Magnetic recording medium

Abstract

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 tT is tT≤5.6 μm, a dimensional change amount Δw in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/N≤Δw, a servo pattern is recorded on the magnetic layer, a standard deviation σPES of a position error signal (PES) value obtained from a servo signal in which the servo pattern is reproduced is σPES≤25 nm, and a maximum value μ1M of a friction coefficient μ1 between a surface on a side of the magnetic layer and an LTO3 head in a case where measurement of the friction coefficient μ1 is performed 250 times is 0.04≤μ1M≤0.5.

1 . A magnetic recording medium
 which has a layer structure including a magnetic layer and a base layer, and   of which an average thickness t T  is t T ≤5.6 μm,   a dimensional change amount Δw in a width direction with respect to a change in tension in a longitudinal direction is 660 ppm/N≤Δw,   a servo pattern is recorded on the magnetic layer,   a standard deviation σPES of a position error signal (PES) value obtained from a servo signal in which the servo pattern is reproduced is σPES≤25 nm, and   a maximum value μ 1M  of a friction coefficient μ 1  between a surface on a side of the magnetic layer and an LTO3 head in a case where measurement of the friction coefficient μ 1  is performed 250 times is 0.04≤μ 1M ≤0.5.   
     
     
         2 . The magnetic recording medium according to  claim 1 , wherein a squareness ratio of the magnetic recording medium in a vertical direction is 65% or more. 
     
     
         3 . The magnetic recording medium according to  claim 1 , wherein the dimensional change amount Δw is 700 ppm/N≤Δw. 
     
     
         4 . The magnetic recording medium according to  claim 1 , wherein the dimensional change amount Δw is 750 ppm/N≤Δw. 
     
     
         5 . The magnetic recording medium according to  claim 1 , wherein the dimensional change amount Δw is 800 ppm/N≤Δw. 
     
     
         6 . The magnetic recording medium according to  claim 1 ,
 wherein the layer structure includes a back layer on a side of the base layer opposite to the side of the magnetic layer, and   a surface roughness R ab  of the back layer is 3.0 nm≤R ab ≤7.5 nm.   
     
     
         7 . The magnetic recording medium according to  claim 1 ,
 wherein the layer structure includes a back layer on a side of the base layer opposite to the side of the magnetic layer, and   a friction coefficient μ between a surface on the side of the magnetic layer and a surface on a side of the back layer is 0.20≤μ≤0.80.   
     
     
         8 . The magnetic recording medium according to  claim 1 , wherein a thermal expansion coefficient α is 5.5 ppm/° C.≤α≤9 ppm/° C., and a humidity expansion coefficient β is β≤5.5 ppm/% RH. 
     
     
         9 . The magnetic recording medium according to  claim 1 , wherein a Poisson's ratio ρ is 0.25≤ρ. 
     
     
         10 . The magnetic recording medium according to  claim 1 , wherein an elastic limit value σ MD  in the longitudinal direction is 0.7 N≤σ MD . 
     
     
         11 . The magnetic recording medium according to  claim 10 , wherein the elastic limit value σ MD  does not depend on a speed V at a time of measuring an elastic limit. 
     
     
         12 . The magnetic recording medium according to  claim 1 , wherein the magnetic layer is vertically aligned. 
     
     
         13 . The magnetic recording medium according to  claim 1 , wherein the layer structure includes a back layer on a side of the base layer opposite to the side of the magnetic layer, and an average thickness t b  of the back layer is t b ≤0.6 μm. 
     
     
         14 . The magnetic recording medium according to  claim 1 , wherein the magnetic layer is a sputtered layer. 
     
     
         15 . The magnetic recording medium according to  claim 14 , wherein an average thickness t m  of the magnetic layer is 9 nm≤t m ≤90 nm. 
     
     
         16 . The magnetic recording medium according to  claim 1 , wherein the magnetic layer contains magnetic powder. 
     
     
         17 . The magnetic recording medium according to  claim 16 , wherein an average thickness t m  of the magnetic layer is 35 nm≤t m ≤120 nm. 
     
     
         18 . The magnetic recording medium according to  claim 16 , wherein the magnetic powder includes ε iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder. 
     
     
         19 . The magnetic recording medium according to  claim 2 ,
 wherein the layer structure includes a back layer on a side of the base layer opposite to the side of the magnetic layer, and   a surface roughness R ab  of the back layer is 3.0 nm≤R ab ≤7.5 nm.   
     
     
         20 . The magnetic recording medium according to  claim 2 ,
 wherein the layer structure includes a back layer on a side of the base layer opposite to the side of the magnetic layer, and   a friction coefficient μ between a surface on the side of the magnetic layer and a surface on a side of the back layer is 0.20≤μ≤0.80.   
     
     
         21 . The magnetic recording medium according to  claim 2 , wherein a thermal expansion coefficient α is 5.5 ppm/° C.≤α≤9 ppm/° C., and a humidity expansion coefficient β is β≤5.5 ppm/% RH. 
     
     
         22 . The magnetic recording medium according to  claim 2 , wherein a Poisson's ratio ρ is 0.25≤ρ. 
     
     
         23 . The magnetic recording medium according to  claim 2 , wherein an elastic limit value σ MD  in the longitudinal direction is 0.7 N≤σ MD . 
     
     
         24 . The magnetic recording medium according to  claim 23 , wherein the elastic limit value σ MD  does not depend on a speed V at a time of measuring an elastic limit. 
     
     
         25 . The magnetic recording medium according to  claim 2 , wherein the magnetic layer is vertically aligned. 
     
     
         26 . The magnetic recording medium according to  claim 2 ,
 wherein the layer structure includes a back layer on a side of the base layer opposite to the side of the magnetic layer, and   an average thickness t b  of the back layer is t b ≤0.6 μm.   
     
     
         27 . The magnetic recording medium according to  claim 2 , wherein the magnetic layer is a sputtered layer. 
     
     
         28 . The magnetic recording medium according to  claim 27 , wherein an average thickness t m  of the magnetic layer is 9 nm≤t m ≤90 nm. 
     
     
         29 . The magnetic recording medium according to  claim 2 , wherein the magnetic layer contains magnetic powder. 
     
     
         30 . The magnetic recording medium according to  claim 29 , wherein an average thickness t m  of the magnetic layer is 35 nm≤t m ≤120 nm. 
     
     
         31 . The magnetic recording medium according to  claim 29 , wherein the magnetic powder includes ε iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder.