▎ 摘　　要

NOVELTY - Black biaxially-oriented polyethylene terephthalate film, comprises 65-85 wt.% film-grade poly(ethylene glycol)-terephthalate chips, and 15-35 wt.% black polyester chips. USE - The black biaxially-oriented polyethylene terephthalate film is useful in flexible printed circuit boards for shielding and insulating. ADVANTAGE - The black biaxially-oriented polyethylene terephthalate film has extremely low light transmittance (light transmittance less than 0.2%) on the basis of ensuring excellent physical and mechanical properties, excellent electrical insulation performance (electric strength ≥ 125 V/μm), and ideal comprehensive performance. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing black biaxially-oriented polyethylene terephthalate film, comprising (a) crystallizing and drying the film-grade polyethylene terephthalate chips and black polyester chips, adding them into double-screw extruder for melting and vacuum treatment, removing moisture and impurities, and extruding into film sheet, where the extrusion temperature is 265-275 ℃, (b) attaching the film sheet obtained in step (i) to chilling roll to form a cast sheet by electrostatic adsorption at 25-35 ℃, where the attaching voltage of the film sheet to the chilling roll is 7.5-8.5 Kv, and the cooling temperature is 25-35 ℃, (c) longitudinally stretching the cast sheet obtained in step (ii) into thick sheet, the preheating temperature before stretching is 80-90 ℃, the stretching temperature is 110-120 ℃, and the stretching ratio is 4- 4.5 times, (d) stretching transversely the thick sheet obtained in step (iii) to obtain a high-strength flame-retardant biaxially-oriented polyethylene terephthalate film, the preheating temperature before stretching is 100-110 ℃, the stretching temperature is 110-120 ℃, and the setting temperature is 200-240 ℃, and (e) flattening the film obtained in step (c) by flattening roller, cooling, rewinding, and cutting to obtain the finished product.