JPH0877600A - Optical information recording medium - Google Patents

Abstract

PURPOSE: To improve the change in recording characteristics by a difference in line speed between inner and outer peripheries of an optical disk driven at a specified angular velocity. CONSTITUTION: A first dielectric layer 12, a recording layer 13, a second dielectric layer 14 and a reflection layer 15 are formed in this order atop a substrate 11 as the optical disk 10 of a phase transition type. The recording layer 13 is divided to an inner peripheral zone 17 and an outer peripheral zone 18 along the radial direction of the disk. The compsn. of the recording layer where the phase transition takes place is changed in the inner and outer peripheral zones. The transition from the crystalline state to the amorphous state stabilizes in the inner and outer peripheral zones and jitters of recording marks decrease if the crystallization speed is made higher the nearer the outer periphery. The disk structure in which the film thickness of the reflection layer 15 is made smaller, the film thickness of the dielectric layer 14 is made larger or the film thichness of the recording layer is made larger in the outer peripheral zone 18 than in the inner peripheral zone 17 is equally well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording member for recording or reproducing information at high speed and high density by using optical means such as a laser beam.

[0002]

2. Description of the Related Art A technique for reproducing or recording information at a high density by using a laser beam is mainly put into practical use as an optical disc. Optical disks, which are optical information recording members, can be roughly classified into a read-only type, a write-once type, and a rewritable type. The read-only type has been put into practical use as a compact disc or a laser disc, and the write-once type and rewritable type have been put into practical use as document files, data files and the like. Rewritable optical disks mainly include magneto-optical disks and phase change disks.

The phase change type optical disk utilizes the fact that the recording layer undergoes a reversible state change between an amorphous state and a crystalline state (or a crystalline state having a structure different from that of the crystalline state) upon irradiation with a laser beam. Recording is performed so that at least one of the refractive index and the extinction coefficient of the thin film changes due to the irradiation of the laser beam. Since the amplitude of transmitted light or reflected light changes in this thin film portion, the amount of transmitted light or reflected light reaching the detection system is detected to reproduce the signal. Alloys such as Te, Se, In, and Sb are mainly used as materials that cause a state change between amorphous and crystalline.

In the phase change type optical disc, one beam overwrite can be used for rewriting the recording mark. The one-beam overwrite is a new signal that erases an already recorded old signal by irradiating a laser beam on a signal track by modulating laser power between a recording level and an erasing level by a recording signal. Is a method of recording. The area irradiated at the recording level becomes amorphous because it is cooled after melting regardless of whether the original state is amorphous or crystalline. Since the area irradiated at the erase level rises above the crystallization temperature, it is crystallized regardless of the original state and a new signal is overwritten.

By the way, in the optical disk recording / reproducing apparatus, the optical disk rotation methods are roughly classified into two methods. The method of rotating the disk so that the linear velocity is the same on the inner and outer circumferences of the disk is called CLV, and the method of rotating the disk at a constant angular velocity is called CAV. For example, when a high speed access is required, such as a data file used for an external memory for a computer, it takes time to change the number of rotations of the disk, so CAV is used. In this case, the linear velocity in the circumferential direction of the disc is high at the outer circumference and slow at the inner circumference.

[0006]

DISCLOSURE OF THE INVENTION In an optical disk recording / reproducing apparatus, when a semiconductor laser emits a laser beam to cause a physical state change in a recording layer, for example, an optical disk using a rewritable phase change material is suitable. In order to obtain excellent recording / reproducing characteristics, it is indispensable to form amorphous recording marks stably and to realize a sufficient erasing rate. However, in the CAV mode, the erasing rate decreases at the outer periphery where the linear velocity is high. On the contrary, in the inner circumference where the linear velocity is low, a recording mark having a sufficient size may not be formed, or recording mark distortion may occur. This is because the time for the spot of the laser beam to pass through one point on the track becomes shorter toward the outer circumference, and the crystallization of the recording layer becomes insufficient, resulting in unerased residue. On the contrary, the inner circumference has a longer transit time of the laser beam, and the region melted here has a lower cooling rate, so that the recording layer is recrystallized and is not sufficiently amorphized.
The unerased portion, mark distortion, etc. as described above both become distortion or noise of the reproduced waveform and cause reproduction jitter.

The present invention has been made in view of the above conventional problems, and a phase change type optical disk is a CAV.
Provided is an optical information recording member capable of stably forming an amorphous recording mark on the entire surface regardless of the inner and outer circumferences of an optical disc and realizing a sufficient erasing rate when used for recording and reproducing in a mode. The purpose is to

[0008]

According to the invention of claim 1 of the present application, a recording layer whose phase state is changed by irradiation of a laser beam and which can be optically detected by irradiation of a laser beam is provided. A disk-shaped optical information recording member provided on a substrate as part of a thin film layer, characterized in that the thin film layer has a different thin film structure depending on a plurality of concentrically divided zones of the disk. Is.

According to the invention of claim 2 of the present application, the phase state is changed by the irradiation of the laser beam, and the phase state can be optically detected by the irradiation of the laser beam. An optical information recording member including the formed first dielectric layer and second dielectric layer, and a disk-shaped substrate that integrally holds the recording layer and the first and second dielectric layers. The recording layer is made of a phase change recording material that reversibly undergoes a phase change between an amorphous phase and a crystalline phase upon irradiation with a laser beam, and the phase change recording material is composed of a plurality of concentrically divided zones of the disk. Are different in composition.

The invention of claim 12 of the present application comprises a phase change recording material which reversibly changes phase between an amorphous phase and a crystalline phase upon irradiation with a laser beam, and which is optically in this phase state upon irradiation with a laser beam. A recording layer that can be detected, a second dielectric layer and a first dielectric layer formed on the upper and lower surfaces of the recording layer, and a laser beam formed on the upper surface of the second dielectric layer. A reflective layer for reflecting and a recording layer, the first
And a second dielectric layer, a disk-shaped substrate holding the reflective layer, wherein the reflective layer has a film thickness of a plurality of concentric zones of the disk. Differently, the outer peripheral zone is characterized by having a smaller film thickness.

According to a fourteenth aspect of the present invention, the invention comprises a phase change recording material that reversibly changes phase between an amorphous phase and a crystalline phase by irradiation with a laser beam, and the phase state recording material is optically changed by irradiation with a laser beam. A recording layer that can be detected, a second dielectric layer and a first dielectric layer formed on the upper and lower surfaces of the recording layer, and a laser beam formed on the upper surface of the second dielectric layer. A reflective layer for reflecting and a recording layer, the first
And a second dielectric layer, and a disk-shaped substrate holding the reflective layer, wherein the second dielectric layer is a plurality of concentrically divided zones of the disk. The film thickness is different depending on the type, and the film thickness is larger in the outer peripheral zone.

According to a fifteenth aspect of the present invention, the invention comprises a phase-change recording material that reversibly changes phase between an amorphous phase and a crystalline phase by irradiation with a laser beam, and the phase state of the phase state is changed optically by irradiation with a laser beam. A recording layer that can be detected, a first dielectric layer and a second dielectric layer formed on the upper and lower surfaces of the recording layer, and a laser beam formed on the upper surface of the second dielectric layer. A reflective layer for reflecting and a recording layer, the first
And a second dielectric layer, and a disk-shaped substrate holding the reflective layer, wherein the recording layer has a film thickness of a plurality of concentric zones of the disk. Differently, the outer peripheral zone is characterized by having a larger film thickness.

According to a sixteenth aspect of the present invention, a recording layer whose phase state is changed by irradiation with a laser beam and which can be optically detected by irradiation with a laser beam is used as a part of the thin film layer. An optical information recording member provided on a substrate, characterized in that the thin film layer has a different thin film structure depending on an inner peripheral zone and an outer peripheral zone divided into concentric circles of the disc.

[0014]

According to the present invention having such characteristics, the disk is concentrically divided into a plurality of zones, and the conditions for causing a phase change are changed depending on the zones. Specifically, (1) When the crystallization rate is increased toward the outer periphery by changing the composition ratio of the recording layer, the crystallization rate in each zone becomes suitable for the linear velocity, and the erasing rate at the inner and outer periphery becomes almost equal. it can. Therefore, a good amorphous mark is recorded over the entire surface of the disc. (2) When the thickness of the reflective layer is made thinner in the outer peripheral zone than in the inner peripheral zone, the cooling rate of the recording layer is optimized for the irradiation of the laser beam of the same power. Therefore, a good amorphous mark is recorded over the entire surface of the disc. (3) When the film thickness of the dielectric layer between the recording layer and the reflective layer is made thicker in the outer zone than in the inner zone, the cooling rate of the recording layer in contact with the dielectric layer against irradiation of a laser beam of the same power is increased. Is optimized. Therefore, a good amorphous mark is recorded over the entire surface of the disc. (4) When the thickness of the recording layer is made thicker in the outer peripheral zone than in the inner peripheral zone, the cooling rate of the recording layer is optimized for the irradiation of the laser beam of the same power. Therefore, a good amorphous mark is recorded over the entire surface of the disc. By adopting any one of the above items, it is possible to perform recording with little mark distortion from the inner circumference to the outer circumference of the disc.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the basic structure of an optical information recording member (hereinafter referred to as an optical disk) in the present invention will be described with reference to FIG. In the figure, the phase change type optical disk 10 is shown.
Is the substrate 11, the first dielectric layer 12, the recording layer 13, the second
The dielectric layer 14, the reflective layer 15, and the protective layer 16 are included. Of these, the dielectric layers 12, 14, the recording layer 13, and the reflective layer 15 are formed on a transparent substrate by a method such as vacuum deposition or sputtering. Further, a transparent protective layer 16 which is in close contact with the reflective layer 15 is provided.

Next, referring to FIG. 1, the optical disc 10 is divided into concentric circles along the radial direction, and the inner side of the inner zone 1
7 and the outside is called the outer peripheral zone 18. Although the optical disc 10 has a two-zone structure here, an optical disc having three or more zones can also be produced. Also, there is an optical disc having a structure without the reflection layer 15 and the protection layer 16. The laser beam for recording and reproduction is incident from the lower side of the substrate 11.

As a material for the substrate 11, glass, quartz, polycarbonate, or polymethylmethacrylate can be used. In addition, the substrate 11 may be a flat flat plate, and may have an uneven groove for a tracking guide on the surface. As the protective layer 16, a resin dissolved in a solvent and applied and dried, or a resin plate bonded with an adhesive can be used.

As a recording layer material used for the recording layer 13, a chalcogen alloy which changes phase between amorphous and crystalline is well known. For example, SbTe system, GeSbT
e system, GeSbTeSe system, GeSbTePd system, Te
GeSnAu system, AgSbTe system, GeTe system, GaS
b type, InSe type, InSb type, InSbTe type, In
SbSe type, InSbTeAg type, etc. can be used.

When GeSbTe is used as the recording layer material, especially xGeTe + (1-x) Sb ₂ Te ₃ + ySb
A composition having a composition satisfying (0 <x ≦ 1, y ≧ 0) is suitable as a material for a rewritable phase change type optical disc. In this regard, the Japanese Journal of
Applied Physics 26 (1987) No. 61
Pages 66 to 66 (Japanese Journal of Applied Physic
s, Vol. 26 (1987) 61-66).

Next, as the dielectric layers 12 and 14, Si is used.
O ₂ , SiO, TiO ₂ , MgO, Ta ₂ O ₅ , Al ₂
O ₃ , GeO ₂ , Si ₃ N ₄ , BN, AlN, SiC,
ZnS, ZnSe, ZnTe, PbS, etc. or a mixture thereof can be used.

The reflective layer 15 includes Au, Al, Cu,
A material containing a metal material such as Cr, Ni, or Ti as a main component or a mixture thereof, and a dielectric multilayer film having a large reflectance at a predetermined wavelength can be used.

Here, the greatest feature of the present invention is that the thin film structure is different in the inner and outer zones of the optical disk. For example, increasing the crystallization rate in the outer zone 18 than in the inner zone. When the optical disc is rotated in the CAV mode, the erasing rate decreases at the outer periphery having a high linear velocity, and conversely, a sufficiently large recording mark cannot be formed at the inner periphery having a low linear velocity, or mark distortion occurs. However, in any case, it was a cause of reproduction jitter.

However, by increasing the crystallization rate of the recording layer toward the outer circumference, the erasing rates at the inner and outer circumferences can be made substantially equal. To change the crystallization rate, GeSbTe
In the recording layer of the system, it is possible by changing the Sb amount or further adding the fourth element. For example, xGeTe + (1-x) Sb ₂ Te ₃ (0 <x ≦
If Sb is further added to the composition represented by 1), the crystallization rate becomes slow.

Ge, SbTe ternary system, Ag, Cu, C
o, Tl, Pd, Au, Bi, Se, Sn, Pt, Ni
The crystallization rate can be slowed down by adding. Furthermore, the thicker reflective layer, thinner recording layer, and thinner dielectric layer on the reflective layer side can increase the cooling rate of the recording layer, resulting in formation of good amorphous marks on the inner circumference. Yes, the jitter can be reduced.

There is also a method of selectively using a recording waveform for forming one recording mark in a plurality of zones. That is, the waveform of the recording laser beam for each zone is changed from the inner zone to the outer zone by "subsequent short pulse width / leading pulse width".
Use a multi-pulse waveform so that becomes larger. By switching the multi-pulse waveform depending on the zone, it is possible to optimize the multi-pulse waveform according to the zone and perform recording with little mark distortion from the inner circumference to the outer circumference.

In the CAV mode, the linear velocity ratio between the innermost peripheral portion and the outermost peripheral portion of the optical disk has a value of about 2-4. On the other hand, one thin film structure can handle a linear velocity ratio of about 2 times, and by dividing the optical disc into at least two zones, a linear velocity ratio of about 4 times can be handled. In addition, by continuously changing the thin film structure in the radial direction of the optical disc,
It may be possible to cope with the difference in linear velocity, but this method has a problem in reproducibility of the film thickness and the composition of the recording layer. Therefore, the method of dividing the optical disc into two zones as in the present invention has high feasibility and good reproducibility.

The optical disc of the present invention will be described in detail below with reference to specific examples. (Embodiment 1) FIG. 2 shows the structure of the optical disc in the first embodiment of the present invention. As shown in the sectional view of this figure, the recording layer 13 of the optical disc 10A of the first embodiment is divided into an inner recording layer 13a and an outer recording layer 13b. First, the film forming process of each layer of the optical disc 10A will be described. 3 and 4 are relationship diagrams of the substrate and the sputtering mask used in the film forming process of the optical disk 10A.

In order to change the composition of the recording layer 13 between the inner peripheral zone 17 and the outer peripheral zone 18, a substrate having a signal recording track made of polycarbonate having a diameter of 130 mm was used as the substrate 11 of the optical disk 10A. As shown in FIG. 2, in the optical disc 10A, a portion having a radius of 22 mm or more and less than 40 mm is an inner peripheral zone 17, and a radius of 40 mm or more and 58 mm.
The following portion was designated as the outer peripheral zone 18. A ZnS—SiO ₂ mixed film was formed on the upper surface of the substrate 11 as the first dielectric layer 12 by sputtering to a thickness of 1300 Å.

Next, an inner peripheral portion sputtering mask 21 having holes only in the inner peripheral portion as shown in FIG. 3 is used so that only the recording layer 13a in the inner peripheral zone 17 has a film thickness of 250Å.
A film was formed by sputtering the target 22 while rotating the substrate 11. Next, as shown in FIG. 4, a target material 42 having a mixture of different compositions is formed by using an outer peripheral sputtering mask 31 having holes only in the outer peripheral portion.
Then, the recording layer 13b of 250 Å was formed by sputtering while rotating the substrate 11. Then, a ZnS—SiO ₂ mixed film having a thickness of 200 is used as the second dielectric layer 14.
Å, an Al film was formed as the reflection layer 15 at 1500 Å by sputtering. Then, a polycarbonate protective layer 16 was provided thereon.

As a method of changing the composition of the recording layer 13 on the inner and outer circumferences of the optical disk, in addition to the above-mentioned method, an inner masking area and an outer masking area as shown in FIG. It is also possible to form recording layers of different compositions by co-sputtering the target 22 and the target 42 by using one mask 41 provided with. As the mask shape, the inner peripheral zone 17 and the outer peripheral zone 18
Other shapes may be used as long as the film thickness can be made uniform. In addition, the film thicknesses of the dielectric layers 12 and 14, the recording layer 13, and the reflective layer 15 are set to the inner zone 17 and the outer zone 18.
When manufacturing an optical disc changed with step 1, sputtering is performed using the inner peripheral portion sputtering mask 21 in FIG. 3 or the outer peripheral portion sputtering mask 31 in FIG. 4 to control the film thickness to a predetermined value. Good. As a method of producing an optical disc in which the film thickness is changed on the inner and outer circumferences, it is also possible to use an inner and outer circumference film thickness control mask 51, as shown in FIG.

In the evaluation of the above optical disk 10A, the wavelength of the laser beam is 780 nm, the NA of the objective lens of the optical head used for recording / reproducing of the recording apparatus is 0.55,
Recording and reproduction were performed by controlling the clock T so that the shortest mark length of the EFM signal is always 0.90 μm with the number of revolutions of the optical disk being 1000 rpm.
Here again, recording is performed 100 times by one-beam overwrite, and the jitter value at the zero cross point of the 3T reproduction signal in the EFM signal is measured. The jitter here is defined as a value of σ / Tw (%), where Tw is the pulse width (window width) of the 3T reproduction signal and σ (standard deviation) is its time variation width.

The jitter thus defined was measured at each position of radius 23, 30, 37, 43, 50, 57 mm of the optical disk. The respective linear velocities in the radius mentioned above are about 2.4, 3.1, 3.9, 4.5, 5.2, 6.0 m / s from the inner circumference side.
Is. When recording at a single frequency so that the recording mark length is 0.9 μm in the inner peripheral zone 17 and the outer peripheral zone 18 of all optical disks, the recording power at which the C / N value is saturated and the recording mark is erased Erasure rate is -20
The median power of the power margin exceeding dB was set.

FIG. 7 is an illustration of a specific recording waveform used in this embodiment. FIG. 7A is an example of an input waveform of an EFM signal that is often used in optical discs. FIG. 7B shows a multi-pulse recording waveform A for driving the semiconductor laser when the input waveform of FIG. 7A is recorded. The width of the leading pulse in the short pulse train is 1.5T, and the width of the subsequent pulse and its interval are 0.5T. FIG. 7C shows a recording waveform B in which the leading pulse width and the trailing pulse width in the short pulse train are widened to 1.5T and 0.75T, respectively. For the optical discs of the first to fifth examples, the multi-pulse recording waveform A shown in FIG. 7B was used.

Table 1 shows an example of the jitter characteristics of the recording marks when the composition of the recording layer 13 is changed in the inner and outer zones of the optical disk. Table 1 shows optical disks (1) to 1 indicated by numbers in the figure.
The optical disk (4) shows the characteristics of (4), and the composition of the recording layer 13 is changed between the inner peripheral zone and the outer peripheral zone. Further, the optical discs (1) to (3) are reference discs in which the recording layers 13 of the inner and outer zones have the same composition. The value of each column of each optical disk is the jitter value of the recording mark recorded in each radius.

[Table 1]

As shown in Table 1, the composition of the recording layer 13 of the optical disc (4) is such that Ge _22.2 Sb _22.2
Te _55.6 ; (2GeTe + Sb ₂ Te ₃ ). In the inner zone 17, Ge _21.1 Sb _26.3 Te _52.6 ; (2Ge
Te + Sb ₂ Te ₃ + 0.5Sb).

As a reference disc, the composition of the recording layer 13 is constant from the inner zone to the outer zone,
Three optical discs (1) to (3) each including only one zone were prepared. Specifically, in the optical disc (1), the composition of the recording layer 13 is Ge _22.2 Sb _22.2 Te _52.6 ; (2GeT
e + Sb ₂ Te ₃ ) and the optical disc (2) is Ge
_21.6 Sb _24.3 Te _54.1 ; (2GeTe + Sb ₂ Te ₃ +
0.25 Sb) and the optical disc (3) has Ge _21.1
Sb _26.3 Te _52.6 ; (2GeTe + Sb ₂ Te ₃ +0.
5Sb).

First dielectric layer 1 of the above four optical disks
2, the material of the second dielectric layer 14, the reflective layer 15, etc.,
The film thickness, the preparation conditions, the film thickness of the recording layer 13, and the preparation conditions are the same. Now, as shown in the data of Table 1, in the case of the optical disc (1), the composition of this recording layer has a high crystallization rate and is suitable for recording / erasing at the linear velocity of the outer peripheral portion.
Also, good recording marks are formed, and the jitter is a small value. However, since the linear velocity is too slow in the innermost peripheral portion, the recording mark is recrystallized and is not sufficiently amorphized, and the recording mark distortion and the jitter value increase.

On the contrary, in the optical disc (3), the crystallization rate of the composition of the recording layer is suitable for the linear velocity at the inner peripheral portion. Therefore, good recording marks are formed and the jitter value is also good. However, since the linear velocity is too high in the outer peripheral portion, the unerased portion is generated during overwriting, and the jitter increases.

In the case of an optical disc (2) having a recording layer whose crystallization speed is approximately between that of the optical disc (1) and that of the optical disc (3), the optical discs (3), (1 The same phenomenon occurs as in (1), which causes an increase in jitter. That is, when the composition of the recording layer 13 is single, no matter what composition is selected, good jitter characteristics cannot be obtained in the entire area from the inner peripheral portion to the outer peripheral portion by CAV rotation.

On the other hand, in the optical disc (4), since the crystallization speeds of the inner and outer zones are suitable for the linear velocity, good recording marks are formed, and the jitter value is small over the entire surface of the optical disk. Has become. As described above, it can be seen that by setting the composition in the recording layer 13 such that the crystallization rate is higher toward the outer peripheral zone, good recording with small jitter can be performed on the entire surface of the optical disc even in the case of CAV.

In this embodiment, only the result in the case of two zones is shown, but the zone is divided into three or more and the recording layer having the crystallization rate corresponding to each linear velocity is formed. , A good jitter value was obtained on the entire surface of the optical disk as in the case where the zone was divided into two. In this embodiment, xGeTe + (1-x) Sb ₂ Te ₃ + ySb (y
In the case of ≧ 0), only the case of x = 2/3 is shown.
Regarding the composition of the recording layer satisfying 1/2, a good jitter value was obtained over the entire surface of the optical disc when the crystallization speed was increased toward the outer peripheral zone.

(Embodiment 2) Next, an optical disk according to a second embodiment of the present invention will be described. The sectional structure of the optical disc 10B of this embodiment is the same as that shown in FIG.
Unlike the first embodiment, the recording layer 13 of this embodiment is xGeT.
e + (1-x) Sb ₂ Te ₃ + yAg (x = 2/3, y
≧ 0). Table 2 shows the characteristics of the optical disk 10B (optical disk (3)) and the reference disks (1) and (2) of this embodiment, and the composition of the recording layer is used as a parameter. Similar to Table 1, it shows the jitter characteristics of recording marks in the inner and outer zones of the optical disc.

[Table 2]

The method of producing the optical disk of this embodiment is the same as that of the first embodiment, and the explanation thereof is omitted. In the optical disc (3) manufactured in this example, the composition of the recording layer 13 was Ge _22.2 Sb _22.2 Te _{55.6 in the} outer peripheral zone 18.
(2GeTe + Sb ₂ Te ₃ ), the inner zone 17
Ge _21.1 Sb _21.1 Te _52.6 Ag _5.2 ; (2GeTe +
Sb ₂ Te ₃ + 0.5Ag).

As the optical disc (1) which is the reference disc, the composition of the recording layer 13 from the inner peripheral zone to the outer peripheral zone is Ge _22.2 Sb _22.2 Te _55.6 ; (2Ge
Te + Sb ₂ Te ₃ ). Similarly, as the optical disc (2), the composition of the recording layer 13 from the inner peripheral zone to the outer peripheral zone is Ge _21.1 Sb _21.1 Te _52.6 Ag _5.2 ;
It was created as (2GeTe + Sb ₂ Te ₃ + 0.5Ag).

First dielectric layer 1 of the above three optical disks
2, each material of the second dielectric layer 14 and the reflective layer 15, the film thickness,
The production conditions, the film thickness of the recording layer 13, and the production conditions are the same as those of the optical disc 10A of the first embodiment. Moreover, the measurement radius of each optical disk was set to be the same as the value in Table 1, and each jitter value was measured. As can be seen from the data in Table 2, in the case of the optical disc (1), the composition of the recording layer 13 has a crystallization rate suitable for the linear velocity at the outer peripheral portion, a good recording mark is formed, and the jitter value is small. . However, since the linear velocity is low in the inner peripheral portion, the recording mark is distorted and the jitter increases.

On the other hand, by adding Ag to the recording layer 13, the crystallization speed can be slowed down. Therefore, the jitter value is improved in the inner peripheral portion of the optical disk (2), but on the other hand, in the outer peripheral portion, the linear velocity is too fast, so that unerased residue occurs at the time of overwriting and the jitter increases. However, in the optical disc (3) of the present embodiment, the crystallization speed and the linear velocity are suitable at the inner and outer circumferences of the optical disc.
Good recording marks can be formed, and the jitter value is good over the entire surface of the optical disc.

As described above, by making the composition of the recording layer 13 such that the crystallization rate is higher toward the outer peripheral zone, it is possible to perform good recording / erasing operation with small jitter over the entire surface of the optical disk even in the case of CAV. Cu and C other than Ag
o, Tl, Pd, Au, Bi, Se, Sn, Pt, Ni
The same results as in the present example were obtained even when a larger amount was added to the outer peripheral zone 18 of the recording layer 13.

(Embodiment 3) Next, an optical disk according to a third embodiment of the present invention will be described. FIG. 8 is a sectional view showing the structure of the optical disc 10C of the third embodiment. In this figure, an optical disk 10C is composed of a substrate 11, a first dielectric layer 12, a recording layer 13, a second dielectric layer 14, a reflective layer 15, and a protective layer 16 as in the first and second embodiments. However, the film thickness of the reflective layer 15 is different between the inner peripheral zone 17 and the outer peripheral zone 18.

Table 3 shows the characteristics of the optical discs (1) to (4). The optical disc (4) has an optical disc 10C of this embodiment in which the thickness of the reflective layer 15 is changed between the inner zone and the outer zone. Is. The optical discs (1) to (3) are reference discs in which the reflective layers 15 in the inner and outer zones have the same film thickness. The method of displaying the data on each optical disk is the same as in the first and second embodiments.

[Table 3]

The composition of the recording layer 13 of the optical discs (1) to (4) is Ge _21.6 Sb _24.3 Te _{54.1 in} both the inner and outer zones.
(2GeTe + Sb ₂ Te ₃ + 0.25Sb).
In the optical disc (4), the reflection layer 15a in the inner peripheral zone 17
With a film thickness of 2000 Å, the reflective layer 1 in the outer peripheral zone 18
The film thickness at 5b was 1250Å. In addition, as a reference disc, the reflective film thickness is 1250Å, 1500 at the entire circumference.
Å, 2000 Å optical disks (1), (2),
(3) was created respectively.

First dielectric layer 1 of the above four optical disks
2. The material and film thickness of the second dielectric layer 14, the forming conditions, the film thickness of the recording layer 13, the material of the reflective layer, and the forming conditions are the same as those in the first embodiment. As shown in the data of Table 3, in the optical disc (2), an increase in jitter is seen at the innermost circumference and the outermost circumference. This is because the cooling speed of the recording layer 13 is low at the innermost circumference because the linear velocity is low, and the melted portion of the recording layer 13 is recrystallized and the mark is distorted. On the contrary, at the outermost circumference, the linear velocity is high, so the cooling rate is high, the time for which the recording layer 13 is kept at high temperature is short, and the crystallization is insufficient.
It is thought that this is because the erase rate decreases.

On the other hand, in the optical disc (1) having a thin reflective layer 15, the cooling rate is small, so that the outermost jitter is improved, but the innermost jitter is large. On the contrary, in the optical disk (3) having the thick reflective layer 15, the cooling rate is increased, so that the jitter at the innermost circumference is improved, but the jitter at the outermost circumference is large. That is, the reflective layer 1
When the film thickness of 5 is the same in the inner peripheral zone and the outer peripheral zone 18, even if the thickness is properly selected, good jitter characteristics could not be obtained in the entire area from the inner periphery to the outer periphery by CAV rotation.

On the other hand, in the case of the optical disc (4) of the present embodiment, since the reflective layer 15 is provided so that the cooling rate of the recording layer 13 is optimized in each of the inner and outer zones, a good amorphous mark is formed. And the jitter value is also small. Thus, the outer peripheral zone 18 is closer to the reflective layer 15
It can be seen that, by reducing the film thickness of, even in the case of CAV, good recording with small jitter can be performed on the entire surface of the optical disc.

(Fourth Embodiment) Next, an optical disk according to a fourth embodiment of the present invention will be described. FIG. 9 is a sectional view showing the structure of the optical disc 10D of the fourth embodiment. In this figure, an optical disk 10D is composed of a substrate 11, a first dielectric layer 12, a recording layer 13, a second dielectric layer 14, a reflective layer 15, and a protective layer 16 as in the first to third embodiments. However, the film thickness of the second dielectric layer 14 is different between the inner peripheral zone 17 and the outer peripheral zone 18.

Table 4 shows the characteristics of the optical discs (1) to (4). In the optical disc (4), the thickness of the second dielectric layer 14 was changed between the inner zone and the outer zone. It is an example optical disc 10D. In addition, optical disc (1)
(3) is the second dielectric layer 1 in the inner and outer zones
4 is a reference disk having the same film thickness. The method of displaying the data on each optical disk is the same as in the first to third embodiments.

[Table 4]

The composition of the recording layer 13 of the optical discs (1) to (4) is Ge _21.6 Sb _24.3 Te _{54.1 in} both the inner and outer zones.
(2GeTe + Sb ₂ Te ₃ + 0.25Sb).
In the optical disc (4), the film thickness of the second dielectric layer 14a in the inner peripheral zone 17 was 170Å, and the film thickness of the second dielectric layer 14b in the outer peripheral zone 18 was 230Å. Further, optical discs (1), (2), and (3) were prepared as reference discs in which the second dielectric layer 14 had film thicknesses of 230Å, 200Å, and 170Å on the inner and outer circumferences, respectively.

In the above four optical disks, the material and film thickness of the first dielectric layer 12, the preparation conditions, the material of the second dielectric layer 14, the film thickness of the recording layer 13 and the material of the reflective layer 15,
The preparation conditions were the same as those of the first embodiment. As shown in the data in Table 4, in the optical disc (2), an increase in jitter is observed at the innermost circumference and the outermost circumference. This is because the linear velocity is slow at the innermost circumference, so that the cooling rate is low, the melt portion of the recording layer 13 is recrystallized and the mark is distorted, and conversely, the linear velocity is fast at the outermost circumference, so the cooling rate is high and the recording layer is This is because 13 is kept at a high temperature for a short time, and it is considered that the erasing rate is lowered due to insufficient crystallization.

On the other hand, in the optical disk (1) in which the second dielectric layer 14 is thick, the cooling rate is small, so that the outermost jitter is improved, but the innermost jitter is large. On the contrary, in the optical disc (3) in which the second dielectric layer 14 is thinned, the cooling rate is increased, so that the jitter at the innermost circumference is improved, but the jitter at the outermost circumference is large.
That is, in the case where the film thickness of the second dielectric layer 14 is the same in the inner peripheral zone 17 and the outer peripheral zone 18, even if the thickness is properly selected, good jitter is obtained in the entire area from the inner periphery to the outer periphery in CAV rotation. No properties were obtained.

On the other hand, in the case of the optical disc (4) of this embodiment, the film thickness of the second dielectric layer 14 is set so that the cooling rate of the recording layer 13 is optimized in each of the inner and outer zones. A good amorphous mark is formed and the jitter value is small. Thus, the outer zone 1
By increasing the thickness of the second dielectric layer 14 by about 8,
It can be seen that even in the case of AV, good recording with small jitter can be performed on the entire surface of the optical disc.

(Fifth Embodiment) Next, an optical disk according to a fifth embodiment of the present invention will be described. FIG. 10 is a sectional view showing the structure of the optical disc 10E of the fourth embodiment. In this figure, an optical disk 10E is composed of a substrate 11, a first dielectric layer 12, a recording layer 13, a second dielectric layer 14, a reflective layer 15, and a protective layer 16 as in the first to fourth embodiments. However, the film thickness of the recording layer 13 is different between the inner peripheral zone 17 and the outer peripheral zone 18.

Table 5 shows the characteristics of the optical disks (1) to (4). The optical disk (4) has an optical disk 10E of the present embodiment in which the film thickness of the recording layer 13 is changed between the inner peripheral zone and the outer peripheral zone. Is. The optical discs (1) to (3) are reference discs in which the second recording layer 13 in the inner peripheral zone and the outer peripheral zone are formed to have the same film thickness. The method of displaying data on each optical disk is the same as that of the first to fourth embodiments.

[Table 5]

As shown in the data in Table 5, the composition of the recording layer 13 of the optical discs (1) to (4) is Ge _21.6 Sb _24.3 Te _54.1 ; (2GeTe + Sb ₂
Te ₃ +0.25 Sb). In the optical disc (4), the film thickness of the recording layer 13a in the inner circumferential zone 17 is 200Å
And the film thickness of the recording layer 13b in the outer peripheral zone 18 is 300
Å As reference discs, optical discs (1), (2) and (3) having recording film thicknesses of 300 Å, 250 Å and 200 Å all over the circumference were prepared.

First dielectric layer 1 of the above four optical disks
The materials and thicknesses of the second and second dielectric layers 14 and the forming conditions, and the materials and forming conditions of the reflective layer 15 are the same as those in the first embodiment. As shown in Table 5, in the optical disc (2), an increase in jitter is seen at the innermost circumference and the outermost circumference. This is because the linear velocity is slow at the innermost circumference, so the cooling rate is small, and the melted portion of the recording layer 13 is recrystallized and the mark is distorted. On the contrary, it is considered that the cooling rate is high at the outermost circumference because the linear velocity is high, the time for which the recording layer 13 is kept at high temperature is short, and the crystallization is insufficient, so that the erasing rate is lowered.

On the other hand, in the optical disc (1) having a thick recording layer 13, the cooling rate is small, so that the jitter at the outermost circumference is improved, but the jitter at the innermost circumference is large. On the contrary, in the optical disc (3) in which the recording layer 13 is thin,
Since the cooling rate is increased, the innermost jitter is improved, but the outermost jitter is large. That is, when the thickness of the recording layer 13 is the same, even if the thickness is properly selected, good jitter characteristics cannot be obtained in the entire area from the inner circumference to the outer circumference by CAV rotation.

On the other hand, in the case of the optical disc (4) according to the present embodiment, since the film thickness of the recording layer 13 is set so that the cooling rate of the recording layer 13 is optimum in the inner and outer zones, a good amorphous mark is obtained. Are formed, and the jitter value is also small. In this way, the outer peripheral zone 18 is closer to the recording layer 1
It can be seen that by increasing the film thickness of No. 3, good recording with small jitter can be performed on the entire surface of the optical disk even in the case of CAV.

[0066]

As described above, according to the present invention, by increasing the crystallization rate of the recording layer of the disc toward the outer circumference, the erasing rates at the inner and outer circumferences can be made substantially equal. Also,
The thicker reflective layer, thinner recording layer, and thinner dielectric layer on the reflective layer can increase the cooling rate of the recording layer, and as a result, a good amorphous mark can be formed on the inner circumference. In this way, when the disk is driven by the CAV method, information can be recorded under the same recording conditions even if the linear velocity changes in the inner and outer zones, and the recording power of the laser beam can be made constant. Further, since the rotational angular velocity of the disk can be made constant, the response speed of the control system relating to the track access of the optical head can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic structure of an optical disc according to each embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of an optical disc according to first and second embodiments of the present invention.

FIG. 3 is an explanatory diagram of a manufacturing apparatus (No. 1) for forming each layer of the optical disc of this embodiment.

FIG. 4 is an explanatory diagram of a manufacturing apparatus (No. 2) for forming each layer of the optical disc of this embodiment.

FIG. 5 is an explanatory diagram of a manufacturing apparatus (No. 3) for forming each layer of the optical disc of this embodiment.

FIG. 6 is an explanatory diagram of a manufacturing apparatus (No. 4) for forming each layer of the optical disc of the present embodiment.

FIG. 7 shows a waveform diagram of a recording signal in the optical disc of the present embodiment, and (a) is a digital input waveform diagram. (B)
FIG. 4 is a waveform diagram of a multi-pulse recording waveform A. (C) is a waveform diagram of a recording waveform B obtained by correcting the recording waveform A for each zone of the optical disc.

FIG. 8 is a sectional view showing a structure of an optical disc according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view showing the structure of the optical disc of the fourth embodiment of the present invention.

FIG. 10 is a sectional view showing the structure of an optical disc according to a fifth embodiment of the present invention.

[Explanation of symbols]

10, 10A, 10B, 10C, 10D, 10E, 91
Optical Disk 11 Substrate 12 First Dielectric Layer 13, 13a, 13b Recording Layer 14, 14a, 14b Second Dielectric Layer 15, 15b, 15b Reflective Layer 16 Protective Layer 17 Inner Zone 18 Outer Zone 21 Inner Sputter Mask 22, 42 target 31 outer peripheral sputtering mask 41 inner-outer simultaneous sputtering mask 51 inner-outer film thickness control mask

Claims (16)

[Claims] 1. A disc provided with a recording layer, which changes a phase state by irradiation of a laser beam and is capable of optically detecting the phase state by irradiation of the laser beam, as a part of a thin film layer on a substrate. The optical information recording member, wherein the thin film layer has a different thin film structure depending on a plurality of concentrically divided zones of the disc. 2. A recording layer whose phase state is changed by irradiation with a laser beam and which can be optically detected by irradiation with the laser beam; and a first layer formed on both surfaces of the recording layer. Second dielectric layer and second
An optical information recording member comprising: a dielectric layer; and a disk-shaped substrate that integrally holds the recording layer and the first and second dielectric layers, wherein the recording layer is the Characterized by a phase-change recording material that undergoes a reversible phase change between an amorphous phase and a crystalline phase upon irradiation with a laser beam, and the composition of the phase-change recording material is different depending on a plurality of concentrically divided zones of the disk. And an optical information recording member. 3. The optical information recording member according to claim 2, wherein the recording layer is made of a material having a different crystallization rate in a phase change for each zone of the disc. 4. The optical information recording member according to claim 3, wherein the recording phase is made of a material having a higher crystallization rate in the phase change in the outer peripheral zone of the disc. 5. The optical information recording member according to claim 2, wherein the recording layer is a phase change recording material containing Ge, Sb, and Te as main components. 6. The recording layer is xGeTe + (1-x)
Sb ₂ Te ₃ + ySb (0 <x ≦ 1, y ≧ 0) is satisfied, and the value of y indicating the composition ratio of Sb is determined by a plurality of concentric zones of the disc. The optical information recording member according to claim 5, wherein the outer peripheral zone is smaller than the zone. 7. The optical information recording member according to claim 6, wherein the recording layer has x = 2/3. 8. The optical information recording member according to claim 6, wherein the recording layer has x = 1/2. 9. The recording layer comprises Ge, Sb, Te and M.
3. The optical information recording member according to claim 2, wherein (M is a metal element or a metalloid element). 10. The optical information recording member according to claim 9, wherein the recording layer has a larger amount of M in an inner peripheral zone of the disc than in an outer peripheral zone. 11. The recording layer has M of at least Ag,
Cu, Co, Tl, Pd, Au, Bi, Se, Sn, P
10. The optical information recording member according to claim 9, comprising at least one of t and Ni. 12. A recording comprising a phase change recording material that reversibly changes phase between an amorphous phase and a crystalline phase upon irradiation with a laser beam, and the phase state can be optically detected upon irradiation with the laser beam. Layer, a second dielectric layer and a first dielectric layer respectively formed on the upper surface and the lower surface of the recording layer, and reflection formed on the upper surface of the second dielectric layer and reflecting the laser beam. An optical information recording member comprising a layer, a recording layer, the first and second dielectric layers, and a disc-shaped substrate holding the reflection layer, wherein the reflection layer is a concentric circle of the disc. An optical information recording member characterized in that the film thickness is different depending on a plurality of zones divided into a plurality, and the film thickness is thinner toward the outer peripheral zone. 13. The reflective layer is made of Au, Al, Cu, C.
13. The optical information recording member according to claim 12, wherein the main component is any one of r, Ni, Ti, and Ag metal materials, or a mixture of the metal materials. 14. A recording which comprises a phase change recording material which reversibly changes phase between an amorphous phase and a crystalline phase upon irradiation with a laser beam, and which can optically detect the phase state upon irradiation with the laser beam. Layer, a second dielectric layer and a first dielectric layer respectively formed on the upper surface and the lower surface of the recording layer, and reflection formed on the upper surface of the second dielectric layer and reflecting the laser beam. An optical information recording member comprising a layer, a recording layer, the first and second dielectric layers, and a disk-shaped substrate holding the reflective layer, wherein the second dielectric layer is The optical information recording member is characterized in that the film thickness varies depending on a plurality of concentrically divided zones of the disk, and the outer peripheral zone has a larger film thickness. 15. A recording comprising a phase-change recording material that reversibly changes phase between an amorphous phase and a crystalline phase by irradiation with a laser beam, and the phase state can be optically detected by irradiation with the laser beam. Layer, a first dielectric layer and a second dielectric layer formed on the upper surface and the lower surface of the recording layer, respectively, and reflection formed on the upper surface of the second dielectric layer and reflecting the laser beam. An optical information recording member comprising a layer, a recording layer, the first and second dielectric layers, and a disk-shaped substrate holding the reflection layer, wherein the recording layer is a concentric circle of the disk. An optical information recording member characterized in that the film thickness is different depending on a plurality of zones divided into a plurality, and that the outer peripheral zone has a larger film thickness. 16. An optical system in which a phase state is changed by irradiation with a laser beam, and the phase state can be optically detected by irradiation with the laser beam is provided on a substrate as a part of a thin film layer. The optical information recording member, wherein the thin film layer has a different thin film structure depending on an inner peripheral zone and an outer peripheral zone of the disk which are divided into concentric circles.