Patent Application
20060127702
1. Field of the Invention
The present invention relates to a magneto-optical recording medium having a recording reproduction layer between a substrate and a protective film layer, wherein a recording head disposed at the protective film layer side produces a magnetic field and a light is projected from the recording head side so that information is recorded on the recording reproduction layer.
2. Description of the Related Art
Hitherto, there is widely used a magneto-optical recording medium such as a magneto-optical disk in which both light and magnetism are used to record information.
Recently, as a higher density recording is required for the magneto-optical recording medium, there are made various proposals for this requirement.
For example, Japanese Patent Application Laid Open Gazette Hei. 9-198731 (reference 1) discloses that there is provided a backing layer made of a soft magnetic material so that a fine CAR (Carrier Noise Ratio) can be obtained even if a short mark is reproduced.
Japanese Patent Application Laid Open Gazette Hei. 11-353725 (reference 2) discloses a layer structure of a magneto-optical recording medium capable of recording with a small external magnetic field.
Japanese Patent Application Laid Open Gazette Hei. 3-105741 (reference 3) discloses that a soft magnetic layer is formed on a substrate.
Japanese Patent Application Laid Open Gazette Hei. 7-320333 (reference 4) also discloses that a magnetic layer is provided (paragraph number 0162, and FIG. 107).
Recently, in order to meet a requirement of a higher density recording, there is proposed a recording system in which a magnetic field and a light are applied from a side of a protective film layer that is thinner as compared with a substrate, instead of the conventional system in which a recording is performed from a side of the substrate.
In case of the recording from the side of the protective film layer, it is possible to increase a numerical aperture of a condenser lens and thereby forming the corresponding small light spot.
In this case, it is merely possible to apply only a relatively weak magnetic field from a recording head so as to have an effect on only a very narrow area, and thus there is actively made a study of a magnetic recording medium having a layer structure capable of obtaining a fine CAR under such a condition.
Here, what records information onto a magneto-optical recording medium is a recording head, and thus when the layer structure of the magneto-optical recording medium is examined, it is also necessary to examine a structure of the recording head.
In an examination of the above-mentioned Japanese Patent references 1 to 4 from this viewpoint, any of the references 1, 2 and 4 relates to a recording from a side of a substrate, and does not consider a recording wherein a magnetic field and a light are applied from a side of a protective film layer.
The reference 3 discloses a recording from a side of a protective film layer as well as a recording from the side of the substrate, and further discloses that a magnetic layer is provided on a magneto-optical recording medium, but fails to recite an association with the structure of the recording head.
In view of the foregoing, it is an object of the present invention to provide a magneto-optical recording medium wherein a magnetic field and a light are applied for recording, the magneto-optical recording medium having a structure for generating a fine level of magnetic field.
To achieve the above-mentioned object, the present invention provides a first magneto-optical recording medium including:
According to the above-mentioned magneto-optical recording medium, the ratio (Bs2×t2/Bs1×t1) is not less than 0.2. And thus, even if a relatively week magnetic field is applied from the recording head, it is possible to apply a sufficiently strong magnetic field to the recording layer, so that a structure suitable for a high density recording can be provided.
When the second soft magnetic layer of the recording head is divided into a plurality of layers, there is adopted a value where the second soft magnetic layer is formed with a single layer on an equivalent basis. For example, when the second soft magnetic layer of the recording head is divided into two layers, where the respective thickness of the two layers is t11 and t12, and the respective saturation magnetic flux density is Bs11 and Bs12, the above-mentioned product Bs1×t1 is expressed by Bs11×t11+Bs12×t12, that is, Bs1×t1=Bs11×t11+Bs12×t12.
To achieve the above-mentioned object, the present invention provides a second magneto-optical recording medium including:
In the second magneto-optical recording medium, the first soft magnetic layer is formed with a metallic foil. And thus it is possible to thickly form the thickness to of the first soft magnetic layer. Accordingly, it is possible to enhance a value of the product (Bs2×t2) of the thickness t2 of the first soft magnetic layer and the saturation magnetic flux density Bs2. And thus, even if a relatively week magnetic field is applied from the recording head, it is possible to apply a sufficiently strong magnetic field for the reproduction recording layer, so that a structure suitable for a high density recording can be provided.
In the first magneto-optical recording medium according to the present invention as mentioned above, it is preferable that the first soft magnetic layer is formed with a metallic foil.
In a case where the first soft magnetic layer is formed with a metallic foil in the first magneto-optical recording medium according to the present invention as mentioned above, and in the second magneto-optical recording medium according to the present invention as mentioned above, it is acceptable that the metallic foil constituting the first soft magnetic layer is put on the substrate. Alternatively, it is acceptable that the metallic foil constituting the first soft magnetic layer is formed in a united body with the substrate.
In any of the first magneto-optical recording medium and the second magneto-optical recording medium according to the present invention as mentioned above, it is preferable that the substrate has a preventing structure for preventing the cured resin layer from going out from the first soft magnetic layer when the cured resin layer is in a non-cured state.
In any of the first magneto-optical recording medium and the second magneto-optical recording medium according to the present invention as mentioned above, it is acceptable that the first soft magnetic layer includes a FeNi magnetic material. Alternatively it is acceptable that the first soft magnetic layer includes a CoZrNb magnetic material.
In the first magneto-optical recording medium according to the present invention as mentioned above, it is acceptable that the first soft magnetic layer is coated on the substrate.
Hereinafter, there will be described a magneto-optical recording medium according to embodiments of the present invention.
In a magneto-optical recording medium 10 shown in
To record information on the magneto-optical recording medium 10, there is disposed a recording head 20 at the side of the protective film layer 15. The recording head 20 includes a soft magnetic layer 21 having a layer thickness t1, a magnetic field generating coil 22, and a condensing lens 23. Lights 31 generated from a light source (not illustrated) are condensed through the condensing lens 23 on the recording reproduction layer 14. And when the magnetic field generating coil 22 is actuated to generate a magnetic field, the magnetic field has an effect on the recording reproduction layer 14 so that information is recorded on the protective film layer 15.
The magneto-optical recording medium is manufactured via a soft magnetic layer forming step (A), a 2P-substrate fabrication step (B), an exfoliation step (C), a film producing step (D), and a protective film forming step (E). Hereinafter, there will be explained the above-mentioned respective steps.
In the soft magnetic layer forming step (A), an epoxy resin adhesive is applied to the substrate 11, and then a metallic foil 52 is disposed on the substrate 11 to adhere to the substrate 11 by pressurization (A-1). Thus, there is formed on the substrate 11 the soft magnetic layer 12 consisting of the metallic foil 52.
Next, in the 2P-substrate fabrication step (B), an ultraviolet cured resin 53 is applied to the soft magnetic layer 12 consisting of the metallic foil formed on the substrate 11, and a quartz glass stamper 61 having recess and convexity corresponding to the pre-groove pattern is superposed to develop and extend the ultraviolet cured resin 53 by pressurization or a spin scheme (B-1). After completion of the development and extension, an ultraviolet-light irradiation device 62 is used to irradiate an ultraviolet ray from a side of the quartz glass stamper 61. Thus, there is formed the cured resin layer 13 in which the ultraviolet cured resin 53 is cured (B-2).
In the exfoliation step (C), the quartz glass stamper 61 is separated from the cured resin layer 13 after the ultraviolet cure (C-1), so that the cured resin layer 13, which is in a state that the pre-groove is formed, appears on the surface (C-2).
Next, in the film producing step (D), one in which the soft magnetic layer 12 is formed on the substrate 11 and then the cured resin layer 13 is formed on the soft magnetic layer 12, is mounted on a spattering device (not illustrated), as in the step (C-2), so that a recording reproduction layer 14 is formed by a spattering. According to the present embodiment, the recording reproduction layer 14 includes a compound layer of a radiation layer (AlCr), a dielectric layer (SiN), a recording layer (TFC), a reproduction layer (GFC), and a dielectric layer (SiN), which are laminated in the named order from the cured resin layer 13 side, and the spattering device produces those layers in the named order.
In the protective film forming step (E), an ultraviolet cured resin film 55 is formed on the recording reproduction layer 14 produced by the spattering device in accordance with a spin coat scheme (E-1), and the ultraviolet cured resin film 55 is irradiated with ultraviolet ray by the ultraviolet-light irradiation device 62, so that the ultraviolet cured resin film is cured to form the protective film layer 15. According to the present embodiment, the thickness of the protective film layer 15 is 15 μm. This is sufficiently thin as compared with the substrate 11, and the recording head 20 (cf.
A horizontal axis of
Generally, it is required for recording information onto a magneto-optical recording medium to generate 300 Oe of the magnetic field. From
Incidentally, it is noted that the thickness t2 of the soft magnetic layer of the magneto-optical recording medium on the point associated with 21.4% in the graph of
In
In order to perform a recording, there is used a recording head having a soft magnetic layer involved in the conditions described in conjunction with
In the soft magnetic layer forming step (A) of the manufacturing method shown in
Here, a substrate 11 is preserved in a plating bath consisting of for example FeNi to form a soft magnetic film consisting of FeNi on the substrate 11. It is acceptable that the substrate 11 is preserved in a plating bath consisting of CoZrNb instead of FeNi to form a soft magnetic film consisting of CoZrNb on the substrate 11.
After the formation of the soft magnetic layer on the substrate 11 according to the plating step (F), a magneto-optical recording medium is manufactured via the steps (B) to (E) shown in
In the plating step (F), there is formed a soft magnetic layer made of FeNi magnetic material having magnetic characteristic Bs2=1.4T, thickness t2=2 μm. Thereafter, as other steps the steps (B) to (E) of
Here, a metallic foil 52 is put on an inside wall of a resin-molding mold 63A and a resin mold 63B is urged to the resin-molding mold 63A, and a resin (here, a polycarbonate resin) is ejected from a resin ejection section 632 into the resin-molding mold 63A to produce a molding product in which the metallic foil 52 and the resin 51 are united with one another.
Here, the resin-molding mold 63A is provided with a circular recess 631 into which the ejected resin flows. And the metallic foil 52 is surrounded by a circular convex portion of the recess 631. An area 511 of the center of the resin 51 is removed to form an aperture.
The molding product includes a substrate 11 made of polycarbonate resin, and a soft magnetic layer 12 made of metallic foil on the substrate 11. On the center of the product is formed a hole 112. On the periphery of the substrate 11 and the periphery of the hole 112 of the center, there are formed circular convex portions 111 with which the soft magnetic layer 12 is surrounded.
After the molding step (G) shown in
While
In the molding step (G) shown in
Incidentally, the manufacturing method of the soft magnetic layer is not restricted to the above-mentioned manufacturing method, and it is acceptable that a metallic foil is joined on, for example, an aluminum substrate by a hot rolling processing.
As mentioned above, according to the present invention, it is possible to record minute marks according to a reduction of intensity of the magnetic field generated by a recording head.
While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by those embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-264284 | Sep 2002 | JP | national |
This application claims the benefit under 35 U.S.C. Section 119, of Japanese Application No. 2002-264284, filed Sep. 10, 2002, which is hereby incorporated by reference in its entirety into this application. This application also claims the benefit under 35 U.S.C. Section 120 of U.S. patent application Ser. No. 10/648,248, entitled MAGNETO-OPTICAL RECORDING MEDIUM, filed Aug. 27, 2003, which is hereby incorporated by reference in its entirety into this application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10648248 | Aug 2003 | US |
| Child | 11339619 | Jan 2006 | US |
