JP2003022587A - Phase change optical disk medium and method for initializing the medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase change optical disk medium which can be initialized by irradiation of laser light through a light transmitting layer side by using a conventional initialization device and which can prevent deposition of foreign matter or the like on the surface of the light transmitting layer where the laser light enters, and to provide a method for initializing the medium. SOLUTION: A metal reflection layer 2, a first dielectric layer 3, a phase change recording layer 4 and a second dielectric layer 5 are deposited on a PC substrate 1, and a PC film 7 is formed thereon with a UV resin 6 interposed. Further, a peelable protective sheet 9 is disposed thereon with a pressure sensitive adhesive layer 8 interposed. The material of each layer is selected in such a manner that the difference in the refractive index between the light transmitting layer 10 composed of the UV resin layer and the PC film, and the protective sheet layer 11 composed of the pressure sensitive adhesive layer and the protective sheet is <=0.2. The total film thickness of the light transmitting layer and the protective sheet layer is controlled to a specified range. The phase change recording layer is initialized by irradiation of laser light through the laminated protective sheet layer side by using a conventional initializing device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase-change type optical disk medium used in a rewritable optical information recording / reproducing apparatus utilizing laser light irradiation and a method for initializing the medium, and more particularly to a phase change type optical disk medium on a substrate. A phase-change type optical disc medium of a system in which a change-recording layer and a light-transmitting layer are sequentially formed, and information is recorded / reproduced on / from the phase-change recording layer by injecting laser light from the light-transmitting layer side and initialization of the medium. Regarding the method.

[0002]

2. Description of the Related Art At present, an optical information recording / reproducing system using a laser beam is capable of accessing a large amount of information in a non-contact manner at high speed, and is therefore put into practical use in various places as a large capacity memory. . An optical information recording / reproducing medium using this optical information recording / reproducing system is a read-only type known as a compact disc or a laser disc, a write-once type that allows the user to record, and a user side capable of repeatedly recording / reproducing. It is classified as a rewritable type. Write-once and rewritable optical information recording / reproducing media are being used as external memory of computers, documents, and image files.

This rewritable optical information recording / reproducing medium includes a phase change type optical disk utilizing the phase change of the recording film and a magneto-optical disk utilizing the change of the magnetization direction of the perpendicular magnetization film. Among them, the phase-change type optical disc does not require an external magnetic field when recording information, unlike the magneto-optical disc, and the recorded information can be easily overwritten, that is, overwritten. It is expected that it will become the mainstream of the type information recording / reproducing medium.

In the phase change type optical disk, the recording film is irradiated with a high-power laser beam to locally raise the temperature of the recording film, thereby causing a phase change between the crystal and the amorphous of the recording film for recording. I do. On the other hand, the reproduction of the recorded information is performed by irradiating a laser beam having a relatively low power as compared with that at the time of recording and detecting a change in the optical constant of the information recording section as a reflected light intensity difference.

For the recording film of the phase change type optical disk, chalcogenide materials such as GeSbTe system, InSbTe system and AgInSbTe system are used. Each of these recording films is formed by a film forming method such as a resistance heating vacuum evaporation method, an electron beam vacuum evaporation method, and a sputtering method. The state of the recording film immediately after film formation is a kind of amorphous state, and in order to form an amorphous recording portion in this recording film, an initialization process for making the entire recording film crystalline is performed. .
Recording is then accomplished by forming an amorphous portion within this crystallized state.

A general recording / reproducing method for a phase-change optical disk is performed by crystallizing or amorphizing the recording film by changing the power of laser light between two levels. That is, at the time of recording, the recording film is irradiated with laser light having a power that raises the temperature of the recording film to the melting point or higher,
The irradiated portion is made amorphous when cooled. When erasing information, the temperature of the recording film is higher than the crystallization temperature,
Irradiation with laser light of such a power that the temperature reaches the melting point or lower. The reproduction is performed by irradiating a low power laser beam to read as a reflected light intensity difference.

The recording film constituting the above-mentioned phase-change type optical disk has a thickness in which spiral or concentric guide grooves, that is, recording tracks (land portions (recesses) and groove portions (convex portions)) are arranged in advance. Is 600 μm or 120
It is formed on a 0 μm transparent disk substrate. The recording track guides the laser light emitted from the optical head of the information recording / reproducing apparatus along the information sequence. The shape of the recording track is such that concave and convex shapes are alternately arranged. When viewed from the optical head, the concave shape, that is, the far side is called the land portion, and conversely, the convex shape, that is, the near side is called the groove portion. Further, the distance from the center of the land portion or the groove portion to the center of the adjacent land portion or the groove portion is called a track pitch.

To form a phase change type optical disk medium using the above recording film and substrate, a thickness of 600 μm or 1
On a 200 μm transparent disk substrate, a first dielectric layer and a recording film and a second dielectric layer, or a first dielectric layer and a recording film, a second dielectric layer and a reflective film, or the like, or A general method is to sequentially arrange the first dielectric layer, the second dielectric layer, the recording film, the third dielectric layer, the reflective film, and the like.

Then, after the above-mentioned steps, bonding with a transparent dummy substrate or bonding with a substrate on which films having the same layer structure are laminated is performed using an ultraviolet curable resin. Further, as described above, in the manufacturing process of the phase-change optical disk, after the above-described series of film forming and bonding steps, the initial phase for uniformly changing the phase of the recording film layer from the amorphous state to the crystalline state is set. Is done. In this initialization step, a method using laser light is generally used, and laser light is incident from the transparent disk substrate side to record and reproduce information on the recording film.

Incidentally, in recent years, along with the demand for higher recording density, the track pitch of recording tracks is narrowed and the concave portion (land portion) of the guide groove and the convex portion (groove portion) between the land portions are formed. ), Land / groove recording in which information is recorded on both of them. At the same time, in order to improve the recording density, miniaturization of the spot diameter of laser light is being promoted.

Since the spot diameter of the laser beam described above depends on λ / NA (λ: wavelength of laser beam, NA: numerical aperture of objective lens) of the recording / reproducing system, the wavelength of the laser beam is shortened and the objective By increasing the numerical aperture of the lens, the spot diameter of the laser light can be made smaller and the recording density can be increased.

However, when the numerical aperture of the objective lens is increased, the coma aberration becomes large, and there is a concern that the signal quality will deteriorate. Coma aberration is an amount that is proportional to the product of the skew angle (tilt angle with respect to the optical axis of the disk), the thickness of the transparent substrate through which the laser light passes, and the cube of the numerical aperture of the objective lens, and is inversely proportional to the laser wavelength. Therefore, as one means for suppressing coma aberration, a method of reducing the thickness of the transparent substrate through which the laser light passes has been proposed.

As a method for reducing the thickness of the transparent substrate through which the laser beam passes, the thickness is 600 μm or 1200 μm.
Proposed is one in which a light reflecting layer, a recording layer, and a thin light transmitting layer are sequentially formed on a transparent substrate, and a laser beam is incident from the thin light transmitting layer side to record and reproduce signals on the recording layer. Has been done. This method is different from the method of recording and reproducing a signal by injecting a laser beam from the side of a transparent substrate having a thickness of 600 μm or 1200 μm, which is widely used in the past, and the incident direction of the laser beam is different, The order of the formed thin films is also opposite to the conventional order.

As a method for forming the above-mentioned thin light transmitting layer, a light reflecting layer and a recording layer are sequentially laminated on a transparent substrate having a thickness of 600 μm or 1200 μm, and then a thickness of 95 μm is formed.
A method of sticking a resin sheet (PC film) of about m through a UV-curing resin with a thickness of several μm, or dropping the UV-curing resin on the recording layer, developing it, and then irradiating it with UV light to cure it and transmitting a thin light. Although a method of forming a layer is known, a method of attaching a resin sheet (PC film) with an ultraviolet curable resin is generally used to uniformly form a thin light transmitting layer on the entire surface of the disk.

The above-mentioned initialization process must be similarly performed on a medium in which a laser beam is made incident from the thin light transmitting layer side to record and reproduce a signal on the recording layer. At this time, the cost can be reduced if the initialization line, which has been used for initialization from the side of the transparent disk substrate having a thickness of 600 μm or 1200 μm, can be shared in the manufacturing line.

[0016]

However, the thickness 6
In an initialization apparatus for an optical disk medium which is used by entering a laser beam from the transparent disk substrate side of 00 μm or 1200 μm, the initialization optical system has a thickness of the transparent disk substrate which has been conventionally used, that is, 600 μm or 1
It is designed for 200 μm. As an example, when using a transparent disk substrate having a thickness of 600 μm,
An objective lens with a numerical aperture (NA) of about 0.6 is used,
When a transparent disk substrate having a thickness of 1200 μm is used, an objective lens having a numerical aperture (NA) of about 0.5 to 0.55 is used.

Using these initialization devices, in order to cope with the above-mentioned increase in recording density, laser light is made incident from the thin light transmitting layer side having a thickness of about 100 μm to record signals on the recording layer. When attempting to initialize the medium of the reproducing method, spherical aberration becomes large on the laser light converging surface, and the image point largely changes depending on the distance from the optical axis, resulting in deterioration of image formation. There was a problem that initialization was insufficient.

Further, in order to make the laser beam incident from the thin light transmitting layer side of about 100 μm to perform initialization,
A very large lens having a numerical aperture (NA) of about 0.8 to 0.85 must be used as the objective lens. Therefore, since the conventionally used initialization device cannot be used at the same time, it is necessary to newly introduce an initialization device having an optical system having a numerical aperture (NA) of the objective lens of about 0.85. The increase was difficult to avoid.

Further, when such a lens having a high NA is used, the above-mentioned objective lens is arranged very close to the optical disc (a distance of about 100 μm) at the time of initialization, so that the surface of the optical disc. There was a problem that the objective lens and the optical disk crashed depending on the accuracy.

Incidentally, in a medium in which a laser beam is incident from the thin light transmitting layer side to record and reproduce a signal on the recording layer, after the initialization process is completed in the manufacturing process, the medium is packed and shipped and used. Cross to. Therefore, since the thin light transmission layer, which is the incident surface of the laser light, is exposed between the initialization process and the packaging, foreign matter such as dust adheres to the incident surface of the laser light, and when the user uses it. There is also a fear that it may cause the initial failure of the.

Particularly, in an apparatus using an optical system having an NA of 0.8 to 0.85, the distance between the head and the medium is only about 100 μm, so that dust of several 100 μm adheres to the light incident surface. , Which causes a fatal failure.
In order to avoid this, it is common to perform storage from the initialization process to the packaging in a clean room, and to use a dust-free material that does not generate dust as the packaging material, etc.
With these manufacturing methods, it has been difficult to avoid an increase in the cost of the medium.

The present invention has been made in view of the above problems, and its main purpose is to provide an optical disk medium for recording / reproducing information by making laser light incident from the thin light transmitting layer side. And a high-quality phase change type optical disc medium in which foreign matter or the like does not adhere to the surface of the thin light transmission layer that is the incident surface of the laser light until just before the user uses it and the initial stage of the medium. It is to provide a method of computerization.

[0023]

In order to achieve the above object, a phase change type optical disk medium of the present invention comprises a substrate, a reflective layer, a first dielectric layer, a phase change recording layer and a first change layer. In a phase-change type optical disc medium having at least two dielectric layers and a light-transmitting layer, laser light is irradiated from the light-transmitting layer side to initialize the phase-change recording layer and record and reproduce information. , A peelable protective sheet layer having a refractive index of 0.2 or less with respect to the refractive index of the light transmitting layer is provided on the light transmitting layer, and the protective sheet layer is bonded to the phase. The change recording layer is initialized, and information is recorded and reproduced with the protective sheet layer peeled off.

In the present invention, the total thickness of the light transmitting layer and the protective sheet layer is about 580 μm to 620.
It is set in the range of μm and the wavelength is approximately 630 nm to 660.
Using an initialization device with a laser light source in the nm range,
The phase change recording layer may be initialized.

In the present invention, the total thickness of the light transmitting layer and the protective sheet layer is set in the range of approximately 1180 μm to 1220 μm, and the wavelength is approximately 760 nm.
Alternatively, the phase change recording layer may be initialized by using an initialization device having a laser light source in the range of 820 nm to 820 nm.

Further, in the present invention, it is preferable that the light transmitting layer is composed of a resin adhesive layer and a PC film layer, and the protective sheet layer is composed of an adhesive layer and a PC film layer.

Further, in the present invention, at least a pair of projecting portions are provided at a position of point symmetry with respect to the center of the optical disc medium at an outer peripheral end portion of the protective sheet layer, and the protective sheet is provided by the projecting portions. The layers can be easily separated, and each of the pair of protrusions is preferably formed in a semicircular shape having a diameter in the range of approximately 5 mm to 10 mm.

In addition, the initialization method of the present invention comprises:
At least the reflective layer, the first dielectric layer, the phase change recording layer, the second dielectric layer, and the light transmission layer are provided from the side of the substrate, and the phase change is performed by irradiating laser light from the side of the light transmission layer. In a method for initializing a recording layer, the phase change recording layer is further provided with a peelable protective sheet layer on the light transmitting layer, and the protective sheet layer is attached. Is to be initialized.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION A phase change type optical disk medium according to the present invention is, in a preferred embodiment thereof, a metal reflective layer, a first dielectric layer, a phase change recording layer and a second dielectric layer on a PC substrate. And a layer are laminated in this order, a PC film is formed thereon with an ultraviolet resin layer interposed therebetween, and a protective sheet is further disposed thereon via an adhesive layer so that the protective sheet can be easily peeled off. Each material is selected so that the difference in refractive index between the light transmission layer formed of the film and the protective sheet layer formed of the adhesive layer and the protective sheet is 0.2 or less, and
By setting the total film thickness of the light transmitting layer and the protective sheet layer within a predetermined range, laser light is emitted from the protective sheet layer side using the conventional initialization device in the state where the protective sheet layer is attached. The phase change recording layer is initialized by irradiation, and information is recorded and reproduced with the protective sheet layer peeled off. Hereinafter, description will be given with reference to FIG. 1 showing a sectional configuration of a phase change type optical disc medium according to an embodiment of the present invention.

As shown in FIG. 1, the phase-change type optical disk medium of the present embodiment has, for example, a guide groove or pre-pit (not shown) for guiding a laser beam formed in advance on the substrate surface, and has a thickness of 1200 μm. , A metal reflection layer 2 having a thickness of about 120 nm, a first dielectric layer 3 having a thickness of about 30 nm composed of a ZnS.SiO ₂ film, and a phase change having a thickness of about 15 nm on a transparent resin substrate 1 having a diameter of 120 mm. The recording layer 4 and the second dielectric layer 5 of ZnS.SiO ₂ film having a thickness of about 130 nm are formed, and after this series of film forming processes, the thickness of the second dielectric layer 5 is set to about 95 μm by the ultraviolet curing resin 6 having a thickness of about 5 μm.
A transparent film 7 having a thickness of about μm is adhered (hereinafter, the ultraviolet curable resin 6 and the transparent film 7 are collectively referred to as a transparent film layer (light transmitting layer) 10). A protective sheet 9 is formed on the transparent film 7 via an adhesive layer 8 having a thickness of about 5 μm (hereinafter referred to as the adhesive layer 8).
A combination of the protective sheet 9 and the protective sheet 9 is referred to as a protective sheet layer 11. ).

In each of the examples described later, a Ge ₂ Sb ₂ Te ₅ thin film is used as the phase change recording layer 4, and a NiCr alloy thin film is used as the metal reflective layer 2. Further, an unstretched PC film made of a polycarbonate resin is used as the transparent film 7, a PC film of the same material is used as the protective sheet 9, and an acrylate sheet is used as the adhesive layer 8. When the transparent film layer (light transmissive layer) 10 and the protective sheet layer 11 are formed and laminated using the above-mentioned materials, respectively, the difference in refractive index between the two can be 0.2 or less. Even if an initialization device that irradiates a laser beam is used, good image formation can be maintained and the initialization can be reliably performed.

When the refractive index difference is larger than 0.2, multiple reflection of light occurs between the transparent film layer 10 and the protective sheet layer 11 at the time of incidence of laser light and reflection from the recording layer, and reproduction It is important to select each material so that the difference in refractive index is 0.2 or less, because it causes an increase in the noise level of the signal.

[0033]

EXAMPLES Examples of the present invention will be described with reference to the drawings in order to describe the above-described embodiments of the present invention in more detail. In this embodiment, a transparent resin substrate is used as the substrate 1, a NiCr alloy film is used as the metal reflection layer 2,
A case is described in which a ZnS.SiO ₂ film is used as the dielectric layers 3 and 5, a Ge ₂ Sb ₂ Te ₅ film is used as the phase change recording layer 4, and a PC film 7 using an ultraviolet curable resin 6 as an adhesive is used as the light transmission layer 10. To do. A protective sheet 9 is provided on the light transmitting layer 10 with an adhesive layer 8 in between, and a protective sheet layer 11 is formed. This protective sheet layer 11
Is not peeled off at the time of factory shipment, and is in the form of being stuck as it is.

An example of the manufacturing process of the phase change type optical disc medium according to this embodiment will be described below. The above-described layers are sequentially formed on the transparent resin substrate 1 in which the guide groove for guiding the laser beam is formed by the following procedure using an in-line type sputtering device.

First, the thickness of the NiCr alloy film is about 12
The 0 nm reflective film layer 2 is made of Ni containing 20 wt% of Cr.
Using a Cr alloy target, the distance between the target and the substrate is 15 cm, and the power density is 1.6 (W
/ Cm ² ), and the gas pressure is 0.08 (Pa). Next, a _first layer of ZnS / SiO ₂ film having a thickness of about 30 nm is formed.
For the dielectric layer 3, a ZnS.SiO ₂ target is used, and the distance between the target and the substrate is 15 c in an argon gas atmosphere.
m, power density 2.2 (W / cm ² ), gas pressure 0.1
The film is formed at (Pa). _Next, Ge 2 _Sb 2 Te ₅ phase change recording layer 4 having a thickness of about 15nm comprised of film, _Ge 2 Sb
₂ Te ₅ target was used, the distance between the target and the substrate was 15 cm, and the power density was 0.27 in an argon gas atmosphere.
(W / cm ² ) and the gas pressure is 1.0 (Pa).
Next, for the second dielectric layer 5 of ZnS.SiO ₂ film having a thickness of about 130 nm, a ZnS.SiO ₂ target was used, and the distance between the target and the substrate was 1 in an argon gas atmosphere.
5 cm, power density 2.2 (W / cm ² ), gas pressure 0.1.
The film is formed under the condition of 1 (Pa). In addition, the film formation time of each layer was appropriately adjusted to obtain a desired film thickness.

After the film formation, the PC film 7 having a thickness of about 95 μm was formed from the ultraviolet curable resin 6 having a thickness of about 5 μm, and the protective sheet 9 was further formed thereon by the adhesive layer 8 having a thickness of about 5 μm. . The cross-sectional view of the medium described above is the same as that shown in FIG. In this embodiment, as shown in FIG. 2, a pair of semicircular tags having a diameter of about 7 mm are arranged at the outer peripheral edge of the protective sheet 9 with the disk center as point symmetry. The following experiment was conducted in order to confirm the effect of the phase change optical disk medium having the above-described configuration.
The result will be described.

[Embodiment 1] In the above-mentioned medium, a protective sheet 9 having a thickness in the range of 440 μm to 550 μm and a thickness of 100 μ is formed through an adhesive layer 8 having a thickness of 5 μm.
A medium affixed to the PC film layer 10 having a thickness of m, that is, a medium having a total thickness of the PC film layer 10 and the protective sheet layer 11 of 545 μm to 655 μm was produced. This medium was initialized by injecting laser light from the protective sheet 9 side using a conventional device for initializing from the transparent substrate side having a thickness of 600 μm. Table 1 shows the conditions of the initialization optical system.
After initialization, the protective sheet layer 11 having each thickness was peeled off, and laser light was incident from the PC film layer 10 side having a thickness of 100 μm to record and reproduce a signal of 0.115 μm / bit. Table 2 shows the total film thickness of the PC film layer 10, the protective sheet 9, the adhesive layer 8 and the PC film layer 10, the protective sheet layer 9 and the adhesive layer 8 of each medium, the state of initialization and C / N.
Show the characteristics.

[0038]

[Table 1] Initializer optical system (for transparent substrate of 600 μm)

[0039]

[Table 2] Dimensions and initialization state and C / N of each medium
Characteristic

From Table 2, it can be seen that a medium having a total film thickness of the PC film layer 10 and the protective sheet layer 11 in the range of 575 μm to 625 μm can be favorably initialized and has a high C / N value. understood. This is because there is a margin of about ± 20 μm for the laser light to be incident on the conventional initialization device, and initialization is not properly performed in other ranges. Therefore, the PC film layer 10 and the protective sheet layer 1
The total film thickness of 1 is preferably in the range of 580 μm to 620 μm.

Next, in order to investigate the initialization state when the laser wavelength fluctuates, the total film thickness of the PC film layer 10 and the protective sheet layer 11 was fixed at 600 μm, and initialization was performed using different laser wavelengths. . Table 3 shows each laser wavelength, the initialization state, and the C / N characteristics.

[0042]

[Table 3] Each laser wavelength, initialization state and C / N characteristics

From Table 3, when the wavelength is 600 nm,
Since the coma aberration increases as described above, the initialization cannot be performed well, and the C / N characteristic is also poor. Also, the wavelength is 690 nm
Then, since the power density is lowered, the initial stage is not good, and the C / N characteristic is poor. Therefore, the laser wavelength used is preferably in the range of 630 nm to 660 nm.

Example 2 In the above-mentioned medium, the thickness of the protective sheet 9 is 1040 μm to 1150 μm.
In the range of 10 to 10 μm through the adhesive layer 8 having a thickness of 5 μm.
A medium adhered to the 0 μm PC film layer 10, that is, a medium in which the total thickness of the PC film layer 10 and the protective sheet layer 11 was 1145 μm to 1255 μm was produced. This medium was initialized by applying a laser beam from the protective sheet side using a conventional device for initializing the transparent substrate side having a thickness of 1200 μm. Table 4 shows the conditions of the initialization optical system. After initialization, the protective sheet layer 11 having each thickness was peeled off, and laser light was incident from the PC film layer 10 side having a thickness of 100 μm to record and reproduce a signal of 0.115 μm / bit. Table 5 shows the PC film layer 1 of each medium.
0, protective sheet 9, adhesive layer 8 and PC film layer 10
The total film thickness of the protective sheet 9 and the adhesive layer 8, the initialized state, and the C / N characteristics are shown.

[0045]

[Table 4] Initializer optical system (for 1200 μm transparent substrate)

[0046]

[Table 5] Dimensions and initialization state and C / N of each medium
Characteristic

From Table 5, it can be seen that the medium having a total film thickness of the PC film layer 10 and the protective sheet layer 11 in the range of 1175 μm to 1225 μm can be favorably initialized and has a high C / N value. I understood. This is because, as in the first embodiment, the thickness margin of the laser light incident on the conventional initialization device is about ± 20 μm, and the initialization is not properly performed in other ranges. Therefore, the total film thickness of the PC film layer 10 and the protective sheet layer 11 is 1180μ.
The range of m to 1220 μm is desirable.

The above medium No. 3 and No. After the medium of No. 8 was initialized, the protective sheet layer 11 was peeled off, and the number of defects such as foreign matter having a size of 15 μm or more attached to the surface of the PC film was measured by a defect inspection device. As a result, 15μ
The number of surface deposits of m or more is zero, and by covering the PC film layer 10 with the protective sheet layer 11,
It can be seen that foreign matter such as dust can be suppressed from adhering to the laser light incident surface.

Next, in order to investigate the initialization state when the laser wavelength fluctuates, the total film thickness of the PC film layer 10 and the protective sheet layer 11 was fixed to 1200 μm, and initialization was performed using different laser wavelengths. . Table 6 shows each laser wavelength, the initialization state, and the C / N characteristics.

[0050]

[Table 6] Each laser wavelength, initialization state and C / N characteristics

From Table 6, when the wavelength is 730 nm,
Since the coma aberration increases as described above, the initialization cannot be performed well, and the C / N characteristic is also poor. Also, the wavelength is 850 nm
In the case, since the power density is lowered, the initialization is not successful, and the C / N characteristic is poor. Therefore, the laser wavelength used is
The range of 760 nm to 820 nm is desirable.

[Comparative Example 1] Here, in the medium after the above film formation, the above-mentioned protective sheet layer 11 was not provided, and the PC film 7 having a thickness of 95 μm was formed via the ultraviolet curable resin 6 having a thickness of 5 μm. Prepared media. This medium,
Initialization was performed by entering laser light from the side of the PC film layer 10 having a thickness of 100 μm using a conventional device for performing initialization from the transparent substrate side having a thickness of 600 μm. The conditions of the initialization optical system are the same as those in Table 1.

As a result of the experiment, under the conditions of the initialization device and the optical system, the phase change recording layer was poorly focused, and there were many places where initialization failed. Also, the thickness of P of 100 μm
Laser light is incident from the C film layer 10 side to
The signal of 5 μm / bit was recorded and played back.
It was confirmed that the value was only about 25 dB, and the signal was not recorded normally.

[Comparative Example 2] Here, as in Comparative Example 1, in the medium after film formation, the above-mentioned protective sheet layer 11 was used.
A medium in which only the PC film layer 10 having a thickness of 100 μm was formed was prepared. This medium has a thickness of 100 μm
In order to initialize from the PC film layer 10 side of No. 3, the initialization was performed using an initialization device having a numerical aperture (NA) of 0.85. Table 7 shows the conditions of the initialization optical system.

[0055]

[Table 7] Initializer optical system (for 0.1 mm light transmission layer)

When the above-mentioned optical disk was initialized under the conditions shown in Table 7, it was possible to completely initialize it on the inner peripheral side of the disk. However, on the outer peripheral side, the surface of the disk was partially shaken so that the disk and the lens collided with each other, so that the entire surface of the disk could not be completely initialized. It should be noted that, when other disks are similarly initialized with the same configuration, it can be seen that the entire disk can be initialized, and some disks can be initialized. Such instability is due to the distance between the disc and the lens being 0.1 mm.
It is thought that the cause is extremely narrow as below.

From the above experimental results, the protective sheet layer 1 having an appropriate film thickness on the surface of the PC film layer (light transmitting layer) 10
By providing No. 1, it is possible to stably initialize the medium without using any initialization equipment having a new optical system, even if the conventional optical system is used.

It should be noted that, after using the medium in which the above initialization can be carried out on the entire surface, after initialization, defects such as foreign matter having a size of 15 μm or more adhered to the surface of the PC film 7 as in the second embodiment. The number was measured by the defect inspection device. As a result, 15μ
The number of surface deposits of m or more was confirmed to be about 46. Since some of these defects have a size of more than 150 μm, it can be seen that the protective sheet layer 11 is effective in suppressing the adhesion of defects.

Comparative Example 3 Here, in the above-described medium, a medium in which a protective sheet 9 having a thickness of 495 μm is attached to a PC film layer 10 having a thickness of 100 μm via an adhesive layer 8 having a thickness of 5 μm, that is, PC A medium having a total thickness of the film layer 10 and the protective sheet layer 11 of 600 μm was produced. The protective sheet 9 was provided with a tag for peeling off the protective sheet layer at only one location on the outer peripheral edge thereof.
FIG. 3 shows a plan view of this disc. The medium of this form was initialized by injecting laser light from the protective sheet layer 10 side using a conventional device for initializing from the transparent substrate side having a thickness of 600 μm. The conditions of the initialization optical system are the same as those in Table 1.

When the above-mentioned initialization of the optical disc was performed under the conditions shown in Table 1, the tracking became unstable during the rotation of the medium, and the initialization could not be normally performed. This is because the protective sheet peeling tag 13 is provided only at one location on the outer peripheral edge of the protective sheet 9, and the balance of the medium is lost.

Therefore, in order to keep the balance of the medium uniform, it is desirable that at least one pair of semicircular tags for peeling off the protective sheet are provided point-symmetrically with respect to the center of the disc. In addition, the above-mentioned semicircular tag is 5 mm in order that the protective sheet layer can be easily peeled off with a fingertip.
A size of about 10 mm is desirable. If it is smaller than 5 mm, it is difficult to grip with a fingertip, and if it is larger than 10 mm, the device itself becomes large in size in order to avoid contact of the tag with the outer wall of the initialization device, which is not preferable.

[Comparative Example 4] Here, in the medium described in the first example, a medium in which only the material of the protective sheet 9 was changed from a PC film to an acrylic material was produced. In this case, the PC film layer 10 and the protective sheet layer 11
The difference in refractive index between the two was 0.25. These media were initialized in the same manner as in the first embodiment, and the C / N value was measured. As a result, the initialized state was the same as in Table 2, but the C / N value was about 5 dB overall. Fell. From the above, the difference in refractive index between the PC film layer 10 and the protective sheet layer 11 is preferably 0.2 or less.

In each of the embodiments described above, the composition of the phase change recording film, the composition of the Al alloy reflective film, the material and the number of layers of the dielectric layer, the method of forming each film, etc. are limited to those described above. However, it can be appropriately selected according to the desired recording / reproducing characteristics and the intended use, and it has been confirmed that similar effects can be obtained with respect to these. Further, it goes without saying that the material and thickness of the substrate are not limited to the resin material and the thickness described above, and the same effect can be obtained even if appropriately selected.

Further, as the light transmission layer, the PC film layer 10 having a thickness of 100 μm was used in the above-mentioned embodiment, but instead of this, a film obtained by applying and curing an ultraviolet curing resin of about 100 μm is used, and a protective sheet is formed thereon. The same effect can be obtained when the layer 11 is adhered and the total thickness of the protective sheet layer 11 and the ultraviolet curable resin 6 is about 600 μm or about 1200 μm. Further, in each of the above-described embodiments, an example in which an in-line type film forming apparatus is used as a thin film forming apparatus forming a medium is shown.
The same effect can be obtained in a film-forming apparatus of a sheet type which processes one by one.

[0065]

As described above, according to the phase change optical disk medium and the method of initializing the medium of the present invention, the following effects can be obtained.

The first effect of the present invention is that the thickness is 100 μm.
In an optical disc medium for recording and reproducing information by making laser light incident from a thin light transmission layer side, a protective sheet layer is provided on the light transmission layer at the time of medium initialization, and laser light is passed through the protective sheet layer. By performing the initialization process while irradiating, it is possible to perform low-cost initialization, and further, a protective sheet layer is provided on the surface of a thin light transmission layer that is the incident surface of laser light until just before the user uses it. Therefore, it is possible to provide a high-quality optical disk medium in which foreign matters do not adhere.

The second effect of the present invention is to provide a pair of tags on the outer peripheral edge of the protective sheet in a point-symmetrical manner with respect to the center of the disc, without disturbing the balance of the medium and for use. This means that sometimes the protective sheet layer can be easily peeled off.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a structure of a phase change optical disc medium according to an embodiment of the present invention.

FIG. 2 is a plan view showing a structure of an optical disc medium according to an embodiment of the present invention.

FIG. 3 is a plan view showing the structure of a conventional optical disk medium (Comparative Example 3).

[Explanation of symbols]

1 Transparent resin board (PC board) 2 Metal reflective layer 3 First dielectric layer 4 Phase change recording layer 5 Second dielectric layer 6 UV curable resin layer 7 Transparent film (PC film) 8 Adhesive layer 9 Protective sheet 10 Transparent film layer (light transmission layer) 11 Protective sheet layer 12 disk center 13 tags 14 tags

Claims (12)

[Claims] 1. A substrate having at least a reflective layer, a first dielectric layer, a phase change recording layer, a second dielectric layer, and a light transmitting layer from the side of the substrate, and from the side of the light transmitting layer. In a phase-change type optical disc medium in which laser light is irradiated to initialize the phase-change recording layer and to record and reproduce information, the difference between the refractive index of the light-transmitting layer and the refractive index of the light-transmitting layer is 0. Two
With a peelable protective sheet layer having the following refractive index,
A phase-change optical disc, wherein the phase-change recording layer is initialized with the protective sheet layer attached, and information is recorded and reproduced with the protective sheet layer peeled off. Medium. 2. The initialization device having a laser light source in which the total thickness of the light transmitting layer and the protective sheet layer is set in the range of approximately 580 μm to 620 μm and the wavelength is in the range of approximately 630 nm to 660 nm. The phase change type optical disc medium according to claim 1, wherein the phase change recording layer is initialized. 3. An initialization device having a laser light source having a total film thickness of the light transmitting layer and the protective sheet layer set to a range of approximately 1180 μm to 1220 μm and a wavelength of approximately 760 nm to 820 nm. The phase change type optical disc medium according to claim 1, wherein the phase change recording layer is initialized. 4. The light transmitting layer comprises a resin adhesive layer and a PC film layer, and the protective sheet layer comprises an adhesive layer and a P layer.
4. The phase change type optical disk medium according to claim 1, wherein the phase change type optical disk medium comprises a C film layer. 5. At least a pair of protrusions are provided at the outer peripheral edge of the protective sheet layer at positions symmetrical with respect to the center of the optical disk medium, and the protective sheet layer is easily peeled off by the protrusions. The phase change type optical disk medium according to claim 1, wherein 6. Each of said pair of said projections has a diameter of approximately 5
The phase change type optical disk medium according to claim 5, wherein the phase change type optical disk medium is formed in a semicircular shape in the range of 10 mm to 10 mm. 7. A substrate having at least a reflective layer, a first dielectric layer, a phase change recording layer, a second dielectric layer and a light transmitting layer from the side of the substrate, and from the side of the light transmitting layer. A method for initializing a phase change type optical disc medium, which comprises irradiating a laser beam to initialize the phase change recording layer, further comprising providing a peelable protective sheet layer on the light transmitting layer, and applying the protective sheet layer. An initialization method for a phase-change type optical disc medium, wherein the phase-change recording layer is initialized in an installed state. 8. The method for initializing a phase-change optical disc medium according to claim 7, wherein the difference between the refractive index of the light transmitting layer and the refractive index of the protective sheet layer is 0.2 or less. 9. An initialization device, wherein the total thickness of the light transmitting layer and the protective sheet layer is set in a range of approximately 580 μm to 620 μm and a laser light source having a wavelength in a range of approximately 630 nm to 660 nm is used. 9. The method of initializing a phase change type optical disc medium according to claim 7, wherein the phase change recording layer is initialized. 10. An initialization device, wherein the total thickness of the light transmitting layer and the protective sheet layer is set in a range of approximately 1180 μm to 1220 μm and a laser light source having a wavelength in a range of approximately 760 nm to 820 nm is used. 9. The method of initializing a phase change type optical disc medium according to claim 7, wherein the phase change recording layer is initialized. 11. At least a pair of projecting portions are provided at a position of point symmetry with respect to the center of the optical disk medium at an outer peripheral end portion of the protective sheet layer, and after the initialization is completed, the projecting portions are used as handles for the protection. 11. The method for initializing a phase change type optical disc medium according to claim 7, wherein the sheet layer is peeled off. 12. The initialization of a phase change type optical disk medium according to claim 11, wherein each of the pair of protrusions is formed in a semicircular shape having a diameter in the range of approximately 5 mm to 10 mm. Method.