Anti-counterfeiting inks for new inks--Introduction to metachromatic inks

In today's diversified security and anti-counterfeiting measures, various new types of anti-counterfeiting technologies emerge in an endless stream, presenting a flourishing situation. An anti-counterfeiting technology, with the popularization of its application, will increase the possibility of forgeries being forged, and the function of anti-counterfeiting will gradually decrease. Therefore, extending the timeliness and uniqueness of anti-counterfeiting technology has always been the goal of anti-counterfeiting technology. And metamerism ink is a new type of ink with a unique anti-counterfeiting function.

Metamerism

We know that each type of object has its own fixed optical properties. Under the illumination of sunlight, the color is fixed. That is, the object absorbs part of the colored light and reflects part of the colored light. As a result, we observe the color of such an object. Moreover, the inherent spectral parameters of the material are certain and it does not change with changes in external conditions. Therefore, the spectral data is the only and most realistic description of the color of the object.

In the evaluation and description of the color system, the characteristics of the color are often expressed in a three-dimensional coordinate system. That is, the color is described by the three basic parameters of hue, lightness, and saturation. In addition, there is a certain relationship between the reproduction of a color and the characteristics of the light source that observes the color. Some two substances show the same color under one light source, but under another light source, they show different colors. It is called metamerism. For the purpose of standard assessment of this phenomenon, the International Commission on Illumination has introduced a metamerism evaluation index for evaluating color metamerism.

Metachromatic inks

Metamerism inks are developed based on the metamerism principle of matter. Under the irradiation of sunlight, the two metachromic inks have the same color visual effect, ie, they have the same expression of color characteristics, but the two inks have different spectral properties. Same-color different-spectrum ink is the use of two colors with the same color, different spectral characteristics of the two pigments, to produce two colors with the same effect, and different spectral characteristics of the ink, a pair of metachromatic spectrum of ink. The anti-counterfeiting function of the metachromatic spectrum ink is mainly determined by the different absorption and reflection ability of the pigments in the ink that play a role of coloration. Both BASF and Ciba-Gakki produce special metachromatic spectrum pigments for the formulation of inks.

The same-color different spectrum ink has obvious anti-counterfeiting effect and is easy to observe; because it needs special pigment series to produce, it has better anti-counterfeit security; the same-color different spectrum ink has good durability and stable performance, unlike the fluorescent ink, which has a problem of the decay cycle. After a certain period of time, the color rendering characteristics will not change.

Identification method

There are two methods for observing and discriminating metachromatic inks used as security inks. One method is that, according to a pair of metameric spectrum inks having different spectral characteristics, that is, having different spectral characteristics, the spectra of the two inks can be measured by the instrument and compared. The second method is simple and easy. It is based on the principle of selective absorption and reflection of light by ink, so that a pair of inks passes through a specific color filter, and one of the inks causes reflected light to occur due to the role of a color filter. Change, at the same time, the color observed by the ink also changes, showing another fixed color; and another ink through the filter, still absorb and reflect the original light, the display color is not change. In this way, we can identify the true and false of the subject matter through two fixed, different colors.

application

The use of the same-color different-spectrum inks is mostly offset printing, which can be used to print or normal printing. The two inks should be printed on the adjacent parts of the substrate to facilitate observation and comparison. And the same-color different spectrum ink can be used in combination with infrared ink to achieve better anti-counterfeiting effect. The combined anti-counterfeit feature is that, under the illumination of the light with a spectral wavelength of 600 to 1000 nm, the visual effects of the two are consistent, an ink is colored under infrared irradiation, and an ink absorbs infrared light to show a colorless state, and the spectral characteristics of the two are also not In the same way, this can achieve double anti-counterfeiting effect.

In foreign countries, the same-color different spectrum ink has been used in printing money. At present, there is no practical application in China. It needs to further recognize it and exert its anti-counterfeiting effect. With the increase in anti-counterfeit demand and the improvement of comprehensive anti-counterfeiting capabilities, this new anti-counterfeiting technology of the same-color different-spectrum ink will certainly be able to bloom.

Source: Coatings Technology Information Network