Magnetic recording medium and method of producing it

A substrate for a magnetic recording medium comprising:

• (a) an aluminum-containing layer;
• (b) an anodic-oxidation film on a surface of said layer, said anodic-oxidation film having defined therein a plurality of cell-pores in each of which a filler material is deposited;
• and
• (c) a plurality of cores comprising a product of a reaction between a reagent selected from the group consisting of
• (i) a solution comprising fluorine,
• (ii) a solution comprising an acid but not comprising fluorine,
• (iii) a solution comprising a base but not comprising fluorine,
• (iv) a solution comprising a strong-acid salt but not comprising fluorine, and
• (v) a gas comprising fluorine and at least one of said anodic-oxidation film and said filler material, said reaction product being a substance different from said filler material and from the substance used to form said aluminum-containing layer, said cores being formed on a surface of said anodic-oxide film in the vicinity of a portion of said plurality of cell-pores, wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is smaller than the number of said cell-pores.

A method of producing a magnetic recording medium comprising the steps of:

• (a) effecting an anodic oxidation process on an aluminum-containing layer to form an anodic-oxidation film on said aluminum-containing layer, said anodic-oxidation film having defined therein a plurality of cell-pores;
• (b) depositing a filler material in said cell-pores;
• (c) treating said anodic-oxidation film with a reagent to form a plurality of cores in the vicinity of a portion of said plurality of pores, wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is less than the number of said cell-pores, said reagent being selected from the group consisting of
• (i) a solution comprising fluorine,
• (ii) a solution comprising an acid but not comprising fluorine,
• (iii) a solution comprising a base but not comprising fluorine,
• (iv) a solution comprising a strong-acid salt but not comprising fluorine, and
• (v) a gas comprising fluorine;
• (d) depositing a metal bed film on said anodic-oxidation film;
• and
• (e) depositing a magnetic film on said metal bed film.

A method of producing a substrate for a magnetic recording medium comprising the steps of:

• (a) effecting an anodic oxidation process on an aluminum-containing layer to form an anodic-oxidation film on said aluminum-containing layer, said anodic-oxidation film having defined therein a plurality of cell-pores;
• (b) depositing a filler material in said cell-pores;
• and
• (c) treating said anodic-oxidation film with a reagent to form a plurality of cores in the vicinity of a portion of said plurality of pores, wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is less than the number of said cell-pores, said reagent being selected from the group consisting of
• (i) a solution comprising fluorine,
• (ii) a solution comprising an acid but not comprising fluorine,
• (iii) a solution comprising a base but not comprising fluorine,
• (iv) a solution comprising a strong-acid salt but not comprising fluorine, and
• (v) a gas comprising fluorine.

A magnetic recording medium comprising:

• an aluminum-containing layer;
• an anodic-oxidation film on a surface of said layer, said anodic-oxidation film having defined therein a plurality of cell-pores in each of which a filler material is deposited;
• and
• a plurality of cores comprised of a substance different from said filler material and from the substance used to form said aluminum-containing layer, said cores being formed on a surface of said anodic-oxidation film in the vicinity of a portion of said plurality of cell-pores, wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, and the number of said cores is smaller than the number of said cell-pores;
• a metal bed film deposited on said anodic-oxidation film;
• and
• a magnetic film deposited on said metal bed film, said magnetic film having a plurality of surface irregularities produced by said plurality of cores, wherein the surface density of said surface irregularities ranges form 10.sup.2 to 10.sup.7 per square millimeter.

A substrate for a magnetic recording medium comprising:

• an aluminum-containing layer;
• an anodic-oxidation film on a surface of said layer, said anodic-oxidation film having defined therein a plurality of cell-pores in each of which a filler material is deposited;
• and
• a plurality of cores comprised of a substance different form said filler material and from the substance used to form said aluminum-containing layer, said cores being formed on a surface of said anodic-oxidation film in the vicinity of a portion of said plurality of cell-pores,
• wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is smaller than the number of said cell-pores.

A substrate for a magnetic recording medium having surface irregularities comprising:

• an aluminum-containing layer;
• an anodic-oxidation film on a surface of said aluminum-containing layer, said anodic-oxidation film having a plurality of cell-pores defined therein;
• and
• a plurality of cores provided in the vicinity of edges of at least a portion of said plurality of cell-pores for causing surface irregularities on said magnetic recording medium, wherein the height of said core is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is less than the number of said cell-pores.

A method of producing a magnetic recording medium comprising the steps of:

• effecting an anodic oxidation process on an aluminum-containing layer to form an anodic-oxidation film on said aluminum-containing layer, said anodic-oxidation film having defined therein a plurality of cell-pores;
• depositing a filler material in said cell-pores;
• treating said anodic-oxidation film with a solution or fluorine-containing gas to form a plurality of cores in the vicinity of a portion of said plurality of pores, wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is less than the number of said cell-pores;
• depositing a metal bed form on said anodic-oxidation film;
• and
• depositing a magnetic film on said metal bed film.

A method of producing a substrate for a magnetic recording medium comprising the steps of:

• effecting an anodic oxidation process on an aluminum-containing layer to form an anodic-oxidation film on said aluminum-containing layer, said anodic-oxidation film having defined therein a plurality of cell-pores;
• depositing a filler material in said cell-pores;
• and
• treating said anodic-oxidation film with a solution or gas to form a plurality of cores in the vicinity of a portion of said plurality of pores, wherein the height of said cores is less than 300 .ANG., the diameter of said cores is less than about 0.7 .mu.m, the surface density of said cores ranges from 10.sup.2 to 10.sup.7 per square millimeter, and the number of said cores is less than the number of said cell-pores.