JP2004006051A - Recording method of information - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording method using a magneto-optic recording medium and which enables the overwrite of information by a magnetic field intensity modulation system. <P>SOLUTION: The magneto-optical recording medium with a recording layer composed of a perpendicular magnetized film and an auxiliary magnetic film having spontaneous magnetization and having a magnetic property in which a squareness ratio of an M-H loop changes from a state of 1 to an intermediate state between 1 and 0 at a temperature below a Curie temperature in the case of warm-up is used. The overwrite of the information is performed by the magnetic field intensity modulation system while warming the magneto-optic recording medium. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a method for recording information, and more particularly, to a method for recording information using a magneto-optical recording medium.

An information recording system using a magneto-optical recording medium enters the stage of practical use, and the overwrite function, that is, when rewriting new information in an area where information is recorded, after erasing previously recorded information once, Development of a magneto-optical recording medium having a function of erasing previously recorded information while simultaneously recording new information, instead of writing new information, has become an increasingly important technical issue.

At present, as an overwrite recording method for a magneto-optical recording medium, an external magnetic field having a constant intensity is applied to the magneto-optical recording medium while the binary information signal corresponds to "0" or "1". A light intensity modulation method of recording information by scanning a pulse-like intensity-modulated light for recording has attracted the most attention. Examples of a magneto-optical recording medium that enables overwrite recording by a light intensity modulation method include those described in JP-A-62-175948, and those described in, for example, International Publication No. WO90 / 02400. There is.

In the magneto-optical recording medium, information is recorded by forming a demagnetization domain (magnetization domain) corresponding to the information signal in a magnetic layer carried on the substrate, and the information is thus recorded on the magnetic layer on which the information is recorded. Information is reproduced by utilizing the fact that the Kerr rotation angle of reflected light changes depending on the direction of magnetization of the magnetic layer when linearly polarized light is irradiated. There are a so-called light intensity modulation method and a magnetic field intensity modulation method for forming a reversal magnetic domain in the magnetic layer. In any of these methods, the temperature of the magnetic layer must be raised to near or above the Curie temperature. . The magneto-optical recording medium is an erasable type information recording medium capable of repeatedly performing erasure and re-recording of information. Even when erasing information, the temperature of the magnetic layer is raised to near the Curie temperature or higher. I have to do it. Conventionally, the temperature of the magnetic layer is raised by focusing a laser beam on the magnetic layer.

Since the magneto-optical recording medium records and erases information by raising the temperature of the magnetic layer to a predetermined temperature, in order to obtain a desired data transfer speed, the Curie temperature of the magnetic layer, the magnetic layer The thermal conductivity of the portion in contact with the magnetic layer, the intensity of the laser beam applied to the magnetic layer, and the linear velocity of the laser beam spot traveling on the magneto-optical recording medium must be set in a well-balanced manner.

A 5-inch magneto-optical disk, which has been put into practical use, is mounted on a magneto-optical disk drive on which a semiconductor laser of 30 to 40 mW is mounted, is rotated at 2400 rpm (constant angular velocity), and has a linear velocity of a laser beam spot. The Curie temperature of the magnetic layer and the thermal conductivity of the portion in contact with the magnetic layer are set so that information can be recorded and erased in an optimal state in the outermost recording area where the magnetic field is highest (150 m / s). In addition, as a related art related thereto, for example, JP-A-56-4090, JP-A-56-54070, JP-A-57-120253, JP-A-57-169996 and the like are listed. be able to.

Conventionally, for example, as described on page 52 of “Easy-to-understand optical disk”, Optronics Co., Ltd., issued December 10, 1985, the transparent substrate and the recording surface of two magneto-optical recording There is known a magneto-optical recording medium having a so-called close-adhesion bonding structure in which the recording medium is bonded via an adhesive. In addition, the inner and outer peripheries of the two optical recording single-plate transparent substrates are bonded via a spacer coated with an adhesive, and an air layer is interposed between the opposing recording surfaces. 2. Description of the Related Art A magneto-optical recording medium having an air sandwich structure is known.

The optical recording veneer is one in which one or more thin films including at least a recording layer or a reflective layer are applied to the preformat pattern forming surface of the substrate, and the transparent substrate is, for example, a transparent ceramic material such as glass or the like. , A transparent plastic material such as polymethyl methacrylate, polymethyl pentene, epoxy, and photocurable resin. On the other hand, polymer adhesives such as adhesives for bonding these optical recording veneers and epoxy adhesives have been awarded prizes.

Further, in this type of optical information recording medium, a transparent thin layer such as an oxide and a nitride is conventionally provided between a transparent substrate and a magneto-optical recording film to serve as an optical multiple interference film and a protective film. Various studies have been conducted to make it work.
JP-A-62-175948 International Publication WO90 / 02400 pamphlet

By the way, in order to realize the overwriting of information, the external magnetic field sensitivity of the magneto-optical recording film must be sufficiently high regardless of whether the light intensity modulation method or the magnetic field intensity modulation method is used. Among the known examples of the magneto-optical recording medium applied to the above-described optical modulation type overwrite recording, the former is such that an auxiliary magnetic film having spontaneous magnetization is laminated on a magneto-optical recording film which is a perpendicular magnetization film. The external magnetic field sensitivity at the time of recording or erasing can be increased as compared with the case of the film alone.

However, even in this case, an external magnetic field of 200 (Oe) or more is required at the time of recording or erasing, and it cannot be said that the external magnetic field sensitivity is sufficiently high for practical use. Further, since the magneto-optical recording film and the auxiliary magnetic film are directly laminated, the exchange coupling force acting between the two films becomes considerably larger than expected. Up to 6 (KOe) initialization magnets are required. Further, there is a problem that the recording magnetic domains are apt to disappear in proportion thereto.

In the magneto-optical recording medium, increasing the data transfer speed is one of the most important technical issues. In order to increase the data transfer speed, the linear velocity of the laser beam spot with respect to the magneto-optical recording medium (for example, the rotation speed of the magneto-optical disk) must be increased, but the linear velocity of the laser beam spot is increased. Then, the irradiation time of the laser beam is shortened and the temperature of the magnetic layer is hardly increased, so that there is a technical problem of either improving the recording sensitivity of the magneto-optical recording medium or increasing the output of the semiconductor laser. Need to be resolved.

In a magneto-optical recording medium having a laminated structure, an inorganic filler is mixed into the adhesive layer to prevent moisture from entering the medium and prevent corrosion of the recording layer or the reflective layer. The moisture content is often reduced, but also in this case, there is a problem that the reactivity between the inorganic filler and the adhesive is poor, so that peeling is likely to occur and the long-term storage property is poor.

Further, in a magneto-optical recording medium in which an oxide layer is formed by a vapor deposition method or a sputtering method, the oxide layer becomes chemically unstable, oxygen is easily released, and the released oxygen is used for magneto-optical recording. The film gradually diffuses into the film, and as a result, the magneto-optical recording film is oxidized, and the recording, reproducing and erasing characteristics of information are deteriorated.

On the other hand, since the oxide layer has low adhesion to a transparent substrate made of synthetic resin such as polycarbonate, when used as an underlayer of a magneto-optical recording film, peeling occurs between the transparent substrate and the underlayer for a long time, and the data The function as storage decreases. For this reason, the conventional magneto-optical recording medium has a problem in reliability.

The present invention has been made in order to solve such a problem, and a first object of the present invention is to provide an information recording and reproducing apparatus using a magneto-optical recording medium capable of recording and reproducing information with an inexpensive and simple head device. It is to provide a recording method.

A second object is to provide a magneto-optical recording medium capable of reducing the size of the initialization magnet and realizing stable recording.

(3) A third object is to provide a magneto-optical recording medium capable of further increasing the data transfer speed by using a semiconductor laser of about 30 to 40 mW which has been practically used conventionally.

(4) A fourth object is to provide a new optical disc which solves the above-mentioned problem caused by a mixture of a ROM area and a rewritable area.

(5) A fifth object is to provide a magneto-optical recording medium having excellent long-term storage characteristics, in which optical recording veneers or optical recording veneers and a protective plate are firmly bonded via an adhesive layer.

(6) A sixth object is to provide a magneto-optical recording medium that prevents oxygen from entering the magneto-optical recording film from the oxide layer and has excellent reliability and durability.

The present invention provides a method for recording information on a magneto-optical recording medium having a recording layer comprising a perpendicular magnetization film on a substrate, wherein the magneto-optical recording medium comprises at least the recording layer and An auxiliary magnetic film having spontaneous magnetization, wherein the medium has a magnetic characteristic in which the squareness ratio of the MH loop changes from a state of 1 to an intermediate state of 1 and 0 at a temperature lower than the Curie temperature when the temperature rises. The method is characterized in that information is overwritten by a magnetic field intensity modulation method while increasing the temperature of the information.

Further, according to the present invention, in order to achieve the first and second objects, as the magneto-optical recording medium, a light capable of recording and reproducing information by applying an external magnetic field of 100 (Oe). It is characterized by using a magnetic recording medium.

Further, according to the present invention, in order to achieve the first and second objects, as the magneto-optical recording medium, an external magnetic field of 50 (Oe) is applied in the recording direction so that the reproduction CN ratio reaches a saturation value. It is characterized by using a magnetic recording medium.

A magneto-optical recording film comprising a rare earth-transition metal based perpendicular magnetic film, wherein the MH loop squareness ratio changes from 1 to an intermediate state between 1 and 0 at a temperature lower than the Curie temperature when the temperature is raised; A magneto-optical recording medium comprising an auxiliary magnetic film having a rare earth-transition metal system in which the square ratio of the MH loop does not change from a state of 1 to an intermediate state of 1 and 0 at a temperature lower than the Curie temperature when the temperature is raised. As compared with a magneto-optical recording medium comprising a magneto-optical recording film composed of a perpendicular magnetic film and an auxiliary magnetic film having spontaneous magnetization, the magnetization direction of the auxiliary magnetic film with a smaller external magnetic field, and thus the magneto-optical recording film The direction of magnetization can be switched upward or downward. Therefore, overwrite recording by the magnetic field intensity modulation method, which has conventionally been considered difficult to commercialize, becomes possible.

The first and second examples of the magneto-optical recording film using a transition metal-rich ferrimagnetic material near the Curie temperature and a rare-earth-rich ferrimagnetic material near the Curie temperature will be described below. The operation of the means configured to achieve the above object will be described in more detail.

(4) A rare earth-transition metal amorphous alloy exhibits ferrimagnetism as a magnetic property in which the partial magnetizations of a rare earth (heavy rare earth metal) and a transition metal are antiparallel. In other words, the direction of magnetization of the entire medium is observed as a difference between the partial magnetization of the rare earth and the partial magnetization of the transition metal, and depending on the magnitude relation between the partial magnetizations, the direction of the entire magnetization may be the partial magnetization direction of the rare earth. (RE-rich) or the partial magnetization direction of the transition metal (TM-rich). In addition, since the partial magnetization of the rare earth is more dependent on temperature than the partial magnetization of the transition metal, the magnetization direction is reversed between room temperature and a specific temperature at which magnetization is lost (Curie temperature) depending on the composition of the alloy. It may have a compensation temperature or may not have this compensation temperature. Further, the coercive force of the medium also changes depending on the magnitude relation of the partial magnetization. In the case of TM-rich at room temperature, the coercive force of the medium gradually decreases as the temperature rises from room temperature, and the coercive force decreases at the Curie temperature. lose. On the other hand, in the case of the RE-rich at room temperature, a magnetic compensation point at which the coercive force diverges infinitely between the room temperature and the Curie temperature appears, and at a temperature lower than the magnetic compensation point, the RE-rich and the magnetic compensation point appear. At higher temperatures, some may become TM-rich.

Before the external magnetic field is applied, the magnetization of the noble metal-transition metal based auxiliary magnetic film is oriented in an in-plane direction (a direction parallel to the film surface of the auxiliary magnetic film), and the temperature is raised to near the Curie temperature. When the external magnetic field is applied in the state, the magnetization direction rises from the in-plane direction to generate a magnetic moment component in the external magnetic field direction. When the external magnetic field is removed, the direction of the magnetization returns to the in-plane direction again.

Hereinafter, the principle of signal overwriting in a magneto-optical recording medium in which this auxiliary magnetic film is laminated on a magneto-optical recording film made of a TM-rich ferrimagnetic material at least near the Curie temperature will be described with reference to FIG. I do. In this figure, reference numeral 4 denotes a magneto-optical recording film, and reference numeral 5 denotes an auxiliary magnetic film. The white arrow in the magneto-optical recording film 4 indicates a rare earth partial magnetization, and the solid arrow indicates a transition metal partial magnetization. Is shown. The length of each arrow represents the magnitude of each partial magnetization.

When the state shown in FIG. 73 (1) is an erased state and the state shown in FIG. 73 (2) is a recorded state, a portion of the erased state shown in FIG. When the external magnetic field H is applied upward (positive direction) while the temperature of the magneto-optical recording film 4 is raised to near the Curie temperature, the direction of the magnetization of the auxiliary magnetic layer 5 rises upward from the in-plane direction, and the external magnetic field is increased. A directional magnetic moment component is produced. As a result, the exchange coupling energy with the partial magnetization of the transition metal in the magneto-optical recording film 4 gradually increases, and when an external magnetic field having a specific magnitude is applied, the exchange coupling energy in the magneto-optical recording film 4 is reduced. The state shown in FIG. 73 (3) in which the partial magnetization of the transition metal is inverted upward and the overall magnetization M is positive. When the external magnetic field H is removed from this state and the auxiliary magnetic film 5 and the magneto-optical recording film 4 are cooled, the direction of magnetization of the auxiliary magnetic film 5 returns to the in-plane direction, and the direction of magnetization of the magneto-optical recording film 4 becomes It is stored upward (the state of FIG. 73 (2)). In addition, an external magnetic field H is applied upward while the auxiliary magnetic layer 5 and the magneto-optical recording film 4 are heated to near the Curie temperature by irradiating a laser beam of a constant intensity to the portion in the recording state of FIG. 73 (2). In this case, no change occurs because the magnetization of the magneto-optical recording film 4 is originally upward. As described above, recording is performed by performing the above operation regardless of the magnetization state of the magneto-optical recording film 4 in the initial state.

On the other hand, the portion in the recording state shown in FIG. 73 (2) is irradiated with a laser beam of a constant intensity to raise the auxiliary magnetic layer 5 and the magneto-optical recording film 4 to near the Curie temperature, and to lower the external magnetic field in the negative direction. As H is applied, the direction of magnetization of the auxiliary magnetic layer 5 rises downward from the in-plane direction to generate a magnetic moment component in the direction of the external magnetic field. As a result, the exchange coupling energy with the partial magnetization of the transition metal in the magneto-optical recording film 4 gradually increases, and when an external magnetic field having a specific magnitude is applied, the exchange coupling energy in the magneto-optical recording film 4 is reduced. The partial magnetization of the transition metal is inverted upward, and the entire magnetization M becomes negative. When the external magnetic field H is removed from this state and the auxiliary magnetic film 5 and the magneto-optical recording film 4 are cooled, the direction of magnetization of the auxiliary magnetic film 5 returns to the in-plane direction, and the direction of magnetization of the magneto-optical recording film 4 becomes It is stored upward (the state of FIG. 73 (1)). In addition, an external magnetic field H is applied downward while irradiating a laser beam of a constant intensity to the erased portion of FIG. 73 (1) to raise the temperature of the auxiliary magnetic layer 5 and the magneto-optical recording film 4 to near the Curie temperature. In this case, no change occurs because the magnetization of the magneto-optical recording film 4 is originally downward. As described above, erasing is performed by performing the above operation regardless of the magnetization state of the magneto-optical recording film 4 in the initial state.

As shown in FIG. 73, in the magneto-optical recording medium in which the auxiliary magnetic film 5 and the magneto-optical recording film 4 are laminated, the optical coupling medium acting between the two films causes the optical magnetic recording medium to have a single layer of magneto-optical recording film. The magnitude of the external magnetic field H causing the magnetization reversal is much smaller than that of the magnetic recording medium. Therefore, the magneto-optical recording medium shown in the first means can perform overwrite recording by a magnetic field intensity modulation method using a small external magnetic field. In the above description, a magneto-optical recording medium that is TM-rich at room temperature has been described as an example. However, a magneto-optical recording medium that is also RE-rich at room temperature and has a compensation point between room temperature and Curie temperature is described. Can perform signal overwriting on the same principle. In the above description, the state of FIG. 73 (1) is the erased state, and the state of FIG. 73 (2) is the recording state. Conversely, the state of FIG. 73 (1) is the recording state, and the state of FIG. , The signal can be overwritten based on the same principle as described above by reversing the application direction of the external magnetic field H.

Next, based on FIG. 74 to FIG. 76, at least in the vicinity of the Curie temperature, signal overrun in the magneto-optical recording medium in which the auxiliary magnetic film 5 is laminated on the magneto-optical recording film made of the RE-rich ferrimagnetic material. The write principle will be described. The meanings of the reference numerals in this figure are the same as those in FIG.

This magneto-optical recording medium shows an MH loop as shown in FIG. 74 up to a certain temperature To which is equal to or lower than the Curie temperature Tc, but in a temperature range from the temperature To to the Curie temperature Tc, FIG. Shows the MH loop as shown. When the state of FIG. 75 (1) is the erased state and the state of FIG. 75 (2) is the recorded state, the medium temperature in the erased state of FIG. 75 (1) is such that To <T ₁ <Tc. When an external magnetic field H is applied upward (positive direction) while irradiating an intense laser beam, the direction of magnetization of the auxiliary magnetic film 5 rises upward from the in-plane direction, and a magnetic moment component in the external magnetic field direction is generated. . As a result, the exchange coupling energy with the partial magnetization of the transition metal in the magneto-optical recording film 4 gradually increases, and at the stage where an external magnetic field Hc ₁ having a certain magnitude is applied, The state shown in FIG. 75 (3) is obtained in which the partial magnetization of the middle transition metal is inverted upward, the partial magnetization of the rare earth element is downward, and the overall magnetization M is downward. When the auxiliary magnetic film 5 and the magneto-optical recording film 4 are cooled and the external magnetic field H is removed from this state, the magnetization direction of the auxiliary magnetic film 5 returns to the in-plane direction, and the magnetization direction of the magneto-optical recording film 4 is changed. Is stored in the downward direction (the state of FIG. 75 (2)).

When a stronger external magnetic field H is applied upward from the state shown in FIG. 75 (3), when the external magnetic field Hc ₂ having a specific magnitude is applied, the auxiliary magnetic layer 5 and the magneto-optical recording film 4 are not connected. The energy of the interaction between the external magnetic field H and the magneto-optical recording film 4 is larger than the energy corresponding to the exchange coupling force stored in the interface magnetic wall between the magnetic layers, and the partial magnetization of the auxiliary magnetic layer 5 is completely reduced. Along with the direction of the external magnetic field, the partial magnetization of the rare earth of the magneto-optical recording film 4 is inverted upward, and the state shown in FIG. When the auxiliary magnetic film 5 and the magneto-optical recording film 4 are cooled and the external magnetic field H is removed from this state, the direction of the magnetization of the auxiliary magnetic film 5 returns to the in-plane direction, and the auxiliary magnetic layer 5 and the magneto-optical recording film are again formed. 4, the energy corresponding to the exchange coupling force stored in the interface domain wall becomes larger than the energy of the interaction between the external magnetic field H and the magneto-optical recording film 4. The partial magnetization of the rare earth is inverted downward, and the state shown in FIG. When a large external magnetic field H is applied to the portion in the recording state of FIG. 75 (2), the state of FIG. 75 (4) is once obtained in the same manner as described above, but the auxiliary magnetic film 5 and the magneto-optical recording are performed. When the film 4 is cooled and the external magnetic field H is removed, the state returns to the original state of FIG. 75 (2). As described above, recording is performed by performing the above operation regardless of the magnetization state of the magneto-optical recording film 4 in the initial state.

Further, an external magnetic field H is applied upward (positively) while irradiating a laser beam having an intensity such that the medium temperature satisfies T ₁ <T ₂ <Tc to the portion in the erased state in FIG. 75 (1 ′). Then, the direction of magnetization of the auxiliary magnetic layer 5 rises upward from the in-plane direction to generate a magnetic moment component in the direction of the external magnetic field. As a result, the exchange coupling energy with the partial magnetization of the transition metal in the magneto-optical recording film 4 gradually increases, and when the external magnetic field Hc ₁ ′ having a specific magnitude is applied, the magneto-optical recording film 4 In FIG. 75 (3 ′), the partial magnetization of the transition metal in No. 4 is inverted upward, the partial magnetization of the rare earth element is lowered, and the entire magnetization M is lowered. When a stronger external magnetic field H is applied upward from the state of FIG. 75 (3 ′), when the external magnetic field Hc ₂ ′ having a specific magnitude is applied, the auxiliary magnetic layer 5 and the magneto-optical recording film 4 The energy of the interaction between the external magnetic field H and the magneto-optical recording film 4 is larger than the energy corresponding to the exchange coupling force stored in the interface magnetic wall between the magnetic layers, and the partial magnetization of the auxiliary magnetic layer 5 is completely reduced. Along with the direction of the external magnetic field, the rare-earth partial magnetization of the magneto-optical recording film 4 is inverted upward, and the state shown in FIG. When the auxiliary magnetic film 5 and the magneto-optical recording film 4 are cooled and the external magnetic field H is removed from this state, the direction of magnetization of the auxiliary magnetic film 5 returns to the in-plane direction, and the partial magnetization of the magneto-optical recording film 4 is reduced. It is quenched in the state of FIG. 75 (4 ′), and jumps to the erased state of FIG. 75 (1 ′) by jumping the broken line part of FIG. 75. Also, when a large external magnetic field H is applied to the portion in the recording state of FIG. 75 (2 ′), the state is once changed to that of FIG. 75 (4 ′), and the external magnetic field H is removed and the auxiliary magnetic field is removed. At the stage when the film 5 and the magneto-optical recording film 4 are cooled, the portion indicated by the broken line in FIG. 75 is jumped to return to the erased state in FIG. As described above, erasing is performed by performing the above operation regardless of the magnetization state of the magneto-optical recording film 4 in the initial state.

As shown in FIG. 75, the magnitude Hc ₂ ′ of the external magnetic field that causes the magnetization reversal in the magneto-optical recording film 4 at a high temperature (at T ₂ ) decreases the coercive force of the magneto-optical recording film 4 due to the high temperature. Therefore, the magnitude of the external magnetic field Hc ₂ that causes the magnetization reversal in the magneto-optical recording film 4 at a low temperature (at T ₁ ) is smaller. That is, since Hc ₂ ′ <Hc ₂ , the external magnetic field H ₁ is adjusted to Hc ₂ ′ <H ₁ <Hc ₂ and the temperature of the auxiliary magnetic layer 5 and the magneto-optical recording film 4 is raised to the temperature T _1. adjust the low level of the power of the laser beam so that, by adjusting the high level of the power of the laser beam so as to raise the temperature of the auxiliary magnetic layer 5 and the magneto-optical recording film 4 to a temperature T _2, the initial magnetic field Overwrite recording by an unnecessary light intensity modulation method can be performed.

The external magnetic field H ₁ , the low-level power of the laser beam, and the high-level power of the laser beam required to realize the above-described overwrite recording can be obtained as follows. First, the low-level power and the high-level power of the laser beam are appropriately set so that T ₀ <T ₁ <T ₂ <T _c . Next, signal recording is performed by variously changing the magnitude of the external magnetic field H and the application direction. When a signal is read from the signal recording section and a correlation diagram between the external magnetic field H and the output value of the reproduction signal is drawn, the graphs of FIGS. 76 (a) and 76 (b) are obtained. Here, the magnitude of the external magnetic field H at which the signal can be recorded at the temperature T ₁ and the signal cannot be recorded at the temperature T ₂ depends on the magnitude of the external magnetic field H ₁ required to realize the overwrite recording of the signal. Size. The value of the external magnetic field _{H 1} is varied by the temperature _T 1, _{T 2.} Therefore, the above test is repeated while variously changing the low-level power and the high-level power of the laser beam and variously changing the temperatures T ₁ and T ₂ to select an optimal laser beam.

In order to realize the overwrite recording as described above, it is preferable that the difference between the Curie temperature of the auxiliary magnetic film 5 and the Curie temperature of the magneto-optical recording film 4 is regulated to 150 ° C. or less. Is preferably as small as possible. In the above description, the states of FIGS. 75 (1) and (1 ′) are set to the erased state, and the states of FIGS. 75 (2) and (2 ′) are set to the recording state. Even if the state of (1 ′) is a recording state and the states of FIGS. 75 (2) and (2 ′) are an erasing state, by applying the external magnetic field H in the opposite direction, the same principle as described above can be obtained. , The signal can be overwritten.

As described above, the present invention is composed of a rare earth-transition metal based perpendicular magnetic film, and when the temperature rises, the MH loop squareness ratio changes from 1 to an intermediate state between 1 and 0 at a temperature lower than the Curie temperature. Since a magneto-optical recording medium including a changing magneto-optical recording film and an auxiliary magnetic film having spontaneous magnetization is used, the squareness ratio of the MH loop changes from 1 to 1 at a temperature lower than the Curie temperature when the temperature is raised. Compared to a magneto-optical recording medium having a rare-earth-transition metal-based perpendicular magnetic film that does not change to an intermediate state of 0 and an auxiliary magnetic film having spontaneous magnetization, the auxiliary magnetism is reduced with a smaller external magnetic field. The direction of the magnetization of the film, and hence the direction of the magnetization of the magneto-optical recording film, can be switched upward or downward, and overwrite recording by the magnetic field intensity modulation method, which has conventionally been considered difficult to put into practical use, becomes possible.

例 Hereinafter, an embodiment that embodies means for achieving the first and second objects will be described.

The magneto-optical recording medium according to the first embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a main part of a magneto-optical recording medium according to the present embodiment. As shown in FIG. 1, the magneto-optical recording medium according to the present embodiment includes a transparent substrate 1 on which a preformat pattern 2 is formed. From the side, an enhancement film 3 made of an inorganic dielectric having a higher refractive index than the transparent substrate 1, a magneto-optical recording film 4, an auxiliary magnetic film 5, and a protective film 6 are sequentially laminated.

The transparent substrate 1 is formed in a desired shape such as a disk shape or a card shape by using a transparent substrate such as a plastic material such as polycarbonate, polymethyl methacrylate, polyolefin, or epoxy, or glass.

On one surface of the transparent substrate 1, a guide groove for guiding a laser spot and a preformat pattern 2 composed of a pre-pit row indicating the address of a recording track defined along the guide groove are formed in fine irregularities. Then, the tracking servo signal and the preformat signal can be optically read. In FIG. 1, the preformat pattern 2 is directly formed on one surface of the transparent substrate 1, but a photocurable resin layer having a refractive index similar to that of the transparent substrate is formed on one surface of the transparent substrate formed in a flat plate shape. And the preformat pattern 2 can be transferred to the surface of the photocurable resin layer.

The enhancement film 3 is provided for causing a reproduction light beam to cause multiple interference between the magneto-optical recording film 4 and the transparent substrate 1 to increase an apparent Kerr rotation angle, and is made of silicon, aluminum, zirconium. , Titanium, tantalum nitride, oxide, or the like, and is made of an inorganic dielectric material having a refractive index larger than that of the transparent substrate 1, and is formed to a thickness of 600 to 1000 °. As a means for forming the enhanced film 3, sputtering is particularly suitable.

(4) The magneto-optical recording film 4 is formed of a rare earth-transition metal based amorphous perpendicular magnetization film having ferrimagnetism. As the rare earth-transition metal amorphous perpendicular magnetization film, a film represented by the following general formula is particularly preferable.

General formula; Tb _x Fe _(100-x-y-z) Co _Y M _Z
However, 15 atomic% ≦ x ≦ 30 atomic%
5 atomic% ≦ y ≦ 15 atomic%
0 atomic% ≦ x ≦ 10 atomic%
M is at least one element selected from Nb, Cr, and Pt.

垂直 By changing the composition of the perpendicular magnetization film variously, it can be made a TM-rich film or a RE-rich film at least immediately below the Curie temperature. This perpendicular magnetization film is formed to a thickness of 200 to 500 ° by sputtering a target formed of an alloy of Tb, Fe, Co, and the additional element M, or a sintered body containing these elements. .

(4) The auxiliary magnetic film 5 is formed of a material having a reflectance to light for reproduction of 70% or more and a thermal conductivity at room temperature in a range of 0.05 to 2.0 W / cm · deg. The thickness is suitably in the range of 200 to 400 °. That is, in the magneto-optical recording medium of this example, the reproducing light transmitted through the magneto-optical recording film 4 is returned to the transparent substrate 1 side by the auxiliary magnetic film 5 so that the incident light and the return light pass through the magneto-optical recording film 4. One of the features is to increase the apparent Kerr rotation angle by the Faraday effect to improve the reproduction CN ratio, so that the higher the reflectance to the reproduction light, the better the result. It is more preferable to have a reflectance of at least 70% with respect to the reproduction light.

If the thermal conductivity of the auxiliary magnetic film 5 is too low, the magneto-optical recording layer 4 is excessively heated during recording or erasing of information, and the magneto-optical recording layer 4 is deteriorated (for example, (Eg, the crystalline perpendicular magnetization film is crystallized), and the preformat pattern 2 of the transparent substrate 1 is likely to be deformed, resulting in a disadvantage that the reproduction output level is reduced within a short period of time. On the other hand, if the thermal conductivity of the auxiliary magnetic film 5 is too high, it is difficult to raise the temperature of the magneto-optical recording layer 4 to a temperature required for recording or erasing information, and the recording sensitivity is reduced, Since recording / reproducing errors due to remaining data increase, a disadvantage arises when a high power laser light source must be mounted.

Figure 2 shows the thermal conductivity of the auxiliary magnetic film 5, a decrease in the reproduction output after repeating recording / erasing operation 10 ⁴ times, and the relation between the laser power required for recording / erasing of information. As is apparent from this graph, the thermal conductivity as the auxiliary magnetic film 5 is used as follows 0.05 W / cm · deg, the reproduction output after repeated recording / erasing operation 10 ⁴ times decreases abruptly It turns out that it is not practical. If the auxiliary magnetic film 5 has a thermal conductivity of 2.0 W / cm.deg or more, a laser power of 10 mW (film surface) or more is required for recording / erasing information, which also makes practical use difficult. You can see that. From these data, the thermal conductivity of the auxiliary magnetic film 5 is determined within the above range.

Specific examples of the auxiliary magnetic film 5 include at least one element selected from a noble metal element group such as Pt, Al, Ag, Au, Cu, and Rh, and a transition metal element group such as Fe, Co, and Ni. Alloy thin film with at least one type of element. By adjusting the composition of the noble metal-transition metal based auxiliary magnetic film, the magnetization is oriented in an in-plane direction (a direction parallel to the film surface of the auxiliary magnetic film) before an external magnetic field is applied. When an external magnetic field is applied while the temperature is raised to near the Curie temperature, the direction of magnetization rises from the in-plane direction to generate a magnetic moment component in the direction of the external magnetic field. One that returns to the direction can be made. Therefore, the magnitude of the external magnetic field required for completely erasing the recorded signal varies depending on the content ratio of the auxiliary magnetic film 5 of this type, even if the constituent elements are the same.

{FIG. 3 shows the relationship between the Pt content in the thin film and the magnetic field in the erasing direction, taking a CoPt alloy thin film as an example (the film thickness is 200). Here, the erasing direction magnetic field is a minimum magnetic field at which recording cannot be performed when information is recorded while applying an external magnetic field in the erasing direction, and is an external magnetic field required to completely erase a recorded signal. Represents the size of As is clear from FIG. 3, the CoPt alloy thin film has a Pt content at which the magnetic field in the erasing direction is minimized. At the request of the drive, the external magnetic field that can be mounted on the drive is at most 300 [Oe]. In order to completely erase the recorded signal by this external magnetic field, the Pt content of the CoPt alloy thin film must be 60 to 95%. It is understood that it is necessary to adjust to atomic%.

The protective layer 6 is formed of the same inorganic dielectric as that of the enhance layer 3 or an organic material such as a photocurable resin. When an inorganic dielectric is used as a protective layer material, it is formed to a thickness of 500 to 2000 °.

(4) Hereinafter, an experimental example and a comparative example of the magneto-optical recording medium according to the first embodiment will be described, and the recording / erasing characteristics of both will be compared.

<Experimental example 1>
On the preformat pattern forming surface of the injection-molded polycarbonate substrate, an SiON enhancement layer of 800 °, a Tb ₁₈ Fe ₆₇ Co ₁₀ Cr ₅ amorphous perpendicular magnetization film of 500 °, and a Pt ₈₀ Co ₂₀ auxiliary magnetic film of 200 ° A 1000 ° SiON protective layer was sequentially sputtered to produce the magneto-optical recording medium shown in FIG. Here, the Pt ₈₀ Co ₂₀ auxiliary magnetic film has a component in a direction perpendicular to the film surface just below the Curie temperature of the auxiliary magnetic film, and the magnetic moment is rotated by the applied external magnetic field, so that the Pt ₈₀ Co ₂₀ auxiliary magnetic film rotates in the external magnetic field direction. In addition, a component is generated and an exchange coupling force is exerted on the magneto-optical recording film, and the reflectance with respect to light for reproduction is 70% or more. Furthermore, since the film thickness was adjusted to 200 °, the thermal conductivity at room temperature was 0.05 to 2.0 W / cm · deg. On the other hand, the Tb ₁₈ Fe ₆₇ Co ₁₀ Cr ₅ amorphous perpendicular magnetization film is TM-rich immediately below the Curie temperature of the magneto-optical recording film, and the magnetic moment of the auxiliary magnetic film is reduced by applying an external magnetic field. When there is a component in the direction of the external magnetic field, the exchange coupling force acts between the magnetic moment of the partial magnetization of the transition metal of both films and the direction of the magnetization of the magneto-optical recording film is directed to the direction of the external magnetic field. Has become something.

<Comparative Example 1>
On the preformat pattern forming surface of the injection-molded polycarbonate substrate, an 800 ° SiON enhancement layer, a 500 ° Tb ₁₈ Fe ₆₇ Co ₁₀ Cr ₅ amorphous perpendicular magnetization film, and a 1000 ° SiON protective layer are sequentially sputtered. Then, the magneto-optical recording medium shown in FIG.

FIG. 5 shows the recording / erasing characteristics of the magneto-optical recording medium according to Experimental Example 1 and the recording / erasing characteristics of the magneto-optical recording medium according to Comparative Example 1. The recording / erasing characteristics referred to herein means a change in the reproduction CN ratio when the magnitude and direction of the external magnetic field applied at the time of recording are changed. The horizontal axis in FIG. 5 indicates the magnitude of the external magnetic field applied at the time of recording. The height and the direction are graduated, and the vertical axis represents the reproduced CN ratio.

As is clear from this figure, in the magneto-optical recording medium of Comparative Example 1, the reproduction CN ratio does not reach the saturation value unless an external magnetic field of about 500 [Oe] is applied in the recording direction. In the magneto-optical recording medium, the reproduction CN ratio reaches a saturation value only by applying an external magnetic field of about 50 [Oe] in the recording direction. This indicates that the magneto-optical recording medium of Experimental Example 1 can perform perfect recording with a smaller external magnetic field. In the magneto-optical recording medium of Comparative Example 1, the reproduction CN ratio cannot be made zero unless an external magnetic field of about 620 [Oe] is applied in the erasing direction. Can make the reproduction CN ratio zero by simply applying an external magnetic field of about 80 [Oe] in the erasing direction. This indicates that the magneto-optical recording medium of Experimental Example 1 can perform complete erasure with a smaller external magnetic field. As described above, the magneto-optical recording medium of Experimental Example 1 can record and reproduce information with a small external magnetic field of about 100 [Oe]. Overwriting by the method is possible. The saturation value of the reproduction CN ratio is substantially the same for both the magneto-optical recording medium of Experimental Example 1 and the magneto-optical recording medium of Comparative Example 1, indicating that the medium has a sufficiently high CN ratio. .

In the first embodiment, the enhancement film 3 is interposed between the transparent substrate 1 and the magneto-optical recording film 4. However, the auxiliary magnetic film 5 has a high reflectance, and a sufficient reproduction CN ratio can be obtained. In this case, this can be omitted.

In the first embodiment, the protective film 6 is provided on the outermost surface of the medium. However, when the auxiliary magnetic film 5 is excellent in corrosion resistance, it can be omitted.

Further, in the first embodiment, the auxiliary magnetic film 5 is directly deposited on the back side of the magneto-optical recording film 4, but between the magneto-optical recording film 4 and the auxiliary magnetic film 5, the enhancement film 3 and the auxiliary magnetic film 5 are disposed. A second enhanced film made of a similar inorganic dielectric can also be provided.

A magneto-optical recording medium according to the second embodiment will be described with reference to FIGS. As shown in FIG. 6, in the magneto-optical recording medium of this embodiment, a heat control layer 8 serving also as a reflective film and a protective film is laminated on the surface of the auxiliary magnetic film 5 instead of the protective layer 6 in the first embodiment. It is characterized by having done. The other parts are the same as those of the magneto-optical recording medium of the first embodiment, and the corresponding parts are denoted by the same reference numerals and description thereof will be omitted.

The thermal control layer 8 includes at least one metal element selected from the group of [Al, Ag, Au, Cu, Be] elements and [Cr, Ti, Ta, Sn, Si, Rb, Pe, Nb, Mo, [Li, Mg, W, Zr] element group. In particular, those made of an AlTi alloy containing 6 to 10 atomic% of Ti and having a film thickness regulated in the range of 500 to 1000 ° are preferable.

When a TbFeCo alloy is used as the material of the magneto-optical recording film 4, the temperature of the film in the laser light irradiation region is set to 200 ° C. or more at the time of recording or erasing information, since the alloy has the Curie point of about 200 ° C. It is necessary to raise the temperature. When the magneto-optical recording film 4 reaches its thermal state by the recording laser light, the center of the laser light irradiation reaches the highest temperature in the film. That is, as shown in FIG. 7, for example, when a recording pit having a fixed size (for example, a diameter of 0.8 μm) is to be formed, it is necessary to heat the inside of the diameter to 200 ° C. or more. That is, a circumferential line having a diameter of 0.8 μm becomes an isotherm of 200 ° C., and the inner part thereof is necessarily at 200 ° C. or higher.

、 At this time, a difference occurs in the temperature at the center of the laser beam irradiation due to the thermal conductivity of the thermal control layer 8. The curve shown in the figure is a curve schematically showing the temperature distribution. The dotted curve B is the case where the thermal control layer 8 having relatively good thermal conductivity is used, and the solid curve A is the thermal control having relatively poor thermal conductivity. 7 is a characteristic curve when a layer 8 is used. As is apparent from this figure, the difference in the thermal conductivity of the thermal control layer 8 causes a difference in the temperature at the central portion in the laser beam irradiated portion. In other words, the maximum temperature of the magneto-optical recording film 4 can be controlled by the thermal conductivity (thermal conductivity, film thickness, etc.) of the thermal control layer 8.

As described above, using a TbFeCo alloy as the magneto-optical recording film and using an AlTi alloy as the metal protective film, the results of examining the dependence of the Ti content in the thermal control layer on the maximum temperature of the magneto-optical recording film are shown. FIG.

横 The horizontal axis in the figure shows the Ti content in the AlTi alloy, and the vertical axis shows the temperature at the center of the laser beam irradiated part. The central temperature is the central temperature when the area where the film surface temperature is 200 ° C. or more has a diameter of 1 μm.

As described _above, Tb _{X Fe} in _(100-X-Y-Z ) Co Y M Z system magneto-optical recording film, the recording and crystallization laser beam irradiated portion becomes equal to or higher than 300 ° C. progresses, reproduction characteristics Therefore, it is necessary to control the temperature so as not to exceed 300 ° C. For that purpose, as is clear from FIG. 8, it is necessary to regulate the Ti content in the AlTi alloy to 10 atomic% or less.

FIG. 9 is a graph showing the relationship between the Ti content in an AlTi alloy and the thermal conductivity K of the alloy at room temperature. As is clear from this figure, the thermal conductivity K of the AlTi alloy changes depending on the Ti content. When the Ti content is 10 atomic%, the thermal conductivity K becomes 0.13 W / cm · deg or more.

か ら From the various experimental results of the present inventors, it has been discovered that the thermal conductivity K of the thermal control layer at room temperature needs to be regulated within the range of 2.0 ≧ K ≧ 0.1 W / cm · deg. If the thermal conductivity K of the thermal control layer at room temperature exceeds 2.0 W / cm · deg, thermal diffusion will be too fast, requiring high laser power for recording and erasing, which is uneconomical. On the other hand, when the thermal conductivity K of the thermal control layer at room temperature is less than 0.1 W / cm · deg, on the contrary, thermal diffusion is too slow, and the recording film has an amorphous structure during repeated recording and reproduction. Relaxation occurs and crystallizes. Therefore, the thermal conductivity K of the thermal control layer at room temperature needs to be regulated in the range of 2.0 ≧ K ≧ 0.1 W / cm · deg. In particular, 0.25 ≧ K ≧ 0.14 W / cm · deg. Those restricted to a range are preferred.

FIG. 10 is a graph showing the relationship between the Ti content in the AlTi alloy and the decrease in the carrier wave level after the recording and erasing cycles. The thickness of the AlTi alloy is set to 750 °, and the recording and erasing are repeated 10,000 times, and thereafter, the carrier wave level of the signal recorded and reproduced is reduced.

As is clear from this figure, when the Ti content in the AlTi alloy slightly exceeds 10 atomic%, the carrier level is lowered, which causes the relaxation of the amorphous structure of the recording film and the crystallization. It is presumed that it has progressed.

In this magneto-optical recording medium, the thickness of each film on the substrate is usually as follows.
1st enhanced film: 600-1000Å
Magneto-optical recording film: 200 to 500 mm
Second enhanced film: 0 to 400 °.

In the case of a magneto-optical recording medium configured as described above, the control of the laser power required in the recording and erasing processes can be performed by adjusting the thermal control layer.

Recording and erasing are performed by laser power of 5 to 10 mW in film surface reaching power {rotating a 5-inch magneto-optical disk at 2400 rpm (linear velocity 7.5 to 15 m / sec)}, and reproduction is performed by laser power of 1 to 3 mW. In order to perform the above, the film thickness of the thermal control layer and the Ti content in the AlTi alloy need to be in the region A in FIG. Above the upper limit of the region A, when erasing is performed at a linear velocity of 15 m / sec (when considering the track offset margin), a laser power of 10 mW or more is required. Below the lower limit of the region A, there is a risk that data may be destroyed when a signal is reproduced with a laser power of 1 to 3 mW.

The thermal control layer also has a function of protecting the recording film, and its effect differs depending on the composition and thickness of the thermal control layer. In the case of the AlTi alloy, the composition whose error rate remains at 1 × 10 ⁶ or less in 1000 hours under the environment of 80 ° C. and 90% RH, and the film thickness are the region C in FIG. It has been confirmed that in a region where the Ti content in the AlTi alloy is 6 atomic% or more, a stable protective effect is obtained when the thickness of the thermal control layer is 500 ° or more. This is a manifestation of the anti-corrosion effect of Ti. If the content of Ti is less than 6 atomic%, the anti-corrosion effect is not always sufficient. Therefore, it is necessary to regulate the Ti content in the AlTi alloy to 6 atomic% or more and the film thickness to 500 ° or more.

From the above, by limiting the Ti content in the AlTi alloy of the thermal control layer to 6 to 10 atomic% and the film thickness to 500 ° or more, durability against recording and erasing cycles, recording, erasing and reproducing power characteristics, In addition, a magneto-optical recording medium having an excellent effect of protecting the recording film can be obtained.

11 and 12 show a specific example of the present invention. FIG. 11 shows an air-sandwich type magneto-optical recording medium, and FIG. 12 shows a close-adhesion type magneto-optical recording medium. Denotes a recording disk single plate, 13 denotes a laminated film of the respective films 3 to 6 shown in FIG. 6, 14 denotes a gap, 15 denotes an inner spacer, 16 denotes an outer spacer, and 17 denotes an adhesive layer. .

In the above embodiment, the case where the thermal control layer is made of an AlTi alloy has been described. However, at least one metal element selected from the [Al, Ag, Au, Cu, Be] element group and [Cr, Ti, Ta, [Sn, Si, Rb, Pt, Nb, Mo, Mg, W, Zr] In an alloy with at least one metal element selected from the group of elements, the thermal conductivity K is set to 2.0 ≧ K ≧ 0.1 W / If the thermal control layer is set to cm · deg, the same effect as in the above embodiment can be obtained.

FIG. 16 is a characteristic diagram showing the relationship between the AlAg alloy composition to which the present invention can be applied and the thermal conductivity of the alloy, and FIG. 17 is a characteristic diagram showing the relationship between the CuTi alloy composition and the thermal conductivity of the alloy. . Similar effects can be obtained by using these AlAg alloys and CuTi alloys as heat control layers and regulating the range of the thermal conductivity.

A magneto-optical recording medium according to the third embodiment will be described with reference to FIGS. The magneto-optical recording medium of this embodiment is characterized in that the composition of the magneto-optical recording film in the first and second embodiments is changed to improve the external magnetic field sensitivity of the magneto-optical recording film. Therefore, portions other than the magneto-optical recording film are the same as those in the first and second embodiments, and a description thereof will be omitted.

The magneto-optical recording film of this example has a rare earth-transition in which either one of nitrogen (N) and oxygen (O), or both N and O are mixed in a total amount of 0.1 to 5.0 atomic%. It is made of a metal-based amorphous perpendicular magnetization film and has a thickness of 200 to 500 °. That is, conventionally, it has been recognized that N and O mixed into the magneto-optical recording film are impurities, and technical studies have been conducted in the direction of preventing the mixing of N and O into the magneto-optical recording film. However, the inventors of the present application have determined the relationship between the mixing ratio of N or O mixed into a rare earth-transition metal amorphous perpendicular magnetization film and the residual Kerr rotation angle, the mixing ratio and perpendicular magnetic anisotropy. As a result of studying the relationship with the constant, the relationship between the mixing ratio and the CN ratio, etc., it was found that there is a proper mixing ratio range of N and O that can reduce only the perpendicular magnetic anisotropy energy without reducing the Kerr rotation angle. I know the fact. According to the study of the present inventors, when N or O or N and O are mixed in a range of 0.1 to 5.0 atomic% into a rare earth-transition metal based amorphous perpendicular magnetization film, the Kerr rotation angle is reduced. , The perpendicular magnetic anisotropy energy alone can be reduced, and the external magnetic field sensitivity of the magneto-optical recording film can be increased. The N, O mixing ratio in the magneto-optical recording film in this example is determined based on such knowledge. As the rare earth-transition metal based amorphous perpendicular magnetization film, any of known compositions having a known composition can be used. Rare earths (for example, Tb, Gd, Nb, Dy) and a transition metal (for example, Fe) can be used. , Co, Ni) and a ternary alloy system containing additional elements (for example, Cr, Ti, Nb).

(4) The method of forming the magneto-optical recording film will be described below.

(A) After forming a first enhanced film on a transparent substrate, forming a rare earth-transition metal based amorphous perpendicular magnetic film by an appropriate method, Is heated in a vacuum vessel adjusted to 1.0 × 10 ^{5 to} 1.0 × 10 ³ Pa to 20 to 120 ° C. for 5 to 90 minutes to nitride or oxidize the amorphous perpendicular magnetization film to obtain a desired layer. Magneto-optical recording film.

(B) After forming the first enhanced film on the transparent substrate, a rare earth-transition metal based amorphous perpendicular magnetization film is formed by a partial pressure of 0.1 to 5.0% of N or O or a mixture of N and O. A film is formed in an atmosphere containing a mixed gas, and a rare earth-transition metal based amorphous perpendicular magnetization film is nitrided or oxidized in this film formation process to obtain a desired magneto-optical recording film.

(4) As a method for creating an atmosphere containing N or O or a mixed gas of N and O at a partial pressure of 0.1 to 5.0% described in (b) above, the following method is available.

(1) After evacuating the vacuum container to a high degree of vacuum of the order of 10 ⁵ Pa, N or O or a mixed gas of N and O is supplied into the vacuum container, and N or O in the vacuum container during the film forming process is supplied. The partial pressure of O or a mixed gas of N and O is adjusted to 0.1 to 5.0%.

(2) The degree of vacuum in the vacuum chamber is adjusted to 1.0 × 10 ^{4 to} 5.0 × 10 ⁴ Pa by evacuation performed before the formation of the rare earth-transition metal amorphous perpendicular magnetization film. Then, air having a partial pressure of 0.1 to 5.0% is left in the vacuum vessel.

As a method for forming a rare earth-transition metal amorphous perpendicular magnetization film, any vacuum film formation method such as sputtering, ion plating, and vacuum deposition can be applied.

FIG. 18 shows the relationship between the N and O mixing rates in the magneto-optical recording film 4 and the perpendicular magnetic anisotropy constant, and FIG. 19 shows the N and O mixing rates in the magneto-optical recording film 4 and the residual curl. This shows the relationship with the rotation angle.

垂直 As shown in FIG. 18, the perpendicular magnetic anisotropy constant Ku of the magneto-optical recording film decreases sensitively with the incorporation of N or O, and gradually decreases as the incorporation ratio of N or O increases. If the mixing ratio of N or O exceeds 5.0 atomic%, the magnetic field becomes lower than the demagnetizing field, and the magnetic moment tilts in the plane.

On the other hand, as shown in FIG. 19, the residual Kerr rotation angle is relatively stable with respect to the incorporation of nitrogen and oxygen, and hardly decreases when the incorporation rate is in the range of 0 to 5.0 at. ing.

21, 22, and 23 show the N mixing ratio and the O mixing ratio in the magneto-optical recording film 4 and the magnitude of the external magnetic field at which the reproducing CN ratio, the saturation recording magnetic field, and the erasing ratio become -40 dB, that is, the erasing magnetic field. Shows the relationship with However, a disk-shaped magnetic recording medium having the film structure shown in FIG. 20 was used as a sample.

Thus, the data in FIGS. 21, 22, and 23 correspond to the data shown in FIGS. 18 and 19, and are most characteristic when the N mixing ratio and the O mixing ratio are in the range of 0 to 5%. The effect is obtained.

FIG. 24 shows an outline of the method of manufacturing the magneto-optical recording medium according to the third embodiment and the comparative example, the reproduction CN ratio, the saturation recording magnetic field, the erasing magnetic field, and the magneto-optical recording of the magneto-optical recording medium manufactured by each method. The N mixing ratio and the O mixing ratio in the film are shown. However, as a sample, a magneto-optical disk was used in which an AlSiON enhanced film having a thickness of 800 ° and a TbFeCo magneto-optical recording film having a thickness of 250 ° were sputtered on the preformat pattern forming surface of a polycarbonate substrate.

As is apparent from this figure, the magneto-optical recording medium according to the third embodiment has the same reproduction CN ratio as that of the magneto-optical recording medium of the comparative example (conventional example), whereas the saturation recording magnetic field is lower than that of the conventional example. , And the erasing magnetic field is reduced to 40% of the conventional example. Therefore, the external magnetic field required for recording and erasing information can be reduced in size and weight, and the magnet power supply unit can be simplified, the power consumption can be reduced, the recording / reproducing apparatus can be downsized, and the recording and erasing operations can be performed. Higher speed can be achieved. Further, when viewed from the medium side, a large margin can be provided for the fluctuation of the distance between the external magnetic field and the magneto-optical recording medium and the fluctuation of the magnetic field due to heat generation, and the magneto-optical recording medium having excellent reliability can be provided. .

In the third embodiment, the first enhanced film (multiple interference film), the magneto-optical recording film (recording film), the second enhanced film (multiple interference film), Although a magneto-optical recording medium in which a heat diffusion film is laminated has been described as an example, the gist of the present invention is not limited to this, and any film structure having at least a magneto-optical recording film may be used. The present invention can be applied to a magneto-optical recording medium.

A magneto-optical recording medium according to the fourth embodiment will be described with reference to FIGS. The magneto-optical recording medium of this embodiment is also characterized in that the composition of the magneto-optical recording film in the first and second embodiments is changed to improve the external magnetic field sensitivity of the magneto-optical recording film. FIG. 25 is a cross-sectional view of a main part of the magneto-optical recording medium according to the present embodiment. As shown in FIG. From the side, an enhancement film 3, a magneto-optical recording film 4, an auxiliary magnetic film 5, and a protective film 10 are sequentially laminated. The transparent substrate 1, the preformat pattern 2, the enhance film 3, and the magneto-optical recording film 4 are the same as those in the first embodiment, and thus the description is omitted. Further, if necessary, a reflective film may be laminated on the protective film 10.

As the auxiliary magnetic film 5, for example, an alloy of a noble metal (Au, Pt, Ag, Cu, Rh, Pd, etc.) and a transition metal (Fe, Co, Ni, Mn, Cr, etc.), specifically, a PtCo alloy, AgCo alloy, PdCo alloy, RhCo alloy, RhFe alloy, AgFe alloy, etc., or ferromagnetic material, such as AlCo alloy, AlFe alloy, or various ferrites, such as Fe ₃ O ₄ , iron garnet, chromite, rare earth-transition metal alloy A ferrimagnetic material or a mixture of these magnetic metals and their oxides or nitrides, wherein the difference between the Curie temperature and the Curie temperature of the magneto-optical recording film 4 is adjusted to within 150 ° C. Used. The thickness of the auxiliary magnetic film 5 is 20 to 1000 °, more preferably 300 to 500 °. The auxiliary magnetic film 5 can be provided on the substrate side with respect to the magneto-optical recording film 4 or on the opposite side. Further, it can be provided in the middle of the magneto-optical recording film 4.

If the auxiliary magnetic film 5 having a Curie temperature whose difference from the Curie temperature of the magneto-optical recording film 4 is within 150 ° C. is formed so as to be in contact with the magneto-optical recording film 4, the auxiliary magnetic film A magnetic interaction occurs with the film 5, and overwriting of signals by the magnetic field intensity modulation method can be realized.

FIG. 26 is a characteristic diagram showing the relationship between the Curie temperature of the auxiliary magnetic film 5 and the required erasing magnetic field. That is, a TbFeCo alloy film having a thickness of 300 形成 was formed as the magneto-optical recording film 4, and a CoPt alloy film having a thickness of 500 と し て was formed thereon as the auxiliary magnetic film 5. The Curie temperature of the auxiliary magnetic film 5 was changed in the range of 10 to 600 ° C. by changing the alloy composition ratio. At this time, the Curie temperature of the magneto-optical recording film 4 was set to 200 ° C.

FIG. 27 is a characteristic diagram showing the relationship between the content of Pt in the CoPt alloy film and the Curie temperature (T _c ) of the alloy film. As shown in this figure, the Curie temperature Tc of the alloy film can be arbitrarily changed by adjusting the Pt content.

(4) Using such a magneto-optical recording medium, information was recorded while an external magnetic field was applied in the erasing direction, the minimum magnetic field strength at which recording could be performed was measured, and this was defined as the required erasing magnetic field. This required erasing magnetic field corresponds to the magnitude of the external magnetic field required to completely erase the recorded signal.

(4) When performing overwriting by the magnetic field intensity modulation method, an external magnetic field that can be mounted on the recording / reproducing apparatus is at most about 200 [Oe] at the request of the recording / reproducing apparatus. As is apparent from the results shown in FIG. 26, when the Curie temperature exceeds 360 ° C., an external magnetic field is shielded, and when the Curie temperature is less than 50 ° C., the magnetic interaction between the magneto-optical recording film 4 and the auxiliary magnetic film 9 is caused. Little effect. As a result, the required erasing magnetic field exceeds 200 [Oe], which is not practical.

On the other hand, if the auxiliary magnetic film 9 which is in direct contact with the magneto-optical recording film 4 and whose Curie temperature is in the range of 50 to 350 ° C. is formed, complete information can be obtained with a small external magnetic field of 200 [Oe] or less. Erasing becomes possible. In particular, if the Curie temperature of the auxiliary magnetic layer 9 is regulated in the range of 100 to 300 ° C., it can be seen that complete erasure of information is possible with an external magnetic field of 100 [Oe] or less.

As the magneto-optical recording film 4, a TbFeCo-based alloy having a composition of 23% by weight of Tb, 66% by weight of Fe, and 11% by weight of Co is used. When a PtCo-based alloy having a composition with a content of 80% by weight and a Co content of 20% by weight is used, the Curie temperature of the magneto-optical recording film 4 is 200 ° C. and the Curie temperature of the auxiliary magnetic film 9 is 180 ° C. The Curie temperature difference between the magneto-optical recording film 4 and the auxiliary magnetic film 9 is 20 ° C.

FIG. 28 shows a comparison between the recording and erasing characteristics of the magneto-optical recording medium according to the embodiment of the present invention shown in FIG. 25 and a conventional magneto-optical recording medium having no auxiliary magnetic film 5. Here, the recording and erasing characteristics refer to changes in the reproduction CN when the magnitude and direction of the external magnetic field applied during recording are changed. The curve A in the figure is a characteristic curve of the magneto-optical recording medium according to the embodiment of the present invention, and the curve B is a characteristic curve of the conventional magneto-optical recording medium.

As is clear from this figure, in the conventional magneto-optical recording medium (curve B), the reproduction CN ratio does not reach the saturation value unless an external magnetic field of about 330 [Oe] or more is applied in the recording direction. In the magneto-optical recording medium according to the embodiment (curve A), the reproduction CN ratio reaches a saturation value only by applying an external magnetic field of about 100 [Oe] in the recording direction. This also indicates that the magneto-optical recording medium according to the example can perform perfect recording with a smaller external magnetic field. Further, in the conventional magneto-optical recording medium (curve B), the reproduction CN ratio cannot be made zero unless an external magnetic field of about 600 [Oe] or more is applied in the erasing direction. The reproducing CN ratio of the magnetic recording medium (curve A) can be made zero only by applying an external magnetic field of about 50 [Oe] in the erasing direction. This also indicates that the magneto-optical recording medium according to the example can perform complete erasure with a smaller external magnetic field. Therefore, it can be proved that the magneto-optical recording medium according to the example has the recording and erasing characteristics that can reliably overwrite information by the external magnetic field modulation method.

FIGS. 29 and 30 are enlarged cross-sectional views of essential parts showing a modification of the present embodiment. In these figures, 1 is a transparent substrate, 3 is an enhanced film, 4 is a magneto-optical recording film, 12 is a protective film, 7 is a reflective film, and 9 is an auxiliary magnetic film. 29, the auxiliary magnetic film 9 is formed between the enhance film 3 and the magneto-optical recording film 4. On the other hand, in the embodiment shown in FIG. 30, the auxiliary magnetic film 9 is formed on both surfaces of the magneto-optical recording film 4.

(4) If the composition of the magneto-optical recording film 4 is adjusted and the magneto-optical recording film 4 which becomes RE-rich at least immediately below the Curie temperature is used, direct overwriting by the light intensity modulation method is also possible. That is, as described above, the rare-earth / transition metal-based amorphous perpendicular magnetization film is changed to a TM-rich film or a RE-rich film at least immediately below the Curie temperature by variously changing the composition. be able to. Then, at least immediately below the Curie temperature, the auxiliary magnetic film 5 shown in the first embodiment or the fourth embodiment is laminated in contact with the magneto-optical recording film of RE-rich, and the magnitude of the external magnetic field and the laser power are appropriately adjusted. By making the selection, direct overwriting by the light intensity modulation method can be performed based on the principle shown in the section of the operation. FIG. 31 shows an example of a configuration of a magneto-optical recording medium capable of performing direct overwrite by a light intensity modulation method.

The magneto-optical recording medium of this embodiment has a magnetic moment component in a direction inclined with respect to a direction perpendicular to the film surface, and when the magnetic film is heated to near its Curie temperature, the inclined magnetic moment component And a rare earth-transition metal alloy-based magnetic film in which both magnetic moment components in the direction perpendicular to the film surface disappear.

FIGS. 37A to 37J illustrate a magneto-optical recording film having a magnetic moment component in a direction inclined with respect to a direction perpendicular to the film surface. In this figure, the rectangles indicate the magnetic films as the magneto-optical recording films, and the arrows in the magnetic films indicate the direction of the magnetic moment in each part. The lower side of the rectangle showing the magnetic film is the interface on the transparent substrate side, and the upper side is the interface on the reflective film side.

As shown in the figure, the magneto-optical recording medium of the present invention has a single-layer magneto-optical recording film. In the magneto-optical recording film of FIG. 37 (a), the magnetic moment is directed vertically upward from the interface on the transparent substrate side to the substantially central portion in the film thickness direction, and the magnetic moment is directed obliquely upward from there. At the interface on the reflection film side, the magnetic moment is directed in the in-plane direction. In the magneto-optical recording film of FIG. 37 (b), the magnetic moment is directed in an in-plane direction at a portion very close to the interface on the transparent substrate side, and the magnetic moment is directed obliquely upward at a portion thereabove. At a substantially central portion of the direction, the magnetic moment points vertically upward. Further, the magnetic moment is inclined in the opposite direction in a portion above the magnetic moment, and the magnetic moment is directed in the in-plane direction at the interface on the reflection film side. In the magneto-optical recording film shown in FIG. 37 (c), the magnetic moment is directed vertically upward in a portion very close to the interface on the transparent substrate side, and the magnetic moment is directed obliquely upward in a portion thereabove. The magnetic moment is directed in the in-plane direction at a substantially central portion of. Further, the magnetic moment is again inclined in the same direction in a portion thereabove, and the magnetic moment is directed vertically upward at the interface on the reflection film side. In the magneto-optical recording film of FIG. 37D, the magnetic moment is uniformly directed obliquely upward from the interface portion on the transparent substrate side to the interface portion on the reflective film side. In the magneto-optical recording film of FIG. 37E, the magnetic moment is spirally rotated from the interface portion on the transparent substrate side to the interface portion on the reflection film side. In the magneto-optical recording film of FIG. 37 (f), a magnetic moment directed obliquely upward and to the left and a magnetic moment directed diagonally to the upper left are alternately formed in the film thickness direction. In the magneto-optical recording film of FIG. 37 (g), the magnetic moment is directed in an in-plane direction at a portion very close to the interface on the transparent substrate side, and the magnetic moment sequentially turns clockwise at a portion above the portion. Eventually it will be vertically upward. Further, the magnetic moment turns in the same direction in a portion above the magnetic moment, and the magnetic moment is directed in an in-plane direction in a substantially central portion in the film thickness direction. Further above, the magnetic moment turns in the opposite direction, and eventually turns vertically upward. Further, the magnetic moment turns in the opposite direction in a portion above the magnetic film, and the magnetic moment is directed in the in-plane direction at the interface on the reflection film side. In the magneto-optical recording film of FIG. 37H, the magnetic moment is directed vertically upward at a substantially central portion from the interface on the transparent substrate side, and the magnetic moment is inclined obliquely upward near the interface on the reflective film side. In the magneto-optical recording film of FIG. 37 (i), the magnetic moment is inclined obliquely upward near the interface on the transparent substrate side, and the magnetic moment is directed vertically upward in the portion from the substantially central portion to the interface on the reflective film side. ing. In the magneto-optical recording film of FIG. 37 (j), the magnetic moment is directed vertically upward from the interface on the transparent substrate side to the substantially central portion, and the magnetic moment is directed obliquely downward from the interface to the interface on the reflective film side. It is inclined.

As is clear from these figures, the magnetic film of the present invention has a single-layer structure, in which a portion where the magnetization moment is directed perpendicularly, obliquely, or in-plane is included. This is fundamentally different from the case where the inner magnetized film is laminated. Among the magneto-optical recording films shown in FIGS. 37 (a) to (j), magneto-optical recording having a portion whose magnetic moment is in a direction not perpendicular to the film surface and a portion which is perpendicular to the film surface in the film thickness direction. The film is adjusted so that when the magneto-optical recording film is heated to near the Curie temperature, the magnetic moment directed in a direction not perpendicular to the film surface disappears together with the magnetic moment directed in a direction perpendicular to the film surface. It is preferable that the temperature at which the magnetic moment oriented in a direction not perpendicular to the film surface disappears and the temperature at which the magnetic moment oriented perpendicular to the film surface disappears be closer, and in particular, the magnetic moment oriented perpendicular to the film surface be reduced. Assuming that the disappearing temperature (Curie temperature) is _Tc , it is preferable that the magnetic moment directed in a direction not perpendicular to the film surface disappears in the range of _Tc ± 50 ° C.

Each of the magneto-optical recording media of this embodiment shows a torque curve as shown in FIG. 38 when the magnetic torque is measured with a magnetic torque meter. That is, the magnitude of the external magnetic field is H _ex , the domain wall coercive force at the measurement temperature is H _c , the perpendicular anisotropic magnetic field at the measurement temperature is H _k , the direction perpendicular to the film surface is 0 °, and the direction perpendicular to the film surface is When the rotation angle of the external magnetic field H _ex is θ, and the external magnetic field having the magnitude of H _c <H _ex <H _k is rotated around the support axis of the sample, the magnetic torque T acting on the support axis of the sample is measured by a magnetic torque meter. When there is a region where ∂ ² T / ∂θ ² <0 exists in the range of 0 ° ≦ θ ≦ 90 ° and the range of 180 ° ≦ θ ≦ 270 ° when (に て T (θ ₀ ) / ∂θ = 0 if made theta ₀ is present, _T (θ _{0) <T that max} consisting region exists), 360 ° ≧ θ ≧ 270 of ° range and 180 ° ≧ θ ≧ 90 of ° In the range, there exists a region where ∂ ² T / ∂θ ² > 0 (however, when θ ₀ where ０T (θ ₀ ) / ∂θ = 0 exists, T ( θ ₀ )> T _min ). However, it goes without saying that the condition that satisfies each of the above expressions is not a non-differentiable point accompanying the domain wall movement.

ト ル ク As a comparative example, FIG. 39 shows a torque curve of a magneto-optical recording medium having a magneto-optical recording film having a single layer of a perpendicular magnetization film. A peak corresponding to B in FIG. 38 does not appear in this torque curve.

The magneto-optical recording medium of this embodiment measures the torque curve at different sample temperatures, and plots the correlation between the sample temperature and the peak values of A and B shown in FIG. All show characteristics as shown in FIG. That is, as the sample temperature increases, the peak value of A and the peak value of B sequentially decrease, and become zero at almost the same temperature (the same temperature in the example of FIG. 40). Note that the temperature at which the peak value of A becomes zero and the temperature at which the peak value of B becomes zero do not necessarily need to coincide, and the temperature at which the peak value of A becomes zero (Curie temperature) is defined as _Tc. It is sufficient that the temperature at which the peak value of B becomes zero falls within the range of T _c ± 50 ° C.

FIG. 41 shows an external magnetic field characteristic of the magneto-optical recording medium according to the present embodiment, and FIG. 42 shows a bit error occurrence characteristic of the magneto-optical recording medium according to the present embodiment. However, a magneto-optical recording medium having a film structure as shown in FIG. 43 was used as a sample. As shown in FIG. 41, the magneto-optical recording medium of the present invention can reach the saturation magnetization by applying an external magnetic field of 50 (Oe) or more in the recording direction or the erasing direction. As shown, by applying an external magnetic field of 50 (Oe) or more in the recording direction, the bit error rate can be minimized.

The magneto-optical recording medium of the present embodiment has a capacity of 150 (Oe) or more in comparison with a conventional magneto-optical recording medium using a perpendicular magnetization film as a magneto-optical recording film (indicated by broken lines in FIGS. 41 and 42). The external magnetic field strength required for recording / erasing can be reduced.

Hereinafter, examples of the method of manufacturing the magneto-optical recording medium according to the present invention and the structure of the magnetic film manufactured by each manufacturing method will be listed.

(1) A first inorganic dielectric layer, a rare earth-transition metal based amorphous perpendicular magnetization film, a second inorganic dielectric layer, and a reflective film are sequentially laminated on a transparent substrate by a continuous sputtering method. After producing the magneto-optical recording medium having the film structure shown in FIG. 9, the magneto-optical recording medium is heated at a temperature of 60 ° C. to 150 ° C. for 2 to 10 minutes. Thus, a magnetic film as shown in FIG. 37D can be formed.

(2) After sputtering the first inorganic dielectric layer on the transparent substrate, a rare-earth-transition metal-based amorphous alloy is formed on the first inorganic dielectric layer while appropriately changing the composition of the sputtering gas. Sputter until thickness is reached. For example, every time the thickness of the magnetic layer reaches ２〜 to 1/10 of the total thickness, the sputtering gas is changed from pure Ar to Ar gas containing 1 to 20% by volume of N ₂ gas or 0.5 to 10% by volume. The gas is switched to an Ar gas mixed with a volume% of O ₂ gas. Thereby, a magnetic film as shown in FIGS. 37 (a), (b), (c) and (g) can be formed. Hereinafter, a second inorganic dielectric layer and a reflective film are laminated on the magnetic film by a continuous sputtering method.

(3) After sputtering the first inorganic dielectric layer on the transparent substrate, magnetic films having different perpendicular magnetic anisotropy are alternately formed on the first inorganic dielectric layer. A combination of magnetic films having different perpendicular magnetic anisotropy includes, for example, a rare earth-transition metal based amorphous alloy, Co as a main component, and a group of (Cr, Fe, Ni, Mn, Pt, Ag). And alloys of at least one metal selected from the group consisting of: Thereby, a magnetic film as shown in FIGS. 37 (a), (b), (c) and (g) can be formed. Hereinafter, a second inorganic dielectric layer and a reflective film are laminated on the magnetic film by a continuous sputtering method.

(4) After sputtering the second inorganic dielectric layer on the transparent substrate, the amount of the rare earth element selected from the group of (Gd, Ce, Dy, Nd) on the second inorganic dielectric layer, or TbFeCo-based alloys having different added amounts of transition metals selected from the group of (Ni, Cr, Mn) are sequentially laminated. Accordingly, a magnetic film having a helical spin structure as shown in FIG. 37 (e) or a magnetic film having a canted spin structure as shown in FIG. 37 (f) due to correlation between exchange interaction between atoms and anisotropic energy. Can be formed. Hereinafter, a second inorganic dielectric layer and a reflective film are laminated on the magnetic film by a continuous sputtering method.

(5) After the first inorganic dielectric layer is sputtered on the transparent substrate, (Nb, Ti, W, Bi, V, Al, Si, Pt, Ag, Rh) is deposited on the first inorganic dielectric layer. TbFeCo-based alloys having different addition amounts of non-magnetic elements selected from the group are sequentially laminated. Thereby, the anisotropic energy is reduced, and a magnetic film having a structure as shown in FIG. 37D can be formed. Hereinafter, a second inorganic dielectric layer and a reflective film are laminated on the magnetic film by a continuous sputtering method.

In the magneto-optical recording medium of the fifth embodiment, the external magnetic field sensitivity can be further enhanced by laminating an auxiliary magnetic film that exerts exchange coupling force on the magneto-optical recording film 4. When the saturation magnetization at the recording temperature is Ms (T _WR ) and the perpendicular magnetic anisotropy energy at the recording temperature is Ku (T _WR ), the auxiliary magnetic film has a rare-earth magnetic property represented by the following formula. A transition metal-addition element alloy thin film can be used.

2πMs ² (T _WR ) ≧ Ku (T _WR )
Examples of rare earths include those whose element symbols are represented by Gd, Tb, Dy, Nd, and Ho. Examples of transition metals include those whose element symbols are represented by Fe, Co, and Ni. Examples of the element system include those whose element symbols are represented by Au, Ag, Cu, Pt, Al, Nb, and Cr. Among these, a GdFeCu alloy, a TbFePt alloy and the like are particularly suitable.

FIG. 44 shows the magnetic field modulation recording characteristics of the magneto-optical recording medium of the present embodiment provided with the auxiliary magnetic film. However, a magneto-optical disk having the film structure shown in FIG. 45 was used as a sample, and signals were recorded under the conditions shown in FIG. As is clear from FIG. 44, the magneto-optical recording medium of this example has a saturation recording magnetic field of 50 (Oe) or less.

The following sixth to ninth embodiments show examples in which the present invention is applied to a super-resolution type magneto-optical recording medium described in, for example, Japanese Patent Application Laid-Open No. 1-143042.

A magneto-optical recording medium according to the sixth embodiment will be described with reference to FIGS. FIG. 46 is a cross-sectional view of a main part of the magneto-optical recording medium according to the present example, and FIG. 47 is a graph illustrating the effect of the present example.

As shown in FIG. 46, in the magneto-optical recording medium of this example, an enhancement film for increasing the apparent Kerr rotation angle and improving the CN ratio of a reproduced signal is formed on the preformat pattern forming surface 2 of the transparent substrate 1. 3, a first to third magnetic films 4a, 4b, 4c made of a rare earth-transition metal based amorphous perpendicular magnetic film having ferrimagnetism, and a protective layer 6 are sequentially laminated. As the transparent substrate 1, a glass substrate on which a preformat pattern 2 was transferred on one side by a so-called 2P method was used. On the preformat pattern 2 of the glass substrate 1, a SiN enhanced film 3 having a thickness of about 850 °, a first magnetic film 4a made of a GdFeCo-based amorphous perpendicular magnetic film having a thickness of about 300 °, A second magnetic film 4b made of a TbFeNb-based amorphous perpendicular magnetic film having a thickness of about 100 °, a third magnetic film 4c made of a TbFeCo-based amorphous perpendicular magnetic film having a thickness of about 400 °, An 800 ° SiN protective layer 14 was continuously sputtered to obtain the magneto-optical recording medium of the sixth embodiment. The composition of the third magnetic film 4c is adjusted so that the Tb sublattice magnetization is dominant at room temperature.

FIG. 47 shows a magneto-optical recording medium according to the sixth embodiment and a TbFeCo-based amorphous perpendicular magnetic film having a composition in which the FeCo sublattice magnetization is dominant instead of the third magnetic film 4c in the magneto-optical recording medium. 4 shows external magnetic field characteristics with a magneto-optical recording medium according to a comparative example provided. In the graph, the vertical axis represents the CN ratio of the reproduced signal, and the horizontal axis represents the magnitude of the applied external magnetic field. The positive value of the external magnetic field indicates a magnetic field in the recording direction, and the negative value indicates a magnetic field in the erasing direction. As is apparent from this graph, the magneto-optical recording medium according to the comparative example in which a TbFeCo-based amorphous perpendicular magnetization film having a composition in which the FeCo sublattice magnetization is dominant was provided as the third magnetic film 4c, While the saturation magnetic field cannot be reached unless an external magnetic field of about 300 [Oe] or more and about 600 [Oe] or more in the erasing direction is applied, the third magnetic film 4c has a composition in which Tb sublattice magnetization is dominant. The magneto-optical recording medium according to the first embodiment provided with the TbFeCo-based amorphous perpendicular magnetization film can reach the saturation magnetic field only by applying an external magnetic field of about 200 [Oe] or more in each of the recording direction and the erasing direction. Can be. Therefore, it is possible to reduce the size, weight, and power consumption of the external magnetic field, and hence the drive device, and to realize overwriting of information by a magnetic field modulation method.

In the examples and the comparative examples, a glass substrate was used as the transparent substrate 1. However, when a resin substrate was used instead, a result similar to the above was obtained. In the above Examples and Comparative Examples, SiN was used as the enhancement film 3 and the protection film 6, but the same applies to the case where other inorganic dielectrics such as SiO ₂ , SiO, Si ₂ N ₃ , and AlN are used. The result was obtained. The same results as above were obtained when a UV resin protective film was formed instead of the inorganic protective film 6. In addition, the same results as above were obtained when the thickness of each film was variously changed. Further, when a GdFe or GdCo-based amorphous perpendicular magnetization film is used as the first magnetic film 4a and a TbFe, TbFeCo, TbFeCoCr, TbFeCoPt-based amorphous perpendicular magnetization film is used as the second magnetic film 4b. Also obtained the same results as described above.

Hereinafter, a magneto-optical recording medium according to the seventh embodiment will be described with reference to FIGS. FIG. 48 is a cross-sectional view of a main part of the magneto-optical recording medium according to the present example, and FIG. 49 is a graph showing the effect of the present example.

光 As shown in FIG. 48, the magneto-optical recording medium of this example is characterized in that an oxide layer 9 is formed on the surface of the third magnetic film 4c. The oxide layer 9 is formed by sequentially sputtering the enhanced film 3 and the first to third magnetic films 4a, 4b, and 4c on the glass substrate 1 and then temporarily stopping the film formation to reduce the amount of oxygen in the sputtering chamber. It is formed by adjusting and heating the third magnetic film 4c. Thereafter, the degree of vacuum in the sputtering chamber is adjusted again, and the protective layer 6 having a predetermined thickness is sputtered, whereby the magneto-optical recording medium of the seventh embodiment can be formed. Portions other than the oxide layer 9 are formed similarly to the magneto-optical recording medium of the sixth embodiment.

FIG. 49 shows the external magnetic field characteristics of the magneto-optical recording medium according to the seventh embodiment and the magneto-optical recording medium according to the sixth embodiment. As is apparent from this graph, the magneto-optical recording medium of this example can reach the saturation magnetic field only by applying an external magnetic field of about 100 [Oe] or more in the recording direction and the erasing direction, respectively. The external recording sensitivity is further improved by about ± 100 [Oe] as compared with the magneto-optical recording medium of the example.

In the seventh embodiment, the heating oxide layer is formed on the surface of the third magnetic film 4c, but the heating oxide layer 9 similar to the above is formed on the surface of the first magnetic film 4a or the second magnetic film 4b. Formed, the same result as described above was obtained. The same results as above were obtained when a heat nitrided layer was formed instead of the heat oxidized layer 9. The heat-nitrided layer is formed by sputtering the magnetic film to be nitrided, adjusting the amount of nitrogen in the sputtering chamber, and heating the magnetic film to be nitrided. In addition, even if the material of the transparent substrate 1, the material of the protective film 6, and the formation position of the heating oxide layer 9 or the heating nitride layer are changed as described in the description of the sixth embodiment, the same result as described above is obtained. Obtained.

Hereinafter, a magneto-optical recording medium according to the eighth embodiment will be described with reference to FIGS. FIG. 50 is a cross-sectional view of a principal part of the magneto-optical recording medium according to the present example, and FIG. 51 is a graph showing the effect of the present example.

As shown in FIG. 50, the magneto-optical recording medium of this example is characterized in that it is provided on the auxiliary magnetic film 5 in contact with the third magnetic film 4c. As the auxiliary magnetic film 5, at a temperature at which a recording magnetic domain is formed in the third magnetic layer 4c (near the Curie temperature or near the compensation temperature of the third magnetic layer 4c), a rare earth-transition in which transition metal sublattice magnetization is dominant is obtained. A metal-based amorphous perpendicular magnetization film is used. In addition, the enhance film 3, the first to third magnetic films 4a, 4b, 4c, and the protective layer 6 are the same as those in the sixth embodiment. The auxiliary magnetic film 5 is continuously sputtered together with other thin films.

FIG. 51 shows a magneto-optical recording medium according to the eighth embodiment, in which a TbFeCo film having the above composition having a thickness of 50 ° is provided as the auxiliary magnetic film 5, and a magneto-optical recording medium according to the sixth embodiment. 3 shows the external magnetic field characteristics of FIG. As is apparent from this graph, the magneto-optical recording medium of this example can reach the saturation magnetic field only by applying an external magnetic field of about 100 [Oe] or more in the recording direction and the erasing direction, respectively. The external recording sensitivity is improved by about ± 100 [Oe] as compared with the magneto-optical recording medium of the example. This is presumably because the formation of the auxiliary magnetic film 5 reduces the stray magnetic field from the surrounding region acting on the region where the recording magnetic domain is to be formed or the region where the erasing is to be performed.

In the eighth embodiment, the auxiliary magnetic film 5 is formed only on the surface side (the protective film 6 side) of the third magnetic film 4a, but on the rear side (the transparent substrate 1 side) of the third magnetic film 4c. The same result was obtained when the auxiliary magnetic film 5 was formed in (2). Further, even when the auxiliary magnetic film 5 similar to the above was formed on the surface of the first magnetic film 4a or the second magnetic film 4b, the same result as described above was obtained. In addition, even when the material of the transparent substrate 1 and the material of the protective film 6 were changed as described in the description of the sixth embodiment, the same results as described above were obtained.

Hereinafter, a magneto-optical recording medium according to the ninth embodiment will be described with reference to FIGS. FIG. 52 is a graph showing the relationship between the amount of Pt added in the auxiliary magnetic film and the perpendicular magnetic anisotropy constant. FIG. 53 is a graph showing the relationship between the amount of Pt added in the auxiliary magnetic film and the residual Kerr rotation angle. FIG. 54 is a graph showing the relationship between the added amount of Pt in the auxiliary magnetic film and the reproduction CN ratio, and FIG. 55 shows the relationship between the added amount of Pt in the auxiliary magnetic film and the minimum erasing magnetic field required to erase the recording signal. FIG.

In the magneto-optical recording medium of this embodiment, the auxiliary magnetic film 5 of the magneto-optical recording medium according to the eighth embodiment is formed of at least one selected from Au, Ag, Al, Cu, Pt, Nb, Ho, Gd, and Cr. Characterized by being formed of a rare earth-transition metal based amorphous alloy to which the element (1) is added. In addition, the enhance film 3, the first to third magnetic films 4a, 4b, 4c, and the protective layer 6 are the same as those in the eighth embodiment. The auxiliary magnetic film is continuously sputtered together with the other thin films. Accordingly, the cross-sectional structure of the magneto-optical recording medium of this embodiment is the same as that of the magneto-optical recording medium of the eighth embodiment (see FIG. 50). FIG. 52 shows the relationship between the amount of Pt added to the auxiliary magnetic film and the perpendicular magnetic anisotropy constant in the magneto-optical recording medium according to the ninth embodiment. As is apparent from this figure, the perpendicular magnetic anisotropy energy of the magneto-optical recording medium of this example decreases as the amount of Pt added in the auxiliary magnetic film increases, and the amount of Pt added in the auxiliary magnetic film decreases by about If it exceeds 13 at%, the axis of easy magnetization is oriented in a direction perpendicular to the film surface. FIG. 53 shows the relationship between the amount of Pt added in the auxiliary magnetic film and the residual Kerr rotation angle in this magneto-optical recording medium. As is apparent from this figure, the residual Kerr rotation angle of the magneto-optical recording medium of this example is almost constant until the amount of Pt added in the auxiliary magnetic film is about 10 at%, but drops sharply when it exceeds 10 at%. I do. From the results shown in FIGS. 52 and 53, it can be seen that the perpendicular magnetic anisotropy energy can be reduced without reducing the Kerr rotation angle by adding Pt up to about 10 atomic% to the auxiliary magnetic film. It can be seen that the external magnetic field sensitivity is increased without lowering the reproduction CN ratio of the magneto-optical recording medium.

FIG. 54 shows the relationship between the reproduction CN ratio and the Pt addition amount of a magneto-optical recording medium in which a TbFeCo film to which Pt is added is provided as an auxiliary magnetic film. However, the thickness of the auxiliary magnetic film is about 50 °, the pulse width of the recording signal is 60 ns, the pitch of the recording magnetic section is 1.53 μm, the linear velocity of the light beam with respect to the medium is 7.54 m / s, and the CN at the maximum output is The ratio was measured. As is apparent from this figure, the reproduction CN ratio of the magneto-optical recording medium of this example is almost constant until the amount of Pt added in the auxiliary magnetic film is about 10 to 12 at%, but when it exceeds that value, it sharply increases. descend. FIG. 55 shows the relationship between the magnitude of the erasing magnetic field of the magneto-optical recording medium used for obtaining the data of FIG. 54 and the amount of Pt added to the auxiliary magnetic film. However, in this example, the magnitude of the external magnetic field necessary for the noise level after erasing to be −40 dB with respect to the carrier wave level during recording was set to the magnitude of the erasing magnetic field. As is clear from this figure, when Pt is added to the auxiliary magnetic film, the required erasing magnetic field decreases as the addition amount increases. However, even if Pt exceeding 10 at% is added, the degree of decrease in the erasing magnetic field is extremely small. From this, about 10 at% of Pt is added to the auxiliary magnetic film made of the rare earth-transition metal amorphous perpendicular magnetic film in which the transition metal sublattice magnetization is dominant at the temperature at which the recording magnetic domain is formed in the third magnetic layer 4c. It can be seen that the addition increases the erasing magnetic field sensitivity to the limit.

In the ninth embodiment, Pt was used as an additive element of the auxiliary magnetic film, but Au, Ag, Al, Cu, Nb, Ho, Gd, Cr or the like may be used instead. Was obtained. In addition, even if the material of the transparent substrate 1, the material of the protective film 6, and the formation position of the auxiliary magnetic film 5 were changed as described in the description of the third embodiment, the same result as described above was obtained.

In the embodiment embodying the means for achieving the first and second objects, in the case where a ferromagnetic material rich in transition metal near the Curie temperature (FIG. 32) is used as the magneto-optical recording film, Although only the case where a rare earth-rich ferrimagnetic material near the Curie temperature is used (FIG. 33) has been described, in addition, a transition metal-rich ferromagnetic material near the Curie temperature (FIG. 34) and a rare earth-rich ferromagnetic material near the Curie temperature are used. Ferromagnetic material (FIG. 35) can also be used. In the present embodiment, only the magnitude of the magnetic moment of the magneto-optical recording film near the Curie temperature is taken into consideration, and the magnitude of the magnetic moment of the magneto-optical recording film at room temperature does not matter at all. For example, as shown in FIG. 36, even at room temperature, a rare-earth-rich ferrimagnetic material, which becomes a transition metal-rich ferrimagnetic material near the Curie temperature, can be treated as a transition metal-rich ferrimagnetic material. it can. 32 to 36, black arrows indicate the magnetic moment of the transition metal, and white arrows indicate the magnetic moment of the rare earth metal.

Next, an embodiment that embodies the means for achieving the second object will be described.

As shown in FIG. 56, the ultraviolet curable resin layer 21 to which the preformat pattern (not shown) is transferred is brought into close contact with one surface of the glass disk 22 by the so-called 2P method, and the transparent substrate 1 with the preformat pattern is placed. Produced.

Next, on the preformat pattern of the transparent substrate 1, from the transparent substrate 1 side, an enhanced layer 3 made of a silicon nitride dielectric having a thickness of about 850 ° and a terbium-iron-cobalt amorphous layer having a thickness of about 300 ° An alloy recording layer 4, a non-stoichiometric iron oxide intermediate layer 23 having a thickness of about 200 °, and a terbium-dysprosium-iron-cobalt amorphous alloy auxiliary layer 5 having a thickness of about 1200 °. And a silicon nitride protective layer 6 having a thickness of about 1000 ° were sequentially laminated to produce a disk single plate 24 shown in FIG. Finally, the two disk single plates 24 manufactured as described above were bonded concentrically, with each layer inside, to manufacture a magneto-optical disk having an air sandwich structure shown in FIG.

透明 A transparent substrate 1 made of polycarbonate having a preformat pattern (not shown) formed on one side was produced by an injection molding method.

Next, on the preformat pattern of the transparent substrate 1, from the transparent substrate side 1, an enhance layer 3 made of silicon nitride dielectric having a thickness of about 850 ° and a terbium-iron-cobalt amorphous layer having a thickness of about 250 ° Recording layer 4 made of a porous alloy, an intermediate layer 23 made of a cobalt oxide having a non-stoichiometric composition having a thickness of about 150 °, an auxiliary layer 85 made of a gadolinium-terbium amorphous alloy having a thickness of about 1200 °, A silicon nitride dielectric protective layer 6 of 1000 Å was sequentially laminated to produce a disk single plate 28 shown in FIG.

Finally, the two disk single plates 28 manufactured as described above were bonded concentrically with each layer inside, thereby manufacturing a magneto-optical disk having a close bonding structure shown in FIG.

When the coercive force-temperature characteristics and the saturation magnetization-temperature characteristics of the recording layer and the auxiliary layer formed on each of the magneto-optical disks of the tenth and eleventh examples were examined, both of them had the characteristics shown in FIG. It turns out. That is, the recording layer 4 has a higher coercive force at room temperature than the auxiliary layer 5 and has a lower Curie point than the auxiliary layer 5. The recording layer 4 has a lower saturation magnetization at room temperature than the auxiliary layer 5.

When the L level laser power required for erasing the recording magnetic domain and the H level laser power required for recording the information were examined for each of the magneto-optical disks of the tenth and eleventh embodiments, both of them were shown in FIG. As shown in FIG. 7, the previously recorded signal can be reproduced by applying an L level laser power of about 4 mW or less, and the information can be reproduced by applying an H level laser power of about 14 mW or more. It turned out that the record could be made.

Further, while variously changing the magnitude of the initialization magnetic field, the signal of 1.85 [MHz] is overwritten on the track on which the signal of 4.93 [MHz] is recorded, and the signal of 4.93 [MHz] is overwritten. The magnitude of the initialization magnetic field where the signal was completely erased and the 1.85 [MHz] signal was overwritten was examined. In each of the magneto-optical disks of the tenth and eleventh embodiments, as shown in FIG. 60, only by applying an initialization magnetic field of about 1 [KOe], the previously recorded signal of 4.93 [MHz] can be obtained. The signal of 1.85 [MHz] which has been completely erased and recorded later has reached the saturation level, and has been initialized compared to the prior art in which an initialization magnetic field of 5 to 6 [KOe] has to be applied. It turns out that the magnet can be made much smaller.

However, with respect to the magneto-optical disk of the tenth embodiment, the signal of 1.85 [MHz] is intensity-modulated to an L level of 6 [mW] and an H level of 14 [mW], and overwritten. For the magneto-optical disk of No. 1, the signal of 1.85 [MHz] was intensity-modulated to an L level of 5.5 [mW] and an H level of 12 [mW], and overwritten by overwriting. The power of the reproducing laser beam was 1.5 [mW].

In addition, not only the magneto-optical disks of the tenth and eleventh embodiments but also the magneto-optical recording media according to all the inventions listed as means for achieving the second object have the same effects as described above. confirmed.

Next, a description will be given of an embodiment that embodies means for achieving the third object.

As shown in FIG. 61, on one surface of a glass plate 31 having a diameter of 10 inches, an ultraviolet curing resin layer 32 to which a preformat pattern 2 has been transferred is formed by a so-called 2P method, and the transparent substrate 1 with the preformat pattern is formed. Produced.

Next, on the preformat pattern 2 of the transparent substrate 1, from the transparent substrate 1 side, an enhanced layer 3 made of silicon nitride having a thickness of about 80 nm, a thickness of about 20 nm, and a Curie temperature of 190 ° C. A magnetic layer 4 made of an amorphous terbium-iron-cobalt alloy having a compensation temperature of 100 ° C., an auxiliary magnetic layer 5 made of a platinum-cobalt alloy having a thickness of about 5 nm, and a thermal control layer made of silicon nitride having a thickness of about 25 nm 8 and an aluminum-titanium alloy reflective layer 7 having a thickness of about 50 nm were sequentially laminated to produce a single disk. Thereafter, the two disk single plates thus manufactured were bonded to each other to manufacture a magneto-optical disk having an air sandwich structure shown in FIG.

This magneto-optical disk is mounted on a drive device, and rotated at 3600 rpm to position a laser beam spot at a portion where the outermost peripheral linear velocity becomes 45 m / s. The recording frequency is 32 MHz, the recording laser power is about 10 mW, and an external magnetic field is applied. The signal was recorded under the condition of 3000e, and the signal was reproduced by irradiating a 4.0 mW reproduction laser beam. As a result, a reproduction C / N of 49 dB could be obtained. FIG. 62 shows the reproduction C / N-recording laser power characteristics of the magneto-optical disk of this example.

As shown in FIG. 61, on one surface of a glass plate 31 having a diameter of 5 inches, an ultraviolet curable resin layer 32 to which a preformat pattern has been transferred is formed by a so-called 2P method to produce a transparent substrate 1 with a preformat pattern. did.

Next, on the preformat pattern 2 of the transparent substrate 1, from the transparent substrate 1 side, an enhanced layer 3 made of silicon nitride having a thickness of about 80 nm, a thickness of about 20 nm, and a Curie temperature of 185 ° C. Magnetic layer 4 made of terbium-iron-cobalt-niobium amorphous alloy having a compensation temperature of 80 ° C., thermal control layer 8 made of silicon nitride having a thickness of about 25 nm, and reflection made of aluminum-titanium alloy having a thickness of about 50 nm The layers 7 were sequentially laminated to produce a magneto-optical disk having a close-adhering structure shown in FIG.

This magneto-optical disk is mounted on a drive device, and rotated at 3600 rpm to position a laser beam spot at a position where the outermost peripheral linear velocity is 22.5 m / s. A recording frequency of 14.8 MHz and a recording laser power of about 6 When a signal was recorded under the conditions of 0.5 mW and an external magnetic field of 300 Oe, and the signal was reproduced by irradiating a 4.0 mW reproduction laser beam, a reproduction C / N of 48 dB could be obtained.

Also, the thickness of the enhancement layer 3 is changed in the range of 70 to 80 nm, the thickness of the magnetic layer 4 is changed in the range of 10 to 30 nm, and the thickness of the thermal control layer 8 is changed in the range of 20 to 100 nm. Even when the thickness of the reflective layer 7 was changed in the range of 70 nm or less and about 50 nm, the same result as described above was obtained.

Hereinafter, an embodiment that embodies means for achieving the fourth object will be described. In the optical disk according to the fourteenth embodiment, a silicon nitride film for enhancing the Kerr rotation angle is formed on a substrate to a thickness of 800 nm, a TbFeCo film as a magneto-optical recording film is formed to a thickness of 20 nm, and a silicon nitride film as a protective film is formed to a thickness of 300 nm. Then, a first optical disc having an aluminum film laminated as a reflective film having a thickness of 50 nm and a second optical disc having an aluminum film formed as a reflective film having a thickness of 30 nm on a substrate are bonded together via an adhesive. Become.

１５ Hereinafter, a fifteenth embodiment that embodies means for achieving the fifth object will be described. In the fifteenth embodiment, the adhesive 17 for bonding the transparent substrate 1 and the inner spacer 15 and the outer spacer 16 in FIG. 11 and the bonding for bonding the recording disks 11 and 12 in FIG. The improvement of agent 17.

The adhesive layer 17 is formed by using an adhesive containing, for example, a hot melt adhesive or an epoxy-based adhesive as a main component and a silane coupling agent or a titanium coupling agent added thereto. Examples of the silane coupling agent include γ-glycidoxypropyltritomexisilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyl Triethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane and the like can be mentioned. As the titanium coupling agent, titanium stearate and the like can be mentioned. The content of the silane coupling agent or the titanium coupling agent with respect to the adhesive is preferably about 0.1% by weight to 10% by weight. As a method for forming the adhesive, for example, a roll coating method, a spray coating method, a screen printing method, or the like can be applied depending on the type of the adhesive to be used.

As another example, an adhesive layer to which an inorganic filler surface-treated with a silane coupling agent or a titanium coupling agent is added can be used.

As the inorganic filler, for example, a granular material or a powdery material such as SiO ₂ , SiO, Al ₂ O ₃ , and AlN can be used. As the silane coupling agent or titanium coupling agent used for the surface treatment, those described above can be used. In addition, as a surface treatment method, a silane coupling agent or a titanium coupling agent is applied to the surface of the inorganic filler, or a silane coupling agent or a titanium coupling agent is impregnated into fine spaces formed in the inorganic filler. You can take the method.

効果 The following is an experimental example of the magneto-optical recording medium according to the fifteenth embodiment, and the effects will be described.

<Experimental examples 1 to 17>
A desired preformat pattern was transferred onto one surface of a glass plate having an inner diameter of 15 mm, an outer diameter of 130 mm, and a thickness of 1.2 mm by a so-called 2P method to produce a replica substrate. Next, a magneto-optical recording film was laminated on the preformat pattern of the replica substrate to produce a magneto-optical recording single plate. Further, an inner peripheral spacer made of aluminum having an inner diameter of 15 mm, an outer diameter of 25 mm, and a thickness of 0.5 mm, and an outer peripheral spacer made of aluminum having an inner diameter of 125 mm, an outer diameter of 130 mm, and a thickness of 0.5 mm are provided. And were prepared. Further, various adhesives were prepared in which an epoxy adhesive (Araldite manufactured by Ciba-Geigy) was used as a main component and a silane coupling agent or a titanium coupling agent in combination as shown in FIG. 63 was added thereto.

A magneto-optical recording veneer is attached to the inner and outer spacers on which the adhesive layer is formed with the adhesive, with the magneto-optical film inward, and silane added to the adhesive. Seventeen types of optical information recording media having different types and combinations of coupling agents or titanium coupling agents and different amounts of addition were prepared. However, the thickness of the adhesive layer was about 30 μm.

After leaving these optical information recording media in an environment of a temperature of 120 ° C. and a relative humidity of 100% for 100 hours, and taking out and observing them, the optical information recording media of Experimental Examples 1 to 12 showed any abnormality in the bonded portion. Never On the other hand, in the optical information recording media of Experimental Examples 13, 15, and 17, peeling occurred at the interface between the replica substrate and the adhesive layer. Further, in the optical information recording media of Experimental Examples 14 and 16, it was observed that the filler was separated from the adhesive layer and diffused onto the magneto-optical film. From these results, it is understood that the content of the silane coupling agent or the titanium coupling agent with respect to the adhesive is preferably about 0.1% by weight to 10% by weight.

<Experimental Examples 18 to 27>
Magneto-optical recording single plates, inner spacers, and outer spacers similar to those used in Experimental Examples 1 to 17 were produced. In addition, various adhesives were prepared in which an epoxy adhesive (Araldite manufactured by Ciba-Geigy) was used as a main component and a filler and a silane coupling agent in the combination shown in FIG. 64 were added thereto.

A magneto-optical recording veneer is attached with the magneto-optical film inward on both the front and back surfaces of the inner spacer and the outer spacer on which the adhesive layer is formed with the adhesive, and a filler added to the adhesive And 17 types of optical information recording media having different types and combinations and different amounts of addition. However, the thickness of the adhesive layer was about 30 μm.

After leaving these optical information recording media in an environment of a temperature of 120 ° C. and a relative humidity of 100% for 100 hours, and taking out and observing them, the optical information recording media of Experimental Examples 18 to 23 showed any abnormality in the bonded portion. Never On the other hand, in the optical information recording media of Examples 24 to 27, peeling occurred at the interface between the replica substrate and the adhesive layer. From this result, it is understood that the content of the filler with respect to the adhesive is preferably 60% by weight or less.

In the fifteenth embodiment, only the adhesion between the replica substrates or between the replica substrate and the spacer has been described. However, in the optical disc having a center hub at the center of the optical recording single plate, the replica substrate is It can also be applied to bonding to a center hub.

In the fifteenth embodiment, an optical disk has been described as an example, but the present invention can also be applied to the manufacture of optical information recording media of other shapes such as optical cards.

１６ Hereinafter, a sixteenth embodiment that embodies the means for achieving the sixth object will be described. The sixteenth embodiment relates to the improvement of the inorganic dielectric layer forming the enhance film 3.

FIG. 65 is a cross-sectional view of a main part of a magneto-optical recording medium according to Example 11, in which an oxide layer 61, a nitride layer 62, and a The magneto-optical recording film 4, the protective layer 6, and the reflective layer 7 are sequentially laminated, and the enhancement film 3 includes the oxide layer 61 and the nitride layer 62.

As the oxide layer 61, for example, a metal or semimetal oxide such as SiO ₂ , ZrO ₂ , Ta ₂ O ₅ , MgO, Y ₂ O ₃ , Al ₂ O ₃ , and CaO is used. The thickness of the oxide layer 1 is regulated in the range of 30 to 800 ° for the above-described reason.

Examples nitride layer 62, for example _{AlN, BN, Si 3 N 4} , TaN, a metal or a nitride of semimetal, such as TiN are used. The thickness of the nitride layer 2 is regulated in the range of 500 to 2000 ° for the reason described above.

Others are the same as those of the magneto-optical recording medium according to each of the above-described embodiments, and a description thereof will not be repeated.

Next, an experimental example and a comparative example of the magneto-optical recording medium according to the sixteenth embodiment will be described. Experimental Examples 1 to 10 according to the sixteenth embodiment, enhance film 3 (the oxide layer 61 / nitride layer 62) is _SiO 2 _/ SiN, respectively, SiMgO / SiN, ZrO 2 / SiN, SiZrO / SiN, ZrYO / SiN , Ta ₂ O ₅ / AlN, AlTaO / SiAlN, SiYO / SiTaN, Y ₂ O ₃ / AlTaN, and CaSiO / SiAlN. On the other hand, in Comparative Examples 1 and 2 according to the sixteenth embodiment, the enhance film 3 is made of SiN and SiO, respectively. The transparent substrate 1 is made of polycarbonate, the magneto-optical recording film 4 is made of Tb-Te-Co, and the reflective layer 7 is made of Al. The thickness of the enhance film 3 is 900 to 1100 °, and the thickness of the Tb-Te-Co recording film is Was set to 300 °, and the thickness of the Al reflecting film was set to 600 °.

加速 FIG. 66 shows the results of acceleration tests performed on the optical disk single plates according to Experimental Examples 1 to 5 and the optical disk single plates according to Comparative Examples 1 and 2 at 80 ° C. and 90% RH.

図 As is clear from this figure, the bit error rate of the conventional device, particularly the comparative example in which an underlayer made of only SiO is formed on a transparent substrate and an optical recording film is formed directly thereon, is very high. On the other hand, those according to Experimental Examples 1 to 5 have very low bit error rates and are stable in performance even after a long period of time. It can be proved that it is an information recording medium.

Finally, an example of a method for manufacturing a magneto-optical recording medium suitable for increasing the external magnetic field sensitivity of the magneto-optical recording film will be described.

(4) If an in-plane magnetic film having an appropriate thickness is provided on the surface of the perpendicular magnetic film, the external magnetic field sensitivity of the magneto-optical recording medium can be improved, and the in-plane magnetic film can be formed by oxidizing the surface of the perpendicular magnetic film. When a perpendicular magnetization film is formed on a transparent substrate, the perpendicular magnetization film is oxidized by moisture contained in the transparent substrate, and an in-plane magnetization film is generated on the surface of the perpendicular magnetization film. Here, if the amount of moisture contained in the transparent substrate is too large, an unnecessarily large in-plane magnetized film is generated, the external magnetic field sensitivity is reduced, and if the amount of moisture contained in the transparent substrate is too small, the necessary film is formed. A thick in-plane magnetized film is not generated, and the external magnetic field sensitivity also decreases. Therefore, by adjusting the amount of water contained in the transparent substrate, an in-plane magnetization film having an optimum thickness can be generated, and a magneto-optical recording medium having high external magnetic field sensitivity can be obtained.

According to experiments, when a transparent substrate made of a polymer compound is used, it is better to form a perpendicular magnetization film in a short time after dehydrating the transparent substrate under the above conditions. Magnetic field sensitivity can be obtained, and the external magnetic field sensitivity decreases as the storage time after the dehydration treatment increases. In particular, when the storage time under the above conditions exceeds 50 minutes, the external magnetic field sensitivity is sharply reduced. On the other hand, when a transparent substrate provided with a transfer layer made of a polymer compound on one side of a glass plate is used, after performing the dehydration treatment of the transparent substrate under the above conditions, a certain amount of time has elapsed. Therefore, a higher external magnetic field sensitivity can be obtained by forming a perpendicular magnetization film. More specifically, the storage of the storage conditions for 4 hours or more under the above-described storage conditions can provide almost the best external magnetic field sensitivity. The following seventeenth to nineteenth embodiments are based on such knowledge.

ポ リ カ ー ボ ネ ー ト A polycarbonate disk-shaped transparent substrate having a preformat pattern on one side (hereinafter referred to as a PC substrate) was prepared by injection molding.

(4) This PC substrate was placed in a baking furnace and heated at a temperature of 80 ° C. under atmospheric pressure for 4 hours or more to perform a dehydration treatment.

The PC substrate was taken out of the baking furnace and stored in an environment where the temperature was 20 ° C. and the relative humidity was 60%. Thereafter, the PC substrate taken out of the baking furnace is housed in a radio frequency (RF) sputtering device, and a SiN enhancement film, a TbFeCo perpendicular magnetization film, a SiN protective film, and an Al reflection film are formed on the preformat pattern forming surface. Were laminated in this order to produce a magneto-optical recording medium having a cross-sectional structure shown in FIG. In FIG. 67, 1 is a PC substrate, 2 is a preformat pattern, 3 is a SiN enhancement film, 4 is a TbFeCo perpendicular magnetization film, 9 is an oxide layer (in-plane magnetization film) of a TbFeCo perpendicular magnetization film, 6 is a SiN protective film, Reference numeral 7 denotes an Al reflection film.

FIG. 68 shows the relationship between the storage time after removing the dehydrated PC substrate from the baking furnace and the recording characteristics of the magneto-optical disk manufactured using the PC substrate. The recording characteristics are measured by irradiating a recorded magneto-optical disk with a laser beam at an erasing level while applying an erasing magnetic field of 180 (Oe), and measuring the residual magnetic field (noise) of the track on which the erasing operation was performed by a PIN photo. The measurement was performed by a differential characteristic detector equipped with a diode differential detector. As shown in the figure, the magneto-optical disk of this example has a higher external magnetic field sensitivity when the perpendicular magnetization film 4 or the like is formed within a short time after the dehydration processing of the PC substrate 1 is performed. As the storage time after the dehydration treatment increases, the external magnetic field sensitivity decreases. From this data, it is understood that it is preferable to form the perpendicular magnetization film 4 and the like within 50 minutes after the dehydration treatment under the above conditions. The reason why the external magnetic field sensitivity sharply decreases after 50 minutes or more after the dehydration treatment is that the dehydrated PC substrate 1 absorbs water with the passage of time, and the surface of the perpendicular magnetization film 4 is excessively oxidized, resulting in excessive It is presumed that this is because an in-plane magnetized film having a large thickness is generated.

In the above embodiment, SiN was used for the enhancement film 3 and the protective film 5. However, the same result as described above was obtained when other inorganic dielectrics such as SiO ₂ , SiO, Si ₂ N ₃ , and AlN were used. was gotten. The same results as above were obtained also when a UV resin protective film was formed instead of the inorganic protective film. In addition, the same results as above were obtained when the thickness of each film was variously changed. Further, when the perpendicular magnetization film 4 was formed of a rare earth-transition metal based amorphous perpendicular magnetization film other than TbFeCo, the same result as described above was obtained.

The PC substrate was dehydrated by heating at 80 ° C. for 1 hour or more in a vacuum chamber evacuated to a degree of vacuum of 20 (Pa) or less. Other conditions were the same as in the first embodiment.

FIG. 69 shows the relationship between the storage time after removing the dehydrated PC substrate from the baking furnace and the recording characteristics of a magneto-optical disk manufactured using the PC substrate. The measurement conditions for the recording characteristics were the same as in the first embodiment. As shown in the figure, the magneto-optical disk of the present example also shows almost the same tendency as that of the first embodiment, but the stability of the external magnetic field sensitivity for 50 minutes after the dehydration processing is further improved. This is presumed to be due to the fact that the PC board is more highly dehydrated in the present embodiment than in the first embodiment, and it takes more time for the PC board to absorb moisture until it affects the external magnetic field sensitivity. Is done.

In the magneto-optical disk of this embodiment, as in the case of the seventeenth embodiment, when the material of the enhance film and the material of the protective film, the thickness of each film, and the material of the perpendicular magnetization film are variously changed, Similar results were obtained.

(4) A disk-shaped transparent substrate made of glass (hereinafter, referred to as a 2P substrate) having a preformat pattern transfer resin layer (hereinafter, referred to as a resin layer) provided on one side was manufactured by a so-called 2P method.

The 2P substrate was placed in a baking furnace and heated at a temperature of 80 ° C. under atmospheric pressure for 4 hours or more to perform a dehydration treatment.

The # 2P substrate was taken out of the baking furnace and stored in an environment at a temperature of 20 ° C. and a relative humidity of 60%. Thereafter, the 2P substrate taken out of the baking furnace is housed in an RF sputtering apparatus, and a SiN enhanced film, a TbFeCo perpendicular magnetization film, a SiN protective film, and an Al reflection film are formed on the preformat pattern forming surface. By laminating in order, a magneto-optical recording medium having a cross-sectional structure shown in FIG. 70 was manufactured. 70, reference numeral 1 denotes a 2P substrate, 22 denotes a glass plate, 21 denotes a resin layer, and other portions corresponding to those in FIG. 67 described above are denoted by the same reference numerals.

FIG. 71 shows the relationship between the storage time after removing the dehydrated 2P substrate from the baking furnace and the recording characteristics of the magneto-optical disk manufactured using the 2P substrate. The method for measuring the recording characteristics is the same as in the above embodiments. As shown in the figure, in the case of the present example, unlike the case of each of the above-described embodiments, a higher external magnetic field sensitivity is obtained when the perpendicular magnetization film is formed after a certain time has elapsed after the dehydration treatment. Obtainable. This is because, in the case of a 2P substrate, since the resin layer is thin, dehydration is performed at a high altitude under the above-mentioned dehydration conditions. As a result, if a perpendicular magnetization film or the like is immediately formed, the oxidation required for improving the external magnetic field sensitivity is reduced. This is presumed to be because a film, that is, an in-plane magnetized film cannot be formed. From the data in FIG. 71, it is understood that it is preferable to form the perpendicular magnetization film 4 or the like after 4 hours or more, more preferably 6 hours or more after the dehydration treatment under the above conditions.

In the magneto-optical disk of the present embodiment, as in the case of the first embodiment, when the enhance film material, the protective film material, the film thickness of each film, and the perpendicular magnetization film material are variously changed, Similar results were obtained.

The twentieth embodiment relates to a preferred combination of a magneto-optical recording film and an auxiliary magnetic film, and a method for manufacturing both films.

In the magneto-optical recording medium of this embodiment, a first enhanced film, a magneto-optical recording film, an auxiliary magnetic film, a second enhanced film, and a heat diffusion film are laminated in this order on a transparent substrate.

The magneto-optical recording film is an amorphous alloy of a rare earth-transition metal-addition element system represented by the following general formula and has no compensation temperature, that is, is formed of a magnetic film in which the rare earth moment is dominant up to the Curie temperature. The auxiliary magnetic film is formed by adding oxygen or nitrogen to this alloy.

_{Formula; (Tb 100-A Q A} ) X Fe 100-X-Y-Z Co Y M Z
However, 25 atom% ≦ X ≦ 40 atom%
5 atomic% ≦ Y ≦ 15 atomic%
0 atomic% ≦ Z ≦ 10 atomic%
0 atomic% ≦ A ≦ 20 atomic%
M is at least one element selected from Nb, Cr, Pt, Ti, and Al;
Q is at least one element selected from Gd, Nd, and Dy. The magneto-optical recording film is formed to a thickness of 100 to 500 °, and the auxiliary magnetic film is formed to a thickness of 5 to 40%. After the sputtering of the first enhanced film and the magneto-optical recording film is completed according to a conventional method, the degree of vacuum in the sputtering chamber is adjusted to 1 × 10 ⁶ to 1 × 10 ⁴ (Pa), and It can be formed by heating under conditions or by heating while introducing a mixed gas of oxygen or nitrogen and a sputtering gas (eg, Ar, Kr, Xe, etc.) into the sputtering chamber. The second enhanced film and the thermal diffusion film are sputtered according to a standard method after the formation of the auxiliary magnetic film. According to this method, all films can be continuously sputtered, so that a magneto-optical recording medium can be manufactured with high productivity.

FIG. 72 shows a magneto-optical recording medium having a Tb _31.7 Fe _56.4 Co _11.9 magneto-optical recording film having a thickness of 400 ° and a TbFeCo auxiliary magnetic film having a thickness of 100% containing 5% oxygen (No. 20 Example product), a magneto-optical recording medium (comparative example product) in which the composition of the magneto-optical recording film is the same as that of the 20th example product and a TbFeCo auxiliary magnetic film containing no oxygen is laminated, and a conventional product 4 shows the magnetic field dependence of C / N. As is clear from this figure, the product of the twentieth embodiment can reach the saturation magnetization with an external magnetic field of 50 (Oe), and does not reach the saturation magnetization unless an external magnetic field of 100 (Oe) or more is applied. The external magnetic field sensitivity is remarkably improved as compared with the comparative example product and the conventional product which does not reach saturation magnetization unless an external magnetic field of 200 (Oe) or more is applied.

FIG. 2 is a sectional view of a main part of the magneto-optical recording medium according to the first embodiment. FIG. 4 is a graph illustrating the effect of the ferromagnetic reflection film in the first embodiment. FIG. 4 is a graph showing a relationship between a composition of a PtCo thin film and a magnetic field in an erasing direction in a first example. FIG. 3 is an explanatory diagram of a magneto-optical recording medium according to Experimental Example 1 and Comparative Example. FIG. 5 is a graph diagram showing a comparison between recording and erasing characteristics of magneto-optical recording media according to each experimental example and a comparative example in the first example. FIG. 7 is a sectional view of a main part of a magneto-optical recording medium according to a second embodiment. FIG. 11 is an explanatory diagram illustrating a temperature distribution of a laser beam irradiation unit in the second embodiment. It is a graph which shows the relationship between the composition of the heat control layer in 2nd Example, and the temperature of a laser beam irradiation part. It is a graph which shows the relationship between the composition of the heat control layer in 2nd Example, and thermal conductivity. FIG. 9 is a graph showing the relationship between the composition of the thermal control layer and the durability against repeated recording and reproduction in the second example. FIG. 7 is a cross-sectional view illustrating a specific structure of a magneto-optical recording medium according to a second embodiment. FIG. 7 is a cross-sectional view illustrating a specific structure of a magneto-optical recording medium according to a second embodiment. FIG. 14 is a diagram illustrating a reproduction signal output characteristic of a magneto-optical recording medium according to each experimental example in the second example. FIG. 11 is a graph showing durability against repeated recording and reproduction of the magneto-optical recording medium according to the second example. It is a graph which shows the relationship between the composition of a heat control layer in 2nd Example, thermal conductivity, and film thickness. It is a graph which shows the relationship between the composition of the heat control layer in 2nd Example, and thermal conductivity. It is a graph which shows the relationship between the composition of the heat control layer in 2nd Example, and thermal conductivity. FIG. 11 is a graph showing the relationship between the N mixing ratio and O mixing ratio in the magneto-optical recording film and the perpendicular magnetic anisotropy constant in the third example. FIG. 13 is a graph showing the relationship between the N mixing ratio and O mixing ratio in the magneto-optical recording film and the residual Kerr rotation angle in the third example. FIG. 13 is a table showing an example of the composition and thickness of each film laminated on the magneto-optical recording medium in the third example. 21 is a graph showing the relationship between the N mixing ratio and O mixing ratio measured using the magneto-optical recording medium of FIG. 20 and the reproduction CN ratio. 21 is a graph showing the relationship between the N mixing ratio and O mixing ratio measured using the magneto-optical recording medium of FIG. 20 and the saturation recording magnetic field. 21 is a graph showing the relationship between the N mixing ratio and the O mixing ratio measured using the magneto-optical recording medium of FIG. 20 and the erasing magnetic field. FIG. 13 is a table showing a method of manufacturing a magneto-optical recording medium according to each of the experimental examples and the comparative examples in the third example, and shows a reproducing CN ratio, a saturation recording magnetic field, an erasing magnetic field, an N mixing ratio, and an O mixing ratio. FIG. 14 is a sectional view of a main part of a magneto-optical recording medium according to a fourth embodiment. FIG. 14 is a graph showing the relationship between the Curie temperature of the auxiliary magnetic film and the required erasing magnetic field in the fourth example. FIG. 14 is a graph showing the relationship between the composition of an auxiliary magnetic film and the Curie temperature in a fourth example. FIG. 14 is a graph showing a comparison between recording and erasing characteristics of a magneto-optical recording medium according to a fourth embodiment and a conventional magneto-optical recording medium. FIG. 14 is a cross-sectional view of a principal part showing a modification of the magneto-optical recording medium according to the fourth embodiment. FIG. 16 is a cross-sectional view of a principal part showing another modification of the magneto-optical recording medium according to the fourth embodiment. FIG. 2 is an explanatory diagram illustrating an example of a configuration of a magneto-optical recording medium capable of overwriting by a light intensity modulation method. FIG. 4 is an explanatory diagram of a transition metal-rich ferrimagnetic material near the Curie temperature. FIG. 4 is an explanatory diagram of a rare-earth-rich ferrimagnetic material near the Curie temperature. FIG. 3 is an explanatory diagram of a transition metal-rich ferromagnetic material near the Curie temperature. FIG. 3 is an explanatory diagram of a rare earth-rich ferromagnetic material near the Curie temperature. FIG. 3 is an explanatory diagram of a ferrimagnetic material that is rich in rare earth at room temperature and rich in transition metal near the Curie temperature. FIG. 14 is an explanatory diagram schematically showing a structure of a magnetic film according to a fifth example. FIG. 14 is a graph illustrating a torque curve of the magneto-optical recording medium according to the fifth example. FIG. 7 is a graph illustrating a torque curve of a magneto-optical recording medium according to a conventional example. FIG. 3 is a graph showing a correlation between a sample temperature and a peak value of a torph curve. FIG. 14 is a graph showing the external magnetic field characteristics of the magneto-optical recording medium according to the fifth example. FIG. 14 is a graph illustrating bit error occurrence characteristics of the magneto-optical recording medium according to the fifth example. FIG. 14 is a cross-sectional view illustrating a film structure of a magneto-optical recording medium according to a fifth example. FIG. 14 is a graph showing the magnetic field modulation recording characteristics of the magneto-optical recording medium of the fifth embodiment having an auxiliary magnetic film. FIG. 14 is a sectional view of a main part of a magneto-optical recording medium according to a fifth embodiment having an auxiliary magnetic film. FIG. 14 is a sectional view of a main part of a magneto-optical recording medium according to a sixth embodiment. FIG. 14 is a graph illustrating the effect of the magneto-optical recording medium according to the sixth example. FIG. 14 is a sectional view of a main part of a magneto-optical recording medium according to a seventh embodiment. FIG. 14 is a graph illustrating the effect of the magneto-optical recording medium according to the seventh example. FIG. 14 is a sectional view of a main part of a magneto-optical recording medium according to an eighth embodiment. FIG. 19 is a graph illustrating the effect of the magneto-optical recording medium according to the eighth example. FIG. 19 is a graph showing the relationship between the perpendicular magnetic anisotropy constant of the magneto-optical recording medium according to the ninth embodiment and the amount of platinum added to the auxiliary magnetic film. FIG. 19 is a graph showing the relationship between the residual Kerr rotation angle of the magneto-optical recording medium according to the ninth embodiment and the amount of platinum added to the auxiliary magnetic film. FIG. 19 is a graph showing the relationship between the reproduction CN ratio of the magneto-optical recording medium according to the ninth embodiment and the amount of platinum added to the auxiliary magnetic film. FIG. 19 is a graph showing the relationship between the minimum erasing magnetic field of the magneto-optical recording medium according to the ninth embodiment and the amount of platinum added to the auxiliary magnetic film. It is a sectional view showing the film structure of the medium concerning a 10th example. It is a sectional view showing the film structure of a medium concerning an 11th example. FIG. 14 is a graph showing coercive force-temperature characteristics and saturation magnetization-temperature characteristics of the recording layer and the auxiliary layer of the tenth and eleventh examples. FIG. 4 is a graph showing the magnitude of laser power required for overwriting information. FIG. 4 is a graph showing the magnitude of an initialization magnetic field required for overwriting information. FIG. 34 is a sectional view of a main part of a magneto-optical recording medium according to a thirteenth embodiment. FIG. 29 is a diagram showing the reproduction C / N-recording laser power characteristics of the magneto-optical disk according to the fourteenth example. It is a table | surface figure which shows the coupling agent composition in an adhesive agent. FIG. 3 is a table showing the composition of a coupling agent and a filler in an adhesive. It is principal part sectional drawing of a magneto-optical recording medium concerning 16th Example. It is a graph which shows the corrosion resistance test result of the magneto-optical recording medium concerning 16th Example. It is principal part sectional drawing of a magneto-optical recording medium concerning 17th Example. It is a graph which shows the relationship between a leaving time and external magnetic field sensitivity. It is a graph which shows the relationship between a leaving time and external magnetic field sensitivity. FIG. 37 is a sectional view of a main part of a magneto-optical recording medium according to a nineteenth embodiment. It is a graph which shows the relationship between a leaving time and external magnetic field sensitivity. FIG. 37 is a graph showing the magnetic field dependence of the CN ratio of the magneto-optical recording medium according to Example 20. FIG. 4 is an explanatory diagram showing the principle of overwriting of a magneto-optical recording medium having an auxiliary magnetic film by a magnetic field intensity modulation method. FIG. 5 is an explanatory diagram showing recording / erasing characteristics of a magneto-optical recording film of RE-rich at a low temperature just below the Curie temperature. FIG. 4 is an explanatory diagram showing the principle of overwriting of a magneto-optical recording medium having an auxiliary magnetic film by a light intensity modulation method. FIG. 4 is an explanatory diagram illustrating a method for selecting an external magnetic field strength and a laser power.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Preformat pattern 3 Enhancement film 4 Magneto-optical recording film 5 Auxiliary magnetic film 6 Protective layer 7 Reflective film 8 Thermal control layer

Claims (1)

A method for recording information on a magneto-optical recording medium including a recording layer made of a perpendicular magnetization film on a substrate,
The magneto-optical recording medium includes at least the recording layer and an auxiliary magnetic film having spontaneous magnetization,
It has magnetic properties such that the squareness ratio of the MH loop changes from a state of 1 to an intermediate state of 1 and 0 at a temperature equal to or lower than the Curie temperature when the temperature is increased,
An information recording method, wherein information is overwritten by a magnetic field intensity modulation method while heating the medium.

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