JP3076585B2 - Optical information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications]

The present invention relates to a so-called on-land recording type optical information recording medium, and more particularly to the shape and dimensions of a guide groove formed in a transparent substrate.

[0002]

[Prior art]

The applicant of the present application has previously disclosed at least a transparent substrate having a V-shaped guide groove, a transparent film having a refractive index larger than that of the transparent substrate, and a magnetic film provided on the transparent film. When information is recorded between the guide grooves and the wavelength of the reproduction light is λ, the depth of the V-shaped groove is λ / 6.
We have proposed a magneto-optical disk which is shallower and deeper than λ / 8 (Japanese Patent Laid-Open No. 63-225945). As reproduction light,
At present, semiconductor lasers having a wavelength of 830 nm are widely used. Therefore, in the magneto-optical recording medium applied to the magneto-optical recording medium driving device on which the semiconductor laser is mounted, the depth of the guide groove is formed to be about 104 to 140 nm.

In this magneto-optical disk, since the guide groove has a V-shape, a high-quality reproduction signal can be obtained when information is recorded on a flat portion (land portion) between the grooves.

Further, the depth of the guide groove is set to be smaller than 1/6 of the wavelength of the reproduction light and
When the reflected light from the magneto-optical disk is detected by the ball-type photodetector, | D ₁ −D ₂ | / (D ₁ + D ₂ ) (where D ₁ and D ₂ are the light detection The output of the element), the modulation of the tracking signal is maximized,
Stable tracking can be performed.

[0005]

[Problems to be solved by the invention]

Incidentally, as a tracking signal detection method for the optical information recording medium, there is a push-pull method using a two-division detector in addition to the method using the above-mentioned ball type photodetector.

In the push-pull method, reflected light from an optical information recording medium is detected by a two-segment photodetector, and the intensity of the reflected light detected by a first photodetector constituting the two-segment detector is determined by I. ₁ , when the intensity of the reflected light detected by the second photodetector is I ₂ and the intensity of the reflection from the mirror surface (flat portion of the optical information recording medium) is I ₀ , | I ₁ −I ₂ | / I _{In this} method, tracking is performed using a signal (push-pull signal) defined by ₀ as a tracking signal.

When the push-pull tracking signal detection method is used, in order to prevent a tracking error,
The magnitude of the push-pull signal needs to be within the range of 0.4 ≦ | I ₁ −I ₂ | / I ₀ ≦ 0.65 when using a standard drive equipped with a two-part detector.

The push-pull signal varies depending on the width and depth of the guide groove. However, in the conventional optical information recording medium described above, since the width dimension of the guide groove is not regulated, when the push-pull tracking signal detection method is applied,
In some cases, the predetermined push-pull signal cannot be obtained, and stable tracking characteristics cannot be obtained.

Conventionally, a magneto-optical recording medium driving device irradiates linearly polarized light with a polarization plane of recording / reproducing laser light parallel to a guide groove, and a polarization device of recording / reproducing laser light. There are those that irradiate linearly polarized light with the surface oriented perpendicular to the guide groove, but the magnitude of the push-pull signal varies depending on the direction of the polarization plane with respect to the guide groove, so when mounted on any of the driving devices, Even when the optical information recording medium has obtained a predetermined push-pull signal, the predetermined push-pull signal may not be obtained when the optical information recording medium is mounted on the other drive device.

Further, conventionally known optical information recording media include:
In addition to a magneto-optical recording medium, there is a type in which a phase-change optical recording film is laminated on a transparent substrate via a transparent intermediate film having a higher refractive index than the transparent substrate. Fluctuates, but it is necessary to obtain the predetermined push-pull signal for any optical information recording medium.

Therefore, an object of the present invention is to provide a driving device having a push-pull type tracking signal detecting means, which is capable of performing a predetermined push-pull operation even when the driving device is attached to any driving device having a different linear polarization direction with respect to the guide groove. An object of the present invention is to provide a magneto-optical recording medium and a phase-change optical information recording medium that can obtain a signal and can obtain stable tracking characteristics.

[0012]

[Means for Solving the Problems]

In order to achieve the above object, the present invention relates to an on-land recording type optical information recording method comprising forming a prepit array between adjacent guide grooves at an interval of 1.0 μm or more and 2.0 μm or less for a magneto-optical recording medium. A medium, wherein the guide groove has a substantially V-shaped cross-sectional shape, and a transparent substrate having a refractive index larger than that of the transparent substrate on the transparent substrate on which the guide groove and the prepit row are formed. In the case where a magneto-optical recording film is laminated via an intermediate film, the wavelength of the laser beam used for recording / reproducing information is λ, the numerical aperture of the pickup lens of the optical head is NA, and the refractive index of the transparent intermediate film is n.
(N; 1.8 to 2.3), the width W of the guide groove is λ / (3.3 · NA) ≦ W ≦ λ / (2.8 ·
NA), the depth d of the guide groove is set to λ / 7.3n ≦ d ≦ λ / 4.0n, and when the polarization plane of the laser light that is linearly polarized light is directed parallel to the guide groove, A predetermined push-pull signal can be obtained even when oriented perpendicular to the guide groove. Further, for the phase change type recording medium, 1.0 μm or more and 2.0 μm or more
An on-land recording type optical information recording medium in which a pre-pit row is formed between adjacent guide grooves at intervals of not more than μm, wherein the guide grooves have a substantially V-shaped cross-sectional shape,
And a phase-change recording film laminated on a transparent substrate on which the guide grooves and the pre-pit rows are formed via a transparent intermediate film having a refractive index larger than that of the transparent substrate. The wavelength of the laser beam used for recording / reproduction is λ, and the numerical aperture of the pickup lens of the optical head is N
A, where n is the refractive index of the transparent intermediate film, the width W of the guide groove is λ / (3.3 · NA) ≦ W ≦ λ / (2.8 ·
NA), the depth d of the guide groove is set to λ / 7.3n ≦ d ≦ λ / 4.0n, and when the polarization plane of the laser light that is linearly polarized light is directed parallel to the guide groove, A predetermined push-pull signal can be obtained even when oriented perpendicular to the guide groove.

[0013]

[Action]

The push-pull signal shows a maximum value at a substantially constant groove depth regardless of the width of the guide groove and the direction of the polarization plane, and the value increases as the groove width increases. Further, when the polarization plane is oriented parallel to the guide groove, the maximum value of the push-pull signal increases as compared with the case where the polarization plane is oriented perpendicular to the guide groove.

Also in the case of circularly polarized light, the maximum value of the push-pull signal increases as the groove width increases.

In addition, these characteristics indicate that at least the laser wavelength λ is 78
The same applies to the range of 0 to 830 nm and the lens NA of 0.5 to 0.6.If the laser wavelength is shortened to about 630 nm, and the diameter of the laser beam spot is reduced in response to the narrowing of the track pitch. In this case, a similar relationship is obtained.

Therefore, the predetermined push-pull signal can be obtained by regulating the groove width and the groove depth of the guide groove to the above values, and stable tracking characteristics can be obtained.

[0017]

【Example】

An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a magneto-optical disk according to an embodiment,
FIG. 2 is an enlarged cross-sectional view of the main part, and FIG. 3 is a tracking characteristic diagram.

As shown in FIG. 1, the magneto-optical disk according to the embodiment is formed in a disk shape having a center hole 1, and has a flat portion having a spiral centered on the center P of the center hole 1. Guide grooves 2 are formed, and pre-pit rows 3 are formed in a predetermined arrangement between adjacent guide grooves 2.

As shown in FIG. 2, this magneto-optical disk has two magneto-optical recording films 6 on the inside and two disk single plates 10 and 10 a bonded together via an adhesive layer 11 to form a double-sided recording type. It constitutes a magneto-optical disk. Each of the disk single plates 10 and 10a has a refractive index larger than the refractive index of the transparent substrate 4 on the concave and convex surface of the transparent substrate 4 in which the guide grooves 2 and the pre-pit rows 3 are preformatted in the form of irregularities. A first transparent film 5,
A magneto-optical recording film 6, a second transparent film 7 made of the same high refractive material as the first transparent film 5, a reflective film 8, and a protective film 9;
Are sequentially laminated.

The transparent substrate 4 is made of, for example, glass (having a refractive index of about 1.5)
Or, it is formed of a transparent resin material such as polycarbonate (having a refractive index of about 1.58) or polymethyl methacrylate (having a refractive index of about 1.5). The preformat patterns such as the guide grooves 2 and the prepit rows 3 can be formed directly on one surface of the transparent substrate 4 or can be transferred via an ultraviolet curable resin (having a refractive index of about 1.5).

As shown in FIG. 2, the guide groove 2 has a substantially V-shaped cross section, a track pitch p of 1.6 μm, an optical pickup having a laser wavelength of 830 nm and a lens NA of 0.53. Is used, the groove width W of the opening is adjusted to 510 ± 30 nm. Also, the groove depth d from the opening to the bottom
Is adjusted to 88 ± 12 nm. However, since the optical information recording medium is generally copied many times from one die (stamper), the groove width W and the groove depth d of the guide groove 2 have a variation of about ± 5 nm. The above numerical values indicate the average value of the variation.

The guide groove 2 having a substantially V-shaped cross section is a general term for grooves in which the groove width gradually decreases from the opening to the bottom, and each corner has a rounded shape. Includes those where the slope from the opening to the bottom is not completely flat.

The first transparent film 5 and the second transparent film 7 multiple-reflect linearly polarized light incident from the transparent substrate 4 at the interface between the first transparent film 5 and the second transparent film 7 to increase the apparent Kerr rotation angle to increase the magneto-optical recording film. No. 6 improves the reproduction sensitivity, and is formed of a transparent material having a refractive index of about 2.0 to 2.3. Such transparent materials include, for example, silicon oxide (SiO), aluminum nitride (A
1N), zinc sulfide (ZnS), and other transparent dielectric materials that do not undergo thermal deformation due to the power of recording / reproducing light are used.

As the magneto-optical recording film 6, a known material such as a perpendicular magnetization film containing a transition metal and a rare earth metal as main components can be used.

The reflection film 8 reflects the transmitted light from the magneto-optical recording film 6 to the transparent substrate 4 side, and is formed of, for example, a metal film having a high reflectance such as aluminum.

The protective film 9 protects the magneto-optical recording film 6 from a corrosive atmosphere, and is formed of, for example, an ultraviolet curable resin.

As the adhesive 11, an epoxy resin, an ultraviolet curable resin, or the like is preferable.

FIG. 3 shows the relationship between the tracking signal read from the magneto-optical disk according to the embodiment and the width and depth of the guide groove 2. The tester used was a light source that emits linearly polarized light having a wavelength of 830 nm, an optical pickup with a lens numerical aperture (NA) of 0.53, and a two-segment photodetector.

The horizontal axis of the graph shows the depth of the guide groove 2 and the vertical axis shows the push-pull signal. The data when the plane of polarization of the linearly polarized light is oriented parallel to the extension direction of the guide groove is represented by ○. Mark and △
The data when the plane of polarization of the linearly polarized light is perpendicular to the guide groove is indicated by the mark and the mark.

As is apparent from this graph, the groove width is 510 ± 30n
m, the magneto-optical disk with a groove depth of 88 ± 12 nm, regardless of the direction of the polarization plane, shows that the push-pull signal and the track cross signal all satisfy the specified specifications, and a sufficiently large value is obtained. .

When a phase change type recording film is formed instead of the magneto-optical recording film 6, the groove width W and the groove depth d of the guide groove 2 are set to be the same as those of the optical information recording medium of the embodiment. By,
A predetermined push-pull signal can be obtained, and stable tracking characteristics can be obtained.

Hereinafter, as a comparative example, an optical information recording medium in which a write-once recording film is formed on a transparent substrate via a thermally deformable base film having a refractive index substantially equal to the refractive index of the transparent substrate,
An optical information recording medium in which a recording film made of an organic dye material or the like is directly spin-coated on a transparent substrate will be described. FIG. 4 is a sectional view of an optical disk according to a first comparative example, and FIG.
The figure is an enlarged sectional view of the main part, and FIG. 6 is the tracking characteristic diagram.

As shown in FIG. 4, this optical disc has a recording film on the inside, and two discs 10 and 10 a are bonded together via an inner peripheral spacer 21 and an outer peripheral spacer 22. Optical disk. Single disk 10,10a
As shown in more detail in FIG. 5, a heat-deformable base film 23 having a refractive index substantially equal to that of the transparent substrate 4, such as nitrocellulose or polytetrafluoroethylene, is formed on the uneven surface of the transparent substrate 4. Is deposited on the base film 23,
For example, it is formed by laminating a write-once recording film 24 mainly containing tellurium and selenium.

In the optical disk of the present embodiment, the groove width W of the opening of the guide groove 2 provided in the transparent substrate 4 is adjusted to 500 ± 50 nm,
The groove depth d from the opening to the bottom is adjusted to 94 ± 12 nm.

The material and shape of the transparent substrate 4 are the same as those of the magneto-optical disk according to the embodiment.

FIG. 6 shows the relationship between the tracking signal read from the optical disc according to the first comparative example and the width and depth of the guide groove 2. The testing machine consists of a light source that emits circularly polarized light with a wavelength of 830 nm, an optical pickup with a lens numerical aperture (NA) of 0.53,
The one provided with a two-segment photodetector was used.

The horizontal axis of the graph shows the depth of the guide shaft 2 and the vertical axis shows the push-pull signal, and each data when the groove width of the guide groove 2 is changed is displayed.

As is clear from this graph, the optical disk of the first comparative example has a groove width W of the guide groove of 500 ± 50 nm and a groove depth d of 9
By setting it to 4 ± 12 nm, the push-pull signal can be adapted to a predetermined specification.

FIG. 7 is an enlarged sectional view of a main part of an optical disc according to a second comparative example.

As shown in FIG. 7, this optical disc has a double-sided recording type optical disc in which two single discs 10 and 10 a are bonded together with the recording film 25 inside through an adhesive layer 11. ing. Each of the disk single plates 10 and 10a is formed by directly spin-coating a recording film 25 made of an organic dye-based recording material or the like on the uneven surface of the transparent substrate 4.

In the second comparative example, the groove width W of the opening of the guide groove 2 formed in the transparent substrate 4 is adjusted to 500 ± 50 nm, and the groove depth d from the opening to the bottom is adjusted. It has been adjusted to 94 ± 12 nm.

In addition, the material and shape of the transparent substrate 4 are the same as those of the magneto-optical disk according to the embodiment.

The optical disc of the second comparative example is optically similar to the optical disc of the first comparative example, and exhibits the same tracking characteristics as shown in FIG. Therefore, the width W of the guide groove is set to 500
By setting the groove depth d to ± 50 nm and the groove depth d to 95 ± 12 nm, a predetermined push-pull signal can be obtained, and a stable tracking characteristic can be obtained.

Next, the optical information recording medium in which the track pitch of the guide groove is formed to 1.5 μm is mounted on a drive device having an optical system in which the wavelength of a laser beam is 780 nm and the lens NA of an optical pickup is 0.55. FIG. 8 shows the relationship between the size of the guide groove and the push-pull signal detected from the optical information recording medium. The structure of the optical information recording medium is the same as that of the optical information recording medium of the second embodiment except that the track pitch of the guide groove is narrow.

As shown in FIG. 8, in the case of this example, the groove width of the opening of the guide groove is adjusted to 450 ± 50 nm, and the groove depth from the opening of the guide groove to the bottom is 88 ± 12 nm. , A push-pull signal having a predetermined value can be obtained.

That is, even when the track pitch is narrowed and the diameter of the laser beam spot irradiated on the medium is reduced, the groove width W of the opening of the guide groove recessed in the transparent substrate is set to λ.
/(3.3·NA)≦W≦λ/(2.8·NA), and by setting the depth d of the guide groove to λ / 7.3n ≦ d ≦ λ / 4.0n,
Stable tracking characteristics can be obtained.

When the track pitch is reduced and the width of the guide groove is increased at the same time, a larger push-pull signal can be obtained. On the other hand, the land portion serving as the information track becomes narrower and the guide groove portion becomes narrower. Since a large amount of light enters the photodetector, the S / N ratio (signal-to-noise ratio) of the reproduced signal is reduced. Therefore, it is practically preferable to adjust the width of the guide groove to the above value.

Although the above embodiment has been described with reference to a double-sided recording type optical disk as an example, the same effect can be obtained with a single-sided recording type.

In the above embodiment, the case where the guide groove is formed in a spiral shape has been described as an example. However, the same effect can be obtained when the guide groove is formed in a concentric shape.

Further, in the present invention, the film structure (refractive index) on the light incident side of the recording film is a problem, and the film structure on the opposite side may be arbitrarily formed regardless of the above embodiment. Can be.

[0051]

【The invention's effect】

As described above, the optical information recording medium of the present invention optimizes the groove width and groove depth of the guide groove, so that even when the polarization plane of the linearly polarized laser light is directed parallel to the guide groove. ,
In addition, even when it is oriented perpendicular to the guide groove, a push-pull signal having a practically preferable value can be obtained, and stable tracking characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of an optical disc according to an embodiment.

FIG. 2 is an enlarged sectional view of a main part of the optical disc according to the embodiment.

FIG. 3 is a tracking characteristic diagram of the optical disc according to the example.

FIG. 4 is a sectional view of an optical disc according to a first comparative example.

FIG. 5 is an enlarged sectional view of a main part of an optical disc according to a first comparative example.

FIG. 6 is a tracking characteristic diagram of the optical disc according to the first comparative example.

FIG. 7 is an enlarged sectional view of a main part of an optical disc according to a second comparative example.

FIG. 8 is a tracking characteristic diagram when a guide groove is narrowed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Center hole 2 ... Guide groove 3 ... Prepit row 4 ... Transparent substrate 5 ... First transparent film 6 ... Magneto-optical recording film 6,7 ... Second transparent film 8 ... Reflective film 9: Protective film 10, 10a: Single disk 11: Adhesive layer

──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Sho Ito 1-280 Higashi Koikebo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-63-225945 (JP, A) JP-A-61-51631 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 7/24 G11B 11 / 105

Claims (2)

(57) [Claims] 1. An on-land recording type optical information recording medium in which a prepit array is formed between adjacent guide grooves at an interval of 1.0 μm or more and 2.0 μm or less, wherein a cross-sectional shape of the guide grooves is substantially equal. A magneto-optical recording film is formed on a transparent substrate formed in a V-shape and having the guide grooves and the prepit rows formed thereon, via a transparent intermediate film having a refractive index larger than that of the transparent substrate. The wavelength of the laser beam used for recording / reproducing information is λ, the numerical aperture of the pickup lens of the optical head is NA, and the refractive index of the transparent intermediate film is n.
(N; 1.8 to 2.3), the width W of the guide groove is λ / (3.3 · NA) ≦ W ≦ λ / (2.8 ·
NA), the depth d of the guide groove is set to λ / 7.3n ≦ d ≦ λ / 4.0n, and when the polarization plane of the laser light that is linearly polarized light is directed parallel to the guide groove, An optical information recording medium, wherein a predetermined push-pull signal is obtained even when the optical information recording medium is oriented perpendicular to the guide groove. 2. An on-land recording type optical information recording medium in which a prepit array is formed between adjacent guide grooves at an interval of 1.0 μm or more and 2.0 μm or less, wherein the cross-sectional shape of the guide grooves is substantially A phase-change recording film is laminated on a transparent substrate formed in a V-shape and having the guide groove and the pre-pit row formed thereon, with a transparent intermediate film having a refractive index larger than that of the transparent substrate. The wavelength of the laser beam used for recording / reproducing information is λ, the numerical aperture of the pickup lens of the optical head is NA, and the refractive index of the transparent intermediate film is n.
(N; 1.8 to 2.3), the width W of the guide groove is λ / (3.3 · NA) ≦ W ≦ λ / (2.8 ·
NA), the depth d of the guide groove is set to λ / 7.3n ≦ d ≦ λ / 4.0n, and when the polarization plane of the laser light that is linearly polarized light is directed parallel to the guide groove, An optical information recording medium, wherein a predetermined push-pull signal is obtained even when the optical information recording medium is oriented perpendicular to the guide groove.