heating pulse a is 12 ns which is shorter than that of the rear heating pulse the width of the last cooling pulse cr is 1 0t therefore when the linear speed is lower than the center linear speed of the linear speed change and the recording density is higher it is possible to keep the overwriting quality and jitter in satisfactory condition the fifth embodiment is illustrated in fig6 the present embodiment is configured such that the pulse number of the multi pulse line can change and the width of the last cooling pulse cr can change in the area where the recording linear speed of the phase change disc 1 is higher than the center linear speed of the linear speed change and recording density is higher the pulse number of the multi pulse line may be n u2212 1 and the rate for channel clock frequency t of the width of the last cooling pulse cr may be high for example in case that the recording density of the dvd disc is 3 9 gb and the information is recorded in the outer area when 3t and 5t marks are recorded where 3t is the shortest mark the pulse number of the rear heating pulse b is two 5 u2212 3 2 at the same time the width of the last cooling pulse cr is 1t therefore when the linear.