Method for producing liquid discharge head and liquid discharge head

A method for producing a liquid discharge head comprising a substrate provided with an energy generating element that generates energy to be used for discharging a liquid, an electrical wiring layer electrically connected to the energy generating element, a connection terminal disposed on the electrical wiring layer and performing electrical connection to the outside, and a diffusion prevention layer between the connection terminal and the electrical wiring layer;

• a channel forming member disposed on the substrate and including a resin forming a liquid flow path;
• and
• an intermediate layer disposed between the channel forming member and the substrate, the method comprising:
• disposing a metal layer to form the diffusion prevention layer on the substrate;
• disposing the connection terminal on the metal layer;
• etching the metal layer with an acid solution using the connection terminal as a mask to form the diffusion prevention layer;
• forming a layer that becomes the intermediate layer on the substrate provided with the connection terminal and the diffusion prevention layer, providing a pattern of a photoresist on the layer becoming the intermediate layer, etching the layer becoming the intermediate layer using the pattern as a mask to form an intermediate layer, and peeling the pattern with an alkaline solution;
• and
• forming the channel forming member on the intermediate layer,
• wherein when the metal constituting the metal layer becoming the diffusion prevention layer is defined as a first metal and the metal constituting the connection terminal is defined as a second metal, in a potential-pH diagram for the first metal-H2O system, the first metal is present in a passivation area or an insensitive area at a potential of the difference between the standard electrode potentials of the first metal and the second metal in a pH range of 1 to 14.