The area of a spacer that is to be provided between the adjacent substrates in a laminate including a plurality of substrates to keep the adjacent substrates apart from each other is smaller than those of the stacked substrates. When pressure is released to bring the laminate obtained by providing the spacers between the substrates from a pressed state in which 0.60 MPa of pressure is applied to the laminate in the stacking direction into a non-pressed state, an amount of change ΔW in thickness per spacer that is calculated from a change in the thickness of the laminate due to the release of pressure is 30 μm or less.

An interconnected corrugated carbon-based network comprising a plurality of expanded and interconnected carbon layers is disclosed. In one embodiment, each of the expanded and interconnected carbon layers is made up of at least one corrugated carbon sheet that is one atom thick. In another embodiment, each of the expanded and interconnected carbon layers is made up of a plurality of corrugated carbon sheets that are each one atom thick. The interconnected corrugated carbon-based network is characterized by a high surface area with highly tunable electrical conductivity and electrochemical properties.

A biaxially orientated polyester film has a P.sub.L/V.sub.L ratio of 0.3 to 1.2, P.sub.L and V.sub.L representing the average diameter of the convex portions and the average diameter of the concave portions, respectively, that are defined on the basis of a slice level with a height of 0 nm (reference plane) in a roughness curve determined for at least one surface using a three dimensional surface roughness meter, and the convex portions accounting for an area ratio of 30% to 51% of the reference plane. The biaxially oriented polyester film is excellent in travelling property, slitting property, and dimensional stability, and serves, when used for magnetic recording medium production, to provide a high density magnetic recording medium having a smooth magnetic layer, suffering little dimensional change due to variations in environmental parameters such as temperature and humidity or due to storage, and having good electromagnetic conversion characteristics with little dropout.

An interconnected corrugated carbon-based network comprising a plurality of expanded and interconnected carbon layers is disclosed. In one embodiment, each of the expanded and interconnected carbon layers is made up of at least one corrugated carbon sheet that is one atom thick. In another embodiment, each of the expanded and interconnected carbon layers is made up of a plurality of corrugated carbon sheets that are each one atom thick. The interconnected corrugated carbon-based network is characterized by a high surface area with highly tunable electrical conductivity and electrochemical properties.

An interconnected corrugated carbon-based network comprising a plurality of expanded and interconnected carbon layers is disclosed. In one embodiment, each of the expanded and interconnected carbon layers is made up of at least one corrugated carbon sheet that is one atom thick. In another embodiment, each of the expanded and interconnected carbon layers is made up of a plurality of corrugated carbon sheets that are each one atom thick. The interconnected corrugated carbon-based network is characterized by a high surface area with highly tunable electrical conductivity and electrochemical properties.

A biaxially oriented polyester film, which exhibits an excellent winding property in a manufacturing process, and realizes an excellent electromagnetic conversion property and less failure of signals of a magnetic recording tape to be produced thereof, is provided. This biaxially oriented polyester film satisfies the formula y≤−24.9X+3.8, where the protrusion height X is 0.075 μm, 0.100 μm, and 0.125 μm, and y denotes a base-10 logarithm value of the number of protrusions having protrusion heights of X or more in a visual field of a region of 282 μm×211 μm, and a protrusion height that corresponds to a 0.4% area of a bearing curve based on protrusion height distribution is 65-90 nm.

A sheet-like spacer to be used when a laminate of a plurality of subs rates is formed for the purpose of processing end faces of the substrates is provided between the adjacent substrates in the laminate to keep the adjacent substrates apart from each other. An area of the spacer is smaller than that of the substrates. A contact angle of a surface of the spacer with respect to pure water is 50° or less.

A sheet-like spacer to be used when a laminate of a plurality of substrates is formed for the purpose of processing end faces of the substrates is provided between the adjacent substrates in the laminate to keep the adjacent substrates apart from each other. An area of the spacer is smaller than that of the substrates. A contact angle of a surface of the spacer with respect to pure water is 50° or less.

A recording medium substrate in an aspect of the present invention is a recording medium substrate having a base paper and a stretched film layer on the base paper, wherein the stretched film layer has a thickness of 70 μm or more, and the recording medium substrate has an average surface roughness of 0.3 μm or less. A recording medium in another aspect of the present invention includes a recording medium substrate, a first ink receiving layer on the recording medium substrate, and a second ink receiving layer on the first ink receiving layer, wherein the first ink receiving layer is in contact with the second ink receiving layer, the first ink receiving layer contains an alumina hydrate and a hydroxy acid, the second ink receiving layer contains an alumina hydrate and a sulfonic acid.

A biaxially oriented polyester film, which exhibits an excellent winding property in a manufacturing process, and realizes an excellent electromagnetic conversion property and less failure of signals of a magnetic recording tape to be produced thereof, is provided. This biaxially oriented polyester film satisfies the formula y24.9X+3.8, where the protrusion height X is 0.075 m, 0.100 m, and 0.125 m, and y denotes a base-10 logarithm value of the number of protrusions having protrusion heights of X or more in a visual field of a region of 282 m211 m, and a protrusion height that corresponds to a 0.4% area of a bearing curve based on protrusion height distribution is 65-90 nm.