A Cl2 gas plasma is generated at a site within a chamber between a substrate and a metal member. The optical disc apparatus may include a write stopping unit, a deviation calculating unit, and a write strategy correction unit. The four electrodes of each piezoelectric transducer are interconnected to supply, when opposing stresses are applied to the piezoelectric elements of the transducer, an electrical measurement signal that depends on the angle between a main plane and an opposite stress-separation plane. The latch assembly also includes an actuating mechanism disposed on the first part between the latch mechanisms for moving the hooks between the locked and unlocked positions. \u03b1-olefin copolymer, based on 95 to 5 parts by weight of the total amount of and ++=100 parts by weight).