JP2001143319A - Optical disk medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To normally detect regular ID signals and to ensure stable recording and reproducing action by decreasing an ID ghost generated during the recording and reproducing action of an optical disk medium. SOLUTION: This optical disk medium has a substrate and a phase transition recording film which is formed on the substrate and gives rise to an optically detectable change in a reflected light quantity when the film is irradiated with a laser beam. The value of the total stress generated in the optical disk medium after the medium is subjected to an initialization treatment to uniformly crystallize the phase transition recording film described above exists in a range from -0.2 [N/cm] to +0.8 [N/cm] when the tensile stress direction is defined as a positive sign and the compressive stress direction as a negative sign.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk medium, and more particularly to an optical disk medium in which a recording area is divided into a plurality of zones and each zone is provided with an ID section for identifying the zone. .

[0002]

2. Description of the Related Art At present, an optical information recording / reproducing method using a laser beam is practically used in various places as a large-capacity memory because large-capacity information can be accessed in a non-contact manner and at a high speed.

[0003] Optical information recording / reproducing media (optical disc media) using this optical information recording / reproducing method include a read-only type known as a compact disc and a laser disc, a write-once type that allows recording by a user, and a Side is classified as a rewritable type capable of repeated recording and reproduction.

[0004] Write-once and rewritable optical information recording / reproducing media are being used as external memories of computers, documents, and image files.

[0005] The optical disk medium has a plurality of zones formed by dividing information tracks each formed of an uneven guide groove;
A recording film, a protective film for protecting the recording film, a metal reflection film provided for adjusting recording / reproducing characteristics, and the like are formed on a substrate provided with an ID portion formed by prepits in each of these zones in advance. It is formed by sequentially laminating.

[0006] Rewritable optical disk media include a phase-change optical disk utilizing a phase change between crystal and non-crystal of a recording film by irradiating a laser beam, and a magneto-optical disk utilizing a change in the magnetization direction of a perpendicular magnetization film. There is.

[0007] Of these, the phase-change type optical disk does not require an external magnetic field when recording information like a magneto-optical disk, and furthermore, it is possible to easily overwrite, ie, overwrite, the recorded information. It is expected that rewritable optical disk media will become mainstream.

In a recording / reproducing method for a phase change optical disk, a high power laser beam is applied to a recording film to locally raise the temperature of the recording film, thereby causing a phase change between the crystal and the non-crystal of the recording film. And record.

At this time, the power of a general laser beam is 2
The recording film is irradiated with a laser beam having a power capable of raising the temperature of the recording film to the melting point or higher during recording, and the irradiated portion becomes amorphous when cooled. When erasing information, a laser beam having a power such that the temperature of the recording film reaches a temperature higher than the crystallization temperature and lower than the melting point is applied.

Reproduction of recorded information is performed by irradiating a laser beam having relatively low power as compared with recording, and detecting a change in an optical constant of the information recording section as a reflected light intensity difference. .

For a recording film of a phase change type optical disc, chalcogenide-based materials such as GeSbTe-based, InSbTe-based and AgInSbTe-based materials are used. For these recording films, a film forming method such as a resistance heating vacuum evaporation method, an electron beam vacuum evaporation method, and a sputtering method is used.

In order to record and erase information on the recording film of the phase change optical disk, it is necessary to initialize the recording film in advance. This is because the state of the recording film immediately after film formation is a kind of amorphous state. In order to perform recording on this recording film and form an amorphous recording portion, the entire recording film is made crystalline. An initialization process is required to perform this operation.

Normally, the initialization process is performed by using a high-power laser beam different from the laser beam for recording or reproduction, that is, a high-power laser beam of several tens to several hundred times the output of the laser beam for recording or reproduction. Using light, the entire surface of the recording film of the phase change optical disk is uniformly crystallized in a short time.

[0014]

However, in the prior art, warping of the substrate due to expansion and contraction of a recording film, a protective film, and the like formed on the substrate causes distortion in the guide groove. For this reason, a pseudo signal (hereinafter referred to as “ID ghost”) which is considered to be affected by an ID portion (pre-pit portion) adjacent to the zone boundary is superimposed on a track error signal which is a signal from a guide groove for guiding a laser beam. Has been detected. Then, depending on the size of the ID ghost, a normal ID signal cannot be normally detected, so that there is a disadvantage that the recording / reproducing operation cannot be performed.

Further, in the phase-change type optical disk, since the substrate is affected by heat and is distorted by initializing the recording film using a high-output laser beam, the ID ghost is further increased. .

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the prior art, and in particular, to reduce the number of ID ghosts so that a normal ID signal can be normally detected and a stable recording / reproducing operation can be performed. To provide
With that purpose.

[0017]

To achieve the above object, according to the first aspect of the present invention, a substrate and a reflection film formed on the substrate and optically detectable when irradiated with a laser beam. In an optical disc medium having a phase change recording film that causes a change in the amount of light, the value of the total stress generated in the optical disc medium after the initialization process for uniformly crystallizing the phase change recording film is determined by the tensile stress direction. When the positive sign and the compressive stress direction are negative signs, -0.2 [N / cm] to +0.8 [N
/ Cm].

Therefore, according to the present invention, since the value of the total stress generated in the optical disk medium after the initialization processing is within the above range, the amount of warpage of the substrate is small,
The distortion of the guide groove can be suppressed.

According to the second aspect of the present invention, an optical disk comprising a substrate and a phase-change recording film which is formed on the substrate and generates a change in the amount of reflected light which can be detected optically when irradiated with a laser beam. In the medium, the value of the total stress generated in the optical disk medium is -0 before the initialization process for uniformly crystallizing the phase change recording film with the tensile stress direction being a positive sign and the compressive stress direction being a negative sign. 0.5 [N / cm] to 0
[N / cm], and -0.2 [N / cm] to +0.8 [N / cm] after the initialization process is performed.
The range is up to.

Therefore, according to the present invention, in the optical disk medium in which the value of the total stress generated before the initialization processing is within the above range, the value of the total stress falls within the above range after the initialization processing. Was confirmed experimentally. In such an optical disk medium, the amount of warpage of the substrate is small, and distortion of the guide groove can be suppressed.

According to a third aspect of the present invention, in the first or second aspect, a structure is provided in which a protective film is provided between the substrate and the phase change recording film.

Therefore, according to the third aspect of the present invention, in addition to having the same function as that of the first or second aspect, a protective film is formed on the phase change recording film when recording or erasing information. It functions to reduce expansion and contraction due to the phase change from giving the substrate warpage or distortion.

According to a fourth aspect of the present invention, in the third aspect of the invention, the protective film is made of silicon dioxide.

Therefore, in the present invention described in claim 4, in addition to having the same function as the above-described invention described in claim 3, silicon dioxide can easily control the value of internal stress by its physical properties. Can be formed.

According to the fifth aspect of the present invention, a plurality of zones obtained by dividing a recording area provided on an information track formed of an uneven guide groove into a plurality of sections and an ID section provided in each of the zones are provided. In the provided optical disc medium, a configuration is adopted in which at least one guard track for not recording and reproducing information is provided between zones.

Therefore, according to the present invention, the distance between zones can be increased by providing a guard track.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the guard track is formed of the same concave and convex guide groove as the information track.

Therefore, according to the present invention described in claim 6, in addition to having the same function as the invention described in claim 5, the guard track has the same shape as the information track. Similarly, laser light can be guided.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] A first embodiment will be described with reference to FIG. FIG. 1 is a partial cross-sectional view of a single-plate structure of an optical disc medium according to a first embodiment of the present invention.

In FIG. 1, reference numeral 11 denotes a substrate made of polycarbonate. On the surface of the substrate 11 made of polycarbonate, an information track composed of an uneven guide groove and an ID part composed of prepits for dividing the information track into a plurality of zones are formed in advance.

A first protective film 12 is formed on the substrate 11 made of polycarbonate. First protective film 12
Is a dielectric film, which is formed here by a SiO ₂ film (silicon dioxide film).

On the first protective film 12 thus formed,
The second protective film 13 is formed. The second protective layer 13 a dielectric film is used, here formed by a ZnS-SiO ₂ film.

On the second protective film 13 thus formed,
The phase change recording film 14 is formed. A chalcogenide-based material is used for the phase change recording film 14, and here, Ge ₂ Sb
Formed by ₂ Te ₅ film.

On the formed phase change recording film 14,
The third protective film 15 is formed. A dielectric film is used for the third protective film 15, and here is formed of a ZnS—SiO ₂ film similarly to the second protective film 13.

On the third protective film 15 thus formed,
The reflection film 16 is formed. A metal film is used for the reflection film 16, and is formed of an AlTi alloy film here. After this series of film forming processes, an ultraviolet curable resin 17 is applied on the reflective film 16.

The value of the total stress generated in the optical disk medium according to the present embodiment formed as described above is such that the tensile stress direction is a positive sign, the compressive stress direction is a negative sign, and -0.2 after initialization. [N / cm] to +0.8 [N /
cm]. Further, desirably, before the initialization process, -0.5 [N / cm] to 0 [N / c]
m].

Here, the value of the total stress generated in the optical disk medium is defined by reference numerals 12 to 16 formed on the substrate 11.
The value obtained by multiplying the resultant stress in the substrate radial direction generated inside the film by the film thickness is obtained from the difference in the amount of warpage of the substrate 11 before and after the film formation. Then, the substrate 11 has reference numerals 12 to 16
The total stress when trying to pull the film is tensile stress, and the total stress when trying to compress the film is compressive stress.

The optical disk medium has a single-plate structure shown in FIG. 1 and a close bonding structure using a disk bonding adhesive (an ultraviolet curing resin or the like).

Since the optical disk medium according to the first embodiment is configured as described above, the amount of warpage of the substrate is small and the distortion of the guide groove can be suppressed.
An ID ghost during the recording / reproducing operation is suppressed to a low level, and a stable recording / reproducing operation can be performed.

Each of the films denoted by reference numerals 12 to 16 shown in FIG. 1 was specifically formed by the following procedure using an in-line type sputtering apparatus.

First, the first protective film 12 made of a SiO ₂ film (dielectric film) is formed by using a Si target and a distance between the target and the substrate of 15 cm in a mixed gas atmosphere in which an oxygen gas is mixed with an argon gas. ], Power density 2.74 [W
/ Cm ² ], a total gas pressure of 0.2 [Pa], and an oxygen gas partial pressure of 0.06 [Pa] so as to have a thickness of 100 [nm].

Subsequently, a ZnS-SiO ₂ film (dielectric film)
The second protective film 13 is made of a ZnS—SiO ₂ target, and has a distance between the target and the substrate of 15 cm in an argon gas atmosphere and a power density of 2.2 W / c.
m ² ] and a gas pressure of 0.5 [Pa] and a thickness of 20 [n].
m].

[0044] _{Subsequently,} Ge 2 _Sb 2 Te ₅ recording film made of the film thickness of 18 [nm] _14, Ge 2 _Sb 2 Te ₅ with a target, the target and the substrate distance 15 in an argon gas atmosphere [cm ], Power density 0.27 [W / c
m ² ] and a gas pressure of 1.0 [Pa].

Subsequently, a ZnS-SiO ₂ film (dielectric film)
The third protective film 15 having a thickness of 20 [nm] was formed under the same conditions as the second protective film 13 so as to have a thickness of 20 [nm].

Subsequently, a thickness 70 of an AlTi alloy film
The reflective film 16 of [nm] uses an AlTi alloy target containing 2 [wt%] of Ti, a distance between the target and the substrate of 15 [cm] in an argon gas atmosphere, and a power density of 1.6 [W / cm ² ]. The film was formed to have a thickness of 70 [nm] under a gas pressure of 0.08 [Pa]. Note that the film formation time of each film was appropriately adjusted to a desired film thickness.

In the above-described forming method, a plurality of sputtering gas pressures used for forming the first protective film 12 made of a SiO ₂ film are changed in the range of 0.06 [Pa] to 1.0 [Pa]. An optical disk medium was manufactured.

For the purpose of measuring the internal stress of the first protective film, a single layer of SiO ₂ film is formed in the same range as the sputtering gas pressure at the time of forming the first protective film.
The internal stress of the _two- layer single layer and the total stress of the optical disk medium were measured.

[0049] Figure 2 shows the relationship between the internal stress of the SiO ₂ film formation time of the sputtering gas pressure and the SiO ₂ film monolayer. From FIG. 2, the internal stress of the SiO ₂ film single layer increases as the sputtering gas pressure increases, and the sputtering gas pressure becomes 0.3 [Pa].
In the vicinity, the sign of the internal stress changes from negative to positive, and it can be seen that the internal stress changes from compressive stress to tensile stress.

FIG. 3 shows the relationship between the internal stress of the single layer of the SiO ₂ film and the total stress of the optical disk medium. From FIG.
As the internal stress of the SiO ₂ film increases, the total stress of the optical disk medium also increases, and the internal stress of the single layer of the SiO ₂ film becomes 1.7 ×
In the vicinity of 10 ⁴ [N / cm ² ], it can be seen that the total stress of the optical disk medium changes from the compression side to the tension side.

Next, the sputtering gas pressure at the time of forming the SiO ₂ film (first protective film 12) is changed from 0.06 [Pa] to 1.0.
A plurality of optical disc media were manufactured by changing the range of [Pa], and I / O before and after initialization of these optical disc media were performed.
The amount of the ID ghost near the portion D (pre-pit portion) was measured.

In the initialization processing, the optical disk medium is set at a linear velocity of 1
The disk was rotated at 1.3 [m / sec] and irradiated with a laser beam of 700 [mW] to initialize the entire recording film of the optical disk medium. At this time, the feed pitch of the optical head was 6 [μm / rotation].

Here, the definition of the measured ID ghost amount will be described with reference to FIGS. FIG. 4 shows an arrangement of ID portions at zone boundaries of the optical disc according to the present embodiment.

In FIG. 4, reference numeral 41 (black portion) indicates a guide groove concave portion, and reference numeral 42 (white portion) indicates a guide groove convex portion. Reference numeral 43 (hatched portion) indicates the ID part-A.
There is a zone having an ID portion -B: 44 (hatched portion) adjacent to the zone having the ID portion -A: 43. This 2
Focusing was performed on the guide groove recessed three tracks away from the boundary of the two zones toward the zone having the ID portion -A: 43, and the track error signal at that time was monitored.

FIG. 5 shows various quantities related to the definition of the ID ghost quantity. In FIG. 5, reference numeral 51 denotes a track error signal. Reference numeral 52 denotes a track jump signal, reference numeral 53 denotes a signal from the ID unit-A: 43,
Reference numeral 54 denotes a pseudo signal (ID ghost) leaked from the ID part-B: 44 adjacent to the zone boundary.

Here, the ID ghost amount is measured by measuring the amplitude 55: β of the ID ghost 54 and defining the ID ghost amount by the ratio to the amplitude 56: α of the track jump signal 52. That is, the ID ghost amount is (β / α) × 10
The measurement was evaluated as 0 [%].

FIG. 6 shows an SiO ₂ film (first dielectric film 1).
The sputtering gas pressure used in the film formation of 2) is 0.06 [P
4 shows the relationship between the total stress value and the amount of ID ghost of an optical disk medium manufactured by changing the range from a) to 1.0 [Pa].

In FIG. 6, the circles A1 to A5 represent the measured and plotted ID ghost amounts of the optical disk medium before initialization, and the values of the total stress on the horizontal axis represent the same batch as the optical disk medium. It was determined from the formed stress measurement sample.

According to the curve connecting the black circles, the ID ghost amount increases as the total stress value of the optical disk medium increases toward the compressive stress side (negative direction) or the tensile stress side (positive direction). From this, it can be seen that the total stress of the optical disk medium contributes as one factor of the occurrence of the ID ghost.

On the other hand, the circles B1 to B5 in FIG. 6 plot the ID ghost amounts measured after the optical disk media corresponding to A1 to A5 were initialized by the method described above.

Here, the value of the total stress on the abscissa axis of the circle is
It was determined using the following procedure. As described above, the initialization process of the optical disk medium is generally performed while irradiating a high-power laser beam for a short time. However, since the initialization process cannot be performed on the stress measurement sample under the same conditions, the stress measurement sample in which the total stress indicated by the black circle in FIG. Experiencing the temperature cycle, comparing with the total stress before initialization,
The amount of change was obtained.

The sample used for this measurement is shown in FIG.
Two types were selected, one having a minus sign (compressive stress) and the other having a plus sign (tensile stress). Specifically, the gas pressure at the time of forming the first protective film 12 made of a SiO ₂ film is 0.09 [Pa], and the total stress immediately after the film formation is −0.8.
79 [N / cm] sample, gas pressure 0.8 [Pa],
+0.321 [N / cm] sample is selected and 20 [° C]
The heating and cooling were performed in the range of from 200 ° C. to 200 ° C. At this time, the temperature gradient for raising the temperature was +5 [° C./min], and the temperature gradient for lowering the temperature was -5 [° C./min].

As mentioned above, a temperature cycle of 20
The range of [° C.] to 200 [° C.] is as follows. That is, the initialization process is performed by irradiating a laser beam having such a power that the temperature of the recording film reaches a temperature higher than the crystallization temperature and lower than the melting point. The crystallization temperature of Ge ₂ Sb ₂ Te ₅ , which is the recording film of the present embodiment, ranges from 160 ° C. to 1 ° C.
70 ° C., the temperature range in the heating furnace is 2
The temperature was set from 0 [° C] to 200 [° C].

FIG. 7 shows the relationship between the amount of change in total stress and the temperature when the above two types of stress measurement samples are heated and cooled in the range of 20 ° C. to 200 ° C. .
In FIG. 7, a mark “■” indicates an SiO ₂ film (first protective film 12).
The gas pressure during film formation was 0.09 [Pa],
a) shows the amount of change in the total stress of the sample.

As shown in FIG. 7, the change in the total stress after the heating and cooling was +0.4 [N] for each of the samples marked with ■ where the total stress before initialization was the compressive stress and the sample marked with □ where the total stress was the tensile stress. / C
m], and it can be seen that the total stress changes to the tensile stress side by heating and cooling.

Therefore, even if the total stress before the initialization is either the compressive stress or the tensile stress, the value of the total stress of the optical disk medium is 0.4 [N / cm] by performing the initialization process. It can be seen that the degree increases to the tensile stress side.

By using this result, the value of the total stress on the abscissa in FIG. 6 is 0.4 [N] uniformly to the value of the total stress before initialization (the value on the abscissa in ●). / Cm].

From FIG. 6, it can be seen that in the range of gas pressures evaluated, the amount of ID ghost after initialization is increased by about 2 to 3 points in all optical disk media as compared to before the initialization.

As described above, although the magnitude of the total stress of the optical disk medium contributes as one factor for generating the ID ghost, the change in the total stress due to the initialization processing causes the I stress.
The change in the D ghost amount cannot be completely explained.

That is, from the graph that the total stress increases by about 0.4 [N / cm] to the tensile stress side (the sign is plus side) by the initialization process, and from the graph drawn by the black circle in FIG. If the amount of the ID ghost is determined only by the size, the optical disk medium on the compressive stress side before the initialization has a reduced amount of the ID ghost after the initialization, and the optical disk medium on the tensile stress side before the initialization has been initialized. After ID
The amount of ghosts should increase.

However, as shown by a circle in FIG. 6, the I.D.
The amount of D ghost also increases after initialization. Therefore,
The cause of the ID ghost cannot be explained only by the magnitude and direction (sign) of the value of the total stress of the optical disk medium, and it is presumed that there is a factor other than the total stress that causes the ID ghost.

One of the factors is considered to be thermal deformation of the substrate due to temperature rise and fall during initialization. Hereinafter, an experiment performed to verify this will be described. Since the recording film used in the phase-change optical disk changes its phase from amorphous to crystalline by the initialization process, it is presumed that there is a change in the internal stress due to the change in the volume of the film.

Therefore, an initialization process was performed using a sample medium having a film configuration in which the recording film in which such a remarkable stress change or the like was observed was omitted, and the amount of ID ghost was measured. Here, the condition at the time of initialization is that since the heat absorption rate is poor due to the film configuration without the recording film, a larger power than the laser power used in the normal initialization is applied and the rotation speed of the disk is reduced,
The temperature of the sample medium was higher.

The structure of this sample medium has a thickness of 60
[Nm] SiO ₂ film is provided, and a thickness of 30 nm is further formed thereon.
0 having thereon a AlTi film [nm], SiO ₂
The gas pressure is set to 0.09 so that the membrane has a large compressive stress.
Film formation was performed as [Pa].

FIG. 8 is a diagram plotting the measured amount of the ID ghost of the sample medium when the number of initializations is changed in the range of 1 to 4 times. In FIG. 8, the number of times of initialization: 0
Indicates an uninitialized state, that is, the amount of ID ghost immediately after film formation. Here, each initialization is repeatedly performed at the same measurement location, and the transition of the ID ghost amount with the increase in the number of initializations is examined.

FIG. 8 shows that the amount of ID ghost increases as the number of times of initialization increases or the laser power at the time of initialization increases. From this, it was confirmed that the amount of ID ghost increases by performing initialization for applying a thermal load to the optical disk medium.

Therefore, it can be said that it is desirable to select a condition at the time of initialization in which the thermal load on the optical disk medium is suppressed as much as possible and the increase in the amount of ID ghost is smaller.

From the above, it can be concluded that the ID ghost is caused by a combined factor of the magnitude of the total stress of the optical disk medium, the change of the total stress due to the initialization process, and the thermal load by the laser beam. Presumed.

Here, the magnitude of the ID ghost amount which affects the recording / reproducing operation of the optical disk medium will be described.
In an R / W (recording / reproducing operation) evaluation in an actual drive,
It has been found that erroneous detection can be avoided if the ID ghost amount is 7% or less at a position three tracks away from the ID boundary (zone boundary).

Accordingly, from FIG. 6, the value of the total stress after the initialization of the optical disk medium is changed from -0.2 [N / cm] to +0.
If it is in the range of 8 [N / cm], the ID ghost amount is 7
[%] Or less, and a normal recording / reproducing operation can be performed.

Further, as the total stress before the initialization, -0.
If it is in the range of 7 [N / cm] to +0.5 [N / cm], the value of the total stress after the initialization is −0.2 [N / c].
m] to +0.8 [N / cm].

However, if the total stress is a relatively large compressive stress of -0.6 [N / cm] or less, peeling of the film between the substrate 11 and the first protective film 12 may be observed. . Also, if the total stress before initialization is on the tensile stress side, the amount of ID ghost increases extremely depending on the selection of the initialization conditions, etc.
It is desirable to be in the range of -0.5 [N / cm] to 0 [N / cm].

[0083] In this embodiment, the first consisting of SiO ₂ film
Although the example in which the value of the total stress of the optical disk medium is changed by adjusting the formation condition of the protective film 12 of the above description, the value of the total stress changes when the stress of the other films constituting the optical disk medium is similarly changed. I do. Therefore, it is necessary to carefully adjust the stress of each film constituting the phase change optical disk and control the value of the total stress to be within the above-mentioned range.

[Second Embodiment] A second embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 shows a second embodiment of the present invention.
10 shows an arrangement of guard tracks in a part of the optical disc medium according to the embodiment.

In FIG. 9, reference numeral 91 (black portion) indicates a guide groove concave portion, and reference numeral 92 (white portion) indicates a guide groove convex portion.
Reference numeral 93 (hatched portion) indicates an ID portion-C, and the ID portion-C: 93 distinguishes the zone-C: 94. Reference numeral 95 (hatched portion) indicates an ID portion -D,
The ID-D: 95 distinguishes the zone-D: 96. Then, zone-C: 94 and zone-D:
A guard track 97 is provided between the guard track 97 and the guard track 97.

The guard tracks 97 are denoted by reference numerals 91 and 92.
As in the case of the guide groove described above, it is formed of a concave portion and a convex portion, and at least one is provided, but it is preferable that the number is provided in the range of 5 to 10.

Since the optical disk medium according to the second embodiment is configured as described above, the distance between the zones is increased, and the ID ghost during the recording / reproducing operation is suppressed to be low. Actions can be taken.

Next, a specific example of the second embodiment will be described with reference to FIGS. 1, 9 and 10. 0.6 [m thick
m], and using a polycarbonate substrate having a diameter of 120 [mm], five types of substrates were manufactured in which the number of guard tracks 97 shown in FIG. 9 was changed from 1 to 20.

On each of the substrates, films 11 to 16 shown in FIG. 1 were formed by the following procedure using an in-line type sputtering apparatus in the same manner as in the first embodiment.

First, the first protective film 12 having a thickness of 100 [nm] made of a SiO ₂ film (dielectric film) is formed by using an Si target in a mixed gas atmosphere in which oxygen gas is mixed with argon gas. Distance between target and substrate 15 [c
m], a power density of 2.74 [W / cm ² ], a total gas pressure of 0.2 [Pa], and a partial pressure of oxygen gas of 0.06 [Pa].

Subsequently, a ZnS-SiO ₂ film (dielectric film)
The 20 nm thick second protective film 13 made of Zn
Using S-SiO ₂ target, target and substrate distance 15 in an argon gas atmosphere (cm), the power density 2.2 [W / cm ^2], was deposited with the gas pressure of 0.5 [Pa].

Subsequently, a phase change recording film 14 of 18 nm thick made of a Ge ₂ Sb ₂ Te ₅ film is used as a Ge ₂ Sb ₂ T
e ₅ target, distance between target and substrate 15 cm in argon gas atmosphere, power density 0.27
[W / cm ² ] and a gas pressure of 1.0 [Pa] were formed.

Subsequently, a ZnS-SiO ₂ film (dielectric film)
The third protective film 15 having a thickness of 20 [nm] made of
The protective film 13 was formed under the same conditions.

Subsequently, a thickness 70 of an AlTi alloy film
The reflective film 16 of [nm] uses an AlTi alloy target containing 2 [wt%] of Ti, a distance between the target and the substrate of 15 [cm] in an argon gas atmosphere, and a power density of 1.6 [W / cm ² ]. The film was formed at a gas pressure of 0.08 [Pa]. Note that the film formation time of each film was appropriately adjusted to a desired film thickness.

After these films were formed, an adhesive bonding structure (such as an ultraviolet curable resin) for bonding disks was used to form an adhesive bonding structure, and five types of optical disk media having different numbers of guard tracks were manufactured.

Using these five types of optical disk media, initialization conditions are appropriately changed, and initialization is performed so that substantially the same recording / reproducing characteristics can be obtained in any of the optical disk media. -D: The ID ghost amount was measured at the guide groove concave portion at the boundary on the 96 side.

FIG. 10 shows the measurement results. In FIG. 10, the linear velocity of the initialization condition indicates the rotation speed of the disk at the time of initialization. The feed pitch of the optical head during initialization was fixed at 6 [μm / rotation].

FIG. 10 shows that depending on the initialization condition, the ID ghost amount is as much as 7 [%] or more even in a track such as the medium-3 separated by 10 guard tracks from the boundary of the zone D: 96. You can see that. This is an ID ghost due to a heat load at the time of initialization, as described in the first embodiment.

However, the larger the number of guard tracks, that is, the zone-C: 94 where the ID ghost is being measured.
The amount of ID ghost decreases as the track at the boundary of # moves away from the boundary of zone-D: 96. When the track is separated by more than 15 tracks, the amount of ID ghost becomes 7% or less under any initialization conditions. You can see that

From these facts, it is possible to provide about 5 to 20 guard tracks (dummy tracks that do not perform the information recording / reproducing operation) at the zone boundaries divided by the respective ID portions, to thereby achieve the initialization condition. As a result, it can be understood that an optical disk medium capable of performing a stable recording / reproducing operation without being affected by an ID ghost can be obtained even when a condition in which a large heat load is applied to the optical disk medium is selected.

However, since the substrate area is limited, as the number of guard tracks increases, the amount of information that can be recorded on the optical disk medium decreases. For this reason, the number of guard tracks is desirably about 5 to 10 tracks. At the same time, it is also essential to select an initialization condition in which the thermal load applied to the optical disk medium is small and the amount of ID ghost does not significantly increase.

In the present invention, the composition of the phase change recording film, the Al alloy reflection film, etc., the thickness of each optical disk medium and the method of bonding are limited to those of the first and second embodiments. However, it is selected as appropriate according to the desired recording / reproducing characteristics and intended use. It has been confirmed that the same effect can be obtained by adjusting the value of the total stress of the optical disk medium so as to be in the above-described range.

Further, in the second embodiment, an optical disk medium provided with a recording film which causes a structural change between crystalline and amorphous and a change in optical properties by heating, cooling, etc. by laser light irradiation Although the description has been made with respect to the phase-change type optical disk described above, the same effect can be obtained with respect to a magneto-optical disk or other optical disk medium having a recording film utilizing a change in the magnetization direction of the perpendicular magnetization film.

[0104]

According to the first and second aspects of the present invention, since the value of the total stress generated in the optical disk medium after the initialization processing is within the above-described range, the amount of warpage of the substrate of the optical disk medium is set. And the distortion of the guide groove is suppressed. As a result, an ID ghost is reduced, and a highly reliable optical disk medium that normally detects a normal ID signal and performs a stable recording / reproducing operation can be obtained.

According to the second aspect of the present invention, in addition to the above-described effects, the value of the total stress generated before the initialization processing falls within the above-described range. The value of the total stress falls. Therefore, by performing the initialization process, it is possible to prevent the value of the total stress after the initialization from fluctuating outside the above-mentioned range, and to prevent the occurrence of defective optical disk media due to the initialization.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, the protective film expands and contracts due to a phase change occurring in the phase change recording film when information is recorded or erased. Acts to alleviate the warping, distortion, and the like of the substrate, so that an increase in ID ghost due to repeated recording / erasing operations can be prevented, and stable recording / reproducing operations can be performed for a long period of time.

According to the fourth aspect of the present invention, in addition to the effect of the third aspect of the present invention, since silicon dioxide can be formed by easily controlling the value of its internal stress, an optical disk medium can be formed. Can easily fall within the above-mentioned predetermined range.

According to the fifth aspect of the present invention, since the distance between the zones is increased by the guard track, the ID ghost is reduced, and the reliability of normally detecting a normal ID signal and performing a stable recording / reproducing operation. An optical disk medium with high performance can be obtained.

According to the sixth aspect of the present invention, in addition to the effect of the fifth aspect of the present invention, the guard track has the same shape as the information track. Can be smoothly guided during the recording / reproducing operation.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a single-plate structure of an optical disc medium according to an embodiment of the present invention.

In a first embodiment of the present invention; FIG is a diagram showing the relationship between the internal stress of the SiO ₂ film formation time of the sputtering gas pressure and the SiO ₂ film monolayer.

FIG. 3 is a diagram showing a relationship between an internal stress of a single layer of a SiO ₂ film and a total stress of an optical disk medium in the first embodiment of the present invention.

FIG. 4 is a diagram showing an arrangement of ID portions at zone boundaries of the optical disc medium according to the first embodiment of the present invention.

FIG. 5 is a diagram showing various quantities related to the definition of an ID ghost quantity in the first embodiment of the present invention.

FIG. 6 is a graph showing a change in a sputtering gas pressure used in forming a SiO ₂ film (first protective film) in a range of 0.06 [Pa] to 1.0 [Pa] in the first embodiment of the present invention. FIG. 5 is a diagram showing a relationship between the total stress and the amount of ID ghost of an optical disk manufactured by the above method.

FIG. 7 is a diagram showing the relationship between the amount of change in the total stress of the optical disk medium and the temperature in the first embodiment of the present invention.

FIG. 8 shows the ID of the sample medium when the number of times of initialization is changed in the range of 1 to 4 times in the first embodiment of the present invention.
It is the figure which measured and plotted the ghost amount.

FIG. 9 is a diagram showing an arrangement of guard tracks in a part of an optical disc medium according to a second embodiment of the present invention.

FIG. 10 is a table showing measurement results of an ID ghost amount in the second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 11 Polycarbonate substrate 12 First protective film made of SiO ₂ film 13 Second protective film made of ZnS-SiO ₂ film 14 Phase change recording film 15 Third protective film made of ZnS-SiO ₂ film 91 Guide groove recess 92 Guide groove convex part 93 ID part-C 94 Zone-C 95 ID part-D 96 Zone-D 97 Guard track

Continued on the front page F term (reference) 5D029 HA07 LA14 LB04 LC11 WA01 WD16 5D090 AA01 BB05 CC06 CC11 CC14 DD02 FF45 GG17 GG27

Claims (6)

[Claims] 1. An optical disk medium comprising: a substrate; and a phase change recording film formed on the substrate and causing a change in the amount of reflected light that is optically detectable when irradiated with a laser beam. The value of the total stress generated in the optical disk medium after the initialization process for uniformly crystallizing the film is -0.2 [N / N, where the tensile stress direction is a positive sign and the compressive stress direction is a negative sign. cm] to +0.8 [N / cm]. 2. An optical disk medium comprising: a substrate; and a phase change recording film formed on the substrate and producing a change in the amount of reflected light that is optically detectable when irradiated with a laser beam. Before the initialization process for uniformly crystallizing the phase change recording film, the value of the generated total stress is set to -0.5 [N / cm] to 0 [N / cm], and -0.2 after the initialization process is performed.
An optical disc medium characterized by being in the range of [N / cm] to +0.8 [N / cm]. 3. Between the substrate and the phase change recording film,
3. The optical disk medium according to claim 1, further comprising a protective film. 4. The optical disk medium according to claim 3, wherein said protective film is made of silicon dioxide. 5. An optical disc medium comprising: a plurality of zones obtained by dividing a recording area provided on an information track formed of an uneven guide groove into a plurality of zones; and an ID section provided in each of the zones. An optical disc medium, comprising at least one guard track for not recording and reproducing information between zones. 6. The optical disk medium according to claim 5, wherein the guard track is formed of the same concave and convex guide groove as the information track.