Heater having heat generating resistor on substrate and image heating apparatus mounting heater thereon

An image heating apparatus for heating an image formed on a recording material, comprising:

• a heater including a substrate, at least two first heat generating resistors and at least one second heat generating resistor formed on said substrate along a longitudinal direction thereof, said second heat generating resistor being provided between said first heat generating resistors in a direction of a shorter side of said substrate;
• wherein said second heat generating resistor includes a first region having a low resisting value per unit length and a second region having a resisting value per unit length greater than that of the first region;
• a first switching element, which is connected electrically between a power source and said first heat generating resistors, for controlling an electrical power supply to said first heat generating resistors;
• and
• a second switching element, which is connected electrically between the power source and said second heat generating resistor, for controlling an electrical power supply to said second heat generating resistor;
• wherein said substrate has a substrate reinforcing layer only along a portion of the longitudinal direction in a surface opposite to a surface on which said first and second heat generating resistors are provided, and, an area of said substrate reinforcing layer regarding the longitudinal direction includes the second region of said second heat generating resistor.