Application of a diffractive microstructure to polyester fibre for security purposes

Abstract

Security enhancement of manufactured fabrics by the embossing of diffractive patterns presents problems of distortion and weakening of the fibre owing to the high temperatures and pressures needed for embossing hard plastics such as polyethylene terephthalate (polyester). In order to carry out the embossing procedure without such damage, a thin layer of softer thermoplastic material was coated on the fibre surface, permitting embossing at lower temperatures and pressures without disturbing the integrity of the fibre. Experimentation has demonstrated the feasibility of such techniques, which result in the fibres showing diffractive effects. This technique can be extended to rotary systems. Initial examination of current thread production systems indicates compatibility with the modifications required to add in-line embossing facilities.

Keywords:

• embossing
• diffractive patterns
• shims
• polyester fabrics
• security marking
• infrared laser beams
• web-based embossing systems