The present technology provides a tape-shaped magnetic recording medium including: a magnetic layer; an underlayer; a base layer; and a back layer, in which the number of recesses having a depth of 20% or more of the thickness of the magnetic layer is 10 or more and 200 or less per surface area of 1600 μm.sup.2, the base layer includes a polyester as a main component, a surface on a side of the back layer has a kurtosis of 2.0 or more and 4.4 or less, the magnetic recording medium has an average thickness t.sub.T of 5.6 μm or less, the magnetic recording medium includes a lubricant, the magnetic recording medium has pores, and the pores have an average diameter of 6 nm or more and 11 nm or less when the diameters of the pores are measured in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.

An object is to provide a magnetic recording medium having excellent traveling stability and a thin total thickness.

The present technology provides a tape-shaped magnetic recording medium including: a magnetic layer; an underlayer; a base layer; and a back layer, in which the number of recesses having a depth of 20% or more of the thickness of the magnetic layer is 10 or more and 200 or less per surface area of 1600 μm.sup.2, the base layer includes a polyester as a main component, a surface on a side of the back layer has a kurtosis of 2.0 or more and 4.4 or less, the magnetic recording medium has an average thickness t.sub.T of 5.6 μm or less, the magnetic recording medium includes a lubricant, the magnetic recording medium has pores, and the pores have an average diameter of 6 nm or more and 11 nm or less when the diameters of the pores are measured in a state where the lubricant has been removed from the magnetic recording medium and the magnetic recording medium has been dried.

A tape-like magnetic recording medium includes a reinforced substrate, and a recording layer arranged on the reinforced substrate, and the reinforced substrate includes a substrate that has a first face and a second face opposed to each other, and has an average thickness of 4 μm or smaller, and a metal layer that contains cobalt, arranged on the first face, the reinforced substrate by itself causing thereon a depth of indentation of 0.25 μm or shallower, when a 0.7-mm-diameter hard sphere is impressed against the second face under 5.0 gf load for 10 seconds.

A tape-like magnetic recording medium includes a reinforced substrate, and a recording layer arranged on the reinforced substrate, and the reinforced substrate includes a substrate that has a first face and a second face opposed to each other, and has an average thickness of 4 μm or smaller, and a metal layer that contains cobalt, arranged on the first face, the reinforced substrate by itself causing thereon a depth of indentation of 0.25 μm or shallower, when a 0.7-mm-diameter hard sphere is impressed against the second face under 5.0 gf load for 10 seconds.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. An anisotropic magnetic field Hk is 12 kOe or more, a center line average roughness Ra of the surface of the magnetic recording medium on the magnetic layer side is 1.2 nm or less, and a ratio θr of a contact angle θ2 with respect to 1-bromonaphthalene, measured on a surface on the magnetic layer side after a 1,1,1,2,2,3,4,5,5,5-decafluoropentane immersion, to a contact angle θ1 with respect to 1-bromonaphthalene, measured on the surface on the magnetic layer side before the 1,1,1,2,2,3,4,5,5,5-decafluoropentane immersion is 0.95 or less.

A biaxially oriented thermoplastic resin film has at least one surface of which has protrusions each having a height of 1 nm or more and less than 2 nm at a density of 110.sup.7 to 110.sup.9 protrusions per mm.sup.2. The thermoplastic resin film is capable of suppressing generation of coarse protrusions and contaminants, and defects in a processing process while having slipperiness.

A magnetic recording medium has a recording surface having an average surface roughness SRa of 3.0 nm or less, the number of projections having a height of 7.5 nm or more included in a unit region (where the unit region is a square region with each side having a length of 30 m) of the recording surface is 256 or more, and the number of projections having a height of 15 nm or more included in the unit region of the recording surface is 0 or more and 104 or less.

A biaxially oriented thermoplastic resin film has at least one surface of which has protrusions each having a height of 1 nm or more and less than 2 nm at a density of 110.sup.7 to 110.sup.9 protrusions per mm.sup.2. The thermoplastic resin film is capable of suppressing generation of coarse protrusions and contaminants, and defects in a processing process while having slipperiness.

The magnetic recording medium includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder. An anisotropic magnetic field Hk is 12 kOe or more, a center line average roughness Ra of the surface of the magnetic recording medium on the magnetic layer side is 1.2 nm or less, and a ratio ?r of a contact angle ?2 with respect to 1-bromonaphthalene, measured on a surface on the magnetic layer side after a 1,1,1,2,2,3,4,5,5,5-decafluoropentane immersion, to a contact angle ?1 with respect to 1-bromonaphthalene, measured on the surface on the magnetic layer side before the 1,1,1,2,2,3,4,5,5,5-decafluoropentane immersion is 0.95 or less.

A magnetic recording medium has a recording surface having an average surface roughness SRa of 3.0 ?m or less, the number of projections having a height of 7.5 nm or more included in a unit region (where the unit region is a square region with each side having a length of 30 ?m) of the recording surface is 256 or more, and the number of projections having a height of 15 nm or more included in the unit region of the recording surface is 0 or more and 104 or less.