JP2001291283A - optical disk - Google Patents

Abstract

(57) [Summary] (with correction) [PROBLEMS] To provide an optical disc which can reduce the influence of land pre-pits on an information signal, can obtain a land pre-pit signal with a sufficient amplitude, and can be manufactured by a conventional process. I do. SOLUTION: A concentric or spiral groove 12, a land prepit 16 provided to connect between adjacent grooves, and a pit 17 having a physical depth substantially equal to the land prepit are formed. An optical disc having a pit area, wherein the wavelength of a laser beam used for recording and reproduction is λ, and the numerical aperture of an objective lens is NA, and the phase depth of the groove is in the range of λ / 6.5 to λ / 11. And the length of the land pre-pit is 0.45λ / NA or less, and the following relationship exists between the length of the land pre-pit (LPP length) and the width of the groove. 0.8 × D <groove width × NA / λ <1.2 × D where D = 0.31−0.33 × LPP length × NA /
λ.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a recordable optical disk.

[0002]

2. Description of the Related Art Generally, in a recordable optical disk, an address needs to be recorded in the disk in advance in order to perform an appropriate recording and reproducing operation of information. In this case, a DVD (Digital Versatile)
Discs such as Disc-R and DVD-RW of a new standard having a narrow track pitch, as disclosed in Japanese Patent Application Laid-Open No. 9-326138, have a predetermined space so as to communicate between grooves. A groove, that is, a land prepit is formed. This will be described with reference to FIG. FIG. 5 is a plan view showing the surface of the optical disk. In the drawing, reference numeral 2 denotes a concentrically or spirally formed groove, that is, a groove, and the groove 2 is meandering at a predetermined cycle. Some grooves do not meander, and a portion between adjacent grooves 2 is referred to as a land 4. The grooves, that is, the land prepits 6 are formed at predetermined intervals along the circumferential direction of the disk so as to connect the adjacent grooves 2 to give specific information, for example, an address. This method has an excellent feature in that the recordable user information area is not reduced as compared with many other optical disk formats in which an address area is separately set.

[0003]

When the above-mentioned land pre-pit is adopted, there is a concern that the land pre-pit signal (hereinafter also referred to as LPP signal) may affect the information signal. is there. Therefore, conventionally, when the interference effect from the structure of the recording film affects the depth of the groove 2 or DVD-R,
An optical disk is manufactured by making the effective phase depth of the groove 2 shallow so that the influence of the land prepits 6 on the information signal is reduced. In addition, by using such a shallow phase depth, it is possible to suppress a decrease in the reflectivity due to the groove 2, and therefore, it is possible to make the signal output compatible with a normal DVD disk. The actual phase depth is about λ / 15. Here, λ is the wavelength of the recording / reproducing laser beam.

On the other hand, as a request for a recordable optical disk, a measure against illegal copying is required. For this reason, there is a demand for recording information such as a disk ID in pits that cannot be recorded or erased. Here, it is convenient to make the physical depths of the pits and the grooves equal, due to restrictions on the manufacturing process of the optical disk. In the case of a coating type optical disk such as a DVD-R, the phase depth may be slightly different even if the physical depth is the same. In this case, as described above, the DVD-R or D
In an optical disk such as a VD-RW, the phase depth of the groove is made shallow in order to suppress the influence of land pre-pits and a decrease in reflectivity. If the groove 2 is shallow, the pits are too shallow, and a sufficient pit reproduction signal cannot be obtained, making it difficult to correctly read the information recorded in the pits.

[0005] The present invention focuses on the above problems,
The purpose was to solve this problem effectively, and the purpose was to reduce the influence of land pre-pits on the information signal, and to obtain this land pre-pit signal with a sufficient amplitude. Another object of the present invention is to provide an optical disk that can be manufactured by the above-described disk manufacturing process.

[0006]

The invention as defined in claim 1 is a method of forming a concentric or spiral groove, a land prepit provided so as to connect between adjacent grooves, and a land prepit. An optical disk having a pit region in which pits having a physical depth substantially equal to the above are provided, where λ is the wavelength of laser light used for recording and reproduction, and NA is the numerical aperture of the objective lens of the optical pickup. The phase depth of the groove is set in the range of λ / 6.5 to λ / 11, and the length of the land prepit is set to 0.
An optical disc characterized by being not more than 45λ / NA, and having the following relationship between the length of the land prepit (LPP length) and the width of the groove. 0.8 × D <groove width × NA / λ <1.2 × D where D = 0.31−0.33 × LPP length × NA /
λ. As a result, it is possible to reduce the influence of the land prepit on the information signal and to obtain the land prepit signal with a sufficient amplitude.

In this case, for example, the reproduction signal intensity of the groove is in the range of 50 to 80% with respect to the reproduction signal intensity of the land located between the grooves, and The difference in the amount of reflected light from the groove in the recording state is less than 5% between the land pre-pit portion and the non-land pre-pit portion.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the optical disk according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing the surface of an optical disk of the present invention, FIG. 2 is an enlarged sectional view showing a groove portion and a land pre-pit portion of the optical disk of the present invention, and FIG. 3 is a diagram showing groove width (standardized by λ / NA) and reflection. FIG. 4 is a graph showing the relationship between the reciprocal of the groove phase depth (normalized by λ) and the jitter. In FIG. 1, concentrically or spirally formed grooves, that is, grooves 12 are formed on the substrate surface of the optical disk 10 (see FIG. 2).
Are meandering at a predetermined cycle. In addition, meandering (wobble)
Some grooves are not subjected to this process, and a portion between adjacent grooves 12 is called a land 14 (see FIG. 2). The grooves, that is, the land prepits 16 are formed at predetermined intervals along the disk circumferential direction so as to connect the adjacent grooves 12, thereby giving specific information, for example, addresses. In a pit area at a specific radial position, a predetermined pit (emboss pit) 17 is formed, for example, in the same manner as a normal ROM, and incorporates, for example, a function for preventing illegal copying. The physical depths of the pits 17 and the land pre-pits 16 are substantially equal. Here, the portion where the information signal is recorded is called a groove. This groove may be convex or concave when viewed from the pickup side. This depends on how you make the disc.

When the wavelength of the laser beam of the light source used for recording and reproduction is λ, the phase depth of the groove 12 is λ.
/6.5 to λ / 11. Beyond this range, in a shallow groove, a good signal cannot be obtained from a pit 17 having the same depth as the groove 7, and in a deep groove, a land pre-pit (also referred to as LPP) 16 adversely affects an information signal. Not only can not be reduced,
The amplitude of the information signal also decreases, and a good signal cannot be obtained. If the numerical aperture of the objective lens of the optical pickup for recording and reproduction is NA, the land pre-pit 16
Is set to 0.45λ / NA or less. This has a contradictory characteristic that a longer length L is advantageous in reproducing the LPP signal, but in this case, the adverse effect on the information signal is increased. Here, land pre-pit 16
It has been found that the width L of the groove 12 can reduce the adverse effect of the land pre-pits 16 on the information signal due to the length L.

Hereinafter, this point will be described. L in FIG.
The theoretical analysis value of the effect on the information signal and the length of the PP signal is shown. Here, the influence is shown by using as an index how much the amount of reflected light (signal intensity) from a groove in an unrecorded state changes between a portion where land prepits exist and a portion where land prepits do not exist. Here, it has been experimentally obtained that, when the value is 8% or less, preferably 5% or less, the influence of the land pre-pits on the information signal is acceptable. In this figure, the groove width is standardized using the NA of the objective lens and the wavelength λ of the laser light from the light source. The actual physical width dimension of the groove 12 is determined by the following equation. (Actual physical width) = (value on the figure) × λ / NA Similarly, the length of the LPP signal (the length of the LPP) is also normalized by NA and λ. The actual physical dimensions of the land pre-pits 16 are as follows: (Actual physical LPP length) = (value on the figure) × λ
/ NA Here, the length of the land pre-pit (LPP length) is
The values on the figure show the cases of 0.25 and 0.37.

FIG. 2 shows a case where the groove has a phase depth of λ / 8. If the depth of the groove is within the range of the above-mentioned condition, a substantially similar relationship is obtained, and furthermore, a result substantially matching the experimental value is obtained. FIG. 3 shows that the longer the land pre-pit length, the greater the effect, and the wider the groove width, the greater the effect. According to a more detailed analysis, the following equation could be derived as a range in which the influence of land pre-pits is relatively low. That is, 0.8 × D <groove width × NA / λ <
1.2 × D where D = (0.31-0.33 × LPP length × NA
/ Λ). If the groove width W exceeds this range, the effect becomes a size that cannot be ignored.

On the other hand, regarding the pit signal, FIG. 4 shows a relational expression between the groove phase depth and the jitter. The horizontal axis in the figure is the reciprocal of the groove phase depth. The values are normalized by λ. Therefore, for example, when the reciprocal value of the groove phase depth is 8, the phase depth is λ / 8. Further, both the groove width and the LPP length are 0.25 in the standardized expression described above. The width of the pit 17 is different from that of the groove, and is set to a width that optimizes the signal. According to FIG. 4, the deeper the pit 17 is,
The signal is good, and when it is λ / 11 or more, good jitter is obtained. On the other hand, the information signal recorded on the groove has characteristics opposite to those described above, and a good signal is obtained at a depth of λ / 6.5 or less. Therefore, both are satisfied when the land prepit depth is set between λ / 11 and λ / 6.5.

Next, the optical disk of the present invention was manufactured and evaluated, and the evaluation results will be described. Wavelength of light source laser beam = 0.4 μm, numerical aperture NA = 0.75
2 shows an optical disk corresponding to. This optical disk is a phase change medium. Here, the groove depth is 0.03 μm, the groove width is 0.11 μm, and the LPP length is 0.16 μm. The track pitch is preferably about 0.36 μm because the information signals, the tracking signals and the like are well balanced and the capacity can be increased.
When a phase change medium is used as the optical disk, the phase depth is determined by the following formula: [Physical depth ×
n / λ]. Therefore, the phase depth in this case is n =
When a substrate of 1.62 material is used, λ / 8.3 is obtained.
It is set at almost the center of the condition. The LPP length is 0.
3 × λ / NA, which satisfies the condition.

When the allowable range of the groove width under these conditions is determined by a conditional expression, the range is from 0.09 μm to 0.135 μm, and this optical disk satisfies the conditions of the present invention.
When a signal was reproduced using this optical disc, the reproduced signal intensity of the groove was between 50% and 80% of the reproduced signal intensity of the mirror portion where the pits 17, lands 14, grooves 12 and the like were not formed. The difference in the amount of reflected light (signal intensity) from the groove in the unrecorded state was 5% or less between the portion having the land prepit and the portion not having the land prepit, and the effect on the information signal was of an order that can be ignored. .
Further, a good signal could be obtained even in the pit area where the pit 17 was formed. In this way, by setting the groove width appropriately while maintaining consistency with the pit signal at a deeper phase depth of the groove, the LPP
It has become possible to suppress the adverse effect of the signal on the information signal. That is, a sufficient signal from the pit can be obtained by the phase depth of the deep groove, and the output fluctuation of the information signal when the LPP signal is present can be suppressed to 5% or less by setting the appropriate groove width. done.

[0015]

As described above, according to the optical disk of the present invention, the following excellent operational effects can be exhibited. The effect of the land prepit on the information signal is reduced, and the land prepit signal can be obtained with a sufficient amplitude. In addition, it is excellent in productivity and advantageous for recording copy protection information and the like on a disc.

[Brief description of the drawings]

FIG. 1 is a plan view showing the surface of an optical disk of the present invention.

FIG. 2 is an enlarged sectional view showing a groove portion and a land pre-pit portion of the optical disc of the present invention.

FIG. 3 is a graph showing a change in a groove width (normalized by λ / NA) and a reflected light amount.

FIG. 4 is a graph showing the relationship between the reciprocal of groove depth (normalized by λ) and jitter.

FIG. 5 is a plan view showing the surface of the optical disc.

[Explanation of symbols]

10 optical disk, 12 groove, 14 land, 1
6: Land pre-pit, 17: Pit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/007 G11B 7/007

Claims (2)

[Claims] 1. A concentric or spiral groove, land prepits provided to connect adjacent grooves, and pits having a physical depth substantially equal to the land prepits are formed. An optical disk having a pit region, wherein the wavelength of a laser beam used for recording and reproduction is λ, and the numerical aperture of an objective lens of an optical pickup is NA, and the phase depth of the groove is λ / 6.5 to λ. / 1
1, the length of the land pre-pit is 0.45λ / NA or less, and the length of the land pre-pit (LPP length) and the width of the groove are An optical disc characterized by the following relationship: 0.8 × D <groove width × NA / λ <1.2 × D where D = 0.31−0.33 × LPP length × NA /
λ. 2. The reproduction signal intensity of the groove is 50 times the reproduction signal intensity of the land located between the grooves.
2. The method according to claim 1, wherein the difference in the amount of reflected light from the groove in an unrecorded state is 5% or less between the land pre-pit portion and the non-land pre-pit portion. An optical disc as described.