JP2001067721A - Optical disk having two layers of recordable, erasable and reproducible phase transition type on one side and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to focus-servo any of first and second recording layers even in an initial state after produced by making a second phase transition recording film of the initial state before irradiating it with a light beam after produced into an initialization-free phase transition recording film unnecessary to crystallize initially by irradiating the whole area with the light beam. SOLUTION: This optical disk having two layers on one side has such a structure that the disk having a first RAM layer and a disk 28 having a second RAM layer are joined to each other with a UV-curable resin film. The dick 28 is obtained by forming a reflecting film 112 consisting of Al-Cr on a transparent substrate 111 and a dielectric protection film 113 consisting of a ZnS-SiO2- mixed film thereon and laminating a phase transition recording film 114 consisting of a three-component alloy of reversibly phase-transiting GeSbTe between the amorphous phase and the crystal phase by irradiation with a laser beam or the like, a dielectric protection film 115 consisting of the ZnS-SiO2- mixed film, a translucent film 116 consisting of Au as a translucent interference film to make it into an L to H medium in this order thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk in which two layers of phase change type capable of recording, erasing and reproduction are provided on one side thereof (hereinafter simply referred to as a single sided two layer phase change type optical disk). In particular, a phase change type in which two layers of a recordable and erasable phase change type which are reversibly changed between an amorphous state and a crystal state by irradiation with a light beam is provided on one surface thereof. Type optical disc, the two layers of which are bonded via an adhesive layer having a predetermined thickness, and a laser beam is condensed on each layer from one side thereof to enable recording, erasing and reproduction of data on one side of the two layers. The improvement of phase change optical disks.

[0002]

2. Description of the Related Art In recent years, optical disks have attracted attention as large-capacity memories. There are three types of optical disks: a read-only type typified by a CD, a write-once type that can be written only once, typified by a CD-R, and a rewritable type typified by an external memory of a computer that can reproduce, record and erase Discs.

Further, rewritable discs are broadly classified into magneto-optical discs and phase-change discs whose reproduction, recording and erasing methods are different. The phase-change optical disk uses a recording film that is reversibly changed in phase between amorphous and crystalline when irradiated with a laser beam.
In such a disk, data was recorded by forming a recording mark (amorphous state) and a background (crystalline state) by irradiation with a laser beam.
The reflectance differs between the recording mark (amorphous state) and the background (crystalline state), and the data was reproduced by detecting the difference in the reflectance. Whether the laser irradiated portion on the recording film becomes amorphous (mark) or crystalline (erased) depends on whether the temperature of the irradiated portion exceeds the melting point of the material constituting the film. Or the temperature exceeds the crystallization temperature. Therefore, a laser beam whose intensity is modulated between a certain reference temperature between the melting point temperature and the crystallization temperature and a certain reference temperature equal to or higher than the crystallization temperature is generated, and the recording film is scanned with the laser beam. Thus, overwriting (recording is performed simultaneously with erasing) is possible.

Further, such phase change type optical disks are roughly classified into two types. That is, the crystal in the erased state is in a state of high reflectance (High), and the recorded mark is in a state of low reflectance (Low).
The medium to be low (hereinafter referred to as H to L) and the crystal in the erased state have a low reflectance state (Low), and the recorded mark has a so-called Low to High reflectance state (High).
There is High (hereinafter referred to as L to H) media.

A phase-change type optical disk has a layer structure including a recording layer, and the layer is generally formed on a plastic substrate such as a disc-like polycarbonate by a sputtering method or
The film is formed by a vacuum film forming method such as an evaporation method. In these film forming methods, generally, high-speed atoms or molecules are attached while colliding with the substrate in the process of attaching the raw material to the substrate. Therefore, the phase-change type recording material is rapidly cooled at the moment when the high-temperature raw material adheres to the substrate, and as a result, the formed recording layer is in an amorphous state due to so-called melting / quenching.

Therefore, in the phase change type optical disk immediately after film formation, the entire surface of the recording layer is amorphous, and is in a recording state (initial recording state) in which the entire surface is recorded in an initial state.
Originally, in an optical disk drive, at the time of the first write operation, that is, an overwrite operation (hereinafter, referred to as OW).
Sometimes, an amorphous recording mark (amorphous) and an erased state (crystal) are formed on the entire amorphous recording layer.
It would be ideal if we could write However, the recording layer in the amorphous state immediately after the film formation is extremely stable in terms of energy because the quenching degree at which the raw material is suddenly cooled immediately after the collision with the substrate is extremely large. There is a problem that a crystalline state cannot be created in the recording layer only by performing the first (first) OW operation.

For this reason, the recording layer of the phase-change optical disk is generally crystallized by an initial crystallization device that generates a high-power laser before being used in a general optical disk drive. In the initial crystallization apparatus, for example, a laser beam having an output of several W class such as an Ar gas laser is generated, and this laser beam is focused by an objective lens so as to form a spot diameter of several tens μm on the disk plate surface. Is done. Since the track pitch of an optical disk is usually 0.5 μm to 1.6 μm, several tens of tracks are crystallized at once by scanning the disk in the circumferential direction with a laser beam while shifting the radial position.
The entire disk is crystallized.

By the way, as described above, there are two types of phase change type optical discs, H to L media and L to H media. In connection with the above-mentioned problem of initial crystallization, L to H media includes: It has been pointed out that it has the following disadvantages. First, in the case of the H to L medium, the crystal state after the initial crystallization is a state having a high reflectance (H state). Strength is obtained. Therefore, in the device system, servo, particularly focus servo, can be easily operated. After recording, the reflectivity of the amorphous portion of the mark decreases, but the recorded portion and the unrecorded portion are assumed to be approximately half, so the reflectivity is about halfway between erasure and recording, It is said that it is not a problem to operate.

On the other hand, in the case of the L to H medium, it is said that there is a problem in operating the servo because the initial crystal state is a state in which the reflectance is low (L state).

In recent years, as the density of an optical disk has increased, recording marks have become increasingly finer. Accordingly, in order to obtain a large signal (amount of change in reflectance) from a fine mark, the reflectivity has to be controlled by an apparatus system. Tends to be as low as possible within the range that can be identified by. That is, assuming that the reflectivity of the recording mark (amorphous portion) is Ra and the reflectivity of the erased state (crystal portion) is Rc, the modulation degree which is an index of the signal magnitude is defined by (Ra (Rc) / Ra). Therefore, when the reflectance Rc is as small as possible, the degree of modulation is as close as possible to 1.0, and a large degree of modulation is obtained. (By the way, the definition of the degree of modulation in the case of H to L media) Is because the crystal has higher reflectivity (Rc (Ra)
/ Rc. In this case, the modulation factor can be increased by reducing the reflectance Ra as much as possible for the same reason. In recent years, as the capacity of optical discs has increased, track pitches and pit pitches have become increasingly narrower.
Taking a rewritable DVD-RAM disk as an example, the track pitch is 0.6 μm and the pit pitch is 0.28 μm
The degree is assumed. However, a red semiconductor laser (wavelength 650 nm or 635 n
In m), it is said that there is a limit in reducing the pit pitch. If a semiconductor laser with a wavelength of 410 nm is put to practical use in the future, the recording density will increase in proportion to the square of the decrease in wavelength, but at present, a semiconductor laser with a wavelength of 410 nm has a low output (only for reproduction). It is said that the output of 5 mW) is only a prototype, and the output of 30 mW or more, which is necessary for recording and reproduction, requires more time for practical use.

Under these circumstances, the wavelength of the semiconductor laser remains red (wavelength: 650 nm), and the recording density remains almost the same as that of a 4.7 GB DVD-RAM on one side, which is being standardized. Attempts have been made to increase only the online capacity of recording and playback. ISOM `98
(International Symposium on Optical Memory 1998 O
ctober 20-22), Th-N-05 “Rewritable Dual Layer Ph
In the case of "ase-Change Optical Disk", a phase change type two-layer disk (hereinafter, simply referred to as a single-sided dual-layer RAM disk) capable of recording and reproducing from one side by laser irradiation as described below is proposed. Have been.

FIG. 1 shows one side described in the above article.
The structure of a two-layer RAM disk is shown schematically. Piece
A two-sided RAM disk is simply a polycarbonate
First RAM layer 132 is provided on a Bonate (PC) substrate 131
And a second RAM layer 134 is provided on another PC board 133.
These are adhered by a UV curable resin film 135 having a thickness of 40 μm.
It is formed in a combined structure. The first RAM layer 132
ZnS-SiO from PC board side _TwoProtective film 132A, GeSbTe recording layer
132B and ZnS-SiO_TwoThe protective film 132C is laminated.
The structure is formed. The second RAM layer 134 is UV cured
From the side of the film 135, the Au interference film 134D, ZnS-SiO_TwoProtective film
134A, GeSbTe recording film 134B, ZnS-SiO_TwoProtective film 13
4C, formed into a laminated structure of Al-CR reflective film 134E
Has been established.

An objective lens 136 for focusing a laser beam
Is controlled by a focus servo circuit (not shown), and the objective lens 136 controls the first RAM layer 132
The first focused laser beam LA1 focused on the recording film 132B and the second RAM layer 134
Is switched to one of the laser beams LA2 in the second focus state in which the recording film 134B is focused.
Each recording film 132B, 134B in the corresponding focus state
Recording and reproduction of data. Originally, if the recording capacity of each layer is 4.7 GB / side, which is standardized, the total of the two sides is 9.4 GB / side, but the optical interference between the first RAM layer 132 and the second RAM layer 134 is one. In consideration of the crosstalk caused by the above, the recording capacity of each layer is reduced to 4.25 GB by slightly lowering the recording density, and the total of the two layers is 8.5.
It is defined in GB.

[0014]

Next, a method of optically designing a single-sided dual-layer RAM disk described in the above paper will be described. First, as a basic design concept, the laser beam LA2 condensed by the objective lens 136 is transmitted to the second RAM.
In order to reach the layer 134, the first RAM layer 132 must have high transmittance as a whole. Second RAM layer 134
It is necessary to be able to perform recording / reproduction even with a weak laser beam transmitted through the first RAM layer 132, so that the entire layer has high sensitivity for recording, and Must have high reflectivity.

Further, in terms of signal processing, reproduced signals from the first RAM layer 132 and the second RAM layer 134 need to be at substantially the same level. Here, the magnitude of the reproduced signal is determined by the recording mark (amorphous portion) and the erased portion (crystal portion) around it.
(Hereinafter, referred to as a reflectance change amount).

If the reflectance of the first RAM layer 132 is r1, the transmittance is t1, and the reflectance of the second RAM layer 134 is r2, the first RAM
The amount of change in reflectance from the layer is ΔR1 = Δr1. 2nd RAM
Since the amount of change in the reflectance from the layer is such that the incident light is transmitted through the first RAM layer, is reflected by the second RAM layer, and is transmitted again through the first RAM layer 132, the change in the reflectance from the second RAM layer 134 is ΔR2 Is multiplied twice by the transmittance of the first RAM layer 132. Therefore, the absolute reflectance change △ R2 from the second RAM layer is
ΔR2 = Δr2 × t1 × t1. Here, as described above, the magnitude of the reproduction signal from the first RAM layer 132 and the second RAM layer 1
It is necessary that the magnitude of the reproduced signal from the signal 34 be substantially the same level in signal processing, and it is necessary that △ R1 = △ R2.

Next, each parameter is defined. The reflectance of the crystal of the first RAM layer is r1c, the absorption is α1c, the transmittance is t1c,
The reflectance of the amorphous is r1a, the absorption is α1a, and the transmittance is t1a. Here, r1c + α1c + t1c = 100, r1a + α1a +
t1a = 100.

In the above-mentioned paper, first, the reflectance r1c is set to 9% so that the servo is electrically performed even when the first RAM layer 132 is in an unrecorded (crystalline) state.

The reflectivity r1c is given by
The larger is better, but the reflected light beam from the second RAM layer 134 returned to the objective lens 136 passes through the first RAM layer 132 twice, as described above.
In view of the fact that the intensity of the reflected light beam from 34 becomes considerably small, it is presumed that the intensity is adjusted to that.

Next, if the above-mentioned parameters are determined under the above-mentioned conditions, the following is obtained. First, since the incident light beam must reach the second RAM layer 134 after transmitting through the first RAM layer 132, the transmittance t1c of the first RAM layer 132
Was set to 50%. In order to set the transmittance as high as 50%, it is necessary that the reflection film 134E is made of metal for cooling in a normal phase change optical disk. Further, the disk of the first RAM layer 132 is not provided with a reflective film. If the transmittance of the first RAM layer 132 is too large, there is a problem that the absorptivity in the first RAM layer 132 is reduced, and the recording sensitivity of the first RAM layer 132 is reduced.

When the above two points are set and the film configuration of the phase change type optical disk of the first RAM layer 132 is designed, other parameters are automatically determined.

As a result of the film design, the parameters of the first RAM layer are r1c = 9%, α1c = 41%, t1c = 50%, r1a = 2
%, Α1a = 28%, and t1a = 70%.

Accordingly, the magnitude of the reproduced signal from the first c layer 132 is: magnitude of the reproduced signal = reflectance change amount △ R1 = r1c (r1a (reflectivity of crystal−reflectivity of amorphous) = 6% Becomes

The magnitude of the reproduction signal from the second RAM layer 134 is: magnitude of the reproduction signal = reflectance change amount △ R2 = △ r2 × t1 × t1
= Magnitude of the reproduced signal from the first RAM layer = 6% Therefore, the transmittance t1 is 0.5 (5
0%), ΔR2 is 24% from a simple calculation.

As described above, the second RAM layer 134 has the first R
In order to enable recording with a small amount of light transmitted through the AM layer 132, it is necessary to increase the sensitivity of the disk. In other words, it is necessary to set a large absorptance of the unrecorded portion (crystal state). Further, in order to prevent the absorbed heat from escaping, it is necessary to set the thickness of the reflecting film to be thin so as to transmit light to some extent in order to suppress the escape of heat from the reflecting film.

Applying the above conditions, ΔR2 = 2
When the film configuration of the second RAM layer is designed under 4%, r2c =
13%, α2c = 65%, t2c = 22%, r2a = 37%,
α2a = 37% and t2a = 26%.

Here, r 2c, α 2c, and t 2c are, respectively, the reflectance, absorptance, and transmittance of the crystalline state of the second RAM layer 134.
r2a, α2a, and t2a respectively represent the reflectance, absorptivity, and transmittance of the amorphous state. Here, it goes without saying that the amount of change in reflectance of the second RAM layer 134 is ΔR2 = r2a (r2c = 24%).

Here, attention should be paid to the second RAM layer 134.
Then, the reflectance r2a of the recording mark (amorphous portion) is higher than the reflectance r2c of the erased state (crystal portion), which is an L to H medium.

This is an inevitable result in designing a phase change disk by increasing the sensitivity, that is, by increasing the sensitivity of the crystal part in the film design. A technician familiar with the field can fully understand.

Therefore, in conclusion, in the above paper, the first RA
The M layer 132 is an H to L medium without a reflective film, and the second RAM layer 134 is an L to H medium.

However, in the single-sided dual-layer RAM disk,
There are the following disadvantages. That is, although the reflectance r2c in the erased state (crystal portion) of the second RAM layer 134 is 13%, the incident light beam is transmitted twice through the first RAM layer 132 in effect, so that the incident light beam passes through the first RAM layer 132 after being transmitted. The absolute value of the returning reflected light is 13 × (0.5 × 0.5) of the incident light = 3.
It will be 25%.

Therefore, when the second RAM layer 134 is used for the first time, if the entire surface is in an unrecorded state, if the servo is applied while focusing on the second RAM layer 134, the reflected light is too weak and the servo is not applied. Problems arise. In general, it is known that the reflectivity at which the servo is easily applied is approximately 5%, and the laser beam from the second RAM layer 134 returned to the objective lens 136 receives 3.2% of the incident light.
At 5%, there is a problem that the focus servo cannot be performed on the second RAM layer 134 during the initial operation.

The present invention has been made in view of the above circumstances, and has as its object to enable focus servo to be performed on both the first and second recording layers even in the initial state after manufacturing. An object of the present invention is to provide a single-sided, two-layer phase change optical disk.

[0034]

According to the present invention, (1) a phase-change type first recording film which reversibly changes phase between amorphous and crystalline by irradiation of a light beam; A phase change type second recording film that reversibly changes phase between amorphous and crystalline by irradiation, and the first recording film is disposed on the light beam incident side, and passes through the first recording film. An adhesive layer having a predetermined thickness that joins the two so that the light beam is applied to the second recording film.
The light beam is condensed on one of the first and second phase change recording films from the incident side to record data on the recording film;
In a single-sided, two-layer phase-change optical disc capable of erasing and reproduction, the second phase-change film is maintained in a crystalline state having a low reflectance at the time of erasing data, and the recording is performed at the time of recording to form a recording mark. The mark is maintained in an amorphous state having a high reflectivity, and in an initial state after the optical disk is manufactured and before the light beam is irradiated, the second phase change recording film is irradiated with the light beam over the entire surface to be initially irradiated. There is provided a single-sided, two-layer phase change optical disk characterized by a non-initialized phase change recording film that does not require crystallization.

(2) According to the invention, in the invention of (1), when the second recording film is formed by vacuum sputtering, a rare gas having the same atomic period as Ar and heavier than Ar as a sputtering gas. Forming the second phase change recording film as a non-initialized phase change film by using a gas to form the second phase change recording film at a sputtering gas pressure of 5 × 10 ⁻² torr or more. There is provided a phase change type optical disk characterized by the following.

(3) According to the invention, in the invention of (1) or (2), the rare gas as a sputtering gas for forming the second recording film by vacuum sputtering is Kr gas or , Xe gas.

(4) According to the invention, in the invention of (1), a rare gas having the same atomic period as Ar and heavier than Ar is used as a sputtering gas when the second recording film is formed by vacuum sputtering. The second phase change recording film is formed at a sputtering gas pressure of 5 × 10 ^-2 torr or more using
Using a mixed gas of gas and Ar gas and a Ge target, a GeN film was provided adjacent to the second phase change recording film, and the second phase change recording film was formed as an uninitialized phase change recording film. A phase change optical disk is provided.

(5) According to the invention, in the invention of (1) or (4), the rare gas as a sputter gas for forming the second recording film by vacuum sputtering is Kr gas or 5. The phase change optical disk according to claim 1, wherein the optical disk is Xe gas.

(6) According to the invention, in the invention of (1) or (4), the GeN film is provided adjacent to one side of the second phase change recording film. A type optical disk is provided.

(7) According to the invention, in the invention of (1) or (4), the GeN film is provided adjacent to both sides of the second phase change recording film. A phase change optical disk is provided.

(8) According to the present invention, in the invention of (1) or (4), the flow ratio N ₂ / N ₂ gas / Ar gas is used.
A phase change optical disk is provided, wherein a GeN film is provided adjacent to the second phase change recording film using a mixed gas of Ar and N ₂ having Ar of 0.3 or more and a Ge target. You.

(9) Further, according to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and becomes amorphous by irradiation of a light beam. A second recording film of a phase change type that reversibly changes phase with the crystal, and the first recording film is disposed on the light beam incident side, and the light beam passing through the first recording film is And a bonding layer having a predetermined thickness for bonding the two so as to irradiate the second recording film, and the light beam is focused on one of the first and second phase change recording films from the incident side. In a single-sided, two-layer phase-change type optical disk capable of recording, erasing, and reproducing data on the recording film by being illuminated, the second phase-change film maintains a crystalline state having a low reflectance when data is erased. When recording to form a recording mark, the recording mark Is maintained at a high reflectivity amorphous state, the recording film and heavy noble gas than the same atoms period a and Ar and Ar is used as sputtering gas when the film formation by the vacuum sputtering method, 5 × 10 The second phase change recording film is formed at a sputtering gas pressure of ^-2 torr or more, and a mixed gas of N2 gas and Ar gas and a Ge target are used to form the second phase change recording film. In the initial state in which the GeN film is provided adjacent to the optical disk and before the light beam is irradiated after the optical disk is manufactured, it is not necessary to perform the initial crystallization by irradiating the entire surface of the second phase change recording film with the light beam. The present invention provides a single-sided, two-layer phase change type optical disc characterized by a non-initialized phase change recording film.

(10) Further, according to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystalline by irradiation with a light beam, and becomes amorphous by irradiation with a light beam A second recording film of a phase change type that reversibly changes phase with the crystal, and the first recording film is disposed on the light beam incident side, and the light beam passing through the first recording film is And a bonding layer having a predetermined thickness for bonding the two so as to irradiate the second recording film, and the light beam is focused on one of the first and second phase change recording films from the incident side. In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing data on the recording film by being illuminated,
The second phase-change film is provided with a single-sided, two-layer phase-change type optical disk, wherein the lower one of the reflectivities of the crystalline region and the amorphous region is set to 25% or more. You.

(11) Further, according to the present invention,
A phase-change type first recording film that reversibly changes phase between amorphous and crystal by light beam irradiation, and a phase change type reversible phase change between amorphous and crystal by light beam irradiation And a second recording film, and the first recording film disposed on the light beam incident side. The two recording films are arranged such that the light beam passing through the first recording film is irradiated on the second recording film. And an adhesive layer having a predetermined thickness to be bonded, wherein the light beam is focused on one of the first and second phase change recording films from the incident side, and data is recorded, erased, and recorded on the recording film. In a single-sided, two-layer phase change optical disc capable of reproduction, the second phase change film has a low reflectance in a crystalline region corresponding to an erased portion, a high reflectance in an amorphous region corresponding to a recording mark portion, 25% reflectance of the crystal region
Thus, there is provided a single-sided, two-layer phase change optical disc.

(12) Further, according to the present invention,
A phase-change type first recording film that reversibly changes phase between amorphous and crystal by light beam irradiation, and a phase change type reversible phase change between amorphous and crystal by light beam irradiation And a second recording film, and the first recording film disposed on the light beam incident side. The two recording films are arranged such that the light beam passing through the first recording film is irradiated on the second recording film. And an adhesive layer having a predetermined thickness to be bonded, wherein the light beam is focused on one of the first and second phase change recording films from the incident side, and data is recorded, erased, and recorded on the recording film. In a reproducible single-sided, two-layer phase change optical disc, the entire surface of the second phase change film is subjected to initial crystallization before the first and second phase change films are bonded together via the adhesive layer. Also, predetermined data is recorded on the phase-change film that has been initially crystallized. Is, then, the first and the phase change type optical disk of a single-sided dual-layer where the second phase change layer, characterized in that bonded by an adhesive layer is provided.

(13) According to the invention, in the invention of (12), after the first and second phase change films are bonded to each other, the average of the second phase change film measured from the incident side is obtained. A phase change optical disc is provided, wherein the reflectivity is about 6% or more.

(14) According to the invention, in the invention of (12), the predetermined data recorded in the second phase change film after the entire surface of the second phase change film is initially crystallized is a predetermined data. A phase-change optical disk characterized in that a space corresponding to a random mark by a modulation method or a recording mark by a single frequency with a duty of 50% and a non-recording mark therebetween is half-half pattern data. Is done.

(15) According to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystal by irradiation of a light beam, and the amorphous and crystal are changed by irradiation of a light beam. A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing data on the recording film, the second phase-change film has a low reflectivity in a crystalline region corresponding to an erased state, and a recording mark The reflectance of the amorphous region corresponding to the portion is high, Before the first and second phase change films are bonded together via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and a predetermined surface is formed on the entire surface of the initially crystallized phase change film. Data is recorded, and thereafter, the first and second phase change films are bonded to provide a single-sided, two-layer phase change optical disc.

(16) According to the invention, in the invention of (15), after the first and second phase change films are bonded to each other, an average of the second phase change film measured from the incident side is obtained. A phase change optical disc is provided, wherein the reflectivity is about 6% or more.

(17) According to the invention, in the invention of (15), the predetermined data recorded in the second phase change film after the entire surface of the second phase change film is initially crystallized is a predetermined data. A phase-change optical disk characterized in that a space corresponding to a random mark by a modulation method or a recording mark by a single frequency with a duty of 50% and a non-recording mark therebetween is half-half pattern data. Is done.

(18) Further, according to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystalline by irradiation with a light beam, and becomes amorphous by irradiation with a light beam. A second recording film of a phase change type that reversibly changes phase with the crystal, and the first recording film is disposed on the light beam incident side, and the light beam passing through the first recording film is And a bonding layer having a predetermined thickness for bonding the two so as to irradiate the second recording film, and the light beam is focused on one of the first and second phase change recording films from the incident side. In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing data on the recording film by being illuminated,
The second phase change film is provided with a single-sided, two-layer phase change optical disk, wherein predetermined data is recorded on the entire surface of the second phase change film when the user purchases the phase change optical disk.

(19) According to the invention, in the invention according to (18), the second phase change film has a low reflectance in a crystal region corresponding to an erased portion and a low reflectance in an amorphous region corresponding to a recording mark portion. A phase change optical disk characterized by a high rate is provided.

(20) According to the present invention, in the invention according to (18), the average reflectance of the second phase change film measured from the incident side is approximately 6% or more. An optical disk is provided.

(21) According to this invention, in the invention of (18), the predetermined data recorded on the second phase change film at the time of purchase by the user is random data according to a predetermined modulation method or duty data. A phase change type optical disc is provided, wherein a space corresponding to a recorded mark and a non-recorded mark at 50% of a single frequency is one of data of a half pattern.

(22) According to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystal by irradiation of a light beam, and the amorphous and crystal are changed by irradiation of a light beam. A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing data on the recording film, the second phase-change film has a low reflectivity in a crystal region corresponding to an erased portion, The reflectance of the amorphous region corresponding to Before the second phase change film and the second phase change film are bonded via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and A single-sided, two-layer phase-change optical disc characterized by recording data so that the entire surface becomes an amorphous region, and thereafter bonding the first and second phase-change films via the adhesive layer. Is done.

(23) According to the invention, in the invention according to (22), after the first and second phase change films are bonded to each other, the second phase change film measured from the incident surface side can be used. A phase change optical disk is provided, wherein the reflectance from the entire amorphous portion is about 8% or more.

(24) According to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystal by irradiation with a light beam, and the amorphous and crystal are changed by irradiation with a light beam A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. A single-sided, two-layer phase-change optical disc capable of recording, erasing and reproducing data on the recording film, wherein the second phase-change film is maintained in a crystalline state having a low reflectance when data is erased. When recording to form a recording mark, the recording mark In a disk maintained in an amorphous state having a high rate, it is not necessary to irradiate the entire surface of the second phase-change recording film with a light beam after the manufacturing to perform initial crystallization in the optical disk manufacturing process. A method for manufacturing a single-sided, two-layer phase-change optical disk characterized by being formed on an uninitialized phase-change recording film is provided.

(25) According to this invention, in the invention of (24), when the second recording film is formed by a vacuum sputtering method, the sputtering gas has the same atomic period as Ar and has the same atomic period.
The second phase-change recording film is formed by using a rare gas heavier than Ar at a sputtering gas pressure of 5 × 10 ^-2 torr or more, and the second phase-change recording film is uninitialized. The present invention provides a method for manufacturing a phase-change optical disk, characterized in that the optical disk is formed on a substrate.

(26) According to the invention, in the invention of (23) or (24), the rare gas as a sputtering gas for forming the second recording film by vacuum sputtering is Kr.
A method for producing a phase-change optical disk, wherein the method is gas or Xe gas.

(27) According to the invention, in the invention of (23), the sputtering gas for forming the second recording film by the vacuum sputtering method has the same atomic period and Ar as the sputtering gas.
The second phase change recording film is formed using a heavier rare gas at a sputtering gas pressure of 5 × 10 ⁻² torr or more, and using a mixed gas of N 2 gas and Ar gas and a Ge target. Wherein a GeN film is provided adjacent to the second phase change recording film, and the second phase change recording film is formed as a non-initialized phase change recording film. Provided.

(28) According to the invention, in the invention of (24) or (26), the rare gas as a sputtering gas for forming the second recording film by vacuum sputtering is Kr.
A method for manufacturing a phase-change optical disk, wherein the method is gas or Xe gas.

(29) According to the invention, in the invention of (24) or (26), the GeN film is provided adjacent to one side of the second phase change recording film. A method for manufacturing a type optical disk is provided.

(30) According to the invention, in the invention of (24) or (26), the GeN film is provided adjacent to both sides of the second phase change recording film. A method for manufacturing a phase change optical disk is provided.

[0064] (31) According to the present invention, in the invention of (24) or (26), the flow rate ratio of N ₂ and N ₂ gas and Ar gas
Manufacturing a phase-change optical disc, wherein a GeN film is provided adjacent to the second phase-change recording film using a mixed gas of Ar and N ₂ having a ratio of / Ar of 0.3 or more and a Ge target. A method is provided.

(32) According to the present invention, the first recording film of the phase change type, which reversibly changes phase between amorphous and crystalline by irradiation of the light beam, and the amorphous and crystalline layers are changed by the irradiation of the light beam. A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. A single-sided, two-layer phase-change type optical disc capable of recording, erasing, and reproducing data on the recording film, wherein the second phase-change film maintains a crystal state having a low reflectance when data is erased. At the time of recording to form a recording mark,
In the method of manufacturing a phase-change optical disk in which the reflectance is maintained in an amorphous state having a high reflectance, the recording mark has the same atomic period and Ar as a sputtering gas when a recording film is formed by a vacuum sputtering method. Heavier noble gases are used and 5
The second phase change recording film is formed at a sputtering gas pressure of × 10 ^-2 torr or more, and the second phase change recording film is formed by using a mixed gas of N2 gas and Ar gas and a Ge target. In the initial state in which a GeN film is provided adjacent to the film and before the optical beam is irradiated after manufacturing the optical disk, the second phase change recording film may be initially crystallized by irradiating the entire surface with the light beam. And a method for manufacturing a single-sided, two-layer phase-change optical disc characterized by being a non-initialized phase-change recording film that does not require any.

(33) According to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and the amorphous and crystalline layers are changed by irradiation of a light beam. A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing data on the recording film, the first and second phase-change films are bonded together via the adhesive layer. The entire surface of the second phase change film is initially crystallized, and Predetermined data is recorded in the crystallization has been phase-change film, then, the first and second phase change film is characterized in that bonded by an adhesive layer one surface 2
Method for manufacturing phase-change optical disk having layers.

(34) According to the present invention, in the invention according to (33), the predetermined data recorded on the second phase change film after the initial crystallization of the entire surface of the second phase change film is a predetermined data. Manufacturing of a phase change optical disk characterized in that a space corresponding to a random data by a modulation method or a recording mark by a single frequency with a duty of 50% and a non-recording mark therebetween is half-half pattern data. A method is provided.

(35) According to the present invention, the first recording film of a phase change type, which reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and the amorphous and crystalline layers are changed by irradiation of a light beam. A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. A single-sided, two-layer phase change optical disc capable of recording, erasing, and reproducing data on the recording film, wherein the second phase change film has a low reflectance of a crystal region corresponding to an erased state, Phase change with high reflectivity in the amorphous area corresponding to the recording mark In the manufacturing method of the optical disk,
Before the first and second phase change films are bonded together via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and the entire surface of the initially crystallized phase change film is formed. A method for manufacturing a single-sided, two-layer phase-change optical disc, characterized in that predetermined data is recorded and thereafter the first and second phase-change films are bonded together.

(36) According to the present invention, in the invention according to (34), the predetermined data recorded on the second phase change film after the initial crystallization of the entire surface of the second phase change film is the predetermined data. A phase change type optical disk characterized in that a space corresponding to a random mark by a modulation method or a recording mark by a single frequency with a duty of 50% and a non-recording mark therebetween is half-half pattern data. A manufacturing method is provided.

(37) According to the present invention, the first recording film of the phase change type, which reversibly changes phase between amorphous and crystalline by irradiation of the light beam, and the amorphous and crystal are changed by the irradiation of the light beam. A second recording film of a phase change type that reversibly changes between the first recording film and the first recording film on the light beam incident side, and the light beam passing through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness that joins the two recording films so as to irradiate the two recording films. The light beam is focused on one of the first and second phase change recording films from the incident side. A single-sided, two-layer phase-change type optical disc capable of recording, erasing and reproducing data on the recording film, wherein the second phase-change film has a low reflectivity in a crystal area corresponding to an erased portion, Phase change type with high reflectance in the amorphous region corresponding to the mark In the method of manufacturing a disc, before the first and second phase change films are bonded together via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and the initial crystallization is performed. Characterized in that data is recorded such that the entire surface of the second phase change film thus formed becomes an amorphous region, and then the first and second phase change films are bonded together via the adhesive layer. A method for manufacturing a two-layer phase change optical disc is provided.

[0071]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a single-sided, dual-layer phase-change optical disc according to the present invention will be described below with reference to the drawings. FIG.
FIG. 1 is a perspective view showing an optical disk according to an embodiment of the present invention, and FIG. 3 is a sectional view schematically showing the structure of the optical disk.

As shown in FIG. 2, the single-sided, two-layer optical disk includes a disk 27 having a first RAM layer (hereinafter, simply referred to as a disk 27 of a first RAM layer) and a disk 28 having a second RAM layer (hereinafter, simply referred to as a disk 27). Disk 2 of the second RAM layer
No. 7. ) Has a structure joined by a UV curable resin film 29 as a joining layer. At the center of the disk, there is a hole through which a spindle connected to a rotation motor of the disk drive is inserted. Around this hole, a clamping area 21 for rotatably clamping the optical disk is provided. . A lead-in area 22 is provided in an inner peripheral area around the clamping area 21 where a data retrieval by a pickup head (not shown) is started, and a lead-out area 23 is provided on the outer periphery. Is provided. This lead-in area 2
The area from 1 to the lead-out area 23 is defined as an information recording area 24 in which information is recorded, and the area between the lead-in area 22 and the lead-out area 23 is defined as a data writing area 25 in which data is written. ing.

Next, the disk 2 of the first and second RAM layers
The structure of 7, 28 will be described in detail with reference to FIGS.

As shown in FIG. 3, the disk 2 of the first RAM layer
7 has a structure obtained by stacking ZnS-SiO ₂ protective film 102, GeSbTe phase change recording film 103 and the ZnS-SiO ₂ protective film 104 in this order on 0.6mm disk-like polycarbonate substrate 101 having a thickness . Here, the ZnS—SiO ₂ protective films 102 and 1
Reference numeral 04 denotes a mixed film made of a mixed material of ZnS and SiO ₂ (hereinafter, simply referred to as a ZnS-SiO ₂ protective film), and a first RAM including a protective film 102, a phase change recording film 103, and a protective film 104. Since the transmittance of the layer 105 is set to 50%, the first RAM layer 105 does not include a metal reflection film to be provided in a normal one-layer phase-change optical disc.

As shown in FIG. 4, the disk 28 of the second RAM layer is composed of a reflective film 112 made of Al-Cr, a ZnS-SiO
_A dielectric protective film 113 made of a _two- layered film is formed, and a laser beam or the like reversibly changes the phase between amorphous and crystalline, for example, from a ternary alloy of GeSbTe. The phase change recording film 114 is laminated, and ZnS-SiO ₂
The dielectric protection film 115 made of a mixed film further has L to H
As a translucent interference film for use as a medium, it has a structure in which a translucent film 116 made of Au is laminated. Here, similarly, the ZnS-SiO ₂ protective films 113 and 115 are similarly a mixed film made of a mixed material of ZnS and SiO ₂ (hereinafter simply referred to as ZnS-SiO _2).
It is called a protective film. ).

The phase-change recording film 114 is melted by laser beam irradiation and rapidly cooled to become amorphous. At this time, the dielectric protection films 113 and 115 have holes formed by evaporation of the recording film 114. It has a function of preventing opening, that is, a function of protecting the recording film from heat. The upper dielectric layer 115 is designed so as to be optically enhanced at the time of signal reproduction by a synergistic effect of the Au translucent layer 116 and the metal reflective layer 112, and the thickness thereof is usually set to 500 to 3000 degrees. ing. The phase change recording film 114 is usually designed to be quite thin because it needs to be melted by laser beam irradiation,
It is set at 50-300 °. Phase change recording film 114
The lower dielectric protection film 113 needs to have a structure in which the heat of the recording layer melted at the time of laser beam irradiation is rapidly cooled as much as possible and becomes amorphous, so that the heat is released to the metal reflection film 112. It is thin and typically has a thickness of about 50-300 °.

In recent years, with the need for high-speed recording with the increase in the data transfer speed, a type of cooling (retaining heat) rather than rapid cooling (releasing heat) has been used for the purpose of improving the sensitivity of a disk. Phase change optical disks are also being studied.
In this case, the lower dielectric layer 113 has a thickness of 300 ° -30
Set to 00 °. The thickness of the metal reflection film 112 is usually set to about 500 ° to 3000 ° for the purpose of enhancing the reproduction signal and escaping heat.

However, in this embodiment, in order to set the recording sensitivity to be considerably higher than usual, there is a case where it is necessary to make the heat escape worse. In this case, the temperature is set from 100 ° to 500 °. May be. The Au translucent film 116 is formed by the laser beam transmitted through the Au film and the recording film 11.
In order to enhance the interference with the reflected light beam from No. 4, appropriate transmission and reflection were required, and the film thickness was usually set to 20 ° to 200 °.

Hereinafter, a method for manufacturing a single-sided double-layer RAM disk as a comparative example and a single-sided double-layer RAM disk according to one embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 6 shows a single-sided, two-layer optical disk as a comparative example, and FIG. 6 schematically shows a sputtering apparatus for manufacturing a non-initialized (initialization unnecessary) phase change optical disk according to an embodiment of the present invention. It is a block diagram shown typically.

(Comparative Example 1) A method of manufacturing a single-sided dual-layer RAM disk as Comparative Example 1 will be described as an experimental example with reference to FIG.

In manufacturing a single-sided dual-layer RAM disk as Comparative Example 1, as shown in FIG.
A rotatable disk-shaped base 8 is provided in the base 0, and a continuous groove having a diameter of 120 mm, a thickness of 0.6 mm, and a width of 0.6 μm is formed on the surface of the base 8 which faces the inside of the apparatus. The polycarbonate disc substrate 9 is set.
The vacuum sputtering apparatus 30 is connected to the vacuum turbo pump 12, and the inside of the vacuum sputter apparatus 30 is 10 ^-6 torr.
Is evacuated to a vacuum.

In the drawing, reference numeral 11 denotes an exhaust system valve.

First, a method of manufacturing the disk 27 of the first RAM layer 27 shown in FIG. 3 using this sputtering apparatus will be described.

The rotation base 8 was rotated at 60 rpm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. Exhaust system capacity is maintained as it is
The gas flow rate is adjusted by a mass flow controller (not shown) and the degree of vacuum in the apparatus is 5 × 10 ^-3 tor.
Set to be r. In this state, the changeover switch 17 is switched to the electrode 13a side of the ZnS-SiO ₂ target 13b, and the RF power supply 16 is connected to the electrode 13a.
RF power of 600 W was provided to the ZnS—SiO ₂ target.
This power supply starts pre-sputtering, and after about 1 minute of pre-sputtering, a shutter
13c is opened, and the formation of the ZnS—SiO ₂ dielectric film on the substrate 9 is started. Five minutes after the start of film formation, the RF power supply 16 is turned off, the shutter 13c is closed, and the substrate 9
A ZnS-SiO ₂ film 101 was formed thereon at a thickness of 510 °.

After the valve 10 is closed and the residual Ar gas and ZnS-SiO ₂ molecules in the apparatus are once exhausted through the exhaust system 12, the valve 10 is opened again to introduce Ar gas. The Ar gas pressure in the sputtering device was set to 5 × 10 ⁻³ torr. In this state, the changeover switch 17 is set to GeSbTe
Was switched to the electrode 14a side of the compound composition target 14b, and 200 W of power was supplied from the power supply 16 to the GeSbTe target. After about one minute of pre-sputtering, the shutter 14c immediately above the target is opened, and the ZnS-Si
The formation of the GeSbTe phase change recording film on the O ₂ protective film was started.
After a lapse of 15 seconds from the start of film formation, the RF power supply 16 is turned off, and the GeSbTe recording film 103 having a thickness of 70 A is replaced with the ZnS-SiO2 film 1.
02 was formed.

After the valve 10 was closed again and the residual Ar gas and GeSbTe molecules in the sputtering device were evacuated, the bubble 10 was opened again and the Ar gas was introduced into the sputtering device 30. After the gas flow rate was adjusted so that the Ar gas pressure became 5 × 10 ⁻³ torr, the changeover switch 17 was again turned on.
The power is switched to the electrode 13a side of the S-SiO ₂ target 13b, and a power of 600 W is supplied from the RF power supply 16 to the ZnS-SiO ₂ target 13b. After about one minute of pre-sputtering, the shutter 13c was opened again, and the formation of ZnS-SiO ₂ was started. 8 minutes after the start of film formation, RF
The power supply 16 is turned off, the shutter 13c is closed,
On the Ge ₂ Sb ₂ Te ₅ recording film 103, an 800A ZnS-SiO ₂ dielectric film 104 was laminated. The sample disk 9 was taken out of the sputtering apparatus 30, and the disk structure 27 of the first RAM layer shown in FIG. 3 was obtained. Since the disk structure 27 of the first RAM layer is common to all experimental examples described below, a plurality of identical disk structures are manufactured in the same process. next,
A second RAM layer disk 28 as Comparative Example 1 shown in FIG. 4 was manufactured.

The inside of the vacuum sputtering apparatus 30 was evacuated to 10 ^-6 torr by the vacuum turbo pump 12. The rotation base 8 was rotated at 60 rpm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. The capacity of the exhaust system was maintained as it was, the flow rate of Ar gas was adjusted by a mass flow controller (not shown), and the vacuum in the apparatus was maintained so that the degree of vacuum in the apparatus was 5 × 10 ⁻³ torr. Changeover switch 17 is Al-C
r is switched to the electrode 15a side of the target 15b, and RF
The power of 200 W from the power supply 16 is the Al-Cr target 15
b. After pre-sputtering was performed for about 1 minute in this state, the shutter 15c was opened, and the formation of the Al-Cr reflective film was started. After 50 seconds had elapsed from the start of the film formation, the RF power was turned off, the shutter 15c was closed, and the Al-Cr reflection film 300A was formed on the substrate. Once the Ar residual gas and the Al-Cr alloy atoms in the sputtering device 30 are exhausted by the exhaust system 12, the valve 10 is opened again, Ar gas is introduced into the sputtering device, and by adjusting a mass flow controller (not shown), The degree of vacuum in the sputtering apparatus was maintained at 5 × 10 ⁻³ torr. Then, the changeover switch 17 was switched to the electrode 13a side of the ZnS-SiO ₂ target 13b, and 600 W of RF power was supplied to the ZnS-SiO ₂ target. After about 1 minute of pre-sputtering in this state, the shutter 13c immediately above the target was opened, and the formation of the ZnS-SiO ₂ dielectric film on the substrate 9 was started. After a lapse of 5 minutes and 30 seconds from the start of film formation, the RF power supply 16 was turned off, and the shutter 13c was opened. In this film forming step, a ZnS-SiO ₂ film having a thickness of 5 was formed on the Al-Cr film.
Film was formed at 50A.

Next, the valve 10 is closed and the exhaust system 12 is closed.
After the residual Ar gas and ZnS-SiO2 molecules in the apparatus are once evacuated, the valve 10 is opened again to introduce Ar gas into the apparatus, and the Ar gas pressure in the sputtering apparatus is reduced to 5 × 10
Set to ^-3 torr. The changeover switch 17 is GeSbTe
Is switched to the side of the electrode 14a of the compound composition target 14b, the power supply 16 is turned on, and the power of 200 W is changed to Ge.
SbTe was supplied to the target. After about one minute of pre-sputtering, the shutter 14c immediately above the target was opened, and the formation of the GeSbTe phase change recording film on the disk substrate 9 was started. After a lapse of 20 seconds from the start of the film formation, the RF power supply 16 is turned off, and the GeSbTe recording film having a thickness of 100 A is formed of ZnS-SiO ₂
A film was formed on the film.

The valve 10 was closed again, and the residual Ar gas and GeSbTe molecules in the sputtering apparatus were exhausted. Thereafter, the bubble 10 is opened, and the Ar gas is
Was introduced within. After the gas flow rate is adjusted so that the Ar gas pressure becomes 5 × 10 ⁻³ torr, the changeover switch 17 is again switched to the electrode 13a side of the ZnS—SiO ₂ target 13b, and the power of 600 W is supplied from the RF power supply 16 to the ZnS—SiO ₂ target. It was supplied to the SiO ₂ target 13b. After about one minute of pre-sputtering, the shutter 13c is opened again, and ZnS-SiO ₂
Was started. After a lapse of 10 minutes and 20 seconds from the start of the film formation, the RF power supply 16 was turned off, the shutter 13c was closed, and a ZnS-SiO ₂ dielectric film having a thickness of 1040 ° was laminated on the GeSbTe recording film.

Finally, the valve 10 was closed again, and Ar residual gas and ZnS—SiO ₂ molecules in the apparatus were exhausted from the sputtering apparatus. Thereafter, the valve 10 was opened again, and Ar gas was introduced. . After the Ar gas pressure is set to 5 × 10 ⁻³ torr, the RF power supply 16 is switched by the changeover switch 17
Connected to the electrode 12a provided under the Au target 12b, RF power of 13.56 MHz was supplied from the RF power supply 16 at 150 W, and sputtering of the Au target with Ar gas was started. After about 1 minute of pre-sputtering, the shutter 12c immediately above the target is opened, and the ZnS-Si
An Au optical interference film was formed on O ₂ to a thickness of 100 °, the RF power supply 16 was turned off, and the shutter 12c was closed.

The sample disk of the second RAM layer 28 for the comparative example 1 manufactured by this normal process was used for the sputtering apparatus 3
Removed from zero.

As is clear from the above description, the film configuration of this disk is composed of a substrate, Al-Cr (300 °), ZnS-SiO
₂ (550 °), GeSbTe (100 °), ZnS-SiO ₂ (10
40 °) and Au (100 °). This disk is named a second RAM layer disk (sample A).

Hereinafter, a method of manufacturing the second RAM layer disk according to the present invention as an uninitialized phase change type optical disk will be described.

According to the study of the present inventor, according to
It is presumed that the reason why the amorphous state of the GeSbTe recording film is very stable is that the collision speed of GeSbTe molecules at the time of adhering to the polycarbonate substrate is so fast that the quenching degree becomes very large. The speed of the source molecules during sputtering appears to depend on the mean free path of the source molecules (the average distance over which the molecules can move freely without colliding with other molecules).

The mean free path of the raw material molecule is, for example,
By increasing the gas pressure of Ar, the number of collisions with Ar atoms increases, and the energy is shortened due to attenuation. Therefore,
A non-initialized disk can be manufactured by increasing the Ar gas pressure to form a GeSbTe recording film.

[0096] In the normal sputtering, a raw material target is hit with an Ar gas to attach a raw material to a substrate. If a GeSbTe recording film is formed with the gas pressure further increased using gaseous Xe, GeSbTe molecules will lose more kinetic energy by colliding with the heavier inert gas, The kinetic energy when reaching the substrate is accordingly reduced. Therefore, an uninitialized phase change disk can be manufactured by sputtering with an inert gas heavier than Ar.

On the other hand, as another method for promoting crystallization from the amorphous state, generally, when a film for generating crystallization nuclei is provided adjacent to an amorphous film, the crystallization nuclei are changed to the crystal of the amorphous film. It is known that it becomes a source of crystal nuclei during crystallization and promotes crystallization.

According to the present inventors, it has been found that a GeN film is suitable as a nucleation film for this crystallization.
It has been found that the synergistic effect between the effect of forming the recording film under the high pressure of the inert gas and the effect of the nucleation film of this crystallization is larger than expected. The reason that the GeN film becomes the source of crystallization nuclei in the phase change recording film is that inactive N atoms are incorporated into the Ge film, so that stress remains in the film after the GeN film is formed. Was speculated.

(Embodiment 1) FIG. 6 shows a sputtering apparatus for manufacturing a second RAM layer disk according to an embodiment of the present invention. This sputtering apparatus employs the same method as the method of manufacturing the second RAM layer disk (sample A) described above, except for the method of forming the GeSbTe phase change recording film. In this sputtering apparatus, a GeN film is formed on a GeSbTe recording film by sputtering a mixed gas of Ar gas and N ₂ gas onto a Ge target.

In the sputtering apparatus shown in FIGS. 5 and 6, the Al-Cr target 15b shown in FIG.
The target 18 has been replaced.

Hereinafter, a film forming method according to the first embodiment will be described with reference to FIG.

First, the inside of the vacuum sputtering apparatus 30 was evacuated to 10 ^-6 torr by the vacuum turbo pump 12. The rotation base 8 was rotated at 60 rpm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. While maintaining the capacity of the exhaust system, the flow rate of Ar gas was adjusted by a mass flow controller (not shown), and the degree of vacuum in the apparatus was controlled to 5 × 10 ⁻³ torr. RF power supply 16 is switch 17
Is connected to the electrode 12a provided below the Au target 12b, and 13.56 MHz from the RF power supply 16
RF power of 150 W was supplied, and sputtering of the Au target with Ar gas was started. After about 3 minutes of pre-sputtering, the shutter 12c immediately above the target is opened, and the Au reflection film is formed on the polycarbonate substrate to a thickness of 300 Å.
The RF power supply 16 is turned off, and the shutter 1
2c was closed.

Incidentally, due to the limitation of the number of targets in the sputtering apparatus, the reflection film is shared with the Au film without using AlMo.

After the gas introduction valve 10 is closed and the Ar residual gas and the Au atoms in the sputtering device 30 are once exhausted by the exhaust system 12, the valve 10 is opened again and the Ar gas is opened.
The gas was introduced into the sputtering apparatus, and the Ar gas pressure in the sputtering apparatus was maintained at 5 × 10 ⁻³ by adjusting a mass flow controller (not shown). Thereafter, the changeover switch 17 was connected to the electrode 13a side of the ZnS-SiO ₂ target 13b, and RF power of 600 W was supplied to the ZnS-SiO ₂ target. After about 1 minute of pre-sputtering, the shutter 13c immediately above the target is opened, and the ZnS-SiO2
The formation of the dielectric film was started. After a lapse of 5 minutes and 30 seconds from the start of film formation, the RF power supply 16 is turned off, and the shutter 13 c
Was also closed. Therefore, on the Au film, the ZnS-SiO2 film is 55% thick.
The film was formed at 0 °.

After the valve 10 is closed and the residual Ar gas and ZnS—SiO 2 molecules in the apparatus are once evacuated by the exhaust system 12, a mixed gas having a ratio of Ar gas to N 2 gas of 1: 1 flows into the chamber 30. And the gas pressure of the mixed gas is 5 × 10 ^-3
Set to be torr. Thereafter, the changeover switch 17 is connected to the electrode 18a side of the Ge target, and R
RF power from F power supply 16 to 250 W is Ge target 1
8b. After the pre-sputtering for about one minute, the shutter 18c was opened, and the formation of the GeN film on the ZnS-SiO ₂ film was started. About 20 seconds after the start of film formation, the RF power 16 was turned off, the shutter 18c was closed, and a GeN film having a thickness of 50 ° was formed.

After the valve 10 is closed and the residual atoms of Ar gas, N 2 gas and Ge are exhausted, the valve 10 is opened again to introduce Kr gas, and the Kr gas pressure in the sputtering device is reduced to 5 × 10 ^-2 torr (usually 5 × 10 ^-3 ).
The changeover switch 17 is switched to the electrode 14a side of the GeSbTe compound composition target 14b, and the power supply 16 is turned on.
Then, 200 W of power was supplied to the GeSbTe target. After about 1 minute of pre-sputtering, the shutter 14c immediately above the target is opened, and the GeSb
The formation of the Te phase change recording film was started. 40 from the start of film formation
After a lapse of seconds, the RF power supply 16 was turned off, and the quenching degree during the film formation was reduced to form the GeSbTe recording film 100 # on the GeN film.

After the valve 10 was closed again and the residual Kr gas and GeSbTe molecules in the sputtering device were exhausted, the bubble 10 was opened and the Ar gas was introduced into the sputtering device 30. After the gas flow rate was adjusted so that the Ar gas pressure became 5 × 10 ⁻³ torr, the changeover switch 17 was again switched to ZnS-
Switching to the electrode 13a side of the SiO ₂ target 13b,
600 W of power was supplied from the RF power supply 16 to the ZnS-SiO ₂ target 13b. After about one minute of pre-sputtering, the shutter 13c was opened again, and ZnS-SiO ₂ film formation was started. 10 minutes and 20 seconds after the start of film formation, the RF power supply 16 is turned off, the shutter 13c is closed, and Ge
A 1040 A ZnS-SiO2 dielectric film was laminated on the SbTe recording film.

Finally, the valve 10 is closed again, and after the Ar residual gas and ZnS-SiO ₂ molecules in the apparatus are exhausted from the sputtering apparatus, the valve 10 is opened again to introduce Ar gas. Was. After the Ar gas pressure was set to 5 × 10 ⁻³ torr, the changeover switch 17 was connected to the electrode 12a side of the Au target 12b, and 150 W of power was supplied from the RF power supply 16 to the Au target 12b. After about one minute of pre-sputtering, the shutter 12c was opened, and the formation of the Au reflection film was started. 1 minute after the start of film formation, RF
The power is turned off, the shutter 12c is closed, and Zn
An Au optical interference film having a thickness of 100 ° was formed on the S-SiO ₂ dielectric. Then, the sample disk is placed in the sputtering device 3
Removed from zero.

Finally, the L to H type second RAM layer disk has the structure shown in FIG. That is,
This disk has a polycarbonate substrate 51, an Au reflection film 52 (300 °), and a ZnS-SiO ₂ dielectric film 53 (550).
Å), a GeN crystallization nucleation film 60 (50 °), a GeSbTe phase change recording film 54 (100 °) having a reduced quenching degree during film formation,
ZnS-SiO ₂ dielectric film 55 (1040 °), Au optical interference film 5
6 (100 °). The sample of the second RAM layer disk 28 is named (Sample B).

[0110] Similarly, when the GeSbTe phase change recording film is formed,
Kr gas pressure is 5 × 10^-1 No. made with torr maintained
The sample of the 2RAM layer disk 28 is named (Sample C)
wear. Here, the formation of the GeSbTe phase change recording film of Sample B was performed.
The Kr gas pressure during film formation is 5 × 10 ^-2 It was torr. This service
The film structure of the sample C is the same as that of the polycarbonate substrate 51 and the Au substrate.
Sputtered film 52 (300 °), ZnS-SiO_TwoThe dielectric film 53 (550
Å), GeN crystallization nucleation film 60 (50 °),
GeSbTe phase change recording film with lower cooling than sample B
54 (100 °), ZnS-SiO_TwoThe dielectric film 55 (1040
A), composed of Au optical interference 56 (100 °).

(Embodiment 2) The Ge target is again sputtered with a mixed gas of Ar gas and N ₂ gas using the sputtering apparatus shown in FIG.
A GeN film is formed on the SbTe recording film.

Hereinafter, the film forming method in Example 2 will be described.

The vacuum sputter device 30 is evacuated to a vacuum of 10 ^-6 torr by the vacuum turbo pump 12, the rotating base 8 is rotated at 60 rpm, the Ar gas introduction valve 10 is opened, and the Ar gas is sputtered. Was introduced within. The flow rate of Ar gas was adjusted by a mass flow controller (not shown) while keeping the capacity of the exhaust system as it was, and the degree of vacuum in the apparatus was set to 5 × 10 ⁻³ torr. RF
The power supply 16 is connected to the electrode 12a provided below the Au target 12b by the changeover switch 17,
RF power of 13.56 MHz from F power supply 16 is 150 W
The Au target was sputtered by the supplied Ar gas. After about 3 minutes of pre-sputtering, the shutter 12c immediately above the target is opened, and the Au reflection film 300 # is formed on the polycarbonate base 9 plate.
Is turned off, and the shutter 12c is closed. still,
Due to the limitation of the number of targets in the sputtering device, the reflective film
It is shared with Au film without using AlMo.

After the gas introduction valve 10 is closed and the Ar residual gas and Au atoms in the sputtering device 30 are once exhausted by the exhaust system 12, the valve 10 is opened again, and the Ar gas is introduced into the sputtering device. The Ar gas pressure in the sputtering apparatus was adjusted to 5 by adjusting the mass flow controller (not shown).
× 10 ^-3 was set. Then, the changeover switch 17
Was switched to the electrode 13a side of the ZnS-SiO ₂ target 13b, and RF power of 600 W was supplied to the ZnS-SiO ₂ target. After the pre-sputtering for about one minute, the shutter 13c immediately above the target was opened, and the formation of the ZnS-SiO ₂ dielectric film on the substrate 9 was started. After 5 minutes and 30 seconds have elapsed from the start of film formation, the RF power supply 16 is turned off and the shutter 13
c was also closed. A 550 A ZnS-SiO ₂ film was formed on the Au film.

After the valve 10 is closed and the residual Ar gas and ZnS—SiO ₂ molecules in the apparatus are once exhausted by using the exhaust system 12, the valve 10 is opened again to introduce the Kr gas.
The Kr gas pressure in the sputtering device is 5 × 10 ^-2 torr (normally 5
× 10 ^-3 ). Then, changeover switch 1
7 is an electrode 14a of a GeSbTe compound composition target 14b
Side, the power supply 16 was turned on, and 200 W of power was supplied to the GeSbTe target. After about one minute of pre-sputtering, the shutter 14c immediately above the target was opened, and the formation of the GeSbTe phase change recording film on the disk substrate 9 was started. Forty seconds after the start of film formation, the RF power supply 16
Was turned off, and the quenching degree at the time of film formation was lowered to form a GeSbTe recording film having a thickness of 100 A on the ZnS-SiO ₂ film.

After the valve 10 is closed again and the residual Kr gas and GeSbTe molecules in the sputtering apparatus are exhausted, the bubble 10 is opened and the mixed gas in which the ratio of Ar gas to N 2 gas is 1: 1. Was introduced into the chamber 30, and the gas pressure of the mixed gas was set to 5 × 10 ⁻³ torr. Thereafter, the changeover switch 17 is switched to the Ge target electrode 18a.
Side, and RF power of 250 W was supplied from the RF power supply 16 to the Ge target 18b. After about one minute of pre-sputtering, the shutter 18c is opened and Ge ₂ Sb ₂ T
deposition of GeN film was started e ₅ recording film. About 20 seconds after the start of the film formation, the RF power 16 was turned off, the shutter 18c was closed, and a 50 ° GeN film was formed.

When the valve 10 is closed, the chamber 30 is closed.
After the mixed gas of Ar and N ₂ and Ge atoms remaining in the chamber are exhausted, the valve 10 is opened again, and the Ar gas is removed from the chamber 3.
0, and the Ar gas pressure was adjusted to 5 × 10 ⁻³ torr. Then, the changeover switch 16 is connected again to the electrode 13a side of the ZnS-SiO2 target 13b, and the RF power supply 1
A power of 6 to 600 W was supplied to the ZnS-SiO ₂ target 13b. After about 1 minute of pre-sputtering, the shutter 13c was opened again, and ZnS-SiO ₂ film formation was started. 10 minutes and 20 seconds after the start of the film formation, the RF power supply 16 was turned off, the shutter 13c was closed, and a ZnS-SiO ₂ dielectric film of 1040 ° was laminated on the GeN ₂ film.

Finally, the valve 10 was closed again, and after the Ar residual gas and ZnS—SiO ₂ molecules in the apparatus were exhausted from the sputtering apparatus, the valve 10 was opened again and Ar gas was introduced. After the Ar gas pressure is set to 5 × 10 ⁻³ torr, the changeover switch 17 is turned on by the electrode 12a of the Au target 12b.
Side, and 150 W of power was supplied from the RF power supply 16 to the Au target 12b. After the pre-sputtering for about 1 minute, the shutter 12c was opened, and the formation of the Au reflection film was started. One minute after the start of film formation, the RF power supply is turned off, the shutter 12c is closed, and the ZnS-SiO ₂
An Au reflection film 100 # was formed on the dielectric.

This sample disk 9 is used for the sputtering device 3
Removed from zero. Finally, as shown in FIG. 7B, the structure of the L-to-H type second RAM layer disk is such that a polycarbonate substrate 51, an Au reflection film 52 (300 °), a ZnS-SiO ₂ dielectric film 53 (550A), and a film are formed. GeSbTe with reduced quenching
Phase change recording film 54 (100 °), GeN crystallization nucleation film 6
1 (50 °), ZnS-SiO ₂ dielectric film 55 (1040 °),
It becomes the Au optical interference film 56 (100 °). This disc sample is named (Sample D).

In the same manner, a sample of the second RAM layer disk 28 produced at a Kr gas pressure of 5 × 10 ^-1 torr at the time of forming the GeSbTe phase change recording film is named (Sample E).
Here, Kr at the time of forming the GeSbTe phase change recording film of Sample D
The gas pressure was 5 × 10 ^-2 torr. This sample E
Is composed of a polycarbonate substrate 51, an Au reflection film 52
(300 °), ZnS-SiO ₂ dielectric film 53 (550 °), GeSbTe whose quenching degree at the time of film formation was further lowered than that of (Sample D)
Phase change recording film 54 (100 °), GeN crystallization nucleation film 6
1 (50 °), ZnS-SiO2 dielectric film 55 (1040 °),
It becomes the Au optical interference film 56 (100 °).

(Embodiment 3) The sputtering apparatus shown in FIG. 6 is used again to perform sputtering on a Ge target using a mixed gas of Ar gas and N ₂ gas.
A GeN film was formed adjacent to the GeSbTe recording film. Hereinafter, the film forming method of the third embodiment will be described.

First, the vacuum sputtering apparatus 30 was evacuated to 10 ^-6 torr using the vacuum turbo pump 12. The rotating base 8 is rotated at 60 rpm, and in this state, Ar
The gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. While maintaining the exhaust system capacity, Ar
The gas flow rate was adjusted by a mass flow controller (not shown), and the degree of vacuum in the apparatus was set to 5 × 10 ⁻³ torr. RF power supply 16 is switch 1
7, is connected to the electrode 12a provided below the Au target 12b, and is supplied from the RF power supply 16 to 13.56 MH.
RF power of z was supplied at 150 W, and sputtering of the Au target with Ar gas was started. After about 3 minutes of pre-sputtering, the shutter 12c immediately above the target is opened, the Au reflection film 300A is formed on the polycarbonate base 9 plate, and the RF power supply 16 is turned off.
2c was closed.

The gas introduction valve 10 was closed, and the Ar residual gas and the Au atoms in the sputtering device 30 were once exhausted by the exhaust system 12. Thereafter, the valve 10 was opened again, Ar gas was introduced into the sputtering apparatus, and the Ar gas pressure in the sputtering apparatus was set to 5 × 10 ⁻³ by adjusting a mass flow controller (not shown). Thereafter, the changeover switch 17 was connected to the electrode 13a side of the ZnS-SiO ₂ target 13b, and RF power of 600 W was supplied to the ZnS-SiO ₂ target. After about one minute of pre-sputtering, the shutter 13c immediately above the target was opened, and the formation of the ZnS-SiO ₂ dielectric film on the substrate 9 was started. After a lapse of 5 minutes and 30 seconds from the start of film formation, the RF power supply 16 was turned off, and the shutter 13c was also closed. By this film formation, a ZnS-SiO2 film was formed to a thickness of 550 ° on the Au film.

After the valve 10 is closed and the residual Ar gas and ZnS—SiO ₂ molecules in the apparatus are once exhausted by using the exhaust system 12, the bubble 10 is opened, and the Ar gas and the N ₂ gas are removed. A mixed gas having a ratio of 1: 1 was introduced into the chamber 30, and the gas pressure of the mixed gas was set to 5 × 10 ⁻³ torr. Thereafter, the changeover switch 17 is switched to the Ge target electrode 18a side, and the RF power supply 16
Was supplied to the Ge target 18b. About 1
After pre-sputtering for minutes, the shutter 18c was opened, and the formation of a GeN film on ZnS-SiO ₂ was started. About 20 seconds after the start of film formation, the RF power 16 was turned off, the shutter 18c was closed, and a GeN film was formed with a thickness of 50 °.

After the valve 10 is closed and the mixed gas of Ar and N ₂ and Ge atoms in the chamber 30 are exhausted, the valve 10 is opened again to introduce the Kr gas, and the Kr gas pressure in the sputtering device is increased. Was set to 5 × 10 ⁻² torr (usually 5 × 10 ⁻³ ). The changeover switch 17 was switched to the electrode 14a side of the GeSbTe compound composition target 14b, the power supply 16 was turned on, and 200 W of power was supplied to the GeSbTe target. After the pre-sputtering for about 1 minute, the shutter 14c immediately above the target was opened, and the formation of the GeSbTe phase change recording film on the disk substrate 9 was started.
Forty seconds later, the RF power supply 16 was turned off, and a GeSbTe recording film having a reduced quenching degree during film formation was formed on the GeN film at 100 °.

After the valve 10 is closed again and the residual Kr gas and GeSbTe molecules in the sputtering apparatus are exhausted, the bubble 10 is opened, and the mixing ratio of Ar gas to N ₂ gas is 1: 1. Was introduced into the chamber 30 and the gas pressure of the mixed gas was set to 5 × 10 −3 torr. afterwards,
The changeover switch 17 is connected to the electrode 18a side of the Ge target, and RF power of 250 W is supplied from the RF power supply 16 to the Ge target.
It was supplied to the target 18b. After about 1 minute of pre-sputtering, the shutter 18c was opened, and the formation of a GeN film on the GeSbTe recording film was started. About 20 seconds after the start of the film formation, the RF power 16 was turned off, the shutter 18c was closed, and a GeN film having a thickness of 50 ° was formed.

When the valve 10 is closed, the chamber 30 is closed.
After the mixed gas of Ar and N ₂ and Ge atoms remaining in the chamber are exhausted, the valve 10 is opened again, and the Ar gas is removed from the chamber 3.
0, and the Ar gas pressure was adjusted to 5 × 10 ⁻³ torr. Then, switched to the electrode 13a side of the changeover switch 16 again ZnS-SiO2 target 13b, the power of 600W from RF power supply 16 is ZnS-SiO ₂ target 13
b. After about one minute of pre-sputtering, the shutter 13c was opened again, and ZnS-SiO ₂ film formation was started. 10 minutes and 20 seconds after the start of film formation, the RF power supply 1
6 is turned off, the shutter 13c is closed, and GeN ₂
ZnS-SiO ₂ dielectric film 1040A on the films are laminated.

Finally, the valve 10 is closed again, and after the Ar residual gas and ZnS-SiO ₂ molecules in the apparatus are exhausted from the sputtering apparatus, the valve 10 is opened again, and Ar gas is introduced and Ar gas is introduced. The gas pressure was set at 5 × 10 ⁻³ torr. Then, the changeover switch 17 was switched to the electrode 12a side of the Au target 12b, and 150 W of power was supplied from the RF power supply 16 to the Au target 12b. After about 1 minute of pre-sputtering, the shutter 12c was opened, and the formation of the Au reflection film was started. After one minute, the RF power is turned off, the chassis 12c is closed, and the Au on the ZnS-SiO ₂ dielectric is
An optical interference film 100 # was formed.

The sample disk 9 is used for the sputtering device 3
Then, an L to H type second RAM layer disk is finally obtained. The structure of the second RAM layer disk 28 is as follows.
As shown in FIG. 7C, the polycarbonate substrate 51, Au
The reflection film 52 (300 °), the ZnS-SiO ₂ dielectric film 53 (55)
0 °), a GeN crystallization nucleation film 62 (50 °), a GeSbTe phase change recording film 54 (100 °) with a reduced quenching degree during film formation,
GeN crystallization nucleation generating film 63 (50A), ZnS-SiO ₂ dielectric film 5
5 (1040A) and Au optical interference film 56 (100 °). The sample of the second RAM layer disk 28 is named (Sample F).

Similarly, the second RAM layer disk sample produced at a Kr gas pressure of 5 × 10 ^-1 torr at the time of forming the GeSbTe phase change recording film is named (Sample G). Here, the Kr gas pressure at the time of forming the GeSbTe phase change recording film of Sample F was 5 × 10 ⁻² torr. The film configuration of the sample G is such that the polycarbonate substrate 51 and the Au reflection film 52 (300
Å), ZnS-SiO ₂ dielectric film 53 (550 °), GeN crystallization nucleation film 62 (50 °), GeSbTe phase change recording film 54 (100
Å), GeN crystallization nucleation film 63 (50 °), ZnS—SiO ₂ dielectric film 55 (1040 °), Au optical interference film 56 (100
Å).

The differences in the properties of the films of the second RAM layer disk 28 from Sample A to Sample G described above are summarized below.

[0132]

[Table 1]

Is as follows.

The second RAM manufactured in the above (Examples 1 to 3)
The sample of the layer disc 28 and the first
As shown in FIG. 1, a single-sided dual-layer RAM disk is obtained by laminating the RAM layer disk 27 with a UV curable resin. The UV curable resin is uniformly applied to a thickness of 40 μm on the ZnS—SiO ₂ film of the first RAM layer disk 27 by a spinner (not shown), and then the second RAM layer disk 28 from sample A to sample G is coated. Au interference film side is UV
The resin was superposed so as to be in contact with the resin, and then irradiated with UV light of 800 W for 20 seconds from the substrate side of the first RAM layer disk to cure the UV resin.

The samples of the single-sided dual-layer RAM disk thus bonded to the structure shown in FIG. 1 are also referred to as samples A to G for convenience.

The prototype phase-change type optical disk sample described above was loaded into the optical disk drive shown in FIG. 8, and evaluation was made by paying attention to the characteristics of the disk, particularly, the performance of initializing the second RAM disk 28.

Prior to this evaluation method, the optical disk drive shown in FIG. 8 will be described first.

The sample disk 31 was rotated at a predetermined rotation speed by a spindle motor 32. In the evaluation of the disc, since a single-sided, dual-layer DVD-RAM is assumed, the rotational speed at the radial position of the disc is set so that the relative speed between the disc 31 and the optical head 33 is kept constant at 8.2 m / s. Is changed successively, and a constant linear velocity method is adopted.

A predetermined signal is input from the input device 36,
For example, in the case of DVD-RAM, 8/16
The signal is digitized into 1 and 0 signals by modulation. The modulated digital signal is sent to the laser driver 37, the laser of the optical head is turned on and off, and data is written on the disk sample 31. For a phase change optical disk,
As shown in FIG. 9, a region where data is to be recorded is irradiated with a high laser power (Pw), and the recording film in that region is melted and quenched to change to amorphous. Further, the region where data has been erased is irradiated with medium laser power (Pe), and the recording film in that region is heated to a temperature higher than the crystallization temperature and crystallized. In FIG. 9, level P
R is the reproduction power at the time of reproduction, and this laser power P
Data is reproduced in R. The data written on the sample disk (amorphous recording mark) has a different reflectance from that of the surrounding data erased portion (crystal portion) during reproduction. Therefore, the disk must be scanned with a weak constant read power. As a result, a signal is detected as a difference in reflection intensity.

The reproduced signal is amplified by a preamplifier 38, an analog signal is converted to a digital signal of 1 or 0 by a binarization circuit 39, and further demodulated by a demodulation circuit 40 based on 8/16 modulation. Is output to the output device 41. In FIG. 8, reference numeral 43 denotes a control system. The laser driver 37 is controlled by the control system 43 at the time of recording, and the linear motor drive control system 46 is controlled by a command from the control system 43 at the time of recording / reproduction. The control condition of the motor 34 is set, whereby the linear motor drive control system 46 controls the linear motor 34 to make the optical head 33 access a predetermined radial position. Further, the focus driving control system 44 is controlled by the control system 43.
The drive signal of the track drive control system 45 is set, and the objective lens actuator of the optical head 33 is controlled by the focus drive control system 44 and the track drive control system 45. It is controlled to follow eccentricity.

Next, a method for evaluating a sample disk will be described below.

The single-sided, dual-layer RAM disk produced this time is:
Since the second RAM layer disk sample was prepared to eliminate the need for initial crystallization, the initial crystallization device was not required,
After producing the disk, the disk was directly loaded into a drive device, and a recording / erasing laser pulse shown in FIG. 9 was irradiated along the track of the disk. In this case, the more stable the amorphous state immediately after the film formation, the more the erase power Pe in FIG.
Then, since crystallization cannot be performed, the same portion must be irradiated with the laser again and again.

When the disk is scanned at a constant linear velocity of 8.2 m / s, the recording signal is modulated by 8/16 modulation. In mark edge recording, the total capacity on both sides of the two layers is 8.8.
For 5 GB, the shortest pit pitch is 0.30
Since the length is 8 μm, in order to form only the shortest mark 3T, recording may be performed with a duty of 50% at a frequency of 13 MHz. If the C / N ratio (Carrier to Noise Ratio) is measured by a spectrum analyzer at the time of reproduction after recording, it is possible to determine whether or not the recording has been performed without initialization based on the measured value. If the C / N value is too low, it is determined that the amorphous recording film immediately after film formation is not sufficiently crystallized by the laser irradiation of Pe, and the same laser pulse of the same portion of the disk is repeatedly irradiated, This operation is repeated until a large reproduction C / N is obtained. At this time, the recording operation was performed with Pw set to 14 mW and Pe set to 5 mW. At the time of reproduction, the disk was scanned by continuous light with Pr set to 1 mW. By the way, the second
Since the RAM layer disk sample is for LtoH recording, the initial state immediately after film formation is entirely amorphous, and its reflectivity is 37% because it is r2a of the single-sided dual-layer RAM described earlier. The incident light is transmitted twice through the first RAM layer, and considering that the transmittance of the first RAM layer is 50%, the second R
The absolute reflectance from the entire surface of the AM layer is 37 × 0.
5 × 0.5 = 9.25%, which is almost the same as the absolute reflectance of the crystal (H) of the first RAM layer (H to L medium) of 9%. For this reason, if writing by overwriting is possible from the initial amorphous state, focus servo can be realized without any problem due to the reflectance from the second RAM layer.
(Because servo is applied when the reflectance from the crystal of the first RAM layer is 9%, there is no problem with focus servo even if the absolute reflectance from amorphous of the second RAM layer is 9.25%.) When the L to H medium of the 2RAM layer is entirely initialized using the initial crystallization apparatus, r2a becomes 13% as described earlier, so the absolute reflection rate becomes 1
3 × 0.5 × 0.5 = 3.25%, and it goes without saying that servo is not activated before recording.

Therefore, it is assumed that the servo is applied to the second RAM layer disk without initializing the entire surface in an amorphous state, and thereafter, the recording can be performed by the first overwriting of the amorphous by the drive device. In other words, if non-initialization can be achieved, the object of the present invention has been achieved.

Hereinafter, the evaluation results of the sample disk will be described.

First, OW recording was performed on the sample A of the conventional example by switching the servo so that the laser focus of the second RAM layer was focused. Reproduction C / N
In the first OW recording, almost no 13 MHz spectrum was emitted. Therefore, it was proved that the amorphous state immediately after the formation of the recording film was extremely stable. 2nd RAM
The same portion of the layer was irradiated with the laser at the same frequency six times, and the C / N finally became 40 dB in the subsequent reproduction. In addition, 9
The number of OWs (15 total OWs) was measured and the reproduction C / N ratio was measured. As a result, the signal increased to 52 dB.

The same experiment was attempted on sample B. As a result, a reproduced C / N exceeding 45 dB was obtained in the first OW. Also, the playback C / N became 52 dB after the same track was OWed three times.

Next, Sample C was evaluated. First OW
Becomes 51 dB in reproduction C / N, and C / N in the second OW
Became 52 dB. Therefore, a synergistic effect of the GeN crystallization nucleation film provided below the GeSbTe recording film and the effect of lowering the cooling degree of the GeSbTe recording film by increasing the pressure of Kr was confirmed.

In the evaluation of Sample D, the first OW
And the C / N was 45 dB in the third OW,
Similarly, in sample E, C / N is 51d in the first OW.
B, C / N was 52 dB in the second OW. Therefore,
It was found that the GeN crystallization nucleation film provided on the GeSbTe recording film had the same crystallization promoting power as the lower one.

Similarly, when the samples F and G were evaluated, the C / N of both samples was 52 in the first OW.
dB has been reached.

From the above results, if the gas pressure of the Kr gas is increased during the formation of the recording film on the second RAM layer disk,
As a result, the kinetic energy of GeSbTe during film formation can be reduced, and the degree of rapid cooling can be reduced.

Further, by providing a GeN crystallization nucleation film in contact with one surface of the GeSbTe recording film of the second RAM layer, crystallization was promoted. This was proved by providing the GeN film on both sides of the recording film, and the C / N reached 52 dB in one OW.

In the embodiment of the present invention, Kr is used as a rare gas having the same atomic period as Ar and a heavy mass, but the same effect has been confirmed in an experiment using Xe gas.

In the embodiments of the present invention, the GeN crystallization nucleation film is formed by sputtering a Ge target with a mixed gas of Ar gas and N ₂ gas mixed at a ratio of 1: 1.
The flow ratio of the Ar gas to the N ₂ gas is uniquely determined by how much N is incorporated in the Ge film. However, in order for the GeN film to be a crystallization nucleus generation source, the Ge film has a certain flow rate. When N atoms are incorporated into the film, stress is generated in the film, which is considered to be a nucleation source. Further, pure Ge is a semiconductor, and therefore has a predetermined optical band gap, and therefore absorbs a red semiconductor laser to some extent. Therefore, Ge
The optical band gap is widened by adding N to the film,
It is also necessary to eliminate red laser absorption.

According to the experimental results of the present inventors, the N atoms taken into the Ge film depend on the RF power applied at the time of film formation, but the N ₂ gas / Ar gas flow ratio is 0.3 or more. If so, another experiment has revealed that the optical band gap of the GeN film is generally wider than 2 eV, the absorption of the red laser is eliminated, and the stress remains in the film to be a crystallization nucleus generation source.

In the present invention, the second R of the single-sided dual-layer RAM disk is
As described in the example of L to H media as AM layer disc,
It goes without saying that even an H-to-L medium has the advantage that a non-initialized disc has the advantage that the entire initialization step can be omitted.

In the present invention, the effect of the present invention has been described with a single-sided dual-layer RAM disk.
The disk was stuck on the side opposite to the laser incidence,
It goes without saying that the same effect can be expected even with a double-sided four-sided disk.

In the embodiments of the present invention, a film formation process of a non-initialized disk using a GeSbTe-based recording film was introduced. However, the present invention is not limited to this, and the present invention is not limited thereto.
It is needless to say that the same effect can be expected even when applied to various phase change recording materials such as a system and an InSe system.

The non-initialized phase-change type optical disk according to the present invention was originally manufactured for the purpose of non-initialization. However, as a result, amorphous is rapidly promoted to crystal by laser irradiation. It should be added that the erasing rate (crystallization efficiency) of the recording mark (amorphous) at the time of overwriting is remarkably improved.

Next, another embodiment of the present invention having preferable optical characteristics of the disk 27 of the first RAM layer and the disk 28 of the second RAM layer shown in FIGS. 7 and 8 will be described.

When the disk 28 of the second RAM layer is an L to H medium, it has been pointed out that there is a problem with the servo in the conventional disk.
It can be solved by the following improvement measures. That is, the reflectance of the crystal in the disk 27 of the first RAM layer,
The absorptance and transmittance are r1c, α1c and t1c, respectively, and the amorphous reflectance, absorptivity and transmittance are r1a, α1a and t1a, respectively. Assuming that the rates are R2c, α2c, t2c and the amorphous reflectance, absorptance, and transmittance are r2a, α2a, and t2a, respectively, for the disk 27 of the first RAM layer, r1c = 18, α1c = 32, and t1c = 50 When setting r1a = 10, α1a = 20, t1a = 70, ΔR1 = r1c−r1a = 8%, for the disk 28 of the second RAM layer, r2c = 40, α2c = 60, t2c = 0 r2a = 72, α2a = 28, t2a = 0, then ΔR2 = Δr2 × 0.5 × 0.5 = (r2a−r2c) × 0.25 = 32 × 0.25 = 8%, and ΔR1 = △ It becomes R2.

In this case, the lower reflectivity of the disk 28 of the second RAM layer is 40% of r2c. However, when the incident light passes through the disk 27 of the first RAM layer twice, it becomes 0.25.
, The absolute reflectance becomes 10%,
This is the same as the lower reflectivity r1a of the disk 27 in the RAM layer, which is a sufficient reflectivity required for operating the servo, and is considered to be no problem.

Of course, according to the above calculation results, the disk 28 of the second RAM layer does not necessarily have to be an L to H medium.
Even if the medium has a low reflectance, no problem arises because the reflectance is 10% even if the medium passes through the disk 27 of the first RAM layer twice. However, assuming a transmittance of 0%, H to L In the case of media, the absorptance of the amorphous becomes larger than the absorptivity of the crystal, and in such a case, the erasing rate deteriorates when trying to OW a previously written amorphous mark with a new mark. This may cause a so-called modulation distortion problem in which a newly written mark is subjected to modulation due to the disappearance of the old mark. This is also commonly known to researchers in the field.

In the above example, the L of the disk 28 of the second RAM layer
Although the reflectivity of Low (crystal) of the to H medium is set to 40%, the absolute reflectivity is required to be 5%, preferably 6% in consideration of servo. Is 5 / 0.25 = 20% or more, preferably 6 / 0.25 = 24% or more.

Hereinafter, specific optical characteristics will be described.

Comparative Example 2 The first example described as Comparative Example 1
The disk structure of the RAM layer 27 was manufactured by the same manufacturing method, and the optical characteristics were measured using the manufactured first RAM layer 27 as Comparative Example 2.

As described above, the first RAM layer 27 has a film structure of a substrate, ZnS-SiO ₂ (510 °), GeSbTe recording film (70 °), and ZnS-SiO ₂ (800 °). The sample of the disk 28 having the first RAM layer is named sample H. This sample H was loaded into an initial crystallization device (not shown), and the entire surface of the recording layer was crystallized with a high-power Ar laser. Thereafter, a semiconductor laser having a wavelength of 650 nm was irradiated from the substrate side, and the reflectance was measured.
The reflectance from the crystal part was about 8%.

Also, the disk structure of the second RAM layer 28 described as Comparative Example 1 was manufactured by the same manufacturing method, and the optical characteristics of the manufactured second RAM layer 28 were measured as Comparative Example 2.

The film configuration of the second RAM layer sample disk for Comparative Example 2 manufactured by this normal process is as follows: substrate, Al-Cr
(300 °), ZnS-SiO ₂ (550 °), GeSbTe (100
Å), ZnS-SiO ₂ (1040 Å), and Au (100 Å). This disk is named a sample of the second RAM layer disk 28 as Sample I.

This sample I disk was also loaded into an initial crystallization device (not shown), and the entire surface of the disk was similarly crystallized. Thereafter, when the reflectance was measured with a semiconductor laser having a wavelength of 650 nm, the reflectance from the crystal was 13%.

A method of manufacturing a disk according to another embodiment of the present invention, in which the second RAM layer disk 28 to be compared with Comparative Example 2 is a phase change type optical disk having a high reflectance will be described below.

Before explaining the manufacturing method of the disk, the papers submitted by the present inventors were cited and the phase change type L to H
The reflectance of the medium will be described. Inventor's literature
Jpn.J.Appl.Phys.Vol.37 (1998) pp3339-3342 Part 1, No.
6A, June 1998 `` High-Density Recording Capability
of Five-Layered Phase-Change Optical Disc ".

This document discloses the structure and reflectance characteristics of a five-layer phase-change optical disk including a phase-change recording film. The disk structure shown here is completely opposite to the film structure of the single-sided dual-layer RAM disk. However, a normal single-sided single-layer disk is irradiated with a laser beam from the substrate side. Is more common. In the structure of this document, an Au interference film, a lower ZnS-SiO ₂ film, a GeSbTe recording film, an upper ZnS-SiO ₂ film,
It is composed of Al alloy.

FIG. 10 shows Graph 1 published in this paper. According to this graph 1, the Au interference film is 110 °, the GeSbTe recording film is 100 °, the upper ZnS—SiO ₂ film is 300 °, the Al alloy reflective film is 1000 °, and the lower ZnS—Si
Taking the thickness of the O ₂ film on the horizontal axis, the reflectivity Ra of the crystal part of the five-layer phase change optical disc and the reflectivity Rc of the amorphous phase,
The results of a simulation in which the ratio Ac / Aa between the absorption rate Ac of the crystal and the absorption rate Aa of the amorphous phase are plotted on the vertical axis are shown. From this graph, it can be seen that the thickness of the lower ZnS—SiO ₂ film is increased from 700 ° to 120 °.
By making it 0 °, Ac / Aa can be made larger than 1. Setting the value of Ac / Aa greater than 1 is
It is well known to engineers in this field that it is indispensable for improving the erasing sensitivity and the erasing rate of the phase change optical disk.

FIG. 11 shows a graph 2 published in the above-mentioned paper. In this graph, the film structure of the phase change optical disk in five layers, Au interference film 110 Å, lower ZnS-SiO ₂ film 850 Å, GeSbTe recording film 100 Å, as Al alloy reflective film 1000 Å, the upper ZnS-SiO ₂ film layer Simulation results are shown in which the thickness is plotted on the abscissa and the reflectance Rc of the crystal of the five-layer disk, the reflectance Ra of the amorphous phase, and the difference (= the magnitude of the reproduced signal) Ra−Rc are plotted on the ordinate. I have. According to this graph, it can be seen that the reflectance of the crystal can be increased to 25% or more by setting the thickness of the upper ZnS-SiO ₂ to about 850 ° or more.

It can be seen that the reflectance of the crystal can be set to 40% by setting the upper ZnS-SiO ₂ film to 1050 °. However, if the upper ZnS-SiO ₂ film is set too thick, Ra-Rc (magnitude of the reproduced signal) will be reduced this time, so that 850 ° to 1050 ° is an intermediate value and the reflectance of the crystal is large. It can be seen that the magnitude of the signal is large. With reference to the above-mentioned document, the disk 28 of the second layer of the single-sided dual-layer RAM disk according to the present invention was manufactured as follows.

(Embodiment 4) First, the first RAM layer disk 27 shown in FIG. 3 with slightly increased reflectivity was manufactured.
In the sputtering apparatus shown in FIG.
While rotating at pm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. The capacity of the exhaust system was maintained as it was, the flow rate of Ar gas was adjusted by a mass flow controller (not shown), and the degree of vacuum in the apparatus was set to 5 × 10 ⁻³ torr. In this state, the changeover switch 17 is switched to the electrode 13a side of the ZnS-SiO ₂ target 13b, the RF power supply 16 is connected to the electrode 13a, and the RF power 600 W
Given to S-SiO ₂ target. This power supply starts pre-sputtering, and after about 1 minute of pre-sputtering, the shutter 14 immediately above the target and immediately above the target
c is opened, and the formation of the ZnS-SiO2 dielectric film on the substrate 9 is started. Five minutes after the start of film formation, the RF power supply 16
Is turned off, the shutter 13c is also closed, and the
A ZnS-SiO ₂ film 101 was formed with a thickness of 510 °.

After the valve 10 is closed and the residual Ar gas and ZnS—SiO ₂ molecules in the apparatus are once exhausted using the exhaust system 12, the valve 10 is opened again to introduce Ar gas. The Ar gas pressure in the sputtering device was set to 5 × 10 ⁻³ torr. In this state, the changeover switch 17 is tilted toward the electrode 14a of the GeSbTe compound composition target 14b,
A power of 200 W is supplied from the power supply 16 to the GeSbTe target. After pre-sputtering for about 1 minute, the shutter 14c immediately above the target is opened, forming a film GeSbTe phase change recording film is started on the ZnS-SiO ₂ protective film. After a lapse of 15 seconds from the start of the film formation, the RF power supply 16 was turned off, and a GeSbTe recording film 103 having a thickness of 85 ° was formed on the ZnS-SiO 2 film 102.

After the valve 10 was closed again and the residual Ar gas and GeSbTe molecules in the sputtering device were exhausted, the bubble 10 was opened again and the Ar gas was introduced into the sputtering device 30. After the gas flow rate was adjusted so that the Ar gas pressure became 5 × 10 ⁻³ torr, the changeover switch 17 was again turned on.
The power is switched to the electrode 13a side of the S-SiO ₂ target 13b, and a power of 600 W is supplied from the RF power supply 16 to the ZnS-SiO ₂ target 13b. After about 1 minute of pre-sputtering, the shutter 13c was opened again, and ZnS-SiO ₂ film formation was started. 8 minutes after the start of film formation, the RF power supply 16 is turned off, the shutter 13c is closed, and Ge
800A ZnS-SiO ₂ dielectric film 1 on ₂ Sb ₂ Te ₅ recording film 103
04 are stacked. The sample disk 9 was taken out from the sputtering apparatus 30, and the disk structure 27 of the first RAM layer shown in FIG. 3 was obtained. The first RAM layer disk 27 has a film configuration of a substrate, ZnS-S
iO ₂ (510Å), GeSbTe recording film (85Å), ZnS-SiO ₂
(800Å). This disk of the RAM layer 27 is named Sample J. After mounting the disk of this sample J in an initial crystallization apparatus (not shown) and crystallizing the entire surface with a high-power Ar laser, a laser having a wavelength of 650 nm was irradiated from the substrate side, and the reflectance was measured. The reflectance from this crystal part was about 18%.

The disk of this sample J will be described later in the second RA.
Two pieces of the same one were manufactured because of the convenience of laminating with an M-layer disc.

Next, the disk 2 of the second RAM layer shown in FIG.
8 and the film structure is the same, but ZnS-SiO _TwoThe film thickness of
The second RAM layer that has been set with reference to and has increased reflectance
Disk 28 was manufactured.

In the disk 28 of the second RAM layer, the inside of the vacuum sputtering apparatus 30 was evacuated to 10 ⁻⁶ torr using the vacuum turbo pump 12. With the rotating base 8 rotating at 60 rpm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus.
The capacity of the exhaust system is maintained as it is, and the flow rate of Ar gas is adjusted by a mass flow controller (not shown).
The vacuum in the apparatus was maintained so that the degree of vacuum in the apparatus was 5 × 10 ⁻³ torr. The changeover switch 17 was switched to the electrode 15a side of the Al-Cr target 15b, and 200 W of power was supplied from the RF power supply 16 to the Al-Cr target 15b. After pre-sputtering was performed for about 1 minute in this state, the shutter 15c was opened, and the formation of the Al-Cr reflective film was started. After a lapse of 2 minutes and 47 seconds from the start of the film formation, the RF power supply was turned off, the shutter 15c was closed, and the Al-Cr reflection film 1000 # was formed on the substrate.
Once the Ar residual gas and Al-Cr alloy atoms in the sputtering device 30 are exhausted by the exhaust system 12, the valve 10 is opened again,
Ar gas was introduced into the sputtering apparatus, and the degree of vacuum in the sputtering apparatus was set to 5 × 10 ⁻³ torr by adjusting a mass flow controller (not shown). Thereafter, the changeover switch 17 is connected to the electrode 13a of the ZnS-SiO ₂ target 13b.
And the RF power of 600 W was supplied to the ZnS—SiO ₂ target. After about 1 minute of pre-sputtering in this state, the shutter 13c immediately above the target was opened, and the formation of the ZnS-SiO ₂ dielectric film on the substrate 9 was started. After a lapse of 10 minutes and 26 seconds from the start of film formation, the RF power supply 16 was turned off, and the shutter 13c was opened. In this film forming step, a ZnS-SiO ₂ film having a thickness of 105 was formed on the Al-Cr film.
The film was formed at 0 °.

Next, the valve 10 is closed and the exhaust system 12 is closed.
After the residual Ar gas and ZnS-SiO ₂ molecules in the apparatus are once evacuated, the valve 10 is opened again to introduce Ar gas into the apparatus, and the Ar gas pressure in the sputtering apparatus is reduced to 5 ×. 10
Set to ^-3 torr. The changeover switch 17 is GeSbTe
Is turned down to the electrode 14a side of the compound composition target 14b, the power supply 16 is turned on, and the power of 200 W is supplied to GeSbTe.
Supplied to the target. After about one minute of pre-sputtering, the shutter 14c immediately above the target was opened, and the formation of the GeSbTe phase change recording film on the disk substrate 9 was started.
After a lapse of 20 seconds from the start of film formation, the RF power supply 16 was turned off, and a GeSbTe recording film having a thickness of 100 ° was formed on the ZnS—SiO ₂ film.

The valve 10 was closed again, and the residual Ar gas and GeSbTe molecules in the sputtering apparatus were exhausted. Thereafter, the bubble 10 is opened, and the Ar gas is
Was introduced within. After the gas flow rate is adjusted so that the Ar gas pressure becomes 5 × 10 ⁻³ torr, the changeover switch 17 is again switched to the electrode 13a side of the ZnS—SiO ₂ target 13b, and the power of 600 W is supplied from the RF power supply 16 to the ZnS—SiO ₂ target. It was supplied to the SiO ₂ target 13b. After about 1 minute of pre-sputtering, the shutter 13c was opened again, and ZnS-SiO ₂ film formation was started. 8 minutes and 30 seconds after the start of film formation,
The RF power supply 16 was turned off, the shutter 13c was closed, and a ZnS—SiO ₂ dielectric film having a thickness of 830 ° was laminated on the GeSbTe recording film.

Finally, the valve 10 was closed again, and Ar residual gas and ZnS-SiO ₂ molecules in the apparatus were exhausted from the sputtering apparatus. Thereafter, the valve 10 was opened again, and Ar gas was introduced. After the Ar gas pressure is set to 5 × 10 ⁻³ torr, the RF power supply 16 is switched by the changeover switch 17 to Au.
Of the target 12b, and RF power of 13.56 MHz was supplied from the RF power supply 16 at 150 W, and sputtering of the Au target with Ar gas was started. After about 1 minute of pre-sputtering, the shutter 12c immediately above the target is opened, and ZnS-SiO ₂
An Au optical interference film was formed thereon with a thickness of 110A, the RF power supply 16 was turned off, and the shutter 12c was closed.
The second RAM layer sample disk 9 for Comparative Example 1 manufactured by this process was taken out of the sputtering apparatus 30.

From the above description, the film configuration of this disk is as follows.
Substrate, Al-Cr (1000Å), ZnS-SiO2 (1050
Å), GeSbTe (100Å), ZnS-SiO ₂ (830Å), Au
(110 °). This disk is named a sample of the second RAM layer disk 28 as a sample K.

After the entire surface of the disk of this sample K was crystallized by an initial crystallization device (not shown), a laser beam having a wavelength of 650 nm was irradiated from the Au film side of the surface of the disk to measure the reflectance. As a result of the measurement, a reflectance of about 40% was obtained as shown in the literature.

In exactly the same way, the second RAM having the following film configuration
A layer disk 28 was made. This disc is a substrate,
AlCr reflecting film (1000Å), ZnS-SiO ₂ film (870Å),
GeSbTe recording film (100Å), ZnS-SiO ₂ film (830Å),
Au optical interference film (110 °). This sample of the second RAM layer disk 28 is named sample L. Similarly, after the entire surface of the disk of this sample L was also initially crystallized, the surface (the Au interference film) was irradiated with a laser beam having a wavelength of 650 nm, and the reflectance was measured. Met.

The samples I, K, and L of the second RAM layer disk 28 manufactured as described above, the sample H of the first RAM layer disk 27, and the two samples J were respectively associated with each other using UV curable resin. It was bonded to a single-sided, dual-layer RAM disk as shown in FIG. The UV curable resin is applied to the ZnS of the first RAM layer disk 27 by a spinner (not shown).
A 40 μm-thick coating is applied uniformly on the entire surface of the SiO ₂ film, and then, the samples I, K, and L are overlaid so that the Au interference film side of the second RAM layer disk is in contact with the UV resin. 800 W U from the substrate side of the layer disc 27
The V resin was irradiated for 20 seconds to cure the UV resin.

The samples of the single-sided, dual-layer RAM disk thus bonded as shown in FIG. 1 are respectively referred to as samples 1 to 3 for convenience. Therefore, the combination of the first RAM layer disk 27 and the second RAM layer disk 28 is such that the sample 1 is obtained by bonding the sample I and the sample H, the sample 2 is obtained by bonding the sample K and the sample J, Sample No. 3 is obtained by bonding sample L and sample J together.

The phase change type optical disk sample produced as described above was loaded into the optical disk drive shown in FIG. 8 and its performance was evaluated.

When the second RAM layer disk is focused, it is possible to make a primary determination depending on whether or not servo is applied by the laser beam reflected from the initial crystal on the L to H medium.

On the other hand, in sample 1, the second RAM
When the L-to-H medium of the layer is initialized on the entire surface of the disk by using an initial crystallization apparatus, the reflectance r2a becomes 13% as described above, so that the absolute reflectance is 13 × 0.5 × 0.
As described above, 5 = 3.25% and the servo does not operate before recording.

Actually, the disk of sample 1 was focused on the second RAM layer disk by the drive device of FIG.
When I tried to apply the servo, the reflectivity was too low and the servo did not work. Therefore, the performance was not evaluated.

The discs of Sample 2 and Sample 3 were obtained by using the first RAM layer disc 27 and the second RAM layer disc 2
Focusing on No. 8 and performing a servo test, it was found that Sample 2 was capable of performing servo operations on both the first RAM layer disk 27 and the second RAM layer disk 28. In sample 3, the servo operation of the second RAM layer disk 28 was not good, but the servo operation could be enabled by slightly increasing the gain. In other words, even if the reflectance of the second RAM layer disk 28 is 25%, the absolute transmittance is reduced to 6.25% by transmitting twice through the first RAM layer disk 27, so that servo is not easily applied. , Somehow proved to be usable.

Next, the signal was recorded at a 13 MHz duty of 50%, and the recorded signal was reproduced with a reproduction light of 1 mW, and the C / N was measured.

In each of Samples 2 and 3, the first RAM layer disk had a recording power Pw of 10 mW and an erasing power Pe of 5 mW. Were both 53 dB.

Next, the second RA of sample 2 and sample 3
For the M-layer disc, the recording power Pw is set to 15 mW in consideration of the transmission loss in the first RAM layer, and the erasing power Pe is set to 8
mW and data recording is executed, and the playback C /
When N was measured, it was 50 dB for sample 2 and 52 dB for sample 3. Therefore, it was confirmed that the reproduction amplitude was slightly reduced by increasing the reflectance of the second RAM layer.

As described above, a single-sided dual-layer RAM disk having a first RAM layer disk and a second RAM layer disk from the side where a laser is incident is provided by providing two phase-change optical disks via an adhesive layer having a predetermined thickness. When the signal polarity of the second RAM layer disk is of the L to H type, setting the reflectance of the L (Low) crystal to at least 25% or more (preferably 40% or more) allows the first RAM layer to be used twice. Even after transmission, the minimum reflected light necessary for servo can be obtained.

In the embodiments of the present invention, the L-to-H type, that is, the phase change type optical disk of which the crystal has a lower reflectivity has been described in the embodiment as the second RAM layer disk. Even with the H type, the lower reflectance (amorphous mark in the case of the L to H type) has a reflectance of 25%.
It goes without saying that the same effect can be expected if the percentage is not less than%.

In the present invention, the effect of the present invention has been described using a single-sided dual-layer RAM disk.
It goes without saying that the same effect can be expected even with a double-sided, four-sided disk in which the M disk is bonded to the surface on the side opposite to the laser incidence.

In the embodiments of the present invention, a process of forming a non-initialized disk using a GeSbTe-based recording film has been introduced. However, the present invention is not limited to this, and the present invention is not limited thereto.
It is needless to say that the same effect can be expected even when applied to various phase change recording materials such as a system and an InSe system.

In the above-described embodiment, an example in which the second RAM layer disk sample does not require the initial crystallization has been described. However, the present invention is not limited to this. This second RAM layer disk may be bonded to the first RAM layer disk after initial crystallization.

Before describing the specific embodiments below, a brief description will be given of how the inventors came up with the idea of initial crystallization of the second RAM layer disk and bonding this second RAM layer disk to the first RAM layer disk. .

As described above, in order to enable the servo operation, the absolute reflectance of the second RAM layer needs to be 5%, preferably 6%. The first RAM layer disk is H to
Since the medium is an L medium, the entire surface of the disk after the initial crystallization is in a crystalline state, and this state is H (high). Since this reflectivity is 9% as described above, it is a sufficient value for the servo operation. Meanwhile, the first RA
When recording on an M-layer disc, recording on the entire surface (amorphous)
Then the whole surface becomes L (Low) and the reflectance is 3% as above
And the servo may not operate. However, usually, the entire surface of the first RAM layer disk is not recorded in this way, and when data is recorded on the first RAM layer disk, a recording mark (amorphous) and an erased portion = initial crystallized portion ( (A crystal) is approximately halved on a straight line, and the amount of light reflected at the time of reproduction also has a reflectance substantially in the middle between amorphous and crystalline. That is, (9 + 3) / 2 = 6
%, And as described above, the limit of servo operation is 5 to 5.
Since it is 6%, it can be said that the first RAM layer disk has no problem with respect to the servo after recording the data.

Similarly, considering the second RAM layer disk, the second RAM layer disk is an L to H disk,
When the unrecorded state is the entire crystal, L (Lo
The reflectance is 13% because of w), but there is a problem that if the light passes through the first RAM layer disk twice, it becomes × 0.25, 3.25%, and the servo operation is not performed.

However, when recording is performed first on the entire surface, the reflectance is approximately half that of the recording mark (amorphous) and the erased portion (crystal), so that (13 + 37) / 2 = 25%. This means that 25 × 0.times.
25 = 6.25%, which indicates that this is the limit reflectivity at which servo is applied.

Therefore, if the data is recorded on the entire surface of the second RAM layer disk before the user uses the disk, there is no problem that the servo does not operate. On the other hand, in order to record data on the entire surface of the disk, the entire surface of the disk must be initially crystallized, and the state must be servo-recorded. In order to perform initial crystallization, it is necessary to execute servo with a laser beam that passes through the first RAM layer twice, but since the servo itself does not operate,
There is a contradiction that data cannot be recorded on the entire surface.

The present inventor has made the following idea based on the above contradictions. That is, single-sided, two-layer RA
In the process of manufacturing the M disk, the above-described problem does not occur if data is recorded on the entire surface of the second RAM layer disk in advance. In other words, if the second RAM layer disk does not transmit through the first RAM layer disk, the lower crystal part has a reflectance of 1
Since it is 3%, attention has been paid to the fact that the servo operation is possible even after the entire surface is initially crystallized. Second
After making the RAM layer disk, as the first step, the second RAM
Before the layer disk is bonded to the first RAM layer disk, the second RAM layer disk is manufactured in a state where the entire surface of the second RAM layer disk is initially crystallized, and thereafter, data is recorded on the entire surface of the disk in a state where servo can be performed. Was done. Then, as a second step, the second RAM layer disk was bonded to the first RAM layer disk to manufacture a disk. Second
Second RAM in which data is recorded on the entire surface of the RAM layer disk
Since the reflectivity of the layered disk structure is approximately 25%, even if the first RAM layered disk is bonded, 25 × 0.
With 25 = 6.25%, the servo operation can be sufficiently performed, and the problem pointed out in the past can be solved.

A further embodiment of the present invention based on the above idea will be described with reference to the drawings. Here, the first RAM layer disk and the second RAM layer disk have the same structure as the structure shown in FIG. 3 and FIG.
Omitted. The manufacturing apparatus is the same as the apparatus shown in FIG.

(Embodiment 5) First, the first RAM layer disk shown in FIG. 3 with slightly increased reflectivity was manufactured. FIG.
In the sputtering apparatus shown in FIG. 5, while the rotating base 8 was rotated at 60 rpm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. The capacity of the exhaust system was maintained as it was, the flow rate of Ar gas was adjusted by a mass flow controller (not shown), and the degree of vacuum in the apparatus was set to 5 × 10 ⁻³ torr. In this state, the changeover switch 17 is switched to the electrode 13a side of the ZnS-SiO ₂ target 13b, the RF power supply 16 is connected to the electrode 13a, and the RF power 600 W is supplied to the ZnS-SiO2 target 13b.
Provided to the SiO ₂ target. This power supply starts pre-sputtering, and after about one minute of pre-sputtering,
The shutter 14c immediately above the target is opened, and the formation of the ZnS-SiO ₂ dielectric film on the substrate 9 is started. Five minutes after the start of film formation, the RF power supply 16 is turned off, the shutter 13c is also closed, and the ZnS-
An SiO ₂ film 101 was formed with a thickness of 510 °.

After the valve 10 is closed and the residual Ar gas and ZnS—SiO ₂ molecules in the apparatus are once exhausted by using the exhaust system 12, the valve 10 is opened again to introduce Ar gas. The Ar gas pressure in the sputtering device was set to 5 × 10 ⁻³ torr. In this state, the changeover switch 17 is tilted toward the electrode 14a of the GeSbTe compound composition target 14b,
A power of 200 W is supplied from the power supply 16 to the GeSbTe target. After pre-sputtering for about 1 minute, the shutter 14c immediately above the target is opened, forming a film GeSbTe phase change recording film is started on the ZnS-SiO ₂ protective film. After a lapse of 15 seconds from the start of the film formation, the RF power supply 16 was turned off, and the GeSbTe recording film 103 having a thickness of 85 ° was formed on the ZnS-SiO ₂ film 102.

[0213] After the valve 10 was closed again and the residual Ar gas and GeSbTe molecules in the sputtering apparatus were exhausted, the bubble 10 was opened again, and the Ar gas was introduced into the sputtering apparatus 30. After the gas flow rate was adjusted so that the Ar gas pressure became 5 × 10 ⁻³ torr, the changeover switch 17 was again turned on.
The power is switched to the electrode 13a side of the S-SiO ₂ target 13b, and a power of 600 W is supplied from the RF power supply 16 to the ZnS-SiO ₂ target 13b. After about 1 minute of pre-sputtering, the shutter 13c was opened again, and ZnS-SiO ₂ film formation was started. 8 minutes after the start of film formation, the RF power supply 16 is turned off, the shutter 13c is closed, and Ge
800A ZnS-SiO ₂ dielectric film 1 on ₂ Sb ₂ Te ₅ recording film 103
04 are stacked. The sample disk 9 is taken out from the sputtering apparatus 30, and the disk structure of the first RAM layer 27 shown in FIG. 3 is obtained. The first RAM layer 27 has a film configuration of a substrate, ZnS-SiO ₂ (510 °), and a GeSbTe recording film (70 °).
Å), ZnS-SiO ₂ (800 Å). This RAM
The sample of the layer disk 27 is named sample M. After mounting the disk of this sample M in an initial crystallization apparatus (not shown) and crystallizing the entire surface with a high-power Ar laser, a laser having a wavelength of 650 nm was irradiated from the substrate side, and the reflectance was measured. The reflectance from this crystal part is about 9%
Met.

Next, the second RAM layer disk 28 shown in FIG.
Although the film structure was the same as that of the first embodiment, a second RAM disk having a higher reflectance was manufactured by setting the thickness of ZnS-SiO ₂ with reference to the above literature.

In this second RAM layer disk, the inside of the vacuum sputtering apparatus 30 was evacuated to 10 ^-6 torr using the vacuum turbo pump 12. With the rotating base 8 rotating at 60 rpm, the Ar gas introduction valve 10 was opened, and Ar gas was introduced into the sputtering apparatus. The capacity of the exhaust system was maintained as it was, the flow rate of Ar gas was adjusted by a mass flow controller (not shown), and the vacuum in the apparatus was maintained such that the degree of vacuum in the apparatus was 5 × 10 ⁻³ torr. The changeover switch 17 was switched to the electrode 15a side of the Al-Cr target 15b, and 200 W of power was supplied from the RF power supply 16 to the Al-Cr target 15b. After pre-sputtering was performed for about 1 minute in this state, the shutter 15c was opened, and the formation of the Al-Cr reflective film was started. After 50 seconds had elapsed from the start of the film formation, the RF power was turned off, the shutter 15c was closed, and the Al-Cr reflection film 300A was formed on the substrate. Once the Ar residual gas and the Al-Cr alloy atoms in the sputtering device 30 are exhausted by the exhaust system 12, the valve 10 is opened again, Ar gas is introduced into the sputtering device, and adjusted by a mass flow controller (not shown). , The degree of vacuum in the sputtering apparatus is 5 × 10 ^-3
set to torr. Then, the changeover switch 17 is set to Z
The nS-SiO ₂ target 13b is tilted toward the electrode 13a, and R
An F power of 600 W was supplied to the ZnS—SiO ₂ target. After about 1 minute of pre-sputtering in this state, the shutter 13c immediately above the target was opened, and the formation of the ZnS-SiO ₂ dielectric film on the substrate 9 was started. After a lapse of 50 seconds from the start of film formation, the RF power supply 16 was turned off, and the shutter 13c was opened. In this film forming step, a ZnS-SiO ₂ film was formed with a thickness of 550 A on the Al-Cr film.

Next, the valve 10 is closed and the exhaust system 12 is closed.
After the residual Ar gas and ZnS-SiO2 molecules in the apparatus are once evacuated, the valve 10 is opened again to introduce Ar gas into the apparatus, and the Ar gas pressure in the sputtering apparatus is reduced to 5 × 10
Set to ^-3 torr. The changeover switch 17 is GeSbTe
Is turned down to the electrode 14a side of the compound composition target 14b, the power supply 16 is turned on, and the power of 200 W is supplied to GeSbTe.
Supplied to the target. After about one minute of pre-sputtering, the shutter 14c immediately above the target was opened, and the formation of the GeSbTe phase change recording film on the disk substrate 9 was started.
After a lapse of 20 seconds from the start of film formation, the RF power supply 16 was turned off, and a GeSbTe recording film having a thickness of 100 ° was formed on the ZnS—SiO ₂ film.

The valve 10 was closed again, and the residual Ar gas and GeSbTe molecules in the sputtering apparatus were exhausted. Thereafter, the bubble 10 is opened, and the Ar gas is
Was introduced within. After the gas flow rate is adjusted so that the Ar gas pressure becomes 5 × 10 ⁻³ torr, the changeover switch 17 is again switched to the electrode 13a side of the ZnS—SiO ₂ target 13b, and the power of 600 W is supplied from the RF power supply 16 to the ZnS—SiO ₂ target. It was supplied to the SiO ₂ target 13b. After about one minute of pre-sputtering, the shutter 13c was opened again, and the formation of the ZnS-SiO ₂ film was started. From the start of film formation after lapse of 10 minutes 20 seconds, RF power supply 16 is turned off, the shutter 13c is closed, ZnS-SiO ₂ dielectric film is laminated to a thickness 1040A on GeSbTe recording film.

Finally, the valve 10 was closed again, and Ar residual gas and ZnS-SiO ₂ molecules in the apparatus were exhausted from the sputtering apparatus. Thereafter, the valve 10 was opened again, and Ar gas was introduced. After the Ar gas pressure is set to 5 × 10 ⁻³ torr, the RF power supply 16 is switched by the changeover switch 17 to Au.
Of the target 12b, and RF power of 13.56 MHz was supplied from the RF power supply 16 at 150 W, and sputtering of the Au target with Ar gas was started. After about 1 minute of pre-sputtering, the shutter 12c immediately above the target is opened, and ZnS-SiO ₂
An Au optical interference film was formed thereon with a thickness of 100 °, the RF power supply 16 was turned off, and the shutter 12c was closed.
The second RAM layer sample disk 9 for Comparative Example 1 manufactured by this process was taken out of the sputtering apparatus 30.

From the above description, the film configuration of this disk is as follows:
Substrate, Al-Cr (300mm), ZnS-SiO _Two(550Å), GeS
bTe (100Å), ZnS-SiO_Two(1040Å), Au (10
0Å). This disk is the second RAM layer disk
Is named sample N.

The sample N was also crystallized on the entire surface of the disk by an initial crystallization device (not shown),
When the reflectance was measured by irradiating a laser beam of m, the reflectance from the crystal was 13% as designed.

With the above-described completely same process and completely the same first
After making a RAM layer disk and a second RAM layer disk and running both disks in exactly the same way on the initial crystallizer,
The entire surface of the disk was initially crystallized. Accordingly, two sets of disks before bonding the first RAM layer structure and the second RAM layer structure were completed.

Next, of the two sets of the first RAM layer and the second RAM layer disks, one of the second RAM layer disks was recorded with random data on the entire surface of the disk by a drive device shown in FIG. The disk drive device of FIG. 8 is the same as the device already described, and a description thereof will be omitted.

Using the phase change type optical disk drive device shown in FIG. 8, one of the second RAM layer disks is used as a single plate (the first R disk).
Before attaching the AM layer disk), random data was recorded on the entire surface of the disk. Recording was performed at a wavelength of 650 from the substrate side.
The measurement was performed with an optical head equipped with a semiconductor laser of nm.

Since the second RAM layer disk is used for a single-sided, dual-layer RAM disk, the film configuration is completely opposite to that of a normal phase change type optical disk. It is better to record with a laser from the side of the Au optical interference film, but the optical head of a phase change optical disk drive for DVD-RAM is usually designed to record through a 0.6 mm thick substrate. Fortunately, in the case of the second RAM layer disk, the AlCr reflective film closest to the substrate was originally set to be as thin as 300 ° in order to increase the recording sensitivity so that recording was possible even after passing through the first RAM layer disk. Even when the laser was irradiated from the substrate side, the laser beam reached the recording film and overwrite recording was possible. At this time, the recording power Pw was set to 14 mW, the erasing power Pe was set to 7 mW, and random data based on 8/16 modulation was recorded on the entire surface of the disk.

When the AlCr reflection film on the substrate side is so thick that laser recording from such a substrate side is not possible, recording is performed from the Au interference film side.
An m-thick dummy substrate may be placed in contact with the Au interference film, and overwrite recording may be performed with the optical head from the dummy substrate side.

Next, the second RAM layer disk on which the entire recording was performed was irradiated with a laser beam for reproduction from the side of the Au optical interference film, and only the reflectivity was measured without using the servo. It was 25%, and by recording the data, it was confirmed that the average value of the reflectance of the crystal was 13% and the reflectance of the amorphous was 37% as calculated.

Next, the two sets of the first RAM layer and the second RAM
Layer discs (one side only for initial crystallization, one side after initial crystallization, whole disk recording), not shown, respectively
Lamination was performed using a lamination device. For bonding,
First, a UV curable resin having a thickness of 40 μm is uniformly applied to the entire surface of the disk using a spinner on the ZnS—SiO 2 film as the uppermost film of the first RAM layer disk.
The UV resin film was superposed so that the interference film was in contact with the UV resin film, and then a UV (ultraviolet) lamp was irradiated from the side of the first RAM layer disk for about 5 seconds to cure the UV resin.

The single-sided dual-layer RAM disk sample thus obtained is a sample 4 in which the second RAM layer disk has only the initial crystallization, and the second RAM layer disk is a sample in which data recording is performed on the entire surface after the initial crystallization. Is named Sample 5.

Next, a method for evaluating a sample disk will be described. The shortest bit pitch is 0.308 μm in order to obtain a total capacity of 8.5 GB on both surfaces of the two layers. Therefore, in order to form only 3T of the shortest mark, the frequency is 13M.
What is necessary is just to record with a duty of 50% of Hz. At the time of reproduction after recording, C / N (Carrir to Noi
By measuring the se ratio, the disc performance can be evaluated by measuring the magnitude of the reproduced signal based on the value.

In addition, the present invention, above all, makes a primary judgment based on whether or not servo is applied by the laser beam reflected from the initial crystal on the L to H medium when the second RAM layer disk is focused. Can be done.

On the other hand, the sample 4 of the conventional example is the second sample.
Since the reflectance of the crystal part of the L-to-H medium of the RAM layer after initializing the entire surface of the disk using the initial crystallization apparatus was 13% before bonding, the absolute reflection rate after bonding was the first RAM layer disk. Is transmitted twice so that 13 ×
0.5 × 0.5 = 3.25% In fact, when the servo of the disk of Sample 4 was attempted to be focused on the second RAM layer disk by the drive device, the servo was not applied because the reflectance was too low. Therefore, the performance was not evaluated.

With respect to the disk of Sample 5, the drive device focused on the first RAM layer and the second RAM layer disks and applied servo. As a result, sample 5 is the first RA
Servo was immediately applied to both the M layer disk and the second RAM layer disk.

Next, recording was performed with a duty ratio of 50% at 13 MHz, reproduced with 1 mW of reproduction light, and C / N was measured. First
When the recording power Pw of the RAM layer disk was set at 10 mW and the erasing power Pe was set at 5 mW, recording was performed, and both the reproduction C / N was 53 dB.

Next, on the second RAM layer disk, overwrite recording was performed on already written random data at the same 13 MHz duty of 50% as described above. At this time, recording power Pw was set at 15 mW in consideration of transmission loss in the first RAM layer, erasing power Pe was set at 8 mW, recording was performed, and reproduction C / N was measured. Turned out to be a level.

As described above, a single-sided dual-layer RAM disk having a first RAM layer disk and a second RAM layer disk from the side where the laser is incident is provided by providing two phase-change optical disks via an adhesive layer having a predetermined thickness. When the signal polarity of the second RAM layer disk is L to H type, after the second RAM layer disk is crystallized before bonding the first RAM layer disk and the second RAM layer disk, predetermined data is recorded on the entire surface of the disk. Then, by bonding to the first RAM layer disk, the average reflectance from the second layer after bonding becomes the minimum reflected light necessary for servo even after transmitting twice through the first RAM layer disk. Can be obtained.

As described in Embodiment 5, if the average reflectance of the crystal part and the amorphous part is about 25% after performing the entire recording before bonding the second RAM layer disk, After bonding, the average reflectance is approximately 6%. Therefore,
As shown in the fifth embodiment, it is not necessary to limit that the reflectivity of the crystal part of the second RAM layer disk is 13% and the reflectivity of the amorphous part is 37%. Overwrite the entire surface of the second RAM layer disk, and then attach the first RAM layer disk to the second RAM layer disk.
Needless to say, it is only necessary that the average reflectance from data is approximately 6% or more when the layer disc is reproduced.

In the present invention, random data is recorded when the entire surface of the second RAM layer disk is recorded before the disks of the first and second RAM layers are bonded to each other. Needless to say, in order to set the arithmetic average accurately, for example, it is only necessary to record the entirety of the shortest mark 3T in the 8/16 modulation with a 13 MHz duty of 50% at 50%.

In the present invention, the effect of the present invention has been described with a single-sided dual-layer RAM disk.
It goes without saying that the same effect can be expected even with a double-sided, four-sided disk in which the M disk is bonded to the surface on the side opposite to the laser incidence.

In the embodiment of the present invention, GeSbTe
Although the film formation process of the uninitialized disk was introduced using the system recording film, the present invention is not limited to this.
It goes without saying that the same effect can be expected even when applied to various phase change recording materials such as InSbTe type and InSe type.

Further, another embodiment of the present invention will be described below.

As described above, in consideration of the normal servo, the absolute reflectance is required to be 5%, preferably 6%. Therefore, considering the first RAM layer disk, since the first RAM layer disk is an HtoL medium, the entire surface of the disk after the initial crystallization is in a crystalline state, and this state is H (hig)
h). Since this reflectivity is 9% as described above, it is needless to say that the reflectivity is sufficient for servo operation. On the other hand, when recording is performed, the entire surface is L (low) if the entire surface is recorded (amorphous). And the reflectance is 3 as described above.
%, And servo is not applied. However, this is not usually the case, and when data is recorded, the recording mark (amorphous) and the erased portion = the initial crystallized portion (crystal) Since the light is almost equally divided on a straight line, the amount of light reflected at the time of reproduction also has a substantially intermediate reflectance between amorphous and crystalline. That is, (9 + 3) / 2 = 6%. As described above, since the limit to which the servo is applied is 5 to 6%, it can be said that the first RAM layer disk has no problem with respect to the servo after recording the data.

Similarly, when considering the second RAM layer disk, the second RAM layer disk is an L to H disk, and when the unrecorded state is the entire crystal, the L
(Low), the reflectivity is 13%, but when transmitted twice through the first RAM layer disk, it becomes × 0.25 and 3.25.
% And servo does not work.

However, when the entire amorphous recording is first performed,
The reflectance is 37%, which is the same as that of the recording mark (amorphous) over the entire surface of the disk.

As described above, when the first RAM layer disk and the second RAM layer disk are pasted together, the reflected light from the second RAM layer disk is transmitted twice back and forth through the first RAM layer structure. The reflectance of the crystal part is 3.25.
% And the servo is not applied, but before the first RAM layer disk and the second RAM layer disk are bonded together, the crystal part of the second RAM layer disk has a reflectance of 13% even if it is a crystal part. No servo problems occur. Also, if the entire surface is initially crystallized before bonding the second RAM layer disk and then the entire surface is amorphous-recorded by a drive device, a reflectance of 37% can be obtained on the entire surface. Thereafter, the first RAM layer disk and the second RAM layer Even if a disc is bonded and transmitted twice through the first RAM layer structure, even if a return light loss occurs, it becomes 37 × 0.25 = 9.25%, and servo does not become a problem even in a drive device.

Originally, immediately after film formation by a vacuum film forming apparatus such as sputtering of the second RAM layer disk, the recording film of the phase change is entirely in an amorphous state. After that, even if the reflectance is measured with a laser beam from the side of the first RAM layer disk, the reflectance does not change to a value of 9.25%. However. As described above, since the phase change recording film immediately after the film formation is chemically very stable, overwrite recording cannot be performed from the first time by laser recording using a drive device. Therefore, after the two disks are bonded together, the entire surface is subjected to initial crystallization, but this time, the reflectivity after the initial crystallization becomes 3.25%, and servo becomes a problem. It is.

The present invention based on the above idea will be described with reference to a sixth embodiment. Here, the structures of the first RAM layer disk and the second RAM layer disk are the same as the structures shown in FIGS. The manufacturing apparatus is the same as the apparatus shown in FIG.

(Comparative Example 3) The first RAM layer disk structure of Comparative Example 3 is manufactured by the same method as the first RAM layer disk structure of Comparative Example 1, and its film structure is a substrate, a ZnS-SiO ₂ protective film ( 510 °), a GeSbTe recording film (70 °), and a ZnS-SiO ₂ protective film (800 °).

The first RAM layer sample disk of Comparative Example 3 was subjected to an initial crystallization apparatus (not shown), and the entire surface was crystallized with a high-power Ar laser. Thereafter, a semiconductor laser having a wavelength of 650 nm was irradiated from the substrate side, and the reflectance was increased. Was measured, the reflectance from the crystal part was about 9%.

Next, a second RAM layer disk shown in FIG. 4 was manufactured.

The vacuum sputtering apparatus 30 was evacuated to 10 ⁻⁶ torr using the vacuum turbo pump 12. While rotating the rotation base 8 at 60 rpm, the Ar gas introduction valve 1
After opening 0, Ar gas was introduced into the sputtering apparatus. The flow rate of Ar gas was adjusted by a mass flow controller (not shown) while keeping the capacity of the exhaust system as it was, and the degree of vacuum in the apparatus was set to 5 × 10 ⁻³ torr. The changeover switch 17 was turned to the electrode 15a side of the AlCr target 15b, and 200 W of power was supplied from the RF power supply 16 to the AlCr target 15b. After pre-sputtering for about 1 minute,
The shutter 15c was opened to start the formation of the AlCr reflection film. After 50 seconds, the RF power is turned off and the shutter 15
c was closed, and an AlCr reflective film 300Å was formed on the substrate.

[0251] The Ar residual gas and Al
After exhausting the Cr alloy atoms in the exhaust system 12, the valve 1
After opening 0, an Ar gas is introduced into the sputtering apparatus, and set to 5 × 10 ⁻³ torr in the sputtering apparatus by adjusting a mass flow controller (not shown). Then, the changeover switch 17 is set to the electrode 13a of the ZnS—SiO ₂ target 13b. And a 600 W RF power was applied to the ZnS-SiO ₂ target. After about one minute of pre-sputtering, the shutter 13c immediately above the target was opened to start forming a ZnS-SiO ₂ dielectric film on the substrate 9.

After 5 minutes and 30 seconds, the RF power supply 16 was turned off, and the shutter 13c was also closed. On the AlCr film, a ZnS-SiO ₂ film was formed at 550 °.

With the valve 10 closed and the exhaust system 12
After once exhausting residual Ar gas and ZnS-SiO ₂ molecules in the device,
again. The valve 10 was opened to introduce Ar gas, and the Ar gas pressure in the sputtering apparatus was set to 5 × 10 ⁻³ torr. The switch 17 is turned to the electrode 14a side of the GeSbTe compound composition target 14b,
A power of 00 W was applied to the GeSbTe target. About 1
After 1 minute of pre-sputtering, shutter 1 just above the target
4c was opened to start forming a GeSbTe phase change recording film on the disk substrate 9. After 20 seconds, the RF power supply 16 was turned off, and a GeSbTe recording film 100 # was formed on the ZnS-SiO ₂ film.

After closing the valve 10 again and exhausting residual Ar gas and GeSbTe molecules in the sputtering apparatus, the bubble 1
After opening 0, Ar gas was introduced into the sputtering apparatus 30.
After adjusting the gas flow rate so that the Ar gas pressure becomes 5 × 10 ⁻³ torr, the changeover switch 17 is again moved to the electrode 13a side of the ZnS—SiO ₂ target 13b, and the RF power supply 16
A power of 0 W was applied to the ZnS-SiO ₂ target 13b.

After about 1 minute of pre-sputtering, the shutter 13c was opened again to start the deposition of ZnS-SiO ₂ . 1
0 minutes and 20 seconds later, the RF power supply 16 is turned off, and the shutter 13 is turned off.
With c closed, ZnS-SiO _{2 of} 1040 ° is placed on the GeSbTe recording film.
A dielectric film was laminated.

Finally, the valve 10 was closed again, and after the Ar residual gas and ZnS—SiO ₂ molecules in the apparatus were exhausted from the sputtering apparatus, the valve 10 was opened again to introduce Ar gas. After setting the Ar gas pressure to 5 × 10 ⁻³ torr, the RF power supply 16 is connected to the electrode 12 a provided below the Au target 12 b by the changeover switch 17, and the RF power of 13.56 MHz is supplied from the RF power supply 16. , And sputtering of an Au target with Ar gas was started. After pre-sputtering for about 1 minute, then the shutter 12c immediately above the target in the open, forming a Au optical interference film 100Å on ZnS-SiO _2, turn off the RF power source 16, closing the shutter 12c.

The second RAM layer sample disk 9 produced by this normal process was taken out of the sputtering apparatus 30.

From the above description, the film configuration of this second RAM layer disk is as follows: substrate, AlCr (300 °), ZnS-SiO ₂ (550
Å), GeSbTe (100Å), ZnS-SiO ₂ (1040Å) /
Au (100Å).

This disk was subjected to an initial crystallization apparatus (not shown) for the second RAM layer sample disk, and after the entire surface of the disk was crystallized, the reflectance was measured with a semiconductor laser having a wavelength of 650 nm. It was 13% as expected.

The above-described process is exactly the same as the first process.
After making a RAM layer disk and a second RAM layer disk and running both disks in exactly the same way on the initial crystallizer,
The entire surface of the disk was initially crystallized. Accordingly, two sets of disks before bonding the first RAM layer structure and the second RAM layer structure were obtained.

Next, one of the two sets of the first RAM layer and the second RAM layer disks will be described below.
Using a drive device, the entire surface of the disk was recorded amorphous.

Using the phase change type optical disk drive shown in FIG. 8, one of the second RAM layer disks was recorded on a single plate (before the first RAM layer disk was bonded) and the entire surface of the disk was amorphous. Recording was performed at a wavelength of 650 from the substrate side.
The measurement was performed with an optical head equipped with a semiconductor laser of nm.

Since the second RAM disk is used for a single-sided dual-layer RAM disk, the film configuration is completely opposite to that of a normal phase-change optical disk.

Normally, the drive device for DVD-RAM is 0.6
Since it is designed so that recording / reproducing can be performed through a substrate having a thickness of mm, it is not possible to perform recording from the surface (Au interference film) side of such a second RAM layer disk. Therefore, in this case, a 0.6 mm-thick dummy substrate was placed in contact with the Au interference film, and amorphous recording was performed over the entire surface of the disk with the optical head from the dummy substrate side. Incidentally, in this full-surface amorphous recording, the recording power Pw (FIG. 4) is 10 mW, the erasing power Pe is not set, and the DC power of 10 mW (no pulse modulation is applied.
C) Recording was performed.

Next, the second RA in which the entire amorphous recording was performed
When the M layer disk was irradiated with the laser beam for reproduction from the Au optical interference film side, only the reflectance was measured without applying servo,
The average reflectance was approximately 32%. According to calculation, the reflectivity of the amorphous is 37%. However, in the DC amorphization by laser, the crystal part slightly remains on both sides of the amorphous line, so that the reflectivity is slightly lower than the calculated value. It seems to have been.

Next, the two sets of the first RAM layer and the second RAM
Each of the layer disks (one of which was subjected to initial crystallization only, and one of which was amorphous recording after initial crystallization) was bonded using a UV bonding apparatus (not shown). First, ZnS-SiO _{2 on} the top film of the first RAM layer disk
A UV curable resin is applied uniformly on the entire surface of the disk with a thickness of 40 μm using a scanner, and thereafter, the Au interference film of the second RAM layer disk is overlapped so as to be in contact with this UV resin film. A UV (ultraviolet) lamp was irradiated from the side of the 1RAM layer disk for about 5 seconds to cure the UV resin.

The single-sided dual-layer RAM disk sample thus obtained is a sample P in which the second RAM layer disk has only initial crystallization, and a sample P in which the second RAM layer disk has undergone amorphous recording after the initial crystallization. A certain case is named sample Q.

Since the evaluation method of the sample disk in the sixth embodiment is the same as the evaluation method already described, the description is omitted.

The sample P having the conventional structure is obtained by using L t of the second RAM layer.
o Since the reflectivity of the crystal part of the H media after initializing the entire surface of the disk using the initial crystallization apparatus was 13% before bonding, the absolute reflectance after bonding was transmitted twice through the first RAM layer disk. In the calculation, 13 × 0.5 × 0.
5 = 3.25%.

In sample P, when the servo was applied by focusing on the second RAM layer disk using the drive device shown in FIG. 8, the reflectivity was too low and servo was not applied. Therefore, the performance was not evaluated.

For sample Q, servo was performed by focusing on the first RAM layer and the second RAM layer disks with the drive device of FIG. As a result, sample Q becomes the first RA
Servo was immediately applied to both the M layer disk and the second RAM layer disk.

Next, recording was performed with a 13 MHz duty of 50%, reproduced with 1 mW of reproduction light, and C / N was measured. First
When the recording power Pw of the RAM layer disk was set at 10 mW and the erasing power Pe was set at 5 mW, recording was performed, and both the reproduction C / N was 53 dB. On the second RAM layer disk, overwrite recording was performed on the already written amorphous mark at the same 13 MHz duty of 50% as described above. At this time, the recording power Pw is
Recording was performed by setting the transmission power in the first RAM layer to 16 mW and the erasing power Pe to 8 mW, and the reproduction C / N was measured. As a result, it was found that the reproduction C / N was 54 dB, which was a level without any problem.

As described above, two phase-change optical disks are provided via an adhesive layer having a predetermined thickness, and a single-sided, dual-layer RAM disk having a first RAM layer disk and a second RAM layer disk from the side where the laser is incident. When the signal polarity of the second RAM layer disk is of the L to H type, before the first RAM layer disk and the second RAM layer disk are bonded to each other, the second RAM layer disk is initially crystallized, and amorphous recording is performed on the entire surface of the disk. , After that, by sticking it to the first RAM layer disc,
Even if the reflectivity from the second layer after bonding is transmitted twice through the first RAM layer disk, reflected light necessary for servo can be obtained.

In the sixth embodiment, after the entire surface is subjected to amorphous recording before bonding the second RAM layer disk, the first RAM
The reflectivity from the amorphous portion of the second RAM layer disk after passing through the layer twice is 32 × 0.25 = 8%, but the absolute reflectance after passing through the first RAM layer twice is at least 6%. I just want to
It is considered that the mark may be further lowered. However, in practice, even if the servo is applied in the entire amorphous recording state, when the data is overwritten, the mark (amorphous) and the mark (amorphous) are Since the space becomes a crystal, the average reflectance is further lowered. Therefore, a value of 8% in the reflectance after two transmissions through the first RAM layer in the state where the entire amorphous recording is performed can be determined to be the minimum reflectance in consideration of the subsequent data recording.

In the sixth embodiment, the effect of the present invention was described with a single-sided double-layered RAM disk. However, such a single-sided double-layered RAM disk was bonded to the four-sided four-sided RAM Needless to say, the same effect can be expected even with a disc.

In the sixth embodiment of the present invention, a film formation process of a non-initialized disk using a GeSbTe-based recording film was introduced. However, the present invention is not limited to this, and the present invention is not limited to this.
It goes without saying that the same effect can be expected even when applied to various phase change recording materials such as SbTe type and InSe type.

[0277]

As described above, according to the present invention, a single-sided, two-layer phase-change optical disk capable of performing focus servo on both the first and second recording layers even in the initial state after manufacturing. Is provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a layer structure of a general single-sided dual-layer RAM disk.

FIG. 2 is a perspective view schematically showing the appearance of the single-sided dual-layer RAM disk shown in FIG.

FIG. 3 is a cross-sectional view schematically showing a film structure of a first RAM layer before bonding in a single-sided dual-layer RAM disk according to one embodiment of the present invention.

FIG. 4 is a sectional view schematically showing a film structure of a second RAM layer before bonding in a single-sided dual-layer RAM disk according to one embodiment of the present invention.

FIG. 5 is a block diagram schematically showing a sputtering apparatus as a film forming apparatus for manufacturing a phase change optical disk as a sample disk.

FIG. 6 is a block diagram schematically showing a sputtering apparatus as a film forming apparatus for manufacturing a phase change optical disk having an uninitialized second RAM layer according to one embodiment of the present invention.

FIGS. 7A, 7B, and 7C are cross-sectional views schematically showing a second RAM layer disk according to another embodiment of the present invention.

FIG. 8 records data on an optical disk, deletes the data,
FIG. 2 is a block diagram showing a configuration of an optical disk drive used for evaluating a disk, which is a general disk drive for reproducing data.

9 is a graph showing laser pulse levels during recording, erasing, and reproducing in the apparatus shown in FIG. 7;

FIG. 10 is a graph showing reflectance characteristics of a five-layer optical disc including a phase change recording film.

FIG. 11 is a graph showing the reflectance characteristics of a five-layer optical disk including a phase change recording film.

[Explanation of symbols]

 27: Disk of the first RAM layer 28: Disk of the second RAM layer 29: UV curable resin film 52: Reflective film 53: Dielectric film, 54: Phase change recording film 56: Optical interference film 62, 63: Crystallization nucleation film 101: Substrate 102, 104: Protective film 103, 104: Phase change film 105: First RAM layer 111: Substrate 113, 115: Protective film 114: Phase change recording film 116: Translucent film

Claims (13)

[Claims] 1. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and reversibly changes phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing, the second phase-change film is maintained in a crystalline state having a low reflectivity at the time of data erasing, and at the time of recording for forming a recording mark. , The recording mark is in an amorphous state with high reflectivity In the initial state before the optical beam is irradiated after the optical disc is manufactured, the second phase change recording film does not need to be initially crystallized by irradiating the entire surface with the light beam. A single-sided, two-layer phase-change optical disc characterized by a phase-change recording film. 2. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and a reversible phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing, the second phase-change film is maintained in a crystalline state having a low reflectivity at the time of data erasing, and at the time of recording for forming a recording mark. , The recording mark is in an amorphous state with high reflectivity A rare gas having the same atomic period as Ar and heavier than Ar is used as a sputtering gas when a recording film is formed by the vacuum sputtering method, and a sputtering gas pressure of 5 × 10 ^-2 torr or more is used. The second phase change recording film is formed, and a GeN film is provided adjacent to the second phase change recording film using a mixed gas of N2 gas and Ar gas and a Ge target,
In the initial state after the optical disk is manufactured and before the light beam is irradiated, the second phase change recording film is a non-initialized phase change recording film that does not need to be irradiated with the light beam to perform initial crystallization. A single-sided, two-layer phase-change optical disk. 3. A phase-change-type first recording film, which reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and reversibly changes phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In the single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing, the second phase-change film has a lower reflectance of at least 25% among the reflectances of the crystalline region and the amorphous region. Characterized in that it is a single-sided, two-layer phase-change optical Disk. 4. A phase-change type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and reversibly changes phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In the single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing, the second phase-change film has a low reflectivity in a crystalline region corresponding to an erased portion and an amorphous region corresponding to a recording mark portion. High reflectivity, and the reflectivity of the crystal region is 25% or less. A single-sided, two-layer phase change optical disc, characterized by being on the top. 5. A first recording film of a phase change type, which reversibly changes phase between amorphous and crystalline by irradiation with a light beam, and a reversible phase between amorphous and crystalline by irradiation with a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase change optical disc capable of recording, erasing, and reproducing, the first and second phase change films are bonded together via the adhesive layer. The entire surface is initially crystallized, and the phase change film is A single-sided, two-layer phase-change optical disc characterized by recording constant data and thereafter bonding the first and second phase-change films with an adhesive layer. 6. A phase-change type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and a reversible phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing, the second phase-change film has a low reflectivity in a crystalline region corresponding to an erased state and an amorphous region corresponding to a recording mark portion. High reflectance, the first and second phase change films Before bonding via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and predetermined data is recorded on the entire surface of the phase crystallized film that has been initially crystallized. A single-sided, two-layer phase change optical disc, wherein the first and second phase change films are bonded to each other. 7. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation with a light beam, and reversibly changes between amorphous and crystalline by irradiation with a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing, a predetermined data is recorded on the entire surface of the second phase-change film when the user purchases the phase-change optical disc. Characterized in that it has a single-sided, two-layer phase change optical disc. H. 8. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and reversibly changes phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase change optical disc capable of recording, erasing, and reproducing, the second phase change film has a low reflectivity in a crystalline region corresponding to an erased portion and a low reflectivity in an amorphous region corresponding to a recording mark portion. Rate is high, and the first and second phase change films are Before bonding via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and the data is set so that the entire surface of the second crystallized film that has been initially crystallized becomes an amorphous region. , And thereafter, the first and second phase change films are bonded together via the adhesive layer. 9. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and reversibly changes phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is A single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing data, wherein the second phase-change film is maintained in a crystalline state having a low reflectivity when data is erased, thereby forming a recording mark. Sometimes, the recording mark is kept in an amorphous state with high reflectivity. In the optical disc manufacturing process, in the optical disc manufacturing process, the second phase change recording film is formed on a non-initialized phase change recording film which does not need to be irradiated with a light beam to entirely crystallize after manufacturing. A method for manufacturing a single-sided, two-layer phase change optical disk. 10. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation with a light beam, and reversibly changes between amorphous and crystalline by irradiation with a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is A single-sided, two-layer phase-change optical disc capable of recording, erasing, and reproducing the data, wherein the second phase-change film is maintained in a crystalline state having a low reflectance when data is erased, and forms a recording mark. At the time of recording, the recording mark is amorphous with high reflectivity. A method of manufacturing a phase-change optical disc to be maintained, and heavy noble gas than the same atoms period a and Ar and Ar as the sputtering gas is used when the recording film by vacuum sputtering is deposited, 5 × 10 ^{- The second} phase change recording film is formed at a sputtering gas pressure of ² torr or more, and N2 gas and Ar
The second method is performed by using a gas mixture of a gas and a Ge target.
The GeN film is provided adjacent to the phase change recording film of
The second phase-change recording film is a non-initialized phase-change recording film that does not need to be irradiated with a light beam on the entire surface to perform initial crystallization. An optical disc manufacturing method. 11. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation with a light beam, and reversibly changes between amorphous and crystalline by irradiation with a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is In a single-sided, two-layer phase change optical disc capable of recording, erasing, and reproducing, the first and second phase change films are bonded together via the adhesive layer. The entire surface is initially crystallized, and the initial crystallized phase change film A method for manufacturing a single-sided, two-layer phase-change optical disc, wherein predetermined data is recorded and then the first and second phase-change films are bonded together by an adhesive layer. 12. A phase-change type first recording film which reversibly changes phase between amorphous and crystal by irradiation of a light beam, and reversibly changes phase between amorphous and crystal by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is A single-sided, two-layer phase change type optical disc capable of recording, erasing, and reproducing, wherein the second phase change film has a low reflectance in a crystalline region corresponding to an erased state and an amorphous phase corresponding to a recording mark portion. For manufacturing phase-change optical disks with high reflectivity in the area In the above, before the first and second phase change films are bonded together via the adhesive layer, the entire surface of the second phase change film is initially crystallized, and A method for manufacturing a single-sided, two-layer phase-change type optical disc, characterized in that predetermined data is recorded on the entire surface, and then the first and second phase-change films are bonded. 13. A phase-change-type first recording film that reversibly changes phase between amorphous and crystalline by irradiation of a light beam, and reversibly changes phase between amorphous and crystalline by irradiation of a light beam. A phase-change type second recording film that changes, and the first recording film disposed on the light beam incident side, and the light beam that has passed through the first recording film is applied to the second recording film. And an adhesive layer having a predetermined thickness for joining the two, and the light beam is focused on one of the first and second phase change recording films from the incident side, and the data on the recording film is A single-sided, two-layer phase-change type optical disc capable of recording, erasing and reproducing, wherein the second phase-change film has a low reflectivity in a crystalline region corresponding to an erased portion and an amorphous region corresponding to a recording mark portion. -Change optical disk manufacturing method with high reflectivity Before the first and second phase change films are bonded together via the adhesive layer, the entire surface of the second phase change light film is initially crystallized, and the second Characterized in that data is recorded so that the entire surface of the phase change film becomes an amorphous region, and then the first and second phase change films are bonded together via the adhesive layer. A method for manufacturing a changeable optical disk.