Heating Roller, Thermal Fixing Apparatus and Method for Producing Heating Roller

A thermal fixing apparatus comprising:

• a heating roller including:
• a core bar having a cylindrical shape;
• a rubber layer arranged on an outer circumferential surface of the core bar to cover the core bar;
• and
• a release layer arranged on an outer circumferential surface of the rubber layer;
• and
• a heating member arranged inside the core bar of the heating roller and configured to heat the heating roller to a temperature of less than 230° C.,
• wherein in a case that a developer is thermally fixed on a recording medium, the heating roller is heated to a temperature within a fixing temperature range including a minute particle-scattering start temperature at which minute particles having mean particle diameter of not more than 300 nm start to scatter from the rubber layer;
• and
• density of the minute particles measured by a test is less than 2,000 pieces/cm3,
• the test being executed by:
• arranging the heating roller inside a casing of which inner volume is 0.175 m3 and which is connected to a minute particle density measuring device configured to measure the density of the minute particles;
• then performing heating of the core bar of the heating roller inside the casing to 230° C. by a heater;
• and then measuring the density of the minute particles inside the casing after elapse of 20 minutes since start of the heating of the core bar.

A method for producing a heating roller, the method comprising the steps of:

• preparing a core bar;
• forming a resin composite layer formed of a resin composite on an outer circumferential surface of the core bar so as to cover the core bar;
• performing primary curing of the resin composite layer at a temperature in a range of not less than 25° C. to not more than 150° C. for a duration of time in a range of not less than 0.5 hours to not more than 4 hours;
• preparing a rubber layer based on the resin composite layer by performing secondary curing of the resin composite layer, after the primary curing, at a temperature in a range of not less than 150° C. to not more than 230° C. for a duration of time in a range of not less than 0.5 hours to not more than 10 hours;
• forming a release layer on an outer circumferential surface of the rubber layer to cover the rubber layer to thereby obtain a roller member including the core bar, the rubber layer and the release layer;
• and
• heating the roller member at a temperature in a range of not less than 200° C. to not more than 250° C. for a duration of time in a range of not less than 1 hour to not more than 20 hours to thereby obtain the heating roller.