US 5,510,140 A · Method for preparing magnetic recording medium

Abstract

A first object of the invention is to provide a magnetic recording medium having minimized dropouts immediately after preparation, a reduced dropout increase and an electromagnetic property loss with the lapse of time, and good durability of coatings such as a magnetic layer. A second object is to provide a magnetic recording medium including a backcoat layer having high durability and antistatic effect in addition to the above advantages. A third object is to achieve a productivity increase and a cost reduction in the manufacture of such a magnetic recording medium. To attain these objects, the invention provides a method for preparing a magnetic recording medium comprising a kneading step of kneading solids and a binder solution, a dispersing step of dispersing the solids in the compound resulting from the kneading step, and a viscosity adjusting step of adding a viscosity adjusting solution to the dispersion resulting from the dispersing step to form a paint composition wherein filtering steps are included after the steps for filtering fluids to be filtered (including the binder solution, compound, dispersion, viscosity adjusting solution, and paint) and a filter means having a 95% cut filtration precision within a specific range is used in each of the filtering steps.

Claims43

Dependent claims

A method of preparing a magnetic recording medium having at least two layers of coating on at least one surface of a non-magnetic substrate, the uppermost layer of coating being a magnetic layer of 0.1 to 0.8 .mu.m thick, comprising:

a step of preparing a paint composition for the uppermost layer of coating, including a paint filtering step of filtering the paint through at least one filter means including an ultimate filter means, the ultimate filter means used in the paint filtering step having a 95% cut filtration precision of 1.0 to 6.0 .mu.m.

A method for preparing a magnetic recording medium having a magnetic layer on a front surface of a non-magnetic substrate and a backcoat layer formed by coating on a back surface of the non-magnetic substrate, the backcoat layer having a thickness of up to 1.0 .mu.m, comprising:

a step of preparing a paint composition for the backcoat layer, including a paint filtering step of filtering the paint through at least one filter means including an ultimate filter means, the ultimate filter means used in the paint filtering step having a 95% cut filtration precision ranging from of 1.0 to 6.0 .mu.m and up to 10 times the thickness of said backcoat layer.

A method for preparing a magnetic recording medium having at least one layer of coating on at least one surface of a non-magnetic substrate, the uppermost layer of coating being a magnetic layer, comprising:

a step of preparing a paint composition for the uppermost layer of coating, including a kneading step of kneading solids and a binder-solution, a dispersing step of dispersing the solids in the compound resulting from the kneading step, and a viscosity adjusting step of adding a viscosity adjusting solution to the dispersion resulting from the dispersing step to form the paint composition, and further including at least one of a compound filtering step of filtering the compound through at least one filter means including an ultimate filter means, and a dispersion filtering step of filtering the dispersion through at least one filter means including an ultimate filter means,
the ultimate filter means used in the compound filtering step and the dispersion filtering step both having a 95% cut filtration precision of at least 15 .mu.m, and the ultimate filter means used in at least one of the compound filtering step and the dispersion filtering step having a 95% cut filtration precision of up to 80 .mu.m.

a step of preparing a paint composition for the uppermost layer of coating, including a kneading step of kneading solids and a binder solution, a dispersing step of dispersing the solids in the compound resulting from the kneading step, and a viscosity adjusting step of adding a viscosity adjusting solution to the dispersion resulting from the dispersing step to form the paint composition, and further including at least one of a binder solution filtering step of filtering said binder solution through at least one filter means including an ultimate filter means, and a viscosity adjusting solution filtering step of filtering said viscosity adjusting solution through at least one filter means including an ultimate filter means,
the ultimate filter means used in the binder solution filtering step having a 95% cut filtration precision of at least 4.0 .mu.m and the ultimate filter means used in the viscosity adjusting solution filtering step having a 95% cut filtration precision of at least 1.0 .mu.m, and
at least one of the requirements that the ultimate filter means used in the binder solution filtering step has a 95% cut filtration precision of up to 80 .mu.m and the ultimate filter means used in the viscosity adjusting viscosity adjusting solution filtering step has a 95% cut filtration precision of up to 30 .mu.m is met.

a step of preparing a paint composition for the backcoat layer of coating, including a dispersing step of dispersing solids in a binder solution and a viscosity adjusting step of adding a viscosity adjusting solution to the dispersion resulting from the dispersing step to form the paint composition, and further including at least one of a binder solution filtering step of filtering said binder solution through at least one filter means including an ultimate filter means, and a viscosity adjusting solution filtering step of filtering said viscosity adjusting solution through at least one filter means including an ultimate filter means,
the ultimate filter means used in the binder solution filtering step having a 95% cut filtration precision of at least 4.0 .mu.m and the ultimate filter means used in the viscosity adjusting solution filtering step having a 95% cut filtration precision of at least 1.0 .mu.m, and
least one of the requirements that the ultimate filter means used in the binder solution filtering step has a 95% cut filtration precision of up to 80 .mu.m and the ultimate filter means used in the viscosity adjusting solution filtering step has a 95% cut filtration precision of up to 30 .mu.m is met.

Dependencies are inferred from the claim text.

Method for preparing magnetic recording medium

Life of this patent

Method for preparing magnetic recording medium

Life of this patent

Abstract

Claims43