Magnetic core element for antenna, thin-film antenna, and card equipped with thin-film antenna

• US 5,567,537 A
• Filed: 04/11/1995
• Issued: 10/22/1996
• Est. Priority Date: 04/11/1994
• Status: Expired due to Term

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: Yoshizawa, Yoshihito, Arakawa, Shunsuke
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): LAM, CATHY FONG FONG
• Application Number:
  US08/419,690
• Time in Patent Office: 560 Days
• Field of Search: 343/787, 343/788, 343/781 CA, 428/692, 428/689, 428/379
• US Class Current: 428/800
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: H01F 1/15308 based on Fe/Ni H01F1/15325 takes precedence
• CPC Class Codes: H01F 1/15316 based on Co H01F1/15325 takes precedence
• CPC Class Codes: H01F 1/15333 containing nanocrystallites, e.g. obtained by annealing
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 7/06 with core of ferromagnetic material H01Q7/02 takes precedence
• CPC Class Codes: Y10T 428/294 including metal or compound thereof [excluding glass, ceramic and asbestos]

Abstract

A magnetic core element for use in a thin antenna. The magnetic core element has a thickness of 25 μm or less and is made of a particular amorphous alloy strip or a particular nano-crystalline alloy strip. A thin antenna having a laminated magnetic core made of the magnetic core elements is highly resistant to deformation and has a high Q-value.

Claims

1. A magnetic core element in the form of an amorphous alloy strip of a thickness of 25 μ

m or less having a chemical composition representation by;

space="preserve" listing-type="equation">(Co.sub.1-a Fe.sub.a).sub.100-b-c-d-e T.sub.b Si.sub.c B.sub.d Y.sub.e(

     1)

where T is at least one element selected from the group consisting of Mn, Ni, Ti, Zr, Hf, Cr, Mo, Nb, W, Ta, Cu, Ru, Rh, Pd, Os, Ir, Pt, Re and Sn;

Y is at least one element selected from the group consisting of C, Ge, Ga, P and Al;

a is a numerical value satisfying 0≦

a≦

0.1; and

b, c, d and e are atomic percentages each satisfying 0≦

b≦

15, 0≦

c≦

20, 5≦

d≦

25, 0≦

e≦

20 and 15≦

c+d≦

30, said magnetic core element being provided with an induced magnetic anisotropy in the width direction or in the thickness direction of said magnetic core.

4. The magnetic core element according to claim 1, wherein the thickness of said magnetic core element is 15 μ

m or less.

2. A magnetic core element in the form of an nano-crystalline alloy strip of a thickness of 25 μ

m or less having a chemical composition represented by;

space="preserve" listing-type="equation">(Fe.sub.1-v M.sub.v).sub.100-x-y-z-w A.sub.x M'"'"'.sub.y M".sub.z X.sub.w(

     2)

wherein M is Co, Ni or a combination thereof;

A is Cu, Au or a combination thereof;

M'"'"' is at least one element selected from the group consisting of Ti, V, Zr, Nb, Mo, Hf, Ta and W;

M" is at least one element selected from the group consisting of Cr, Mn, Al, Sn, Zn, Ag, In, platinum group elements, Mg, Ca, Sr, Y, rare earth elements, N, O and S;

X is at least one element selected from the group consisting of B, Si, C, Ge, Ga and P;

v is a numerical value satisfying 0≦

v≦

0.5; and

x, y, z and w are atomic percentages each satisfying 0≦

x≦

10, 0.1≦

y≦

20, 0≦

z≦

20 and 2≦

w≦

30, at least 50% of the alloy structure comprising crystal grains of an average grain size of 100 nm or less.

3. The magnetic core element according to claim 2, wherein said magnetic core element is provided with induced magnetic anisotropy in the width direction or in the thickness direction of said magnetic core element.

5. The magnetic core element according to claim 2, wherein the thickness of said magnetic core element is 15 μ

m or less.

6. A thin antenna comprising a laminated magnetic core and at least one coil wound around said laminated magnetic core and having a Q-value of 25 or more at 134 kHz, said laminated magnetic core having a thickness of 3 mm or less and being composed of a plurality of magnetic core elements in the form of amorphous alloy strips of a thickness of 25 μ

m or less having a chemical composition represented by;

space="preserve" listing-type="equation">(CO.sub.1-a Fe.sub.a).sub.100-b-c-d-e T.sub.b Si.sub.c B.sub.d Y.sub.c(

     1)

wherein T is at least one element selected from the group consisting of Mn, Ni, Ti, Zr, Hf, Cr, Mo, Nb, W, Ta, Cu, Ru, Rh, Pd, Os, Ir, Pt, Re and Sn;

Y is at least one element selected from the group consisting of C, Ge, Ga, P and Al;

a is a numerical value satisfying 0≦

a≦

0.1; and

b, c, d and e are atomic percentages each satisfying 0≦

b≦

15, 0≦

c≦

20, 5≦

d≦

25, 0≦

e≦

20 and 15≦

v+d≦

30, said magnetic core element being provided with an induced magnetic anisotropy in the width direction or in the thickness direction of said magnetic core.

8. The thin antenna according to claim 6 or 7, wherein the thickness of said laminated magnetic core is 1 mm or less.

9. The thin antenna according to claim 6 or 7, wherein the inductance at 134 kHz of said antenna is 1 mH or more.

10. The thin antenna according to claim 8, wherein the inductance at 134 kHz of said antenna is 1 mH or more.

11. The thin antenna according to claim 6 or 7, wherein said laminated magnetic core suffers from no cracks after deflecting said laminated magnetic core until the distance between the center portion on the surface of said laminated magnetic core and a line connecting both the ends of the surface of said laminated magnetic core reaches 5 mm when the length of said laminated magnetic core is 20 mm or more.

12. A card equipped therein with said thin antenna according to claim 6 or 7 and a transmitting circuit and/or receiving circuit.

13. The card according to claim 12, wherein said card after deflected until the distance between the center portion on the surface of said card and a line connecting both the ends of the surface of said card reaches 1 mm shows the same antenna efficiency as that before subjected to said deflection.

7. A thin antenna comprising a laminated magnetic core and at least one coil wound around said laminated magnetic core and having a Q-value of 25 or more at 134 kHz, said laminated magnetic core having a thickness of 3 mm or less and being composed of a plurality of nano-crystalline alloy strips of a thickness of 25 μ

m or less having a chemical composition represented by;

space="preserve" listing-type="equation">(Fe.sub.1-v M.sub.v).sub.100-x-y-z-w A.sub.xM'"'"'.sub.y M".sub.z X.sub.w(

     2)

wherein M is Co, Ni or a combination thereof;

A is Cu, Au or a combination thereof;

M'"'"' is at least one element selected from the group consisting of Ti, V, Zr, Nb, Mo, Hf, Ta and W;

M" is at least one element selected from the group consisting of Cr, Mn, Al, Sn, Zn, Ag, In, platinum group elements, Mg, Ca, Sr, Y, rare earth elements, N, O and S;

X is at least one element selected from the group consisting of B, Si, C, Ge, Ga and P;

v is a numerical value satisfying 0≦

v≦

0.5; and

x, y, z and w are atomic percentages each satisfying 0≦

x≦

10, 0.1≦

y≦

20, 0≦

z≦

20 and 2≦

w≦

30, at least 50% of the alloy structure comprising crystal grains of an average grain size of 100 nm or less.