JP2000298882A - Optical recording medium - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To achieve high recording density and realize reliable recording and reproduction. SOLUTION: A pit 2b is formed as a concavo-convex pattern according to a recorded signal in a lead-in area 1a (pit section) used only for reproduction, and a rewritable signal area 1b (groove section) is formed. A groove 2c is formed along the recording track. In the lead-in area 1a and the program area 1b, the wavelength of light used for recording and reproduction is λ, the lens numerical aperture is NA, the track pitch in the lead-in area 1a is Tp, and the track pitch in the program area 1b is Tg. Sometimes, Tg +
0.01 (1.22λ / NA) <Tp <Tg + Tg / 3
It is formed so as to satisfy the following relationship.

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 having a signal recording layer formed on a substrate, and more particularly to an optical recording medium having a read-only pit portion and a signal rewritable groove portion. About.

[0002]

2. Description of the Related Art An optical recording medium is a recording medium in which a signal recording layer is irradiated with a laser beam by a recording / reproducing apparatus to record and / or reproduce a signal (hereinafter referred to as recording / reproducing). As an optical recording medium, a read-only optical disk, a magneto-optical disk capable of rewriting a signal, a phase change optical disk, and the like are known. The optical recording medium is rotatably housed in a disk cartridge, for example, and is used detachably with respect to a recording / reproducing apparatus. Further, it may be used integrally with the recording / reproducing device.

[0003] The optical recording medium has a signal recording layer formed on a substrate, and signals are recorded / reproduced on / from this signal recording layer. In the case of a read-only optical disk, pits are formed in a signal recording layer as a concavo-convex pattern corresponding to a recording signal. In the case of a magneto-optical disk, a signal recording layer formed of a magneto-optical material is irradiated with a laser beam and a magnetic field is applied to record a magnetic domain according to a recording signal. It is configured to read using an optical effect.

On the other hand, a phase-change type optical disk is provided with a signal recording layer formed of a phase-change material. The signal is recorded and reproduced by the recording method. Further, a so-called write-once optical disc, such as a CD-R or a DVD-R, in which a signal recording layer is provided with a colorant layer formed of an organic dye material such as cyanine or phthalocyanine is also provided. .

In any of the above-described optical recording media, signal recording / reproduction is performed along recording tracks. In some cases, a guide groove called a groove is formed in the signal recording layer along the recording track in the optical recording medium. The recording / reproducing apparatus records and reproduces a signal along a groove formed on an optical recording medium, thereby suppressing crosstalk of a signal between adjacent recording tracks. Playback can be performed.

[0006]

As described above, the optical recording medium includes a pit portion, which is a region where pits are formed and is used only for reproduction as described above, and a region where a groove is formed and is used for rewritable. One having both a certain groove portion has been proposed. In this case, for example, a pit portion is provided at a portion (lead-in area) accessed first by the recording / reproducing device or at a terminal portion (lead-out area) of the groove portion, and information on the recording medium is provided. And information indicating the end of the groove portion and the like are recorded in the pit portion in advance.

[0007] The optical recording medium is similarly configured to have both a pit portion and a groove portion. Specific application data and the like are recorded in the pit portion, and the groove portion is rewritably used. Further, a so-called partial ROM or hybrid disc has been proposed.

An optical recording medium having both a pit portion and a groove portion as described above, when mounted on a recording / reproducing apparatus, has an effect on the pit portion formed in the lead-in area.
First, rough access is performed without performing tracking servo. At this time, the recording / reproducing apparatus determines the pit position by utilizing the fact that the signal waveform detected by the recording / reproducing head is different between the position where the pit is formed and the so-called land position where the pit is not formed. . Thereafter, the recording / reproducing apparatus positioned the recording / reproducing head on the pit, and after the rotation of the optical recording medium reached a predetermined number of revolutions, the recording / reproducing apparatus was recorded on the pit using the tracking servo corresponding to the pit position. Play the signal.

Therefore, it is necessary for the optical recording medium to be able to easily determine the pit position and the land position when the tracking servo is not functioning.

On the other hand, in recent years, it has been demanded that an optical recording medium be a small-sized and large-capacity recording medium by recording signals at high density. For this reason, the optical recording medium is required to cope with high recording density by, for example, forming an interval between recording tracks (hereinafter, referred to as a track pitch) narrow.

However, when the optical recording medium has both a pit portion and a groove portion, if the pit portion has a narrow track pitch, crosstalk between adjacent pits increases, and As described above, it is difficult to determine the pit position and the groove position. Further, if the pit width is reduced in order to suppress the crosstalk at the pit portion, the signal output detected at the pit position decreases. This causes a problem that the gain of the tracking servo at the pit position is reduced.

The increase in crosstalk in the pit portion as described above can be achieved by increasing the recording density only by forming the track pitch narrower, and by increasing the wavelength λ of the laser beam used for recording / reproduction and the aperture of the objective lens. This is particularly noticeable when the number NA is not changed. Therefore, it has been difficult to increase the recording density of the optical recording medium by narrowing the track pitch while maintaining compatibility with a recording / reproducing apparatus having a conventional optical system.

Accordingly, the present invention enables recording and reproduction even when used with a conventional recording and reproduction apparatus,
An object of the present invention is to provide an optical recording medium that achieves high recording density by adjusting a track pitch between a pit portion and a groove portion.

[0014]

An optical recording medium according to the present invention has a read-only pit portion in which pits are formed as a concavo-convex pattern corresponding to a recorded signal, and a groove is formed along a recording track. A rewritable groove portion. In the pit portion and the groove portion, the wavelength of light for recording and / or reproducing the signal is λ, the numerical aperture of the lens is NA, the track pitch of the pit portion is Tp, and the track pitch of the groove portion is T.
g, Tg + 0.01 (1.22λ / NA) <
It is formed so as to satisfy the relationship of Tp <Tg + Tg / 3.

In the optical recording medium configured as described above, since the track pitches of the pit portion and the groove portion are formed as described above, even when the track pitch of the groove portion is formed narrow, The pit position can be easily determined by the recording / reproducing device.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, a magneto-optical disk will be described as an example of an optical recording medium to which the present invention is applied, but the present invention is not limited to a magneto-optical disk. INDUSTRIAL APPLICABILITY The present invention is widely applicable to an optical recording medium that performs recording and reproduction by irradiating a laser beam, for example, a phase-change optical disk, and a write-once system including a colorant layer formed of an organic dye material. It may be a type optical disk or the like.

In the following description, a magneto-optical disk 1 as shown in FIGS. 1 and 2 will be described. The magneto-optical disk 1 is a rewritable optical recording medium capable of repeatedly recording and erasing a recording signal, and is housed in, for example, a disk cartridge (not shown).
It is used detachably with respect to a recording / reproducing device (not shown).

The magneto-optical disk 1 is shown in FIGS.
As shown in the figure, on the substrate 2 formed in a substantially disk shape as a whole,
Each layer such as a layer for recording a magnetic signal is laminated. The magneto-optical disk 1 is provided with a lead-in area 1a on the innermost peripheral side, and is provided with a program area 1b in contact with the lead-in area 1a. Have been. A lead-out area 1c is provided on the outermost side. The lead-in area 1a is an area which is first accessed by the recording / reproducing device, and is used exclusively for reproduction. The lead-out area 1c is an area having a function as a margin of the program area 1b, for example, so that the recording / reproducing head of the recording / reproducing apparatus does not move due to an impact and the servo is not disengaged.

As shown in FIGS. 2 and 3, the magneto-optical disk 1 has a first dielectric layer 3, a signal recording layer 4, a second dielectric layer 5, a light Layer 6 and protective film layer 7
Are sequentially laminated. FIG. 2 is an enlarged perspective view of a main part showing a portion surrounded by A in FIG. 1, that is, a lead-in area 1a. FIG. 3 is an enlarged perspective view of a main part showing a portion surrounded by B in FIG. 1, that is, a program area 1b.

When the magneto-optical disk 1 is mounted on the recording / reproducing apparatus, first, the lead-in area 1a is accessed. In the lead-in area 1a, a large number of pits 2b are formed along recording tracks, as described later, and information on the magneto-optical disk 1 is recorded in advance. The recording / reproducing apparatus irradiates a laser beam from the main surface 2a facing the outside of the substrate 2 toward the pit 2b by an optical head, and detects the return light reflected by the laser light on the light reflection layer 4 and returned. I do. The recording and playback device is
The information recorded in the lead-in area 1a is read by utilizing the fact that the amount of return light decreases at the portion where the pit 2b is formed.

The magneto-optical disk 1 has a program area 1
When a recording signal is recorded on the recording / reproducing apparatus b, laser light is emitted from the main surface 2a facing the outside of the substrate 2 by the optical head of the recording / reproducing apparatus, and recording is performed by the recording magnetic head of the recording / reproducing apparatus. A magnetic field corresponding to the signal is applied. At this time, in the magneto-optical disk 1, the signal recording layer 4 is irradiated with laser light, the temperature rises, and the coercive force decreases. Therefore, the magnetic domain corresponding to the recording signal is generated by the magnetic field applied by the recording magnetic head. It is recorded on the recording layer 4.

When the recording signal recorded on the signal recording layer 4 of the program area 1b is reproduced by the recording / reproducing apparatus, the magneto-optical disk 1 emits a laser beam having a lower output than that at the time of recording from the optical head. Is done. At this time, in the magneto-optical disk 1, the return direction of the laser beam reflected by the signal recording layer 4 is changed by the magneto-optical effect such as the Kerr effect and the Faraday effect.
The recording / reproducing apparatus detects the direction of the magnetic field of the magnetic domain recorded in the signal recording layer 4 of the program area 1a by detecting the polarization direction of the return light, and thereby reproduces the recording signal.

The substrate 2 is formed of a hard material having a property of transmitting laser light. As a hard material for forming the substrate 2, for example, various resin materials such as polycarbonate resin, acrylic resin, polyolefin resin, and epoxy resin, and glass materials such as quartz glass are used.

In the area of the lead-in area 1a, a large number of pits 2b are formed on the substrate 2 as an uneven pattern according to a recording signal, as shown in FIG. In other words, in the magneto-optical disk 1, the lead-in area 1
a is provided with a pit portion. In the lead-in area 1a, a recording track is formed along a row of pits 2b.

In the following description, the track pitch of the recording track in the lead-in area 1a is
The interval between the rows of the adjacent pits 2b, that is, the interval indicated by an arrow Tp in FIG.

The substrate 2 has a program area 1b
As shown in FIG. 3, the groove-shaped grooves 2c are formed so as to be parallel to each other in the circumferential direction. In other words, the magneto-optical disk 1 has a configuration in which a groove portion is provided in the program area 1b.
In the program area 1b, the lead-in area 1
As in the case of a, a recording track is formed along the groove 2c. The magneto-optical disk 1 is
The groove 2c is formed to meander with a small amplitude in a constant cycle in the radial direction, so that the recording and reproducing apparatus can read the meandering cycle of the groove 2c when performing recording and reproduction.

Thus, the recording / reproducing apparatus can operate the magneto-optical disk 1 based on the groove 2c meandering at a constant cycle.
Can keep the rotation speed stable at all times. The groove 2c is used as a reference for positioning when recording / reproducing a recording signal with respect to the signal recording layer 4 by the recording / reproducing apparatus, and has a function of indicating a recording position of the recording signal on the magneto-optical disk 1, that is, an address. Have. Thus, the recording / reproducing apparatus can quickly and accurately perform positioning when performing recording / reproducing on the magneto-optical disk 1.

In the following description, the track pitch of the recording track in the program area 1b means
An interval between adjacent grooves 2c, that is, an interval indicated by an arrow Tg in FIG.

The lead-out area 1c has a structure in which a groove 2c is formed in the same manner as the program area 1b. However, the lead-out area 1c may have a configuration in which a large number of pits 2b are formed similarly to the lead-in area 1a, and for example, information indicating the end of the program area 1b is recorded in advance. That is, the lead-out area 1c may be a pit portion or a groove portion.

The first dielectric layer 3 is made of, for example, Si ₃ N ₄ ,
SiN, AlN, Al ₂ O ₃ , AlSiNO, HfO ₂ ,
ZnS, ZrO ₂ , Y ₂ O ₃ , MgO, SiO ₂ , Mg
It is formed in a thin film form on the substrate 2 by using a material such as F ₂ and LiF by a thin film forming technique such as various sputtering methods. However, the material for forming the first dielectric layer 3 has a light-transmitting property with respect to a laser beam incident to record and reproduce a recording signal, does not transmit oxygen and water molecules, and It is desirable to use a material that does not contain
It is desirable to use N, Si ₃ N ₄ or AlN.

The signal recording layer 4 includes a magneto-optical signal layer,
It is formed on the first dielectric layer 3 in the form of a thin film. In the magneto-optical recording layer, the coercive force decreases due to the temperature rise exceeding the Curie temperature, and the magnetization is reversed in the direction of the external magnetic field.
It is formed of a material having magneto-optical properties such as the Kerr effect and the Faraday effect, for example, TbFeCo, TbFe
It is formed of a rare earth / transition metal alloy such as CoCr and GdFeCo. Note that the signal recording layer 4 may be formed as a single layer only by a magneto-optical recording layer, or may be a CAD (Center Aperture Ditector) disk or M
As proposed in an SR (Magnetically induced Super Resolution) disk or the like, it may be formed in a multilayer structure in which a dielectric layer and the like are further laminated. Further, the concave and convex shape of the groove 2 b of the substrate 2 is transferred to the signal recording layer 4.

The second dielectric layer 5 is formed in a thin film on the signal recording layer 4 by using the same material as the first dielectric layer 3.

The light reflecting layer 6 is formed on the second dielectric layer 5 in the form of a thin film. The light reflection layer 6 has a function as a reflection layer that reflects the laser light transmitted through the signal recording layer 4 and the second dielectric layer 5, and the heat of the laser light applied to the signal recording layer 4 reduces the heat. And has a function as a heat sink for preventing heat from being stored in the signal recording layer 4. In the magneto-optical disk 1, since the light reflection layer 6 has a function as a reflection layer, it is possible to improve the use efficiency of the laser beam during recording and reproduction. Light reflection layer 6
It is desirable to use a non-magnetic metal element or a compound thereof which is a thermally good conductor, alone or in combination, for example, and is formed of, for example, Au, Al or the like.

The protective film layer 7 is formed as a thin film on the light reflecting layer 6 by, for example, curing an ultraviolet curable resin applied by a spin coater or the like. Since the magneto-optical disk 1 includes the protective film layer 7, it is possible to prevent the signal recording layer 4 and the light reflection layer 6 from being deteriorated due to oxidation or the like. Further, it is possible to prevent each layer formed on the substrate 2 from being damaged.
The protective film layer 7 may be formed to include various lubricants, or may be formed by applying various lubricants to the main surface 7a facing outward. Thus, when the magneto-optical disk 1 is configured such that the recording magnetic head of the recording / reproducing apparatus slides on the main surface 7a of the protective film layer 7, the wear of the recording magnetic head and the protective film layer 7 is reduced. In addition, heat generation and the like can be prevented.

By the way, in the magneto-optical disk 1,
A track pitch Tp in the lead-in area 1a;
The track pitch Tg in the program area 1b is

[0036]

(Equation 1)

It is formed so as to satisfy the following relationship.
Note that a in Equation 1 represents a beam spot diameter, and when the wavelength of light irradiated by the recording / reproducing device is λ and the lens numerical aperture of the recording / reproducing device is NA, a = 1.22λ / N
A.

In the following, the advantage due to the fact that the track pitches Tp and Tg of the lead-in area 1a and the program area 1b of the magneto-optical disk 1 are formed so as to satisfy Equation 1 will be described.

In an optical recording medium, in order to realize a higher recording density, it is attempted to shorten the wavelength of a laser beam used for recording and reproduction, increase the lens numerical aperture of a recording and reproduction apparatus, and increase the track pitch. Is made narrower. In general, a substrate of an optical recording medium is formed of a resin material such as a polycarbonate resin by an injection molding method using a master disc called a stamper. Even when a conventional optical recording medium has both a pit portion and a groove portion, the track pitch in the pit portion and the groove portion is formed to be equal.

In the optical recording medium, when the optical recording medium is mounted on the recording / reproducing apparatus, first, the lead-in area is roughly accessed without performing the tracking servo. At this time, the recording / reproducing apparatus determines the pit position by utilizing the fact that the signal waveform detected by the recording / reproducing head is different between the position where the pit is formed and the so-called land position where the pit is not formed. . afterwards,
The recording / reproducing apparatus positions the recording / reproducing head on the pits, and after the rotation of the optical recording medium reaches a predetermined number of revolutions, uses the tracking servo corresponding to the pit position to read the signal recorded in the pits. Reproduce. Therefore, it is necessary for the optical recording medium to be able to easily determine the pit portion and the groove portion when the tracking servo is not functioning.

FIG. 4 shows the movement of the optical recording medium when the recording / reproducing head first accesses the lead-in area.
Shown in FIG. 4 is a schematic plan view showing a pit portion provided in the lead-in area, and an arrow C in FIG. 4 is a passage path of the recording / reproducing head. FIG. 5 shows an outline of a signal waveform detected by the recording / reproducing apparatus at this time. In addition,
The portion indicated by arrow D in FIG. 5 is the position where the pit is formed,
That is, it is a signal waveform detected when the recording / reproducing head passes through the recording track. The portion indicated by arrow E in FIG. 5 is a signal waveform detected when the recording / reproducing head passes a position where no pit is formed between recording tracks, that is, a so-called land position.

In the optical recording medium, as shown in FIG. 5, the amplitude G of the signal waveform detected at the land position is smaller than the amplitude F of the signal waveform detected at the recording track. Thereby, the recording and reproducing apparatus determines whether the position of the recording and reproducing head is a recording track or a land position,
Tracking servo can be performed on a recording track.

However, in the conventional optical recording medium, when the track pitch in the pit portion is formed to be narrow, crosstalk between the recording tracks increases, and the amplitude F of the signal waveform in the recording tracks decreases. There has been a problem that the amplitude becomes substantially equal to the amplitude G of the signal waveform at the land position.
For this reason, when the conventional optical recording medium is formed with a narrow track pitch corresponding to the increase in the recording density, it becomes difficult for the recording / reproducing apparatus to determine the recording track and the land position. Reproduction may not be able to be started.

However, the magneto-optical disk 1 is given by
As shown in the figure, the track pitch Tp in the lead-in area 1a is different from the track pitch T in the program area 1b.
It is formed larger than g. Therefore, the magneto-optical disk 1 can achieve a high recording density by narrowing the track pitch Tg in the program area 1b, and can suppress crosstalk in the lead-in area 1a. This makes it possible to reliably determine the recording track and land position of the magneto-optical disk 1 by the recording / reproducing device. Therefore, the magneto-optical disk 1 can be used as a large-capacity recording medium capable of performing stable and reliable recording and reproduction.

On the other hand, in an optical recording medium, the lead-in area is generally limited by various standards, and the same recording information is stored in order to prevent the pit from being unreadable if a pit has a defect. Recorded multiple times.

Therefore, even in the magneto-optical disk 1, the track pitch Tp in the lead-in area 1a cannot be increased without limit. So, below,
The upper limit of the track pitch Tp in the lead-in area 1a will be described.

The tracking servo is performed on the optical recording medium by using, for example, a three spot method. In this case, assuming that the track pitch of the recording track is t, the two sub-spots arranged before and after in the scanning direction of the main spot are + t /
The highest sensitivity is obtained when offset by 4, -t / 4. When the track pitch t changes by Δt, the optical recording medium is provided with an MTF (Modula) for the optical system having the sub spots offset by ± t / 4.
It is expected that the degree of modulation of the track cross signal will be reduced without taking into account the deterioration of the transfer function.

Here, when the deviation amount of the sub spot from the main spot is d = t / 4, the tracking error signal TE in the case of detracking by t / n is represented by the following equation (2). be able to.

[0049]

(Equation 2)

Here, the track pitch t is t '= t-Δ
Considering the case where detracking is performed by t ′ / n at the time t, similarly, considering that MTF is not considered, the following equation 3
While the amplitude of the track cross signal TC does not change, the tracking error signal TE ′ decreases as shown in Expression 4.

[0051]

(Equation 3)

[0052]

(Equation 4)

FIG. 6 shows a change in the signal level I of the tracking error signal when the track pitch displacement Δt changes. Note that FIG. 6 shows the signal level I of the tracking error signal normalized by the signal level I ₀ when the track pitch remains t. The horizontal axis indicates the difference Δt between the track pitches t and t ′. As can be seen from FIG. 6, when the track pitch in the groove portion is narrowed to increase the recording density without changing the optical system used for the optical recording medium and the track pitch in the pit portion, this The signal level of the tracking error signal in the groove of the optical recording medium decreases.

An optical recording medium having a narrow track pitch as described above requires a tracking error signal TE 'in order to enable reliable recording and reproduction even when used for a conventional recording and reproducing apparatus. Is 7 which is the signal level of the tracking error signal TE of the conventional optical recording medium.
It needs to be about 0%. In this case, the difference Δt between the track pitches t and t ′ is t / 3, and the track pitch t ′ is 2t / 3. Therefore, in the optical recording medium, it is desirable that the track pitch in the pit portion is kept at t and the track pitch in the groove portion is 2t / 3.

As a result, in the optical recording medium, since the track pitch in the pit portion remains at the original track pitch, the pit can be reliably read even when used in a conventional recording / reproducing apparatus. In addition, it is possible to increase the recording density by forming the track pitch in the groove portion narrow. In this case, the track pitch in the pit portion Tp can be expressed as Tp = Tg + Tg / 3.

In the magneto-optical disk 1, as shown in Equation 1, the lead-in area 1a provided with the pit portion is provided.
And the track pitch Tg in the program area 1b provided with the groove portion is Tp.
It is formed so as to be <Tg + Tg / 3. Therefore, even when the magneto-optical disk 1 is used for a conventional recording / reproducing apparatus, the pits 2b formed in the lead-in area 1a can be reliably read as described above. In addition, the magneto-optical disk 1 can be formed such that the track pitch Tg in the program area 1b is narrowed to the limit that the signal level of the tracking error signal can be secured to a minimum necessary level.

In the magneto-optical disk 1, the track pitch Tp in the lead-in area 1a is Tg + 0.0 with respect to the track pitch Tg in the program area 1b.
1a <Tp, and is formed to be wider than the track pitch Tg. In the lead-in area 1a, the track pitch Tp is formed to be wider by about 1% of the beam spot diameter a than the track pitch Tg in the program area 1b.
Crosstalk can be suppressed by about 2%. Here, as shown in FIG. 5, the crosstalk refers to a crosstalk of a detection signal in a pit portion detected by a recording / reproducing head when the tracking servo is not functioning, that is, a so-called traverse signal. Further, here, the ratio of the amplitude of the leak signal due to the pit 2b at the land to the maximum amplitude of the traverse signal is expressed as a percentage.

As described above, in the magneto-optical disk 1, the track pitch Tp in the lead-in area 1a is
It is formed wider than the track pitch Tg in the program area 1b. Therefore, the recording / reproducing apparatus can reliably determine the lead-in area 1a and the program area 1b when performing recording / reproducing on the magneto-optical disk 1. In addition, the magneto-optical disk 1 has a higher track density Tg in the program area 1b than the track pitch Tp in the program area 1b. It can be a medium.

Incidentally, in the magneto-optical disk 1,
The following three cases can be cited as positions where the track pitch transition region where the track pitch switches from Tp to Tg is provided.

In the first case, the lead-in area 1
This is a case where a track pitch transition area is provided at the boundary between the program area 1a and the program area 1b. That is, the magneto-optical disk 1 is formed on the recording track from the pit 2b to the groove 2c.
May be formed such that the track pitch is immediately switched from Tp to Tg at the position where the track pitch changes to. As a result, the track pitches of the recording tracks formed in the lead-in area 1a are all formed by Tp, and the track pitches of the recording tracks formed in the program area 1b are all formed by Tg. Therefore, in the magneto-optical disk 1, the boundary between the lead-in area 1a and the program area 1b becomes clear.

In the second case, the lead-in area 1
This is a case where a track pitch transition area is provided in a. The same recording information is recorded in the lead-in area 1a a plurality of times in the lead-in area 1a in order to prevent the pit 2b from becoming unreadable when there is a defect, similarly to the other optical recording media described above. Therefore, in the magneto-optical disk 1, it is very rare that the pit 2b formed at the rearmost end of the lead-in area 1a is read. Therefore, the magneto-optical disk 1 is formed so that the track pitch is switched from Tp to Tg at the rearmost end of such a lead-in area 1a, so that no inconvenience occurs during recording and reproduction.

In the third case, the program area 1
This is a case where a track pitch transition area is provided in b. Generally, in an optical recording medium having both a pit portion and a groove portion, the polarity of a tracking signal is inverted due to a difference in width between the pit and the groove. Therefore, in such an optical recording medium, continuous access from the pit portion to the groove portion is not performed, and a portion within a few hundred tracks from the start position of the groove portion is a buffer zone, and is not used for recording and reproduction. Therefore, the magneto-optical disk 1 is formed such that the track pitch is switched to Tp or Tg in the portion which serves as the buffer zone in the program area 1b. Nothing.

In the magneto-optical disk 1, the positions at which the track pitch transition areas are provided are not limited to the three cases described above, and the track pitch may be changed according to the risk of the pit 2b being interrupted or the target disk format. The switching position may be determined.

In the magneto-optical disk 1, as described above, the lead-out area 1c is replaced with the lead-in area 1a.
It may be configured as a pit portion in the same manner as described above. In this case, in the optical recording medium 1, the position at which the track pitch between the program area 1b and the lead-out area 1c is switched may be provided at the boundary between the program area 1b and the lead-out area 1c, as described above. Alternatively, it may be provided in the program area 1b or the lead-out area 1c.

[0065]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a case will be described in which a crosstalk is measured for a magneto-optical disk manufactured based on the above-described magneto-optical disk 1.

Example 1 In Example 1, a track pitch in the lead-in area was 1.6 μm, and a track pitch in the program area was 1.5 μm. . When measuring the crosstalk of the magneto-optical disk of the first embodiment, an optical system having a laser beam wavelength λ of 780 nm and a lens numerical aperture NA of 0.45 was used. That is, the beam spot diameter a at this time is 2.1 μm from a = 1.22 × λ / NA.
The pit width in the lead-in area was formed to be 250 nm.

Therefore, the magneto-optical disk of the first embodiment is formed such that the track pitch in the lead-in area is 4.7% wider than the track pitch in the program area with respect to the beam spot diameter. The difference in track pitch between the lead-in area and the program area is t / 15 on the basis of the track pitch t in the program area.

Example 2 In Example 2, a magneto-optical disk was manufactured in the same configuration as in Example 1 except that the track pitch in the lead-in area was 1.525 μm. The magneto-optical disk of the second embodiment is formed such that the track pitch in the lead-in area is wider than the track pitch in the program area by 1.2% with respect to the beam spot diameter. The difference between the track pitch between the lead-in area and the program area is the track pitch t of the program area.
Is 0.25 t / 15 on the basis of.

Comparative Example 1 In Comparative Example 1, a magneto-optical disk was manufactured in the same configuration as in Example 1 except that the track pitch in both the lead-in area and the program area was 1.5 μm.

Comparative Example 2 In Comparative Example 2, a magneto-optical disk was manufactured in the same configuration as in Example 1 except that the track pitch in the lead-in area was 1.512 μm. The magneto-optical disk of Comparative Example 2 had a track pitch in the lead-in area of
The beam spot diameter is formed to be 0.6% wider than the track pitch in the program area.

The result of measuring the crosstalk in the lead-in area of each magneto-optical disk manufactured as described above was
As shown in FIG. The crosstalk of each magneto-optical disk is 42.3%, 49.93%, 51.6%, 51.
17%. In the case of a magneto-optical disk, if the crosstalk in the lead-in area is 50% or less, it is easy for the recording / reproducing device to determine the lead-in area and the program area, and the pits formed in the lead-in area are good. It can be read.

As can be seen from the results shown in FIG. 7, the magneto-optical disks of Examples 1 and 2 produced by applying the present invention both have a crosstalk of less than 50%. Good recording and reproduction could be performed. On the other hand, the magneto-optical disk of Comparative Example 1 manufactured in the same manner as the conventional magneto-optical disk and the magneto-optical disk of Comparative Example 2 in which the track pitch in the lead-in area is too narrow with respect to the present invention were both used. 50 crosstalk
%, Which indicates that it is difficult to determine the lead-in area and the program area.

[0073]

As described above, the optical recording medium according to the present invention is formed such that the track pitches p and t of the pit portion and the groove portion respectively satisfy the relationship of t + 0.01a <p <t + t / 3. Be done. Thus, even when the track pitch of the groove portion is formed to be narrow in order to increase the recording density, the pit portion can be easily determined by the recording / reproducing apparatus. Therefore, the optical recording medium according to the present invention can achieve a high recording density and can be used as a large-capacity recording medium, and can reliably signal even when used for a recording / reproducing apparatus having a conventional optical system. Recording and reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a magneto-optical disk according to the present invention.

FIG. 2 is an enlarged perspective view of a main part showing a lead-in area of the magneto-optical disk.

FIG. 3 is an enlarged perspective view of a main part showing a program area of the magneto-optical disk.

FIG. 4 is a schematic diagram for explaining a movement when a recording / reproducing head accesses a magneto-optical disk having a pit portion.

FIG. 5 is a schematic diagram showing a signal waveform detected when a recording / reproducing head accesses a magneto-optical disk having a pit portion.

FIG. 6 is a diagram for explaining a decrease in a tracking error signal with respect to a track pitch in a lead-in area.

FIG. 7 is a diagram showing crosstalk of each magneto-optical disk manufactured in the example.

[Explanation of symbols]

1 magneto-optical disk, 1a lead-in area, 1b
Program area, 1c lead-out area, 2 substrates, 3rd dielectric layer, 4 signal recording layer, 5th dielectric layer, 6 light reflection layer, 7 protective film layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tanaka Fuji 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Mitsuo Arima 6-35-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Katsuhiko Otomo 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Manabu Sato 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony F term in reference (reference) 5D029 JB09 WA17 WB15 WC05 WC06 WC09 WC10 WD10 WD22

Claims (4)

[Claims] 1. A read-only pit portion having a pit as a concavo-convex pattern corresponding to a recorded signal,
A groove formed along a recording track to allow a signal to be rewritten; and the pit and the groove record and / or record the signal.
Alternatively, when the wavelength of light to be reproduced is λ, the lens numerical aperture is NA, the track pitch in the pit portion is Tp, and the track pitch in the groove portion is Tg, Tg + 0.01 (1.22λ / NA) < Tp <Tg + T
An optical recording medium formed so as to satisfy a relationship of g / 3. 2. The pit portion has a track pitch of T
2. The optical recording medium according to claim 1, wherein a track pitch transition region that transitions from p to Tg or from Tg to Tp is provided. 3. The optical recording medium according to claim 1, wherein the groove portion is provided with a track pitch transition region in which a track pitch transitions from Tp to Tg or from Tg to Tp. 4. A track pitch from Tp to Tg or from Tg to Tg at a boundary between the pit portion and the groove portion.
2. The optical recording medium according to claim 1, wherein a track pitch transition region that transitions to p is provided.