Reversible thermochromic compositions

A reversible thermochromic system comprising

• (a) a β-phenylvinylketone or a ω-phenyl polyacetylenyl ketone containing at least one acidic hydrogen and
• (b) a base;
• with the proviso that the system is free of thymol blue and phthalein derivatives,
• wherein component (a) is a compound of formula (I),
• wherein
• X is
• or CHR7—CO—R8;
• or X is C1-C30alkyl, C2-C30alkenyl, C2-C30alkinyl, C7C12aryl, C7-C12aralkyl, C8-C12aralkenyl or C8-C12aralkynyl, each of which is unsubstituted or substituted;
• n is an integer from 1 to 10;
• R and R′ are independently hydrogen, C1-C30alkyl, C2-C30alkenyl, C2-C30alkynyl, C6-C12aryl, C7-C12aralkyl, C8-C12aralkenyl or C8-C12aralkynyl;
• R1, R2, R2′, R3, R3′, R4, R5, R5′, R6 and R6′ are independently hydrogen, hydroxy, C1-C30alkyl, C2-C30alkenyl, C2-C30alkynyl, C6-C12aryl, C7-C12aralkyl, C8-C12aralkenyl, C8-C12aralkynyl, halogen, NO2, CN, NR9R10, OR11, SR11, S(═O)R11, S(═O)2R11, CO—R11, CO—O—R11, O—CO—R11, CO—NR9R10 or NR9—CO—R11, whereby the alkyl, alkenyl, alkynyl, aryl, aralkyl, aralkenyl and aralkynyl are substituted or unsubstituted;
• R7, R9 and R10 are independently hydrogen or as defined for R8;
• R8 and R11 are independently C1-C30alkyl, C2-C30alkenyl, C2-C30alkynyl, C6-C10aryl, C7-C12aralkyl, C8-C12aralkenyl or C8-C12aralkynyl, whereby the alkyl, alkenyl, alkynyl, aryl, aralkyl, aralkenyl and aralkynyl are substituted or unsubstituted;
• the substituted alkyl, alkenyl, alkynyl, aryl, aralkyl, aralkenyl and aralkynyl are substituted by halogen, hydroxy, NO2, CN, CO—R12, COO—R12, CONR13R14, OCO—R12, NR13CO—R12, NR13R14, O—R12, S—R12, S(═O)—R12 and/or S(═O)2—R12;
• or the substituted aryl, aralkyl, aralkenyl and aralkynyl are substituted by C1-C30alkyl, C2-C30alkenyl and/or C2-C30alkynyl;
• R12 is independently C1-C30-alkyl, C2-C30alkenyl, C2-C30alkynyl, C6-C12aryl, C7-C12aralkyl, C8-C12aralkenyl or C8-C12aralkynyl;
• and
• R13 and R14 are independently hydrogen or as defined for R12;
• and
• wherein R1 and/or R4 are hydroxy and
• wherein component (b) is a secondary or tertiary amine or a secondary or tertiary phosphine of formula NHR26R27, NR26R27R28, PHR26R27 or PR26R27R28 wherein
• R26,R27 and R28are independently C1-C30alkyl, C7-C12aralkyl, C2-C30alkenyl, C8-C12aralkenyl, C2-C30alkynyl or C8-C12aralkynyl, which are unsubstituted or substituted by one or more COO—R13, CONR13R14, OCO—R12, NR13CO—R12, NR12R13, O—R12, S—R12, SO—R12 and/or S(═O)2—R12;
• or the aralkyl, aralkenyl and aralkynyl are substituted by C1-C30alkyl, C2-C30alkenyl and/or C2-C30alkynyl,
• where R12 is C1-C30alkyl, C2-C30alkenyl, C2-C30alkynyl, C6-C10aryl, C7-C12aralkyl, C8-C12aralkenyl or C8-C12aralkynyl and R13 and R14 are independently hydrogen or as defined for R12 or
• wherein component (b) is a secondary or tertiary sterically hindered amine of formula (Z)
• wherein G4, G5, G6 and G7 are independently methyl or ethyl,
• E is hydrogen, C1-C18alkyl or C3-C18alkenyl and
• E10 is a carbon atom which is unsubstituted or substituted by OH, ═O or by one or two organic residues containing in total 1-500 carbon atoms or 1-500 carbon atoms and 1-200 heteroatoms, wherein the component (b) has a molecular weight of at least 150 g per mole.