Prepreg and manufacturing method for same

A prepreg comprising reinforcing fibers and an epoxy resin composition, having a fiber content of 90% by mass or less, and meeting the following requirements (a) and (b):

• (a) the epoxy resin composition in the region (I) ranging from a depth of D/4 to 3D/4, wherein D represents the average thickness of the prepreg (and D is 3 μm or more), from the surface of the prepreg has a viscosity of 50,000 Pa·s or more and 300,000 Pa·s or less at 25° C., and
• (b) when defining two regions (II) ranging from either surface of the prepreg into a depth of 0.5 the epoxy resin composition at least in either of the regions (II) has a viscosity of 10,000 Pa·s or more and 40,000 Pa·s or less at 25° C.

A method for prepreg production comprising a step in which an epoxy resin composition B having a viscosity of 10,000 Pa·s or more and 40,000 Pa·s or less at 25° C. is disposed on at least one side of a prepreg precursor containing a reinforcing fiber sheet and an epoxy resin composition A having a viscosity of 50,000 Pa·s or more and 300,000 Pa·s or less at 25° C. in such a manner that meets the following requirements (c), (d), and (e):

• (c) the prepreg has a fiber content of 90% by mass or less,
• (d) the epoxy resin composition B has an areal weight of 1 g/m2 or more, and
• (e) the ratio of the areal weight of the epoxy resin composition A to the areal weight of the epoxy resin composition B (or the epoxy resin composition B having the larger areal weight in the case where different epoxy resin compositions B are disposed along the two surfaces of the prepreg precursor) is 2 or more.