Magnetic recording medium and magnetic coating composition for magnetic recording medium

Patent metadata

Field	Value
Publication number	US-9761261-B2
Application number	US-201514673144-A
Country	US
Kind code	B2
Filing date	Mar 30, 2015
Priority date	Mar 31, 2014
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

An aspect of the present invention relates to a magnetic recording medium, which comprises a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein the magnetic layer further comprises a compound which has a weight average molecular weight of equal to or more than 1,000 but less than 20,000 and is denoted by formula (1):

wherein, in formula (1), A 1 denotes a monovalent polymer group, each of R 1 and R 2 independently denotes a single bond or a divalent connecting group, R 11 denotes a hydrogen atom or a monovalent substituent, m denotes an integer of equal to or greater than 2, multiple instances of R 1 , R 2 , A 1 , and R 11 that are present can be identical or different, A 2 denotes a hydrogen atom or a monovalent substituent denoted by —OR 3 —Z, R 3 denotes a single bond or a divalent connecting group, Z denotes a monovalent acid group, among multiple instances of A 2 that are present, at least one denotes a monovalent group denoted by —O—R 3 —Z, and X denotes a connecting group of valence m.

First claim

What is claimed is:

1. A magnetic recording medium, which comprises a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein
the magnetic layer further comprises a compound which has a weight average molecular weight of equal to or more than 1,000 but less than 20,000 and is denoted by formula (1):

wherein, in formula (1), A 1 denotes a monovalent polymer group having a polyester structure, each of R 1 and R 2 independently denotes an alkylene group, R 11 denotes a hydrogen atom or a monovalent substituent, m denotes an integer of equal to or greater than 2, multiple instances of R 1 , R 2 , A 1 , and R 11 that are present can be identical or different, A 2 denotes a hydrogen atom or a monovalent substituent denoted by —OR 3 —Z, R 3 denotes an alkylene group, Z denotes a monovalent acid group which is a carboxyl group, a carboxyl salt group, a sulfonic acid group, or a sulfonate group, among multiple instances of A 2 that are present, at least one denotes a monovalent group denoted by —O—R 3 —Z, and X denotes a connecting group of valence m which comprises a structure selected from the group consisting of a cyclic structure and a branched structure.

2. The magnetic recording medium according to claim 1 , wherein the binder has a weight average molecular weight ranging from 20,000 to 120,000.

3. The magnetic recording medium according to claim 1 , wherein the ferromagnetic powder has an average particle size ranging from 10 nm to 50 nm.

4. The magnetic recording medium according to claim 1 , wherein the magnetic layer comprises the compound which has a weight average molecular weight of equal to or more than 1,000 but less than 20,000 and is denoted by formula (1) in a quantity ranging from 0.5 to 50 weight parts per 100 weight parts of the ferromagnetic powder.

5. The magnetic recording medium according to claim 1 , wherein the binder is selected from the group consisting of polyurethane resin and vinyl chloride resin.

6. The magnetic recording medium according to claim 1 , wherein the connecting group X in formula (1) is selected from the following connecting groups:

7. The magnetic recording medium according to claim 1 , wherein the compound denoted in formula (1) is selected from the group consisting of the following compounds 1 to 7:

8. A magnetic coating composition, which is a magnetic coating composition for a magnetic recording medium and comprises:
ferromagnetic powder;
binder;
solvent; and
a compound which has a weight average molecular weight of equal to or more than 1,000 but less than 20,000 and is denoted by formula (1):

wherein, in formula (1), A 1 denotes a monovalent polymer group having a polyester structure, each of R 1 and R 2 independently denotes an alkylene group, R 11 denotes a hydrogen atom or a monovalent substituent, m denotes an integer of equal to or greater than 2, multiple instances of R 1 , R 2 , A 1 , and R 11 that are present can be identical or different, A 2 denotes a hydrogen atom or a monovalent substituent denoted by —O—R 3 —Z, R 3 denotes an alkylene group, Z denotes a monovalent acid group which is a carboxyl group, a carboxyl salt group, a sulfonic acid group, or a sulfonate group, among multiple instances of A 2 that are present, at least one denotes a monovalent group denoted by —O—R 3 —Z, and X denotes a connecting group of valence m which comprises a structure selected from the group consisting of a cyclic structure and a branched structure.

9. The magnetic coating composition according to claim 8 , wherein the binder has a weight average molecular weight ranging from 20,000 to 120,000.

10. The magnetic coating composition according to claim 8 , wherein the ferromagnetic powder has an average particle size ranging from 10 nm to 50 nm.

11. The magnetic coating composition according to claim 8 , which comprises the compound which has a weight average molecular weight of equal to or more than 1,000 but less than 20,000 and is denoted by formula (1) in a quantity ranging from 0.5 to 50 weight parts per 100 weight parts of the ferromagnetic powder.

12. The magnetic coating composition according to claim 8 , wherein the binder is selected from the group consisting of polyurethane resin and vinyl chloride resin.

13. The magnetic coating composition according to claim 8 , wherein the solvent is ketone solvent.

14. The magnetic coating composition according to claim 8 , wherein the connecting group X in formula (1) is selected from the following connecting groups:

15. The magnetic coating composition according to claim 8 , wherein the compound denoted in formula (1) is selected from the group consisting of the following compounds 1 to 7:

Assignees

• Fujifilm Corp

Inventors

• Aoshima Toshihide
• Kikuchi Wataru
• Katayama Kazutoshi
• Mikami Tatsuo

Classifications

• G11B5/7023

  containing polyesters, polyethers, silicones, polyvinyl resins, polyacrylresins or epoxy resins (G11B5/7022 takes precedence) · CPC title

• G11B5/714 Primary

  characterised by the dimension of the magnetic particles · CPC title

• G11B5/7021 Primary

  containing a polyurethane or a polyisocyanate · CPC title

• G11B5/7013

  characterised by the dispersing agent · CPC title