JP2001084645A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain excellent responsiveness for a long period of time without deterioration in spite of the repetition of writing/reading by providing the above medium with a high-thermal conductivity thin film directly formed at least one surface of a super-high resolution. SOLUTION: Polycarbonate is used for a substrate 1 and AlN is used for the high-thermal conductivity thin film 2. A film consisting of an inorganic material essentially consisting of a transition metal oxide deposited by evaporation using a sintered compact consisting of 90 wt.% Co3O4 and 10 wt.% SiO2 as a target is used for the super-high resolution film 3. A phase transition material of a Ge-Sb-Te system is used for the recording film 6. The heat accumulated in the super-high resolution film 3 diffuses into the high-thermal conductivity thin film 2 and is eventually efficiently radiated. Consequently, the temperature elevation of the super-high resolution film by repetitive reproduction operations is small. At this time, the high-thermal conductivity thin film 2 is so constituted that its thermal conductivity is made higher than the thermal conductivity of the substrate 1 existing on the side opposite to the super-high resolution film 3 with which the same is in contact.

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 capable of reading / writing information at a high recording density.
The present invention relates to an optical information recording medium which has high reliability with respect to repetition of a recording / reproducing operation and is suitable as a disk-shaped storage medium which can cope with high-speed rotation.

[0002]

2. Description of the Related Art As a recording medium of an optical information recording system, a CD (compact disk) and an LD (laser disk) have been conventionally used, and more recently, a DVD (digital video disk) having a recording density seven times or more that of a CD. Has been put to practical use. However, the improvement of the information storage capacity of a recording medium is always a proposition, and in order to handle a large amount of information such as computer graphics, it is necessary to achieve a higher density.

[0003] By the way, DVD (Digital Video
One of the techniques for increasing the density of recording on discs) is the application of super-resolution films. Note that this super-resolution film is a thin film formed on the light incident surface side of a recording film made of an inorganic material containing a transition metal oxide as a main component. It has a function of reducing the spot diameter, and enables high recording density.

Here, one of the phenomena responsible for the mechanism of reducing the spot diameter by the super-resolution film is a light absorption and saturation phenomenon. This is a phenomenon obtained by having nonlinear optical characteristics such that light having an intensity is transmitted and light having an intensity lower than that is absorbed.

At present, such a super-resolution film includes, for example, a phthalocyanine-based organic film and a chalcogenide-based compound which are found in JP-A-8-96412 and the like. Japanese Patent No. 162564 proposes an attempt to provide a heat radiation layer in contact with a thermochromic layer in a storage medium using a thermochromic material of an organic material as a super-resolution film.

[0006]

The prior art described above does not give sufficient consideration to the deterioration of the optical information storage medium, and has a problem in the reliability of repetition of the recording / reproducing operation. When used under severe operating conditions such as a RAM (random access memory) for a computer, it has been difficult to guarantee a sufficient number of recording / reproducing operations.

When the recording density of a DVD or the like is increased, the energy density of a laser beam irradiated at the time of writing / reading information becomes extremely high locally in a recording medium. In addition, since an organic material is used for the super-resolution film, deterioration of the super-resolution film occurs due to repetition of recording and reproduction, and the above-described problem occurs.

In the prior art, an optical information recording medium that achieves super-resolution by using a thermochromic substance includes:
While rotating the disk that is the base,
If the (same track) is repeatedly irradiated with laser light for reproduction, the temperature rises due to heat accumulation, and the thermochromic phenomenon may be saturated.

For this reason, as the number of laser beam irradiation increases, the transmittance does not return to the original value, and the size of the light transmitting portion increases, so that the effective spot diameter cannot be reduced and the specification performance cannot be maintained. There is a problem that if the transmittance changes slowly due to a temperature change, it is difficult to cope with high-speed access.

Therefore, in the prior art, a super-resolution film having high super-resolution characteristics which can guarantee a long-time repetitive still reproduction operation, is capable of high-speed response, is excellent in productivity, and exhibits its function sufficiently. There is a problem that it is difficult to obtain an optical recording medium having a film structure that can be formed.

An object of the present invention is to provide an optical information recording medium which has a high recording density, does not deteriorate even when information is repeatedly written / read, and can maintain excellent responsiveness for a long period of time. Is to do.

[0012]

An object of the present invention is to provide an optical information storage device comprising a super-resolution film made of an inorganic material containing at least a transition metal oxide between a substrate and a recording film made of a phase change material. In the medium, a high thermal conductive thin film directly formed on at least one surface of the super-resolution film is provided, and the high thermal conductive thin film is placed on the surface opposite to the surface where the high thermal conductive thin film is in contact with the super-resolution film. This is achieved by forming the material having a higher thermal conductivity than the thermal conductivity of the member formed in the above.

Here, a high thermal conductive thin film directly formed on at least one surface of the super-resolution film is provided, and the high thermal conductive thin film has a thermal conductivity higher than that of the super-resolution film. It may be formed of a material having the same.

Further, the object is to provide a super-resolution film made of an inorganic material containing at least a transition metal oxide on the one surface of a substrate on which information is recorded on one surface by forming pits. In the optical information recording medium, a high-thermal-conductivity thin film formed between the super-resolution film and one surface of the substrate is provided, and the high-thermal-conductivity thin film is referred to as a super-resolution film. This is achieved by forming the material having a higher thermal conductivity than that of the member formed on the surface opposite to the contacting surface.

Here, the high thermal conductive thin film may be formed of a material having a thermal conductivity higher than that of the super-resolution film.

Further, in any one of the above, the super-resolution film is made of cobalt, iron, nickel, chromium, vanadium,
The first oxide containing at least one element selected from manganese and the second oxide containing at least one element selected from silicon, titanium, sodium, and calcium are formed of a material containing In any case, the object of the present invention can be achieved, and at this time, the metal element forming the first oxide may be cobalt.

Further, at this time, the thermal conductivity of the material constituting the high thermal conductive thin film may be set to 0.01 [cal / cm.sec..degree. C.] or more. The transmittance of the high thermal conductive thin film at the wavelength of the light used may be 80% or more.

At this time, the high thermal conductive thin film may be at least one compound selected from metal oxides, metal nitrides, metal carbides, metal halides, and metal sulfides. When the high thermal conductive thin film is made of alumina, silica-alumina, zirconia-alumina, beryllia, aluminum nitride, zirconia nitride, silicon nitride, tantalum nitride, titanium nitride, silicon carbide, tantalum carbide, titanium carbide, boron carbide, magnesium fluoride, fluorine fluoride It may be a crystalline compound selected from calcium fluoride, barium fluoride, and zinc sulfide.

The thickness of the super-resolution film is 10 nm or more and 500 nm or less, and the thickness of the high thermal conductive thin film is 10 nm.
m or more and 400 nm or less.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical information storage medium according to the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows a first embodiment of the present invention.
This is an embodiment when applied to an optical disk for M,
In the figure, 1 is a substrate, 2 is a high thermal conductive thin film, 3 is a super-resolution film, 4 is a protective film, 5 is a reflective film, and 6 is a recording film.

In this embodiment, the substrate 1 is made of polycarbonate, the high thermal conductive thin film 2 is made of AlN, and the super-resolution film 3 is made of 90% by weight of Co ₃ O ₄ -10% by weight of SiO ₂ . A film made of an inorganic material containing a transition metal oxide as a main component and deposited using a body as a target is used. Protective film 4
The SiO ₂ is in, and the reflective film 5 using s husband Al-Ti, the recording film 6 using a Ge-Sb-Te-based phase change material.

The optical disk shown in FIG. 1 was manufactured by the following steps. First, as the substrate 1, a thickness of 0.6 m
A disc-shaped member having a diameter of 120 mm and a diameter of 120 mm is prepared. Then, on one surface (the upper surface in the figure) of the high thermal conductive thin film 2
Is formed to a thickness of 25 nm, and a super-resolution film is
The film was formed to a thickness of nm. After forming a protective film 4 with a thickness of 90 nm thereon, a recording film 6 was formed with a thickness of about 20 nm. Further, after forming the protective film 4 to a thickness of about 90 nm, a reflective film 5 was formed thereon to a thickness of about 200 nm.

In this manner, the substrate 1 on which a plurality of films are formed
Were bonded together with the reflective film 5 as a back, and then bonded using an ultraviolet curable resin to obtain a desired optical disk for RAM. Here, for the substrate 1, polycarbonate, polyolefin, glass, or the like is used according to the required specifications. In the first embodiment, for example,
As described above, polycarbonate is used.

Next, the high thermal conductive thin film 2 is made of, for example, Al ₂ O
₃ (alumina), SiO ₂ -Al ₂ O ₃ (silica-alumina), Zr
O ₂ -SiO ₂ (zirconia-alumina), BeO (beryllia), AlN (aluminum nitride), ZrN (zirconia nitride), Si ₃ N ₄ (silicon nitride), TaN (tantalum nitride), TiN
(Titanium nitride), SiC (silicon carbide), TaC (tantalum carbide), TiC (titanium carbide), B ₄ C (boron carbide), MgF ₂ (magnesium fluoride), CaF ₂ (calcium fluoride), BaF
₂ Made of any material selected from metal oxides, metal nitrides, metal carbides, metal halides, and metal sulfides with high thermal conductivity such as (barium fluoride) and ZnS (zinc sulfide). However, in the first embodiment, AlN is used as described above.

Next, FIG. 2 shows a second embodiment in which the present invention is similarly embodied as an optical disk for RAM. The optical disk for RAM of FIG. 2 is different from the embodiment described in FIG. The point is that the high thermal conductive film 2
And that the positional relationship between the super-resolution film 3 and the super-resolution film 3 is opposite.

That is, in the embodiment of FIG. 1, the high thermal conductive film 2 is formed on the substrate 1 first, and then the super-resolution film 3 is formed. In the embodiment of FIG. First, a super-resolution film 3 is provided, and then a high thermal conductive thin film 2 is formed.

Next, the operation of these embodiments will be described. In the optical disks for RAM shown in FIGS. 1 and 2, light for writing information is incident from the substrate 1 side as shown by arrows in the drawings. When reading information,
After passing through the recording film 6, the light is rejected by the reflection film 5 and returns to the light source side to be introduced into a pickup (not shown).

At this time, the incident light is a laser beam. When the recording density is increased by the super-resolution film 3, the energy density of the beam becomes particularly high. A considerable amount of heat is locally generated therein, and the temperature rises.

However, at this time, in this embodiment, since the high thermal conductive film 2 is in contact with one surface of the super-resolution film 3, when the heat is generated in the super-resolution film 3, this heat is It works so as to efficiently dissipate, and as a result, the temperature rise of the super-resolution film 3 can be suppressed.

FIG. 3 shows the ratio of the amplitude of the reproduction signal by the shortest pit and the amplitude of the reproduction signal by the longest pit of the recording track to the number of repetitions of information writing / reading of the optical disk, that is, the amplitude ratio characteristic. By evaluating this characteristic, the strength of the signal obtained from the shortest pit can be determined, and the performance can be verified.

In FIG. 3, the solid line shows the characteristics of the optical disk according to the embodiment of the present invention shown in FIGS. 1 and 2, and the broken line shows the characteristics of the optical disk prepared as a comparative example without forming the high thermal conductive thin film. Here, the longest pit length of the target optical disk is 0.7 μm, and the shortest pit length is 0.3.
μm, and the reproduction conditions are a linear velocity of 10 m / s and a reproduction power of 3.0 mW.

As is apparent from FIG. 3, the optical disk having the high thermal conductive thin film, that is, the optical disk according to the embodiment of the present invention shown in FIGS. Irrespective of the order of the super-resolution films 3, the amplitude ratio which initially showed 85% is the number of times of repetitive reproduction of 1500
There was almost no change even after exceeding 0 times.

On the other hand, the comparative optical disk having no high thermal conductive thin film has the same initial characteristics as the 85% amplitude ratio, but it decreases as the number of repetitions increases, and the number of repetitions reaches 12,000. By the way, it is less than 60%.

This is because, in the comparative example, the time required for the super-resolution film to be exposed to a high temperature due to the repetitive reproduction operation is prolonged, which causes deterioration, and the resolution improving function of the super-resolution film is not realized. Indicates that you can no longer read.

More specifically, in the case of an optical disk having no high thermal conductive thin film, when information is read from the optical disk under the above-mentioned reproducing conditions, it takes less than a few milliseconds to several tens of milliseconds to complete one round of the same track. It is considered that the heat was not completely radiated from the resolution film, and as a result, the time during which the super-resolution film was exposed to a high temperature was prolonged, and the amplitude ratio was reduced by the repeated operation.

On the other hand, in the case of the embodiment shown in FIGS. 1 and 2, that is, in the case of an optical disk provided with a high thermal conductivity thin film, at least one of the upper and lower surfaces of the super-resolution film has high thermal conductivity. The heat stored in the super-resolution film is diffused to the high-thermal-conductivity thin film and is efficiently radiated due to the provision of the conductive thin film. As a result, the temperature of the super-resolution film increases due to the repetitive reproduction operation. It is considered that the deterioration was sufficiently suppressed.

At this time, the thermal conductivity of the high thermal conductive thin film is
The member on the side opposite to the super-resolution film with which it is in contact
(For example, the substrate 1 in the case of the embodiment of FIG. 1 and the protective film 4 in the case of the embodiment of FIG. 2). I know.

From the above, it is desirable that the thermal conductivity of the high thermal conductive thin film 2 be higher than the thermal conductivity of the substrate 1 in the case of the embodiment of FIG. In this case, it is desirable that the thermal conductivity of the protective film 4 be higher than that of the protective film 4.

Next, as a comparative example, an optical disk in which an amorphous SiO ₂ film having low thermal conductivity was formed in place of the high thermal conductivity thin film, and a high thermal conductivity thin film as in the embodiment shown in FIG. 1 or FIG. Using an optical disk on which an AlN film is formed as a thin film,
FIG. 4 shows the results of evaluating the dependence of the refractive index of the super-resolution film on the laser intensity for these.

In FIG. 4, the solid line indicates the characteristics of the optical disk on which the high thermal conductive thin film made of AlN is formed,
The characteristics of the comparative example in which an SiO ₂ film was formed are shown here, where white circles indicate a linear velocity of 6 m / s, and black circles indicate a linear velocity of 10 m / s.
/ S.

First, as is apparent from the characteristics indicated by the broken line in FIG. 4, in the comparative example in which the SiO ₂ film is provided, the change in the refractive index decreases as the linear velocity increases, and the resolution improving function of the super-resolution film decreases. You can see. This is because the change in temperature of the super-resolution film due to laser irradiation was reduced by the high-speed rotation of the disk.

On the other hand, from the characteristics of the solid line, as in the embodiment of the present invention, in the disk provided with the AlN film having high thermal conductivity, a large change in the refractive index can be obtained even when the linear velocity is changed. It can be seen that a sufficiently large change in the refractive index can be obtained even at a linear velocity.

Here, when the laser intensity required to cause a change in the refractive index of the super-resolution film in such an optical disk was verified, the optical disk provided with the high thermal conductive thin film according to the present invention was about 1 mW. It has been found that a change in the refractive index occurs at a smaller laser intensity.

Next, FIG. 5 shows the signal intensity characteristics represented by C / N when the mark length (pit length) is changed for the above two types of optical discs. The broken line is the characteristic of the optical disk according to the present invention having the high thermal conductive thin film of the present invention, and the broken line is the characteristic of the comparative example in which the SiO ₂ film was formed instead of the high thermal conductive thin film. In the case of s, the black circle indicates the case of the linear velocity of 10 m / s.

As shown in the figure, in the case of the comparative example indicated by the broken line, as the linear velocity increases, the C / N decreases at a larger mark length. In the case of (1), it can be seen that a high C / N is maintained up to a small mark length even when the linear velocity increases.

From this, it is possible to read a signal having a small mark length by providing a high thermal conductive thin film, that is, in the case of the present invention, and therefore, according to the present invention, it is possible to achieve higher density recording. It can be seen that it is possible to cope with a large capacity.

Next, the dependence of the resolution improving function of the super-resolution film on the thickness of the high thermal conductive thin film and the super-resolution film was examined. When examining the thickness of the high thermal conductive thin film,
Regardless of the film made of any material, if the film is so thick that the light transmittance drops below 80%, light is scattered, and a problem that sufficient light does not return to the pickup is observed.

On the other hand, when the transmittance is 80% or more, the reflected light is efficiently introduced into the pickup.
It can be seen that data can be read under a good S / N ratio. Therefore, from this, it is preferable that the transmittance of the high thermal conductive thin film is 80% or more.

When the above-mentioned materials are used, the thickness of the highly thermally conductive thin film at which the transmittance becomes 80% differs depending on the material.
However, in any case, when the film thickness exceeds 400 nm,
Light transmittance is reduced due to scattering, etc., and the transmittance is 80%
Below.

On the other hand, if the film thickness is small, the stored heat cannot be sufficiently transferred, and cannot play a role as a high thermal conductive thin film. Specifically, when any of the above materials is used, the film pressure is 10 n
If it is less than m, the heat conduction effect is weakened.

As a result of the above, it is desirable that the thickness of the high thermal conductive thin film of the present invention be 10 nm or more and 400 nm or less.

Next, the super-resolution film is made of a material whose refractive index changes according to temperature, and is a first oxide having at least one element selected from cobalt, iron, nickel, chromium, vanadium and manganese. When a super-resolution film is formed using a material in which a second oxide having at least one element selected from silicon, titanium, sodium, and calcium is mixed, a change in refractive index due to laser irradiation is large, which is preferable. . Here, the content of the first oxide is desirably from 80% by weight to 98% by weight.

Further, when the film thickness required for obtaining the resolution improving function by the super-resolution film was examined, it was found that even when the above-mentioned high thermal conductive thin film was formed, the maximum was 500 n.
If the super-resolution film is formed to a thickness of at least m, the region that can be sufficiently heated is reduced, and the function of improving the resolution by the high thermal conductive thin film is weakened.

On the other hand, when the super-resolution film was thinner than 10 nm, sufficient super-resolution characteristics could not be obtained. As a result, the thickness of the super-resolution film in the present invention is desirably 10 nm or more and 500 nm or less.

Therefore, according to the above embodiment, even if the recording density is increased, there is no fear of deterioration due to repeated writing / reading of information, and the RAM maintains excellent responsiveness for a long period of time.
Optical disk can be easily obtained.

Next, a third embodiment of the present invention will be described.
This will be described with reference to FIG. In the embodiment of FIG. 6, as shown, a high-thermal-conductivity thin film 2 is formed on both surfaces of a super-resolution film 3 to form an optical disk for RAM. It is the same as the embodiment and, therefore, this embodiment corresponds to a combination of the embodiment of FIG. 1 and the embodiment of FIG.

The RAM optical disk shown in FIG.
It was produced by the following steps. First, as in the embodiment shown in FIG. 1, a high thermal conductive thin film 2 made of AlN is formed on one surface of a polycarbonate disc-shaped substrate 1 to a thickness of 25 nm, and a superconducting film made of Co ₃ O ₄ is formed on the upper surface thereof. 1 resolution film
It was formed with a thickness of 00 nm.

Further, a high thermal conductive thin film 2 also made of AlN is formed thereon to a thickness of 120 nm,
An O ₂ protective film 4 was formed to a thickness of 50 nm. Further, after the recording film 6 of the phase change material is formed to a thickness of 20 nm, the SiO ₂ protective film 4 is formed again to a thickness of 40 nm, and finally, the reflective film 5 made of Al-Ti is formed to a thickness of 100 nm. Formed.

Here, the thickness of the substrate 1 is 0.6 mm, and in this embodiment, the two substrates 1 formed as described above are formed by using an ultraviolet ray effect resin, After forming a 1.2 mm thick optical disk, the change in the ratio of the reproduction amplitude of the shortest pit and the longest pit in repeated reproduction was examined as described above. The reproduction conditions at this time were the same as those in the first embodiment described with reference to FIG.

As a result, since the optical disk shown in FIG. 6 also has the high thermal conductive thin film 2, the number of repetitions is one.
It was found that the ratio between the reproduction amplitude of the shortest pit and the reproduction amplitude of the longest pit did not change even after more than 8000 times, and therefore, it was found that deterioration of the signal due to repeated reproduction could be sufficiently suppressed.

Next, when the change in the refractive index with respect to the laser light intensity of the super-resolution film 3 was examined, even when the linear velocity was 10 m / s, the change in the refractive index was observed by the laser irradiation with the intensity of only 1 mW. . When irradiation was performed at an intensity of 4 mW, the refractive index of the super-resolution film 3 was 2.12, and a large change in the refractive index was realized.

Next, optical disks were manufactured by using various high thermal conductive materials shown in Table 1 below for the high thermal conductive thin film 2. The optical disk at this time has the same structure as the embodiment of FIG.

[0063]

[Table 1]

Table 1 shows the names of materials that can be used for the high thermal conductive thin film and their thermal conductivity κ (cal / cm · se
c · ° C), and 3 m / s, 6 m / s, 10 m / s, 12 m
/ S amplitude ratio when rotating the disk at linear velocity (%)
Here, the amplitude ratio is obtained by the same method as in the embodiment of FIG. On the other hand, the thermal conductivity κ of the super-resolution film used in this embodiment is 0.01.

From Table 1, it can be seen that the thermal conductivity κ is 3.1, 0.53,
0.10 and BN, BeO,
It is understood that a high thermal conductivity thin film made of MoSi ₂ can provide a high amplitude ratio even at a linear velocity of 12 m / s, while MgO, SiC, Al ₂ O ₃ , AlN, and ZrB whose thermal conductivity is less than 0.1. _In Fig. ₂ , a high amplitude ratio was obtained up to a linear velocity of 10 m / s, but at a linear velocity of 12 m / s, the amplitude ratio was about 70%, indicating that a sufficient amplitude ratio could not be obtained.

From this table, it can be seen that the thermal conductivity κ is 0.07
In the case of the following high thermal conductive thin films of TiC, Si ₃ N ₄ , and TiN, a high amplitude ratio was obtained up to a linear velocity of 6 m / s, but the amplitude ratio decreased at a linear velocity of 10 m / s or more. found to put away, SiO ₂ further thermal conductivity κ is less than 0.01
In the case of ZrO ₂ and ZrO ₂ , a high amplitude ratio was obtained at a linear velocity of 3 m / s, but a high amplitude ratio was not obtained at a linear velocity of 6 m / s.

From the above, considering the practical access speed of the optical disk, it is not preferable to use SiO ₂ or ZrO ₂ . Further, in order to obtain a sufficient amplitude ratio even at a linear velocity of 6 m / s or more, it is preferable to use a material having a thermal conductivity κ of 0.01 or more as the high thermal conductive thin film. Then, the thermal conductivity κ of the super-resolution film used in this embodiment is 0.5.
Therefore, if the high thermal conductivity thin film has a thermal conductivity of 0.01 or more in the thermal conductivity κ of the super-resolution film, the function of the super-resolution film can be obtained even at high speed rotation. Can be sufficiently expressed.

Further, the thermal conductivity κ of the high thermal conductive thin film is equal to
When it is 07 or more, a high amplitude ratio can be obtained even at a high speed of 10 m / s or more. More preferably, when the thermal conductivity κ is 0.10 ° C. or more, the linear velocity becomes 12 m / s.
A high amplitude ratio could be obtained even under a disk rotation of s.

The high thermal conductive material having a thermal conductivity κ higher than that of the super-resolution film used in the embodiment of the present invention is not shown in Table 1, but In addition, SiO ₂ —Al ₂ O ₃ , ZrO ₂ —SiO ₂ ,
_{ZrN, TaN, TaC, B 4} C, MgF 2, CaF 2, Ba
F ₂ , ZnS and the like can be cited, and even if the present invention is carried out using these, the same effects as in the above embodiment could be obtained.

Here, the same was true for the optical disk in which the high thermal conductive thin film shown in FIG. 6 was formed above and below the super-resolution film, and the same good characteristics were obtained.

The above is an embodiment in which the optical information recording medium according to the present invention is applied to an optical disk for a RAM.
The present invention is also applicable to an OM (read only memory) disk. Hereinafter, an embodiment of the present invention using this ROM optical disk will be described.

FIG. 7 shows a ROM according to an embodiment of the present invention.
In the figure, reference numeral 7 denotes pits written with information. In addition, the substrate 1, the high thermal conductive thin film 2, the super-resolution film 3, the protective film 4, and the reflective film 5 This is the same as the previously described embodiment. The arrow in the figure indicates the direction of light for reproduction.

The embodiment shown in FIG. 7 is similar to the embodiment shown in FIG.
Except for the recording film 6 in the embodiment of the AM optical disc,
In this case, information is recorded by the pits 7, where the substrate 1 is polycarbonate, the high thermal conductive thin film 2 is AlN, and the super-resolution film 3 is 90% by weight Co ₃ O ₄ −.
Thin film was deposited to 10 wt% SiO ₂ sintered body as the target, SiO ₂ the protective layer 4, is it the reflecting film 5 Al-
Ti was used for each.

Next, the optical disk shown in FIG. 7 was prepared as follows. First, using a laser, ROM
A pit pattern having information for use is formed on a predetermined photoresist, and then the pit pattern is transferred to a Ni plate for a mold to form a mold, and the mold is injection-molded with polycarbonate. The substrate 1 on which the pits 7 are formed is obtained. Here, the substrate 1 has a thickness of 0.6 mm,
The pit 7 was a disk having a diameter of 120 mm. The size of the pit 7 was set to 0.7 μm for the shortest pit and 0.3 μm for the minimum pit.

Next, on the substrate 1, AlN is first formed as a high thermal conductive thin film 2 to a thickness of 25 nm, and a sintered body of 90 wt% Co ₃ O ₄ -10 wt% SiO ₂ is deposited thereon. Super-resolution film 3 having a thickness of 100 nm
Then, after forming an SiO ₂ protective film 4 to a thickness of 120 nm, an Al—Ti-based reflective film 5 is formed to a thickness of 100 nm.
Formed.

The substrate 1 thus formed is laminated with an ultraviolet-curing resin, with the reflective film 5 as a back, and 1.2 substrates are bonded.
mm ROM disk. At the same time, as a comparative example, a ROM having the same configuration only with no high thermal conductive thin film
Discs were also made. Then, the ROM optical disk according to the embodiment of FIG. 7 was verified by comparison with that according to the comparative example.

First, since the ROM optical disk according to the embodiment of FIG. 7 has the high thermal conductive thin film 2, even if the number of readouts exceeds 15,000, the ratio of the reproduction amplitude of the shortest pit to the reproduction amplitude of the longest pit is obtained. That is, it was found that there was no change in the amplitude ratio, and signal deterioration due to repeated reproduction was extremely small. On the other hand, in the optical disc according to the comparative example having no high thermal conductive thin film, the amplitude ratio decreases as the number of repetitions increases, and after performing 12000 times, the amplitude ratio decreases.
Cut 5%.

Therefore, according to the embodiment shown in FIG. 7, it is possible to sufficiently increase the storage density without concern about the performance degradation, and there is no fear of the performance degradation due to the information reproducing operation. In addition, it is possible to easily obtain a high-density ROM optical disk capable of maintaining excellent responsiveness for a long period of time.

Next, FIG. 8 shows another embodiment in which the present invention is applied to an optical disk for ROM. In this embodiment, the super-resolution film 3 and the high thermal conductive thin film in the embodiment of FIG. The film forming order from the second substrate 1 is reversed, and the other configurations are the same. Therefore, according to the embodiment of FIG. 8, the same operation and effect as those of the embodiment of FIG. 7 can be obtained.

In the embodiments shown in FIGS. 7 and 8, as described above, 90% by weight of Co ₃ O ₄ −
The case where a thin film targeting a sintered body of 10% by weight of SiO ₂ is used and AlN is used as the high thermal conductive thin film 2 has been described, but the super-resolution film and the high thermal conductive thin film made of the above-mentioned other materials are used. Similar effects were obtained when used.

Next, FIG. 9 shows an embodiment in which the present invention is further applied to an optical disk for ROM. In this embodiment, both surfaces of the super-resolution film 3 (lower and upper surfaces in FIG. 9) are shown. Is characterized in that a high thermal conductive thin film 2 is provided, and the other configuration is the same as the embodiment of FIG. 7 and the embodiment of FIG. 8, and thus corresponds to a combination of these embodiments.

The ROM optical disc shown in FIG.
It was produced by the following steps. First, a thickness of 0.6 mm and a diameter of 120 m on which pits 7 in which information is recorded in advance is formed.
m on a substrate 1 made of a disc-shaped polycarbonate.
1N is deposited to a thickness of 25 nm, and 90 wt% Co ₃ O ₄ -10 wt% SiO 2 is formed on the upper surface of the high thermal conductive thin film 2.
_Using the sintered body of No. ₂ as a target for vapor deposition, a super-resolution film 3 having a thickness of 50 nm was formed, and a high thermal conductive thin film 2 of AlN was formed thereon to a thickness of 25 nm.

Next, the protective film 3 made of SiO _{2 is}
After forming the reflective film 5 of Al-Ti system,
m to obtain a substrate 1, and the substrate 1 is
The desired two ROM disks were obtained by adhering two sheets with the reflective film 5 as a back and bonding them using an ultraviolet curable resin.

The ROM optical disk having the high thermal conductive thin film 2 on both surfaces of the super-resolution film 3 has a ratio of the reproduction amplitude of the shortest pit to the reproduction amplitude of the longest pit even if the number of times of repeated reproduction of information exceeds 16000 times. It was found that there was no change in a certain amplitude ratio, and signal deterioration due to repeated reproduction was sufficiently suppressed.

Therefore, according to the embodiment shown in FIG.
There is no concern about performance degradation, sufficient storage density can be achieved, there is no risk of performance degradation due to information reproduction operation, and excellent responsiveness is maintained for a long period of time. A high-recording-density optical disk for ROM that can be easily obtained can be obtained.

In the embodiment shown in FIG. 9, as described above, the super-resolution film 3 is 90% by weight Co ₃ O ₄ -10.
Using a thin film targeting a sintered body of weight% SiO ₂ ,
Although the case where AlN is used as the high thermal conductive thin film 2 has been described, it is needless to say that the same operation and effect can be obtained even when the super-resolution film and the high thermal conductive thin film made of other materials described above are used. Absent.

[0087]

According to the present invention, performance degradation of an optical information storage medium due to repetition of writing / reading can be sufficiently suppressed with a simple structure of providing a high thermal conductive thin film made of a predetermined material. Therefore, according to the present invention, it is possible to easily increase the storage density and the response speed of the optical information storage medium, and to provide a high-performance RAM optical disk or ROM having a large storage capacity and a short access time. An optical information storage medium such as an optical disk can be easily provided at low cost.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing an embodiment in which an optical information storage medium according to the present invention is applied to a RAM disk.

FIG. 2 is a partial sectional view showing another embodiment in which the optical information storage medium according to the present invention is applied to a RAM disk.

FIG. 3 is a characteristic diagram showing an example of a reproduction repetition characteristic in one embodiment of the optical information storage medium according to the present invention.

FIG. 4 is a characteristic diagram showing an example of laser intensity dependence of a refractive index of a super-resolution film in one embodiment of the optical information storage medium according to the present invention.

FIG. 5 is a characteristic diagram showing an example of mark length dependence of C / M in an embodiment of the optical information storage medium according to the present invention.

FIG. 6 is a partial sectional view showing still another embodiment in which the optical information storage medium according to the present invention is applied to a RAM disk.

FIG. 7 is a partial sectional view showing another embodiment in which the optical information storage medium according to the present invention is applied to a ROM disk.

FIG. 8 is a partial sectional view showing another embodiment in which the optical information storage medium according to the present invention is applied to a ROM disk.

FIG. 9 is a partial sectional view showing still another embodiment in which the optical information storage medium according to the present invention is applied to a ROM disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 High thermal conductive thin film 3 Super-resolution film 4 Protective film 5 Reflective film 6 Recording film 7 Pits

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Naito 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Tetsuo Nakazawa 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi Research Laboratory, Hitachi, Ltd. Address F-term in Central Research Laboratory, Hitachi, Ltd. (Reference) 5D029 MA27 MA39

Claims (11)

[Claims] 1. An optical information storage medium comprising a super-resolution film made of at least a transition metal oxide-based inorganic material between a substrate and a recording film made of a phase change material, wherein the super-resolution film is Providing a high thermal conductive thin film directly formed on at least one surface of the member, and forming the high thermal conductive thin film on a member formed on the surface opposite to the surface where the high thermal conductive thin film is in contact with the super-resolution film. An optical information recording medium formed of a material having a higher thermal conductivity than the conductivity. 2. An optical information storage medium comprising a super-resolution film made of an inorganic material containing at least a transition metal oxide between a substrate and a recording film made of a phase change material. Providing a high thermal conductive thin film directly formed on at least one surface of the light emitting device, wherein the high thermal conductive thin film is formed of a material having a thermal conductivity higher than that of the super-resolution film. Information recording medium. 3. An optical information recording apparatus comprising: a substrate on which information is recorded on one surface by forming pits; and a super-resolution film made of an inorganic material containing at least a transition metal oxide as a main component on the one surface. In the medium, a high-thermal-conductivity thin film formed between the super-resolution film and one surface of the substrate is provided, and the high-thermal-conductivity thin film is contacted with the super-resolution film. An optical information recording medium formed of a material having a higher thermal conductivity than that of a member formed on the opposite surface of the optical information recording medium. 4. An optical information recording medium having a super-resolution film made of an inorganic material containing a transition metal oxide as a main component on one surface of a substrate on which information is recorded on one surface by forming pits. In, providing a high thermal conductive thin film formed between the super-resolution film and one surface of the substrate, the high thermal conductive thin film, a thermal conductivity higher than the thermal conductivity of the super-resolution film An optical information recording medium formed of a material having the same. 5. The invention according to claim 1, wherein the super-resolution film contains at least one element selected from cobalt, iron, nickel, chromium, vanadium, and manganese. An optical information recording medium formed of a material containing a first oxide and a second oxide containing at least one element selected from silicon, titanium, sodium, and calcium. 6. The optical information recording medium according to claim 5, wherein the metal element forming the first oxide is cobalt. 7. The invention according to claim 1, wherein the material constituting the high thermal conductive thin film has a thermal conductivity of 0.0
An optical information recording medium having a temperature of 1 [cal / cm · sec · ° C.] or more. 8. The high thermal conductive thin film according to claim 1, wherein a transmittance of the high thermal conductive thin film at a wavelength of light used for reading or writing of information is 80%. An optical information recording medium characterized by the above. 9. The invention according to claim 1, wherein the high thermal conductive thin film is formed of a metal oxide, a metal nitride, a metal carbide, or a metal halide. The optical information recording medium according to claim, wherein the optical information recording medium is at least one compound selected from the group consisting of a compound and a metal sulfide. 10. The claims 1 to 4, and 7 to 10.
The invention according to any one of claims 9, wherein the high thermal conductive thin film is made of alumina, silica-alumina,
Zirconia-alumina, beryllia, aluminum nitride,
Zirconia nitride, silicon nitride, tantalum nitride, titanium nitride, silicon carbide, tantalum carbide, titanium carbide, boron carbide,
An optical information recording medium characterized by being a crystalline compound selected from magnesium fluoride, calcium fluoride, barium fluoride, and zinc sulfide. 11. The invention according to claim 1, wherein the super-resolution film has a thickness of 10 nm or more and 500 nm or less,
An optical information recording medium, wherein the thickness of the high thermal conductive thin film is 10 nm or more and 400 nm or less.