Plate-like ferrite particles with magnetoplumbite structure and magnetic card using the same

• US 6,099,957 A
• Filed: 11/10/1999
• Issued: 08/08/2000
• Est. Priority Date: 03/04/1997
• Status: Expired due to Term

• Current Assignee: TODA Kogyo Corporation
• Original Assignee: TODA Kogyo Corporation
• Inventors: Yamamoto, Akinori, Sanada, Kazutoshi, Yamamoto, Shigehisa
• Primary Examiner(s): RESAN, STEVAN A
• Application Number:
  US09/437,236
• Time in Patent Office: 272 Days
• Field of Search: 428/323, 428/329, 428/402, 428/403, 428/405, 428/407, 428/447, 428/694 BH, 428/900
• US Class Current: 428/323
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/855 Coating only part of a support with a magnetic layer
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2995 Silane, siloxane or silicone coating
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer
• CPC Class Codes: Y10T 428/31663 As siloxane, silicone or silane

Abstract

The present invention relates to plate-like ferrite particles with magnetoplumbite structure having a composition represented by the general formula of AO·n{(Fe_1-(a+b) Bi_a M_b)₂ O₃ } wherein A is Ba, Sr or Ba--Sr; M is Zn--Nb, Zn--Ta or Zn--Sn; n is from 5.5 to 6.1; a is from 0.001 to 0.005; b is from 0.050 to 0.120; and the ratio of b/a is from 20 to 50. The plate-like ferrite particles with magnetoplumbite structure have an appropriate particle size, a low coercive force, a large saturation magnetization, a small switching field distribution (S.F.D.) and an excellent temperature stability, and a magnetic card containing the plate-like ferrite particles with magnetoplumbite structure.

Claims

1. A magnetic card comprising:

(i) a substrate; and

(ii) magnetic recording layer formed on said substrate comprising said plate-like ferrite particles with magnetoplumbite structure, having a composition represented by the general formula of AO·

n{(Fe_1-(a+b)Bi_a M_b)₂ O₃ } wherein A is Ba, Sr or Ba--Sr;

M is Zn--Nb, Zn--Ta or Zn--Sn;

n is from 5.5 to 6.1;

a is from 0.001 to 0.005;

b is from 0.050 to 0.120; and

the ratio of b/a is from 20 to 50, and a binder resin.

2. A magnetic card comprising:

(i) a substrate; and

(ii) magnetic tape laminated on said substrate comprising said base film, comprising said plate-like ferrite particles with magnetoplumbite structure, having a composition represented by the general formula of AO·

n{(Fe_1-(a+b) Bi_a M_b)₂ O₃ } wherein A is Ba, Sr or Ba--Sr;

M is Zn--Nb, Zn--Ta or Zn--Sn;

n is from 5.5 to 6.1;

a is from 0.001 to 0.005;

b is from 0.050 to 0.120; and

the ratio of b/a is from 20 to 50, and a binder resin.

3. A magnetic card according to claim 2, wherein said magnetic recording layer comprising 100 parts by weight of the binder resin and 50 to 2,000 parts by weight of the plate-like ferrite particles with magnetoplumbite structure.

4. A magnetic card according to claim 2, wherein the plate-like ferrite particles with magnetoplumbite structure have an average plate surface diameter of 0.30 to 1.50 μ

m, an average thickness of 0.05 to 0.60 μ

m and an average plate ratio (plate surface diameter/thickness) of 3 to 7.

5. A magnetic card according to claim 2, wherein the plate-like ferrite particles with magnetoplumbite structure have a coercive force of 300 to 1,400 Oe, a saturation magnetization of not less than 56 emu/g and a switching field distribution of not more than 1.30.

6. A magnetic card according to claim 2, wherein the plate-like ferrite particles with magnetoplumbite structure have a temperature stability relative to coercive force of -1.5 to +1.5 Oe/°

C.

7. A magnetic card according to claim 2, wherein the plate-like ferrite particles with magnetoplumbite structure have an apparent density of 0.70 to 1.00 g/cm³ and a tap density of 1.75 to 2.10 g/cm³.

8. A magnetic card according to claim 2, wherein the plate-like ferrite particles with magnetoplumbite structure have on the surface thereof, a coat comprising at least one compound selected from the group consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon.

9. A magnetic card according to claim 8, wherein the amount of said coat is in the range of 0.01 to 2.00% by weight, calculated as Al or SiO₂, based on the total weight of the particles.

10. A magnetic card according to claim 8, wherein the plate-like ferrite particles with magnetoplumbite structure have an apparent density of 0.70 to 1.00 g/cm³ and a tap density of 1.75 to 2.10 g/cm³.

11. A magnetic card according to claim 2, wherein the plate-like ferrite particles with magnetoplumbite structure have on the surface thereof an attached agent comprising at least one treating agent selected from the group consisting of (a) polyester-based high-molecular dispersant having an amino group, (b) polyester-based high-molecular dispersant having an acid group, (c) silane-based coupling agent having an aminopropyl group, (d) silane-based coupling agent having a mercapto group, and (e) coordinate-type titanium-based coupling agent.

12. A magnetic card according to claim 11, wherein the amount of said treating agent attached, is in the range of 0.1 to 2.0% by weight based on the total weight of the particles.

13. A magnetic card according to claim 11, wherein the plate-like ferrite particles with magnetoplumbite structure have an apparent density of 0.70 to 1.00 g/cm³ and a tap density of 1.75 to 2.10 g/cm³.