JPH05109120A - Optical recording medium - Google Patents

Abstract

PURPOSE:To execute high-density recording with good C/N characteristics and decreased crosstalks by setting the width of a recording and reproducing region larger at the time of superposing an optical recording layer on a guide layer for tracking. CONSTITUTION:A thin film of Al 21 is deposited by evaporation on a transparent substrate 12 and a photoresist mask 22 is applied thereon and is etched to form the guide layer 14. An interference layer 16 of transparent dielectrics, such as SiO, having the refractive index higher than the refractive index of the substrate 12 is deposited by evaporation. The optical recording layer 18 is then deposited by evaporation. The optical recording layer 18 includes a magneto-optical material of an amorphous alloy, such as TbFeCo, phase shift recording material, such as TeOx, Te, Bi, dyes, etc. The optical recording layer 18 is protected with a protective layer 20, such as SiO2. Magnetization conversion, phase transition and pit formation are generated and the recording is executed when the recording layer 18 is irradiated with a laser beam. Reproduction is executed by the light quantity change of the reflected light of the laser beam from the recording layer 18 and the rotation of the polarization thereof. The track pitch is selected at P<=1.4mum and the width of the guide layer 14 at <region of the optical recording layer 18 (recording and reproducing region 32).

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 for optically recording and reproducing information, and more particularly to a structure of an optical recording medium capable of recording information at high density and reproducing information with high accuracy. It is a thing.

[0002]

2. Description of the Related Art Conventionally, an optical recording medium 80 of this type is shown in FIG.
As shown in FIG. 0, a tracking guide groove 81 is provided in a transparent substrate 82 made of acrylic, polycarbonate, glass, etc., and TbFe is provided on the transparent substrate 82.
Magneto-optical recording material such as Co, GdTbFe, TbCo, G
An optical recording layer 83 made of a phase change recording material such as eSbTe, a perforated recording material such as a metal or a dye, and SiO2, A
A protective layer 84 made of an oxide such as 1N or a nitride is laminated.

Further, such an optical recording medium 80 is shown in FIG.
When the groove width is WG, the inter-groove distance is WL and the track pitch is P as in No. 1, P = WG + WL is formed. Further, when the spot diameter of the laser light 91 on the optical recording medium 80 is dS, the track pitch P is made to be substantially equal to the spot diameter dS of the laser light.

In the optical recording medium 80,
When the optical recording layer 83 is irradiated with laser light through the substrate 82 and the recording layer 83 is heated, the magnetization is reversed, phase change or pit formation occurs, and recording is performed. The reproduction is performed by irradiating the optical recording layer 83 with a laser beam and detecting the rotation of the polarization plane of the reflected light from the optical recording layer or the change of the reflected light amount.

However, in the conventional optical recording medium 80 shown in FIG. 10, if the track pitch P is further reduced to increase the recording density as shown in FIG. 12, and the track pitch P is made smaller than the spot diameter dS of the laser beam 91. When reproducing the information recorded on a specific track 92, a spot of the laser beam is also applied to a part of the bit 94 recorded on the adjacent track 93, and the bit 94 is reproduced, so that crosstalk increases. was there.

In order to solve this drawback, as shown in FIG. 13, there is also an optical recording medium 100 having a structure in which a guide layer 102, an interference layer 103 and a recording layer 104 are sequentially formed on a substrate 101 in a spiral shape. Such an optical recording medium 100 is shown in FIG.
4, the width of the guide layer 103 is Ws, and the area of the optical recording layer irradiated with laser light from between the guide layers 103, that is, the width of the recording / reproducing area 110 is Wr, the width Ws of the guide layer and the recording / reproducing The width Wr of the region 110 is formed to be substantially equal. Then, also in the optical recording medium 100, recording / reproducing is performed by the same method as the optical recording medium 80.

[0007]

However, in the conventional optical recording medium shown in FIG. 13, since a part of the laser beam applied to the optical recording layer 104 is blocked by the guide layer 102, an increase in crosstalk is suppressed. Recording / playback area 1
Since the width Wr of 10 and the width Ws of the guide layer 102 are almost equal,
There is a problem that the C / N characteristic is bad.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to sequentially stack a guide layer having a predetermined pattern for tracking and an optical recording layer on a substrate. By forming and blocking a part of the laser light irradiated onto the optical recording layer by the guide layer, the track pitch can be reduced, the C / N characteristics can be excellent, and high density recording can be performed. The object is to provide an optical recording medium with less increase in

[0009]

In order to achieve this object, in the optical recording medium of the present invention, a guide layer having a predetermined pattern for tracking is formed on a substrate, and the optical recording layer is laminated thereon. There is. Further, the width of the portion where the guide layer is removed, that is, the width of the recording / reproducing area is defined to be larger than the width of the portion where the guide layer is not removed, which is sandwiched between the adjacent recording / reproducing areas. The width of the recording / reproducing area may be equal to or longer than the shortest bit length of the recording bits. The track pitch may be 1.4 μm or less.

[0010]

In the optical recording medium of the present invention having the above structure,
Since the width of the recording / reproducing area is wider than the width of the portion where the guide layer is not removed, the C / N characteristic is excellent and high density recording by narrowing the track pitch becomes possible. Further, even if the laser beam having a spot diameter larger than the track pitch is irradiated, the laser beam is not irradiated to the adjacent recording area because the guide layers are provided on both sides of the recording / reproducing area. As a result, since the information recorded in the recording / reproducing area adjacent to the recording / reproducing area to be reproduced at the time of reproduction is not reproduced, crosstalk does not increase. Further, by setting the width of the recording / reproducing area to be equal to or more than the shortest bit length of the recording bit, the C / N characteristic is further improved, and by setting the track pitch to 1.4 m or less, higher density recording can be achieved. It will be possible.

[0011]

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 according to an embodiment of the present invention. The optical recording medium 10 is constructed by sequentially laminating a guide layer 14, an interference layer 16, an optical recording layer 18, and a protective layer 20 on a transparent substrate 12 such as glass.

The guide layer 14 is a metal film of Al, Ta or the like,
It is made of a semiconductor such as C or Si, a nitride such as TiN or Ta2O5, a compound such as an oxide, or an organic substance such as a pigment, and is fixed in a spiral or concentric shape on the substrate. This guide layer is made by well-known photolithography. That is, as shown in FIG.
A guide layer material 21 such as Al or Ta is sputtered on the substrate 12,
It is formed by a thin film forming means such as a vacuum evaporation method. A photoresist is applied thereon by a spin coating method or the like, exposed by a laser exposure method or the like, and developed to form a spiral or concentric photoresist 22 as shown in FIG. Further, the guide layer material 21 in the portion where the photoresist 22 is not formed is etched by etching using an acid or alkali solution, plasma etching, or the like. Finally, the photoresist is removed with an organic solvent or the like to form the guide layer 14 as shown in FIG.

The interference layer 16 is made of SiO, TiO2, ZrO.
2. A transparent dielectric film such as SiAlON having a higher refractive index than the substrate, and is formed by a well-known sputtering method or vacuum evaporation method.

As shown in FIG. 2E, the optical recording layer 18 is made of, for example, TbFeCo containing a rare earth and a transition metal as main components.
Magneto-optical material T which is an amorphous alloy such as GdTbFe
It is made of a phase change recording material such as eOx, a metal such as Te and Bi, a perforated recording material such as a dye, and has a substantially uniform thickness on the interference layer 16 by a sputtering method, a vacuum deposition method, a spin coating method or the like. It is provided.

The protective layer 20 is for protecting the optical recording layer 18 from chemical changes as shown in FIG. 2 (e).
It is made of 1N or the like and is formed by a sputtering method, a vacuum deposition method, a spin coating method, or the like.

Then, in such an optical recording medium 10,
When the optical recording layer 18 is irradiated with laser light through the substrate 12 and the recording layer 18 is heated, magnetization reversal, phase change or pit formation occurs, and recording is performed. The reproduction is performed by irradiating the laser beam of the optical recording layer 18 and detecting the rotation of the polarization plane of the reflected light from the optical recording layer or the change of the reflected light amount.

Here, as shown in FIG. 3, the track pitch is P, the width of the guide layer 14 is Ws, and the area of the optical recording layer 18 irradiated with laser light from between the guide layers 14, that is, the width of the recording / reproducing area 32. When Wr, P ≦ 1.4 μm Ws <Wr That is, the track pitch is 1.4 μm or less, which is narrower than the conventional 1.6 μm, and the width of the recording / reproducing area 32 is equal to the guide layer 1.
It is determined to be larger than the width of 4. Therefore, since the width of the recording / reproducing area is sufficiently wide, it is possible to achieve high density recording with good C / N characteristics by narrowing the track pitch to 1.4 μm or less. Moreover, as shown in FIG. 4A, the portion of the laser light 31 that protrudes from the recording area 32 is shielded by the guide layer 14, so that it does not reach the adjacent recording / reproducing area and is recorded in the recording / reproducing area 41. Bits are not played. Therefore, the crosstalk does not increase despite the narrow track pitch of 1.4 μm or less. Even if the bit 42 spreads to the lower side of the guide layer 14 due to thermal diffusion during recording as shown in FIG.
Is blocked by the guide layer 14 and does not reach below it, the bit recorded in the recording area 41 is not reproduced and the crosstalk does not increase.

Although one embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be modified in various ways and can be implemented in other modes.

For example, assuming that the width of the recording / reproducing area is Wr and the shortest bit length of the recording bit 51 is bs as shown in FIG. 5, bs ≦ Wr, that is, is the width of the recording / reproducing area equal to the shortest bit length of the recording bit? It may be more than that. By doing so, it is possible to prevent the deterioration of the C / N characteristics even if the pitch is narrowed.

Further, the material of the guide layer 14 is not particularly limited, and the reflectance thereof is also not particularly limited. Further, a material having a high light absorption rate may be used.

Further, as shown in FIG. 6, S is also provided under the guide layer 14.
You may provide the interference layer 15 which consists of transparent dielectrics whose refractive index is higher than a board | substrate, such as iO and SiAlON. Due to the Kerr effect enhancement by this, the C / N characteristic is further improved. Further, the interference layer is not always necessary, and an optical recording layer may be provided directly on the guide layer 14 as shown in FIG.
Further, protective layers may be provided on both sides of the recording layer. In addition, the materials for the interference layer, the protective layer, and the substrate are not particularly limited.

Further, as shown in FIG. 8, glass with a groove, polycarbonate or the like may be used for the substrate 61. At this time, the guide layer 14 may be provided only in the groove portion or between the grooves, and the optical recording layer 18 may be provided thereon.

Further, as shown in FIG. 9, an optical recording layer 72 may be provided on a substrate 71, and a guide layer 74 and a protective layer 76 may be formed thereon. At this time, recording / reproduction is performed from the side opposite to the substrate 71.

The track pitch is not particularly limited, but 1.4 μm or less is desirable for high density.

The track pitch and the width of the guide layer do not have to be constant over the entire surface of the optical recording medium, and may be changed as needed.

A protective layer may be provided on both sides or one side of the guide layer.

[0028]

As is clear from the above description,
According to the present invention, the width of the recording / reproducing area formed by removing the guide layer having the predetermined pattern formed on the substrate is equal to the width of the portion where the guide layer sandwiched between the adjacent recording / reproducing areas is not removed. Since it is formed wider than the width, high density recording is possible by narrowing the track pitch with good C / N characteristics. Furthermore, by blocking a part of the laser light applied to the recording layer by the guide layer, it is possible to suppress an increase in crosstalk.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of an optical recording medium of the present invention.

2A to 2E are cross-sectional views showing a manufacturing process of the optical recording medium of FIG.

FIG. 3 is a diagram showing details of the optical recording medium of FIG.

FIG. 4 is a diagram showing details of the optical recording medium of FIG.

FIG. 5 is a diagram showing another embodiment of the optical recording medium.

FIG. 6 is a sectional view of another embodiment of the optical recording medium.

FIG. 7 is a sectional view of another embodiment of the optical recording medium.

FIG. 8 is a sectional view of another embodiment of the optical recording medium.

FIG. 9 is a sectional view of another embodiment of the optical recording medium.

FIG. 10 is a sectional view illustrating a conventional optical recording medium.

FIG. 11 is a diagram showing details of a conventional optical recording medium.

FIG. 12 is a diagram showing details of a conventional optical recording medium.

FIG. 13 is a cross-sectional view illustrating another conventional optical recording medium.

FIG. 14 is a diagram showing details of another conventional optical recording medium.

[Explanation of symbols]

 10 optical recording medium 12 substrate 14 guide layer 16 optical recording layer 32 recording / reproducing area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Riki Matsuda 15-1 Naesehiro-cho, Mizuho-ku, Nagoya-shi Brother Industrial Co., Ltd. Within the corporation

Claims (3)

[Claims] 1. In an optical recording medium having a substrate, a guide layer having a predetermined pattern for tracking, and an optical recording layer for recording information, the width of the recording / reproducing area from which the guide layer is removed is adjacent. An optical recording medium, characterized in that the guide layer sandwiched between the recording / reproducing areas to be fitted is larger than the width of the portion not removed. 2. The optical recording medium according to claim 1, wherein the width of the recording / reproducing area is equal to or more than the shortest bit length of recording bits. 3. The optical recording medium according to claim 1, wherein the track pitch is 1.4 μm or less.