs of various thicknesses were used in laser and conventional dye systems. Numerous dyeing methods were applied, their effects on the morphological and optical properties of POFs were determined. The optimum dyeing conditions for laser dyes were 85 for 45 minutes where an extended dyeing period of 60 minutes was suitable for basic dyes. Fibre damages occurred as the dyebath temperature reached near the glass transition temperature of PMMA. The K/S values of basic dyeing were better than those of laser dyeing system, but the optical transmission of the dyed POF was much reduced. Transmission power loss of POFs in simulated woven structures and real woven fabrics was measured. Three woven structures of POFs were fabricated and studied, i.e., plain weave, 2x2 and 1x3 twills. An attempt of mathematical calculation on the macrobending attenuation of POFs has been made. The radiated light from bent fibres in the three woven structures was measured by a power-meter, confirming the lateral light emitting distribution along the fibre. Fibre diameter, packing density and weave structures affected the luminescence power distribution of the fibre. By combining the techniques, some fashion garments with textile display structures of modified POFs were designed and produced. Due considerations were given to system design, power source, light source, coupling, control integrated circuitry and textile display panels. Fabrication of light emitting textile panels provides a platform as the basis for future development of opto-electronic textiles that can be applied in various fields.