Solvochromic effect pigments, method of production and use thereof

A process for manufacturing an effect pigment having solvochromic properties comprising substrates in platelet form and a coating applied to the substrates, wherein the coating comprises

• an optional layer 1 comprising at least one of tin oxide, tin hydroxide and/or tin oxide hydrate,
• a layer 2 comprising at least one of metal oxide, metal hydroxide and/or metal oxide hydrate,
• a layer 3 comprising at least one of metal oxide, metal hydroxide and/or metal oxide hydrate, wherein a majority of the metal oxide, metal hydroxide and/or metal oxide hydrate of the layers 2 and 3 comprise two different metal ions selected from—Ti, Fe and Zr, and
• a spacer layer 4 located in between layers 2 and 3, wherein the layer 4 has a porous structure comprising cavities and connector and a median area of cavity size distribution A50 in a range of 80 to 600 nm2,
• the process comprising:
• (i) optionally applying an uncalcined layer comprising at least one of tin oxide, tin hydroxide and/or tin oxide hydrate to the substrates in platelet form,
• (ii) sequentially applying three uncalcined layers A, B and C each consisting essentially of a single metal oxide, metal hydroxide and/or metal oxide hydrate, where the layers A, B and C are arranged directly one on top of another and wherein the metal ions of layers A, B and C are selected from Ti, Fe and Zr, wherein the metal ion from layer B is different to the metal ions of layers A or C,
• (iii) separating the effect pigment obtained in (ii) from the liquid phase and drying the product,
• (iv) calcining the dried effect pigment obtained from (iii) at a temperature in a range of 300° C. to 600° C., wherein the metal ions present in layer B diffuse at least partly into layer A and/or layer C during the calcination step to form the layer 4.