JP3287860B2 - Optical information recording method and recording medium - Google Patents

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 method such as a write-once optical disk or a rewritable optical disk and a recording medium used therefor, and more particularly to an optical information recording method capable of recording and reproducing a good signal level. It relates to a recording medium.

[0002]

2. Description of the Related Art An optical information recording medium includes a disk-shaped medium and a card-shaped one, and hereinafter, the optical information recording medium is generally referred to as an optical disk. Conventionally, write-once optical discs include, for example, those that form an information pit by melting a recording layer by laser beam irradiation, those that form an information pit by changing the recording layer from, for example, an amorphous phase to a crystalline phase, or two or more layers. And the like, in which an information pit is formed by alloying a metal recording layer having the above layer structure. As a rewritable optical disk, for example, an optical disk utilizing a phase change between a crystalline phase and an amorphous phase, an optical disk utilizing magneto-optical recording, and the like are available. Furthermore, as a read-only optical disk, a compact disk (CD) having uneven pits formed on a substrate,
Laser disks (LDs) and the like are widely known.

In order to perform recording / reproduction using the above-mentioned optical disk, for example, a laser beam converged by a lens system is applied to the optical disk to record information, and at the time of reproduction, a laser having a weaker power than at the time of recording. Irradiates the optical disk with this light,
The reflected light is received by a detector as an information signal, and the information signal is detected as a change in the amount of reflected light. For example, in the above-mentioned read-only optical disk, uneven pits and a reflection film are formed on a substrate, and reproduction is performed by detecting a change in the amount of reflected light from the pits. That is, when the optical disc is irradiated with a minute laser spot, the amount of reflected light returning to the detector (detector) due to interference or diffraction at the concave / convex pit portion where information is recorded decreases.
In the flat portion, information is reproduced by utilizing the fact that the amount of reflected light corresponding to the reflectance of the reflective film is obtained.

Therefore, the shape of the concave and convex pits is λ / 4 (λ is the wavelength of the laser) at which the pit depth is the optical depth (refractive index of the substrate × depth) and the interference effect is maximized. The width is about 1/2 to 1 of the light spot diameter (diameter at 1 / e ² value of the Gaussian intensity distribution) so that the diffraction effect is maximized.
Normally, it is set to / 3 so that the change in the amount of reflected light can be made the largest. As described above, the information recording method of the read-only optical disk uses the phase change of the concave and convex pits, and the reflectance of the reflective film itself does not change. On the other hand, there is a type in which a recording film is formed on a substrate, and the reflectance of the recording film changes according to information recording. That is, at least one of the refractive index and the extinction coefficient of the recording film changes due to the information recording, the reflectance changes, and as a result, the amount of reflected light reaching the detector changes.

[0005] The above-mentioned recording / reproducing methods include, for example, the Transactions of the Institute of Electronics and Communication Engineers, '83 / 5 Vo.
l. J66-C No. 5, page 385 to page 392, JP-A-2-73537 and JP-A-2-113451.
And the like.

[0006]

In the type in which the reflectivity of the recording film changes due to the information recording described above, at least one of the refractive index and the extinction coefficient changes and no phase change occurs. When using the change in reflectance, the interference effect is usually used, so when the refractive index or extinction coefficient of the recording film changes, it is not that there is no phase change at all, and there are many types with little phase change. I can say. On the other hand, many recordable optical disks are provided with tracking grooves (grooves). Since a tracking group obtains a tracking signal by a push-pull method, it is usual that the groove depth is λ / 8 and the groove width is 0.4 to 0.8 μm.
Therefore, when recording is performed on an optical disk having a tracking group, it is necessary to consider the phase of the groove and the phase change of the recording film, but this is not considered in the prior art. Was.

An object of the present invention is to solve such a conventional problem. The first object of the present invention is to provide a good relationship between the phase of the group and the phase change of the recording film so as to obtain a good relationship. A second object of the present invention is to provide a recording method capable of recording and reproducing a signal level, and an improved optical information recording medium for realizing the method.

[0008]

The first object SUMMARY OF THE INVENTION, in consideration of the relation between the phase change and the groove of the phase of the recording film, so that the signal output of the recording and reproducing is maximized Group - Bed or <br This is achieved by recording on the land. Here, the land indicates a flat area between the groups. The first means for achieving the first object of the present invention will be described more specifically as follows.

(1) A method for performing recording on an optical information recording medium having a recording layer on a substrate having a groove , on which a reflectance and a phase are optically changed by irradiation with a laser beam, is provided. An optical change occurs between the high reflectance state and the low reflectance state, and when the phase in the high reflectance state is φh and the phase in the low reflectance state is φ1, N and n are integers and the depth of the groove is when satisfying the equation (1) with an optical depth wavelength of Saga laser light as lambda,

Equation 3] (4N-1) λ / 4 < depth <(4N + 1) λ / 4 ... (1) when the phase difference was set to _{Δφ 3 = φh-φl, (} 2n-1) π <Δφ 3 <emergence line recording in the groove of the optical information recording medium is 2n [pi],
Or 2n [pi] <and _{Δφ 3 <(2n + 1)} π in which the recording method of the optical information recording line cormorants optical histological information recording medium recorded in a land portion between the grooves of the medium. Also,
(2) Reflected by laser beam irradiation on substrate with grooves
A method for performing recording on an optical information recording medium provided with a recording layer in which an optical change in rate and phase occurs, wherein an optical change in the recording layer occurs between a high reflectance state and a low reflectance state,
When the phase in the pre-high reflectivity state is φh and the phase in the low reflectivity state is φl, N and n are integers, and the depth of the groove is the optical depth, where λ is the wavelength of the laser beam. Satisfy
In case

Equation 4] (4N + 1) λ / 4 < depth <(4N + 3) λ / 4 ... (2) when the phase difference was set to Δφ ₃ = φh-φl, is _{2nπ <Δφ 3 <(2n +} 1) π UGA line recording in the groove of the optical information recording medium,
Or (2n-1) π <a [Delta] [phi ₃ <method of recording a is the optical information recording line cormorants optical histological information recording medium recorded in a land portion between the grooves of the medium 2n [pi].

[0010] The second object, phase variation and glue the recording film so that the signal output of the record reproduction is maximized - Bed phase
Prescribe the relationship with change and record it in a groove or land
This is achieved by an optical information recording medium adapted to perform the following . More specifically, the means for achieving the second object of the present invention will be described below.

[0011] For (3) a recording layer whose optical change occurs in the reflectance and phase change by the laser beam irradiation on a substrate having a groove is provided, the optical information recording medium as the recording area of a land portion between the groove The optical change occurs between a high reflectance state and a low reflectance state, and the phase in the high reflectance state is φ
h, when the phase in the low reflectivity state is φ1, the recording layer is a recording layer satisfying the phase relationship of φh> φ1, and (4) the recording layer is formed on a substrate having a groove. An optical information recording medium having a recording layer in which an optical change in reflectance and phase change is generated by laser light irradiation, and the groove as a recording area
On the other hand , when the optical change occurs between the high reflectance state and the low reflectance state, and the phase in the high reflectance state is φh and the phase in the low reflectance state is φ1, the recording layer is φh <Φ
This is achieved by providing a recording layer that satisfies the phase relationship of 1. Further, the optical information recording of the above (3) or (4)
In the medium, preferably, (5) the recording layer has a multilayer structure, and the recording area of the recording layer is alloyed or diffused by laser light irradiation to change the reflectance as an optical change .

[0012]

The following is a detailed description of how the above-mentioned solution according to the present invention acts on the recording / reproducing process of the optical information recording medium to obtain a good signal level.
FIG. 2 is a principle explanatory diagram of the optical disk device schematically showing the relationship between the optical disk 21 and the optical system of the recording / reproducing apparatus. The optical disk 21 is also used for tracking control.
It comprises a substrate 23 having a groove (group) 22 which can be used, a recording layer 24 for recording optical information and a protective layer 25 formed sequentially on the substrate. 2, in order to read information from the optical disk 21, the optical disk 21 is irradiated with laser light from a semiconductor laser 26 through a collimator lens 27, a half mirror 28, and an objective lens 29, and reflected light is emitted from the objective lens 29 and c. -Focusing is performed on the detector 31 by the mirror 28 and the lens 30. At the time of recording, the recording layer 24 of the optical disc 21 is irradiated with a stronger laser power than at the time of reproduction to change the optical characteristics of the recording layer.
Information can be recorded. Here, the half mirror
Although optical elements such as were used, it is not limited to this,
Various optical elements such as a polarizing beam splitter, a wave plate, a prism and the like can also be used.

FIG. 3 is a block diagram of a simulation experiment for analyzing a reproduction signal level in the above-described information reproducing method. The laser beam incident on the objective lens is a Gaussian distribution beam (32), the incident beam after passing through the objective lens is determined by FFT (high-speed Fourier transform) (33), and the reflected beam from the optical disk is obtained. The beam is obtained using the incident beam after FFT and the complex reflectance of the disk (3).
4) The reflected beam after passing through the objective lens was obtained again by FFT (35), and the reflected beam intensity on the detector was calculated (36). In the following, the ratio between the amount of reflected light and the amount of incident light was determined using the complex reflectance of the disk. The above simulation method is described in IEICE Transactions '83 / 5
Vol. J66-C No. 5, page 387 to page 389, the phase of the group was considered as the complex reflectance of the disk, but the phase change of the recording layer was not considered. The present invention has been achieved by considering the phase of the groove and the phase change of the recording layer.

FIG. 4 shows a groove (groove) 4 having a width W and a depth d.
2 shows a state in which a substrate 41 provided with a laser beam 2 is irradiated with a laser beam. The complex reflectivity R in the case of forming the group is given by the following equations (3) and (4) because the phase of the group 42 is ahead of the reference plane 43 by 2 knd. Note that the reference surface refers to a surface on which an outer peripheral portion of the laser beam hits.

[Expression 5] Reference plane: R = r ₀ (3)

[6] Group - Bed _{plane: R = r 0 exp (2iknd} ) ... (4) where, r ₀ is the amplitude reflectance, n is the refractive index of the substrate, k = 2
π / λ and λ are the wavelengths of the laser beam.

On the other hand, FIG. 5 shows a state where a substrate 45 having a land 46 having a width W and a depth d is irradiated with a laser beam. Complex reflectance R when a land is formed
Means that the phase of the land 46 is 2 knd more than that of the reference plane 43.
Since they are late, the following equations (5) and (6) are obtained.

[Expression 7] Reference plane: R = r ₀ (5)

## EQU8 ## Land surface: R = r ₀ exp (−2iknd) = r ₀ exp (2ikn (−d)) (6) Therefore, when equations (3) and (4) are used as complex reflectivity, The lands can be considered to be -d deep grooves.

FIG. 6 shows the groove depth d and the amount of reflected light /
The relationship between the incident light amounts is shown. Here, the incident beam (λ = 8)
30 nm) as a Gaussian distribution, and the NA of the objective lens is set to 0.
6, the beam shape on the reflection surface of the optical disk has a Gaussian distribution, and the 1 / e ² beam diameter is 1.2 μm. In the following description, this condition is set unless otherwise specified. The groove width was 0.7 μm, the groove pitch was 1.6 μm, and the amplitude reflectance r ₀ was 1 (= 100%). Hereinafter, although the ratio of the amount of reflected light / the amount of incident light is used in the drawings, this is collectively referred to as the amount of reflected light. As shown in FIG. 6, the amount of reflected light has a relationship of λ / 2 with respect to the groove depth. Therefore, in order to examine the relationship between the amount of reflected light and the groove depth d, the range of -λ / 4 to λ / 4 may be examined.

Next, the case where the complex reflectance R of the recording layer changes will be described. FIG. 7 shows a structure in which a recording layer 50 and a protective layer 53 are provided on the substrate 41 shown in FIG. In order to simplify the calculation, it is assumed that the recording film 50 does not exist on the wall surface of the groove, the recording layer is set to the recording layer 50a in the groove to be irradiated with the laser beam, and the recording layer 50 around the recording layer 50a.
b has an unrecorded complex reflectance. Also,
In the laser beam scanning direction along the group 42, the recording layer 50a in the recording state is assumed to have a sufficiently long range with respect to the laser beam spot diameter. Although the state in which the recording film does not exist on the wall surface of the groove hardly occurs in reality, it can be said that a relationship sufficiently close to the real thing can be obtained from the viewpoint of optical characteristics. The complex reflectivity of the unrecorded recording layers 50b and 50c is r ₁ exp (iφ ₁ ), and the complex reflectivity of the recorded recording layer 50a is r ₂ exp (i
φ ₂ ), the complex reflectivity R of the disk in consideration of the phase of the groove is given by the following equations (7), (8) and (9). Note that r ₁ is the amplitude reflectance in an unrecorded state, and r ₂ is the amplitude reflectance in a recorded state (the same applies to any of the following expressions).

## EQU9 ## Unrecorded reference plane 50b: R = r ₁ exp (iφ ₁ ) (7)

## EQU10 ## Recorded groove surface 50a: R = r ₂ exp [i (2knd + φ ₂ )] (8)

[Number 11] unrecorded guru - Breakfast surface 50c: R = r ₁ exp [i (2knd + φ _1)] ... (9)

Here, since it is not the absolute value of the phase but the phase difference that is optically significant, if Δφ = φ ₂ −φ ₁ with respect to the phase on the reference plane, the equation (7) ),
(8) and (9) can be expressed as the following equations (10), (11) and (12).

[Expression 12] Unrecorded reference surface 50b: R = r ₁ (10)

## EQU13 ## Recorded groove surface 50a: R = r ₂ exp [i (Δφ + 2knd)] (11)

[Number 14] unrecorded guru - Breakfast surface _{50c: R = r 1 exp (} i2knd) ... (12)

FIG. 8 shows a case where the recording layer 55 and the protective layer 58 are provided on the substrate 45 shown in FIG. 5, and the recording layer 55a of the land 46 is in a recording state. As in the case of FIG. 7, the complex reflectance R of the disk
Is given by the following equations (13), (14) and (15).

[Expression 15] Unrecorded reference surface 55b: R = r ₁ (13)

The recorded land surface 55a: R = r ₂ exp [i (Δφ−2knd)] (14)

[Equation 17] Unrecorded land surface 55c: R = r ₁ exp (−i2knd) (15)

FIG. 9 shows the relationship between the amount of reflected light and the groove depth d when the optical disks shown in FIGS. 7 and 8 are used.
Here, the expressions (13), (14), and (15) described in FIG. 8 are used as the complex reflectivity R up to the groove depth d = −λ / 4 to 0, and the groove depth d = 0 to 0. Complex reflectance R up to λ / 4
(10), (11), and (12) described in FIG.
Was used. Further, the groove width W = 0.7 μm and the pitch = 1.6.
μm, the amplitude reflectance r ₁ = 0.7 in the unrecorded state, and the amplitude reflectance r ₂ = 0.5 in the recorded state. That is, FIG.
Shows the case where the amplitude reflectance r ₁ in the unrecorded state is large and the amplitude reflectance r _{2 in the} recorded state is small. In the same figure, a curve 61 shows the relationship in the unrecorded state, a curve 62 shows a relationship in the recorded state when the phase difference Δφ = 0, a curve 63 shows a relationship in the recorded state when the phase difference Δφ = π / 4, and a curve 64 shows the relationship in the recorded state. The relationship at the phase difference Δφ = −π / 4 in the recording state is shown. In the unrecorded state, r ₁ =
r ₂ = 0.7 and Δφ = 0.

FIG. 9 shows that the unrecorded state 61 and the phase difference Δ
When φ = 0, the recording state 62 is a symmetrical curve, and if the depth d is the same for both the group and the land, the same reflected light amount is obtained. Since the intensity of the reproduced signal at the detector is proportional to the amount of reflected light, the level of the reproduced signal of the recorded information is proportional to the difference between the amount of reflected light in the unrecorded state and the amount of reflected light in the recorded state. Therefore, the phase difference Δφ = 0
In this case, the same reproduction signal level can be obtained for both the group and the land. However, when the phase difference Δφ occurs, the reproduction signal level differs between the groove and the land as can be seen from the curves 63 and 64. In order to increase the reproduction signal level, that is, the difference in the amount of reflected light between the recorded state and the unrecorded state, it is preferable to record in a group (when d <λ / 4) when Δφ is π / 4. On the other hand, when Δφ is −π / 4, it is better to record on a land (when d <λ / 4).
Hereinafter, recording in the group will be referred to as group recording, and recording in the land will be referred to as land recording.
Further, as described above, the relationship between the amount of reflected light and the groove depth d is repeated at a period of λ / 2, so that when λ / 4 <d <λ / 2, the relationship between groove recording and land recording is reversed. Needless to say. That is, in the range of λ / 4 <d <λ / 2, when Δφ is π / 4, the reproduction signal level is higher in land recording, and when Δφ is −π / 4, groove recording is higher. However, the reproduction signal level is large. Further, d is λ / 2
If greater, the above relationship is repeated every λ / 4.

FIG. 10 shows that the amplitude reflectance r _{1 in} the unrecorded state of the recording layer is small, the amplitude reflectance r _{2 in the} recorded state is large,
9 shows the relationship between the amount of reflected light and the groove depth d when the relationship is opposite to that of FIG. Amplitude reflectance r ₁ = 0.5,
r ₂ = 0.7, and other conditions are the same as those in FIG. In FIG. 10, a curve 65 shows the relationship in the unrecorded state, a curve 66 shows a relationship in the recorded state when the phase difference Δφ = 0, a curve 67 shows a relationship in the recorded state when the phase difference Δφ = π / 4, and a curve 68 shows the recorded state. Phase difference Δφ = -π
/ 4 are shown. In the unrecorded state, r ₁ = r ₂ = 0.5 and Δφ = 0. As shown in the figure, in order to increase the difference in reflected light amount between the recorded state and the unrecorded state, recording is performed on a land (when d <λ / 4) when the phase difference Δφ of the recording layer is π / 4. Is good, while Δφ is-
It can be seen that it is better to record in the group when π / 4 (where d <λ / 4). This is the opposite relationship from the case of FIG.

FIGS. 11 and 12 show the relationship between the amount of reflected light and the phase difference Δφ in the recording state with the groove depth d as a parameter. There are three types of groove depths, d = 0 and d = ± λ / 8. In FIG. 11, the amplitude reflectances are r ₁ = 0.7 and r ₂ = 0.5.
In FIG. 12, the opposite states r ₁ = 0.5, r ₂ = 0.
7 was set. Other conditions are the same as those in FIG. As is clear from these figures, when the groove depth d = 0, the reflected light amount is an even function with respect to Δφ as shown by curves 71 and 75. This is because when Δφ = 0, the amount of reflected light is the groove depth d.
Is similar to an even function. Curve 72,
Numeral 76 indicates the relationship when the groove depth d = λ / 8, and curve 7
Numerals 3 and 77 show the relationship when the groove depth d = -λ / 8. In FIGS. 11 and 12, the level in the unrecorded state at the groove depth d = ± λ / 8 is indicated by an arrow. Table 1 shows the conditions for increasing the difference in the amount of reflected light between the recorded state and the unrecorded state.

[0024]

[Table 1]

As described above, it can be seen that conditions for obtaining a good reproduction signal level are different depending on the relationship between the amplitude reflectances r ₁ and r ₂ , the phase difference Δφ, and the groove depth d. In the above, each parameter value has been shown. However, when arranged, when N is an integer and the groove depth d satisfies the following equation (1), a suitable recording area is as shown in Table 2. Here, λ is the wavelength of the laser spot.

(4N−1) λ / 4 <groove depth d <(4N + 1) λ / 4 (1)

[0026]

[Table 2]

Further, regarding the phase difference Δφ, FIG.
As can be seen from FIG. 12, since the relationship has a period of 2π, the relationship can be expanded to the relationship shown in Table 3 where n is an integer.

[0028]

[Table 3]

The above relationship is obtained by replacing Δφ = φ ₁ −φ ₂ with:
The phase with the larger amplitude reflectance is φh and the phase with the smaller amplitude reflectance is φ
When l is rewritten using the phase difference Δφ ₃ = φh−φl, the relationship shown in Table 4 is obtained.

[0030]

[Table 4] As is apparent from Table 4, regardless of the magnitudes of the amplitude reflectances r ₁ and r ₂ , the cases are divided into two cases ₁ and ₂ shown in Table 5.

[0031]

[Table 5]

When the groove depth d is in the range of the following equation (2),

(4N + 1) λ / 4 <groove depth d <(4N + 3) λ / 4 (2) Since the relationship between the groove and the land is reversed, the magnitude of the amplitude reflectance is reduced in the same manner as described above. Regardless, it is divided into two cases 3 and 4 shown in Table 6.

[0033]

[Table 6]

In a normal optical disk, the groove depth d is often in the range of −λ / 4 <groove depth d <λ / 4, and the phase difference Δφ ₃ is also −π <Δφ ₃ <π. In general, when Δφ ₃ <0, that is, when φh <φl, group recording is suitable. When Δφ ₃ > 0, that is, when φh> φl, land recording is usually performed. It may be said that is suitable.

In the above description, the recording width is equal to the groove width or the land width.
FIG. 16 shows how the amount of reflected light changes when the groove width and land width are fixed at fixed values and the recording width is changed. In FIG. 13, the amplitude reflectances r ₁ = 0.7, r ₂ = 0.
5, groove width = 0.7 μm, groove depth d = λ / 8. A curve 80 is a case where the groove depth d = 0 and Δφ = ± π / 4. Δφ = π / 4 (that is, Δφ ₃ = −π / 4),
The curve 81 shows the relationship when recording is performed on the land, and the curve 82 shows the relationship when recording is performed on the group. Since the amount of reflected light in the unrecorded state is at a point having a recording width of 0, it can be seen that groove recording in which the amount of reflected light greatly changes as the recording width increases is suitable for increasing the reproduction signal level. this is,
This corresponds to Case 1 described above.

In FIG. 14, the amplitude reflectance is set to r ₁ = 0.5 and r ₂ = 0.7, which are opposite to those in FIG. Curve 85 is
This is the case where the groove depth d = 0 and Δφ = ± π / 4. Δ
With φ = π / 4 (ie, Δφ ₃ = π / 4), curve 86
Indicates the relationship when recording is performed on the land, and curve 87 indicates the relationship when recording is performed on the group. In this case, in order to increase the reproduction signal level, land recording in which the amount of reflected light greatly changes due to an increase in the recording width is suitable. This corresponds to case 2 above.

In FIG. 15, the amplitude reflectance r ₁ = 0.7, r ₂
= 0.5 and Δφ = -π / 4. At this time, Δφ ₃ =
Since it is .pi. / 4, the land recording (curve 92), in which the amount of reflected light changes greatly due to the increase in the recording width, can have a higher reproduction signal level than the groove recording (curve 91). This also corresponds to Case 2 above.

In FIG. 16, the amplitude reflectance is set to r ₁ = 0.5 and r ₂ = 0.7, which are inversely related to FIG. 15, and Δφ = −π /
And 4. At this time, since Δφ ₃ = −π / 4, the group recording (curve 96), in which the amount of reflected light changes greatly due to the increase in the recording width, takes a higher reproduction signal level than the land recording (curve 97). be able to. This corresponds to Case 1 above.

In the above description, the groove shape is rectangular, but the present invention is not limited to this, and various groove shapes such as a U shape, a V shape, a stepped shape, a gentle shape, and a gentle groove shape may be used. The present invention can be applied by using an effective groove width and groove depth.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, representative embodiments of the present invention will be described in detail with reference to the drawings. <Embodiment 1> FIGS. 17 and 18 are partial sectional views of an optical information recording medium according to an embodiment of the present invention. In FIG. 17, 100 is polymethyl methacrylate (PMMA)
The substrate and the recording layer are composed of 101 Sb ₂ Se ₃ film and 1
02 is a two-layer structure of a Bi film, and 103 is a protective layer made of, for example, an ultraviolet curing resin. FIG. 18 shows the recording unit 105 that has performed recording by laser irradiation. Since the recording portion is alloyed by heating, a large phase difference before and after recording can be obtained. In addition, since diffusion occurs between the two layers during alloying, it can be said that the reflectance changes due to the diffusion.

The refractive index of the PMMA substrate is 1.49, and the refractive index of the protective film is 1.50. Sb ₂ Se ₃ film before recording the optical constants are amorphous is 3.8-i0.1.
The optical constant of the Bi film is 2.6-i4.5, and the optical constant of the Sb-Se-Bi alloy after recording is 4.5-i3.0. The complex reflectance was determined using these constants. For example, the thickness of the Sb ₂ Se ₃ film is 25 nm, and the thickness of the Bi film is 3
0 nm, and the thickness of the Sb—Se—Bi alloy after recording was 5 nm.
Assuming that it is 5 nm, the complex reflectance R ₁ before recording and the complex reflectance R ₂ after recording are as follows: R ₁ = r ₁ exp (iφ ₁ ) = 0.308exp (0.61πi) R ₂ = r ₂ exp (Iφ ₂ ) = 0.670 exp (0.89πi) Δφ = φ ₂ −φ ₁ = 0.28π, and a phase difference Δφ of π / 4 or more is obtained. Therefore, this recording layer is suitable for applying the recording method according to the present invention.

Incidentally, ordinary reflectance (energy reflectance)
Is obtained by the square of the amplitude reflectance, the following reflectance before recording = | r ₁ | ² = 0.095 = 9.5% reflectance after recording = | r ₂ | ² = 0. 449 = 44.9%.

FIGS. 19 and 20 show the reflectance, phase φ ₁ , φ ₂ , and phase difference Δφ when the thickness of the Bi film is fixed at 30 nm and the thickness of the Sb ₂ Se ₃ film is changed. Indicated. Here, the film thickness of the alloy film after recording is set to the film thickness of the Bi film and Sb ₂ S
was the sum of the thickness of the e ₃ film. From FIG. 19, it can be seen that the polarity of the phase difference Δφ is inverted near the Sb ₂ Se ₃ film thickness of 35 nm.

FIG. 1 shows the amount of reflected light calculated when the recording layer is provided on a substrate having a groove from the amplitude reflectance and the phase obtained as described above.
Here, the groove width was 0.7 μm, the pitch was 1.6 μm, the groove depth d was λ / 8, and the recording width was 0.7 μm. In the figure, curve 1 shows the relationship in the unrecorded state, curve 2 shows the relationship when recording is performed on the group, and curve 3 shows the relationship when recording is performed on the land. As described above, the polarity of the phase difference Δφ is inverted near the Sb ₂ Se ₃ film thickness of 35 nm, and the levels of the curves 2 and 3 are inverted around this. Therefore, Sb ₂ Se ₃ film thickness is less large land recording reproduction signal level when 35nm, when the above Sb ₂ Se ₃ film thickness 35nm Group - is larger in the blanking recording reproduced signal level (however, film The thickness range is 60 nm or less).

As described above, when the Sb ₂ Se ₃ film thickness is 35 nm or less, since r ₁ <r ₂ and 0 <Δφ <π, 0 <Δφ
₃ <π, which is suitable for land recording. When the Sb ₂ Se ₃ film thickness is 35 nm or more, r ₁ <r ₂ , −π <Δφ <0, and therefore −π <Δφ ₃ <0, so that groove recording is performed. Suitable. From the above, in the case of land recording designed the Sb ₂ Se ₃ film thickness 10nm or 35nm or less, Group - 60 nm or more 35nm the Sb ₂ Se ₃ film thickness when performing blanking recording
It is better to design below.

FIG. 21 shows a sectional structure of a main part of an optical disk used in this embodiment. On a PMMA substrate 110 having a groove, a 25 nm-thick Sb ₂ Se ₃ film 111 and a 30
A Bi film 112 of nm in thickness was formed by sputtering, and then an ultraviolet-curable resin protective layer 113 was formed, and then bonded together with an adhesive (not shown). The depth d of the groove is 70 nm corresponding to λ / 8 in optical depth, and the groove width Wg = 0.7.
The μm land width Wl was 0.9 μm and the pitch was 1.6 μm. In this embodiment, the recording layer whose reflectance is increased by recording is used.
This also shows that the present invention is effective.

Using the above disk, recording and reproduction were performed by an optical head mainly comprising a semiconductor laser having a wavelength of 830 nm and an objective lens having an NA of 0.6. Recording frequency 8MH
z, recording radius 70 mm, disk rotation speed 1800 rp
m, recording laser power 12 mW, C / N 60 dB for land recording, C / N 54 dB for group recording
I got The difference in C / N is 6 dB, and the land recording has a signal level (C level) of 5 dB compared to the groove recording.
B, the noise level (N level) was superior by 1 dB. The reason that the noise level is lower in the land recording is presumably because the influence of light scattering in the groove is small. In addition, the signal level is higher in land recording because the phase difference Δφ ₃ of the recording film is in the range of 0 <Δφ ₃ <π. That is, as described above, in this disk configuration, the complex reflectivity R ₁ before recording and the complex reflectivity R ₂ after recording are represented by the following formula: R ₁ = r ₁ exp (iφ ₁ ) = 0 _{.308exp (0.61πi) R 2 = r} 2 exp (iφ 2) = 0.670exp (0.89πi) Δφ = φ 2 -φ 1 = because it is 0.28Pai, phase difference at this time is [Delta] [phi ₃ = .phi.h −φ1 = φ ₂
−φ ₁ = 0.28π, which satisfies 0 <Δφ ₃ <π.
Therefore, in this embodiment, a high C / N of 60 dB or more was achieved by employing the land recording method. Note that the reflectance of the recording layer is obtained by the square of the amplitude reflectance.
Therefore, the reflectance before recording is | r ₁ | ² = (0.3
08) ² ≒ 0.095, 9.5%, reflectivity after recording is |
r ₂ | ² = (0.670) ² ≒ 0.449 and 44.9%
That is, the reflectivity is increased by recording.

Next, the difference between the signal levels of land recording and groove recording in this embodiment will be considered by simulation. The simulation method is as described above. Hereinafter, simulation results will be described with reference to FIGS. 22 and 23 show the relationship between the recording width and the amount of reflected light for group recording and land recording, respectively, when the recording layer according to the present embodiment is used. The groove depth d was λ / 8, the pitch was 1.6 μm, and the groove width and land width were parameters. FIGS. 24 and 25 show the relationship between the groove width and the land width and the amount of reflected light when the recording width is a parameter. As described above, the amount of reflected light changes depending on the recording width, the groove width, and the land width. However, when the recording width was observed by a microscope, the recording width was about 0.9 μm. FIG. 2 shows the relationship between the groove and land width and the amount of reflected light.
6 are shown together.

In FIG. 26, a curve 120 indicates the amount of reflected light when not recording, a curve 121 indicates the amount of reflected light in groove recording, and a curve 122 indicates the amount of reflected light in land recording. In this embodiment, the groove width Wg is 0.7 μm and the land width Wl is 0.9 μm.
8%, and the signal level in groove recording is 16.5%. Accordingly, the signal level difference between the two was as follows: 20log ₁₀ (27.8 / 16.5) = 4.5 dB, which substantially matched the signal level difference of 5 dB according to the present embodiment. From this, it is understood that it is an important point to sufficiently obtain the relationship between the phase change of the recording film and the phase of the groove to obtain a high signal level.

<Embodiment 3> In the above embodiment, a phase change is caused by alloying after recording, but in this embodiment, a phase change is caused by a phase change of the recording film. Since the phase change can be reversibly changed between a crystalline state and an amorphous state, information can be rewritten.

FIG. 27 shows the structure of the optical disk used in this embodiment. A 70 nm-thick Z
First interference film 131 made of nS—SiO ₂ , thickness 20 n
m recording film 132 of In ₃ SbTe ₂ , thickness 110
second interference film 133 made of ZnS-SiO ₂ in nm, a reflection film 134 made of Ni-Cr having a thickness of 120nm are sequentially formed by sputtering, then forming a UV-curable resin protective layer 113, further adhesive (Fig. (Not shown).

The refractive index of the substrate is 1.49, the refractive index of the first and second interference films is 2.0, the refractive index of the protective film is 1.50,
The optical constant of the reflective film is 4.3-i3.9, and the optical constant of the recording film is 4.2-i0.94 in the amorphous state and 4.2-i1.7 in the crystalline state. The complex reflectance Ra at the time of and the complex reflectance Rc at the time of the crystalline state are as follows. Ra = ra × exp (iφa) = 0.639exp (0.652πi) Rc = rc × exp (iφc) = 0.523exp (0.606πi) Since ra> rc, the phase difference is represented by the following equation: Δφ ₃ = φh -Φ1 = φa−φc = 0.046π. In this embodiment, since 0 <Δφ ₃ <π, land recording is performed to obtain a high signal level.

FIG. 28 shows the reflectances | Ra | ² , | Rc | ² , and the phase difference φ when the thickness of the In ₃ SbTe ₂ recording film is changed.
a-φc is shown. From this figure, when the thickness of the In ₃ SbTe ₂ recording film is 60 nm or less, 0 <Δφ ₃ <π, and
Land records are suitable. FIG. 29 and FIG. 29 show the relationship between the recording width and the amount of reflected light when the groove depth d of the substrate 130 is 70 nm corresponding to λ / 8 in optical depth, the groove width is 0.7 μm, and the pitch is 1.6 μm. 30. The thickness of the recording film is 2
0 nm. In FIG. 29, the unrecorded state is an amorphous state having a high reflectivity, and the recorded state is a crystalline state having a low reflectivity. Since the unrecorded reflected light amount level corresponds to a recording width of 0 μm, a larger signal level can be obtained by land recording.

In FIG. 30, the unrecorded state is a low-reflectance crystalline state, and the recorded state is a high-reflectivity amorphous state. Also in this case, a larger signal level can be obtained by land recording. Therefore, no matter which of the two states, the crystalline state and the amorphous state, is set to the recording state, land recording can obtain a larger signal level. This is regardless of the recording state, large recording method of the signal level by [Delta] [phi ₃ (land recording or Group - Bed recording) shows the ability to select.

In the third embodiment, the extinction coefficient of the optical constant of the recording film is changed. However, the present invention is not limited to this. You may do. Further, in the above-described embodiment, a disc for detecting a change in the amount of reflected light has been described. However, it is needless to say that the present invention can be applied to a disc in which the amount of transmitted light changes.

[0056]

According to the present invention, since the phase change of the recording film can be used, there is an effect that a large signal level can be obtained. In the case of using land recording with a low noise level, the recording film thickness or optical constant can be set to a condition in which the recording film changes phase so as to be suitable for land recording, and a high C / N or high S / N disk can be set. Is obtained.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram of a recording method using an optical disc according to an embodiment of the present invention.

FIG. 2 is a schematic view of a conventional optical disc and an optical system of a recording / reproducing apparatus.

FIG. 3 is a block diagram of a simulation experiment used in the present invention to analyze a reproduction signal level.

FIG. 4 is a partial cross-sectional view of an optical disk for explaining the phase of complex reflectance in a simulation experiment according to the present invention.

FIG. 5 is a partial cross-sectional view of another optical disk for explaining the phase of complex reflectance in a simulation experiment according to the present invention.

FIG. 6 is a characteristic diagram showing a relationship between a reflected light amount and a groove depth in a simulation experiment according to the present invention.

FIG. 7 is a partial cross-sectional view of another optical disk for explaining the phase of complex reflectance in a simulation experiment according to the present invention.

FIG. 8 is a partial cross-sectional view of another optical disc for explaining the phase of complex reflectance in a simulation experiment according to the present invention.

FIG. 9 is a characteristic diagram showing an example of a characteristic showing a relationship between a reflected light amount and a groove depth in a simulation experiment according to the present invention.

FIG. 10 is a characteristic diagram showing an example of a characteristic showing a relationship between a reflected light amount and a groove depth in a simulation experiment according to the present invention.

FIG. 11 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a phase difference Δφ in a simulation experiment according to the present invention.

FIG. 12 is a characteristic diagram showing an example of a characteristic showing a relationship between a reflected light amount and a phase difference Δφ in a simulation experiment according to the present invention.

FIG. 13 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a recording width in a simulation experiment according to the present invention.

FIG. 14 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a recording width in a simulation experiment according to the present invention.

FIG. 15 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a recording width in a simulation experiment according to the present invention.

FIG. 16 is a characteristic diagram showing an example of a characteristic indicating a relationship between a reflected light amount and a recording width in a simulation experiment according to the present invention.

FIG. 17 is a partial sectional view of an optical disc according to an embodiment of the present invention.

FIG. 18 is a partial sectional view of an optical disc according to an embodiment of the present invention.

FIG. 19 is a characteristic diagram showing the relationship between the Sb ₂ Se ₃ film thickness, the reflectance, and the phase difference Δφ in the optical disc of one embodiment according to the present invention.

FIG. 20 is a characteristic diagram showing the relationship between Sb ₂ Se ₃ film thickness and phase in the optical disc of one embodiment according to the present invention.

FIG. 21 is a partial sectional view of an optical disc according to an embodiment of the present invention.

FIG. 22 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a recording width in the optical disc of one embodiment according to the present invention.

FIG. 23 is a characteristic diagram showing an example of a characteristic indicating a relationship between a reflected light amount and a recording width in the optical disc of one embodiment according to the present invention.

FIG. 24 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a groove width in the optical disc of one embodiment according to the present invention.

FIG. 25 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a land width in the optical disc of one embodiment according to the present invention.

FIG. 26 is a characteristic diagram showing an example of a characteristic indicating a relationship between a reflected light amount and a land and groove width in the optical disc of one embodiment according to the present invention.

FIG. 27 is a partial sectional view of an optical disc according to an embodiment of the present invention.

FIG. 28 is a characteristic diagram showing the relationship between the In ₃ SbTe ₂ film thickness, the reflectance, and the phase difference in the optical disc of one embodiment according to the present invention.

FIG. 29 is a characteristic diagram illustrating an example of a characteristic indicating a relationship between a reflected light amount and a recording width in the optical disc of one embodiment according to the present invention.

FIG. 30 is a characteristic diagram showing an example of a characteristic indicating a relationship between a reflected light amount and a recording width in the optical disc of one embodiment according to the present invention.

[Explanation of symbols]

1 ... unrecorded state characteristic curve showing the amount of reflected light 2 ... Group - Bed characteristic indicating the amount of light reflected at the recording curve 3 ... characteristic curve 100 ... PMMA substrate 101 ... Sb ₂ Se ₃ film 102 indicating the amount of reflected light when the land recording ... Bi film 103 ... Protective layer 105 ... Recording part.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Jin Yanagihara 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Video Media Research Laboratories (72) Koichi Moriya Inventor Koichi Moriya 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock (72) Inventor Masaaki Kurebayashi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. 292 Yoshida-cho, Yoshika-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Hitachi, Ltd.Video Media Research Laboratory (72) Inventor Katsuo Konishi 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Hitachi, Ltd.Video Media Research Laboratory (72) Inventor Katsuyuki Tanaka 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Hitachi, Ltd. Visual Media Lab In-house (72) Inventor Norio Goto 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd.Video Media Research Laboratory (72) Inventor Akio Maruyama 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. (72) Inventor Kiei Kodera 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Yokohama Works, Hitachi, Ltd. (56) References JP-A-2-113451 (JP, A) JP-A-3-157830 (JP) , A)

Claims (5)

(57) [Claims] 1. A method for performing recording on an optical information recording medium provided with a recording layer on a substrate having a groove, on which a reflectance and a phase are optically changed by laser light irradiation, wherein the recording layer has an optical surface. When a phase change occurs between the high reflectance state and the low reflectance state, the phase in the high reflectance state is φh, and the phase in the low reflectance state is φl, the depth of the groove changes the wavelength of the laser light. Equation (1) is satisfied with the optical depth as λ, and 0 <groove depth <λ / 4 (1) When the phase difference is Δφ ₃ = φh−φ1, −π <Δφ ₃ <0. A recording method for an optical information recording medium, wherein recording is performed in a groove of the optical information recording medium. 2. A method for performing recording on an optical information recording medium having a recording layer in which a reflectance and a phase are optically changed by irradiation of a laser beam on a substrate having a groove, wherein the recording layer has When a phase change occurs between the high reflectance state and the low reflectance state, the phase in the high reflectance state is φh, and the phase in the low reflectance state is φl, the depth of the groove changes the wavelength of the laser light. where λ satisfies the expression (1) with an optical depth, and 0 <groove depth <λ / 4 (1) When the phase difference is Δφ ₃ = φh−φ1, 0 <Δφ ₃ <π. A recording method for an optical information recording medium, wherein recording is performed on lands between grooves of the optical information recording medium. 3. A recording layer on which a reflectance and a phase are optically changed by laser light irradiation is provided on a substrate having a groove.
An optical information recording medium on which information is recorded in the groove portion, wherein the optical change of the recording layer occurs between a high reflectance state and a low reflectance state, and the phase in the high reflectance state is φh, When the phase in the low reflectivity state is φ1, the depth of the groove satisfies the formula (1) with the optical depth, where λ is the wavelength of the laser beam, and 0 <groove depth <λ / 4 (1) An optical information recording medium, wherein -π <Δφ ₃ <0 when the phase difference is Δφ ₃ = φh−φ1. 4. An optical information recording medium in which a recording layer in which a reflectance and a phase are optically changed by laser light irradiation is provided on a substrate having a groove, and information is recorded on a land portion between the grooves. The optical change of the recording layer occurs between the high reflectance state and the low reflectance state, and when the phase in the high reflectance state is φh and the phase in the low reflectance state is φ1, the depth of the groove is Satisfies the formula (1) with the optical depth, where λ is the wavelength of the laser beam, and 0 <groove depth <λ / 4 (1) When the phase difference is Δφ ₃ = φh−φ1, 0 < An optical information recording medium, wherein Δφ ₃ <π. Wherein the said recording layer and multi-layer structure, the recording area of the recording layer, characterized in that the arrangement for changing the reflectance as the optical change by alloying claim 3 or 4, wherein the laser beam irradiation Optical information recording medium.