JP2536202B2 - Method for manufacturing magneto-optical recording medium - Google Patents

Description

The present invention relates to a method for manufacturing an overwritable magneto-optical recording medium using a magnetic multilayer film and an initial auxiliary magnetic field.

[Prior Art] In recent years, attention has been paid to a magneto-optical recording method that enables overwriting of information by using an initial auxiliary magnetic field and a magnetic multilayer film. This system uses (a) a multi-layered magneto-optical recording medium having a first layer having perpendicular anisotropy as a recording / reproducing layer and a second layer having perpendicular anisotropy as a recording auxiliary layer as (a) a recording medium. (B) moving the recording medium, (c) applying only an initial auxiliary magnetic field so that only the magnetization of the recording auxiliary layer is aligned upward or downward before recording, (d) ) Irradiating the recording medium with a laser beam, (e) modulating the intensity of the laser beam in a pulse shape according to binary information to be recorded, (f) the recording medium portion irradiated with the laser beam (G) forming one of a bit having upward magnetization and a bit having downward magnetization when the intensity of the pulse-modulated laser beam is at a high level. In this case, the other bit is formed when the intensity of the laser beam is at a low level, and the overwritable recording method is disclosed (for example, see Japanese Patent Laid-Open No. 62-175948).

[Problems to be Solved by the Invention] Among overwritable magnetic multilayer films, a medium called paratype (P type) needs to transfer magnetization information of a recording layer to a recording auxiliary layer. M-
The H loop must be a loop having only one step of the reversal magnetic field as shown in FIG. 2 at the temperature at the time of low level laser irradiation. However, if the bonding force between the two layers is too weak, a two-stage loop as shown in FIG. 3 is formed, and overwrite cannot be performed.

Among overwritable magnetic multilayer films, a medium called anti-para type (A type) is MH.
The loop must have a three-stage reversal magnetic field as shown in FIG. 4 at the temperature at the time of low-level laser irradiation. However, if the bonding force between the two layers is too weak, a two-stage loop as shown in FIG. 5 is created, and overwrite cannot be performed.

The present invention has been made to solve the above-mentioned conventional problems, and provides a method for manufacturing an overwritable magneto-optical recording medium in which the coupling force between magnetic multilayer films is strengthened to an appropriate value. With the goal.

[Means for Solving the Problems] The present invention comprises forming a spacer layer on a substrate, forming a magnetic multilayer film on the spacer layer, and then forming a protective layer on the magnetic multilayer film. In the method of manufacturing an overwritable magneto-optical recording medium, after forming a spacer layer, reverse sputtering is performed, and then a magnetic multilayer film is formed, which is a method of manufacturing a magneto-optical recording medium.

[Operation] The para-type magneto-optical recording medium having the magnetic multilayer film forms a two-stage loop as shown in FIG. 3 because the coupling force between the recording / reproducing layer and the recording auxiliary layer is too weak. .
Therefore, if reverse sputtering is performed on the spacer layer formed on the substrate before forming the first magnetic layer, the bonding force between the above two layers is strengthened, and the one-step structure as shown in FIG. An overwritable magnetic multilayer film having an MH loop having a reversal magnetic field can be obtained.

The anti-para type magneto-optical recording medium having the magnetic multilayer film has a two-stage loop as shown in FIG. 5 because the coupling force between the recording / reproducing layer and the recording auxiliary layer is too weak. . Therefore, if the spacer layer formed on the substrate is reverse-sputtered before forming the first magnetic layer, the above-mentioned coupling force between the two layers is strengthened, and as shown in FIG.
An overwritable magnetic multilayer film having an MH loop having a stepwise reversal magnetic field is obtained.

[Examples] FIG. 1 is a partial cross-sectional view of a magneto-optical recording multilayer film medium manufactured by the method of the present invention. The medium composition is substrate 1 / spacer layer 2 / first magnetic layer 3 / second magnetic layer 4 / third magnetic layer.
5 / Protective layer 6. Here, as the substrate 1, a substrate made of polycarbonate resin, epoxy resin, or glass is used. The substrate may or may not have a groove. Alternatively, a groove may be formed on the glass with an ultraviolet curable resin or the like. As the spacer layer 2 and the protective layer 6, silicon nitride, silicon oxide, tantalum oxide, aluminum nitride, aluminum oxide, or the like can be used. The first magnetic layer 3, the second magnetic layer 4, and the third magnetic layer 5 are amorphous alloy thin films made of a combination of rare earth and transition metal. In this case, as the rare earth, for example, single or plural elements from Tb, Gd, Dy, Nd, Ho and the like are used, and as the transition metal, single or plural elements from Fe, Co, Ni and the like are used. Also a small amount
It is also possible to add Ti, Mo, etc.

Example 1 In the case of a medium (paratype) formed in the order of polycarbonate substrate / silicon nitride sputter / reverse sputter / TbFe alloy sputter / NdFeCo alloy sputter / TbFeCo alloy sputter / silicon nitride sputter First, as a comparative example, polycarbonate (with a groove) Substrate / silicon nitride (800Å) / TbFe alloy (1000Å) / N
A medium having a film structure of dFeCo alloy (60 Å) / TbFeCo alloy (1000 Å) / silicon nitride (800 Å) was prepared without reverse sputtering the silicon nitride of the spacer layer. All depositions are RF
By continuous sputtering of a magnetron sputtering device. TbFe
Table 1 shows the characteristics of the single layers of NdFeCo layer, NdFeCo layer and TbFeCo layer at 25 ° C.

The Kerr loop of this medium is 2 ° as shown in FIG. 3 at a medium temperature of 100 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. TbFe alloy layer and Tb
This is because the magnetic coupling force between the FeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon nitride film formed on the polycarbonate substrate before sputtering the TbFe layer. The reverse sputtering conditions are a power of 200 W and a time of 20 minutes. Of the 830 Å silicon nitride film formed on the polycarbonate substrate by reverse sputtering, 30 Å silicon nitride was scattered by sputtering.

The Kerr loop of this medium became a loop having a one-step reversal magnetic field at 100 ° C. as shown in FIG. This is because the magnetic coupling force between the TbFe alloy layer and the TbFeCo alloy layer was strengthened by the reverse sputtering of the silicon nitride layer (spacer layer). As a result, when the low-level laser was irradiated, the magnetization information of the TbFeCo layer (recording auxiliary layer) was transferred to the TbFe layer (recording layer), and overwriting became possible.

Example 2 Polycarbonate Substrate / Silicon Nitride Sputtering / Inverse Sputtering / TbFeCo Alloy Sputtering / NdFeCo Alloy Sputtering / TbFe Alloy Sputtering / Silicon Nitride Sputtering in order of medium (paratype) First, as a comparative example, polycarbonate (with groove) Substrate / Silicon nitride (800Å) / TbFeCo alloy (600Å) /
NdFeCo alloy (60Å) / TbFe alloy (1200Å) / silicon nitride (8
A medium having a film structure of 00Å) was prepared without performing reverse sputtering of the silicon nitride of the spacer layer. All film formation is by continuous sputtering of RF magnetron sputtering equipment. TbFe layer, N
Table 2 shows the characteristics of the single dFeCo layer and TbFeCo layer at 25 ° C.

The Kerr loop of this medium is 2 ° as shown in FIG. 3 at a medium temperature of 100 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. TbFe alloy layer and Tb
This is because the magnetic coupling force between the FeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon nitride film formed on the polycarbonate substrate before sputtering the TbFeCo layer. The reverse sputtering conditions are a power of 200 W and a time of 20 minutes. Of the 830 Å silicon nitride film formed on the polycarbonate substrate by reverse sputtering, 30 Å silicon nitride was scattered by sputtering.

The Kerr loop of this medium became a loop having a one-step reversal magnetic field at 100 ° C. as shown in FIG. This is because the magnetic coupling force between the TbFe alloy layer and the TbFeCo alloy layer was strengthened by the reverse sputtering of the silicon nitride layer (spacer layer). As a result, when the low-level laser was irradiated, the magnetization information of the TbFeCo layer (recording auxiliary layer) was transferred to the TbFe layer (recording layer), and overwriting became possible.

Example 3 Polycarbonate substrate / silicon nitride sputter / reverse sputter / GdTbFeCo alloy sputter / NdFeCo alloy sputter / TbFeCo
In the case of a medium (paratype) formed in the order of alloy sputter / silicon nitride sputter First, as a comparative example, a polycarbonate (with a groove) substrate / silicon nitride (800Å) / GdTbFeCo alloy (500
A medium having a film structure of Å) / NdFeCo alloy (100 Å) / TbFeCo alloy (1000 Å) / silicon nitride (800 Å) was prepared without reverse sputtering the silicon nitride of the spacer layer. All film formation is by continuous sputtering of RF magnetron sputtering equipment. Table 3 shows the characteristics of the single layers of TbFeCo layer, NdFeCo layer and GdTbFeCo layer at 25 ° C.

The Kerr loop of this medium is 2 ° as shown in FIG. 3 at a medium temperature of 130 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. TbFeCo alloy layer and
This is because the magnetic coupling force between the GdTbFeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon nitride film formed on the polycarbonate substrate before sputtering the GdTbFeCo layer. The reverse sputtering conditions are a power of 100 W and a time of 40 minutes. Of the 830 Å silicon nitride film formed on the polycarbonate substrate by reverse sputtering, 30 Å silicon nitride was scattered by sputtering.

The Kerr loop of this medium became a loop having a one-step reversal magnetic field at 130 ° C. as shown in FIG. This is because the magnetic coupling force between the TbFeCo alloy layer and the GdTbFeCo alloy layer was strengthened by the reverse sputtering of the silicon nitride layer (spacer layer). As a result, when irradiated with a low level laser, Gd
The magnetization information of the TbFeCo layer (recording auxiliary layer) is now transferred to the TbFeCo layer (recording layer), enabling overwriting.

Example 4 Epoxy substrate / silicon nitride sputter / reverse sputter / GdDyF
In the case of a medium (paratype) deposited in the order of eCo alloy sputter / GdNdFeCo alloy sputter / DyFeCo alloy sputter / silicon nitride sputter First, as a comparative example, epoxy resin (with a groove) substrate / silicon nitride (800Å) / GdDyFeCo alloy (430Å) ) /
A medium having a film structure of GdNdFeCo alloy (80Å) / DyFeCo alloy (800Å) / silicon nitride (800Å) was prepared without performing reverse sputtering of the silicon nitride of the spacer layer. All depositions are RF
By continuous sputtering of a magnetron sputtering device. GdDy
25 ℃ in single layer of FeCo layer, GdNdFeCo layer and DyFeCo layer
Table 4 shows the various characteristics.

The Kerr loop of this medium is 2 ° as shown in FIG. 3 at a medium temperature of 150 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. DyFeCo alloy layer and
This is because the magnetic coupling force between the GdDyFeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon nitride film formed on the epoxy substrate before sputtering the GdDyFeCo layer. The reverse sputtering conditions are a power of 100 W and a time of 20 minutes. By reverse sputtering,
Of the 815Å silicon nitride film formed on the epoxy resin substrate, 15Å silicon nitride was scattered by sputtering.

The Kerr loop of this medium became a loop having a one-step reversal magnetic field at 130 ° C. as shown in FIG. This is because the magnetic coupling force between the DyFeCo alloy layer and the GdDyFeCo alloy layer was strengthened by the reverse sputtering of the silicon nitride layer (spacer layer). As a result, when irradiated with a low level laser, Gd
The magnetization information of the DyFeCo layer (recording auxiliary layer) is now transferred to the DyFeCo layer (recording layer), enabling overwriting.

Example 5 Polycarbonate substrate / silicon oxide sputter / reverse sputter / GdTbFeCo alloy sputter / NdFeCo alloy sputter / TbFeCo
In the case of a medium (paratype) formed in the order of alloy sputter / silicon oxide sputter First, as a comparative example, a polycarbonate (with a groove) substrate / silicon oxide (800Å) / GdTbFeCo alloy (300
A medium having a film structure of Å) / NdFeCo alloy (100 Å) / TbFeCo alloy (700 Å) / silicon oxide (800 Å) was prepared without reverse sputtering of the silicon oxide of the spacer layer. All film formation is by continuous sputtering of RF magnetron sputtering equipment.
25 in single layer of TbFeCo layer, NdFeCo layer and GdTbFeCo layer
Table 5 shows the characteristics at ° C.

The Kerr loop of this medium is 2 ° as shown in FIG. 3 at a medium temperature of 130 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. TbFeCo alloy layer and
This is because the magnetic coupling force between the GdTbFeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon oxide film formed on the polycarbonate substrate before sputtering the GdTbFeCo layer. The reverse sputtering conditions are a power of 100 W and a time of 60 minutes. Of the 830 Å silicon oxide film formed on the polycarbonate substrate by reverse sputtering, 30 Å silicon oxide was scattered by sputtering.

The Kerr loop of this medium became a loop having a one-step reversal magnetic field at 130 ° C. as shown in FIG. This is because the magnetic coupling force between the TbFeCo alloy layer and the GdTbFeCo alloy layer was strengthened by the reverse sputtering of the silicon oxide layer (spacer layer). As a result, when irradiated with a low level laser, Gd
The magnetization information of the TbFeCo layer (recording auxiliary layer) is now transferred to the TbFeCo layer (recording layer), enabling overwriting.

Example 6 Polycarbonate substrate / tantalum oxide sputter / reverse sputter / GdTbFeCo alloy sputter / NdFeCo alloy sputter / TbF
In the case of a medium (paratype) deposited in the order of eCo alloy sputter / tantalum oxide sputter First, as a comparative example, a polycarbonate (with a groove) substrate / tantalum oxide (800Å) / GdTbFeCo alloy (30
A medium having a film structure of 0Å) / NdFeCo alloy (100Å) / TbFeCo alloy (700Å) / tantalum oxide (800Å) was prepared without reverse sputtering of tantalum oxide in the spacer layer.
All film formation is by continuous sputtering of RF magnetron sputtering equipment. Table 6 shows the characteristics of the single layers of the TbFeCo layer, the NdFeCo layer and the GdTbFeCo layer at 25 ° C.

The Kerr loop of this medium is 2 ° as shown in FIG. 3 at a medium temperature of 130 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. TbFeCo alloy layer and
This is because the magnetic coupling force between the GdTbFeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the tantalum oxide film formed on the polycarbonate substrate before sputtering the GdTbFeCo layer. The reverse sputtering conditions are a power of 100 W and a time of 60 minutes. 830Å deposited on a polycarbonate substrate by reverse sputtering
Of the tantalum oxide of, 30 Å of tantalum oxide was scattered by sputtering.

The Kerr loop of this medium became a loop having a one-step reversal magnetic field at 130 ° C. as shown in FIG. This is because the magnetic coupling force between the TbFeCo alloy layer and the GdTbFeCo alloy layer was strengthened by the reverse sputtering of the tantalum oxide layer (spacer layer). As a result, when irradiated with a low level laser,
The magnetization information of the GdTbFeCo layer (recording auxiliary layer) is now transferred to the TbFeCo layer (recording layer), enabling overwriting.

Example 7 Polycarbonate substrate / silicon nitride sputter / reverse sputter / GdTbFeCo alloy sputter / NdFeCo alloy sputter / TbFeCo
In the case of a medium (anti-para type) formed in the order of alloy sputter / silicon nitride sputter First, as a comparative example, a polycarbonate (with a groove) substrate / silicon nitride (800Å) / GdTbFeCo alloy (400
A medium having a film structure of Å) / NdFeCo alloy (100 Å) / TbFeCo alloy (800 Å) / silicon nitride (800 Å) was prepared without reverse sputtering the silicon nitride of the spacer layer. All film formation is by continuous sputtering of RF magnetron sputtering equipment.
25 in single layer of TbFeCo layer, NdFeCo layer and GdTbFeCo layer
Table 7 shows the properties at ° C.

The Kerr loop of this medium is 2 ° C as shown in FIG. 5 at a medium temperature of 130 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. TbFeCo alloy layer and
This is because the magnetic coupling force between the GdTbFeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon nitride film formed on the polycarbonate substrate before sputtering the GdTbFeCo layer. The reverse sputtering conditions are a power of 100 W and a time of 40 minutes. Of the 830 Å silicon nitride film formed on the polycarbonate substrate by reverse sputtering, 30 Å silicon nitride was scattered by sputtering.

The Kerr loop of this medium became a loop having a three-stage reversal magnetic field at 130 ° C. as shown in FIG. This is because the magnetic coupling force between the TbFeCo alloy layer and the GdTbFeCo alloy layer was strengthened by the reverse sputtering of the silicon nitride layer (spacer layer). As a result, when irradiated with a low level laser, Gd
The magnetization information of the TbFeCo layer (recording auxiliary layer) is now transferred to the TbFeCo layer (recording layer), enabling overwriting.

Example 8 Polycarbonate substrate / silicon nitride sputter / reverse sputter / GdDyFeCo alloy sputter / GdNdFeCo alloy sputter / DyFeC
o Medium sputtered with alloy sputter / silicon nitride sputter (anti-para type) First, as a comparative example, polycarbonate (with groove) substrate / silicon nitride (800Å) / GdDyFeCo alloy (430
A medium having a film structure of Å) / GdNdFeCo alloy (80 Å) / DyFeCo alloy (800 Å) / silicon nitride (800 Å) was prepared without reverse sputtering the silicon nitride of the spacer layer. All film formation is by continuous sputtering of RF magnetron sputtering equipment. Table 8 shows the characteristics of the single layers of the GdDyFeCo layer, the GdNdFeCo layer and the DyFeCo layer at 25 ° C.

The Kerr loop of this medium is 2 ° as shown in FIG. 5 at a medium temperature of 150 ° C. when irradiated with a low level laser.
It became a loop with a reversal magnetic field in stages. DyFeCo alloy layer and
This is because the magnetic coupling force between the GdDyFeCo alloy layers is too weak.

Next, a medium having the same film structure was formed by including a step of reverse-sputtering the silicon nitride film formed on the polycarbonate substrate before sputtering the GdDyFeCo layer. The reverse sputtering conditions are a power of 100 W and a time of 30 minutes. Of the 825Å silicon nitride film formed on the polycarbonate substrate by the reverse sputtering, 25Å silicon nitride was scattered by the sputtering.

The Kerr loop of this medium became a loop having a three-stage reversal magnetic field at 130 ° C. as shown in FIG. This is because the magnetic coupling force between the DyFeCo alloy layer and the GdDyFeCo alloy layer was strengthened by the reverse sputtering of the silicon nitride layer (spacer layer). As a result, when irradiated with a low level laser, Gd
The magnetization information of the DyFeCo layer (recording auxiliary layer) is now transferred to the DyFeCo layer (recording layer), enabling overwriting.

[Effects of the Invention] As described above, according to the method of the present invention, the magnetic coupling force between the recording layer and the recording auxiliary layer of the magneto-optical recording medium is strengthened to an appropriate value for overwriting. Will be possible.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an example of a magneto-optical recording medium manufactured by the method of the present invention, and FIG. 2 is M of a para-type overwrite magneto-optical recording medium obtained by the method of the present invention.
FIG. 3 is a characteristic diagram showing a −H loop, FIG. 3 is a characteristic diagram showing a MH loop of a para-type overwrite magneto-optical recording medium according to the prior art, and FIG. 4 is an anti-para type over-pass obtained by the method of the present invention. M- of magneto-optical recording medium for writing
FIG. 5 is a characteristic diagram showing the H loop, and FIG. 5 is a characteristic diagram showing the MH loop of the conventional anti-para-type magnetic recording medium for overwrite. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Spacer layer 3 ... 1st magnetic layer, 4 ... 2nd magnetic layer 5 ... 3rd magnetic layer, 6 ... Protective layer

Claims (1)

(57) [Claims] 1. An overwritable magneto-optical recording medium comprising forming a spacer layer on a substrate, forming a magnetic multilayer film on the spacer layer, and then forming a protective layer on the magnetic multilayer film. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein after forming the spacer layer, reverse sputtering is performed, and then a magnetic multilayer film is formed.