JPH04318345A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To provide a heat treating method for the magneto-optical recording medium which lessens the deformation of substrates and lessens the decrease in reproduced output by the repetition of recording and erasing. CONSTITUTION:Magneto-optical recording layers including at least a magnetic film are vacuum formed on the preformat pattern forming surface of the substrate 7. The laminate of bellow the substrate and the magnetic films is heat- treated at the glass transition temp. of glass or plastic material constituting the pattern forming surface and under the temp. conditions and time conditions to generate a magnetic characteristic change of max. 50% in the magnetic films during or after the formation of the magnetic films. The film formation of the magneto-optical recording layers is executed in 1st to 4th sputtering chambers 1, 2, 3, 5 and the heat-treatment is executed with an infrared lamp 9 of a heat treating chamber 4.

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, and more particularly to a heat treatment of a substrate and a magnetic film formed on one side of the substrate.

0002

[Prior Art] Magneto-optical recording media are information recording media that are characterized by high density, non-contact, non-volatile, and rewritable properties. Among them, magneto-optical disks are being put into practical use as next-generation information recording media. It's coming. At present, the mainstream information recording film provided on magneto-optical disks is a magnetic film that does not require heat treatment during film formation, especially a perpendicularly magnetized film made of an amorphous rare earth-transition metal alloy. .

However, rare earth-transition metal-based amorphous alloys are different from garnet-based oxides, which are formed into films while heating the substrate to high temperatures; 9, No. 2 (1985), pp. 97-1
As described on page 00, magnetic properties such as coercive force and perpendicular magnetic anisotropy energy tend to change when heated to high temperatures, and the reproduction output decreases as information is repeatedly recorded and erased. The shortcomings of doing so have been pointed out.

The main cause of such a reduction in reproduction output is that the structure of the magnetic film is relaxed by exposure to high temperatures, and heat treatment is performed during or after the formation of the magnetic film to improve the structure of the magnetic film from the beginning. If you relax it to some extent,
The magnetic film can be brought into a thermodynamically stable state, and problems such as a decrease in reproduction output can be improved.

Conventionally, as a method for preventing a decrease in reproduction output based on this knowledge, for example, Japanese Patent Application Laid-Open No. 62-298046
As described in the above publication, a method for manufacturing a magneto-optical recording medium has been proposed in which a magnetic film is heat-treated to near the Curie temperature.

[0006]

However, many of the magnetic films currently used for magneto-optical recording have a Curie temperature of around 200°C, and even if the heating method is devised, heating to this temperature will cause the substrate to deteriorate. It is difficult to prevent thermal deformation. In particular, when a plastic substrate with a low heat resistance temperature is used as the substrate, or when a glass substrate with a photocurable resin replica layer provided on one side is used,
This causes a problem in that the preformat pattern such as the guide groove is significantly deformed, making it impossible to obtain desired tracking characteristics.

The present invention has been made in order to eliminate the drawbacks of the prior art described above, and is a heat treatment method for magneto-optical recording media that causes less deformation of the substrate and less decrease in reproduction output due to repeated recording and erasing. The purpose is to provide a method.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned objects, the present invention first provides a signal surface of a glass substrate having a replica layer of a preformat pattern made of a photocurable resin on one side. , in a method for manufacturing a magneto-optical recording medium including a step of forming a magneto-optical recording layer including at least a magnetic film, a laminate of the glass substrate and the magnetic film is formed during or after the formation of the magnetic film. A heat treatment method is used in which heat treatment is performed at a temperature below the glass transition temperature of the photocurable resin material constituting the replica layer and under temperature and time conditions that cause a maximum change in magnetic properties of 50% in the magnetic film.

Second, on the signal surface of a plastic substrate on which a preformat pattern is directly formed,
In a method for manufacturing a magneto-optical recording medium including a step of forming a magneto-optical recording layer including at least a magnetic film, during or after forming the magnetic film, a laminate of the plastic substrate and the magnetic film is formed, A heat treatment method is used in which heat treatment is performed at a temperature below the glass transition temperature of the plastic material constituting the plastic substrate and under temperature and time conditions that cause the magnetic film to change its magnetic properties by up to 50%.

Furthermore, thirdly, a method for manufacturing a magneto-optical recording medium including the step of forming a magneto-optical recording layer containing at least a magnetic film on the signal surface of a glass substrate having a preformat pattern directly cut on one side. During or after the formation of the magnetic film, the laminate of the glass substrate and the magnetic film is heated at a temperature below the glass transition temperature of the glass material constituting the glass substrate, and at a temperature of up to 50% on the magnetic film.
A heat treatment method is used in which heat treatment is performed under temperature and time conditions that cause a change in magnetic properties of %.

[0011] The above heat treatment is preferably carried out in an inert gas atmosphere or in vacuum in order to prevent oxidation of the magnetic film. When the above heat treatment is performed in a vacuum, the degree of vacuum in the treatment tank is reduced to 1/102 [Torr].
It is particularly preferable to adjust as follows. Furthermore, coercive force or perpendicular magnetic anisotropy energy can be used as the magnetic properties of the magnetic film that are the basis of the temperature and time conditions when performing the heat treatment.

[0012] The present invention applies to all magneto-optical recording media having a magnetic film that does not require heat treatment during film formation, but in particular [terbium, gadolinium, neodymium,
at least one element selected from the element group [dysprosium, holmium, praseodymium]; at least one element selected from the [iron, cobalt] element group;
[Niobium, tantalum, titanium, chromium, platinum, rhodium, palladium] A light source equipped with a perpendicularly magnetized film made of an alloy (especially an amorphous alloy) containing at least one element selected from the element group It has a remarkable effect when applied to magnetic recording media.

[0013]

[Operation] As mentioned above, by keeping the heating temperature below the glass transition temperature of the substrate material, it is possible to prevent large deformation of the substrate and deformation of the preformat pattern that would affect the tracking characteristics.

[0014] Furthermore, by setting the temperature and time conditions of the heat treatment based on changes in the magnetic properties of the magnetic film, it is possible to relax the structure of the magnetic film to the maximum extent that does not adversely affect information recording. can. Experiments have shown that there is no adverse effect on information recording even when heat treatment is applied to a magnetic film that has not been subjected to heat treatment, such that the coercive force and perpendicular magnetic anisotropy energy are reduced by up to 50%. understood.

Therefore, by employing the heat treatment method as described above, it is possible to produce a magneto-optical recording medium in which the substrate is less deformed and the reproduction output is less reduced due to repeated recording and erasing.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. <First Example> FIG. 1 is an explanatory diagram of a vacuum film forming apparatus for carrying out the method for manufacturing a magneto-optical recording medium according to this example, in which 1 is a first sputtering chamber, 2 is a second sputtering chamber, and 3 is a 3rd sputtering chamber, 4 heat treatment chamber, 5 4th sputtering chamber, 6 each chamber 1-
5 is a substrate holder provided, 7 is a substrate attached to the substrate holder 6, 8a, 8b, 8c, 8d are targets provided in each sputtering chamber 1, 2, 3, 5, and 9 is a heat treatment chamber 4. It is equipped with an infrared lamp.

As the substrate 7, a glass substrate was used, on one side of which a replica layer of a preformat pattern made of photocurable resin was provided. These substrates 7 are attached to the substrate holder 6 with the signal surfaces facing the targets 8a to 8d.

The targets 8a and 8c are made of a material for forming an inorganic dielectric film, such as SiN, on the substrate 7 or on the magnetic film formed in the second sputtering chamber 2, and the target 8b is A magnetic film, for example, at least one element selected from the element group [terbium, gadolinium, neodymium, dysprosium, holmium, praseodymium] on the inorganic dielectric film formed in the sputtering chamber 1;
The main component is at least one element selected from the [iron, cobalt] element group and at least one element selected from the [niobium, tantalum, titanium, chromium, platinum, rhodium, palladium] element group. It consists of a material that forms an alloy film. Further, the target 8d is made of a material for forming a metal reflective film, such as AlTi, on the inorganic dielectric film formed in the third sputtering chamber 3.

A method of manufacturing a magneto-optical disk using the above-mentioned vacuum film forming apparatus will be explained below.

First, one or more disk-shaped substrates 7 are attached to the substrate holder 6 and housed in the first sputtering chamber 1, and a first inorganic dielectric film is formed on the signal surface of the substrate 7 under predetermined vacuum conditions. Deposit a film. Next, the substrate 7 on which the first inorganic dielectric film has been formed is transferred to the second sputtering chamber 2 together with the substrate holder 6, and under predetermined vacuum conditions, a magneto-optical film is formed on the first inorganic dielectric film. A magnetic film serving as a recording layer, for example, a perpendicular magnetization film made of an amorphous rare earth-transition metal alloy is formed. next,
The substrate 7 on which the magnetic film has been formed is transferred together with the substrate holder 6 to the third sputtering chamber 3, and a second inorganic dielectric film is formed on the magnetic film under predetermined vacuum conditions. Next, the substrate 7 on which the second inorganic dielectric film has been formed is transferred to the heat treatment chamber 4 together with the substrate holder 6, and in an inert gas atmosphere or in vacuum (preferably the degree of vacuum is 1/102 Torr or less). The infrared lamp 9 is turned on to heat the magnetic film. The heating conditions are temperature and time conditions that are below the glass transition temperature of the photocurable resin material constituting the replica layer and that cause a 20% change in magnetic properties in the magnetic film.

During the heat treatment, as shown in FIG. 3, changes in the magnetic properties of the magnetic film (perpendicular magnetic anisotropy energy is illustrated in FIG. 3), heating temperature, and heating time are considered. Measure the relationship and set the actual heating conditions using this graph as a reference. That is, from the graph of FIG. 3, in this example, the magnetic film is heated at 200° C. for 30 seconds. Thereafter, the film was slowly cooled to prevent the film from peeling off from the substrate due to stress caused by the difference in coefficient of thermal expansion between the substrate and each film.

Next, the substrate 7 that has been subjected to a predetermined heat treatment is transferred to the fourth sputtering chamber 5 together with the substrate holder 6, and a metal reflective film is formed on the second inorganic dielectric film under a predetermined vacuum condition. A magneto-optical disk having the film structure shown in FIG. 2 was manufactured by laminating the following layers. In FIG. 2, 11 is a first inorganic dielectric film, 12 is a magnetic film, 13 is a second inorganic dielectric film, and 14 is a metal reflective film.

Finally, this magneto-optical disk is coated with each film 11 to
They were bonded together with thermosetting resin with No. 14 facing inside to produce a double-sided recording type magneto-optical disk.

Second Example A plastic substrate with a preformat pattern directly formed on one side was used as the substrate, and each film was formed and heat treated in the same manner as in the first example. The heating conditions are temperature and time conditions that are below the glass transition temperature of the substrate plastic material and cause a 10% change in magnetic properties in the magnetic film. Specifically, according to the graph of FIG. 3, the temperature was 120° C. for 30 minutes.

<Third Example> Using the vacuum film forming apparatus shown in FIG. A second inorganic dielectric film and a reflective film made of AlCr were sequentially laminated. However, no heat treatment was performed during this film formation process.

After film formation, two magneto-optical disks with the same structure are bonded together with a thermosetting resin, with each film on the inside.
One thousand sets of double-sided recording type magneto-optical disks were manufactured.

Next, these 1000 sets of double-sided recording type magneto-optical disks are stored simultaneously in a heater-heated dryer, and the inside of the dryer is kept in an inert gas atmosphere or vacuum (preferably the degree of vacuum is 1/102 Torr or less). After adjusting the temperature, heat treatment was performed at a temperature below the glass transition temperature (145° C.) of the polycarbonate resin and under temperature and time conditions that caused a 20% change in magnetic properties in the magnetic film.

As with the first embodiment, the heating conditions were as follows: the heating temperature was 130°C, and the heating time was 55°C.
I set the time.

<Fourth Example> Using the vacuum film forming apparatus shown in FIG. 1, a first inorganic dielectric film made of SiNx and a first inorganic dielectric film made of SiN , a magnetic film made of TbFeCoPtNb, a second inorganic dielectric film made of SiNx, and a reflective film made of Ti were sequentially laminated. However, no heat treatment was performed during this film formation process.

After the film formation is completed, this magneto-optical disk is stored in a heat treatment tank, and the inside of the heat treatment tank is adjusted to an inert gas atmosphere or a vacuum (preferably the degree of vacuum is 1/102 Torr or less), as shown in FIG. Infrared rays from an infrared lamp 9 are irradiated from the glass substrate 7 side as shown in FIG. Heat treatment was performed under the following conditions.

As with the first embodiment, the heating conditions were as follows: the heating temperature was 250°C, and the heating time was 55°C.
It was set to seconds.

Finally, two magneto-optical disks having the same structure were bonded together with a thermosetting resin with each film facing inside to produce a double-sided recording type magneto-optical disk.

FIG. 5 shows the change in reproduction CN ratio when repeatedly recording and erasing was performed on the same recording area of the magneto-optical disks according to the first to third embodiments, and the changes in the reproduction CN ratio when no heat treatment was performed after film formation. Repeated recording and recording in the same recording area of a magneto-optical disk
3 shows a change in reproduction CN ratio when erasing is performed. Also,
FIG. 6 shows the external magnetic field dependence of the magneto-optical disks according to the first to third embodiments and the external magnetic field dependence of the magneto-optical disk which was not subjected to post-film-forming heat treatment. In addition, in order to ensure strict measurement, information was recorded and erased using a laser power 20% higher than the laser power used for normal recording and erasing.
I deleted it.

As shown in FIG. 5, the magneto-optical disks of the first and fourth embodiments can be used to record information 108 times or more.
Even if erasing is repeated, the reproduced CN ratio does not decrease at all. On the other hand, the magneto-optical disks of the second and third embodiments have 10
The reproduction CN ratio decreases slightly after 6 cycles, but the degree of decline is much smaller than that of magneto-optical discs that were not heat-treated (displayed as untreated in the graph), and after 108 cycles. Even if the recording and erasing of information is repeated as described above, a reproduction CN ratio of about 47 [dB] or more can be obtained.

Furthermore, as shown in FIG. 6, the magneto-optical disks of the first to fourth embodiments all have higher dependence on external magnetic fields than untreated magneto-optical disks.
Information can be recorded and erased using an external magnetic field of about ±100 [Oe].

Of course, the magneto-optical disks of the first to fourth embodiments do not cause any laser beam spot track-off or pre-pit signal read error during recording/erasing operations, and prevent deformation of the preformat pattern. was also found to be effective.

[0037] These effects can be obtained by applying a maximum of 50% to the magnetic film.
It was also obtained when heat-treated under temperature and time conditions that caused a change in magnetic properties of %. In addition to the magneto-optical disk having the film structure shown in FIG. 2, there is also a magneto-optical disk in which only the magnetic film 12 is formed on the substrate 7 as shown in FIG. A magneto-optical disk on which a magnetic film 12 is formed via a body layer 11, and furthermore, as shown in FIG. 9, three layers of magnetic films 12a having different compositions are formed on a substrate 7.
, 12b, 12c were sequentially laminated to form the recording layer 12, similar results were obtained.

[0038]

[Effects of the Invention] As explained above, according to the present invention,
Since the heating temperature is kept below the glass transition temperature of the substrate material, it is possible to prevent large substrate deformation and deformation of the preformat pattern that would affect tracking characteristics, and it is also possible to prevent changes in the magnetic properties of the magnetic film. Since the temperature and time conditions for the heat treatment are set as follows, the structure of the magnetic film can be relaxed to the maximum extent that does not adversely affect information recording. Therefore, it is possible to produce a magneto-optical recording medium in which the substrate is less deformed and the reproduction output is less reduced due to repeated recording and erasing.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a vacuum film forming apparatus.

FIG. 2 is a cross-sectional view showing an example of a film structure of a magneto-optical disk.

FIG. 3 is a graph showing the relationship between heating temperature, heating time, and perpendicular magnetic anisotropy energy.

FIG. 4 is an explanatory diagram showing another example of a heating method.

FIG. 5 is a graph diagram showing the relationship between the number of repetitions of recording/erasing and the reproduction CN ratio.

FIG. 6 is a graph diagram showing the dependence of the reproduced CN level on an external magnetic field.

FIG. 7 is a cross-sectional view showing another example of the film structure of a magneto-optical disk.

FIG. 8 is a cross-sectional view showing still another example of the film structure of a magneto-optical disk.

FIG. 9 is a cross-sectional view showing still another example of the film structure of a magneto-optical disk.

[Explanation of symbols]

1 First sputtering chamber 2 Second sputtering chamber 3 Third sputtering chamber 4 Heat treatment chamber 5 Fourth sputtering chamber 6 Board holder 7 Board 8a-8d Target 9 Infrared lamp 11 First inorganic dielectric layer 12 Magnetic film 13 Second inorganic dielectric layer 14 Reflection layer

Claims (8)

[Claims] 1. A magneto-optical recording medium comprising the step of depositing a magneto-optical recording layer containing at least a magnetic film on the signal surface of a glass substrate provided with a replica layer of a preformat pattern made of a photocurable resin on one side. In the manufacturing method, during or after the formation of the magnetic film, the laminate of the glass substrate and the magnetic film is heated at a temperature equal to or lower than the glass transition temperature of the photocurable resin material constituting the replica layer, and 1. A method for manufacturing a magneto-optical recording medium, which comprises heat-treating a magnetic film under temperature and time conditions that cause a change in magnetic properties of up to 50%. 2. A method for manufacturing a magneto-optical recording medium, comprising the step of forming a magneto-optical recording layer containing at least a magnetic film on the signal surface of a plastic substrate on which a preformat pattern is directly formed. During or after film formation, the laminate of the plastic substrate and the magnetic film is heated at a temperature below the glass transition temperature of the plastic material constituting the plastic substrate, and the magnetic properties of the magnetic film are changed by up to 50%. 1. A method for manufacturing a magneto-optical recording medium, which comprises performing heat treatment under temperature and time conditions that cause the formation of the temperature and time conditions. 3. A method for manufacturing a magneto-optical recording medium, comprising the step of forming a magneto-optical recording layer containing at least a magnetic film on the signal surface of a glass substrate having a preformat pattern directly cut on one side, wherein the magnetic film During or after film formation, the laminate of the glass substrate and the magnetic film is heated at a temperature below the glass transition temperature of the glass material constituting the glass substrate, and the magnetic properties of the magnetic film are changed by up to 50%. 1. A method for manufacturing a magneto-optical recording medium, which comprises performing heat treatment under temperature and time conditions that cause the formation of the temperature and time conditions. 4. The method for manufacturing a magneto-optical recording medium according to claim 1, wherein the heat treatment is performed in an inert gas atmosphere or in vacuum. 5. In claim 4, when the heat treatment is performed in a vacuum, the degree of vacuum in the treatment tank is reduced to 1/102.
Torr] or less. 6. The method of manufacturing a magneto-optical recording medium according to claim 1, wherein the magnetic property of the magnetic film is coercive force or perpendicular magnetic anisotropy energy. 7. In any one of claims 1 to 3, the magnetic film comprises at least one element selected from the group of elements [terbium, gadolinium, neodymium, dysprosium, holmium, praseodymium], and [iron, At least one element selected from the element group [cobalt] and at least one element selected from the element group [niobium, tantalum, titanium, chromium, platinum, rhodium, palladium]
1. A method for manufacturing a magneto-optical recording medium, characterized in that the medium is formed of an alloy whose main components are: 8. The method of manufacturing a magneto-optical recording medium according to claim 7, wherein the alloy is an amorphous alloy.