JPH05325278A - Manufacture of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To enhance durability of the magneto-optical recording medium. CONSTITUTION:The magneto-optical recording medium is formed by successively laminating on a substrate at least a dielectric layer, a magnetic layer, and a reflective layer. It is manufactured by highly evacuating a chamber to <=5X10<-5>Pa, introducing an inert gas into the chamber, applying a prescribed power to a target, and forming the reflective layer by a sputtering process while maintaining the ratio of a film-forming speed (Dr)(Angstrom /min) to gas pressure p (Pa), Dr/p to >=6X10<-2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magneto-optical recording medium.

[0002]

2. Description of the Related Art Conventionally, a magneto-optical recording medium has a relatively simple structure in which a dielectric layer is formed as an enhance layer on a substrate, a magnetic layer is formed, and then a dielectric layer is formed again. Has been adopted. However, the magneto-optical recording medium having such a structure has a problem that the CN characteristic is generally poor. Therefore, in order to obtain a magneto-optical recording medium having better CN characteristics, a magneto-optical recording medium having a structure in which a reflective layer mainly containing Al, Ni or the like is further formed is considered.

On the other hand, in the magnetic layer of the magneto-optical recording medium,
It is difficult to find a single magnetic material with good reading characteristics because of low Curie temperature, easy recording, high coercive force, high storage stability, and large magneto-optical Kerr rotation angle. Therefore, a function-separated exchange-coupling multilayer film in which two different magnetic materials are laminated by separating the necessary functions and used as a recording layer and a reproducing layer, respectively, has been proposed as a magneto-optical recording medium (Japanese Patent Laid-Open No. 57-57). -78652).

In order to realize high-density and high-sensitivity recording in the exchange-coupling multilayer film, a magnetic film having an appropriate Curie temperature and a high coercive force is used as a recording layer, and a magneto-optical Kerr rotation is used as a reproducing layer. A magnetic film having a large angle and a relatively high Curie temperature is desirable. In particular, Gd as a rare earth metal
Since the magnetic film using Fe and Co as the transition metals has a large magneto-optical Kerr rotation angle and good reading characteristics, it is used as a reproducing layer.

The ratio C / N between the reproduced signal and the noise of the magneto-optical recording medium is proportional to the magnitude of the bias magnetic field applied at the time of erasing and writing information, but the saturation bias magnetic field at which the change of C / N is saturated. Hb exists as a characteristic peculiar to the medium. That is, reducing the saturation bias magnetic field Hb can reduce the bias magnetic field required for erasing and writing information, which leads to downsizing of the device and shortening of access time.

Although the magnetic field sensitivity changes due to various factors, it is particularly sensitive to changes in the saturation magnetization magnitude Ms of the magnetic layer. Therefore, in order to reproduce the magneto-optical recording medium having a constant magnetic field sensitivity with good reproducibility, it is necessary to improve the reproducibility of the saturation magnetization magnitude Ms.

[0007]

However, in a magneto-optical recording medium having a reflective layer, its optical characteristics sometimes deteriorate, and the read loss rate becomes large, for example.
Alternatively, the writing and calling characteristics may be significantly deteriorated. This is based on the fact that the reflective layer is corroded to reduce the reflectance, or hillocks are generated by crystallization to deteriorate the flatness.

Further, when the reflective layer is formed, it is easily affected by an inert gas such as Ar or oxygen, and as a result, durability may be deteriorated.

Therefore, the present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a magneto-optical recording medium having particularly excellent durability.

On the other hand, when a magnetic thin film using Gd as a rare earth metal is formed by the sputtering method, it is easily affected by oxidation and unstable plasma generated in the initial stage of sputtering, resulting in deterioration of magnetic field sensitivity. Sometimes.

Therefore, another object of the present invention is to provide a magneto-optical recording medium excellent in magnetic field sensitivity in view of the problems of the above-mentioned prior art.

[0012]

According to the present invention for achieving the above object, in a method of manufacturing a magneto-optical recording medium in which at least a dielectric layer, a recording layer and a reflective layer are sequentially laminated on a substrate, the inside of the chamber is set to 5 After a high vacuum of × 10 ^-5 Pa or less, an inert gas was introduced into the chamber, a predetermined electric power was applied to the target, and the reflective layer was formed by a sputtering method at a deposition rate Dr (Å / min). And a gas pressure p (Pa) ratio Dr / p is maintained at a value of 6 × 10 ² or more to form a film.

Further, according to the present invention, at least a dielectric layer on a substrate, a reproducing layer made of a magnetic thin film having a high Curie temperature, a small coercive force and an easy axis of magnetization perpendicular to the film surface, and adjacent to the reproducing layer. A chamber in a method of manufacturing a magneto-optical recording medium in which a recording layer formed of a magnetic thin film having a low Curie temperature or magnetic compensation temperature, a large coercive force, and an easy axis of magnetization perpendicular to the film surface, and a reflective layer are sequentially stacked. After the inside is evacuated to a high vacuum of 5 × 10 ⁻⁵ Pa or less, an inert gas is introduced into the chamber, a predetermined electric power is applied to the target, and the reflection layer is formed by a sputtering method at a deposition rate Dr.
A method of manufacturing a magneto-optical recording medium, characterized in that a film is formed while maintaining a ratio Dr / p of (Å / min) to a gas pressure p (Pa) at 6 × 10 ² or more.

Further, according to the present invention, at least a dielectric layer on a substrate, a reproducing layer made of a magnetic thin film having a high Curie temperature, a small coercive force and an easy axis of magnetization perpendicular to the film surface, and adjacent to the reproducing layer. In a method of manufacturing a magneto-optical recording medium in which a recording layer made of a magnetic thin film having a low Curie temperature or magnetic compensation temperature, a large coercive force, and an easy axis of magnetization perpendicular to the film surface, and a metal reflective layer are sequentially laminated, After the chamber is evacuated to a high vacuum of 5 × 10 ⁻⁵ Pa or less, an inert gas is introduced into the chamber, a predetermined electric power is applied to the target, and the reproduction layer is formed at a film forming speed Dr by a sputtering method.
A method of manufacturing a magneto-optical recording medium, characterized in that a film is formed while maintaining a value of a ratio Dr / p between (Å / min) and a gas pressure p (Pa) at 7 × 10 ² or more.

Further, according to the present invention, the value of Dr / p is set to 7 × 10 ^2.
While maintaining the above, the reproducing layer is used, and the value of Dr / p is 6 × 1.
The method for producing a magneto-optical recording medium is characterized in that the reflective layer is formed by a sputtering method while maintaining the value at 0 ² or more.

Further, in the present invention, the substrate is a transparent substrate,
In the method of manufacturing the magneto-optical recording medium, the reflective layer is a metal reflective layer.

[0017]

According to the manufacturing method of the present invention, by changing the film forming rate according to the gas pressure, a relatively high film forming rate can be achieved especially in a region where the gas pressure is relatively lower than that of the conventional sputtering method. By doing so, a magneto-optical recording medium having excellent durability and magnetic field sensitivity can be obtained.

The mechanism by which the above effects are obtained is not clear yet, but by lowering the gas pressure, it is possible to prevent the inclusion of impurities such as oxygen, water, and inert gas molecules remaining in the chamber. It is presumed that the structure of the thin film that constitutes the reproducing layer becomes dense, so that the magnetic field sensitivity is improved, and that the structure of the thin film that constitutes the reflective layer becomes dense, so that the durability as a magneto-optical recording medium is improved. It Furthermore, since the energy of sputtered particles is increased by relatively increasing the film formation rate, the mixing of sputtered particles on the substrate progresses, promoting the densification and homogenization of the reproduction layer to be formed,
It is estimated that the magnetic characteristics are stabilized and the bias magnetic field acts effectively.

As a material for forming the substrate, a resin substrate such as polycarbonate, polymethylmethacrylate, or epoxy resin is preferable. Particularly, polycarbonate has advantages such as a low water absorption rate and a high glass transition point. preferable.

Further, in the present invention, a dielectric layer as an enhancement layer of the magnetic layer and a protective layer of the substrate is usually formed between the substrate and the magnetic layer. Also, on the recording layer,
A dielectric layer is deposited to protect the recording layer. Examples of the material of the dielectric layer include SiO _x , SiN _x , and Al.
Dielectric materials such as oxides and nitrides such as N _x and ZnS are used. Among them, Si nitride, Al nitride, or a mixture thereof is preferable from the viewpoint of optical characteristics and protective function.

In the present invention, the magnetic layer composed of the reproducing layer and the recording layer is an amorphous layer mainly containing a transition metal and a rare earth metal, and the form thereof may be a single layer or ,
Two or more layers in which a transition metal-based layer and a rare earth metal-based layer are alternately stacked may be used. Furthermore, in order to improve the corrosion resistance of such a magnetic layer,
It is preferable to contain Cr, Ta, Al, Pt, Ti, W and / or V and the like, and Cr is most effective.

In particular, the composition of the reproducing layer having a high Curie temperature and a small coercive force is Gd-Fe-Co-X (X is Cr, T).
at least one of a, Al, Pt, Ti, W and V
In the case of the element type), the film formation rate Dr (Å / mi)
By setting the ratio Dr / p of n) to the gas pressure p (Pa) to 7 × 10 ² or more, a magneto-optical recording medium having excellent magnetic field sensitivity can be provided. Further, as long as it is a magnetic material having a high Curie temperature and a low coercive force, a material other than the above GdFeCo system may be used.

For the reflective layer, a known metal material mainly containing Al, Ni or the like can be used.

In the method of the present invention, when forming the reflection layer or the reproduction layer, an inert gas such as Ar, Kr, or He is introduced into the chamber until a predetermined gas pressure p (Pa) is reached, and the reflection is performed. By adjusting the electric power applied to the target that is a constituent metal component of the layer or the reproduction layer, the film formation rate Dr (Å / min) is set according to the gas pressure, and
Is 6 × 10 ² or more or 7 × 10 ² or more, and a reflective layer or a reproducing layer is formed on the substrate mounted on the substrate holder.

The magnetron sputtering method is preferable as the sputtering method, and DC power or R is applied to the alloy target.
F power is applied to generate plasma to form a reflective layer or a reproducing layer. In particular, regarding the reproducing layer, DC power or RF power is applied to a transition metal target, a rare earth metal target or an alloy target of those metals to generate plasma of each metal, and the reproduction layer is formed by the binary simultaneous sputtering method. It is preferable to form a film.

In the optical recording medium of the present invention, each layer is sequentially formed on the substrate as described above, and the upper surface and the side surface thereof are covered with an organic resin protective layer such as an ultraviolet curable resin.
The storage stability can be further enhanced.

Further, two magneto-optical recording media can be made into a double-sided recording type magneto-optical recording medium by adhering the two supporting substrates to each other via an adhesive such as a hot melt adhesive.

[0028]

[Effects of the Invention] The film forming rate Dr (Å / min) when forming a reflective layer by the sputtering method is set so that Dr / p is 6 × 10 ² or more with respect to gas pressure p (Pa). By setting, a magneto-optical recording medium having excellent durability can be obtained. Similarly, when forming the reproducing layer, the Dr / p is set to 7 ×.
By setting it to be 10 ² or more, it is possible to obtain a magneto-optical recording medium having excellent magnetic field sensitivity.

[0029]

【Example】

Example 1 On a polycarbonate substrate with a φ130 mm pre-groove, Si was added to prevent oxidation and enhance interference effects.
N is 1020Å and TbFeCoCr is 20 as a magnetic layer.
0Å, and SiN to enhance the anti-oxidation and interference effect
Of 300 .ANG., And AlCr450 .ANG. As a reflection layer under the conditions as shown in Table 1 were successively formed in succession while the film forming chamber of the magnetron sputtering apparatus was kept in vacuum to produce a magneto-optical recording medium.

A target of Al ₉₉ Cr ₁ was used as the material of the reflective layer.

The obtained recording medium was put in an environment of high temperature and high humidity of 80 ° C. and 90% for 1000 hours, and the ratio of BER (bit error rate) to the initial value was obtained. The measurement results are as shown in Table 1.

Example 2 On a polycarbonate substrate with a φ 130 mm pre-groove, in order to obtain an oxidation prevention and interference prevention effect, S
iN is 940Å and GdFeCoCr is 10 as a magnetic layer.
0Å, TbFeCoCr is 200Å, and SiN is 300Å in order to enhance the oxidation prevention and interference effect, and AlCr is 450Å as the reflective layer under the conditions shown in Table 1, sequentially.
Magneto-optical recording media were continuously manufactured while the film forming chamber of the magnetron sputtering apparatus was kept in vacuum.

As the target for forming the reflective layer, the same target as in Example 1 was used.

The obtained recording medium was put in an environment of high temperature and high humidity of 80 ° C. and 90% for 1000 hours, and the ratio of the BER to the initial value was calculated. The measurement results are as shown in Table 1.

Example 3 A magneto-optical recording medium was prepared in the same manner as in Example 2 except that the film forming rate Dr and the gas pressure p of the reflective layer were changed as shown in Table 2.

The obtained recording medium was put in an environment of high temperature and high humidity of 80 ° C. and 90% for 1000 hours, and the ratio of BER to the initial value was obtained. The measurement results are as shown in Table 1.

Example 4 On a polycarbonate substrate having a φ 130 mm pre-groove, in order to obtain an oxidation prevention and interference prevention effect, S
iN is 650Å and GdFeCoCr is 10 as a magnetic layer.
0Å, 200Å TbFeCoCr, as a reflective layer
Under the conditions shown in, AlCr is 450 Å and SiN3
A magneto-optical recording medium was manufactured by sequentially applying 00Å while keeping the film forming chamber of the magnetron sputtering device in a vacuum.

As the target for forming the reflective layer, the same target as in Example 1 was used.

The obtained recording medium was put in an environment of high temperature and high humidity of 80 ° C. and 90% for 1000 hours, and the ratio of BER to the initial value was obtained. The measurement results are as shown in Table 1.

Comparative Example 1 A magneto-optical recording medium was produced in the same manner as in Example 1 except that the film forming rate Dr and the gas pressure p of the reflective layer were changed as shown in Table 1. The obtained magneto-optical recording medium was put in an environment of high temperature and high humidity of 80 ° C. and 90% for 1000 hours, and the ratio of the BER to the initial value was obtained. The measurement results are as shown in Table 1.

Comparative Example 2 A magneto-optical recording medium was prepared in the same manner as in Example 2 except that the film forming rate Dr of the reflective layer and the gas pressure p were changed as shown in Table 1. The obtained magneto-optical recording medium was put in an environment of high temperature and high humidity of 80 ° C. and 90% for 1000 hours, and the ratio of the BER to the initial value was obtained. The measurement results are as shown in Table 1.

[0042]

[Table 1] It can be seen from Table 1 that the magneto-optical recording medium according to the method of the present invention has a small ratio of BER to the initial value of 1.5 to 1.8 and is in a stable state which is almost the same as the initial state.

Example 5 On a polycarbonate substrate with a pre-groove of φ130 mm, in order to obtain an oxidation prevention and interference prevention effect, S
iN is 940Å and GdFeCoCr is 10 as a reproducing layer.
0 Å, TbFeCoCr is 200 Å as the recording layer, and SiN is 300 to increase the oxidation prevention and interference effect.
Å, Al was used as a reflective layer in succession without breaking the vacuum, and a magnetron sputtering device was continuously used to manufacture a magneto-optical recording medium.

When producing GdFeCoCr, Gd ₅₀
Co ₅₀ and Fe _93.5 Co ₄ Cr _2.5 targets were used as TbF
When manufacturing eCoCr, Tb, Fe _63.5 Co ₃₄ C
A target of r, Fe _97.5 Co _2.5 was used. The composition ratio of the rare earth and the iron group is Gd ₅₀ Co ₅₀ , Fe _93.5 Co ₄ C
r _2.5 , or Tb, Fe _63.5 Co ₃₄ , Fe _97.5 Co
_2. controlled by varying the power applied to the _fifth target, while keeping the value of Dr / p to 7 × 10 ² or more Gd
FeCoCr was produced.

The recording / reproducing characteristics of the disk by the magnetic field modulation method were measured at a position of 2400 rpm and a radius of 36 mm. The measurement results are shown in Table 2.

Examples 6 to 7 Comparative Examples 3 to 4 Under the same conditions and the same composition as in Example 5, except that the film forming rate Dr and the gas pressure p of GdFeCoCr were changed as shown in Table 2. A magneto-optical recording medium was produced. The recording / reproducing characteristics of the magnetic field modulation method of the disk are 2400 rp
It was measured at a position of m and radius of 36 mm. The measurement results are shown in Table 2.

[0047]

[Table 2] It can be seen from Table 2 that the magneto-optical recording medium according to the present invention has a small saturation bias magnetic field Hb of 90 to 120 and is excellent in magnetic field sensitivity.

Claims (5)

[Claims] 1. A method of manufacturing a magneto-optical recording medium in which at least a dielectric layer, a magnetic layer and a reflective layer are sequentially laminated on a substrate, and after the chamber is evacuated to a high vacuum of 5 × 10 ⁻⁵ Pa or less, it is inactive. A gas is introduced into the chamber, a predetermined power is applied to the target, and the reflective layer is formed by a sputtering method at a deposition rate Dr (Å / min) and a gas pressure p (Pa).
A method for manufacturing a magneto-optical recording medium, characterized in that a film is formed while maintaining a ratio Dr / p of 6 × 10 ² or more. 2. A reproducing layer comprising at least a dielectric layer on a substrate, a magnetic thin film having a high Curie temperature, a low coercive force, and an easy axis of magnetization perpendicular to the film surface, and a Curie temperature arranged adjacent to the reproducing layer. Alternatively, in a method of manufacturing a magneto-optical recording medium in which a magnetic thin film having a low magnetic compensation temperature, a large coercive force, and an easy axis of magnetization perpendicular to the film surface, and a reflective layer are sequentially stacked, a chamber containing 5 × 10 ^-5 P
After a high vacuum of a or less, an inert gas is introduced into the chamber, a predetermined power is applied to the target, and the reflective layer is formed by a sputtering method at a film formation rate Dr (Å / min) and a gas pressure p ( The method for producing a magneto-optical recording medium according to claim 1, wherein the film is formed while maintaining a value of a ratio Dr / p with Pa) of 6 × 10 ² or more. 3. A reproducing layer comprising at least a dielectric layer on a substrate, a reproducing layer made of a magnetic thin film having a high Curie temperature, a small coercive force and an easy axis of magnetization perpendicular to the film surface, and a Curie temperature arranged adjacent to the reproducing layer. Alternatively, in a method of manufacturing a magneto-optical recording medium in which a magnetic thin film having a low magnetic compensation temperature, a large coercive force, and an easy axis of magnetization perpendicular to the film surface, and a reflective layer are sequentially stacked, a chamber containing 5 × 10 ^-5 P
After a high vacuum of a or less, an inert gas is introduced into the chamber, a predetermined electric power is applied to the target, and the reproduction layer is formed by a sputtering method at a film formation rate Dr (Å / min) and a gas pressure p ( A method for producing a magneto-optical recording medium, characterized in that the film is formed while maintaining the value of the ratio Dr / p with Pa) at 7 × 10 ² or more. 4. The method for manufacturing a magneto-optical recording medium according to claim 2, wherein the reflective layer is formed by a sputtering method while maintaining the value of Dr / p at 6 × 10 ² or more. 5. The method of manufacturing a magneto-optical recording medium according to claim 1, wherein the substrate is a transparent substrate and the reflective layer is a metal reflective layer.