JPH0885261A - Optical information recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE: To provide a phase changeable type optical information recording medium and manufacture thereof capable of preventing the degradation of recording marks due to long period play back and having an excellent repeating property of recording and erasing without giving a great effect to the recording and erasing characteristics. CONSTITUTION: The optical information recording medium is of the type that the phase change is caused between the crystal and the non-crystal, thereby performing recording and erasing of information, and the composition of antimony(Sb), tellurium(Te), germanium(Ge), and phosphorus(P) in the recording layer is represented by a following formula at an atomic number ratio. It is [number 1] (Sbx Tey Gez )100-w .Pw , 5<=x<=60, 35<=y<=65, 5<=z<=65, 0<w<=40, x+y+z=100. Thus, the decreasing quantity of C/N and repeating characteristics of recording and erasing being accompanied by the increase in the number of playing back (pulse number) is improved extremely.

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 causing a crystal-amorphous phase change in a recording layer, and more particularly, to improve reliability of recorded data and The present invention relates to an optical information recording medium having high repeatability. Among optical information recording media, the so-called phase change type optical disk, which records and erases information by utilizing the reversible phase change between the crystalline and amorphous phases of the optical recording layer, is called a laser light power. It has an advantage that old information can be erased and new information can be recorded at the same time (hereinafter referred to as "overwrite") simply by changing.

As a recording material of an overwritable phase change type optical disk, an In--Sb alloy (Appl.Phys.Let) having a low melting point and a high absorption efficiency of laser light is used.
t. 50, 667, 1987) and In-Sb-
Te alloy (Appl. Phys. Lett. Volume 50,
Page 16, 1987) or a chalcogen alloy such as a Ge-Te-Sb alloy (Japanese Patent Laid-Open No. 62-53886).

By overwriting, a portion of the recording layer irradiated with a high-power laser beam having an amorphization level is amorphized by rapid heating / cooling to a temperature equal to or higher than the melting point to form a recording mark. The portion irradiated with the laser light having the power of the crystallization level is crystallized by increasing the temperature to a crystallization-possible temperature lower than the melting point and gradually cooling, and becomes an erased portion. Such overwriting puts the optical disk on the drive,
It is performed by irradiating the disk surface with a laser beam while rotating it at a predetermined linear velocity.However, in order to completely perform erasing with one laser beam passage, the crystallization rate (amorphous The quality-to-crystal transition rate) must be the rate at which the laser beam is completely crystallized while passing through a point on the optical disc. That is, since the time required for the laser beam to pass through one point of the optical disk depends on the rotational speed (linear speed) of the optical disk, the crystallization speed of the recording layer material must be higher than this linear speed.

If the crystallization rate is too fast, the once melted portion may be partially crystallized during cooling, so it is necessary to remarkably increase the cooling rate for amorphization. Occurs and is not preferable in terms of recording sensitivity. Further, a material having a low crystallization temperature (temperature at which crystallization starts) may be selected in order to increase the erasing speed. However, by increasing the crystallization speed or lowering the crystallization temperature in this way, the recording mark (amorphous portion) formed during recording gradually becomes a crystal with a low energy level due to long-term reproduction. However, there is a problem that the reliability of the recorded data becomes insufficient because the recording marks are erased and deteriorated and the recording marks disappear.

In order to prevent the deterioration of the recording mark due to the reproduction for a long time, conventionally, a transition metal is added to the chalcogen alloy and the Ge ratio of the Sb-Te-Ge alloy is increased. .

[0006]

However, in the method of adding the transition metal among the conventional methods, the addition of about 1 at (atomic ratio)% improves the stability of the recording mark but decreases the erasing speed, Particularly, in a medium which records at a high speed, there are problems that a practical composition range is narrowed (called a margin with respect to the composition), and the contrast of reflectance between amorphous and crystal is lowered.

Further, in the method of increasing the Ge ratio of the Sb-Te-Ge alloy, there is a problem that the melting temperature increases as the amount of Ge increases and the recording sensitivity decreases. The present invention has been made by paying attention to such unsolved problems of the conventional technique, and can prevent deterioration of a recording mark due to reproduction for a long time without causing a large change in recording / erasing characteristics. An object of the present invention is to provide an optical information recording medium that can be formed and has excellent repetitive characteristics, and a manufacturing method thereof.

[0008]

According to the invention of claim 1 for solving the above-mentioned problems, a phase change between crystal and amorphous is caused in a recording layer provided on one surface of a transparent substrate. In the optical information recording medium for recording and erasing information, the antimony (Sb) and tellurium (T) of the recording layer
The composition of e), germanium (Ge) and phosphorus (P) is represented by the following formula in atomic ratio.

[Equation 2] An optical information recording medium characterized by the above.

In order to improve the erasing ratio and enhance the stability of the recording mark, another element such as Pd, Pt, A may be added if necessary.
Elements such as g, Au, Pb, Sn, Bi, Hf, and Nb may be added, or a phosphorus compound of these elements may be added to the target as a manufacturing method. As the substrate, a transparent substrate which has been conventionally used as a substrate for an optical disk can be used, but polycarbonate, glass or the like having good optical characteristics, high mechanical strength and excellent dimensional stability is used. It is preferable.

In addition, a protective layer made of at least one selected from metal or metalloid oxides, carbides, nitrides, fluorides and sulfides is provided on at least one of immediately above and below the recording layer. It may be. The protective layer material includes ZnS, SiO ₂ , SiO, and Ta.
₂ O ₅ , ZrO _{2 and} other oxides, SiC, TiC, C and other carbides, Si ₃ N ₄ , AlN and other nitrides, SmS, Sr
Examples thereof include a mixture with a sulfide such as S and one or more kinds of substances selected from fluorides such as MgF ₂ .

On the side opposite to the light incident side of the recording layer, A
A reflective layer made of a metal such as 1, Cr, Ni, Au, Hf, Pd and Ti or an alloy thereof may be provided, and for example, an Al-Ti alloy, an Al-Cr alloy, an Al-Si alloy, an Al-Hf alloy. , Al-Ta alloy, Al-Pd alloy, Al-Si-Mn alloy and the like are preferable. On the surface of the reflective layer opposite to the light incident side of the recording layer, UV curable resin (urethane type, acrylic type, silicon type, polyester type, etc.) or hot melt is used to protect and strengthen the thin film forming the reflective layer. A layer made of a system adhesive or the like may be provided.

The recording layer, the protective layer and the reflective layer generally have a structure as shown in FIG. That is, the first protective layer 2, the recording layer 3, the second protective layer 4, and the reflective layer 5 are laminated in this order on the transparent substrate 1. The thickness of each layer varies depending on the required characteristics, but in the case of an ordinary optical disc, the thickness of the first protective layer is 100 nm to 600 nm, the recording layer is 10 nm to 50 nm, and the second protective layer is in consideration of productivity and the like. Is 10 to 50 nm,
The reflective layer preferably has a thickness of 50 nm to 300 nm.

Further, when recording / erasing at a higher speed is required, the composition has an antimony (Sb) abundance ratio of 5 ≦ x ≦ 5.
0, tellurium (Te) abundance ratio 45 ≦ y ≦ 60, germanium (Ge) abundance ratio 5 ≦ z ≦ 50, and phosphorus abundance ratio 0 <w ≦ 15 are more preferable, and deterioration of the recording mark due to reproduction for a long time is preferable. It is possible to construct a medium that is excellent in repeatability while preventing the above-mentioned phenomenon and without impairing the recording / erasing characteristics.

The invention of claim 2 is a method suitable for manufacturing the optical information recording medium of claim 1, wherein the recording layer provided on one surface of the transparent substrate has a crystal-amorphous layer. In the method for manufacturing an optical information recording medium in which information is recorded / erased by causing a phase change, the recording layer is made of antimony (Sb), tellurium (Te), germanium (Ge) and phosphorus (P). In order to be composed of an alloy, a sintered body is manufactured by a sputtering method as a target, and the sintered body which is the target of the sputtering has a phosphorus powder, an antimony (Sb) phosphorus compound, a tellurium (Te) phosphorus compound, or A method of manufacturing an optical information recording medium, characterized in that a powder of a germanium (Ge) phosphorus compound is mixed and contained in a predetermined amount.

That is, it is possible to use only Ar as the atmosphere gas at the time of film formation, and use a mixture of Sb-Te-Ge alloy and phosphorus powder as a target. Furthermore, Sb, Te,
Instead of Ge, or in addition to Sb, Te, Ge, antimony compound (SbP), tellurium compound (P ₄ T
e ₁₀ , P ₂ Te ₅ ), germanium compound (P ₄ G
The inclusion of e _10), it is possible to form a Sb-Te-Ge-P alloy.

The invention of claim 3 is a method suitable for manufacturing the optical information recording medium of claim 1, wherein the recording layer provided on one surface of the transparent substrate is crystalline-amorphous. In a method of manufacturing an optical information recording medium in which information is recorded / erased by causing a phase change between particles, the recording layer is formed of antimony (Sb), tellurium (Te), germanium (G).
e) and phosphorus (P) to form an alloy, a sintered body is manufactured by a sputtering method as a target, and P (gas phosphorus) or a gas containing phosphorus and Ar are mixed as an atmosphere gas for the sputtering. A method for manufacturing an optical information recording medium, characterized in that gas is used.

That is, by using an Sb-Te-Ge alloy as a target, the flow rate of the gas obtained by vaporizing Ar and phosphorus as the atmosphere gas at the time of film formation is adjusted, or a gas containing phosphorus, for example, PF ₃ , PF ₅ , PCl ₃ , PCl ₅ , P
It can be added using ₂ H ₄ , PH ₃ or the like. As the method for forming the recording layer of the optical information recording medium of the present invention, besides the sputtering method, a vapor deposition method and other conventionally known methods can be adopted.

[0018]

According to the present invention, the recording layer of the optical information recording medium is S
By using b-Te-Ge-P, it is possible to prevent deterioration of recording marks due to reproduction for a long time and to construct a medium having excellent repeating characteristics without impairing recording / erasing characteristics. Here, when phosphorus is mixed with a semiconductor or a metal, the ability to make them amorphous (glass forming ability) becomes high. This is because the element phosphorus is a highly covalent element,
This is because it has the property of easily making other substances amorphous.
Due to the glass-forming ability of phosphorus, the Sb-Te-Ge-P alloy has a lower degree of structural freedom and higher rigidity as compared with the Sb-Te-Ge alloy, so that structural stability is increased, and It is considered that since the activation energy between the amorphous and the crystal becomes high, the reactivity becomes low and the stability increases. As a result, deterioration of the recording mark is less likely to occur even after long-time reproduction.

Further, the high glass-forming ability leads to difficulty in crystallization, and the larger the amount of phosphorus added, the slower the crystallization rate. As described above, the crystallization rate needs to be moderately higher than the linear velocity of the disc, so the amount of phosphorus added is determined according to the composition of the Sb-Te-Ge alloy and the linear velocity of the disc. That is, when the linear velocity of the disk is low, a large amount of phosphorus can be added, but as the speed increases, the optimum amount of phosphorus added decreases. However, since phosphorus has a low sublimation temperature, when the abundance ratio w of phosphorus in the Sb-Te-Ge-P alloy exceeds 40, the phosphorus is vaporized by the rapid heat during recording, and the recording / erasing characteristics and the repetitive characteristics are deteriorated. The risk of deterioration increases. Therefore, the abundance ratio w of phosphorus is 0 <w ≦ 40.

With respect to the composition of Sb-Te-Ge, the crystallization rate and the melting temperature change depending on the composition. The crystallization rate mainly depends on Sb and Te. When the abundance ratio x of antimony (Sb) exceeds 60, or the abundance ratio y of tellurium (Te) is 35 or less, or 6
When it exceeds 5, the crystallization speed becomes slow and the erasing property deteriorates. For example, it becomes difficult to erase even at a linear velocity as low as 1.2 m / s. Therefore, the abundance ratio of antimony (Sb) is 5 ≦ x ≦ 60, and the abundance ratio of tellurium (Te) is 3
5 ≦ y ≦ 65.

Further, germanium (Ge) has a great influence on the melting temperature, the melting temperature rises as the abundance ratio z of germanium increases, and if it exceeds 65, the recording sensitivity decreases. Furthermore, when the abundance ratio z of germanium becomes 5 or less, the melting temperature and the crystallization temperature decrease,
Since the recording marks are easily crystallized, the recording marks are deteriorated by the reproduction and storage for a long time. Therefore, the abundance ratio z of germanium (Ge) is 5 ≦ z ≦ 65.
Is.

The inventions of claims 2 to 3 are effective methods for producing the optical information recording medium of the present invention such that the composition of the recording layer becomes a predetermined amount. That is, according to the second aspect, the optical information of the present invention can be obtained by incorporating phosphorus powder, antimony (Sb) phosphorus compound, tellurium (Te) phosphorus compound or germanium (Ge) phosphorus compound into the target sintered body. A recording medium can be easily created. Further, according to the method of claim 3, a mixed gas of Ar and P (gas phosphorus) or a gas containing phosphorus is used as an atmosphere during film formation by sputtering, whereby the optical information recording medium of the present invention is obtained. Can be easily created.

[0023]

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

[0024]

Example 1 A phase change type optical disk having the layer structure shown in FIG. 1 was manufactured by the following procedure. First, it has a central hole, a diameter of 130 mm, a thickness of 1.2 mm, and 1.
ZnS and SiO are formed on the groove surface side of the substrate 1 made of a polycarbonate resin on a disk on which grooves having a pitch of 6 μm are formed.
_A 180 nm first protective layer 2 is formed by RF sputtering from a target of a mixture of ₂ (SiO ₂ abundance ratio 20 mol%).

Next, on this first protective layer 2, Sb-T
An e-Ge-P alloy is formed as the recording layer 3 with a thickness of 25 nm. Here, the recording layer 3 was formed by a sputtering method, and the target used was an alloy of Sb, Te, and Ge containing phosphorus. Further, a second protective layer 4 having a thickness of 20 nm is formed on the recording layer 3 similarly to the first protective layer 2, and a reflective layer 5 made of an Al alloy is formed to have a thickness of 200 nm. Then, 10 μm of UV curable resin 6 was applied by spin coating and cured by ultraviolet rays.

When the recording layer 3 is formed, Sb-
The composition of the Te-Ge alloy is constant (Sb: 25 at%, T
e: 55 at%, Ge: 20 at%), and sputtering is performed using a target containing phosphorus (P) in each ratio, and the content ratio x, y, z of each atom in the obtained thin film is w was calculated by measuring fluorescent X-rays. The results are shown in Table 1.

[0027]

[Table 1]

Each sample of the phase change type optical disk thus obtained was rotated at 1800 rpm by applying a driving device. A laser beam having a wavelength of 830 nm is modulated between a peak power of 18 mW and a bias power of 9 mW, and a recording signal of 3.7 MHz (duty ratio) corresponding to 1.5T which is a close-packed pattern of 2-7 modulation. Fifty
%) Pattern was overwritten 100 times. The recording characteristics at this time are shown in Table 1, and the phosphorus atom content ratio w is 0 <w.
No. ≦ 40 Recording was possible (○) for Nos. 2 to 4, but No. 4 of w = 41.5. Regarding No. 5, it was impossible to record (x) because an opening due to a laser beam was observed.

Further, in order to evaluate the resistance to the reproduction light, the read power of 2.0 m was applied to each of the obtained samples.
The reproduction was repeated at W, and the relationship between the number of times of reproduction light irradiation (hereinafter referred to as the number of passes) and the C / N (carrier-to-noise ratio) of the reproduction signal was examined. The result is shown by a graph in FIG. Figure 2
Is standardized with the C / N at the time of the first time (one time) recording being 0, and is described by the amount of decrease from that value. As can be seen from the graph of FIG. 2, the larger the amount of phosphorus in the recording layer, the smaller the decrease in C / N with the increase in the number of passes and the higher the resistance to reproducing light. If w ≧ 1.7 or more, 1
Even after reproduction of 10 million times, the decrease amount of C / N is 2d
It is B or less, and the resistance to the reproducing light is remarkably improved as compared with the recording layer made of the conventional Sb-Te-Ge alloy in which w = 0. The cause of the C / N decrease was mainly due to an increase in noise, not a decrease in carrier.

Next, in order to evaluate the repetitive characteristics, the obtained sample was modulated between a peak power of 18 mW and a bias power of 9 mW, 3.7 MHz and 1.3 MHz.
The decrease in C / N at 3.7 MHz was examined when 8 MHz was recorded alternately and overwriting was performed up to 1 million times. FIG.
Similarly to FIG. 2, the value of C / N at the time of the first (one time) recording is standardized as 0, and the variation amount of C / N from that value is shown. As can be seen from the graph of FIG. 3, the larger the amount of P in the recording layer is, the more the number of repetitions increases and the C / N increases.
Is small and the resistance to repeated recording / erasing is high. If w is 12.2, the C / N reduction amount is 2 dB or less even after 100,000 repetitions, and the recording layer is made of the conventional Sb-Te-Ge alloy with w = 0. In comparison, the resistance to repetition is improved by 10 dB (3 times the signal amplitude).

[0031]

Example 2 By the same procedure as in Example 1, a central hole was formed, a diameter of 130 mm, a thickness of 1.2 mm, and 1.6 on one side.
A phase-change optical disk having a layer structure shown in FIG. 1 was produced on the groove surface side of a substrate 1 made of a polycarbonate resin on a disk having grooves with a pitch of μm.

Here, when the recording layer 3 is formed, the amount of phosphorus in the alloy is kept constant (P: 8 at%), and the target containing Sb-Te-Ge alloy in each proportion is used. And the content ratio x, y, z, w of each atom in the obtained thin film was calculated by measuring fluorescent X-rays. Table 2 shows the composition of the recording layer prepared by changing the Te ratio so that the remaining Sb and Ge ratio is 1: 1.

[0033]

[Table 2]

In order to evaluate the erasing characteristics of the thus obtained phase-change type optical disk, each sample was put into a driving device and a laser beam having a wavelength of 830 nm was used for peak power 12
Modulate between mW and 6 mW of bias power, 1.5
After the T pattern was recorded, the laser beam was rotated at 600 rpm to emit unmodulated DC light to erase, and it was examined whether the erase ratio of 1.5T at this time was saturated in one erase operation.
Here, the erase ratio is an index indicating how much the previously recorded data is erased when new data is recorded on the recorded data,

[0035]

(Equation 3)

It is represented by In Table 2, No. 2-4
As for No. 6, the erase ratio was saturated by one erase operation, that is, the erase was possible (○), but the No. 1 and y
= 30 No. For No. 5, the erase ratio was not saturated by one erase operation, so that the composition (x) had low erase characteristics.

[0037]

[Third Embodiment] A procedure similar to that of the first embodiment has a center hole, a diameter of 130 mm, a thickness of 1.2 mm, and a diameter of 1.6 on one side.
A phase-change optical disk having a layer structure shown in FIG. 1 was produced on the groove surface side of a substrate 1 made of a polycarbonate resin on a disk having grooves with a pitch of μm.

Here, when the recording layer 3 is formed, the amount of phosphorus in the alloy is kept constant, and sputtering is carried out by using a target containing Sb-Te-Ge alloy in respective ratios.
The content ratio x, y, z, w of each atom in the obtained thin film was calculated by measurement of fluorescent X-rays. Table 3 shows phosphorus and Te in the recording layer.
Is kept constant (P: 8 at%, Te: 50 at%), and the ratio of Sb and Ge is changed.

[0039]

[Table 3]

In order to evaluate the data storage characteristics of the thus obtained phase change optical disk, an accelerated disk test was conducted. Drive each sample to 1800
Data was recorded by rotating at a rpm of a laser beam having a wavelength of 830 nm between a peak power of 18 mW and a bias power of 9 mW. After recording a random pattern, 80
Put in a thermo-hygrostat at 80 ℃ and relative humidity of 80% 10
The data was read after 00h, and the storage stability of the recording mark was evaluated by the data error rate (byte error rate).
The evaluation standard was No. when the bite error rate was evaluated as good (∘) when it was less than 3 times the value before it was put into the constant temperature and humidity chamber, and bad (x) when it was 3 times or more. 2-4
Was less than 3 times, but N of z = 2.5
o. With respect to No. 1, the storability of recording marks exceeded 3 times and was poor.

[0041]

[Embodiment 4] By the same procedure as in Embodiment 1, a central hole is formed, a diameter is 130 mm, a thickness is 1.2 mm, and one side is 1.6.
A phase-change optical disk having a layer structure shown in FIG. 1 was formed on the groove surface side of a substrate 1 made of a polycarbonate resin on a disk having grooves with a pitch of μm.

Here, when the recording layer 3 is formed, the amount of phosphorus (P) in the alloy is kept constant (P: 8 at%), whereas the Sb-Te-Ge alloy is contained in each ratio. Sputtering was performed using the target thus obtained, and the content ratio x, y, z, w of each atom in the obtained thin film was calculated by measurement of fluorescent X-rays. The results are shown in Table 4.

[0043]

[Table 4]

In order to evaluate the data recording characteristics of the thus obtained phase change type optical disk, each sample was driven by a driving device to rotate at 1800 rpm and a wavelength of 830.
The evaluation was performed while changing the peak power variously while fixing the laser light of nm at the bias power of 9 mW. With recording power, peak power with C / N exceeding 50 dB,
As defined, recording with a recording sensitivity of 20 mW or less was evaluated as good recording (◯), and when the power did not reach 50 dB, recording was defective (x). No. Regarding Nos. 2 and 3, the recording sensitivity was 20 mW or less and the recording was good (∘). For 1, the recording sensitivity is 2
There was a recording defect (x) of 0 mW or more.

[0045]

As described above, according to the present invention, the recording layer is made of an Sb-Te-Ge-P-based alloy (Sb atomic ratio x: 5≤x≤60, Te atomic ratio y: 35). ≤ y ≤ 6
5, Ge atomic ratio z: 5 ≦ z ≦ 65, P atomic ratio w: 0
By using a material of <w ≦ 40), it is possible to prevent deterioration of the recording mark due to long-term reproduction and to improve durability against repetition without giving a large change to the recording / erasing characteristics. An optical information recording medium with high data reliability can be obtained.

Further, according to the methods of claims 2 to 3, it is an effective method for producing the optical information recording medium of claim 1 so that the composition of the recording layer becomes a predetermined amount, and it is mass production of the optical information recording medium. Will be easier.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a layer structure of a phase change optical disc of the present invention.

FIG. 2 shows the number of times of irradiation of reproduction light (number of passes) and C / N of reproduction signal for each sample having different P content ratio (w).
It is a graph which shows the relationship with (carrier-to-noise ratio).

FIG. 3 is a graph showing the relationship between the number of times recording / erasing is repeated and C / N (carrier to noise ratio) for each sample having a different P content ratio (w).

[Explanation of symbols]

 1 Transparent Substrate 2 First Protective Layer 3 Recording Layer 4 Second Protective Layer 5 Reflective Layer

Claims (3)

[Claims] 1. A crystal-amorphous phase change is caused in a recording layer provided on one surface of a transparent substrate,
In an optical information recording medium for recording / erasing information, the composition of antimony (Sb), tellurium (Te), germanium (Ge) and phosphorus (P) in the recording layer is represented by the following formula in atomic number ratio. [Equation 1] An optical information recording medium characterized by the above. 2. A method for manufacturing an optical information recording medium, wherein information is recorded / erased by causing a crystal-amorphous phase change in a recording layer provided on one surface of a transparent substrate. In order to configure the recording layer with an alloy of antimony (Sb), tellurium (Te), germanium (Ge) and phosphorus (P), a sintered body is manufactured as a target by a sputtering method. A method for producing an optical information recording medium, characterized in that a phosphorus powder or an antimony (Sb) phosphorus compound, a tellurium (Te) phosphorus compound or a germanium (Ge) phosphorus compound is contained in the binder in advance. 3. A crystal-amorphous phase change is caused in a recording layer provided on one surface of a transparent substrate,
In a method of manufacturing an optical information recording medium for recording / erasing information, in order to form the recording layer with an alloy of antimony (Sb), tellurium (Te), germanium (Ge) and phosphorus (P), sintering is performed. A method for manufacturing an optical information recording medium, which is manufactured by a sputtering method using a body as a target, and a mixed gas of P (gas phosphorus) or a gas containing phosphorus and Ar is used as an atmosphere gas for the sputtering.