Magnetic tape having characterized magnetic layer

Patent metadata

Field	Value
Publication number	US-10854230-B2
Application number	US-201816038884-A
Country	US
Kind code	B2
Filing date	Jul 18, 2018
Priority date	Jul 19, 2017
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

The magnetic tape includes a magnetic layer including ferromagnetic powder, non-magnetic powder, and a binding agent and a back coating layer including non-magnetic powder and a binding agent, in which the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, an Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, an intensity ratio of a peak intensity of a diffraction peak of a (110) plane with respect to a peak intensity of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0, a vertical squareness ratio of the magnetic tape is 0.65 to 1.00, and a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding a surface of the back coating layer is equal to or smaller than 0.060.

First claim

What is claimed is:

1. A magnetic tape comprising:
a non-magnetic support;
a magnetic layer including ferromagnetic powder, non-magnetic powder, and a binding agent on one surface side of the non-magnetic support; and
a back coating layer including non-magnetic powder and a binding agent on the other surface side of the non-magnetic support,
wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder,
a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm,
an intensity ratio Int(110)/Int(114) of a peak intensity Int(110) of a diffraction peak of a (110) plane with respect to a peak intensity Int(114) of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0,
a vertical squareness ratio of the magnetic tape is 0.65 to 1.00, and
a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding a surface of the back coating layer is equal to or smaller than 0.060.

2. The magnetic tape according to claim 1 ,
wherein the logarithmic decrement is 0.010 to 0.060,and
the logarithmic decrement is determined by the following method:
securing a measurement sample of the magnetic tape with the measurement surface, which is the surface on the backcoat 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 n th wave is denoted by An, and the logarithmic decrement is calculated using the difference between the next minimum displacement and maximum displacement of the n th wave (A n+1 in the above equation).

3. The magnetic tape according to claim 1 ,
wherein the center line average surface roughness Ra measured regarding the surface of the magnetic layer is 1.2 nm to 1.8 nm.

4. The magnetic tape according to claim 2 ,
wherein the center line average surface roughness Ra measured regarding the surface of the magnetic layer is 1.2 nm to 1.8 nm.

5. The magnetic tape according to claim 1 ,
wherein the vertical squareness ratio of the magnetic tape is 0.65 to 0.90.

6. The magnetic tape according to claim 2 ,
wherein the vertical squareness ratio of the magnetic tape is 0.65 to 0.90.

7. The magnetic tape according to claim 3 ,
wherein the vertical squareness ratio of the magnetic tape is 0.65 to 0.90.

8. The magnetic tape according to claim 4 ,
wherein the vertical squareness ratio of the magnetic tape is 0.65 to 0.90.

9. The magnetic tape according to claim 1 , further comprising:
a non-magnetic layer including non-magnetic powder and a binding agent between the non-magnetic support and the magnetic layer.

Assignees

• Fujifilm Corp

Inventors

• Kasada Norihito
• Tada Toshio
• Ozawa Eiki
• Kurokawa Takuto

Classifications

• G11B5/70678 Primary

  Ferrites · CPC title

• G11B5/71

  characterised by the lubricant · CPC title

• G11B5/714

  characterised by the dimension of the magnetic particles · CPC title

• G11B5/712

  characterised by the surface treatment or coating of magnetic particles · CPC title

• G11B5/84

  Processes or apparatus specially adapted for manufacturing record carriers · CPC title