ZINC-SULPHIDE PHOSPHOR HAVING PHOTO- AND ELECTROLUMINESCENT PROPERTIES, PROCESS FOR PRODUCING SAME, AND SECURITY DOCUMENT, SECURITY FEATURE AND METHOD FOR DETECTING SAME Russian patent published in 2018 - IPC C09K11/54 C09K11/58 C09K11/61 C09K11/62 C09K11/64 C09K11/74 B42D25/30 B42D25/36 G07D7/05 G07D7/12 

FIELD: chemistry.

SUBSTANCE: invention relates to inorganic chemistry and can be used in the manufacture of security features in security or value documents. Zinc-sulphide phosphor is a powder with an average grain size of 2–20 mcm and has chemical formula ZnS: A_a, M_b, X_c, where A is Cu, which can be replaced with Ag and/or Au; M is Al, which can be replaced with Bi, Ga and/or In; X is at least one of F, Cl, Br and I; 0<(a+b+c)<0.12; 0.0001<a<0.008; 0.6⋅a<b<4⋅a; 2⋅b<c<4⋅b. When excited by an electric field, said phosphor emits blue light, when excited by ultraviolet rays with a wavelength of 345–370 nm it emits blue light, and when excited by UV rays with a wavelength of 310–335 nm - green light. To obtain said phosphor, a mixture consisting of ZnS and compounds containing Cu, Al and halogens F, Cl, Br or I is prepared. Obtained mixture is annealed at 800–1300 °C in the presence of activated carbon. Calcined mixture is cooled to obtain a semi-finished product, which is etched with a mineral acid, followed by adding Cu, dried, annealed at 200–600 °C, treated with dilute mineral acid, washed, dried and again annealed at 200–500 °C. Resulting zinc sulphide phosphor is washed, ground and sieved. Annealing of the mixture can be carried out in air or in a N₂ atmosphere containing H₂. To detect and/or authenticate a security feature comprising said phosphor, it is first excited by UV rays at a wavelength of 345–370 nm and it is checked whether the radiation is observed in the blue portion of the visible spectrum. Phosphor is then excited with UV rays with a wavelength of 310–335 nm and it is checked whether the emission is observed in the green portion of the visible spectrum. After that, the phosphor is excited with an electric field and it is checked whether the radiation is observed in the blue portion of the visible spectrum. If the corresponding radiation is detected during said verification stages, a confirmation signal is generated.

EFFECT: invention provides reliable protection of value documents.

12 cl, 8 dwg, 6 ex