Photochromic Products

In comparison to other organic photochromic compounds, some spirooxazine compounds are great in light fatigue resistance. This allows applications which require moderate photochromic product life to become a reality and to be commercially viable. One of these applications is in your community of ophthalmic and sunglass lenses. Fascination with the development of a plastic photochromic lens for ophthalmic and/or sunglass lens application is high since about seventy percent of the lens market is now plastic. Many large optical companies around the globe have already been actively pursuing development of plastic photochromic lenses for days gone by ten years. Sometimes, and particularly in the dye industry, the word irreversible photochromic is used to describe materials that undergo a permanent color change upon exposure to ultraviolet or visible light radiation. Because by definition photochromics are reversible, there’s technically no such thing as an “irreversible photochromic”—this is loose usage, and these compounds are better known as “photochangable” or “photoreactive” dyes.

• Formerly, the lenses were made of glass and the photochromic systems were predicated on silver halides.
• Our interval thermochromic pigment passed EN-71 & RoHS and is safe for food grade packing and toys.

This dependence of the degree of darkening of the lens on temperature varies somewhat in one brand to the other. Generally, these photochromic lenses usually do not darken at higher temperatures (e.g., 35 °C) as much as they do at lower temperatures (e.g., 20 °C). All plastic photochromic lenses as listed in the above table are made of diethylene glycol bis, usually referred to as CR-39, that is a trade mark of PPG Industries. Because the activated color of the spirooxazine derivatives used to make these photochromic lenses is blue, these lenses will assume the blue color when exposed to sunlight. The colour of the lens can be altered with other non-photochromic passive dyes. As a consequence, the unactivated luminous transmittance of the lens will decrease.

Although spirooxazine compounds have excellent light fatigue resistance, they do degrade slowly on contact with sunlight. Therefore, each one of these photochromic lenses have a finite use life, so far as photochromic function can be involved, which is usually

The dyes should also provide pretty much constant performance over many cycles of photocoloration, an attribute known as fatigue resistance. The irreversible photochromic products show their colours when exposed to UV however, not visible light. Unlike the reversible photochromic products, its colour will not revert to their original colours once the UV is dimmed or blocked. The permanently changed molecule structure of irreversible photochromic pigments after absorption of sunlight/UV allows a colour appears irreversibly. Our irreversible photochromic pigment passed EN-71 & RoHS and is safe for food grade packing and toys.