JP2000079761A - Optical information recording medium, recording method, and manufacture of optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the initial crystallization while making the most of the phase change rewritability of an eutectic composition, and reduce a jitter as a disk property by forming a phase change type optical recording layer to be a composition represented by a specified composition formula. SOLUTION: A phase change type optical recording layer is formed to be a composition represented by the formula. In this case, in the formula, X represents at least one kind from among Ag, Au, Pd, Pt or Zn, M represents at least one kind from among Sn, Ge, Si and Pb, and 0.0<=α<=0.1, 0.5<=δ<=0.7, 0.15<=ε<=0.4, 0.03<=β+γ<=0.25, and α+β+γ+δ+ε=0.1 are satisfied. Among them, X has an effect to facilitate the initialization of an amorphous membrane right after a membrane formation. Then, by limiting the composition in such a manner, when an override is performed at most at approx. 6 times of a CD line speed, as a CD-E which has an interchangeability especially with CD, the composition can be selectively used as a composition which is excellent in overwrite durability and age-stability repeatedly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recordable and erasable optical information recording medium utilizing a reflectance difference or a reflected light phase difference caused by a phase change caused by laser light irradiation, and a recording method and a manufacturing method thereof.

[0002]

2. Description of the Related Art Optical discs include a read-only type, an optical recordable type, and a rewritable type.
It has already been put to practical use as an audio disk, and even as a large-capacity computer disk memory. The phase change type optical disk utilizes the fact that the reflectance or the phase of the reflected light changes before and after the phase change, and does not require an external magnetic field to detect the difference in the amount of reflected light and perform reproduction. Compared to the magneto-optical type, the phase-change type is advantageous in that the drive can be easily manufactured due to the fact that a magnet is not required and the optical system is simple, and that the size and cost can be reduced. Further, there is an advantage that recording / erasing can be performed only by modulating the power of the laser beam, and one-beam overwriting, in which erasing and re-recording are performed simultaneously with a single beam, is also possible.

In a phase change recording method capable of one-beam overwriting, it is general that a recording bit is formed by amorphizing a recording film, and erasing is performed by crystallization. In this case, since the as-depo state is generally amorphous, it is necessary to crystallize the entire surface of the disk in a short time in order to make the initial state a crystalline state. This step is called initial crystallization. Usually, this initial crystallization is performed by irradiating a rotating disk with a laser beam focused to several tens to hundreds of microns.

Conventionally, regarding the recording layer material of an optical disc,
Alloy materials near the eutectic composition have high amorphous forming ability,
Since crystallization involves phase separation, it cannot be crystallized by heating for a short time of less than 100 nsec, and has been considered to be unsuitable as a recording layer of an overwritable optical recording medium. In particular, when attention is paid to a GeSbTe-based ternary alloy, T
e ₈₅ Ge ₁₅ practical crystallization rate in eutectic composition near has not been obtained. On the other hand, in the vicinity of the Sb ₇₀ Te ₃₀ eutectic composition, although it is an extremely rudimentary method in which only the change in reflectance is monitored, Sb _x Te _1-x (0.58 <x <0.75) 2
U.S. Pat. No. 5,015,548 discloses that the original alloy can be repeatedly recorded and erased between a crystalline state and an amorphous state.

The present inventors have focused on a binary alloy composed of SbTe for simplicity, and are not bound by the conventional theory. Regarding the crystallization / amorphization characteristics near the eutectic composition, the present invention is more suitable for high-density recording. The optical disk evaluation machine was used to reconsider the suitability for mark length recording. As a result, Sb ₇₀ Te ₃₀
Although the initial crystallization of the recording layer mainly composed of the SbTe alloy in the vicinity of the eutectic composition is difficult, once the initial crystallization is performed, the subsequent recording and erasing by the amorphous-crystalline phase change can be performed at extremely high speed. I found what I could do.

According to the findings of the present inventors, the greatest advantage of using such a material near the eutectic composition is that the initialized state and the reflectance in the peripheral portion of the amorphous mark or in the erased mark are considered. Are unlikely to occur. This is a phenomenon peculiar to an alloy near the eutectic point where crystal growth is controlled by phase separation. However, if such a material is used to increase the crystallization speed in the solid phase, the recrystallization speed during resolidification when forming an amorphous mark becomes extremely high, and the outer peripheral portion of the molten region is increased. However, there is a problem that the recrystallization tends to cause insufficient formation of the amorphous mark. That is, in the vicinity of the eutectic point, the crystallization speed is governed by the diffusion speed of atoms for phase separation, and high-speed erasure by crystallization cannot be performed unless the material is heated to just below the melting point where the diffusion speed is maximized. Further, as compared with the recording layer of the GeTe-Sb ₂ Te ₃ pseudo-binary alloy composition near that are widely used today, it is narrow temperature range higher crystallization rate is obtained, and is biased to a high temperature. Therefore, in order to achieve both a high crystallization rate and formation of a sufficiently large amorphous mark, it is necessary to particularly increase the cooling rate near the melting point during resolidification.

[0007] The present inventors have further found that near this eutectic composition, G
When the ternary material to which e or In was added was evaluated, the GeSbTe ternary alloy in the vicinity of the SbTe eutectic was:
When a specific recording pulse pattern is used, GeTe-Sb ₂ widely known in repeated overwriting is used.
It has been found that there is an advantage that the deterioration is smaller than that of the material near the Te ₃ pseudo binary alloy, or the jitter of the mark edge when the mark length is recorded is small. Further, it was also found that the crystallization temperature was higher than that of the Sb ₇₀ Te ₃₀ binary eutectic alloy, and the stability with time was excellent. However, it is extremely difficult to once crystallize and initialize the entire surface of the amorphous film formed by the film formation as compared with the SbTe eutectic alloy, and thus it is not suitable for mass production.

In order to solve these problems, Sb ₇₀ T
JP as documents added third element e ₃₀ 1-115
No. 685, JP-A-1-115686, JP-A-1-251342, JP-A-1-303643, etc., are particularly effective as additional elements, and two or more elements are simultaneously added. However, there is no disclosure of a quaternary system or more. Other examples of adding a third element to a SbTe binary system containing this eutectic composition are disclosed in JP-A-1-100745 and JP-A-1-1001-1.
00746, JP-A-1-100747, and JP-A-1-100748. However, in these series of known documents contains as host also Sb ₄₀ Te ₆₀ metal compound composition, is not necessarily focused on Sb ₇₀ Te ₃₀ eutectic composition, thus, Sb ₇₀ Te ₃₀ eutectic composition of specific issues It does not disclose a method for solving the problems of difficulty in initialization and insufficient stability with time to form a more reliable and practical medium.

The phase change medium in the vicinity of the SbTe eutectic composition has a serious problem that the productivity is low and it cannot be put to practical use because the initialization operation for crystallizing the recording layer after film formation is difficult. . For this reason, it has been considered that only a material near the intermetallic compound composition that is easy to initialize or a pseudo binary alloy thereof exhibits practical characteristics. In recent years, Sb
It has been reported that simultaneous addition of Ag and In to the vicinity of the eutectic composition of ₇₀ Te ₃₀ can simultaneously improve the stability over time due to In and facilitate the initialization by Ag (Japanese Unexamined Patent Application Publication No. Hei. JP-A-232779, JP-A-5-1857
No. 32). This indicates that by adding a suitable amount of the binary or ternary element in a specific combination, the properties of the binary material of the Sb ₇₀ Te ₃₀ eutectic composition can be dramatically improved and reach a practical level. Useful materials among such recording layers have been clarified only in very limited cases because of the need to optimize the combination and composition of the quaternary or quinary alloys (Japanese Patent Laid-Open No. 8-267926, etc.). ). There are also unknown limited combinations and compositions,
Further improvements are expected, but their discovery requires a great deal of effort, as with ordinary multi-element alloys.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to make use of the phase change rewritable property of the eutectic composition,
An object is to facilitate initial crystallization (initialization) and reduce jitter as disk characteristics.

[0011]

Means for Solving the Problems The present inventors have found that when a composition having five specific elements in the characteristic range among the conventionally known compositions near SbTe eutectic is used for the recording layer, The inventors have found that the above objects can be achieved, and have completed the present invention. That is, the gist of the present invention is to provide an optical information in which a phase change type optical recording layer is provided on a substrate, and recording / reproducing of information on the phase change recording layer is performed by a phase change between a crystalline state and an amorphous state. In the recording medium, the phase change type optical recording layer

[0012]

Embedded image

(Where X is at least one of Ag, Au, Pd, Pt or Zn, M is Sn, Ge,
At least one of Si and Pb, 0.0 ≦ α ≦ 0.
1, 0.001 ≦ β ≦ 0.1, 0.01 ≦ χ ≦ 0.1
5, 0.5 ≦ δ ≦ 0.7, 0.15 ≦ ε ≦ 0.4, 0.
03 ≦ β + χ ≦ 0.25, α + β + χ + δ + ε = 1.
0) An optical information recording medium characterized by having the following composition:

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The layer structure of a disc according to the present invention is, as schematically shown in FIG. 1, for example, on a substrate 1, at least a lower protective layer 2, a phase-change recording layer 3, an upper protective layer 4, a reflective A layer 5 is provided. The protective layers 2 and 4, the recording layer 3, and the reflective layer 5 are formed by a sputtering method or the like. It is desirable to form a film using an in-line apparatus in which a target for a recording film, a target for a protective film, and if necessary, a target for a reflective layer material are installed in the same vacuum chamber, from the viewpoint of preventing oxidation and contamination between layers. It is also excellent in productivity. Further, a protective coat made of an ultraviolet curable resin may be provided on the reflective layer 5 and below the substrate 1. Further, in addition to the above-described layer structure, a diffusion preventing layer or the like may be provided above or below the phase change recording layer 3.

The recording layer used in the present invention is made of XGaMSb.
Te alloy thin film (X is Ag, Au, Pd, Pt or Z
at least one of n, M is Sn, Ge, Si, P
b), and based on the vicinity of the Sb ₇₀ Te ₃₀ eutectic point composition in the SbTe binary alloy system,
The point is that at least one of a, Si, Sn, Ge, and Pb is added in a specific amount. Preferably, a specific amount of at least one of Ag, Au, Pd, Pt and Zn is added.

It is considered that the recording medium of the present invention basically utilizes the fact that the Sb phase and the Sb ₂ Te ₃ phase are phase-separated on a line showing a constant Sb ₇₀ Te ₃₀ ratio. That is, in a non-equilibrium supercooled state in which an amorphous mark is formed in an optical recording medium, if excessive Sb is contained, fine Sb clusters first precipitate during resolidification. Since this Sb cluster becomes a crystal nucleus and remains in the amorphous mark,
Subsequent erasing (recrystallization) of the amorphous film is considered to be completed in a short time without taking time for phase separation.

The recording characteristics of the recording medium of the present invention, that is, the reversible process of amorphous and crystallization is almost Sb / T
It is determined by the e ratio, that is, the amount of excess Sb contained in the eutectic Sb ₇₀ Te ₃₀ eutectic composition. It is considered that when the amount of Sb increases, the number of Sb cluster sites precipitated in a quenched state increases, and the generation of crystal nuclei is promoted. This means that even if the same crystal growth rate is assumed from each crystal nucleus, the time required for filling the grown crystal grains is reduced, and as a result, the time required for crystallization of the amorphous mark is reduced. Means Therefore, it is advantageous when erasing by laser light irradiation at a high linear velocity for a short time. On the other hand, the cooling rate of the recording layer also depends on the linear velocity during recording. That is, even with the same layer configuration, the cooling rate decreases as the linear velocity decreases. Therefore, a composition having a lower critical cooling rate for forming an amorphous phase at a lower linear velocity, that is, a composition having a smaller excess Sb amount is desirable. In summary, based on the Sb ₇₀ Te ₃₀ eutectic composition, a composition having a large excess Sb content is more suitable for a high linear velocity.

The composition of each element contained in the recording layer of the present invention is in the following range. That is, the composition

[0019]

Embedded image

In the formula, the lower limit of α is 0.0 and the upper limit is 0.1, preferably 0.01 or more, and most preferably 0.06. The lower limit of β is 0.001, and the upper limit is 0.1, preferably 0.03. The lower limit of χ is 0.01, and the upper limit is 0.15, preferably 0.1
0. The lower limit of δ is 0.5, preferably 0.55, and the upper limit is 0.7, preferably 0.65. ε
Has a lower limit of 0.15 and an upper limit of 0.4. Β + χ is 0.03 as a lower limit and 0.25, preferably 0.13 as an upper limit. In the above composition, α + β + χ + δ + ε = 1.0. In short, these numerical values indicate the component ratio of the metal, and X or M may be two or more types, but in this case, the total amount is used as a basis. According to the study of the present inventors, by limiting the composition as described above,
Particularly, when the CD-E compatible with a CD is overwritten at most about 6 times the linear velocity of the CD (7.2 to 8.4 m / s), the composition is excellent in repeated overwriting durability and stability over time. Can be used selectively.

In the above composition, Ga and M (Sn, G
e, Si, and Pb) have the effect of increasing the crystallization temperature and increasing the stability over time. When only M is added, about 3 atomic% or more is necessary in order to obtain temporal stability, but if it exceeds 15 atomic%, initial crystallization is rapidly difficult in exchange for improvement of temporal stability. There is a problem that becomes. On the other hand, when Ga is added alone, 3 atomic% is necessary for preserving the storage stability at room temperature and facilitating the initialization operation, but if it exceeds 10 atomic%, phase separation is likely to occur. However, it is not preferable because segregation occurs due to repeated overwriting. On the other hand, in order to guarantee the repetitive overwrite durability of 10,000 times or more, it is necessary to reduce the above-mentioned Ga addition amount to less than 3 atomic%. On the other hand, in order to make the aging stability of the amorphous mark and the initialization work easy. Is not enough. Therefore, in the present invention, by adding a small amount of Ga and M at the same time, it is possible to improve the thermal stability of the amorphous state without making the initialization operation difficult and without causing segregation due to repeated overwriting. In addition, the stability of the amorphous recording bit with time is improved. That is, the total amount of addition of M and Ga is 3
It is at least 25 atomic%. If it is less than 3 atomic%, the effect of improving the stability over time is insufficient, and if it exceeds 25 atomic%, segregation due to repetitive overwriting and difficulty in initialization are caused no matter what ratio of M or Ga content is added. Invite. On the other hand, if the content of Ga or M alone exceeds 10 atomic% or 15 atomic%, respectively, it is not preferable because the above-mentioned problem easily occurs. G in M
e is particularly preferable because addition of a small amount of 5% or less is effective in raising the crystallization temperature and improving thermal stability and hardly causing segregation.

X (Ag, Au, Pd, Pt, Zn) has an effect of facilitating initialization of an amorphous film immediately after film formation. Depending on the initialization method, the addition of less than 10 atomic% is sufficient, and if it is too much, the stability over time may be rather deteriorated, or the jitter at the end of the recording mark may be worsened. Also, if the amount is too small, the effect tends to be insufficient. Although the mechanism by which the addition of the element X facilitates the initialization is not necessarily clear, the fine ZnSb phase and the A
It is considered that an XSb phase such as a gSb phase precipitates and functions as a crystal nucleus. Above all, Zn and Ag are preferable because they can be easily crystallized and the jitter is hardly deteriorated. Especially Ag
Is preferable because jitter does not deteriorate. X = A for SbTe eutectic
g, Au, Pd, Pt, Zn, and M = Si, Sn,
By adding Ge, Pb and Ga, the crystallization time in the initialization operation is shortened while maintaining the stability of the amorphous mark with time. By adding X, M, and Ga, the base SbTe becomes eutectic because of Sb ₆₀ Te ₄₀
From seem shifted about Sb ₆₅ Te _35. Therefore, it is used in the present invention.

[0023]

Embedded image

The linear velocity dependency of the alloy as a whole depends on the amount of excess Sb based on this composition as described above. To cope with a high linear velocity, it is sufficient to increase the excess Sb amount as described above, but if too much, the stability of the amorphous bit is impaired, so that 0.5 ≦ δ ≦ 0.7 Is preferred. More preferably, 0.55 ≦ δ ≦
0.65.

The recording layer may contain an element other than the above five elements. The thickness of the recording layer is usually 5-
It is 40 nm, preferably 15-30 nm. The substrate of the recording medium in the present invention may be any one of glass, plastic, and a substrate provided with a photocurable resin on glass. However, plastic is preferable because of ease of molding, and particularly, productivity including cost. In view of the above, a polycarbonate resin is preferable. The material of the protective layer that can be used above and below the recording layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. Generally, it is a dielectric material having high transparency and a high melting point.
a, Sr, Y, La, Ce, Ho, Er, Yb, Ti,
Zr, Hf, V, Nb, Ta, Zn, Al, Si, G
e, oxides such as Pb, sulfides, nitrides, carbides and Ca,
Fluorides such as Mg and Li can be used. These oxides, sulfides, nitrides, carbides and fluorides do not necessarily have to have a stoichiometric composition, and it is effective to control the composition for controlling the refractive index and the like, or to use a mixture thereof. is there. Considering the repetitive recording characteristics, a mixture of dielectrics is preferred. More specifically, ZnS or rare earth sulfide and oxide,
Mixtures of heat-resistant compounds such as nitrides and carbides may be used.
The lower protective layer provided between the recording layer and the substrate is also required to have a function of suppressing the thermal deformation of the plastic substrate in particular. Therefore, the film thickness is usually 50 nm or more. Preferably, the thickness is 50 to 500 nm because it becomes easy. Usually, from this range, the reflectance, the reflectance difference before and after recording, and the phase difference are selected in consideration of the optical interference effect so as to have appropriate values. The same material is used for the upper protective layer provided between the recording layer and the reflective layer, and the thickness range is usually 10 to 50 nm.
The greatest reason is that heat radiation to the reflective layer is effectively applied. By adopting a layer configuration that promotes heat radiation and increases the cooling rate during resolidification of the recording layer, a high erasing ratio can be realized by high-speed crystallization while avoiding the problem of recrystallization. If the thickness of the upper protective layer is too large, the time for the heat of the recording layer to reach the reflective layer becomes longer, and the heat radiation effect by the reflective layer may not work effectively. That is, it can be considered that the reflection layer is a pump for drawing out heat, and the upper protective layer is a pipe for transmitting a heat flow to the pump. The thick protective layer means that the piping is long, and no matter how high the performance of the pump (that is, even if the heat conduction of the reflective layer is large), it does not work effectively. The flow rate of the pipe is also affected by the thickness of the pipe, that is, the thermal conductivity of the upper protective layer. However, since the thermal conductivity of a thin film having a thickness of less than 100 nm is generally two to three orders of magnitude smaller than the bulk thermal conductivity, there is no significant difference. , Thickness is an important factor. On the other hand, if the upper protective layer is too thin, the recording layer may be undesirably broken easily due to deformation or the like during melting. In addition, the heat dissipation effect is so large that the power required for recording tends to be unnecessarily large.

As the material of the reflection layer, a substance having a high reflectance is preferable, and is usually a metal such as Au, Ag, or Al.
In particular, a metal containing 90 at% or more of at least one selected from the group consisting of Au, Ag, and Al which has a large thermal conductivity and a large heat dissipation effect even through the upper dielectric layer is preferable. Ta, T for controlling the thermal conductivity of the reflective layer itself and improving the corrosion resistance
A small amount of i, Cr, Mo, Mg, V, Nb, Zr, etc. may be added. In particular, an alloy of Al _x Ta _1-x (0.9 <x <1) has excellent corrosion resistance and is effective in improving the reliability of the medium. The thickness of the reflective layer is preferably 50 nm or more in order to completely reflect incident light without transmitted light. On the other hand, if the film thickness is too large, there is no change in the heat radiation effect and the productivity is unnecessarily deteriorated, and cracks are easily generated. Particularly when the thickness of the upper protective layer is 40 to 50 nm,
In order to increase the thermal conductivity of the reflective layer, the amount of impurities contained should be 2
It is preferred to be less than atomic%.

The layer structure for promoting heat radiation as described above is as follows.
The phase change medium is called a “quenched structure” and is known per se (JP-A-2-56746, Jpn.JA).
ppl. Phys. , Vol. 28 (1989), su
ppl. 28-3, page 123). As a recording method, the phase change medium of the present invention has been GeTe-Sb ₂ T
than when modulated by two values of recording power Pw and the erasing power Pe, which has been used in e ₃ pseudo binary alloy system, it is desirable to provide a off pulse section.

Although overwriting of binary modulation is possible, in the present invention, a power margin and a linear velocity margin during recording can be increased by using a ternary modulation method having an off-pulse section as shown in FIG. Can be. Specifically, in the present invention, by using the above-described medium in combination with the following recording method, and accurately controlling the cooling rate during resolidification of the recording layer, the present invention is suitable for mark length recording. The characteristics of the recording layer material can be more fully exhibited. It will be possible to show it even more without regret. FIG. 2 shows a preferred example of a laser power irradiation pattern during optical recording.

When forming a mark having a length nT (T is a reference clock cycle, n is a natural number), the time nT is divided into nk pulses as follows.

[0030]

Embedded image α ₁ T, β ₁ T, α ₂ T, β ₂ T,..., Α _m T, β _m T,

(However, n−j = α ₁ + β ₁ ... Α _m +
β _m (0 ≦ j ≦ 2), m = nk (k = 0, 1, 2) and n _min −k ≧ 1) Melting the recording layer at the time of α ₁ T (1 ≦ i ≦ m) And sufficient recording power Pw (> Pe), and β ₁ T (1 ≦
At the time of i ≦ m), bias power Pb of 0 <Pb ≦ 0.5 Pe (however, at β _m T, 0 <Pb ≦ Pe) is applied to perform overwriting.

FIG. 3A shows a case where Pb = Pe,
(B) The temperature change of the recording layer when Pb = 0 (extreme case) is schematically shown. The position between the first pulse P1 and the second pulse P2 of the three divided pulses is assumed. In FIG. 3A, the influence of heating by the subsequent recording pulse extends forward, so that the cooling rate after the first recording pulse irradiation is slow, and Pe is irradiated even in the off pulse section, so that the temperature in the off pulse section is low. The lowest temperature TL reached by the drop remains near the melting point. On the other hand, in FIG. 3B, since Pb in the off-pulse section is almost 0, the TL drops to a point sufficiently lower than the melting point, and the cooling rate in the middle is high. The amorphous mark is melted during the first pulse irradiation, and is formed by rapid cooling during the subsequent off-pulse.

As described above, it is considered that a composition near the SbTe eutectic, such as the phase change recording layer of the present invention, shows a large crystallization rate only near the melting point. Therefore, taking the temperature profile shown in FIG. 3A is important for suppressing recrystallization and obtaining a good amorphous mark.
Conversely, by controlling the cooling rate and T _L , recrystallization is almost completely suppressed, and an amorphous mark having a clear contour substantially matching the molten region is obtained, so that low jitter is obtained at the mark edge. . On the other hand, the conventional GeTe-Sb ₂ T
In the case of the e ₃ pseudo binary alloy, there is no significant difference in the amorphous mark forming process in any of the temperature profiles of FIGS. 3 (a) and 3 (b). The reason for this is that although the rate is slightly slower over a wide temperature range, recrystallization occurs. In this case, a certain degree of recrystallization occurs regardless of the pulse division method, which tends to result in coarse grains around the amorphous mark and deteriorate the jitter at the mark end. In this composition of the recording layer, the off-pulse is not indispensable, but rather the overwriting by the conventional binary modulation is simple and desirable. That is, such a ternary modulation method produces a specific effect on the medium of the present invention.

It has already been mentioned that the initial crystallization in which the recording layer using SbTe eutectic is crystallized in a solid phase at a temperature higher than the crystallization temperature is slow in crystallization and poor in productivity. This is considered to be because it is necessary to once separate phases from the amorphous state immediately after the film formation to form a stable crystalline state. Normally, this phase separation requires heating for 1 μsec or more in the solid phase (below the melting point). For example, when Ge ₂ Sb ₂ Te ₅ is used as a recording layer, recording of Ge ₁₀ Sb ₆₆ Te ₂₄ or the like is performed under a condition that a disk after film formation (as-deposited or as-deposited) can be crystallized at a sufficiently high speed. When the initial crystallization of the disk of the layer is attempted, many parts remain in an amorphous state without being crystallized. However, according to the knowledge of the present inventors, once initialized, crystallization (erasing) can be performed at a high speed thereafter. as-depo. One of the reasons that the film in the state is difficult to crystallize is considered to be that the as-depo amorphous state is unlikely to be crystallized unlike the amorphous state of the recording mark. Further, it is considered that the fact that crystal nuclei hardly exist in the recording layer in the as-depo state is a cause of difficulty in crystallization. In fact, when observing the portion where the initial crystallization was attempted with an optical microscope, the advanced portion of the crystallization is observed in the form of an island having a high reflectance. This can be understood from the fact that crystallization has progressed only in the portion where the crystal nuclei are formed.

However, in the present invention, the above problem can be solved by using a recording layer having a specific composition. Further, in the present invention, melting initialization is effective as a method for shortening the time required for initialization and surely performing initialization by one light beam irradiation. For example, a light beam (gas or semiconductor laser light) focused to a diameter of about 10 to several hundred μm or a long axis of 50 to several hundred μm and a short axis of 1 to 10 μm
Heating is locally performed using a light beam converged in an elliptical shape of about m, and is melted only at the center of the beam. as a result,
While there is no danger of the recording medium being destroyed, in addition, the heating at the periphery of the beam causes the molten portion to be preheated, so that the cooling rate is reduced, and favorable recrystallization is performed. Although the melt initialization itself is a known method, it is particularly effective for the present invention. By using this method, for example, the initialization time can be reduced to one tenth of that of the conventional solid-phase crystallization, the productivity can be significantly reduced, and a change in crystallinity during erasing after overwriting is prevented. it can.

[0036]

The present invention will be described in detail with reference to the following examples. In the following, standard evaluation methods and standards for rewritable CDs are used, but the medium of the present invention is not necessarily limited to a medium of a specific format. In examining the alloy recording layer shown below, Ag ₅ Ga ₂ G
e ₃ Sb ₆₃ Te ₂₇ , Ag ₅ Ga ₅ Ge ₃ Sb ₆₁ Te ₂₆ ,
Ag ₅ Ga ₅ Sb ₆₃ Te ₂₇ , Zn ₅ In ₂ Sb ₆₃ T
e ₃₀ , Ga ₅ Sb ₆₅ Te ₃₀ alloy target, Sb, G
Cosputter was used with at least two types of targets among e, Ag, and alloys such as Sb ₂ Te ₃ . The composition was adjusted by adjusting the discharge power of each target. The composition of the obtained alloy thin film was measured by X-ray fluorescence intensity constituted by chemical analysis.

Example 1 (ZnS) on a polycarbonate substrate₈₀(SiO_Two)₂₀
103 nm layer, Ag as recording layer_4.4Ga_1.7Ge
_5.6Sb_64.8Te_23.516 nm layer, (ZnS) ₈₀(S
iO_Two)₂₀Layer 41 nm, Al₉₉Ta₁200 alloy layers
nm, sequentially laminated by magnetron sputtering method,
Further, a disk is made by providing an ultraviolet curable resin of 4 μm.
Was. This disc is the length of the major axis of the elliptical illumination beam.
With a short axis of about 1.5 μm
Linear velocity 4m / s, beam feed speed using disk initialization device
Degree (disc radial direction) 40μm / rotation, laser power
-Scan at 350mW three times, and then
(Laser wavelength 780 nm, NA = 0.55)
And 8 mW DC light at a linear velocity of 2.4 m / s
Irradiate with tracking once for each group
Initial crystallization was performed. Initial crystallization was performed without any problem.
Recording was performed by the method as shown in FIG. That is, the optical disk
Evaluation equipment (laser wavelength 780nm, NA 0.55)
At a linear velocity from 1.2 m / s to 4.8 m / s
EFM random signal (clock frequency 4.32 MHz
In each case, set the recording linear velocity / 1.2 times according to the linear velocity.
Was recorded. Α during recording₁= 1, α_i=
0.5 (i ≧ 2), β_i= 0.5 (i ≧ 1) and Pe
/Pw=0.5, constant, and Pw from 8 mW to 17 mW
Shake to record. In this case, Pb is 0.1.
It was constant at 8 mW, and m = n-1. Jitter measurement
The measurement was performed at 2.4 m / s. The results at this time are shown in FIG.
You. It can be seen from FIG. 4 that good characteristics are obtained.
Further, the recorded signal was at a temperature of 80 ° C. and 80% RH.
No degradation after 100 hours in the environment
Was.

Example 2 (ZnS) on a polycarbonate substrate₈₀(SiO_Two)₂₀
103 nm layer, Ag as recording layer_4.8Ga_4.8Ge
_5.5Sb_59.9Te_25.016 nm layer, (ZnS) ₈₀(S
iO_Two)₂₀Layer 41 nm, Al₉₉Ta₁200 alloy layers
nm, sequentially laminated by magnetron sputtering method,
Further, a disk is made by providing an ultraviolet curable resin of 4 μm.
Was. This disc is the length of the major axis of the elliptical illumination beam.
With a short axis of about 1.5 μm
Linear velocity 4m / s, beam feed speed using disk initialization device
Degree (disc radial direction) 40μm / rotation, laser power
-Scan at 360mW three times, and then
(Laser wavelength 780 nm, NA = 0.55)
9mW DC light at a linear velocity of 2.4m / s
Irradiate with tracking once for each group
Initial crystallization was performed. Initial crystallization can be performed without problems
Was. Recording was performed by the method as shown in FIG. That is,
Disk evaluation device (laser wavelength 780 nm, NA 0.5
Using 5), a line from 1.2 m / s to 4.8 m / s
EFM random signal (clock frequency 4.32M) at speed
Hz to the linear velocity each time, and the recording linear velocity / 1.2
Was doubled). Α during recording₁= 1, α
_i= 0.5 (i ≧ 2), β_i= 0.5 (i ≧ 1),
Pe / Pw = 0.5 is constant and Pw is 17 from 8 mW.
Recording was performed by shaking to mW. In this case, Pb is
It was constant at 0.8 mW, and m = n-1. Jitter measurement
The measurement was performed at 2.4 m / s. The result at this time is shown in FIG.
Show. It can be seen that better characteristics are obtained than in FIG.
You. However, for the recorded signal, a temperature of 80 ° C., 8
After measuring for 1 minute after leaving for 100 hours in an environment of 0% RH
The maximum value of the Cl error is 17 blocks / sec to 9
Increased to 9 blocks / sec.

Comparative Example 1 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
A 100 nm layer, a Ge ₁₂ Sb ₆₇ Te ₂₃ layer as a recording layer of 20 nm, a (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer of 20 nm,
An Al _99.5 Ta _0.5 alloy layer was sequentially laminated by magnetron sputtering to a thickness of 200 nm, and a UV-curable resin was further provided with a thickness of 4 μm to produce a disk. The length of the major axis of the elliptical irradiation beam was set to 80 μm and the minor axis was set to 1.3.
Initial crystallization was attempted in the same manner as in the example by using an optical disk initialization apparatus having a size of about μm, but only initial crystallization with incomplete unevenness was obtained. When high laser power was used to eliminate unevenness, defects occurred due to thermal degradation.

Comparative Example 2 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
The layer was 80 nm, and the recording layer was Zn ₅ In ₂ Sb ₆₂ Te _31.
20 nm for the layer and 20 n for the (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer.
m, an Al _99.5 Ta _0.5 alloy layer was sequentially laminated by a magnetron sputtering method to a thickness of 200 nm, and a UV-curable resin was further provided at 4 μm to produce a disk. This disc was prepared by setting the major axis of the elliptical irradiation beam to 80 microns,
Using an optical disk initialization device having a short axis length of about 1.4 μm, a linear velocity of 4.5 m / s and a beam feed rate of 50 μm
m / rotation (disc radial direction) laser power 250m
When the initial crystallization was attempted with W, the initial crystallization was successful. Optical disk evaluation device (laser wavelength 780 nm, N
A0.55) using EFM at a linear velocity of 2.4 m / s
Recording of a random signal (clock frequency 4.32 MHz was doubled) was performed. The recording is performed by using a method as shown in FIG. 2, and α ₁ = 1, α _i = 0.5 (i ≧ 2), β _i = 0.5
(I ≧ 1), Pw = 13 mW, Pe = 6.5 mw,
Pb was set to 0.8 mW. The value of the jitter indicating the actual signal characteristics was less than 10% of the clock cycle at the shortest mark length, and the initial characteristics were good. Also, after overwriting 1000 times, the jitter was also good at less than 10% of the clock cycle. However, the recorded signal is at a temperature of 80
It deteriorated after being left for 100 hours in an environment of 80 ° C. and 80% RH, and jitter reached 20% of the clock cycle. It was found that the amorphous bits partially recrystallized and disappeared.

Comparative Example 3 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
The layer was 103 nm, and the recording layer was Ag ₅ Ga ₅ Sb ₆₃ Te.
₂₇ A layer co-sputtered with 0.03 A of Sb ₂ Te ₃ at 300 W is 16 nm, and a (ZnS) ₈₀ (SiO ₂ ) ₂₀ layer is 41
A 200 nm thick Al ₉₉ Ta ₁ alloy layer was sequentially laminated by magnetron sputtering, and a 4 μm ultraviolet curable resin was further provided to produce a disk. This disc,
Using an optical disc evaluation device using an elliptical irradiation beam having a major axis length of 108 μm and a minor axis length of about 1.5 μm,
Linear speed 4m / s, beam feed speed (disc radial direction)
Scan three times at 40 μm / rotation, and further track 9.5 mW DC light once at each land and group at a linear velocity of 2.4 m / s using an optical disk evaluation device (laser wavelength 780 nm, NA 0.55). To perform initial crystallization. Initial crystallization was performed without any problem. Optical disk evaluation device (laser wavelength 780 nm,
1.2 m / s to 4.8 m / s using NA 0.55)
An EFM random signal was recorded at a linear velocity of up to (recording linear velocity / 1.2 times the clock frequency of 4.32 MHz in accordance with the linear velocity in each case). The recording is performed by using a method as shown in FIG. 2, and α ₁ = 1, α _i = 0.5 (i ≧
2), β _i = 0.5 (i ≧ 1), and Pe / Pw = 0.
The recording was performed while Pw was kept constant at 5 and the Pw was varied from 8 mW to 17 mW. In this case, Pb was constant at 0.8 mW, and mn-1. The jitter was measured at 2.4 m / s. FIG. 6 shows the result at this time. FIG. 6 shows that good characteristics are obtained. However, the recorded signal was 100 ° C under high temperature and high humidity of 80 ° C and 80% RH.
After some time, it had begun to crystallize and disappear.

Example 3 (ZnS) ₈₀ (SiO ₂ ) ₂₀ on a polycarbonate substrate
The layer is 103 nm, and the recording layer is Ag _4.7 Ga _4.7 Ge
_4.6 Sb ₆₁ . ₃ Te ₂₄ . ₇ layers of 16 nm, (ZnS) _80
20 layers of (SiO ₂ ) and an Al _99.5 Ta _0.5 alloy layer were sequentially laminated by magnetron sputtering at a thickness of 41 nm and an Al _99.5 Ta _0.5 alloy layer. This disk was subjected to a linear velocity of 4 m / s and a beam feed rate (radial direction of the disk) using an optical disk initialization device in which the major axis of the elliptical irradiation beam was 108 μm and the minor axis was about 1.5 μm. Scanning was performed three times at 40 μm / rotation and a laser power of 230 mW. Further, using an optical disk evaluation device (laser wavelength: 637 nm, NA: 0.60), DC light of 5 mW at a linear velocity of 3.5 m / s was applied to each of the land and the group. The initial crystallization was performed by irradiating with tracking each time. Using an optical disk evaluation device (laser wavelength 637 nm, NA 0.60), 3.0
An 8-16 modulated random signal having a basic clock frequency of 26.2 MHz was recorded at a linear velocity of m / s. The recording was performed using the method as shown in FIG. 2, and α ₁ = 0.3 and α _i = 0.25
(I ≧ 2), β _i = 0.25 (i ≧ 1), and Pw = 1
Recording was performed at 0 mW and Pe = 5 mW. For the measurement of jitter, reproduction was performed at 3.5 m / s, and σ / T = 10.5% was obtained.

[0043]

According to the present invention, initial crystallization can be facilitated and jitter can be reduced while utilizing the rewritable characteristics of the eutectic composition.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a layer configuration of an optical information recording medium of the present invention.

FIG. 2 is an explanatory diagram showing an example of a laser power irradiation pattern during optical recording on an optical information recording medium according to the present invention.

FIG. 3 is an explanatory diagram of a temperature profile of a recording layer.

FIG. 4 is a contour diagram of a mark jitter according to the first embodiment.

FIG. 5 is a contour diagram of mark jitter according to the second embodiment.

FIG. 6 is a contour diagram of mark jitter of Comparative Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower protective layer 3 Phase change type recording layer 4 Upper protective layer 5 Reflective layer 6 Protective coat layer

Claims (9)

[Claims] 1. A phase-change optical recording layer is provided on a substrate,
In an optical information recording medium in which recording / reproduction of information to / from a phase change recording layer is performed by a phase change between a crystalline state and an amorphous state, the phase change type optical recording layer has the following structure. (Where X is at least one of Ag, Au, Pd, Pt or Zn, M is at least one of Sn, Ge, Si and Pb, 0.0 ≦ α ≦ 0.1, 0.00
1 ≦ β ≦ 0.1, 0.01 ≦ χ ≦ 0.15, 0.5 ≦ δ
≦ 0.7, 0.15 ≦ ε ≦ 0.4, 0.03 ≦ β + χ ≦
0.25, α + β + χ + δ + ε = 1.0). 2. A method according to claim 1, wherein at least a lower protective layer, a phase-change optical recording layer, an upper protective layer, and a reflective layer are provided on the substrate, wherein the crystalline state is an unrecorded state, and the amorphous state is a recorded state. 2. The optical information recording medium according to claim 1, wherein amorphous bits are overwritten by modulating the light intensity of the value. 3. The optical information recording medium according to claim 1, wherein M is Ge. 4. The optical information recording medium according to claim 2, wherein the reflection layer is made of a metal containing at least one atom selected from the group consisting of Au, Ag, and Al in an amount of 90 atomic% or more. 5. The recording layer has a thickness of 15-30 nm, the upper protective layer has a thickness of 10-50 nm, and the reflective layer has a thickness of 50-5.
The optical information recording medium according to any one of claims 2 to 4, which has a thickness of 00 nm. 6. The recording method according to claim 1, wherein the recording is performed by a ternary modulation method having an off-pulse section. 7. The recording method according to claim 6, wherein the bias power Pb at the time of the off-pulse is set to 0 <Pb ≦ 0.5 Pe with respect to the erase power Pe. 8. An amorphous mark having a length of nT (T is a reference clock cycle and n is a natural number of 2 or more) is formed when recording information with mark length modulation by irradiating a focused light beam. At this time, an erasing power Pe capable of recrystallizing the amorphous mark is applied between the marks, and when forming an nT mark, the time nT is pulse-divided into nk pulses as follows. α ₁ T, β ₁ T, α ₂ T, β ₂ T,..., α _m T, β _m T, (however, α ₁ + β ₁ + α ₂ + β ₂ +... α _m + β _m
= N−j (0 ≦ j ≦ 2), m = nk (k = 0, 1,
2) and the minimum value of n is k + 1 or more), α ₁ T (1 ≦ i ≦
m) Recording power P sufficient to melt the recording layer at a certain time
Irradiation with w (> Pe), 0 <Pb ≦ 0.5Pe in the time of β ₁ T (1 ≦ i ≦ m) (However, in β _m T, 0 <Pb ≦ Pe may be satisfied. 7. The recording method according to claim 6, wherein the bias power Pb is applied. 9. The method for manufacturing a recording medium according to claim 1, wherein after forming the phase-change recording layer, the recording layer is irradiated with an energy beam to be crystallized. A method for producing an optical information recording medium, characterized in that when performing an initialization operation, the recording layer is locally melted and crystallized by resolidification.