NOVELTY - The cap assembly of a secondary battery, comprises a cap formed of a metal, a safety vent formed of a metal having electric conductivity and disposed below the cap, and a positive temperature coefficient (PTC) resistance layer, which includes a conductive polymer composition having PTC characteristics and is disposed between the cap and the safety vent. A metal layer is formed between the PTC resistance layer and the safety vent, and includes a material having specified electric conductivity. A surface of the PTC resistance layer is attached to a bottom surface of the cap.    USE - The cap assembly is useful for a secondary battery, which is useful in various types of electric and electronic appliances.    ADVANTAGE - The cap assembly can be easily and economically manufactured with reduced internal electrical resistance, and provides large capacity, high operational voltage, less weight and high energy density per weight unit to the secondary battery.    DETAILED DESCRIPTION - The cap assembly of a secondary battery, comprises a cap formed of a metal, a safety vent formed of a metal having electric conductivity and disposed below the cap, and a positive temperature coefficient (PTC) resistance layer, which includes a conductive polymer composition having PTC characteristics and is disposed between the cap and the safety vent. A metal layer is formed between the PTC resistance layer and the safety vent, and includes a material having specified electric conductivity. A surface of the PTC resistance layer is attached to a bottom surface of the cap, and another surface of the PTC resistance layer is attached to an upper surface of the safety vent and metal layer. A current blocking circuit substrate is interposed between the PTC resistance layer and the safety vent. The metal layer and the current blocking circuit are sequentially disposed below the PTC resistance layer. A bottom surface of the metal layer is attached to a terminal disposed on an upper surface of the current blocking circuit substrate. An insulating material is disposed below the safety vent, and a lower cap formed of a metal is disposed below the insulating material. A subplate formed of a metal is disposed below the lower cap. A gasket surrounds circumferential surfaces of the cap, the safety vent and the PTC resistance layer, and insulates a can and the cap assembly of the secondary battery from each other. An INDEPENDENT CLAIM is included for a secondary battery.    DESCRIPTION OF DRAWING(S) - The figure shows an exploded perspective view of elements of a secondary battery including a cap assembly.    Can (10)    Open portion of can (11)    Bead (17)    Electrode assembly (20)    Positive electrode tab (24)    Negative tab. (25)