JP2848992B2 - Optical recording medium and substrate for optical recording medium used therefor - Google Patents

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 track on which optically reproducible data can be recorded, and more particularly, to an optical recording medium having a tracking track for tracking a track on which data can be recorded. The present invention relates to a recording medium and a substrate for an optical recording medium used therein .

[0002]

2. Description of the Related Art Generally, an optical recording medium, such as an optical disk or a magneto-optical disk, is formed so as to be optically distinguishable from a recording track so that a recording / reproducing beam can accurately track a data recording track on the disk. A data recording track having a tracking track and sandwiched between the tracking tracks (hereinafter, referred to as a recording track) includes:
Address data and the like for giving the position information of the recording track to the control system of the optical head are formed in advance as pre-pits.

[0003] The pre-pits are usually λ / 4n so as to give maximum modulation to a reproduction beam (tracking beam) applied to the optical recording medium so as to pass through the substrate.
(Λ: wavelength of the reproduction beam, n: refractive index of the substrate) is a concave portion having a depth that is an odd number times, and a groove formed in the substrate is generally used as a tracking track.

As a method of detecting a tracking error of such an optical disc, for example, using a single beam, a beam reflected and diffracted on the disc is divided by a two-division photodiode arranged symmetrically with respect to the track center. The tracking error is detected by extracting the difference as an output difference between the two light receiving units. The so-called push-pull method, the data recording / reproducing main beam for recording tracks and ± 1 divided by a diffraction grating in addition to the main beam There is known a three-beam method for detecting a tracking error by using the next light as an auxiliary beam and calculating the output difference between two light receiving units for receiving reflected light of the auxiliary beam.

By the way, in such an optical recording medium, as shown in FIGS. 15 and 16, for example, when the prepit length and the prepit interval are reduced to increase the recording density,
When the spot diameter of the reading light is constant, the amplitude W ₁₆ (brightness / darkness difference) of the reflected light amount decreases, and the S / N of the pre-pit decreases. This tendency is particularly remarkable in prepits formed on recording tracks on the inner peripheral portion of the disk-shaped optical recording medium.

This is because when the spot of the reading light enters between the pre-pits, interference of the preceding and following pre-pits makes it impossible to obtain a sufficient amount of reflected light. Therefore, if the pit size of the pre-pit is reduced to reduce the influence of that part, the signal output does not improve after all because the spot of the reading light on the pre-pit does not become sufficiently dark. That is, if the spot of the reading light is constant even if the pit shape is changed, if the recording density of the address data is increased, there is a problem that a sufficient signal output cannot be obtained in a portion where the pit interval is narrowed.

[0007]

[0008]

[0009]

SUMMARY OF THE INVENTION The present invention relates to a pre-pit
Part of the optical recording medium can be improved.
Given a uniform tracking error signal across the surface
In both cases, A in the pre-pit area caused by the DC offset
Prevents the leakage of pulse-like signals generated in the T signal,
Optical recording medium from which AT signal with low noise can be obtained and the same
To provide a substrate for an optical recording medium used for
Things.

[0010]

That is, the present invention provides a truck
Between the king track and the tracking track
An area having a recording track, wherein the width of the recording track is a specific area
Optical recording wider than the width of the recording track in other areas
A recording medium, and a tracking track of the specific area.
Is the width of L ₃ , and the width of the tracking track in the other area is L
When set to _1, that L ₁ and L ₃ are in the following relationship
An optical recording medium characterized by the following. 0.60 ≦ L ₃ / L ₁ ≦ 0.95

The present invention also provides a tracking glue.
Track and recording track sandwiched by the tracking groove
And the tracking groove depth in a specific area is different
Recording shallower than the depth of the tracking groove in the area
The medium, the tracking groove of the specific area
The depth is d ₂ , and the depth of the tracking groove in other areas is
When d ₁ is set, d ₁ and d ₂ have the following relationship.
An optical recording medium characterized in that: 0.8 ≦ d ₂ / d ₁ ≦ 0.95

Also, the present invention provides tracking on a surface.
Grooves and recording tracks sandwiched by the tracking grooves
Rack, and the width of the recording track is in a specific area.
Optical recording medium wider than the width of the recording track in other areas
A tracking track of the specific area.
Is the width of L ₃ , and the width of the tracking track in the other area is L
When set to _1, that L ₁ and L ₃ are in the following relationship
It is a substrate for an optical recording medium characterized by the following. 0.60 ≦ L ₃ / L ₁ ≦ 0.95

The present invention also provides a tracking glue.
Track and recording track sandwiched by the tracking groove
Has, a shallow optical recording medium substrate than the depth of the tracking grooves in Ryojo depth tracking glue blanking of other specific areas, the specific Ryojo tracking Guru
The depth of the groove is d ₂ , the tracking groove in the other area
When the depth of d is d ₁ , d ₁ and d ₂ have the following relationship:
A substrate for an optical recording medium, characterized by having
You. 0.8 ≦ d ₂ / d ₁ ≦ 0.95

Further , the present invention provides a tracking tracking device.
And a recording track sandwiched between the tracking tracks
An optical recording medium comprising:
Tracking in the pre-pit area with pits
The width of the rack is L ₃ , and the tracking tra
The width of the click when the _{L 1, L 1} and _{L 3,} the pre
Offset of tracking error signal in pit area
Off the tracking error signal in the amount and other areas
Set volume is set to be substantially equal
An optical recording medium characterized in that:

The present invention also relates to a track groove and the track.
An optical recording medium with recording tracks sandwiched by rack grooves
And a pre-pit having pre-pits on the recording track.
The track groove depth in the slot area to d ₂ ,
When the depth of the track groove is d ₁ , d ₁ and d ₁
d ₂ is the tracking error in the pre-pit area
Signal offset and tracking error in other areas
So that the offset amount of the
An optical recording medium characterized by being set.

[0016]

[0017]

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged plan view of a prepit area showing one embodiment of the optical recording medium according to the present invention, and FIG. 2 is a graph showing a signal output (reflected light amount) of the prepit area.
In FIG. 1, I is a data area, II is a pre-pit area, and III is a closest pit area in the pre-pit area.
Reference numeral 1 denotes a groove which is a tracking track, and 1 'denotes a groove formed in the pre-pit area II.
Further, reference numeral 3 denotes pre-pits formed on the recording track 2.

The width L _{3 of the} groove 1 ′ is equal to the width L ₄ of the recording track 2 ′ in the pre-pit area II.
It is set as larger than the width L ₂ of the recording track 2. However, L ₄ <L ₅ (light spot diameter). As a result, the area occupied by the groove in the light spot 4 for irradiating the recording track is reduced, and therefore, even if the diffracted reflected light from the groove interferes with the 0th-order diffracted light, a decrease in the amount of reflected light can be prevented. As a result, as shown in FIG. 2, the amount of reflected light can be maintained even in the pre-pit area, especially between the pre-pits in the closest pit area III, and a sufficient signal output can be obtained.

In the present invention, the close-packed pre-pit region refers to a region where the interval between adjacent pre-pits is smaller than the spot diameter of the light beam.

In the present invention, the recording track 2 '
Relationship in a width L ₄ of the width L ₂ of the recording track 2, i.e. L ₂
/ L ₄ is At a range of L ₄ does not exceed the L ₅ 0.7~1.
A value of 0, especially 0.7 to 0.8 is a preferable area because the signal output of the pre-pits, particularly between the pits in the densest pit area, can be suppressed from decreasing the amount of reflected light.

In the present invention, the light spot diameter means a diameter at which the intensity of the light beam becomes 1 / e ² of the central intensity.

In the present invention, the depth of the groove 1 is set to a value shallower than λ / 4n and deeper than λ / 8n. That is, when a groove is used as a tracking track, the tracking error signal becomes maximum when the depth of the groove is λ / 8n (n: refractive index of the substrate, λ: wavelength of the recording and / or reproducing light beam). However, as shown in FIG. 7, when the groove depth is reduced from λ / 4n at which the degree of diffraction modulation is maximum, a groove crossing signal used for discriminating a recording track from a groove during track seek. Since the degree of modulation is reduced, it is preferable to set the depth slightly higher than λ / 8n.
It is desirable to set λ / 7n, especially λ / 5n to λ / 6n.

In the above embodiment, the groove 1
Relationship the relationship of the following formulas (1) and the width L ₁ of the wide L ₃ and groove 1 ', it is preferable that the particular relation of the following formula (2).

[0025]

0.61 ≦ L ₃ / L ₁ ≦ 0.95 (1) 0.7 ≦ L ₃ / L ₁ ≦ 0.95 (2)

That is, in the tracking using the push-pull method, when the objective lens is decentered for micro seek or the like, the light spot is displaced even on the 2D-PD, and the light spot is located at the center of the track. Also, a DC offset in which the AT signal does not become 0 occurs. As a countermeasure, for example, the offset amount is corrected by subtracting the offset amount from the AT signal. However, the ratio of the offset amount to the AT signal is A when the eccentricity of the objective lens and the groove shape are constant.
It is proportional to the amplitude of the T signal. On the other hand, in the conventional optical recording medium, when the push-pull method is used for tracking, in the pre-pit area, the reflected light diffracted by the pre-pit interferes with the reflected light in other parts of the recording track, so that the amount of reflected light is small. And the amplitude of the tracking error signal (AT signal) tends to decrease.

Therefore, the offset amount is smaller in the pre-pit area than in the data area, and a difference is generated between the two areas, and the offset correction in the data area causes an offset in the pre-pit area. There's a problem. (Hereinafter, this phenomenon is referred to as “leakage.”) However, the groove width L of the groove 1 ′ in the pre-pit area
₃ is narrowed so as to satisfy the above relationship, the data area I
Since the ratio of the offset amount to the amplitude of the AT signal in the pre-pit area II can be increased as compared with the above, even if the amplitude of the AT signal is reduced in the pre-pit area as described above, the offset amount will be the data area and the pre-pit area. And the difference can be almost eliminated, and the offset can be surely corrected.

This is because the diffraction efficiency of the light beam by the groove decreases as the groove width becomes narrower, and the diffraction efficiency of the light beam on the 2D-PD becomes lower.
Since the ratio of the first-order diffracted light to the first-order diffracted light increases, A
This is because there is a characteristic that the ratio of the offset amount to the amplitude of the T signal increases.

Next, FIGS. 3, 4 and 5 are plan views showing a second embodiment of the optical recording medium of the present invention and its AA 'line.
FIGS. 3 to 5 are schematic cross-sectional views taken along line BB 'and line BB'. In FIGS. 3 to 5, 1 is a groove in a data area I, 1 'is a groove in a pre-pit area II, and 3 is a recording track. 2
These are the pre-pits formed on the substrate.

In the present embodiment, the groove 1 '
Is one that is shallower than the depth d ₁ of the groove 1 in the data area as shown its depth d ₂ is in FIGS. That is, according to the present embodiment, the pre-pit area II
In this case, the interference between the diffracted reflected light by the groove 1 'and the 0th-order diffracted light is weakened, and the decrease in the amount of reflected light is suppressed. As shown in FIG. 6, it is possible to suppress the decrease in the amplitude of the reflected light amount and to secure the signal output of the pre-pit.

In the present embodiment, the depth d _{1 of the} groove ₁
As described above, for example, the width of the groove 1 is 0.5
In the case of an optical disk having a preformat of 1.6 μm and a track pitch of 1.6 μm, and recording / reproducing with a light beam having a wavelength λ and a spot diameter of 1.5 μm, the groove depth is set to λ /
It is known that the tracking error signal becomes the maximum at 8n (n: the refractive index of the substrate), but as shown in FIG. 7, the groove depth is reduced from λ / 4n at which the degree of modulation is the maximum. Since the degree of modulation of the signal traversing the groove used for discriminating the recording track and the groove during track seek decreases,
It is preferable to set slightly deeper than / 8n, specifically, λ / 5n to λ / 7n, particularly λ / 5n to λ / 6n.

The groove 1 in the pre-pit area II
Is preferably formed at least shallower than d ₁ , and when the depth d ₂ is reduced to about λ / 8n, even in the pre-pit region, particularly in the close-packed pre-pit region III,
A sufficient amount of reflected light can be obtained between the prepits, and a tracking error hardly occurs. As shown in FIG. 8, the above-mentioned groove crossing signal modulation degree is obtained by changing the amount of reflected light of the recording track portion by a change in the amount of reflected light observed when the light spot is scanned in the direction crossing the groove.
_{When top} , the amount of light reflected by the groove is I _bottom , and the amount of light reflected by the mirror surface portion is I ₀ ,

[0033]

## EQU2 ## This is a value represented by (I _top -I _bottom ) / I ₀ .

And, in the above embodiment, d ₂
Λ / 6n to λ / 8n is particularly preferable.
That is, in the case of the push-pull method, as shown in I and II in FIG. 9, when the groove depth in the data area and the pre-pit area is set to an area deeper than λ / 8n, the recording track portion is diffracted by the pre-pit. Since the reflected light interferes with the reflected light in other parts, the amount of reflected light decreases. On the other hand, the groove is also set in a region deeper than λ / 8n,
Tracking error signal (AT signal) due to low reflected light quantity
Tends to decrease.

This is because, for example, when the optical head is moved to a specific recording track, it is general to count the number crossing the recording track by counting the AT signal. A small signal tends to cause an error such as a count error.
However, as shown in III of FIG. 9, by setting the value of d ₂ within the above range, the amount of light reflected by the groove increases, and it is possible to prevent a decrease in the amplitude of the AT signal in the pre-pit area, and the uniformity is achieved over the entire surface of the disk. It is possible to obtain an optical disk that gives an AT signal of an amplitude.

In this case, although the modulation degree of the signal across the groove in the pre-pit area is reduced, the modulation degree of the signal across the groove is considerably small due to the influence of the pre-pit from the beginning. There is no problem because some measures are taken on the side so as not to use the groove crossing signal in the pre-pit area.

When the depth d ₂ of the groove 1 ′ is set within the above range, a decrease in the amplitude of the AT signal can be prevented, and the depth of the pre-pit is made shallow as long as the diffraction effect of the light beam is not largely impaired. I can do it.

That is, the mechanism for adding the amplitude of the AT signal in the pre-pit area can be explained as follows. Since the pre-pit is located at a position shifted by exactly 180 degrees with respect to the period of the groove, the push-pull signal by diffraction of only the pre-pit has exactly the opposite phase to the AT signal by diffraction of only the groove. Therefore, the push-pull signal due to the diffraction of only the prepit acts in the direction to cancel the AT signal due to the diffraction of only the groove. This causes a decrease in the amplitude of the AT signal in the pre-pit area. Since the depth at which the push-pull signal appears best is λ / 8n, λ / 8n
As the depth of the pre-pit becomes shallower in the range up to, the push-pull signal due to diffraction of only the pre-pit becomes larger, and the amplitude of the AT signal decreases. Therefore, it has not been possible to make the prepit depth shallower not only to ensure the contrast of the prepit signal but also to reduce the AT signal amplitude.

However, according to the present embodiment, the amount of reflected light at the groove portion is ensured by making the groove shallower (see FIG. 10), so that not only the pre-pit signal but also the AT signal in the pre-pit area can be improved. Because you can
The depth of the prepit can be reduced, for example, by about 100 to 200 μm. When the pre-pit depth is small, for example, when molding by an injection molding method or the like, there is an effect that the shape of the pre-pit region of the stamper can be transferred to the disk substrate with higher accuracy.

Further, in the second embodiment, d ₁
And d ₂ as

[0041]

Equation 3] _{0.80 ≦ d 2 / d 1 ≦} 0.95 as setting exactly as made, prevents "leakage" of the at AT signals in the prepit region of the above, higher quality AT signal can be obtained.

That is, according to the above-described embodiment, the amplitude of the AT signal can be increased by making the groove depth shallow toward λ / 8n, and the 2D-PD can be formed with a decrease in diffraction efficiency due to the shallow groove. Since the ratio of the 0th-order diffracted light to the 1st-order diffracted light at the time increases, the ratio of the offset amount to the amplitude of the AT signal sharply increases.

Therefore, the difference in the offset amount between the pre-pit area and the data area as described above is obtained by making the groove depth of the pre-pit area shallower than the groove depth of the data area as described above. It can be made almost negligible. At this time, as described above, a pre-pit signal is improved, and a disk with a high-quality signal in which the amplitude of the AT signal in the pre-pit area is also improved can be obtained.

Next, another embodiment of the optical recording medium of the present invention will be described. FIG. 11A is a partially enlarged view showing another embodiment of the optical recording medium of the present invention, and FIG. 11B shows a signal output when the substrate is formed in the shape of FIG. 11A.

In the optical recording medium of FIG. 11, the groove is narrowed only in the densest pit area III of the pre-pit area. In this case as well, the signal output at the portion where the pit interval is narrowed is higher than that of the conventional optical recording medium. I do.

FIG. 12 (a) is an enlarged plan view showing still another embodiment of the optical recording medium of the present invention, in which the groove is narrowed only in the area corresponding to the pits in the close-packed pre-pit area III, and the width of the recording track is reduced. Is widely formed. Also with this configuration, as shown in FIG. 12B, the signal output at the portion where the pit interval is narrowed can be increased as compared with the conventional optical recording medium. In the embodiment shown in FIGS. 11 and 12, the groove in the pre-pit region may be made shallow instead of narrowing the groove (forming a wider recording track). In the embodiment of FIG. 11 and FIG. 12, the groove may be both narrowed and shallowed in the pre-pit region.

Next, a method for manufacturing such an optical recording medium will be described. That is, a photoresist coated on a glass disk is exposed to laser light, developed, and developed.
In the normal master making method for forming a pattern corresponding to the pre-pits 3, the output of the laser light for pattern exposure of the groove 1 is reduced in the pre-pit area, so as to be shown in FIG. 1, FIG. 3, FIG. 11 and FIG. A master having a pattern corresponding to such a preformat is formed.

Then, after the surface of the master is made conductive, an injection method, a 2P method is used by using a stamper obtained by depositing a metal film by electroforming and stripping the master.
The optical recording medium substrate of the present invention can be obtained by molding the optical recording medium substrate according to a well-known molding method such as a molding method, a casting molding method, and a compression method. And
On this substrate, a magneto-optical recording layer such as a Tb-Fe-Co amorphous thin film and an organic recording layer containing an organic dye are formed, and then a reflection film, a protection substrate and a protection film are formed as necessary. To obtain an optical recording medium.

In the stamper manufacturing process, by reducing the beam diameter in the pre-pit region when exposing the resist, a stamper capable of forming an optical recording medium substrate having a narrow tracking groove width in the pre-pit region is obtained. be able to.

In this method, for example, when exposing a pattern corresponding to the tracking groove in the data area to the photoresist, two beams are superimposed to increase the spot diameter on the resist surface, and the light beam is applied to the tracking groove in the pre-pit area. In the corresponding pattern,
Such a stamper can be obtained by performing exposure while reducing the spot diameter by cutting one of the beams.

Further, as another method of manufacturing the optical recording medium of the present invention, when the optical recording medium substrate is formed by injection molding, the transfer rate is reduced by adjusting the molding conditions. be able to.

That is, FIG. 13 is an explanatory sectional view of the stamper 6 and the resin 5 showing a state of transfer at the time of injection molding. Since the prepit pattern 3 is higher than the groove pattern, when the transfer rate is reduced by adjusting the molding conditions such as lowering the stamper temperature, for example, when polycarbonate is used as the resin, the metal temperature is set to around 90 ° C. By doing so, the pre-pits 3 of the molded optical recording medium substrate
The groove in the vicinity can be formed thin and shallow as shown in FIG.

[0053]

Next, the present invention will be described in more detail with reference to examples.

Reference Example 1 In the present invention, a conventional magneto-optical disk serving as a reference for evaluation was produced by the following method. First, a stamper was prepared as follows. Photoresist (trade name: AZ-1300SF; 250 mm in diameter and 10 mm in thickness)
Hoechst Japan) with a thickness of 2000 by spin coating.
Å was applied.

Next, the outer diameter of the resist master was 128 m.
m, doughnut-shaped area with inner diameter of 58 mm, width 0.5μ
m, a pitch of 1.6 μm, a depth of 900 °, and a radius r = 35 mm formed on a spiral optical disk groove and a data recording track sandwiched between the grooves, a length in a direction parallel to the groove being 0.9 μm. A pattern having a close-packed pre-pit region consisting of pit groups having a depth of 1750 ° and a pitch of 1.6 μm was exposed using a laser cutting machine while rotating the resist master at 900 rpm. However, for cutting the groove pattern corresponding to the pre-pit area, the power of the exposure laser was set to 15 mW at a position of a radius of 35 mm.

Next, after development processing, Ni is deposited to a thickness of 1000 ° on the resist pattern by sputtering, Ni is further deposited to a thickness of 300 μm by electroforming, and then the Ni film is peeled from the resist master. Made a stamper. Using this stamper, a polycarbonate optical disk substrate having a diameter of 130 mm and a thickness of 1.2 mm having a preformat shown in FIG. 1 was produced by an injection molding method. The mold temperature of the injection molding apparatus during molding is 95
° C.

When the optical disk substrate thus obtained was observed with an electron microscope, the width of the recording track was 0.95 μm in both the data area and the pre-pit area, and the depth and width of the tracking groove were 90 μm in both the data area and the pre-pit area.
0 °, 0.65 μm. Then, after depositing of SiO ₂ protective film, the protective film of Tb-Fe-Co amorphous thin film and SiO ₂ sequentially sputtering the surface of the preformat transfer side of the optical disk substrate, a rubber-based hot melt adhesive After applying the agent (Meltron 3S42; manufactured by Diabond Co., Ltd.), a polycarbonate protective substrate having a diameter of 130 mm and a thickness of 1.2 mm was attached to obtain a magneto-optical disk.

This magneto-optical disk was mounted on a magneto-optical disk drive (wavelength: 830 nm, L ₅ : 1.5 μm), and prepits of a recording track near r = 35 mm were reproduced. At this time, the contrast of the pre-pit signal in the closest pre-pit area, the contrast of the tracking error signal (AT signal) in the data area and the closest pre-pit area (the degree of modulation of the signal across the groove), and the contrast of the AT signal in the closest pre-pit area The offset amount for the contrast was measured.

The contrast of the pre-pit signal allows the tracking servo of the disk drive to operate normally, and reproduces the signal reproduced by the reproduction light spot while accurately tracing the recording track (trade name: RTD710; Sony Tektronix Corporation)
Play At a waveform obtained by observing with Ltd.), DC output voltage of the V ₁ specular pit-free, the maximum output voltage when the reproducing beam spot V ₂ is between pits and the pit, the V ₃ When the minimum output voltage when the light spot is on the pit,

[0060]

## EQU4 ## This is a value represented by (V ₂ −V ₃ ) / V ₁ .

Table 1 shows the results.

[0062]

[Table 1]

Example 1 First, a stamper was prepared as follows. 250m diameter
A photoresist (trade name: AZ-1300SF; manufactured by Hoechst Japan) was applied to a thickness of 2000 mm on a glass plate having a thickness of 10 mm and a thickness of 2000 mm.

Next, the outer diameter of this resist master is 128 m.
m, doughnut-shaped area with inner diameter of 58 mm, width 0.5μ
m, a pitch of 1.6 μm, a depth of 900 °, and a radius r = 35 mm formed on a spiral optical disk groove and a data recording track sandwiched between the grooves, a length in a direction parallel to the groove being 0.9 μm. A pattern having a close-packed pre-pit region consisting of pit groups having a depth of 1750 ° and a pitch of 1.6 μm was exposed using a laser cutting machine while rotating the resist master at 900 rpm. However, the cutting of the groove pattern corresponding to the pre-pit region was performed by changing the power of the exposure laser from 15 mW to 13.5 mW at a radius of 35 mm.

Next, after development processing, Ni is deposited to a thickness of 1000 ° on the resist pattern by sputtering, Ni is further deposited to a thickness of 300 μm by electroforming, and then the Ni film is peeled from the resist master. Made a stamper. Using this stamper, a polycarbonate optical disk substrate having a diameter of 130 mm and a thickness of 1.2 mm having a preformat shown in FIG. 1 was produced by injection molding. The mold temperature of the injection molding apparatus during molding is 95
° C. Further, the depth d ₁ of the tracking groove in the data area of this substrate was 900 °, and the depth d ₂ of the tracking groove in the pre-pit area was 765 °.

Next, a protective film of SiO ₂ , Tb-Fe-C
o After forming an amorphous thin film and a protective film of SiO ₂ sequentially by a sputtering method, a rubber-based hot melt adhesive (Meltron 3) is used.
S42: Diabond Co., Ltd.), and the diameter 1
A protective substrate made of polycarbonate having a thickness of 30 mm and a thickness of 1.2 mm was bonded to obtain a magneto-optical disk.

The magneto-optical disk was mounted on a magneto-optical disk drive (wavelength: 830 nm, L ₅ : 1.5 μm), and prepits of a recording track near r = 35 mm were reproduced. At this time, the contrast of the pre-pit signal in the densest pre-pit area and the tracking error signal (A
The contrast of the T signal) (the degree of modulation of the signal across the groove) and the offset amount with respect to the contrast of the AT signal in the densest pre-pit area were measured in the same manner as in Reference Example 1.

Examples 2 and 3 and Comparative Examples 1 and 2 In the same manner as in Example 1, except that the depth of the tracking groove in the pre-pit area was changed as shown in Table-2. A magneto-optical disk was manufactured and evaluated in the same manner as in Example 1.

[0069]

[Table 2]

Table 3 shows the evaluation results of the magneto-optical disks of Examples 1 to 3 and Comparative Examples 1 and 2 . However, the evaluation criteria are shown in Table 4 below.

[0071]

[Table 3]

[0072]

[Table 4]

In the present invention, the offset amount is the ratio of the "leakage" amount to the amplitude of the AT signal in the pre-pit area. The smaller this value is, the smaller the offset in the pre-pit area is. Is shown.

In the stamper manufacturing process of Comparative Example 3, Example 4, and Example 1, instead of lowering the power of the laser for photoresist exposure in the data area and the pre-pit area, the spot diameter was changed to the pre-pit area. The recording track width (L ₂ ) and tracking groove width (L ₁ ) of the data area and the recording track width (L ₄ ) of the pre-pit area are the same as in the first embodiment except that the stamper is manufactured. 1 having the tracking groove width (L ₃ ) values shown in Table 5 were obtained.

[0075]

[Table 5] For this magneto-optical disk, the pre-pit reproduction contrast of the closest pre-pit area and the offset amount of the closest pre-pit area were evaluated in the same manner as in Example 1. The results are shown in Table-6.

[0076]

[Table 6]

Embodiment 6 In the embodiment 1, when exposing the pattern corresponding to the pre-pit area tracking groove at the time of manufacturing the stamper, the exposure of the data area and the power and the spot diameter are not changed and the data area and the pre-pit area are not changed. A stamper corresponding to a pattern in which both the depths of the tracking grooves were 900 ° and the widths were both 0.65 μm was obtained. Next, using this stamper, an optical disk substrate was formed by injection molding in the same manner as in Example 1. However, the transfer rate from the stamper was reduced by setting the mold temperature to 90 ° C.

When the optical disk substrate thus obtained was observed with an electron microscope, the width of the recording track was wide in the pre-pit portion and narrow in other regions as shown in FIG. As shown in FIG. Further, the depth of the groove was 800 ° in the pre-pit portion and 900 ° in the other area.

Next, an optical disk was prepared using this substrate and evaluated in the same manner as in Example 1. The results are shown in Table-8. FIG. 17 shows the signal output of this optical disk.

[0080]

[Table 7]

[0081]

[Table 8]

FIG. 18 shows the signal output of the optical disk of the first embodiment. From FIGS. 17 and 18, it can be seen that the optical disk with the reduced transfer rate has a larger signal at the portion where the pre-pit interval is narrowed.

[0083]

As described above, according to the present invention, by making the groove in the pre-pit area thinner or shallower, the signal output at the portion where the pre-pit interval is narrowed does not decrease, and a uniform and good S / N ratio is obtained. It is possible to obtain an optical recording medium in which a pre-pit reproduction signal having a predetermined ratio is provided and at the same time, leakage into the AT signal in the pre-pit area is prevented.

[0084]

[Brief description of the drawings]

FIG. 1 is an enlarged plan view of a prepit area of an optical recording medium according to the present invention.

FIG. 2 is a schematic diagram showing a signal output of a pre-pit area of the optical recording medium of FIG.

FIG. 3 is an enlarged plan view of a prepit area of another embodiment of the optical recording medium according to the present invention.

FIG. 4 is a sectional view taken along the line AA ′ in a direction perpendicular to a track of a data area of the optical recording medium of FIG. 3;

FIG. 5 is a diagram showing B of a close-packed prepit area of the optical recording medium of FIG. 3;
It is B 'line sectional drawing.

FIG. 6 is a schematic diagram showing a signal output of a pre-pit area of the optical recording medium of FIG.

FIG. 7 is a schematic diagram showing a relationship between a tracking error signal, a groove crossing signal modulation degree, and a groove depth.

FIG. 8 is an explanatory diagram of a modulation degree of a signal traversing a groove.

FIG. 9 is a schematic diagram showing a relationship between a tracking error signal in a data area and a pre-pit area of a conventional optical recording medium and a pre-pit area of the optical recording medium according to the present invention.

FIG. 10 is a schematic diagram showing the relationship between the depth of a groove and the amount of reflected light.

FIG. 11 is a schematic view showing still another embodiment of the optical recording medium according to the present invention.

FIG. 12 is a schematic view showing still another embodiment of the optical recording medium according to the present invention.

FIG. 13 is a schematic sectional view at the time of injection molding of the optical recording medium according to the present invention.

FIG. 14 is an enlarged plan view of an optical recording medium manufactured by the method of FIG.

FIG. 15 is an enlarged plan view of a pre-pit area of a conventional optical recording medium.

16 is a schematic diagram showing a signal output of a pre-pit area of the optical recording medium of FIG.

FIG. 17 is a graph showing a reproduction signal output of the magneto-optical disk of the sixth embodiment .

FIG. 18 is a graph showing a reproduction signal output of the magneto-optical disk of Reference Example 1.

[Explanation of symbols]

 1, 1 'groove 2, 2' recording track 3 pre-pit 4 light spot 5 resin 6 stamper I data area II pre-pit area III densest pre-pit area

Claims (31)

(57) [Claims] 1. A recording system comprising : a tracking track; and a recording track sandwiched between the tracking tracks.
When the track width is in a specific area, recording tracks in other areas
Optical recording medium that is wider than the width of the
The width of the tracking track is L ₃ , and the tracking of other areas
When the width of the ring track and the _{L 1, L 1} and _{L 3} is lower
An optical recording medium having the following relationship. 0.60 ≦ L ₃ / L ₁ ≦ 0.95 2. The optical recording medium according to claim 1, wherein the specific area is a pre-pit area having a pre-pit on the recording track. 3. The optical recording medium according to claim 1, wherein said specific area is a close-packed pre-pit area. 4. The optical recording medium according to claim 1, wherein a width of a recording track in the specific area is smaller than a diameter of a light spot formed on a surface of the substrate by a light beam for recording and / or reproduction. 5. The width of the recording track of the specific region L ₄
When the width of the recording track of the other areas was L _2,
L ₂ / _{L 4} relationship _{0.7 ≦ L 2 / L 4 <} 1.0 at which claim 1 wherein the optical recording medium. 6. L ₂ / _{L 4} relationship 0.7 ≦ _L 2 / _{L 4}
6. The optical recording medium according to claim 5, wherein ≤0.8. 7. L ₃ / _{L 1} relationship 0.7 ≦ _L 3 / _{L 1}
The optical recording medium according to claim 1 , wherein ≤ 0.95. 8. An optical recording medium according to claim 1, wherein said optical recording medium is used for a recording apparatus for detecting a tracking error by a push-pull method. 9. The optical recording medium according to claim 1, wherein said optical recording medium is used for a reproducing apparatus for detecting a tracking error by a push-pull method. 10. The optical recording medium according to claim 1, wherein said tracking track is a groove formed on a substrate. 11. shallower than the depth of the groove is λ / 4n λ / 8n (where, lambda is the wavelength of the illumination light beam, n represents the refractive index of the substrate) 請 Motomeko 10 which is set deeper than the The optical recording medium according to the above. 12. A groove having a depth of not less than λ / 7n and not less than λ / n.
The optical recording medium according to claim 11 , wherein the optical recording medium has a diameter of 5n or less. 13. A groove having a depth of λ / 6n or more and λ /
13. The optical recording medium according to claim 12 , wherein the number is 5n or less. 14. The optical recording medium according to claim 1, wherein said specific area is an area between prepits. 15. A tracking groove and the track
It has a recording track sandwiched by
Tracking groove depth in other areas
An optical recording medium shallower than the depth of the groove.
Let d be the tracking groove depth in a specific area ₂ ,other
D is the tracking groove depth of the area ₁ And when
d ₁ And d ₂ Have the following relationship:
Optical recording medium. 0.8 ≦ d _Two / D ₁ ≤0.95 16. The optical recording medium according to claim 15 , wherein said specific area is a prepit area having a prepit on said recording track. 17. The optical recording medium according to claim 15 , wherein said specific area is a close-packed pre-pit area. 18. An optical recording medium according to claim 15 , wherein said optical recording medium is used for a recording apparatus for detecting a tracking error by a push-pull method. 19. The optical recording medium according to claim 15 , wherein said optical recording medium is used for a reproducing apparatus for detecting a tracking error by a push-pull method. 20. 請 said groove is formed on the substrate
16. The optical recording medium according to claim 15, wherein: 21. When the depth of the groove of the other region was _{d 1 λ / 8n <d 1} <λ / 4n ( where, lambda is the wavelength of the illumination light beam, n represents the refractive index of the substrate) Claims that are
16. The optical recording medium according to 15 . 22. The above d ₁ is λ / 7n ≦ d ₁ ≦ λ / 5n
22. The optical recording medium according to claim 21, wherein 23. When d ₁ is λ / 6n ≦ d ₁ ≦ λ / 5n
The optical recording medium according to claim 22, which is: 24. The groove depth of said specific area is d ₂ ,
When the depth of the groove of the other region as d _1, λ / 8
n ≦ _d 2 <optical recording medium according to claim 15, wherein the _{d 1.} 25. The d ₂ is λ / 8n ≦ d ₂ ≦ λ / 6n.
The optical recording medium according to claim 24, wherein 26. The optical recording medium according to claim 15 , wherein said optical recording medium is a disk-shaped optical recording medium. 27. The optical recording medium according to claim 15 , wherein said specific area is an area corresponding to a space between prepits. 28. A tracking groove and a track on a surface thereof.
It has a recording track sandwiched by racking grooves,
When the width of the recording track is in a certain area,
A substrate for an optical recording medium wider than the width of the recording track,
Let L be the width of the tracking track in the specific area. ₃ ,other
Set the tracking track width of the area to L ₁ And L
₁ And L ₃ Has the following relationship:
Substrate for media. 0.60 ≦ L ₃  / L ₁  ≤0.95 29. Tracking groove and track
It has a recording track sandwiched by
The tracking groove depth of the area is the track of another castle
Substrate for an optical recording medium shallower than the depth of the groove.
And the depth of the tracking groove of the specific castle is d ₂
 , The depth of the tracking groove in other areas is d ₁ age
When d ₁ And d ₂ Has the following relationship
A substrate for an optical recording medium, comprising: 0.8 ≦ d ₂ / D ₁ ≤0.95 30. Tracking track and said track
Recording medium with recording tracks sandwiched by
Having a pre-pit on the recording track.
The tracking track width in the repit area
L ₃ , The width of the tracking track in other territories is L
₁ And L ₁ And L ₃ Is the pre In the pit area
Tracking error signal offset amount and other areas
And the offset amount of the tracking error signal in the
Characterized in that they are set to be substantially equal
Optical recording medium. 31. A track groove and sandwiched between the track grooves
An optical recording medium provided with a recording track,
In the pre-pit area having pre-pits on the rack
Track groove depth d ₂ , Track grooves in other areas
The depth of d ₁ Then, d ₁ And d ₂ Is the preppi
Offset of tracking error signal in cut area
Amount and offset of the tracking error signal in other areas.
Is set to be substantially equal to the
An optical recording medium characterized by the following.