JP2000057634A - Optical disk medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower asymmetry and to improve interchangeability by specifying the duty ratios of header parts arranged zigzag on the virtual extension lines of boundary portions between groove tracks and land tracks to a specific range. SOLUTION: The duty ratios of the mark parts consisting of recessed parts of prepits are recommended to be set slightly longer and to be set in a range of 50 to 58 in order to lower the asymmetry of differential signals when the address information recorded as the prepits is reproduced by the differential signals. The regulation of the lengths of the mark parts is executed by regulating the lengths of corresponding pulses at the time of cutting a stamper. Since the header parts VFO are basically composed of 4T0 signals, the lengths of the cutting pulses are regulated to (4+x)T0 in order to make the lengths of the mark parts slightly longer. In actuality, the good asymmetry is obtd. if the constant (x) is selected at 0 to 0.7. The duty ratios of 50 to 58 are obtd. as the duty ratios of the mark parts with the optical disk produced by the stamper manufactured in the manner described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a groove / land recording system for recording information on both a groove track and a land track. A header recorded as prepits is staggered at the boundary between the groove track and the land track. The present invention relates to an optical disk medium having a substrate having a format arranged in the optical disk medium.

[0002]

2. Description of the Related Art Optical disk media have attracted attention because of their high density and large capacity, and have been used in various applications. For example, a read-only optical disk includes a compact disk and a CD-ROM dedicated to data reproduction, and is widely used in the music field, computer field, game field, and the like. A write-once optical disc medium that can be recorded only once is used in a document filing system, a data filing system, and the like, particularly in a field where data security is important.

[0003] Furthermore, a rewritable optical disk medium capable of erasing and re-recording recorded information is capable of restoring and updating data and can be used repeatedly by rewriting, thereby contributing to an expanded use of the optical disk medium. As expected. As such a rewritable optical disk, a magneto-optical disk medium and a phase-change optical disk medium have been put to practical use, and are used for data files and the like. In particular, the phase-change optical disk medium records and erases information using a recording material that reversibly changes in phase between crystalline and amorphous due to temperature changes, and changes the power of the laser beam. It is easy to overwrite such that old information is erased and new information is recorded at the same time simply by causing the digital video disc to be rewritable.

[0004] In a rewritable digital video disk, a method of recording data on both lands and grooves, which is called land / groove recording, has been adopted in order to realize a large capacity. This land / groove recording has attracted attention as a promising high-density technology because the density can be doubled while keeping the track pitch the same, and is one of the core technologies that will be the core of the future.

[0005] The address information is pre-pits, as shown in FIG.
Generally, addresses are arranged in a zigzag pattern on the virtual extension game at the boundary of No. 2.
(Complimentary Allocated Pit Address). For example, in the groove track 11, the prepits 13 are respectively arranged by being shifted from the center line of the groove track 11 by ト ラ ッ ク track pitch in the inner circumferential direction and the outer circumferential direction, and the prepits 13 arranged in a staggered manner are land tracks. As viewed from 12, the arrangement of the first half and the second half is reversed.

Address information recorded as pre-pits is generally detected by a push-pull method (difference signal) as shown in FIG. 2, utilizing the difference in reflected light between a portion with and without a pre-pit. . The difference signal indicates a difference between I1 and I2 when Ia + Ib and Ic + Id in FIG. 2 are represented by I1 and I2, that is, a signal defined by I1−I2. By using the push-pull method, for example, if the polarity of the address reproduction signal of the land is made positive, the address reproduction signal of the groove becomes negative, and if this polarity difference is used, the land or the groove can be easily identified. Also.

A DVD having a single-sided recording capacity of 2.6 gigabytes
-In the RAM, the header part recorded as the pre-pit includes a VFO, an address mark, a physical ID (Identificatio).
n Data), IED (ID Error Detection Code), and postamble. In order to allow the drive to read the header portion without errors, many standards are set for the signal output of the header portion. Among them, asymmetry is an important standard item for accurately detecting address information. The asymmetry is defined by the following equation.
(See FIG. 3) (Iβ−Iα) / 2IAM

[0008]

However, when the prepits arranged in a zigzag pattern are reproduced by the push-pull method (difference signal), it is difficult to reduce the asymmetry. As a result, for example, the drive can recognize the address mark. Address information could not be detected accurately, and errors tended to occur. This problem is a serious problem in an optical disc that needs to maintain compatibility between a plurality of drives, and improvement has been desired.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and provides an optical disk medium having excellent compatibility which can detect pre-pits arranged in a staggered manner without error. The task is to provide.

[0010]

In order to solve the above-mentioned problems, the present inventors have made it possible to reduce the asymmetry of a reproduced signal due to a difference signal of pre-pits arranged in a staggered manner, by using a drive to store address information without error. Assuming that it is important for detection, and as a result of intensive studies from the viewpoint of reducing asymmetry, the present invention has been completed.

That is, the present invention provides a substrate having a format having a groove track and a land track, and having a header portion arranged in a staggered manner on a virtual extension line of the boundary between the groove track and the land track, and a laser. In an optical disk medium of a groove land recording system having a thin film layer for reproducing and / or recording information by light, a duty, which is a ratio of a mark portion length to one cycle of a header portion VFO, is 5
An optical disc medium characterized by being in a range of 0 to 58.

The duty of the mark portion length with respect to one cycle of the header portion VFO is obtained as follows. Duty = [mark part length / (mark part length + blank part length)] × 100 When address information recorded as prepits is reproduced by the difference signal shown in FIG. 2, the I1 side (Ia + Ib) and the I2 side (Ic + I)
With d), the phase appears to be reversed due to the effect of diffraction. According to the study of the present inventors, in order to reduce asymmetry in the I1-I2 difference signal, the mark length of the header portion prepit (the length of the concave portion in the track direction) is set to be equal to the normal mark length and blank length. As a result, the asymmetry of the reproduced signal as seen from the difference signal can be reduced.

The duty of the header portion VFO can be generally derived by measuring the groove shape of an injection-molded optical disk substrate with an atomic force microscope (hereinafter abbreviated as AFM). FIG. 4 shows an example of the measurement result of the header portion VFO by AFM. Here, the length of the mark portion is defined by the mark length in the track direction at a position half the mark depth. When such a concave mark is measured using the AFM, the tip of the needle used at the time of measurement is
Normally, since the radius of curvature is about 10 nm, the measurement is made smaller than the actual mark length, and it is necessary to correct this effect. In order to suppress the asymmetry of the header part reproduction signal due to the difference signal, the duty of the mark length of the header part VFO after the correction is preferably in the range of 50 to 58, more preferably 52 to 56.

In order to adjust the length of the mark portion, the length of the corresponding pulse is controlled when cutting the stamper, that is, the length of the pulse to be cut by a certain length is made longer or shorter than the original length. It is common to make adjustments by performing operations such as the above. In a DVD-RAM having a single-sided recording capacity of 2.6 gigabytes, an operation is performed to adjust the length obtained by multiplying the channel clock period To = 34.27 nsec by a certain constant x, that is, 34.27 × nsec. For example, the header part VFO is 4
Since it is composed of a To signal, if the length is increased by 34.27 × nsec, the cutting pulse length is (4 + x).
To be shortened by 34.27 × nsec, the cutting pulse length becomes (4-x) To. According to the study of the present inventors, in order to suppress asymmetry of the header portion due to the difference signal, it is preferable to set the cutting pulse length as long as (4 + x) To, and in this case, set the constant x to 0 to 0. 7 and more preferably 0.1 to 0.5. The duty of the mark length of the header portion VFO of the optical disk molded substrate manufactured by using the stamper manufactured in this manner is substantially equal to or more than 50 and equal to or less than 58.

In the 2.6-gigabyte DVD-RAM format, since about 70% of the header portion is composed of VFO, the effect of the present invention can be obtained only by applying the above-described mark length correction to VFO. Can be. VFO other address mark, a physical ID, IED, the mark length correction for postamble, or, with correction for the mark lengths other than 4T _0, may be carried out mark length compensation as described above, setting the time of cutting Considering the trouble of (3), it is considered that there is no problem if the mark length is set to be 34.27 × nsec uniformly for all the mark lengths in all the header areas.

The groove depth of the prepit portion of the substrate used in the present invention is preferably in the range of 65 nm to 75 nm. Also, groove width of header part (radial length of concave part)
Is defined as the groove width at half the groove depth, the so-called half width, and the track pitch (recording track width)
85% to 100%, more preferably 90%
% To 97%.

The groove depth of the groove track of the substrate used in the present invention may be the same as the groove depth of the pre-pit portion, but need not be the same, and recording and reproduction required for land / groove recording are not required. What is necessary is to satisfy the characteristics and the servo characteristics. In the present invention, the structure of the disk medium is not particularly limited, whether it is a laminated structure or a single plate structure. However, a plastic substrate having a substrate thickness of 0.6 mm or less generally has a laminated structure. It is used for

As the material of the substrate used in the present invention,
Usually, plastics are used. As such plastics, plastic materials such as polycarbonate, acrylic resin, epoxy resin, and polystyrene can be cited, but polycarbonate resins are widely used in terms of optical and strength. The type of the material of the thin film layer for reproducing and / or recording information with the laser beam used in the present invention is not particularly limited, but in the rewritable type, a phase change material such as GeTeSb or AgInSbTe or a magneto-optical material such as TbFeCo is used. For the material and the write-once type, a cyanine-based or phthalocyanine-based dye material is generally used.

The method for forming these thin films is also not particularly limited, and known methods such as vacuum evaporation, sputtering, ion beam sputtering, ion beam evaporation,
Methods such as ion plating, electron beam evaporation, and plasma polymerization can be appropriately employed depending on the purpose, material, and the like.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below by way of specific examples.

[0021]

Embodiments 1 to 3 and Comparative Examples 1 and 2 As shown in FIG. 1, a header section 14 recorded as prepits 13 in a groove land recording system for recording information on both a groove track 11 and a land track 12 is shown. Uses a format conforming to the 2.6 gigabyte DVD-RAM format, which is arranged in a staggered manner at the boundary between the groove track 11 and the land track 12, and uses a header part VF.
Various stampers in which the duty of the O mark length was changed were manufactured.

Next, injection molding was carried out using the produced stamper to produce a disk-shaped transparent optical disk substrate having a diameter of 120 mm and a substrate thickness of 0.6 mm. A polycarbonate resin was used as a material of the substrate. The header portion VF of the plastic disk substrate thus manufactured
The O mark shape (cross-sectional profile) was measured. The measurement was performed using an atomic force microscope (AFM), and the half widths of the mark in the track direction and in the radial direction were measured.

On the other hand, a 100 nm thick
ZnS-SiO_TwoProtective layer consisting of 25 nm thick S
bTeGe recording layer, 20 nm thick ZnS-S
iO _TwoProtection layer made of 100 nm thick Al
Were sequentially laminated by a sputtering method.
Next, an ultraviolet curable resin is spin-coated on the formed thin film.
And apply UV light with a high-pressure mercury lamp.
The composition was irradiated and cured to form a protective coat layer.

Further, the two single-sided discs thus produced were bonded together with the recording film forming side facing inward using a cationically polymerized UV-curable adhesive to produce a phase-change optical disc medium having a full-surface adhesive structure. Using the optical disk medium thus manufactured, the header was reproduced with a difference signal, and the asymmetry was measured. The conditions of the optical disk drive used for the measurement were as follows: the wavelength of the laser beam λ = 650 nm,
The reproduction signal of the header part was obtained from the push-pull signal with the numerical aperture of the objective lens NA = 0.6 and the linear velocity of 6 m / s.

Table 1 shows the duty and asymmetry of the mark length of the VFO, and the address error rate (AER).
The relationship is shown below.

[0026]

[Table 1]

At this time, the groove depth of the mark is about 70 nm,
The VFO mark width in the radial direction was 0.69 μm. As can be seen in Examples 1 to 3 and Comparative Examples 1 and 2, when the duty of the mark length of the header portion VFO of the optical disk molded substrate is in the range of 50 or more and 58 or less, the absolute value of asymmetry becomes 0.05 or less. As a result, it can be seen that an address error rate on the order of -5 is obtained.

[0028]

According to the present invention, a format comprising a groove land recording system for recording information on both a groove track and a land track, wherein the header portion is arranged in a staggered manner at the boundary between the groove track and the land track. As a result, it is possible to provide an optical disk medium having excellent compatibility that can suppress the asymmetry of a header portion reproduction signal composed of prepits and detect address information satisfactorily without causing an error.

[Brief description of the drawings]

FIG. 1 is a plan view of a format of an optical disk medium used in the present invention, in which a header portion is arranged in a staggered manner on a virtual extension line between a groove track and a land track.

FIG. 2 is a conceptual diagram of a signal wiring used in an optical pickup.

FIG. 3 is a conceptual diagram of a reproduced waveform of a header portion as viewed from a difference signal.

FIG. 4 is a sectional view of a groove of a VFO mark portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 Groove track 12 Land track 13 Pre-pit 14 Header part consisting of pre-pits arranged in a zigzag pattern 15 Quadrant photodetector output; Ia 16 Quadrant photodetector output; Ib 17 Quadrant photodetector output; Ic 18 Quadrant photodetector output; Id 19 DC Output I1 (= Ia + Ib) from coupling amplifier 20 Output I2 (= Ic + Id) from DC coupling amplifier 21 Sum signal; I1 + I2 22 Difference signal; I1-I2 23 Quadrant photodetector 24 DC coupling amplifier 25 Amplitude Iα 26 Amplitude Iβ27 Amplitude IAM 28 Mark length in half width of VFO mark part 29 Mark part groove depth 30 Mark part groove bottom 31 Blank part

Claims (1)

[Claims] 1. A substrate having a format having a groove track and a land track, and having a header portion arranged in a staggered manner on a virtual extension line at the boundary between the groove track and the land track; In an optical disk medium of a groove land recording type having a thin film layer for performing reproduction and / or recording,
An optical disc medium, wherein a duty, which is a ratio of a length of a mark portion to one cycle of a header portion VFO, is in a range of 50 or more and 58 or less.