Magnetic recording medium including a radiation-cured material layer having a specified structure and composition
View Patent ↗A magnetic recording medium is provided that includes a non-magnetic support and, in order, above the non-magnetic support, a radiation-cured material layer cured by exposing a layer that includes a radiation curable compound to radiation, and a magnetic layer that includes a fine ferromagnetic powder and a binder, a compound having one or more ether groups and three or more radiation curable functional groups per molecule being employed as the radiation curable compound, and the number of magnetic layer surface micro projections having a height measured by atomic force microscopy (AFM) of 10 to 20 nm being 5 to 1,000 per 100 (μm) 2 . There is also provided the magnetic recording medium wherein it further includes a non-magnetic layer that includes a non-magnetic powder and a binder.
1. A magnetic recording medium comprising:
a non-magnetic support and, in order, above the non-magnetic support;
a radiation-cured material layer cured by exposing a layer consisting essentially of a radiation curable compound to radiation;
a non-magnetic layer comprising a non-magnetic powder and a binder; and
a magnetic layer comprising a ferromagnetic powder and a binder;
the radiation curable compound comprising a compound having one or more ether groups and three or more radiation curable functional groups per molecule; and
the number of magnetic layer surface micro projections having a height measured by atomic force microscopy (AFM) of 10 to 20 nm being 5 to 1,000 per 100 (μm) 2 ;
wherein the radiation-cured material layer has a thickness of 0.2 to 0.8 μm,
the radiation curable compound has no cyclic structure,
the radiation curable functional group is a (meth)acrylic acid residue,
the radiation curable compound has 3 to 6 (meth)acrylic acid residues per molecule,
the radiation curable compound has 1 to 3 ether groups per molecule, and
the radiation curable compound is selected from the group consisting of dipentaerythritol hexaacrylate, a propionic acid-modified dipentaerythritol tetraacrylate, a propionic acid-modified dipentaerythritol triacylate, ditrimethylolpropane tetraacrylate, and a caprolactone-modified dipentaerythritol hexaacrylate.
2. The magnetic recording medium according to claim 1 , wherein the radiation-cured material layer has a thickness of 0.3 to 0.6 μm.
3. The magnetic recording medium according to claim 1 , wherein there are 5 to 100 magnetic layer surface micro projections per 100 (μm) 2 having a height, measured by atomic force microscopy (AFM), of 10 to 20 nm.
4. The magnetic recording medium according to claim 1 , wherein the ferromagnetic powder is a ferromagnetic alloy powder having a major axis length of 20 to 50 nm.
5. The magnetic recording medium according to claim 1 , wherein the binder in the magnetic layer is selected from the group consisting of a polyurethane resin, an acrylic resin, a cellulose resin, and a vinyl chloride resin.
6. The magnetic recording medium according to claim 1 , wherein the non-magnetic powder is selected from the group consisting of a metal, a metal oxide, a metal carbonate, a metal sulfate, a metal nitride, a metal carbide, and a metal sulfide.
7. The magnetic recording medium according to claim 1 , wherein the non-magnetic support is selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and polyamide.
8. The magnetic recording medium according to claim 1 , wherein the non-magnetic support has a center plane average roughness of 3 to 10 nm for a cutoff value of 0.25 mm.
9. The magnetic recording medium according to claim 1 , wherein the ferromagnetic powder is an acicular ferromagnetic metal powder having a crystallite size of 4 nm to 1 μm and a major axis length of 10 to 100 nm.
10. The magnetic recording medium according to claim 1 , wherein the binder in the non-magnetic layer is selected from the group consisting of a polyurethane resin, an acrylic resin, a cellulose resin, and a vinyl chloride resin.