JP2005190659A - Optical information recording and reproducing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for performing optical information recording and reproduction having high signal quality by using an optical information recording medium capable of performing high density land/groove recording where crosstalk from an adjacent track is suppressed even when a short wavelength light source and an optical head having a high NA are used. <P>SOLUTION: Information is reproduced from the optical information recording medium for land/groove recording of a Low-to-high recording system having a substrate 1 and a recording layer 2. The information is reproduced by irradiating the recording layer 2 with light having 390 to 440 nm wavelength from the substrate 1 side by using an objective lens having a numerical aperture of 0.65 and when the wavelength of the light is defined as λ and the refractive index of the substrate 1 in the wavelength λ is defined as ns, the depth D of a part G' corresponding to the groove to a part L' corresponding to the land in the recording layer 2 is specified to satisfy the relation of λ/5.8ns≤D≤λ/5ns. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium on which information is recorded / reproduced using light such as a laser beam, and further to an optical information recording / reproducing method and an optical information recording / reproducing apparatus using the same. Optical information in which information is recorded in both the portion corresponding to the inside of the tracking guide groove and the portion corresponding to the portion between the adjacent guide grooves with respect to the recording layer provided on the surface of the substrate having the tracking guide groove. The present invention relates to a recording medium and an optical information recording / reproducing method and apparatus using the same.

  As an optical information recording medium used for recording / reproducing information by laser beam irradiation, MO (magneto-optical disk) or CD-R, CD-RW, DVD-R, DVD-RAM, DVD- RW is generally known. As a means for increasing the recording density in the optical information recording medium, a flat portion (land) between adjacent tracking guide grooves (grooves) formed in a substantially circular shape in parallel with each other on the substrate surface is used. ) And land / groove recording, in which recording is performed on the recording layer portion corresponding to both the inside of the guide groove (Japanese Patent Laid-Open No. 57-50330 [Patent Document 1] and Japanese Patent Laid-Open No. 9-73665). (Patent Document 2), JP-A-9-198716 [Patent Document 3], JP-A-10-64120 [Patent Document 4], etc.).

  In recent years, a technique for increasing the NA of an objective lens of an optical head constituting an apparatus for recording / reproducing information to about 0.85 has been proposed as a technique for increasing the recording density. By increasing the NA, the beam diameter when the laser beam is condensed can be reduced, so that a finer mark can be recorded and reproduced. When the NA is increased in this way, the surface of the optical information recording medium on which the tracking guide groove is formed is used instead of irradiating the laser beam from the side of the support substrate having a thickness of 0.6 to 1.2 mm as in the prior art. A light transmission layer having a thickness of about 0.1 mm is formed, and information can be recorded / reproduced by irradiating a laser beam from the light transmission layer side.

  In addition, research on increasing the recording density by shortening the wavelength of the laser light source has been actively conducted. By using a blue-violet semiconductor laser having a wavelength of about 405 nm compared to a red semiconductor laser conventionally used for DVD recording / reproduction, it is expected to realize a recording density three times or more.

  On the other hand, in order to improve the signal quality of the optical information recording medium, the reflectance of the recording layer before recording is lowered, and the reflectance of the recording layer after recording is increased. LH) recording method is effective. This is because the degree of modulation can be increased by keeping the reflectance of the recording layer before recording low, so that the reflection of the recording layer after recording used in conventional DVD-RAM and DVD-RW This is because the C / N can be increased as compared with a high-to-low (HL) recording method in which the rate is low.

Combining these technologies, that is, performing land / groove recording on an LH optical information recording medium with high signal quality using a short wavelength light source such as a blue-violet semiconductor laser and a high NA optical head. Thus, it is conceivable to dramatically increase the recording density.
JP 57-50330 A Japanese Patent Laid-Open No. 9-73665 JP-A-9-198716 JP-A-10-64120

  Incidentally, one of the major technical problems when performing land / groove recording is leakage of signals from adjacent tracks, so-called crosstalk. If the pitch of the guide groove for tracking is reduced to increase the recording density, the crosstalk component from the information recorded on the adjacent track increases, so that information can be accurately reproduced on the target track (self track). It becomes difficult.

  One of the objects of the present invention is a high-quality LH signal capable of high-density land / groove recording with suppressed crosstalk from adjacent tracks even when a short wavelength light source or a high NA optical head is used. An optical information recording medium of the type is provided.

  Another object of the present invention is to provide a method and apparatus for recording and reproducing optical information using such an optical information recording medium.

According to the present invention, the object as described above is achieved.
In an optical information reproducing method for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
Information is reproduced by irradiating the recording layer with light having a wavelength of 390 to 440 nm from the substrate side using an objective lens having a numerical aperture of 0.65, and
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. An optical information reproducing method characterized by satisfying the relationship
Is provided.

According to the present invention, the object as described above is achieved.
In an optical information reproducing apparatus for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
It comprises at least a light source that emits light with a wavelength of 390 to 440 nm and an objective lens with a numerical aperture of 0.65, and reproduces information by irradiating the recording layer with the light from the substrate side,
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. An optical information reproducing device characterized by satisfying the relationship of
Is provided.

According to the present invention, the object as described above is achieved.
In an optical information reproducing method for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
Information is reproduced by irradiating the recording layer with light having a wavelength of 390 to 440 nm from the substrate side using an objective lens having a numerical aperture of 0.65, and
The amount of reflected light when irradiating light to a non-recording area in which the land portion and the groove portion are not alternately arranged is I1, and the portion corresponding to the groove portion in the information unrecorded state under the same condition and the land An optical information reproducing method characterized in that a value of R = 0.5 (I2 + I3) / I1 is within a predetermined range, where I2 and I3 are reflected light amounts when the portion corresponding to the portion is irradiated with light. ,
Is provided.

  In one aspect of the present invention, the value of R is 0.5 to 0.75. In one aspect of the present invention, the value of R is 0.6 to 0.7.

According to the present invention, the object as described above is achieved.
In an optical information reproducing apparatus for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
It comprises at least a light source that emits light with a wavelength of 390 to 440 nm and an objective lens with a numerical aperture of 0.65, and reproduces information by irradiating the recording layer with the light from the substrate side,
The amount of reflected light when irradiating light to a non-recording area in which the land portion and the groove portion are not alternately arranged is I1, and the portion corresponding to the groove portion in the information unrecorded state under the same condition and the land An optical information reproducing apparatus characterized in that the value of R = 0.5 (I2 + I3) / I1 is within a predetermined range, where I2 and I3 are the amounts of reflected light when the part corresponding to the part is irradiated with light. ,
Is provided.

  In one aspect of the present invention, the value of R is 0.55 to 0.7. In one aspect of the present invention, the value of R is 0.6 to 0.7.

According to the present invention, the object as described above is achieved.
In an optical information reproducing method for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
Information is reproduced by irradiating the recording layer with light having a wavelength of 390 to 440 nm from the substrate side using an objective lens having a numerical aperture of 0.65, and
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. And the sum of the width of the groove part and the width of the land part is in the range of 0.5 to 1.2 μm,
Is provided.

According to the present invention, the object as described above is achieved.
In an optical information reproducing apparatus for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
It comprises at least a light source that emits light with a wavelength of 390 to 440 nm and an objective lens with a numerical aperture of 0.65, and reproduces information by irradiating the recording layer with the light from the substrate side,
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. And the sum of the width of the groove part and the width of the land part is in the range of 0.5 to 1.2 μm,
Is provided.

In addition, according to the present invention, the object as described above is achieved.
Information is recorded / reproduced by irradiating light in a spot shape, and at least a recording layer and a light transmission layer are provided in this order on a substrate having a guide groove for tracking the spot light. The recording layer is irradiated with the light in a spot shape from the transmission layer side, and corresponds to the first portion of the recording layer corresponding to the inside of the guide groove and the flat portion between the guide grooves adjacent to each other. An optical information recording medium for recording on both of the second portions of the recording layer,
When the wavelength of the light is λ and the refractive index of the light transmitting layer at the wavelength λ is nf, the first portion with respect to the second portion of the surface of the recording layer on the light transmitting layer side The depth d of the optical disk satisfies the relationship of λ / 5.8nf ≦ d ≦ λ / 5nf, and the recording layer has a higher reflectivity than before recording by performing recording. recoding media,
Is provided.

  In one aspect of the present invention, the depth d is substantially the same as the depth inside the guide groove with respect to the flat portion between the guide grooves. In one aspect of the present invention, a dielectric layer exists between the substrate and the recording layer. In one aspect of the present invention, a reflective film exists between the substrate and the dielectric layer. In one aspect of the present invention, a dielectric layer exists between the recording layer and the light transmission layer.

In addition, according to the present invention, the object as described above is achieved.
Information is recorded / reproduced by irradiating light in a spot form, and at least a recording layer is provided on a substrate having a guide groove for tracking the spot-like light, and the recording layer is provided from the substrate side. Is irradiated with the light in a spot shape, and a second portion of the recording layer corresponding to a first portion of the recording layer corresponding to the inside of the guide groove and a flat portion between the guide grooves adjacent to each other. An optical information recording medium for recording on both parts,
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the second portion with respect to the first portion of the surface of the recording layer on the substrate side is D. Satisfies the relationship of λ / 5.8ns ≦ D ≦ λ / 5ns, and the recording layer has a higher reflectance than before recording by performing recording,
Is provided.

  In an aspect of the present invention, the depth D is substantially the same as the depth inside the guide groove with respect to the flat portion between the guide grooves. In one aspect of the present invention, a reflective film exists on the side of the recording layer opposite to the substrate. In one aspect of the present invention, a dielectric layer exists between the substrate and the recording layer.

In addition, according to the present invention, the object as described above is achieved.
Information is recorded and reproduced by irradiating light in a spot shape, and at least a recording layer is provided on a substrate having a guide groove for tracking the spot light, and corresponds to the inside of the guide groove. An optical information recording medium for recording on both the first portion of the recording layer and the second portion of the recording layer corresponding to the flat portion between the guide grooves adjacent to each other,
Corresponding to the inside of the guide groove in an unrecorded state under the same condition, the reflected light amount when irradiating light to a non-recording area where the guide groove and the flat portion between the guide grooves are not formed is set to I ₁ The amount of reflected light when irradiating the portion corresponding to the flat portion between the guide groove and the flat portion between the guide grooves is I ₂ and I ₃ , respectively, and the value of R = 0.5 (I ₂ + I ₃ ) / I ₁ is 0. An optical information recording medium, wherein the recording layer has a reflectance higher than before recording by performing recording,
Is provided.

  In one aspect of the present invention, a dielectric layer may exist between the substrate and the recording layer, and a reflective film may exist between the substrate and the dielectric layer.

  In one aspect of the present invention, a dielectric layer may be present on the side of the recording layer opposite to the substrate, and a reflective film may be present on the side of the dielectric layer opposite to the recording layer.

Furthermore, according to the present invention, the object as described above is achieved.
Using an objective lens having a numerical aperture of 0.8 to 0.9, light having a wavelength of 390 to 440 nm is spot-formed on both the first portion and the second portion of the recording layer of the optical information recording medium. An optical information recording / reproducing method, wherein information is recorded / reproduced by irradiation
Is provided.

Furthermore, according to the present invention, the object as described above is achieved.
An optical head for irradiating light in a spot shape to both the first portion and the second portion of the recording layer of the optical information recording medium is provided, and the optical head has a wavelength of 390 to 440 nm. An optical information recording / reproducing apparatus comprising: a semiconductor laser that emits light; and an objective lens having a numerical aperture of 0.8 to 0.9;
Is provided.

  It has been well known that the crosstalk in land / groove recording changes by changing the groove depth. The present inventor has found that the groove depth capable of reducing crosstalk is different in the L-H recording method than in the H-L recording method. FIG. 6 shows the relationship between groove depth and crosstalk. In FIG. 6, the horizontal axis represents the wavelength of the laser beam as λ, the refractive index of the light transmitting layer or substrate existing on the side where the laser beam is incident on the recording layer as n, and the groove depth as λ / (a The value of a in the case of n) is shown, and the vertical axis shows the amplitude of the crosstalk signal. A smaller a corresponds to a deeper groove. As shown in FIG. 6, the groove depth that can reduce crosstalk is deeper in the LH system than in the H-L system. However, as the groove depth is increased, the noise of the substrate increases significantly, so even if the crosstalk can be suppressed, the signal quality at the target track (self track) will be degraded. High density recording cannot be performed. By selecting the groove depth within the above range, that is, by setting the value of a in FIG. 6 within the range of 5 to 5.8, while ensuring the signal quality of the self-track necessary for high density recording. Thus, crosstalk from adjacent tracks can be suppressed and the recording capacity can be increased.

  According to the present invention, land / groove recording can be performed at a high recording density using a high NA optical head on an L-H optical information recording medium with high signal quality.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partially enlarged sectional view showing an embodiment of an optical information recording medium according to the present invention. On the surface (upper surface) of the disk-shaped support substrate 1 having a thickness of about 1.2 mm, a tracking guide groove extending in a substantially circular shape is formed around the center of the substrate, and between the adjacent guide grooves. A flat portion (land) L is formed. The inside (bottom part) of the tracking guide groove is a groove G in particular. The depth (groove depth) of the groove G with respect to the land L is D. The width of the land L and the width of the groove G are typically substantially equal, and preferably within an error of 10%. The arrangement pitch of the grooves G is, for example, 0.5 to 1.2 μm.

  A dielectric layer 4 is formed on the upper surface of the substrate 1, and a recording layer 2 on which optical information is recorded is formed on the dielectric layer 4. A dielectric material is formed on the recording layer 2. A layer 5 is formed, and a light transmission layer 3 having a refractive index nf is formed on the dielectric layer 5. Information is recorded / reproduced on / from the recording layer 2 by irradiating the laser beam LB from the light transmitting layer 3 side. A material such as polycarbonate (PC) or aluminum (Al) can be used for the substrate 1. The light transmission layer 2 has a thickness of about 0.1 mm, may be a PC film bonded with an ultraviolet curable resin or the like, or may be a layer made of an ultraviolet curable resin with a thickness of about 0.1 mm. When the PC film is bonded, the thickness of the PC film is much larger than the thickness of the UV curable resin adhesive layer, and therefore the refractive index of the PC film may be used as the refractive index nf of the light transmission layer 3. it can.

  As the recording layer 2, a material whose optical reflectance or phase changes by laser light irradiation, for example, a known phase change recording material such as GeSbTe, a known photorefractive material, or the like can be used. The recording layer 2 has a concavo-convex shape corresponding to the land-groove shape on the surface of the substrate 1, and a portion corresponding to the substrate groove G (ie, the first portion) G ′ and a portion corresponding to the substrate land L (ie, the portion) A second part) L ′ is formed. On the upper surface of the recording layer 2, the depth (groove depth) of the groove corresponding portion G ′ with respect to the land corresponding portion L ′ is d. Typically, the thickness of the recording layer 2 is the same in the land corresponding portion L ′ and the groove corresponding portion G ′, and the thickness of each of the dielectric layers 4 and 5 is also the same as the portion corresponding to the land and the groove. Therefore, the groove depth d is substantially equal to D. Here, the groove depth d is selected so that λ / 5.8nf ≦ d ≦ λ / 5nf holds, where λ is the wavelength of the irradiation laser beam. The thickness of the recording layer 2 is, for example, 10 to 30 nm, preferably 10 to 20 nm. In addition to the function as a protective layer, the dielectric layers 4 and 5 have a layer configuration including these (including the thickness of the dielectric layers 4 and 5) as appropriate, so that the recording medium of the LH recording system is used. It also has a function that contributes to realizing the above.

  If necessary, a metal layer as a reflective film may be provided between the upper surface of the substrate 1 and the dielectric layer 4.

  Information recording / reproduction is performed by the LH recording method on both the groove corresponding portion G ′ and the land corresponding portion L ′ of the recording layer 2. In order to realize the L-H recording method, each layer and their film thickness and other layer configurations are appropriately set according to a known design method.

  FIG. 2 is a schematic diagram for explaining an embodiment of an information recording / reproducing method and apparatus for the optical information recording medium as described above. The optical information recording medium 10 rotates around a vertical rotation center passing through the center thereof. Above the recording medium 10, an optical head 20 constituting a recording / reproducing apparatus is arranged. In the optical head 20, a laser beam emitted from a semiconductor laser 21 as a light source is irradiated in a spot shape on the groove corresponding part G ′ or the land corresponding part L ′ of the recording layer 2 of the recording medium 10 through the collimating lens 22 and the objective lens 23. Is done. The reflected light from the recording medium 10 reaches the light detection system 25 through the objective lens 23 and the beam splitter 24. A reproduction signal, a tracking signal, and the like are obtained by the light detection system 25. The wavelength λ of the laser light emitted from the semiconductor laser 21 is, for example, 390 to 680 nm, preferably 390 to 440 nm. As the objective lens 23, a lens having a large numerical aperture (NA) of, for example, 0.6 to 0.9, preferably 0.8 to 0.9 is used.

  In addition, this invention is not limited to what irradiates a laser beam from the light transmissive layer 3 side, You may irradiate a laser beam from the board | substrate 1 side. In this case, a substrate that is light transmissive is used. As described above, since the thickness of the dielectric layer 4 is typically the same in the portion corresponding to the land L and the portion corresponding to the groove G, the land corresponding to the groove corresponding portion G ′ is formed on the lower surface of the recording layer 2. The depth (groove depth) of the corresponding portion L ′ is approximately D. The groove depth D is selected so that λ / 5.8 ns ≦ D ≦ λ / 5 ns holds, where λ is the wavelength of the irradiation laser light and ns is the refractive index of the substrate 1. When a reflective layer is formed, it is disposed above the recording layer 2 via a dielectric layer 5. Also in this case, information recording / reproduction is performed by the LH recording method on both the groove corresponding portion G ′ and the land corresponding portion L ′ of the recording layer 2.

  Next, another embodiment of the present invention will be described. In the above embodiment, the relationship between the groove depth and the refractive index of the light transmission layer or the substrate is specified, but in this embodiment, the relationship between the amount of reflected light of the irradiation light at a plurality of predetermined locations of the recording medium is specified. This also makes it possible to perform recording / reproduction with good jitter characteristics.

Specifically, in this embodiment, the recording medium 10 has a layer configuration equivalent to that of the information recording area in which the land-groove alternate structure as shown in FIG. A non-recording area (for example, an area located inside or outside in the radial direction with respect to the information recording area) in which a uniform flat portion is formed in an area sufficiently wider than the light beam spot diameter without any alternate arrangement of grooves ) When the laser beam is spot-irradiated on the recording layer, the amount of reflected light is I _1, and the laser beam is spot-irradiated on the groove-corresponding portion and land-corresponding portion of the recording layer in the information recording area in the unrecorded state under the same conditions It is effective for realizing good jitter characteristics that the value of R = 0.5 (I ₂ + I ₃ ) / I ₁ is 0.55 to 0.7 where I ₂ and I ₃ are reflected light amounts, respectively. Turned out to be . R is preferably 0.6 to 0.7.

Here, an average value of the reflected light amount from the groove corresponding portion and the reflected light amount from the land corresponding portion is adopted as the reflected light amount of the information recording area. The reason is mainly due to the fact that the width may be different between the groove and the land. In the case of land / groove recording, it is typical that the groove and land have the same width and the values of I ₂ and I ₃ are almost equal. However, the groove and land have different widths due to manufacturing errors and the like. There are cases where the values of ₂ and I ₃ are different, and this is the case.

  According to this embodiment, instead of the relationship between the groove depth and the refractive index of the light transmission layer or the substrate, the same effect can be achieved by defining the relationship between the amounts of reflected light at a plurality of locations that are easy to measure. be able to.

  The following examples further illustrate the present invention.

(Example 1)
Using a disk-shaped PC substrate with a thickness of 1.1 mm as the substrate, the Al reflective film is 100 nm, the ZnS-SiO ₂ dielectric layer is 40 nm, the GeSbTe recording layer is 15 nm, and the ZnS-SiO ₂ dielectric layer is 100 nm in order, by sputtering. Lamination was performed to obtain a recording medium (disk). A PC substrate having a guide groove pitch of 0.56 μm and a guide groove depth of 35 nm to 55 nm was used. Further, a PC film having a thickness of 0.1 mm was bonded with an ultraviolet curable resin. The refractive index (nf) of the PC film at a wavelength of 400 nm was 1.6.

  After initializing (crystallizing) the disk, it was rotated at a linear velocity of 5.1 m / s, and an optical head equipped with a laser light source with a wavelength (λ) of 400 nm and an objective lens with NA = 0.85 was used. Jitter was measured by irradiating a laser beam from the opposite side and performing land / groove recording under the linear density condition of 0.116 μm / bit by the LH recording method. The reflectivity of the disc was 6% before recording (unrecorded information state) and 20% after recording (recorded information state).

  The measurement result of jitter is shown in FIG. FIG. 3 shows both jitter when no data is recorded on the adjacent track (noted as XT) and jitter when data is recorded on the adjacent track (noted as XT). . Jitter in the self track when there is no recording in the adjacent track and there is no crosstalk is better as the groove depth is shallower, and when it is deeper than 50 nm, noise due to the substrate increases, so the jitter in the self track is significantly degraded. Resulting in. On the other hand, when recording is performed on adjacent tracks, jitter is significantly degraded due to the influence of crosstalk when the groove depth is less than 43 nm. By setting the groove depth in the range of 43 to 50 nm, that is, in the range of λ / 5.8nf to λ / 5nf, it is possible to obtain good jitter characteristics including crosstalk.

(Comparative Example 1)
A disk-shaped PC substrate with a thickness of 1.1 mm was used as the substrate, the Al reflective film was 100 nm, the ZnS-SiO ₂ dielectric layer was 15 nm, the GeSbTe recording layer was 15 nm, and the ZnS-SiO ₂ dielectric layer was 45 nm in order, by sputtering. Lamination was performed to obtain a recording medium (disk). A PC substrate having a guide groove pitch of 0.56 μm and a guide groove depth of 35 nm to 55 nm was used. Further, a PC film having a thickness of 0.1 mm was bonded with an ultraviolet curable resin. The refractive index of the PC film at a wavelength of 400 nm was 1.6.

  After initializing (crystallizing) the above disk, rotate it at a linear velocity of 5.1 m / s, and use an optical head equipped with a laser light source with a wavelength of 400 nm and an objective lens with NA = 0.85. Then, the laser beam was irradiated, and land / groove recording was performed under the linear density condition of 0.116 μm / bit by the HL recording method, and jitter was measured. The reflectivity of the disc was 18% before recording and 2% after recording.

  The measurement result of jitter is shown in FIG. The jitter in the self track with no recording in the adjacent track is better as the groove depth is shallower, and when it is deeper than 50 nm, the jitter in the self track is remarkably deteriorated. On the other hand, when recording is also performed on adjacent tracks, jitter is significantly degraded due to the effect of crosstalk when the groove depth is shallower than 37 nm, and even when the groove depth is deeper than 43 nm. An increase in jitter due to the influence of talk cannot be ignored.

  As can be seen from the comparison between the first comparative example and the first embodiment (comparison between FIG. 3 and FIG. 4), the preferred groove depth differs between the HL recording method and the LH recording method, and the LH recording method. It can be seen that the jitter can be further reduced.

(Example 2)
A disk-shaped PC substrate with a thickness of 1.1 mm was used as the substrate, and the Al reflective film was sputtered to 100 nm, the ZnS-SiO ₂ dielectric layer to 45 nm, the GeSbTe recording layer to 13 nm, and the ZnS-SiO ₂ dielectric layer to 110 nm in this order. To obtain a recording medium (disk). A PC substrate having a guide groove pitch of 0.6 μm and a guide groove depth of 38 nm to 60 nm was used. Further, a PC film having a thickness of 0.1 mm was bonded with an ultraviolet curable resin. The refractive index of the PC film at a wavelength of 432 nm was 1.6.

  After initializing (crystallizing) the disk, it was rotated at a linear velocity of 5.1 m / s, and an optical head equipped with a laser light source with a wavelength (λ) of 432 nm and an objective lens with NA = 0.85 was used. Jitter was measured by irradiating a laser beam from the opposite side and performing land / groove recording under a linear density condition of 0.125 μm / bit by the LH recording method. The reflectivity of the disk was 5% before recording and 21% after recording.

  The measurement result of jitter is shown in FIG. The jitter in the self track with no recording in the adjacent track is better as the groove depth is shallower, and when it is deeper than 54 nm, the jitter in the self track is remarkably deteriorated. On the other hand, when recording is also performed on the adjacent track, if the groove depth is shallower than 46 nm, the jitter is remarkably deteriorated due to the influence of crosstalk. By setting the groove depth in the range of 46 to 54 nm, that is, in the range of λ / 5.86 nf to λ / 5 nf, it is possible to obtain good jitter characteristics including crosstalk.

(Example 3)
A 1.1 mm thick PC substrate was used as the substrate, the Al reflective film was 100 nm, the ZnS-SiO ₂ dielectric layer was 65 nm, the GeSbTe recording layer was 13 nm, and the ZnS-SiO ₂ dielectric layer was 150 nm in order, and then laminated by sputtering. A recording medium (disc) was obtained. A PC substrate having a guide groove pitch of 1.0 μm and a guide groove depth of 62 nm to 98 nm was used. Further, a PC film having a thickness of 0.1 mm was bonded with an ultraviolet curable resin. The refractive index of the PC film at a wavelength of 660 nm was 1.58.

  After initializing (crystallizing) the disk, it was rotated at a linear velocity of 5.1 m / s, and an optical head equipped with a laser light source with a wavelength (λ) of 660 nm and an objective lens with NA = 0.85 was used. Jitter was measured by irradiating a laser beam from the opposite side and performing land / groove recording under the linear density condition of 0.21 μm / bit by the LH recording method. The reflectivity of the disc was 6% before recording and 25% after recording.

  Similar to Example 1 and Example 2, the groove depth at which the jitter characteristics including crosstalk become good was examined. As a result, the groove depth was in the range of 72 to 83 nm, that is, λ / 5. It was found that good jitter characteristics including crosstalk can be obtained by setting the following range.

Example 4
Using a PC substrate with a thickness of 0.6 mm as the substrate, the ZnS-SiO ₂ dielectric layer was deposited by sputtering to 100 nm, the GeSbTe recording layer to 15 nm, the ZnS-SiO ₂ dielectric layer to 40 nm, and the Al reflective film to 100 nm by sputtering. A recording medium (disc) was obtained. After the Al reflective film was formed, a dummy 0.6 mm PC substrate on which nothing was formed was bonded to an ultraviolet curable resin, and then evaluated. A PC substrate having a guide groove pitch of 0.7 μm and a guide groove depth of 35 nm to 55 nm was used. The refractive index (ns) at a wavelength of 400 nm of the PC substrate was 1.6.

  After initializing (crystallizing) the disk, it was rotated at a linear velocity of 5.1 m / s, and an optical head equipped with a laser light source with a wavelength (λ) of 400 nm and an objective lens with NA = 0.65 was used. Jitter was measured by irradiating laser light from the side and performing land / groove recording under a linear density condition of 0.152 μm / bit by the LH recording method. The reflectivity of the disc was 6% before recording and 20% after recording.

  As a result of measuring the jitter, as in the first embodiment, by setting the groove depth in the range of 43 to 50 nm, that is, in the range of λ / 5.8 ns to λ / 5 ns, good jitter including crosstalk can be obtained. It was possible to obtain characteristics.

  Table 1 below summarizes the results of Examples 1 to 4 above.

表１から分かるように、いずれの波長においても溝深さをλ／5.8nf（又はλ／5.8ns）以上λ／5nf（又はλ／5ns）以下の範囲内とすることで、クロストークを含めて良好なジッタ特性が得られる。

As can be seen from Table 1, crosstalk is included by setting the groove depth at any wavelength within the range of λ / 5.8nf (or λ / 5.8ns) to λ / 5nf (or λ / 5ns). And good jitter characteristics can be obtained.

(Example 5)
For the optical disk used in Example 4, the above I ₁ , I ₂ , and I ₃ were measured using the optical head used in Example 4, and the value of R = 0.5 (I ₂ + I ₃ ) / I ₁ When the relationship between this and jitter was examined, the results shown in Table 2 were obtained. Note that the jitter is the average of the values recorded at the center corresponding to the land and the groove corresponding to the land corresponding to the land corresponding to the land and the groove corresponding to the groove of each disk. is there.

表２に示すように、Ｒが０．５５から０．７までの範囲において良好な特性が得られ、特に０．６から０．７までの範囲において最も良好な特性が得られた。

As shown in Table 2, good characteristics were obtained when R was in the range of 0.55 to 0.7, and in particular, the best characteristics were obtained in the range of 0.6 to 0.7.

Further, similarly for the optical disks used in Examples 1 to 3, I ₁ , I ₂ , and I ₃ were measured using the optical heads used in the respective examples, and R = 0.5 (I _When the value of ₂ + I ₃ ) / I ₁ was calculated and the relationship between the calculated value and jitter was examined, an optical disk with good jitter characteristics may have an R value in the range of 0.55 to 0.7. confirmed.

  That is, for the optical information recording medium of the LH recording system, the NA of the objective lens of the optical head and the wavelength of the laser light, the thickness of the recording layer, or the refractive index of the light transmission layer or the substrate take various values. It was found that good characteristics can be obtained in the range of R from 0.55 to 0.7.

  In this embodiment, the land width and the groove width are the same. However, when the land width and the groove width are different from each other by about 10%, the same results are obtained for the preferable range of R. It was.

(Comparative Example 2)
An optical information recording medium of the HL recording system was produced using the same PC substrate as in Example 4, and the relationship between R and jitter was examined using the same optical head as in Example 4. As a result, it was confirmed that the R range in which the jitter is good is 0.7 to 0.8, and the preferred R range is different from that of the LH recording system. Also, the jitter value at the R in the preferred range was larger than that in the fifth embodiment.

  Therefore, it was confirmed that the LH recording method is suitable for increasing the recording density.

It is a partial expanded sectional view of the optical information recording medium concerning this invention. 1 is a schematic diagram for explaining a method and apparatus for recording / reproducing information with respect to an optical information recording medium according to the present invention. It is a figure which shows an example of the jitter characteristic of the optical information recording medium concerning this invention. It is a figure which shows an example of the jitter characteristic of the optical information recording medium from which a reflectance becomes low after recording. It is a figure which shows an example of the jitter characteristic of the optical information recording medium concerning this invention. It is a figure which shows the relationship between the groove depth of an optical information recording medium, and crosstalk.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate L Land G Groove 2 Recording layer L 'Land corresponding part G' Groove corresponding part 3 Light transmitting layer 4, 5 Dielectric layer 10 Optical information recording medium 20 Optical head 21 Semiconductor laser 22 Collimating lens 23 Objective lens 24 Beam splitter 25 Light detection system

Claims (10)

In an optical information reproducing method for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
Information is reproduced by irradiating the recording layer with light having a wavelength of 390 to 440 nm from the substrate side using an objective lens having a numerical aperture of 0.65, and
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. An optical information reproducing method characterized by satisfying the relationship: In an optical information reproducing apparatus for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
It comprises at least a light source that emits light with a wavelength of 390 to 440 nm and an objective lens with a numerical aperture of 0.65, and reproduces information by irradiating the recording layer with the light from the substrate side,
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. An optical information reproducing apparatus satisfying the relationship: In an optical information reproducing method for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
Information is reproduced by irradiating the recording layer with light having a wavelength of 390 to 440 nm from the substrate side using an objective lens having a numerical aperture of 0.65, and
The amount of reflected light when irradiating light to a non-recording area in which the land portion and the groove portion are not alternately arranged is I1, and the portion corresponding to the groove portion in the information unrecorded state under the same condition and the land An optical information reproducing method characterized in that a value of R = 0.5 (I2 + I3) / I1 is within a predetermined range, where I2 and I3 are reflected light amounts when the portion corresponding to the portion is irradiated with light. . The optical information reproducing method according to claim 3, wherein the value of R is 0.5 to 0.75. The optical information reproducing method according to claim 4, wherein the value of R is 0.6 to 0.7. In an optical information reproducing apparatus for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
It comprises at least a light source that emits light with a wavelength of 390 to 440 nm and an objective lens with a numerical aperture of 0.65, and reproduces information by irradiating the recording layer with the light from the substrate side,
The amount of reflected light when irradiating light to a non-recording area in which the land portion and the groove portion are not alternately arranged is I1, and the portion corresponding to the groove portion in the information unrecorded state under the same condition and the land An optical information reproducing apparatus characterized in that the value of R = 0.5 (I2 + I3) / I1 is within a predetermined range, where I2 and I3 are the amounts of reflected light when the part corresponding to the part is irradiated with light. . The optical information reproducing apparatus according to claim 6, wherein the value of R is 0.55 to 0.7. The optical information reproducing apparatus according to claim 7, wherein the value of R is 0.6 to 0.7. In an optical information reproducing method for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
Information is reproduced by irradiating the recording layer with light having a wavelength of 390 to 440 nm from the substrate side using an objective lens having a numerical aperture of 0.65, and
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. And the sum of the width of the groove part and the width of the land part is in the range of 0.5 to 1.2 μm. In an optical information reproducing apparatus for reproducing information from a low-to-high recording land / groove optical information recording medium having a substrate and a recording layer,
It comprises at least a light source that emits light with a wavelength of 390 to 440 nm and an objective lens with a numerical aperture of 0.65, and reproduces information by irradiating the recording layer with the light from the substrate side,
When the wavelength of the light is λ and the refractive index of the substrate at the wavelength λ is ns, the depth D of the recording layer corresponding to the groove to the land corresponding portion is λ / 5.8 ns ≦ D ≦ λ / 5 ns. And the sum of the width of the groove portion and the width of the land portion is in the range of 0.5 to 1.2 μm.

Images