Cationically curable composition and method for the joining, casting and coating of substrates using the composition

A cationically curable composition comprising

• a) at least one cationically polymerizable component;
• b) a first photoinitiator releasing an acid when irradiated with actinic radiation of a first wavelength λ1;
• c) a second photoinitiator releasing an acid when irradiated with actinic radiation of a second wavelength λ2, wherein the second photoinitiator comprises an aryl sulfonium salt,
• wherein the second wavelength λ2 is shorter than the first wavelength λ1, wherein the first and the second photoinitiators are selected such that the first photoinitiator can be activated at a first wavelength λ1 of 460 nm without the second photoinitiator being activated simultaneously, and wherein, after the activation of the first photoinitiator, an absorption band of the second photoinitiator at a wavelength λ2 of 365 nm is above the absorption of the first photoinitiator and the decomposition products formed after the activation so that, after irradiation of the composition with actinic radiation of the first wavelength the second photoinitiator shows an absorption of actinic radiation of the second wavelength λ2 in the composition that is sufficient to activate the second photoinitiator and to fix the composition, wherein skin formation takes place in the composition.