JP2985100B2 - Optical information recording medium and recording method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical information recording medium and a recording method therefor, and in particular, by setting a ratio of a depth and a width of a pre-groove to a predetermined value range. And an optical information recording medium having improved reproduction signal characteristics such as jitter, crosstalk, and the like, and a recording method thereof.

[Prior Art] As this type of optical information recording medium, a light-transmitting substrate having a pregroove formed as a guide groove in a spiral shape, a light-absorbing layer provided on the substrate and containing an organic dye,
A light reflecting layer provided on the light absorbing layer, and a protective layer further provided on the light reflecting layer, capable of optically writing and reading information and having a reproduction signal satisfying the CD standard. Information recording media are known.

As the shape of the pregroove of such a conventionally known optical information recording medium, the track pitch is 1.5 to 1.7 μm and the width is 0.1 μm.
The thickness is about 3 to 0.7 μm and the depth is about 60 to 100 nm. The optical information recording medium was irradiated with a laser beam having a recording power of 6 to 9 mW to deform the substrate by about 30 to 40 nm, thereby forming optical pits in the pre-groove portion and recording optical information.

Therefore, the jitter and block error rate after recording optical information under certain conditions (under optimal conditions)
Although sufficient to satisfy the CD standard, jitter may increase depending on recording conditions. Even with a low jitter, the power margin (allowable power for recording) is narrow. In addition, the comparison between our products shows a greater cross-talk. Here, the jitter is the fluctuation or fluctuation of the digital signal in the time axis direction, and the crosstalk is a parameter indicating the influence of a signal from an adjacent track, and specifically, a track portion and an inter-track portion ( (The non-track portion).

That is, since the laser power of the recording light differs depending on each recording device, depending on the recording device used,
In some cases, recording is performed with a power higher than the optimum power of a certain optical information recording medium, and when the pre-groove of this optical information recording medium is formed to be shallow, optical pits formed by the recording light Extends to the land portions on both the left and right sides of the pregroove, and the pit shape becomes non-uniform. As a result, the reproduced waveform is disturbed, that is, the jitter is increased.

In addition, the optical pits extending to the land portions cause the pits to expand in the width direction of the pits with respect to the pit depths to be recorded, so that there is a problem that the crosstalk in the reproduced waveform is also increased.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-described problems, and uses an optical absorption layer and deforms a substrate or the like by recording light to perform optical information recording medium. It is an object of the present invention to provide an optical information recording medium capable of clearly obtaining a reproduced signal even when recording is performed with a power higher than the optimum power, and a recording method thereof.

In particular, it is an object of the present invention to provide an optical information recording medium capable of reducing jitter to 40 ns or less and an optical information recording medium which can satisfy the CD standard.

[Means for Solving the Problems] That is, a first aspect of the present invention provides a light-transmitting substrate having a pregroove formed on one main surface, a light-absorbing substance provided on the substrate and absorbing recording light. An optical information recording medium for recording information by irradiating the light absorbing layer with the recording light, wherein the light absorbing layer in a land portion located on the left and right of the pre-groove. And from the layer boundary between the substrate and the bottom of the layer boundary in the pre-groove portion is d sub, and when the width of the pre-groove is w sub, w sub / d sub ≦ 6 .
5 is an optical information recording medium characterized in that

That is, by reducing the ratio of the width to the depth of the pre-groove portion, it is intended to limit the area where the pit is formed.

The imaginary part of the complex refractive index of the light absorbing layer is k abs, the real part thereof is n abs, the thickness of the light absorbing layer is d av, the wavelength of the reproduction light is λ, and ρ = N
abs ・ d av / λ, 0.05 ≦ ρ ≦ 1.6 and ka
bs ≦ 0.3.

According to a second aspect of the present invention, there is provided an optical information recording apparatus comprising: using the optical information recording medium according to the first aspect, irradiating the recording light onto the light absorbing layer from the substrate side to perform optical information recording. This is a recording method of the information recording medium.

The pre-groove depth d sub in the present invention
In other words, the difference between the deepest part and the topmost part of the pre-groove with respect to the horizontal plane of the substrate is referred to. The width w sub of the pre-groove is a half-value width (depth d su
The value of the ratio d sub / w sub is 6.5 or less, that is, unlike the conventional pregroove, that is, the depth is made deeper, Is made narrower, the effect of absorbing the recording light by the light absorbing layer is enhanced, and the deformation of the substrate, that is, the formation of pits is made clearer.

Next, the present invention will be described more specifically with reference to FIGS. 1 to 5.

FIG. 1 is a partially cutaway perspective view of an optical information recording medium 1 according to the present invention, FIG. 2 is a longitudinal sectional view of a main part of the optical information recording medium 1 before recording, and FIG. FIG. 3 is a longitudinal sectional view of a main part after recording No. 1;

The optical information recording medium 1 includes a light-transmitting substrate 2, a light absorbing layer 3 formed on the substrate 2, a light reflecting layer 4 formed on the light absorbing layer 3, and a light reflecting layer 4. And a protective layer 5 formed thereon. Note that an intermediate layer (not shown) may be provided between the substrate 2 and the light absorbing layer 3 and between the light absorbing layer 3 and the light reflecting layer 4 as necessary.

The substrate 2 has a pre-groove 6 formed in a spiral shape as a guide groove. On the left and right sides of the pregroove 6, portions other than the pregroove 6, that is, lands 7 are located.

Note that the substrate 2 and the light absorbing layer 3 are in contact with each other by a first layer boundary 8. The light absorbing layer 3 and the light reflecting layer 4 are in contact with each other by a second layer boundary 9. The light reflecting layer 4 and the protective layer 5 are in contact with each other by a third layer boundary 10.

As shown in FIG. 3, when the optical information recording medium 1 is irradiated with a recording light (recording laser light) L1, the light absorbing layer 3 generates heat by absorbing the energy of the laser light L1, thereby causing the substrate 2 to emit heat. The pits 11 are formed due to thermal deformation on the side. In some cases, an optical change may occur in the light absorbing layer 3.

In particular, as shown in FIG. 2, the depth from the first layer boundary 8 at the land 7 located on the left and right of the pre-groove 6 to the bottom of the first layer boundary 8 at the pre-groove 6 Is d sub.

As described above, the value of the ratio between the width w sub and the depth d sub of the pre-groove is set to 6.5 or less, the depth is made deeper, and the width is made narrower, so that the recording light by the light absorbing layer 3 is increased.
The effect of absorbing L1 is enhanced, and the deformation of the substrate 2, that is, the formation of the pits 11 is made clearer.

From the second layer boundary 9 at the land 7,
The depth of the bottom of the second layer boundary 9 at the pregroove 6 (from the surface of the light absorbing layer 3 at the land 7,
(Depth of the bottom of the surface at the pregroove 6)
Is d abs.

The imaginary part of the complex refractive index of the light absorption layer 3 is represented by k abs, and its real part is represented by n abs.

The average thickness of the light absorbing layer 3 is d av. Here, the average film thickness d av is (volume of light absorbing layer 3) / (light absorbing layer 3).
Is the area of the region in which is formed).

The thickness of the light absorbing layer 3 at the pregroove 6 portion is d
gr.

The thickness of the light absorption layer 3 at the land 7 is d ln.

The wavelength of the reproduction light (reproduction laser light) L2 is λ.

The real part n abs of the complex refractive index of the light absorbing layer 3 is
The thickness d gr of the light absorbing layer 3 at the pregroove 6 portion,
Assuming that an optical parameter ΔC defined by the film thickness d ln at the land 7 and the wavelength λ of the reproduction light (reproduction laser light) L2 is ΔC = n abs (d rg−d ln) / λ, It is desirable that 0.12 ≦ ΔC ≦ 0.75.

That is, the thickness d gr of the pregroove 6 and the land 7
The difference from the film thickness d ln of the portion was made larger than before, so that the pregroove 6 portion could absorb more light. Therefore, pits 11 formed by deformation of the substrate 3 or decomposition of the dye are easily formed,
Since the land 7 has a small thickness, it does not absorb much light, and the pits 11 are not easily formed. That is, the pit 11 does not spread to the land 7 portion, and the pit 11 can be formed clearly.

Even when recording is performed with a power higher than the optimum power, excess heat is absorbed by the light absorbing layer 3 in the pre-groove 6 and the pits 11 can be prevented from reaching the lands 7. .

Further, the pit 11 has a film thickness of the pregroove 6 portion.
Since the difference between d gr and the film thickness d ln of the land 7 is defined as the product of the complex refractive index of the light absorbing layer 3, the larger the complex refractive index of the light absorbing layer 3, the greater the reproduction. The diffraction angle of the diffracted light at that time is widened, and ideal pits 11 can be formed.

In particular, by satisfying the relationship of ΔC = n abs (d gr−d ln) / λ 0.12 ≦ ΔC ≦ 0.75, even if the laser power of the recording light is stronger than the optimum power, the jitter specified in the CD standard Can be set to 40 ns or less. Further, the modulation degree, push-pull, crosstalk, and the like defined in the CD standard can be improved.

That is, when ΔC is larger than 0.75, the optical phase difference between the land 7 and the pre-groove 6 becomes too large, so that the jitter cannot be reduced to 40 ns or less and the modulation factor is also increased. Becomes difficult. In addition, since the contrast in the radial direction is increased, tracking becomes difficult, and even if the optical parameter ρ = n absd av / λ described below is set to a value within a predetermined range,
It becomes difficult to increase the reflectivity in the pre-groove 6 to 70% or more.

As a result of the examination, ΔC is desirably 0.4 or less for manufacturing reasons (the film thickness difference becomes large and variations easily occur) or to increase the reflectance.

When ΔC is smaller than 0.12, the difference in film thickness between the land 7 and the pre-groove 6 becomes small.
11 is easy to spread, crosstalk and jitter are large, and the power window (power margin) is narrow.

By setting ΔC to 0.15 or more, the jitter can be further improved, specifically, 30 ns or less.

Next, an optical parameter defined by ρ = n sbs · d av / λ will be described.

From the results of experiments and simulations by the present inventors, ρ = n abs · d av /
We note that λ is a very important parameter.

That is, in the optical information recording medium 1 having the configuration in which the light absorbing layer 3 and the light reflecting layer 4 are provided on the substrate 2, the reflectance specified in the CD standard is 70% or more, and the modulation of the modulation amplitude in the reproduction signal is performed. I11 / Itop indicated as a degree is 0.6 or more (however, “Itop” is the maximum reflected light amount in the CD playback signal, and “I11” is diffracted by the longest recorded pit and returned to the objective lens. This is an optical modulation component corresponding to the difference between the amount of reflected light and the amount of reflected light that is reflected by the non-pit portion and returned to the objective lens), and an output signal with a modulation degree I3 / Itop of 0.3 to 0.7 (however, "I3"
Is an optical modulation component corresponding to the difference between the reflected light amount diffracted by the recorded shortest pit and returned to the objective lens and the reflected light amount reflected by the non-pit portion and returned to the objective lens.) In order to obtain it, the real part n abs of the complex refractive index of the light absorbing layer 3 and the film thickness dg of the pregroove 6 part are required.
ρ given by the average film thickness of r and the film thickness d ln of the land 7 or the average film thickness d av and the wavelength λ of the reproduction light
By setting n abs · d av / λ within the range of 0.05 ≦ ρ ≦ 1.6, the reflectance can be easily adjusted to 70%, which conforms to the CD standard.
It is known that this can be done.

If ρ is smaller than 0.05, the film thickness d av of the light absorbing layer 3 must be considerably reduced, which is not practical for manufacturing.

Therefore, in the range of 0.05 ≦ ρ ≦ 0.6, 0.30
The range of ≦ ρ ≦ 0.6 is practical, the range of 0.1 or more is desirable for obtaining a sufficient degree of modulation, and the range of 0.45 ± 0.1 is most desirable for obtaining stable recording characteristics with a large degree of modulation. It can be said that it is a range.

Further, as shown in FIG. 4, even if ρ is in the range of 0.6 or more, if the peak point is on the graph, the reflectance is 70%.
Is possible.

In the range of 0.6 <ρ <1.6, there are two peak points, always in the range of 0.6 <ρ <1.10 and in the range of 1.10 <ρ <1.6, and they can obtain a high reflectance at the peak point. I know I can.

When ρ> 1.6, the film thickness is large, so that it is difficult to control the film thickness, which is not practical for manufacturing.

The graph showing the relationship between ρ and the reflectance is expressed as a combined function of an exponential function and a periodic function, and the amplitude of the periodic function increases as ρ increases.

The amplitude of such a periodic function changes with the complex refractive index and the thickness of the layers constituting the optical information recording medium 1, their homogeneity, and the like as parameters. For example, if the refractive index of the layer on the side where light is incident from the light absorbing layer 3 is small, the reflectance shifts in the direction in which the reflectance increases in the entire graph.

This graph shows the imaginary part k of the complex refractive index of the light absorption layer 3.
It is expressed by an exponential function using abs and dav as parameters, and it is also known that as kabs increases, the attenuation of the reflectance of the entire graph increases as shown in FIG.

The light absorbing layer 3 is homogeneous and the real part n ab of its complex refractive index
The present inventors have found from the simulations that there is no change in the period of the point indicating the peak in the graph unless there is an uneven distribution in s and the film thickness d av.

In addition, depending on the conditions, the reflectance at the bottom point of the graph in FIG. 4 can be increased by controlling the above parameter conditions. However, when ρ is set near the bottom point, It is difficult to increase the degree of modulation, and in some cases, the reflectance may be higher than before recording. Therefore, it is desirable that ρ is set near the peak point.

 The above-mentioned k abs will also be mentioned.

In order to obtain a high reflectance, it is necessary that k abs is 0.3 or less.

The present inventors have found that the numerical setting of k abs is an important parameter. Ie this k ab
If s is 0.3 or less, the reflectance increases as it approaches 0. Therefore, this range is most desirable. However, as the recording sensitivity approaches 0, the recording sensitivity becomes worse. Specifically, a range of 0.01 or more is desirable, and in practice, about 0.05 is desirable.

When ρ is in the range of 0.05 to 0.6, the imaginary part k abs of the complex refractive index of the same layer is desirably 0.3 or less. And ρ
Is in the range of 0.6 to 1.6, k abs is desirably 0.2 or less.

 Next, the material and physical properties of each layer will be described.

First, the light-transmitting substrate 2 is made of a highly transparent material having a refractive index to laser light in the range of 1.4 to 1.6 and mainly formed of a resin having excellent impact resistance, such as a glass plate, an acrylic plate, and an epoxy resin. Use a plate or the like. It is desirable to mold a resin such as polycarbonate by injection molding. Further, the substrate 2 may be coated with another layer, for example, a solvent-resistant layer such as SiO2 or an enhancement layer.

These materials are molded by means such as injection molding.
The thickness of the substrate 2 should be 1.1 mm to 1.5 mm so as to conform to the CD standard.
mm is desirable.

As the tracking guide means formed on the surface of the substrate 2 on the light absorption layer 3 side, the pre-groove 6 (FIGS. 2 and 3) formed in a spiral shape is desirable. The pre-groove 6 is used to guide tracking when recording a data signal. The pre-groove 6 is not limited to a spiral shape and may meander.

The so-called track pitch between the pregroove 6 and the adjacent pregroove 6 is desirably 1.6 μm.

Next, the light absorbing layer 3 is a layer made of a light absorbing material formed on the tracking guide means of the substrate 2, and is irradiated with a laser to generate heat, melt, sublime, deform or modify. It is. This light absorbing layer 3 is preferably a layer containing a light absorbing organic dye such as a cyanine dye. That is, for example, a cyanine-based dye or the like dissolved in a solvent is uniformly coated on the surface of the substrate 2 by means such as a spin coating method to form the substrate.

Next, the light reflection layer 4 is formed as needed, and is a metal film. For example, gold, silver, copper, aluminum, or an alloy containing these is formed by means such as a vapor deposition method and a sputtering method. To form Since it is necessary to have a reflectance of 70% or more, a metal film mainly composed of gold or an alloy containing gold is preferable among them.

Further, in order to prevent the light reflecting layer 4 from being oxidized, the light reflecting layer 4
Another layer such as an oxidation-resistant layer may be provided on the substrate.

Next, the protective layer 5 is also formed as needed, and is formed of a resin having excellent impact resistance similar to that of the substrate 2. For example, an ultraviolet curing resin is applied by a spin coating method, and is irradiated with ultraviolet rays to be cured to form the resin. In addition, epoxy resin,
An acrylic resin, a silicone-based hard coat resin, or the like may be used.

[Operation] The optical information recording medium according to the present invention can be recorded by a known optical information recording device. The optical information recording medium 1 is arranged such that the surface of the light-transmitting substrate 2 faces the laser irradiation means of the optical information recording apparatus, that is, the side where the pickup is provided. While the optical information recording medium 1 is being rotated by a spindle motor, a laser spot modulated into a signal conforming to the CD standard is tracked according to the tracking guide means, and is picked up from the substrate 2 side of the optical information recording medium 1 by a pickup. By irradiating the light absorbing layer 3, the light absorbing layer generates heat, and the heat deforms the substrate 2, thereby forming pits 11.

In recording, it is desirable to irradiate a laser spot having a wavelength λ of around 780 nm. Also, in relation to the CD standard, the linear velocity must be 1.2 to 1.4 m / sec,
The recording power may be about 6 to 9 mW.

In the present invention, as the shape of the pre-groove 6, the value of the ratio of its width w sub to its depth d sub is 6.5 or less, which is smaller than the conventional one. That is, the ratio of the depth to the width of the pit 11 formed by the deformation of the substrate 2 or the decomposition of the dye in the light absorbing layer 3 is smaller than a predetermined value. Therefore, a large amount of light-absorbing material is accommodated in the narrow and deep pre-groove 6, and even if recording is performed with a power higher than the optimum power, excess heat is absorbed by the light-absorbing layer 3 in the pre-groove 6. Thus, it is possible to prevent the pits 11 from reaching the lands 7. The heat thus absorbed is confined here, and a clean pit 11 with good edges can be created. That is, the rate of diffusion of heat based on the absorption of the recording laser beam L1 of the light absorbing layer 3 to the outside is suppressed, and the heat is confined in the pregroove 6 to form a clear deformed portion (pit 11) on the substrate 2 surface. be able to.

Since the sensitivity of the light absorbing layer 3 is generally higher as the thickness thereof is larger, the inside of the pre-groove 6 has higher sensitivity than the inside of the land 7. Therefore, the recorded pits 11 are unlikely to spread over an area wider than the width of the pre-groove 6, and it is easy to form a clear and large deformed portion on the surface of the substrate 2; Since the radial direction of the recording medium 1 or the axial direction of the pre-groove 6 is partitioned, the width of the pits 11 does not increase, and it is possible to suppress the causes of crosstalk and jitter in a reproduced signal.
These values can be reduced.

Further, the pits 11 of the optical information recording medium 1 according to the present invention.
Because the ratio between the pit depth and the pit width is large, the diffraction angle of the diffracted light (read laser light) at the time of reproduction is widened,
An ideal pit 11 having a small push-pull, a large modulation degree, and a small jitter after recording is formed. When the refractive index n abs is large, the optical shape of the pit 11 can be made good.

In particular, by satisfying the relationship of d sub / w sub ≦ 6.5 in an optical information recording medium capable of obtaining a reproduction signal satisfying the CD standard, the jitter can be reduced to 30 nm or less and the optical information satisfying the CD standard can be obtained. In a recording medium, stable reproduction can be ensured by a normal CD player (see FIG. 6). Further, the crosstalk specified in the CD standard can be made good.

Furthermore, a parameter ρ = about the thickness of the light absorbing layer 3
By setting n absd av / λ in the range of 0.05 to 1.6 and setting the imaginary part k abs of the complex refractive index of the light absorption layer to 0.3 or less, the CD standard is satisfied and the block error rate and the jitter are low. It can be an optical information recording medium.

Examples Next, examples of the optical information recording medium according to the present invention will be described below.

(Example 1) On a disk-shaped polycarbonate substrate on which a spiral pregroove having a width w sub of 390 nm and a depth d sub of 130 nm was formed, 30 wt. 8, 50 parts by weight of the cyanine dye No. 2 and 20 parts by weight of 4-nitroso-4'-iododiphenylamine shown in FIG. 8 were dissolved in diacetone alcohol to give a concentration of 70 g / l, and applied. In addition, a light reflection layer made of gold film and a UV-cured protective layer on the light reflection layer
And

w sub / d sub = 390/130 = 3.00, n abs = 2.5, d
gr = 194 nm, dln = 123 nm, and ΔC = 0.23.

Optimal power 6.5mw, 7.5mw, 8.5m under these conditions
Recording was performed with w. The respective jitter and crosstalk are shown in the table of FIG. From this table, it can be seen that jitter and crosstalk are small at the optimum power, and that these increases are small even when the power is further increased.

The jitter of the pit portion and the non-pit portion in FIGS. 9 and 10 is the total value of the variations in the signal lengths of the pit portion and the non-bit portion with reference to the signal lengths of 3T and 11T. It is shown by.

(Comparative Example) On a disc-shaped polycarbonate substrate on which a spiral pre-groove having a width w sub of 620 nm and a depth d sub of 70 nm was formed, a light absorbing layer and light were formed in the same manner as in Example 1 described above. A reflective layer and a protective layer were formed to obtain a CD.

w sub / d sub = 620/70 = 8.86, n abs = 2.5, dg
r = 151,4 nm and d ln = 116.4 nm, ΔC = 0.11
It is.

Optimal power 7.0mw, 8.0mw, 9.0m under these conditions
Recording was performed with w. The respective jitter and crosstalk are shown in the table of FIG. From this table, it can be seen that the jitter and the crosstalk are greater at the optimum power than at the first embodiment, and that the increasing tendency becomes more remarkable even when the power is further increased.

(Example 2) A light absorbing layer was formed on a disc-shaped polycarbonate substrate on which a spiral pregroove having a width w sub of 500 nm and a depth d sub of 77 nm was formed in the same manner as in Example 1 described above. A light reflecting layer and a protective layer were formed to obtain a CD.

w sub / d sub = 500/77 = 6.49, n abs = 2.5, dg
r = 162 nm, dln = 115 nm, and ΔC = 0.15.

Recording was performed on such a CD at a recording light wavelength of 770 to 810 nm and an optimum power of 6.8 mw to 7.8 mw. This jitter is 3T
(T is the reference time width) 30nsec at the rise, 25 at the fall
The rise time of nsec and 11T was 23 nsec, the fall time was 20 nsec, and the crosstalk was 0.30.

It can be seen that the jitter and crosstalk are small as in Example 1, and that these increases are small even if the power is further increased.

[Effect of the Invention] As described above, according to the present invention, the ratio of the width to the depth of the pre-groove is set to a predetermined value of 6.5 or less and the pre-groove is formed deeper and narrower than the conventional one. In the case of performing recording with the above-mentioned deformation, the deformation of the substrate is limited to the inside of the pre-groove, so that the recording with the uniform pit width and edge can be performed. Therefore, it is possible to provide an optical information recording medium that is compliant with the current CD standard, and that can satisfy the jitter standard value (40 ns or less) specified in the CD standard.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view of an optical information recording medium 1 according to the present invention, and FIG. 2 is a view for explaining an optical information recording medium 1 and a method for recording optical information on the optical information recording medium 1. FIG. 3 is a longitudinal sectional view of an essential part in a state where pits 11 are formed in the pre-groove 6, and FIG. 4 is a view showing a relationship between ρ (= n abs · d av / λ) and reflectance. 5 is a graph showing the relationship between the complex refractive index k abs and the reflectance of the light absorbing layer 3, FIG. 6 is a graph showing the relationship between d sub / w sub and jitter, and FIG. 7 is a cyanine dye. FIG. 8 shows the structural formula of cyanine dye No. 2, FIG. 9 shows a table showing the results of Example 1 of the present invention, FIG. 10 shows the structural formula of Comparative Example 1 It is a table showing a result. DESCRIPTION OF SYMBOLS 1 ... Optical information recording medium 2 ... Translucent board 3 ... Light absorption layer 4 ... Light reflection layer 5 ... Protective layer 6 ... Pregroove (guide groove) 7 ... Land 8 ... First 9: second layer 10: third layer 11: pit d sub: light absorption layer 3 and substrate 2 at land 7
From the first layer boundary 8 to the depth d abs at the bottom of the first layer boundary 8 at the pre-groove 6. The second between the light absorbing layer 3 and the light reflecting layer 4 at the land 7 From the layer boundary 9, the depth n abs at the bottom of the second layer boundary 9 in the portion of the pre-groove 6 ... a real part of the complex refractive index of the light absorbing layer 3 k abs ... the complex refractive index of the light absorbing layer 3 .., The average thickness of the light absorbing layer 3 d gr... The film thickness of the light absorbing layer 3 at the pregroove 6 d ln... The film thickness w sub of the light absorbing layer 3 at the land 7 …… the width of the pre-groove 6 λ …… the wavelength of the reproduction light L1 …… the laser light for recording L2 …… the laser light for reproduction

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Emiko Hamada 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Yuden Co., Ltd. (56) References JP-A-61-129747 (JP, A)

Claims (2)

(57) [Claims] 1. A light-transmitting substrate having a pre-groove formed on one main surface, and a light-absorbing layer containing a light-absorbing substance that absorbs recording light and is laminated on the substrate. An optical information recording medium for recording information by forming pits in said pre-groove by irradiating said recording light to a light absorbing layer, said light reflecting layer reflecting said recording light on said light absorbing layer Further, the depth from the layer boundary between the light absorbing layer and the substrate in the land portion located on the left and right of the pre-groove to the bottom of the layer boundary in the pre-groove portion is d sub
When the width of the pre-groove is w sub, 1.5 ≦ w sub / d sub ≦ 6.5, and the imaginary part of the complex refractive index of the light absorbing layer is k abs, and the real part is n abs, the thickness of the light absorbing layer is d av, the wavelength of the reproduction light is λ, and when ρ = n abs · d av / λ, 0.05 ≦ ρ ≦ 0.6 and k abs ≦ 0.3 While the light absorbing layer absorbs the recording light, the pits are formed on the main surface of the substrate in the pre-groove portion, and the light absorbing layer is irradiated with reproduction light to cause an optical phase difference. An optical information recording medium for reproducing information. 2. A light-transmitting substrate having a pre-groove formed on one main surface, and a light-absorbing layer laminated on the substrate and containing a light-absorbing substance that absorbs recording light. A recording method for an optical information recording medium for recording information by forming pits in the pre-groove by irradiating the recording light on the light absorbing layer, wherein the recording light is reflected on the light absorbing layer. A light reflecting layer is laminated, and the depth from the layer boundary between the light absorbing layer and the substrate in the land portion located on the left and right of the pre-groove to the bottom of the layer boundary in the pre-groove portion is d su, b
When the width of the pre-groove is w sub, 1.5 ≦ w sub / d sub ≦ 6.5, and the imaginary part of the complex refractive index of the light absorbing layer is k abs, and the real part is n abs, the thickness of the light absorbing layer is d av, the wavelength of the reproduction light is λ, and ρ = n abS · d av / λ, 0.05 ≦ ρ ≦ 0.6 and k abs ≦ 0.3 By irradiating the light absorbing layer with the recording light from the substrate side, the light absorbing layer absorbs the recording light, and the pits are formed on the main surface of the substrate in the pre-groove portion, A recording method for an optical information recording medium, comprising irradiating a light absorbing layer with reproduction light and performing optical information recording such that reproduction is performed by an optical phase difference.