FIELD: information protection.
SUBSTANCE: invention can be used in protection of documents from forgery. A protective paint for printing of a machine-readable protective sign is proposed, containing one or more IR radiation-absorbing materials selected from a group consisting of iron (II) orthophosphates without crystallization water of the general formula Fe3(PO4)2 with a crystal graftonite structure, metal-containing iron (II) orthophosphates without crystallization water, metal-containing iron (II) phosphonates without crystallization water, metal-containing iron (II) pyrophosphates without crystallization water, metal-containing iron (II) metaphosphates without crystallization water of the general formula FeaMb(POc)d, where a is a number from 1 to 5, b is a number from >0 to 5, c is a number from 2.5 to 5, d is a number from 0.5 to 3, and M is one or more metals selected from a group consisting of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, transition metals (block d) selected from Sc, Y, La, Ti, Zr, Hf, Nb, Ta, Cr, Mo, W, Mn, Cu, Zn, Co, Ni, Ag, Au, metals and semimetals of the third, the fourth, and the fifth main groups, selected from B, Al, Ga, In, Si, Sn, Sb, Bi, and lanthanoids, and mixtures thereof. The protective paint is a protective paint fixed by oxidation, or a protective paint cured under the action of radiation in UV and visible range, or a protective paint fixed under the action of heat, or a combination thereof. A machine-readable protective sign and its production method, a protected document and its authentication method are also proposed.
EFFECT: invention allows for increase in a degree of document protection.
15 cl, 3 dwg, 15 tbl
