Mechanical seal

A mechanical seal, comprising:

• a case-side sealing ring fixed to a seal case;
• and
• a shaft-side sealing ring held on a rotary shaft via an annular packing made of an elastic material, shaft-side sealing ring being movable in an axial direction of the shaft;
• said mechanical seal being configured such that the case-side sealing ring and the shaft-side sealing ring are rotated relative to each other while opposing seal end surfaces thereof are in contact, thereby forming a shield seal between a liquid area, which is an area on either an inner or an outer peripheral side of the seal end surfaces, and an gas area, which is on another side;
• wherein
• the shaft-side sealing ring is formed from a ceramic or cemented carbide;
• the shaft-side sealing ring has a seal end surface formed at a distal end part thereof, and an inner peripheral part of the shaft-side sealing ring has a sealing ring-side seal surface which is concentric and parallel to a shaft-side seal surface which is an outer peripheral surface of the rotary shaft;
• the annular packing is provided between the sealing ring-side seal surface and the shaft-side seal surface so as to be relatively movable in the axial direction in such state that a space between the seal surfaces is sealed;
• and
• a diamond film is formed on the sealing ring-side seal surface.