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

• US 9,984,710 B2
• Filed: 12/14/2016
• Issued: 05/29/2018
• Est. Priority Date: 12/16/2015
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Kasada, Norihito
• Primary Examiner(s): Bernatz, Kevin M
• Application Number:
  US15/378,907
• Publication Number:
  US 20170178675A1
• Time in Patent Office: 531 Days
• Field of Search: None
• CPC Class Codes: G11B 5/68 comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/78 Tape carriers
• CPC Class Codes: G11B 5/84 Processes or apparatus specially adapted for manufacturing record carriers

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 thereof, wherein the centerline average surface roughness Ra as measured on the surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm, the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the magnetic layer side of the magnetic tape is less than or equal to 0.050, and the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the backcoat layer side 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 a backcoat layer comprising nonmagnetic powder and binder on a surface on the other side of the nonmagnetic support,

wherein the centerline average surface roughness Ra as measured on a surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm,

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

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 on the magnetic layer side and the logarithmic decrement on the backcoat layer side are determined by the following method:

securing a measurement sample of the magnetic tape with the measurement surface, which is either the surface on the magnetic layer side or 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 centerline average surface roughness Ra is greater than or equal to 1.2 nm but less than or equal to 1.8 nm.

3. The magnetic tape according to claim 1,

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

4. 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 a backcoat layer comprising nonmagnetic powder and binder on a surface on the other side of the nonmagnetic support,

wherein the centerline average surface roughness Ra as measured on a surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm,

the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the magnetic layer side of the magnetic tape according to the method of claim 1 is greater than or equal to 0.010 but less than or equal to 0.050, 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 of claim 1 is greater than or equal to 0.010 but less than or equal to 0.060, and

wherein the method of manufacturing the magnetic tape comprises forming a magnetic layer and forming a backcoat layer, wherein

the forming of a magnetic layer comprises:

coating a magnetic layer-forming composition comprising ferromagnetic powder, binder, a curing agent, and solvent on a nonmagnetic support, either directly or over another layer, to form a magnetic coating layer,

drying the magnetic coating layer by a heat treatment, and

curing the magnetic coating layer by subjecting the magnetic coating layer to a curing treatment,

with cooling the magnetic coating layer after the coating but before the drying, and burnishing a surface of the magnetic coating layer after the drying but before the curing; and

forming of a backcoat layer comprises;

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

drying the nonmagnetic coating layer by a heat treatment, and

curing the nonmagnetic coating layer by subjecting the nonmagnetic coating layer to a curing treatment,

with cooling the nonmagnetic coating layer after the coating but before the drying, and burnishing a surface of the nonmagnetic coating layer after the drying but before the curing.

5. The method of manufacturing a magnetic tape according to claim 4,

wherein the cooling in the forming of a magnetic layer is conducted by placing the magnetic coating layer in a cooling atmosphere ranging from −

10°

C. to 0°

C.

6. The method of manufacturing a magnetic tape according to claim 4,

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

7. The method of manufacturing a magnetic tape according to claim 4,

wherein the cooling in the forming of a backcoat layer is conducted by placing the nonmagnetic coating layer in a cooling atmosphere ranging from −

10°

C. to 0°

C.

8. The method of manufacturing a magnetic tape according to claim 4,

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

9. The method of manufacturing a magnetic tape according to claim 4,

wherein the curing agent contained in the magnetic layer-forming composition and the curing agent contained in the backcoat layer-forming composition are thermosetting compounds, and the curing in the forming of a magnetic layer and the curing in the forming of a backcoat layer are carried out by heat treatments.

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

wherein the thermosetting component is polyisocyanate.