| abstract |
The invention relates to a photochromic gamma butyrolactone having the general formula (I):-n in which X represents CH₂ or C(CH₃)₂; R₁, R₂ and R₄ independently represent a group selected from hydrogen, alkyl or aryl (including substituted aryl), with the proviso that one of R₁ and R₂ is always hydrogen, and R₃ is a 3-thienyl, 3-furyl, 3-benzothienyl or 3-benzofuryl group in which the 2-position is substituted with an alkyl, aralkyl or aryl group (including substituted aryl). n The lactones are useful in photolithography and in the production of security inks and markings and in the production of data recording materials. |