JP2001184720A - Information recording medium and method for recording and reproducing information - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information recording medium having large capacity, little dependency on the wavelength and high reflectance. SOLUTION: The information recording medium has a recording layer in which recording is performed by the change of the film-thickness and which consists of a low melting point material or combined materials having an eutectic composition any of which have <=600 deg.C melting point and a recording supporting layer which is adjacent to the recording layer and consisting of organic dyestuff or a polymer material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium capable of recording digital information such as video, audio and computer data by a recording beam such as a laser beam and an electron beam, and a method for recording and reproducing the information. About.

[0002]

2. Description of the Related Art Conventionally, there are various information recording media in which a thin film (recording layer) made of a heat mode recording material is carried on a substrate and information can be additionally recorded by a photothermal action of the recording layer. A recording layer formed by deforming, sublimating and evaporating a metal layer containing Te, Bi or the like as a main component or a dye layer of cyanine, phthalocyanine or azo type; Te-Ge type; As -Te-Ge system, T
Those using a change in the atomic arrangement (phase change) such as an EO system can be used.

[0003] With the widespread use of compact discs (CDs), writable media having a high reflectivity and capable of obtaining an output signal conforming to the CD format for information reproduction, so-called CD-Rs, are also available. Widespread. As described in, for example, JP-A-2-168446, a CD-R is formed by laminating an organic dye layer, a metal reflective layer, and an ultraviolet curable resin layer as a protective layer on a signal surface of a transparent substrate in this order. The organic dye layer absorbs laser light and converts it into heat, and the heat changes the organic dye itself that constitutes the organic dye layer to change its optical characteristics. Information is recorded by deforming a part of the transparent substrate which is the base of the dye layer.

[0004] In recent years, digital versatile discs, so-called DVDs, having a much larger capacity than CDs have appeared on the market. DVD is 1.2mm thicker than CD
The thickness of the laser beam is set to 0.6 mm and the thickness is reduced to half, and the two substrates are bonded together.
The single-side capacitance is 4.7 by shortening the wavelength to 650 nm.
This achieves a large capacity of 9.4 GB on both sides. For DVDs, a single-sided dual-layer reading method has been proposed for the first time, in which information formed on two substrates is read out by irradiating reproduction light from one of the substrates. For the full-fledged spread of DVDs, writable media compatible with DVDs is indispensable.
One-time writable DVD using R technology
R, DVD-RAM using phase change technology, etc.
It has been commercialized. In addition, writable media compatible with the single-sided, dual-layer reading method proposed for the first time for DVDs are also being developed.

[0005]

Among the above-mentioned mediums on which information can be additionally written, those using a metal layer mainly composed of Te, Bi, etc., have their information deformed, that is, formed with holes by surface tension or the like. Since recording is performed, there is a disadvantage that a close bonding structure is impossible. In addition, it is difficult to control how the holes expand by surface tension, and a rim is formed around the holes,
It is difficult to form small diameter marks.

[0006] Those using dyes such as CD-R are recorded / recorded.
There is a problem that the change in reflectance with respect to the reproduction wavelength is large, and reproduction becomes difficult when the laser wavelength is shortened.
In addition, since a metal reflective layer is laminated on the dye layer, light does not pass therethrough, and it is impossible to develop a single-sided, dual-layer read-out type write-once medium proposed for DVD.

A device utilizing phase change, such as a Te-Ge system, has a drawback that the phase change operating temperature is high and the recording sensitivity is poor, or the reflectance is extremely lowered when light absorption is increased to increase the sensitivity. The phase change type can be applied to a single-sided, dual-layer read-out type write-once medium, but the decrease in reflectance is remarkable in this case.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide an information recording medium having a large capacity, a small wavelength dependency and a high reflectance.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted various studies to achieve the above-mentioned object. As a result, a recording film and a recording auxiliary layer in contact with the recording film are formed, and the recording film is irradiated with a light beam. It has been found that the above problem can be solved as much as possible by recording information by deforming both the recording auxiliary layer and the recording auxiliary layer.

A recording auxiliary layer and a recording layer are provided on a substrate, and the recording auxiliary layer is formed in contact with one or both sides of the recording layer. The recording auxiliary layer is formed by irradiating a light beam with at least one of the recording auxiliary layers. Information is recorded by physically deforming the layer.

A recording layer and a recording auxiliary layer are formed in this order on a substrate, and information recording is performed by physically deforming the substrate, the recording auxiliary layer, and the recording layer by light beam irradiation. Configuration.

When a recording auxiliary layer is formed on the recording layer opposite to the substrate, the surface of the recording auxiliary layer on the recording layer side is physically deformed, but the surface on the side opposite to the recording layer hardly undergoes physical deformation. A configuration without such a configuration may be employed.

The physical deformation of the recording layer is accompanied by a change in the film thickness.
It is preferable that the film thickness of the recording layer is smaller than the film thickness of the unrecorded part in at least a part of the part where information is recorded, and the film thickness of the recording layer is at least part of the part where information is recorded. More preferably, it is 0.

[0014] At least a part of the portion where information is recorded may have a change in the atomic arrangement of the recording layer.

The recording layer preferably has a melting point of 600 ° C. or lower.

It is more preferable that the recording layer contains at least two kinds of elements as main components, and the melting points of these elements are 600 ° C. or less. For example, Bi, In, Pb, Sn, Te,
At least two types can be selected from materials including Tl, Zn, Na, and Ga. Specifically, In
-Bi-based, Bi-Na-based, Pb-Bi-based, Sn-Bi
System, In-Pb system, In-Sn system, In-Tl system, In
A combination of -Zn-based, Sn-Pb-based, Tl-Sn-based, Zn-Sn-based and the like is possible. Further, those having a eutectic composition with a melting point of 600 ° C. or less and a content of these elements at or near the eutectic composition may be used.

The recording layer mainly contains two types of elements, and at least one of these elements has a melting point of 600 ° C. or more, and the element has a melting point of 600 ° C. or less with the other element. It is more preferable that the eutectic composition has a eutectic composition of not more than ℃ and the content of the two elements is a eutectic composition or a composition in the vicinity thereof. For example, Bi, In, Pb, Sn, T
e, Tl, Zn, Na, Ga, Ag, Al, Ca, G
e, Sb, Si, Au, Cu, Ni, Ce, La, M
At least two types can be selected from materials including g, Pr, Pd, and Pt. Specifically, Ag-A
1 system, Ag-Bi system, Ag-Ca system, Ag-In system, A
g-Pb system, Ag-Sb system, Ag-Sn system, Ag-Te
System, Ag-Tl system, Al-Au system, Al-Cu system, Al
-Ge-based, Al-Si-based, Al-Sn-based, Al-Te
System, Al-Zn system, Au-Bi system, Au-Ge system, Au
-Pb-based, Au-Sb-based, Au-Sn-based, Au-Si
System, Au-Te system, Au-Tl system, Ni-Ce system, Cu
-La system, Cu-Mg system, Cu-Pr system, Cu-Sb
System, Ga-Te system, Ge-Te system, Zn-Ge system, In
-Sb, Pb-Pd, Pt-Pb, Pb-Sb
System, Sb-Te system, Tl-Sb system and the like are possible.

Examples of the material constituting the recording auxiliary layer include organic dye materials such as polymethine dyes, anthraquinone dyes, cyanine dyes, phthalocyanine dyes, xanthene dyes, triphenylmethane dyes, pyrylium dyes, and azulene dyes. A material composed of a dye, a metal-containing azo dye, or the like can be used. Further, as a material for forming the recording auxiliary layer, a material made of a polymer material can be used. As the polymer material, a material having transparency to recording / reproducing light is preferable. As these materials,
If it is soluble in a solvent, it can be formed by a spin coating method, and if it is not soluble, it can be formed by a vapor deposition method.

These recording auxiliary layers have a thermal decomposition temperature or a glass transition temperature, and the temperature is preferably lower than the melting point of the recording layer. Further, the difference between the thermal decomposition temperature or glass transition temperature of the recording auxiliary layer and the melting point of the recording layer is 400
It is more preferable that the temperature is not higher than ° C.

The disk may have a structure in which two substrates are bonded together with the recording layer sandwiched therebetween. Further, as a disk form, a so-called single plate structure in which two substrates are not bonded to each other can be adopted.

Each of these two substrates has a recording layer, and information is recorded on each recording layer by irradiating a light beam from either one of the substrates.
The substrate on the light beam irradiation side, the recording auxiliary layer, and the recording layer may be configured to transmit at least 40% of the light beam.

Further, as a disk form, it is possible to provide at least two recording layers on one substrate.

At this time, information may be recorded on each recording layer by irradiating a light beam from the substrate side, or information may be recorded on each recording layer by irradiating the light beam from the side opposite to the substrate. Recording may be performed.

As described above, when information is recorded on a plurality of recording layers by irradiating a light beam from a certain direction,
The recording layer on the light beam incident side and the recording layer on the opposite side may have different film thicknesses.

The element which is the main component of the recording layer on the light beam incident side is the same as the element which is the main component of the recording layer on the opposite side, and the content of the element which is the main component is equal to the light beam. The recording layer on the incident side and the recording layer on the opposite side may be different.

Further, at least one of the elements that are the main components of the recording layer on the light beam incident side is different from at least one of the elements that are the main components of the recording layer on the opposite side. It may be an element.

The melting point of the recording layer on the light beam incident side may be different from the melting point of the recording layer on the opposite side.

A spiral or concentric guide groove is formed on the substrate, and either one of the guide grooves or between two adjacent guide grooves (referred to as a guide groove) is used as a recording track. A configuration for recording information can be employed. Alternatively, a guide groove may be formed spirally or concentrically on the substrate, and both the guide groove and between the guide grooves may be used as recording tracks, and information may be recorded on the recording tracks.

When each of the two substrates has a recording layer, and information is recorded on each of the recording layers by irradiating a light beam from one of the substrates, a spiral formed on the substrate is formed. Alternatively, it is preferable that the shape of the concentric guide groove is different between the light beam incident side and the opposite side.

At this time, the depth of the guide groove of the substrate on the light beam incident side is smaller than the depth of the guide groove of the opposite substrate, or the width of the guide groove of the substrate on the light beam incident side is
It is more preferable that the width is wider than the width of the guide groove of the opposite substrate.

The information recording medium of the present invention can obtain excellent characteristics when the recording density is high.

For example, when the distance (track pitch) in the radial direction of the recording track is TP, the wavelength of the light beam is λ, and the numerical aperture of the lens for condensing the light beam is NA,
When TP / (λ / NA) is 0.7 or less, more excellent characteristics can be obtained. At this time, it is preferable that the track pitch is 1 μm or less, and the track pitch is 0.75 μm.
It is particularly preferable if the thickness is not more than μm.

Further, when the shortest length of the recording mark is 0.7 μm or less, more excellent characteristics can be obtained. If the shortest length of the recording mark is 0.5 μm or less, particularly excellent characteristics can be obtained.

The address information and the like of the information recording medium can be preformed on the substrate as a preformat signal. As a form in which address information or the like is formed in advance on the substrate as a preformat signal, a concave or convex emboss pit or a wobble method of modulating the width of a groove portion or a land portion according to information is possible. As the wobble method, a method in which only one side surface on the inner peripheral side or the outer peripheral side of the groove portion or both the inner peripheral side and the outer peripheral side of the groove portion meanders can be adopted.

The roles of the recording layer and the recording auxiliary layer in the information recording medium of the present invention are as follows. When the medium is irradiated with a laser, the medium first reaches a temperature at which the recording auxiliary layer undergoes thermal decomposition or glass transition. Next, the temperature of the recording film reaches the melting point, and the recording film becomes deformable. The recording film is deformed by the generation of gas due to the thermal decomposition of the recording auxiliary layer, expansion or deformation due to glass transition, and forms a recording mark. At this time, when the deformation of the recording layer is accompanied by a change in the film thickness, the reflectance differs depending on the film thickness, so that the intensity of the reproduced signal can be increased. In particular, when the film thickness of the recording layer is almost zero, the reflectivity of that portion is extremely reduced, and the difference in reflectivity with the other portion is very large, so that the reproduction signal strength is particularly large. Can be. Thus, when the deformation of the recording layer involves a change in film thickness,
There is no practical means to return this part to its original state. Therefore, there is an advantage that the information once recorded cannot be falsified. In addition, when the recording layer is deformed and the atomic arrangement is changed, not only the reflectance difference due to the deformation of the recording part and the non-recorded part but also the optical constants of the two parts are different, so that the reproduction signal intensity can be increased. .

In the process of forming a recording mark, the recording layer first reaches its melting point and becomes deformable due to the magnitude relationship between the absorption rate of the recording layer and the absorption rate of the recording auxiliary layer with respect to the laser beam wavelength used for recording. Thereafter, the recording auxiliary layer may reach a thermal decomposition temperature or a glass transition temperature to form a recording mark. For example, when the light absorption coefficient of the recording auxiliary layer is larger than that of the recording layer, or when the thermal conductivity of the recording layer is 1 W
When the temperature of the recording layer is extremely high, that is, not less than / cmK, the mark forming process as described above may occur. If the melting point of the recording layer is higher than the thermal decomposition temperature or the glass transition temperature of the recording auxiliary layer, clear marks can be formed, which is preferable. Even below the temperature, mark formation is possible.

The recording layer is deformed when the surface on the laser beam incident side is mainly deformed (shown in FIG. 1) and when the surface on the side opposite to the laser beam incident side is mainly deformed (shown in FIG. 2). A case is conceivable in which both the surface on the laser beam incident side and the surface on the opposite side are deformed (shown in FIG. 3). When the deformation of the recording layer is the formation of holes, it can be considered as a variation or combination of these (shown in FIGS. 4 to 8).

While the recording auxiliary layer is deformed together with the deformation of the recording layer, the recording auxiliary layer may be deformed by expanding or forming a cavity. FIGS. 9 to 11 show how the recording auxiliary layer is deformed when the recording layer is deformed as shown in FIG. When the recording auxiliary layer is formed in contact with the recording layer on the side opposite to the substrate, if only the surface in contact with the recording layer is mainly deformed, a resin material that does not thermally deform on the opposite side may be provided as a protective film. There is an advantage that does not affect the record. For this purpose, it is preferable to form the recording auxiliary layer with a film thickness that is at least twice the groove depth.

One of the recording auxiliary layers can be substituted by a substrate. At this time, the substrate has a thermal decomposition temperature or a glass transition temperature and can be made of a material which is easily deformed by heat, such as polycarbonate, polymethyl methacrylate, polymethyl pentene, polyolefin, epoxy, and acryl. In this case, the manner of deformation of the substrate can be considered to be the same as the manner of deformation of the recording auxiliary layer.

The above-described Bi alloy or Te alloy recording layer forms holes by surface tension. The advantage of hole formation by surface tension is that holes are sharply formed with a certain threshold power when the recording power is gradually increased. On the other hand, the disadvantages are that it is difficult to control the surface tension and it is difficult to control the size of the holes, so it is easy to make large holes.When forming a long hole in the light beam irradiation direction, the irradiation start position and end position of the light beam And the widths of the holes are different. However, according to the method of the present invention, the size of the recording mark can be controlled by the melting point of the recording film, the thermal decomposition temperature of the recording auxiliary layer, the glass transition temperature, and the like.
Further, a long mark having a substantially constant width can be formed by a combination of the melting point of the recording film, the thermal decomposition temperature of the recording auxiliary layer, the glass transition temperature, and the recording waveform. Similarly, the width of such a long mark can be controlled relatively freely. Therefore, it is possible to cope with a high-density recording in which a track pitch is narrow or a small mark and a long mark such as mark edge recording must be formed with high precision. In particular, when the track pitch is TP, the wavelength of the light beam is λ, and the numerical aperture of the lens for condensing the light beam is NA, TP / (λ / NA) becomes
If the value is 0.7 or less, crosstalk in which information recorded on the adjacent track leaks out increases,
It is necessary to form the recording mark particularly narrow. As described above, the medium of the present invention is a suitable medium in such a case. In particular, the medium is suitable when the track pitch is smaller than 1 μm, and further when the track pitch is smaller than 0.75 μm. In addition, when the shortest mark length of the recording mark is 0.7 μm or less, it is more suitable for the case of 0.5 μm, and particularly suitable when the length of the longest recording mark is three times or more the length of the shortest recording mark. is there.

The element constituting the recording layer has a melting point of 60
Elements at 0 ° C. or lower, ie, Bi, In, Pb, Sn, T
e, Tl, Zn, Na, and Ga are preferable, but Bi, In, Pb, Sn, and Tl are more preferable among these elements.
Further, Bi, In, Pb, and Sn are particularly preferable. N
a and Ga have melting points as low as 100 ° C. or less, which is advantageous in terms of recording sensitivity, but it is difficult to form a film by sputtering or the like. Zn, T
e has a relatively high melting point among these elements. In combination of these elements, In-Bi system, Bi-Na
System, Pb-Bi system, Sn-Bi system, In-Pb system, In
-Sn-based, In-Tl-based, In-Zn-based, Sn-Pb
System, Tl-Sn system, and Zn-Sn system are preferable. Of these, In-Bi system, Pb-Bi system, Sn-Bi system, and In-P
A b-based, In-Sn-based, and Sn-Pb-based are particularly preferred. Among the combinations of these elements, those having a eutectic composition have a particularly low melting point near the composition, which is preferable in terms of recording sensitivity.

When one or both elements have a melting point of at least 600 ° C. and a eutectic composition of the two or a composition near the eutectic element is used as a constituent element of the recording layer, the melting point of the recording layer is determined during recording. Recording is possible, but when the recording mark part melted by recording is cooled, segregation occurs and the composition area of 600 ° C or higher is easily formed in at least a part of the recording mark part, and the information once recorded is erased Alternatively, even if an attempt is made to overwrite (overwrite) the portion, the recording layer does not melt due to the high melting point component formed at the time of recording, and the information cannot be tampered with. As a combination of such elements, Ag-A
1 system, Ag-Bi system, Ag-Ca system, Ag-In system, A
g-Pb system, Ag-Sb system, Ag-Sn system, Ag-Te
System, Ag-Tl system, Al-Au system, Al-Cu system, Al
-Ge-based, Al-Si-based, Al-Sn-based, Al-Te
System, Al-Zn system, Au-Bi system, Au-Ge system, Au
-Pb-based, Au-Sb-based, Au-Sn-based, Au-Si
System, Au-Te system, Au-Tl system, Ni-Ce system, Cu
-La system, Cu-Mg system, Cu-Pr system, Cu-Sb
System, Ga-Te system, Ge-Te system, Zn-Ge system, In
-Sb, Pb-Pd, Pt-Pb, Pb-Sb
Systems, Sb-Te systems and Tl-Sb systems are preferred. Among them, a combination containing Au, Ag, Cu, and Al is preferable in that the reflectance is high. Combinations having particularly high reflectivity are Ag-Al, Al-Au, and Al-Cu. Further, Bi, In, Pb, Sn, Te, Zn, Tl
Is preferred in that the melting point is low. In particular, the combination having a low melting point is an Ag-Bi-based
System, Ag-Pb system, Ag-Sn system, Ag-Te system, Ag
-Tl system, Al-Sn system, Al-Zn system, Au-Bi
System, Au-Ge system, Au-Pb system, Au-Sb system, Au
-Sn system, Au-Si system, Au-Tl system, Ge-Te
System, Zn-Ge system, Pb-Pd system, Pt-Pb system, Pb
-Sb type and Tl-Sb type.

It is also possible to add another element to the recording layer. For example, Sc, Ti, V, Cr, Mn, F
e, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo,
Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta,
W, Re, Os, Ir, Pt, and Au have an effect of improving recording sensitivity because of absorbing laser light, an effect of improving oxidation resistance, and the like. However, since these elements have a high melting point, an excessively added amount causes a decrease in recording sensitivity. Therefore, the addition amount is preferably 15 atomic% or less, more preferably 10 atomic% or less. Among these elements, Ni, Cu, Zn, Pd, Ag, Pt, Au
Are listed as elements constituting the recording layer, but they are used as additive elements only when they are not used in the recording layer. Among the above-mentioned elements, Ti, V, Cr, and F are more preferable as the additional elements.
e, Co, Ni, Zr, Nb, Mo, Pd, Ag, T
a, W, Pt, and Au. These have a higher effect of improving oxidation resistance.

Further, N and O can be added to the recording layer. N has the effect of reducing noise by reducing the crystal grain size when the recording layer is crystalline. O exists as an oxide of at least one of the elements constituting the recording layer, and has the effect of reducing the thermal conductivity of the recording layer and improving the recording sensitivity.
The addition amount is preferably 20 atomic% or less, particularly preferably 15 atomic% or less.

The addition of S, Se and Sb improves the oxidation resistance. Oxidation resistance is further improved by including a large amount of these elements near the surface of the recording layer. Of these elements, Sb is listed as an element constituting the recording layer, but is used as an additional element only when it is not used in the recording layer.

The information recording medium of the present invention may be a medium capable of recording / reproducing on one side and two layers. The structure consists of forming a recording layer and a recording auxiliary layer on two substrates, bonding them together with a transparent material, and irradiating a laser beam from one of the substrates to record information on both recording layers. And reproduction of information recorded in both recording layers. As the bonding material, a material having good flatness such as an ultraviolet curable resin or a double-sided tape can be used. Further, the information recording medium of the present invention can be a medium in which two recording / reproducing layers are formed on one substrate. The configuration is
Two recording layers and a recording auxiliary layer were formed on one substrate, and a laser beam was incident from the substrate side or the side opposite to the substrate, and information was recorded on both recording layers and recorded on both recording layers. It reproduces information. In these cases, the recording layer and the recording auxiliary layer formed on the substrate on which the recording / reproducing laser beam is incident are referred to as a first layer, and the opposite layer is referred to as a second layer. In order to record information on the second layer or reproduce information on the second layer, the first layer must transmit at least a part of the recording / reproducing laser light.

The reflectance, transmittance and absorptivity of the first layer are represented by r ₁ ,
t ₁ , a ₁ , reflectivity, transmittance and absorptance of the second layer are represented by r ₂ ,
The total reflectance from the first layer is R ₁ , the total reflectance from the second layer is R ₂ , the total absorptance of the first layer is A ₁ , and the total reflection of the second layer is t ₂ and a _2. Assuming that the rate is A ₂ , the following relationship holds for these parameters. _{r 1 + t 1 + a 1} = 1 r 2 + t 2 + a 2 = 1 R 1 = r 1 R 2 = r 2 × t 1 2 A 1 = a 1 A 2 = a 2 × t 1 the first and second layers In order for the signal quality of the two layers to be the same, the two must have the same reflectance, and for the same recording sensitivity of both layers, the two must have the same absorptance. , therefore, it is necessary _{r 1 = r 2 × t 1} 2 a 1 = a 2 × t 1. Since t ₁ is a value smaller than ₁ , r ₁ <r ₂ a ₁ <a ₂ must be satisfied. That is, the reflectance of the first layer must be lower than the reflectance of the second layer, and the absorptance of the first layer must be lower than the absorptance of the second layer. The transmittance t ₁ of the first layer
Is preferably at least 40%, because this relationship can be easily satisfied. As a method of setting the reflectance and the absorptance of the first layer and the reflectance and the absorptance of the second layer to different values, there is a method of changing the film thickness of both recording layers. When the thickness of the first layer is set smaller than that of the second layer, the above relational expression can be satisfied. At this time, it is preferable to make the transmittance of the second layer substantially zero because the reflectance and the absorptance of the second layer can be further increased.

On the other hand, it is necessary to satisfy r ₁ <r ₂ from the viewpoint of signal strength, but there is a method of making the recording sensitivities of the first layer and the second layer substantially equal even if a ₁ ≧ a ₂ . According to this method, the melting point of the second layer is made lower than that of the first layer so that recording can be performed with a small absorption rate. According to this method,
Since the temperature at which recording is possible is low even if the absorptance of the two layers is low, recording is possible even with irradiation of laser light having the same power as that of the first layer. Methods for changing the melting point include changing the composition of the recording layer and changing the constituent elements. Also,
At this time, it is preferable to change the thermal decomposition temperature or the glass transition temperature by changing the film thickness of the recording auxiliary layer or changing the material and composition.

As described above, when recording information on the two recording layers or reproducing the recorded information by irradiating a laser beam from one side, deformation of both the recording layer and the recording auxiliary layer is performed. A medium such as the present invention, in which a recording mark is formed by the method described above, has a good recording sensitivity, so that it is not necessary to increase the absorptance of the recording layer itself as in the conventional medium, and the reflectivity can be increased. This effect is further enhanced if a material having a high reflectance and a low melting point as described above is selected for the recording layer.

When the recording layer and the recording auxiliary layer are formed by a sputtering method, a vapor deposition method, a spin coating method, or the like, the surface of each layer opposite to the substrate may have a different shape from the substrate. In particular, when the film is formed by the spin coating method, the grooves and the uneven pits formed on the substrate tend to be buried, and the shape of the substrate and the shape of the film on the side opposite to the substrate are greatly different. In the case where two recording layers are provided and light is incident from one side to perform recording and reproduction on both layers, the first layer is the substrate surface on the light incident side, and the second layer is the recording surface on the light incident side. When the same substrate is used because it is the surface of the layer or the recording auxiliary layer opposite to the substrate surface, parameters relating to grooves or pits formed in advance on the substrate, that is, a push-pull signal,
The divided push-pull signal, the signal amplitude of the prepit, and the like are different between the first layer and the second layer. Therefore,
By changing the groove shape and pit shape of the substrate carrying the first layer and the substrate carrying the second layer, the parameters relating to the grooves or pits can be made uniform.

In the information recording medium of the present invention, the reflectance of the information recording medium can be controlled by adjusting the refractive index and the thickness of the layer laminated on the substrate. When the reflectance of the information medium of the present invention is controlled, recording and reproduction can be performed by a recording and reproducing apparatus for another information recording medium. For example, D
The reflectivity of VD-RAM media and general MO media is about 20
%. Therefore, by adjusting the reflectance of the information recording medium of the present invention to 10 to 30%, the DVD-RAM
It can be used in recording and reproducing devices for recording media and general MO media.

[0052]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with reference to examples.

[0053]

(Example 1) On a surface of a polycarbonate resin plate having a diameter of 120 mm and a thickness of 0.6 mm, concave and convex pits containing address information and the like, a width of 0.3 μm and a depth of 35 at a pitch of 0.74 μm were used.
A substrate 1 in which a U-shaped groove of nm was formed in advance was prepared. This substrate 1 was placed in a sputtering chamber in a sputtering apparatus having excellent film thickness uniformity and reproducibility. Using AuSn alloy as a target, Au ₇₀ Sn ₃₀ (atomic%)
After forming a nm, a recording auxiliary layer 3 comprising a cyanine dye
Was applied by a spin coating method. Further, an ultraviolet curable resin protective layer 4 was formed on the uppermost layer by spin coating.

In the same manner, Au is placed on another similar substrate 1 '.
₇₀ Sn ₃₀ (atomic%) recording layer 2 ', cyanine dye recording auxiliary layer
3 ', forming an ultraviolet curing resin protective layer 4', two substrates,
Lamination was performed with the adhesive layer 5 with the UV-curable resin protective layers 4 and 4 'inside. At this time, adjust the diameter of the adhesive layer to 11
When the thickness is 8 mm or more, peeling of the adhesive layer due to impact such as dropping becomes difficult.

The disk manufactured as described above was subjected to a linear velocity of 3.
The laser beam was rotated at 49 m / s, and a semiconductor laser beam having a wavelength of 660 nm was condensed by an objective lens having an NA of 0.6 and irradiated onto a recording film through a substrate, thereby performing recording and reproduction on a guide groove. The recording laser power was 12 mW, and a random signal modulated by 8-16 was recorded. At this time, a multi-pulse recording waveform for dividing the recording pulse into a plurality was used.

When the recorded random signal was reproduced, the jitter was 7.5%. The reflectance was 65% in the unrecorded area, 20% in the recorded area, and the signal modulation was about 70%. When the recording mark was observed with an optical microscope and a scanning electron microscope, the following was observed. The film thickness at the center of the recording mark of the recording film was almost 0.

Deformation of the substrate and the dye recording auxiliary layer was observed. It is also recognized that the substrate and the dye are filled in the region where the recording film thickness is almost zero, and it can be estimated from this that the deformation of the substrate and the dye recording auxiliary layer is expansion.

A cavity was observed in a part of the expanded portion of the substrate.
This can be presumed to be gas generated by decomposition of the substrate.

Almost no deformation was observed on the surface of the dye recording auxiliary layer opposite to the recording layer. Au ₇₀ S as recording layer
very similar characteristics with those an Au content of n ₃₀ was varied in the range of 10 to 90 atomic% was obtained.

Further, Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb,
Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, T
When a, W, Re, Os, Ir, and Pt are added elements,
This has the effect of improving the recording sensitivity. Of these, Ti,
V, Cr, Fe, Co, Ni, Zr, Nb, Mo, P
When d, Ag, Ta, W, and Pt were added, the oxidation resistance was improved. However, when these elements were added in an amount of 15 atomic% or more, the recording sensitivity was reduced. The effect of improving the recording sensitivity was particularly high when the addition was 10 atomic% or less.

When N was added to the recording layer, the effect of reducing noise was obtained. The addition amount is preferably 20 atomic% or less, particularly preferably 15 atomic% or less. In addition, O
When O is added, O exists as at least one kind of oxide of the elements constituting the recording layer, and has the effect of reducing the thermal conductivity of the recording layer and improving the recording sensitivity. The addition amount is preferably 20 atomic% or less, particularly preferably 15 atomic% or less.

The addition of S, Se and Sb to the recording layer has the effect of improving oxidation resistance. In particular, these elements
By including a large amount near the surface of the recording layer, there is an effect that the oxidation resistance is further improved.

As the recording layer, instead of Au ₇₀ Sn ₃₀ , In
-Bi-based, Bi-Na-based, Pb-Bi-based, Sn-Bi
System, In-Pb system, In-Sn system, In-Tl system, In
Similar characteristics were obtained when a Zn-based, Sn-Pb-based, Tl-Sn-based, or Zn-Sn-based was used. Further, as a recording layer, an Ag-Al-based, Ag-Bi-based, Ag-Ca
System, Ag-In system, Ag-Pb system, Ag-Sb system, Ag
-Sn-based, Ag-Te-based, Ag-Tl-based, Al-Au
System, Al-Cu system, Al-Ge system, Al-Si system, Al
-Sn system, Al-Te system, Al-Zn system, Au-Bi
System, Au-Ge system, Au-Pb system, Au-Sb system, Au
-Si system, Au-Te system, Au-Tl system, Ni-Ce
System, Cu-La system, Cu-Mg system, Cu-Pr system, Cu
-Sb system, Ga-Te system, Ge-Te system, Zn-Ge
System, In-Sb system, Pb-Pd system, Pt-Pb system, Pb
Similar characteristics were obtained when using -Sb, Sb-Te and Tl-Sb systems.

In this embodiment, the recording layer was formed directly on the substrate. However, the same result can be obtained by using a medium in which a recording layer and a recording auxiliary layer are sequentially formed after forming a cyanine dye as a recording auxiliary layer on the substrate. Obtained. At this time, set the groove depth of the substrate to 150
When it was set to nm, the groove characteristics were also good.

(Example 2) On a surface of a polycarbonate resin plate having a diameter of 120 mm and a thickness of 0.6 mm, concave and convex pits containing address information and the like, and a width of 0.3 μm and a depth of 0.74 μm were provided.
A substrate 1 in which a U-shaped groove of 35 nm was formed in advance was prepared. This substrate 1 was placed in a sputtering chamber in a sputtering apparatus having excellent film thickness uniformity and reproducibility. AuSn alloy was used as a target, and Au ₇₀ Sn ₃₀ (atomic%) recording layer 2 was
After forming a nm, a recording auxiliary layer 3 comprising a cyanine dye
Was applied by a spin coating method. Further, an ultraviolet curable resin protective layer 4 was formed on the uppermost layer by spin coating.

Next, on the surface of the polycarbonate resin plate having the same diameter and thickness as 1, pits including address information and the like, 0.44 μm width of 0.74 μm pitch and 150 nm depth
A substrate 1 ″ in which a U-shaped groove was formed in advance was prepared. After forming the cyanine dye recording auxiliary layer 3 'thereon, the Au ₇₀ Sn ₃₀ (atomic%) recording layer 2' is formed to 30 nm, and then the cyanine dye recording auxiliary layer 3 'is formed. Lamination was performed with the cured resin protective layer 6. The thickness of the UV-curable resin protective layer 6 was 55 μm ± 5 μm.

The disk manufactured as described above was subjected to a linear velocity of 3.
The laser was rotated at 49 m / s, and laser light was incident from the substrate 1 side to record information on the recording layers 2 and 2 ′. Recording laser power is 15m when recording on either recording layer
W. When recording on the recording layer 2 ', the substrate
Recording was performed in the portion between the grooves 1 ', that is, in the portion that looks like a groove when viewed from the laser beam incident side. When the recorded random signal was reproduced, the jitter was 8% for both layers.
The reflectivity of both layers was 18% in the unrecorded area and 5% in the recorded area, and the signal modulation was about 72%.

(Example 3) A substrate 1 having a land portion and a groove portion (groove portion) on a surface of a polycarbonate resin plate having a diameter of 55 mm and a thickness of 0.6 mm was prepared. Land width is 0.5
The U-shape is 6 μm and the groove is 0.64 μm wide and 55 nm deep. Since the land portion and the groove portion usually aim at recording on both of them, the track pitch in the sense of the width for recording information is 0.60 μm for both the land portion and the groove portion. However, in consideration of the correction of the optical phase with respect to the incident light, the appropriate width at which the reproduction signals from both are balanced is α, where α is the set track pitch, and the land width Dl is 0.90α ≦ Dl ≦ 0.99α. Becomes On the other hand, when the width of the groove portion is Dg, Dg + Dl = 2α in a form complementing the track pitch with respect to the land portion.

A wobble including address information and the like was applied to the boundary between the land and the groove. FIG. 14 shows this state. A so-called one-sided wobble method in which one boundary is a straight line and only the other boundary is modulated is optimal. The width Dl 'of the land in this portion is preferably 0.50α≤Dl'≤1.50α.

The address signal recorded by the one-side wobble is detected by a radial push-pull signal.

This substrate 1 was placed in a sputtering chamber in a sputtering apparatus having excellent film thickness uniformity and reproducibility. Si was used as a target, and an Ar gas mixed with 30% of N2 gas was introduced to laminate a dielectric layer of SiN. By controlling the refractive index and the film thickness, the reflectance of the medium is adjusted. For example, the refractive index of the dielectric of the underlayer is suitably 1.9 to 2.3, and the film thickness A at that time is preferably λ / 15 ≦ A ≦ λ / 5, where λ is the recording / reproducing laser wavelength. By setting / 12 ≦ A ≦ λ / 9, the reflectance can be controlled particularly well. In this embodiment, the SiN dielectric layer has a refractive index of 2.1 and a thickness of 60.
nm.

Thereafter, a recording auxiliary layer 3 made of a cyanine dye was applied by spin coating. Al on it
_{A 70} Ag ₃₀ (at%) recording layer 2 was formed to a thickness of 40 nm. Further, an ultraviolet curable resin protective layer 4 was formed on the uppermost layer by spin coating. In this embodiment, an example is shown in which the stacking order of the recording layer and the auxiliary recording layer is reversed. The same effect can be obtained even if such a configuration change is performed.

The medium was not bonded and was used as a single plate. As described above, a so-called write-once medium that can be recorded once can be formed.

The uniformity of the thin film formed by spin coating decreases as the diameter increases.

Diameter Uniformity Less than 60 mm 3% or less 60mm or more and less than 100mm 3 to 7% 100mm or more 7% or more Therefore, the diameter of the disk is preferably less than 100mm, and most preferably less than 60mm from the necessity of uniform spin coating of the auxiliary recording layer. . However, if the diameter is too small, the recording capacity is reduced, so that a diameter of 15 mm or more is necessary from that viewpoint. Therefore, the disk diameter is 15mm or more and 100
It is preferably less than 15 mm, and most preferably 15 mm or more and less than 60 mm.

The reflectance of the medium is 10% or more and 30% in the unrecorded area.
The following is preferable. In the medium of this embodiment, the reflectance of the unrecorded area is 15%, and the reflectance of the recorded portion is 25%.
The signal modulation was about 60%. Reflectance of 10 in unrecorded area
A so-called write-once type medium that can record once and can be reproduced by the same drive by detecting the sum signal with a general magneto-optical recording medium drive by setting the percentage to 30% or less. can do.

Using the disk manufactured as described above,
An example in which recording and reproduction are performed by a magneto-optical recording medium driving device having a differential detection system will be described. The medium of the present invention can record on one or both of the land and the groove. In this embodiment, recording was performed only in the groove portion, and the performance was examined.

The medium is rotated so as to have a linear velocity of 5.0 m / s, and a semiconductor laser beam having a wavelength of 650 nm is condensed by an objective lens having an NA of 0.6 and irradiated on a recording film through a substrate to form a group.
Recording and reproduction were performed on the disk. The recording laser power was 10 mW. At this time, a multi-pulse recording waveform for dividing the recording pulse into a plurality was used. NRZ modulated shortest mark length 0.3
PRML reproduction was performed by recording a 5 μm random signal. Consequently, 2 × 10 at the bit error rate ^- to give a ^5.

When the recorded portion was observed with a microscope,
Deformation of the substrate and the dye recording auxiliary layer was observed. Similar characteristics were obtained by using a recording layer in which the Al content of Al ₇₀ Ag ₃₀ was changed in the range of 10 to 90 atomic%.

Further, Sc, Ti, V, Cr, M
n, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb,
Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, T
When a, W, Re, Os, Ir, and Pt are added elements,
This has the effect of improving the recording sensitivity. Of these, Ti,
V, Cr, Fe, Co, Ni, Zr, Nb, Mo, P
When d, Ag, Ta, W, and Pt were added, the oxidation resistance was improved. However, when these elements were added in an amount of 15 atomic% or more, the recording sensitivity was reduced. As in the case of the first and second embodiments, the effect of improving the recording sensitivity was particularly high when the addition was 10 atomic% or less.

Similarly, when N is added to the recording layer,
There was an effect of reducing noise. 20 atomic%
Or less, particularly preferably 15 atomic% or less. When O is added to the recording layer, O exists as at least one kind of oxide of the element constituting the recording layer, and has an effect of improving the recording sensitivity by reducing the thermal conductivity of the recording layer. . The addition amount is preferably 20 atomic% or less, particularly preferably 15 atomic% or less.

As the recording layer, instead of Al ₇₀ Ag ₃₀ , In
-Bi-based, Bi-Na-based, Pb-Bi-based, Sn-Bi
System, In-Pb system, In-Sn system, In-Tl system, In
Similar characteristics were obtained when a Zn-based, Sn-Pb-based, Tl-Sn-based, or Zn-Sn-based was used. Further, as a recording layer, an Ag-Al-based, Ag-Bi-based, Ag-Ca
System, Ag-In system, Ag-Pb system, Ag-Sb system, Ag
-Sn-based, Ag-Te-based, Ag-Ti-based, Al-Au
System, Al-Cu system, Al-Cr system, Al-Ge system, Al
-Si, Al-Sn, Al-Ti, Al-Zn
System, Au-Bi system, Au-Ge system, Au-Pb system, Au
-Sb system, Au-Si system, Au-Te system, Au-Tl
System, Ni-Ce system, Cu-La system, Cu-Mg system, Cu
-Pr-based, Cu-Sb-based, Ga-Te-based, Ge-Te
System, Zn-Ge system, In-Sb system, Pb-Pd system, Pt
Similar similar characteristics were obtained when using -Pb, Pb-Sb, Sb-Te, and Tl-Sb systems.

[0083]

According to the present invention, an information recording medium having a large capacity and a small wavelength dependency can be provided.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention in which a surface of a recording layer on a laser beam incident side is mainly deformed.

FIG. 2 shows an embodiment of the present invention in which the surface of the recording layer opposite to the laser beam incident side is mainly deformed.

FIG. 3 shows an embodiment of the present invention in which both the laser beam incident side surface and the opposite side surface of the recording layer are deformed.

FIG. 4 shows an embodiment of the present invention in which a hole is formed in a recording layer by laser beam incidence.

FIG. 5 shows another embodiment of the present invention in which holes are formed in the recording layer by laser beam incidence.

FIG. 6 shows another embodiment of the present invention in which a hole is formed in a recording layer by laser beam incidence.

FIG. 7 shows another embodiment of the present invention in which holes are formed in the recording layer by laser beam incidence.

FIG. 8 shows another embodiment of the present invention in which a hole is formed in a recording layer by laser beam incidence.

FIG. 9 shows an embodiment of the present invention in which both the surface on the laser beam incident side and the surface on the opposite side of the recording layer are deformed, and only the surface of the recording auxiliary layer in contact with the recording layer is deformed.

FIG. 10 shows one embodiment of the present invention in which both the surface on the laser beam incident side and the surface on the opposite side of the recording layer are deformed to form a cavity in the recording auxiliary layer.

FIG. 11 shows an embodiment of the present invention in which both the surface on the laser beam incident side and the surface on the opposite side of the recording layer are deformed, and a cavity is formed at the interface between the recording layer and the recording auxiliary layer.

FIG. 12 shows a laminated structure of a medium according to the first embodiment of the present invention.

FIG. 13 shows a laminated structure of a medium according to a second embodiment of the present invention.

FIG. 14 shows an embodiment of the present invention in which a wobble including address information is arranged at a boundary between a land and a groove.

FIG. 15 shows a laminated structure of a medium according to a third embodiment of the present invention.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Recording auxiliary layer 4 UV curable resin protective layer 5 Adhesive layer 6 Cavity

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hitoshi Watanabe 1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell Co., Ltd. Inside Maxell Co., Ltd. (72) Inventor Koji Takazawa 1-88 Ushitora, Ibaraki-shi, Osaka Prefecture F-term within Hitachi Maxell Co., Ltd. 5D029 JB05 JB22 JB23 JB35 JC11 KB12 RA02 WA20 WB11 WB17 WC01 WC05 WC06 5D090 AA01 BB03 FF11 GG02

Claims (37)

[Claims] 1. An information recording medium having at least a recording auxiliary layer and a recording layer on a substrate, wherein the recording auxiliary layer is formed in contact with one side or both sides of the recording layer, and the recording auxiliary layer is formed by irradiation with a light beam. An information recording medium wherein information recording is performed by physically deforming at least one of the recording layers. 2. The information recording medium according to claim 1, wherein a recording layer and a recording auxiliary layer are formed on the substrate in this order, and the substrate, the recording auxiliary layer, and the recording layer are physically illuminated by light beam irradiation. An information recording medium characterized in that information is recorded by deforming the recording medium. 3. The information recording medium according to claim 1, wherein a recording auxiliary layer is formed on a side of the recording layer opposite to the substrate, and a surface of the recording auxiliary layer on the recording layer side is physically formed. An information recording medium characterized in that the surface opposite to the recording layer hardly undergoes physical deformation. 4. The information recording medium according to claim 1, wherein the physical deformation of the recording layer is accompanied by a change in the film thickness, and the film thickness of the recording layer in at least a part of the information recorded portion is the unrecorded portion. An information recording medium characterized by being smaller than the film thickness. 5. The information recording medium according to claim 4, wherein the thickness of the recording layer is substantially zero in at least a part of the portion where information is recorded. 6. The information recording medium according to claim 1, wherein a change in the atomic arrangement of a recording layer occurs in at least a part of a portion where information is recorded. 7. The information recording medium according to claim 1, wherein the melting point of the recording layer is 600 ° C. or less. 8. The information recording medium according to claim 7, wherein the recording layer contains at least two kinds of elements as main components, and the melting points of these elements are 600 ° C. or less. 9. The information recording medium according to claim 8, wherein at least two kinds of elements contained in the recording layer have a melting point of 600.
An information recording medium having a eutectic composition of not more than ° C and a content of the two elements being a eutectic composition or a composition in the vicinity thereof. 10. The information recording medium according to claim 7, wherein the recording layer contains two types of elements as main components, and at least one of these elements has a melting point of 600 ° C. or more, and Has an eutectic composition having a melting point of 600 ° C. or lower with another element, and the content of the two elements is at or near the eutectic composition. 11. The information recording medium according to claim 1, wherein the recording auxiliary layer is made of an organic dye material. 12. The information recording medium according to claim 1, wherein the recording auxiliary layer is made of a polymer material. 13. The information recording medium according to claim 11, wherein the recording auxiliary layer has a thermal decomposition temperature or a glass transition temperature, and the temperature is lower than the melting point of the recording layer. Information recording medium. 14. The information recording medium according to claim 13, wherein a difference between a thermal decomposition temperature or a glass transition temperature of the recording auxiliary layer and a melting point of the recording layer is 400 ° C. or less. . 15. The information recording medium according to claim 1, wherein the information recording medium has a structure in which two substrates are bonded together with a recording layer sandwiched therebetween. 16. The information recording medium according to claim 15, wherein each of the two substrates has a recording layer, and irradiates a light beam from one of the substrates to record information on each of the recording layers. An information recording medium characterized in that the substrate on which recording and light beam irradiation are performed, the recording auxiliary layer and the recording layer transmit at least 40% of the light beam. 17. The information recording medium according to claim 1, wherein at least two recording layers are provided on one substrate. 18. The information recording medium according to claim 17, wherein information is recorded on each recording layer by irradiating a light beam from the substrate side. 19. The information recording medium according to claim 17, wherein information is recorded on each recording layer by irradiating a light beam from a side opposite to the substrate. 20. The information recording medium according to claim 16, wherein the recording layer on the light beam incident side and the recording layer on the opposite side have different film thicknesses. Information recording medium. 21. The information recording medium according to claim 16, 18 or 19, wherein the element is a main component of the recording layer on the light beam incident side and the main component of the recording layer on the opposite side. An information recording medium wherein the elements are the same, and the content of the element serving as the main component differs between the recording layer on the light beam incident side and the recording layer on the opposite side. 22. An information recording medium according to claim 16, 18 or 19, wherein at least one element among the elements which are the main components of the recording layer on the light beam incident side, An information recording medium, characterized in that at least one of the elements serving as the main components of the recording layer is a different element. 23. The information recording medium according to claim 21, wherein the melting point of the recording layer on the light beam incident side is different from the melting point of the recording layer on the opposite side. . 24. The information recording medium according to claim 1, wherein a guide groove is formed spirally or concentrically on the substrate, and the guide groove is formed on the guide groove or between two adjacent guide grooves (referred to as a space between guide grooves). An information recording medium, characterized in that one of them is a recording track and information is recorded on the recording track. 25. The information recording medium according to claim 1, wherein a guide groove is formed spirally or concentrically on the substrate, and both the guide groove and between the guide grooves are used as recording tracks, and information is recorded on the recording tracks. An information recording medium characterized by recording. 26. The information recording medium according to claim 24, wherein the shape of the spiral or concentric guide groove formed on the substrate differs between the light beam incident side and the opposite side. An information recording medium characterized by the following. 27. The information recording medium according to claim 26, wherein the depth of the guide groove of the substrate on the light beam incident side is smaller than the depth of the guide groove of the substrate on the opposite side. Medium. 28. The information recording medium according to claim 26, wherein the width of the guide groove of the substrate on the light beam incident side is wider than the width of the guide groove of the substrate on the opposite side. . 29. The information recording medium according to claim 24, wherein a distance (track pitch) in a radial direction of the recording track is TP, a wavelength of the light beam is λ, and a lens for condensing the light beam. When the numerical aperture is NA,
An information recording medium, wherein TP / (λ / NA) is 0.7 or less. 30. The information recording medium according to claim 29, wherein the recording track has a radial interval of 1 μm or less. 31. The information recording medium according to claim 29, wherein the interval between the recording tracks in the radial direction is 0.75 μm or less. 32. The information recording medium according to claim 24, wherein a plurality of length marks are recorded on the recording track, and the length of each mark in the track direction corresponds to the information. An information recording medium characterized by the following. 33. The information recording medium according to claim 32, wherein the edge of each mark in the track direction corresponds to "1" of information, and the other portions correspond to "0" of information. Information recording medium. 34. The information recording medium according to claim 32, wherein a minimum length in a circumferential direction of a recording mark formed on said recording track is 0.7 μm or less. . 35. The information recording medium according to claim 32, wherein the minimum length of the recording mark is 0.5 μm.
m or less. 36. The information recording medium according to claim 34, wherein the recording mark has a plurality of circumferential lengths, and the length of the longest recording mark is at least three times the length of the shortest recording mark. An information recording medium, characterized in that: 37. An information recording medium having at least a recording auxiliary layer and a recording layer on a substrate, wherein the recording auxiliary layer is formed in contact with one or both sides of the recording layer by irradiating a light beam with at least the recording auxiliary layer. The information recording is performed by physically deforming one of the recording layers and the recording layer, and the information is reproduced by optically reading out the change in the reflectance accompanying the deformation of the recording auxiliary layer and the recording layer. Recording / reproducing method of the characteristic information.