Reversibly activatable diacetylenes and their use as colour-formers

A packaging laminate (10) comprising a base layer (11), one or more outer layers (13, 14), and a diacetylene compound, wherein the diacetylene compound is of formula I:

• Y—C≡C—C≡C—(CH2)n-T-Q-Z (I)
• wherein:
• n=an odd integer;
• T=CO, CS or a bond;
• Q=NH, S, O, OCONH, NHCONH, NH—CHE-CONH, NHCOO or NHCSNH wherein E is H or a C1-20 alkyl group;
• Z=H or a hydrocarbon group containing 1 to 20 carbon atoms;
• and
• Y=H or any group comprising at least one carbon atom.

A packaging laminate for a packing container having a mark (18) of informative character visible from outside the container, the packaging laminate (10) comprising a substrate layer (11) of paper or paperboard and an outer liquid-tight layer (13, 14) of polyolefin on each side of the substrate layer (11), wherein one surface of the substrate layer (11) is at least partly coated with a print ink containing a diacetylene compound and/or a polymerisation product thereof, wherein the diacetylene compound is of formula I:

• Y—C≡C—C≡C—(CH2)n-T-Q-Z (I)
• wherein:
• n=an odd integer;
• T=CO, CS or a bond;
• Q=NH, S, O, OCONH, NHCONH, NH—CHE-CONH, NHCOO or NHCSNH wherein E is H or a C1-20 alkyl group;
• Z=H or a hydrocarbon group containing 1 to 20 carbon atoms;
• and
• Y=H or any group comprising at least one carbon atom.