US 6,670,030 B1Granted

Biaxially oriented laminate polyester film for magnetic recording medium

AssigneeTeijin Limited

InventorsToshikazu Uchida, Mitsuo Tojo, Toshifumi Osawa, Akira Kameoka, Tomokatsu Ura, Masahiko Kosuge

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Abstract

A biaxially oriented laminate polyester film for magnetic recording medium, which is a laminate film comprising a base layer (A) formed of a polyester resin and a coating layer (B) which exists on one surface of the base layer (A) and contains a binder resin, added fine particles and a surfactant, wherein the base layer (A) is a biaxially oriented film which substantially contains no fine particles added or contains 0.001 to 0.1% by weight of added fine particles having an average particle diameter of 0.005 to 0.3 μm, the coating layer (B) has a surface having a central plane roughness (SRa) of 5 nm or less, the surface of the coating layer (B) has protrusions having a major diameter of 0.05 μm or more in a density of 80,000 pieces/mm2 or less and has extra-large protrusions having a major diameter of 10 μm or more in a density of 20 pieces/cm2 or less. Further, a thin film layer (C) may be further laminated on a surface on the side of the base layer (A) of the laminate polyester film which side is not in contact with the coating layer (B). According to the present invention, there is provided a biaxially oriented laminate polyester film useful as a base film for a magnetic recording medium which has excellent running durability and electromagnetic conversion characteristics and is almost free from drop-out.

Claims28

Dependent claims

(1) the base layer (A) substantially contains no added fine particles or contains 0.001 to 0.1% by weight of added fine particles having an average particle diameter of 0.005 to 0.3 μm,
(2) the coating layer (B) contains a binder resin, added fine particles and a surfactant, the added fine particles having an average particle diameter of 10 to 50 nm and being contained in an amount of 0.5 to 30% by weight, and the coating layer (B) having a thickness of 3 to 40 nm,
(3) the coating layer (B) has a surface which satisfies the following surface characteristics (a) to (d):
(a) the surface has 80,000 pieces/mm2 or less of protrusions having a major diameter of 0.05 μm or more when measured on the basis of a surface photograph taken and enlarged at a magnification of 5,000 with a scanning electron microscope,
(b) the surface has 1 to 40 pieces/μm2 of protrusions, measured on the basis of a surface photograph taken and enlarged at a magnification of 35,000 with a scanning electron microscope,
(c) the surface has 10 pieces/cm2 or less of extra-large protrusions having a major diameter of 10 μm or more, and has 5 pieces/cm2 or less of the extra-large protrusions having a height of 100 nm or higher, and
(d) the surface has a central plane average roughness (SRa) of 5 nm or less and
(4) wherein the base layer (A) contains (a) at least one compound selected from the group consisting of an alkali metal compound, an alkaline earth metal compound and a manganese compound, (b) a phosphorus compound and (c) at least one compound selected from the group consisting of a germanium compound, a titanium compound and an antimony compound in an amount ratio satisfying the following expressions (1) to (6) simultaneously:
25≦M≦250 (1)
0.1≦(M/P)≦6.0 (2)
0≦Ti≦12.5 (3)
0≦Ge≦110 (4)
0≦Sb≦50 (5)
0.3<(Ti+Ge)≦110 (6),
wherein M is a content (ppm) of a total of an alkali metal element, an alkaline earth metal element and a manganese element from the compound (a), P is a content (ppm) of a phosphorus element, Ti is a content (ppm) of a titanium element, Ge is a content (ppm) of a germanium element and Sb is a content (ppm) of an antimony element, in the polyester.

12 more elements

(1) the base layer (A) substantially contains no added fine particles or contains 0.001 to 0.1% by weight of added fine particles having an average particle diameter of 0.005 to 0.3 μm,
(2) the coating layer (B) contains a binder resin, added fine particles and a surfactant, the added fine particles having an average particle diameter of 10 to 50 nm and being contained in an amount of 0.5 to 30% by weight, and the coating layer (B) having a thickness of 3 to 40 nm,
(3) the coating layer (B) has a surface which satisfies the following surface characteristics (a) to (d):
(a) the surface has 80,000 pieces/mm2 or less of protrusions having a major diameter of 0.05 μm or more when measured on the basis of a surface photograph taken and enlarged at a magnification of 5,000 with a scanning electron microscope,
(b) the surface has 1 to 40 pieces/μm2 of protrusions, measured on the basis of a surface photograph taken and enlarged at a magnification of 35,000 with a scanning electron microscope,
(c) the surface has 10 pieces/cm2 or less of extra-large protrusions having a major diameter of 10 μm or more, and has 5 pieces/cm2 or less of the extra-large protrusions having a height of 100 nm or higher, and
(d) the surface has a central plane average roughness (SRa) of 5 nm or less and
(4) wherein the base layer (A) contains a magnesium compound, a calcium compound, a titanium compound and a phosphorus compound in an amount ratio satisfying the following expressions (7) to (10) simultaneously:
25≦(Mg+Ca)≦200 (7)
0.3≦Mg/Ca≦10 (8)
0.5≦(Mg+Ca)/P≦6.0 (9)
0.3≦Ti≦12.5 (10),
wherein Mg, Ca, Ti and P represent contents (ppm) of a magnesium element, a calcium element, a titanium element and a phosphorus element, respectively, in the polyester.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/582,820Filed 3 Jul 2000
Priority: JP 10-3119632 Nov 1998
Granted: 30 Dec 2003
Term ends: Not estimatedThe source records don’t support an estimate.

Classification14 codes

G11B 5/73935
Polyester substrates, e.g. polyethylene terephthalate: characterised by roughness or surface features, e.g. by added particles
G11B 5/73929
Polyester substrates, e.g. polyethylene terephthalate: comprising naphthalene ring compounds, e.g. polyethylene naphthalate substrates
G11B 5/73931
Polyester substrates, e.g. polyethylene terephthalate: two or more layers, at least one layer being polyester
Y10S 428/90
Stock material or miscellaneous articles: magnetic feature