Japan's Toppan Printing Co. has developed a new film for food and medicine packaging that blocks ultraviolet light but is also transparent, so the contents of the package can be seen.

To make the film, the company starts with a clear film and coats it with an ink specially designed to allow the passage of visible light but to absorb and reflect light in the ultraviolet part of the spectrum.

UV-blocking packaging is typically made using aluminum, so the contents are completely hidden from view. Other UV-blocking inks have been developed for coating on clear films, but these are less specific to the UV band and the film ends up appearing opaque.

Toppan's new film allows passage of less than 1 per cent of UV light, protecting foods and medicines from the degrading effects of the radiation while allowing consumers to see what is inside the package.

The company plans to market the new film for food products like high-end candies, where appearance is important, and for medicines, since for safety reasons it is better if people can visually confirm the medicines in their possession.