Patent ID: 8821831

Claim:
A process for producing a crystalline titanium oxide film including an anatase-type oxide, the process comprising the following steps (a-1) and (b): (a-1) a step of forming titanium nitride on the surface of a sheet of titanium or titanium alloy, which includes: placing the sheet of titanium or titanium alloy on a carbon plate in an atmosphere; placing another carbon plate on the sheet of titanium or titanium alloy; reducing pressure of the atmosphere surrounding the sheet of titanium or titanium alloy arranged between the carbon plate and the another carbon plate to 10 Pa or less by discharging atmospheric gas; introducing nitrogen gas and/or ammonia gas into the atmosphere surrounding the sheet of titanium or titanium alloy arranged between the carbon plate and the another carbon plate, and heating the sheet of titanium or titanium alloy arranged between the carbon plate and the another carbon plate at 750° C. to 1050° C. and forming the titanium nitride on the surface of the sheet of the titanium or titanium alloy, the carbon plates acting as an oxygen trapping agent during the nitriding; and (b) a step of immersing the sheet of nitrided titanium or titanium alloy obtained in step (a-1) above in an electrolyte containing an inorganic acid and/or organic acid, applying voltage, and anodizing the titanium nitride to titanium oxide.