JPH0935334A - Optical disk and method for accessing optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk with which production is easy and reading errors of information are decreased. SOLUTION: Pits 5 are formed in the header region of the groove part 4 of a substrate 2 and header information is expressed by the presence or absence and lengths of holes. The relation dp/dg between the depth dp of the pits 5 and the depth dg of the groove parts 4 is set within a range of 1.3 to 1.8. The crosstalks to adjacent land parts 3 from the header region of the groove part 4 are thereby decreased. A dielectric layer, recording layer and protective layer are successively formed on the substrate 2 and a protective substrate is adhered to the film surface, by which the production of a magneto-optical disk 1 is completed. The region on tracks having no header information is accessed in accordance with the header information of the adjacent tracks in the case such a region is accessed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk such as a magneto-optical disk or a phase change optical disk and a method for accessing this optical disk.

[0002]

2. Description of the Related Art In recent years, an optical recording / reproducing method satisfying various requirements including high density, large capacity, high access speed, and high recording and reproducing speed, recording apparatus, reproducing apparatus and recording medium used therefor. Efforts are being made to develop. Among the wide range of optical recording / reproducing methods, the magneto-optical recording / reproducing method and the phase change recording / reproducing method are the most attractive because of the unique advantage that the recorded information can be rewritten repeatedly. There is.

Here, taking a magneto-optical disk as an example, an optical disk manufacturing process will be briefly described with reference to FIG. FIG.
In FIG. 2, 20 is a substrate with a guide groove made of plastic or the like, 23 is a land portion which is a convex portion of the substrate 20, and 24 is a groove portion which is a concave portion. First, as shown in FIG. 12A, a glass master 22 coated with a photoresist 21.
Is prepared, and a portion corresponding to the groove portion 24 of the resist 21 is exposed. Then, by performing development, as shown in FIG.
A master (master) as shown in (b) is obtained. Nickel electroforming is performed on this master to produce a nickel stamper 26 of FIG. 12C, and injection molding is performed using this stamper 26 to produce a substrate 20 with guide grooves as shown in FIG. 12D. Finally, a recording layer (not shown) is formed on the substrate 20 to complete the manufacture of the magneto-optical disk.

In such an optical disc, either the land portion or the groove portion is used as a recording / reproducing track. Each track is divided into units called sectors, and information recording / reproduction is performed in sector units. Further, each sector has a data area for recording data directly used by the user and a header area for recording header information indicating the position (address) of the sector on the disk.

The method of recording header information includes a method of forming geometrical irregularities (hereinafter referred to as prepits) indicating header information on a substrate having guide grooves in a manufacturing process (preformat), and a method of forming a header after manufacturing a disc. There is a method (soft format) for writing information to the recording layer. Like the user data, the header information is 1 optical disc 1
Most discs currently on the market adopt the pre-formatting method out of the two methods, because the contents are not different between the sheets and are the same for most discs.

On the other hand, in optical discs, land / groove recording has attracted attention for the purpose of further improving the capacity. This is a recording method that uses both the land portion and the groove portion as recording tracks. In this land / groove recording, since both the land portion and the groove portion are used as recording tracks, there arises a problem that signal crosstalk between the tracks becomes large. As a method of solving this problem, the depth of the groove portion is λ / (6n) with respect to the wavelength λ of the reproduction laser light and the refractive index n of the substrate with the guide groove.
It is known that the signal crosstalk between adjacent land portions and groove portions can be made extremely small if it is set to a certain degree (for example, Japanese Patent Laid-Open No. 57-138065).

However, this crosstalk reducing method is applied to the marks representing the data to be magneto-optically recorded or phase change recorded in the data area of the optical disc, and therefore cannot be applied to the prepits formed in the header area. In the case of land / groove recording, a header area must be provided in both the land portion and the groove portion, so that crosstalk between the header areas provided in the adjacent land portion and group portion becomes a problem. Further, if the header area of the land part and the data area of the groove part are adjacent to each other, crosstalk between the header area and the data area becomes a problem.

In order to solve such a problem, the depth of the groove, the depth (or height) of the prepit, and the width of the prepit are set so that the crosstalk becomes small for each of the land portion and the groove portion. It has to be controlled and in practice it is nearly impossible to obtain a master and stamper under many of these restrictions with normal manufacturing processes.

[0009]

As described above, when land / groove recording is performed in the conventional optical disk, the space between the header areas or the space between the header areas and the data areas provided in the adjacent land portion and group portion. There has been a problem that signal crosstalk becomes large and information reading error occurs. Further, if it is attempted to reduce this crosstalk, it is difficult to manufacture a master and a stamper, which makes it very difficult to mass-produce optical discs. The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical disk that can be easily mass-produced and has few information reading errors, and an access method for this optical disk.

[0010]

The optical disc of the present invention comprises:
A substrate with a guide groove is provided, and the substrate with the guide groove has a depth dp of a pit or a height d of a hill.
The pits or hills are formed on only one of the lands or the grooves so that h is equal to or more than the groove depth dg. By using such a substrate with guide grooves, crosstalk from the header region to the adjacent track can be reduced.

The access method of the present invention is defined in claim 2.
When the area on the first track is accessed, the header information is detected and accessed from the pit or hill provided on the first track to access the area on the second track. When accessing, header information is detected from a pit or a hill provided on the first track adjacent to the second track, and the access is performed based on the detected header information.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. FIG. 1 (a) is an external view of a magneto-optical disk showing an embodiment of the present invention, and FIG. 1 (b) is an oblique view of a portion B of the magneto-optical disk of FIG. 1 (a) taken along the line AA. It is an enlarged view seen from above. Reference numeral 1 is a magneto-optical disk, and 2 is a guide grooved substrate having a land portion 3 which is a convex portion and a groove portion 4 which is a concave portion when viewed from the side opposite to the incidence of laser light (the upper side in FIG. 1). Reference numeral 5 denotes a hole-shaped pit formed in the header area of the groove portion 4, and the header information is expressed by the presence or absence of the hole and its length.

In an actual magneto-optical disk, the substrate 2
A recording film and a protective film are formed on the above, but these are omitted in FIG. 1B to make the pit 5 easy to see. Next, a method of manufacturing such a magneto-optical disk 1 will be described. 2A to 2C are process cross-sectional views for explaining the method of manufacturing the magneto-optical disk 1.

First, the outer diameter is 350 mm, the inner diameter is 70 mm,
A synthetic quartz master 12 having a thickness of 6 mm and a surface roughness of 5 nm or less is prepared, and concentrated sulfuric acid and hydrogen peroxide solution are mixed in a volume ratio of 4:
The master 12 is immersed in a liquid mixed at a ratio of 1 (liquid temperature is 40 ° C.) for 5 minutes, and then spin washed with ultrapure water. Subsequently, a primer (anchor coat manufactured by Transyl Co., Ltd.) was spin-coated on the surface of the quartz master 12, and then a thickness of 190 n was obtained.
m positive resist 11 (Hoechst AZ1350)
Is spin coated and prebaked at 100 ° C. for 30 minutes.

Then, a laser beam having a spot diameter of about 0.9 μm is continuously irradiated onto the area of the quartz master 12 having a radius of 55 to 149 mm by a cutting machine equipped with an Ar ion laser having a wavelength of 457.9 nm to form a resist 11. The portion 14 corresponding to the groove portion 4 is exposed (FIG. 2A). At this time, the rotation speed of the master 12 is 900 rpm, and the land portion 3 adjacent to the land portion 3 from the center of the land portion 3 is rotated.
The track pitch P, which is the length to the center of the track, is 1.4 μm,
The exposure was performed with a laser power such that the width Wg of the groove portion 4 was about 0.7 μm.

Then, an inorganic alkaline developer (AZ developer manufactured by Hoechst) and ultrapure water are mixed at a volume ratio of 3: 5 and spin-developed with a diluted developer, and then 120 ° C.
Post bake for 30 minutes (Fig. 2 (b)). The development conditions are as follows: pre-pure water application time 54 seconds, developer application time 98
Second, pure water shower time 90 seconds, spin drying time 90 seconds.

Next, the master 12 thus developed is subjected to a reactive ion etching apparatus (DEA50 manufactured by Nidec Anerva).
After being placed in the chamber of 6) and evacuating to a vacuum degree of 1 × 10 ⁻⁴ Pa, CHF 3 gas is introduced and reactive ion etching is performed using the resist 11 as a mask. At this time, the gas flow rate is 6 sccm, the gas pressure is 0.3 Pa, the RF power is 400 W, the self-bias voltage is −530 V, the electrode distance is 100 mm, and the etching depth is 79 nm.

Then, the master 12 is immersed in a liquid in which concentrated sulfuric acid and hydrogen peroxide are mixed at a volume ratio of 4: 1 to remove the residual resist 11, and spin cleaning is performed with ultrapure water. The liquid temperature at the time of removal is 100 ° C., and the treatment time is 5 minutes. Thus, the portion 1 corresponding to the land portion 3 as shown in FIG.
3, a master 12 having a portion 14 corresponding to the groove portion 4 is obtained.

Then, after a primer (anchor coat manufactured by Transyl Co.) is spin-coated on the surface of the synthetic quartz master 12, a positive resist 16 having a thickness of 190 nm is formed.
(Hoechst AZ1350) was spin coated to give 10
Pre-bake at 0 ° C. for 30 minutes (FIG. 2 (d)). As a result, the portion 14 corresponding to the groove portion 4 is covered with the resist 16
Completely covered by.

Then, using a cutting machine similar to that shown in FIG. 2A, an E / 0 modulator (Electro Optical Modula) is used.
give a pattern signal for recording header information to
The laser light is applied to the area of the master 12 having a radius of 56 to 148 mm while being modulated by an E / O modulator, and the resist 1
The portion 15 corresponding to the pit 5 of 6 is exposed. At this time, the rotation speed of the master 12 is 900 rpm, the spot diameter of the laser light is about 0.4 μm, and the distance between the spot center of the laser light and the center of the groove portion 4 in the radial direction (left and right direction in FIG. 1B). Is 0 μm and the width Wp of the pit 5 is about 0.
It was exposed with a laser power of 3 μm.

Further, as the pattern signal, the track numbers are 1, 2, 3, ...
The number of sectors per track is 60 and the sector numbers are 1, 2, 3, ...
Next, development and post-baking are performed under the same conditions as in the step of FIG. 2B (FIG. 2E). Then, using the same reactive ion etching apparatus as described above, reactive ion etching is performed using the resist 16 as a mask. However, the etching depth is 127 nm.

Then, the residual resist 1 is formed under the same conditions as above.
Remove 6 and spin wash with ultrapure water. Thus, FIG.
The master 12 having the land portions 3, the groove portions 4, and the portions 13 to 15 respectively corresponding to the pits 5 as shown in FIG.
(Master) is obtained. Next, nickel electroforming is performed on this master 12 to produce a nickel stamper 17 as shown in FIG.

Then, an ultraviolet curable resin (Photo Polymer) is injected between the stamper 17 and the glass substrate, and the resin layer having the stamper surface transferred is formed on the glass substrate by the 2P method in which the resin is cured by ultraviolet rays. , Track pitch P 1.4 μm, width Wp of the groove portion 4 (= land portion 3
Width) 0.7 μm, the depth of the groove portion 4 dg 79 nm,
Pit 5 width Wp 0.3 μm, pit 5 depth dp12
A substrate 2 with a guide groove of 7 nm is prepared.

Further, injection molding using the stamper 17,
A plastic guide grooved substrate may be produced by performing injection compression molding. Finally, a dielectric layer made of Si3 N4 (not shown), TbFeC, is formed on the substrate 2.
The recording layer made of o and the protective layer made of Si3 N4 are sequentially formed, and the protective substrate is adhered to the film surface with an ultraviolet curing adhesive to complete the manufacture of the magneto-optical disk 1.

In the magneto-optical disk 1 thus manufactured,
The relationship between the depth dg of the groove portion 4 and the depth dp of the pit 5 is dp ≧ dg (dp / dg = 1.61 in this embodiment).
However, this is due to the following reasons. As an array method of sectors on an optical disk, there are an aligned method in which the sectors are aligned as shown in FIG. 3A and a no-aligned method in which the sectors are not aligned as shown in FIG. 3B. To do. In FIG. 3, 4n is a groove portion and 3n is a land portion adjacent to the inner peripheral side of the groove portion 4n.

In this embodiment, the pits 5 (header information) are present only in the header area of the groove portion 4n, and there is no pit 5 in the header area of the land portion 3n. Is aligned, there is no problem with crosstalk between the header areas of the groove portion 4n and the land portion 3n. However, in the case of the non-aligned method, the land portion 3n adjacent to the header area of the groove portion 4n may be a data area, so the header area and the land portion 3n of the groove portion 4n may be formed.
The crosstalk between the data areas of is a problem.

Here, the pits 5 provided in the header area are detected in the form of a change in the amount of reflected light due to diffraction, and the data magneto-optically recorded in the data area is reflected light according to the direction of the magnetization direction of the recording layer. Is detected in the form of a change in the polarization plane. Therefore, since the signal strength obtained from the header area is larger than that in the data area, crosstalk from the data area to the header area is hardly a problem, and crosstalk from the header area to the data area is a problem. Therefore, a method of reducing crosstalk from the header area to the data area is required.

In addition, since the pits 5 are provided only in the groove portion 4, the area of the land portion 3 which is a conventional header area can be used as a data area, but in this case also the crosstalk becomes a problem. . So pit 5
The crosstalk was measured while changing the depth dp of the sample, and the conditions for reducing the crosstalk were investigated.

Here, the track pitch P is 1.4 μ.
m, the width of the groove portion 4 (= the width of the land portion 3) Wg is 0.
7 μm, depth dg of groove portion 79 is 79 nm, pit 5
Has a width Wp of 0.3 μm and the pit 5 has a length of 2.4 μm,
A magneto-optical disk using a substrate with guide grooves in which the pitch of the pits 5 is 4.8 μm is used as a measurement target. The polarization state of the laser beam is horizontal polarization, the laser wavelength λ is 680 nm, the numerical aperture (NA) of the objective lens is 0.55, the pupil diameter D of the objective lens and the spot of the laser beam incident on the objective lens. Reproduction was performed with an optical pickup having a ratio D / W of the diameter W of 0.8 and a wavefront aberration of 0.024λ [rms value].

The crosstalk CT is the carrier component C1 [d when reproducing the groove portion 4 in which the pit 5 is formed.
Bm], and the carrier component C2 [dBm] when the land portion 3 having no pit 5 is reproduced is defined by the following equation. CT = C2-C1 (1) The crosstalk CT is preferably −25 to −30 dB or less, and more preferably −35 dB or less.

FIG. 4 is a diagram showing the relationship between the crosstalk CT and dp / dg measured under the above conditions. The condition that can reduce the crosstalk CT is dp / dg =
About 1.6 is the best, dp / dg = 1.3 to 1.8 is preferable at −30 dB or less, and dp / dg = 1.5 to 1.
It can be seen that 7 is more preferable at -35 dB or less. Thus, in the magneto-optical disk 1 of FIG. 1, dp / dg = 1.
By setting 61, crosstalk from the header area of the groove portion 4 to the data area of the land portion 3 can be reduced.

The magneto-optical disk 1 manufactured as described above is for land / groove recording. However, since the pits 5 exist only in the groove portions 4, it is not possible to access the land portions 3 by the conventional method. Requires different methods.
Therefore, the access method of the present invention will be described next.

FIG. 5 shows a portion C of the magneto-optical disk 1 shown in FIG.
2 is a diagram showing a state of a recording / reproducing track in FIG.
0i, 10i + 1 are sectors of track (groove part) 4n, 10j-1, 10j are sectors of track (land part) 3n, 11i, 11i + 1 are header areas, 12i, 12
i + 1 is a data area.

Further, VFO1, VFO2 and VFO3 are P
Continuous data pattern for LL lock, AM is an address mark for indicating the start position of address data, ID1,
ID2 and ID3 are addresses (track number and sector number), PA is a postamble for use when the error detection code (CRC) does not fit within a predetermined length, G
AP is a blank part with no data or a test part (ALPC) for controlling the laser power level, D
S is data S for indicating the start position of user data
YNC and DA are user data, and BUF is an area for a fluctuation margin of disk rotation.

Then, VFO1, VFO2, A recorded by pits 5 in the header areas 11i, 11i + 1.
M, ID1 to ID3, and PA are header information. Since it is possible to access the sector 10i or 10i + 1 of the track 4n in which the header information is recorded by a well-known technique, a description thereof will be omitted and a method of accessing the sector 10j of the track 3n will be described.

The sector 10j is a sector forming a pair with the sector 10i. The address of the sector 10i is the track number n and the sector number i, whereas the address of the sector 10j is the track number n and the sector number j. At this time, i = j may be satisfied or i ≠ j may be satisfied.
Also, the track numbers are the same, but they do not have to be the same.

Address management is performed by a pair of a sector of a track in which the header information is recorded and a sector of a track adjacent thereto in which the header information is not recorded. The correspondence relationship between these addresses is shown in FIG. It may be set arbitrarily according to the form of management.

A recording / reproducing apparatus (not shown) for recording / reproducing data on / from the magneto-optical disk 1 stores the above-mentioned address correspondence, and when the sector 10j is accessed, the paired sector 10i is first accessed. To do. Then, after reading the address of the sector 10i from the header area 11i, the tracking servo that causes the laser beam of the optical pickup to follow the track 4n is turned off, and the detection polarity of the tracking error is reversed.

Here, the reason why the detection polarity is inverted is as follows. The tracking error is detected by the push-pull method which is a well-known tracking error detection method. In the push-pull method, the output difference between the two light receiving parts in the optical pickup that receives the reflected light from the magneto-optical disk 1 is taken out as a tracking error signal, so tracking is performed when the laser beam accurately tracks the track. -The error signal becomes 0.

The polarities (+/-) of the tracking error signal are calculated when moving from the groove portion 4 to the land portion 3 and when moving from the land portion 3 to the groove portion 4.
Is different. As a result, in the present embodiment, the track 4n
Is tracked and then moved to the track 3n, it is necessary to invert the detection polarity in order to correctly detect the tracking error.

Subsequently, the recording / reproducing apparatus moves the laser beam to the inner circumference side of one track as shown by the locus R in FIG. 5, and when the track 3n is reached, the tracking servo is turned on again. At this time, a certain amount of time is required from the input of the tracking servo to the stable follow-up operation, so after a certain amount of time has elapsed from the input and settling, the processing of the signal obtained by the optical pickup is started and reproduced. Get the output (that is, do not play if the output was obtained by the optical pickup before this).

When the DS pattern recorded in the sector 10j is detected, it is determined that the sector is the target sector 10j, and the data is read. This allows the data recorded in the sector 10j to be reproduced. Also, sector 1
In the case of recording at 0j, recording may be started after a certain time has elapsed from the re-input of the tracking servo.

In this way, the sector 10j can be accessed. In this embodiment, the sector forming a pair with the sector of the track 4n is the sector on the inner track 3n, but may be the sector on the outer track. Further, in the present embodiment, the case of accessing using the one-beam optical pickup has been described, but the two-beam optical pickup may be used. In this case,
First information recorded with header information on the first laser beam
It is sufficient to trace the second track and the second beam in which the header information is not recorded on the second beam.

At this time, if the first beam is arranged so as to precede the second beam in the circumferential direction (track direction) so that the header information of the first track can be read out first, It is possible to shorten the time from reading the header information of the first track to accessing the second track.

As described above, in the present embodiment,
By forming the pits 5 only in the groove portions 4, the master may be manufactured while paying attention to the control of the depth dg of the groove portions 4 and the depth dp of the pits 5. Therefore, pits (or hills, which will be described later) are provided on both the land and the groove, and the depth of the groove, the depth and the width of the pit (hill) are controlled so that crosstalk is reduced for each of the land and the groove. As compared with the case, the master and the stamper can be easily manufactured.

Further, since the header area is provided only in the groove portion 4, the area of the land portion 3 which is a conventional header area can be used as a data area, and the recording capacity can be increased. In addition, newly added land section 3
Even if the data area and the header area of the groove portion 4 are adjacent to each other, or are also adjacent to each other by the no-align method, due to the above-described crosstalk reducing effect, no signal reading error occurs.

Embodiment 2 FIG. 6 is an enlarged view of a portion of a magneto-optical disk according to another embodiment of the present invention as seen obliquely from above as in FIG. 1 (b). The same portions as those in FIG. It is attached. 2a is a substrate with a guide groove, 5
a is a pit formed in the header area of the land portion 3.

Next, a method of manufacturing such a magneto-optical disk will be described. In order to manufacture the magneto-optical disk of the present embodiment, when exposure is performed after the step of FIG. 2D, instead of the portion 14 corresponding to the groove portion 4, the portion 13 corresponding to the land portion 3 is formed. The resist 16 may be exposed. Then, if the same etching as in the first embodiment is performed, the portion 13 corresponding to the land portion 3 is etched, so that the master (1 in FIG. 2F) in which a pit is formed in the land portion is formed.
2) is obtained. The subsequent steps are exactly the same as in the first embodiment.

Next, also in the present embodiment, the pit 5a
The above-mentioned crosstalk was measured while changing the depth dp of the above, and conditions for reducing the crosstalk were investigated. The conditions of the magneto-optical disk to be measured and the optical pickup are all the same as in the first embodiment. Then, the carrier component when reproducing the land portion 3 in which the pits 5a are formed is C1.
If [dBm] and the carrier component when reproducing the groove portion 4 without the pit 5a are C2 [dBm], the crosstalk CT is defined by the equation (1) as in the first embodiment.

FIG. 7 is a diagram showing the relationship between the crosstalk CT and dp / dg measured under the above conditions. The condition that can reduce the crosstalk CT is dp / dg =
The best value is about 1.5, dp / dg = 1.1 to 1.8 is preferably -30 dB or less, and dp / dg = 1.25 to 1.25.
It can be seen that 1.6 is more preferable at -35 dB or less.

Thus, in the magneto-optical disk of the present embodiment, if dp / dg is set within the above range, crosstalk from the header area of the land portion 3 to the data area of the groove portion 4 can be reduced. . Further, in the access method described in the first embodiment, if the description of the land portion 3 and the groove portion 4 is replaced with each other, the above-described access method can be established in the same manner in the present embodiment. As described above, the same effect as that of the first embodiment can be obtained.

Embodiment 3. FIG. 8 is an enlarged view of a portion of a magneto-optical disk according to another embodiment of the present invention as seen obliquely from above like FIG. 1 (b), and 2b is a substrate with a guide groove. Further, 5b is a projection-like hill formed in the header area of the land portion 3, and the presence or absence of the projection and the length thereof represent header information.

Next, a method of manufacturing such a magneto-optical disk will be described. In order to manufacture the magneto-optical disk of the present embodiment, the irregularities of the master 12 shown in FIG. Therefore, this master 12 is used as it is as a stamper (17 in FIG. 2), or nickel electroforming is performed on the master 12 to prepare a master for this embodiment in which the concavities and convexities are reversed, and a nickel oxide film is formed. After forming a peeling film such as the above, nickel electroforming may be performed to produce a nickel stamper. The subsequent steps are exactly the same as in the first embodiment.

Also in the present embodiment, the above-mentioned crosstalk is measured while changing the height dh of the hill 5b,
The conditions under which this crosstalk can be reduced were investigated. Here, the track pitch P is 1.4 μm, the width of the groove portion 4 (= width of the land portion 3) Wg is 0.7 μm, and the groove portion 4 is
Depth dg of 79 nm, width Wh of the hill 5b is 0.3μ
m, the length of the hill 5b is 2.4 μm, and the pitch of the hill 5b is 4.8 μm. The conditions of the optical pickup are all the same as those in the first embodiment.

The land portion 3 on which the hill 5b is formed
C1 [dBm] as the carrier component when reproducing
The carrier component when the groove portion 4 is reproduced is C2 [d
Bm], the crosstalk CT is defined by the equation (1). FIG. 9 is a diagram showing the relationship between crosstalk CT and dh / dg measured under the above conditions. The condition that can reduce the crosstalk CT is dh / dg =
1.4 is the best, dh / dg = 1.05 to 1.7
Is preferably -30 dB or less, and dh / dg = 1.2 to
It can be seen that 1.5 is more preferable at -35 dB or less.

Thus, in the magneto-optical disk of the present embodiment, if dh / dg is set within the above range, crosstalk from the header area of the land 3 to the data area of the groove 4 can be reduced. . In the access method described in the first embodiment, if the description of the pit 5 and the hill 5b and the description of the land portion 3 and the groove portion 4 are exchanged, the above-described access method can be realized in the same manner in the present embodiment. As described above, the same effect as that of the first embodiment can be obtained.

Embodiment 4 FIG. FIG. 10 is an enlarged view of a portion of a magneto-optical disk according to another embodiment of the present invention as seen obliquely from above as in FIG. 1 (b). 2c is a substrate with a guide groove, 5c is a groove portion 4 It is a hill formed in the header area of. In order to manufacture the magneto-optical disk of the present embodiment, the irregularities of the master manufactured in the second embodiment may be reversed. Therefore, the master manufactured in the second embodiment can be used as it is as a stamper, or the master described in the third embodiment can be used to manufacture a master for this embodiment in which the concavities and convexities are reversed to prepare a nickel stamper. Good.

Also in this embodiment, the above-mentioned crosstalk is measured while changing the height dh of the hill 5c,
The conditions under which this crosstalk can be reduced were investigated. The conditions of the magneto-optical disk to be measured and the optical pickup are all the same as in the third embodiment. Then, the carrier component when reproducing the groove portion 4 in which the hill 5c is formed is C1 [d
Bm] and the carrier component when reproducing the land portion 3 is C2 [dBm], the crosstalk CT is defined by the equation (1).

FIG. 11 is a diagram showing the relationship between crosstalk CT and dh / dg measured under the above conditions. As conditions for reducing crosstalk, dh / dg = 1.
25 is the best, dh / dg = 1.05 to 1.5 is preferably -30 dB or less, and dh / dg = 1.1 to 1.
It can be seen that 4 is more preferable at -35 dB or less. Thus, in the magneto-optical disk of the present embodiment, dh /
By setting dg within the above range, crosstalk from the header area of the groove portion 4 to the data area of the land portion 3 can be reduced.

Further, in the access method described in the first embodiment, if the description of the pit 5 and the hill 5c is replaced with each other, the above-described access method can be applied in the same manner in the present embodiment. Thus, the same effect as that of the first embodiment can be obtained. From the results of Embodiments 1 to 4 above, at least d is a condition for reducing the crosstalk CT.
It is necessary that p ≧ dg or dh ≧ dg.

Although the magneto-optical disk has been described in the first to fourth embodiments, it is sufficient to provide pits or hills on the substrate having the guide groove, and therefore other recording such as phase change recording or perforation recording is performed. The present invention can be applied to an optical disc for a method.

[0062]

According to the present invention, by using a substrate with a guide groove in which pits or hills are formed on only one of a land or a groove, the area which was the conventional header area of a track without pits or hills can be recorded. It can be used as an area and the recording capacity can be increased.
Also, by making the pit depth or hill height equal to or greater than the groove depth, crosstalk from the header area to the adjacent track can be reduced, so that the header area and the data area of the adjacent track are adjacent to each other. Even if
There is no error in reading the data area. Also, since it is only necessary to prepare the master while paying attention to the depth of the pit or the height of the hill and the depth of the groove, it is necessary to provide the pit or the hill on both the land and the groove to control the crosstalk to be small. Compared to the case, the master and the stamper can be easily manufactured, and the mass production of optical disks can be facilitated.

When accessing the area of the first track, the header information is detected from the pit or hill provided in this track to access, and when accessing the area of the second track, By accessing based on the header information of the adjacent first track, it is possible to access both the first and second tracks in the optical disc in which the header information is recorded only on the first track, and the land and the groove are Both can be used as recording / reproducing tracks.

[Brief description of drawings]

FIG. 1 is an external view of a magneto-optical disk according to an embodiment of the present invention and an enlarged view of a part of the magneto-optical disk as seen obliquely from above.

2A to 2D are process cross-sectional views for explaining a method of manufacturing the magneto-optical disk of FIG.

FIG. 3 is a diagram showing how sectors are arranged on an optical disc.

4 is a diagram showing a relationship between crosstalk and dp / dg in the magneto-optical disc of FIG.

5 is a diagram showing a state of recording / reproducing tracks in a part of the magneto-optical disk of FIG. 1. FIG.

FIG. 6 is an enlarged view of a portion of a magneto-optical disk according to another embodiment of the present invention as seen obliquely from above.

7 is a diagram showing the relationship between crosstalk and dp / dg in the magneto-optical disc of FIG.

FIG. 8 is an enlarged view of a portion of a magneto-optical disk according to another embodiment of the present invention, which is viewed obliquely from above.

9 is a diagram showing a relationship between crosstalk and dh / dg in the magneto-optical disc of FIG.

FIG. 10 is an enlarged view of a portion of a magneto-optical disk according to another embodiment of the present invention, which is viewed obliquely from above.

11 is a diagram showing a relationship between crosstalk and dh / dg in the magneto-optical disk of FIG.

FIG. 12 is a process sectional view for explaining a conventional method for manufacturing an optical disc.

[Explanation of reference numerals] 1 ... Magneto-optical disk, 2 ... Substrate with guide groove, 3 ... Land portion, 4 ... Groove portion, 5 5a ... Pit, 5b, 5c ...
Hill, dp ... Pit depth, dh ... Hill height, dg ...
The depth of the groove.

Claims (2)

[Claims] 1. A substrate with a guide groove having a land that is a convex portion, a groove that is a concave portion, and a hole-shaped pit or a protruding hill that represents header information including positional information on a disc is used. An optical disc using both lands and grooves as recording / reproducing tracks, wherein the guide grooved substrate has pits or hills such that a pit depth dp or a hill height dh is not less than a groove depth dg. Is an optical disc formed on only one of a land and a groove. 2. A hole-shaped pit or a protruding hill representing header information including position information on the disc is provided only on the first track of the two types of tracks of the land or groove, and the pit depth. A method for accessing an area on the optical disc, wherein the height of the hill or the hill is equal to or greater than the depth of the groove, the method comprising: accessing the area on the first track;
When header information is detected and accessed from a pit or hill provided on the first track, and an area on the second track is accessed,
An access method for an optical disk, characterized in that header information is detected from a pit or a hill provided on a first track adjacent to the second track, and access is performed based on the detected header information.