JPS61248232A - Optical recording method and optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a reproduced S/N signal and the increase in a bit error rate by the influence of a guide track by reading out the information written into a recording layer by the 1st light beam and detecting a tracking error signal by the 2nd light beam. CONSTITUTION:The recording layer 13 is formed on a substrate 11 and a guide track base layer 16 and a filter layer 21 are formed thereon. The 1st and 2nd light beams having the wavelengths different from each other are irradiated from the guide track layer side. The layer 13 is formed of a material which reads out the recorded information by the wavelength of the light beam 101 for signal detection or permits further the recording thereof. The material which has the high transmittivity to the wavelength of the beam 101 and has the high reflectivity to the light of the beam 103 for detecting the tracking error is used for the filter layer 21. The groove shape of the guide track layer 15 is so set that the tracking error can be most efficiently detected by the wavelength of the beam 103.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording method and a recording medium in which information is read by irradiating a light beam while positioning using a guide track.

Optical recording media that reproduce information recorded on a recording layer by irradiating a light beam such as a laser beam are attracting attention. As such optical recording media, for example, magneto-optical disks and optical disks are known. A magneto-optical disk is a magnetic thin film that is perpendicularly magnetized and uses the thermal effect of light to write reversal magnetic domains to record information, and uses the magnetic optical effect to read the information. . Furthermore, optical disks record information by forming microscopic irregularities and micropatterns with different reflectances or transmittances on the surface, and these micropatterns are irradiated with a laser beam to read out information based on the difference in light intensity. .

In such optical recording media, when reading recorded information by irradiating a laser beam, or writing or erasing information using a laser beam, it is necessary to use a laser to accurately capture the irradiation position of the beam without error. A guide track is required to guide the beam. This point is especially important in high-density recording, and the guide track allows accurate positioning of minute recording patterns during reproduction, recording, and erasing.

Conventionally, guide tracks have been formed by using light interference, for example, by providing minute irregularities with a pitch of about 1.5 to 3 μm and a groove depth set to a light interference width of about 178λ.

FIG. 9 is a sectional view showing a conventional optical recording medium 10 with guide tracks, in which a recording layer 13 is formed on a substrate 11 on which group-shaped guide tracks are formed. However, in such optical recording media, the influence of the pregroove causes a decrease in the intensity of the reproduced signal and an increase in noise and pit error rate.

FIG. 10 shows an optical recording medium 10 in which a recording layer 13 is formed on a transparent substrate 11, and a guide track layer 15 is further formed thereon by a 2P method or the like.

However, in this case, it is difficult to focus and irradiate both the recording layer 13 and the guide track portion with one light beam.

Furthermore, when two light beams are used to irradiate each layer in a focused manner, the recording layer 13 needs to be a semi-transparent film, resulting in a decrease in efficiency.

The present invention can accurately and efficiently extract both the reproduced signal and the tracking error signal, and also prevents the influence of the guide track on the reproduced signal to improve the S/N ratio. An object of the present invention is to provide an optical recording method and an optical recording medium that can perform the following steps.

The optical recording method of the present invention irradiates an optical recording medium having a guide track layer and a recording layer stacked with first and second light beams having different wavelengths from the guide track layer side, The first light beam is transmitted through the guide track layer and reflected at or after passing through the recording layer, while the second light beam is reflected at the guided and rack portions of the guide track layer, and is reflected by the first light beam. It is characterized in that information written in the recording layer is read out and a tracking error signal is detected using a second light beam.

The optical recording medium of the present invention has a recording layer and a guide track layer laminated in sequence on a substrate, and a filter layer is formed in the guide track portion, and the filter layer reflects light in the part of the wavelength range. At the same time, the recording layer transmits light in some other wavelength ranges, and also reflects at least part of the light in some other wavelength ranges that passes through the filter layer and enters the recording layer. It is characterized by

Further, still another optical recording medium of the present invention has a reflective layer, a recording layer, and a guide track layer stacked one after another on a substrate, and a filter layer is formed in the guide track portion, and the filter layer is partially disposed in the guide track portion. The recording layer reflects light in a wavelength range and transmits light in a part of the other wavelength range, and the recording layer transmits light in a part of the other wavelength range that passes through the filter layer and enters the recording layer. Further, the reflective layer is characterized in that it reflects at least part of the light that passes through the recording layer.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram for explaining the optical recording method of the present invention, in which a recording layer 13 and a guide track layer 1 are provided on a substrate 11.
5 and the protective layer 17 are sequentially laminated to form the recording medium 10. Reading of information recorded on this recording medium is performed by combining two light beams, a signal detection light beam 101 and a tracking error detection light beam 103, which have different wavelengths. The signal detection light beam 101 is irradiated so as to be focused on the recording layer 13, while the tracking error detection light beam 103 is irradiated so as to be focused on the guide track portion of the guide track layer 15.

The signal detection light beam 101 passes through the protective layer 17 and the guide track layer 15 and is reflected by the recording layer 13, and is reflected by Kerr rotation if the recording medium is a magneto-optical recording medium or by reflection elasticity if it is an optical disk. , reading of recorded information is performed. Since the distance between the recording layer 13 and the guide track section is large, it is possible to prevent the deterioration of the S/N ratio of the reproduced signal and the increase in the pit error rate due to the influence of the guide track section. On the other hand, the tracking error detection light beam 103 passes through the protective layer 17 and is reflected by the guide track portion of the guide track layer 15 . In this way, in order to control the optical paths of the two light beams, the relationship between the wavelengths of the signal detection light beam and the tracking error detection light beam, as well as the spectral transmission (reflection) characteristics of the guide track layer and recording layer, must be determined. Adjustment is necessary. For example, if the spectral characteristics of the guide track layer have a transmission spectrum T and a reflection spectrum R as shown in FIG. λ, each of the above optical paths can be realized.

The protective layer 17 is one that transmits light of wavelengths λ and λ2, and the recording layer is one that reflects light of wavelength λ2.

Figure 3 shows information recording when using a magneto-optical disk.
It is a figure explaining a reproduction|regeneration and an erasing mechanism. Two light beams λ2 . λ, are made parallel by collimator lenses 33, 39, respectively. Further, the recording/reproducing beam λ2 is made into linearly polarized light through a polarizer 35 for reproduction. Two light beams λ2. λ2 are superimposed into one beam by a filter 37.

The filter 37 is one that transmits light with a wavelength of λ2 and reflects light with a wavelength of λ□, but a polarizing beam splitter is used to transmit the light beam λ2 and reflect the light beam λ depending on the polarization direction. You can also.

Superimposed light beam λ1. λ2 is half mirror 4
3 and is focused on the magneto-optical disk 12 by the objective lens in the actuator 45.

Here, by slightly shifting the light beams λ and λ2 from the parallel beams using the collimator lenses 33 and 39, the positions of the focal points of the light beams λ1 and λ2 are shifted, so that the light beams λ1 and λ2 are respectively aligned with the magneto-optical disk 1. The actuator 45 moves the objective lens in two axial directions to perform focus and track servo. It has a position adjustment function. The light beam λ1 reflected by the magneto-optical disk 12.
λ2 is reflected by a half mirror 43 and separated by a filter 49 into a light beam λ1 and a light beam λ2.

The light beam λ2 is focused on the recording layer of the optical recording magnetic disk 12 and reflected. The light beam λ2 has a wavelength λ
The plane of polarization is rotated approximately 45 degrees by a 1/2 wavelength plate 51, and is split into two by a polarization beam splitter (PBS) 53 depending on the polarization direction, and then sent to a PIN photodiode 55.
57.

It is detected by the PIN photodiodes 55 and 57, amplified by the differential amplifier 59, and recorded information is read out by the differential method. Here, the half wavelength plate 51 is P
It is used for the purpose of balancing the two signal strengths incident on the IN photodiode 55 and 57, and the PB
This serves as a substitute for rotating S53 around the optical axis, and the device can be made more compact.

On the other hand, the light beam λ reflected by the filter 49 is focused and reflected by the guide track of the magneto-optical disk 12, and is reflected by the two cylindrical lenses 61.6.
A focusing error signal and a tracking error signal are simultaneously detected by the 3- and 4-divided photodiode 65. The detected error signal is fed back to the actuator 45 to perform focusing and tracking servo.

Electromagnet 47 is used during recording and erasing.

In Fig. 3, the focusing error is detected using the light beam λ□ focused on the guide track, but if the focusing error is detected using the light beam λ2 focused on the recording layer, it is possible to detect the focusing error by using the light beam λ2 focused on the recording layer. The influence on focus servo can be removed. This can be done, for example, by splitting a part of the light beam λ°2 with a herb mirror or the like and using the split light.

FIG. 4 is a sectional view illustrating the optical recording method of the present invention in which information written on the recording layer is reproduced by transmitted light. A track layer 15 and a protective layer 17 are sequentially laminated. The signal detection light beam 101 passes through the protective layer 17, the guide track layer 15, and the recording layer 13, is reflected by the first reflective layer 19, and the information recorded on the recording layer 13 is reproduced by the transmitted light. In the case of a magneto-optical disk that utilizes the magneto-optic effect of the recording layer, it is possible to utilize the Faraday effect with a large rotation angle, thereby improving reproduction sensitivity.

The tracking error detection light beam 103 is reflected by the guide track portion of the guide track layer 15 as in FIG.

FIG. 5 shows an example of the structure of the optical recording medium of the present invention, in which the substrate 1
1, a recording layer 13. Guide track layer 15, protective layer 1
7 are sequentially laminated, and the guide track layer 15 has a filter layer 21 formed on the surface of a guide track base layer 16 to constitute a guide track portion.

The signal detection light beam 101 has a protective layer 17 and a filter layer 2.
1. The light passes through the guide track layer 15 and is reflected by the recording layer 13. On the other hand, the tracking error detection light beam 1
03 is reflected by the filter layer 21 forming the guide track portion of the guide track layer 15. In this case, the optical paths of the two light beams 101 and 103 can be adjusted by controlling the spectral characteristics of the filter layer 21.
The system of the present invention can be realized by forming a guide track using the P method or using a pregroove substrate, and forming a filter layer thereon. The filter layer also acts as a heat insulating layer for the guide track layer. If the temperature of the recording layer is about 200°C during recording and erasing, if the pre-groove layer is made of resin such as photopolymer or acrylic resin, the pre-groove layer will be deformed during recording, so rewriting is not possible. There was a problem when doing it. By providing a filter layer, it can be insulated, recording,
Even if the recording medium is heated to a high temperature (150° C. or higher) during erasing, the guide track layer can be formed of a resin such as a photopolymer or acrylic resin. The filter layer 21 is
Two light beams used λ2. A material having spectral characteristics as shown in FIG. 2 with respect to λ2 is used. Such a filter layer is made of ZnS-MgF2 or TiO2-5in
It can be formed from a dichromic mirror made of alternately laminated films of high refractive materials and low refractive materials, such as .

Such an optical recording medium is obtained by forming a recording layer 13 on a substrate 11, forming a guide track base layer 16 thereon by the 2P method, and further forming a filter layer 21 thereon. Here, the recording layer 13 is formed of a material from which recorded information can be read or further recorded depending on the wavelength of the signal detection light beam 101. Filter layer 21
As already explained, a beam having a high transmittance for the wavelength of the signal detection light beam 101 and a high reflectance for the tracking error detection beam 103 is used.

The shape of the group of the guide track layer 15 is set to the wavelength of the tracking error detection light beam 103 so that the tracking error can be detected most efficiently. This can be obtained, for example, by forming a filter layer on the grouped guide track base layer 16 by vacuum deposition, sputtering, or the like. The protective layer 17 is transparent to the two light beams 101 and 103. Furthermore, if the guide track base layer 16 and the protective layer 17 have different refractive indexes, the wavefront of the signal detection light beam 101 will be disturbed and the spot diameter on the recording layer 13 will become larger. It is desirable to form the layer 17 with a material having a small difference in refractive index.

Further, an intermediate layer can be provided between each layer if desired, and for example, a heat insulating layer can be newly provided between the recording layer and the guide track layer.

FIG. 6 shows another embodiment of the optical recording medium of the present invention, which is the same as that shown in FIG. S except that a reflective layer 19 is provided between the recording layer 13 and the substrate 11. . The signal detection light beam 101 passes through the recording layer and is reflected by the reflective layer 19, and the information recorded on the recording layer 13 is reproduced by the transmitted light.

In a magneto-optical recording medium that utilizes the magneto-optic effect of the recording layer, the Faraday effect with a large rotation angle can be used, so the reproduction sensitivity is improved.

FIG. 7 shows another example of the structure of the optical recording medium, which is basically the same as that shown in FIG. In this example, a filter layer 21 is formed on a substrate 25 with pregrooves, and this is bonded to a recording layer 13 formed on a substrate 11 using an adhesive layer 23. In this case, the adhesive layer 23 acts as a guide track base layer and the pre-grooved substrate 25
The unevenness of the filter layer 21 regulated by the group shape forms a guide track portion. In addition, the substrate 11 on which the recording layer 13 is formed and the filter layer 2 are connected via a spacer.
The pre-grooved substrate 25 formed with the seventh
The portion corresponding to the adhesive layer 23 in the figure can also be made into an air layer. The pre-grooved substrate 25 can be created by injection molding a transparent resin such as acrylic resin.
It is preferable that the difference in refractive index between the substrate 25 and the adhesive layer or air layer is small.

FIG. 8 shows another example of the structure of the optical recording medium, which is the same as FIG. 7 except that a reflective layer 19 is provided between the substrate 11 and the recording layer 13. Reproduction can be performed using light transmitted through the recording layer 13.

The materials of the substrate and each layer depend on the relationship with the two light beams used, but typical materials are as follows.

An appropriate substrate is used, such as a magneto-optical recording medium whose recording layer is a crystalline metal oxide magnetic thin film.
A heat-resistant substrate is used when the substrate is placed under high temperature during film formation. Specific examples of the substrate include metals such as aluminum, stainless steel, copper, and nickel, heat-resistant glasses such as quartz glass, Pyrex glass, Vycor glass, borosilicate glass, aluminosilicate glass, and crystallized glass, soda glass, GGG
(Gallium, Gadolinium, Garnet), Lithium Tantalate, Sapphire, Single Crystal Silicon, A1. Ceramic materials such as O, heat-resistant plastics such as polyimide and polyamide, plastics such as acrylic resin and polycarbonate resin are examples of recording layers in optical discs that read recorded information based on the reflected intensity of light.
Dyes such as Te0X, In-8b, and cyanine dyes are used.

A crystalline metal oxide magnetic material, TbFe, is used as a recording layer in a magneto-optical recording medium in which recorded information is read using the magneto-optic effect.

GdTbFe, TbFeCo, GdTbFeCo.

Amorphous magnetic materials such as GdDyFe.

A polycrystalline alloy film such as MnB1Cu or PtMnSb is used. Crystalline metal oxide magnetic materials are excellent in terms of stability and light transmittance, and specific examples thereof include the following.

(1) Magnetobrambite system M e MaxF e□t-XO19 (Me: B
At least one of a, Pb, Sr, and Ca M a : Co v T iS G a g A 1
1 Rh t S c e I n HB i+ T a
s S n v Cr t M n H2n , S
b, Nb, V, Pd, Re.

Pt, Os, Zr, Tc, La, Ge.

Ru, W, Te, Pt, Ce, Pb* At least one of Ni, Mg, Ir, Cu, etc. y-
z○2° (Me: at least one or more of Ba, Pb, Sr, Ca, Mb: Fe, Zn, Ni, Mg, Co, Cu.

At least one type of divalent metal such as pb M c : Al, Ga, Cr, F
e, In, Sc.

Ti, Bi, Get Rh, Re, Ru.

T a + V+ S n, N iIMny P
at least one kind such as b eI r + N b t S b y:O≦y≦2 z:Os2≦16) (3) Cobalt spinel-based CogMd, F 193-11-11104 (M d
: A I HCr w M n t A I HN
l + T l pS n , Z n , Cu ,
M g , Rh s V + G a * S b
r S c p B x ; Y t E u HTb
, E r, Yb, Ho+Dy+・Tm+Gd, Sm, P
b, Re, Ru, etc. 〇≦1≦2 m:0≦m≦3) (4) Garnet-based M"2M"pFes-po.

(Ml: y r Bx + p b + c a g
La g Ba g Sm, Eu, Gd, Er, Tm,
At least one member of Yb*Co, I, u, Pr, Nd, Ho, Dy, etc. M": Ga, Al, V, Si, Rh, Cu.

Ni, Lu, Sc, Zr, In, G.

At least one kind of p:O≦p≦5) The film thickness of the magnetic layer depends on the light beam used, but in the case of crystalline metal oxide magnetic material, 0.1 to 10 μm is appropriate; Further, it is appropriate that the amorphous magnetic material has a thickness of O, OS to 2 μm, and that the polycrystalline alloy film has a thickness of 0.05 to 5 μm.

The magnetic layer may be formed on the substrate by a normal thin film forming method such as sputtering. For example, when forming a translucent magnetic film made of a crystalline metal oxide magnetic material, this magnetic material is generally deposited on a substrate using a method such as vacuum evaporation, sputtering, or ion blasting at a substrate temperature of 400 to 700°C. It is made to adhere to a film thickness of about 0.1 to 10 μm. The magnetic layer thus obtained is perpendicularly magnetized. Also, 500℃
Although it is possible to form a magnetic film at a substrate temperature of less than
Heat treatment at ~800°C is performed while applying a magnetic field if necessary.

As described above, forming a magnetic layer requires a high substrate temperature, but in the magneto-optical disk of the present invention, the magnetic layer can be formed prior to forming the guide track, so there are no restrictions when forming the magnetic layer. . Further, the guide track can be formed using plastic by the 2P method or the like.

Prior to forming the magnetic layer, in order to improve the crystal orientation of the magnetic layer, Fe30. (1
11) Face, M n Z n F e 204 (111)
, a-Fe20. (page 001), AIN (page 001)
, Z n O (001), MgO (111), or the like can be provided for epitaxial growth. The thickness of the base layer is suitably in the range of 0.05 to 1 μm.

The guide track layer can be formed by a conventional method such as the 2P method. The recording layer and guide track section have a thickness of 5 to 20 μm in order to suppress the influence of the guide track during reproduction.
It is preferable to separate them by a certain amount.

As a reflective layer, Ag+ptt Al, Cu.

Zn! Cr t Rh + T x N t T
aN etc. are used.

Next, a specific example of the configuration of a magneto-optical disk will be explained.

A 0.3 μm thick A film was deposited on a Si wafer substrate by vapor deposition.
u reflective film, 0.2μ by DC magnetron sputtering method
A ZnO film (base layer) with a thickness of
oTiFe,. A perpendicularly magnetized film (recording layer) with C-axis orientation of 01B was formed. Furthermore, a guide track layer was formed thereon by a 2P method, and then a filter layer made of a multilayer film of MgF and ZnS was formed by a vapor deposition method. Furthermore, a UV-cured resin protective layer similar to that of the guide track base layer was provided thereon to obtain a magneto-optical disk having the structure shown in FIG.

Here, the filter layer is Z n S (88 nm) −M
g'F2 (150nm) -ZnS (88nm
) −M g F, (300nn+) −Z n S (
88nm)-MgF2(150nm)-Zn
The filter layer has a reflectance of about 90% at λ=780 nm, and a transmittance of about 90% at λ=83 nm.

The thickness of the guide track layer is about 10 μm, and the shape of the guide track (group) is groove MO, 5 μm, groove depth 70 μm.
nm, track pitch 2.5 μm, λ=830n
The optimum value was set for detecting a tracking error signal using light of m.

In this magneto-optical disk, a semiconductor laser with λ=780 nm is used for recording, reproducing, and erasing information, and a semiconductor laser with λ=830 nm is used to detect tracking errors, so that information can be reproduced.

According to the present invention, the playback S/L due to the influence of the guide track
Deterioration of the N signal and increase in the pit error rate can be prevented, and by controlling the spectral transmission characteristics of each layer, the reproduced signal and the track error signal can be efficiently detected using light beams of two different wavelengths.

Further, by providing a filter layer in the guide track portion of the guide track layer, two beams can be used more efficiently, and the guide track can be easily created by the 2P method or the like. Furthermore, by providing a filter layer, this acts as a heat insulating layer, and even in optical recording media where the recording layer is exposed to high temperatures (150°C or higher) during recording and erasing, the guide track layer is made of resin such as photopolymer or acrylic resin. can be formed. Furthermore, when applied to magneto-optical disks, it becomes possible to utilize the Faraday effect, and the reproduction sensitivity can also be increased.

When producing an optical recording medium, guide tracks can be created after forming the recording layer, so even if high temperatures are required when forming the recording layer, guide tracks and pre-grooved plastic substrates using the conventional 2P method can be created. etc. can be used.

[Brief explanation of drawings]

FIG. 1, FIG. 4, FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are cross-sectional views showing an example of the structure of the optical recording medium of the present invention and a recording method using the same, respectively. FIG. 2 is a graph showing the spectral transmission characteristics (T) and spectral reflection characteristics (R) of the filter layer. FIG. 3 is a diagram illustrating a method for recording, reproducing and erasing information on a magneto-optical disk. FIGS. 9 and 10 are diagrams explaining a conventional optical recording medium and a recording method using the same. 10... Recording medium 11... Substrate 12... Magneto-optical disk 13... Recording layer 15... Guide track layer 16... Guide track base layer 17
...Protective layer 19...Reflection
Layer 21...Filter layer 23...Adhesive layer 25...Substrate with pregroove 31...Laser light source for recording and reproduction 35...Bolarizer 41...Laser light source for force tracking/tracking

Claims (1)

[Claims] 1. An optical recording medium having a stacked guide track layer and a recording layer is irradiated with first and second light beams having different wavelengths from the guide track layer side, and the first light beam is transmitted through the guide track layer and reflected at or after passing through the recording layer, while the second light beam is reflected at the guide track portion of the guide track layer and is written on the recording layer by the first light beam. The second
An optical recording method characterized by detecting a tracking error signal using a light beam. 2. A recording layer and a guide track layer are sequentially laminated on a substrate, and a filter layer is formed in the guide track portion, and the filter layer reflects light in a part of the wavelength range and reflects light in the other part. The recording layer transmits light in a wavelength range of , and the recording layer reflects at least part of the light in some other wavelength range that passes through the filter layer and enters the recording layer. recoding media. 3. A reflective layer, a recording layer, and a guide track layer are sequentially laminated on a substrate, and a filter layer is formed in the guide track portion, and the filter layer reflects light in some wavelength ranges and reflects light in other wavelength ranges. The recording layer transmits light in a part of the wavelength range that passes through the filter layer, and the reflective layer transmits light in a part of the wavelength range that enters the filter layer. An optical recording medium characterized by reflecting at least a portion of incoming light.