JPH10188381A - Optical disk and optical disk recording and/or reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record and reproduce an information signal with a recording and/or reproducing means disposed on the side of a protective cover by forming a recording part in laminating a reflecting layer and a recording layer successively on the surface side formed with projecting and recessing parts of a guide groove, etc., of a substrate and providing the protective cover that is thinner than the substrate to cover the recording part so as to protect this recording part. SOLUTION: The protective cover 8 serves as physical and mechanical protection for the recording part to be covered with, and its surface is optically smooth enough. Its thickness is formed to be thin as little as possible as well as a photosetting resin layer 7. An optical pickup for projecting a light beam is disposed on the side of the protective cover 8, and a recording magnetic layer 2 of the recording part 6 is irradiated with the light beam via this protective cover 8 and the photosetting resin layer 7. A magnet for impressing upon a magnetic field is also disposed on the side of the protective cover 8, so that the optical pickup and the magnet are disposed on the same surface side to record the information signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical disk used as a recording medium for information signals and an optical disk recording and / or reproducing apparatus using the optical disk.

[0002]

2. Description of the Related Art Conventionally, a magnetic thin film provided on a substrate is irradiated with a light beam to partially raise the temperature beyond a Curie point or a temperature compensation point to extinguish the coercive force. An optical disc has been proposed in which an information signal is recorded by applying a magnetic field and reversing the direction of magnetization in the direction of the recording magnetic field. This optical disk is used as a recording medium of an optical disk recording and / or reproducing device such as an external storage device of a computer and a recording device of audio and video information.

In general, this type of optical disk has a light-transmitting transparent substrate made of polycarbonate or the like on one surface thereof.
A recording magnetic layer having an easy axis of magnetization in the direction perpendicular to the film surface and having a large magneto-optical effect, for example, a recording unit in which a rare earth-transition metal alloy amorphous thin film, a reflective layer, and a dielectric layer are sequentially stacked, and a transparent substrate Is known in which a signal is read by irradiating a light beam from a light source.

For example, US Pat. No. 4,610,912 discloses an optical disk in which a dielectric layer, a recording magnetic layer, a dielectric layer, and a metal reflection film are sequentially laminated on a transparent substrate. The metal reflection film is provided for the purpose of increasing the apparent Kerr rotation angle together with the two dielectric layers,
The light beam transmitted through the recording magnetic layer is reflected to enable efficient reading.

[0005] In the optical disks proposed so far, the recording magnetic layer is disposed closer to the transparent substrate than the reflective layer.
In addition, an optical disk having a recording magnetic layer on both surfaces is bonded to a transparent substrate provided with the above-described recording portion via an ultraviolet-curing resin or the like in a state where the reflective layer is back to back. It is configured so that light irradiation is performed through the.

[0006]

By the way, an optical modulation method and a magnetic field modulation method are known as recording methods on an optical disk. The magnetic field modulation method is considered to be more advantageous than the optical modulation method in that it allows overwriting, that is, rewriting of information signals.Optical disks employing the magnetic field modulation method reverse the magnetic field of the recording magnetic layer at high speed. It is necessary to arrange a magnet for applying a magnetic field as close to the recording magnetic layer as possible.

On the other hand, in the case of an optical disk which reads signals from the transparent substrate side, it is necessary to secure mechanical strength with the transparent substrate carrying the recording magnetic layer, and the thickness of the transparent substrate is increased to some extent, for example, about several mm. It is necessary to

In an optical disk having the above-described structure, an optical pickup for irradiating a light beam is disposed on the transparent substrate side, and a magnet for applying a magnetic field must be disposed on the opposite side.

If the optical pickup and the magnet are arranged to oppose each other on both sides of the optical disc with the optical disc interposed therebetween, the size of a disc recording and / or reproducing apparatus using the optical disc as a recording medium is increased.
Further, when a light beam is irradiated from the side of the transparent substrate made of polycarbonate, the influence of the birefringence of the transparent substrate becomes a problem, and it is impossible to record and reproduce information signals with good recording and reproducing characteristics.

Further, particularly when an optical disk capable of recording on both sides is constructed so as to read signals from the transparent substrate side, the distance from the recording layer involved in recording becomes too large regardless of the arrangement of the magnets. This makes it extremely difficult to perform double-sided recording using the magnetic field modulation method. Even if an optical modulation method is adopted, the above-mentioned structure would make the disk itself very thick if it is a double-sided optical disk, and the disk recording and / or
Alternatively, it is disadvantageous for a demand for a reduction in size, thickness, and weight of the playback device.

Therefore, the present invention has been proposed in view of such a conventional situation, and realizes a good recording / reproducing characteristic of an information signal, and makes a disk recording and / or reproducing apparatus smaller and thinner. It is an object of the present invention to provide an optical disk which can achieve the above-mentioned characteristics and is less affected by birefringence.

Further, the present invention makes it possible to reduce the distance between the magnet and the recording layer even when a magnetic field is applied from the light beam irradiation surface side, and to efficiently record and reproduce information signals. It is an object of the present invention to provide an optical disk that can be used, and to provide a double-sided optical disk that can be reduced in overall thickness.

[0013]

An optical disk according to the present invention proposed to achieve the above-mentioned object has a substrate on which projections and depressions such as guide grooves are formed, and a surface on which the projections and depressions of this substrate are formed. On the side, a recording section formed by sequentially laminating a reflective layer and a recording layer, and a protective cover thinner than at least a substrate provided over the recording section so as to protect the recording section are provided. .

The protective cover can be provided on the recording section via an adhesive layer.

The protective cover covering the recording section is approximately 0.1 mm.
Made with thickness.

The optical disk according to the present invention is formed by sequentially laminating a substrate having guide grooves and other irregularities formed on both surfaces thereof and a reflective layer and a recording layer on each of the irregular surfaces of the substrate. The recording device includes a recording unit and a protective cover that is provided to cover each recording unit so as to protect each recording unit and that is thinner than at least the substrate, and enables information signals to be recorded on both surfaces of the substrate.

Each protective cover on this optical disk also
It can be provided on each recording unit via an adhesive layer.

Further, according to the present invention, a recording layer is provided by sequentially laminating a reflective layer and a recording layer on the surface of the substrate on which the irregularities such as guide grooves are formed, and the recording section is protected. An optical disc comprising a protective cover provided at least to cover the recording section and thinner than a substrate; and an optical disc recording apparatus comprising a recording and / or reproducing means arranged opposite to a surface of the optical disc provided with a protective cover. And / or a playback device.

The recording and / or reproducing means used in this optical disk recording and / or reproducing apparatus may comprise an optical pickup for irradiating the optical disk with a light beam and a magnetic field applying means for applying a magnetic field to the optical disk. it can.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk according to the present invention and an optical disk recording and / or reproducing apparatus using the optical disk will be described below with reference to the drawings.

As shown in FIG. 1, an optical disc according to the present invention has a recording magnetic layer 2, a dielectric layer 3,
A recording section 6 including a recording layer 4 and a reflective layer 5 is laminated, and the surface of the recording section 6 is further covered with a photocurable resin layer 7 and a protective cover 8.

The substrate 1 has a thickness of about several mm, here 1.
The substrate is a 2 mm disc-shaped substrate, and as the material, glass and the like are used in addition to plastic materials such as acrylic resin, polycarbonate resin, polyolefin resin, and epoxy resin.

Since the optical disk according to the present invention does not irradiate a light beam from the substrate 1 side, the substrate 1 is not necessarily required to be transparent. For example, a substrate having a high light reflectance such as an aluminum substrate may be used. If used, it is possible to omit the reflective layer 5 and use the substrate 1 itself as a reflective layer.

On one surface 1a of the substrate 1 on which the recording section 6 is provided, a guide groove or an address code having a depth of about 1/4 of the wavelength of a light beam used for recording and reproducing information signals. Irregularities 1b such as pits are provided.

The recording section 6 has a four-layer structure including a recording magnetic layer 2, a first dielectric layer 3, a second dielectric layer 4, and a reflective layer 5, as shown in FIG. It is arranged on the substrate 1 side of the recording magnetic layer. That is, on the substrate 1, the reflection layer 5, the second dielectric layer 4, the recording magnetic layer 2, the first
Are stacked in this order.

Of these, the first dielectric layer 3 and the second
As the dielectric layer 4, an oxide, a nitride, or the like can be used. However, a material that does not transmit oxygen and water molecules, does not contain oxygen, and can sufficiently transmit a used light beam is preferable. Silicon nitride, aluminum nitride, or the like is preferable.

The recording magnetic layer 2 is an amorphous ferromagnetic layer having an easy magnetization direction in a direction perpendicular to the film surface, and has not only excellent magneto-optical properties but also a large coercive force at room temperature. Further, it is desirable to have a Curie point around 200 ° C. Examples of the recording material satisfying such conditions include a rare earth-transition metal alloy amorphous thin film and the like.
A bFeCo-based amorphous thin film is preferable. The recording magnetic layer 2 may be added with a small amount of an additional element such as Cr for the purpose of improving corrosion resistance.

The reflection layer 5 is preferably made of a film having a high reflectivity that reflects a light beam by 70% or more at the boundary with the second dielectric layer 4, and is preferably a non-magnetic metal deposited film. The reflective layer 5 is preferably a thermally good conductor, and aluminum is suitable in consideration of availability, ease of film formation, and the like.

These layers 2, 3, 4, and 5 are formed by a so-called vapor phase plating technique such as vapor deposition or sputtering. At this time, the thickness of each of the layers 2, 3, 4, and 5 can be set arbitrarily, but is usually set to hundreds to thousands. These film thicknesses are preferably determined in consideration of not only the optical properties of each layer alone but also the combination of the film thicknesses. This is because, for example, when the film thickness of the recording magnetic layer 2 is thinner than the wavelength of the light beam, the light beam transmits through the recording magnetic layer and interferes with the light reflected at each layer boundary, and the effective effect of the recording magnetic layer 2 is increased. Optical and magneto-optical characteristics greatly depend on the combination of film thicknesses.

On the other hand, the photo-curable resin layer 7 serves to eliminate the unevenness 1b due to the guide groove or the like provided on the substrate 1 and also serves as an adhesive layer for the protective cover 8 described later, and is cured by ultraviolet rays, electron beams or the like. The photocurable resin used is used. The photocurable resin layer 7 needs to transmit a light beam sufficiently, and it is necessary to select a photocurable resin having excellent optical characteristics such as transparency. The photocurable resin layer 7 is also required to have a waterproof property in order to prevent the recording section 6 from being corroded, and satisfies these requirements from known photocurable resins such as an acrylic ultraviolet curable resin. It is preferable to select and use one. In this example, in order to make the waterproof hardening more secure, the recording unit 6 is slightly retracted from the peripheral edge of the substrate 1, and this portion is covered with the photocurable resin layer 7 and the protective cover 8, The structure is such that the end face of the recording section 6 is exposed to the periphery of the substrate and corrosion is prevented from progressing from this portion.

It should be noted that the thickness of the photocurable resin or the like 7 can eliminate unevenness 1b due to the guide groove or the like formed in the substrate 1,
In addition, it is sufficient that sufficient adhesiveness can be ensured. In order to reduce the distance between the magnet for applying an external magnetic field and the recording section 6, the thinner the better, the better.

The protective cover 8 serves to cover the recording section 6 and protect it physically and mechanically. The optical disk according to the present invention is irradiated with a light beam from the protective cover 8 side. Therefore, its surface needs to be optically sufficiently smooth. Therefore, examples of the material include glass-based materials such as tempered glass and crystal glass, and plastic-based materials such as polycarbonate and epoxy resin.

Like the photocurable resin layer 7, the thickness of the protective cover 8 is made as small as possible in order to reduce the distance between the magnet for applying an external magnetic field and the recording section 6 when recording an information signal. Desirably. Also,
Since it is not necessary to maintain the mechanical strength of the disk, the protective cover 8 can be selected to be as thin as possible, for example, about 0.1 mm thick.

The protective cover 8 is also required to have excellent optical characteristics such as transparency. However, since the thickness is very thin as compared with the substrate, even if birefringence occurs to some extent, the effect is not affected. Is small.

In an optical disk recording / reproducing apparatus using an optical disk as a recording medium as described above, an optical pickup for irradiating a light beam is disposed on the side of the protective cover 8, and the optical pickup is provided via the protective cover 8 and the photo-curable resin layer 7. The recording magnetic layer 2 of the recording unit 6 is irradiated with a light beam. Also, a magnet for applying a magnetic field is arranged on the protective cover 8 side similarly to the optical pickup, and the optical pickup and the magnet are arranged on the same surface side to record information signals. At this time, since the thicknesses of the protective cover 8 and the photocurable resin layer 7 are thin, it is possible to bring the magnet closer to the recording magnetic layer 2, and it is possible to sufficiently cope with the magnetic field modulation method.

As described above, by arranging the optical pickup and the magnet on the same surface side of the optical disk, it is possible to constitute a recording / reproducing means integrating the optical pickup and the magnet. The size and thickness of the playback device itself can be easily reduced. In designing an optical disk recording / reproducing apparatus, restrictions on loading and chucking of a disk are reduced, and the degree of freedom can be increased.

Further, since the light beam is emitted from the side of the protective cover 8, the influence of the birefringence of the substrate, which has been a problem so far, is eliminated, and good recording / reproducing characteristics can be realized.
It is possible to cope with an increase in the capacity of an optical disc.

The optical disk according to the present invention can be applied not only to the above-mentioned single-sided disk but also to a double-sided disk.

FIG. 2 shows an example in which the present invention is applied to a double-sided disk. The substrate 11 is shared, and the recording section 16 and the photo-curable resin layer 1 are formed on both sides of the substrate 11, respectively.
7. A protective cover 18 is provided.

Each surface of the substrate 11 on which the recording section 16 is formed is provided with irregularities 11b such as guide grooves and address code pits, similarly to the single-sided optical disk described above.

Each recording unit 16 provided on each surface of the substrate 11
As shown in FIG. 2, the reflective layers 15 and the second dielectric layer 14 are stacked so that the reflective layer 15 is disposed closer to the substrate 11 than the recording magnetic layer 12, respectively. It has a structure in which a recording magnetic layer 12 and a first dielectric layer 13 are stacked in this order. The materials, thicknesses, and the like of the layers constituting the substrate 11, the photocurable resin layer 17, the protective cover 18, and the recording unit 16 are the same as those of the above-described single-sided optical disk.

In this double-sided optical disk, since the substrate 11 is common, the thickness can be reduced to approximately half as compared with the conventional double-sided disk obtained by laminating the substrates. Asperities 11b such as guide grooves and address code pits
Can be formed by one molding, which is advantageous in terms of productivity.

For each recording section 16, as in the case of a single-sided optical disk, the recording and reproduction of information signals is performed by a magnetic field modulation method using an optical disk recording and reproducing apparatus in which an optical pickup and a magnet are arranged on the same side. Can be. An optical disk recording / reproducing apparatus using a double-sided optical disk as a recording medium may be configured to simultaneously access both sides of the optical disk.

Although specific embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, in each of the above-described embodiments, the recording unit has a four-layer structure including a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer. It is possible, and depending on the case, the recording section may be composed of only the recording layer and the reflective layer, or may have a multilayer structure of four or more layers.

[0045]

According to the optical disk of the present invention, a recording layer is formed by sequentially laminating a reflective layer and a recording layer on the surface of a substrate on which irregularities such as guide grooves are formed, so that the recording section is protected. Since a protective cover that is thinner than at least the substrate is provided so as to cover the recording section, recording and / or reproducing of information signals can be performed by arranging recording and / or reproducing means on the protective cover side. The means can be brought close to the recording layer, and information signals can be recorded and / or reproduced with good recording and reproduction characteristics.

Further, since the recording and / or reproducing means is arranged on the side of the protective cover which is thinner than the substrate, the influence of birefringence can be reduced, and good recording / reproducing characteristics of information signals can be realized.

Further, the optical disk recording and / or reproducing apparatus using the optical disk according to the present invention as a recording medium can be configured such that the recording and / or reproducing means is arranged only on one side of the optical disk. The arrangement of the loading mechanism and the chucking mechanism is not restricted, and the apparatus itself can be easily made thinner and smaller.

Further, in the double-sided optical disk, since the substrate is common, the optical disk can be made thinner, and information signals can be recorded and / or reproduced from both sides, and the recording density can be increased. High density can be realized.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing a single-sided optical disc according to the present invention.

FIG. 2 is an enlarged sectional view of a main part showing a double-sided optical disc according to the present invention.

[Explanation of symbols]

1,11 substrate, 2,12 recording magnetic layer, 5,15
Reflective layer, 6,16 recording part, 7,17 Photo-curable resin layer, 8,18 Protective cover

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 7/24 541 G11B 7/24 541F

Claims (8)

[Claims] 1. A substrate having irregularities such as guide grooves formed thereon, a recording portion formed by sequentially laminating a reflective layer and a recording layer on the surface of the substrate having the irregularities formed thereon, and protecting the recording portion. An optical disk comprising a protective cover provided so as to cover the recording section and to be thinner than at least the substrate. 2. The optical disk according to claim 1, wherein the protective cover is provided on the recording unit via an adhesive layer. 3. The optical disk according to claim 1, wherein the protective cover has a thickness of about 0.1 mm. 4. A substrate in which projections and depressions such as a guide groove are formed on both surfaces, a recording section formed by sequentially laminating a reflective layer and a recording layer on each surface of the substrate where depressions and projections are formed, and An optical disc, comprising: a protective cover provided to cover each of the recording sections so as to protect the recording section, the protective cover being thinner than at least the substrate. 5. The optical disk according to claim 4, wherein the protective cover is provided on the recording section via an adhesive layer. 6. The optical disk according to claim 4, wherein the protective cover has a thickness of about 0.1 mm. 7. A recording section is provided by sequentially laminating a reflective layer and a recording layer on the surface of the substrate on which the irregularities such as the guide grooves are formed, and the recording section is protected so as to protect the recording section. An optical disc comprising a protective cover provided at least to cover the recording section and thinner than the substrate; and an optical disc recording comprising a recording and / or reproducing means arranged opposite to a surface of the optical disc provided with a protective cover. And / or a playback device. 8. The optical disc according to claim 7, wherein said recording and / or reproducing means comprises: an optical pickup for irradiating the optical disc with a light beam; and a magnetic field applying means for applying a magnetic field to the optical disc. Recording and / or playback device.