JPH117658A - Optical recording medium and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium capable of having a high recording capacity. SOLUTION: The optical recording medium is formed with a supporting body which consists of a thermoplastic resin and which is 0.3-1.2 mm thick, with a guiding groove 202 on the supporting body, and with at least a reflection film 203, a phase change type recording film 204, and a 3-177 μm thick light transmitting layer 205 successively on the guiding groove 202; assuming that the irregularity of thickness in the light transmitting layer 205 is Δt, the medium satisfies the following relation between the N.A. (numerical aperture) of a reproducing or recording/reproducing optical system and a wave length λ, namely, Δt<=±5.26(λ/N.A.<4> ) (μm).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a guide groove, a reflective film, and a phase-change type recording film on one main surface of a support, and a light for irradiating light for reading or recording information from these. The present invention relates to an optical recording medium having a configuration in which a transmission layer is formed. More specifically, the present invention relates to an optical recording medium capable of increasing the capacity by defining the relationship between the thickness of the light transmitting layer and the thickness unevenness, and an optical disc apparatus for recording or recording / reproducing the optical recording medium. is there.

[0002]

2. Description of the Related Art As a next-generation optical disk medium, an optical disk medium capable of recording and reproducing NTSC for 4 hours on one side has been proposed. This enables the current VTR (Video Tape Record) by enabling recording and playback for 4 hours as a home video disk recorder.
er) to provide a function as a new recording medium.

[0003] Also, CD (Compact Disc)
By selecting the same shape and size as above, it is possible to make the product comfortable for users who are accustomed to the simplicity and convenience of the CD.

[0004] Furthermore, utilizing the speed of access as the biggest feature of the disk form, it is not only a compact and simple recorder, but also a product incorporating various functions such as instant recording, playback, trick play, and editing. Can be realized.

[0005] In order to realize such a product, for example, a storage capacity of 8 GB or more is required.

[0006]

However, conventionally,
In the case of a CD having a single recording layer on only one side, there is no optical recording medium capable of realizing a storage capacity of 8 GB or more.

A DVD (Digita) that has already been proposed
1 Versatile Disc), the wavelength λ = 0.65 μm, the N.V.
A. When = 0.6, the storage capacity is 4.7 GB. If the capacity is to be increased without changing the signal format such as the ECC (Error Collection Code) and the modulation method, for example, to realize 8 GB or more, 4.7 × (0.65 / 0.60 × NA / λ) ² ≧ 8. From this, N.I.
A. /Λ≧1.20. Therefore, shortening the wavelength λ, or A. It is necessary to increase either.

In order to satisfy the above conditions, for example, A.
When the height is increased, it is necessary to reduce the thickness of the light transmission layer of the optical recording medium through which the reproduction light is irradiated and transmitted. This is because the allowable amount of the angle (tilt angle) at which the disc surface deviates from the perpendicular to the optical axis of the optical pickup becomes small, and this tilt angle is easily affected by aberration due to the thickness of the support. is there.

[0009] For the same reason, it is necessary to reduce the thickness unevenness of the light transmitting layer to a certain value or less.

Therefore, the present invention provides a particularly high N.D. A. It is an object of the present invention to provide an optical recording medium which can record large-capacity information of, for example, 8 GB or more.

[0011]

The optical recording medium of the present invention is made of a thermoplastic resin and has a support having a thickness of 0.3 to 1.2 mm, a guide groove on the support, and a guide groove on the guide groove. In order,
It has a recording area composed of at least a reflective film and a phase change type recording film, and at least 3 to 177 in the recording area.
When a light transmitting layer having a thickness of μm is formed, and the thickness unevenness of the light transmitting layer is represented by Δt, the N.V. A. And between the wavelength λ, Δt ≦ ± 5.26 (λ / N.A. 4) (μm) (N.
A. Is the numerical aperture).

According to the present invention, an optical recording medium having a large recording capacity and excellent signal characteristics can be realized.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. In addition,
In this embodiment, the optical disc is a light guide having a guide groove on a support, for example, a substrate, a reflective film and a phase-change recording film on the guide groove, and a light transmitting layer formed on these. An example is described in which the present invention is applied to an optical disc having a configuration in which a signal is recorded and reproduced by irradiating a laser beam to the optical disc. It can also be applied to other various shapes.

Generally, the disc skew margin Θ and the wavelength λ of the recording / reproducing optical system, A. The thickness t of the light transmitting layer is correlated, and based on the example of a compact disk (CD) whose practicality has been sufficiently demonstrated, the relationship between these parameters and Θ is described in Japanese Unexamined Patent Publication No. Hei. 22
No. 5650. According to this, Θ ≦ ±
84.115 ° (λ / NA ³ / t),
This can be applied to the optical recording medium of the present invention.

Here, considering the specific limit value of the skew margin 場合 when mass-producing the optical disk,
It is reasonable to set it to 0.4 °. This is because, when considering mass production, if the size is smaller than this, the yield decreases and the cost increases. CDs for existing recording media
Is 0.6 ° for DVD and 0.4 ° for DVD.

Accordingly, when Θ = 0.4 °, the wavelength of the laser is shortened and the N.V. A. Calculating how much the thickness of the light transmitting layer should be set by the conversion, first, λ = 0.65 μm
, N.N. A. Is N. From A / λ ≧ 1.20, it is required to be 0.78 or more. Further, assuming that the wavelength of the laser will be further reduced in the future and λ = 0.4 μm, A. If the condition of ≧ 0.78 is not changed, the thickness t of the light transmitting layer becomes t = 177 μm. In this case, it can be understood that the thickness of the entire optical disc is about 1.38 mm at the maximum, in consideration of diverting manufacturing equipment for CDs or the like having a substrate thickness of 1.2 mm.

On the other hand, the lower limit of the thickness of the light transmitting layer is determined by whether or not the protection function of the light transmitting layer which also has a role of protecting the recording film or the reflective film is secured. That is, the thickness is required to be 3 μm or more in consideration of the reliability of the optical recording medium and the influence of the collision of the second group lens on the light transmitting layer surface described later.

As described above, in order to increase the storage capacity of the optical recording medium, N.I. A. It is essential to increase / λ. In this case, for example, in order to achieve a storage capacity of 8 GB, at least N.I. A. Must be 0.7 or more, and the wavelength λ of the laser beam must be 0.68 (μm) or less. Further, as described above, there is the above-described relationship between the thickness of the light transmitting layer and the skew. However, in consideration of the current red laser to the blue laser expected to be widely used in the future, the thickness of the light transmitting layer is It is appropriate to set the length to 3 to 177 μm.

In order to achieve the recording capacity (8 GB), it is necessary to change the track pitch P and the linear density d. The condition may be such that (0.74 / P) × (0.267 / d) × 4.7 ≧ 8d ≦ 0.1161 / P (μm / bit). D ≦ 0.20 when P = 0.56 μm
6 μm / bit, which corresponds to the DVD ROM (Re
ad Only Memory), and advances in signal processing technology for recording and reproduction (specifically, PRML (P
ertial ResponseMaximam Likelihood) and EC
When the redundancy of C is reduced, the linear density is expected to increase by about 15%, and P can be increased accordingly. From this, P is derived at a maximum of 0.64 μm.

Further, the tolerance for the track pitch variation ΔP becomes strict. If the recording / reproducing parameters of a CD or a DVD are diverted as they are, the track pitch of the DVD is reduced to 0.1.
From 74 μm and the tolerance ± 0.03, ΔP ≦ ± 0.03P / 0.74 = ± 0.04P. Therefore, if P = 0.56, ΔP ≦ ±
0.023 μm.

Further, with respect to the thickness unevenness of the light transmitting layer, further improvement in accuracy is required.

When the thickness of the light transmitting layer deviates from the design center of the reproducing objective lens, the amount of aberration given to the spot by the thickness unevenness is determined by N.I. A. And is proportional to the wavelength. Therefore, high N.I. A. In order to increase the recording density by reducing the wavelength or shortening the wavelength, the thickness unevenness of the light transmitting layer is more severely limited. As a specific system example, in the case of a CD, the N.V. A. = 0.45 has been put to practical use, and the standard for the thickness unevenness of the light transmitting layer is ± 100 μm. DVD
In the case of A. = 0.6 ± 30 μm
It is prescribed. On the basis of the permissible amount ± 100 μm in CD, the thickness unevenness Δt is represented by the following equation. Δt = ± (0.45 / N.A. ) 4 × (λ / 0.78) × 100 = ± 5.26 × (λ / N.A. 4) μm (N.A. is the numerical aperture)

Here, the wavelength is 0.68 μm and the N.D. A. FIG. 1 shows the result of an experiment conducted on the relationship between the thickness unevenness of the light transmitting layer and the jitter value at 0.875. From FIG. 1, it can be seen that, for example, in a DVD, where the jitter standard is 8% when there is no perturbation such as skew, the thickness unevenness of the corresponding light transmitting layer is about ± 7 μm. The numerical value derived from the above equation is ± 6 μm, and a good signal can be obtained from a disk medium satisfying this standard.

Therefore, as the recording density of the optical recording medium increases, the thickness irregularity Δ
t is, ± 5.26 × (λ / N.A . 4) (μm) must be less than or equal to.

The thickness of the light transmitting layer is assumed to be uniform on the surface of the optical disk irradiated with the recording / reproducing laser, and aberration can be corrected by shifting the focus point. However, if the thickness of the light transmitting layer is uneven in this area (in the spot), it cannot be corrected by adjusting the focus point. This amount must be suppressed to ± 3λ / 100 or less with respect to the thickness center value.

Further, regarding the eccentricity E, 50 μm
E ≦ 50 × P / 0.74 = 67.57P (μ
m).

From the above, the conditions necessary for an optical recording medium to achieve a high storage capacity of 8 GB are summarized as follows. If the recording / reproducing optical system has λ ≦ 0.68 μm and A. /Λ≧1.20, the thickness t of the light transmitting layer in the recording area is 3 to 177 μm, and the thickness unevenness of the light transmitting layer is Δt ≦ ± 5.26 (λ / NA. ⁴ ) (μm) Track pitch P ≦ 0.64 (μm) Tolerance ΔP ≦ ± 0.04P (μm) Linear density d ≦ 0.1161 / P (μm / bit) Disk skew Θ ≦ 84.115 × (λ / N.A.
³ / t) Eccentricity E ≦ 67.57P (μm) Surface roughness Ra ≦ ± 3λ / 100 (within spot irradiation area)

A support, for example, a substrate is prepared by an injection molding method using a stamper that realizes the pitch and the pitch unevenness that meet the specifications required for the optical recording medium of the present invention described above. Such a high-precision stamper with little pitch unevenness is difficult to achieve with a conventional structure in which a screw is used for feeding. Therefore, the stamper is manufactured using a master exposure apparatus having a linear motor feeding structure. Furthermore, the optical system can be covered with a cover to eliminate air fluctuations, or by installing a vibration isolator between the laser and the exposure device to remove the vibration of the cooling water of the exposure laser. Make it.

In this embodiment, as shown in FIG. 2, a guide groove 202 is formed on a support, that is, a substrate 201, and a reflection film 203, a phase change type recording film 204, The transmission layer 205 is formed. In this case, since recording and reproduction are performed from the light transmitting layer 205 side, grooves (pits) are formed on the substrate in advance in consideration of deformation of the signal shape due to film formation.

For example, in the case of a ROM having a storage capacity of 10 GB, assuming that the asymmetry of signal pits when viewed from the substrate 201 (support) side is 25%,
The asymmetry when viewed from the opposite side is 10%. That is, in the present embodiment, in order to read a signal from the light transmission layer 205 on the opposite side to the substrate 201 side, for example, to form a pit having an asymmetry of 10% when viewed from the light irradiation side, The pit shape to be formed needs to be 25% asymmetry.

In this specification, as shown in FIG. 3, the guide groove structure of the recordable optical disk is shown as a portion exposed to laser during mastering, that is, a concave portion as viewed from the light transmitting layer side in FIG. The portion is referred to as a groove 101. The width of the flat portion excluding the tapered portion, ie, the inclined portion, from the groove is referred to as a groove width WG. On the other hand, in FIG. 3, a portion that is convex when viewed from the light transmission layer side is referred to as a land 102, and a continuous groove 101 is designated.
And the total width of the land 102 is referred to as a track pitch 103.

As shown in FIG. 4, the width at the center of the depth of the groove 101 is referred to as the full width at half maximum WH of the groove, and is expressed by (full width at half maximum WH of groove / track pitch 10).
3) x100 (%) is referred to as groove duty.

Similarly to the above-described asymmetry of the ROM disk, the groove duty of the guide groove formed on the recording disk changes when a reflection film or a phase change recording film is formed. That is, when viewed from the light transmitting layer side, the concave portion (groove) of the guide groove is formed at the portion of the phase change recording film.
In order to make the width between the protrusion and the land (land) a desired ratio, it is necessary to manufacture a stamper in anticipation of the change in the groove duty in advance. That is, when recording is performed on a groove, the groove width becomes narrow due to the formation of the reflection film and the phase change recording film. Therefore, it is necessary to select the gap between the transfer grooves of the stamper beforehand to form the guide groove. It is.

When a signal is recorded on both the land and the groove, the crosstalk of the signal is λ (1 + 2
m) / 8 (where m is 0 or a natural number) is the minimum,
It has been confirmed that the deeper the groove between the land and the groove, the smaller the effect of cross-erase. Therefore, considering the ease of forming the substrate and the like, λ / 8 or 3λ / 8 is practical to satisfy both characteristics. For example, when signals are recorded on both the land and the groove by the phase change method, in order to secure 50% of the land and the groove duty in the phase change recording film portion, the signal is recorded on the substrate as viewed from the light transmitting layer side. The duty of the groove (concave portion) is set to 58 to 3 depending on the groove depth λ / 8 or 3λ / 8.
It is necessary to set it to about 65% or 65 to 75%.

FIG. 5 is a signal characteristic curve diagram when the present invention is applied to a phase change recording disk. Curve 110 is
The measurement result of the relationship between the groove duty (%) and the jitter value (%) when a signal is recorded in the groove is shown. As shown in FIG. 5, the groove duty (%)
Is 58 or more, it can be seen that the jitter can be reduced.
On the other hand, when the groove duty (%) exceeds 65 (%), interference (crosstalk) of recording signals on adjacent tracks increases, and signal quality deteriorates. Therefore, it is desired that the groove duty (%) is set to 58 to 65 (%).

FIG. 6 is a measurement curve diagram showing the relationship between the groove duty and the signal level when signals are recorded on both lands and grooves when the present invention is applied to a phase change recording disk. It is. The curves 120 and 121 in FIG. 6 represent the groove duty (%).
And measurement results of the relationship between the signal level of the land portion and the signal level of the groove signal.

As shown in FIG. 6, the depth of the groove (1 /
8) When λ is set, the groove duty (%) is 6
It can be seen that the signal level balance between the groove and the land is almost balanced at about 0%. From FIG. 6, when the groove duty (%) is in the range of 58 to 65 (%),
It can be seen that the balance between the signal levels of the groove and the land is almost balanced, indicating that the condition is good.

In the optical disk of the present invention described above,
In order to read or record information from the light-transmitting layer formed on the opposite side of the support, that is, the substrate, in the example shown below, the optical disk of the present invention uses a guide groove on the substrate 201 as shown in FIG. The reflective film 20 is formed on the
3. It is assumed that the first dielectric layer 301, the phase change recording film 204, the second dielectric layer 302, and the light transmission layer 205 are formed thereon.

As shown in FIG. 7, in each of the layers constituting the optical disk, the reflection film 203 is made of Al or Al alloy by ion beam sputtering to a thickness of 50 to 200 nm.
The first dielectric layer 301 is formed, for example, of ZnS and Si
Formed to a thickness of 10 to 30 nm using a mixture of O ₂ ,
The phase-change type recording film 204 is made of, for example, GeSbTe.
The second dielectric layer 302 is formed to a thickness of 0 to 30 nm.
Is 50 to ₂ using, for example, a mixture of ZnS and SiO2.
It can be formed to a thickness of 00 nm. Note that Au can be used for the reflective film 203, and in this case, DC
It is formed to a thickness of 50 to 120 nm by (direct current) sputtering.

As the first and second dielectric layers 301 and 302, metals such as Al and Si, and nitrides, oxides and sulfides of metalloid elements can also be used. For example, AlN, Si ₃ N ₄ , SiO ₂ , Al ₂ O ₃ , Z
nS, MgF ₂ or the like can be used. However, the condition is that there is no absorption in the semiconductor laser wavelength region.

In a conventional phase change type optical disc, a thickness of at most 1 is provided between a phase change type recording film and a guide groove on a substrate.
Since only a 00 nm dielectric layer is formed,
The structure of the guide groove is faithfully reflected on the recording film.

However, in the optical disk of the present invention, a reflection film 203 having a thickness of, for example, about 200 nm and a first dielectric layer 301 are provided between the phase-change recording film 204 and the guide groove 202 on the substrate 201. Because of the thickness,
It is difficult to reflect the structure of the guide groove 202 on the substrate 201 on the phase-change recording film while keeping the shape as it is. In particular, the surface properties of the substrate 201 affect the crystallinity of the reflective film 203, and the shape of the interface formed by the particle size depending on the composition of the reflective film 203 further affects the properties of the phase-change recording film 204. It is known to have an effect.

Therefore, the reflective film 203 constituting the optical disk of the present invention is formed by depositing Al to a thickness of 50 to 200 nm by ion beam sputtering, using Au, 0.5 wt% to 10 wt%, Particularly preferably 3.0% by weight
Al alloy containing not less than 10 wt% Ti or A containing 0.5 wt% to 10 wt% Cr
An alloy is formed by a DC sputtering method. As a result, an optical disk having excellent signal characteristics can be manufactured.

FIG. 8 shows the measurement results of the relationship between the number of signal rewrites and the jitter value when the Al reflective film was formed by ion beam sputtering or DC sputtering. Curve 61 in FIG. 8 shows that Al is formed as a reflective film to a thickness of 100 nm using ion beam sputtering.
When a film having a thickness of 150 nm is formed on the curve 62, the curve 63
3 shows the measurement results of the relationship between the number of signal rewrites and the jitter value (%) in each case where Al was formed to a thickness of 150 nm by the DC sputtering method. As shown in FIG. 8, when the reflection film is formed by using the ion beam sputtering method, the overwrite jitter of the phase-change disk can be maintained at 15% or less up to about 10,000 rewrites. . That is, the quality can be guaranteed up to the number of rewritable times of these optical discs of about 10,000. When the reflection film of the phase change disc is formed of Al, the ion beam sputtering method is used instead of the DC sputtering method. By doing so, a disk having excellent characteristics can be manufactured.

FIG. 9 shows the measurement results of the relationship between the number of signal rewrites and the jitter value when Au was formed as a reflective film by the DC sputtering method. In FIG. 9, curves 71, 72, 7
No. 3 shows that Au was 60 nm by DC sputtering, and 9
This is a case where the film is formed to a thickness of 0 nm or 120 nm.

As shown in FIG. 9, when Au is used as the reflection film, the overwrite jitter of the phase-change disk can be maintained at 15% or less, up to about 10,000 rewrites. Curves 71, 72 and 73 in FIG.
Compared with the result shown by, and the result when Al shown by the curve 63 in FIG. 8 was formed by the DC sputtering method,
It can be seen that Au is more suitable as a reflective film than Al.

FIG. 10 shows that when Al was formed as a reflective film by DC sputtering (curve 81), an alloy containing 0.5% by weight or more and 10% by weight or less of Ti in Al was used.
When the film is formed by the sputtering method (curve 82), when Al is formed by the ion beam sputtering method (curve 83)
Shows the relationship between the recording frequency (MHz) and the carrier-to-noise ratio (C / N) in each case.

As shown in FIG. 10, curves 81 and 83
In comparison, when the reflective film was formed by the ion beam sputtering method, the carrier-to-noise ratio (C / N) was improved compared to when the film was formed by the DC sputtering method, and good results were obtained. Recognize. Curves 81 and 82
It can be seen that better results can be obtained when the reflective film is formed of an alloy of Al and Ti than when the reflective film is formed of Al alone. Comparing the curve 82 and the curve 83, when a reflective film is formed by a DC sputtering method using an alloy containing 0.5% by weight or more and 10% by weight or less of Ti in Al, Al is used. It can be seen that excellent results similar to those obtained when a reflective film was formed by ion beam sputtering can be obtained.

In the case where the reflective film is formed of an alloy containing 0.5% by weight or more and 10% by weight or less of Cr instead of Ti in the above Al alloy, the reflective film is formed of an alloy of Al and Ti. Good results are obtained as in the case of the above.

On the other hand, FIG. 11 shows the relationship between the Ti concentration (% by weight) of the Al alloy and the reflectance of the reflective film made of the Al alloy. According to FIG. 11, the Al alloy Ti
If the concentration (% by weight) exceeds 10% by weight, the reflectance of the reflective film decreases to 72% or less, and a sufficient signal cannot be obtained. Accordingly, the Ti concentration (% by weight) of the Al alloy needs to be 0.5% by weight or more and 10% by weight or less.

In the phase-change type optical disk having the structure shown in FIG.
μm, groove width 0.35 μm, groove depth about 53n
A reflective film 203 shown below is formed on a 1.2 mm thick polycarbonate substrate mastered under the condition of m, and ZnS and Si of 18 nm thick are formed on the reflective film 203.
A first dielectric layer 301 of a mixture of O ₂ was deposited. Furthermore the GeSbTe alloy having a thickness of 24nm was deposited and formed as a phase-change recording film 204 on top of this, deposits a second dielectric layer 302 made of a thick mixture 100nm of ZnS and SiO ₂ on top of this Formed. Then, a light-transmitting layer 205 having a thickness of 100 μm was formed on this by using polycarbonate.

In the above optical disk, the reflection film 20
As No. 3, a structure in which Al was formed to a thickness of 60 nm by ion beam sputtering was manufactured. Then, under the conditions of a recording laser power of 6 mW, an erasing laser power of 2.7 mW, a reproducing laser power of 0.5 mW, and a linear velocity of 2.86 m / s, an information signal was recorded in a groove while changing the bit length, and reproduction was performed. In FIG. 12, curve 21
0 is the recording frequency (MHz) under the conditions described above,
The relationship with the carrier noise ratio (C / N) is shown. As shown in FIG. 12, when Al was formed as the reflective film by the ion beam sputtering method, good signal characteristics were obtained.

Further, in the above-mentioned optical disk, a structure was prepared in which Au was formed as the reflective film 203 to a thickness of 60 nm by the DC sputtering method. And
Recording laser power 6mW, erase laser power 2.7
mW, reproducing laser power 0.5 mW, linear velocity 2.86
Under the condition of m / s, the information signal was recorded in the groove while changing the bit length, and reproduction was performed. In FIG. 13, a curve 211 indicates a relationship between the recording frequency (MHz) and the carrier noise ratio (C / N) under the above-described conditions. As shown in FIG.
When Au was formed as a reflective film by the DC sputtering method, good signal characteristics were obtained.

Further, in the above-mentioned optical disk, a reflective film 203 having a structure in which an alloy containing 97% by weight of Al and 3% by weight of Ti was formed to a thickness of 60 nm by DC sputtering was manufactured. Then, under the conditions of a recording laser power of 6 mW, an erasing laser power of 2.7 mW, a reproducing laser power of 0.5 mW, and a linear velocity of 2.86 m / s,
The information signal was recorded on the groove while changing the bit length, and the information was reproduced. In FIG. 14, a curve 212 indicates a relationship between the recording frequency (MHz) and the carrier noise ratio (C / N) under the above-described conditions. As shown in FIG.
In the case where an alloy containing 97% by weight and 3% by weight of Ti was formed by DC sputtering, good signal characteristics were obtained.

On the other hand, as a comparative example, an optical disk having the above-described optical disk and having a configuration in which Al alone was formed as the reflective film 203 to a thickness of 60 nm by DC sputtering was manufactured. The recording laser power is 6 mW, the erasing laser power is 2.7 mW, and the reproducing laser power is 0.5 m
Under the conditions of W and a linear velocity of 2.86 m / s, an information signal was recorded in a groove while changing the bit length, and reproduction was performed. FIG.
The curve 213 shows the relationship between the recording frequency (MHz) and the carrier-to-noise ratio (C / N) under the above conditions. As shown in FIG. 15, when Al was formed as the reflective film by the DC sputtering method, as can be seen from FIG. 10, noise increased and good signal characteristics could not be obtained.

As can be seen from FIGS. 12 to 15, in the optical disc of the present invention, when Al is formed by an ion beam sputtering method, when Au is formed by a DC sputtering method, 97 wt% Ti It can be seen that good signal characteristics can be obtained when an alloy containing 3% by weight is formed by DC sputtering, but good signal characteristics cannot be obtained when Al is formed by DC sputtering. Further, when a reflective film is formed by a DC sputtering method using Au or an alloy of Al and Ti, the cost can be reduced as compared with the ion beam sputtering method.

A case of manufacturing an optical disk as an example of the optical recording medium of the present invention will be described with reference to the drawings.
In this case, as shown in FIG. 16, the substrate 10 needs to have a certain degree of rigidity when a disk is formed of a single plate, and therefore it is preferable that the thickness is about 0.6 mm or more. In addition, as shown in FIG. 22, when an optical recording medium having a structure in which two substrates are bonded to each other is manufactured, it is preferable that the thickness is about 0.3 mm, which is half of that.

Next, an information signal portion 11 made of a phase-change recording film or a reflection film is formed on the guide groove of the substrate 10. For example, when the optical disk is a ROM, a reflective film such as Al is formed to a thickness of 20 to 60 nm.

The phase-change recording film can be formed of chalcogenite, that is, a chalcogen compound or a simple chalcogen. For example, Te, Se alone, GeTe, Sb ₂ Te ₃ , Sb ₂ Se ₃ , Ge
Sb ₂ Te ₄ , GeSb ₄ Te ₇ , Ge ₂ Sb ₂ T
e ₅ , GeSbTeSe, InSbTe, AgInSb
Te, TeO _X, can be used chalcogenide-based material such as InSe, to the guide on the groove, after forming the reflection film of the Al film or the like is formed on the reflective film.

The optical disk of the present invention has a configuration in which recording and reproduction light is irradiated from the surface opposite to the substrate 10 through the recording and reproduction objective lens L. Therefore, as shown in FIG. A light transmitting layer 12 is formed on the film 11 using an ultraviolet curable resin. The light transmitting layer 12 can be formed by, for example, drop-rotating and stretching an ultraviolet-curable resin on the above-described film-forming surface on the substrate, followed by photo-curing. The viscosity of the ultraviolet curable resin is 300 cps
More than 6000 cps or less is suitable for forming the light transmitting layer 12 having the thickness described above. For example, 25
When an ultraviolet curable resin having a viscosity of 5800 cps at 5 ° C. is applied, after the ultraviolet curable resin is dropped on the substrate,
By rotating the substrate at 2000 rpm for 11 seconds, the light transmitting layer 12 can be finally formed to about 100 μm.

Here, when forming the light transmitting layer 12, the substrate 10
When an ultraviolet curable resin is dropped at an inner peripheral portion, for example, at a position having a radius of 25 mm, and is rotated and stretched, a difference in inner and outer peripheral thicknesses is generated due to a relationship between centrifugal force and viscous resistance. This amount is 30 μm or more, and cannot satisfy the described thickness range.

In order to avoid this, when the ultraviolet curable resin is dropped, the ultraviolet curable resin is dropped from the center of the substrate 10 while the center hole 13 of the substrate 10 is filled with some means. It is effective to do. For example, a sheet of polycarbonate having a thickness of 0.1 mm is Φ30 mm in diameter.
After processing into a circular shape of mm and adhering to the central hole 13 portion, ultraviolet curable resin is dropped, rotational stretching is performed, and the ultraviolet curable resin is cured by irradiating ultraviolet rays, and then the central hole 13 is punched out again. According to this method, the difference between the inner and outer circumferences is 10 μm (p−
A thickness within p) can be achieved.

When the light transmitting layer 12 is formed, it is conceivable that the light transmissive layer 12 protrudes from the outermost periphery of the optical disc. Therefore, the diameter of this optical disc is set to 120 mm + 5 mm as the maximum value based on the diameter of a CD (120 mm). It is desirable to keep.

As shown in FIG. 18, the light transmitting layer 12 can also be formed by bonding a polycarbonate sheet 14 having a thickness of, for example, 100 μm onto the substrate 10 via an ultraviolet curable resin 15. it can. In this case, the thickness unevenness of the sheet 14 and the ultraviolet curable resin 1 for adhesion are used.
5, the thickness unevenness of the light transmitting layer 12 formed by the substrate 1
The sheet 14 processed to the same diameter as 0 is placed on the substrate 10 via the UV-curable resin 15 for bonding, and the sheet 14 is weighted with the UV-curable resin 15 and is rotationally stretched so that the total thickness becomes 10 μm. can do.

The present invention relates to a multi-layer structure in which a second information recording layer 18 is formed via an intermediate layer 16 on a first information recording layer 17 formed by injection molding of a substrate 10 as shown in FIG. The present invention can also be applied to an optical disk having a structure.

In the optical disk having the above-described structure, skew is easily generated. In order to reduce the skew, as shown in FIG. 20, an ultraviolet curable resin may be applied as a skew correction member 19 on the surface of the substrate 10 opposite to the light transmitting layer 12. The skew correction member 19 may use the same material as the light transmission layer 12, or may use a material having a higher curing shrinkage than the material of the light transmission layer 12.

In order to record / reproduce an optical recording medium having a high recording density, a high N.D. A. A pickup having an objective lens is required. In this case, it is necessary to make the distance between the objective lens and the light transmitting layer surface (hereinafter referred to as WD) narrower than the conventional distance. However, in this case, it is expected that the objective lens collides with and damages the light transmitting layer surface.

In order to prevent this, as shown in FIG. 21, the protective transparent layer 2 having a pencil hardness of H or more is formed on the light transmitting layer 12.
It is effective to adopt a configuration in which 0 is applied. Further, when the light transmitting layer 12 is thin, it is liable to be affected by dust, and in order to avoid this, it is effective to provide the protective transparent layer 20 with an antistatic function.

The present invention has a structure in which not only a single-plate structure but also two substrates 51 and 52 each having a half thickness of a finally obtained substrate 50 are bonded as shown in FIG. Is also good.

As shown in FIG. 23, one substrate 5
0 may have a signal recording layer and a light transmitting layer 12 on both sides.

The optical recording medium of the present invention is not limited to the above-mentioned manufacturing method, but can be manufactured by the following manufacturing method. As shown in FIG. 24A, a thickness of 100 μm extruded or cast
A m-polycarbonate sheet 40 is prepared, and pressed against a stamper 41 heated to a temperature higher than the glass transition point and a roller 42 by applying a pressure of, for example, 280 kgf.

After the above-described operation, by processing into a predetermined size, as shown in FIG. 24B, a thin substrate 43 in which the pits or guide grooves of the stamper 41 are transferred to the sheet 40 can be manufactured.

Subsequently, a phase change recording film or a reflection film is formed on the guide groove by the same steps as in the above-described manufacturing method.

Then, on a disk-shaped transparent substrate 50 having a thickness of, for example, 1.1 mm separately formed by injection molding,
The ultraviolet curable resin is dropped, the thin substrate 43 is placed and pressed, and the substrate is bonded by irradiating ultraviolet rays from the transparent substrate 50 side, as shown in FIGS. 24C, D and E, respectively. An optical recording medium having a multilayer recording layer can be formed.

Next, the depth of pits or grooves formed on the substrate will be described. Hereinafter, the refractive index of the light transmission layer is set to N. The depth of the pit or groove at which the maximum modulation is obtained is (λ / 4) / N, and the ROM or the like is set to this depth.

In the case of obtaining a tracking error signal by push-pull in groove recording or land recording, the push-pull signal becomes maximum when the depth of the pit or land is (λ / 8) / N.

Further, when recording is performed on both the land and the groove, the groove depth should take into consideration the characteristics of the servo signal as well as the characteristics of crosstalk and cross-erase. / 6) / N ~
(Λ / 3) / N is minimized, and it is confirmed that deeper cross erase has less influence. In addition, in consideration of the groove inclination and the like, when trying to satisfy both characteristics, (3
λ / 8) / N is optimal. The high-density optical recording medium of the present invention can be applied within the above-described depth range.

Next, at the high N.P. A. An example of realizing is described. FIG. A. 1 shows a configuration of a lens of an optical disc device for realizing the above. The optical disk device shown in FIG. 25 has a laser light source having a wavelength of 680 nm.

In this optical disk device, a second lens 32 is disposed between the first lens 31 and the disk 21. As described above, by adopting the two-group lens configuration, the N.D.
A. Can be set to 0.7 or more, and the distance (WD) between the first surface 32a of the second lens 32 and the surface of the disk 21 can be reduced. Further, it is desirable that the first surface 31a, the second surface 31b, the third surface 32a, and the fourth surface 32b of the first lens 31 and the second lens 32 have an aspheric shape, respectively. By using this two-group lens, high-density recording and reproduction of the optical recording medium described above can be performed.

[0080]

According to the present invention, the capacity of the recording signal is 8G.
A phase-change type optical recording medium B was obtained.

Further, according to the present invention, a phase-change type optical recording medium having excellent characteristics could be obtained by adjusting the composition of the reflection film and the film formation method.

Further, according to the present invention, by adjusting the duty of the concave portion of the guide groove on the substrate, even when a phase-change film or a reflective film is formed on the guide groove, when viewed from the side of the light transmitting layer. Thus, an optical recording medium was obtained in which the width of the concave portion (groove) and the convex portion (land) of the guide groove was formed at a desired ratio in the phase change recording film.

According to the present invention, it is possible to increase the recording capacity as compared with the conventional one while using a simple recording / reproducing apparatus.

[Brief description of the drawings]

FIG. 1 shows experimental data on a change in a jitter value due to a thickness error of a substrate.

FIG. 2 is a schematic sectional view of a main part of an optical disk according to an example of the present invention.

FIG. 3 shows a guide groove structure of a recordable optical disk.

FIG. 4 shows a guide groove structure of a recordable optical disk.

FIG. 5 shows a relationship between a groove duty and a jitter value.

FIG. 6 shows a relationship between a groove duty and a signal level.

FIG. 7 is a schematic sectional view of a main part of an optical disk according to an example of the present invention.

FIG. 8 shows the relationship between the number of rewrites and the jitter value.

FIG. 9 shows the relationship between the number of rewrites and the jitter value.

FIG. 10 shows a recording frequency (MHz) and a carrier-to-noise ratio (C).
/ N).

FIG. 11 shows the relationship between the concentration (% by weight) of Ti in an Al alloy and the reflectance of a reflective film.

FIG. 12 shows a recording frequency (MHz) and a carrier noise ratio (C).
/ N).

FIG. 13 shows a recording frequency (MHz) and a carrier noise ratio (C).
/ N).

FIG. 14 shows a recording frequency (MHz) and a carrier noise ratio (C).
/ N).

FIG. 15 shows a recording frequency (MHz) and a carrier noise ratio (C).
/ N).

FIG. 16 shows a schematic diagram of an optical recording medium of the present invention.

FIG. 17 shows a schematic diagram of the optical recording medium of the present invention.

FIG. 18 is a schematic view showing another example of the optical recording medium of the present invention.

FIG. 19 is a schematic view of another example of the optical recording medium of the present invention having a two-layer structure.

FIG. 20 is a schematic view of another example of the optical recording medium of the present invention.

FIG. 21 is a schematic view showing another example of the optical recording medium of the present invention.

FIG. 22 is a schematic view of another example of the optical recording medium of the present invention having a two-layer structure.

FIG. 23 is a schematic view of an optical recording medium having a structure in which information recording layers are formed on both surfaces of a substrate of another example of the optical recording medium of the present invention.

FIG. 24A is a view showing a manufacturing step of an example of the optical recording medium of the present invention. B shows a manufacturing process diagram of an example of the optical recording medium of the present invention. C shows a process drawing of an example of the optical recording medium of the present invention. D shows a process drawing of an example of the optical recording medium of the present invention. E shows a process drawing of an example of the optical recording medium of the present invention.

FIG. 25 is a schematic view of a two-unit lens used in an optical system for recording and reproducing an optical disk to which the present invention is applied.

[Explanation of symbols]

10, 50, 51, 52, 201 ... substrate, 11 ... information signal part, 12, 205 ... light transmitting layer, 13 ... Heart hole, 14 ...
Sheet, 15: UV curable resin, 16: Intermediate layer, 17
... first information recording layer, 18 ... second information recording layer, 19 ...
Skew correction member, 20: protective transparent layer, 21: optical disk, 31: first lens, 32: second lens, 40 ...
Polycarbonate sheet, 41 stamper, 42 roller, 43 thin substrate, 101 groove, 102
Land, 103: track pitch, 202: guide groove, 2
03: reflection film, 204: phase change type recording film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masahiko Kaneko 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Mitsuo Naito 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Motohiro Furuki 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (12)

[Claims] 1. A thermoplastic resin, comprising 0.3 to 1.2.
mm, a guide groove on the support, and, on the guide groove, at least a reflective film and a recording area composed of a phase-change recording film. A light transmitting layer having a thickness of 3 to 177 μm is formed. When the thickness unevenness of the light transmitting layer is represented by Δt, reproduction,
Alternatively, the N.V. A. And between the wavelength λ, Δt ≦ ± 5.26 (λ / N.A. 4) (μm) (N.
A. An optical recording medium characterized by satisfying the following relationship: 2. The method according to claim 1, further comprising:
2. The optical recording medium according to claim 1, wherein a second dielectric layer is formed. 3. The reflection film is made of Al or an Al alloy,
2. The optical recording medium according to claim 1, wherein the optical recording medium is formed by ion beam sputtering. 4. The optical recording medium according to claim 1, wherein the reflection film is formed by depositing Au by a DC sputtering method. 5. The optical recording apparatus according to claim 1, wherein the reflection film is formed by depositing an Al alloy containing 0.5% by weight or more and 10% by weight or less of Cr by DC sputtering. Medium. 6. The optical recording apparatus according to claim 1, wherein the reflection film is formed by depositing an Al alloy containing 0.5% by weight or more and 10% by weight or less of Ti by a direct current sputtering method. Medium. 7. The optical recording apparatus according to claim 1, wherein the reflection film is formed by depositing an Al alloy containing Ti in an amount of 3.0% by weight or more and 10% by weight or less by a DC sputtering method. Medium. 8. The reflection film is made of Al or an Al alloy,
The first dielectric layer is formed by depositing a mixture of ZnS and SiO ₂ to a thickness of 10 to 30 nm by ion beam sputtering. The phase-change recording film is made of GeSbTe by 10 to 30 n.
The second dielectric layer is formed by depositing a mixture of ZnS and SiO ₂ to a thickness of 50 to 200 nm. The optical recording medium as described in the above. 9. The reflection film is formed by depositing Au to a thickness of 50 to 120 nm by a DC sputtering method, and the first dielectric layer is formed by mixing a mixture of ZnS and SiO ₂ with 10 μm. The phase-change recording film is formed of GeSbTe by 10 to 30 nm.
The second dielectric layer is formed by depositing a mixture of ZnS and SiO ₂ to a thickness of 50 to 200 nm. The optical recording medium as described in the above. 10. The recording / reproducing of a signal is performed only in the groove, and the duty of the concave portion is 58 to 65% when the guide groove formed on the support is viewed from the light transmitting layer side. The optical recording medium according to claim 1, wherein: 11. Recording and reproduction of a signal on both the land and the groove are performed. When the guide groove formed on the support is viewed from the light transmitting layer side, the duty of the concave portion is 58 to 75%. The optical recording medium according to claim 1, wherein 12. A thermoplastic resin, comprising 0.3 to 1.
A support having a thickness of 2 mm, a guide groove on the support,
On the guide groove, a recording area comprising at least a reflective film and a phase change type recording film, and a light transmitting layer are sequentially provided, and the thickness of the light transmitting layer is 3 to 177 μm in at least the recording area. An optical disk device for recording or recording / reproducing an optical disk having a wavelength of 680n
m or less, and a laser beam source for focusing laser light on the optical disk signal recording surface. A. An optical disk device comprising: a lens having a size of 0.7 or more.