JP2003006859A - Optical information recording method and optical information recording medium - Google Patents

Abstract

(57) Abstract: In the present invention, good recording can be performed even when a conventional recording strategy in which one set of pulse lengths of a multi-pulse section is T is used as it is at a higher recording linear velocity. It is an object of the present invention to propose a method capable of performing the above, and to provide a recording medium suitable for the method. SOLUTION: At least three of recording, erasing and biasing are performed by utilizing a reversible phase change between an amorphous phase and a crystalline phase of a recording layer.
An optical information recording method for forming an amorphous mark using a laser beam modulated to a value power, characterized in that at least a bias power value is variable according to a recording linear velocity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to optical information recording,
More specifically, the present invention relates to an optical information recording method using a laser beam modulated to at least three-valued power of recording, erasing, and bias, and a phase change type optical information recording medium used therefor.

[0002]

2. Description of the Related Art As a conventional technique, Japanese Patent Laid-Open No. 2000-3131.
The 70 _{JP, ((Sb X Te 1-} X) Y Ge 1-Y) Z M 1-Z 0.7 ≦ x ≦ 0.9 0.8 ≦ y <1 0.88 ≦ z <1 M A recording method by a mark length modulation method using a phase change type optical information recording medium of: In and / or Ga is disclosed. Here, it is defined that Pb <Pe because it is advantageous that the bias power Pb is small in order to create the quenching condition, but there is no disclosure about the relationship with the recording linear velocity.

[0003]

An optical recording medium capable of recording / reproducing and erasing information by irradiating a semiconductor laser beam has a magneto-optical recording system in which magnetization is reversed by utilizing heat and a crystal is used. There is a phase change recording method that can record and erase by utilizing an amorphous reversible phase change. The latter is capable of single beam overwriting, and the drive side optical system also
It is characterized by being simpler and has been applied as a recording medium for computers and audiovisual.

As a recording material, it is easy to form an amorphous material
Moreover, composition segregation does not easily occur even after repeated recording.
Therefore, various compounds centered on chalcogen and close to eutectic
A nearby composition is used. What has been put to practical use
As GeTe and Sb₂Te ₃Mixture of Sb and Sb
-Sb₂Te₃Ag and In are added to the pseudo binary eutectic composition.
There is a system.

The use of the phase change recording medium is expected to expand to high density image recording in the future, but for that purpose, it is necessary to realize high speed overwriting, and at present, the DVD-
As a phase-change type optical recording medium having a recording density equivalent to that of a ROM, an optical recording medium capable of recording at twice or more the reproducing / recording linear velocity of a DVD-ROM has been developed.

FIG. 1 shows an example of a system which has been conventionally used as a recording system for recording an amorphous phase mark on a crystal phase. Recording / erasing is performed by modulating the laser power into three values of recording power Pw, bias power Pb, and erasing power Pe. In the space portion, Pe is continuously irradiated to crystallize and erase the already recorded mark. In the mark portion, subsequently, a pulse train of Pw and Pb is irradiated. Since the recording layer is melted by Pw and then is rapidly cooled by being modulated to Pb, the melted region becomes an amorphous phase. Further, by modulating to Pe, the rear end of the amorphous portion is crystallized and a mark of a predetermined length is formed.

The time length of the mark is nT (n: integer,
T: reference clock), a set of pulse lengths of an intermediate portion (hereinafter, this intermediate portion is referred to as a multi-pulse portion) excluding the first pulse and the last pulse for forming the nT mark Conventionally, (Pw irradiation time) + (Pb
(Irradiation time of) = T is generally set. However, if the recording linear velocity becomes faster and the reference clock T becomes shorter, the irradiation time of Pw becomes shorter even if the ratio of the irradiation time of Pw and the irradiation time of Pb of a set of pulses is changed. If the upper limit of is set, the recording layer cannot be melted in a sufficient area, and a desired mark is not formed. The upper limit of Pw is stipulated by the performance of the LD used, and at present, an LD with a wavelength of 660 nm is used.
In the case of, the upper limit is 15 to 16 mW. In order to avoid this, it is conceivable to make the upper protective layer thicker and the reflective heat dissipation layer thinner so as to have a heat insulating structure than the conventionally used disk structure. The cross-erase between the tracks becomes large, and the thermal condition varies depending on the size of the front and rear marks and spaces even in the track direction, resulting in a large jitter. It is also possible to remove the restriction that the pulse length of one set of the multi-pulse part is T and apply a new strategy pattern, but considering the ease of developing the control system on the drive side, the conventional recording strategy is used. It is desirable to be able to support higher recording linear velocities by extending the.

Therefore, according to the present invention, there is provided a method capable of excellent recording even when the recording strategy that a set of pulse lengths of the multi-pulse portion which is conventionally used is T is used as it is up to a higher recording linear velocity. The object is to propose and provide a recording medium suitable for it.

[0009]

The above object of the present invention can be achieved by the following means. According to claim 1, the reversible phase change between the amorphous phase and the crystalline phase of the recording layer is utilized to form the amorphous mark by the laser light modulated to at least three-valued power of recording, erasing and bias. The optical information recording method is characterized by the fact that at least the value of bias power is variable according to the recording linear velocity.

Second, in the first optical information recording method, when the recording linear velocities V1 and V2 are V1> V2, the bias power Pb1 and the recording linear velocity V2 at the recording linear velocity V1 are set. Bias power Pb2 at the time is Pb1 ≧ Pb2
Is the main feature.

Thirdly, in the above first to second optical information recording methods, the main feature is that the value of the bias power is variable when recording is performed at a recording linear velocity of 10 to 20 m / s.

Fourthly, in the optical information recording medium recorded by the above first to third optical information recording methods, the amorphous mark phase is crystallized by crystal growth from the adjacent crystal phase at the time of recording and erasing. The most main feature is to use a recording layer in which the recording is erased as the recording progresses.

Fifth, the fourth recording layer is Sb-Sb ₂
The main feature is that it is based on a Te ₃ pseudo binary eutectic composition Sb-Te alloy.

Sixth, the atomic ratio of the fifth recording layer is 0.
The main feature is that 9 or more are represented by the following formula. The formula XαSbβTeγ X represents In or Ga, or a mixture of In and Ga α, β, and γ represents an atomic ratio, and is in the following range. 0.01 ≦ α ≦ 0.1 0.60 ≦ β ≦ 0.90 γ = 1-α-β

Seventh, the sixth recording layer has at least G
Its main feature is the inclusion of e.

Eighth, the sixth recording layer has at least A
Its main feature is the inclusion of g.

Ninth, in the fourth to eighth optical information recording media, at least the first protective layer, the recording layer, the second protective layer, and the reflective heat dissipation layer are arranged on the transparent substrate in order from the laser beam incident direction. The main feature is that Ag or an Ag alloy is used as the reflection and heat dissipation layer.

Tenth, in the above ninth optical recording medium,
The second protective layer is formed of a mixture of at least ZnS and SiO _2, and SiC is provided between the second protective layer and the reflection / heat dissipation layer.
The main feature is that a third protective layer containing as a main component is formed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Conventionally, it has been said that a bias power Pb value close to zero is desirable for forming an amorphous state. However, in order to solve the above-mentioned problems, the present inventors have
It has been found that when the recording linear velocity is high, by increasing the value of Pb, a region sufficient for mark formation is melted, and amorphous formation is not hindered, so that good recording can be performed.

FIG. 2 shows the results of thermal simulation and mark shape simulation when recording was performed at a recording linear velocity of 17 m / s. The layer structure is (ZnS) ₈₀ (SiO ₂ ) ₂₀ of 76 nm and Sb-S as the first protective layer on the transparent substrate.
b ₂ Te ₃ eutectic composition Sb—Te alloy-based recording layer of 16 nm, second protective layer of (ZnS) ₈₀ (S
iO _{2) 20} to 10 nm, SiC as a reflective heat dissipation layer (4n
It is assumed that m) + Ag (140 nm) are laminated in this order. Groove is not considered. A laser beam with a wavelength of 660 nm and a beam radius of 420 nm is incident from the substrate side, and the absorption and heat conduction of the light when scanning at a constant recording linear velocity while modulating the power is obtained by numerical calculation, and the figure reaches the maximum. The temperature distribution is shown by a curve like a contour line. The central portion shown by this curve is the region where the melting point is reached. The mark shape simulation was performed based on the model that an amorphous phase is formed in the cooled and melted part based on the result of the thermal simulation, and then partly crystallized by crystal growth from the adjacent crystal phase. It is a thing. The crystal growth gradually proceeded from about 300 ° C., and the growth rate was set to be maximum near the melting point of about 550 ° C. If the parameters such as the crystal growth rate are appropriately set according to the recording layer material, the mark shape that can be observed in the TEM photograph can be almost simulated with such a model.

FIG. 2A shows the case where Pb = 0.1 mW. The temperature of the first pulse following Pe rises, but the second and subsequent pulses after irradiation with Pb = 0.1 mW and cooling to near room temperature do not take much time even if Pw is applied. The temperature does not rise and the melting area is small. Therefore, the formed mark is small and is divided in the middle.

FIG. 2B shows a simulation result when the irradiation times of Pw, Pb, and Pe are the same as those in (a) and Pb = 2 mW. It can be seen that, since the temperature drop during Pb irradiation is small, the temperature can be raised to the melting point or higher in a short time even after the second pulse. Therefore, the mark can be formed without being divided. Although depending on the crystal growth rate of the recording layer, a part of the amorphous phase once formed is crystallized by increasing Pb, but when the recording linear velocity is high, the degree is small. If the value of is set appropriately, the conventional strategy pattern can be extended and recording can be performed with sufficient modulation without causing insufficient heating even at high recording linear velocity. The results of actual recording will be shown in Examples described later, but it was found that as the degree of modulation increases, the jitter also improves, and good recording can be performed.

Materials practically used as the phase change recording layer include a recording layer based on Sb-Sb ₂ Te ₃ eutectic composition Sb-Te alloy as a base, and a mixture of GeTe and Sb ₂ Te ₃ as a base. The materials that have been made are known. During recording and erasing, the crystallization progresses by the crystal growth from the interface between the amorphous phase and the crystalline phase in the former, whereas the latter crystallizes from the nucleus after the nuclei are formed inside the amorphous phase. It progresses in the form of growth. This can be inferred from the observation of crystal grains in both TEM photographs. Even when using the latter type of material in which crystallization progresses due to nucleation, when recording at a high recording linear velocity, by increasing the value of Pb, the melting region can be expanded and a larger mark can be formed. The advantage is that the degree can be increased. However, even if the degree of modulation increases, the jitter does not improve so much. This is because when the crystallization progresses only by crystal growth, the position of the mark edge is determined only by the crystal growth rate near the melting point, so control is relatively easy, whereas crystallization from nucleation occurs. It is thought that it is difficult to control the position of the edge of the mark when proceeding, because it depends on the nucleation probability in the relatively low temperature part, the crystal growth rate in the relatively high temperature part, and their history. To be Therefore, as the recording layer material, a simpler strategy can be applied to the type of material in which crystallization progresses by crystal growth from the adjacent crystal phase.

As a type of material in which crystallization progresses by crystal growth from adjacent crystal phases, Sb-Sb ₂ Te
A system based on a mixture of In and Sb ₂ Te ₃ is also known in addition to the system based on Sb—Te alloy having a composition close to ₃ eutectic (Jpn. J. Appl. Phys., 34, 1).
56 (1988)). However, from the viewpoint of repetitive recording characteristics, it is better to use a system based on an Sb-Sb ₂ Te ₃ eutectic composition Sb-Te alloy.

The Sb-Sb ₂ Te ₃ pseudo binary system is Sb ₇₀ T
This Sb-Sb ₂ Te ₃ pseudo-2 has a eutectic point near e ₃₀
Sb-Te having a composition near the eutectic eutectic is a phase change recording material having excellent repetitive recording characteristics. However, the stability of the amorphous phase is poor, and all marks disappear after storage at 70 ° C. for about 50 hours. Further, when a disc is made of only Sb-Te and recording is attempted, at a recording density of 0.267 μm / bit, a jitter (here, data
The value obtained by normalizing to clock jitter σ with T is called jitter) cannot be set to 10% or less, and the modulation at this time is not set to 50% or more.
On the other hand, when In or Ga is added, 0.2
At a density of 67 μm / bit, the jitter was 10% or less, and the modulation could be 60% or more. In or Ga has the effect of improving the recording sensitivity and can increase the recording density. Further, since it also has the effect of increasing the crystallization temperature, storage stability is also improved. I
In the system to which n or Ga was added, there was no change in jitter or modulation after storage at 70 ° C. for 50 hours. At this time, if the addition amount of In or Ga with respect to Sb-Te is less than 1%, the effect does not appear and 10%
If it exceeds, there are problems that the overwrite property is deteriorated and the reflectance after the initial crystallization is not uniform. Further, the crystal growth rate must be high for high-speed overwriting, and it is necessary to adjust the composition ratio of In, Ga, Sb, or Te so as to have appropriate crystal growth. When In or Ga is 1 to 10%, Sb is 60
A disk having good characteristics having an appropriate crystal growth rate could be produced if the content was ˜90%.

Furthermore, when Ge is added to In or Ga-Sb-Te, the storage stability is further improved, and
The addition facilitated the initialization. However, the total amount of Ag and Ge added to In or Ga-Sb-Te must be less than 10%. If it is more than this range, the recording sensitivity and the overwrite characteristic are deteriorated.

[Embodiment] An embodiment showing the effect of the bias power when an optical recording medium having a structure compatible with a DVD-ROM is used will be described below. Example 1 The basic structure of the optical recording medium is 12 cm in diameter and 0.
The first protective layer, the recording layer, the second protective layer, and the reflection / heat dissipation layer are formed on a polycarbonate disc substrate with a guide groove having a track pitch of 6 mm and a track pitch of 0.74 μm, and an organic protective film formed on the reflection / heat dissipation layer is further provided. With a diameter of 12 cm and a thickness of 0.
A 6 mm polycarbonate disk is adhered. Recording and reproduction is performed by irradiating a laser beam from the substrate side.

In the case of this embodiment, polycarbonate is used as the transparent substrate and (ZnS) 80 is used as the first protective layer.
(SiO ₂ ) 20 76 nm, Sb-Sb as a recording layer
₂ Te ₃ near eutectic composition Based on Sb-Te alloy, G
17n with a and 3 atomic% of Ge added
m, (ZnS) ₈₀ (SiO ₂ ) ₂₀ as the second protective layer
0 nm, 140 nm of Ag as a reflection and heat dissipation layer, and 4 n of SiC to prevent sulfuration of Ag between Ag and the second protective layer.
m were laminated by sputtering.

The evaluation was carried out at a wavelength of 660 nm and NA = 0.65.
Linear density of 0.267 μm /
The random pattern was recorded by the bit and EFM + modulation methods, and the jitter σ / T and the modulation degree were examined. All reproduction was performed at 3.5 m / s.

FIG. 3 shows the results of evaluation of the jitter and the degree of modulation when the recording linear velocity was changed with Pb = 0.1 mW as a comparative example. The recording strategy, Pw, and Pe are adjusted each time so as to be optimal at each recording linear velocity, but the jitter deteriorated from a recording linear velocity of about 14 m / s to a sharp decrease. Modulation rate is also 14m / s
It is presumed that the mark could not be written due to insufficient heating because the size decreased rapidly from the extent.

Example 2 Pb = at a recording linear velocity of 7 m / s and 10.5 m / s
When 0.1 mW and 14.5 m / s, Pb = 0.8 mW,
1.2 mW at 17 m / s, 1.8 at 20 m / s
The result in the case of mW is shown in FIG. The phenomenon that the jitter and the modulation are abruptly deteriorated on the high recording linear velocity side seen in the comparative example is improved. P on the high recording linear velocity side
It is presumed that insufficient heating could be prevented by increasing b.

Further, as a result of conducting various similar evaluations with respect to disks having the same layer structure having different recording layer compositions such as the ratios of Sb and Ga, it was found that increasing Pb is effective in that the recording linear velocity is approximately 10 to 20 m. It was found that the time was / s. When the recording linear velocity is slower than this, if Pb is increased, cooling becomes insufficient and the modulation degree decreases. Therefore, it is desirable that Pb be as close to 0 as possible. If it is faster than 20 m / s, Pb
Even if the value is increased, good recording cannot be performed with the conventional strategy.

The evaluation was also made for the case where the reflection / heat dissipation layer was made of Al alloy and the thickness of the second protective layer was set to 20 nm. Jitter was 10% even under the condition that Pb was adjusted to increase the degree of modulation. Could not be: This is because it is more difficult for heat to be dissipated in the reflective heat dissipation layer than in the case of Ag or Ag alloy, and therefore the thermal conditions differ depending on the size of the marks and spaces before and after, and the jitter increases. It is considered that

When Ag or Ag alloy is used as the reflection / heat dissipation layer and ZnS-SiO ₂ is used as the second protective layer, a layer for preventing sulfuration of Ag is necessary. Several kinds of materials such as ZnO and SiNx were evaluated as the sulfurization preventing layer, and it was found from the results of the high temperature accelerated test that SiC was excellent as the sulfurization preventing layer.

In the above, a method and a medium for making it possible to apply a recording strategy in which a set of pulse lengths of a multi-pulse part which has been generally used conventionally is T at a higher recording linear velocity have been described. However, these are not limited to the case where the pulse length of one set of the multi-pulse part is T, and may be similarly applied when a good amorphous mark cannot be formed due to insufficient heating.

[0036]

According to the first aspect of the present invention, the reversible phase change between the amorphous phase and the crystalline phase of the recording layer is utilized, and the laser light modulated into at least three-valued power of recording, erasing and bias is used. In the optical information recording method for forming an amorphous mark, at least the value of the bias power is variable according to the recording linear velocity. Good recording is possible even when the recording strategy in which one set of pulse lengths is the reference clock is used as it is up to a higher recording linear velocity.

In the optical information recording method according to claim 2, when the recording linear velocities V1 and V2 are V1> V2, the bias power Pb1 at the recording linear velocity V1 is obtained.
The bias power Pb2 at the recording linear velocity V2 is Pb1 ≧
According to the optical information recording method characterized by being Pb2, it is possible to eliminate insufficient heating that occurs when the recording linear velocity is high.

In the optical information recording method according to claim 1 or 2, the value of the bias power is variable when recording at a recording linear velocity of 10 to 20 m / s. According to the method, a good mark can be formed by making the value of the bias power Pb variable at this recording linear velocity.

The optical information recording medium recorded by the optical information recording method according to any one of claims 1 to 3 has a crystal structure in which amorphous mark phases are adjacent to each other during recording and erasing. According to the optical information recording medium characterized by using the recording layer in which the recording is erased by the progress of the crystallization due to the crystal growth from the phase, the crystallization can be easily controlled, and thus a simple strategy can be applied. .

The optical recording layer according to claim 5 or 4 is characterized in that the recording layer is based on a Sb-Sb ₂ Te ₃ pseudo binary eutectic composition Sb-Te alloy. According to the medium, it is possible to provide a recording medium having excellent repeatability.

According to the optical information recording medium of the sixth aspect, wherein the atomic ratio of the recording layer of 0.9 or more is represented by the following formula, the optical information recording medium has high sensitivity and high recording density. It is possible to provide a possible optical recording medium. The formula XαSbβTeγ X represents In or Ga, or a mixture of In and Ga α, β, and γ represents an atomic ratio, and is in the following range. 0.01 ≦ α ≦ 0.1 0.60 ≦ β ≦ 0.90 γ = 1-α-β

According to the optical information recording medium of the seventh and sixth aspects, wherein the recording layer contains at least Ge, an optical recording medium excellent in storage stability of amorphous marks is provided. it can.

According to the optical information recording medium of the eighth aspect or the sixth aspect, wherein the recording layer contains at least Ag, the optical recording medium is excellent in the uniformity of the reflectance after the initial crystallization. Can be provided.

According to a ninth aspect, at least a first protective layer, a recording layer, a second protective layer, and a reflection heat dissipation layer are formed on a transparent substrate in order from the laser beam incident direction, and the reflection heat dissipation layer is Ag, Alternatively, according to the optical information recording medium of claims 4 to 8, characterized in that an Ag alloy is used, an optical recording medium with small jitter can be provided.

According to a tenth aspect of the present invention, the second protective layer is formed of at least a mixture of ZnS and SiO _2, and a third protective layer containing SiC as a main component is provided between the second protective layer and the reflection / heat dissipation layer. According to the optical recording medium of claim 9, which is formed, it is possible to provide an optical recording medium having excellent storage stability of the reflection / heat dissipation layer.

[Brief description of drawings]

FIG. 1 is an example of a recording method used in a conventional technique.

FIG. 2 is a diagram showing the results of thermal simulation and mark shape simulation when recording was performed at a recording linear velocity of 17 m / s.

FIG. 3 is a diagram showing the results of evaluation of jitter and modulation when Pb = 0.1 mW and the recording linear velocity is changed.

FIG. 4 shows Pb = 0.1 mW at a recording linear velocity of 7 m / s and 10.5 m / s and Pb = 0.8 at a recording linear velocity of 14.5 m / s.
It is a figure which shows the result at the time of 1.2 mW in case of mW, 17 m / s, and 1.8 mW in case of 20 m / s.

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) G11B 7/24 G11B 7/24 535H 535 538E 538 B41M 5/26 X (72) Inventor Hiroko Tashiro Nakamagome, Ota-ku, Tokyo 1-3-6 Ricoh Co., Ltd. (72) Inventor Yuji Miura 1-3-6 Nakamagome, Ota-ku, Tokyo In-house Ricoh Co., Ltd. (72) Hajime Jobara 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 in Ricoh Co., Ltd. (72) Inventor Mirai Mizutani 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H111 EA04 EA12 EA23 FA01 FA12 FA14 FA18 FA23 FA25 FA27 FA29 FB05 FB09 FB12 FB17 FB21 FB30 5D029 JA01 LA13 LA17 LB11 MA13 5D090 AA01 CC01 CC14 FF21 KK03

Claims (10)

[Claims] 1. A reversible phase change between an amorphous phase and a crystalline phase of a recording layer is used to record, erase, and bias at least 3.
An optical information recording method for forming an amorphous mark by a laser beam modulated to a value power, wherein at least a bias power value is variable according to a recording linear velocity. 2. The optical information recording method according to claim 1,
When the recording linear velocities V1 and V2 are V1> V2,
Bias power Pb1 at recording linear velocity V1, recording linear velocity V
The optical information recording method is characterized in that the bias power Pb2 at the time of 2 is Pb1 ≧ Pb2. 3. The optical information recording method according to claim 1, wherein the value of bias power is variable when recording is performed at a recording linear velocity of 10 to 20 m / s. 4. The optical information recording medium recorded by the optical information recording method according to claim 1, wherein the amorphous mark phase is a crystal from an adjacent crystal phase during recording and erasing. An optical information recording medium characterized by using a recording layer in which recording is erased by progress of crystallization due to growth. 5. The recording layer according to claim 4 is Sb-Sb ₂ T.
The optical information recording medium, characterized in that the e ₃ pseudo binary eutectic vicinity composition Sb-Te alloy is obtained based. 6. The atomic ratio of the recording layer according to claim 5, which is 0.9.
An optical information recording medium characterized by the above being represented by the following formula 1. XαSbβTeγ (1) X represents In or Ga, or a mixture of In and Ga α, β, and γ represents an atomic ratio, and is in the following range. 0.01 ≦ α ≦ 0.1 0.60 ≦ β ≦ 0.90 γ = 1-α-β 7. The recording layer according to claim 6 is at least Ge.
An optical information recording medium comprising: 8. The recording layer according to claim 6 is at least Ag.
An optical information recording medium comprising: 9. At least a first protective layer, a recording layer, a second protective layer, and a reflective heat radiation layer are formed on a transparent substrate in order from the laser beam incident direction, and the reflective heat radiation layer is Ag,
Alternatively, an Ag alloy is used.
8. The optical information recording medium described in 8. 10. The second protective layer is formed of a mixture of at least ZnS and SiO _2, and a third protective layer containing SiC as a main component is formed between the second protective layer and the reflection / heat dissipation layer. The optical information recording medium according to claim 9, which is characterized in that.