JPH04192132A - Optical information recording medium and its recording method - Google Patents

Abstract

PURPOSE:To realize the sure tracking by having a specified relation among the depths between a tracking layer at a land part and the substrate and between a recording layer and the layer boundary, a reflective index between the substrate and the tracking layer and the wavelength of the reproduced light. CONSTITUTION:When the optical information recording medium 1 is irradiated with laser light L1 from the substrate side 2 on the light absorbing layer (recording layer) provided on the tracking layer 3 from the substrate side 2, the recording layer 4 generates heat and the surface of the substrate 2 is locally deformed and a pit 16 is formed. In this constitution, dsub is the depth from the layer border between the layer 3 at a part of the land part 8 being present on the left and right of the pregroove 7 and the substrate 2 to the lowest part of the layer boundary being at a part of the pregroove 7, dtrk is the depth from the layer border between the layer 3 at the land 7 part and the recording layer 4 to the layer border at the pregroove 7, nsub and ntrk are real number parts of the double refractivities of the substrate 2 and the substrate 3, lambda is a wavelength of the reproduced light and those have a relation to satisfy the equation; When an optical pregroove depth is DELTASsub=dsub {nsub-ntrk (1-dtrk/dsub-)}/lambda, 0.01<=¦DELTASsub¦<=0.35.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical information recording medium and a recording method therefor. The present invention also relates to an optically writable and readable optical information recording medium having a recording layer made of a dye or the like, and a recording method thereof.

[Prior Art] This type of optical information recording medium is produced by forming pits in advance on the above-mentioned light-transmitting substrate using means such as a press, and then coating a metal reflective film on the surface on which the bits are formed. Compact discs (hereinafter referred to as rCDJs) have been put into practical use as playback-only optical information recording media and are widely used.

In addition, optical information recording media are being considered that go beyond such read-only media and allow the user to record information by irradiating the substrate with a laser beam as necessary.

For example, Japanese Patent Application Laid-Open No. 54-89605 has at least a light-transmitting substrate, an auxiliary layer provided on this substrate and absorbing laser light, and an information storage layer provided on this auxiliary layer, An optical information recording medium on which information can be optically written and read is disclosed.

Also, JP-A-58-189851 or JP-A-59-
No. 171,689 and others disclose a method of recording on such an optical information recording medium by deforming the counterfeit adjacent to the light absorption layer.

In addition, for tracking during recording, a groove called a pregroove is formed on the substrate in a spiral shape along the circumferential direction. A method of stably tracking by detecting phase changes in laser light is also known.Furthermore, for such tracking, optical information is produced by forming a light absorption layer such as an organic dye on a transparent substrate with pregrooves. Recording media are also known.

There is also an optical information recording medium that uses a light-transmitting substrate with pregrooves for tracking, and is provided with a light-absorbing layer, a light-reflecting layer, and a protective layer to obtain a reproduction signal that satisfies the CD standard. It is publicly known. .

Normally, tracking is performed using the amount of returned light inside and outside the pregroove or the phase difference of the laser beam. form,
Furthermore, in optical information recording media in which a light reflective layer is formed on the pregroove, when pits are formed in the pregroove, the length and width of these bits vary, which causes signal non-uniformity and deviation. occurs. Therefore, distortion of the reproduced signal occurs, such as an increase in jitter and an increase in block error rate (BLER).

In addition, the organic dyes and the like are usually applied thinly onto a substrate by a spin code method, but due to the centrifugal force generated by the rotation of the substrate in the spin code method,
There are many cases where the pregroove on the substrate and the pregroove on the light absorption layer are misaligned, and the recording beam does not track the center of the pregroove on the substrate, resulting in sufficiently stable recording on the land area. If this is not done, the shift in focus offset during recording will also become large.

In order to eliminate such disadvantages such as distortion of the reproduced signal due to variations in bit length and width, it is effective to reduce the depth of the pregroove. Since both recording/reproducing characteristics and tracking characteristics must be satisfied by appropriately selecting the material, film thickness, etc., there is a limit to how shallow the pregroove can be.

That is, if the pregroove is made extremely shallow, it becomes difficult to ensure a phase difference between the inside and outside of the pregroove during tracking, and tracking characteristics deteriorate, especially when using a push-pull method that utilizes the phase difference.

In addition, just as there is a limit to reducing the depth of the pregroove, in order to obtain a large phase difference, the refractive index of the light absorption layer had to be larger than the refractive index of the substrate. There were also limits to the range of material selection for the absorbent layer.

Therefore, the modulation degree, push-pull signal after recording, etc.
It becomes difficult to comply with standards.

In particular, this tendency is remarkable for materials whose real part of the complex refractive index of the light absorption layer is small, and if the real part of the complex refractive index is not sufficiently large compared to the substrate material, it is difficult to use the material as a light absorber. could not.

Regarding optical information recording media in which a layer having a tracking function is formed separately from the recording layer, Japanese Patent Application Laid-Open No. 2-11385
There is a disclosure in the issue.

[What the invention aims to solve] [D] The present invention has been made in view of the above-mentioned problems, and provides an optical information recording medium and its optical information recording medium that can easily obtain reproduction signals specified in the CD standard. The challenge is to provide a recording method.

Specifically, firstly, even if the depth of the pregroove is deep, the unevenness of the surface of the light absorption layer or recording layer is small, so the waveform distortion is small, and even if the material has a low refractive index, An object of the present invention is to provide an optical information recording medium that can perform stable tracking during recording and can perform tracking well.

Second, in an optical information recording medium that satisfies the CD standard,
To provide an optical information recording medium in which jitter, crosstalk, and push-pull satisfy the CD standard, and even when the material of the light absorption layer has a small refractive index, a reproduced signal satisfying the CD standard can be obtained. Let this be one problem.

Third, it is an object of the present invention to provide a method for recording optical information on an optical information recording medium to achieve the above-mentioned i* problem.

[Means for Solving the Problems] In other words, the present invention requires a recording layer such as a light absorption layer of a conventional optical information recording medium to have both functions of recording and reproducing characteristics and tracking characteristics, which is one of the causes of the above-mentioned disadvantages. Taking note of this fact, we decided to separate optical absorption or recording/reproduction characteristics from tracking characteristics, provide a separate tracking layer exclusively for tracking, and limit the depth of the optical pregroove.

That is, by providing a high refractive index tracking layer, it is possible to perform sufficient tracking in a disk drive even if the unevenness of each layer on this layer is sufficiently small or even without any unevenness.

Further, good recording can be obtained even when a light absorption layer or a recording layer is provided on the high refractive index tracking layer, the real part of the complex refractive index of which is not higher than that of the substrate.

Specifically, the first invention is an optical information recording medium that has a substrate that is transparent and has a pregroove formed therein, a tracking layer formed on the substrate, and a recording layer provided on the tracking layer. The depth from the layer boundary between the tracking layer and the substrate in the land portions located on the left and right sides of the pregroove to the bottom of the layer boundary in the pregroove portion is defined as dsub, and Let dtrk be the depth from the layer boundary between the tracking layer and the recording layer in the portion to the bottom of the layer boundary in the pregroove portion, and let nsub be the real part of the complex refractive index of the substrate. , the real part of the complex refractive index of the tracking layer is n trk, the wavelength of the reproduction light is λ, and the optical pregroove depth is Δ5sub=dsu
b (nsub-ntrk (1-dtrk/dsub
)}/λ, 0.01≦1ΔS sub
The optical information recording medium is characterized in that l≦0°35.

Note that a light reflective layer may be provided on the recording layer, and a protective layer may be provided on the light reflective layer.

Further, it is desirable that n trk −n sub>O.

Furthermore, it is desirable that dtrk≦50 nm.

A second invention is a recording method in the optical information recording medium as described above, characterized in that the recording light is irradiated from the substrate side to the recording layer side.

Next, the present invention will be explained in more detail based on FIGS. 1 to 199.

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 longitudinal sectional view of a main part of the optical information recording medium 1.

This optical information recording medium 1 includes a transparent substrate 2 and a transparent substrate 2.
A tracking N3 formed above, a light absorption layer 4 as a recording layer formed on this tracking layer 3, a light reflection layer 5 formed on this light absorption layer 4, and this light reflection layer 5.
It has a protective layer 6 formed thereon.

A pregroove 7 is formed in the substrate 2 in a spiral shape. A portion other than the pregroove 7, that is, a land 8 is located on the left and right sides of the pregroove 7.

Note that the base@2 and the tracking layer 3 are in contact with each other via the first layer boundary 11. Tracking layer 3 and light absorption layer 4
and are in contact with each other by a second layer boundary 12. The light absorption layer 4 and the light reflection layer 5 are in contact with each other through a third layer boundary 13.

The light reflecting layer 5 and the protective layer 6 are in contact with each other through a fourth layer boundary 14 .

As shown in FIG. 2, when the optical information recording medium 1 is irradiated with recording light (recording laser light) LL from a recording device, for example, a semiconductor laser device 1iL5, the light absorption layer 4 absorbs the energy of this laser light L1. As a result, heat is generated, thermal deformation occurs on the substrate 2 side, and pits 16 are formed. In some cases, optical changes may occur in the light absorbing layer.

In particular, as shown in FIG. 2, the depth of the pregroove 7 on the substrate 2, that is, the portion of the pregroove 7 is Let d sub be the depth to the bottom of the first layer boundary 11 in .

Pregroove 7 on the tracking layer 3 on the substrate 2
, that is, the depth from the second layer boundary 12 in the land 8 portion to the bottommost depth of the second layer boundary 12 in the pregroove 7 portion is d trk.

Let nsub be the real part of the complex refractive index of the substrate 2.

The real part of the complex refractive index of the tracking layer 3 is n tr
Let it be k.

Let dgr be the film thickness at the pregroove 7 portion of the light absorption pI4.

The film thickness at the land 8 portion of the above light absorption M4 is dln
shall be.

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

Furthermore, let the optical pregroove depth be ΔS sub. This optical pregroove depth ΔS sub will be described below.

First, when light is irradiated from the substrate 2 side, the second layer boundary 1 in the land 8 portion when the first layer boundary 11 on the substrate 2 side of the tracking layer 3 in the pregroove 7 is taken as a reference.
The optical distance to 2 is n5ub0dsub+ntrk
Represented by @din.

Furthermore, the optical distance from the first layer boundary 11 on the substrate 2 side of the tracking layer 3 in the pre-groove 7 to the second layer boundary 12 in the pre-groove 7 portion is expressed by ntrklldgr. Ru.

Therefore, if the optical distance difference is ND, then ND= (nsub-dsub+ntrk-din)
-ntrk#dgr =nsub-dsub-ntrk (dzr-dln)
It is.

At this time, d gr + d trk = d 1n + d sub, that is.

d gr - d 1n = d sub - d trk. Therefore, ND= n5ub0d sub −n trk (ds
ub-d trk).

Therefore, the optical pregroove depth Δ5sub=ND/
λ is d sub (n sub −nLrk (1−d t
rk/d5ub) }/λ.

In the present invention, this optical pregroove depth ΔS
Let sub be within the range of 0.01≦lΔS sub l≦0.35. When changing ΔS sub within this range, one phase difference can be made appropriately large.

If 1Δ5subl is smaller than 0.01, the tracking error signal becomes small and tracking becomes difficult, which is not desirable.

If IΔ5subl is larger than 0.35, the difference in brightness between the pregroove 7 portion and the land 8 portion becomes large, and the whole becomes dark, making it difficult to increase the reflectance, which is not desirable.

The most desirable range of lΔ5subl is 0.03 to 0.
It is 20.

Note that in the case of Δ5sub>0, it is desirable to perform recording on the pregroove 7 portion using the semiconductor laser device 1t15 as shown in FIG.

If Δ5sub<O, it is desirable to record on the land 8 portion as shown in FIG.

Conventionally, in an optical information recording medium in which a light absorption layer 4 is provided on a substrate 2 provided with a pregroove 7, tracking information is detected based on an optical phase difference caused by unevenness between the pregroove 7 portion and the land 8 portion. . Therefore, the light absorption layer 4 is formed along the uneven shape of the pregroove 7, but this causes an increase in BLER due to subtle dust etc. in the pregroove 7, and jitter due to subtle changes in the pregroove edge. This often resulted in negative effects such as an increase in

In the present invention, the tracking layer 3 having a different refractive index from that of the substrate 2 is provided above the pregroove 7, and the irt! It has been found that by making the second layer boundary 12 almost smooth, sufficient tracking is possible due to the optical difference caused by the film thickness between the land 8 on the substrate 2 and the tracking layer 3 on the pregroove 7.

In this case, if the tracking layer 3 is made of a material that is not affected by the adverse effects and is highly deformed by heat, a larger degree of modulation can be obtained.

Next, the difference n in the refractive index between the substrate 2 and the tracking layer 3
trk −n sub can be positive or negative, but it is 0
Larger is desirable.

If n trk −n sub is 0 or more, even if the top surface of tracking N3 is completely flat, the pregroove 7
Since there is a difference in the optical length (product of refractive index and optical path length) between the land 8 and the land 8, tracking is made possible by the brightness and darkness caused by the phase difference of the light, and for this purpose the pregroove 7 is formed more shallowly. can do.

If n trk −n sub is O, tracking cannot be performed.

Next, d_trk is desirably 50 nm or less, so that the optical bits 16 can be formed uniformly and the aforementioned focus offset deviation can be prevented.

When dtrk is greater than 50 nm, optical pits 16
This is not very desirable as it causes variations in the formation of the particles.

Next, 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, Acrylic board, epoxy board, polycarbonate, etc. are used.

Next, the tracking layer 3 can be made of a resin or a pigment that satisfies the above-mentioned characteristics, or a mixture thereof; for example, 5i02, glass, diamond, a pigment,
Examples include resin and rubber.

Next, the light absorption layer 4 is a layer made of a light absorption material formed on the tracking guide means of the substrate 2.
This layer generates heat, melts, sublimates, deforms, or denatures when irradiated with a laser. This light absorption layer 4 is formed of, for example, a cyanine dye or the like dissolved in a solvent.

In addition to optical modulation, it is also possible to utilize the magneto-optic effect of laser light that accompanies conversion of a magnetic field.

Next, the light reflection layer 5 is a metal film, and is formed of, for example, gold, chain, copper, aluminum, or an alloy containing these by means such as vapor deposition or sputtering.

Next, the protection M16 is formed of a resin having excellent impact resistance similar to that of the substrate 2, such as an ultraviolet curing resin.

Note that the present invention applies not only to recording media based on the CD standard, but also to recording media based on the CD standard.
This can also be applied to various optical information recording media in which tracking is performed using the phase difference of the pregroove.

[Operation] Recording can be performed on the optical information recording medium according to the present invention using a known optical information recording device. An overview is given below. That is, 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 (for example, the semiconductor laser device 15), that is, the pickup of the optical information recording apparatus is provided. While this optical information recording medium 1 is being rotated by a spindle motor, a laser spot modulated into a signal compliant with the CD standard is tracked by a pickup according to the tracking guide means, and the light absorption layer 4 of the optical information recording medium 1 is The bits 16 are formed by irradiating the same.

In the optical information recording method according to the present invention, the wavelength λ is 78
A semiconductor laser spot of around 0 nm can be irradiated. In addition, when conforming to the CD standard, the linear velocity is 1
．． It needs to be 2 to 1.4 m/sec, and the recording power may be about 6 to 9 mW. In other words, recording can be performed in a commercially available CD player by designing the recording power to be higher than that during playback. .

Note that in the optical information recording medium 1 according to the present invention, when the light absorption layer 4 is irradiated with the recording laser beam L1 from the substrate 2 side, the light absorption layer 4 absorbs the laser beam L1 and generates heat, and the substrate 2 The surface of the substrate 2 is locally deformed, and pits 16 are formed on the surface of the substrate 2.
It is desirable that the

In the present invention, a tracking layer exclusively for tracking is provided separately, and the depth of the optical pregroove is limited, so the depth of the pregroove, the unevenness of the surface of the recording layer, the material of the recording layer, etc. are affected. Therefore, it is possible to obtain a reproduced signal that satisfies the CD standard by making reliable tracking possible.

[Example] Next, examples of the optical information recording medium and the method of recording optical information on the optical information recording medium according to the present invention will be described below.

(Example 1) Width 0.5μm, depth 1100n, and pitch 1.6μm
Thickness 1.m with spiral pregroove 7 formed.
A polycarbonate substrate having a diameter of 2 mm, an outer diameter of 120 mm, and an inner diameter of 15 mm was molded by injection molding.

1,1'-dibutyl 3°3.3' as cyanine dye
, 0.30 g of 3'tetramethyl indocica-podianine perchlorate and 0.30 g of silicone RTV resin (manufactured by Shin-Etsu Chemical Co., Ltd., KE-9583) were mixed,
Dissolved in 10ml of diacetone alcohol, applied this to the surface of the pregroove on the substrate by spin-coding while changing the rotation speed appropriately, and then heated at 70°C for 30 minutes.
A tracking layer 3 having an average thickness of 280 nm was formed by rinsing for 0 minutes.

Depth d t in the pregroove of this tracking layer
rk is 12 nm, *substrate refractive index n trk is 2.1, the wavelength λ of the reproduction light is 780 nm, the refractive index n sub of polycarbonate is 1.58, and the pregroove depth d sub is 1100 n. The optical pregroove depth 1ΔS sub I in this substrate is 0.03
It is 4. Further, n trk −n sub is 0.52.

Next, 07 g of tetra-t-butyl phthalocyanine-pb forceps was dissolved in 10 ml of isopropyl alcohol and coated on the tracking layer to form a light absorption layer with an average thickness of 1100 nm.

An Au film with a thickness of 60 nm was formed on the entire surface of this disk by vacuum evaporation. Further, an ultraviolet curable resin was spin-coded on top of this light reflective layer, and was cured by irradiating ultraviolet rays to form a protective layer with a thickness of 10 μm.

When recording was performed on the optical information recording medium thus obtained using a semiconductor laser with a wavelength of 780 nm at a linear velocity of 1.4 m/see,
The optimum power was 10.8 mW. EF with this power
The M signal is recorded on the land portion, and this optical information recording medium is inserted into a commercially available CD player (Aurex XR-V73
, wavelength of the reproduction light 780 nm, reproduction power Q, 5 mW laser), the reflectance was 77.3%, and the modulation degree Il determined from the eye pattern of the reproduced signal was
l/ I top is 0.65, and I 3/ I to
p is 0.35, block error rate is 2.0XIO-
3. Push-pull value was 0.055. These are C
It fully satisfies the criteria set forth in the D standard.

(Example 2) Width 0.5 μm, depth 250 nm, and pitch 1.6 μm
0.20 g of the same cyanine dye as in Example 1 and 0.2 g of polyurethane (Pandenx, manufactured by Dainippon Ink Chemical Industries, Ltd.) were mixed on a polycarbonate substrate having a spiral pregroove 7 of m in diameter, and 10 m of diacetone alcohol was added.
1, and applied it to the surface of the pregroove on the substrate by spin-coding while changing the rotation speed appropriately, and then heated at 80°C for 60 minutes to form a tracking layer with an average thickness of 170 nm. Formed.

Depth d t in the pregroove of this tracking layer
rk is 50 nm, the complex refractive index n trk is 2.1, the wavelength λ of the reproduction light is 780 nm, the refractive index n sub of polycarbonate is 1.58, and the pregroove depth d sub is 250 nm, so this substrate The optical pregroove depth 1Δ5subl in is 0.032. Further, n trk −n sub is 0.52.

Next, 1.1'-dibutyl3. 3.　3'.

32 Tetramethyl 4. 5. 0.7 g of 4', 5'-dibenzoindodicarbocyanine perchlorate was dissolved in 10 ml of diacetone alcohol and applied onto the tracking layer to form a light absorption layer with an average thickness of 140 nm.

An Au film with a thickness of 60 nm was formed on the entire surface of this disk by vacuum evaporation. Further, an ultraviolet curable resin was spin-coded on top of this light reflective layer, and was cured by irradiating ultraviolet rays to form a protective layer with a thickness of 10 μm.

When recording was performed on the thus obtained optical information recording medium using a semiconductor laser with a wavelength of 780 nm at a linear velocity of 1.4 m/sec,
The optimum power was 5.2mW, and with this power EFM
The signal is recorded in the pre-groove section, and this optical information recording medium is inserted into a commercially available CD player (Aurex XR-V
73), the reflectance was 70.2%, and the modulation degree obtained from the eye pattern of the reproduced signal was 11/I.
top is 0.80, I3/I7 op is 0.47. The block error rate was 1.2×10-” and the push-pull value was 0.063. These fully satisfied the criteria set by the CD standard.

[Effects of the Invention] As described above, according to the present invention, even if the pregroove depth is deep, the waveform distortion due to unevenness on the surface of the light absorption layer is small, and the material of the light absorption layer has a small refractive index. Even if there is such a problem, it is possible to provide an optical information recording medium that can perform tracking well.

Furthermore, in an optical information recording medium that satisfies the CD standard, even if the jitter, crosstalk, and push-pull satisfy the CD standard, and the material of the light absorption layer has a small refractive index, the reproduced signal that satisfies the CD standard is It is possible to provide an optical information recording medium that can obtain the following information.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of an optical information recording medium 1 according to the present invention, and FIG. Fig. 3 is a longitudinal sectional view of the main part showing how recording is performed on land 8 when Δ5sub<O. 1. Optical information recording medium 2...Transparent substrate 3.) Racking layer 4. Light absorption layer (recording M) 5.. ...Light reflective layer 6, Protective layer 7, Pregroove 8, Land 11, First layer boundary 12, ... , Second layer boundary 13 , Third layer boundary 14... Fourth layer boundary 15... Semiconductor laser device 16 , Bit dsub From the first layer boundary 11 between the tracking layer 4 and the substrate 2 in the land 8 portion to the bottom depth dtrk of the first layer boundary 11 in the pregroove 7 portion, ..the land 8 portion From the second layer boundary 12 between the tracking layer 4 and the light reflective layer 4 in Real part n t
rk, , , , ) real part dgr of the complex refractive index of racking M4 , , , , ) pregroove 7 of ranking layer 4
Film thickness at the land 8 portion of the racking layer 4 λ0000100. Wavelength of reproduction light ΔS sub, , optical pregroove depth L 1
2. Laser beam for recording. ．． ．． ．． ．． ．． Light for reproduction

Claims (1)

[Claims] (1) An optical information recording medium comprising: a substrate that is transparent and has a pregroove formed; a tracking layer provided on the substrate; and a recording layer provided on the tracking layer. dsub is the depth from the layer boundary between the tracking layer and the substrate in land portions located on the left and right sides of the pregroove to the bottom of the layer boundary in the pregroove portion, and dsub is the depth of the land. dtrk is the depth from the layer boundary between the tracking layer and the recording layer in the pregroove portion to the bottom of the layer boundary in the pregroove portion, nsub is the real part of the complex refractive index of the substrate, and The real part of the complex refractive index of the layer is ntrk, the wavelength of the reproduction light is λ, and the optical pregroove depth is ΔSsub=dsub{ns
An optical information recording medium characterized in that, when ub-ntrk(1-dtrk/dsub)}/λ, 0.01≦|ΔSsub|≦0.35. (2) In the optical information recording medium, a light reflective layer is provided on the recording layer, and a protective layer is provided on the light reflective layer.
) optical information recording medium. (3) Claim (1) characterized in that in the optical information recording medium, dtrk≦50 nm.
) optical information recording medium. (4) It has a substrate that is transparent and has a pregroove formed thereon, a tracking layer provided on this substrate, and a recording layer provided on this tracking layer, and this recording layer is irradiated with recording light. An optical information recording method for recording information by: from the layer boundary between the tracking layer and the substrate in land portions located on the left and right sides of the pregroove to the bottommost portion of the layer boundary in the pregroove portion. dsub is the depth from the layer boundary between the tracking layer and the recording layer in the land portion to the bottom of the layer boundary in the pregroove portion, and dtrk is the complex of the substrate. The real part of the refractive index is nsub, the real part of the complex refractive index of the tracking layer is ntrk, the wavelength of the reproduction light is λ, and the optical pregroove depth is ΔSsub=dsub{ns
ub-ntrk(1-dtrk/dsub)}/λ, 0.01≦|ΔSsub|≦0.35, and the recording light is irradiated onto the recording layer from the substrate side. A recording method for an optical information recording medium.