Patent ID: 9105294
Filing Date: 2015-08-11
Classification: G11B

Abstract:
1. A magnetic recording medium comprising: a substrate; an underlayer formed over the substrate, the underlayer defining a coating surface and comprising a non-magnetic metal oxide pigment having an average pigment particle size of between about 35 to 100 nanometers and making up between about 55 to 75 weight percent of the underlayer, and further comprising about 10 to 25 weight parts of carbon black per 100 weight parts of non-magnetic metal oxide pigment; and a magnetic layer formed over the coating surface of the underlayer, and comprising abrasive particles having an average major axis length of more than 3.05 times greater, and up to approximately 5 times greater, than the thickness of the magnetic layer; wherein the underlayer defines an average thickness less than or equal to approximately 890 nanometers; and wherein an average surface roughness (Ra) of the underlayer after calendering is less than or equal to approximately 3.6 nanometers, and an average surface roughness depth (Rz) of the underlayer decreases by greater than or equal to approximately 40 percent after calendering.