Bonded body made from different materials and method for producing the same

A method for producing a bonded body made from different materials, the bonded body comprising a first member and a second member, wherein the first member contains any one of a macromolecular material, a metallic material, and an inorganic material, the second member contains at least a thermoplastic resin, which differs from the macromolecular material, and the bonded body is obtained by bonding a first joint surface of the first member to a second joint surface of the second member, the method comprising the steps of:

• forming a hydrophobic water-repellent film on the first joint surface, wherein the water-repellent film contains C and Si, has an atomic concentration ratio C/Si of greater than 1 (atomic %/atomic %), and has a water contact angle greater than that of the first joint surface;
• subjecting the water-repellent film to an activation treatment to thereby convert a surface of the water-repellent film into a film having an atomic concentration ratio C/Si of less than 1 (atomic %/atomic %), a molten nylon 6 contact angle of less than 25°, and high hydrophilicity;
• placing the first joint surface on the second joint surface, and heating the first joint surface and the second joint surface to melt the second member;
• and
• cooling and solidifying the molten second member, thereby bonding the first joint surface and the second joint surface while generating a trans-crystal on the second joint surface in the vicinity of an interface between the second joint surface and the first joint surface.