JPH06111376A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide the optical recording medium having a high-density recording capacity by successively laminating a guide layer for tracking with which recording and reproducing are possible, a transparent interference layer with which recording and reproducing are possible and a recording layer on a substrate. CONSTITUTION:The guide layer 14 for tracking with which recording and reproducing are possible, the transparent interference layer 16 with which recording and reproducing are possible, the recording layer 18 and a protective layer 20 are successively laminated on the substrate 12. The layer 14 is worked to continuous or discontinuous patterns. The recording and reproducing to and from the layer 18 and the layer 16 are executed in the tracks of the parts where the layer 14 does not exist. The discrimination thereof is executed by changing a focus position. The discrimination of the recording to the layer 18 and the layer 14 is likewise executed by changing the focus position. The recording and reproducing to and from the layer 16 and the recording and reproducing to and from the layer 14 are respectively executed by each track. Respectively independent pieces of information are recorded and reproduced to and from the layer 18, the layer 14 and the layer 16 as well by such constitution. The optical recording medium having the high-density recording capacity is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium used for an optical disk memory, an optical card, etc. for recording / reproducing information with a laser beam.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, an optical recording medium 30 records information on a well-known rare earth iron-based magneto-optical recording medium by local heating by irradiating a laser beam and polarizes reflected light. Information can be read by the surface rotation and the change of the reflected light intensity. These are generally formed by stacking an interference layer 33 for Kerr effect enhancement, a recording layer 34, and a reflective layer 36 on a substrate 32 on which irregularities are formed in a spiral shape or a concentric circle while keeping the shapes following the irregularities of the substrate. . In such an optical recording medium, there is only one recording layer, and tracking is performed using the well-known push-pull method. That is, it is a method of irradiating a tracking laser beam from the substrate side, detecting diffraction of reflected light caused by unevenness of the substrate by a two-divided photodetector, and applying servo.

Further, the guide film structure optical disc has a recording medium similar to that of the above-mentioned optical disc, and information recording / reading is also performed according to the same principle. However, a guide film made of a metal film or the like is formed in a pattern on the substrate for tracking.

[0004]

However, even in the disc having the guide film structure, the disc has only one recording layer as in the conventional optical recording medium, and there is a demand for the increase of the recording capacity which is caused by the demand of the optical disc. I couldn't respond.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to form a tracking guide layer by using a non-translucent material capable of recording and reproducing. Further, by forming the interference layer using a translucent material capable of recording and reproducing, it is possible to record and reproduce independent information on the recording layer, the guide layer, and the interference layer, and the recording capacity is larger than the conventional one. An object is to provide an optical recording medium having a high density.

[0006]

To achieve this object, in an optical recording medium of the present invention, a tracking guide layer made of a recordable / reproducible material, an interference layer made of a recordable / reproducible material, and a recording layer are provided. And the guide layer is processed into a continuous or discontinuous pattern.

[0007]

In the optical recording medium of the present invention having the above structure, the guide layer is made of a recordable / reproducible material such as rare earth iron-based or platinum / cobalt-based material, and the interference layer is a garnet-based recording material or organic material. It is formed of a recordable / reproducible material such as a dye-based recording material. Information can be recorded / reproduced in the interference layer and the guide layer independently of the recording layer by changing the focus position of the laser.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an essential part of an optical recording medium 10 according to an embodiment of the present invention. The optical recording medium 10 is provided with a tracking guide layer 1 on a transparent substrate 12 such as glass.
4, the interference layer 16, the recording layer 18, and the protective layer 20 are sequentially laminated.

The tracking guide layer 14 is formed by a well-known photolithography method, and the material thereof is a terbium iron cobalt alloy of a rare earth iron recording film. That is, a guide layer film is uniformly formed on the substrate 12 by means such as vacuum deposition and sputtering, and a resist is applied thereon by a spin coating method or the like. Next, the resist is continuously or discontinuously removed into a predetermined shape such as a spiral shape by a laser exposure method or the like. For example, as shown in FIG. 2, a continuous recording portion 41 and a discontinuous format portion 42 are provided side by side. Further, the resist is removed and the exposed guide layer portion is etched by etching using an acid, alkaline aqueous solution, or plasma etching. After that, the resist is removed.

The interference layer 16 is, for example, a BiYFeAlO film, which is a bismuth-substituted garnet recording material, or a BiDyF film.
The eAlO film is formed by a sputtering method, a thermal decomposition method, or the like.

The recording layer 18 is a terbium iron cobalt alloy which is a rare earth iron type recording film and is formed by means such as vacuum deposition and sputtering.

The protective layer 20 is made of aluminum or the like and is formed by means such as vacuum vapor deposition and sputtering.

Recording and reproduction on the recording layer of the optical recording medium 10 are performed as follows. That is, when the recording layer 18 is irradiated with the laser beam 22 through the substrate 12, the Kerr rotation angle of the reflected light is changed in relation to the local magnetization direction in the recording layer 18 by the magneto-optical effect, and the Kerr rotation of the reflected light is changed. Information is read based on the corners.
When writing information, the recording layer 18 is locally heated to the Curie point or the compensation temperature by irradiation of the laser beam 22, and the direction of the external magnetic field is controlled to a desired direction when the local portion is cooled to correspond to the magnetization direction. Record the information you provided.

In the case of a Bi-substituted garnet-based recording material, recording / reproducing on / from the interference layer 16 is performed by the same principle as that of the recording layer 18, that is, laser light 22 is applied to the interference layer 16 through the substrate 12. Then, due to the magneto-optical effect, the Kerr rotation angle of the reflected light is changed in relation to the local magnetization direction in the interference layer 16, and the information is read based on the Kerr rotation angle of the reflected light. Further, when writing information, the interference layer 16 is locally heated to the Curie point or the compensation temperature by irradiation of the laser beam 22, and the direction of the external magnetic field is controlled to a desired direction when the local portion is cooled to correspond to the magnetization direction. Record the information you provided.

Recording and reproduction on the recording layer 18 and the interference layer 16 are performed on the track from which the guide layer 14 has been removed, and the distinction is made by changing the focus position.
The recording between the recording layer 18 and the guide layer 14 is also distinguished by changing the focus position. Also the interference layer 1
Recording / reproduction on the recording medium 6 and recording / reproduction on the guide layer 14 are performed for each track.

Further, in the optical recording medium 10 having the above structure, the laser light 22 incident from the substrate 12 side is guided by the guide layer 14.
The light is reflected by the recording layer 18 and is transmitted through the interference layer 16 in the portion where the guide layer 14 is not present. By utilizing the diffraction of both reflected lights, good tracking servo can be performed by the push-pull method as in the conventional case. At this time, the thickness of the interference layer is not particularly limited, but (λ / 8n ₁ ) (λ: laser light wavelength, n ₁ :
When the refractive index is set to (interference layer refractive index), the tracking signal becomes maximum, and when it is set to (λ / 6n ₁ ), both the tracking signal and the recording signal from the recording layer become good.

Although one embodiment of the present invention has been described in detail above with reference to FIGS. 1 and 2, the present invention can be implemented in other modes.

For example, as shown in FIG. 3, a Faraday layer 19 may be provided on the recording layer 18 and an enhancement layer 13 may be provided on the substrate 12. Or either of them may be sufficient. The effect of the Faraday layer is that the laser beam 22 incident from the substrate 12 side passes through the recording layer 18 and the Faraday layer 19, is reflected by the protective layer 20, and then passes through the recording layer 18 again. The Faraday effect is caused by this multiple reflection, and the C / N of the signal from the recording layer can be increased. The Faraday layer 19 is made of a material such as SiAlON and is formed by means such as vapor deposition and sputtering, and its film thickness is not particularly limited, but is set to a value that does not interfere with tracking. The effect of the enhancement layer 13 is that multiple reflection occurs between the substrate 12 and the guide layer 14 and the C / N of the recording signal from the guide layer increases due to the Kerr effect enhancement.
The enhance layer 13 is made of a material such as SiAlON,
It is formed by means such as vapor deposition and sputtering.

As described above, this embodiment can provide a three-fold high density optical recording medium having a recording / reproducing guide layer and an interference layer.

Instead of glass as the substrate material, acrylic resin, polycarbonate resin, amorphous polyolefin resin, gadolinium gallium garnet (Gd)
It is also possible to use a crystal substrate such as 3Ga5O12).

The guide layer may be formed by exposure with a mask provided with a predetermined pattern or by a lift-off method which does not require an etching process.

Further, the guide layer and the recording layer may be not only a terbium iron cobalt alloy but also a platinum / cobalt multilayer film or the like. For the interference layer, not only an oxide-based recording material such as Bi-substituted garnet-based recording material but also an organic dye-based recording material such as fulgide compound can be used, and it does not need to be completely transparent, and tracking and information recording are possible. There may be absorption to the extent that regeneration is possible.

Further, the tracking method is not limited to the push-pull method, and the three-beam method can be similarly favorably performed.

[0025]

As is apparent from the above description, in the optical recording medium of the present invention, since information can be recorded / reproduced in / from the interference layer and the guide layer independently of the recording layer, the recording density becomes three times higher. A recording medium having a high density can be produced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an essential part of an optical recording medium that is an embodiment of the present invention.

FIG. 2 is an example of a guide layer pattern.

FIG. 3 is a sectional view of an essential part of an optical recording medium that is another embodiment of the present invention.

FIG. 4 is a cross-sectional view of essential parts showing an example of a conventional magneto-optical recording medium.

[Explanation of symbols]

 12 glass substrate 14 guide layer 16 interference layer 18 recording layer 20 protective layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Matsuda 15-1 Naeshiro-cho, Mizuho-ku, Nagoya City Brother Industries, Ltd. (72) Inventor Hamaguchi ▲ Takuya 15-1 Naeshiro-cho, Mizuho-ku, Nagoya Brother Industries, Ltd.

Claims (1)

[Claims] 1. An optical recording medium, wherein a tracking guide layer capable of recording and reproducing, a translucent interference layer capable of recording and reproducing, and a recording layer are sequentially laminated on a substrate. Medium.