JP2001357562A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium having stable servo characteristics in which accurate address information can be obtained from prepit signals in an unrecorded state and after recording, and reproducing signals of high quality can be obtained. SOLUTION: The optical recording medium is manufactured by using the following substrate. The substrate has a land-groove structure and prepits formed in the land between grooves. The groove width G1 of the groove formed in the position not near the prepit and the width G2 of the groove near the prepit, and the track pitch TP satisfy the relation of G1/TP=0.42 to 0.58, G2/TP=0.30 to 0.40 and G2/G1=0.60 to 0.90. The groove near the prepit is adjacent to the whole length of the prepit and is extended over the ends of the prepit in the longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tape, a card,
The present invention relates to an optical recording medium for recording information by light, such as a disk, and more particularly to an optical recording medium such as a compact disk (hereinafter, also referred to as CD) or a digital video disk (hereinafter, also referred to as DVD) in the form of a disk. .

[0002]

2. Description of the Related Art In recent years, with the spread of CDs, write-once optical disks (hereinafter, also referred to as CD-Rs) complying with the CD standard have been developed and used. Recently, DVDs aiming at higher-density recording have been developed and put into practical use. In addition, similarly to the CD-R, a recordable DVD (also called a DVD-R) and a rewritable DVD (also called a DVD-RW) Are also being developed and put into practical use. DVD-R and D
The general structure of the VD-RW is as shown in FIG.

The optical recording medium shown in FIG. 3 is provided on a transparent resin substrate (9) having lands (7) and grooves (6).
A recording layer (10), a reflective layer (11) and an adhesive layer (12) are formed in this order, and a substrate (13) is further laminated on the adhesive layer (12). The substrate (13) is laminated to increase the overall strength. Adhesive layer (12) instead of substrate (13)
Is applied thickly to form a protective layer, which may improve the overall strength.

[0004] In recording and reproducing such an optical recording medium, stable servo characteristics and accurate address information are required. Further, it is necessary to obtain a high-quality reproduction signal from the optical recording medium after recording.

As a DVD-R servo signal, a radial push-pull signal is used during recording, and a phase difference signal from a recorded pit is used during reproduction. Using these signals, it is ensured that the pickup head runs stably on the optical recording medium during recording and reproduction.

On the other hand, optical recording media having various structures for obtaining accurate address information have been proposed. One example is an optical recording medium described in JP-A-9-326138. This optical recording medium has a meandering (wobble;
It has wobbled grooves, and prepits are formed at predetermined intervals in an area between these grooves (ie, a land area). The prepit is formed as a notch that connects adjacent grooves. The address information is obtained by a pre-pit signal detected from the pre-pit. According to the optical recording medium in which the pre-pits are formed, address information can be accurately obtained even when the track pitch is narrow.

[0007]

A radial push-pull signal output used as a servo signal when recording a signal on an optical recording medium is particularly affected by the depth and width of a groove formed on a substrate. The depth and width of the groove at which the radial push-pull signal output is maximized are respectively λ
/ 8n (λ is the wavelength of the light source of the pickup head, n is the refractive index of the substrate) and TP / 2 (TP is the track pitch of the substrate). However, in consideration of the balance with other characteristics, the groove of the substrate is generally formed to have a depth and width different from the above dimensions so as to exhibit a predetermined performance as the entire optical recording medium. Therefore, the radial push-pull signal output generally has a value smaller than the maximum value.

[0008] The radial push-pull signal is also reduced for the following reasons. First, there is recording of a signal on an optical recording medium. The signal is recorded on the optical recording medium by irradiating the recording layer with a laser or the like from the pickup head to degrade or decompose the recording layer and deform the substrate. It becomes smaller than that at the time of recording.

The radial push-pull signal tends to be further reduced or fluctuated under the influence of an increase in the eccentricity or warpage of the optical recording medium. As a result, problems such as the tracking of the pickup head being lost easily occur.

Some recording devices for recording signals on an optical recording medium have a function of checking the optimum recording power of each optical recording medium before recording a signal. Specifically, such an apparatus is configured to record a signal by changing the power of a laser or the like, reproduce the portion, examine the power having the best characteristic, and then start signal recording. . Generally, with such devices, for example, DVD
In the case of -R, recording is performed by changing the power in the range of about 4 to 12 mW. Therefore, in a portion where recording is performed with a higher power than the recording power used in a normal apparatus, the drop of the push-pull signal is further increased, and the tracking becomes more unstable. In consideration of variations in devices such as a pickup head and tilt control, recording may be performed at a power higher by about 2 mW than the above-mentioned power, but in that case, tracking becomes more unstable.

According to the optical recording medium described in Japanese Patent Application Laid-Open No. 9-326138, a signal from a prepit is large in an unrecorded state, and address information can be obtained accurately. However, when a recording pit is formed in a groove and a recording pit is also formed on a side of the prepit, a signal from the prepit tends to be small. As a result, it is difficult to accurately obtain the pre-pit signal, and the error of the signal is increased as compared with the case where the pre-pit signal is not recorded, and it is difficult to accurately obtain the address information.

In order to reduce the influence of the pre-pit signal from the recording pit and to suppress an increase in the error of the pre-pit signal, it is preferable to make the notch of the pre-pit longer. However, when the notch of the pre-pit is lengthened, there arises a problem that a data error obtained by converting a reproduction signal obtained from the recording pit increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a stable servo characteristic, accurate address information based on a pre-pit signal, and high quality with a low data error. It is an object to provide an optical recording medium from which a reproduction signal can be obtained.

[0014]

In order to solve the above-mentioned problems, an optical recording medium according to the present invention has a land / groove structure, and has an optical recording medium comprising a substrate having prepits formed in lands between grooves. In the medium, the groove width is narrow in the vicinity of the prepit, and the groove width G1 of the groove not located in the vicinity of the prepit, the groove width G2 of the groove in the vicinity of the prepit, and the track pitch TP are as follows: G1 / TP = 0.42 0.58 G2 / TP = 0.30-0.40 G2 / G1 = 0.60-0.90, the groove near the prepit is adjacent to the prepit along the entire length of the prepit, and the length of the prepit is It extends beyond both ends in the vertical direction. Here, the “length” is a dimension of the land / groove extending in the length direction, and the “width” is perpendicular to the length direction and parallel to the main surface of the recording medium. Means a dimension in a different direction. Also, the terms "groove width" and "track pitch" are used in their ordinary meaning. “Groove width” is a half-value width in the depth direction of the groove.

[0015] With such features, the optical recording medium of the present invention can exhibit stable servo characteristics and can provide accurate address information and a high-quality reproduced signal.

The optical recording medium of the present invention is, in other words, an optical recording medium having a land-groove structure and a substrate having prepits formed on lands between grooves.
An optical recording medium in which a relatively wide groove and a relatively narrow groove are alternately connected to form the entire groove, and the narrow groove extends adjacent to the prepit and longer than the prepit. is there. The relationship among the groove width G1 of the wide groove, the groove width G2 of the narrow groove, and the track pitch TP is the same as described above.

Alternatively, the optical recording medium of the present invention is an optical recording medium having a land-groove structure and a substrate having pre-pits formed on lands between the grooves, wherein the groove has a wide portion and a width. G1, G2, and TP satisfy the above relationship when the groove width of the wide portion is G1, the groove width of the narrow portion is G2, and the track pitch is TP. It can also be said that the optical recording medium is adjacent to the entire length of the prepit and extends longer than the prepit.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.
An optical recording medium in which recording pits are formed in a groove will be described.

The optical recording medium according to the present invention includes all optical recording media for recording information by light, such as tapes, cards, disks, and the like. The present invention is particularly preferably applied to a CD-R, DVD-R, DVD-RW or the like in the form of a disc.

The specific land / groove structure of the substrate constituting the optical recording medium can be determined according to the performance required for the optical recording medium. For example, the present invention can be applied to an optical recording medium having a substrate on which a meandering (wobble) groove is formed and an optical recording medium having a substrate on which a groove having no meandering is formed. The substrate on which the non-serpentine grooves are formed has, for example, a disk shape in which the grooves draw a smooth curve along the circumferential direction.

The optical recording medium of the present invention has pre-pits formed on the lands of the substrate. The prepit is a cutout extending over the entire width of the land, and may be a groove that connects grooves. Alternatively, the prepit may be formed on at least one edge of the land, and in that case, a data error from the reproduction signal can be reduced. Here, "land edge" means that the length direction is the direction in which the land / groove extends, and the width direction is the direction perpendicular to the length direction and parallel to the main surface of the recording medium. , In the width direction of the land.

It is preferable that the notch-shaped pre-pit is formed only at one edge of the land and is formed so as to be always located on the same side of the land. When the optical recording medium is in the form of a disk, prepits are formed only on one of the inner and outer edges of the land.

The cut-out prepits are formed as long as the portions where the prepits are present on both sides in the cross section cut along the width direction do not exist over the entire length of the land.
It may be formed on both edges of the land. Therefore,
When only the portion where the prepit is formed at one edge of the land is taken out and viewed, no prepit exists at the other edge. In the section where the pre-pits exist on both sides in the cross section cut along the width direction, when the pre-pit is detected by causing the optical pickup to follow the land,
Prepits may not be detected due to no phase difference.

In the optical recording medium of the present invention, the width of the groove formed on the substrate is reduced near the prepit, and the groove width G1 of the groove not located near the prepit is obtained.
The groove width G2 and the track pitch TP of the groove near the prepit satisfy the above-mentioned predetermined relationship, and the groove near the prepit is adjacent to the prepit along the entire length of the prepit and extends beyond both ends in the longitudinal direction of the prepit. It is characterized by doing. FIG. 1 is a plan view schematically showing a part of an example of a substrate constituting an optical recording medium of the present invention.

The substrate (1) of the optical recording medium shown in FIG. 1 has a land / groove structure. Prepits (5) are formed on one edge of the land (4) of the substrate (1). The grooves are formed so as to have different groove widths. The groove width G2 of the groove (3) near the prepit adjacent to the prepit (5) is smaller than the groove width G1 of the groove (2) not located near the prepit. The groove (3) near the prepit extends beyond both ends in the length direction of the prepit (that is, longer than the prepit).

The groove in the vicinity of the pre-pit does not need to have the shape as shown. For example, as shown in FIG. 1, the widths of the lands on both sides in contact with the groove are widened and the groove near the prepit is not formed, but only the land on the side where the prepit is formed is widened and the width of the land near the prepit is reduced. A narrow groove may be formed.

When the prepit is a cutout extending over the entire width of the land and connects the grooves, there are two grooves adjacent to the prepit. Therefore, no matter which groove has the narrow portion, the groove near the prepit is adjacent along the entire length of the prepit. In that case, it is preferable to provide a narrow portion of the groove in one of the grooves so as to be adjacent to the prepit, depending on the method of detecting the prepit.

Although the present invention is not bound by any theory, the reason why the optical recording medium of the present invention has stable servo characteristics and can obtain accurate address information from the pre-pit signal is as follows. It is inferred.

Among the servo signals, the radial push-pull signal used when recording a signal on the optical recording medium is greatly affected by the depth and width of the groove of the substrate as described above. However, the depth of the groove greatly affects the reflection level of the optical recording medium. In the case of a write-once or rewritable optical recording medium as shown in FIG. 3, the depth of the groove is generally about λ / 10n in consideration of the balance between the required reflection level and the radial push-pull signal. This depth is not the depth (λ / 8n) at which the radial push-pull signal output is maximized.

The groove width of the substrate greatly affects the error of the pre-pit signal and the data error obtained from the reproduced signal of the recording pit as described below. Therefore, in the case of a write-once or rewritable optical recording medium as shown in FIG. 3, the width of the groove is generally narrower than TP / 2 in consideration of the balance between the data error and the radial push-pull signal.

FIG. 2 is a plan view schematically showing a substrate constituting a conventional optical recording medium. In FIG. 2, the pre-pit (5 ') is provided adjacent to the groove (3') at one edge of the land (4) so as to form a cutout occupying a part of the land width. . 2 indicate a wide groove (2 ') and a prepit (5 ") having the same size as a prepit (5') formed on a substrate having a small groove width. For this reason, the error of the prepit signal of the optical recording medium having the substrate on which the wide groove is formed is at the same level as that of the optical recording medium having the substrate on which the narrow groove is formed. A signal is recorded on each of an optical recording medium having a substrate with a narrow groove and an optical recording medium having a substrate with a large groove width, and a data error when the signal is reproduced is compared.

FIG. 4 and FIG. 5 schematically show reproduction signals obtained from an optical recording medium composed of a substrate having a narrow groove width and a substrate having a wide groove width, respectively. In FIGS. 4 and 5, 3T signals (A in FIG. 4 and E in FIG. 5) (1T corresponds to the period of the reference frequency) and 14T
The signals (B in FIG. 4 and F in FIG. 5) are shown. FIG.
Schematically shows the relationship between the width of the groove and the degree of modulation of the reproduction signal. The modulation factor is given by the following equation, modulation factor = (IH-IL)
/ IH (where IH indicates the maximum level of the 14T signal,
IL indicates the minimum level of the 14T signal). The degree of modulation is affected by the deterioration and decomposition of the recording layer when forming the recording pits, the deformation of the substrate, and the like, and is also affected by the depth and width of the groove of the substrate.

When the depth of the substrate and the material of the recording layer are the same, the degree of modulation depends on the groove width of the substrate. As shown in FIG. 6, when the groove width becomes 0 μm or the same as the track pitch, that is, when the groove has a flat surface, the degree of modulation becomes minimum. Groove width is 1 / track pitch
When it is about 2, the modulation degree becomes maximum.

When an optical recording medium is constituted by a substrate on which a narrow groove (corresponding to the solid line in FIG. 2) is formed, each signal is as shown in FIG. In the pre-pit portion, the reflection level is high because the width of the groove is widened (that is, it is close to a plane). As a result, the reproduction signal level in that portion is higher than in the other portions, and the amplitude of the reproduction signal in the pre-pit portion increases as shown in FIG.
In FIG. 6, the modulation degree of an optical recording medium constituted by a substrate having a narrow groove width is I, and becomes large as J in a prepit portion. Accordingly, the minimum level of the reproduced signal and the amplitude of the reproduced signal in the pre-pit portion are as shown in FIG. 4 so as to correspond to such a change in the modulation degree.

On the other hand, when a substrate having a wide groove (corresponding to the broken line in FIG. 2) is used,
The modulation degrees of the portion where the prepits are not adjacent and the portion where the prepits are adjacent are K and L, respectively. The difference between KL is I-
Not as large as the J difference. Therefore, the amplitude of the reproduced signal does not change, and the signal is curved in the pre-pit portion by an amount corresponding to the increase in the reflection level, as shown in FIG.

Each signal of the reproduction signal has a predetermined level (FIG. 4).
In FIG. 5, D is sliced and detected in H). Therefore, in an optical recording medium using a substrate with a wide groove width, more signals that have changed from the original signal length in the pre-pit portion are detected more than those using a substrate with a narrow groove width. Resulting data errors increase.

When an optical recording medium is formed by using the substrate as shown in FIG. 1, the radial push-pull signal is dominantly influenced by the wide groove (2) and has a large value. Can be secured. FIG. 7 schematically shows a reproduced signal level when a signal is recorded on an optical recording medium using this substrate and reproduced. FIG. 7 simply shows a 3T signal (M) and a 14T signal (N). In this optical recording medium, according to the relationship between the groove width and the modulation degree shown in FIG. 6, the modulation degree changes according to the groove width, and thus each reproduced signal is as shown in FIG. Therefore, a data error when this is sliced at a predetermined level P can be suppressed as low as when a substrate having a narrow groove width is used. As described above, according to the optical recording medium of the present invention, stable servo characteristics are secured, accurate address information can be obtained from the pre-pit signal, and a high-quality reproduction signal with reduced data errors can be obtained. .

In the substrate having a land / groove structure constituting the optical recording medium of the present invention, a groove having a groove width G2 smaller than the groove width G1 of the other part of the groove is formed near the prepit. It is characterized by. The narrow groove near the prepit is adjacent to the prepit along the entire length of the prepit. Therefore, when the prepit is considered as a part of the groove, the groove width is apparently large in a portion adjacent to the prepit.

If there is a region where the groove width gradually increases between the groove not located near the prepit and the groove located near the prepit, that portion is conveniently included in the groove not located near the prepit. .
However, the groove width of that portion is not G1.

The groove width G1 of the groove not located near the pre-pit, the groove width G2 of the groove near the pre-pit, and the track pitch TP ensure stable servo characteristics in the optical recording medium, obtain accurate address information, and reproduce. In order to suppress a data error from a signal, it is preferable to satisfy the following relationship.

The ratio G1 / TP of the groove width G1 of the groove not located near the prepit to the track pitch TP is preferably in the range of 0.42 to 0.58,
It is more preferably in the range of 0.44 to 0.56, and even more preferably in the range of 0.46 to 0.54. When G1 / TP is less than 0.42 or larger than 0.58, the radial push-pull signal becomes small, and when recording the signal on the optical recording medium, the servo characteristics become unstable with respect to high recording power. There is a tendency.

The groove width G of the groove near the prepit
2 and the track pitch TP, G2 / TP, is 0.30
Preferably in the range of ~ 0.40,
It is more preferably in the range of 0.39, and 0.34
Even more preferably, it is in the range of 0.39 to 0.39. G
When 2 / TP is smaller than 0.30, it is difficult to form a groove uniformly, and the change of a reproduction signal from a recording pit becomes large, thereby deteriorating jitter. Also, 0.4
If the value is larger than 0, data errors from the reproduction signal increase, and a high-quality reproduction signal cannot be obtained.

The ratio G2 / G1 of the groove width G1 of the groove not located in the vicinity of the prepit to the groove width G2 of the groove in the vicinity of the prepit is preferably in the range of 0.60 to 0.90, preferably 0.65 to 0. 0.87, more preferably 0.70 to 0.87. If G2 / G1 is smaller than 0.60, the difference between G2 and G1 increases, that is, the change in the groove width increases, and the servo characteristics tend to become unstable. When G2 / G1 is larger than 0.90, it is difficult to stabilize servo characteristics while suppressing each error (a pre-pit signal error and a data error from a reproduced signal).

The groove near the prepit is adjacent to the prepit along the entire length of the prepit, and extends beyond both ends of the prepit in the length direction. Therefore, the groove near the pre-pit is longer than the pre-pit. When the length of the pre-pit is not constant over the entire width as shown in FIG. 1, the total length of the pre-pit corresponds to the length at a portion in contact with the groove (or a boundary portion with the groove: corresponding to a broken line in FIG. 1). Both ends in the length direction are both ends in the length direction at a portion in contact with the groove.

Both ends in the length direction of the groove in the vicinity of the prepit are preferably located at 0.2 to 4.0 μm, more preferably 0.4 to 4.0 μm, from both ends in the length direction of the prepit.
3.0 μm position, even more preferably 0.4-2.5
at the position of μm. When the distance between both ends in the length direction of the groove near the prepit and both ends in the length direction of the prepit is less than 0.2 μm, it is possible to sufficiently obtain the effect of reducing the width of the groove near the prepit. As a result, it is difficult to balance the stabilization of the servo characteristics and the suppression of each error. If the distance between the longitudinal ends of the groove near the prepit and the longitudinal ends of the prepit is greater than 4.0 μm, the influence on the radial push-pull signal becomes large, and the servo characteristics become unstable. . It is preferable that both ends in the length direction of the groove near the prepit are equidistant from both ends in the length direction of the prepit. In some cases, the distance between one end and one end of the prepit may be different from the distance between the other end and the other end of the prepit.

The groove in the vicinity of the pre-pit has a generally adopted shape and size except that the width of the groove is reduced. Therefore, the cross-sectional shape of the groove cut along the width direction is the same as that of the groove not located near the prepit.

The shape of the prepit is not particularly limited, and may be a cutout of a land connecting the grooves. Alternatively, as shown in FIG. 1, notched pre-pits formed on at least one edge of the land and adjacent to the groove may be used.

As the width of the pre-pit is smaller, the width of the groove in the pre-pit portion is smaller, so that the reflection level is suppressed from increasing. As a result, the curvature of the reproduced signal in the pre-pit portion is reduced, and an increase in data error is suppressed. If a pre-pit is formed at one edge of the land and a notch is not present at the other edge, such a pre-pit has almost no effect on the reproduction signal from the recording pit adjacent to the pre-pit via the other edge. Absent. As a result, the occurrence of a data error in the pre-pit portion is further suppressed. In the case where the prepit is formed on at least one edge of the land, the width of the prepit is preferably not more than 3/4 of the width of the part where the prepit is not formed in the land where the prepit is formed adjacent to the groove near the prepit. Preferably 1
/ 3 to 3/4, more preferably 1/3 to 2 /
Even more preferably, it is 3.

The "land on which the prepit adjacent to the groove near the prepit is formed" refers to the land on the side where the prepit is formed, of the two lands adjacent to the groove near the prepit, and the "land where the prepit is formed" The “non-formed portion” refers to a portion of the land adjacent to the groove near the prepit where no prepit is formed. Therefore, the portion has a larger width than the portion of the land adjacent to the groove that is not located near the pre-pit.

The edge of the land where the prepit is formed is determined by which side (for example, the left or right side, or the inner or outer side) the prepit is to be detected by the optical pickup or the like that follows the groove of the optical recording medium. Is done. For example, when a reproduction optical pickup or a recording optical pickup follows a groove of a disk-type optical recording medium such as a DVD, when the optical pickup detects a prepit formed on a land adjacent to the outer periphery of the groove, The pre-pit is formed so as to be adjacent to the outer peripheral edge of the groove, that is, located at the inner peripheral edge of the land.

The level of the bottom surface of the prepit may be the same as that of the bottom surface of the groove, or may be higher or lower than the bottom surface of the groove. In the present invention, it is preferable that the bottom level of the prepit is the same as that of the groove bottom from the viewpoint of manufacturing efficiency.

When the optical recording medium of the present invention is a writable optical recording medium, it is preferable that the modulation degree of a reproduced signal obtained from the recording pit when the recording pit is formed on the recording layer is 0.8 or less. . The modulation factor is given by the formula, modulation factor = (IH
−IL) / IH (where IH indicates the maximum level of the 14T signal, and IL indicates the minimum level of the 14T signal). The modulation degree of the reproduction signal is specified to specify the recording depth of the recording pit. When the degree of modulation is large, the recording depth of the recording pit is generally deep. If the modulation degree of the reproduction signal exceeds 0.8, the difference between the phase difference on the land side and the phase difference on the prepit side becomes small when a recording pit is formed adjacent to the prepit. as a result,
The pre-pit signal after recording tends to decrease and the pre-pit signal error tends to increase. The modulation degree is more preferably 0.4 to 0.8, even more preferably 0.6 to 0.8.
0.75. The degree of modulation can be changed, for example, by changing the type of material (for example, dye) constituting the recording layer.

The substrate constituting the optical recording medium of the present invention is C
It can be formed of the same material as the substrate used for the DR and the DVD-R. Specifically, the substrate is a polycarbonate resin, a polyolefin resin, an acrylic resin,
It is preferable to use an epoxy resin or glass.

The pre-pits, grooves, and grooves in the vicinity of the pre-pits are formed, for example, by forming a mold or stamper used for molding a substrate of an optical recording medium into a shape such that desired pre-pits and grooves are formed on the substrate. Can be easily formed. That is, in the process of manufacturing the stamper, when the photoresist is cut by exposure to laser light, the cutting may be performed so that desired pre-pits and the like are formed. Since the spot of the laser beam used in the cutting is round, the starting point and the ending point of the cutting, that is, both ends in the length direction of the prepit, and the junction between the wide groove and the narrow groove, etc. However, the desired effect can be obtained without impairing the characteristics of the optical recording medium of the present invention.

The optical recording medium of the present invention can be manufactured by a conventional method using the substrate having the land / groove structure described above. For example, when manufacturing a CD-R or DVD-R, the structure shown in FIG. 3 can be used. FIG. 3 shows a cross section cut along a width direction of a portion where no prepit is formed. The illustrated optical recording medium is formed by sequentially forming a recording layer (10) and a reflective layer (11) on a substrate (9), and laminating the substrate (13) thereover via an adhesive layer (12). It is. Instead of the substrate (13), a thick adhesive layer (12) may be applied to form a protective layer, thereby improving the overall strength.

The recording layer (10) is composed of an azo dye, a polymethine dye (cyanine dye, merocyanine dye, styryl dye, squarylium dye, aminovinyl dye, etc.), a macrocyclic azaannulene dye (phthalocyanine dye) , Naphthalocyanine dyes, porphyrin dyes, subphthalocyanine dyes), triphenylmethane dyes, fluoran dyes, quinone dyes, cationic dyes, indophenol dyes, condensed ring dyes such as perylene, etc. One or more dyes selected from the group can be formed by vacuum evaporation or solution coating (eg, spin coating). The recording layer may be in the form of a single layer containing only one kind or plural kinds of dyes, or in the form of a plurality of such layers laminated.

The reflection layer (11) is made of gold, silver, aluminum,
It can be formed by forming a film of copper, chromium, platinum, nickel, titanium, or an alloy thereof by a sputtering method, a vacuum evaporation method, or the like. The protective layer (adhesive layer) (12) can be formed of an ultraviolet curable resin selected from an epoxy resin, a urethane resin, a silicon resin and the like. A substrate (13) may be laminated on the adhesive layer (12) to secure the strength of the optical recording medium. The substrate (13) is, for example, a substrate having no groove and made of the same material as the substrate (9) and having the same thickness as the substrate (9).

[0058]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the optical recording medium of the present invention will be described below.

Example 1 A polycarbonate resin having a diameter of 120 with the following land / groove structure was used.
A substrate having a thickness of 0.6 mm and a thickness of 0.6 mm was prepared. Track pitch (TP): 0.74 μm Groove width (G
1): 0.37 μm Groove width (G2) of the groove near the prepit: 0.
Positions at both ends in the longitudinal direction of the groove near the 27 μm prepit (G
2L): 0.8 μm from both ends in the longitudinal direction of the prepit Groove depth: 43 nm Prepit: notch having a width of 0.22 μm and length of 0.55 μm Depth of the prepit (bottom): depth of the groove (bottom) Same as) Prepit location: Inner edge of land

On this substrate, the following three types of materials were sequentially deposited in a vacuum of 10 ^-4 Torr or less to form a recording layer. First layer: tin chloride phthalocyanine (manufactured by Aldrich) Second layer: bis [10- (3-methyl-2-pyridylazo) -9-phenanthroato] nickel Third layer: 5,10,15,20-tetrakis (4 -Methoxyphenyl) -21H, 23H-porphine cobalt (II) (manufactured by Aldrich)

Next, silver was sputtered on the recording layer to form a reflective layer having a thickness of 100 nm. A 6 mm-thick substrate made of the same material as the above substrate was adhered to the substrate via an ultraviolet-curable acrylic resin to obtain an optical recording medium.

The screw [10-] constituting the second layer of the recording layer
A method for synthesizing (3-methyl-2-pyridylazo) -9-phenanthrolat] nickel is as follows.

(1) Synthesis of 2-hydrazino-3-picoline 80 g of 2-bromo-3-picoline and 90 ml of ethanol were charged into a reaction vessel, and 300 g of hydrazine monohydrate was added at room temperature with stirring over 30 minutes. It was dropped. After completion of the dropwise addition, the temperature was raised to 80 ° C., and the mixture was stirred for 25 hours. The heating was stopped and the reaction solution was cooled to 20 ° C. or lower, and the precipitate was collected by filtration.
The precipitate was washed with hexane and dried to obtain 40 g of a crystal.

(2) Synthesis of 10- (3-methyl-2-pyridylazo) -9-phenanthrole 550 ml of acetic acid and 28 g of 9,10-phenanthrenequinone were charged into a reaction vessel, and the temperature was raised to 100 ° C. while stirring. After that, 19 g of 2-hydrazino-3-picoline obtained in (1) was added. After stirring for 2 hours at this temperature, the reaction was filtered hot. Next, an aqueous sodium hydroxide solution was added dropwise to the filtrate, and the mixture was filtered. The crystals were sequentially washed with warm water and methanol, and then dried to obtain 12 g of crystals.

(3) Synthesis of bis [10- (3-methyl-2-pyridylazo) -9-phenanthrolato] nickel In a reaction vessel, 2 g of the azo dye obtained in (2) and methanol 4
5 ml was charged and heated to 50 ° C. while stirring. Next, 0.89 g of nickel acetate tetrahydrate was added, and the mixture was heated to 60 ° C. and stirred for 2 hours. After allowing to cool, the mixture was filtered, and the crystals were washed with warm water and dried to obtain 2.1 g of crystals.

Example 2 The groove widths G1 and G2 were set to 0.34 μm and 0.26 μm, respectively.
A substrate was formed in the same manner as in Example 1, except that Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

Example 3 The groove width G1 and the groove width G2 were 0.39 μm and 0.28 μm, respectively.
A substrate was formed in the same manner as in Example 1, except that Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

Example 4 The groove width G1 and the groove width G2 were 0.37 μm and 0.26 μm, respectively.
A substrate was formed in the same manner as in Example 1 except that the positions (G2L) at both ends in the length direction of the groove near the prepit were 0.5 μm from both ends in the length direction of the prepit. Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

(Embodiment 5) The groove width G1 and the groove width G2 were set to 0.34 μm and 0.28 μm, respectively.
A substrate was formed in the same manner as in Example 1 except that the positions (G2L) at both ends in the longitudinal direction of the groove near the prepit were respectively 2.0 μm from both ends in the longitudinal direction of the prepit. Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

The following optical recording medium was manufactured for comparison with the above embodiment. Comparative Example 1 A substrate was formed in the same manner as in Example 1 except that the groove width G1 and the groove width G2 were the same (0.26 μm). Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

Comparative Example 2 A substrate was formed in the same manner as in Example 1 except that the groove width G1 and the groove width G2 were the same (0.36 μm). Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

Comparative Example 3 The groove width G1 and the groove width G2 were 0.34 μm and 0.21 μm, respectively.
A substrate was formed in the same manner as in Example 1, except that Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

Comparative Example 4 The groove width G1 and the groove width G2 were 0.29 μm and 0.24 μm, respectively.
A substrate was formed in the same manner as in Example 1, except that Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

(Comparative Example 5) The groove width G1 and the groove width G2 were 0.40 μm and 0.23 μm, respectively.
A substrate was formed in the same manner as in Example 1, except that Using this substrate, an optical recording medium was produced in the same manner as in Example 1.

With respect to the optical recording media of Examples and Comparative Examples produced in this manner, the error rate of the pre-pit signal in the unrecorded state and after recording in which recorded pits were formed,
In addition, a data error obtained from the reproduced signal was measured. The recording pit is an optical disk evaluation device DDU-1000 (recording laser wavelength 636n) manufactured by Pulstec Industrial Co., Ltd.
m). The error rate of the pre-pit signal and the data error from the reproduction signal were measured using Kenwood's optical disc evaluation devices DR-3330 and DR-3340, respectively.

Further, the servo characteristics of the optical recording media of the examples and the comparative examples were evaluated. Servo characteristics are determined by taking into account the recording power used in the actual recording device.
Evaluation was made by observing a change in servo signal output and tracking deviation when recording at W (12 mw + 2 mW of DVD-R standard). The servo signal output with a small change in the servo signal output and stable servo characteristics without occurrence of tracking deviation was evaluated as ○, and the servo signal output with a large change or tracking deviation was evaluated as Δ.

Table 1 shows the evaluation results of the performance of each optical recording medium together with the G1 / TP, G2 / TP, G2 / G1, and G2L of the substrate constituting each optical recording medium.

[0078]

[Table 1]

In all of the embodiments corresponding to the optical recording medium of the present invention, the servo characteristics are stable, the unrecorded and recorded pre-pit signal errors measured in each embodiment, and the data obtained from the reproduced signal. All errors were low. On the other hand, in Comparative Example 1, since the groove width was narrow over the whole, the data error of the reproduction signal was small, but the servo characteristics were lacking in stability. In Comparative Example 2, although the servo characteristics were stable because the groove width was wide as a whole, the data error of the reproduced signal was large. G2 / TP, G1 /
Comparative Example 3, in which TP and G2 / G1 are not within the scope of the present invention,
Nos. 4 and 5 did not have stable servo characteristics. In Comparative Example 3, since the groove width (G2) of the groove near the pre-pit was narrow, G2 / TP was small, and G2 / G1 was small compared to the embodiment, the data error obtained from the reproduced signal was large, and the servo characteristics were large. Was not stable, and the quality of the reproduced signal was poor.

[0080]

As described above, the optical recording medium of the present invention exhibits stable servo characteristics, and can reduce the pre-pit signal error in an unrecorded state and after recording, as well as the data error. It is possible to obtain a high quality reproduced signal. Therefore, according to the present invention, it is possible to provide various types of optical recording media such as a write-once type and a rewritable type having excellent performance.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a substrate used for an optical recording medium of the present invention.

FIG. 2 is a schematic plan view of a substrate used for a conventional optical recording medium.

FIG. 3 is a schematic sectional view of a general write-once optical recording medium.

FIG. 4 is a graph schematically showing a reproduction signal level from an optical recording medium using a substrate having a narrow groove width.

FIG. 5 is a graph schematically showing a reproduction signal level from an optical recording medium using a substrate having a wide groove width.

FIG. 6 is a graph schematically showing a relationship between a groove width and a modulation factor.

FIG. 7 is a graph schematically showing a reproduction signal level from the optical recording medium of the present invention.

[Explanation of symbols]

 1, 9, 13 Substrate 2 Groove 3 Groove near pre-pit 2 ', 3' Groove 4 Land 5, 5 ', 5 "pre-pit 6 Groove 7 Land 10 Recording layer 11 Reflective layer 12 Protective layer (or adhesive layer)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor To ▲ Saki ▼ Yoshihiro 1006 Ojidoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 5D029 WA27 WA34 WA34 WB14 WC10 WD12

Claims (7)

[Claims] 1. An optical recording medium having a land / groove structure and a substrate having prepits formed on lands between the grooves, wherein the width of the groove is reduced in the vicinity of the prepit, and in the vicinity of the prepit. Groove width G of groove not located at
1. The groove width G2 of the groove near the pre-pit and the track pitch TP are as follows: G1 / TP = 0.42 to 0.58 G2 / TP = 0.30 to 0.40 G2 / G1 = 0.60 to 0.90 An optical recording medium that satisfies the relationship, wherein the groove near the prepit is adjacent to the prepit along the entire length of the prepit and extends beyond both ends in the length direction of the prepit. 2. A groove in the vicinity of a prepit is adjacent to the prepit along the entire length of the prepit, and both ends in the length direction are 0.2 to 4.0 from both ends in the length direction of the prepit.
The optical recording medium according to claim 1, wherein the optical recording medium extends so as to be at a position of μm. 3. The pre-pit is a notched pre-pit formed on at least one edge of a land,
3. The light according to claim 1, wherein the width of the prepit is equal to or less than 幅 of the width of a portion of the land adjacent to the groove near the prepit where the prepit is not formed. recoding media. 4. The optical recording medium according to claim 3, wherein the cut-out prepits are formed only on one edge of the land and are always located on the same side of the land. 5. The optical recording apparatus according to claim 4, wherein the optical recording medium is in the form of a disk, and the notch-shaped prepit is formed only on one of the inner peripheral edge and the outer peripheral edge of the land. Medium. 6. The notch-shaped prepit is formed at both edges of the land without the presence of the prepit on both sides in the cross section cut along the width direction. The optical recording medium according to the above. 7. The optical recording medium is a writable optical recording medium, wherein a modulation degree of a reproduction signal obtained from the recording pit when the recording pit is formed on the recording layer is 0.8 or less. The optical recording medium according to any one of the above items.