Sumitomo patents near infrared anti-counterfeit ink

Sumitomo Metal Mining has been granted a US patent for a security ink based on near infrared (NIR) absorbing particles that it says have advantages over other inks used for offset printing applications.

The Japanese company has come up with an ink whose behaviour is unchanged by environmental exposure to temperature or sunlight, is long-lasting, offers greater contrast and doesn’t need to be dispersed in organic solvents that aren’t compatible with some print surfaces.

The ink is based on NIR-absorbing hexaboride particles dispersed in vegetable oil “whose authenticity can be judged mechanically and reliably not depending on a visual judgment,” according to the patent.

The abstract of the patent appears below:

Near infrared absorbing fine particle dispersion liquid and method for producing the same, anti-counterfeit ink composition using near infrared absorbing fine particle dispersion liquid, and anti-counterfeit printed matter using near infrared absorbing fine particles

Abstract: Provided are a near infrared absorbing fine particle dispersion liquid having an absorption ability in a near infrared region, a clear contrast, and applicable to offset printing, and a method for producing the same, an anti-counterfeit ink composition using the near infrared absorbing fine particle dispersion liquid and an anti-counterfeit printed matter using near infrared absorbing fine particles. Also provided are a near infrared absorbing fine particle dispersion liquid containing a solvent of one or more kinds selected from vegetable oils or vegetable oil-derived compounds; near infrared absorbing fine particles in an amount of 2 mass % or more and 25 mass % or less, selected from one or more kinds of hexaboride fine particles expressed by a general formula XB.sub.a (wherein element X is at least one or more kinds selected from a group consisting of La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr, and Ca, satisfying 4.0.ltoreq.a.ltoreq.6.2); and a dispersant soluble in the solvent and having a fatty acid in its structure, wherein viscosity is 180 mPa/S or less, and an anti-counterfeit ink composition containing the near infrared absorbing fine particle dispersion liquid. Also provided is an anti-counterfeit printed matter excellent in anti-counterfeit effect due to the printed matter containing the near infrared absorbing fine particles.

US Patent No. 10,604,665