Magnetic recording media having a binder comprising a low molecular weight high glass transition temperature vinyl polymer

• US 5,178,953 A
• Filed: 01/12/1990
• Issued: 01/12/1993
• Est. Priority Date: 01/12/1990
• Status: Expired due to Term

• Current Assignee: Quantegy Recording Solutions, LLC
• Original Assignee: Ampex Media Corporation
• Inventors: Anglin, David L.
• Primary Examiner(s): Sluby, P. C.
• Assistant Examiner(s): Resan, Stevan A.
• Application Number:
  US07/464,117
• Time in Patent Office: 1,096 Days
• Field of Search: 428/424.6, 428/694, 428/695, 428/900, 428/425.9, 428/522, 252/62.54, 252/62.55, 252/62.56
• US Class Current: 428/424.6
• CPC Class Codes: G11B 5/7022 containing mixtures of polyurethanes or polyisocyanates with other polymers
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/3158 Halide monomer type [polyvinyl chloride, etc.]
• CPC Class Codes: Y10T 428/31609 Particulate metal or metal compound-containing
• CPC Class Codes: Y10T 428/31935 Ester, halide or nitrile of addition polymer

Abstract

Disclosed are magnetic particle coating compositions employing a low molecular, high T_g vinyl polymers characterized by having one or more primary alcohol containing groups pendant to the polymer chain.

Claims

1. A magnetic particle recording medium comprising a non-magnetic substrate having a magnetic layer placed thereon wherein said layer is derived from a magnetic particle coating composition which comprises a) magnetic particles, b) polyurethane, c) polyisocyanate, and d) a low molecular weight, high Tg vinyl polymer having a Tg of about 40°

C. or more and a number average molecular weight of about 15,000 or less and characterized by having one or more primary alcohol containing groups pendant to the non-terminal portions thereof.

2. A magnetic particle recording medium as defined in claim 1 wherein said magnetic particle coating composition further comprises an organic solvent.

3. A magnetic particle recording medium as defined in claim 2 wherein said organic solvent comprises a ketone solvent.

4. A magnetic particle recording medium as defined in claim 3 wherein said ketone solvent is selected from the group consisting of cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone.

5. A magnetic particle recording medium as defined in claim 3 wherein said ketone solvent is a mixture of cyclohexanone and tetrahydrofuran.

6. A magnetic particle recording medium as defined in claim 1 wherein said magnetic particles are metal particles.

7. A magnetic particle recording medium as defined in claim 6 wherein said metal particles are iron metal powder.

8. A magnetic particle recording medium as defined in claim 1 wherein said magnetic particles are metal oxide particles.

9. A magnetic particle recording medium as defined in claim 1 wherein said polyurethane employed in said magnetic particle coating composition has a Tg of about 25°

C. or less.

10. A magnetic particle recording medium as defined in claim 9 wherein said polyurethane has a number average molecular weight of from about 10,000 to about 200,000.

11. A magnetic particle recording medium as defined in claim 1 wherein said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 10,000 or less.

12. A magnetic particle recording medium as defined in claim 11 wherein said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 5,000 or less.

13. A magnetic particle recording medium as defined in claim 12 wherein said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 3,000 or less.

14. A magnetic particle recording medium as defined in claim 1 wherein the Tg of the magnetic layer is about 30°

C. or more.

15. A magnetic particle recording medium as defined in claim 1 wherein said magnetic particle coating composition further comprises a vinyl chloride/vinyl acetate/vinyl alcohol terpolymer having a number average molecular weight of about 20,000 or more and a Tg of about 40°

C. or more.

16. A magnetic particle recording medium as defined in claim 1 wherein said magnetic particle coating composition further comprises an abrasive, a dispersant, and a lubricant.

17. A method of increasing the Tg of the magnetic layer of a magnetic particle recording medium, wherein said magnetic layer is derived from a magnetic particle coating composition comprising magnetic particles, polyurethane and polyisocyanate, said method comprises adding to said composition a low molecular weight, high Tg vinyl polymer having a Tg of about 40°

C. or more and a number average molecular weight of about 15,000 or less and characterized by having one or more primary alcohol containing groups pendant to the non-terminal portions thereof.

18. A method as defined in claim 17 wherein said low molecular weight, high Tg vinyl polymer is added to said magnetic particle coating composition in an amount sufficient to provide a Tg in the magnetic layer of about 30°

C or more.

19. A method as defined in claim 18 wherein said low molecular weight, high Tg vinyl polymer is added to said magnetic particle coating composition in an amount sufficient to provide a Tg in the magnetic layer of about 40°

C or more.

20. A method as defined in claim 17 wherein said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 10,000 or less.

21. A method as defined in claim 20 wherein said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 5,000 or less.

22. A method as defined in claim 21 wherein said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 3,000 or less.

23. A magnetic recording medium comprising a non-magnetic substrate, a magnetic layer and a backcoat derived from a backcoat composition which comprises a) an organic solvent, b) polyurethane, c) polyisocyanate, d) a low molecular weight, high Tg vinyl polymer having a Tg of about 40°

C. or more and a number average molecular weight of about 15,000 or less and characterized by one or more primary alcohol containing groups pendent to the non-terminal portions thereof, and e) an antistat.

24. A magnetic recording medium as defined in claim 23 wherein in said backcoat composition said organic solvent comprises a ketone solvent.

25. A magnetic recording medium as defined in claim 24 wherein said ketone solvent is selected from the group consisting of cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone.

26. A magnetic recording medium as defined in claim 24 wherein said ketone solvent is a mixture of cyclohexanone and tetrahydrofuran.

27. A magnetic recording medium as defined in claim 23 wherein, in said backcoat composition, said polyurethane has a Tg of about 25°

C. or less.

28. A magnetic recording medium as defined in claim 27 wherein said polyurethane has a number average molecular weight of from about 10,000 to about 200,000.

29. A magnetic recording medium as defined in claim 23 said low molecular weight, high Tg vinyl polymer has a number average molecular weight of about 3,000 or less.

30. A magnetic recording medium as defined in claim 23 wherein said backcoat composition further comprises a dispersant and/or a lubricant.

31. A magnetic recording medium as recited in claim 23 wherein said magnetic layer is derived from a magnetic particle coating composition which comprises (a'"'"') magnetic particles, (b'"'"') polyurethane, (c'"'"') polyisocyanate, and (d'"'"') a low molecular weight, high Tg vinyl polymer characterized by having one or more primary alcohol containing groups pendant to the non-terminal portions thereof.