Preparation of light-focusing plastic fiber by heat-drawing process

A light-focusing plastic fiber (LFF) was prepared by the heat-drawing process of the following perform at 106–120 °C under 5–7 g/mm2 stress and draw ratio DR=6–370: preform, a light-focusing plastic rod obtained from the photocopolymerization of methyl methacrylate (MMA) with vinyl benzoate (VB) or vinyl o-chlorobenzoate (VOCB), consisting of linear copolymers. LFF’s of radius rp=0.140 mm and rp=0.071 mm were produced by heat drawing of 4/1 (wt/wt) MMA-VB preform (P series) under DR=121 and of 4/1 (wt/wt) MMA-VOCB preform (Q series) under DR=370, respectively. The refractive-index profile, n (r) ∼r/rp, near the center axis is slightly changed by heat drawing. The internal loss of light transmission of the P-series product is in the range of 4–5 dB/m.