JP2003217172A - Recording medium, optical probe and information recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform high density recording by enhancing the utilization efficiency of light of a recording layer. <P>SOLUTION: Stripes 22 with low resistance or dots 41 with low resistance constituted of a metal material are provided along the face opposed to an optical probe 8 of the recording layer 24 for recording information in a recording medium 2 and the face on the side opposite thereto and in the direction parallel to the direction of a data row. An electric field by near field light generated at a minute aperture 11 at the tip of the optical probe 8 by irradiating the optical probe 8 with a laser beam is focused on the stripes 22 with low resistance or the dots 41 with low resistance, the recording layer 24 is efficiently heated and a recording mark is written. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording medium for storing various kinds of information, an optical probe and an information recording / reproducing apparatus for recording or reproducing information on or from the recording medium, and an information recording / reproducing apparatus, and more particularly to improving recording density. It is about.

[0002]

2. Description of the Related Art Information recording / reproducing apparatuses currently in practical use for recording / reproducing information on / from an optical memory such as an optical disk focus light to a diffraction limit of light determined by the wavelength of light and the numerical aperture of an objective lens. The information is recorded by irradiating the recording medium with the generated laser light and thermally and magnetically modulating the recording layer,
Information is reproduced by detecting the intensity and polarization of reflected light that is modulated by the recording pits that record information. When this information recording / reproducing apparatus is used, the recording density of the optical memory is determined by the diffraction limit of light, and there is a limit to cope with the recent increase in the amount of information surrounding information devices such as computers, There is a demand for a large-capacity optical memory that achieves a recording density that exceeds the diffraction limit of light.

Promising as such a large-capacity optical memory is an information recording / reproducing apparatus or recording medium using so-called near-field light for recording and reproducing information by using near-field light. . The near field means that light incident from one of two media with different refractive indexes under the condition of total reflection or more is totally reflected at the reflective boundary surface, but only the non-propagating electromagnetic field component exudes beyond the partial boundary surface. This is a non-propagating electromagnetic field region. This near field exudes only in the vicinity of the aperture that is smaller than the wavelength of the incident light,
It is said that it has a lateral extent of about the same as the opening size. Therefore, the resolution exceeding the diffraction limit of light can be obtained by reducing the aperture size.

For example, the near-field optical head disclosed in Japanese Unexamined Patent Publication No. 2000-21005 is provided on a slider that makes a relative motion while contacting with a recording medium or flying while keeping a substantially constant distance between them. An optical probe that generates light is made of an optically transparent material in the shape of a quadrangular pyramid, and the entire optical probe is covered with a metal coating. This optical probe is irradiated with linearly polarized laser light to form a surface plasma on the metal surface. A wave is generated, which is collected at the edge of the quadrangular pyramid and further propagated and condensed at the tip so as to obtain high light utilization efficiency.

As shown in FIG. 19, the opening diameter D is 10
The tip of the optical probe 50 in which the outer periphery of the conical quartz 51 whose tip is exposed at 0 nm is covered with the aluminum light-shielding film 52, the metal reflection film 54, the dielectric layer 55, the recording layer (phase change recording film) on the glass substrate 53. FIG. 20 shows the result of simulating the electric field distribution when the optical probe 50 is irradiated with a laser beam using a calculation model in which a distance of 20 nm is set for the recording medium 58 in which 56) and the dielectric layer 57 are laminated. Figure 2
0, (a) shows the electric field distribution in the direction parallel to the polarization direction of the irradiated laser light, (b) shows the electric field distribution in the direction perpendicular to the polarization direction of the laser light, and (c) shows the optical probe 5.
0 shows the in-plane electric field distribution in the gap between 0 and the recording medium 58, and (d) shows the in-plane electric field distribution in the recording layer 56. As shown in the figure, the near-field light around the tip of the optical probe 50 is
It was confirmed that the electric field stayed in the gap between the optical probe 50 and the recording medium 58 and did not enter the recording medium 58 side, and almost no electric field existed in the recording layer 56.

In the recording medium disclosed in Japanese Patent Laid-Open No. 2000-285505, a thin metal layer is provided on a part of the surface of the recording layer, and the metal layer is used for detecting the distance from the optical probe. Then, the accuracy of the relative positional relationship between the recording medium and the optical probe is improved.

[0007]

When the recording medium is opposed to the tip of the optical probe as described above, most of the electric field of the near-field light stays in the gap between the optical probe and the surface of the recording medium, and the recording layer of the recording medium. Has the disadvantage that it is very inefficient because it requires almost no electricity. Further, since the electric field distribution spreads in the recording layer, the electric field cannot be concentrated in a small area, and the resolution of writing and reading of the recording mark decreases, improving the light utilization efficiency and the near-field which are independent performances of the optical probe. Even if the reduction of the light spot diameter is improved, it is not utilized at all in the recording medium, and it is difficult to improve the light utilization efficiency and recording density actually used for writing or the like.

Further, Japanese Unexamined Patent Publication No. 2000-285505 describes that a thin metal layer provided on a part of the surface of the recording layer is used to improve the accuracy of the relative positional relationship between the recording medium and the optical probe. However, even if a metal layer is provided on the surface of the recording layer facing the optical probe, the light utilization efficiency and recording density for the recording layer cannot be improved.

It is an object of the present invention to provide a recording medium, an optical probe, and an information recording / reproducing apparatus capable of improving the above disadvantages and increasing the light utilization efficiency for the recording layer to perform high-density recording. Is.

[0010]

A recording medium according to the present invention is a recording medium for recording information by near-field light generated by an optical probe, along a recording layer for recording information,
A low resistance stripe made of a metal material is provided parallel to the data column direction, and the electric field generated by the near-field light generated by the optical probe is concentrated on the low resistance stripe to efficiently heat the recording layer to write a recording mark. Characterize.

In another recording medium according to the present invention, low resistance dots made of a metal material are provided in parallel with a data row direction along a recording layer for recording information, and the low-field light generated by an optical probe is used. It is characterized in that the recording layer is written more efficiently by concentrating the electric field on the low resistance dots to heat the recording layer more efficiently.

The above-mentioned low-resistance stripes or low-resistance dots are provided along the surface of the recording layer opposite to the surface facing the optical probe, and an electric field generated by near-field light generated by the optical probe is applied to the low-resistance stripes or low-resistance dots. The recording mark is written by concentrating it directly above and heating the recording layer efficiently.

When the distance between the low resistance stripes or the low resistance dots is p, the width is w, and the aperture diameter of the optical probe is d, w <(d / 2) and (2p-w)> d Low-resistance stripes or low-resistance dots are provided in parallel so as to satisfy the relationship, and light utilization efficiency and resolution are simultaneously improved.

Further, the low-resistance stripes or low-resistance dots are made to meander in a constant cycle, or the low-resistance stripes or low-resistance dots are made to meander in one side and the other side at different cycles to obtain a highly accurate tracking error signal. And easy to get.

An optical probe according to the present invention is an optical probe which irradiates the recording medium with near-field light to record information on the recording medium and reproduces the information recorded on the recording medium,
A small opening is formed in a part of the metal light-shielding film at the tip of the core for introducing the laser light so as to face the recording medium, and the electric field is concentrated at the boundary between the minute opening and the metal light-shielding film to improve the light utilization efficiency. Improve the resolution.

In another optical probe according to the present invention, the tip of the core for introducing the laser beam is formed into a protrusion shape, the outer peripheral surface of the core is covered with a metal light-shielding film, and the electric field is concentrated on the tip of the optical probe. Improves light utilization efficiency and resolution.

Further, the tip of the core for introducing the laser beam is formed into a pyramid shape, and a part of the pyramid-shaped slope is covered with a metal light-shielding film to suppress the bimodal characteristic of the metal aperture and improve the light utilization efficiency. .

An information recording / reproducing apparatus according to the present invention uses the above optical probe to record information on a recording medium having a low resistance stripe or a low resistance dot and reproduce the information recorded on the recording medium to generate an optical signal. It is characterized by improving the utilization efficiency and resolution of the.

Further, when recording and reproducing information on the recording medium, the polarization direction of the near-field light generated at the tip of the optical probe becomes a direction orthogonal to the data row direction of the recording medium. By irradiating a laser beam on the substrate, the electric field generated by the near-field light generated by the optical probe is concentrated on the low-resistance stripe or the low-resistance dot to improve the light utilization efficiency and resolution.

Further, when the low resistance stripes or the low resistance dots are provided in parallel to the data row direction and the information is recorded / reproduced on / from the recording medium, the near-field light generated from the optical probe causes the low resistance stripes or the low resistance stripes of the recording medium. The optical probe is vibrated so as to meander at a constant cycle with respect to the low resistance dot, and a tracking error signal is easily obtained with high accuracy.

[0021]

1 is a block diagram of an information recording / reproducing apparatus of the present invention. As shown in the figure, the information recording / reproducing apparatus 1 records / reproduces information on / from the recording medium 2 while the circular recording medium 2 is rotated by a spindle motor (not shown). The head 3 has an optical system 4 for irradiating recording / reproducing laser light. Optical head 3
Has a slider 7 attached to an arm 5 having an optical system 4 via a suspension 6, and an optical probe 8 attached to the slider 7.

The optical probe 8 is formed of an optical fiber 9 made of, for example, a quartz core. As shown in the sectional view of FIG. 2 (a), the tip of the optical fiber 9 is, for example, buffered hydrofluoric acid.
After sharpening the core with a mixed solution of hydrofluoric acid, ammonium fluoride and water and depositing the metal light-shielding film 10, FIB is performed.
The metal light shielding film at the tip portion is removed by (Focused Ion Beam), and the opening 11 is provided at the tip of the core. The metal light-shielding film 10 is made of a metal such as Al, Au, Ag, Cu, or an alloy containing Al, Au, Ag, Cu as a main component and other elements, such as AgPdCu, AgAuCu, A.
gCu, AgZn, AgCuAl, AgRuZr, Ag
NiAlTi, AlCu, AlSiCu, CuTi or the like is used. That is, these metals have low resistance, and therefore the electric field is likely to concentrate in a part.

The optical system 4 comprises a semiconductor laser device (LD) 1
A laser beam is emitted from 2 and collimated by a collimator lens 13 into parallel light.
After passing through the four-wave plate 15, the objective lens 16 collects the light and irradiates the optical probe 8. The light applied to the optical probe 8 is converted into a near-field light of a minute size at the tip of the optical probe 8. Information can be recorded on the recording layer provided on the recording medium 2 by the converted near-field light, and high-density recording can be realized. When reproducing the information recorded on the recording medium 2, the light reflected from the recording layer is reflected by the optical probe 8.
After passing through the objective lens 16 and the quarter wavelength plate 15, the light is reflected by the polarization beam splitter 14, condensed by the condenser lens 17 on the photodetector 18, and the light intensity is detected by the photodetector 18 to reproduce information. . The light emitted from the LD 12 to the recording medium 2 and the light reflected from the recording medium 2 to the photodetector 18 may be separated by the method using a half mirror instead of the polarization separation method shown in FIG. .

As shown in the sectional view of FIG. 2A, the recording medium 2 is a substrate 21 made of polycarbonate or glass, and is formed on the surface of the substrate 21, and is shown in the top view of FIG. 2B. As described above, the low resistance stripes 22 arranged in parallel to the data writing direction, and the dielectric layer 2 laminated on the surface of the substrate 21 having the low resistance stripes 22.
3 and the recording layer 24 and the protective layer 25. The low resistance stripe 22 is made of Ag, Au, Al, Ni, Cr, Ta, T.
i, Mo, Mg, Cu, Sn, Zn, Pb, In, B
Metals such as i, W, Ir, Tl, Pt, and bismuth, or alloys thereof, such as AgPdCu and AgAuC containing Ag, Al, Cu, and Au as main components and other elements added.
u, AgCu, AgZn, AgCuAl, AgRuZ
r, AgNiAlTi, AlCu, AlSiCu, Cu
It can be Ti. These metals have low resistance, and Ag is particularly preferable because it has excellent surface smoothness.
Further, a substance having a resistance value similar to that of a metal, particularly a resistance value similar to an optical frequency may be used. Dielectric layer 2
3 and the protective layer 25 are ZnS—SiO ₂ , Al ₂ O ₃ , and Al.
It may be formed of a translucent thin film material such as N or SiO ₂ , or an ultraviolet curable resin may be used by a spin coating method, or the translucent thin film and the ultraviolet curable resin may be laminated. Also, an adhesive layer may be provided on the translucent thin film and a transparent substrate such as polycarbonate or glass may be adhered. The recording layer 24 is formed of a phase change recording material or a write-once recording material. As a phase change recording material, Sb /
In addition to SbTe having a Te ratio in the range of 1 to 4, SbTe, Ag, In, Ge, Ga, Al, Sn, B, Si
A composition containing at least one element selected from the group For example, AgInSbTe, GeSbTe, G
eInSbTe, GeGaSbTe, GaSbTe, and the like. Examples of write-once recording materials include Bi, In, Pb,
Sn, Te, Zn, Ga, Ag, Al, Ge, Sb, S
At least two kinds of elements selected from the group of elements such as i, Au, Cu, Ni, Mg, and C are mixed and used. For example, BiTe, InTe, SnTe, ZnTe, GaT
e, AgTe, AlTe, GeTe, SbTe, CTe
Tellurium compounds such as Also, Bi
SbTe, InSbTe, GaSbTe, AgSbT
It is also possible to use chalcogen compounds such as e, AlSbTe, GeSbTe. Further, in order to improve sliding resistance between the optical probe 8 and the surface of the recording medium 2, a sliding resistance layer made of a carbon material or silicon nitride may be provided on the protective layer 25.

The information recording / reproducing apparatus 1 configured as described above.
When information is recorded on the recording medium 2, the near-field light linearly polarized in the data column direction of the recording medium 2, that is, the direction perpendicular to the extending direction of the low resistance stripe 22 is generated at the tip of the optical lobe 8. A laser beam is incident on the optical probe 8 from the optical system 4. That is, the laser light is incident as linearly polarized light in a direction perpendicular to the extending direction of the low resistance stripe 22. The wavelength of the laser light is longer than the opening diameter of the minute opening 11 of the optical probe 8. As shown in FIG. 2A, the central axis of the optical probe 8 is the low resistance stripe 22.
2B, the electric field is concentrated on the boundary 19 between the minute aperture 11 of the optical fiber 9 and the metal light shielding film 10 and parallel to the polarized light, as shown in FIG. 2B. On the other hand, the near-field light is an AC electric field having the frequency of the incident laser beam (actually, there is also a magnetic field, but only the electric field will be described for simplification of explanation).
When the center line of the low resistance stripe 22 is on the center axis of 1, the potential of the low resistance stripe 22 becomes neutral with respect to the electric field. Further, since the metal forming the low resistance stripe 22 has a very low resistance, the potential becomes equal regardless of the location of the low resistance stripe 22. The lines of electric force generated from the portion 19 where the electric field is concentrated at the boundary between the minute opening 11 and the metal light shielding film 10 are concentrated on the low resistance stripe 22 through the protective layer 25, the recording layer 24 and the dielectric layer 23. As a result, the electric field is concentrated right above the low resistance stripe 22, and the electric field is effectively applied to this portion 24a of the recording layer 24. That is, since the electric field is concentrated on the low resistance stripe 22, the resolution is high,
Moreover, the recording layer 24 is efficiently heated by the near-field light, and the recording mark can be written. Further, the written data can be efficiently read.

Here, for example, when the polarization of the near-field light generated by the optical probe 8 is parallel to the extending direction of the low resistance stripe 22, the electric field has the width of the low resistance stripe 22 as shown in FIG. 2B. The low-resistance stripe 22 is dispersed in a wide area without being concentrated in a limited area, electromagnetic energy is not concentrated, and the recording layer 24 cannot be efficiently heated. So low resistance stripe 2
It is necessary to make laser light incident on the optical probe 8 from the optical system 4 so that near-field light linearly polarized in a direction perpendicular to the stretching direction of 2 is generated at the tip of the optical probe 8. Further, in order to concentrate the electric field on the low resistance stripe 22, it is necessary to regulate the opening diameter of the minute opening 11 at the tip of the optical probe 8 and the width and interval of the low resistance stripe 22 within a certain range. Here, as shown in FIG. 3, the light utilization efficiency and resolution were examined by computer simulation with the opening width of the minute opening 11 being d, the width of the low resistance stripe 22 being w, and the pitch of the low resistance stripe 22 being p. It was confirmed that the light utilization efficiency and resolution can be improved at the same time under the following conditions. w <d / 2 and (2p-w)> d where (2p-w)> d is the minute aperture 11 of the optical probe 8.
It means that there should be no low-resistance stripe 22 other than the low-resistance stripe 22 to be written or read under the portion of.

Next, a method of forming the low resistance stripe 22 on the substrate 21 of the recording medium 2 will be described. As an example of a method of forming the low resistance stripe 22, Stephen Y. Chou,
e al, "Inprint Lithography with25-Nanometer Resol
ution ", SCIENCE, Vol.272, No.5April 1966, pp85-87, includes the template transfer method (imprint lithography method). This method is shown in (a) of the process diagram of FIG. As shown, a metal film 30 is formed on a substrate 21 made of plastic such as glass or polycarbonate.
Are deposited in advance. Then, as shown in (b), a mold 31 formed of quartz or SiC or the like and having concave and convex grooves on the lower surface is arranged on the metal film 30, and as shown in (c), the mold 31 is formed of the metal film 30. Press on the surface. After that, the mold 31 is removed as shown in (d). When the mold 31 is removed, unevenness is formed on the surface of the metal film 30 according to the uneven shape of the mold 31. The metal film 3 on which this unevenness is formed
When 0 is etched by RIE or the like, the concave portion is removed first. When the etching is stopped here, as shown in (e), low-resistance stripes 22 having a constant width and a constant pitch are formed on the surface of the substrate 21. The recording medium 2 can be formed by sequentially depositing the dielectric layer 23, the recording layer 24, and the protective layer 25 on the low resistance stripe 22.

As a second method of forming the low resistance stripe 22, GM white size, JC love, "New technology for making nano composition", Nikkei Science, December 2001, pp.
There is a soft lithography method which is described in detail in 30-41. In this method, as shown in (a) of the process diagram of FIG. 5, a photoresist master 33 having a plurality of ridges is formed by surface photolithography or electron beam lithography of a master substrate 32. On the master 33, as shown in (b), a liquid of polydimethylsiloxysan (PDMS) before being solidified is poured.
The liquid of this PDMS is the master substrate 32 and the master 33.
Then, the PDMS stamp 34 is formed by copying the concavo-convex pattern formed in (1) and hardening it in a rubber shape. The PDMS stamp 34 is peeled off from the master substrate 32 as shown in (c). Then, as shown in (d), the PDMS stamp 34 is placed on the surface of the metal film 30 deposited on the substrate 21, and the groove portion 35 is formed by the concave groove of the metal film 30 and the PDMS stamp 34. Then, as shown in FIG.
Then, the liquid polymer 36 is poured from an injection hole (not shown).
When the liquid polymer 36 is solidified, the PDMS stamp 34 is removed as shown in (f), and a solidified polymer pattern 37 is formed on the surface of the metal film 30.
When this metal film 30 is etched by RIE or the like, a low resistance stripe 22 is formed on the surface of the substrate 22 leaving only the polymer pattern 37, as shown in FIG.

As a third method for forming the low resistance stripe 22, there is a method using photolithography etching lift-off. In this method, as shown in (a) of the process chart of FIG. 6, a resist pattern 38 is formed on the surface of a quartz substrate 21 by using an I-line stepper exposure machine or the like. Then, the surface of the substrate 21 on which the resist pattern 38 is formed is side-etched with buffered hydrofluoric acid,
The opening 39 is formed as shown in FIG. After that, a metal film 4 of Ag or the like is formed on the surfaces of the resist pattern 38 and the substrate 21.
0 is deposited. Then, by removing the resist pattern 38 with acetone ultrasonic waves, the low resistance stripe 22 made of a metal such as Ag can be formed on the surface of the substrate 21, as shown in (d).

In the recording medium 2, the case where the low resistance stripe 22 is formed on the surface of the substrate 21 has been described.
As shown in FIG. 7, low resistance dots 41 may be formed on the surface of the substrate 21 and arranged in a matrix pattern that is orthogonal at a constant pitch. 7, (a) is a cross-sectional view in the x direction orthogonal to the data string of the recording layer 24, (b) is a top view,
(C) is a cross-sectional view in the y direction, which is the direction of the data row.
The shape of the low resistance dot 41 may be a square as shown in FIG. 7, or may be a rectangle or another shape.
For example, the low resistance dot 41 is formed in a quadrangular shape, the side length in the x direction is wx, the side length in the y direction is wy, the pitch in the x direction and the y direction is px, py, and the minute aperture of the optical probe 8 is formed. 11
When the diameters in the x and y directions of are, px and py, the light use efficiency and resolution can be realized at the same time by forming the low resistance dot 41 so as to satisfy the following conditions. wx <dx / 2 and (2px-wx)> dx wy <dy / 2 and (2py-wy)> dy Further, the low resistance dot 41 having a constant length in the x direction and the y direction is provided as an optical probe in the recording layer 24. By providing on the side opposite to 8, the metal region is limited also in the y direction, which is the data column direction of the recording layer 24, as compared with the case where the low resistance stripe 22 is provided, and the electric field is more concentrated and the resolution and light utilization are increased. The efficiency can be improved. The low resistance dots 41 can be formed on the substrate 21 by the same method as that for forming the low resistance stripe 22.

Also in this case, the polarization direction of the near-field light is the recording layer 2
4 is set in a direction orthogonal to the data column direction. When actually recording / reproducing, the recording medium 2 moves relative to the optical probe 8 in the data column direction. At this time, as shown in FIG. 8, it is assumed that the low resistance dot 41 is displaced with respect to the optical probe 8 in the x direction orthogonal to the data row of the recording layer 24, and so-called tracking displacement is caused. At this time, the low resistance dot 41 is formed on one portion LP where the electric field of the optical probe 8 is concentrated.
, The coupling capacitance between the portion LP where the electric field is concentrated and the low resistance dot 41 becomes large, and the potential of the low resistance dot 41 approaches the potential of the portion LP. Therefore, the electric field generated between them becomes weak. Further, the other portion RP of the optical probe 8 where the electric field is concentrated is separated from the low resistance dot 41, and the electric field generated between the low resistance dot 41 and the portion RP where the electric field is concentrated becomes weak. Therefore, the reflected light from the recording layer 24 directly above the low resistance dot 41 becomes weak. That is, when the tracking shift occurs, the signal obtained from the reflected light of the recording medium 2 becomes weak, so that the tracking shift can be detected from this change. In this case, the tracking deviation can be detected with high sensitivity by making the polarization direction of the near-field light coincident with the direction in which the tracking deviation occurs. That is, when the polarization direction of the near-field light is parallel to the data row, the distance from the portion where the electric field is concentrated in the metal light shielding film 10 of the optical probe 8 to the low resistance dot 41 even if tracking deviation occurs. Since the fluctuation is small, the attenuation of the reflected light due to the tracking deviation is small. For this reason, the sensitivity of tracking deviation detection becomes low, and in order to prevent this and detect tracking deviation with high sensitivity, the polarization direction of the near-field light is set to the direction orthogonal to the data row direction of the recording layer 24.

Further, in order to obtain the tracking error signal, it is preferable to relatively move the center of the optical probe 8, that is, the near-field spot and the center of the low resistance stripe 22 or the low resistance dot 41. As one of the methods of moving the optical probe 8 and the centers of the low resistance stripes 22 and the low resistance dots 41 relative to each other, as shown in FIGS. It may be formed so as to meander in a sin wave shape at a constant cycle with respect to 24 data strings. In FIGS. 9 and 10, the meandering period of the low resistance stripe 22 and the low resistance dot 41 and the opening diameter d of the minute opening 11 of the optical probe 8 are shown to be about the same size for the sake of description. The cycle of meandering of the low resistance stripe 22 and the low resistance dot 41 is made much larger than the opening diameter d of the minute opening 11 of the optical probe 8.

For example, the meandering period of the low resistance stripe 22 is L (m), and the relative moving speed (linear speed) between the optical probe 8 and the recording medium 2 is v (m / s). When the optical probe 8 and the recording medium 2 move relative to each other, the low-resistance stripe 22 meanders. Therefore, the center position of the low-resistance stripe 22 is a constant period T from immediately below the central axis of the minute opening 11 of the optical probe 8. L / v shifts. Thus, the center position of the low resistance stripe 22 is located at the minute opening 11 of the optical probe 8.
If it is deviated from the central axis of, the electric field generated between the low resistance stripe 22 and the other portions LP and RP where the electric field of the optical probe 8 concentrates becomes weak, and the reflected light from the recording layer 24 directly above the low resistance stripe 22 becomes weak. Become. Here, from the state where the center of the meandering of the low resistance stripe 22 and the central axis of the minute aperture 11 of the optical probe 8 coincide, that is, the on-track state, the low resistance stripe 22 is in the x direction orthogonal to the data string of the recording layer 24. In the case of left / right deviation, the left / right deviation amount becomes constant with respect to the central axis of the minute opening 11 of the optical probe 8, and the reduction amount of the reflected light from the recording layer 24 directly above the low resistance stripe 22 becomes equal. Therefore, the optical signal intensity of the reflected light from the recording layer 24 is, as shown in FIG.
It changes with 2. When the center of the meandering of the low-resistance stripe 22 is laterally offset with respect to the central axis of the minute opening 11 of the optical probe 8, that is, in the off-track state, the optical signal intensity of the reflected light from the recording layer 24 is , The displaced direction becomes large, and as shown in FIGS. 11 (b) and 11 (c),
The light intensity signal is obtained by inverting the phase by 180 degrees according to the direction shifted to the left and right in the cycle T. Further, if the center of the low resistance stripe 22 is largely deviated from the central axis of the minute opening 11, its amplitude also becomes large. Therefore, a tracking error signal can be obtained by synchronously / phase-detecting and amplifying the optical signal intensity of the reflected light from the recording layer 24 generated by the meandering low resistance stripe 22 at the frequency f = t / T. In practice, a region (synchronization region) for generating a reference signal serving as a reference is provided before the region where the meandering low resistance stripe 22 is present. When phase detection is performed using this as a reference signal,
In the case of the track, the frequency becomes 2f = 2 / T, the phase-detected signal becomes insensitive to the signal having the frequency twice the reference signal, and the tracking error signal is generated when the track is off. Can be detected. Since the frequency of this tracking error signal is significantly lower than that of the information signal from the recording mark, only the tracking error signal can be taken out by the frequency filter. Also, when the substrate 21 is provided with the low resistance dots 41 that meander, a tracking error signal can be obtained in the same manner.

In the above description, the case where the low resistance stripes 22 and the low resistance dots 41 are formed so as to meander in a sinusoidal shape at a constant cycle with respect to the data row of the recording layer 24 has been described, but FIG. 12 and FIG. As described above, the low resistance stripes 22 and the low resistance dots 41 may be meandered at different cycles on the left and right sides in the x direction orthogonal to the data row of the recording layer 24. For example, as shown in FIG. 12, one side of the low resistance stripe 22 in the x direction, for example, the right side, meanders in a sin wave pattern with a period L, and the other side, for example, the left side, has a different period, for example, a period 2L. sin Wake in a wavy shape. In this case, the low resistance stripe 22 is displaced from right below the central axis of the minute opening 11 of the optical probe 8 at a constant period T = L / v due to the meandering on the right side. Therefore, a signal of frequency f appears in the cycle T for the reason described above. On the other hand, due to the meandering on the left side, the low resistance stripe 22 has a period 2T = 2L /
It will shift by v. Therefore, the frequency f
The / 2 signal appears.

When the center of the meandering of the low resistance stripe 22 coincides with the center of the minute aperture 11, that is, when the track is on-track, the widths of the meandering of the low resistance stripe 22 are equal, and therefore the signal of the period T is obtained. And a signal of period 2T appears with the same intensity. On the other hand, when the center of the meandering of the low resistance stripe 22 is closer to the right than when the center of the small aperture 11 coincides with the center of the minute opening 11, that is, when the track is off-tracking to the right, it is caused by the meandering of the left side. The signal strength of the cycle 2T is larger. On the contrary, the low resistance stripe 22
When the center of the meander of (1) shifts to the left side, the signal intensity of the period T caused by the meandering of the right side becomes larger. Therefore, the reference signals of the period T and the period 2T are created from the synchronization area where the reference signal serving as the reference is generated, and the optical signal intensity signal of the reflected light from the recording layer 24 is synchronously / phase-detected and amplified by each. When the synchronous / phase detection is performed in the cycle T, only the signal in the cycle T is obtained, and the signal in the cycle 2T becomes insensitive. Similarly, when the synchronous / phase detection is performed in the period 2T, only the signal in the period 2T is obtained, and the signal in the period T becomes insensitive. In this way, the signals of the period T and the period 2T can be separated, and by subtracting the signal obtained from the period T and the signal obtained from the period 2T, the central axis of the optical probe 8 and the low resistance stripe 22 are separated. The tracking error signal can be obtained by obtaining the direction and magnitude of the deviation from the center. Further, as described above, since the frequency of the tracking error signal is extremely lower than that of the information signal from the recording mark, only the tracking error signal can be taken out by the frequency filter. Up to now, the case where the frequency of the right meander and the frequency of the left meander are doubled has been described, but if a narrow band filter is used instead of the phase detection, the same effect can be obtained with other frequency settings as long as they are different frequencies. Obtainable. Even when the low resistance dot 41 is provided, a tracking error signal can be similarly obtained. In addition,
Instead of meandering the low resistance stripe 22 and the low resistance dots 41 in a sin wave shape, the low resistance stripe 22 and the low resistance dot 41 may meander in a rectangular wave or a triangular wave shape.

Further, instead of meandering the low resistance stripes 22 and the low resistance dots 41, the low resistance stripes 22 parallel to the data rows of the recording layer 24 are arranged on the substrate 21 of the recording medium 2 or in a matrix form orthogonal to each other at a constant pitch. The optical probe 8 may be vibrated at a constant cycle in the x direction orthogonal to the data row of the recording layer 24 with respect to the formed low resistance dot 41.
As a method of vibrating the optical probe 8, FIG.
As shown in (a), an optical probe 8 composed of an optical fiber
The optical system 4 side is fixed to the slider 7 and held by a so-called cantilever structure in which the tip is free, and the metal light shielding film 10 of the optical probe 8 is grounded. And the optical probe 8 of the slider 7
Fixed electrodes 42 are provided on both surfaces of the recording layer 24 facing the tip and in a direction orthogonal to the data row. An alternating voltage is independently applied between the two fixed electrodes 42 and the metal light shielding film 10. By applying this AC voltage, the fixed electrode 4
2 and the tip portion of the optical probe 8, an electrostatic attraction acts, and the tip of the optical probe 8 can be vibrated at a constant cycle in a direction orthogonal to the data row of the recording layer 24 to detect a tracking error signal. .

Further, as shown in FIG. 14B, a pair of piezoelectric elements 43 are provided on the optical system 4 side of the optical probe 8 in a direction orthogonal to the data row of the recording layer 24, and the metal light shielding film 10 is formed. As a common electrode, an AC voltage is independently applied to the pair of piezoelectric elements 43, or as shown in FIG.
The metal light-shielding film 10 is formed of a magnetic material, and the coils 44 are provided on both surfaces of the slider 7 that face the tip of the optical probe 8 and that are orthogonal to the data rows of the recording layer 24. Is applied, the tip of the optical probe 8 can be vibrated at a constant cycle in a direction orthogonal to the data row of the recording layer 24.

Instead of directly vibrating the optical probe 8, a vibration mechanism similar to the above is provided between the suspension 6 and the slider 7 so that the optical probe 8 has a constant period in the direction orthogonal to the data row of the recording layer 24. You may make it vibrate with.

When the optical probe 8 is vibrated in this way, in order to obtain the same tracking error signal frequency as when the low resistance stripe 22 meanders at the cycle L (m), the optical probe 8 and the recording medium are obtained. If the moving speed (linear speed) relative to 2 is v (m / s), then f = (v /
The optical probe 8 may be vibrated at a frequency determined by L).

In the above description, the optical probe 8 is replaced by the optical fiber 9
Although the case where the optical probe 8 is formed is described above, the present invention can be similarly applied to the flat plate type optical probe 8 as shown in the configuration diagram of FIG. This flat plate type optical probe 8 is shown in FIG.
As shown in (a) and (b), a quartz flat substrate, a semiconductor substrate, or a substrate 45 in which a semiconductor film is laminated on a glass substrate 45.
Then, a metal light-shielding film 10 is formed on one surface, and the metal light-shielding film 10 is subjected to photolithography, etching, RIE.
The minute opening 11 may be provided by a so-called semiconductor processing technique such as (Reactive Ion Etching). Also in this case, a structure having a protrusion shape like a fiber probe may be used.

Further, in the above description, the optical probe 8 in which the tip of the optical fiber 9 is processed into the shape of a truncated cone or the optical probe 8 formed in a flat plate type has been described.
As shown in the cross-sectional view of (a) and the top view of (b), the tip portion of the optical probe 8 is formed in the shape of a quadrangular pyramid, and the metal light-shielding film 10 is provided on the entire outer peripheral surface of the shape of the protrusion. As shown in the sectional view of (a) and the top view of (b), the metal light-shielding film 10 may be provided only on one surface of the projecting slope having a quadrangular pyramid tip. By thus forming the tip of the optical probe 8 in the shape of a quadrangular pyramid, for example, a reference, Laser Research 2000
As shown in “Study of High Transfer Rate, Optical Recording Density Optical Disk Head” on pages 590 to 599 of September issue,
A light condensing effect like that of a lens can be provided to improve the light utilization efficiency. Further, as shown in FIG. 18, an optical probe 8 provided with a metal light-shielding film 10 only on one surface of a quadrangular pyramid protrusion-shaped slope is disclosed in, for example, the Proceedings of the 21st Annual Meeting of the Laser Society of Japan. .2001) 203, Satoshi Miki, Akiya Goto, as shown in "Analysis of probe head for near-field recording by FDTD method", due to the influence of surface plasmons localized at the metal edge of the optical probe 8, By strengthening the electric field at the tip and introducing asymmetry,
The bimodal characteristics peculiar to the metal aperture can be suppressed, the half-value width of about 70 nm can be obtained, and the light utilization efficiency can be improved.

Further, although the recording medium 2 in which the recording layer 24 is formed of the phase change recording material or the write-once recording material has been described above, the rewritable recording medium having the magneto-optical recording layer or the read-only ROM. It can be similarly applied to the mold recording medium.

Further, although the example using the phase detection for obtaining the tracking error signal is shown, the tracking error signal can be obtained in the same manner by using the method of detecting the signal in synchronization with the phase, for example, the sample hold circuit. You can

[0044]

As described above, according to the present invention, a low-resistance stripe made of a metal material is provided in parallel with a data column direction along a recording layer for recording information, and near-field light generated by an optical probe is generated. By concentrating the electric field by the low resistance stripe, the recording layer can be efficiently heated to write a recording mark, the light utilization efficiency and resolution can be improved, and information can be recorded at high density.

Further, low resistance dots made of a metal material are provided in parallel with the data column direction along the recording layer for recording information, and the electric field generated by the near-field light generated by the optical probe is concentrated on the low resistance dots. Thus, the recording layer can be more efficiently heated to write the recording mark.

Further, a low resistance stripe or a low resistance dot is provided along the surface of the recording layer opposite to the surface facing the optical probe, and an electric field generated by the near-field light generated by the optical probe is applied to the low resistance stripe or the low resistance dot. Concentrate right above
The recording layer can be efficiently heated to write a recording mark, and the light utilization efficiency and resolution can be further improved.

When the distance between the low resistance stripes or the low resistance dots is p, the width is w, and the aperture diameter of the optical probe is d, w <(d / 2) and (2p-w)> d By providing low resistance stripes or low resistance dots in parallel so as to satisfy the relationship, it is possible to improve light utilization efficiency and resolution at the same time.

Further, by making the low resistance stripes or low resistance dots meander in a constant cycle, or by making the low resistance stripes or low resistance dots meander in one side and the other side in different cycles, the light utilization efficiency is improved. It is possible to improve the resolution and easily obtain the tracking error signal with high accuracy.

Further, by providing a minute opening opposed to the recording medium in a part of the metal light shielding film at the tip of the core for introducing the laser light of the optical probe, the minute opening and the metal light shielding film are provided at the boundary. The electric field can be concentrated to improve the light utilization efficiency and resolution.

Further, the tip of the core for introducing the laser beam of the optical probe is formed into a projection shape, the outer peripheral surface of the core is covered with a metal light-shielding film, and the electric field is concentrated on the tip of the optical probe.
The light utilization efficiency and resolution can be further improved.

Further, the tip of the core for introducing the laser beam is formed into a pyramid shape, and a part of the pyramidal slope is covered with a metal light-shielding film to suppress the bimodal characteristic of the metal opening.
The light utilization efficiency can be improved.

Further, by using the above optical probe in an information recording / reproducing apparatus to record information on a recording medium having a low resistance stripe or a low resistance dot, and reproducing the information recorded on the recording medium, It is possible to improve the utilization efficiency and resolution of, and record information at high density.

When recording and reproducing information on the recording medium, the optical probe is arranged so that the polarization direction of the near-field light generated at the tip of the optical probe is orthogonal to the data string direction of the recording medium. By irradiating a laser beam on the substrate and concentrating the electric field generated by the near-field light generated by the optical probe in the low resistance stripe or the low resistance dot, the light utilization efficiency and resolution can be improved.

Further, when low-resistance stripes or low-resistance dots are provided in parallel with the data row direction, the near-field light generated from the optical probe when recording / reproducing information on / from the recording medium is the low-resistance stripes or By vibrating the optical probe so that the low resistance dot meanders at a constant cycle, the tracking error signal can be easily obtained with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of an information recording / reproducing apparatus of the present invention.

FIG. 2 is a configuration diagram of an optical probe and a recording medium.

FIG. 3 is a cross-sectional view showing an arrangement of a low resistance stripe of a recording medium with respect to a minute opening of an optical probe.

FIG. 4 is a process chart showing a method of forming a low resistance stripe.

FIG. 5 is a process drawing showing a second method of forming a low resistance stripe.

FIG. 6 is a process drawing showing a third method of forming a low resistance stripe.

FIG. 7 is a configuration diagram of a second recording medium and an optical probe.

FIG. 8 is a schematic view showing the operation of the second recording medium and the optical probe.

FIG. 9 is a configuration diagram of a third recording medium and an optical probe.

FIG. 10 is a configuration diagram of a fourth recording medium and an optical probe.

FIG. 11 is a change characteristic diagram of optical signal intensity of reflected light from a recording medium having a meandering low resistance stripe.

FIG. 12 is a configuration diagram of a fifth recording medium and an optical probe.

FIG. 13 is a configuration diagram of a sixth recording medium and an optical probe.

FIG. 14 is a cross-sectional view showing a vibration mechanism of the optical probe.

FIG. 15 is a block diagram of another information recording / reproducing apparatus of the present invention.

FIG. 16 is a cross-sectional view of a flat plate type optical probe.

FIG. 17 is a configuration diagram of a seventh recording medium and an optical probe.

FIG. 18 is a configuration diagram of an eighth recording medium and an optical probe.

FIG. 19 is a configuration diagram of a calculation model.

FIG. 20 is an electric field distribution diagram simulated by a calculation model.

[Explanation of symbols]

1; information recording / reproducing apparatus; 2; recording medium; 3; optical head;
4; Optical system, 5; Arm, 6; Suspension, 7; Slider, 8; Optical probe, 9; Optical fiber, 10; Metal light shielding film, 11; Micro aperture, 12; LD, 13; Collimator lens, 14; Polarized light Beam splitter, 15; 1/4
Wave plate, 16; Objective lens, 17; Condensing lens, 18;
Photodetector, 21; substrate, 22; low resistance stripe, 2
3; dielectric layer, 24; recording layer, 25; protective layer, 41; low resistance dot.

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) G11B 7/24 G11B 7/24 561T 7/007 7/007 7/09 7/09 C 7/135 7 / 135 A (72) Inventor Hiroshi Miura 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 5D029 HA06 NA07 VA01 WA02 WA03 WA18 WB11 WC06 WD12 5D090 AA01 BB03 BB05 CC01 CC04 DD01 FF02 FF11 GG03 GG22 GG38 KK02 LL01 5D118 AA13 BA01 BB03 BB07 BC04 BF02 BF03 CC06 CD03 DA25 DC10 5D119 AA11 AA22 AA28 AA43 BA01 BB02 BB04 CA06 DA01 DA05 EA02 EB02 EC20 EC34 FA05 JA35 JA64 MA05 MA06 5D789 AA11 AA22 AA28 AA43 BA01 BB02 BB04 CA06 CA21 CA22 CA23 DA01 DA05 EA02 EB02 EC20 EC34 FA05 JA35 JA64 JA66 MA05 MA06

Claims (12)

[Claims] 1. In a recording medium for recording information by near-field light generated by an optical probe, a low resistance stripe made of a metal material is provided parallel to a data column direction along a recording layer for recording information. A recording medium characterized by the above. 2. In a recording medium for recording information by near-field light generated by an optical probe, low resistance dots made of a metal material are provided parallel to a data column direction along a recording layer for recording information. A recording medium characterized by the above. 3. The recording medium according to claim 1, wherein the low resistance stripes or the low resistance dots are provided along the surface of the recording layer opposite to the surface facing the optical probe. 4. When the distance between the low resistance stripes or the low resistance dots is p, the width is w, and the aperture diameter of the optical probe is d, w <(d / 2) and (2p-w)> d. 4. The recording medium according to claim 1, wherein low-resistance stripes or low-resistance dots are provided in parallel so as to satisfy the relationship of. 5. The recording medium according to claim 1, wherein the low resistance stripes or the low resistance dots meander in a constant cycle. 6. The recording medium according to claim 1, wherein the low resistance stripes or the low resistance dots meander on one side and the other side at different periods. 7. An optical probe for irradiating the recording medium according to any one of claims 1 to 6 with near-field light to record information on the recording medium and reproducing the information recorded on the recording medium. An optical probe, characterized in that a minute opening is provided so as to face a recording medium in a part of a metal light-shielding film at the tip of a core for introducing laser light. 8. An optical probe for irradiating the recording medium according to claim 1 with near-field light to record information on the recording medium and reproducing the information recorded on the recording medium. An optical probe characterized in that a tip of a core for introducing laser light is formed into a projection shape, and a metal light-shielding film is coated on an outer peripheral surface of the core. 9. An optical probe for irradiating the recording medium according to claim 1 with near-field light to record information on the recording medium, and reproducing the information recorded on the recording medium. An optical probe characterized in that a tip of a core for introducing laser light is formed into a pyramid shape, and a part of an inclined surface of the pyramid shape is covered with a metal light shielding film. 10. An information recording / reproducing apparatus comprising the optical probe according to claim 7, 8 or 9. 11. The information recording / reproducing apparatus according to claim 10, wherein a laser is provided on the optical probe such that the polarization direction of the near-field light generated at the tip of the optical probe is orthogonal to the data row direction of the recording medium. An information recording / reproducing apparatus characterized by irradiating light. 12. The information recording / reproducing apparatus according to claim 11, wherein the near-field light generated from the optical probe when the recording medium according to claim 1 is irradiated with the near-field light from the optical probe. However, the information recording / reproducing apparatus is characterized in that the optical probe is vibrated so as to meander at a constant cycle with respect to the low resistance stripes or the low resistance dots of the recording medium.