EP0368194A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Magneto-optical system
Assignee: Hitachi Ltd
•
Filing: 1989-11-06
•
Granted: —
•
Expires: 2009-11-06
Abstract
Abstract In a magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a film of four-layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1) provided with guide tracks, temperature distribution of the magneto-optical recording layer (3) is controlled by controlling the thermal diffusivity of the metallic layer (5), and recording/reproduction/erasing repetition characteristics are improved thereby. In the disk of the present structure, the temperature is elevated in a broader area from the center of laser beam, and thus a thoroughly broad erasing domain width taking a track offset into account can be obtained and not recording domains remain after the erasing. The reproduced signal output is increased by 4 dB, as compared with that obtained by a disk of three-layer structure without any metallic layer, because the beam utilization efficiency is increased owing to both Kerr effect and Faraday effect. When the disk of the present structure is subjected to field modulation recording, tails of arrow-feather-shaped recording domains peculiar to the field modulation recording can be shortened and interbit interferences can be overcome, resulting in an increase in C/N (S/N) ratio and the high density recording can be made. By endowing a Kerr enhancement action to the second dielectric layer (4) and a protective action on the magneto-optical layer (3) to the first dielectric layer (2), only the reliability can be improved without lowering the C/N ratio. By improving the corrosion resistance of the magneto-optical recording layer, the first dielectric layer (2) can be omitted to the contrary, and a magneto-optical disk of simple structure can be obtained and used as memory for domestic applications or communication fields. <IMAGE>
Inventors
- 👤 Fumiyoshi Sanikopo Takaidohigashi 401 Kirino
- 👤 Harukazu Miyamoto
- 👤 Shigenori Okamine
- 👤 Noriyuki Ogihara
- 👤 Masahiko Takahashi
- 👤 Norio Ohta
- 👤 Toshio Niihara
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 02:36
CPC Classifications
G; G11; G11B; G11B7/00; G11B7/24; G11B7/241; G11B7/252; G11B7/254; G11B11/00; G11B11/10; G11B11/105; G11B11/10502; G11B11/1053; G11B11/10582; G11B11/10586; G11B11/10589; G11B11/10591; G11B11/10593; G11B7/242; G11B7/243; G11B7/2433; G11B11/10504; G11B11/10508; G11B11/10517; G11B11/10519; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 44
Claim 1
Independent Claim
65 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a four layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1), a heat flow from the magneto-optical recording layer (3) being caused by the presence of the metallic layer (5).
Claim 2
Dependent Claim
65 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a four layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1), a heat flow from the magneto-optical recording layer (3) being caused by the presence of the metallic layer (5).
Claim 3
Dependent Claim
42 words
A magneto-optical disk according to Claim 1, wherein the metallic layer (5) is composed of at least one element selected from Al, Au, Pt, Rh, Pd and Cu as a host element, thereby controlling the thermal diffusivity of the metallic layer (5).
Claim 4
Dependent Claim
64 words
A magneto-optical disk according to Claim 2, wherein the metallic layer (5) further contains at least one of unselected host elements or 1 to 30 at.% of at least one of Ni, Nb, Ta, Ti, Zr, Co, Mn and Cr on the basis of the total elements, thereby adjusting the concentration of the host element and controlling the thermal conductivity of the metallic layer.
Claim 5
Dependent Claim
27 words
A magneto-optical disk according to Claim 1, wherein the thickness of the metallic layer (5) is adjusted, thereby controlling the thermal diffusivity of the metallic layer (5).
Claim 6
Dependent Claim
66 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a 4-layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1), the thickness of the magneto-optical recording layer (3) being adjusted, thereby controlling the temperature distribution of the magneto-optical recording layer (3).
Claim 7
Dependent Claim
66 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a 4-layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1), the thickness of the magneto-optical recording layer (3) being adjusted, thereby controlling the temperature distribution of the magneto-optical recording layer (3).
Claim 8
Dependent Claim
78 words
A magneto-optical disk for recording reproduction or erasing with a laser beam, which comprises a film of four-layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1), the metallic layer (5) consisting of a layer of high reflectivity material provided at the second dielectric layer (4) side and a layer of high corrosion-resistant material at the opposite side.
Claim 9
Dependent Claim
78 words
A magneto-optical disk for recording reproduction or erasing with a laser beam, which comprises a film of four-layer structure consisting of a first dielectric layer (2), a magneto-optical recording layer (3), a second dielectric layer (4) and a metallic layer (5), laid on a disk substrate (1), the metallic layer (5) consisting of a layer of high reflectivity material provided at the second dielectric layer (4) side and a layer of high corrosion-resistant material at the opposite side.
Claim 10
Dependent Claim
32 words
A magneto-optical disk according to Claim 6, wherein a concentration gradient is provided in the metallic layer (5) between the layer of high reflectivity material and the layer of high corrosion-resistant material.
Claim 11
Dependent Claim
61 words
A magneto-optical disk according to Claim 6, wherein the high reflectivity material is at least one element selected from Al, Cu, Rh, Pd, Au and Pt and the high corrosion-resistant material is at least one element selected from Co, Ti, Ta, Nb, Cr, Ni, Zr, W and Mn, the concentration of the high corrosion-resistant material being not more than 30 at.%.
Claim 12
Dependent Claim
97 words
A magneto-optical disk which comprises a magneto-optical recording layer (3) laid on a substrate (1), the magneto-optical recording layer (3) being substantially continuously irradiated with a light beam upon focussing of the light beam, the light beam being moved relatively to the disk, while applying a modulation magnetic field to the magneto-optical recording layer (3) at the same time, thereby forming recording domains on the magneto-optical recording layer (3), and recording information in the form of recording domains, the shape of the magnetic domains being controlled by controlling the thermal diffusivity of the magneto-optical recording layer (3).
Claim 13
Dependent Claim
97 words
A magneto-optical disk which comprises a magneto-optical recording layer (3) laid on a substrate (1), the magneto-optical recording layer (3) being substantially continuously irradiated with a light beam upon focussing of the light beam, the light beam being moved relatively to the disk, while applying a modulation magnetic field to the magneto-optical recording layer (3) at the same time, thereby forming recording domains on the magneto-optical recording layer (3), and recording information in the form of recording domains, the shape of the magnetic domains being controlled by controlling the thermal diffusivity of the magneto-optical recording layer (3).
Claim 14
Dependent Claim
47 words
A magneto-optical disk according to Claim 9, wherein the length of projections of the recording domains in the moving direction of the light beam is smaller than 0.7 times the width of the recording domains in the direction perpendicular to the moving direction of the light beam.
Claim 15
Dependent Claim
30 words
A magneto-optical disk according to Claim 9, wherein the magneto-optical recording disk comprises at least the magneto-optical recording layer (3) and a metallic layer (5), laid on the substrate (1).
Claim 16
Dependent Claim
35 words
A magneto-optical disk according to Claim 9, wherein the magneto-optical recording disk comprises at least a magneto-optical recording layer (3), a dielectric layer (2) and a metallic layer (5), laid successively on the substrate (1).
Claim 17
Dependent Claim
49 words
A magneto-optical disk according to Claim 11 or 12, wherein thermal diffusivity K M of the metallic layer (5) is in the following relationship: K M > vD wherein v is moving speed of the light beam, and D is diameter of focused light spot of the light beam.
Claim 18
Dependent Claim
28 words
A magneto-optical disk according to Claim 12, wherein thermal diffusivity Kα of the dielectric layer (2) is smaller than thermal diffusivity K M of the metallic layer (5).
Claim 19
Dependent Claim
48 words
A magneto-optical disk according to Claim 11 or 12, wherein product or multiplied value of thermal diffusivity and thickness k R of the magneto-optical recording layer (3) is smaller than product or multiplied value of thermal diffusivity K M and thickness 1 M of the metallic layer (5).
Claim 20
Dependent Claim
50 words
A magneto-optical disk according to Claim 12, wherein thermal diffusivity Kα of the dielectric layer (2) is in the following relationship: wherein to is thickness of the dielectric layer (2), v is moving speed of the light beam and D is diameter of focused light spot of the light beam.
Claim 21
Dependent Claim
26 words
A magneto-optical disk according to Claim 11, wherein thermal diffusivity of the metallic layer (5) is larger than thermal diffusivity of the magneto-optical recording layer (3).
Claim 22
Dependent Claim
59 words
A magneto-optical disk according to Claim 12, wherein the dielectric layer (2) is composed of one or a mixture or compound of two or more of AIN x , SiN x , ZrO x , SiO x , TaO x , ZnS, ZnO x , TiO x , Y 2 0 3 , and Sm 2 0 3 .
Claim 23
Dependent Claim
33 words
A magneto-optical disk according to Claim 9, wherein reproduced signal intensity of the magneto-optical disk is once saturated to light beam power and then has a given saturation value to a higher power.
Claim 24
Dependent Claim
77 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a four-layer structure consisting of a first dielectric layer (2) of inorganic compound, a magneto-optical recording layer (3), a second dielectric layer (4) of inorganic compound and a metallic layer (5), laid on a substrate provided with guide tracks, the second dielectric layer (4) provided between the magneto-optical recording layer (3) and the metallic layer (5) being given a light multiple interference effect.
Claim 25
Dependent Claim
77 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a four-layer structure consisting of a first dielectric layer (2) of inorganic compound, a magneto-optical recording layer (3), a second dielectric layer (4) of inorganic compound and a metallic layer (5), laid on a substrate provided with guide tracks, the second dielectric layer (4) provided between the magneto-optical recording layer (3) and the metallic layer (5) being given a light multiple interference effect.
Claim 26
Dependent Claim
53 words
A magneto-optical disk according to Claim 20, wherein refractive index of the second dielectric layer (4) of inorganic compound provided between the magneto-optical recording layer (3) and the metallic layer (5) has a difference by at least 0.4 from refractive index of the layers on both sides of the second dielectric layer (4).
Claim 27
Dependent Claim
35 words
A magneto-optical disk according to Claim 20, wherein the magneto-optical recording layer (3) is composed of material having a perpendicular magnetization anisotropy, preferably an alloy of a rare earth element and an iron group element.
Claim 28
Dependent Claim
39 words
A magneto-optical disk according to Claim 20, wherein the magneto-optical recording layer (3) is composed of an alloy consisting of one or two elements selected from Gd, Tb, Dy and Ho and one or both of Fe and Co.
Claim 29
Dependent Claim
50 words
A magneto-optical disk according to Claim 20, wherein the magneto-optical recording layer (3) is composed of an alloy consisting of one or two elements selected from Gd, Tb, Dy, and Ho, at least one element selected from Nd, Pr, Ce and Sm, and one or both of Fe and Co.
Claim 30
Dependent Claim
22 words
A magneto-optical disk according to Claim 20, wherein the magneto-optical recording layer (3) has a thickness of not more than 50 nm.
Claim 31
Dependent Claim
35 words
A magneto-optical disk according to Claim 20, wherein the magneto-optical recording layer (3) is composed of a material containing 1 to 8 at.% of at least one element selected from Nb, Ti, Ta and Cr.
Claim 32
Dependent Claim
49 words
A magneto-optical disk according to Claim 20, wherein the magnetic-optical recording layer (3) is composed of a material containing 1 to 15 at.% in total of at least one element selected from Nb, Ti, Ta and Cr and at least one element selected from Pt, Pd, Rh and Au.
Claim 33
Dependent Claim
43 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a three-layer structure consisting of a magneto-optical recording layer (3), a dielectric layer (2) and a metallic layer (2), laid on a disk substrate (1) provided with guide tracks.
Claim 34
Dependent Claim
43 words
A magneto-optical disk for recording, reproduction or erasing with a laser beam, which comprises a three-layer structure consisting of a magneto-optical recording layer (3), a dielectric layer (2) and a metallic layer (2), laid on a disk substrate (1) provided with guide tracks.
Claim 35
Dependent Claim
36 words
A magneto-optical disk according to Claim 28, wherein the magneto-optical recording layer (3) is composed of an alloy of a rare earth element and an iron group element as host elements, the alloy being preferably amorphous.
Claim 36
Dependent Claim
42 words
A magneto-optical disk according to Claim 29, wherein the rare earth element is one or two elements selected from Dy, Ho, Tb, Gd, Nd, Pr and Sm, and the iron group element is one or two elements selected from Fe and Co.
Claim 37
Dependent Claim
56 words
A magneto-optical disk according to Claim 28, the magneto-optical recording layer (3) is composed of a rare earth element and an iron group element as host elements and either or both of at least one element selected from Cr, Ti, Ta, Nb, and AI and at least one element selected from Pt, Pd, Rh and Au.
Claim 38
Dependent Claim
36 words
A magneto-optical disk according to Claim 28, where temperature distribution of the magneto-optical recording layer (3) is changed by controlling materials and thermal diffusivity of the dielectric layer (2), thereby adjusting disk recording or erasing sensitivity.
Claim 39
Dependent Claim
43 words
A magneto-optical disk according to Claim 28, wherein the metallic layer (5) is composed of one element selected from Al, Cu, Au, Pt and Rh as a host element or an alloy of the elements, and the metallic layer (5) is preferably amorphous.
Claim 40
Dependent Claim
32 words
A magneto-optical disk according to Claim 33, wherein the metallic layer (5) contains 0.5 to 40 at.% of one or two elements selected from Ni, Ti, Ta, Cr, Nb, Zr and Si.
Claim 41
Dependent Claim
36 words
A magneto-optical disk according to Claim 28, wherein temperature distribution of the magneto-optical layer (3) is changed by controlling materials and thermal diffusivity of the metallic layer (5), thereby adjusting a disk recording or erasing sensitivity.
Claim 42
Dependent Claim
37 words
A magneto-optical disk according to Claim 28, wherein a nitride layer is provided on one or both boundary sides of the magneto-optical recording layer (3), and the thickness of the nitride layer is at least 30 ,4.
Claim 43
Dependent Claim
40 words
A magneto-optical disk according to Claim 31, wherein sum total of the additive elements to the alloy of rare earth element and iron group element as the material for the magneto-optical recording layer (3) is 0.5 to 15 at at.%.
Claim 44
Dependent Claim
18 words
A magneto-optical disk according to Claim 28, wherein recording of information is carried out by field modulation recording.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.