# US 10,482,913 B2 · Magnetic tape having characterized magnetic layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,482,913 B2 - Document ID: US10482913B2 - Status: Granted - Kind: B2 - Application number: 15/900,345 - Filed: 2018-02-20 - Published: 2018-08-23 - Granted: 2019-11-19 - Earliest claimed: 2017-02-20 - Assignees: FUJIFILM Corporation - Applicants: FUJIFILM Corporation - Inventors: Norihito Kasada - Web page: https://patentgrep.com/patent/US10482913B2 ## CPC - G11B 5/712: characterised by the surface treatment or coating of magnetic particles - G11B 5/00813: {magnetic tapes} - G11B 5/70: on a base layer - G11B 5/70615: {containing Fe metal or alloys (G11B5/70621 takes precedence)} - G11B 5/70678: {Ferrites} - G11B 5/7085: {non-magnetic abrasive particles} - G11B 5/78: Tape carriers - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A magnetic tape includes a non-magnetic support; a non-magnetic layer including non-magnetic powder and a binding agent on the non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic layer. The total thickness of the non-magnetic layer and the magnetic layer is less than or equal to 0.60 μm. The magnetic layer includes an abrasive, and the percentage of a plan view maximum area of the abrasive confirmed in a region having a size of 4.3 μm×6.3 μm of the surface of the magnetic layer with respect to the total area of the region, obtained by plane observation performed by using a scanning electron microscope, is greater than or equal to 0.02% and less than 0.06%. Also, the logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is less than or equal to 0.050. ## Claims ### Claim 1 A magnetic tape comprising: a non-magnetic support; a non-magnetic layer including non-magnetic powder and a binding agent on the non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic layer, wherein the total thickness of the non-magnetic layer and the magnetic layer is equal to or smaller than 0.60 μm, the magnetic layer includes an abrasive, the percentage of a plan view maximum area of the abrasive confirmed in a region having a size of 4.3 μm ×6.3 μm of the surface of the magnetic layer with respect to the total area of the region, obtained by plane observation performed by using a scanning electron microscope is equal to or greater than 0.02% and less than 0.06%, the logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is 0.010 to 0.050, and the logarithmic decrement on the magnetic layer side is determined by the following method: securing a measurement sample of the magnetic tape with the measurement surface, which is the surface on the magnetic layer side, facing upward on a substrate in a pendulum viscoelasticity tester; disposing a columnar cylinder edge which is 4 mm in diameter and equipped with a pendulum 13 g in weight on the measurement surface of the measurement sample such that the long axis direction of the columnar cylinder edge runs parallel to the longitudinal direction of the measurement sample; raising the surface temperature of the substrate on which the measurement sample has been positioned at a rate of less than or equal to 5° C./min up to 80° C.; inducing initial oscillation of the pendulum; monitoring the displacement of the pendulum while it is oscillating to obtain a displacement-time curve for a measurement interval of greater than or equal to 10 minutes; and obtaining the logarithmic decrement Δ from the following equation: Δ = ln ⁡ ( A 1 A 2 ) + ln ⁡ ( A 2 A 3 ) + … ⁢ ⁢ ln ⁡ ( A n A n + 1 ) n wherein the interval from one minimum displacement to the next minimum displacement is adopted as one wave period; the number of waves contained in the displacement-time curve during one measurement interval is denoted by n, the difference between the minimum displacement and the maximum displacement of the nth wave is denoted by An, and the logarithmic decrement is calculated using the difference between the next minimum displacement and maximum displacement of the nth wave (An+1 in the above equation). ### Claim 2 (depends on 1) The magnetic tape according to claim 1, wherein the percentage of the plan view maximum area of the abrasive confirmed in a region having a size of 4.3 μm ×6.3 μm of the surface of the magnetic layer with respect to the total area of the region, obtained by plane observation performed by using a scanning electron microscope is 0.02% to 0.05%. ### Claim 3 (depends on 1) The magnetic tape according to claim 1, wherein the total thickness of the non-magnetic layer and the magnetic layer is 0.20 μm to 0.60 μm. ### Claim 4 (depends on 1) The magnetic tape according to claim 1, wherein the BET specific surface area of the abrasive is 14 to 40 m2/g. ### Claim 5 (depends on 1) The magnetic tape according to claim 1, wherein the abrasive is alumina powder. ### Claim 6 (depends on 1) The magnetic tape according to claim 1, wherein the magnetic layer includes an aromatic hydrocarbon compound including a phenolic hydroxyl group. ### Claim 7 (depends on 1) The magnetic tape according to claim 1, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder. ### Claim 8 (depends on 7) The magnetic tape according to claim 7, wherein the ferromagnetic hexagonal ferrite powder includes Al.