Photochromics (PCs) change from clear when indoors to color when outdoors. Specifically, PCs change color in response to ultraviolet (UV) light, usually from the sun or a black light.
Photochromic behavior can be either Reversible or Irreversible. (Technically, all photochromism is defined as reversible but for simplicity we will use the term irreversible photochromic to describe irreversible photochemical reaction that yields a visible color change.)
Reversible Photochromics (PCs) transform from clear to color by changing their chemical structure after absorbing UV light, usually from the sun or a UV light. The UV light causes the PCs to absorb color (like a dye), and then change back to clear when the UV source is removed. They can cycle thousands of times depending upon the application. They can also change from one color to a different color by combination with a permanent pigment.Standard LCR Hallcrest photochromic ink will change from clear to color when activated by UV light. The company also markets a irreversible solvent based screen ink / label that permanently changes from clear/ white to blue at 254 nm
The most famous reversible photochromic application is color changing lenses for glasses, as found in Transitions® eye-glasses. Reversible PCs are also found in novelty applications such as tee shirts, toys, cosmetics, and industrial applications.
LCR Hallcrest Photochromic Inks have an ultraviolet color change response usually from the sun or a black light. The inks are effectively colorless indoors and turn into vibrant colors outdoors. When brought back inside, the inks become clear again. The inks become intensely colored after only 15 seconds in direct sunshine and return to clear after about 5 minutes indoors. Perfect for textiles and other applications where there is a period of exposure followed by non-exposure to UV light.
A wide range of Reversible PC Products, from raw materials to finished inks, powders, dyes and finished products is available. A PC material can be custom synthesized or formulated specifically for your application, including a color to color change. LCR Hallcrest does not offer permanent change photochromic inks at this time. Please let us know if we can be of assistance in creating your custom product!