JPH03270115A - Manufacture of optomagnetic recording medium - Google Patents

Abstract

PURPOSE:To manufacture a magnetic film of an optomagnetic recording medium adapted for an overlight having stable magnetic characteristic with one target by forming the film by a sputtering method while applying high frequency power to a substrate supporting base. CONSTITUTION:A protective film 2 made of dielectric such as SiN is formed on a transparent substrate 1 made of polycarbonate resin, etc. The amplitude of high frequency power to be applied to a substrate supporting base is altered, and a magnetic film (recording layer 3) made of rare earth element and transition metal having various relation to Curie temperature, a coercive force, a magnetic film 4 having different composition ratio from the layer 3 and different magnetic characteristic and a protective film 5 made of the dielectric are sequentially laminated by a magnetron sputtering method by applying a DC power of 150W to one target 6. The layer 3 becomes the Curie temperature or higher even in the case of emitting a light of low intensity, the magnetization of the layer 3 is oriented in the magnetization direction of the layer 4 to form a recording pit.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a magneto-optical recording medium.

[Prior Art] Magneto-optical recording media on which information can be erased and rewritten are
Generally, it has an illumination structure in which a protective film, a magnetic film having perpendicular magnetic anisotropy, and a protective film are laminated in this order on a transparent substrate, or it has a structure in which a reflective film is further laminated on the above protective film. ing. A recording method for a magneto-optical recording medium that has these structures and allows new information to be overwritten (overwrite) regardless of the presence or absence of recorded information is the magnetic field modulation recording method. and optical modulation recording method.

The magneto-optical recording medium is overridden by modulating the magnetic field applied to the magneto-optical recording medium under intense laser beam irradiation. To perform override using the magnetic field modulation recording method, the distance between the magnetic film of the magneto-optical recording medium and the recording head must be small, so the magneto-optical recording medium used has a single-plate structure with the magnetic film on only one side. It is preferable. Further, it is preferable that the composition of the magnetic film is such that the intensity of the magnetic field applied for recording is low.

In the optical modulation recording method, a protective film, two magnetic films with different magnetic properties, and a protective film are sequentially laminated on a transparent substrate.
The material that forms the magnetic film on the incident side of the linear light that is irradiated to record information (hereinafter referred to as the supplementary i-layer) is a magnetic film that is laminated on the side opposite to the incident side of the linear light (hereinafter referred to as the supplementary i-layer). An auxiliary magnetic field for initialization and a magnetic field for recording in the opposite direction are applied to the magneto-optical recording medium, which has a higher coercive force and a lower Curie temperature at room temperature than the material forming the material (this is called the recording layer). Overriding is performed by applying a magnetic field and modulating the intensity of the irradiated laser light in accordance with the information to be recorded (Japanese Patent Laid-Open No. 62-17594).
(See Publication No. 8). To explain this specifically, first, by applying an auxiliary magnetic field for initialization, the direction of magnetization of the auxiliary layer is aligned in the erasing direction. If a laser beam with an intensity of erasing level is irradiated in this state, the magnetic field of the auxiliary layer is thermally transferred to the recording layer, and the magnetization of the recording layer is directed in the erasing direction. Here, if high-intensity light at a writing level is irradiated in accordance with the information to be recorded, the magnetization of the auxiliary layer and the recording layer disappears. If a recording magnetic field is applied to a magnetic film whose magnetization has disappeared,
Since the magnetization direction of the recording layer is in the recording direction opposite to the erasing direction, new information is recorded.

Furthermore, JP-A No. 63-64651 discloses a structure in which a protective film, three layers of magnetic films with different magnetic properties, and a protective film are sequentially laminated on a transparent substrate, and the light emitted to record information is The material that forms the magnetic film on the side opposite to the incident side (hereinafter referred to as the auxiliary layer) forms a magnetic film (hereinafter referred to as the recording layer) that is laminated on the side of the auxiliary layer where the linear light enters. The auxiliary layer is a material that has a lower coercive force and a higher Curie temperature at room temperature than the material that forms the magnetic film (hereinafter referred to as the transfer layer) that is laminated on the linear light incident side of the recording layer. It is shown that overriding can be performed by an optical modulation recording method using a magneto-optical recording medium that has a lower coercive force and a higher Curie temperature at room temperature than the material used to form the recording medium.

The above two-layer magnetic film is made of GdDyFe-GdTbFe,
TbFeGdTbFe, TbDyFe-GdDyFe
It is laminated and formed by a combination of the above 3
The magnetic film of the layer is GdFeCo-GdDyFe-GdT
bFe, GdFeCo-TbFe-GdTbFe.

It is formed by laminating a combination of TbDyFe-GdDyFe-GdFeCo or the like. Furthermore, the above-mentioned two-layer or three-layer magnetic film can also be formed by laminating magnetic films composed of the same rare earth element and transition metal but having different composition ratios.

[Problems to be Solved by the Invention] The magnetic field modulation recording method described above has a problem in that it is difficult to modulate the magnetic field at high speed, so it is not possible to create an overlapping structure at high speed, and therefore it is not possible to increase the amount of information recorded. There are some drawbacks such as points. In addition, in the above-mentioned optical modulation recording method, two or three types of alloy targets with different alloy compositions are used to form the magnetic films of each layer in order to stack two or three layers of magnetic films with different magnetic properties. Do you use it?
The sputtering method is performed using two or three types of alloy targets having the same alloy composition but different composition ratios, or multiple targets made of a single metal or an alloy and multiple electrodes are used to perform the sputtering method. It is necessary to perform the sputtering method by adjusting the power applied to the sputtering method.

In addition, when forming a magnetic film by sputtering, as the number of bottom films formed using an IfM target increases, the composition ratio of rare earth elements and transition metals in the resulting magnetic film gradually changes. There is a problem that the magnetic properties of the magnetic film change due to the change in the magnetic properties of the magnetic film. For this reason, the number of base films formed per target used for forming a magnetic film is smaller than the number of base films formed per target used for forming a protective film or the like.

One object of the present invention is to provide a method for manufacturing a magneto-optical recording medium having stable magnetic properties. One object of the present invention is to provide a method for manufacturing a magnetic film in a magneto-optical recording medium, which has stable magnetic properties and is suitable for overwriting by an optical modulation recording method, using one target.

[Means for Solving the Problems] According to the present invention, the above! One purpose is to apply high-frequency power to the conductive substrate support when forming a magnetic film made of rare earth elements and transition metals by sputtering on a transparent substrate placed on the conductive substrate support. This is achieved by providing a method for manufacturing a magneto-optical recording medium characterized by the following.

According to the present invention, another object of the above is to sputter a magnetic film made of a rare earth element and a transition metal having a two-layer structure onto a transparent substrate placed on a conductive substrate support. When the magnetic film is formed by a method, the magnetic film is composed of a magnetic film a on the incident side of the light irradiated to record information and a magnetic film A laminated on the side opposite to the incident side of the linear light. Different magnitudes of high-frequency power are applied to the substrate support when forming the magnetic film a and when forming the magnetic film so that the magnetic film has a lower coercive force and a higher Curie temperature at room temperature than the magnetic film a. Or, when a magnetic film consisting of a rare earth element and a transition metal having a three-layer structure is formed by sputtering on a transparent substrate placed on a conductive substrate support, the magnetic film records information. a magnetic film c' on the incident side of the light irradiated on the magnetic film c', a magnetic film a° laminated on the side opposite to the incident side of the light beam on the magnetic film c', and a magnetic film laminated on the magnetic film a'. magnetic film b°, where magnetic film b° has a lower coercive force and higher Curie temperature at room temperature than magnetic film a°, and magnetic film C° has a lower temperature at room temperature than magnetic film b'. When forming the magnetic film a°, when forming the magnetic film b′, and when forming the magnetic film c, so as to have a coercive force and a high Curie temperature.
This is achieved by providing a method for manufacturing a magneto-optical recording medium, which is characterized in that high-frequency power of different magnitude is applied to a substrate support during the formation of a magneto-optical recording medium.

[Example] Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A schematic cross-sectional view of one example of a magneto-optical recording medium manufactured according to the present invention is shown in FIG. The magneto-optical recording medium having the cross-sectional structure shown in FIG. 1 is made of polycarbonate resin, amorphous polyolefin resin, polymethyl methacrylate resin,
On a transparent substrate 1 made of glass or the like, SiN, Af
N, At! A protective film 2 made of a dielectric material such as 5iNSSiO, a magnetic film made of a rare earth element and a transition metal (hereinafter referred to as
This is referred to as the recording layer 3), a magnetic film made of the same rare earth elements and transition metals as the recording layer 3 but with a different composition ratio and different magnetic properties (hereinafter referred to as the auxiliary layer 4), and the above-mentioned auxiliary layer 4. The protective film 5 made of the dielectric material exemplified above is sequentially laminated. The material forming the auxiliary layer 4 has a lower coercive force and a higher Curie temperature at room temperature than the material forming the recording layer 3. Light is irradiated from the transparent substrate l side to record, reproduce, or erase information.

When performing override using the optical modulation recording method, if the above-mentioned auxiliary layer 4 is irradiated with high intensity light, the auxiliary layer 4
becomes above the Curie temperature, and when a recording magnetic field is applied, the direction of magnetization is directed to the magnetization direction of the recording magnetic field, but when irradiated with low intensity light, the auxiliary layer 4 does not reach above the Curie temperature. First, the direction of magnetization does not change even if a recording magnetic field is applied. The above-mentioned recording layer 3 has a property that the temperature is higher than the Curie temperature even when irradiated with low-intensity light, and the magnetization of the recording layer 3 is oriented in the direction of magnetization of the auxiliary layer 4 to form a recording bit. The recorded information is reproduced by irradiating the recording layer 3 with light and detecting the direction of magnetization of the recording pits.

As shown in the figure. The sputtering apparatus shown in FIG. 2 includes a target 6 made of a rare earth element and a transition metal constituting a recording layer 3 and an auxiliary layer 4, a target power source 7 that generates electric power to be applied to the target 6, and a transparent substrate 1. It includes a conductive substrate support 8 made of stainless steel or the like, and a substrate support power source 9 that generates high-frequency power to be applied to the substrate support 8. The target 6 and the substrate support 8 are each grounded to a chamber 10 of the sputtering apparatus. When forming a magnetic film by magnetron sputtering using a target with a diameter of 3 inches, the DC power applied to the target is 5
A range of 0 to 250 W is preferred.

Furthermore, when using a substrate support with a diameter of 15 to 20 cm, the high frequency power applied to the substrate support is 20 to 20 cm.
Preferably, it is in the range of 0W.

Using the sputtering apparatus shown in Fig. 2, Tbv
Using a 3-inch diameter target made of tPe*aCOs (atomic ratio), gas was introduced so that the gas pressure was 0.2 Pa, and high-frequency power (150 W) was applied to the target using a DC type substrate support. Frequency: 13.7MH
FIG. 3 shows the relationship between the Curie temperature and coercive force of magnetic films obtained by varying the size of z). Third
In the figure, the solid line (a) shows the relationship between the Curie temperature and coercive force of the magnetic film obtained by forming the film while applying 30 W of high-frequency power to the substrate support, and the broken line (b) shows the relationship between the Curie temperature and the coercive force of 10
The relationship between the Curie temperature and coercive force of a magnetic film obtained by forming a film while applying 0 W of high frequency power to a substrate support is shown. As is clear from FIG. 3, by changing the magnitude of the high frequency power applied to the substrate support, magnetic films having various relationships between Curie temperature and coercive force can be obtained.

Using a Si target, Ar gas and N gas were introduced at gas pressures of 0.09 Pa and 0.03 Pa, respectively, and 160 W of high frequency power was applied to the Si target using a reactive sputtering method. Using a support made of SiN on the polycarbonate resin transparent substrate I, A gas was introduced so that the gas pressure was 0.2 Pa, 150 W of DC power was applied to the alloy target, and the substrate support 8 was placed on the polycarbonate resin transparent substrate I. 50W of high frequency power (frequency 13.7
The recording layer 3 is formed to a film thickness of about 300 MHz by a magnetron sputtering method applying MHz), and then the high frequency power applied to the substrate support 8 is
A film thickness of 850mm was obtained using the same magnetron sputtering method except that W was used. Auxiliary layer 4 was formed so as to be ↓. In the same manner as in the case of forming the protective film 2 on the auxiliary layer 4, a protective film 5 made of SiN was laminated to a thickness of 800 mm. Overwriting of the information recorded on the magneto-optical recording medium produced as described above under the conditions of the frequency I M II z using the optical modulation recording method was possible under the conditions of an initial magnetic field of 4 KOe and a recording magnetic field of 2000 e.

Example 2 A schematic cross-sectional view of another example of a magneto-optical recording medium manufactured according to the present invention is shown in FIG. The magneto-optical recording medium having a horizontal cross-section as shown in FIG. The magnetic If (referred to as I3) is made of the same rare earth elements and transition metals as the transfer layer 13, but has a different composition ratio and different magnetic properties.
This is hereinafter referred to as the recording layer 14), which is made of the same rare earth elements and transition metals as the transfer layer 13 and the recording layer 14.
A magnetic film having a different composition ratio and magnetic properties (hereinafter referred to as auxiliary layer 15) and a protective film 16 made of the dielectric material exemplified above are sequentially laminated. The material forming the auxiliary layer 15 has a lower coercive force and higher Curie temperature at room temperature than the material forming the R layer 14, and the material forming the transfer layer 13 has a lower coercive force and higher Curie temperature at room temperature than the material forming the auxiliary layer 15. It has a low coercive force and a high Curie temperature. Light is irradiated from the transparent substrate 11 side to record, reproduce, or erase the IM.

Using the sputtering apparatus shown in FIG. 2, using an alloy target 6 made of a rare earth element and a transition metal, the magnitude of the high frequency power applied to the substrate support 8 is adjusted to the transfer layer 13.
A three-layered magnetic film having the above-mentioned correlation between coercive force and Curie temperature can be formed by appropriately changing the values when forming the recording layer 14 and the auxiliary layer 15.

When performing override using the optical modulation recording method, if the above-mentioned auxiliary 415 is irradiated with high intensity light, the auxiliary 5
15 becomes above the Curie temperature, and when a recording magnetic field is applied, the magnetization direction or the magnetization direction of the recording magnetic field is oriented.However, when irradiated with low intensity light, the auxiliary layer 15 becomes above the Curie temperature. Therefore, the direction of magnetization does not change even when a recording magnetic field is applied. When the recording layer 14 is irradiated with low-intensity light, it reaches a temperature higher than the Curie temperature, and the magnetization becomes the auxiliary layer! It has the property of being oriented in the magnetization direction of 5. The transfer layer 13 has a property that the magnetization of the recording layer 14 is transferred to form recording pits. Transfer layer 1
3 is irradiated with light and the recorded information is reproduced by detecting the magnetization direction of the recording pit.

Examples of the above! The thicknesses of the protective film and magnetic film of the magneto-optical recording medium shown in Example 2 can be set according to their optical properties and thermal conductivity, but the thickness of the protective film 2 or 12 is usually the same. is in the range of 400 to 1200, and magnetic H (recording layer 3 + Urasuke layer 4 or transfer layer 1
3 + recording layer 14 + auxiliary layer 15) film thickness is 600 to 230
0 people, and the thickness of protective film 5 or 16 is 30
Preferably, the number is in the range of 0 to 1200 people.

Example 3 A schematic sectional view of another example of a magneto-optical recording medium manufactured according to the present invention is shown in FIG. The magneto-optical recording medium having the cross-sectional structure shown in FIG. Become. Light is irradiated from the transparent substrate 18 side to record, reproduce, or erase information.

Using the sputtering apparatus shown in FIG. 2, Tbt7
Polycarbonate resin was sputtered using a magnetron sputtering method using a 3-inch diameter target made of FesiCOs (atomic ratio), introducing Ar gas at a gas pressure of 0.2 Pa, and applying 150 W of DC power to the target. When forming a magnetic film on a transparent substrate, high frequency power (frequency: 13
．． FIG. 6 shows the relationship between the coercive force of the magnetic films obtained by depositing the magnetic films with different magnitudes (7 MHz) and the magnitude of the high frequency power applied to the substrate support. As is clear from Figure 6, the coercive force of the obtained magnetic film changes depending on the magnitude of the high-frequency power applied to the substrate support, so that a magnetic film with uniform magnetic properties can be obtained. By appropriately changing the magnitude of high-frequency power, a large number of films can be formed from one target.

Is it possible to set the thickness of the protective film, magnetic film, and reflective film of the magneto-optical recording medium shown in Example M3 according to their optical properties and thermal conductivity? The thickness of the magnetic film 20 is in the range of 100 to 400, the thickness of the protective film 21 is in the range of 300 to 1,200, and the thickness of the reflective film H is in the range of 200 to 1,200. Preferably, the number is in the range of 800 people.

Also included in the magneto-optical recording medium manufactured by the present invention is a magneto-optical recording medium having a structure in which the cross-sectional structure shown in FIG. 5 is bonded together with the reflective film O. inside.

Targets for forming magnetic films used in the present invention include TbFe, TbDyFe, GdDyFe, (i
dTbFe.

It is preferable to use an alloy target made of GdFeCo or the like, or an alloy target made of these materials to which elements such as Ti, Cr, or Pt are added.

[Effects of the Invention] According to the present invention, a magneto-optical recording medium having stable magnetic properties is manufactured. In addition, a magneto-optical recording medium having stable magnetic properties and suitable for overwriting using an optical modulation recording method can be manufactured using a single target.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a magneto-optical recording medium manufactured according to the present invention, FIG. 2 is a schematic configuration diagram of an example of a sputtering apparatus used for forming a magnetic film according to the present invention, and FIG. 1 is a diagram showing the relationship between the Curie temperature and coercive force of a magnetic film obtained by varying the high-frequency power applied to the substrate support, and FIGS. FIG. 6, a schematic cross-sectional view of another example of a magnetic recording medium, shows the relationship between the coercive force of a magnetic film formed by varying the magnitude of the high-frequency power applied to the substrate support and the difference in the high-frequency power applied. It is a figure showing the relationship with size. 1, It, 18...Transparent substrate, 3
．． 4.13.14.15.20...Magnetic film, 6
...
Target, 7
... Target power supply, 8 ... Board support stand, 9 ... Board support stand power supply.

Claims (3)

[Claims] 1. When a magnetic film made of a rare earth element and a transition metal is formed by sputtering on a transparent substrate placed on a conductive substrate support, high-frequency power is applied to the substrate support. A method for manufacturing a magneto-optical recording medium. 2. 2 on a transparent substrate placed on a conductive substrate support stand.
When forming a magnetic film made of a rare earth element and a transition metal having a layered structure by a sputtering method, a magnetic film a is formed on the incident side of light that is irradiated to record information on the magnetic film.
and a magnetic film b laminated on the side opposite to the light incident side, and when forming the magnetic film a, the magnetic film b has a lower coercive force and a higher Curie temperature at room temperature than the magnetic film a. and a method for manufacturing a magneto-optical recording medium, which comprises applying high-frequency power of different magnitudes to the substrate support during the formation of the magnetic film b. 3. 3 on a transparent substrate placed on a conductive substrate support stand.
When forming a magnetic film made of a rare earth element and a transition metal having a layered structure by a sputtering method, a magnetic film c on the incident side of light that is irradiated to record information on the magnetic film is formed by a sputtering method.
', a magnetic film a' laminated on the opposite side of the light incident side on the magnetic film c', and a magnetic film b laminated on the magnetic film a'.
', the magnetic film b' has a lower coercive force and a higher Curie temperature at room temperature than the magnetic film a', and the magnetic film c'
When forming the magnetic film a', when forming the magnetic film b', and when forming the magnetic film c', different sizes were used so that the magnetic film had a lower coercive force and a higher Curie temperature at room temperature than the magnetic film b'. A method for manufacturing a magneto-optical recording medium, comprising applying high frequency power to a substrate support.