JP2005158211A - Initialization method of phase change optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optimum initialization method for a phase change optical recording medium capable of recording in a wide linear velocity range in which a recordable linear velocity is 3.5 m / s and a recordable linear velocity is 14 m / s.
A phase change optical recording medium having at least a first protective layer, a recording layer made of a material represented by the composition formula AgαXβSbδTeεGeγ, a second protective layer, and a reflective layer on a transparent substrate provided with a guide groove. An initialization method for initialization under conditions of an irradiation light power density of 15 to 22 mW / μm ² and an irradiation light beam linear velocity of 8 to 12 m / s.
In the above composition formula, X is at least one element selected from Ga, In, Tl, Pb, Sn, Bi, Cd, Hg, Mn, Dy, Cu, and Au, and α, β, δ, ε, and γ are Atomic%, α + β + δ + ε + γ = 100, when α = β = 0, 60 ≦ δ ≦ 90, 0 ≦ ε ≦ 30, 1 ≦ γ ≦ 10, and α + β> 0, 5 ≦ α + β + γ ≦ 10, 0 ≦ α ≦ 2, 0 ≦ β ≦ 8, 60 ≦ δ ≦ 90, 0 ≦ ε ≦ 30, 1 ≦ γ <10.
[Selection] Figure 2

Description

  The present invention relates to an optimal initialization method for a phase change optical recording medium capable of recording in a wide linear velocity range of 3.5 to 14 m / s.

In recent years, a recording medium capable of recording and reproducing a large amount of data at a high density and at a high speed has been demanded as the amount of information increases. Phase change optical recording media that record and reproduce information by irradiating a light beam, especially phase change optical discs, are excellent in signal quality and can be increased in density, and can easily be overwritten by one beam for high speed access. It is an excellent recording medium.
In general, such a phase change optical disk has at least a first protective layer, a reversible phase of an amorphous phase and a crystalline phase on a light-transmitting substrate on which a concave guide groove for guiding scanning of laser light is formed. A phase change recording layer that changes, a second protective layer, and a reflective layer made of metal are provided in this order, and a resin protective layer is further provided on the reflective layer. In the case of a bonded optical disk, the above structure is used for one or both, and the structure is bonded via an adhesive layer. When reproducing an optical disc on which data has been recorded, the reflectance difference or reflected light phase difference associated with the reversible phase change phenomenon between the amorphous phase and the crystalline phase of the recording layer is usually used, and the crystalline state is not recorded or erased. It is in a state.

The above structure is generally formed through a vacuum process such as sputtering or vacuum vapor deposition, and the state immediately after film formation of the recording layer thus formed, that is, the as-depo state is not. Often it is crystalline. Therefore, a step of crystallizing the recording layer called “initialization” is provided. The reason for providing this step is that the amorphous recording layer in the as-depo state requires a very long time for crystallization, unlike the amorphous state (mark) formed by overwrite recording. This is thought to be because the as-depo state recording layer has almost no crystal nuclei.
On the other hand, the recording principle of the phase change optical disk is as follows.
The recording layer is switched to the amorphous phase / crystalline phase using a focused laser beam pulsed at three output levels. At this time, the highest output level is used for melting the recording layer, the intermediate output level is used to heat the recording layer to a temperature just below the melting point and higher than the crystallization temperature, and the lowest level is used for the recording layer. Used to control heating or cooling. The recording layer melted by the laser pulse with the highest output level becomes amorphous or microcrystalline by the subsequent rapid cooling, resulting in a decrease in reflectivity and a recording mark. Further, all laser pulses with an intermediate output become crystalline and can be erased. In this way, by changing the writing laser pulse between the output levels, crystalline regions and amorphous regions can be alternately formed in the recording layer, and information is recorded.

By the way, the actual recording characteristics of an optical disc on which data is recorded by such a manufacturing process / recording method often largely depend on the characteristics of the recording layer material itself. Typical physical property values representing the characteristics of the recording layer material include a composition ratio, a melting point, a crystallization temperature, an optical constant, and the like. There is a "crystallization limit speed".
This “crystallization limit speed” means that when a rotating optical disk is irradiated with DC light of a constant power and the dependency of the optical disk reflectivity on the irradiated light beam linear velocity (optical disk rotation speed) is evaluated, as shown in FIG. It means the linear velocity at which the sudden decrease in reflectance starts. This is because the “constant power DC light” is regarded as an intermediate output pulse (erasing pulse) in the above recording principle, and when the linear velocity of the irradiation light beam of the recording / reproducing system is increased, crystallization (erasing) can be performed up to any linear velocity. It is an evaluation method focusing on whether it is possible. Taking FIG. 1 as an example, when the linear velocity is equal to or higher than the crystallization limit velocity (thick line in the figure) of the recording layer, the reflectance is lowered, which means that satisfactory crystallization (erasure) is not realized. Therefore, conventionally, the linear velocity of the irradiation light beam for initialization and overwriting (exactly, erase pulse) is performed in a linear velocity region sufficiently lower than the crystallization limit velocity of the recording layer in order to obtain a good erase ratio. It has been desirable.

However, in the case of a phase change optical recording medium which can be recorded in a wide linear velocity region where the lowest recordable linear velocity is 3.5 m / s and the highest recordable linear velocity is 14 m / s. Since it was necessary to design a high linear velocity recording medium that sufficiently satisfies the recording characteristics in high speed recording, the crystallization limit speed of this recording layer is 4 m / s higher than the linear velocity (14 m / s) in high linear velocity recording. It had to be designed around 10 m / s, which is a slow rate (in our experience, in order to obtain good high-speed recording characteristics with a linear velocity of 14 m / s, recording at a crystallization limit speed of around 14 m / s is required. Although it was known that it was desirable to use a material, it was difficult for such a recording material having a high crystallization limit speed to obtain good low linear velocity recording characteristics with the current recording method. Then, as usual, initialization was performed in a linear velocity region sufficiently slower than the crystallization limit velocity of the recording layer, and overwrite recording was performed at a recording linear velocity of 14 m / s, and the characteristics were evaluated. The erasure rate is low (from about 1 to 10 times), and there is a problem that rewriting has to be repeated several times before obtaining a stable erasure rate after initialization.
The cause of such a decrease in the erasure rate at the beginning of repeated recording is not clear, but based on the above fact, the crystal state of the recording layer after initialization and the crystal formed by rewriting the amorphous mark by overwrite erasure Since the state is different, the non-uniformity of reflectance occurs, and as a result, an increase in jitter may have occurred.

In the wide linear velocity recording medium having the lowest recordable linear velocity of 3.5 m / s and the highest recordable linear velocity of 14 m / s as in the present invention, the above-mentioned problem of jitter increase is particularly noticeable in recording at 14 m / s. It becomes. Now, taking FIG. 1 as an example, the crystal state after erasing at 2.4 × speed in the linear velocity region relatively slower than the crystallization limit velocity is “crystal state A”, and the linear velocity relatively higher than the crystallization limit velocity is The crystal state after erasing at 4 × speed in the region is referred to as “crystal state B”.
In the quadruple speed region, it is possible to reproduce the “crystal state A” by irradiating a sufficiently high power erasing pulse, so that an increase in jitter can be suppressed, but it is sufficiently high in the quadruple speed region where amorphization easily occurs. Since the power erasing pulse cannot be irradiated, the crystal state after erasing becomes “crystal state B” different from “crystal state A”. (On the other hand, the reason why the erasure rate is stabilized after the overwrite frequency is about 10 times or more is that the crystal state after initialization is overwritten by overwriting the amorphous mark by the overwrite frequency 10 times (“ This is considered to be due to the transition to the crystalline state B ") and the reflectance becomes uniform.)
Therefore, the reflectance after initialization and the reflectance after quadruple speed overwriting (reflectance of crystals re-formed by overwrite erasing of the marks recorded at the first time) are made equivalent to improve the recording characteristics at the initial stage of repeated recording. This has become an essential issue.

  Note that the following Patent Documents 1 to 14 are known as conventional techniques relating to a phase change optical recording medium that suppresses an increase in jitter value that is observed until the number of times of overwriting is several times, and a method for initializing the optical recording medium. However, Patent Documents 1 to 8 do not have a description of specific initialization conditions / methods (power density, linear velocity, etc.), and Patent Documents 9 to 14 have a description of the initialization method, Phase change optical recording in which the initialization condition is different from that of the present invention or is too wide and information is recorded / reproduced by irradiating a laser beam in a linear velocity range of 3.5 to 14 m / s targeted by the present invention. Not suitable for media initialization conditions.

Patent Document 1: Phase change optical recording medium in which the ratio Z of crystallization of the recording layer after initialization is in the range of 0.37 ≦ Z ≦ 0.46.
Patent Document 2: Phase change optical recording medium comprising a mixed film in which metal particles are dispersed in a dielectric and provided with a seed layer having an action of controlling the crystal grain size of the recording layer.
Patent Document 3: Overwriting 100 times or more by rotating a disk and irradiating a light beam that is wide in a direction perpendicular to the rotation direction and has two or more peak power levels in the rotation direction A phase change optical recording medium in which the average value of the crystal grain size after initialization is within twice the average value of the crystal grain size of the subsequent recording layer.
Patent Document 4: It consists of a step of alternately irradiating a laser beam at a power level at which the recording layer melts and a power level at which it is crystallized, and a step of finally irradiating a laser beam at a power level at which the recording layer is crystallized. An initialization method in which the crystal state of the crystal layer is the same as the crystal state after recording and erasing several tens of times.
Patent Document 5: Phase change optical recording medium in which the recording layer has a maximum crystal grain width of 50 to 500 nm after initialization.
Patent Document 6: Phase change optical recording medium in which the recording layer crystallization ratio Z after initialization is in the range of 0.50 ≦ Z ≦ 0.85.
Patent Document 7: Phase change optical recording medium in which the amorphous state immediately after sputtering has short-range order, and the solid number distribution with respect to the crystal grain size after crystallization has a plurality of maximums.
Patent Document 8: Initialization method in which the maximum width of crystal grains after initialization is 0.01 to 0.1 μm.

Patent Document 9: A beam is shaped so that the beam spot shape of the laser beam used for initialization becomes an oval shape on the recording film surface, and the major axis direction of this oval spot is substantially perpendicular to the recording track direction. An initialization method in which a beam is irradiated in such a state that at least a part of the recording layer is melted at least once.
Patent Document 10: A method of performing initialization after reforming an amorphous material immediately after film formation.
Patent Document 11: Recording after initialization is performed by overwriting at least twice.
Patent Document 12: Laser beam intensity distribution (distribution in the direction perpendicular to the track) used for initialization is obtained by calculating the average intensity of the half-value width of the maximum intensity at 10% from the end of each half-value width. Initialization method to make it smaller than strength.
Patent Document 13: Initialization method for irradiating optical recording medium with laser beam having power density P (mW / μm ² ) of 1.0 ≦ P ≦ 5.0 and irradiation time T (μsec) of 1 ≦ T ≦ 100 .
Patent Document 14: An initialization method in which laser light is irradiated at a linear velocity of 7 m / s or more in a state where the focus of the laser light is off the recording layer position of the optical recording medium.

JP-A-10-55539 Japanese Patent Laid-Open No. 10-106027 JP-A-10-112065 JP-A-11-144336 JP 2000-195111 A JP 2000-195113 A JP 2000-343826 A JP 2002-133711 A JP-A-9-212918 JP-A-10-241211 JP 2001-126265 A JP 2000-195112 A JP 2000-313170 A JP 2001-283477 A

  An object of the present invention is to provide an optimum initialization method for a phase change optical recording medium that can be recorded in a wide linear velocity range in which a recordable linear velocity is 3.5 m / s and a recordable linear velocity is 14 m / s. .

The above problems are solved by the following inventions 1) to 12) (hereinafter referred to as the present invention 1 to 12).
1) Irradiation to a phase change optical recording medium having at least a first protective layer, a recording layer made of a material represented by the following composition formula, a second protective layer, and a reflective layer on a transparent substrate provided with a guide groove. An initialization method characterized by initializing under conditions of an optical power density of 15 to 22 mW / μm ² , an irradiation light beam linear velocity of 8 to 12 m / s, and an irradiation light beam feed width of 10 to 50 μm / r.
AgαXβSbδTeεGeγ
In the formula, X is at least one element selected from Ga, In, Tl, Pb, Sn, Bi, Cd, Hg, Mn, Dy, Cu, and Au, and α, β, δ, ε, and γ are It is atomic% and satisfies the following requirement (1) or (2).
(1) α = β = 0
δ + ε + γ = 100
60 ≦ δ ≦ 90
0 ≦ ε ≦ 30
1 ≦ γ ≦ 10
Or
(2) α + β> 0
α + β + δ + ε + γ = 100
5 ≦ α + β + γ ≦ 10
0 ≦ α ≦ 2
0 ≦ β ≦ 8
60 ≦ δ ≦ 90
0 ≦ ε ≦ 30
1 ≦ γ <10
2) The initialization method according to 1), wherein the thickness of the recording layer is in the range of 8 to 20 nm.
3) The phase change optical recording medium has an oxide layer containing zirconium oxide (ZrO ₂ ) as an essential component between the recording layer and the first protective layer and / or between the recording layer and the second protective layer. The initialization method according to 1) or 2), wherein
4) The initialization method according to 3), wherein the main component of the oxide layer is zirconium oxide.
5) The initialization method according to 3) or 4), wherein the oxide layer contains titanium oxide.
6) The initialization method according to 5), wherein the content of titanium oxide is 60 mol% or less of the entire oxide layer material.
7) The initialization method according to any one of 3) to 6), wherein the oxide layer further contains a Group IIa oxide excluding rare earth oxide or beryllium.
8) The initialization method according to 7), wherein the content of the Group IIa oxide excluding rare earth oxide or beryllium is in the range of 1 to 10 mol% with respect to zirconium oxide.
9) The initialization method according to any one of 3) to 8), wherein the oxide layer has a thickness of 1 to 20 nm.
10) The initialization method according to any one of 1) to 9), wherein a spot size of the irradiation light beam for initialization is 200 μm ² or less and a light source output is 0.7 to 2.5 W.
11) The initialization irradiation light beam linear velocity is set within a velocity range of ± 2 m / s with respect to the crystallization limit velocity of the recording layer, and the initialization according to any one of 1) to 10) Method.
12) The feed width of the initialization irradiation light beam having an elliptical beam shape is not less than 1 / n and not more than (n−1) / n of the laser spot size (half-value width) in the elliptical long axis direction (provided that 2 ≦ The initialization method according to any one of 1) to 11), wherein n ≦ 5) is set as a reference, and the same portion is prevented from being irradiated multiple times.

Hereinafter, the present invention will be described in detail.
The crystal state after initialization of the recording layer of the phase change optical recording medium greatly depends on the initialization method. If the spot size (beam diameter) of the irradiation light used for initialization and overwrite erasure is different, the output power and feed width also differ, so the way heat is transferred to the actual optical recording medium is greatly different, and the linear velocity is simply adjusted. The above problem could not be solved simply by doing.
Therefore, as a result of repeated examinations of various initialization conditions in order to make the reflectivity after initialization equivalent to the reflectivity after overwriting, initialization was performed for specific phase change optical recording media under specific conditions. It has been found that the erasure rate at the initial stage of repeated recording improves if this is done.
That is, as the phase change optical recording medium, at least the first protective layer, the amorphous phase and the crystalline phase are reversibly changed on the transparent substrate provided with the laser light guide groove. A material composed of a recording layer, a second protective layer, and a reflective layer made of a material represented by the above composition formula is used. Further, when Ag is contained in the reflective layer and sulfur is contained in the second protective layer, it is desirable to provide an anti-sulfurization layer between the two layers in order to prevent deterioration of the reflective layer due to the sulfurization reaction of Ag.

In order to realize a phase change optical recording medium capable of recording / reproducing information by irradiating a laser beam in a wide range of linear velocity of 3.5 to 14 m / s, Sb and Te are used as main constituent elements. Recording layer material containing Ge, or containing Ge and Ag as essential elements, and at least one selected from X (Ga, In, Tl, Pb, Sn, Bi, Cd, Hg, Mn, Dy, Cu, Au) It is necessary to use a recording layer material to which a seed element is added. This recording layer material not only realizes wide linear velocity recording but also easily eliminates the non-uniformity of the reflectance after initialization and the reflectance after overwriting by the initialization methods of the present invention 1 and the present invention 10-12. It has been confirmed that it is a recording layer material.
Hereinafter, the optimum composition range of each element will be described.
An Sb—Te binary alloy having a composition near Sb ₇₀ Te ₃₀ in which the molar ratio of Sb to Te is 7: 3 is a phase change recording material that is less susceptible to compositional segregation due to overwriting and excellent in repeated recording characteristics. It is possible to adjust the crystallization limit speed by changing the blending ratio of Sb and Te. When the Sb ratio is increased, the crystallization limit speed is increased and the transfer speed can be increased. In the phase change optical recording medium that is the subject of the present invention, the composition range of Sb is 60 ≦ Sb ≦ 90 (atomic%).

  Since most of the ααXβSbδTeεGeγ used in the present invention is Sb—Te, it can be considered that Sb—Te is a base material, and other Ag, X, and Ge play the role of additive elements. The inventors examined the relationship with the disk characteristics by paying attention to the total amount of these additive elements. When α = β = 0, it is necessary to satisfy 1 ≦ γ ≦ 10, and α + β> 0. In the case of (both α and β are not 0), it has been found that a range satisfying 5 ≦ α + β + γ ≦ 10 is desirable. That is, it has been clarified that if the total amount of Ag, X and Ge (hereinafter referred to as total addition amount) is too large, the initial disk characteristics, particularly jitter, deteriorate, and if the total addition amount is too small, the storage reliability deteriorates. If the total amount added is large, the influence on the Sb-Te which is the base material becomes large and adversely affects the phase change phenomenon. If the total amount is small, the properties of Sb-Te itself become remarkable, which is a problem of Sb-Te. This seems to be due to the remarkable deterioration of storage reliability.

Ge is an indispensable additive element because the storage reliability of the phase change optical recording medium can be drastically improved by adding a small amount without increasing the crystallization temperature as much as Ga.
In addition, Ga can increase the crystallization limit speed with a small addition amount, and has the effect of increasing the crystallization temperature of the recording layer material, so that it is possible to provide an optical recording medium with excellent mark stability. is there. However, if the amount of Ga added is too large, the crystallization temperature becomes too high, and it becomes difficult to obtain a uniform and highly reflective crystal state at the time of initialization, so the Ga composition range should be 8 atomic% or less. preferable.
In has the same effect as Ga, but does not increase the crystallization temperature as high as Ga. Therefore, when considering the problem of initialization, it is effective to use it as an element supplementing Ga.
In addition to Ga and In, Tl, Pb, Sn, Bi, Cd, and Hg also have an effect of increasing the crystallization limit speed.

The reason why the crystallization limit speed is increased by adding these elements is unclear, but if the crystallization of the Sb—Te alloy is promoted, among these elements, the same valence as Sb can be obtained. Ga, In, and Bi, which are easy to take numbers, are more preferable, and Sn that is closest to Sb and has a high affinity with Sb is also preferable.
However, if the addition amount is too large, it is expected to cause deterioration of reproduction light and initial jitter, so that the composition range must be 8 atomic% or less.
In addition, according to the investigation of various additive elements by the present inventors, it has been found that Mn and Dy also have the same effect as In. In particular, Mn increases the crystallization speed and increases the Ge addition amount to a great extent. It is also known that it is an additive element that does not need to be increased and has excellent storage reliability.
Moreover, it is desirable to contain Cu and / or Au together with the additive element. Since these elements are additive elements effective in storage reliability, a desired wide linear velocity optical recording medium is realized by appropriately combining with the above additive elements, and the reflectivity after initialization and the overwrite reflectivity are realized. It is possible to design a recording material that can easily eliminate the non-uniformity.
Considering the above various conditions, the initialization method of the present invention is intended for an optical recording medium using a recording layer material having the composition defined in the first aspect of the present invention.

The film thickness of the recording layer is desirably in the range of 8 to 20 nm. When it is thinner than 8 nm, the recording characteristics are remarkably deteriorated by repeated overwriting. If it is thicker than 20 nm, uniform initialization of the recording layer becomes difficult, and the light transmittance becomes insufficient, so that a high reflectance cannot be obtained and the modulation factor is lowered. The film thickness of the preferred recording layer is in the range of 10 to 17 nm, more preferably 10 to 12 nm.
Furthermore, the amorphous state (as-depo state) immediately after the recording layer is formed changes depending on the film forming conditions. In the as-depo state, atoms are more randomly arranged on the substrate, and the larger the randomness, the longer the time required for initialization, making it difficult to obtain a desired crystal state. However, in sputtering at low gas pressure and high voltage, the sputtered particles flying on the substrate are considered to have larger kinetic energy than under normal conditions, and an alignment film with a certain degree of ordering is formed. It is easy to obtain a desired crystal state after initialization. Therefore, it is preferable to employ a sputtering method with a low gas pressure and a high voltage when forming the recording layer.

Further, in the phase change optical recording medium capable of recording in the wide linear velocity region of the recording linear velocity of 3.5 m / s to 14 m / s as described above, an oxide layer containing zirconium oxide (ZrO ₂ ) as an essential component. Is provided in contact with the recording layer, that is, between the recording layer and the first protective layer and / or between the recording layer and the second protective layer, the initialization failure tends to be further improved. I understand. This is because the oxide layer containing ZrO ₂ has a lower thermal conductivity than ZnS—SiO ₂ conventionally used as a protective layer, so that the initialization energy is efficiently absorbed in the recording layer, and the initial stage due to the lack of energy. This is thought to be due to the elimination of defects. Therefore, the effect increases as the content ratio of zirconium oxide in the oxide layer increases.
In particular, as in the present invention 4, when the main component of the oxide layer containing zirconium oxide (ZrO ₂ ) as an essential component is zirconium oxide, the characteristics of zirconium oxide are greatly reflected as the characteristics of the oxide layer. It is effective. In the present invention 4, “the main component is ZrO ₂ ” means that the content ratio of ZrO ₂ is the highest among the materials constituting the oxide layer.
Such an effect can be expected even when the oxide layer is provided with a thickness of about 1 nm, for example. Improvement of initialization failure can also be achieved by increasing the film thickness in addition to increasing the content ratio of zirconium oxide contained in the oxide layer. However, on the other hand, since the storage reliability of the recording medium deteriorates when the film thickness is increased, the storage reliability is reduced by reducing the thickness of the oxide layer to about 1 to 20 nm, preferably about 2 to 6 nm. It is desirable to prevent the deterioration of the material.

Further, the oxide layer containing ZrO ₂ as a main component preferably contains titanium oxide in addition to ZrO ₂ , and further preferably contains a rare earth oxide or a Group IIa oxide excluding beryllium. This is because it is possible to further reduce the thermal conductivity of the oxide layer by adding titanium oxide, and it is also effective in adjusting optical characteristics and reducing reliability deterioration, while rare earth oxidation. The group IIa oxide excluding the product or beryllium has the effect of reducing the volume change with respect to the temperature of ZrO ₂ , and the reason is that the stability against the temperature change at the time of initialization and recording is improved.
In order to obtain such an effect, the content of titanium oxide should be 60 mol% or less of the entire oxide layer material, and the content of Group IIa oxides excluding rare earth oxides or beryllium is based on ZrO _2. 1 to 10 mol% is desirable. The titanium oxide content is not necessarily limited to this range, but if it exceeds 60 mol%, the above range is suitable because the effect of the oxide layer containing ZrO ₂ becomes unclear. Further, preferable rare earth oxides or Group IIa oxides excluding beryllium include oxides such as Y, Mg, and Ca. In the case of an oxide layer in which an oxide such as Y, Mg, or Ca is simply dissolved in ZrO ₂ , since the storage reliability of the recording medium is significantly deteriorated, it is added in combination with an oxide such as TiO _2. It is desirable.

Next, it is necessary to initialize the optical recording medium as described above under specific initialization conditions of irradiation light power density of 15 to 22 mW / μm ² and irradiation light beam linear velocity of 8 to 12 m / s. It is possible to obtain a phase change optical recording medium that solves the above-described problems and has good initial characteristics of repeated recording.
This initialization condition is characterized in that the irradiation light power density is increased and the irradiation light beam linear velocity is increased as compared with the conventional initialization condition. Among these, for the irradiation light power density, when a recording layer material having a high crystallization limit speed is used for high linear velocity recording, it tends to become difficult to initialize as the crystallization limit speed of the recording layer material increases. When a high output initialization power is required, and even if a high output initialization power has a constant linear velocity and feed width, the power density ranges from 15 to 22 mW / μm ² as shown in FIG. When initialization was performed, the initial characteristics of repeated recording (particularly DOW1 characteristics: recording characteristics for the first overwriting) were further improved.

On the other hand, for the irradiation light beam linear velocity for initialization, as shown in FIG. 3, the spot size of the irradiation light beam and the feed width of the irradiation light beam are fixed, and the DOW1 characteristic depends on the linear velocity at a recording linear velocity of 14 m / s. As a result of the investigation, the DOW1 characteristic tended to improve as the irradiation light beam linear velocity increased at each output power, and the highest improvement effect was obtained when the linear velocity was around 8-12 m / s. Determined from.
Regarding the irradiation light power density, if these conditions are not met, if irradiation light power capable of sufficient initialization is applied, heat is accumulated in multiple tracks, and the temperature rises more than necessary, causing amorphousization. If it is too good, it will damage the entire disc.
On the other hand, with respect to the irradiation light beam linear velocity (not shown in FIG. 3), the recording material targeted for the present invention has an irradiation light velocity exceeding 12 m / s for a recording material having a crystallization limit velocity in the vicinity of 10 m / s. When initialized, satisfactory crystallization is not performed, resulting in initialization failure.

Inventions 10 to 12 relate to more preferable initialization conditions.
For example, when the phase-change optical recording medium is a disk-shaped disk, the initialization process rotates the disk at a constant linear velocity while irradiating an elliptical laser beam that is long in the disk radial direction, and then the elliptical laser. A method is adopted in which the recording layer is gradually annealed and crystallized by moving the beam in the radial direction with a feed width shorter than the spot size (half width) in the major axis direction of the beam.
Various light sources such as semiconductor lasers and gas lasers can be used for initialization, but initialization using a large LD (semiconductor laser) is excellent in terms of film uniformity, disk signal characteristics, and productivity. To preferred. In this case, in consideration of the current situation where the maximum output limit value of the currently developed LD is about 2.5 W, in order to stably initialize the irradiation light power density defined in the present invention 1, It is desirable that the size (area) of the light source used for initialization is 200 μm ² or less. For example, if a beam output is set to about 1.3 W using a light source with a spot size of 75 μm ² , the beam profile is uniform and stable. Light can be obtained. The lower limit of the spot size is not particularly limited, but if it is too small, the time required for initialization becomes longer and the productivity is lowered. Therefore, it is desirable to select an appropriate size according to the output of the LD.

  Further, the non-uniformity of the reflectivity after initialization and the reflectivity after overwrite associated with the phase change optical recording medium which can be recorded in a wide linear velocity range of linear velocity of 3.5 to 14 m / s as the object of the present invention. In general, the above problem can be solved by setting the irradiation light beam linear velocity of initialization within a range of ± 2 m / s with respect to the crystallization limit velocity of the target recording layer material. It was confirmed that the improvement effect at a high linear velocity in the vicinity of 0 to 1 m / s was the highest. If initialization is performed at a high irradiation light beam linear velocity exceeding 2 m / s with respect to the crystallization limit speed of the recording layer material, satisfactory crystallization cannot be realized, and irradiation light beam rays slower than −2 m / s are also achieved. It was confirmed that initialization at a speed is not practical because the initialization process takes time, and it is difficult to solve the problems of reflectance after initialization and reflectance non-uniformity after overwriting.

Regarding the irradiation light beam feed width, the minor axis direction of the elliptical beam is made coincident with the circumferential direction, the optical disk is rotated and scanned in the minor axis direction, and in the major axis (radius) direction every round (one rotation). Move it to initialize the entire surface. In this case, it is necessary to set the moving distance (feed width) in the radial direction per rotation to be shorter than the long axis of the beam so that “initialization unevenness” does not occur. If initialization is performed so that the irradiation is not repeated many times, not only the productivity is improved, but also the initialization non-uniformity derived from the energy distribution in the radial direction of the disk is avoided, and the recording linear velocity is 14 m / It was found that the DOW1 characteristic in s can also be improved.
In FIG. 4, the irradiation light beam linear velocity is constant, and the irradiation light beam feed width dependency of the DOW1 characteristic at the recording linear velocity of 14 m / s at each irradiation light power density (the spot size (half width) in the minor axis direction is 1 μm). However, it has been clarified that the DOW1 characteristic tends to be improved as the feed width increases at each power density (or the spot size diameter in the major axis direction).

In order to perform initialization without irradiating the same radius portion of the disk repeatedly, it is necessary to equalize the irradiation light beam feed width and the beam long axis. However, since the irradiation light beam actually has a beam profile, sufficient irradiation light power density cannot be obtained at the beam end, and there is a concern that the disk reflectivity after initialization varies depending on the radial position (uneven initialization). Is done. Therefore, preferably, the feed width of the initialization irradiation light beam having an elliptical beam shape is 1 / n or more of the laser spot size (half-value width) in the elliptical long axis direction, where n is an integer, and (n−1) / Set to n or less. In the case of overlapping (when n is not 1), the DOW1 characteristic tends to be improved as the feed width is larger than in FIG. It is not necessary to literally be a fraction of an integer on the basis of “1 / integer of the beam long axis length”, and an error of about ± 5% from the integral fraction to the beam long axis length is Of course, such a case is also included in the embodiment of the present invention.
On the other hand, in the case of a shape other than a disk-shaped disc, it is better to initialize so that the same part is not irradiated many times in a similar manner. There is.

Embodiments of the present invention will be described with reference to the drawings.
5-7 shows an example of the structure of embodiment in this invention. In this phase change optical recording medium, zirconium oxide (ZrO ₂ ) is an essential component on the interface of the recording layer in addition to the first protective layer, the phase change recording layer, the second protective layer, the antisulfuration layer, and the reflective layer on the substrate. An oxide layer is provided, and a bonding substrate is further provided through a resin protective layer.
The essence of the present invention is that the erasure rate at the initial stage of repeated recording is improved by initializing the specific phase change optical recording medium satisfying the requirements of the present invention 1 to 9 under specific conditions. Therefore, if it is a phase change optical recording medium satisfying the requirements specified in the present invention 1 to 9, for example, it corresponds to a general Blue-Ray (blue wavelength) disk type optical recording medium as shown in FIG. In addition, the present invention can be applied to the case corresponding to a general two-layer optical recording medium as shown in FIG. In the case of FIG. 9, for example, the first information layer is formed after the second information layer is initialized by the initialization method of the present invention.

  According to the present invention, it is possible to provide an optimal initialization method for a phase change optical recording medium that can be recorded in a wide linear velocity range in which a recordable linear velocity is 3.5 m / s and a recordable linear velocity is 14 m / s.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these Examples.
The phase change optical recording media (optical disks) of the examples and comparative examples are both formed by sputtering on a polycarbonate substrate with a guide groove having a diameter of 12 cm, a thickness of 0.6 mm, and a track pitch of 0.74 μm. A protective layer, a recording layer, a second protective layer, an antisulfuration layer, and a reflective layer are formed in this order, and a resin protective layer is formed thereon by spin coating, and finally a similar substrate for bonding (diameter 12 cm) , A polycarbonate substrate having a thickness of 0.6 mm). However, in the case of providing the oxide layer as in the present inventions 3 to 9, the oxide layer forming step was added before and / or after the recording layer forming step.

Example 1
The first protective layer is ZnS (80 mol%)-SiO ₂ (20 mol%) in thickness of 55 nm, and the oxide layer mainly composed of ZrO ₂ is ZrO containing 8 mol% Y ₂ O _{3. 2} (80 mol%)-TiO ₂ (20 mol%) with a thickness of 3 nm, the recording layer with Ag ₁ In ₄ Sb ₇₁ Te ₂₁ Ge ₃ with a thickness of 11 nm, and the second protective layer with ZnS (80 mol) %)-SiO ₂ (20 mol%) with a thickness of 11 nm, an anti-sulfurization layer with an Si thickness of 4 nm, and a reflective layer with an Ag thickness of 140 nm to produce an optical disc. Initialization was performed under the conditions shown in the column of Example 1.
After initialization, the reflectance was measured using an optical disk evaluation apparatus (DDU-1000 manufactured by Pulse Tech Co., Ltd.) having a pickup with a wavelength of 660 nm and NA of 0.65, and the in-peripheral distribution and in-plane distribution were evaluated. Further, after the reflectance measurement, a random signal is repeatedly recorded (twice) by the EFM + modulation method at a recording linear velocity of 14.0 m / s and a linear density of 0.267 μm / bit, and a reproducing linear velocity of 3.5 m / s. The recording characteristic (DOW1 characteristic), that is, jitter was evaluated at a reproduction power of 0.7 mW. The jitter is a value obtained by normalizing data to clock jitter (data to clock jitter) σ by the detection window width Tw.
Further, in order to investigate the storage reliability, the recording characteristics were evaluated again after the disk was left in a constant temperature bath at 80 ° C. and 85% RH for 300 hours.
The evaluation results are shown in Table 2. The evaluation criteria are as follows.
Regarding the distribution of the reflectance within the circumference, “uniform” when the reflectance fluctuation width is less than 1% within the same circumference, “slightly fluctuation” when the reflectance fluctuation is 1-2%, and “non-uniformity” when the reflectance exceeds 2%. "
Regarding the in-plane distribution of reflectivity, the variation with respect to the average reflectivity of each circumference is “uniform” when it is less than 1%, “slightly fluctuates” when it is 1-2%, and “not good” when it exceeds 2%. Uniform ”.
Regarding the DOW1 characteristic, a case where the jitter is 9% or less is “◯”, a case where the jitter is larger than 9% and 10% or less is “Δ”, and a case where the jitter is larger than 10% is “×”.
Regarding storage reliability, “◯” indicates that the jitter fluctuation after being left in an 80 ° C. and 85% RH constant temperature bath for 300 hours is within 0.5%, and “△” indicates that the jitter variation is greater than 0.5% and less than 1.0%. “,” When the jitter fluctuated in excess of 1.0% was marked “x”. In Comparative Examples 1 to 4, the storage reliability was not evaluated.
As can be seen from the table, in this example, good results could be obtained in all items of the DOW1 characteristics at the in-peripheral distribution, the in-plane distribution of the disk reflectivity, and the recording linear velocity of 14 m / s. In addition, even after being left in a thermostatic bath, the characteristics were not deteriorated, and good storage reliability could be obtained.

Example 2
The same optical disk as in Example 1 was used, and the initialization was performed under the same conditions as in Example 1 except that the irradiation light power density was changed to 16.0 mW / μm ² and the irradiation light beam linear velocity was changed to 9 m / s. .
The evaluation results are as shown in Table 2 and, as in Example 1, are good in all items of disk reflectivity in-circumference distribution, in-plane distribution, DOW1 characteristics at 14 m / s of recording linear velocity, and storage reliability. The result was obtained.

Example 3
The same optical disk as in Example 1 was used, and initialization was performed under the same conditions as in Example 2 except that the irradiation light power density was changed to 15.3 mW / μm ² and the irradiation light beam feed width was changed to 18 μm / r. .
The evaluation results are as shown in Table 2, and in the same manner as in Examples 1 and 2, in all items of disk reflectivity in-circumference distribution, in-plane distribution, DOW1 characteristics and storage reliability at a recording linear velocity of 14 m / s. Good results could be obtained.

Example 4
Using the same optical disk as in Example 1, initialization was performed under the conditions shown in the column of Example 4 in Table 1 for evaluation.
The evaluation results are as shown in Table 2, and in the same manner as in Examples 1 to 3, in all items of disk reflectivity in-circumference distribution, in-plane distribution, DOW1 characteristics and storage reliability at a recording linear velocity of 14 m / s. Good results could be obtained.

Example 5
An optical disc was produced in the same manner as in Example 1 except that the recording material was changed to Ag ₁ In ₃ Sb ₇₂ Te ₂₀ Ge ₄ , and initialization was performed and evaluated under the same conditions as in Example 1.
The evaluation results are as shown in Table 2. As in Examples 1 to 4, in all items of disk reflectivity in-circumference distribution, in-plane distribution, DOW1 characteristics and storage reliability at a recording linear velocity of 14 m / s. Good results could be obtained.

Example 6
An optical disk was produced in the same manner as in Example 1 except that the recording material was changed to Ag ₁ Ga ₃ Sb ₇₀ Te ₂₁ Ge ₅ , and initialization was performed under the same conditions as in Example 1 for evaluation.
The evaluation results are as shown in Table 2, and in the same manner as in Examples 1 to 5, in all the items of the DOW1 characteristics and storage reliability of the disk reflectance in the circumferential distribution, in-plane distribution, and recording linear velocity of 14 m / s. Good results could be obtained.

Example 7
An optical disc was produced in the same manner as in Example 1 except that the recording material was changed to Sb ₇₄ Te ₂₁ Ge ₅ , and initialization was performed and evaluated under the same conditions as in Example 1.
The evaluation results are as shown in Table 2. Like in Examples 1 to 6, good in all items of disk reflectivity in-circumference distribution, in-plane distribution, DOW1 characteristics and storage reliability at a recording linear velocity of 14 m / s. I was able to get a good result.

Example 8
Except that the film thickness of the recording layer was changed to 18 nm, an optical disc was produced in the same manner as in Example 1, and initialization was performed and evaluated under the same conditions as in Example 1.
The evaluation results are as shown in Table 2. There are slight fluctuations in the in-plane distribution and in-plane distribution of the disk reflectivity, and the DOW1 characteristic (jitter) at a recording linear velocity of 14 m / s exceeds 9%. However, relatively good results were obtained as the characteristics of the entire disk.

Example 9
An optical disk was produced in the same manner as in Example 1 except that the oxide layer containing ZrO ₂ as a main component was not provided. The optical disk was initialized and evaluated under the same conditions as in Example 1.
The evaluation results are as shown in Table 2. The two items of DOW1 characteristics and storage reliability at a recording linear velocity of 14 m / s were good, but the disc reflectance was slightly different in the circumferential distribution and in-plane distribution. There was a change.

Example 10
An optical disc was produced in the same manner as in Example 1 except that the thickness of the oxide layer containing ZrO ₂ as a main component was 20 nm. The optical disc was initialized and evaluated under the same conditions as in Example 1.
The evaluation results are as shown in Table 2 and the distribution of disk reflectivity in the circumference and in-plane distribution was good, but the two items of DOW1 characteristics and storage reliability at a recording linear velocity of 14 m / s deteriorated. I have.

Example 11
An optical disk was produced in the same manner as in Example 1 except that the thickness of the oxide layer containing ZrO ₂ as a main component was 8 nm. The optical disk was initialized and evaluated under the same conditions as in Example 1.
The evaluation results are as shown in Table 2, and the items of the DOW1 characteristic at the disc reflectance reflectance distribution, in-plane distribution, and recording linear velocity of 14 m / s were good, but the storage reliability was deteriorated. It was.

Comparative Example 1
The same optical disk as in Example 1 was used, and initialization was performed and evaluated in the same manner as in Example 1 except that the irradiation light beam linear velocity was changed to 6 m / s.
The evaluation results are as shown in Table 2. The in-peripheral distribution and in-plane distribution of the disk reflectivity were uniform, but the DOW1 characteristics at a recording linear velocity of 14 m / s were not improved.

Comparative Example 2
The same optical disk as in Example 1 was used, and initialization was performed and evaluated in the same manner as in Example 1 except that the irradiation light beam linear velocity was changed to 14 m / s.
The evaluation results are as shown in Table 2. The in-peripheral distribution and in-plane distribution of the disk reflectivity were non-uniform and the reflectivity fluctuated, and the DOW1 characteristic at a recording linear velocity of 14 m / s was not improved.

Comparative Example 3
Using the same optical disk as in Example 1, initialization was performed under the conditions shown in the column of Comparative Example 3 in Table 1 for evaluation.
The evaluation results are as shown in Table 2. The in-peripheral distribution and in-plane distribution of the disk reflectivity were non-uniform and the reflectivity fluctuated, and the DOW1 characteristic at a recording linear velocity of 14 m / s was not improved.

Comparative Example 4
Using the same optical disk as in Example 1, initialization was performed under the conditions shown in the column of Comparative Example 4 in Table 1 for evaluation.
The evaluation results are as shown in Table 2. The in-peripheral distribution and in-plane distribution of the disk reflectivity were non-uniform and the reflectivity fluctuated, and the DOW1 characteristic at a recording linear velocity of 14 m / s was not improved.

The figure for demonstrating the crystallization limit speed. The figure which shows the irradiation light power density dependence for initialization of DOW1 characteristic when recording with the recording linear velocity of 14 m / s after initializing the optical disk of Example 1 with constant linear velocity and feed width. The figure which shows the irradiation light beam linear velocity dependence of the DOW1 characteristic at the time of recording with the recording linear velocity of 14 m / s after initialization with the spot size of the optical beam of Example 1, and initialization with constant feed width. When the optical discs of Examples 1 and 5 were initialized at each irradiation light power density at a constant irradiation light beam linear velocity and then recorded at a recording linear velocity of 14 m / s, the DOW1 characteristic dependency on the irradiation light beam feed width The figure shown. The figure which shows an example of the structure of embodiment in this invention. The figure which shows the other example of the structure of embodiment in this invention. The figure which shows the further another example of the structure of embodiment in this invention. The figure which shows the further another example of the structure of embodiment in this invention. The figure which shows the further another example of the structure of embodiment in this invention.

Claims (12)

Irradiation light power to a phase change optical recording medium having at least a first protective layer, a recording layer made of a material represented by the following composition formula, a second protective layer, and a reflective layer on a transparent substrate provided with a guide groove An initialization method characterized by initializing under conditions of a density of 15 to 22 mW / μm ² and an irradiation light beam linear velocity of 8 to 12 m / s.
AgαXβSbδTeεGeγ
In the formula, X is at least one element selected from Ga, In, Tl, Pb, Sn, Bi, Cd, Hg, Mn, Dy, Cu, and Au, and α, β, δ, ε, and γ are It is atomic% and satisfies the following requirement (1) or (2).
(1) α = β = 0
δ + ε + γ = 100
60 ≦ δ ≦ 90
0 ≦ ε ≦ 30
1 ≦ γ ≦ 10
Or
(2) α + β> 0
α + β + δ + ε + γ = 100
5 ≦ α + β + γ ≦ 10
0 ≦ α ≦ 2
0 ≦ β ≦ 8
60 ≦ δ ≦ 90
0 ≦ ε ≦ 30
1 ≦ γ <10   2. The initialization method according to claim 1, wherein the thickness of the recording layer is in the range of 8 to 20 nm. The phase change optical recording medium has an oxide layer containing zirconium oxide (ZrO ₂ ) as an essential component between the recording layer and the first protective layer and / or between the recording layer and the second protective layer. The initialization method according to claim 1, wherein the initialization method is provided.   4. The initialization method according to claim 3, wherein the main component of the oxide layer is zirconium oxide.   The initialization method according to claim 3 or 4, wherein the oxide layer contains titanium oxide.   6. The initialization method according to claim 5, wherein the content of titanium oxide is 60 mol% or less of the whole oxide layer material.   The initialization method according to claim 3, wherein the oxide layer further contains a rare earth oxide or a Group IIa oxide excluding beryllium.   The initialization method according to claim 7, wherein the content of the Group IIa oxide excluding rare earth oxide or beryllium is in the range of 1 to 10 mol% with respect to zirconium oxide.   9. The initialization method according to claim 3, wherein the oxide layer has a thickness of 1 to 20 nm. 10. The initialization method according to claim 1, wherein the spot size of the irradiation light beam for initialization is 200 μm ² or less and the light source output is 0.7 to 2.5 W.   The initialization method according to any one of claims 1 to 10, wherein an initialization irradiation light beam linear velocity is within a velocity range of ± 2 m / s with respect to a crystallization limit velocity of the recording layer. The feed width of the initialization irradiation light beam having an elliptical beam shape is 1 / n or more and (n−1) / n or less (where 2 ≦ n ≦ n) of the laser spot size (half-value width) in the elliptical long axis direction. The initialization method according to any one of claims 1 to 11, which is set based on 5) and prevents the same portion from being irradiated twice or more times.

Images