Magneto-optical recording medium

• US 4,839,226 A
• Filed: 10/05/1987
• Issued: 06/13/1989
• Est. Priority Date: 10/03/1986
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Sawada, Yasuo, Machida, Hajime
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Monroe, James B.
• Application Number:
  US07/104,217
• Time in Patent Office: 617 Days
• Field of Search: 428/694, 428/900, 428/336, 428/431, 428/469, 428/471, 428/472, 428/697, 428/701, 428/702, 365/122, 360/131-135, 369/13, 369/288, 430/945, 252/62.56, 252/62.57, 252/62.58, 252/62.59
• US Class Current: 428/336
• CPC Class Codes: G11B 11/10584 characterised by the form, e.g. comprising mechanical protection elements
• CPC Class Codes: G11B 11/10586 characterised by the selection of the material
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/3162 Cross-linked polyester [e.g., glycerol maleate-styrene, etc.]

Abstract

A magneto-optical recording medium is disclosed, which comprises a transparent substrate, a magnetic oxide layer formed on the substrate, and band-shaped reflection layers formed on the magnetic oxide layer.

Claims

1. A magneto-optical recording medium comprising a transparent substrate, a magnetic oxide layer formed on said substrate, and band-shaped reflection layers in the same plane formed on said magnetic oxide layer,

wherein said magnetic oxide layer comprises:

a magnetoplumbite-type ferrite having general formula (I);

space="preserve" listing-type="equation">MeO.n(M.sub.x Fe.sub.(2-x) O.sub.3) (I)

wherein Me represents at least one element selected from the group consisting of Ba, Pb, Sr and La;

M represents one element or a combination of at least two elements which constitute a three-valence element or element group as a whole;

x, 0<

x≦

2; and

n, 5≦

n≦

6,

a garnet-type magnetic oxide having general formula (II);

space="preserve" listing-type="equation">(R.sub.3)(M.sup.3+.sub.y Fe.sup.3+.sub.5-y)O.sub.12 (II)

wherein R represents at least one element selected from the group consisting of Y, Bi, Pb, Ca, Sr, Ba, La, Sm, Eu, Gd, Er, Tm, Yb, Lu, Pr, Nd, Ho and Dy;

M represents at least one element selected from the group consisting of Ga, Al, V, Si, Ge, Co, Zn, Lu, Sc, Cr, Zr, Ti, Tb, Gd and Dy, by which Fe can be replaced;

y, 0≦

y≦

3;

or a cobalt spinel-type magnetic oxide having general formula (III);

space="preserve" listing-type="equation">Co.sub.x M.sub.y Fe.sub.2-(x+y) O.sub.4 (III)

wherein M represents at least one element selected from the group consisting of Al, Cr, Mn, Ni, Ti, Zn, Sn, Cu, Mg, Rh, V, Ga, Sb, Sc, Bi, Y, Su, Eu, Tb, Er, Yb, Ho, Dy, Tm, Gd, Sm, Pb, Re and Ru, by which Fe can be replaced; and

x, y, 0<

x+y<

3, 0≦

y≦

=2; and

wherein said band-shaped reflection layer has a reflectance of 30% or 80%, and a heat conductivity of less than 0.25 cal/cm.sec.°

C. at 20°

C.

2. The magneto-optical recording medium as claimed in claim 1, wherein said magnetic oxide layer comprises a magnetoplumbite-type ferrite having general formula (I):

space="preserve" listing-type="equation">MeO.n[M.sub.x Fe.sub.(2-x) O.sub.3 ] (I)

wherein Me represents at least one element selected from the group consisting of Ba, Pb, Sr and La;

M represents one element or a combination of at least two elements which constitute a three-valence element or element group as a whole;

x, 0≦

x<

2; and

n, 5≦

n≦

6.

3. The magneto-optical recording medium as claimed in claim 1, wherein said magnetic oxide layer comprises a garnet-type magnetic oxide having general formula (II):

space="preserve" listing-type="equation">[R.sub.3 ][M.sup.3+.sub.y Fe.sup.3+.sub.5-y ]O.sub.12 (II)

wherein R represents at least one element selected from the group consisting Y, Bi, Pb, Ca, Sr, Ba, La, Sm, Eu, Gd, Er, Tm, Yb, Lu, Pr, Nd, Ho and Dy;

M represents at least one element selected from the group consisting of Ga, Al, V, Si, Ge, Co, Zn, Lu, Sc, Cr, Zr, Ti, Tb, Gd and Dy, by which Fe can be replaced;

y, 0≦

y≦

3.

4. The magneto-optical recording medium as claimed in claim 1, wherein said magnetic oxide layer comprises a cobalt spinel-type magnetic oxide having general formula (III):

space="preserve" listing-type="equation">Co.sub.x N.sub.y Fe.sub.2-(x+y) O.sub.4 (III)

wherein M represents at least one element selected from the group consisting of Al, Cr, Mn, Ni, Ti, Zn, Sn, Cu, Mg, Rh, V, Ga, Sb, Sc, Bi, Y, Su, Eu, Tb, Er, Yb, Ho, Dy, Tm, Gd, Sm, Pb, Re and Ru, by which Fe can be replaced; and

x, y, 0<

x+y<

3, 0≦

y≦

=2.

5. The magneto-optical recording medium as claimed in claim 1, wherein said magnetic oxide layer has a thickness of 1000 Å

or more.

6. The magneto-optical recording medium as claimed in claim 1, wherein said magnetic oxide layer has a thickness ranging from 2000 Å

to 5000 Å

.

7. The magneto-optical recording medium as claimed in claim 1, wherein said transparent substrate is made of a glass selected from the group consisting of quartz glass, crystallized glass, and aluminosilicate glass.

8. The magneto-optical recording medium as claimed in claim 1, wherein said transparent substrate is made of a single or polycrystal of a material selected from the group consisting of garium.gadolinium.garnet (GGG), lithium tantalate Al₂ O₃ and MgO.

9. The magneto-optical recording medium as claimed in claim 1, wherein said band-shaped reflection layer comprises a metal selected from the group consisting of Al, Nd, Cr and Pt.

10. The magneto-optical recording medium as claimed in claim 1, wherein said band-shaped reflection layer comprises an alloy selected from the group consisting of Fe--Ni, stainless steel, nickel chrome steel, and chromel.

11. The magneto-optical recording medium as claimed in claim 1, wherein each of said band-shaped reflection layers has a width ranging from 3/10 to 7/10 of the track pitch of said reflection layers.

12. The magneto-optical recording medium as claimed in claim 1, further comprising an undercoat layer between said substrate and said magnetic oxide layer, and a protective layer on said reflection layer.

13. The magneto-optical recording medium as claimed in claim 12, wherein said undercoat layer is a film made of a component selected from the group consisting of ZnO (001-plane), Mn-Zn ferrite (111-plane), Co spinel ferrite (111-plane), Co-Zn ferrite (111-plane) and MgO (111-plane).

14. The magneto-optical recording medium as claimed in claim 12, wherein said protective layer comprises a component selected from the group consisting of SiO₂, SiO, TiO₂, ZnO, Al₂ O₃, AlN, Si₃ N₄, C, TaC, TiC and ZrC.

15. The magneto-optical recording medium as claimed in claim 1, further comprising a het emitting undercoat layer between said substrate and said magnetic oxide layer, and a heat insulating layer between said magnetic oxide layer and said band-shaped reflection layers.

16. The magneto-optical recording medium as claimed in claim 15, wherein said heat emitting layer comprises a ferrite selected from the group consisting of Co spinel ferrite and Ni spinel ferrite.

17. The magneto-optical recording medium as claimed in claim 15, wherein said heat emitting undercoat layer has a thickness of about 0.1 μ

m to about 0.5 μ

m.

18. The magneto-optical recording medium as claimed in claim 15, wherein said heat insulating layer comprises a component selected from the group consisting of Si_x O_y, Si_x N_y, SiC, Al₂ O₃, ZrO₂, ThO₂, CaO, CeO₂, HfO₂, and BeO.

19. The magneto-optical recording medium as claimed in claim 1, further comprising an undercoat layer between said substrate and said magnetic oxide layer, and a heat emitting layer and a heat insulating layer between said magnetic oxide layer and said reflection layers, with said heat insulating layer being overlaid on said heat emitting layer.

20. The magneto-optical recording medium as claimed in claim 19, wherein said heat emitting layer comprises a ferrite selected from the group consisting of Co spinel ferrite and Ni spinel ferrite.

21. The magneto-optical recording medium as claimed in claim 19, wherein said heat emitting layer has a thickness ranging from about 0.1 μ

m to about 0.5 μ

m.