JPH0628710A - Optical information recording medium and its manufacture and initializing method therefor - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium whose erasure ration is more improved than that of a conventional medium and which has excellent recording-erasure repetitive characteristic, its manufacturing method and its initializing method. CONSTITUTION:In an optical information recording medium having a recording layer, a protective layer and a reflection heat radiation layer on a base plate, the recording layer consists of Ag, In, Sb, Te and the surface roughness of the protective layer between the recording layer and the base plate is selected to be 30-150Angstrom . After the protective layer is formed as a film on the base plate in the manufacture of the recording medium, the base plate is plasma-processed in the gaseous mixture of Ar and N2 to obtain a prescribed surface roughness. Furthermore, in the case of initialization, an Ar laser is used at first and then a semiconductor laser is used for the initialization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, in particular a phase change type information recording medium, which causes a phase change in a recording layer material by irradiating a light beam to record and reproduce information. The present invention also relates to a rewritable information recording medium, which is applied to optical memory related equipment.

[0002]

2. Description of the Related Art As one of optical memory media capable of recording, reproducing and erasing information by irradiation of electromagnetic waves, especially laser beams, so-called phase change utilizing a transition between a crystalline-amorphous phase or a crystalline-crystalline phase. Recording media are well known. In particular, since it is possible to overwrite with a single beam, which is difficult for a magneto-optical memory, and the optical system on the drive side is simpler, research and development has recently become active. As a typical example, USP3
Ge-Te, G, as disclosed in 530441.
e-Te-Sn, Ge-Te-S, Ge-Se-S, G
e-Se-Sb, Ge-As-Se, In-Te, Se
Examples include so-called chalcogen alloy materials such as —Te and Se—As. Further, for the purpose of improving stability, high-speed crystallization, etc., a Ge—Te system containing Au (JP-A-61-21969
2), Sn and Au (JP-A-61-270190),
For the purpose of proposing a material obtained by converting Pb (Japanese Unexamined Patent Publication No. 62-19490) and improving repeatability of recording / erasing.
Proposals have also been made for a material (JP-A-62-73438) in which the composition ratio of Te-Se-Sb and Ge-Te-Sb is specified. However, none of them can satisfy all the characteristics required for the phase-change rewritable optical memory medium. In particular, prevention of a reduction in the erase ratio due to the unerased portion at the time of overwriting and improvement of the number of repeated recordings are the most important issues to be solved.

Japanese Unexamined Patent Publication No. 63-251290 proposes a recording medium having a recording layer composed of a multi-component compound single phase whose crystal state is substantially ternary or more. Here, the term “substantially ternary or higher multi-component compound monolayer” refers to a compound having a stoichiometric composition of ternary or higher (for example, In ₃ SbTe ₂ ) in the recording layer.
It is supposed to contain 0 atomic% or more. It is said that the recording and erasing characteristics can be improved by using such a recording layer. However, it has drawbacks such as a low erase ratio. Under these circumstances, it has been desired to develop an optical information recording medium having a high erasing ratio and excellent repetitive characteristics. As a method for this, development of a protective layer material suitable for a recording layer material has been promoted, and ZnS, SiO ₂ , Al ₂ O ₃ , Ta ₂ O have been developed.
₅ , materials such as SiN and AlN are used. However, no combination of these materials has been obtained which satisfies all the properties required for an optical memory medium.

[0004]

The present invention achieves a dramatic improvement in the erase ratio as compared with the above-mentioned prior art, and the recording-
The present invention provides an optical information recording medium having excellent erasing repetition characteristics.

[0005]

As a result of intensive studies for improvement, the present inventors have found a combination of a recording material and a protective layer material which meets the above-mentioned object.

That is, according to the present invention, in an optical information recording medium having a recording layer, a protective layer, and a reflection / radiation layer on a substrate, the recording layer is made of Ag, In, Sb, Te, and the protective layer between the recording layer and the substrate. Is characterized by having a surface roughness of 30Å to 150Å.

The present inventors can achieve the above object by using the optical information recording medium having such a structure.

The present invention also provides a method of manufacturing an optical information recording medium having such a structure, wherein after forming a protective layer on a substrate, Ar is formed.
It is characterized in that plasma treatment is performed in a mixed gas atmosphere of N ₂ and N ₂ so that the surface roughness of the protective layer is from 30 Å to 150 Å, and then the recording layer is formed. The use of this method can achieve the above object.

Further, the present invention is characterized in that, in the method of initializing the optical information recording medium, the initialization is first performed by the Ar laser and then by the semiconductor laser. Using this method, the erase ratio can be greatly improved.

The present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a configuration example of the present invention. A heat resistant protective layer 2, a recording layer 3, a heat resistant protective layer 4, and a reflective heat dissipation layer 5 are provided on a substrate 1. It is not always necessary to provide the heat-resistant protective layer on both sides of the recording layer, but it is desirable to provide the heat-resistant protective layer 2 when the substrate is a material having low heat resistance such as polycarbonate resin.

The recording layer according to the present invention contains Ag, In, Sb and Te as constituent elements. These elements form a uniform amorphous phase during recording.
On the other hand, at the time of erasing, depending on the composition, there may be a case where a uniform crystal phase is formed and a case where the phase is separated and an AgSbTe ₂ phase or the like is precipitated. Ag concentration is 5 atomic% or more and 17 atomic% or less, In
It is preferable that the concentration of S is 6 at% or more and 18 at% or less, the concentration of Sb is 33 at% or more and 77 at% or less, and the Te concentration is 13 at% or more and 36 at% or less.

The recording layer of the present invention is formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD,
It can be formed by a photo CVD method, an ion plating method, an electron beam evaporation method, or the like. In addition to the vapor phase growth method, a wet process such as a sol-gel method can be applied. The thickness of the recording layer is 100 to 10000Å, preferably 200 to 2
It is good to set it to 000Å. When the thickness is less than 100Å, the light absorption ability is remarkably lowered and the recording layer cannot serve as a recording layer. If it is thicker than 10000Å, uniform phase change at high speed is difficult to occur.

As the heat resistant protective layer between the recording layer and the substrate according to the present invention, ZnS, SiO ₂ , AlN and Si are used.
N, Al ₂ O ₃ or the like can be used. The thickness of these protective layers is 500Å to 5000Å, more preferably 1500Å to 2500Å, and the surface roughness is 30.
Å to 150Å are suitable. When the surface roughness is 30 Å or more, the repeating characteristics are improved, but when it is 150 Å or more, the C / N decreases. The surface roughness was measured using a stylus-type surface roughness meter, and the ten-point average roughness of JIS B0601 was used.

Such a heat resistant protective layer can be formed by various vapor phase growth methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. In particular, the sputtering method is excellent in reproducibility.

The surface roughness of the protective layer is controlled by surface treatment after film formation. As a method of surface treatment, there is a method such as chemical etching, but plasma surface treatment is excellent in terms of disc characteristics and controllability. Table 1 shows typical surface treatment conditions.

[0016]

[Table 1]

Ar gas may be used alone as the plasma treatment atmosphere, but it is preferable to use a mixed gas of Ar and N ₂ . This makes it possible to improve repetitive characteristics as compared with the case where Ar gas is used alone.

For the reflection / heat dissipation layer, a metal material such as Al, Ag, Au, or an alloy thereof can be used. The reflection heat dissipation layer is not always necessary, but it is preferable to provide it in order to release excess heat and reduce the heat load on the disk. Such a reflective heat dissipation layer can be formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method and electron beam evaporation method. The thickness of the reflective heat dissipation layer is 100 to 3000 Å, preferably 500 to 20
It is good to set it to 00Å. When it is thinner than 100Å, it does not function as a reflection and heat dissipation layer, and conversely 2000Å
If the thickness is larger than the above range, the sensitivity is lowered and the interfacial peeling is likely to occur.

The material of the substrate is usually glass, ceramics, or resin, and a resin substrate is preferable in terms of moldability and cost. Typical examples of the resin are polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin,
Examples thereof include acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, urethane resin, and the like, but polycarbonate resin and acrylic resin are preferable in terms of processability and optical characteristics. . The shape of the substrate may be disk-shaped, card-shaped or sheet-shaped.

As a method of initializing the optical information recording medium, a method of first performing initialization with an Ar laser and then performing initialization with a semiconductor laser is used. By doing so, the erasing ratio could be improved as compared with the case where the Ar laser or the semiconductor laser was used alone. The reason for this is not clear, but it is considered that the structure of the recording layer is changed by combining the initialization methods. The power of the Ar laser is in the range of 300 mW to 2 W, the disk linear velocity is in the range of 1.3 m / s to 10 m / s, and the laser feed speed is 5 um / rotation to 20 um /
Suitable range of rotation. The power of the semiconductor laser is 5
Range of mW to 20mW, linear velocity of 1.3m / s to 10
A range of m / s is suitable.

As the electromagnetic wave used for recording, reproducing and erasing, various kinds such as laser light, electron beam, X-ray, ultraviolet ray, visible ray, infrared ray and microwave can be adopted.
A compact and compact laser diode is best suited for mounting on a drive.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 An AlN protective layer 2000 was formed on a polycarbonate substrate having a pitch of about 1.6 μm and a depth of about 700 Å and a thickness of 1.2 mm and a diameter of 120 mm by RF sputtering.
Å, Ag-In-Sb-Te recording layer (composition ratio is Ag: I
n: Sb: Te = 12: 13: 51: 24) 200Å,
An optical disk was manufactured by sequentially stacking an AlN protective layer 1500Å and an Ag reflective layer 500Å.

Table 2 shows the surface treatment conditions after forming the AlN protective layer.
Shown in. By changing the RF power, the surface roughness of the substrate-side protective layer was changed to examine the influence on the disk characteristics. The surface roughness of the protective layer was measured by a stylus type surface roughness meter and expressed as a ten-point average roughness of JISB0601.

[0025]

[Table 2]

Initialization of the optical disk was performed by a semiconductor laser. The power was 10 mW and the linear velocity was 1.3 m / s.

The evaluation of the optical disk is performed with a wavelength of 780 nm and NA.
This was done using a 0.5 pickup. The linear velocity of the disk was 1.3 m / s. Recording frequency 720kHz, 20
Overwrite recording of 0kHz signal alternately at 720k
The C / N and the erasing ratio of the Hz signal were used as characteristic values.

FIG. 2 shows the relationship between the surface roughness of the protective layer and the disc repeatability. As the characteristic value of the disc repeating characteristic, the number of overwrite recordings in which C / N is reduced by 3 dB was used. It can be seen that when the surface roughness is 30 Å or less, the repetitive characteristics are sharply deteriorated, which is not preferable.

The relationship between the surface roughness of the protective layer and C / N is shown in FIG. C / N decreases with increasing surface roughness, especially 15
It was found that when it is 0 Å or more, it drops sharply and is not suitable for practical use.

Example 2 A disk was produced in the same manner as in Example 1 except that a mixed gas of Ar and N ₂ was used instead of Ar gas under the surface treatment conditions of the AlN protective layer. As a result, the number of repetitions was 5000 times when Ar gas was used, but reached 8000 times when a mixed gas of Ar and N ₂ was used, and the repetition characteristics can be improved by changing the introduced gas to NO. I understood.

Example 3 Signals were recorded in the same manner as in Example 2. However, as an initialization method, initialization by an Ar laser (600 mW,
After performing 5 m / s and 5 um rotation, initialization with a semiconductor laser (10 mW, 1.3 m / s) was performed. The results are shown in Table 3. For comparison, the case of initialization by Ar laser is also shown.

[0032]

[Table 3]

As can be seen from Table 3, the erase ratio is improved by performing the initialization with the semiconductor laser after the initialization with the Ar laser.

[0034]

As is clear from the description of the embodiments, the present invention has excellent performance as a phase change type optical recording medium, and in particular, the erasing ratio and repetitive characteristics are dramatically improved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a configuration of an optical information recording medium of the present invention,

FIG. 2 is a graph showing the relationship between the surface roughness of the protective layer and the number of times of repeated overwrite recording,

FIG. 3 is a graph showing the relationship between the surface roughness of the protective layer and C / N.

[Explanation of symbols]

 1 substrate 2 and 4 heat resistant protective layer 3 recording layer 5 heat dissipation layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location G11B 7/00 W 9195-5D (72) Inventor Hiroko Iwasaki 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 Ricoh Co., Ltd.

Claims (3)

[Claims] 1. An optical information recording medium having a recording layer, a protective layer, and a reflection and heat dissipation layer on a substrate, wherein the recording layer is Ag, In,
An optical information recording medium comprising Sb and Te, wherein the surface roughness of the protective layer between the recording layer and the substrate is 30Å to 150Å. 2. A method for manufacturing an optical information recording medium having a recording layer, a protective layer, and a reflection / heat dissipation layer on a substrate, wherein after forming the protective layer on the substrate, plasma treatment is performed in an Ar / N ₂ mixed gas atmosphere. The surface roughness of the protective layer is adjusted to 30Å to 150Å, and then the recording layer is formed. 3. An optical information recording medium having a recording layer, a protective layer and a reflection / heat dissipation layer on a substrate, wherein the recording layer is Ag, In, Sb,
A method for initializing an optical information recording medium, which is made of Te and has a surface roughness of a protective layer between a recording layer and a substrate of 30Å to 150Å, which is initialized by Ar laser.
Next, an initialization method for an optical information recording medium, characterized by performing initialization by a semiconductor laser.