Method for preparing a photo-crosslinkable composition

A method for preparing a photocrosslinkable composition, comprising the following steps:

• (a) a reaction for hydrolysis and condensation of an [(epoxycycloalkyl)alkyl]trialkoxysilane in solution in an organoaqueous medium containing water, in a water/monomer initial molar ratio of between 3 and 15, and at least one water-miscible solvent, at a pH of between 1.6 and 4.0, by heating the solution at a temperature of between 50 and 70° C. for a period of between 180 and 350 minutes, so as to obtain a solution of an organomineral hybrid prepolymer, in which all or virtually all of the alkoxysilane groups have been hydrolyzed, and which comprises on average at least 4 (epoxycycloalkyl)alkyl groups per molecule,
• (b2) evaporating the solvent phase of the reaction mixture of step (a) for 120 to 300 minutes, under a reduced pressure of between 20 and 30 mbar, at a temperature of between 45° C. and 65° C., until a solids content of between 60% and 85% is obtained,
• (c2) preparing, at room temperature and with stirring, a homogeneous solution of at least one photoinitiator, at least one photosensitizer in a solvent chosen from the group consisting of 1-methoxy-2-propanol, N -methylpyrrolidone (NMP), propylene glycol methyl ether acetate (PGMEA), acetone, ethanol and propylene glycol and dimethyl ether,
• (d2) mixing, at room temperature, the concentrated composition obtained in step (b2) with the homogeneous solution obtained in step (c2) by stirring for a period of between 30 and 60 minutes, the mixing ratio being such that the resulting composition has a solids content of between 40% and 70% by weight,
• (e) filtering the resulting composition through a filter comprising pores with an average size of between 1 μm and 5 μm, and
• (f) storing the resulting liquid filtrate at a temperature below 0° C.