| abstract |
Optical filtering elements having two opposed surfaces and including at least one thin layer of stable non-reflective fluorescent material provide transparent articles which, when exposed to incident electromagnetic radiation at one surface of the fluorescent layer, absorb certain wavelengths within the fluorescent layer and emit other wavelengths at the opposed surface of the fluorescent layer. In preferred embodiments, when radiation (light) in the visible range (about 400 nm to about 700 nm) is incident on the element from one side, certain wavelengths of radiation which transverse the element are absorbed in the fluorescent layer and other radiation of greater, but also visible wavelengths are emitted from the opposed side without fluorescent light being reflected by the fluorescent layer at the incident side. Methods of forming such optical filtering elements include providing a thin coating or layer including stable fluorescent material on an optical element by means of a solution or coating composition including stable fluorescent material, forming transparent sheets or films containing stable fluorescent material and utilizing them as optical filtering elements or incorporating them in an optical structure, or in other ways incorporating thin layers of stable fluorescent material within an optical element. In order to avoid glare and reflection of fluorescent light at the incident side, preferred embodiments require layers of stable fluorescent material which are about 1 mil (0.0254 mm) or less in thickness. |