Surface modification method

A method for surface-modifying a treatment target made of a fluorine-based resin containing a fluorine atom, the method comprising:

• a plasma step of activating a process gas containing any one selected from the group consisting of carbon monoxide, carbon dioxide, hydrogen, water vapor, ethanol, propanol, hexanol, ethylene glycol, and ammonia as an additive component by plasma and bringing the process gas into contact with the treatment target;
• wherein the plasma step includes:
• a generation step of generating plasma discharge near atmospheric pressure by applying an electric field to an interelectrode space defined by a pair of electrodes;
• a supply step of supplying the process gas to the interelectrode space;
• a contact step of bringing the process gas in the interelectrode space or having passed through the interelectrode space into contact with the treatment target;
• and
• a modification step of, through a reaction caused by the contact, adjusting a residual ratio of fluorine atoms on a surface of the treatment target to 60% or less of a residual ratio before the contact and providing a carbon atom, a hydrogen atom or an oxygen atom to the surface of the treatment target,
• wherein an amount of energy input in the plasma step is 0.9 J/cm2 to 135.0 J/cm2 per unit area of the surface of the treatment target, with the proviso that when the additive component is carbon monoxide, carbon dioxide, water vapor, ethanol, propanol, hexanol, ethylene glycol, or ammonia, the amount of energy input is 5 J/cm2 to 60 J/cm2, and when the additive component is hydrogen, the amount of energy input is 30 J/cm2 to 120 J/cm2.