To provide a direct drawing type original plate of a lithographic printing plate, with which poor conveyance such as a slippage in conveyance, a meandering or the like is reduced.
This original plate 10 of a lithographic printing plate is produced by providing a photosensitive layer 14 having a sensitivity to laser beams on the surface 12a of a support 12. The rear surface 12b of the support 12 has surface mean roughnesses Ra, which are different in the directions or in the longitudinal direction x and in the widthwise direction y of the support 12. When Ral represents the surface mean roughness Ra in the direction, in which the surface mean roughness is larger than that in the other direction and Ras represents the surface mean roughness Ra in the direction, in which the surface mean roughness is smaller than that in the other direction, Ral and Ras satisfy equation: 1.1≤Ral/Ras≤5.0 in the original plate 10.
HOTTA HISASHI
UESUGI AKIO
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