JPH10247339A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a sufficient C/N and an overwrite erasability by making optical recording medium include an optical absorption quantity control element and a light quantity control element in an optical recording medium wherein recording and erasing of information is carried out according to phase transition between amorphous state and crystal state. SOLUTION: A proper optical absorption quantity state is achieved by using an optical absorption quantity control element satisfying Aa<=Ac (Aa and Ac are optical absorption rates of a recording layer in amorphous and crystal states, respectively) according to optical wavelength and recording condition, or composition and material of an optical recording medium. By using an optical control element satisfying Tc<=Ta (Ta and Tc are optical transmittances of a recording layer in amorphous state and crystal state, respectively), practically used optical energy is adjusted. And, it is assumed that, in a phase transition type recording medium, a part of a recording layer in amorphous state is used as recording signal, where the medium has a high reflectance in an unrecorded state, namely, an amorphous state and has a low reflectance in a recording state. To device an effect of the light quantity control element remarkably, a light quantity control is performed under such conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to
The present invention relates to an optical information recording medium capable of recording, erasing, and reproducing information. In particular, the present invention provides a method for erasing recorded information,
The present invention relates to a rewritable phase-change optical recording medium, such as an optical disk, an optical card, or an optical tape, having a rewritable function and capable of recording an information signal at high speed and high density.

[0002]

2. Description of the Related Art A phase change optical recording medium is one of optical recording media for recording, reproducing and erasing information by irradiating a laser beam. The technology of the conventional rewritable phase change optical recording medium is as follows.

The above-mentioned optical recording medium has a recording layer containing tellurium as a main component. During recording, a laser beam pulse concentrated on the crystalline recording layer is irradiated for a short time to partially melt the recording layer. . The molten part is quenched by heat diffusion, solidifies,
A recording mark in an amorphous state is formed. The light reflectance of this recording mark is lower than that of the crystalline state and can be reproduced optically as a recording signal. At the time of erasing, the recording mark is irradiated with a laser beam and heated to a temperature lower than the melting point of the recording layer and higher than the crystallization temperature to crystallize the amorphous recording mark and return to the original unrecorded state. . For the recording layer of these rewritable phase-change optical recording media, alloys such as Ge ₂ Sb ₂ Te ₅ (N. Yamada e.
tal. Proc. Int. Symp. on Optical Memory 1987
p61-66) are known.

An optical recording medium using these Te alloys as a recording layer has a high crystallization rate and only modulates the irradiation power.
High-speed overwriting with one circular beam is possible. In optical recording media using these recording layers, usually,
A dielectric layer having heat resistance and translucency is provided on both sides of the recording layer to prevent the recording layer from being deformed and having openings during recording. Furthermore, on the dielectric layer on the side opposite to the light beam incident direction, a metal reflective layer of light reflective Al or the like is laminated and provided to improve the signal contrast at the time of reproduction by an optical interference effect, and by a cooling effect. There is known a technique for facilitating formation of a recording mark in an amorphous state and improving erasing characteristics and repetition characteristics. In particular, the “quenching configuration” in which the dielectric layer between the recording layer and the reflective layer is configured to be thinner than about 50 nm
Is superior to the "slow cooling configuration" in which the dielectric layer is thickened to about 200 nm in that the deterioration due to repeated recording rewriting is relatively small, and that the power margin of the erasing power is wide (T. Ohta et al.). al, Japanese Journal of Applied
Physics, Vol. 28 (1989) Suppl. 28-3 pp123-128).

However, in the above-described phase change optical recording medium having a general configuration, the difference in reflectance between the recorded amorphous recording mark and the crystalline state is large, and the amount of light absorption in the amorphous state of the recording layer is large. Becomes higher than the light absorption amount in the crystalline state. Therefore, whether the part before overwrite recording is crystalline,
Depending on whether the mark is an amorphous mark, there is a difference in the temperature rise state during recording, and as a result, the shape and formation position of the newly overwritten recording mark are modulated by the signal before overwriting, and the erasure rate and jitter This was the cause of limiting the characteristics. These problems become more serious with an increase in recording density and recording speed. In particular, in the case of mark edge recording, which provides information at both ends of a recording mark, which has been recently adopted as a recording method of higher density, jitter deteriorates. Is a more severe problem.

As a means for solving such a problem that the amount of light absorption in the amorphous state becomes higher than the amount of light absorption in the crystalline state, for example, the following technique is known. That is, JP-A-5-15
No. 9360 discloses that when a Ti layer having a thickness of about 50 nm is formed as an absorption correction layer after a second dielectric layer having a thickness of 220 nm, the amount of light absorbed at a laser wavelength of 830 nm is larger than that of a crystal part. 63%, 6 for amorphous part
It is described that the overwriting erasure rate of different frequency signals can be improved by the effect of the absorption amount correction. Further, in order to reduce the thermal load of the light absorption layer due to the temperature rise due to the light absorption, a technique of forming a relatively thick Al alloy having a thickness of about 50 nm as the heat radiation layer is described.

In Japanese Patent Application Laid-Open No. Hei 8-124218, a first dielectric layer, a recording layer, a second dielectric layer, a reflective layer, and a third dielectric layer are sequentially deposited on a substrate, and the light is transmitted as a reflective layer. It is described that the effect of correcting the absorption amount can be obtained by using an ultra-thin metal film or Si, Ge having a refractive index greater than 1.5 as the third dielectric layer. I have.

In the high-density recording of an optical recording medium, a technique of increasing the density of information by mark edge recording and the like and a narrower track pitch by narrowing the recording track pitch to increase the density are simultaneously performed.

As the track pitch becomes narrower, there is a problem that adjacent tracks are affected, that is, cross erase occurs. This is because, in a phase change recording medium, the recording layer undergoes a crystal-amorphous phase change utilizing heat generated by light absorption, so that a heat source generated in the medium spreads in the direction of an adjacent track. This spread heat is generated in the form of erasing recorded marks on adjacent tracks.

[0010]

SUMMARY OF THE INVENTION The present inventors have paid attention to the conventional absorption amount control element, and have confirmed that the absorption amount control has a large effect on jitter reduction in recording / erasing characteristics. . However, as the effect has been enhanced, diligent studies have been made on the fact that the light power margin at the time of recording / erasing becomes smaller, and that the so-called cross-erasing characteristics are significantly deteriorated.

As a result, with the conventional function of controlling the amount of light absorption, it is possible to prevent the light power incident on the recording layer from changing depending on whether the recording layer is in a crystalline state or an amorphous state. However, the effect is obtained by utilizing the absorption coefficient of a constituent layer called a light absorption correction layer. In this case, the presence of the absorption coefficient causes the light absorption correction layer to generate heat. It has been found that this heat generation makes it difficult to remove the surplus generated heat near the recording layer after the optical power is applied, in order to reduce the temperature gradient near the recording layer.

In order to avoid cross erasure, it is necessary to quickly disperse the excess heat generated in the recording layer and prevent the temperature increase in the adjacent track area. When a material having an absorption coefficient at the light wavelength used for recording is used for the purpose of obtaining the recording layer, heat is generated not only in the recording layer but also in the absorption correction layer, and as a result, the heat generation around the recording layer is caused. The thermal gradient becomes smaller. Furthermore, Japanese Patent Application Laid-Open No. 8-124218 discloses a case in which Si is used as the absorption correction layer, but the thermal conductivity is considerably small at about 1.8 W / mK. That is, the heat generated in the recording layer tends to spread in the direction of the adjacent track due to the small thermal gradient around the recording layer, the use of a low thermal conductivity material, and the like.

As described above, the correction of the amount of absorption is an indispensable technique in high linear velocity, high density recording from the viewpoint of improving the jitter characteristics. Also, in order to increase the areal density of recording signals in a recording medium, it is necessary to reduce the track pitch. However, for the above-mentioned reasons, there is no known invention which achieves both the absorption correction and the narrow track pitch. That is, in the present invention, in the optical recording medium provided with the light absorption amount correction element, in addition to having appropriate recording / erasing sensitivity over a wide frequency range, sufficient C / N and sufficient overwrite erasability are ensured. It is an object of the present invention to provide an optical recording medium with reduced cross erasure that occurs during high-density recording.

[0014]

Means for Solving the Problems To solve the above problems, the present invention comprises the following constitutions. That is, information can be recorded, erased, and reproduced by irradiating the recording layer formed on the substrate with light, and information recording and erasing are performed by a phase change between an amorphous state and a crystalline state. An optical recording medium according to claim 1, further comprising a light absorption control element and a light control element.

According to the present invention, information can be recorded, erased, and reproduced by irradiating a recording layer formed on a substrate with light, and information can be recorded and erased between an amorphous state and a crystalline state. In the optical recording medium performed by the phase change of, the light absorption Aa when the recording layer is in an amorphous state and the light absorption Ac when the recording layer is in a crystalline state are represented by the relationship of Aa ≦ Ac. And the transmittance Tc when the recording layer is in the amorphous state and the transmittance Tc when the recording layer is in the crystalline state.
Is an optical recording medium satisfying the relationship of Tc ≦ Ta.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the term "substrate" refers to a substrate that carries an optical recording medium. As a substrate,
Although not particularly limited, for example, various kinds of transparent synthetic resins, transparent glass, and the like can be used. For the purpose of avoiding the influence of dust and scratches on the substrate, recording is performed from the substrate side using a converged light beam using a transparent substrate. Examples of such a transparent substrate include glass, polycarbonate, polymethyl methacrylate, polyolefin resin, epoxy resin, and polyimide resin. In particular, a polycarbonate resin and an amorphous polyolefin resin are preferable because they have low optical birefringence, low hygroscopicity, and are easy to mold. When heat resistance is required, an epoxy resin is preferred. The substrate may be flexible or rigid. The flexible substrate is used in the form of a tape, a sheet, or a card. The rigid substrate is used in the form of a card or a disk. In addition, after forming a recording layer and the like, these substrates use an air sandwich structure using two substrates,
An air incident structure or a close bonding structure may be used. The thickness of the substrate is not particularly limited.
It is practical that the thickness is 01 mm or more and 5 mm or less. 0.01mm
If it is less than 5 mm, even when recording with a light beam converged from the substrate side, it is easily affected by dust, and if it is 5 mm or more,
It becomes difficult to increase the numerical aperture of the objective lens, and the spot size of the irradiation light beam increases, so that it becomes difficult to increase the recording density.

In the present invention, the recording layer refers to a layer made of a material capable of repeating a phase change between a crystalline state and an amorphous state by light irradiation. For example, it refers to a material that can repeat a phase change between a crystalline state and an amorphous state in the following order. That is, at the time of information recording, a concentrated laser light pulse is irradiated for a short time to partially melt the recording layer. The melted portion is quenched by thermal diffusion and solidified to form an amorphous recording mark. At the time of erasing, the recording mark is irradiated with a laser beam and heated to a temperature lower than the melting point of the recording layer and higher than the crystallization temperature to crystallize the amorphous recording mark and return to the original unrecorded state. . The composition and composition of the material of the recording layer are not particularly limited,
The recording layer material containing Te as a component can be suitably used because the volume fluctuation between crystal and amorphous is small. As such a recording layer material, for example, Pd-Ge-S
b-Te alloy, Nb-Ge-Sb-Te alloy, Pd-N
b-Ge-Sb-Te alloy, Ni-Ge-Sb-Te alloy, Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy, In-Sb-Te alloy, Ag-In-Sb-Te alloy, In-Se alloy and the like are available. Especially Pd-Ge-Sb
-Te alloy, Nb-Ge-Sb-Te alloy, Pd-N
The b-Ge-Sb-Te alloy is preferable because it has a short erasing time, is capable of repeating recording and erasing many times, and has excellent recording characteristics such as C / N and erasing rate. -Ge-Sb-Te alloys are preferred because of their excellent properties.

Further, the light absorption control element referred to in the present invention means that the recording layer in the phase change recording medium has different optical constants in the crystalline state and the amorphous state, respectively. It refers to an element that controls the difference in light absorption. A suitable light absorption amount state can be realized by using this light absorption amount control element depending on the light wavelength and recording conditions to be used, and the configuration and material of the optical recording medium. Aa ≦ Ac (where Aa is the recording Light absorption when the layer is in an amorphous state, Ac
It is preferable to use a light absorption amount control element that satisfies (light absorption rate when the recording layer is in a crystalline state). At present, in a phase change recording medium, a portion where the recording layer is in an amorphous state is used as a recording signal, and the medium reflectance at this time is set to a high reflectance in an unrecorded state, that is, a crystalline state, and a low reflectance in a recording state. Is common. In this configuration, in many cases, the amount of light absorbed by the recording layer in the recorded state is larger than the amount of light absorbed in the unrecorded state. Therefore, it is better to control the amount of light absorption under the above conditions in order to significantly derive the effect of the light absorption amount control element.

The light absorption control element may be realized by using any method such as selection of the structure of the optical recording medium and the type of material used. preferable. Because, in general, a phase change optical recording medium is realized by a multilayer film including a recording layer.
In this case, for example, when the amount of light absorption is controlled by selecting the constituent material of each layer, the unique physical properties of each constituent material, for example, the thermal conductivity and specific heat, the refractive index, the absorption coefficient, and the like greatly change. . As a result, in a method based on a selection of a material or a combination of constituent layers having a plurality of elements, controlling the light absorption amount easily affects other recording characteristics. Therefore, it is important to be able to easily control the amount of light absorption. In this case, a new light absorption amount control layer has a feature that the recording medium can be easily designed without significantly hindering other characteristics. Because you can have it.

The light quantity control element in the present invention refers to an element for controlling the intensity of light incident on an optical recording medium in the medium. In other words, it refers to an element that adjusts the light energy used in the optical recording medium by controlling the amount of light passing through the disk.

Preferably, the light quantity controlling element is: Tc ≦ Ta (Ta is the light transmittance when the recording layer is in an amorphous state;
It is preferable to use a light quantity control element that satisfies (transmittance when the recording layer is in a crystalline state). As described above, in the phase change recording medium, a portion where the recording layer is in an amorphous state is used as a recording signal, and the medium reflectivity at this time is high in an unrecorded state, that is, in a crystalline state, and low in a recorded state. It is general that In this configuration, the light transmittance of the recording layer in the recorded state is often smaller than the light transmittance in the unrecorded state. Therefore, it is better to perform light quantity control under the above conditions in order to remarkably bring out the effect of the light quantity control element.

Further, the light quantity control element may be realized by any method, but it is preferable to constitute the light quantity control layer. This is because, similarly to the case of the light absorption amount control element, it is more effective to function as a light amount control layer in that a disk can be easily designed without changing other recording medium characteristics. is there.

In the optical recording medium, at least a first protective layer, a recording layer, a second protective layer, a light absorption control layer, and a light control layer are laminated in this order on a substrate. preferable. Further, an overcoat layer or a hard coat layer may be provided. In this configuration, the configuration of a general phase change optical recording medium (substrate, first protective layer, recording layer,
This is because the medium configuration can be realized by adding the (light absorption amount control layer, light amount control layer) to the (second protection layer), that is, by adding elements to the conventional configuration.

Preferably, the main component of the first protective layer is a dielectric. This is because a dielectric can be suitably used to prevent thermal damage to the substrate. In particular, as a main component of the first protective layer, Si ₃ N _x (3 <
More preferably, at least one of X ≦ 4), SiO _x (0 <X ≦ 2), and ZnS is included. Because
This is because these materials can be suitably used for controlling the adhesiveness to the recording layer.

The main component of the second protective layer is preferably a dielectric, as in the case of the first protective layer. Further, Si ₃ N _x (3 <X ≦ 4), SiO _x (0 <
X ≦ 2), and more preferably at least one of ZnS.

The main component of the light absorption control layer is T
It is preferable to include at least one of i, Cr, Fe, Ni, Zn, Zr, Nb, Mo, and W. This is because these elements are relatively stable and can be easily formed on another material or the like by using a method such as sputtering as a thin film formation method. In addition, the refractive index and the extinction coefficient are relatively high, and the effect of controlling the amount of absorption can be easily obtained.

Preferably, the light absorption control layer also functions as a heat conduction control element. Because, in order to control the excess heat generated by light absorption, in addition to controlling the amount of light absorption, by controlling the thermal conductivity, the time change of the temperature around the recording layer after recording light irradiation is controlled. This is because the cross erasing characteristics can be more effectively improved.

Specifically, when the thermal conductivity of the light absorption control layer satisfies 1.5 ≦ S ≦ 25 (S is the thermal conductivity, the unit is W / mK), it can be suitably used. When a recording layer material containing Te as one of the components as described above is used, each has a specific thermal conductivity. For example, in the case of a phase change recording material typified by Ge ₂ Sb ₂ Te ₅ or the like, the thermal conductivity is about 0.5 W / mK. In order to properly record and erase information in this state of inherent thermal conductivity, it is necessary to maintain sufficient heat in the recording layer to cause a phase change and quickly reduce excess heat generated in the recording layer. Need to be removed. If the thermal conductivity of the light absorption control layer is within the above range,
This is because the above contradictory requirements are satisfied regardless of the material and thickness of each layer.

For this purpose, for example, in the light absorption control layer, Ag, Al, Au, Bi, C,
Co, Cu, Fe, Ga, Ge, Hf, In, Mo,
N, Nb, Ni, O, Pb, Si, Sn, Ti, W, Z
It is preferable to use one or more of n and Zr. This is because these additive elements can be relatively easily added to the above-mentioned light absorption control layer, exist in a stable state, and can control the thermal conductivity within the above range.

Preferably, the main component of the light quantity control layer is a dielectric. This is because it is easy to form a relatively rigid and stable layer by a thin film forming method such as sputtering. In addition, there are many optically stable materials,
This is because, in the configuration in which the light quantity control layer is the last thin film layer as described above, it can be more suitably used. Further, as a main component of the light quantity control layer, Si ₃ N _x (3
<X ≦ 4), SiO _x (0 <X ≦ 2), and ZnS. This is because, as described above in the section of the first protective layer, in controlling the adhesion to each layer, in addition to being preferably used, these materials are most likely to be in contact with the outside world. This is because appropriate hardness and stability are required.

The optical characteristics of the light absorption control layer are such that at least at the center wavelength of light used for recording, 2 ≦ n ≦ 4.5 and 0.2 ≦ k ≦ 4 (n is a refractive index, and k is a refractive index. If it satisfies the extinction coefficient, it can be used more preferably. When a recording layer material containing Te as one of the components is used, it also has a unique optical constant, but by using a light absorption control layer having an optical constant in the above range, the material and thickness of each layer can be reduced. This is because more effective absorption amount control can be performed. For example, case of Ge ₂ Sb ₂ Te ₅ material, n~4.0, k~2.0 (amorphous state) N～4.0, a K～3.0 (crystalline state). For example, when controlling the amount of light absorption in the recording layer by changing the thickness of the amount of light absorption and light interference inside the medium,
Although there are optical constants suitable for the interference, the optical constants in the above-described range facilitate the control of the interference suitably.

The optical characteristics of the light quantity control layer are more preferably satisfied by satisfying 1.2 ≦ n ≦ 2.2 and 0 ≦ k ≦ 0.1 (n is a refractive index and k is an extinction coefficient). Can be used. This is because, in the case of a phase change recording material containing Te as one of the components, an appropriate optical constant of the light absorption control layer can be selected, as described above for the light absorption control layer. This is because, in the case where the light quantity is controlled by interference, the above-mentioned suitable optical constant conditions exist in consideration of the reflection and transmittance at the interface between the layers.

Next, a method for manufacturing the optical recording medium of the present invention will be described. Examples of a method for forming the absorption correction layer, the recording layer, the reflection layer, and the like in the form of a substrate include a method of forming a thin film in a vacuum, such as a vacuum evaporation method, an ion plating method, and a sputtering method. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled. The film thickness of the formed recording layer and the like can be easily controlled by monitoring the deposition state with a quartz crystal film thickness meter or the like.

The formation of the recording layer and the like may be performed while the substrate is fixed, or moved or rotated. The substrate is preferably rotated on its own axis because of excellent in-plane uniformity of the film thickness, and more preferably combined with revolution.

After forming an absorption correction layer or a reflection layer within a range that does not significantly impair the effects of the present invention, ZnS, SiO ₂ ,
A dielectric layer such as ZnS—SiO ₂ , and / or
A protective layer such as an ultraviolet curable resin may be provided as necessary. Further, a hub or the like may be provided on the substrate as needed. Furthermore, after forming the absorption correction layer or the reflection layer, or after forming the above-mentioned resin protective layer, the two substrates may be bonded to each other with an adhesive.

It is desirable that the recording layer is crystallized by irradiating a laser beam or a light such as a xenon flash lamp in advance before actual recording.

[0037]

The present invention will be described below with reference to examples. However, the present invention is not limited by the following examples.

However, the compositions of the absorption correction section, the recording layer, and the reflection layer were confirmed by ICP emission analysis (manufactured by Seiko Denshi Kogyo KK). Further, the C / N and the erasing rate (difference in the intensity of the reproduced carrier signal after recording and after erasing) were measured by a spectrum analyzer.

(Example 1) Thickness 0.6 mm, diameter 120
The recording layer, the dielectric layer, and the absorption correction layer were formed by a high-frequency sputtering method while rotating a polycarbonate substrate with spiral grooves having a pitch of 1.2 μm and a pitch of 1.2 μm while rotating the substrate at 40 rpm.

First, the inside of the vacuum vessel was evacuated to 1 × 10 ^-5 Pa, and then SiO 2 was evacuated in an Ar gas atmosphere of 2 × 10 ^-1 Pa.
₂ was added by 20 mol% to sputter ZnS to form a first dielectric layer. Subsequently, Pd, Nb, Ge, Sb,
An alloy target made of Te is sputtered to obtain a composition Pd
A recording layer of _0.3 Nb _0.5 Ge _18.5 Sb _26.7 Te ₅₄ (atomic%) was formed. Further, a second dielectric layer made of the same material as the first dielectric layer is formed.
A dielectric layer was formed, and a light absorption control layer was laminated thereon. Further, SiO ₂ was laminated as a light quantity control layer.

Further, after removing these optical recording media from the vacuum container, an acrylic ultraviolet curable resin is spin-coated and cured by irradiation with ultraviolet light to form a resin layer having a thickness of 10 μm. The optical recording medium of the present invention was obtained by bonding with a recording medium. Table 1 shows details of the configuration.

[0042]

[Table 1] Table 2 shows the amounts of light absorption and transmission at this time.

[0043]

[Table 2] As can be seen from Table 2, Ac> Aa by controlling the absorption amount.
And at the same time, the amount of light transmitted through the disk is designed to be reduced by about 5% in the crystalline state.

This optical recording medium is rotated under the condition of a linear velocity of 12 m / s, and recording and erasing are performed on a track having a radius of 40 mm by using an optical head having a numerical aperture of an objective lens of 0.6 and a wavelength of a semiconductor laser of 380 nm. An experiment was performed. The shape of the beam condensed by the optical head was a substantially concentric Gaussian beam, and the beam diameter was about 1 μm. In the experiment of recording and erasing, the modulation method was set to 1-7 RLL,
The maximum recording frequency was 13.5 MHz (2T), the minimum recording frequency was 3.38 MHz (8T), and the pulse duty was 50%. No recording compensation was used. Measurement item is 2T
C / N, erasing rate by 2T overwriting after 8T recording, jitter before and after overwriting, cross erasing characteristics (after recording 8T signal on central track, recording 7T signal on adjacent track, carrier on central track Drop amount)
Was measured. Table 3 shows the measurement results.

[0045]

[Table 3]

From the results shown in Table 3, it can be seen that the disk manufactured in the present embodiment has the erasing ratio and the before-and-after jitter at a level sufficient for a rewritable recording medium. Furthermore, despite the beam spot diameter being about 1 μm, 1.
At a track pitch of 2 μm, cross erasure is 0.0d
B.

(Comparative Example 1) In the disk configuration used in the example, the light amount control layer was omitted, and a disk capable of controlling the absorption amount almost the same as in the example 1 was manufactured. As a result, the results shown in Table 4 were obtained.

[0048]

[Table 4]

From the results shown in Table 4, it can be seen that the erasing rate and the jitter characteristics were the same as in Example 1 by making the absorption amount correction effect almost the same, but the cross erasing characteristics were obtained. Got worse. Thus, it was confirmed that effective energy control by the light quantity control layer was extremely effective.

Example 2 Next, the material of each layer was changed, and the layer structure was designed so that almost the same optical characteristics as in Example 1 could be obtained. Table 5 about used constituent materials. Shown in

[0051]

[Table 5] When the disk characteristics of the above six types of samples were evaluated, the results shown in Table 6 were obtained.

[0052]

[Table 6] Embodiment 1 By performing light amount control in addition to light absorption amount control,
The same characteristics as those obtained in were obtained. The cross erasing characteristics were 0.0 dB in each case.

Example 3 As a result of Example 2, it was found that the recording / erasing power was different depending on the material of each constituent layer, and that the erasing rates were different. Therefore, an attempt was made to provide a thermal conductivity control element to the light absorption control layer in order to fill the difference in the erasure rate due to the difference in thermal conductivity. Using the disk configuration used in Example 1 as a prototype, samples as shown in Table 7 were produced.

[0054]

[Table 7] The measurement results in Table 8 were obtained for the above samples.

[0055]

[Table 8]

From the results shown in Table 8, it was found that the erasure rate can be changed by the thermal conductivity of the light absorption control layer. It was also confirmed that the cross erase characteristics could be maintained within a certain thermal conductivity control range.

Example 4 An experiment was conducted on the optical requirements of the light absorption control layer using simulation.
Of the constituent layers used in Example 1, the amount of light absorption was calculated by changing the optical constant of the light absorption amount control layer ideally. Table 9 shows the results.

[0058]

[Table 9]

From the results of Example 1 and the like, it is known that good erasing characteristics can be obtained by generating a light absorption difference of about 5 to 10%. Therefore, Table 9
It can be seen from the tendency of the difference in the amount of absorption shown in FIG.

[0060]

According to the present invention, by including both the light absorption control element and the light control element, excess heat generation can be controlled by adjusting the heat absorption substantially before entering the recording layer. You can now do.
By doing so, it was possible to reduce cross erasure that occurs when high-density recording is performed, while ensuring sufficient C / N and overwrite erasability over a wide frequency range.

Claims (21)

[Claims] An information recording, erasing, and reproducing operation can be performed by irradiating a recording layer formed on a substrate with light.
An optical recording medium in which recording and erasing of information is performed by a phase change between an amorphous state and a crystalline state, the optical recording medium including a light absorption control element and a light control element. 2. The light absorption ratio A when the recording layer is in an amorphous state.
a and the light absorption rate Ac when the recording layer is in a crystalline state,
2. The optical recording medium according to claim 1, wherein a relationship of Aa ≦ Ac is satisfied. 3. The light transmittance T when the recording layer is in an amorphous state.
a and the transmittance Tc when the recording layer is in a crystalline state is T
2. The optical recording medium according to claim 1, wherein a relationship of c ≦ Ta is satisfied. 4. Recording, erasing, and reproducing information can be performed by irradiating a recording layer formed on a substrate with light.
An optical recording medium in which recording and erasing of information is performed by a phase change between an amorphous state and a crystalline state, wherein the light absorption rate Aa when the recording layer is in an amorphous state and the recording layer is in a crystalline state. In this case, the light absorption Ac satisfies the relationship of Aa ≦ Ac, and the light transmittance Ta when the recording layer is in an amorphous state and the transmittance Tc when the recording layer is in a crystalline state are Tc ≦ Ta
An optical recording medium characterized by satisfying the following relationship: 5. The optical recording medium according to claim 1, wherein the light absorption control element is configured as a light absorption control layer. 6. The optical recording medium according to claim 1, wherein the light quantity control element is configured as a light quantity control layer. 7. An optical recording medium having at least a first optical recording medium on a substrate.
The optical recording medium according to claim 1, wherein a protective layer, a recording layer, a second protective layer, a light absorption control layer, and a light control layer are laminated in this order. 8. The optical recording medium according to claim 7, wherein a main component of the first protective layer is a dielectric. 9. The method according to claim 9, wherein the first protective layer comprises Si ₃ N _x (3
9. A composition comprising at least one selected from the group consisting of <X ≦ 4), SiO _x (0 <X ≦ 2), and ZnS.
The optical recording medium according to the above. 10. A recording layer comprising at least Te as a main component.
The optical recording medium according to claim 7, wherein the optical recording medium is made of an alloy containing: 11. The main component of the recording layer is Ge, Sb, T
11. The optical recording medium according to claim 10, comprising e. 12. The optical recording medium according to claim 7, wherein a main component of the second protective layer is a dielectric. 13. The method according to claim 13, wherein the second protective layer comprises Si ₃ N as a main component.
13. The optical recording medium according to claim 12, comprising at least one selected from _x (3 <X ≦ 4), SiO _x (0 <X ≦ 2), and ZnS. 14. A light absorption control layer comprising Ti,
The optical recording medium according to claim 7, comprising at least one selected from the group consisting of Cr, Fe, Ni, Zn, Zr, Nb, Mo, and W. 15. The method according to claim 15, wherein the light absorption control layer comprises Ag,
Al, Au, Bi, C, Co, Cu, Fe, Ga, G
e, Hf, In, Mo, N, Nb, Ni, O, Pb, S
The optical recording medium according to claim 14, comprising at least one selected from i, Sn, Ti, W, Zn, and Zr. 16. The optical recording medium according to claim 7, wherein a main component of the light quantity control layer is a dielectric. 17. A light quantity control layer comprising Si ₃ N
_{x (3 <X ≦ 4)} , SiO x (0 <X ≦ 2), an optical recording medium according to claim 16, wherein the at least one selected from ZnS. 18. The optical recording medium according to claim 7, wherein the light absorption control layer also functions as a heat conduction control element. 19. The thermal conductivity of the light absorption control layer is 1.5 ≦
8. The optical recording medium according to claim 7, wherein S ≦ 25 (S is thermal conductivity, unit is W / mK). 20. The optical characteristics of the light absorption control layer are such that at least 2 ≦ n ≦ 4 at the center wavelength of light used for recording.
5, and 0.2 ≦ k ≦ 4 (n is the refractive index, k is the extinction coefficient)
8. The optical recording medium according to claim 7, wherein the following condition is satisfied. 21. The optical characteristic of the light quantity control layer is at least 1.2 ≦ n ≦ 2 at the center wavelength of light used for recording.
2, and 0 ≦ k ≦ 0.1 (n is the refractive index, k is the extinction coefficient)
8. The optical recording medium according to claim 7, wherein the following condition is satisfied.