Magnetic recording medium having non-magnetic layer and characterized vertical squareness ratio, and magnetic recording and reproducing device
The magnetic recording medium includes: a non-magnetic support; and a non-magnetic layer including a non-magnetic powder and a magnetic layer including a ferromagnetic powder on the non-magnetic support in this order, in which a vertical squareness ratio is 0.70 to 1.00, a center line average roughness Ra measured regarding a surface of the magnetic layer with an atomic force microscope is equal to or smaller than 2.5 nm, and an interface variation rate between the magnetic layer and the non-magnetic layer in a cross section image obtained by imaging with a scanning electron microscope is equal to or less than 2.5%.
1. A magnetic recording medium comprising:
a non-magnetic support; and
a non-magnetic layer including a non-magnetic powder and a magnetic layer including a ferromagnetic powder on the non-magnetic support in this order,
wherein the vertical squareness ratio is 0.70 to 1.00,
the center line average roughness Ra measured regarding the surface of the magnetic layer with an atomic force microscope is equal to or smaller than 2.5 nm,
an interface variation rate between the magnetic layer and the non-magnetic layer in a cross section image obtained by imaging with a scanning electron microscope (SEM) is equal to or less than 2.0%, and
the interface variation rate between the magnetic layer and the non-magnetic layer is obtained as follows:
providing a sample of the magnetic recording medium for cross section observation,
capturing 10 SEM images in randomly selected portions of the sample at an acceleration voltage of 5 kV, an imaging magnification of 200,000, and at 960 pixel×1280 pixel,
specifying the interface between the magnetic layer and the non-magnetic layer and the interface between the non-magnetic layer and the non-magnetic support, based on the captured SEM images,
obtaining the arithmetical mean T of the thickness of the non-magnetic layer based on the captured SEM images, and
calculating the interface variation rate between the magnetic layer and the non-magnetic layer from the following formula:
Interface variation rate (%)=(σ/T)×100
where σ is the standard deviation of thickness of the non-magnetic layer obtained regarding the 10 SEM images, and T is the arithmetical mean of the thickness of the non-magnetic layer.
2. The magnetic recording medium according to claim 1 ,
wherein the void volume of the non-magnetic layer in the cross section image obtained by imaging with a scanning electron microscope is equal to or less than 10.0%.
3. The magnetic recording medium according to claim 1 ,
wherein the non-magnetic powder of the non-magnetic layer includes carbon black.
4. The magnetic recording medium according to claim 3 ,
wherein the specific surface area of the carbon black included in the non-magnetic layer is 280 to 500 m 2 /g.
5. The magnetic recording medium according to claim 3 ,
wherein the non-magnetic layer includes 30.0% by mass or more of the carbon black with respect to the total amount of the non-magnetic powder.
6. The magnetic recording medium according to claim 1 ,
wherein the thickness of the non-magnetic layer is equal to or less than 1.00 μm.
7. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer includes a non-magnetic powder.
8. The magnetic recording medium according to claim 7 ,
wherein the non-magnetic powder of the magnetic layer includes colloidal particles.
9. The magnetic recording medium according to claim 8 ,
wherein the colloidal particles are silica colloidal particles.
10. The magnetic recording medium according to claim 1 , further comprising:
a back coating layer including a non-magnetic powder on a surface of the non-magnetic support opposite to a surface provided with the non-magnetic layer and the magnetic layer.
11. A magnetic recording and reproducing device comprising:
the magnetic recording medium according to claim 1 ; and
a magnetic head.
12. The magnetic recording and reproducing device according to claim 11 ,
wherein the void volume of the non-magnetic layer in the cross section image obtained by imaging with a scanning electron microscope is equal to or less than 10.0%.
13. The magnetic recording and reproducing device according to claim 11 ,
wherein the non-magnetic powder of the non-magnetic layer includes carbon black.
14. The magnetic recording and reproducing device according to claim 13 ,
wherein the specific surface area of the carbon black included in the non-magnetic layer is 280 to 500 m 2 /g.
15. The magnetic recording and reproducing device according to claim 13 ,
wherein the non-magnetic layer includes 30.0% by mass or more of the carbon black with respect to the total amount of the non-magnetic powder.
16. The magnetic recording and reproducing device according to claim 11 ,
wherein the thickness of the non-magnetic layer is equal to or less than 1.00 μm.
17. The magnetic recording and reproducing device according to claim 11 ,
wherein the magnetic layer includes a non-magnetic powder.
18. The magnetic recording and reproducing device according to claim 17 ,
wherein the non-magnetic powder of the magnetic layer includes colloidal particles.
19. The magnetic recording and reproducing device according to claim 18 ,
wherein the colloidal particles are silica colloidal particles.
20. The magnetic recording and reproducing device according to claim 11 ,
wherein the magnetic recording medium comprises a back coating layer including a non-magnetic powder on a surface of the non-magnetic support opposite to a surface provided with the non-magnetic layer and the magnetic layer.