Light absorbing layer for photo-chromic systems
AssigneeBASF SE
InventorsKathleen Hoekstra, David Nichols, Ross Birney
Life of this patent
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Abstract
A composition which comprises a light absorbing layer adhered to an underlying layer containing a photo-chromic colorant, which photo-chromic colorant has been activated by exposure to UV light to undergo a reversible color change, and wherein the rate of color reversion is dependent on temperature, is provided. The ultraviolet light and/or visible light absorbing layer may also contain components which reflect rather than absorb light and can be conveniently applied via thermal transfer or ink jet to a substrate comprising the photo-chromic colorant to protect it from unwanted exposure to UV and/or certain wavelengths visible light. The composition is conveniently employed in a temperature time indicator (TTI).
Claims11
A time temperature indicator (TTI) comprising a light absorbing layer which is adhered to an underlying substrate, which underlying substrate comprises a photo-chromic colorant,
- which photo-chromic colorant has been activated by exposure to UV light to undergo a reversible color change, which color reversion occurs at a rate that is dependent on temperature and/or time,
- wherein the light absorbing layer is applied to the underlying substrate immediately after the photo-chromic colorant has been activated by exposure to UV light,
- wherein the light absorbing layer comprises a binder, said binder comprising a wax, a natural polymer and/or a synthetic polymer and
- from about 35 to about 60% by weight, based on the total weight of the layer, of a light absorbing composition
- which light absorbing composition comprises one or more components selected from the group consisting of hydroxyphenylbenzotriazole, benzophenone, benzoxazone, α-cyanoacrylate, oxanilide, tris-aryl-s-triazine, formamidine, cinnamate, malonate, benzilidene, salicylate and benzoate ultraviolet light absorbers
- and wherein the light absorbing layer is sufficiently transparent in the visible light region to allow the reversible color change of the photochromic material to be visible.
Dependencies are inferred from the claim text.