JP2003266949A - Phase change type optical information recording medium and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change type optical information recording medium making it possible to reduce or eliminate an initializing process time, and a manufacturing method therefor. <P>SOLUTION: (1) The phase change type optical information recording medium is formed by laminating at least a first dielectric layer, a recording layer, a second dielectric layer and a reflecting layer sequentially on a base. The recording layer has a first recording layer (crystallization accelerating layer) containing Ge and a second recording layer constituted mainly of SbTe having a composition ratio approximate to a eutectic composition (70≤Sb≤80 and 20≤Te≤30 in atom.%), and the reflectance before the start of recording is 60% or more of that after the recording. (2) In the manufacturing method of the phase change type optical information recording medium formed by laminating at least the first dielectric layer, the recording layer, the second dielectric layer and the reflecting layer sequentially on the base, the base is heated to a temperature lower than the deflection temperature under load of a base material on the occasion of forming the second recording layer in the case when the recording layer has the first recording layer (crystallization accelerating layer) and the second recording layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type optical information recording medium having a high reflectance after film formation to the extent that an address signal can be recognized and eliminating or reducing initialization using a laser, and a method thereof. It relates to a manufacturing method. More specifically, a phase change type optical information recording medium in which a first recording layer (crystallization promoting layer) for forming a recording film having high crystallinity is provided to reduce the reflectance difference before and after recording, and a method for manufacturing the same. Regarding

[0002]

2. Description of the Related Art A phase change type optical information recording medium is generally called a plastic substrate / dielectric material layer / chalcogen phase change recording layer / dielectric material layer / cooling reflection layer made of Al or Ag alloy. It has a layered structure consisting of four layers of functional thin films. The chalcogen-based phase change recording layer used here has a crystalline or amorphous structure due to thermal history. Usually, a crystalline state having high reflectance is recorded before information recording, and an amorphous mark having low reflectance is formed by information recording. In the production process, when the film formation process for each layer is completed, the layer is in an amorphous state, and the reflectance is low and the address information for writing information cannot be read. It is shipped after being changed. The process of changing to the crystallized state is called the initialization process.

A method using a semiconductor laser (Japanese Patent No. 2892818) is most frequently used as an initialization method. However, this initialization process takes a longer time than other steps in the process of manufacturing the optical information recording medium, and thus has a problem that many initialization devices must be installed. Therefore, as a method of shortening the time, a method using a semiconductor laser array (Japanese Patent Laid-Open No. 10-
112065), a method using a flash lamp (Japanese Patent No. 02846129), and the like. However, the method using a flash lamp may heat the substrate and cause the substrate itself to be deformed.As a countermeasure against this, light irradiation is performed through a filter that attenuates the absorption wavelength region of the substrate. A method has been adopted (Japanese Patent Laid-Open No. 10-188363).

Further, Japanese Patent Laid-Open No. 2001-297482 discloses a phase change type rewritable optical recording element which can be used without using an initial setting step or a predating step. Layers are disclosed. However, what it is specifically disclosed in this publication, sublayer consisting essentially of Sb and TEIn _m
According to the embodiment (Example 1), only Sb target and TeIn _{0.37 are used.}
When a recording disk was created using the target, the reflectance was about 7%, which was too low to enable sufficient tracking for recording, and when kept at room temperature for 16 hours, the reflectance was up to 10.5%. It is stated that the number has increased ([0
035] to [0036]). From this description, it is understood that the ordinary sputtering method as described in this publication cannot obtain an element (medium) having a satisfactory reflectance unless a treatment of keeping the room temperature after the recording film is formed. . Moreover, this publication has a recording layer composed of a first recording layer containing Ge, which is an essential constituent of the present invention, and a second recording layer containing SbTe as a main component in a composition ratio near the eutectic composition. , There is no description about a phase change type optical information recording medium having practically sufficient reflectance, that such a medium can be manufactured by ordinary sputtering, and further, in order to obtain a medium with higher reflectance, the second recording There is no description or suggestion of heating the substrate to a temperature below the over-deflection temperature of the substrate material during layer formation.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a recording mark is formed by changing the physical properties (crystalline state and amorphous state) of a recording layer by irradiating a laser beam and heating to form a recording mark portion and other portions. In a phase-change type optical information recording medium utilizing the difference in the reflectance of the read laser light due to the difference in the state of the recording medium, a recording medium capable of reducing or eliminating the initialization process time, and a manufacturing method thereof, that is, After the film forming process of each layer constituting the recording medium, the conventional (complete) initialization process is not necessary.
An object of the present invention is to provide a recording medium having a high reflectance in which the recording layer is crystallized and a method for manufacturing the recording medium.

[0006]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 10). 1) An optical information recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate, and the recording layer is a first recording layer containing Ge (promoting crystallization). Layer) and SbTe (atomic%) at a composition ratio near the eutectic composition
And has a second recording layer containing 70 ≦ Sb ≦ 80, 20 ≦ Te ≦ 30) as a main component, and the reflectance before recording is 60% or more of the reflectance after recording. Phase change type optical information recording medium. 2) The phase change type optical information recording medium as described in 1), wherein the first recording layer containing Ge contains Bi in an amount smaller than the composition ratio of Ge. 3) The phase change type optical information recording medium according to 1), wherein the first recording layer containing Ge is composed of two layers of a Ge layer and a Bi layer thinner than the Ge layer. 4) The phase change type optical information recording medium according to any one of 1) to 3), wherein the reflectance before recording is 80% or more of the reflectance after recording. 5) A method for manufacturing an optical information recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate, wherein the recording layer is a first recording layer (crystallized). (Acceleration layer) and the second recording layer, the method for producing a phase-change optical information recording medium, characterized in that the substrate is heated to a temperature lower than the excessive deflection temperature of the substrate material when the second recording layer is formed. . 6) A method for manufacturing an optical information recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate, wherein the recording layer is a first recording layer (crystallized). (Acceleration layer) and a second recording layer, the substrate is heated to a temperature lower than the over-deflection temperature of the substrate material during the second recording layer deposition or in the upstream step of the second recording layer deposition step, and A method of manufacturing a phase-change optical information recording medium, which comprises introducing Ar gas or a rare gas containing Ar gas into a vacuum chamber for a film. 7) The pressure of the introduced Ar gas is 2 × 10 ⁻³ to 2 × 1.
0 6 characterized in that it is a ^-2 Torr) method of manufacturing the phase-change optical information recording medium according. 8) The method for producing a phase change type optical information recording medium according to any one of 5) to 7), wherein the film forming rate of the second recording layer is 1.4 nm / sec or more. 9) The method for producing a phase change optical information recording medium according to any one of 5) to 8), wherein the film forming method is DC discharge sputtering having a pulsed waveform. 10) The method for producing a phase change type optical information recording medium according to 9), wherein the pulsed waveform has a frequency of 1 to 100 kHz and a ratio of a voltage effective for sputtering is 75% or more.

The present invention will be described in detail below. In order to eliminate the initialization process or reduce the specific gravity of the initialization process, the reflectance of the completed optical information recording medium after completion of film formation must be high. The high reflectance means that the recording layer of the completed optical information recording medium is in the crystallized state or has a structure close to the crystallized state. In order to obtain a structure close to such a crystallized state, it is necessary to adopt materials, structures and processes for facilitating the crystallization of the recording layer. Among the phase change recording materials, SbTe, which is called eutectic system, has a relatively low crystallization temperature, so the substrate temperature when forming a lower dielectric layer (underlayer) with a film thickness of about 200 nm on the substrate. As a result, the reflectance as an optical information recording medium after film formation is 60% or more. However, with SbTe alone, the stability of the mark after recording is low, and when the temperature rises to around 80 ° C. in the storage state, the recorded amorphous state mark is crystallized and the mark becomes unreadable.

On the other hand, in the present invention, a material capable of improving storage stability, particularly a first recording layer containing Ge, which has been confirmed to be particularly effective, is formed first to ensure storage stability. And Sb with a composition ratio near the eutectic composition with high reflectance
Te (in atomic%, 70 ≦ Sb ≦ 80, 20 ≦ Te ≦ 3
0) as a main component to form a second recording layer to form a recording layer having at least these two layers, whereby the reflectance before recording is 60% or more of the reflectance after recording. Succeeded in obtaining a type optical information recording medium. When the reflectance is 60% or more, the time required for laser initialization before recording can be shortened. In addition, the recording material of the composition near the eutectic system,
It is resistant to thermal shock during repeated recording, has excellent repeated recording characteristics, and has excellent physical properties that can be applied to high density recording and recording many times. In addition, "main component"
Means that 95% by mole or more of the second recording layer material is SbTe.
Means that.

Ge is an essential component as the material of the first recording layer in order to secure the storage characteristics of the optical information recording medium. However, if the first recording layer is made of Ge alone, the discharge may become unstable during film formation. Therefore, the first recording layer is composed of Ge and a material that promotes crystallization promotion of the second recording layer. Constitute. This promotes crystallization of the second recording layer, reduces the ratio of the reflectance before the start of recording and the reflectance after recording, and improves the reflectance of the entire recording layer to improve the laser initial phase of the optical information recording medium. Can be reduced. As a specific example of the material for exhibiting crystallization promotion, B
i (melting point 270.95 ° C.) has the largest crystallization promoting effect, and other melting points such as In (melting point 156.4 ° C.), Sn (melting point 231.97 ° C.), Se (melting point 220.2 ° C.) Mention may be made of low metal elements. Therefore, Ge
The first recording layer material containing
InGe, SnGe, SeGe, BiInG for ternary
e, BiSnGe, BiSeGe, InSnGe, In
SeGe and SnSeGe can be mentioned. Furthermore,
It is possible to use quaternary or quaternary elements, but since the effect of promoting crystallization of Bi is greatest, the higher the Bi content, the more advantageous in terms of increasing the relative reflectance. However, when Bi is larger than Ge, the reflectance of the amorphous level is increased due to the recording characteristics, the signal ratio is reduced, and the modulation characteristics are deteriorated.

The thickness of the first recording layer is 1.2-4.
8 nm, preferably 1.8 to 2.8 nm, and the thickness of the second recording layer is 10 to 25 nm, preferably 13 to 17 n.
m. When the first recording layer has a laminated structure, the Ge layer has a film thickness of 0.7 to 2.6 nm, preferably 1.1 to 1.5 nm, and is a layer film made of another material such as Bi. The thickness is 0.5 to 2.2 nm, preferably 0.7 to 1.
3 nm. An advantage of the laminated structure of the first recording layer is that Ge, which is effective in improving storage stability, and a material, which is effective in promoting crystallization of the second recording layer, can be appropriately produced in an arbitrary ratio. That is, it becomes easy to change the ratio according to the purpose such as improvement of storage stability and further promotion of crystallization. Furthermore, if the reflectance before the start of recording is 80% or more of the reflectance after recording, it is not necessary to perform initialization again with a laser, and the manufacturing process can be reduced by one step.

As a method of manufacturing the above-mentioned phase change type optical information recording medium, first, as one of the most effective methods for reducing the ratio of the reflectance before recording to the reflectance after recording, crystallization transition is caused. A method of applying heat so as to facilitate the process, specifically, during the film formation of the phase change recording layer (the second recording layer in the present invention) or in the step upstream of the film forming step of the phase change recording layer. And a step of heating the substrate and the recording layer material to a temperature lower than the over-deflection temperature of the substrate material (125 ° C. for polycarbonate). Among the above methods, a method of simply heating the substrate in the step upstream of the film forming step of the phase change recording layer has already been proposed as Japanese Patent Application No. 2001-81859 filed by the present applicant. Can also be applied to the manufacture of the optical information recording medium of the present invention. However, since the reflectance may be saturated at a certain temperature or more by simply heating the substrate, the present invention has also presented a method and conditions capable of further improving the reflectance.

Heating the substrate by the above method has the following three technical effects. The first is that when the thickness of the first dielectric layer is small, the substrate temperature can be controlled without depending on the process conditions and film thickness of the film formation of the first dielectric layer. At the time of film formation, the recording layer material is more easily crystallized by heat, and thirdly, the degassing of the substrate progresses, and the decrease in reflectance due to the adsorbed gas and moisture can be prevented. Furthermore, by heating the substrate, the initialization by laser irradiation can be reduced even when the first dielectric layer (lower protective layer) having a normal thin film thickness is provided, or the light which does not require initialization by laser irradiation can be used. The information recording medium can be easily manufactured. Further, by forming the recording layer into two layers, crystallization can be performed at a temperature lower than the crystallization temperature of the material. Even if a material having the same composition including a crystallization promoting material does not increase the reflectance after film formation at the same time, the reflectance after film formation increases only when the film is formed into two layers. This is probably because the first layer including the crystallization promoting layer serves as a seed crystal, and the promoting material is formed as a crystal nucleus while diffusing the promoting material during the film formation of the second recording layer.

Further, when Ar (argon) gas or a rare gas containing Ar gas is introduced into the vacuum chamber during heating, the reflectance after film formation can be improved, and the reflectance is higher than when Ar gas is not contained. A reflectance and a more uniform reflectance distribution can be obtained. In Figure 1, Ar introduced during heating
3 shows the relationship between the flow rate and the relative reflectance before recording. That is, when the temperature immediately before film formation of the second recording layer was controlled to 45 ° C. [measured with an E-type film thermocouple (SE4699 manufactured by Anritsu Keiki Co.)], the flow rate of Ar was changed, and the film formation rate was changed. It is the result of measuring the relative reflectance of the medium obtained in (1) before recording. From this figure, it is shown that the relative reflectance is 80% or more when the film forming rate is 1.4 nm / sec or more, and
It can be seen that when the Ar flow rate is in the range of 0 to 70 sccm, the relative reflectance is improved as compared with the case where Ar is not introduced (on the y axis). The preferable pressure of Ar gas to be introduced is 2 ×
It is 10 ^{−3 to} 2 × 10 ⁻² Torr (see Example 3). If the pressure of the Ar gas is too large, the substrate heated by Ar, which is the atmospheric gas, will be cooled, and the reflectance will be rather decreased.

As another method for improving the reflectance, there is a method in which the film forming rate of the second recording layer is 1.4 nm / sec or more. According to this method, a higher reflectance can be obtained as compared with the case where the film forming speed is slower than this, and the reflectance before recording can be 80% or more of the reflectance after recording. it can. In general, a film having good crystallinity can be obtained by slowly forming a film, but in the present invention, a film having good crystallinity can be obtained at a high film formation rate by using a crystallization promoting material and heating before film formation. Is obtained. However, the mechanism is not clear so far. FIG. 2 shows the relationship between the film formation rate of the second recording layer and the relative reflectance before recording. That is, the substrate temperature immediately before forming the second recording layer was controlled to be 45 ° C. [E-type film thermocouple (SE4 manufactured by Anritsu Keiki Co., Ltd.
699)], the relationship between the film forming speed in the case of forming a film without introducing argon during heating and the relative reflectance before recording of the obtained medium was measured. Equivalent to. From this figure, it can be seen that the relative reflectance is 80% or more at a film forming rate of 1.4 nm / sec or more.

By the way, when the film thickness of the second recording layer is 20 nm, the film forming time is 2. When the film forming rate is 8 nm / sec.
5 seconds, no problem in film formation controllability, but film formation rate is 20
In the case of nm / sec or more, the film formation time becomes 1 second or less, and the film thickness controllability at the time of film formation, that is, the effective controllability of the sputtering time at a given sputtering power is limited, and as a result, each The film thickness varies from recording medium to recording medium and affects the recording and storage characteristics. The reason why there is a limit to the effective controllability of the sputtering time is that in the normal sputtering method, the discharge ignition may be delayed for 0.05 to 0.2 seconds immediately after the start of discharge. For example, when the film formation time is 1 second and the discharge ignition delay is 0.2 seconds, the error reaches 20% as the film thickness, which affects the recording characteristics of the optical recording medium. As a countermeasure, a method of sharing the actual film formation time per unit time without changing the film formation rate per unit time, that is, the film formation method may be DC discharge sputtering having a pulse-like waveform. As a result, stable high-speed film formation is possible with little variation in the recording layer thickness.

The reason why the pulsed voltage application is good at the start of discharge, that is, although the discharge ignition is delayed for 0.05 to 0.2 seconds immediately after the negative voltage is applied to the sputter cathode, is the reason why the pulse waveform is applied. It is considered that this voltage is due to the discharge trigger function. However, even if a pulsed DC (direct current) is applied to the cathode, it has no effect when the film formation time is longer than or equal to the film formation time. Further, it is considered that there is substantially no effect if the discharge is not pulsed in a stable and continuous cycle. Furthermore, at least by pulsing, the film formation is performed at a high film formation speed during the substantial time during which the sputtering process is performed, and the total film formation time is lengthened to an extent sufficient to reach the stable region of film thickness controllability. There is a need. Except when there is originally a film formation time that is longer than the time to reach the stable film thickness controllability range, especially when the film formation time is shorter than the time to reach the stable film thickness controllability range, the frequency and duty (target It is necessary to consider the time ratio of applying a negative charge). In the range where reproducibility can be obtained, the effective film formation rate may be obtained in advance and corrected during film thickness control.

Further, according to the present invention, the frequency of the pulse-like waveform is 1 to 100 kHz, and the time ratio becomes a voltage effective for sputtering (that is, a negative voltage is supplied to the cathode electrode and a negative charge is applied to the target). Is preferably 75% or more. Under this condition, stable high-speed film formation can be performed without discharge delay. On the other hand, when the time ratio is less than 75%, it is necessary to consider the coefficient in consideration of the influence of discharge delay. In Figure 3, the pulse-like waveform is 50k.
An example of a pulse waveform when the period is 20 μs in Hz is shown. In the figure, the cathode voltage is the voltage applied to the sputtering target, the reverse potential is the reverse potential for canceling the charges remaining on the target surface, the reverse time is the time for applying the reverse potential, and the reverse time from the cycle. Is the time to apply a negative charge to the target, and the ratio is the duty (%).

FIG. 4 shows the relationship between the duty and the film thickness / effective sputtering time (nm / sec). The duty is 75%.
It has been observed that when the ratio is less than 1, the film formation rate is effectively reduced. If the duty is less than 75%, it is necessary to correct the film thickness as described above. Further, the substrate is heated while introducing the Ar gas or a rare gas containing Ar gas at the time of forming the second recording layer or at the upstream step of the second recording layer forming process, and at the same time as the process at the time of forming the second recording layer. Film speed 1.4nm
/ Sec or more, the as d of the optical information recording medium
epo. The reflectance (after film formation) can be further improved. The substrate used in the present invention needs to be transparent to the extent that recording / reproducing / erasing is possible when light is emitted from the substrate side, but in other cases, it may be transparent or opaque.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1 (Example of Producing Medium with Reflectivity of 60% or More without Heating by Providing First Dielectric Layer with Thickness of about 72 nm) Using Ni Stamper with Groove Information of Optical Information Recording Medium Each layer of the optical information recording medium was sequentially formed on the molded polycarbonate substrate having a thickness of 0.6 mm by using a magnetron sputtering apparatus for forming a multilayer film having a film forming chamber or a large number of film forming targets. First, as the first dielectric layer, ZnS.SiO ₂ (ZnS 80 mol%-
SiO ₂ 20 mol%) film was formed. Next, as a phase change recording layer, first, Bi ₄₉ Ge ₅₁ with a film thickness of 2.5 nm
Then, a second recording layer made of Sb ₇₈ Te ₂₂ (crystallization temperature of 124 ° C.) having a film thickness of 20 nm was formed. The temperature of the substrate at this time was measured with an E-type film-like thermocouple (SE4699 manufactured by Anritsu Keiki Co., Ltd.) under the same conditions as in the processes so far.
The temperature was 33 ° C. immediately before the formation of the phase change recording layer. Next, as a second dielectric layer, a ZnS.SiO ₂ film having a film thickness of 12 nm and having the same composition as that of the first dielectric layer was formed. Next, after forming a 4 nm-thickness SiC film as a reaction prevention layer between S of the second dielectric layer and Ag of the reflection layer, Ag of 140 nm thickness was formed.
The reflective layer of was formed. Finally, an overcoat layer made of an ultraviolet curable resin was formed and further bonded to a grooveless substrate having a thickness of 0.6 mm to obtain an optical information recording medium having a plate thickness of 1.2 mm.

The reflectance of the optical information recording medium manufactured as described above was measured by a characteristic evaluation device (Pulstec Industrial Co., Ltd.-RW automatic evaluation system DDU-1000).
It measured and evaluated using the semiconductor laser of wavelength 650nm. First, the optical information recording medium was erased with a signal erase / laser intensity of 7 mW, and the reflectance value after erasing was compared with the portion immediately after film formation without erasing. The reflectance of the portion was 69% of the reflectance of the portion erased by the signal erase laser intensity. When this non-erased part was processed with a laser initialization device, the initialization was completed in 32 seconds, which is about half of the initialization time that normally takes about 60 seconds,
The initialization time has been greatly reduced. The reflectance of the optical information recording medium after the laser initialization is 19% as a converted value when an Ag sputtered film having a film thickness of 140 nm formed on glass is used as a comparison target of the reflectance of 87.7%. Became a rate. The value of 19% is the same reflectance as that of a normal laser initialization process product. The jitter and modulation of the optical information recording medium after initialization were measured and found to be 6.5% and 64%, respectively. After checking the recording, place this optical information recording medium in a high temperature and high humidity tank at 80 ° C and 85% RH for 10 minutes.
When it was stored for 0 hour and the jitter and the modulation were measured again, they were 7.1% and 62%, respectively, and the changes were not at a problematic level.

Example 2 (Example of Providing First Dielectric Layer with Film Thickness of 72 nm and Heating to Produce Medium with Reflectivity of 60% or More) In the same manner as in Example 1, an optical information recording medium was produced. . First, a first dielectric layer having the same composition and the same film thickness as in Example 1 was formed. Next, as the phase change recording layer, first, the film thickness 2.
After forming a Bi ₄₉ Ge ₅₁ film having a thickness of 5 nm, the substrate was heated from the front with a control temperature of 120 ° C. using an infrared lamp of 3 kW to form a first recording layer. The temperature of the substrate at this time was measured by an E-type film thermocouple (SE4699 manufactured by Anritsu Keiki Co., Ltd.) under the same conditions as in the processes up to that point, and it was 45 ° C. immediately before the formation of the phase change recording layer. . Table 1 shows the relationship between the control temperature and the surface temperature of the polycarbonate substrate. Further, a second recording layer having the same composition and the same film thickness as in Example 1 was formed before the substrate temperature was lowered. The film forming method at this time was an ordinary DC sputtering method, and the film forming rate was 1.4 nm / sec. Subsequent second dielectric layers and thereafter were formed in exactly the same manner as in Example 1 to obtain an optical information recording medium.

The reflectance of the obtained optical information recording medium immediately after film formation was measured and evaluated in the same manner as in Example 1.
Comparing the reflectance with and without mW erase, the reflectance of the non-erased portion was 80% of the reflectance of the erased portion. The reflectance as an optical information recording medium is 18.
It was 0%. Further, the recording characteristics and storage characteristics of this optical information recording medium were examined. Evaluation is 650 nm, NA 0.6
Using a drive having an optical pickup of, linear recording density 0.267 μm / bit, track pitch 0.74 μ
m, the recording linear velocity was 8.5 m / sec, and the signal was modulated by 8/16. As a result, the initial jitter of this disc was in the 6% range. Even after rewriting 1000 times, 8
% Was maintained, and the change in characteristics of repeated recording and erasing was relatively small and good. As a storage test, 80 ℃ 85% RH
A storage test was carried out for 100 hours under the condition (1), and the life was judged by the presence or absence of a change in jitter of more than 1%, but the change in jitter was 1% or less, and the storage characteristics were good.

Example 3 (Reflectance of 1% with introduction of Ar gas)
Improved Example) An optical information recording medium was produced in exactly the same manner as in Example 2 except that Ar gas was introduced into the vacuum chamber of the sputtering apparatus when the substrate was heated. The amount of Ar introduced at this time was 5 sccm, and the gas pressure in the vacuum chamber was 2.0 × 10 5 as shown in Table 2.
^-3 Torr. The reflectance of the obtained optical information recording medium immediately after film formation was measured and evaluated in the same manner as in Example 2. In comparison of the reflectance with and without the 7 mW erase, the reflectance of the non-erased portion was the erased portion. The reflectance was 81%, which was an improvement of 1%. Furthermore, the distribution of reflectance was within ± 1.5% over the entire surface and was almost uniform.

Example 4 (Example in which the reflectance was improved by 4.9% by performing pulse DC sputtering on the second recording layer) The second recording layer was formed by the pulse DC sputtering method at an increased film forming speed. An optical information recording medium was produced in exactly the same manner as in Example 2 except for the above points. The pulse cycle at this time is 50k
Hz, and the time ratio of applying a negative voltage to the sputtering electrode serving as the cathode was 80%. Further, the film formation rate was set to a condition that the value of the negative voltage was 24 nm / sec when it was not pulsed: DC voltage −558 V, current 2.7 A (= about 1.5 kW).
The sputtering time was 1.04 seconds. The reflectance of the obtained optical information recording medium immediately after film formation was measured and evaluated in the same manner as in Example 2. In comparison of the reflectance with and without the 7 mW erase, the reflectance of the non-erased portion was the erased portion. The reflectance was 84.9%, which was an improvement of 4.9%.

Example 5 (Refer to the reflectance of 5.9 by introducing Ar gas and performing pulse DC sputtering on the second recording layer.
%) Example) An optical information recording medium was prepared in exactly the same manner as in Example 2 except that Ar gas was introduced at the time of heating the substrate and the second recording layer was formed by pulsed DC sputtering at an increased film forming rate. It was made. The amount of Ar introduced at this time was 30 sccm, and the pulse conditions and the film formation rate were the same as in Example 4. The reflectance of the obtained optical information recording medium immediately after film formation was measured and evaluated in the same manner as in Example 2. In comparison of the reflectance with and without the 7 mW erase, the reflectance of the non-erased portion was the erased portion. The reflectance was 85.9%, which was an improvement of 5.9%.

Example 6 (Example of sputtering without Ar gas) An optical information recording medium was produced under exactly the same conditions as in Example 3 except that Ar was not introduced into the vacuum chamber. At that time, the gas pressure in the vacuum chamber was a high vacuum degree of less than 10 ⁻⁵ Torr as shown in Table 2. The reflectance of the obtained optical information recording medium immediately after film formation was measured and evaluated in the same manner as in Example 3, and in the reflectance comparison with and without 7 mW erase, the reflectance of the non-erased portion was the erased portion. Of 80%. However, in the central part and the peripheral part where the stainless steel substrate fixing jig comes into contact, the reflectance is somewhat (5 to 5).
10%). In order to eliminate this uneven distribution of reflectance, it was necessary to perform additional laser initialization for uniformization.

Example 7 (Example of Normal Sputtering of Recording Layer) Instead of the pulse DC sputtering in Example 4, a normal sputter film having no pulse shape was formed. Deposition rate is 2
It was set to 4 nm / sec, that is, 0.83 sec for forming the second recording layer having a film thickness of 20 nm. The actual film thickness after film formation was measured and found to be 15 to 20 for a film thickness setting of 20 nm.
The result was slightly dispersed in the range of nm.

Comparative Example 1 (Example in which normal sputtering is performed and the recording layer is not divided into two layers) A target is formed so that the composition ratio of Bi, Ge, Sb, and Te is the same as in Example 1, and the recording layer is formed. An optical information recording medium was prepared under exactly the same conditions as in Example 1 except that the film was formed into a two-layered film having a thickness of 22.5 nm, and this medium was measured and evaluated in exactly the same manner as in Example 1. However, I could not erase because the groove information could not be read. Therefore, when the position was fixed and only the absolute reflectance was measured, it was 5% or less. Next, when the laser initialization was performed, it took 60 seconds. When the laser-initialized optical information recording medium was measured in the same manner as in Example 1, the same results were obtained for jitter, modulation, and changes after storage at high temperature and high humidity.

Comparative Example 2 (Example in which a first dielectric layer having a film thickness of about 72 nm is provided and heating is performed at a temperature equal to or higher than the over-deflection temperature of the substrate material) In Example 2, the substrate temperature is the over-deflection temperature of the polycarbonate which is the substrate material ( 130 ℃ above 125 ℃)
When heated up to this point, the polycarbonate substrate was deformed due to the temperature and the stress of the formed film, and became so sticky that the flatness of the substrate could not be retained.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

According to the present invention, the reflectance before the start of recording,
And a high-temperature storage reliability, a laser initialization load is reduced or initialization is unnecessary, and a phase change type optical information recording medium having a more uniform reflectance distribution, and a manufacturing method thereof are provided. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the flow rate of Ar introduced during heating and the relative reflectance before recording.

FIG. 2 is a diagram showing a relationship between a film formation rate of a second recording layer and a relative reflectance before recording.

FIG. 3 is a schematic diagram showing an example of a voltage waveform of pulsed DC sputtering.

FIG. 4 is a diagram showing a print voltage application duty and a substantial film formation rate when a pulse is applied.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsunari Hanaoka             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yuji Miura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H111 EA03 EA04 EA23 EA31 FA12                       FA21 FB02 FB05 FB09 FB10                       FB12 FB30 GA03                 5D029 JA01 JB03 JB05 JC02                 5D121 AA01 EE03 EE17 EE18 EE27                       EE28 GG07

Claims (10)

[Claims] 1. An optical information recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate, and the recording layer contains Ge. (Crystallization promoting layer) and SbTe having a composition ratio near the eutectic composition
It has a second recording layer containing (at atomic%, 70 ≦ Sb ≦ 80, 20 ≦ Te ≦ 30) as a main component, and the reflectance before recording is 60% or more of the reflectance after recording. A characteristic phase change type optical information recording medium. 2. The phase-change optical information recording medium according to claim 1, wherein the first recording layer containing Ge contains Bi in an amount smaller than the composition ratio of Ge. 3. The phase change type optical information recording medium according to claim 1, wherein the first recording layer containing Ge is composed of two layers, a Ge layer and a Bi layer thinner than the Ge layer. 4. The phase-change optical information recording medium according to claim 1, wherein the reflectance before recording is 80% or more of the reflectance after recording. 5. A method of manufacturing an optical information recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate, wherein the recording layer is the first recording layer. In the case of having a layer (crystallization promoting layer) and a second recording layer, the substrate is heated to a temperature lower than the excessive deflection temperature of the substrate material when the second recording layer is formed, and the phase change optical information recording is characterized. Medium manufacturing method. 6. A method of manufacturing an optical information recording medium in which at least a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer are sequentially laminated on a substrate, wherein the recording layer is the first recording layer. When having a layer (crystallization promoting layer) and a second recording layer, the substrate is heated to a temperature lower than the over-deflection temperature of the substrate material during the formation of the second recording layer or in the upstream step of the second recording layer forming step. In addition, the method for producing a phase-change optical information recording medium, characterized in that Ar gas or a rare gas containing Ar gas is introduced into the vacuum chamber for film formation. 7. The pressure of Ar gas introduced is 2 × 10 ^−3.
7. The method for manufacturing a phase-change optical information recording medium according to claim 6, wherein the phase change optical information recording medium is about 2 × 10 ⁻² Torr. 8. The method for manufacturing a phase change optical information recording medium according to claim 5, wherein the film forming rate of the second recording layer is 1.4 nm / sec or more. 9. The method for producing a phase change optical information recording medium according to claim 5, wherein the film forming method is DC discharge sputtering having a pulsed waveform. 10. The frequency of the pulsed waveform is 1 to 100 k.
10. The method for producing a phase-change optical information recording medium according to claim 9, wherein the ratio is Hz and the ratio of the voltage effective for sputtering is 75% or more.