JPH06111378A - Optical recording medium and substrate for the same - Google Patents

Abstract

PURPOSE:To obtain the optical recording medium whose sector position can surely be detected in an optical recording medium which has sector discrimination information recorded in its recording layer, and the substrate for the optical recording medium which is increased in density by narrowing down track pitches and also has high productivity. CONSTITUTION:The optical recording medium consists of the transparent substrate 12, a guide film 14 which is formed spirally thereupon, and an interference layer 16, a recording layer 18, and a protection layer 20 which are laminated thereupon in order. When laser light 30 crosses a track crossing groove 22, diffraction and interference are caused nearby an end part 32 to decrease the intensity of reflected light, thereby generating a sector position detection signal. After the start position of a sector 24 is detected with this signal, sector discrimination information on the address, etc., of the sector 24 is recorded as a mark 40 in the recording layer 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the recording of information by light,
The present invention relates to an optical recording medium for reproducing or erasing and its substrate.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 14, a substrate 100 used for an optical recording medium for recording, reproducing or erasing information in sector units has a guide groove 102 for generating a tracking error signal and a start of a sector. A pit 104 for generating a signal for identifying a position, a sector number, etc. is provided between two adjacent guide grooves 102. The width of the pit 104 is 1/3 to 1/2 of the track pitch.
It is chosen to the extent. Such a substrate 100 is made of a resin such as polycarbonate or acrylic and is manufactured by injection molding. An optical recording medium is constructed by sequentially stacking a protective layer, a recording layer, etc. on the substrate 100.

In addition, a pit for generating a signal for identifying the start position of a sector, a sector number, etc. is not provided, only a guide groove is provided on a substrate, and a protective layer, a recording layer, etc. are sequentially laminated on the guide groove. There is also an optical recording medium configured. In this case, since information is recorded, reproduced, or erased in sector units, as shown in the sectional view in the track direction shown in FIG. 15A, a sector mark 204 for generating a signal for identifying the start position of a sector, Sector identification information such as an address 205 for identifying a sector number is recorded in the recording layer 202 in advance before recording data. Note that FIG.
2 shows a case where a magneto-optical recording material such as terbium iron cobalt amorphous alloy (TbFeCo) is used as the recording layer, and each data is recorded in the magnetization direction indicated by the arrow. The same applies when the recording layer is made of a phase-change material or the like and information is recorded by changing the reflectance.

[0004]

However, in order to identify the sector, the pit 10 is formed between the guide groove 102 and the guide groove 102.
When the substrate 100 on which No. 4 is formed is used, if the track pitch is narrowed for higher density, the guide groove 102
Need to be narrower and the pit smaller. However, it is difficult to accurately form the narrow guide groove 102 and the small pit 104, and there is a problem that defective formation increases during injection molding, resulting in a significant decrease in productivity or difficulty in production.

In the case where a substrate provided with only guide grooves is used and sector identification information such as a sector mark 204 and an address 205 for identifying a sector number is recorded in advance on the recording layer 202 before data is recorded, Since the density is increased, the problem of pit formation failure does not occur even if the track pitch is narrowed. However, as shown in FIG. 15B, when the recording layer 202 has a defect 206 such as oxidation or a pinhole, the sector identification information is not correctly recorded on the recording layer 202 or cannot be reproduced. was there. In particular, if the sector mark 204 is not correctly recorded due to the defect 206 or the like, the start position of the sector cannot be detected during reproduction, and therefore all information thereafter cannot be reproduced. However, since a plurality of pieces of information such as the address 205 are usually recorded and coded so that errors can be corrected, if the sector start position can be detected by the sector mark 204 and the range of the defect 206 is narrow, Can be played.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical recording medium in which sector identification information is recorded in a recording layer.
An object of the present invention is to provide an optical recording medium whose sector position can be detected with certainty, and an optical recording medium substrate with high productivity that is compatible with high density due to narrow track pitch.

[0007]

To achieve this object, an optical recording medium according to the present invention comprises a substrate and a recording layer, and information is recorded, reproduced or erased in sector units to record sector identification information. It is recorded on a layer and the substrate has a sector position detection signal generating means. Further, the tracking error signal generating layer is also provided in a layer different from the substrate.

Further, the optical recording medium substrate of the present invention has sector position detection signal generating means whose width in the direction perpendicular to the track is wider than half the track pitch.

[0009]

In the optical recording medium of the present invention having the above structure,
The substrate is provided with sector position detection signal generating means,
When this portion is irradiated with laser light, a light amount change occurs due to light diffraction or interference, and by detecting this, the sector position can be detected. That is, when the information is reproduced from the recording layer, the start position of the sector can be reliably detected even if the recording layer has a defect. Further, in the sector position detection signal generating means provided on the optical recording medium substrate of the present invention, the width in the direction perpendicular to the track is wider than half the track pitch, and the tracking error signal generating layer is a layer different from the substrate. Since it is provided in the above, the substrate can be easily manufactured by injection molding even when the track pitch is narrowed, and the productivity is increased.

[0010]

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

An optical recording medium 10 to which the present invention is preferably applied, as shown in FIG. 1, has a transparent substrate 12, a guide film 14 formed in a spiral shape on the transparent substrate 12, and an interference layer sequentially laminated thereon. It comprises a layer 16, a recording layer 18, and a protective layer 20. Board 1
2 has a track crossing groove 22 which is a sector position detection signal generating means. The track crossing groove 22 is provided so as to cross a plurality of tracks sandwiched by the guide films 14 as shown in FIG. 2, which is a plan view showing the optical recording medium substrate 12 to which the present invention is preferably applied. There is. Such a substrate 12 is made of acrylic resin, polycarbonate resin,
It is manufactured by injection molding a resin such as an amorphous polyolefin resin. The optical recording medium substrate 12 is not provided with a guide groove, the width of the track crossing groove 22 in the direction perpendicular to the track is larger than the track pitch, and the length in the track direction can be easily injection-molded. Has been chosen. For this reason, formation defects are less likely to occur during injection molding, and productivity is improved.

As shown in the plan view of FIG. 2 and the perspective view of FIG. 3, a guide film 14 is spirally provided on the substrate 12. In a certain track, one sector 24 extends from one track crossing groove 22 to the next track crossing groove 22. The guide film 14 is also continuously provided in the track crossing groove 22 as shown in the perspective view of FIG. Examples of the material of the guide film 14 include aluminum,
Metals such as tantalum, gold, silver, copper and titanium, and compounds such as titanium nitride are used. The guide film 14 is formed by well-known thin film forming means such as a sputtering method and fine processing by photolithography. When the guide film 14 is formed by photolithography, the photoresist may be exposed using a mask having the same pattern as the guide film 14. Alternatively, a so-called optical disk mastering technique may be used in which the substrate 12 is rotated and an argon laser is irradiated to perform exposure.

The interference layer 16 and the protective layer 20 include, for example,
SiO ₂ , SiAlON, SiN, transparent oxides such as AlN, nitrides, etc.
For the recording layer 18, a magneto-optical recording material made of, for example, a rare earth transition metal alloy such as TbFeCo or GdTbFe is used, and each layer is formed by a well-known thin film forming means such as a sputtering method.

Next, a method for detecting the sector position in the optical recording medium 10 of the present invention will be described with reference to the plan view of the substrate 12 shown in FIG. The laser light 30 is applied to the recording layer 18 through the substrate 12. At this time, part of the laser light 30 is reflected by the guide film 14. Here, by setting the thickness of the interference layer 16 to about λ / (8n _I ), a push-pull signal used as a tracking error signal is obtained,
Tracking by the well-known push-pull method becomes possible. However, λ is the wavelength of the laser light 30, and n _I is the refractive index of the interference layer 16. The laser light 30 moves along the guide film 14 as the optical recording medium 10 rotates, and the guide film 14 serves as a tracking error signal generating layer. At this time, if the sum of the track pitch w _P and the width w _G of the guide film 14 is equal to or larger than the spot diameter w _{L of the} laser light used for reproduction, the crosstalk becomes small and the track pitch is narrowed to increase the density. Is possible.

As described above, when the laser beam 30 moving along the guide film 14 crosses the track crossing groove 22, the track crossing groove 22 is set to have a depth of, for example, λ / (4n _S ). Diffraction and interference occur near the end 32 of the groove 22, and the intensity of reflected light is reduced. However, the refractive index of the substrate 12 is n _S. As the laser light 30 moves from the left to the right in FIG.
When the spot diameter is sufficiently longer than 0, a sector position detection signal as shown in FIG. 5A is obtained. That is, the start position of the sector 24 can be detected by this sector position detection signal. If the length of the track crossing groove 22 is about the same as the spot diameter of the laser beam 30,
A sector position detection signal as shown in (b) is obtained. The start position of the sector 24 can also be detected by such a sector position detection signal. Since the track crossing groove 22 is formed in the substrate 12, it is not easily affected by the defect of the recording layer 18, and the sector start position can be detected reliably.

After detecting the start position of the sector 24, the sector identification information such as the address of the sector 24 is recorded as the mark 40 on the recording layer 18 as shown in FIG. In this case, by repeatedly recording the same sector identification information about 3 to 6 times, even if there is a defect in the recording layer 18 and a part thereof cannot be reproduced, the sector identification information is reproduced from the remaining part. can do.

Although one embodiment of the present invention has been described in detail above with reference to FIGS. 1 to 5, the present invention can be implemented in other modes.

That is, the sector position detection signal generating means is not limited to the track crossing groove 22 and various modifications are possible. For example, as shown in FIG. 6, a convex protrusion 50 may be provided on the substrate 12. With this projection 50, a sector position detection signal similar to that shown in FIG. 5 can be obtained.

Further, as shown in FIG. 7, a track cross band 53 may be provided on the substrate 52, and a sector position detection signal similar to that shown in FIG. 5 can be obtained. In this case, the substrate 5
Since the surface of 2 may be a flat surface, glass or other dielectric material, which is difficult to injection-mold, can be used as the substrate 52. For example, SiO ₂ , SiN, or SiAlO is formed in the track crossing zone 53.
A transparent dielectric such as N or AlN is used. Further, the track cross band 53 may be formed of an ultraviolet curable resin or the like.

Alternatively, as shown in FIG. 8, a dielectric layer 55 may be provided on the substrate 52 and a part thereof may be removed to form the track crossing groove 56, which is similar to that shown in FIG. A sector position detection signal is obtained.

The number and arrangement of the sector position detection signal generating means such as the track crossing groove 22 and the number of sectors per track are not particularly limited. For example, in FIG.
As described above, the number and intervals of the track crossing grooves 22 may be changed for each sector. As a result, the track crossing groove 22
The sector can be identified also by detecting the number of sectors.

Further, the number of sectors per track does not always have to be constant, and may change from track to track. For example, as shown in FIG. 10, the number of sectors may be increased toward the outer circumference of the track. As a result, the recording capacity can be further increased. At this time, the track crossing groove 2
By making the width of the second track in the vertical direction larger than half the track pitch, formation defects are reduced as compared with the case of forming sector marks using conventional pits.
Productivity is improved.

Further, the sector position detection signal generating means is not limited to detecting the start position of the sector. For example, it may be used to detect the end position of a sector. In this case, it is detected that a new sector is started from the position next to the position where the signal obtained in FIG. 5 is detected. Further, the sector position detection signal generating means may be provided in the middle of the sector. Further, it may be provided at a plurality of positions in one sector. For example, as shown in FIG. 11, the track crossing groove 22 is provided not only at the start position of the sector 61 but also at the position 60 for separating the index portion 61 where the address and the like are recorded and the data portion 62 where the data is recorded. Good.
As a result, the start position of the data section 62 can be reliably detected, and the reliability during reproduction is improved.

Further, the pattern of the guide film is not particularly limited, and the guide film 65 may be formed concentrically as shown in FIG. Since the concentric pattern can be manufactured by using the phase shift mask having a pitch twice the track pitch, the track pitch can be narrowed with high accuracy.

If necessary, a so-called mirror portion, which is an area where the pattern of the guide film 14 is not formed, may be formed. The offset during tracking can be corrected by this mirror unit.

Further, the material of the guide film 14 is not particularly limited. For example, it may be formed of a material that absorbs light. In this case, the tracking is performed by detecting the change in the amount of reflected light due to the tracking shift by the well-known three-beam method.

Further, a transparent dielectric material such as SiO ₂ , SiN, AlN is
/ And a thickness of (8n _G), it may be formed guiding film 14. In this case, the interference layer 16 becomes unnecessary.

Further, the recording layer 18 is not only a rare earth transition metal alloy other than TbFeCo, a multilayer film of PtCo or PdCo, an oxide magnetic material such as rare earth iron garnet, and a magneto-optical material combining these, but also Te, Bi, etc. A perforated type, a phase change type material such as GeSbTe or TeO _x , an organic material such as a pigment may be used.

The materials for the interference layer 16 and the protective layer 20 are not particularly limited. Further, they may be composed of a multilayer film using a plurality of materials.

The structure of the optical recording medium 10 is not limited to the structure shown in FIG. For example, as shown in FIG. 13, the dielectric layer 70 may be provided on the substrate 12 and the guide layer 14 may be provided thereon. Further, the reflective layer 71 may be provided on the protective layer 20. For example, by providing the dielectric layer 70, the apparent Kerr effect of the magneto-optical recording layer 18 is increased, and the reproduction characteristic is improved. Further, by making the magneto-optical recording layer 18 thin and providing the reflective layer 71, the Faraday effect of the magneto-optical recording layer 18 can be utilized, and the reproducing characteristic is improved. When the recording layer 18 is a phase change material, the dielectric layer 70 is provided to improve the recording sensitivity and the protective layer 20.
By reducing the thickness and providing the reflective layer 71, it is possible to improve recording sensitivity and overwrite characteristics.

The interference layer 16 is not always necessary and may not be provided. In this case, the difference in reflectance between the guide film 14 and the recording layer 18 may be detected, and tracking may be performed by, for example, the three-beam method.

When the recording layer is a transparent or translucent material such as a dye or an oxide magnetic material, a guide film may be provided on the recording layer. Further, the guide film does not need to be a material such as metal that reflects light, and may be a transparent dielectric, and a reflective layer may be provided thereon.

The shape of the optical recording medium of the present invention does not have to be disk-shaped, and may be card-shaped or the like, and is not particularly limited.

[0034]

As is apparent from the above description, in the optical recording medium of the present invention, the sector position detection signal generating means is provided on the substrate. Therefore, when information is reproduced from the recording layer, Even if there is a defect, the start position of the sector can be reliably detected. Further, in the sector position detection signal generating means provided on the optical recording medium substrate of the present invention, the width in the direction perpendicular to the track is wider than half the track pitch, and the tracking error signal generating layer is a layer different from the substrate. Since it is provided in the above, the substrate can be easily manufactured by injection molding even when the track pitch is narrowed, and the productivity is increased.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the track direction of an optical recording medium that is an embodiment of the present invention.

FIG. 2 is a plan view showing a substrate and a guide film of an optical recording medium.

FIG. 3 is a perspective view showing a substrate and a guide film of an optical recording medium.

FIG. 4 is a plan view of the optical recording medium as viewed from the substrate side.

FIG. 5 is an explanatory diagram showing a sector start position signal obtained from an optical recording medium.

FIG. 6 is a sectional view in the track direction showing another embodiment of the optical recording medium.

FIG. 7 is a cross-sectional view in the track direction showing another embodiment of the optical recording medium.

FIG. 8 is a sectional view in the track direction showing another embodiment of the optical recording medium.

FIG. 9 is a plan view showing another embodiment of the substrate for optical recording medium and the guide film.

FIG. 10 is a plan view showing another embodiment of the substrate for optical recording medium and the guide film.

FIG. 11 is a sectional view in the track direction showing another embodiment of the optical recording medium.

FIG. 12 is a plan view showing another embodiment of the substrate for optical recording medium and the guide film.

FIG. 13 is a sectional view in the track direction showing another embodiment of the optical recording medium.

FIG. 14 is a perspective view showing a conventional optical recording medium.

FIG. 15 is a cross-sectional view of essential parts showing a conventional optical recording medium.

[Explanation of symbols]

 10 Optical Recording Medium 12 Substrate for Optical Recording Medium 14 Guide Film (Tracking Error Signal Generation Layer) 18 Recording Layer 22 Track Crossing Groove (Sector Position Detection Signal Generation Means) 24 Sector

Claims (3)

[Claims] 1. An optical recording medium comprising a substrate and a recording layer, in which information is recorded, reproduced or erased in sector units, and sector identification information is recorded in the recording layer, wherein the substrate is a sector position detection signal. An optical recording medium having a generating means. 2. The optical recording medium according to claim 1, further comprising a tracking error signal generating layer. 3. A substrate for an optical recording medium, comprising sector position detection signal generating means whose width in the direction perpendicular to the track is wider than half the track pitch.