Alnico-based magnetic particles for security ink

Abstract

AlNiCo-based magnetic particles according to the present invention are hard magnetic particles each comprising: a core particle containing Al, Ni, and Co; and an inorganic shell enclosing the core particle, wherein the core particle is an ultra-fine particle having D50 of smaller than 12 [mu]m, D50 being the particle size corresponding to 50% in the core particle diameter cumulative distribution,and wherein the core particle has a composition uniformity of equation 1, equation 2, and equation 3 below. The equation 1 is 10 <= UNF(Al), the equation 2 is 10 <= UNF(Ni), and the equation 3 is 10<=UNF(Co). In equation 1, UNF(Al) is the value obtained by dividing the average Al composition among core particles by the standard deviation of the Al composition on the basis of weight% of the composition. In equation 2, UNF(Ni) is the value obtained by dividing the average Ni composition among core particles by the standard deviation of the Ni composition on the basis of weight% of the composition. In equation 3, UNF(Co) is the value obtained by dividing the average Co composition among core particles by the standard deviation of the Co composition on the basis of weight% of the composition.

Description

technical field [0001] The present invention relates to AlNiCo-based magnetic particles for anti-counterfeiting inks and anti-counterfeiting inks containing the same, and relates in detail to the ability to have uniform hard magnetic properties and improved anti-counterfeiting properties because the magnetic particles have excellent compositional uniformity according to designed values AlNiCo-based magnetic particles for anti-counterfeit ink and anti-counterfeit ink containing them. Background technique [0002] Anti-counterfeiting substances can be said to be necessary in fields where counterfeiting needs to be prevented. As an example, in the field of anti-counterfeiting printing, anti-counterfeiting substances are used for valuable documents such as checks, stamps, gift certificates, vouchers, bonds, etc. [0003] It is known that the magnetic particles in the anti-counterfeiting material are coated with inorganic substances to form core-shell structure magnetic particle...

AI Technical Summary

Problems solved by technology

1) If the magnetization density of the magnetic particles is too large or small, it will be difficult for expensive identification equipment to measure the inherent signal of the magnetic particles

2) When the size of the magnetic particles is too large or small, it is difficult for the magnetic particles to effectively reflect sunlight, so it becomes difficult to conceal the dark magnetic particles, which leads to a sharp decrease in its anti-counterfeiting performance, and may be used in anti-counterfeiting printing. Problems such as poor printing caused during the process

[0012] However, the water atomization process mainly uses water (H 2 O) as a cooling medium, so the oxidation of the produced powder is a big problem

[0013] In addition, the gas spray method uses a non-reactive gas (N 2 , Ar, He) or air (air) as the cooling medium, so there are few problems of oxidation and impurities mixed in during the production of powder, so high-quality powder can be produced, but the cooling effect is relatively low, so it may occur during the production process Fine segregation is technically difficult to produce magnetic particles of a specific shape, and the yield is very low at about 5%, which has a problem of greatly reducing commercial availability

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