MAGNETIC PARTICLES, BASE CONTAINING SUCH PARTICLES, PROTECTED DOCUMENT, AND METHOD FOR DETECTING SUCH PARTICLES Russian patent published in 2003 - IPC

FIELD: counterfeit protection of documents. SUBSTANCE: base of counterfeit-protected document has base material and elongated particles inside base material, magnetic properties of particles being different from respective magnetic properties of base material. Particles have magnetic saturation field over 100 A/m and magnetic flux density higher than 0.1 T. Base may have paper or plastic sheet. Particle length and shape are such that its demagnetization coefficient is lower than 1/250, cross-sectional area diameter is smaller than 30 microns, magnetic saturation field is greater than 100 A/m, magnetic flux density is 0.1-1 T. Method for detecting particles in base whose electromagnetic properties are other than those of particles involves several steps. EFFECT: enhanced reliability of distinguishing original documents from counterfeits; impossibility of copying original documents. 40 cl, 8 dwg, 1 tbl