JPH06162575A - Optical information recording medium and its information recording and reproducing method and recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide the recording medium and recorder which are less deteriorated in signal quality by a fluctuation in recording power and having high recording signal quality by forming recording thin-film layers exhibiting phase changes on a substrate having rugged grooves for suppressing the diffusion of heat generated by irradiation with a laser beam. CONSTITUTION:This optical information recording medium is provided with the recording thin-film layers 22, 23, 24, 25 which generate the optically detectable changes by the irradiation with the light beam on a substrate 21. The rugged guide grooves 27 of a width W narrower than the spot diameter of the above-mentioned light beam are formed on the surface of the substrate to be provided with the recording thin-film layers. The optical constants of the recording thin-film layers are changed by the irradiation with the laser beam. The detectable change is mainly by a change in the phase of the reflected light or transmitted light of incident light. The change in the phase is generated in the direction where the phase difference generated between the ruggedness of the substrate of the guide grooves is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, a recording / reproducing method and a recording / reproducing apparatus for recording / reproducing information at high speed and with high density using light, heat or the like.

[0002]

2. Description of the Related Art When a light beam having a uniform phase such as a laser beam is converged by a lens system, a light spot whose diameter is on the order of the wavelength of the light can be formed. Therefore, it is possible to form a light spot having a high energy density per unit area even from a light source having a small output. By utilizing this characteristic, it is possible to change a minute area of a substance, and it is also possible to read out the change of the minute area. An optical information recording medium uses this for recording / reproducing information. Hereinafter, the term "optical recording medium" or simply "medium" will be used.

The basic structure of an optical recording medium is that a recording thin film layer whose state is changed by the irradiation of laser spot light is provided on a substrate having a flat surface. Signal recording / reproduction on this medium is performed by the following method.
The recording medium is moved by, for example, rotating means such as a motor or translation means, and the focused laser beam is irradiated onto the recording thin film surface of the medium. The recording thin film absorbs laser light and heats up. When the output of the laser light is increased above a certain threshold, the state of the recording thin film changes and information is recorded. This threshold value is an amount that depends on the thermal characteristics of the base material, the relative speed to the light spot of the medium, and the like, in addition to the characteristics of the recording thin film itself. The recorded information is irradiated with a laser beam spot whose output is sufficiently lower than the threshold value, and some optical characteristics such as transmitted light intensity, reflected light intensity or their polarization direction are different between the recorded part and the unrecorded part. It detects that and reproduces.

As the recording thin film, Bi, Te, a metal thin film containing them as a main component, or a compound thin film containing Te is known. These are shape change-type recordings utilizing the fact that a thin film is melted or evaporated by laser light irradiation to form small holes. The signal reproduction from the recorded portion is performed by detecting the difference in the reflected light amount or the transmitted light amount generated between the small hole portion and its peripheral portion.

Further, there is a phase change type recording thin film which shows an optical change without a shape change. In the phase-change recording thin film, the phase state changes depending on the irradiation condition of the laser beam, and the complex refractive index changes during that time. Generally, the refractive index n of a complex refractive index and the extinction coefficient k change in the same direction, and most substances considered as optical recording media have two values when the phase state changes from an amorphous state to a crystalline state. Will increase. The signal reproduction from the recording thin film is performed by irradiating a weak light onto the signal pattern formed as the phase difference and measuring the amount of transmitted light or the amount of reflected light from the medium.

Light is a wave and is described by its amplitude and phase. Information from the recording medium is detected by detecting a change in the amount of transmitted light or reflected light on the photodetector of the reproduction optical system.The cause of the change is the transmitted light amplitude or reflected light in a minute area of the film itself. There are cases where the amplitude changes (amplitude change recording) and cases where the phase of transmitted light or reflected light changes (phase change recording). The reproduced signal is obtained as a change of the complex refractive index due to the phase change, which is a combination of the changes of both the amplitude change and the phase change. Currently in this
An optical disk using a phase-change recording material that has been put into practical use mainly uses the amplitude change of reflected light and corresponds to the former amplitude change recording. On the other hand, phase change recording has been proposed as a recording method for increasing the signal recording density as compared with amplitude change recording (Japanese Patent Laid-Open No. 2-73537).

The phase-change optical disk records a signal by irradiating a rotating recording medium with a laser beam whose intensity is modulated to form a local phase state difference (recording mark) on the recording thin film. The signal is reproduced by detecting the difference generated between the states as the reflectance difference. The size of the obtained recording mark is the size of the light spot to be condensed,
That is, the wavelength order is obtained. For example, when the laser light having a wavelength of about 780 nm is narrowed down by using a lens system having an NA of about 0.5, the half-value intensity width is narrowed down to a spot having a width of about 0.9 μm.
The intensity of the light spot generally has a Gaussian distribution or a distribution close to it. When recording is performed with a strong power using such a spot, a phase change occurs in a range of about 0.5 to 1 μm and the recording state is obtained.

FIG. 2 shows a recording mark that gives the maximum signal change when the phase change recording thin film has a structure showing amplitude change recording (a) and a structure showing phase change recording (b). And the light spot. In the structure shown in amplitude change recording (a), the amplitude change recording mark 3 formed on the recording thin film 2 on the substrate 1 mainly changes in reflectance. Weak light I for reproduction on mark 3
_{When the} light spot 4 consisting of ₀ is scanned, the light amount change on the photodetector obtained by the reproduction optical system, that is, the condition that the signal amplitude is maximum, that is, the reflected light I ₂ of the recording mark portion and the reflection in the unrecorded state The condition for maximizing the difference of the light I ₁ is that the size of the phase-changed recording mark 3 is equal to or larger than that of the reproduction spot 4.

On the other hand, also in the case of phase change recording, the state change of the recording thin film 2 itself is the same as the amplitude change as shown in (b), and the recording mark 6 is formed by the same light irradiation. The recording mark that shows the ideal phase change recording is
The reflected light I ₄ having the same intensity as the reflected light I _{3 in the} unrecorded state is reflected with respect to the incident light amount I ₀ , and the phase of the light changes by φ. The recording state due to this phase change works in the same manner as when the unevenness pit 7 is formed on the plane portion with respect to the light spot as shown in FIG. 1C and the phase changes due to the unevenness of the unevenness. Here, the condition for showing the maximum signal amplitude by the phase change recording is a condition under which the light diffraction effect due to the phase difference becomes maximum when the reproduction spot 4 scans the recording mark. That is, in the light spot 4, when the light intensity of the region incident on the recording mark 6 is equal to the light amount incident on the peripheral portion, the effect of interference is greatest, and the light amount to the photodetector is minimum. In this case, the reflected light amount I ₄ from the recording mark and the reflected light I ₃ from the unrecorded portion interfere with each other and the reflected light amount is minimized under the condition of canceling each other, so that the maximum signal amplitude of the phase change recording is obtained.

In this way, comparing the two recording modes with the recording mark showing the maximum amplitude, the phase change recording mark 6 is
Since the recording can be performed in a shape smaller than the reflectance change recording mark 3, it is understood that the phase change recording can perform high-density recording / reproduction. If phase change recording can be realized,
It is possible to provide a recording medium compatible with a read-only optical disc such as a compact disc which has concave and convex pits as recording information.

[0011]

However, since the phase change medium showing the phase change recording is the heat mode recording utilizing the heat of light, the light irradiation part of the recording thin film is accompanied by the thermal diffusion phenomenon. . That is, the temperature of the portion that has absorbed the light energy rises, and at the same time, the heat generated at the same time diffuses to the lower temperature portion. Therefore, there is a problem in that the size of the recording mark formed in the irradiation portion changes not only according to the intensity distribution of the irradiation light but also in accordance with the amount of energy (irradiation power) applied. In the case of the conventional change of reflected light, the mark shape has a spot diameter (light intensity is 1 /
the maximum signal amplitude equal to e ² and composed magnitude). The pitch of marks recorded in the track direction is set to a value equal to or less than the spot diameter from the viewpoint of increasing the recording density as much as possible. Therefore, in order to stably reproduce the signal from the recording section, it is necessary to set the size of the recording mark within a certain range. For that purpose, it is necessary to set the energy of light irradiated during recording, that is, the recording power within a certain range. When the change in mark shape with respect to the recording power is large, this power range becomes small, and it becomes extremely difficult to design a recording device that includes fluctuations and variations in the recording laser light. Phase change recording can be said to be suitable for high density recording because the mark shape for obtaining the same amplitude can be made relatively smaller than amplitude change recording. However, forming a small recording mark has a problem that it becomes more difficult to maintain a permissible width with respect to recording power fluctuation, that is, the recording power within a certain permissible range.

An object of the present invention is to provide a recording medium for stably forming minute recording marks, and a recording method and apparatus therefor.

[0013]

In order to solve the above-mentioned problems, an optical information recording medium and a recording / reproducing method of the present invention are arranged so that a substrate is irradiated with a light beam condensed through a lens to optically record information. Is a recording medium provided with a recording thin film layer for recording data, the substrate having an uneven guide groove having a width narrower than a spot diameter of the focused light beam on the surface, Area of the recording thin film layer in the first state when the light beam having the second intensity lower than the first state is changed by irradiating the light beam having the second intensity In the region of the second state, the phase of the reflected light is different, and in the direction of decreasing the phase difference generated between the concave portion and the convex portion of the guide groove, the second state is changed.
It has a configuration in which the phase changes to a state.

[0014]

According to the present invention, by forming the recording thin film layer exhibiting a phase change on the substrate having the guide groove by the above-mentioned structure, the heat generated by the light beam is diffused in the thin film surface direction to prevent the edge of the guide groove from diffusing. Therefore, it is possible to perform recording in which the shape of the recording mark in the width direction is within a certain range with respect to the fluctuation of the recording power. Further, by recording by the irradiation of the light beam, which shows the same phase change as the depth of the guide groove and the opposite phase change, it is possible to obtain the same signal amplitude as that in the case of recording on the flat surface portion.

As a result, by using the phase change recording medium, it is possible to obtain a recording medium and a device which have a high recording density and can cope with the environment at the time of recording and the aging of the optical system of the device.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium and a recording method therefor according to an embodiment of the present invention will be described below with reference to the drawings.

First, a configuration example of a recording medium exhibiting a phase change will be described. FIG. 1 shows the structure of the recording medium and a cross-sectional view of the thin film structure. While rotating the optical disc 10, which is one of the optical recording media, by a rotating means such as a motor, the optical system 11 focuses the light beam on the recording thin film layer on the optical disc. The optical system is a laser light source 1 such as a semiconductor laser.
2 and the objective lens 13 for condensing the light beam, and the photodetector 14 for detecting the reflected light from the optical disk. Based on the signal from the photodetector 14, control for causing the light beam 15 to follow a specific track on the optical disc and reproduction of the signal recorded on the optical disc are performed.

The cross-sectional structure of the optical disc irradiated with the light beam is shown in the above figure. The substrate 21 is provided with a transparent layer 22, such as an optically transparent dielectric material, a recording layer 23, a transparent layer 24, and a reflective layer 25. Further, a transparent and protective protective layer 26 is provided thereon. In addition to this, although not shown in the drawing, a structure in which the protective layer 26 is not provided may be used. In this case, considering air (refractive index 1.0) instead of the protective layer, they are optically equivalent and the same effect can be obtained. A material having a refractive index different from that of the substrate 21 is used for the transparent layer 22.

By setting the thickness t2 of the recording layer, the thicknesses t1 and t3 of the transparent layer, and the thickness t4 of the reflective layer to specific values, a medium having a large phase change can be obtained.
It should be noted that a thin film structure showing a phase change, here, the recording layer 23,
A layer structure in which the transparent layers 22 and 24 and the reflective layer 25 are integrated is described as a recording thin film layer.

As the substrate 21, a transparent and smooth flat plate such as glass or resin is used. The shape of the substrate differs depending on the application, and is a circular flat plate for an optical disk, a square flat plate for an optical card, or a tape shape for an optical tape. As will be described in detail later, a guide groove 27 having an uneven shape is formed on the surface of the substrate to make the best use of the optical characteristics of phase change recording and to secure the shape of the recording mark. As the protective layer 26, a resin dissolved in a solvent and applied and dried, or a resin plate adhered with an adhesive can be used.

The recording layer 23 is made of a material that causes a phase change between amorphous and crystal, for example, SbTe system, InTe.
System, GeTeSn system, SbSe system, TeSeSb system, S
nTeSe system, InSe system, TeGeSnO system, TeG
A chalcogen compound such as eSnAu type or TeGeSnSb type is used. Te-TeO ₂ system, Te-TeO ₂ -Au
Oxide-based materials such as those based on Te-TeO ₂ -Pd-based can also be used. In addition, AgZn-based materials having a crystal-crystal phase transition, I
A metal compound such as nSb type can also be used. These materials can be selected in combination or composition depending on the intended use of the recording medium, such as when a phase transition occurs in only one direction or when a reversible change occurs a number of times depending on the intended use. .

As the optically transparent transparent layer 24, SiO is used.
Oxides such as ₂ , SiO, TiO ₂ , MgO, and GeO ₂ , S
i ₃ N ₄ , BN, nitride such as AlN, ZnS, ZnTe,
Sulfides such as PbS can be used. Au, A as the reflective layer
A metal material such as l or Cu, or a dielectric multilayer film having a large reflectance at a predetermined wavelength can be used.

The film thickness of each recording thin film layer can be obtained by optical calculation. By the matrix method, the complex refractive index of each layer, the reflectance with respect to the film thickness, and the phase of the reflected light were calculated (for example, Hiro Kubota "Wave Optics" Iwanami Shoten, 19
71, see Chapter 3). In addition, the substrate 21 and the adhesion protection layer 26
Is an infinite film thickness (ignoring the effect of the base material-air interface, the adhesion protection layer-air interface), the reflectance is determined as the ratio of the light incident from the substrate to the base material,
The phase was determined based on the phase at the interface between the substrate 21 and the transparent layer 22. Note that the phases are equivalent at a period of 2π.

For the optical calculation, the wavelength of the irradiation light is 780
nm, and the optical constant of each layer with respect to this wavelength was defined. Each thin film layer, each material is formed on the glass substrate by a sputtering method, the thin film thickness obtained at the beginning is measured, and its transmittance and reflectance are measured by a spectrophotometric system, and those values are calculated. The optical constant was calculated based on the original. Recording layer 2
As an optical constant in the as-formed state (amorphous state) by sputtering using a ternary compound of germanium, antimony and tellurium having a composition of Ge ₂ Sb ₂ Te ₅ which is a phase change material as 3, The rate (n + ki) was (4.5 + 1.3i). In a crystalline state where this was heat treated at 300 ° C. for 5 minutes (5.5
It became + 3.4i). In this way Ge ₂ Sb ₂ Te
₅ shows a phase change between amorphous and crystalline, and this state shows a reversible change depending on the irradiation condition of laser light. Polycarbonate resin (PC) is used for the substrate 1, zinc sulfide (ZnS) is used for the transparent layers 2 and 4, and gold (Au) is used for the reflective layer 5, and the complex refractive index is (1.58 + 0i), (2.
10 + 0i) and (0.18 + 4.64i).

Optical calculation was performed by changing the film thickness of each layer,
From the results, the optimum film thickness conditions were determined from the following three points so that the phase change effectively acts as the optical recording medium.

1) Amorphous state of recording layer (recording portion)
And the condition that the phase difference of the reflected light from the crystalline state (unrecorded portion: peripheral portion other than the amorphous state) is maximum, that is, the phase difference is close to (1 ± 2s) π (s is an integer).

2) In the optical change caused by the change in the state of the recording layer, the reflectance of the recorded portion is equal to that of the unrecorded portion so that the change in the amplitude does not reduce the effect of improving the recording density due to the change in the phase. The reflectance of the area is higher than that of the unrecorded area.

3) The reflectance of the state is as high as possible from the viewpoint of the reliability of the servo operation when the device is constructed and the obtained signal amplitude is large.

The calculation results obtained by changing the film thickness of each layer show a large phase change when the recording layer 23 has a thickness of 40 nm or less. Among them, the thickness of the recording layer 23 is 15 nm,
When the thickness of 5 is 50 nm and the thicknesses of the transparent layers 22 and 24 are 116 nm and 35 nm, respectively, the reflectance in the amorphous state is 6.8%, the reflectance in the crystalline state is 7.6%, and the amount of phase change is It became (-0.86) π. Hereinafter, examples of the present invention will be described in detail using the phase change recording layer having this film thickness configuration.

As a method of securing the operation margin against the power fluctuation at the time of recording which is the object of the present invention, the phase change medium is formed on the substrate having the guide groove 27 of a specific shape. The effect of limiting the shape of the recording mark by the guide groove is shown in FIG.
The model will be used for explanation.

(A) shows an example in which the recording thin film layer 32 is formed on the substrate 31 having a flat surface, and (b) shows the recording thin film layer 32 provided on the substrate 21 having the guide grooves 27 having irregularities on the surface. It has a different structure. Under the respective conditions, the shape of the recording mark when the power of the irradiation light is low is changed to the wavy lines 33, 3
4 and the shapes of the recording marks formed when the recording power is high are shown by solid lines 35 and 36. In the case of recording on the flat surface portion as shown in FIG. 7A, when the recording power becomes higher, the recording mark expands in both the track direction and the track vertical direction due to the thermal diffusion 37 in the film surface direction of the thin film. Such a change in the recording mark shape results in a change in the signal amplitude during reproduction, resulting in an error during signal demodulation. On the other hand, when a signal is recorded on the guide groove as shown in (b), the recording mark 36 is the same as when recording on a flat surface when the recording power is low, but when the power is high, the recording mark 36 becomes a track of the recording mark. A recording mark 38 having a shape in which the expansion of the mark in the vertical direction is suppressed can be obtained. That is, thermal diffusion 38 in the direction perpendicular to the track is small. This is because the guide groove increases the effective distance for heat diffusion,
Further, it is conceivable that the film thickness of the recording thin film layer at the edge portion is reduced. Due to this heat shielding effect, the difference in the size (area) of the obtained recording mark with respect to the change in the recording power becomes small, so that the fluctuation in the signal amplitude becomes small and the operating power margin seen from the optical recording device is expanded. It becomes possible.

The shape of the guide groove must be within a certain range according to the phase change amount of the recording thin film layer. Even if the size of the recording mark is the same, the signal amplitude at the time of reproduction differs between recording on the plane and recording on the guide groove. When the guide groove is present, the reproduction signal is the result of superimposing the phase change caused by the recording mark and the phase difference caused by the step between the irregularities of the guide groove. Therefore, the amount of reflected light when the light spot moves on the recording mark 36 is between the track and the convex portion of the guide groove in the vertical direction because the track direction component is mainly due to the phase difference generated between the concave portions of the guide groove. It is determined by the phase difference caused by. That is, the phase difference generated at the convex portion of the guide groove often acts in the direction of decreasing the phase difference term of the recording thin film. For this reason, in this embodiment, the recording mark indicating the phase change is formed in the direction in which the phase difference caused by the unevenness of the guide groove is offset.

The recording mode of the phase-change recording medium used in this embodiment will be described in the form of forming a mark in an amorphous state on the crystalline state (peripheral portion). For example, the recording mode in the reverse direction may be used. Further, the recording may be performed by utilizing the state change between the crystalline state and another crystalline state. Further, regarding the groove shape of the substrate, a convex shape on the laser light side is used, but conversely, it may be concave on the laser light side. Further, regarding the groove depth of the concave and convex grooves, λ / 4n (n: refractive index of the substrate) will be described. The same effect as the present invention is shown depending on the configuration of the servo system of the recording device or the allowable amount of servo. Any value is fine.

In this embodiment, rewriting of the phase change medium will not be described in detail, but the present invention uses the phase change recording material used for the conventional amplitude change, and changes the phase by changing the film thickness constitution. The same effect can be obtained even after rewriting.

In addition to the four-layer structure shown in FIG. 2, the structure of the recording thin film showing a phase change is a three-layer structure in which transparent layers 22 and 24 are provided on both sides of the recording layer 23 as shown in FIG. Construction,
Alternatively, as in (b), a two-layer structure in which the transparent layer 22 is provided between the substrate 21 and the recording layer 23 can also be realized. For example, when a ternary alloy thin film having a composition of Te ₄₉ O _23P d ₂₈ was used as the recording layer 3 and the complex refractive index of this thin film was measured,
The amorphous state was (3.1 + 1.2i), and the crystalline state after heat treatment at 300 ° C. for 5 minutes was (3.9 + 1.6i). As a result of obtaining the film thickness constitution from the optical calculation, as the two-layer structure, the transparent layer 24 is ZnS and the recording layer is Te ₄₉ O _23P.
Using a thin film of composition d ₂₈ , each film thickness is 97 nm,
When it was set to 20 nm, the amount of phase change was about (−π / 2). The same material is used for the three-layer structure, and the transparent layer 2
2, the recording layer 23 and the transparent layer 24 at 76 nm and 30 respectively
nm and 130 nm, the amount of phase change is about (-π
/ 2). Even in the above thin film structure,
It is possible to obtain a disk having a similar phase change structure. Furthermore, if a recording layer having a small imaginary part of the complex refractive index, that is, a small attenuation coefficient and a large refractive index change between the two states is applied, the phase change can be achieved even in a single-layer structure in which only the recording layer is formed on the substrate. Recording can be realized.

(Embodiment 1) The structure of the guide groove for limiting the shape of the recording mark with respect to the change in recording power will be described. FIG. 5 shows the amount of reflected light which is incident on the photodetector of the optical system when the groove depth d is changed with the width of the guide groove being constant. The amount of light reflected from the flat surface portion (d = 0) is used as a reference and shown as a relative value. The amount of reflected light decreases as the groove becomes deeper, and shows a minimum change at λ / 4n. Further, when it becomes λ / 4n or more, the amount of light increases, and at λ / 2n, the phase of the reflected light from the groove becomes equal to one rotation (λ = 2π), and the amount of reflected light becomes equivalent to that of a plane. From the figure, it can be said that the condition that the change of the guide groove, that is, the maximum change of the reflected light amount in the phase change recording is the case where the phase recording mark having the flat portion and the λ / 4n depth is formed. The figure shows an ideal state in which the shape of the edge portion of the guide groove is assumed to be vertical. When the edge portion is a slope due to the formation conditions of the substrate, the curve is in the direction of large depth d. It shifts and the minimum value of the reflected light amount becomes larger than zero.

FIG. 6 is a conceptual diagram when phase change recording is performed on a substrate in which the depth d of the guide groove is changed. As described above, the recording state of the phase change recording does not occur due to the shape change, but since only the phase changes without changing the reflectance of the thin film, it can be regarded as the recording in which the unevenness is formed. 6 (a), (b), and (c) in this order, 0,
The case of a guide groove having a depth of λ / 8n or λ / 4n is shown. The amount of phase change generated in the recording thin film was set to −π, which indicates the maximum phase difference between the recorded mark portion and the unrecorded portion. Where λ / n
= 2π, the groove depth is indicated by λ, and the phase difference is described by π. Flat surface, guide groove 60, 61
The phase change due to the recording mark caused by the recording above is
As described with reference to FIG. 1, the incident light beam 15 operates similarly to the case where the concave and convex pits are formed. Therefore, in FIG. 6, in order to facilitate understanding of the phase relationship between the guide grooves 60 and 61 and the recording mark, a virtual mark 62 in which the phase is expressed by unevenness is used. When recording on a phase-change medium, in this case the state where an amorphous recording mark is formed on a crystalline state, an uneven pit of λ / 4 corresponding to a phase difference of −π is formed on a flat surface or guide grooves 61 and 62. It becomes the formed shape. In the case of (b), the amount of reflected light at this time is the phase 3 generated between the unevenness (virtual mark) due to the phase change, the concave surfaces 60 and 61 of the guide groove, and the plane 63 in each structure.
It is represented by the composition of two components. Here, in the case of (c) with the groove depth λ / 4n, the virtual mark 62 and the flat surface 63 of the substrate become the same plane as in the case of (a) recorded on the flat surface portion, which occurs between the unrecorded portion and the recorded mark. The difference in the amount of reflected light becomes maximum.
As a result, it can be seen that the same amount of phase change as that of the conventional reproduction-only pit signal can be obtained.

For example, when the phase change medium having the above-described structure is formed on a substrate having a guide groove having a depth of λ / 4n and a signal is recorded in this guide groove, the phase change amount of the recording mark is -0.86π. Therefore, the step between the virtual mark and the plane is +
The recording was performed with 0.14π, and the depth of the normal guide groove was about 1/7. Even in this case, a sufficient level can be obtained as the signal amplitude. Note that this −0.
For a recording medium showing a phase change of 86π, ideally a guide groove giving a phase difference of 0.86π, that is, 0.2
The maximum amplitude can be obtained by using the guide groove having a depth of 15λ.

As described above, in order to make maximum use of the phase change of the phase change medium, the phase change amount due to the recording thin film layer and the absolute value of the phase difference due to the guide groove are made to coincide, and the direction of the phase has the opposite polarity. To be. Further, the same effect can be obtained even if the absolute value of any of the phase differences is a value obtained by adding a value that is an integral multiple of λ (phase change amount = 2π).

However, as shown in FIG. 5, the groove depth λ / 4
In the conventional push-pull tracking method, a control signal cannot be obtained from n unrecorded guide grooves in the conventional push-pull tracking method because the irradiated light is in a non-reflective condition. In order to solve this, in FIG. 7, a sample servo method that can separate the data area 71 and the servo area 72 is adopted. Sample pits 74 and 75, which are deviated by p on both sides from the center line of the recording track constituted by the continuous guide groove 73, are arranged in the data area, and the tracking signal is generated based on the reproduction signal from the sample pit 74. Is the way to get. At the time of tracking servo, servo is performed so that the amount of reproducing light from the rear sample pits 74 and 75 forming a pair with the front sample pit becomes constant, and the continuous groove 73 in the data area is formed.
Then, tracking control is performed by holding the control signal from the above-mentioned sample pit. In the case of this sample pit, even if the depth of the pit is λ / 4n, a signal can be obtained from any one of the pits, so that a stable tracking servo state can be obtained. The phase change signal is recorded by modulating the laser light according to the timing signal from the clock pit 76. Similarly, it is desirable that the focus signal is mainly servoed outside the region of the continuous groove.

Next, a method of setting the groove width W1 of the guide groove will be described. The width W1 of the guide groove for recording this mark was changed stepwise to measure the signal with respect to the recording power. The thin film having the above-mentioned layer structure is rotated at a linear velocity of 10 m / s, and a semiconductor laser beam of 780 nm is irradiated with a numerical aperture NA.
An experiment for recording a 6 MHz signal was performed by focusing on the recording layer with a lens of 0.5. The power of the laser light was set to a bias level of 5 mW, the power of the peak level was changed stepwise, and the signal quality (C / N) for each power was measured. As a result, when recording on a plane without grooves,
The peak power of 15 mW was shown as the maximum change, whereas in the range of the groove width of 0.2 to 0.8 μm, the C / N was within the range of ± 5% of the recording power fluctuation and within the range of ± 1 dB or less. Existed. Particularly, in the range of 0.3 to 0.6 μm, the change of the signal amplitude was small with respect to the increase of the peak power ± 10%. In addition, the power at which the signal amplitude has a constant value shifted to the higher power side as the groove width increased. As a result of observing the recording state in the power region where the signal amplitude change was small with a transmission electron microscope, it was confirmed that the mark width was limited at the edge of the guide groove. This means that the step at the edge portion of the groove hinders the diffusion of heat from the center of the recording mark. From this result, by using a substrate whose groove width is set to the above condition, it becomes possible to perform recording with a constant recording width with respect to fluctuations in recording power. That is, in the case of forming a small mark such as phase change recording, it is possible to obtain good recording conditions by optimally selecting the heat insulation conditions for the groove edges.

The groove width condition shown here is a wavelength of 780 nm,
This is the result in the case of a light spot determined by the numerical aperture = 0.5, and when the diaphragm is changed by the design of the optical system, the relationship of the following equation is established. 0.2-obtained under the above conditions
For a groove width of 0.8 μm, that is, a power fluctuation of ± 5%, C
The groove width W1 at which the change in / N is ± 1 dB or less is expressed by the following equation, where λ is the wavelength and NA is the numerical aperture.

0.13 ≤ W1 × NA / λ ≤ 0.51 (Equation 1) In the case where the film thickness constitution of each thin film layer of the recording medium or the thermal conductivity of the constituent substances is greatly different from the above embodiment, It is necessary to select not only the groove width, but also the groove depth and the groove edge shape as required.

(Embodiment 2) As a method of obtaining the heat insulating effect by the edge of the groove width, it is more effective to surround the periphery of the recording mark with the groove edge. In a conventional phase change medium utilizing the change in reflectance, as a method of improving the durability of repeated recording, instead of a guide track consisting of continuous grooves,
A method for forming capsule-shaped pits has been proposed (Jpn.J.Appl.Phys.Vol.31 (1992) p.482). It has been reported that by irradiating the center of the capsule-shaped pit with a laser beam for a short time, the total irradiation energy at the time of recording can be made smaller than that of the conventional method, so that the recording life of the thin film is improved. In this embodiment, a recording medium is obtained by forming a thin film exhibiting a phase change on a substrate provided with pit capsules having the same arrangement. FIG. 8 shows that the portion corresponding to the guide groove shown in Example 1 is formed by a pit capsule in which circular concave and convex pits are provided close to each other. The tracking system uses the sample servo system described above, and the pit capsule 81 is a clock pit 7.
6 are formed at regular intervals, and the pitch Cp of each pit capsule in the track direction is twice or less than the diameter W2 of the capsules and provided close to each other. At the time of recording a signal, the light beam irradiates a laser pulse at a constant time interval from the timing at which the clock pit 76 is detected, thereby recording at the center of a predetermined pit capsule.

FIG. 9 shows a conceptual view of a recording state when the recording thin film layer is formed on the pit capsule 81 and a mark is formed on the recording thin film layer as viewed from the phase. On the surface of the substrate 91, a pit / 4 pit capsule 81 having a depth d was provided.
When the recording thin film layer is irradiated with recording light on a thin film in a crystalline state (unrecorded state), an amorphous state recording mark is formed,
The phase difference generated between them is −π. The recording mark in the amorphous state, with respect to the incident light beam 15,
As indicated by the virtual mark 92, the step due to the pit capsule disappears, and the height becomes equivalent to that of the flat surface portion 93.

Next, the experimental results of recording a signal by actually forming a phase change thin film on the substrate having the pit capsule 81 will be described. Recording was performed by setting the diameter of the capsules to 0.7 μm, providing pit capsule rows arranged at a pitch of 0.8 μm, and forming amorphous marks alternately on each capsule. The recording optical system was recorded under the same conditions as the continuous groove, with a recording pulse width of 20 ns, and the pit capsules were alternately irradiated with pulses. As a result, C /
N showed a substantially constant value in the range of ± 15% or more centered on 18 mW, and it was found that the heat insulating effect of the recording mark was effectively exerted by the edge of the pit capsule. Further, comparing the same examination with the measurement result of the thin film showing the conventional reflectance change, although the change of C / N with respect to the recording power was equal, the absolute value of C / N of the signal amplitude was 6 dB or more. It turned out to be a big rise. That is, the pit capsule has the effect of improving the thermal damage in the case of the recording using the conventional reflectance change, but from the viewpoint of signal detection, on the contrary, the pit capsule shows the signal amplitude of the reflectance change. Function to decrease. On the other hand, when the phase change medium is used, it is possible to secure a large signal amplitude and a large recording power operation margin. Furthermore, the effect of suppressing thermal damage to the thin film is
It is possible to make it as small as the reflectance change.

As described above, by using the substrate using the pit capsule, it is possible to greatly expand the permissible range with respect to the power fluctuation during recording. Further, it is possible to perform recording with higher signal quality than the conventional reflectance change recording of the same system.

Although the effect of the guide groove using the pit capsule shown here further promotes the heat-shielding effect of the continuous groove, the signal obtained during reproduction is the same as when recording in the continuous groove. Can be treated to. Therefore, in the following embodiments, in order to simplify the description, the description of the guide groove will be described including two concepts of a continuous groove and a capsule pit.

(Embodiment 3) In Embodiments 2 and 3, the method of using the guide groove of the sample servo system was used. Here, a method of recording using the guide groove in the continuous servo system will be described.

Table 1 shows the change in the light quantity with respect to the groove depth and the stability of the servo operation. As the servo method, the astigmatism method or knife edge method is used for focus control.
This is a comparison when the three-spot method used for a read-only disc is used for tracking control.

[0051]

[Table 1]

In the conventional servo system, it can be seen from (Table 1) that there is no condition that simultaneously satisfies the two conditions of a large signal amplitude and a servo signal being obtained. As a method of solving this, the following embodiments show a method of recording / reproducing a signal by enabling focus control of a recording medium using a guide groove near a depth λ / 4n.

FIG. 10 shows the relationship between the optical system (a) of the present optical information recording apparatus, the modulation waveform of light, and the obtained recording mark. Light is emitted while the optical recording medium 100 is rotated by the motor 101. The light from the semiconductor laser 102 becomes 0th order and ± 1st order diffracted light at the beam splitting diffraction grating 103 and becomes parallel light at the collimator lens 104, and the PBS 105, the λ / 4 plate 106, and the objective lens 107.
And is condensed into three light spots on the recording thin film surface of the recording medium 100. The reflected light from the recording thin film passes through the objective lens 107 and the λ / 4 plate 106, and the PBS 10
It is reflected by 5, and is condensed by a cylindrical lens 108 on a photodetector 109 having a plurality of light receiving surfaces. Based on the output signal from the photodetector 109, the signal is amplified to create a reproduction signal, a focus error signal, or a tracking error signal, and the voice coil 107b performs a servo operation.

FIG. 11 shows the structure of a light spot on the optical recording member. A guide groove 110 formed from a continuous groove having irregularities
Then, three spot rows of the 1 spot 111 corresponding to the 0th order of the diffracted light of the diffracted photons and the 2nd sub-spots 112 and 113 corresponding to the ± 1st order diffracted lights are condensed. After that, the primary spot 111 is the main spot,
The secondary and tertiary spots are also called sub-spots. The center axis connecting the respective spots is tilted in the direction of the guide groove 110, and as the tilt amount, the main spot 111 and the sub-spots 112 and 113 are displaced by about 1/4 of the track pitch Tp in the guide groove direction. To place. Focusing control and tracking control of the light beam are performed by detecting reflected light or transmitted light from the sub-spots 112 and 113. A signal is recorded on the recording medium by the main spot 111, and the recorded information signal is reproduced by detecting reflected light or transmitted light from the recording medium.

When the main spot 111 is located at the center of the guide groove 110 as shown in the figure, the reflected light from the guide groove does not enter the photodetector due to diffraction. However, the sub-spots 112 and 113 are irradiated at a position displaced from the center of the guide groove by a certain distance. Therefore, a certain amount of light is incident on the photodetector at each of the sub-spots 112 and 113. Utilizing this fact, the present invention obtains a control signal.

The phase change material used in the phase change recording of this embodiment is recorded by intensity modulation of a single light beam. FIG. 10B shows the change in laser light intensity during recording and the obtained recording mark. Note that each power is a change in the intensity of the main spot 111. The power of the main spot is obtained by irradiating the recording thin film on the track 110 on the optical disc with light modulated from the reproducing power Pr between the peak power Pp and the bias power Pb corresponding to the information signal. When such a light is irradiated, the irradiated portion changes the peak power irradiated portion 3a into an amorphous state and the bias power irradiated portion 3b into a crystalline state. This is whatever the previous recording status was,
It will be in each state regardless. Due to the above characteristics, the phase change medium is used for overwriting.

The problem here is that the main beam 11
Since 1 and the sub-beams 112 and 113 are emitted from the same semiconductor laser, the change in the main beam is a change in the power of the sub-beam at the same time. The optical recording device
It is necessary to have a certain allowable range with respect to fluctuations in irradiation power in consideration of changes in the operating environment and optical system, and changes over time in the optical recording medium. Therefore, when recording is performed with the maximum expected peak power, the sub-beam 11
It is necessary that the recording signal of the recording track or the adjacent track is not erased by 2 and 113. here,
The light quantity ratio between the sub beam and the main beam separated by the diffraction grating sets the following condition within a certain range. The maximum peak power Pp-max of the main beam that amorphizes during recording and the minimum bias power Pb-min that crystallizes.
Then, between the main beam power P-main and the power P-sub of one of the sub-beams, a value that satisfies the relationship of P-main / P-sub> Pp-max / Pb-min (Equation 2) To do. With the above configuration, it is possible to prevent the above-mentioned erasure of the recording mark by the sub beam.

FIG. 12 shows the structure of the photodetector. (A) is for a conventionally used three-beam servo,
(B) shows the configuration of the present invention. The servo system shown in (a) uses the detector 120 for detecting the reflected light from the main spot 111.
Focusing control is performed by receiving the light on the surface of the sub-spots 112 and 113, and the reflected light from the sub-spots 112 and 113 is detected by the photodetectors 121 and 122, and the tracking control signal TE is obtained from the intensity difference between them to perform control. I was going. However, as shown in (Table 1), when a guide groove having a depth of λ / 4n is used, in the unrecorded state, when a light beam is irradiated onto the guide groove, no reflection condition occurs and reflected light becomes It will not be incident on the detector. Therefore, focus servo by the main beam becomes impossible.

In order to solve this, as shown in FIG. 12B, the reflected light of the sub-spots 112 and 113 is divided into four detectors 124 and 125, and the output signals of the detectors 124 and 125 are used to detect the light on the photo detector. Focus control is performed by making the distribution constant. As described above, the sub-spot is located at a position displaced by about 1/4 of the track pitch of the guide groove, so that a constant amount of light is incident on the photodetector even when the main beam is in the center of the guide groove. As a result, λ / 4n
Servo is possible in the guide groove of.

Here, the two detectors 124 and 12 are used.
Although an example of performing focus control by using 5 at the same time is shown,
Only one of the detectors may be used. Further, the light-receiving surface of the photodetector 123 for the main spot is one, but if the light-receiving surface is divided into four, it is possible to perform control using the conventional three-beam servo together. When the knife edge method is applied as the focus control method, the lens 108 shown in FIG. 10 may be an ordinary spherical lens, and a shield plate for shielding a part of the reflected light may be provided just before the photodetector 109. .

(Embodiment 4) In Embodiment 3, the focus control is carried out by using the sub-spots of the three irradiation spots. Here, the conventional photodetection system shown in FIG. 12 (a) is used. The present invention relates to a method capable of servo operation depending on the system.

When the guide groove of λ / 4n is used as shown in (Table 1), focus control is impossible in the unrecorded state. Further, in the recording state, the reflected light from the main spot is incident on the photodetector. Utilizing this fact, in the present embodiment, focus control can be performed by the conventional photodetector by performing pseudo recording when forming the optical recording medium.

FIG. 13 shows the manufacturing process of the optical recording medium of the present invention. As a process for forming the disc itself,
A substrate forming step 131 for forming a substrate having a guide groove on the surface by a method such as injection molding, a film forming step 132 for forming a recording thin film layer on the substrate by a sputtering method or the like,
There is a protection processing step 133 for forming a protective layer such as resin on the thin film layer. The recording thin film at this stage is in an amorphous state as it is formed. Next, initialization A134 is performed to change the amorphous state to the crystalline state. This state is the unrecorded state shown in Examples 1, 2, and 3. In the present invention, initialization B135 of irradiating the recording medium in this state with laser light is further performed. Initialization B is
The wavelength of the laser light used for irradiation is different from that of the laser light for actually recording data. Here, an Ar laser is used as a laser light source, and for example, the semiconductor laser section of the optical system shown in FIG. 10 is replaced with an optical component adapted to the wavelength of the Ar laser, whereby focus control is performed on the optical recording medium. I do. In this case, since the depth of the guide groove is adapted to the above-mentioned semiconductor laser having a wavelength of 780 nm, the groove depth becomes 1.5 times at the wavelength of 524 nm of the Ar laser. That is, a groove having a depth of λ / 4n of 780 nm corresponds to 3λ / 8n at 524 nm, and a sufficient amount of light is incident on the detector even in the main beam, which enables focus control. The tracking control is performed using the reflected light of the sub beam as in the conventional case. By such a process, the Ar laser light is modulated at a predetermined frequency by the AO modulator or the EO modulator while the focus / tracking control is performed, so that a constant light and shade pattern is formed on the guide groove of the optical recording medium. A recording mark composed of is formed. Once this state is obtained, focus control can be performed by the optical system equipped with the semiconductor laser shown in FIG. 10, and subsequent data recording can be performed. The recording mark formed in the initialization B is
It should be in a form that can be distinguished from the data signal in the actual use state. To this end, it is possible to confirm the unrecorded state by providing an identification signal indicating that the data is not real data in a specific area on the recording medium or by making the pattern different from the data pattern.

Although the control method using three spots for servo was used here, the groove depth is 524n as described above.
In the case of m, 3λ / 8n, and a sufficient tracking error signal can be secured even by the push-pull method. In this way, focusing or tracking using a single laser spot is also possible by selecting the wavelength of the laser light used for initialization according to the disk configuration.

On the other hand, the recording mode has been described so far only when the recording medium forms crystals and amorphous marks. However, if the change gives an optical phase difference, the recording mode is in the opposite direction or between the crystals and the crystals. It may be a record using the state change of. Regarding the groove shape,
Although the convex shape is shown on the laser beam side, conversely, it may be concave on the laser beam side. Further, the groove depth of the concavo-convex groove has been described only for λ / 4n, but it may be any value having the same effect as that of the present invention depending on the configuration of the servo system of the recording apparatus or the allowable amount of servo.

Although the rewriting of the phase change medium was not described in detail in the present embodiment, the present invention only changes the film thickness constitution by using the conventional phase change medium, and the repeated recording, particularly the overwriting. The same characteristics can be obtained for the light characteristics.

(Embodiment 5) Here, as shown in FIG. 14, the fact that the recording mark obtained by the phase change recording medium acts on the reproduction spot as in the case of the reproduction-only disc having the concave and convex pits is used. It is possible to divide the same disk plane into a read-only area and a recordable / reproducible area, and to reproduce information from both areas using the same optical system and signal processing circuit. Substrate 141 used for this
For example, a read-only area 143 including concave and convex pits is provided on the inner peripheral side, and a recording and reproducing area 144 including continuous concave and convex grooves or capsule pit rows is provided on the outer peripheral side. This board 1
An optical disk is formed by forming the recording thin film layer 142 on 41.

FIG. 15A shows a perspective sectional view of the reproduction-only area, and FIG. 15B shows a perspective sectional view of the recording / reproducing area using the continuous groove. The reproduction-only pit array 152 and the groove 153 of the recording / reproducing area may be either the sample servo system shown in the first embodiment or the continuous groove system shown in the third embodiment. It is important that the same signal format is used in the area. For example, when the recording / reproducing area is the sample format, the reproduction-only area is also provided with sample pits for the sample format. With the above configuration, it is possible to reproduce the signals formed in the reproduction-only area and the recording / reproduction area without switching the servo system.

In order to simplify the signal demodulation, it is desirable that the signal amplitude in the reproduction-only area and the signal amplitude from the recording mark in the recording / reproducing area are equal. To this end, it is important to satisfy the following conditions.

1) The recording thin film 151 showing the phase change is formed under the same condition in both the read-only area and the recording / reproducing area. That is, the reflectivity in the unrecorded state is the same as the reflectivity in the read-only area.

2) Depth d3 of uneven pits in the reproduction-only area
And the depth of the guide groove d4 or the sample pit in the recording / reproducing area is the same.

3) Width W3 of uneven pits in the reproduction-only area
And the width of the guide groove W4 or the sample pit in the recording / reproducing area is the same.

4) The amount of phase change when a recording mark is formed on the recording thin film is equal to the groove depth of the recording / reproducing area or the phase difference due to the sample pit, and its polarity is opposite.

5) The reflectance of the unrecorded state of the recording thin film and that of the state where the recording mark is formed are equal.

Under the above conditions, it is possible to reproduce the signals from the reproduction-only area and the recording / reproduction area by using the same optical system and signal processing system, and a plurality of functions can be realized by a simple and low-cost system. It is possible to obtain the optical disc and the reproducing apparatus thereof.

(Embodiment 6) Up to this point, recording was performed on either one of the concavo-convex portions of the heat-shielding guide groove, but here, as shown in FIG. 16, both sides of the concave and convex portions of the guide groove are recorded. The recording method will be described. When information is recorded / reproduced in both of the guide grooves, there is a problem that the recording marks of adjacent tracks affect the reproduction track. For example, when the light beam 162 is focused on the track 161 to reproduce the information on the groove, the reproduction signal includes not only the track 161 but also the adjacent land track 1.
What includes both signals 63 and 164 is superimposed as crosstalk. This crosstalk amount shows different values depending on the depth d5 of the guide groove.

FIG. 1 shows the experimental results when the phase change medium is provided on the substrate in which the crosstalk amount and the groove depth d5 are changed.
7 shows. The measurement conditions used were the same as the optical system and recording conditions used in Example 1. The substrate used for recording has a land pitch of 1.6 μm, and the groove widths W5 and W6 of the land portion and the groove portion are the same so that the amplitudes of the signals recorded in both grooves are equal. Result is,
There was a tendency that the recording signal was large and the crosstalk amount was small when the groove depth was near λ / 8n. This indicates that the amount of phase change of the recording thin film used is 0.86π, so that the crosstalk becomes the minimum under the condition of around 1/2 of the phase difference caused by the groove. The above result makes it possible to provide an optical disc having a high track density by forming a phase change recording thin film on a substrate having continuous grooves.

A guide groove shown in FIG. 18B can be considered as a method of limiting the width of the mark in the direction perpendicular to the track. A second guide groove having a depth d15 and a third guide groove having a depth d14 are provided on both the concave portion and the convex portion of the first guide groove having the conventional depth d13. The depths of the second and third guide grooves are set to be about twice the depth of the groove forming the land groove as described above. By providing the guide groove having the above-described configuration, it is possible to maintain a good diffraction effect of the spot in the vertical direction of the track when considering the inside of the concave portion or the inside of the convex portion of the first guide groove.

The land / groove recording device will not be described in detail, but in addition to the conventional recording / reproducing device,
Which of the land and the groove is used to record information or which information is to be reproduced can be handled by providing a function of reversing the tracking polarity according to the target track.

(Embodiment 7) In the method of recording a signal on both the land and the groove shown in Embodiment 6, as shown in FIG. 14, the same plane is divided to provide a reproduction-only area and a recording / reproduction area. Can be deployed in a way.

As shown in FIG. 18, the reproduction-only area 143 has a depth d10 in consideration of crosstalk under the same conditions.
Guide grooves having the same groove widths W11 and W12 are formed, and the depth d11,
It is obtained by forming uneven pits made of d12.
The recording / reproducing area 144 formed at a different position on the same plane as the reproduction-only area is provided with the guide groove used in the sixth embodiment. In all of the basic configurations, a guide groove for heat insulation having the same shape as in the case of forming a long uneven pit in the track direction of the recording / reproducing area is provided. That is, the land and groove steps d13 and d10 in each region are made equal. Concavo-convex pit depth and heat shield groove depth d14, d
It is desirable that the widths of the concave and convex pits and the widths W11, W12, W14, and W15 of the heat shield guide grooves are equal to each other. Further, it is necessary to design the medium in which the conditions (1), (4) and (5) shown in the fifth embodiment are added. Under the above conditions, it is possible to obtain a composite type optical disc having a higher track density than that of the fourth embodiment and a reproducing apparatus therefor.

[0082]

As described above, according to the present invention, by forming a recording thin film layer showing a phase change on a substrate having an uneven groove for suppressing diffusion of heat generated by laser light irradiation, Less deterioration of signal quality due to fluctuations,
In addition, it is possible to provide a recording member and a recording device having high recording signal quality.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the overall configuration of an optical information recording device of the present invention and the configuration of an optical recording medium.

FIG. 2 is a conceptual diagram of signal reproduction of amplitude change recording and phase change recording.

FIG. 3 is a conceptual diagram of a mark shape limiting effect of a recording mark by the guide groove of the present invention.

FIG. 4 is a cross-sectional view of second and third configuration examples of the optical information recording medium of the present invention.

FIG. 5 is a characteristic diagram showing the guide groove depth dependence of the amount of reflected light obtained from an unrecorded recording medium.

FIG. 6 is a conceptual diagram of a state in which phase change recording is performed on guide grooves having different depths.

FIG. 7 is a plan view showing the structure of the guide groove in the first embodiment of the present invention.

FIG. 8 is a plan view showing the structure of a pit capsule according to the second embodiment of the present invention.

FIG. 9 is a conceptual diagram of a state in which a phase change recording line is formed on a pit capsule in the example.

FIG. 10 is a diagram for explaining an optical information recording device in a third embodiment of the present invention.

FIG. 11 is a layout view of light spots on the optical recording medium in the example.

FIG. 12 is a configuration diagram of a photodetector of the optical information recording apparatus in the example.

FIG. 13 is a flowchart of an initialization processing step in the fourth embodiment.

FIG. 14 is a configuration diagram of a recording member according to a fifth embodiment of the present invention.

FIG. 15 is a detailed configuration diagram of a recording member in the example.

FIG. 16 is a configuration diagram of an optical information recording member according to a sixth embodiment of the present invention.

FIG. 17 is a characteristic diagram showing the guide groove depth dependency of the amount of crosstalk from adjacent tracks in the example.

FIG. 18 is a configuration diagram of an optical information recording member according to a seventh embodiment of the present invention.

[Explanation of symbols]

 15 Light Beam 21 Base Material 22, 24 Transparent Layer 23 Recording Thin Film Layer 25 Reflective Layer 26 Protective Layer 27 Guide Groove

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Yamada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kenichi Nagata 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (26)

[Claims] 1. A recording medium for optically recording information by condensing a light beam onto a recording thin film layer formed on a substrate through a lens, wherein the surface of the substrate condenses the light. The recording thin film layer is provided with an uneven guide groove having a width narrower than the beam spot diameter, and the recording thin film layer is changed from the first state to the second state by irradiation with the light beam having the first intensity,
When a light beam having a second intensity lower than the above is irradiated, the phase of the reflected light is different between the region of the first state and the region of the second state of the recording thin film layer, and the concave portion and the convex portion of the guide groove are different. An optical information recording medium, characterized in that the phase is changed from the first state to the second state in a direction of reducing the phase difference generated between the parts. 2. A recording medium for optically recording information by condensing a light beam on a recording thin film layer formed on a substrate through a lens, wherein the surface of the substrate is uneven. The groove and the region where the guide groove is interrupted are provided with uneven pits on both sides with respect to the center line in the track direction of the guide groove, and the thin film layer can be detected because the optical constant is changed by irradiation of a light beam. The change is mainly due to a change in the phase of the reflected light or the transmitted light of the incident light, and the phase change is generated in a direction to reduce the phase difference generated between the unevenness of the substrate. Optical information recording medium. 3. The phase change due to the recording thin film layer is equal in magnitude to the phase difference caused by the concave-convex guide grooves of the substrate, and the polarities of the change are opposite to each other. 1. The optical information recording medium according to 1 or 2. 4. The wavelength of the light beam is λ, the refractive index of the substrate is n,
When the numerical aperture of the lens that focuses the light beam on the recording thin film layer is NA, the depth D of the uneven guide groove is λ / 4n.
The optical information recording medium according to claim 3, wherein the optical information recording medium is equivalent to or less than. 5. When the wavelength of the light beam is λ and the numerical aperture of a lens for focusing the light beam on the recording thin film layer is NA, the groove width W of the uneven guide groove is 0.13 ≦ W × The optical information recording medium according to claim 1 or 2, wherein the relationship NA / λ ≤ 0.51 is satisfied. 6. A recording medium for optically recording information by condensing a light beam onto a recording thin film layer formed on a substrate through a lens, wherein the substrate has the condensed light on its surface. An uneven guide groove having a width narrower than the spot diameter of the light beam is provided, and the recording thin film layer changes from the first state to the second state by irradiation with the light beam having the first intensity, When irradiated with a light beam of low second intensity,
The phase of the reflected light is different between the region in the first state and the region in the second state of the recording thin film layer, and the first phase is reduced in the direction in which the phase difference generated between the concave portion and the convex portion of the guide groove is reduced. An optical information recording medium, wherein a phase is changed from a state to a second state, and an unrecorded state of a recording area of the recording thin film layer is provided with a recording mark having a pattern distinguishable from a data signal. 7. A recording medium for optically recording information by condensing a light beam on a recording thin film layer formed on a substrate through a lens, the surface of the substrate being fixed on a track. A pit capsule array consisting of circular irregularities provided at intervals of, and a sample pit at a position deviated from the center line of the pit capsule array in the track direction, the optical constant of the recording thin film layer is changed by irradiation of a light beam. The detectable change is mainly due to the change in the phase of the reflected light or the transmitted light of the incident light, and the change in the phase occurs in the direction of reducing the phase difference generated between the unevenness of the pit capsules. An optical information recording medium characterized by the above. 8. The phase change due to the recording thin film layer is as large as the phase difference caused by the pit capsule of the substrate,
8. The optical information recording medium according to claim 7, wherein the polarities of the changes are in the opposite relationship. 9. The wavelength of the light beam is λ, the refractive index of the substrate is n,
The numerical aperture of the lens that focuses the light beam on the recording thin film layer is NA
And the depth D of the uneven pit capsule is λ / 4.
8. The optical information recording medium according to claim 7, which is equal to or less than n. 10. An optical information recording medium having a recording / reproducing area on the substrate for producing a state change that can be optically detected by irradiation of a light beam, wherein the surface of the substrate is provided with a recording thin film layer. And a first guide groove having the same width as the convex portion, the optical constant of the recording thin film layer is changed by irradiation of a light beam, and a detectable change is caused by a change in phase of reflected light or transmitted light of incident light. An optical information recording medium characterized in that both the concave portion and the convex portion of the guide groove are information recording areas. 11. The optical information recording medium according to claim 10, wherein the amount of change in phase caused by a change in the state of the recording thin film layer is approximately twice the amount of phase difference caused by the uneven groove. 12. The optical information recording medium according to claim 11, wherein the depth of the concave and convex grooves is about λ / 8n, where n is the refractive index of the substrate with respect to the light beam. 13. A second guide groove or pit capsule row is provided in the center of the concave portion of the first guide groove, and a third guide groove or pit capsule row is provided in the center of the convex portion of the first guide groove. The optical information recording medium according to claim 10, characterized in that 14. The depth of the first guide groove is set to the second and the third.
14. The optical information recording medium according to claim 13, which is about twice as large as the guide groove or the pit capsule. 15. The optical information according to claim 14, wherein the depth of the first concave-convex groove is λ / 8n, where λ is the wavelength of the illuminating light beam and n is the refractive index of the substrate. recoding media. 16. An optical information recording comprising a read-only area in which information is formed in advance as a concavo-convex shape and a recording / reproducing area in which a state change optically detectable by irradiation of a light beam is provided on the same plane of a substrate. A recording thin film layer having the same structure is formed on both surfaces of the read-only area and the recording / reproducing area of the medium, and the recording thin film layer has a changeable optical constant upon irradiation with a light beam, which can be detected. The change is due to a change in the phase of the reflected light or the transmitted light of the incident light, and is characterized in that the phase is changed in a direction to reduce the phase difference generated between the unevenness of the guide groove. Optical information recording medium. 17. A reproduction-only area and a recording / reproduction area are each provided with a guide groove having a first concavo-convex shape, and the recesses and projections of the guide groove have the same width in the tracking direction. A pit formed of the second unevenness is provided on both the concave portion and the convex portion, and a recording thin film layer having the same structure is formed on the surface of both the read-only area and the recording / reproducing area. An optical information recording medium characterized in that an optical constant is changed by irradiation, and a change which can be detected is mainly due to a change in phase of reflected light or transmitted light of incident light. 18. The optical system according to claim 16, wherein the surface of the substrate forming the recording area is provided with guide grooves or capsule pits having the same depth as the unevenness of the read-only area. Information recording medium. 19. The surface of a substrate forming a recording area is provided with a guide groove having a width in the tracking direction which is equal to that of the concave-convex pits in the reproduction-only area, or a capsule pit having the same diameter. Item 16. The optical information recording medium according to item 16 or 17. 20. The phase change caused by the change in the state of the recording thin film layer is as large as the phase difference caused by the concave and convex pits in the read-only area, and the polarities of the change are opposite to each other. The optical information recording medium according to claim 16 or 17. 21. The recording layer is composed of a phase change medium exhibiting a reversible change between an amorphous state and a crystalline state depending on light irradiation conditions.
18. An optical information recording medium according to any one of items 7, 10, 16 and 17. 22. A first transparent layer having a refractive index different from that of the substrate is provided on a substrate, a recording thin film layer is provided thereon, a second transparent layer is provided thereon, and a reflective layer is provided thereon. An optical information recording medium having a different structure, wherein the thickness of the first transparent layer, the recording thin film layer, the second transparent layer and the reflective layer is set to the value of transmitted light or reflected light of incident light when the recording material is changed. 22. The optical information recording medium according to claim 21, wherein the optical information recording medium is selected so that the phase changes. 23. An information recording / reproducing method for an optical information recording medium according to claim 8, wherein reflected light or transmitted light from pits on the surface of the base material on which the recording thin film layer is provided is detected, and their light amount difference is detected. An information recording / reproducing method for an optical information recording medium, characterized by performing information recording / reproducing while performing tracking control based on the above. 24. An apparatus for recording information on a recording medium having a recording thin film layer which causes a change which can be optically detected by irradiation of a light beam, wherein the recording medium is provided with a recording thin film layer of a base material. The surface is provided with a guide groove on the unevenness, the recording thin film layer has an optical constant changed by irradiation of a light beam, the detectable change is due to a change in the phase of reflected light or transmitted light of the incident light, The light beam is composed of a plurality of spot rows of at least three or more, and the line connecting the centers of the spot rows is arranged so as to be inclined with respect to the guide groove. The information signal of the recording thin film layer is reproduced by detecting the reflected light or the transmitted light, and the transmitted light or the reflected light from the second and third spots located before and after the first spot is detected. Recording and reproducing apparatus of the optical information recording medium and performing tracking control such that the first spot the guide-grooves to follow the Rukoto. 25. The focus control is performed by receiving transmitted light or reflected light from the second and third spots by a photodetector divided into at least two or more. Recording / reproducing apparatus for optical information recording medium. 26. A first substrate is provided on a substrate having an uneven guide groove.
The optical constant is changed by irradiating the optical beam, and the detectable change is the initialization process of the optical recording member that records the information signal mainly by using the change of the phase of the reflected light or the transmitted light of the incident light. A second light beam having a wavelength different from that of the first light beam, and controlling the second light beam to follow a guide groove on the second light beam at a predetermined frequency. An optical information recording method, wherein recording marks are formed at regular intervals on the recording medium by modulating.