Color shifting multilayer polymer fibers and security articles containing color shifting multilayer polymer fibers

摘要

Polymer fibers are formed with concentric alternating layers of different polymer materials. The layers pairs have cross-sectional thicknesses selected for reflecting light at a selected visible wavelength. A cross-sectional dimension of the core is at least ten times an average of the selected thicknesses of the alternating layers. Some articles formed by the fibers are formed by attaching one fiber to another: the color of the fibers at the point of attachment is different from the colors of the fibers elsewhere. The fibers may be deformed to change its color properties by elongating the cross-section of the polymer fiber along a first cross-sectional axis. In some embodiments, the fibers are polarization sensitive.

主权项

1. A polymer fiber, comprising:
a core formed of a polymer material; and an arrangement of discrete concentric layer pairs surrounding the core, each layer pair comprising a first layer of a first polymer material having a first refractive index and a second layer of a second polymer material having a second refractive index different from the first refractive index, the concentric layer pairs having cross-sectional thicknesses selected for reflecting light at a selected visible wavelength, a cross-sectional dimension of the core being at least ten times an average of the selected thicknesses of the first and second layers, and wherein at least one of the first and second polymer materials is birefringent; and wherein thicknesses of the layers of the first polymer material and the layers of the second polymer material are selected so that the fiber reflects visible light within a selected portion of the visible spectrum in a first polarization state and incident perpendicular to a fiber longitudinal axis and transmits visible light in the first polarization state that lies outside the selected portion of the visible spectrum and incident perpendicular to the fiber longitudinal axis.