JP2001010232A - Phase change type optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a phase change type optical recording medium having a wide overwritable linear velocity range and being excellent in rewriting characteristics and high-density recording. SOLUTION: This optical recording medium has at least a phase change type recording layer provided on a substrate. In this case, the recording layer is composed of Sb, Te and M (M is Ag, In). The sphere of the composition is in a region surrounded by straight lines A, B, C and D in a triangular diagram having vertexes of Sb, Te and M, and Ag <=In.

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 erasing information by changing the arrangement of atoms by irradiating light. And a phase change type optical recording medium excellent in high density recording.

[0002]

2. Description of the Related Art Information recording by laser beam irradiation,
As one of the rewritable and erasable optical memory media, a so-called phase-change type optical recording medium utilizing a transition between crystal and amorphous or between two crystal phases of crystal 1 and crystal 2 is well known. . The phase-change optical recording medium includes a recording layer mainly composed of chalcogen such as Te and Se, a light-transmitting dielectric layer sandwiching the recording layer from both sides, and a reflection layer provided on the opposite side to the laser light incident side. It is composed of a protective layer. As typical material systems, GeSbTe-based materials and AgInSbTe-based materials are well known and have been put to practical use.

[0003] The recording principle is as follows. The recording layer immediately after film formation is in an amorphous state and has a low reflectance. First, the recording layer is heated by irradiating a laser beam to bring the entire surface of the disk into a crystalline state having a high reflectance. This is called initialization. The initialized optical disk is locally irradiated with a laser beam to melt and rapidly cool the recording film, thereby changing the phase to an amorphous state. The optical properties (reflectance, transmittance, complex refractive index, etc.) of the recording film change with the phase change, and information is recorded. The reproduction is performed by irradiating a weak laser beam and detecting a reflectance difference or a phase difference between the crystal and the amorphous. In rewriting, a recording peak power superimposed on a low-energy erasing power causing crystallization is applied to a recording layer to overwrite a recording mark already recorded without going through an erasing process.

Japanese Patent Application Laid-Open No. 1-277338 discloses (Sb
xTe1-x) 1-yMy (where x is 0.4≤x <0.
7, y is a number y ≦ 0.2, M is Ag,
Al, As, Au, Bi, Cu, Ga, Ge, In, P
It is at least one element selected from the group consisting of b, Pt, Se, Si, Sn and Zn. An optical recording medium having a recording layer made of an alloy having a composition represented by (1) has been proposed. In this medium, the crystallization temperature is increased by adding a third element to the SbTe binary system, the stability of the amorphous state is improved, and the erasing speed is further increased. However, this publication does not describe a specific embodiment of a multi-system medium of four or more systems. In addition, 1 at high linear velocity
The rewriting performance of the beam overwrite is not shown, and the number of repetitions of writing and erasing is 1,000, which is insufficient for the characteristics as a rewritable medium. No mention is made of high-density recording.

The present inventors have found a AgInTe-based recording material as a new material for solving the drawbacks of the optical recording material, and have disclosed it in Japanese Patent Application Laid-Open No. 2-175285. It has already been clear that a phase change optical recording medium having extremely excellent performance can be obtained by this disclosed technology, but further improvements have been required due to an increase in transfer speed and an increase in recording density.

[0006]

(1) An optical disk capable of high-speed recording with a large capacity is required for a video disk recorder. However, since a phase change medium has a constant crystallization speed, a rewritable line is required. The range of speed is limited. In particular, crystallization hardly proceeds at a high linear velocity, and it is necessary to optimize the composition of the recording material and the structure of the medium. At high linear velocities, recording and erasing powers increase, and it is necessary to improve sensitivity. (2) The phase change medium generally has insufficient rewriting characteristics. In particular, in the case of mark edge recording which is high-density recording, there is a problem that the distribution of the mark length is widened due to repeated overwriting and an error occurs. Deterioration of recording / reproducing characteristics due to repetitive overwrite recording, particularly, an increase in jitter occurs. (3) It is difficult to realize a rewritable medium having a high recording density equivalent to a DVD-ROM with an optical system longer than the laser wavelength used for cutting the DVD-ROM and having a small numerical aperture (NA). (4) In order to achieve DVD-ROM reproduction compatibility, a modulation degree of 60% or more and a reflectance of 15% or more are required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a phase change type optical recording medium capable of direct overwriting over a linear velocity of 3.5 m / s or more and capable of high density recording. (Hereinafter referred to as an optical recording medium)
Is to provide.

[0008]

According to a first aspect of the present invention, there is provided an optical information recording medium having at least a phase change type recording layer provided on a substrate, wherein the composition of the recording layer is Sb, Te, M
(M is Ag, In), the composition range is a region surrounded by straight lines A, B, C, and D in a triangular diagram having Sb, Te, and M as vertices, and Ag
A phase-change optical recording medium satisfying ≦ In is a second invention in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are laminated on a substrate in this order. When the thickness d1 of the body layer is 50 ≦ d1 ≦ 90 nm or 180 ≦ d
1 ≦ 220 nm, thickness d2 of the recording layer is 15 ≦ d2 ≦ 30
nm, the thickness d3 of the second dielectric layer is 8 ≦ d3 ≦ 25 nm,
3. The phase-change optical recording medium according to claim 1, wherein the thickness d4 of the reflective layer is 75 ≦ d4 ≦ 300 nm.
The substrate thickness is 0.6 mm and the groove depth d5 is 30 ≦ d5 ≦ 35.
nm, groove width w1 is 35 <w1 <50% of track pitch
And a phase-change optical recording medium according to claim 2.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the optical recording medium according to the present invention will be described below in detail. FIG. 1 shows a schematic cross-sectional view of a typical layer configuration of the optical recording medium of the present invention. (A) a laminate (not shown) of substrate 1 / first dielectric layer 2 / recording layer 3 / second dielectric layer 4 or (a) substrate 1 / first dielectric layer 2 /
A laminate of recording layer 3 / second dielectric layer 4 / reflective layer 5 (where light enters from substrate 1 side) or (c) substrate / reflective layer / second dielectric layer / recording layer / first layer Dielectric layer / protective layer (here, light enters from the protective layer side, not shown). On the reflective layer, a metal oxide, a metal nitride, a metal sulfide, an inorganic protective layer such as a metal carbide, or a resin layer such as an ultraviolet curable resin, or bonded to another substrate within a range that does not impair the effects of the present invention. May be provided with an adhesive layer, an adhesive sheet, or the like.

The substrate 1 and the protective layer 6 may be provided with a hard coat layer or an antistatic layer for the purpose of preventing scratches and dust from adsorbing. For applications where recording sensitivity is important, the reflective layer 5
Is preferable, and the recording layer is provided with the reflective layer 5 in the case of recording at a high recording density or in the application where the repetition durability of the recording is emphasized. For high-density recording, the configuration (c) having an extremely thin transparent protective layer or transparent protective sheet in order to use a high numerical aperture (NA) and reduce the influence of aberration due to the substrate 1 is preferable.

As a material of the substrate 1 of the present invention, various transparent synthetic resins, transparent glass and the like can be used. In order to avoid the influence of dust, scratches on the substrate, etc., it is preferable to use a transparent substrate and perform recording from the substrate side with a focused light beam.As such a transparent substrate material, glass, polycarbonate, polymethyl methacrylate, Polyolefin resin, epoxy resin, polyimide resin and the like can be mentioned. In particular, polycarbonate resins are preferred because they have low optical birefringence, low hygroscopicity, and are easy to mold.

In order to further improve the recording density, so-called table reading may be performed in the configuration (c). In this case, since the light beam does not pass through the substrate, an opaque substrate can be used. Although the thickness of the substrate is not particularly limited, a thickness of 0.01 mm to 5 mm is practical. 0.0
If it is less than 1 mm, even when recording with a light beam focused from the substrate side, it is susceptible to dust, and if it is more than 5 mm, it becomes difficult to increase the numerical aperture of the objective lens, and the irradiation light beam spot size , It becomes difficult to increase the recording density. The substrate may be flexible or rigid. Flexible substrates can be tape, sheet, car
Use in the form of a letter. The rigid substrate is used in the form of a card or a disk. In addition, these substrates may be formed into an air sandwich structure, an air incident structure, or a close bonding structure using two substrates after forming a recording layer or the like.

A laser light guide groove is formed in the substrate 1. In consideration of compatibility with DVD-ROM, DPD (differential phase detection) tracking can be performed after recording, the degree of modulation is 60% or more, and the reflectance is 1
To show 5% or more, the track pitch must be 0.74 μm.
m, the groove depth d5 is set at 30 ≦ d5 ≦ 35 nm, and the groove width w1 is set at 35 <w1 <50% of the track pitch. If the groove depth d5 is smaller than 30 nm, the radial contrast is reduced. Conversely, if the groove depth d5 is deeper than 35 nm, the reflectivity decreases. Further, the degree of modulation is lower than 60%. Groove width w1
Is smaller than 35%, the degree of modulation decreases, and conversely, the groove width w1
Is larger than 50%, the jitter increases. Here, the groove width refers to the width of the groove portion at a point where the groove depth, which is the distance between the groove surface and the land surface, is halved.

The dielectric layers 2 and 4 of the present invention protect the substrate 1 and the recording layer 3 from heat, for example, to prevent the substrate 1, the recording layer 3 and the like from being deformed by heat during recording and thereby deteriorating the recording characteristics. There is an effect of improving the signal contrast at the time of reproduction by the effect and the optical interference effect. Further, there is an effect that the crystallization of the recording layer 3 is promoted and the erasing rate is improved. The dielectric layers 2 and 4 are made of ZnS, SiO2, Si3N
4. There are inorganic thin films such as Al2O3. Especially Si, G
e, a thin film of a metal or semiconductor oxide such as Al, Ti, Zr, Ta, a thin film of a metal or semiconductor nitride such as Si, Ge, Al, or a metal or semiconductor carbide such as Ti, Zr, Hf, or Si Thin film, ZnS, In2S
3, thin films of sulfides of metals or semiconductors such as TaS4 and GeS2, and films of a mixture of two or more of these compounds are preferred because of their high heat resistance and chemical stability.

Further, it is preferable that the atoms forming the dielectric layers 2 and 4 do not diffuse into the recording layer 3. These oxides, sulfides, nitrides, and carbides do not always need to have a stoichiometric composition, and it is effective to control the composition for controlling the refractive index and the like, or to use a mixture thereof. Especially ZnS
The mixed film of SiO2 and SiO2 is preferable because deterioration of recording sensitivity, C / N, erasing rate, and the like hardly occurs even when recording and erasing are repeated. First dielectric layer 2 and second dielectric layer 4
May be composed of different compounds instead of the same.

The recording layer 3 of the present invention is made of a phase-change optical recording material composed of antimony Sb, tellurium Te, and M (M is Ag, In), which can take at least two states, a crystalline state and an amorphous state. You. The crystal state in the erased state is mainly composed of a crystal phase of Sb, and forms a crystal phase composed of a combination of two or more elements of antimony Sb, tellurium Te, and M (M is Ag, In). In some cases.
The crystal state is not limited to a single phase, and two or more crystal phases may coexist. In the amorphous state, which is a recording state, an X-ray diffraction pattern is not shown, but a short-range order may be locally present, and a regular electron beam diffraction pattern may be shown.

As recording materials, antimony Sb and tellurium T
e and M (M is Ag, In) as main components and Cu, Ba, Co, Cr, Ni, Pt, Si, Sr,
Au, Cd, Li, Mo, Mn, Zn, Fe, Pb, N
a, Cs, Ga, Pd, Bi, Sn, Ti, V, Ge,
A total of at least one element selected from the group consisting of Se, S, As, Tl, In, Pd, Pt, and Ni is 0.01%.
Atomic (hereinafter, at)% or more and less than 3 at% can be contained.

The crystallization speed is strongly controlled by the content of antimony Sb, and the crystallization speed increases as the Sb content increases, and the transfer speed can be increased. in addition,
Since it is a Te-based alloy containing Sb as a component, it is also excellent in oxidation resistance. However, if the amount of Sb is excessive, the overwrite performance is repeatedly reduced, and if the amount of Sb is excessive, a crystalline state is formed immediately after the film formation, and a high reflectance is exhibited. If the amount of M (M is Ag, In) is excessive, the recording sensitivity is reduced, and the reversible change from amorphous to crystalline and back to amorphous is not exhibited. No longer exhibits an irreversible phase change from crystalline to crystalline. The ratio of Ag to In tends to increase the number of rewrites when Ag ≦ In, but the detailed reason is currently being analyzed. Regarding the amount of Te, if it is excessive, it tends to be amorphous, and crystallization does not proceed at a high linear velocity.
Erasing becomes impossible.

As the material of the reflection layer 5 of the present invention, metals such as Al, Au and Ag having light reflectivity, alloys containing these as a main component and containing additional elements such as Ti and Cr, and Al, Au, Examples include a mixture of a metal such as Ag and a metal compound such as a metal nitride such as Al and Si, a metal oxide, and a metal chalcogenide. Al, Au, Ag
Such metals and alloys containing these as main components are preferable because of their high light reflectivity and high thermal conductivity. As an example of the above-mentioned alloy, Cr, Si, Mg,
Cu, Pd, Ti, Hf, Ta, Nb, Mn, Pd, Z
r, at least one element such as Cr, Ag, at least one element such as Cr, Ag, Cu, Pd, Pt, and Ni; or Ag, at least one of Pd, Cu, and the like. Some have one element added. In particular, since the corrosion resistance is good and the repetition performance is extended, the reflective layer 5 is added with a total of 0.5 a
Al-Cr alloy, Al-T containing at least t% and less than 3 at%
i alloy, Al-Ta alloy, Al-Zr alloy, Al-Ti
It is preferable to be composed of an alloy containing Al as a main component, either of a -Cr alloy or an Al-Si-Mn alloy.

The thickness of each layer of the optical recording medium 10 of the present invention is
It largely depends on the optical constant (refractive index n and extinction coefficient k) at the reproduction wavelength. Considering compatibility with DVD-ROMs, it is desirable that the degree of modulation be at least 60% and the reflectivity be at least 15%. In order to satisfy such optical characteristics at a reproduction wavelength of 635-660 nm, the thickness d1 of the first dielectric layer 2 must be 50 ≦ d1 ≦ 90 nm or 180 ≦
d1 ≦ 220 nm, and the thickness d2 of the recording layer 3 is 15 ≦ d2 ≦
30 nm, and the thickness d3 of the second dielectric layer 4 is 8 ≦ d3 ≦ 25.
nm, and the thickness d4 of the reflective layer 5 is set to 75 ≦ d4 ≦ 300 nm.

The first dielectric layer 2 of the present invention and the second dielectric layer
The dielectric layer 4 is preferably transparent at the recording / reproducing wavelength and has a refractive index n1 at the recording / reproducing wavelength in the range of 1.9 ≦ n1 ≦ 2.2. As the thickness of the first dielectric layer 2 increases, the wavelength showing the minimum value of the reflectance shifts to the longer wavelength side. The reflectance at 650 nm, which is the DVD reproduction wavelength, is 1
In order to secure 5% or more and prevent a decrease in recording sensitivity due to an increase in reflectance at the recording wavelength of 635 nm, a change in spectral reflectance in this wavelength region needs to be small. For this purpose, the thickness d1 of the first dielectric layer 2 is set to 50 ≦ d1 ≦ 90 nm.
Alternatively, it is in the range of 180 ≦ d1 ≦ 220 nm.

The thickness of the recording layer 3 changes the value of the reflectance. If the thickness of the recording layer 3 is small, the reflectance increases and the recording sensitivity decreases, which is not preferable. Also, the rewriting performance is deteriorated, and the number of repetitive overwrites is reduced. Conversely, recording layer 3
When the thickness of the recording layer 3 is large, the reflectance is lowered and a large amount of energy is required to melt the recording layer 3, which is not preferable. The thickness d2 of the recording layer 3 is in the range of 15 ≦ d2 ≦ 30 nm.

The thickness of the second dielectric layer 4 changes the value of the reflectance. As the thickness of the second dielectric layer 4 increases, the reflectance decreases. When the thickness of the second dielectric layer 4 is small, the reflectance increases, and the recording sensitivity decreases. When the thickness of the second dielectric layer 4 is small, the distance between the second dielectric layer 4 and the reflection layer 5 becomes narrow, and a rapid cooling structure is required, so that a large recording power is required to form a mark. Conversely, when the thickness of the second dielectric layer 4 is increased, the distance between the second dielectric layer 4 and the reflective layer 5 is increased, and a slow cooling structure is formed, whereby the rewriting performance is deteriorated and the number of repeated overwrites is reduced. The thickness d3 of the second dielectric layer 4 is in the range of 8 ≦ d3 ≦ 25 nm.

The thickness of the reflective layer 5 changes depending on the thermal conductivity of the metal or alloy forming the reflective layer 5. For example, in the case of an Al—Cr alloy, the thermal conductivity decreases as the Cr content increases, so that it is not suitable for a recording strategy unless the thickness of the reflective layer 5 is increased. Cr
When the content is large, the recording layer 3 is easily heated and hardly cooled, and has a so-called slow cooling structure. In order to control the formation of recording marks with a recording strategy,
It is necessary to take measures such as shortening the leading pulse described later, shortening the multi-pulse, and extending the cooling pulse.
The reflection layer 5 does not change optically when the thickness exceeds 50 nm,
It does not affect the value of reflectivity, but has a greater effect on the cooling rate. Forming a thickness of 300 nm or more requires time in manufacturing. Therefore, the thickness is suppressed as much as possible by using the reflective layer 5 made of a material having high thermal conductivity. The thickness d4 of the reflective layer 5 is in the range of 75 ≦ d4 ≦ 300 nm.

It is preferable to use a laser beam as a light source for recording on the optical recording medium of the present invention.
Considering compatibility with OM, the recording and reproducing wavelength is 6
It is preferably from 35 nm to 660 nm. Further, recording and reproduction can be performed using a short-wavelength laser beam exhibiting blue. It is also possible to use a light source in which the primary light in the infrared region has been shortened in wavelength using a secondary harmonic generation element (SHG element).

The recording is performed by irradiating the crystalline recording layer 3 with a laser beam pulse or the like to form an amorphous recording mark. Erasing can be performed by crystallization of the amorphous recording mark by laser beam irradiation. In practice,
By applying a recording peak power superimposed on a low-energy erasing power causing crystallization to the recording layer 3, overwriting is performed on the already recorded recording mark without going through the erasing process.

At this time, the recording laser pulse is divided into a plurality of pulses shorter than the recording mark length. FIG. 2 shows an example of the divided pulse pattern. 3T and 6T of 8-16 modulation method
When recording a mark, it is preferable that the divided pulse pattern has a waveform as shown in FIG. 2, for example. The recording laser pulse is mainly composed of three pulses: a leading pulse Tf, a multi-pulse T1, and a cooling pulse Tc. Three
In the case of the T signal, a single pulse may be used instead of a plurality of pulses. The laser power is modulated by at least two values of the recording peak power P1 and the erasing power P2.
Furthermore, the laser power P3 between the divided recording pulses or the cooling power P4 after the final pulse may be added and modulated in four values.

P1 is a power level at which the recording layer 3 is melted to form an amorphous mark, and is usually set to about 8 to 15 mW. P2 is a power level at which the recording layer 3 is heated to a temperature higher than the crystallization temperature when direct overwriting is performed to erase an amorphous mark, and is usually 1/1 of P1.
2 or more, for example, about 4 to 9 mW. P3 is preferably smaller than the erasing power P2 and a non-zero laser power. Normally, the laser power P3 is 0.2 to 1.0 m
W range. By doing so, the erasing rate is improved, the recrystallization of the recorded mark after melting can be prevented, and the recording power margin is widened.

Since the temperature at the tip of the mark is hard to rise, the leading divided pulse Tf is set to be 2 to 4 times smaller than the other divided pulses.
In some cases, it is better to double the length. Usually, it is set to about 0.5T to 1T. In FIG. 2, the pulse length T of the divided pulse
The interval T2 between 1 and the divided pulse is preferably set to T1 + T2 = T. In addition, it is possible to more effectively prevent the recrystallization of the recording mark when T1 is shorter than T2. That is, in some cases, it is preferable that T1 ≦ T2. When the crystallization speed of the recording material is high, the thickness of the reflective layer 5 is small, and the cooling of the supplied laser power is slow, the jitter value can be reduced by setting T1 to 0.2T to 0.3T. Good recording is possible with a decrease. However, T1 needs to be larger than 0.1T. If it is less than 0.1T, the previously recorded amorphous mark cannot be erased.

The cooling pulse Tc greatly affects the formation of the subsequent mark, and in the case of slow cooling as described above,
Increasing Tc reduces the jitter value and improves signal quality. The power level of the normal cooling pulse has a relationship of P3 ≧ P4, and its length is set in a range of 0.5T to 1T.

Next, a method for manufacturing the optical recording medium 10 of the present invention will be described. Reflective layer 5, recording layer 3, dielectric layers 2 and 4
As a method of forming such a film on the substrate 1, a known method of forming a thin film in a vacuum, for example, a vacuum deposition method (resistance heating type or electron beam type), an ion plating method, a sputtering method (DC or AC sputtering, reaction Sputtering). In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled.
In the sputtering method, for example, the recording layer 3 in a mixed state can be easily formed by simultaneously sputtering each target with a recording material and an additive material.
It is preferable to use a batch type film forming apparatus for simultaneously forming a plurality of substrates in a vacuum chamber or a single wafer type film forming apparatus for processing substrates one by one.

The thickness of the reflective layer 5, the recording layer 3, the dielectric layers 2 and 4, etc. to be formed is controlled by controlling the power and time of a sputtering power supply, or by using a quartz vibrating type film thickness meter. Monitoring is easy. The formation of the reflection layer 5, the recording layer 3, the dielectric layers 2, 4 and the like may be performed while the substrate 1 is fixed, or may be moved or rotated. Since the in-plane uniformity of the film thickness is excellent, the substrate 1
Are preferably rotated, and more preferably combined with revolution. When the substrate 1 is cooled by cooling the substrate carrier with water or air as needed, the amount of warpage can be reduced.

[0033]

Examples of the present invention will be described below. In the example,
Recording and reproduction were performed using an optical disk drive tester (DDU1000) manufactured by Pulstec, equipped with a laser diode having a wavelength of 639 nm and an objective lens with NA = 0.60. The reproduction power Pr was constant at 0.7 mW regardless of the linear velocity.

[0034]

Examples 1 to 15 Evaluations were made at a linear velocity of 3.5 m / s using an 8-16 modulation random pattern. The clock period T is 38.2 nanoseconds (ns) and the bit length is 0.26
7 μm / bit. Recording is performed at the same density as that of the DVD-ROM, and the capacity is equivalent to 4.7 GB. Slicing was performed at the center of the amplitude of the reproduced signal, and clock to data jitter was measured. To detect marks, use a time interval analyzer (TA, manufactured by Yokogawa Electric Corporation).
320) was used. The medium has a diameter of 120 mm and a thickness of 0.6
mm on a polycarbonate resin substrate. An empty groove is formed in the substrate at a track pitch of 0.74 μm. The groove depth was 30 nm and the groove width was 40%.

The first dielectric layer 2, the recording layer 3, the second dielectric layer 4, and the reflective layer 5 were formed in a vacuum order by sputtering while rotating the substrate 1 at a planetary speed of 60 revolutions per minute. First, the inside of the vacuum chamber was evacuated to 6 × 10 -5 Pa, and then 1.6 × 10 -1 Pa Ar gas was introduced. S
First 215 nm-thick ZnS to which 20 mol% of iO2 is added is formed on the substrate 1 by high frequency magnetron sputtering.
The dielectric layer 2 was formed. Then, Sb, Te, Ag, I
The four-element single target consisting of n was sputtered with a DC power supply to form a recording layer 3 having a thickness of 25 nm. FIG. 3 shows the composition of the recording layer 3 obtained.

In the composition analysis, the same recording layer 3 was separately separated by 100 n.
A thickness of m was formed on a silicon substrate and analyzed by ICP emission spectrometry. Further, a second dielectric layer 4 of the same material as that of the first dielectric layer 2 is formed to a thickness of 10 nm, and an Al layer is formed thereon.
A disk substrate was formed by forming a reflective layer 5 having a composition of Al97.5Cr2.5 and a thickness of 300 nm on a two-element single target composed of -Cr by DC sputtering.

After the disk substrate is taken out of the vacuum chamber, an acrylic UV curable resin (XR11 manufactured by Sumitomo Chemical Co., Ltd.) is spin-coated on the reflective layer 5 and cured by UV irradiation to form a 10 μm-thick resin layer (protective film). 6) was formed to obtain the optical recording medium 10 of the present invention. Further, a slow-acting ultraviolet curable resin was applied on the protective film 6 by using a screen printing method, and disks formed in the same manner were bonded and pressed and cured to produce a double-sided disk.

The optical recording medium 10 thus manufactured is irradiated with a wide-beam laser beam having a beam width in the track direction wider than the radial direction, thereby heating the recording film to a temperature higher than the crystallization temperature to initialize the recording film. Was done.

Thereafter, recording was performed from the side of the substrate 1 to a groove portion, which is a guide groove of the phase change recording layer 3. The groove is
It is convex when viewed from the direction of incidence of the laser beam. The recording strategy used the recording strategy shown in FIG. The width of each pulse is Tf = 0.5T, T1 = 0.3T, T2 =
0.7T and Tc = 0.6T. The power levels are P1 = 15.0 mW, P2 = 8.0 mW, P3 =
0.5 mW, P4 = 0.5 mW. The clock-to-data jitter, reflectivity and modulation of the reproduced signal were measured. Here, the modulation degree is a value obtained by dividing the amplitude I14 of the longest mark signal 14T by the RF level I14H on the 14T space side.

First, after recording a single 3T mark at a linear velocity of 3.5 m / s, the mark was erased by irradiating the mark with continuous light while changing the linear velocity, and the erasing rate at that time was measured. Here, the erasing rate indicates a difference between the carrier level of the 3T mark at the time of recording and the carrier level of the 3T mark after continuous light irradiation, and the larger the value, the better the erasing performance. The linear velocity at the time of erasure is 3.5 m / s (recording and constant velocity. DVD-RO
M linear velocity. ) 7.0 m / s (2x speed), 10.5 m / s
(3 times speed). FIG. 4 shows the relationship between the erasure rate and the linear velocity. FIG. 4 is an enlarged view of a part of FIG. 5, which is a triangular diagram showing the composition of Sb, Te, and M (Ag + In). In FIG. 5, the three vertices of the triangle are represented by a point X of M (Ag + In) 100% and a point Y of Te100
%, The point Z is Sb 100%, the bottom Sb 70%, Te
A straight line connecting the point X and the point W is defined as a straight line E where 30% of the point W is the eutectic point of the Sb-Te binary alloy.

In FIG. 4, the area (a) has a linear velocity of 3.
5 m / s, the area of (a) has a linear velocity of 7.0 m / s,
The region (c) shows a composition range where the linear velocity is 10.5 m / s and the erasure rate is 27 dB or more. In FIG. 4, the plotted symbols correspond to the compositions of the recording layer shown in FIG. In FIG. 3, the erasure rate is 27 dB.
Those indicating the above were marked with a circle. As is clear from FIG. 4, the erasable composition region approaches the straight line E as the linear velocity at the time of erasure increases, and shifts to a region where the Sb amount is large and the M amount is small at a higher linear velocity. It can be seen that the range is also reduced.

In a region where the amount of Sb is smaller and the amount of Te is larger than the straight line E, the degree of modulation increases. It is considered that the crystallization speed is reduced in this region, and an amorphous mark is easily formed. However, if excessive Te is contained, Sb55.0Te36.0M9.0 of Example 12 (Ag4.4In
In the case of 4.6) at% composition, even when the linear velocity is 3.5 m / s, when the erasing power is increased, an amorphous is formed, and it is not preferable to further increase the amount of Te.
Furthermore, after 1000 times of overwriting, it became impossible to measure the jitter. On the other hand, Sb66.6Te23.5M9.9 of Example 10 containing excess Sb (Ag4.
7In5.2) at% composition, linear velocity 10.5m / s
However, although crystallization proceeds, it is difficult to form an amorphous mark, and it is not preferable to increase the Sb amount further since the modulation degree becomes 40% or less.

Sb47.0 of Example 1 in a region with a large amount of M
Te32.0M21.0 (Ag8.0In13.0) a
With the t% composition, the modulation was 60%, but the number of rewrites was low, and the jitter could not be measured after 200 times. It was not preferable to further increase the amount of M. On the other hand, M
Sb67.1Te26.
In the 8M6.1 (Ag2.9In3.2) at% composition,
The crystallization temperature decreased to 162 ° C., and the crystallization became easier. However, if the amount of M is further reduced, the storage stability of the recording mark is lowered, which is not preferable. As described above, the composition range in which recording and overwriting can be performed at a linear velocity of 3.5 m / s to 7.0 m / s is a range indicated by (a) in FIG. It became clear.

[0044]

According to the optical recording medium of the present invention, the following effects can be obtained. Recording and rewriting are possible at a wide linear velocity. It has high sensitivity and can record and rewrite with the current laser power. Excellent repetitive overwrite performance. A rewritable medium with a high recording density equivalent to a DVD-ROM can be realized. A modulation degree of 60% or more and a reflectance of 15% or more can be obtained, and reproduction compatibility with DVD-ROM can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a typical layer configuration of an optical recording medium according to the present invention.

FIG. 2 is a diagram showing a divided pulse pattern of a recording laser.

FIG. 3 is a table showing a composition of a recording layer used in an optical recording medium according to the present invention.

FIG. 4 is an explanatory diagram showing the linear velocity dependency of the erasure rate in the optical recording medium according to the present invention.

FIG. 5 is an explanatory diagram showing a composition range of a recording layer in the optical recording medium according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 1st dielectric layer 3 recording layer 4 2nd dielectric layer 5 reflective layer 6 protective layer 10 optical recording medium

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) G11B 7/24 561 G11B 7/24 561M (72) Inventor Katsunori Oshima 3-chome Moriyacho, Kanagawa-ku, Yokohama-shi, Kanagawa 12 Japan Victor Co., Ltd. (72) Inventor Junji Kuroda 3-12 Moriyacho, Kanagawa-ku, Yokohama, Kanagawa Japan F-term (reference) 2H111 EA04 EA12 EA23 EA32 FA01 FA12 FA21 FB09 FB12 FB17 FB21 FB30 5D029 JA01 JB35 LB07 MA14 WB11 WB17 WC01 WC10 WD10

Claims (3)

[Claims] 1. An optical information recording medium having at least a phase-change recording layer provided on a substrate, wherein the recording layer composition is Sb, T
e, M (M is Ag, In) and the composition range is Sb, Te, and M.
And a straight line B, a straight line B, a straight line C, and a straight line D, wherein Ag ≦ In. 2. A method according to claim 1, wherein at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are laminated on the substrate in this order, and the first dielectric layer has a thickness d1 of 50 ≦ d1 ≦ 90 nm or 180 ≦ d1 ≦ 220 nm, and the recording layer thickness d2 is 15 ≦
d2 ≦ 30 nm, and the thickness d3 of the second dielectric layer is 8 ≦ d3 ≦
25 nm, thickness d4 of the reflective layer is 75 ≦ d4 ≦ 300 nm
2. The phase-change optical recording medium according to claim 1, wherein: 3. The substrate thickness is 0.6 mm and the groove depth d5 is 30.
≦ d5 ≦ 35 nm, and the groove width w1 is 35 <the track pitch.
3. The phase-change optical recording medium according to claim 2, wherein w1 <50%.