Magnetic tape having controlled surface properties of the backcoat layer and method of manufacturing the same

• US 10,026,435 B2
• Filed: 08/19/2016
• Issued: 07/17/2018
• Est. Priority Date: 08/21/2015
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Kasada, Norihito, Oyanagi, Masahito, Tada, Toshio, Sugiyama, Takuro
• Primary Examiner(s): Bernatz, Kevin M
• Application Number:
  US15/241,631
• Publication Number:
  US 20170053671A1
• Time in Patent Office: 697 Days
• Field of Search: None
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/7358 specially adapted for achieving a specific property, e.g. average roughness [Ra]
• CPC Class Codes: G11B 5/78 Tape carriers
• CPC Class Codes: G11B 5/842 Coating a support with a liquid magnetic dispersion

Abstract

The magnetic tape has a magnetic layer containing ferromagnetic powder and binder on the surface on one side of a nonmagnetic support and has a backcoat layer containing nonmagnetic powder and binder on the surface on the other side of the nonmagnetic support, wherein the backcoat layer is less than or equal to 0.30 μm in thickness; and the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the backcoat layer side of the magnetic tape is less than or equal to 0.060.

Claims

1. A magnetic tape,

which comprises a magnetic layer comprising ferromagnetic powder and binder on a surface on one side of a nonmagnetic support and comprises a backcoat layer comprising nonmagnetic powder and binder on a surface on the other side of the nonmagnetic support, wherein:

the backcoat layer is less than or equal to 0.30 μ

m in thickness; and

the logarithmic decrement as determined by a pendulum viscoelasticity test on a surface on the backcoat layer side of the magnetic tape is greater than or equal to 0.010 but less than or equal 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;

2. The magnetic tape according to claim 1,

wherein the logarithmic decrement as determined by a pendulum viscoelasticity test on a surface on the backcoat layer side of the magnetic tape is greater than or equal to 0.010 but less than or equal to 0.050.

3. The magnetic tape according to claim 2,

wherein the nonmagnetic powder contained in the backcoat layer is selected from the group consisting of carbon black and nonmagnetic inorganic oxide powder.

4. The magnetic tape according to claim 2,

which comprises a nonmagnetic layer comprising nonmagnetic powder and binder between the magnetic layer and the nonmagnetic support.

5. The magnetic tape according to claim 1,

wherein the nonmagnetic powder contained in the backcoat layer is selected from the group consisting of carbon black and nonmagnetic inorganic oxide powder.

6. A method of manufacturing a magnetic tape,

wherein the magnetic tape is a magnetic tape which comprises a magnetic layer comprising ferromagnetic powder and binder on a surface on one side of a nonmagnetic support and comprises a backcoat layer comprising nonmagnetic powder and binder on a surface on the other side of the nonmagnetic support, wherein:

the backcoat layer is less than or equal to 0.30 μ

m in thickness; and

the logarithmic decrement as determined by a pendulum viscoelasticity test on a surface on the backcoat layer side of the magnetic tape according to the method recited in claim 1 is greater than or equal to 0.010 but less than or equal to 0.060, and

the method of manufacturing the magnetic tape comprises forming a backcoat layer, with the forming of a backcoat layer comprising;

coating a backcoat layer-forming composition comprising nonmagnetic powder, binder, a curing agent, and solvent on a surface of a nonmagnetic support to form a coating layer;

heating and drying the coating layer by a heat treatment; and

curing the coating layer by subjecting the coating layer to a curing treatment;

with cooling the coating layer after the coating but before the heating and drying; and

burnishing a surface of the coating layer after the heating and drying but before the curing.

7. The method of manufacturing a magnetic tape according to claim 6,

wherein the cooling is conducted by placing the coating layer in a cooling atmosphere of −

10°

C. to 0°

C.

8. The method of manufacturing a magnetic tape according to claim 7,

wherein the solvent contained in the backcoat layer-forming composition comprises ketone solvent.

9. The method of manufacturing a magnetic tape according to claim 6,

wherein the solvent contained in the backcoat layer-forming composition comprises ketone solvent.

10. The method of manufacturing a magnetic tape according to claim 6,

wherein the curing agent is a thermosetting compound and the curing is conducted by a heat treatment.

11. The method of manufacturing a magnetic tape according to claim 10,

wherein the thermosetting compound is polyisocyanate.

12. The method of manufacturing a magnetic tape according to claim 6,

wherein the logarithmic decrement as determined by a pendulum viscoelasticity test on a surface on the backcoat layer side of the magnetic tape is greater than or equal to 0.010 but less than or equal to 0.050.

13. The method of manufacturing a magnetic tape according to claim 12,

wherein the nonmagnetic powder contained in the backcoat layer is selected from the group consisting of carbon black and nonmagnetic inorganic oxide powder.

14. The method of manufacturing a magnetic tape according to claim 6,

wherein the nonmagnetic powder contained in the backcoat layer is selected from the group consisting of carbon black and nonmagnetic inorganic oxide powder.

15. The method of manufacturing a magnetic tape according to claim 6,

wherein the magnetic tape comprises a nonmagnetic layer comprising nonmagnetic powder and binder between the magnetic layer and the nonmagnetic support.