JPH0850739A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To realize an optical information recording medium in which repeating times of recording and reproducing are improved while maintaining optical properties despite a scanning speed. CONSTITUTION:A first dielectric layer 2, a recording thin film layer 3 a second dielectric layer 4 and a reflecting laser 5 are sequentially laminated on a board 1. Further, a thermal diffusion auxiliary layer 8 for diffusing the heat of the layer 5 to the optically substantially transparent for laser light rays for recording and reproducing is formed on the upper layer of the layer 5. Thus, equivalent effect to the increase of the thermal capacity of the layer 5 is obtained as seen from the incident side of the light. Even if the linear speed at the time of recording and reproducing is low, the repeating times of recording and reproducing can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium for recording and reproducing signals by irradiating a recording thin film layer formed on a substrate with a high energy beam to cause a phase change in the recording thin film layer. It is about.

[0002]

2. Description of the Related Art As an optical information recording medium (hereinafter, simply referred to as a recording medium), a recording material thin film layer (hereinafter, referred to as a recording material thin film layer composed of a metal thin film or an organic thin film on a disk-shaped, card-shaped, cylindrical, etc. substrate. Recording thin film layer) is formed. When this recording thin film layer is irradiated with a high-energy beam focused on a minute light spot of a submicron order diameter, a local state change occurs in the recording thin film layer. A technique for accumulating a signal by utilizing such a state change is already widely known. In particular, a recording medium using a magneto-optical material thin film or a phase-change material thin film as a recording thin film layer has been actively researched and developed because signals can be easily rewritten.

The recording medium usually has a multilayer film structure as shown in FIG. That is, in the recording medium A shown in FIG. 7, the substrate 1 composed of a resin plate, a glass plate or the like
A first dielectric layer (also referred to as an undercoat layer) 2 which also functions as an optical interference layer is provided on the above. Then, a light absorbing recording thin film layer 3 is provided on the upper surface of the first dielectric layer 2, and a second dielectric layer (also referred to as an overcoat layer) 4 which is a light interference layer is provided thereon. Next, the reflection layer 5 that improves the light absorption efficiency of the recording thin film layer 3 and functions as a heat diffusion layer is provided. Each of these layers is sequentially formed by a method such as sputtering or vacuum deposition, and finally a protective plate 7 is provided via the adhesive layer 6 to complete the recording medium A.

Next, in order to record a signal, a laser beam focused to a predetermined spot diameter is irradiated from the lower side of the substrate 1. Then, the laser beam passes through the substrate 1 made of a transparent material, and the first dielectric layer 2, the recording thin film layer 3, and the second
Through the dielectric layer 4 to reach the reflective layer 5. A part of the laser beam is transmitted from the reflective layer 5 to the adhesive layer 6 side, but the rest is reflected by the reflective layer 5 and irradiates the recording thin film layer 3. At this time, the spot of the laser beam heats a part of the recording thin film layer 3 and changes the state of the part. If this state change is a phase change type, it changes depending on the heating temperature, for example, it becomes amorphous by rapid heating and rapid cooling, and crystallizes by slow cooling. At this time,
A part of the recording thin film layer 3 tries to be heated and evaporated, but the evaporation is prevented due to the existence of the first dielectric layer 2 and the second dielectric layer 4. In particular, the first dielectric layer 2 functions as a protective layer that prevents the heat of the recording thin film layer 3 from being transferred to the substrate 1 and softening the substrate 1.

To reproduce the signal thus recorded, the recording medium A is irradiated with a converged laser beam. At this time, the reflectivity varies depending on the phase state (crystalline or amorphous state) of the recording thin film layer 3, and the output from the substrate 1 toward the outside also depends on the relationship with the refractive index or the permittivity with the first dielectric layer 2. The amount of reflected light that is reflected changes. Thus, the signal is reproduced by detecting the intensity of the reflected light beam.

The material and the film thickness of each layer differ depending on the purpose of using the recording medium A and its use conditions. For example, in order to rapidly diffuse the heat generated in the recording thin film layer 3 to the reflective layer 5, the film thicknesses of the recording thin film layer 3 and the second dielectric layer 4 are selected to be several tens of nm or less. Alternatively, Au or Al alloy having a large thermal conductivity is used as the reflective layer 5, and a sufficiently thick film thickness is selected so that almost no light is transmitted. The above configuration is commonly referred to as a quench configuration.

Recently, it has been revealed that it is important to optimize the relative magnitude of the amount of light absorption between the crystalline region and the amorphous region in order to reduce the strain. Has become. To achieve this, for example, A
It is disclosed that one solution is to make the thickness of the u reflective layer as thin as about 20 nm or less.
This is described, for example, in Japanese Patent Laid-Open No. 1-149238, Yamada et al .: "High Speed Overwrite Optical Disc", IEICE Technical Report Vol. 92, No. 377, P92, or JP-A-5-298747. Further, Japanese Patent Laid-Open No. 4-102243 discloses the use of a Si reflective layer instead of the metallic reflective layer 5 as a means for achieving the same object.

[0008]

When the reflective layer is thinned for the purpose of using it for high-speed overwriting, the function of the reflective layer as a heat diffusion layer is inevitably lowered, and the irradiation of laser beam is carried out. The cooling rate of the heating unit after completion is reduced.
Also, when a material having a low thermal conductivity is used for the reflective layer, the cooling rate is similarly reduced. For example, the thermal conductivity of crystallized silicon is said to be about 1/3 that of aluminum at around room temperature. Since the thermal conductivity of silicon itself decreases as the temperature rises, it becomes disadvantageous as a thermal diffusion layer under low linear velocity conditions, especially when a disk is rotated as a recording medium to perform a recording / reproducing operation.

In the case of heat mode recording, a decrease in cooling rate immediately affects recording sensitivity, erasing sensitivity, etc., but if recording, reproduction and rewriting are repeatedly performed on the recording medium, the number of repetition cycles is limited. Also affects.
More specifically, when the cooling rate is lowered, the time period during which the recording portion (recording thin film layer) is kept in a high temperature state becomes longer, and more thermal damage is likely to occur. Therefore, a recording medium designed for high-speed recording and reproduction is
If it is used under a low speed condition, that is, a condition in which the relative speed between the recording medium and the recording beam is small, there is a drawback that the allowable number of recording / reproducing cycles becomes small.

The present invention has been made in view of the above conventional problems, and optimizes the heat dissipation state of the reflective layer even when the reflective layer is thin, and allows the recording / reproducing allowable cycle of the recording thin film layer. An object of the present invention is to realize an optical information recording medium capable of improving the number of times regardless of the scanning speed of the recording medium.

[0011]

According to a first aspect of the present invention, there is provided a substrate which is a base of an information recording medium, a first dielectric layer provided on an upper surface of the substrate, and a first dielectric layer. A recording layer which is provided on the upper surface and causes a reversible state change between a crystalline phase and an amorphous phase by irradiation with a laser beam, a second dielectric layer provided on the upper surface of the recording layer, and a second dielectric An optical information recording medium provided on the upper surface of a layer, the reflective layer reflecting a part of a laser beam to the recording layer side, the upper surface of the reflective layer being substantially transparent to the laser beam. A heat diffusion auxiliary layer for diffusing the heat of the reflective layer is provided.

According to a second aspect of the invention of the present application, a protective layer which becomes an incident surface of a laser beam and protects a thin film laminated inside, a first dielectric layer provided on an upper surface of the protective layer, and a first dielectric layer are provided.
A recording layer that is provided on the upper surface of the dielectric layer and that causes a reversible state change between a crystalline phase and an amorphous phase by irradiation with a laser beam; and a second dielectric layer that is provided on the upper surface of the recording layer. A reflective layer that is provided on the upper surface of the second dielectric layer and reflects a part of the laser beam to the recording layer side; and a reflective layer that is provided on the upper surface of the reflective layer and is substantially transparent to the laser beam, A heat diffusion auxiliary layer for diffusing light, an isolation layer having a film thickness that does not cause light interference and provided on the upper surface of the heat diffusion auxiliary layer, and a substrate provided on the upper surface of the isolation layer and serving as a base of the information recording medium. , Are provided.

[0013]

According to the invention of the present application having such characteristics,
As seen from the laser beam incident side, the provision of a heat diffusion auxiliary layer that is optically transparent behind the reflection layer and diffuses the heat of the reflection layer is equivalent to increasing the heat capacity of the reflection layer. It has a layered structure. Therefore, even if the reflective layer is thin,
The heat diffusion efficiency can be secured. By doing so, even if the scanning speed of the recording medium is reduced, the spot heat accumulated in the reflective layer is also diffused appropriately, and the influence on the phase change of the recording layer is reduced. Further, the degree of freedom in optical design as a recording medium is increased.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical information recording medium in one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing the arrangement of an optical information recording medium (recording medium B) in this example. In this embodiment, the wavelength (λ) of the laser beam for irradiation is designed to be 780 nm.
A ZnS—SiO ₂ mixed film (undercoat layer) having a thickness of 92.9 nm was formed as the first dielectric layer 2 on a substrate 1 made of polycarbonate and having a thickness of 1.2 mm and a diameter of 120 mm.
To provide. Then, on the upper surface of the first dielectric layer 2, the thickness 22
A recording thin film layer 3 composed of a Ge ₂ Sb ₂ Te ₅ alloy thin film of nm is provided. Then, the second dielectric layer 4 is formed on this film.
As a result, a ZnS—SiO ₂ mixed film (upper layer) having a thickness of 157 nm is provided. An Au thin film layer having a thickness of 10 nm is provided as a reflective layer 5 on this layer, and a SiC layer having a thickness of 156 nm is provided as a heat diffusion assisting layer 8 on this layer, and each layer is laminated. The actually measured value of the optical constant (complex refractive index) of the heat diffusion auxiliary layer 8 is 2.5, and the film thickness of 156 nm corresponds to approximately λ / (2n) of the laser beam. However, n is the real part of the optical constant.

The above layers are sequentially formed by a sputtering method using Ar gas. Next, an ultraviolet curable resin layer having a thickness of about 10 μm is applied on the heat diffusion auxiliary layer 8 by a spin coating method and irradiated with ultraviolet rays to be cured to form a protective layer 9. In the recording medium B thus configured, a laser beam is made incident on the recording thin film layer 3 from the substrate 1 side at the time of recording a signal. The lower surface of the substrate 1 has a depth of 60 in order to guide a laser beam used for recording and reproduction along a track.
Spiral continuous grooves (grooves) having a width of nm and a width of 0.6 μm are engraved at a pitch of 1.2 μm.

FIG. 2 shows the cycle characteristics between the recording medium B having the thermal diffusion auxiliary layer 8 and the conventional recording medium A prepared separately for comparison and having no thermal diffusion auxiliary layer 8. Two
The optical characteristics (not shown) of the two recording media A and B are almost the same. The optical constants of the respective layers obtained by actual measurement are 4.55 + i1.3 when the recording thin film layer 3 is in an amorphous state.
5, it is 5.57 + i3.38 in the crystalline state.
In the first dielectric layer 2 and the second dielectric layer 4, the optical constant is 2.1, and in the reflective layer, 0.18 + i4.6.
It is 4. The calculation performed from the values of these optical constants shows that when the incident light is 100%, the absorptance of the recording thin film layer 3 is about 53% (Ac) in the crystal part and about 39% (Aa) in the amorphous part. is there. The reflectance of the recording medium is about 23% in the crystal part and about 7% in the amorphous part.
And the absorption ratio Ac / A between the crystal part and the amorphous part.
a was approximately 1.35.

To evaluate the recording characteristics, a laser beam is binary-modulated between a peak level (amorphization level) and a bias level (crystallization level) according to a recording signal, and a new signal is erased while erasing an old signal. Method of recording (so-called 1
Beam overwrite method) was used. A disc, which is a recording medium, was rotated at 1800 rpm, and overwriting was repeated at a position of diameter φ106 (linear velocity 10 m / s). The signal is in single frequency mode with 50% duty, and f1
Two signals (6.58 MHz) and f2 (1.88 MHz) were recorded alternately. The laser wavelength is 780 nm, and the N.V. A was 0.55. Regarding the recording power, the peak power is 14 mW and the bias power is 7 mW.
(Shown as 14/7 in FIG. 2) and a peak power of 11 mW,
The bias power was 5.5 mW (indicated by 11/5 in FIG. 2) under two conditions. The vertical axis of FIG. 2 represents the ratio of noise to the carrier signal (CNR), and the horizontal axis represents the number of repetitions of the recording operation (cycle number).

As is apparent from FIG. 2, the number of cycles depends on the power condition in the recording medium A having no heat diffusion auxiliary layer, and under the low power condition (11/5), the number of cycles almost changes during 10,000 cycles. However, in the high power condition (14/7), the cycle number C / N was decreased. On the other hand, in the recording medium B provided with the thermal diffusion auxiliary layer 8, it is found that the C / N does not change for 10,000 cycles under any power condition.

Materials used for the substrate 1 include PMMA and polycarbonate (P
C), a transparent resin plate such as amorphous polyolefin, a glass plate, a metal plate such as Al or Cu, or an alloy plate based on these is used. When an opaque substrate 1 such as a metal plate is used, it is necessary to reverse the stacking order of the layers in FIG. 1 and make the laser beam incident from the protective layer side.
At this time, if it is necessary to avoid the influence of light reflection from the substrate surface, an optical isolation layer (hereinafter, simply referred to as an isolation layer) 10 is provided on the upper surface of the substrate 1 as in the recording medium C shown in FIG. Set up. The isolation layer 10 may be a resin layer or a dielectric layer, but needs to be thick enough to neglect the light coherency.

On the other hand, as a means for guiding the laser beam used for recording / reproducing, concentric circular grooves may be used instead of the spiral grooves, or pit rows may be engraved with irregularities. The first dielectric layer 2 and the second dielectric layer 4 serve as a protective layer to suppress the thermal damage on the surface of the substrate 1 as described above, and the recording thin film layer 3 is sandwiched between the first dielectric layer 2 and the second dielectric layer 4. The deformation and evaporation of No. 3 can be suppressed. The first dielectric layer 2 and the second dielectric layer 4 have a higher melting point than the substrate 1 and the recording thin film layer 3, are transparent to a laser beam used for recording and reproduction, and have a hardness. It is necessary to have properties such as being large and not easily scratched. Also for this, the protective layer material used in a normal phase change type optical disk can be applied as it is.

That is, the first dielectric layer 2 and the second dielectric layer 4 are replaced by ZnS-SiO ₂ of the first embodiment,
For example, oxides such as SiO ₂ , ZrO ₂ , TiO ₂ and Ta ₂ O ₅ , nitrides such as BN, Si ₃ N ₄ , AlN and TiN, sulfides such as ZnS and PbS, carbides such as SiC, C
fluoride such aF _2, selenides ZnSe, etc., and ZnSe-SiO _2, SiNO such as mixtures thereof,
Alternatively, a diamond thin film, diamond-like carbon or the like can be used.

Next, the material used for the recording thin film layer 3 is a phase change material which undergoes reversible state change upon irradiation with a laser beam, and in particular, reversible between amorphous and crystal due to spot heat caused by irradiation with a laser beam. The one that causes a physical phase change is used. Typically, Ge-Sb-Te, Ge-T
e, In-Sb-Te, Sb-Te, Ge-Sb-Te
-Pd, Ag-Sb-In-Te, Ge-Bi-Sb-
Te, Ge-Bi-Te, Ge-Sn-Te, Ge-S
b-Te-Se, Ge-Bi-Te-Se, Ge-Te
A system such as —Sn—Au or a system obtained by adding an additive such as oxygen or nitrogen to these systems can be used.

These thin films are usually in an amorphous state when they are formed, but when they absorb the energy of a laser beam or the like, they are crystallized and the optical density becomes high. When actually used as a recording medium, at the time of recording a signal, the entire recording thin film layer 3 is crystallized in advance, a laser beam is narrowed and irradiated, and the irradiated portion is made amorphous to change the optical constant. Further, at the time of reproducing the signal, the recording thin film layer 3 is irradiated with a laser beam weakened to the extent that no phase change is caused, and the change in the intensity of the reflected light and the change in the intensity of the transmitted light are detected to reproduce the signal.

It has already been shown in Japanese Patent Laid-Open No. 5-298747 that the thickness of the recording layer is limited under the condition (eg Ac / Aa ≧ 1) for optimizing the light absorption amount in the crystal part and the amorphous part. ing. That is, the thickness of the recording thin-film layer 3 is irrespective of whether the layer is in the recorded state or the unrecorded state.
It is set so that a part of the laser beam can pass through the recording thin film layer 3.

For example, when the recording thin film layer 3 is made of a phase change material, the phase change material film (crystal phase) is used as a material for the first dielectric layer 2 and the second dielectric layer 4. Considering the transmittance when sandwiched between material layers (assuming infinite thickness) of the same material, the transmittance is at least about 1%, preferably 2 to
It is necessary to be about 3% or more. Further, the transmittance value needs to be about 10% or more as compared with the case where the phase change material film has an amorphous phase, and it is desirable to select each film thickness so that the condition is satisfied.

When the components reflected by the reflective layer 5 and re-incident in the recording thin film layer 3 are eliminated, the light interference effect is reduced. In this case, even if the film thicknesses of the second dielectric layer 4 and the reflective layer 5 are slightly changed, the reflectance of the entire recording medium and the recording thin film layer 3 are reduced.
It becomes impossible to control the absorption efficiency and so on. Therefore, also in the present invention, the film thickness limiting condition as disclosed in the specification of Japanese Patent Application Laid-Open No. 5-298747 is directly applied.

As the metal thin film used for the reflective layer 5, Au is most suitable because it has high reflectance, high touch resistance, and high thermal conductivity. Other than that, Al, C
It is possible to use a metal thin film of u, Ni or the like, or an alloy containing these as the main components and an additive. A as an additive
l, Cr, Cu, Ge, Co, Ni, Ag, Pt, P
The characteristics such as optical constants can be finely adjusted by using at least one material selected from the material group such as d, Co, Ta, Ti, Bi, Sb, and Mo.

The minimum condition for the heat diffusion auxiliary layer 8 is that the heat conductivity is higher than that of the resin material. In that sense,
All materials applied to the dielectric layer material used for the first and second dielectric layers can be used. However, a transparent material having a high thermal conductivity is desirable.

Y. S. I by Touloukian et al.
Volume 1 and Volume of Thermo Physical Properties of Matter published by FI / PLENUM
According to me2, published by Maruzen Co., Ltd., and edited by the Chemical Society of Japan, Chapter 2, Section 6.5, Chemical Handbook, various materials are proposed in addition to the above-mentioned SiC. For example, Si alone,
Oxide of Ta, nitride of at least one element selected from the group of Zr, Si, Ta, Ti, B and Al, or at least one selected from the group of Zr, Si, W, Ta, Ti and B There are two elements such as carbides. These materials are particularly suitable for use in the present invention because they have a high thermal conductivity of about one digit as compared with other oxides and nitrides and are chemically stable.

FIG. 4 is a diagram in which various substances mainly composed of a dielectric material are classified according to the magnitude of thermal conductivity. When the same material name had various values, the highest value was used. Alkaline earth elements Be, Mg, Ca, Sr, B of Group 2b of the Periodic Table
The oxide of a or the composite oxide between them has a large thermal conductivity, but is not suitable from the viewpoint of stability and toxicity.

The signal rewritable optical information recording medium of the present embodiment is similar to the case of forming an ordinary optical thin film,
Each layer can be formed by sequentially stacking each layer by a method such as vacuum deposition, magnetron sputtering, DC sputtering, ion beam sputtering, and ion plating. Whether or not the recording medium is designed as designed can be verified by measuring the reflectance and the transmittance of the completed recording medium using a spectrum meter and comparing them with values calculated in advance. In this case, the absorption in the recording thin film layer 3 and the absorption in the reflective layer 5 cannot be separated and directly measured, but the accuracy can be improved by performing the same verification with at least two kinds of wavelengths.

The structure of the recording medium may be a single plate structure as in the case of FIG. 1, but in addition to this, another protective plate 11 is bonded via a hot melt type adhesive layer 6 as shown in FIG. May be. Further, as shown in FIG. 6, two recording media may be laminated so as to be vertically symmetrical about the adhesive layer 6. Further, if necessary, a configuration in which the first dielectric layer 2 is omitted and a configuration in which the second dielectric layer 4 is omitted are also possible.

How to select the film thickness of each layer when the recording medium is required to have a certain optical property will be described in detail in the examples of Japanese Patent Application Laid-Open No. 5-298747. Therefore, this method can be used as it is. That is, no matter how many layers are laminated,
Given the optical constants of the substances forming each layer and the film thickness,
The reflectance, transmittance, and absorptance of each layer can be uniquely determined by the matrix method (see, for example, Hiro Kubota, "Wave Optics," Iwanami Shoten, 1971, Chapter 3). Therefore,
If the reflectance, the transmittance, and the absorptance are calculated by changing the film thickness of each layer by a constant step size, the result can be mapped for each item.

With such a map, it is possible to reversely select the film thickness of each layer that realizes a desired reflectance, transmittance, absorptance, etc. based on the map. However, as can be easily estimated, it is desirable that the number of layers to be incorporated in the optical calculation is as small as possible. That is, not only the labor required for calculation can be saved, but also the calculation accuracy can be improved. Therefore, the film thickness of the final layer, the heat diffusion auxiliary layer 8, is λ / 2 so that it can be excluded from the calculation.
It is preferable to select it in the vicinity of an integral multiple of n (λ is the laser wavelength and n is the refractive index of the thermal diffusion layer).

A material layer transparent to this wavelength is λ / 2n
Even if it is formed with a thickness that is an integral multiple of, the optical characteristics of the entire recording medium viewed from the recording surface side do not change. Even if the thickness of the heat diffusion auxiliary layer 8 does not exactly match an integral multiple of λ / 2n, heat can be efficiently diffused. However, from an optical point of view, the accuracy of the film thickness of the heat diffusion auxiliary layer 8 is ± λ
It is desirable to suppress the fluctuation to about / 8n.

The complex refractive index (optical constant) of the substance forming each layer is calculated, for example, by forming a thin film on a glass plate and measuring the film thickness, reflectance and transmittance, or by an ellipsometer. Can be obtained by the method of using.

As another embodiment, the heat diffusion auxiliary layer 8 is made of Si.
The media to which the film and the Ta ₂ O ₅ film were applied were constructed respectively.
A recording medium having no heat diffusion auxiliary layer was also prepared for comparison. The substrate 1 of the disk is 1.2 m, which is the same as the above-mentioned embodiment.
81m thick Ta using m-thick polycarbonate plate
_{The 2} O ₅ thin film is used as the first dielectric layer 2 and a G layer having a thickness of 30 nm is used.
The alloy thin film of e _21.5 Sb _24.7 Te _53.8 is used as the recording thin film layer 3, and the ZnS—SiO ₂ thin film (SiO ₂ : 2) of 154 nm is used.
5 mol%) as the second dielectric layer 4, and the thickness of A is 10 nm.
Each layer was formed by the sputtering method using the u thin film as the reflective layer 5. Then, as the heat diffusion auxiliary layer 8, a Si layer, T
by sputtering a ₂ O ₅ layer or ZnS-SiO ₂ layer was formed respectively 99 nm, 186 nm, a thickness of 186 nm. The film thickness of the thermal diffusion auxiliary layer 8 is λ / (2
n).

When the above-mentioned two recording media were evaluated by the above-mentioned evaluation method, the recording medium with the thermal diffusion auxiliary layer 8 showed a longer cycle number than both of the recording media without the thermal diffusion auxiliary layer 8. . In addition, it was found from the comparison of the three materials that the number of cycles of the recording medium using the Si layer having the highest thermal conductivity was the longest.

[0039]

As described above, according to the present invention, even if the reflective layer forming a part of the recording medium is thinned, the heat storage state of the laser beam in the recording layer and the reflective layer can be optimized, and at the time of recording / reproducing. Signals can be recorded and reproduced under low linear velocity conditions. Further, the allowable number of times of recording and reproduction is increased, the signal level due to the phase change is less likely to deteriorate, and an excellent recording medium can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of an optical information recording medium in a first embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the reflectance change amount and the light absorptance difference between a recording medium having a thermal diffusion auxiliary layer and a recording medium having no thermal diffusion auxiliary layer, with the number of cycles as an axis.

FIG. 3 is a diagram in which various materials used for each layer of the optical information recording medium are classified by thermal conductivity.

FIG. 4 is a sectional view showing the structure of the optical information recording medium in the second embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of the optical information recording medium in the third embodiment of the present invention.

FIG. 6 is a sectional view showing a structure of an optical information recording medium in a fourth example of the present invention.

FIG. 7 is a cross-sectional view showing a configuration example of a conventional optical information recording medium.

[Explanation of symbols]

 1 Substrate 2 First Dielectric Layer 3 Recording Thin Film Layer 4 Second Dielectric Layer 5 Reflective Layer 6 Adhesive Layer 7 Protective Plate 8 Thermal Diffusion Auxiliary Layer 9 Protective Layer 10 Isolation Layer 11 Protective Plate

Claims (12)

[Claims] 1. A substrate serving as a base of an information recording medium, a first dielectric layer provided on the upper surface of the substrate, and a crystal provided by laser beam irradiation provided on the upper surface of the first dielectric layer. A recording layer that causes a reversible state change between a phase and an amorphous phase, a second dielectric layer provided on the upper surface of the recording layer, and a laser provided on the upper surface of the second dielectric layer. In an optical information recording medium comprising a reflective layer that reflects a part of a light beam to the recording layer side, on the upper surface of the reflective layer, the heat of the reflective layer is substantially transparent to the laser beam. An optical information recording medium comprising a heat diffusion auxiliary layer for diffusing. 2. A protective layer that serves as an incident surface of a laser beam and protects a thin film laminated inside, a first dielectric layer provided on an upper surface of the protective layer, and the first dielectric layer. A recording layer which is provided on the upper surface and which causes a reversible state change between a crystalline phase and an amorphous phase by irradiation with a laser beam; a second dielectric layer provided on the upper surface of the recording layer; A reflective layer provided on the upper surface of the dielectric layer and configured to reflect a part of the laser beam to the recording layer side, and provided on the upper surface of the reflective layer, and substantially transparent to the laser beam, the reflective layer A heat diffusion auxiliary layer for diffusing the heat of, an isolation layer provided on the upper surface of the heat diffusion auxiliary layer and having a film thickness that does not cause interference of light, and an isolation layer provided on the upper surface of the isolation layer, the base of the information recording medium. Optical information storage device, which is characterized in that Media. 3. The optical information recording medium according to claim 1, wherein the reflective layer is made of a metal thin film and has a film thickness of 20 nm or less. 4. When the recording layer undergoes a phase change between a crystalline portion and an amorphous portion due to the incidence of a laser beam, the absorptance of the crystalline portion is Ac and the absorptance of the amorphous portion is Aa. Then, the film thickness of each layer including the first dielectric layer, the second dielectric layer, the recording layer, and the reflective layer is adjusted so that the absorption ratio Ac / Aa of the laser beam is 1 or more. The optical information recording medium according to claim 1 or 2, wherein the optical information recording medium is set. 5. When the wavelength of a laser beam used for recording and reproduction is λ, the refractive index of the heat diffusion auxiliary layer is n, and a positive integer is m, the film thickness of the heat diffusion auxiliary layer is approximately (m ×). λ) / (2
Xn), The optical information recording medium according to claim 1 or 2. 6. The optical information recording medium according to claim 1, wherein the heat diffusion auxiliary layer is made of Si. 7. The optical information recording medium according to claim 1, wherein the heat diffusion auxiliary layer is composed of an oxide of Ta. 8. The thermal diffusion auxiliary layer is made of Zr, Si, T.
The optical information recording medium according to claim 1 or 2, wherein the optical information recording medium comprises a nitride of an element selected from a, Ti, B, and Al. 9. The thermal diffusion auxiliary layer is formed of Zr, Si, W,
The optical information recording medium according to claim 1 or 2, wherein the optical information recording medium comprises a carbide of an element selected from Ta, Ti, and B. 10. The optical information recording medium according to claim 1, wherein the thermal diffusion auxiliary layer is formed of either a diamond thin film or a diamond-like carbon film. 11. The optical information recording medium according to claim 1, wherein the reflective layer is made of an Au thin film. 12. The recording layer is mainly composed of a Ge—Sb—Te alloy.
The optical information recording medium described.