Composite magnetic recording media

• US 9,105,294 B2
• Filed: 03/16/2010
• Issued: 08/11/2015
• Est. Priority Date: 03/16/2010
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Jensen, Tryg R., Brodd, Adam A., Jennings, C. Thomas, Owen, David J.
• Primary Examiner(s): RICKMAN, HOLLY C
• Application Number:
  US12/725,369
• Publication Number:
  US 20110229739A1
• Time in Patent Office: 1,974 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70626 containing non-metallic substances
• CPC Class Codes: G11B 5/7085 non-magnetic abrasive particles
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles
• CPC Class Codes: G11B 5/7368 Non-polymeric layer under the lowermost magnetic recording layer base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739

Abstract

Composite magnetic recording media are described. A composite structure is a structure that is formed of multiple components. For example, a composite magnetic recording medium may include a substrate, an underlayer formed over the substrate, the underlayer defining a coating surface, and a magnetic layer formed over the coating surface of the underlayer. Composite magnetic recording media constructed according to the materials and techniques disclosed may provide dimensional flexibility while exhibiting improved physical or electromagnetic characteristics. In some examples, dimensional flexibility may be achieved by pairing a substrate greater than or equal to approximately 4000 nanometers thick with an underlayer less than or equal to approximately 890 nanometers thick.

Claims

1. A magnetic recording medium comprising:

a substrate;

an underlayer formed over the substrate, the underlayer defining a coating surface and comprising a non-magnetic metal oxide pigment having an average pigment particle size of between about 35 to 100 nanometers and making up between about 55 to 75 weight percent of the underlayer, and further comprising about 10 to 25 weight parts of carbon black per 100 weight parts of non-magnetic metal oxide pigment; and

a magnetic layer formed over the coating surface of the underlayer, and comprising abrasive particles having an average major axis length of more than 3.05 times greater, and up to approximately 5 times greater, than the thickness of the magnetic layer;

wherein the underlayer defines an average thickness less than or equal to approximately 890 nanometers; and

wherein an average surface roughness (Ra) of the underlayer after calendering is less than or equal to approximately 3.6 nanometers, and an average surface roughness depth (Rz) of the underlayer decreases by greater than or equal to approximately 40 percent after calendering.

2. The magnetic recording medium of claim 1, wherein the underlayer defines an average thickness greater than or equal to approximately 380 nanometers, and the substrate defines an average thickness greater than or equal to approximately 4000 nanometers and less than or equal to approximately 6000 nanometers.

3. The magnetic recording medium of claim 2, wherein the underlayer defines an average thickness between approximately 710 nanometers and approximately 813 nanometers, and the substrate defines an average thickness between approximately 4750 nanometers and approximately 5250 nanometers.

4. The magnetic recording medium of claim 1, wherein the ratio of carbon black weight parts to nonmagnetic metal oxide pigment weight parts is less than or equal to approximately 0.25, and wherein the magnetic layer further comprises an activator and a polyhydric binder that includes at least six hydroxyl functional groups.

5. The magnetic recording medium of claim 1, wherein the magnetic layer comprises an activator and a polyhydric binder that includes at least 98 hydroxyl functional groups.

6. The magnetic recording medium of claim 5, wherein the activator includes an isocyanate functional group, the polyhydric binder includes a poly(vinyl acetal) binder, and the magnetic layer further comprises a urethane binder and a vinyl chloride binder.

7. The magnetic recording medium of claim 6, wherein the magnetic layer comprises a plurality of metal particles with an average longitudinal length for each particle of the plurality of metal particles less than or equal to approximately 40 nanometers.

8. The magnetic recording medium of claim 1, wherein an average compressibility ratio of the underlayer is greater than or equal to approximately 14 percent.

9. The magnetic recording medium of claim 8, wherein the magnetic recording medium exhibits an average two-pass abrasivity loss of less than or equal to approximately 2.5 micrometers.

10. The magnetic recording medium of claim 9, wherein the average compressibility ratio of the underlayer is less than or equal to approximately 20 percent, the average surface roughness (Ra) of the underlayer is greater than or equal to approximately 1.1 nanometers, and the magnetic recording medium exhibits a two-pass abrasivity loss greater than or equal to approximately 0.25 micrometers.

11. A magnetic recording medium comprising:

a substrate;

an underlayer formed over the substrate, the underlayer defining a coating surface and comprising a non-magnetic metal oxide pigment having an average pigment particle size of between about 35 to 100 nanometers and making up between about 55 to 75 weight percent of the underlayer, and further comprising about 10 to 25 weight parts of carbon black per 100 weight parts of non-magnetic metal oxide pigment; and

a magnetic layer formed over the coating surface of the underlayer, and comprising abrasive particles having an average major axis length of more than 3.1 times greater, and up to approximately 5 times greater, than the thickness of the magnetic layer;

wherein the underlayer defines an average thickness less than or equal to approximately 890 nanometers; and

wherein an average surface roughness (Ra) of the underlayer after calendering is less than or equal to approximately 3.6 nanometers, and an average surface roughness depth (Rz) of the underlayer decreases by greater than or equal to approximately 40 percent after calendering.

12. The magnetic recording medium of claim 11, wherein the underlayer defines an average thickness greater than or equal to approximately 380 nanometers, and the substrate defines an average thickness greater than or equal to approximately 4000 nanometers and less than or equal to approximately 6000 nanometers.

13. The magnetic recording medium of claim 12, wherein the underlayer defines an average thickness between approximately 710 nanometers and approximately 813 nanometers, and the substrate defines an average thickness between approximately 4750 nanometers and approximately 5250 nanometers.

14. The magnetic recording medium of claim 11, wherein the ratio of carbon black weight parts to nonmagnetic metal oxide pigment weight parts is less than or equal to approximately 0.25, and wherein the magnetic layer further comprises an activator and a polyhydric binder that includes at least six hydroxyl functional groups.

15. The magnetic recording medium of claim 11, wherein the magnetic layer comprises an activator and a polyhydric binder that includes at least 98 hydroxyl functional groups.

16. The magnetic recording medium of claim 15, wherein the activator includes an isocyanate functional group, the polyhydric binder includes a poly(vinyl acetal) binder, and the magnetic layer further comprises a urethane binder and a vinyl chloride binder.

17. The magnetic recording medium of claim 16, wherein the magnetic layer comprises a plurality of metal particles with an average longitudinal length for each particle of the plurality of metal particles less than or equal to approximately 40 nanometers.

18. The magnetic recording medium of claim 11, wherein an average compressibility ratio of the underlayer is greater than or equal to approximately 14 percent.

19. The magnetic recording medium of claim 18, wherein the magnetic recording medium exhibits an average two-pass abrasivity loss of less than or equal to approximately 2.5 micrometers.

20. The magnetic recording medium of claim 19, wherein the average compressibility ratio of the underlayer is less than or equal to approximately 20 percent, the average surface roughness (Ra) of the underlayer is greater than or equal to approximately 1.1 nanometers, and the magnetic recording medium exhibits a two-pass abrasivity loss greater than or equal to approximately 0.25 micrometers.