JPH04182944A - Optical information recording medium and recording method thereof - Google Patents

Abstract

PURPOSE:To allow the execution of recording at the uniformized width and edges of pits by specifying the optical parameter relating to a difference between the film thickness in pregroove parts and the film thickness in land parts and forming the pregrooves narrow and deep. CONSTITUTION:When the real number part of the double refractive indices of a light absorption layer is designated as nabs, the film thickness in the pregroove parts of the light absorption layer as dgr, the film thickness in the land parts of the light absorption layer as dln, the wavelength of reproducing light as lambda, and further, 0.12<= C<=0.75 is set, C=nads(dgr-dln)/lambda is specified. The film thickness of the pregrooves 6 formed with pits 11 by the deformation of a substrate 2 or the decomposition, etc., of the dyes of the light absorption layer 3 increases and the film thickness decreases in the right and left land 7 parts. The fine pits 11 having the good edges are formed in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording medium and a recording method thereof, and is particularly based on the difference between the film thickness in the pregroove portion and the film thickness in the land portion. The present invention relates to an optical information recording medium and a recording method thereof, in which reproduction signal characteristics such as jitter and crosstalk are improved by setting optical parameters within a predetermined value range.

[Prior Art] This type of optical information recording medium includes a light-transmitting substrate on which a pre-groove is formed as a spiral guide groove, a light-absorbing layer provided on the substrate and containing an organic dye, and a light-transmitting layer formed on the substrate and containing an organic dye. Optical information having a light reflective layer provided on the second side of the absorption layer and a protective layer further provided on the light reflective layer, information can be written and read optically, and the reproduced signal satisfies the CDJU rating. Recording media are known.

The shape of the pregroove of such a conventionally known optical edge recording medium is such that the track pitch is about 1.5 to 1.7 μm, the width is about 0.3 to 0.7 μm, and the depth is about 60 to 1100 nm. This optical information recording medium has a recording power of 6 to 9 mW.
By irradiating the substrate with laser light to deform the substrate by approximately 30 to 40 nm, optical bits are formed in the pregroove portion, and optical information is recorded.

Therefore, optical information can be transmitted under certain conditions (under optimal conditions).
Jitter and block error rate after recording are CD
Although it is sufficient to meet the standards, jitter may increase depending on the recording conditions.Also, even if the jitter is low, the power margin (allowable power for recording) is narrow. Also, when comparing our products, crosstalk is also larger. Note that jitter is the fluctuation or fluctuation of a digital signal in the time axis direction, and crosstalk is a parameter that indicates the influence of signals from adjacent tracks. It is expressed as the ratio of the amplitude of the HF signal in the non-track area).

In other words, the laser power of the recording light differs depending on each recording device, so depending on the recording device used, recording may be performed with a power stronger than the optimum power for a certain optical information recording medium, and the If the pregroove is formed shallowly, the optical bits formed by the recording light will extend to the lands on both the left and right sides of the pregroove, making the bit shape uneven and resulting in a reproduction waveform. In other words, the jitter becomes large.

Furthermore, the optical bits that extend to the land portion cause the bits to spread in the width direction relative to the recorded bit depth, resulting in a problem of increased crosstalk in the reproduced waveform.

[Problem to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, and provides an optical information recording method that uses a light absorption layer to record optical information by deforming a substrate etc. with recording light. It is an object of the present invention to provide an optical information recording medium and a recording method therefor that can clearly obtain a reproduced signal even when recording is performed with a power stronger than the optimum power.

In particular, the object of the present invention is to provide an optical information recording medium and a recording method thereof that can reduce jitter to 40 ns or less in an optical information recording medium that can satisfy the CD standard.

[Means for Solving the Problems] That is, the first invention includes a light-transmitting substrate with a pregroove formed on one main surface, and a light-absorbing material provided on the substrate to absorb recording light. an optical information recording medium that records information by irradiating the light absorption layer with the recording light, wherein nabs is the real part of the complex refractive index of the light absorption layer; The film thickness at the pregroove portion of the light absorption layer is dgr, the film thickness at the land portion of the light absorption layer is dln, the wavelength of the reproduction light is λ, and ΔC=nabs (dzr-dln)
The optical information recording medium is characterized in that 0.12≦ΔC≦0.75 when /λ.

That is, by making the film thickness of the land portion smaller than the film thickness of the pregroove portion, the area where the bit is formed is limited.

The imaginary part of the complex refractive index of the light absorption layer is kabs, the real part thereof is nabs, the thickness of the light absorption layer is dav, the wavelength of the reproduction light is λ, and ρ=nabs. −dav/λ, 0.05≦ρ
≦1.6, and k abs≦0.3.

A second invention is an optical information recording medium according to the first invention, characterized in that optical information is recorded by irradiating the recording light from the substrate side onto the light absorption layer. This is a recording method for an information recording medium.

Next, the present invention will be explained in more detail based on 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 vertical cross-sectional view of a main part of the optical information recording medium 1 before recording, and FIG. FIG.

This optical information recording medium 1 includes a transparent substrate 2 and a transparent substrate 2.
It has a light absorption layer 3 formed on top, a light reflection layer 4 formed on this light absorption layer 3, and a protective layer 5 formed on this light reflection layer 4. In addition.

If necessary, an intermediate layer (not shown) may be provided between the substrate 2 and the light absorbing layer N3 and between the light absorbing layer 3 and the light reflecting layer 4.

A spiral pregroove 6 is formed in the substrate 2 as a guide groove. On the left and right of this pregroove 6,
A portion other than the pregroove 6, that is, a land 7 is located.

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

As shown in FIG. 3, when the optical information recording medium 1 is irradiated with the recording light (recording laser light) LL, the light absorption layer 3 absorbs the energy of the laser light L1 and generates heat, and the substrate 2 Thermal deformation occurs on the side, forming pits 11. In some cases, optical changes may occur in the light absorption layer 3.

In particular, as shown in FIG.
The depth to the bottom of the first outer layer 8 in the pregroove 6 portion is defined as dsub.

By setting the values of @w sub and depth d sub of the pregroove to 6.5 or less, making the depth deeper and the width narrower, the recording light L1 by the light absorption layer 3 is
The purpose of this is to enhance the absorption effect and make the deformation of the substrate 2, that is, the formation of the pits 11, more clear.

In other words, the pre-groove depth d sub refers to the difference between the deepest part and the highest part of the pre-groove when the horizontal plane of the substrate is used as a reference, and the pre-groove width w sub
is the half width for this depth d sub (depth d su
+a) of the width at a depth of 1/2 of b, and unlike conventional pregrooves, the value of the ratio d sub / w sub is set to 6.5 or less, that is, the depth is made deeper, By making the width narrower, the absorption effect of the recording light by the light absorption layer is increased, and the deformation of the substrate, that is, the formation of bits, is made more clear.

From the second outer layer 9 in the land 7 portion to the bottommost depth of the second outer layer 9 in the pregroove 6 portion (from the surface of the light absorption layer 3 in the land 7 portion to the pregroove 6 The depth of the bottom of the surface at the portion of d abs is defined as d abs.

Let kabs be the imaginary part of the complex refractive index of the light absorption layer 3, and let nabs be the real part.

Let dav be the average thickness of the light absorption layer 3. Note that the average film thickness dav here is expressed by (volume of light absorption layer 3)/(area of region in which light absorption layer 3 is formed).

The film thickness at the pregroove 6 portion of the light absorption layer 3 is dg
Let it be r.

Let dln be the film thickness of the light absorption layer 3 at the land 7 portion.

Further, the wavelength of the reproduction light (laser light for reproduction) L2 is assumed to be λ.

In the present invention, the real part nabs of the complex refractive index of the light absorption M3, the film thickness dgr at the pregroove 6 part of the light absorption layer 3, the film thickness dln at the land 7 part, and the reproduction light (reproduction laser beam ) the optical parameter ΔC defined by the wavelength λ of L2.

If ΔC=nabs (dzr-dl,n)/λ, then 0.12≦ΔC≦0.75.

That is, the film thickness d of the pregroove 6 portion is r and the land 7
The difference between the film 11Xdln and the film 11Xdln is made larger than before, so that the pregroove 6 part can absorb more light. Therefore, bits 11 formed by deformation of the substrate 3 or decomposition of the dye are likely to be formed, and the land 7 portions do not absorb much light because of their thin film thickness, so that the bits 11 are difficult to be formed. In other words, bit] J- does not extend to land 7, and is clearly bit 1.
1 can be formed.

Further, even when recording is performed with a power stronger than the optimum power, excess heat is absorbed by the light absorption 13 in the pregroove 6, and it is possible to prevent the bit 11 from reaching the land 7 portion.

Furthermore, since the bit 11 is defined as the product of the double refractive index of the light absorption 13 for the difference between the film thickness dzr of the pregroove 6 portion and the film thickness dln of the land 7 portion, the light absorption layer The larger the r.sub.3 refractive index, the wider the diffraction angle of the diffracted light during reproduction, and the more ideal the bit 11 can be formed.

In particular, the above ΔC= nabs (dgr − d In) /λ, 0
．． By satisfying the relationship 12≦8C≦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 kept to 40 ns or less. Furthermore,
Modulation degree specified in the CD standard.

Push-pull and crosstalk can also improve this quality.

That is, when ΔC is larger than 0.75, the optical phase difference between the land 7 portion and the pregroove 6 becomes too large, making it impossible to reduce the jitter to 40 ns or less, and the modulation degree also increases. It becomes difficult to do so. Also, because the contrast in the radial direction increases,
Tracking becomes difficult, and even if the optical parameter ρ=nabs-dav/λ described below is set to a value within a predetermined range, it becomes difficult to increase the reflectance within the pregroove 6 to 70% or more. Put it away.

As a result of the study, it was found that 8C was used for manufacturing reasons (the difference in film thickness becomes large and variations tend to occur), or to increase the reflectance. 4 or less is desirable.

When ΔC is smaller than 0.1-2, the difference in film thickness between the land 7 portion and the pregroove 6 becomes small, so even if recording is performed on the pregroove 6, the bit 11- is likely to spread, crosstalk and jitter are large, and the power window (power margin) becomes unsatisfactory.

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

Next, optical parameters defined by ρ=nabs-dav/λ will be explained.

From the results of experiments and simulations by the present inventors, this ρ= n abs・
We focused on the fact that dav/λ is a very important parameter.

That is, in the optical information recording medium 1 having a structure including a light absorption layer 3 and a light reflection layer 4 on a substrate 2, the reflectance specified in the CD standard is 70% or more and the modulation in the reproduced signal '#A I 11/ shown as the modulation degree of @
I top is 0. 6 or more, and modulation depth I 3/I
top is 0. In order to obtain an output signal of 3 to 0.7, the real part n abs of the complex refractive index of the optical absorption 13,
The average film thickness of the film thickness dgr of the pre-groove 6 part and the film thickness dln of the land 7 part, or the average film thickness dav,
ρ=nabs-da■/ given by the wavelength λ of the reproduction light
It has been found that by setting λ within the range of 0.05≦ρ≦1.6, it is possible to easily increase the reflectance to 70% or more, which conforms to the CD standard.

If ρ is smaller than 0.05, the film thickness of the light absorption layer 3 must be increased by a considerable amount, which is not practical in terms of manufacturing.

Therefore, in the range of 0.05≦ρ≦0.6,
0.30≦ρ≦0. The range of 6 is practical, and in order to obtain a sufficient modulation depth, the range of 0.6 is practical. A range of 1 or more is desirable, and in order to obtain stable recording characteristics with a large degree of modulation, a range of 0.
It can be said that the range of 45±0.1 is the most desirable range.

Furthermore, as shown in FIG. 4, ρ is 0. Even if it is in the range of 6 or more, if it is at the peak point on the graph, the reflectance is 7.
It is possible to exceed 0%.

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 1.10<
ρ<1.6, and it is known that high reflectance can be obtained at these peak points.

When ρ>1.6, the film thickness becomes thick, making it difficult to control the film thickness, which is not practical in terms of manufacturing.

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

The amplitude of such a periodic function changes using parameters such as the complex refractive index, film thickness, and homogeneity of the layers constituting the optical information recording medium 1. For example, if the refractive index of the layer on the side where light enters from the light absorption layer 3 is small, the reflectance as a whole shifts in the direction of increasing the reflectance.

Also, this graph shows the imaginary part ka of the complex refractive index of the light absorption layer 3.
It is also known that it is expressed by an exponential function with bs and dav as parameters, and as shown in FIG. 5, the larger kabs becomes, the greater the attenuation of reflectance across the graph becomes.

The light absorption layer 3 is homogeneous, and the real part of its complex refractive index n a
The inventors have found through simulations that unless there is non-uniform distribution in bs and film thickness dav, there is no change in the period of the points showing the peaks in the above graph.

Note that depending on the conditions, it is possible to increase the reflectance at the bottom point of the graph in FIG. 4 by controlling the above parameter conditions, but if ρ is set near the bottom point, It is difficult to obtain a large degree of modulation, and in some cases, the reflectance may increase compared to before recording. Therefore, it is desirable to set ρ near the peak point.

The above kabs will also be mentioned.

In order to obtain high reflectance, this k abs should be 0. It must be 3 or less.

Note that the present inventors have discovered that the numerical setting of k abs is an important parameter. In other words, this k
abs is 0. If it is 3 or less, the reflectance improves as it approaches 0. Therefore, this range is the most desirable. However, since recording sensitivity deteriorates as the value approaches O, it is necessary that the value be larger than O.

Specifically, a range of 0.01 or more is desirable, and actually around 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 0. It is desirable that it is 3 or less. Also, ρ is 0. In the range of 6 to 1.6,
It is desirable that kabs is 0.2 or less.

Next, the materials and physical properties of each layer will be explained.

First, the transparent substrate 2 is made of a highly transparent material with a refractive index in the range of 1.4 to 1.6 with respect to laser light, and is mainly made of resin with excellent impact resistance, such as a glass plate, Use acrylic board, epoxy board, etc. In addition,
It is desirable to mold resin such as polycarbonate by injection molding. Also, there are other fakes on the board 2, such as 5i0
It may be coated with a solvent-resistant layer or an enhancement layer such as No. 2.

These materials are molded by means such as injection molding. The thickness of the substrate 2 is 1.1 mm to comply with the CD standard.
~1.5 mm is desirable.

As the tracking guide means formed on the surface of the substrate 2 on the light absorption layer 3 side, it is desirable to use the pregroove 6 (FIGS. 2 and 3) formed in a spiral shape. The pregroove 6 is used to guide tracking when recording a data signal. The pregroove 6 is not limited to a spiral shape, but may be meandering.

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

Next, the light-absorbing layer 3 is a layer made of a light-absorbing substance formed on the tracking guide means of the substrate 2, and is a layer that generates heat, melts, sublimates, deforms, or denatures when irradiated with a laser. It is. This light absorption layer 3
is preferably a layer containing a light-absorbing organic dye such as a cyanine dye. That is, for example, it is formed by uniformly coating the surface of the substrate 2 with a cyanine dye or the like dissolved in a solvent by means such as a spin coating method.

Next, the light reflecting layer 4 is formed as necessary and is a metal film, for example, made of gold, silver, copper, aluminum, or an alloy containing these, by means of vapor deposition, sputtering, etc. Forms the anus. 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 desirable among these.

Furthermore, in order to prevent oxidation of the light-reflecting layer 4, another layer such as a 1lfa layer may be provided on the light-reflecting layer 4.

Next, the protective layer 5 is also formed as required, and is made of a resin having excellent impact resistance similar to that of the substrate 2. For example, it is formed by applying an ultraviolet curable resin by a spin code method and curing it by irradiating it with ultraviolet rays. In addition, epoxy resin, acrylic resin, silicone hard coat resin, etc. may also be used.

[Operation] Recording can be performed on the optical information recording medium according to the present invention using a known optical information recording device. The optical information recording medium 1 is arranged so that the surface of the transparent substrate 2 faces the side on which the laser irradiation means, that is, the pickup of the optical information recording apparatus is provided. While this optical information recording medium 1 is rotated by a spindle motor, a laser spot modulated into a signal compliant with the CD standard is tracked by a pickup from the substrate 2 side of the optical information recording medium 1 while tracking according to the tracking guide means. By irradiating the light absorption layer 3, the light absorption layer generates heat, which deforms the substrate 2, thereby forming the bit 11.

Note that during recording, it is desirable to irradiate a laser spot with a wavelength λ of around 780 nm. Further, in relation to the CD standard, the linear velocity must be 1.2 to 1.4 m/see, and the recording power may be approximately 6 to 9 mW.

In the present invention, the value of the optical parameter ΔC related to the difference between the film thickness dKr in the pregroove 6 portion and the film thickness dln in the land 7 portion is set to O.15 to 0.7.
I gave it a 5. That is, the film thickness is large in the pregroove 6 where the bit 11 is formed due to deformation of the substrate 2 or decomposition of the dye in the light absorption layer 3, and the film thickness is small in the left and right lands 7 portions. 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 stronger than the optimum power, excess heat will be absorbed by the light-absorbing layer 3 in the pre-groove 6. , it is possible to prevent the bit 11 from reaching the land 7 portion. The heat thus absorbed is trapped here,
You can make 11 clean bits with good edges.

That is, the heat generated by the absorption of the recording laser beam L1 by the light absorption layer 3 is confined within the pregroove 6 with a suppressed rate of diffusion to the outside, and a clear deformed portion (
bit 11).

In general, the thicker the light absorption layer 3 is, the higher the sensitivity is, so the inside of the pregroove 6 has higher sensitivity than the inside of the land 7. Therefore, the recorded bits 11 are difficult to spread over an area wider than the width of the pregroove 6, and it becomes easy to form a clear and large deformed portion on the surface of the substrate 2, and physically in a direction perpendicular to the pregroove 6 (optical information Since the radial direction of the recording medium 1 or the width direction of the pregroove 6) is partitioned, the width of the bit 11 does not increase, making it possible to suppress the causes of crosstalk and jitter in the reproduced signal, and to reduce these values. can.

Furthermore, bit 11 of the optical information recording medium 1 according to the present invention
Because the ratio between the bit depth and the bit width is large, the diffraction angle of the diffracted light (reading laser light) during reproduction is widened.
Ideal bits 11 with small push-pull after recording, large modulation degree, and little jitter are formed. Furthermore, when the refractive index n abs is large, the optical shape of the bit 11 can be made good.

Especially in optical information recording media that can obtain reproduction signals that satisfy the CD standard, d sub/w sub≦6.
．． By satisfying the relationship 5, the jitter can be reduced to 30n.
m or less and which satisfies the CD standard, it is possible to ensure stable playback performance with a normal CD player (see FIG. 6).

Furthermore, the crosstalk specified in the CD standard can also be made good.

Furthermore, the parameter ρ=n regarding the film thickness of the light absorption layer 3
abs-da/λ is set in the range of 0.05 to 1.6, and the imaginary part k abs of the complex refractive index of the light absorption layer is set to 0.05 to 1.6.
By setting it to 3 or less, an optical information recording medium that satisfies the CD standard and has a low block error rate and low jitter can be obtained.

[Embodiments] Next, embodiments of the optical information recording medium according to the present invention will be described below.

(Example 1) @wsub is 390 nm, and depth d s
30 parts by weight of cyanine dye No. 1 shown in FIG. 7 and 50 parts by weight of cyanine dye No. 2 shown in FIG. 20 parts by weight of 4-nitroso-4'-iododiphenylamine dissolved in diacetone alcohol to a concentration of 70 g/liter was coated, and a light reflective layer made of gold film and an upper layer thereon were applied. A UV-cured protective layer was formed on the sample to form a CD.

wsub/dsub=390/130=3.00 and nabs==2. 5, d gr = 194 nm
, and dln=123 nm, and ΔC=0.23.

Optimal puff under these conditions - 6, 5 mw, 7, 5
Recordings were made at 8.5 mw. The respective jitters and crosstalks are shown in the table of the flS9 diagram. From this table, it can be seen that jitter and crosstalk are small at optimal power, and even if the power is further increased, these increases are small.

Note that the jitter in the bit part and non-bit part in Figures 9 and 10 is the total value of the variation in the signal length of the pit part and non-bit part when the signal length of 3T and 11T is used as the reference. This is shown in .

(Comparative example) @wsub is 620 nm and depth d sub is 7
A light absorption layer, a light reflection layer, and a protective layer were formed in the same manner as in Example 1 above on a disc-shaped polycarbonate substrate on which a 0 nm spiral pregroove was formed, and a CD
And so.

wsub/dsub=620/70=8.86,
nabs=2. 5, dgr=151.4 nm, and dln=116.4 nm, and ΔG=0.11.

Under these conditions, the optimal power is 7, 0 mw, 8,
Recording was performed at 0 mw and 9.0 mw. The respective jitters and crosstalks are shown in the table of FIG. From this table, it can be seen that at the optimum power, jitter and crosstalk are larger than those of Example 1, and even if the power is further increased, these increasing trends become more pronounced.

(Example 2) A light absorption layer and a light absorbing layer were formed in the same manner as in Example 1 above on a disc-shaped polycarbonate substrate in which a spiral pregroove with @wsub of 500nrn and a depth dsub of 77nm was formed. forming a reflective layer and a protective layer, C
It was set as D.

wsub/dsub=! 500/77=6.49, nabs=2.5. dgr=220nm, and dl
n=172nrn, and ΔC=0.15.

In such CDs, the recording light wavelength is 770-81.0
Recording was performed at nm, J & suitable power of 6.8 mw to 7.8 mw. This jitter is 30nsec in the non-bit part of 3T (T is the reference time width), 25nsec in the bit part, and 11T.
(non-via) 23nsec in part, 20nsec in bit part
c, and the crosstalk was 0.35.

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

[Effects of the Invention] As described above, according to the present invention, the optical parameter ΔC related to the difference between the film thickness in the pregroove portion and the film thickness in the land portion is set to 0.12 to 0.75, and the pregroove is Since the pits are deeper and narrower than conventional ones, when recording that involves deformation of the substrate or light absorption layer, the deformation of the substrate will be limited to the pregroove, so the width of the pit and the edge Able to keep proper records. Therefore, in accordance with the current CD standard,
In particular, the jitter standard (1!! (
40 ns or less) can be provided.

[Brief explanation of 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 partially cutaway perspective view of an optical information recording medium 1 according to the present invention. Figure 3 is a longitudinal view of the main part with pits 11 formed in the pregroove 6. Figure 4 is a graph of the relationship between p (=nabs-dav/λ) and reflectance. . Fig. 5 is a graph showing the relationship between the complex refractive index kabs and reflectance of the light absorption layer 3, Fig. 6 is a graph showing the relationship between dsub/wsub and jitter, and Fig. 7 is a graph showing the relationship between cyanine dye No. 1. Figure 8 is a diagram showing the structural formula of cyanine dye No. 2. Figure 9 is a table showing the results of Example 1 of the present invention. Figure 10 is a table showing the results of Comparative Example 1. It is. 1... Optical information recording medium 2... Transparent substrate 3... Light absorbing layer 4... Light reflecting layer 5. 1'1M1 6 , , , , Pre-groove (guide groove) 7 , , ,
, Land 8 , First layer boundary 9...Second layer boundary 10...Third layer boundary 11, Pit dsub, , , the light absorption layer 3 in the land 7 portion
From the first layer boundary 8 between the substrate 2 and the substrate 2, the depth of the bottom of the first outer layer 8 in the pre-groove 6 part d abs, ..., the light absorption layer 3 and the light reflection in the land 7 part From the second outer layer 9 with the layer 4, the bottommost depth of the second outer layer 9 in the part of the pregroove 6 nabs, , real part k of the complex refractive index of the light absorption layer 3
abs, , imaginary part d of the complex refractive index of the light absorption layer 3
av, , , average film thickness d gr of light absorption layer 3 , ,
, , Film thickness d In of the light absorption layer 3 at the pregroove 6 part , , Film thickness wsub of the light absorption layer 3 at the land 7 part , , Width of the pregroove 6 λ01.810
0. Wavelength of reproduction light

Claims (1)

[Claims] (1) A light-transmitting substrate with a pregroove formed on one main surface, and a light-absorbing layer provided on the substrate and containing a light-absorbing material that absorbs recording light. and an optical information recording medium in which information is recorded by irradiating this light absorption layer with the recording light, wherein the real part of the complex refractive index of the light absorption layer is nabs, and the pregroove of the light absorption layer is The film thickness at the part is dg
When r, the film thickness at the land portion of the light absorption layer is dln, the wavelength of the reproduction light is λ, and ΔC=nabs(dgr-dln)/λ,
An optical information recording medium characterized in that 0.12≦ΔC≦0.75. (2) The imaginary part of the complex refractive index of the light absorption layer is kabs, the real part thereof is nabs, the thickness of the light absorption layer is dav, the wavelength of the reproduction light is λ, and ρ=nabs. - The optical information recording medium according to claim 1, characterized in that, when dav/λ, 0.05≦ρ≦1.6 and kabs≦0.3. (3) A light-transmitting substrate with a pregroove formed on one main surface, and a light-absorbing layer provided on the substrate and containing a light-absorbing substance that absorbs recording light, the light-absorbing layer An optical information recording method for recording information by irradiating the recording light onto the light absorbing layer, wherein the real part of the complex refractive index of the light absorbing layer is nabs, and the film thickness of the light absorbing layer at the pregroove portion is dg.
When r, the film thickness at the land portion of the light absorption layer is dln, the wavelength of the reproduction light is λ, and ΔC=nabs(dgr-dln)/λ,
0.12≦ΔC≦0.75, and performing optical information recording by irradiating the light absorption layer with the recording light from the substrate side.