A method for making a magnetic recording tape, in accordance with one approach, includes coupling an underlayer to a substrate, the substrate comprising a poly ether ether ketone (PEEK). A method for making a magnetic recording tape in accordance with another approach includes coupling an underlayer to a substrate via radiation-induced grafting, the substrate comprising a poly ether ether ketone (PEEK). A recording layer may be coupled to the underlayer.

The magnetic recording medium includes a non-magnetic support; a magnetic layer that includes ferromagnetic powder on one surface side of the non-magnetic support; and a back coating layer that includes non-magnetic powder on the other surface side of the non-magnetic support, in which a difference between a spacing measured on a surface of the back coating layer by optical interferometry under a pressure of 0.5 atm after n-hexane cleaning and a spacing measured on the surface of the back coating layer by optical interferometry under a pressure of 13.5 atm after n-hexane cleaning is 3 nm or less.

There is provided a magnetic recording medium which has a layer structure including a magnetic layer and a base layer, and of which an average thickness t.sub.T is t.sub.T5.6 m, a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/Nw, a servo pattern is recorded on the magnetic layer, a standard deviation PES of a position error signal (PES) value obtained from a servo signal in which the servo pattern is reproduced is PES25 nm, and a maximum value .sub.1M of a friction coefficient .sub.1 between a surface on a side of the magnetic layer and an LTO3 head in a case where measurement of the friction coefficient .sub.1 is performed 250 times is 0.04.sub.1M0.5.

A magnetic recording tape, in accordance with one approach, includes a substrate comprising a poly ether ether ketone (PEEK). An underlayer is positioned above the substrate. A recording layer is positioned above the underlayer.

A method for making a magnetic recording tape, in accordance with one approach, includes coupling an underlayer to a substrate, the substrate comprising a poly ether ether ketone (PEEK). A method for making a magnetic recording tape in accordance with another approach includes coupling an underlayer to a substrate via radiation-induced grafting, the substrate comprising a poly ether ether ketone (PEEK). A recording layer is coupled to the underlayer.

An object of the present invention is to more conveniently provide a copolyester for a polyester film which exhibits excellent dimensional stability and in particular excellent dimensional stability against environmental changes in, for example, temperature and humidity, and has a small film elongation percentage at 110 C. A copolyester of the present invention comprises: (A) an aromatic dicarboxylic acid component; (B) an alkylene glycol component; and (C1) a dimer acid component and/or (C2) a dimer diol component, wherein the copolyester contains, with reference to a molar number of a total dicarboxylic acid component, 0.5 to 3.5 mol % of the dimer acid component (C1) and/or 0.3 to 5.0 mol % of the dimer diol component (C2).

Provided is a magnetic tape cartridge of a single reel type in which a magnetic tape is wound around a reel, in which the magnetic tape includes a non-magnetic support, and a magnetic layer including a ferromagnetic powder and a binding agent on the non-magnetic support, a tape thickness is equal to or smaller than 5.2 m, a tape width difference (BA) between a tape width A at a position of 10 m1 m from a tape outer end and a tape width B at a position of 50 m1 m from a tape inner end is 2.4 m to 12.0 m, and the tape width A and the tape width B are values measured 100 days from the date of magnetic tape cartridge manufacture.

There is provided a magnetic recording medium which has a layer structure including a magnetic layer and a base layer, and of which an average thickness t.sub.T is t.sub.T5.6 m, a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/Nw, a servo pattern is recorded on the magnetic layer, a standard deviation PES of a position error signal (PES) value obtained from a servo signal in which the servo pattern is reproduced is PES25 nm, and a maximum value .sub.1M of a friction coefficient .sub.1 between a surface on a side of the magnetic layer and an LTO3 head in a case where measurement of the friction coefficient .sub.1 is performed 250 times is 0.04.sub.1M0.5.

There is provided a magnetic recording medium which has a layer structure including a magnetic layer and a base layer, and of which an average thickness t.sub.T is t.sub.T5.6 m, a dimensional change amount w in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/Nw, a servo pattern is recorded on the magnetic layer, a standard deviation PES of a position error signal (PES) value obtained from a servo signal in which the servo pattern is reproduced is PES25 nm, and a maximum value .sub.1M of a friction coefficient .sub.1 between a surface on a side of the magnetic layer and an LTO3 head in a case where measurement of the friction coefficient .sub.1 is performed 250 times is 0.04.sub.1M0.5.

In the magnetic tape cartridge, a tape has a tape thickness of 5.3 m or less, and a difference W.sub.innerW.sub.outer between a tape width W.sub.inner at a position of 50 m1 m from a tape inner end and a tape width W.sub.outer at a position of 50 m1 m from a tape outer end is 4.1 m to 19.9 m as a value measured on 100th day from a date of magnetic tape cartridge manufacture, and a difference G.sub.innerG.sub.outer between a servo band interval G.sub.inner in a range of 49 m to 51 m from the tape inner end and a servo band interval G.sub.outer in a range of 49 m to 51 m from the tape outer end is 3.9 m to 0.0 m as a value measured on 100th day from the date of magnetic tape cartridge manufacture.