Flexible magnetic recording media having superior peel strength

Claim 2

A magnetic recording media having superior peel strength comprising (i) an oriented polyester film, (ii) a primer coating on at least one side of said film consisting essentially of a water-soluble alkali metal salt of an unsaturated fatty acid having from 10 to 18 carbon atoms, (iii) a ferromagnetic coating applied over said primer coating, said ferromagnetic coating comprising ferromagnetic particles dispersed in a polymeric binder; said primer coating being present at a weight effective to improve the adhesion of said ferromagnetic coating to said film.

Claim 3

The magnetic recording media of claim 1 wherein said ferromagnetic particles are selected from the group consisting of ferric oxide, chromium dioxide, and barium ferrite.

Claim 4

The magentic recording media of claim 2 wherein said ferromagnetic particles comprise ferric oxide.

Claim 5

The magnetic recording media of claim 3 wherein said ferric oxide particles additionally have cobalt adsorbed onto their surface.

Claim 6

The magnetic recording media of claim 2 wherein said ferromagnetic particles comprise chromium dioxide.

Claim 7

The magnetic recording media of claim 1 wherein said oriented polyester film is biaxially oriented polyethylene terephthalate film.

Claim 8

The magnetic recording media of claim 6 wherein said unsaturated fatty acid is selected from the group consisting of oleic, palmitoleic, ricinoleic, and petroselinic.

Claim 9

The magnetic recording media of claim 7 wherein said unsaturated fatty acid is oleic acid.

Claim 10

The magnetic recording media of claim 8 wherein said primer coating consists essentially of sodium oleate.

Claim 11

The magnetic recording media of claim 6 wherein said polymeric binder comprises a polyurethane/polyester block copolymer.

Claim 12

The magnetic recording media of claim 10 wherein said polyurethane/polyester block copolymer is the reaction product of (A) a hydroxyl-terminated polyester, which itself is a reaction product of a difunctional alcohol having hydrolytic stability, and a dicarboxylic acid selected from the group consisting of adipic acid, azelaic acid, 1,12-dodecanedioic acid, and mixtures thereof, said polyester having a hydroxyl number of about 50 to 250; (B) a chain extender comprising a primary or a secondary alcohol selected from the group consisting of 1,4-butanediol; 1,3-butanediol; 1,5-pentanediol; 1,6-hexandiol; and 2,5-hexandiol, the resultant hydroxyl number of said polyester and chain extender being about 130 to 300; and (C) an aromatic diisocyanate; wherein the relative proportions of (A), (B) and (C) are selected to produce a ferromagnetic coating having a polyurethane segment content in the range of about 37 to 40 percent by weight, and a polyester segment molecular weight in the range of about 500 to 1500, wherein said ferromagnetic particles comprise chromium dioxide particles, and wherein said particles are present in the range of from 80 to 88% by weight of said ferrmmagnetic coating.

Claim 13

The magnetic recording media of claim 11 wherein said difunctional alcohol is 1,4-cyclohexanedimethanol.

Claim 14

The magnetic recording media of claim 12 wherein said chain extender is 1,4-butanediol.

Claim 15

The magnetic recording media of claim 11 wherein said aromatic diisocyanate is 4,4-methylene-bis-(1,4-phenylene) diisocyanate.

Claim 16

The magnetic recording media of claim 11 further having a backcoat layer comprising non-ferromagnetic particles dispersed in a polymeric binder.

Claim 17

A magnetic recording media produced by the process comprising (i) extruding a substantially amorphous polyester resin in sheet-like form and subsequently cooling said resin to form cast polyester sheet, (ii) subsequently orienting said polyester sheet in the longitudinal direction, thereby forming monoaxially oriented polyester film, (iii) coating said sheet with an aqueous solution consisting essentially of a water-soluble alkali metal salt of an unsaturated fatty acid having from 10 to 18 carbon atoms; (iv) subsequently orienting said monoaxially oriented polyester film in the transverse direction, thereby forming biaxially oriented polyester film, (v) heatsetting said biaxially oriented polyester film, (vi) subsequently overcoating said polyester film with a ferromagnetic coating composition comprising (a) a solvent selected from the group consisting of tetrahydrofuran, methylethylketone, methylisobutylketone, and cyclohexanone, (b) ferromagnetic particles, (c) a pre-polymer, (vii) curing said pre-polymer to produce a coating comprising ferromagnetic particles dispersed in a polymeric binder.

Claim 18

A magnetic recording media produced by the process comprising (i) extruding a substantially amorphous polyester resin in sheet-like form and subsequently cooling said resin to form cast polyester sheet, (ii) subsequently orienting said polyester sheet in the longitudinal direction, thereby forming monoaxially oriented polyester film, (iii) coating said sheet with an aqueous solution consisting essentially of a water-soluble alkali metal salt of an unsaturated fatty acid having from 10 to 18 carbon atoms; (iv) subsequently orienting said monoaxially oriented polyester film in the transverse direction, thereby forming biaxially oriented polyester film, (v) heatsetting said biaxially oriented polyester film, (vi) subsequently overcoating said polyester film with a ferromagnetic coating composition comprising (a) a solvent selected from the group consisting of tetrahydrofuran, methylethylketone, methylisobutylketone, and cyclohexanone, (b) ferromagnetic particles, (c) a pre-polymer, (vii) curing said pre-polymer to produce a coating comprising ferromagnetic particles dispersed in a polymeric binder.

Claim 19

The film of claim 16 wherein said film is subjected to a corona discharge treatment prior to the application of said aqueous solution.

Claim 20

The film of claim 17 wherein said oriented polyester film is biaxially oriented polyethylene terephthalate film.

Claim 21

The film of claim 18 wherein the primer coating produced by application of said aqueous solution is present at a weight within the range of about 1×10 -8 to 2×10 -5 lbs per square foot of film surface on a dry weight basis.

Claim 22

The film of claim 19 wherein said primer coating consists essentially of an alkali metal salt of oleic acid.

Claim 23

The film of claim 20 wherein said primer coating consists essentially of sodium oleate.

Claim 24

The magnetic recording media of claim 16 wherein said prepolymer comprises (A) a hydroxyl-terminated polyester which itself is a reaction product of a hydrolytically stable difunctional alcohol, (B) a chain extender, and (C) an aromatic diisocyanate.

Claim 25

The magnetic recording media of claim 22 wherein said difunctional alcohol is 1,4-cyclohexanedimethanol.

Claim 26

The magnetic recording media of claim 22 wherein said chain extender is 1,4-butanediol.

Claim 27

The magnetic recording media of claim 22 wherein said aromatic diisocyanate is 4,4-methylene-bis-(1,4-phenylene) diisocyanate.

Claim 28

A magnetic recording media produced by the process comprising (i) extruding a substantially amorphous polyester resin in sheet-like form and subsequently cooling said resin to form cast polyester sheet, (ii) coating said sheet with an aqueous solution consisting essentially of a water-soluble alkali metal salt of an unsaturated fatty acid having from 10 to 18 carbon atoms; (iii) subsequently orienting said polyester sheet in the longitudinal direction, thereby forming monoaxially oriented polyester film, (iv) subsequently orienting said monoaxially oriented polyester film in the transverse direction, thereby forming biaxially oriented polyester film, (v) heatsetting said biaxially oriented polyester film, (vi) subsequently overcoating said polyester film with a ferromagnetic coating composition comprising (a) a solvent selected from the group consisting of tetrahydrofuran, methylethylketone, methylisobutylketone, and cyclohexanone, (b) ferromagnetic particles, (c) a pre-polymer, (vii) curing said pre-polymer to produce a coating comprising ferromagnetic particles dispersed in a polymeric binder.

Claim 29

A magnetic recording media produced by the process comprising (i) extruding a substantially amorphous polyester resin in sheet-like form and subsequently cooling said resin to form cast polyester sheet, (ii) coating said sheet with an aqueous solution consisting essentially of a water-soluble alkali metal salt of an unsaturated fatty acid having from 10 to 18 carbon atoms; (iii) subsequently orienting said polyester sheet in the longitudinal direction, thereby forming monoaxially oriented polyester film, (iv) subsequently orienting said monoaxially oriented polyester film in the transverse direction, thereby forming biaxially oriented polyester film, (v) heatsetting said biaxially oriented polyester film, (vi) subsequently overcoating said polyester film with a ferromagnetic coating composition comprising (a) a solvent selected from the group consisting of tetrahydrofuran, methylethylketone, methylisobutylketone, and cyclohexanone, (b) ferromagnetic particles, (c) a pre-polymer, (vii) curing said pre-polymer to produce a coating comprising ferromagnetic particles dispersed in a polymeric binder.