JP2972435B2 - Information optical recording medium and recording / reproducing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rewritable information optical recording medium such as an optical disk for recording and reproducing information by a laser beam, and a method for recording and reproducing the same.

[0002]

2. Description of the Related Art Generally, rewritable information optical recording media include a magneto-optical type using the Kerr effect and a phase change type using a reversible change between two states, a crystalline state and an amorphous state. There are things.

The phase change type is TeGeSnO.
There are various types such as a film having a phase change layer (Japanese Patent Application Laid-Open No. 62-78749). FIG. 2 shows a typical information optical recording medium.

The information optical recording medium shown in FIG. 2 has a first transparent interference layer 22 on a substrate 1, a phase change layer 23 on it, a second transparent interference layer 24 on it, and a NiCr alloy on it. And the like, and a protective film 27 of a UV curable resin is sequentially provided thereon. In some cases, the information optical storage medium is configured as shown in FIG. 2 and recording and reproduction of information is performed by irradiating a laser beam through the substrate 1, but by applying a hot melt agent on the protective layer 27. In some cases, recording and reproduction are performed by bonding the two sets of information optical recording media shown in FIG. 2 so that the substrate 1 is on the outside.

[0005] A laser beam for recording and reproduction is made incident through the substrate 1 and approximately φ1.4 near the phase change layer 23.
The light is focused by a focusing servo so as to have a thickness of μm. As a laser light source, a semiconductor laser having a wavelength of about 830 nm is used.

As the substrate 1, a polycarbonate resin plate, a glass plate with a photopolymer, or an acrylic resin plate with a photopolymer is used. The substrate 1 has guide grooves and guide pits for tracking servo. Generally formed.

To record information, high-power laser light is applied corresponding to information "1", and intermediate-power laser light is applied corresponding to information "0". As a result, the phase change layer 23 in the portion irradiated with the high power is melted and then rapidly solidified to form an amorphous recording mark. On the other hand, the portion of the phase change layer irradiated with the intermediate power is brought into a crystalline state without melting.

[0008] To reproduce information, a laser beam having a low power that does not change the state of the phase change layer is irradiated while moving, so that the amount of reflected light from the medium varies depending on the state of the phase change layer. This is performed by detecting

[0009]

However, such a conventional information optical recording medium and its recording / reproducing method are currently being developed in various places, but the problem is that high-speed rewritable recording is possible. High recording sensitivity, good signal quality such as C / N, erasing rate, etc., no deterioration even when used repeatedly many times, and the above recording / reproducing characteristics even when stored in a high temperature and high humidity environment for a long time. Although there is no deterioration, there is no material that can handle all of them at present.

[0010]

According to a first aspect of the present invention, there is provided an information optical recording medium having a first transparent interference layer, a phase change layer, a second transparent interference layer, a reflection layer, a deformation suppressing layer, and a protective layer on a substrate. Are provided at least in this order, and the laser beam is focused on the phase change layer through the substrate and radiated to irradiate the information by making the phase change layer correspond to a crystalline state or an amorphous state,
An information optical recording medium in which information is reproduced by irradiating a laser beam while focusing and moving the phase change layer through the substrate, wherein the first transparent interference layer has a thickness of 100 to 150 nm. A film of a mixture of ZnS and SiO ₂ , wherein the phase-change layer has a thickness of 20 to 50 nm.
₁ Sb ₂ Te ₄ is a film having a compound composition of ZnS and SiO ₂ having a thickness of 150 to 300 nm.
And the reflective layer has a thickness of 20 to 100.
nm, and the deformation suppressing layer is made of an AlTi alloy film having a thickness of 10 to 300 nm.

According to a second aspect of the present invention, there is provided a recording / reproducing method for an information optical recording medium, comprising a first transparent interference layer having a thickness of 100 to 150 nm and a mixture of ZnS and SiO ₂ formed sequentially on a substrate, and a Ge ₁ Sb. thickness using a compound composition ₂ Te ₄ is 20~50n
m phase change layer and a mixture of ZnS and SiO ₂ with a thickness of 1
Information formed by stacking at least a 50-300 nm second transparent interference layer, a NiCr alloy reflective layer having a thickness of 20-100 nm, an AlTi alloy having a deformation inhibiting layer having a thickness of 10-300 nm, and a protective layer. By using an optical recording medium and performing high-power laser light irradiation and intermediate-power laser light irradiation corresponding to the binary information to be recorded, the cooling rate of the phase-change layer after the temperature rise is compared with the critical speed. The state of the phase change layer is recorded by making the state of the phase change layer correspond to an amorphous state and a crystalline state, and irradiating a low-power laser beam to correspond to a case where the phase change layer is fast and a case where the state is slow. The information is reproduced by reading the difference.

[0012]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of an information optical recording medium showing an embodiment of the present invention.

The information optical recording medium shown in FIG. 1 is made of a mixture of ZnS and SiO ₂ having a thickness of 100 to 15 on a substrate 1.
A first transparent interference layer 2 having a thickness of 0 nm is provided, and Ge ₁ S is formed thereon.
A phase change layer 3 having a compound composition of b ₂ Te ₄ and a thickness of 20 to 50 nm is provided, and a second transparent interference layer 4 of a mixture of ZnS and SiO ₂ having a thickness of 150 to 300 nm is provided thereon. A reflective layer 5 having a thickness of 20 to 100 nm made of a NiCr alloy is provided thereon, and a reflective layer 5 of an AlTi alloy having a thickness of 10 to 100 nm is provided thereon.
A deformation suppressing layer 6 having a thickness of 300 nm is provided, and a protective layer 7 made of a UV curable resin or the like is sequentially provided thereon. While the information optical recording medium may be configured as shown in FIG. 1 to record and reproduce information by injecting a laser beam through the substrate 1, a hot melt agent may be applied on the protective layer 7. In some cases, recording and reproduction are performed by bonding the two sets of information optical recording media of FIG. 1 so that the substrate 1 is on the outside.

A recording / reproducing laser beam enters through the substrate 1 and is approximately φ1.21 μm near the phase change layer 3.
The light is condensed by a focusing servo so as to have a diameter of m to φ1.4 μm. As a laser light source, wavelength 670-
A semiconductor laser of about 830 nm is used.

As the substrate 1, a polycarbonate resin plate, a glass plate with a photopolymer, or an acrylic resin plate with a photopolymer is used. This substrate 1 has
It is desirable to form guide grooves and guide pits for tracking servo. Track pitch is 0.8-1.
It is around 6 μm.

First transparent interference layer 2 and second transparent interference layer 4
It is desirable that the film of the mixture of ZnS and SiO ₂ has a refractive index of about 2.2 by setting the content of SiO ₂ to 10 to 20 mol%.

The phase change layer 3 preferably has a compound composition of Ge ₁ Sb ₂ Te ₄ , but a film to which a small amount of N is added may be used.

The reflection layer 5 is made of N having a Ni content of 80% by weight.
An iCr alloy film is desirable. Since this film does not have high or low reflectivity, the absorptance in the phase change layer 3 can be made almost equal between the case where the phase change film is in the crystalline state and the case where it is in the amorphous state.

The deformation suppressing layer 6 is preferably made of a material having a high thermal diffusivity such as an Al alloy.

C at a medium linear velocity of 11.3 m / sec
/ N, erasure rate, jitter, recording sensitivity and medium linear velocity 2
C / N at 2.6 m / sec, erasure rate, jitter,
It is considered that the reason why the recording sensitivity of the medium of the present invention is good is that the respective film materials and thicknesses are optimally laminated from the viewpoint of optical characteristics, thermal characteristics, and mechanical characteristics. The reason why the long-term storability in a high-temperature, high-humidity environment is good is that various media have been prepared and found, and the causal relationship between each film material and the thickness is not clear, but was obtained comprehensively.

The reason why the characteristics are not deteriorated even when recording / reproducing is repeated many times is not clear, but it is considered that the thermal load during recording is alleviated by the deformation suppressing layer. A specific example will be described below with reference to FIG.

As a first specific example, a guide groove is formed at a pitch of 1.4 μm and has a diameter of 130 mm and a thickness of 1.2 m.
m polycarbonate resin substrate 1 is placed in a sputtering apparatus and evacuated to 1 × 10 ⁻⁶ Torr or less, and then the polycarbonate resin surface is reverse-sputtered by about 0.2 nm, and then a mixture of ZnS and SiO ₂ (SiO ₂
(A content of 17 mol%) is sputtered with argon gas to form a 140 nm thick ZnS and S
A first transparent interference layer 2 of a mixture with iO ₂ was provided. Next, a GeSbTe phase change layer 3 having a thickness of 25 nm was formed by sputtering a Ge ₁ Sb ₂ Te ₄ target with argon gas. Next, a second transparent interference layer of a mixture of ZnS and SiO ₂ having a thickness of 200 nm is formed by sputtering a sintered target of a mixture of ZnS and SiO ₂ (the content of SiO ₂ is 17 mol%) with argon gas. 4 were provided.

On top of that, NiCr (Ni content is 80%)
(% By weight) The target was sputtered with argon gas to provide a 50 nm thick NiCr reflective layer 5. An AlTi (Ti content is 1% by weight) target was sputtered thereon with argon gas to provide a 30 nm thick AlTi deformation suppressing layer 6 thereon. After that, it is taken out from the sputtering apparatus into the atmosphere, and UV light is
The cured resin is spin-coated and UV-irradiated
A protective layer 7 of V-cured resin having a thickness of 10 μm was formed, and the structure was as shown in FIG. Such two disks are mounted on a substrate 1
Were bonded together with hot melt so that each film was on the outside and each film was on the inside. By irradiating an elliptical laser beam at a constant medium linear velocity of 5.65 m / sec, the phase-change layer in the area where information is to be recorded is brought into a crystalline state, and then the entire area where information is to be recorded is formed. Initialization was performed by performing ternary recording of a random pattern ten times, thereby producing an information optical recording medium.

The information optical recording medium manufactured in this manner is rotated at 3600 rpm, and a semiconductor laser beam having a wavelength of 780 nm is passed through the substrate 1 on the phase change layer 3 to approximately φ1.
Irradiation was performed with the aperture being reduced to 4 μm. The reproduction power used for tracking servo and focusing servo is 1.5
mW. 30 mm radius position (media linear velocity is 11.
At 3 m / sec), when a signal with a recording frequency of 2.12 MHz was overwritten on a signal of 8.37 MHz with a high power of 13 mW and an intermediate power of 5 mW at a duty of 50%, a C / N of 54 dB was obtained. The erasure rate at that time was 25 dB, and it was confirmed that the medium was an information optical recording medium having good recording / reproducing characteristics. A signal of a recording frequency of 2.12 MHz is overwritten on a position of a radius of 60 mm (media linear velocity of 22.6 m / sec) with a high power of 19 mW at a duty of 50% and an intermediate power of 10 mW on a signal of 8.37 MHz. When recording was performed, C of 54 dB
/ N was obtained, and the erasing rate at that time was 29 dB, confirming that the medium was an information optical recording medium having good recording / reproducing characteristics.

Even if such recording / reproduction evaluation was repeated 200 times, no deterioration was observed in the characteristics. Further, even after this information optical recording medium was stored in a high-temperature, high-humidity environment at 80 ° C. and 90% for 1000 hours, it was confirmed that the information optical recording medium was usable without any oxidation or peeling.

As compared with the information optical recording medium of the specific example, a medium having no deformation suppressing layer was produced, and the recording / reproduction evaluation was repeated 200 times.

As a second specific example, the thickness of the first transparent interference layer 2 is set to 130 nm by the same operation as in the first specific example.
An information optical recording medium was manufactured in which the thickness of the phase change layer 3 was 25 nm, the thickness of the second transparent interference layer 4 was 210 nm, the thickness of the reflection layer 5 was 50 nm, and the thickness of the deformation suppressing layer 6 was 105 nm. . When the recording / reproducing characteristics and the long-term storability in a high-temperature, high-humidity environment were evaluated in the same manner as in the first specific example, it was confirmed that the medium was an information optical recording medium that could be put to practical use.

As a third specific example, the thickness of the first transparent interference layer 2 is set to 130 nm by the same operation as in the first specific example.
An information optical recording medium was manufactured in which the thickness of the phase change layer 3 was 25 nm, the thickness of the second transparent interference layer 4 was 210 nm, the thickness of the reflection layer 5 was 30 nm, and the thickness of the deformation suppressing layer 6 was 50 nm. . When the recording / reproducing characteristics and the long-term storability in a high-temperature, high-humidity environment were evaluated in the same manner as in the first specific example, it was confirmed that the medium was an information optical recording medium that could be used practically.

As a fourth specific example, the thickness of the first transparent interference layer 2 is set to 125 nm by the same operation as in the first specific example.
An information optical recording medium was manufactured in which the thickness of the phase change layer 3 was 25 nm, the thickness of the second transparent interference layer 4 was 220 nm, the thickness of the reflection layer 5 was 20 nm, and the thickness of the deformation suppressing layer 6 was 40 nm. . When the recording / reproducing characteristics and the long-term storability in a high-temperature, high-humidity environment were evaluated in the same manner as in the first specific example, it was confirmed that the medium was an information optical recording medium that could be used practically.

[0030]

According to the information optical recording medium and the recording / reproducing method of the present invention, high-speed rewritable recording is possible, recording sensitivity is high, and signal quality such as C / N and erasing rate is good.
In addition, there is an effect that information light recording which does not deteriorate even when used repeatedly many times and which does not deteriorate in the recording / reproducing characteristics even when stored in a high temperature and high humidity environment for a long time is possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st transparent interference layer 3 Phase change layer 4 2nd transparent interference layer 5 Reflection layer 6 Deformation suppression layer 7 Protective layer 22 1st transparent interference layer 23 Phase change layer 24 2nd transparent interference layer 25 Reflection Layer 27 Protective layer

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-207703 (JP, A) JP-A-4-360039 (JP, A) JP-A-59-92449 (JP, A)

Claims (3)

(57) [Claims] A first transparent interference layer, a phase change layer, a second transparent interference layer, a reflection layer, a deformation suppressing layer, and a protective layer, which are provided on a substrate in this order; The information is recorded by making the phase change layer correspond to a crystalline state or an amorphous state by focusing and irradiating the phase change layer, and irradiating the laser light while focusing and moving the laser light to the phase change layer through the substrate. The first transparent interference layer is a film of a mixture of ZnS and SiO ₂ having a thickness of 100 to 150 nm, and the phase change layer is 20-50nm thickness
And a second transparent interference layer having a thickness of 150 to 300 nm and a film of Ge ₁ Sb ₂ Te _4.
a film of a mixture with iO ₂ , wherein the reflective layer has a thickness of 20 to
An information optical recording medium comprising a 100 nm NiCr alloy film, and the deformation suppressing layer being a 10-300 nm thick AlTi alloy film. 2. ZnS and SiO formed sequentially on a substrate
₂ , a first transparent interference layer having a thickness of 100 to 150 nm and a compound composition of Ge ₁ Sb ₂ Te ₄ having a thickness of 20 to 150 nm.
A 50 nm phase change layer, a second transparent interference layer made of a mixture of ZnS and SiO ₂ and having a thickness of 150 nm to 300 nm, and NiC.
an information optical recording medium comprising at least a reflective layer having a thickness of 20 to 100 nm made of an r alloy, a deformation suppressing layer having a thickness of 10 to 300 nm made of an AlTi alloy, and a protective layer,
By performing high-power laser light irradiation and intermediate-power laser light irradiation in accordance with the binary information to be recorded, when the cooling rate of the phase change layer after heating is higher or lower than the critical speed. In correspondence with, the information of the phase change layer is recorded in correspondence with the amorphous state and the crystalline state,
A recording / reproducing method for an information optical recording medium, comprising reading out a difference in a state of the phase change layer by irradiating a low power laser beam to reproduce information. 3. The medium linear velocity is 11.3 to 22.6 m / s.
3. The recording / reproducing method for an information optical recording medium according to claim 2, wherein recording is performed within a range of ec.