Epolin produces coatings and security inks that can be viewed with night vision (NV) instruments to appear black against a normal night vision background. The reason this occurs is because the NV system has a visible light filter over the detector allowing only near infrared light to pass. This is detected as a black image.
The problem at this point is that the image can be easily read with the naked eye which defeats the goal of secrecy. To block the visible light it is necessary to place the filter on the object to be detected. The message will then appear flooded with either a black or deeply colored overmark. When viewed with a NV device, the message can still be read although it now cannot be detected visually. Overcoatings are now available to do this.
They are part of a family of dyes that come under the 7276 series. The variants, 7276 A,B,C,E,F differ in that they block the visible spectrum plus an increasing portion of the near infrared.