JPH06309667A - Disk-shaped recording medium - Google Patents

Abstract

PURPOSE:To further simplify the structure of an optical system by making it possible to increase the recording capacity of a reproduction-only area without decreasing the recording capacity of a recordable area. CONSTITUTION:Laminated films 3 including a phase transition material film 2 which can be crystallized after melting, are formed continuously over the reproduction-only area Zr, recordable area Zw and TOC area Zt of a transparent substrate 1 in an optical disk D, which is spatially separated to the reproduction- only area Zr, the recordable area Zw and the TOC area Zt, having phase pits P formed on the surface corresponding to the reproduction-only area Zr and TOC area Zt of the transparent substrate 1. The phase transition material film 2 becomes to a liquid phase partially in the melt crystallized region within the scanning spot of reading-out light and the light reflectivity changes at the time of reading out the information signals for the reproduction-only area Zr. The film restores the crystalline state after the reading out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped recording medium in which an information signal is reproduced or recorded by irradiating a laser beam.

[0002]

2. Description of the Related Art For example, an optical disc such as a digital audio disc, a so-called compact disc, or a video disc, has an aluminum reflection film formed on a transparent substrate on which phase pits are formed in advance in accordance with an information signal. It is configured by forming a protective film or the like on the film.

Recently, an optical disc has been proposed which is spatially separated into a read-only area and a recordable area. This optical disc is formed by forming the phase pits only on the surface of the transparent substrate corresponding to the reproduction-only area.

In the above-mentioned optical disc, the resolution of signal reproduction for the phase pits is almost determined by the wavelength λ of the light source of the reproduction optical system and the numerical aperture NA of the objective lens, and the period of the phase pits formed on the transparent substrate is Good reproduction signals can be obtained when the diffraction limit (λ / 2NA) or more is satisfied.

Therefore, when high density recording (formation) of phase pits is attempted in the above optical disc, for example, the wavelength λ of a semiconductor laser, which is a light source of a reproducing optical system, is used.
Can be shortened and the numerical aperture NA of the objective lens can be increased.

[0006]

By the way, in an optical disc spatially separated into a read-only area and a recordable area, each recording capacity is at most half. In such an optical disc, if a video signal relating to a background image displayed on a monitor is to be recorded as a phase pit in a reproduction-only area, the recording capacity may be insufficient.

Therefore, it is conceivable to set the recording capacity of the read-only area to a large value, but in this case, the recording capacity of the recordable area becomes small, and the amount of recordable data that can be handled is greatly limited. Occurs.

As another method, for example, by reducing the formation pitch of the phase pits in the reproduction-only area,
A method is conceivable in which the recording capacity of the read-only area is made high and the data is read by a short wavelength laser.

However, in this case, as a short wavelength laser,
It is conceivable to use short-wavelength lasers such as green and blue, but these short-wavelength lasers do not have the output enough to achieve signal recording, and currently high-speed modulation cannot be realized. . Therefore, a laser light source for signal reproduction (short wavelength laser) for the reproduction-only area and a light source for signal recording / reproduction (normally used laser) for the recordable area are required, and the structure of the optical system becomes complicated. There's a problem.

As described above, in the conventional optical disc, the recording capacity of the read-only area cannot be increased without reducing the recording capacity of the recordable area, and a large amount of data such as a video signal is recorded in the read-only area. Under the present circumstances, it is not possible to record (form) phase pits as phase pits, and there is a problem that the information processing using an optical disk as a recording medium cannot be made multifunctional and the usage is limited.

The present invention has been made in view of the above problems, and an object of the present invention is to increase the recording capacity of a read-only area without reducing the recording capacity of a recordable area. An object of the present invention is to provide a disk-shaped recording medium that does not require a complicated structure of the optical system and can use the conventional optical system as it is.

[0012]

According to the present invention, in a disk-shaped recording medium D having phase pits P formed on a transparent substrate 1, a read-only area Zr and a recordable area Z are spatially arranged.
w, and the phase pits P are formed on the surface corresponding to the reproduction-only area Zr of the transparent substrate 1, and continuously over the recordable area Zw from the reproduction-only area Zr of the transparent substrate 1.
After melting, the phase change material film 2 that can be crystallized is formed, and at least when the information signal is read to the read-only area Zr, the phase change material film 2 is partially melted and crystallized in the scanning spot SP of the reading light L. A liquid phase is formed in the region C, the light reflectance is changed, and after reading, the crystal state is restored. In this case, the phase change material film 2 can be formed of a chalcogenite-based material.

[0013]

In general, the phase change material film undergoes the following state changes according to the output of the reading light L (the output and the pulse width of the writing light). That is, the reading light L
Even if the phase change material film 2 is not melted and is in a crystallized state while maintaining the initial state (hereinafter, referred to as a non-melted state), the phase change material film 2 is melted while the reading light L is irradiated. When the liquid crystal is in a liquid phase and is in a liquid phase, but the read light L passes through and then returns to a crystallized state when solidified by cooling (hereinafter, referred to as a melt crystallized state), the read light There is a case in which, when L is passed and then changed to a solid phase by cooling, it changes to an amorphous state, that is, an amorphous state (hereinafter, referred to as a molten amorphized state).

Here, the range (area) of the output of the reading light L corresponding to the above-mentioned three kinds of state changes is defined as follows. First, the output range of the reading light L in which the phase change material film 2 is in a non-melting state is the non-melting region A, and the output range of the reading light L in which the phase change material film 2 is in the melting and crystallization state is the melting and crystallization region. The range of the output of the read light L in which B and the phase change material film 2 are in the molten amorphous state is defined as the molten crystallization region C.

In the disk-shaped recording medium D according to the present invention, the phase change material film 2 which can be crystallized after melting is continuously formed from the read-only area Zr of the transparent substrate 1 to the recordable area Zw. Therefore, for example, the reading of the information signal from the reproduction-only area Zr is performed as follows.

First, the output of the read light L to the reproduction-only area Zr is set in the range of the above-mentioned melt crystallization area B, for example. Then, the light intensity of the reading light L within the scanning spot SP has an intensity distribution substantially conforming to the Gaussian distribution as shown in FIG. 6 (see the broken line A). Further, the temperature distribution of the phase change material film 2 due to the irradiation of the reading light L has a peak at a position delayed from the center of the scanning spot SP by a distance corresponding to the scanning speed of the reading light L in the scanning direction. Distribution (see solid line B).

Now, it is assumed that the pitch between the phase pits P is so narrow that two phase pits P are included in the scanning spot SP. Further, the phase pit P that first enters the scanned spot SP is defined as a head pit Pa, and the phase pit P that next enters is defined as a next-stage pit Pb. Then, when the scanning spot SP moves on the leading pit Pa,
The temperature of the phase change material film 2 on the leading pit Pa gradually rises, but the leading pit Pa is optically read out before the temperature at which the phase change material film 2 becomes liquid phase is reached.

After that, when the scanning spot SP is applied to the next stage pit Pb by the scanning, the temperature of the phase change material film 2 on the next stage pit Pb rises. However, the temperature rise does not reach the phase of the phase change material film 2 on the next-stage pit Pb becoming liquid phase. On the other hand, since the phase change material film 2 on the leading pit Pa in the same scanning spot SP is continuously irradiated with light by the scanning spot SP, its temperature further rises, and the phase change material film 2 is It will become a liquid phase.

Therefore, in this case, for example, the phase change material film 2 on the leading pit Pa is lowered in light reflectivity due to its liquid phase, and optical reading of the leading pit Pa by the scanning spot SP becomes impossible. Optical reading by this scanning spot SP is possible only for the next-stage pit Pb.

That is, in reading the information signal from the reproduction-only area Zr, the temperature distribution in the scanning spot SP on the disk-shaped recording medium D due to the relative movement of the read light L with respect to the disk-shaped recording medium D is used. Then, the liquid phase state is partially generated in the phase change material film 2 in the high temperature region Px generated in the spot SP, thereby lowering the light reflectance of the portion Px, for example, the liquid state portion Px. Optical reading is disabled for the phase pit P inside.

That is, a region Px for optically extinguishing the phase pit P is formed in a part of the scanning spot SP,
Equivalently, the area of the effective area Pz of the scanning spot SP is reduced. As a result, the arrangement pitch of the phase pits P can be made smaller than the diameter of the scanning spot SP, high density formation of the phase pits P can be achieved, and the read-only area Z can be achieved.
The recording capacity of r can be greatly increased. In addition,
After the scanning spot SP has passed, the phase change material film 2 on the leading pit Pa and the next pit Pb returns to the crystallized state by cooling after passing.

On the other hand, writing of the information signal in the recordable area Zw is performed as follows. That is, as described above, the phase change material film 2 changes to the non-melting state, the melting crystallization state, and the melting amorphization state depending on the output of the writing light L and the pulse width. Therefore, in this writing operation, writing is performed with the output and pulse width of the writing light L set in the range of the molten amorphized region C in the above example. At this time, the portion irradiated with the writing light L set in the range of the molten amorphized region C is amorphized,
The pit information is optically newly written.

Next, when reading the information signal from the recordable area Zw, the output of the reading light L is set to the range of the non-melting area A in the above example, and the reading is performed. To do. In this read operation, the recorded pit information is optically changed due to the difference between the light reflection in the crystallized portion and the light reflection in the amorphized portion (pit information) of the phase change material film 2 on the recordable area Zw. Read to. In this case, since the output of the reading light is set in the range of the non-melting region, the amorphized portion is not erased, that is, crystallized, at the time of reading.

As described above, in the disc-shaped recording medium according to the present invention, the phase change material film 2 extends from the read-only area Zr where the phase pits P are formed to the recordable area Zw.
Therefore, the recording capacity of the read-only area Zr can be increased without reducing the recording capacity of the recordable area Zw. Further, since the light source 15 that is the source of the read light L and the write light L can be configured by one light source as in the conventional case, it is not necessary to complicate the structure of the optical system, and the conventional optical system can be used as it is. Can be used.

[0025]

1 to 6 show an embodiment (hereinafter, simply referred to as an optical disk according to an embodiment) in which the disc-shaped recording medium according to the present invention is applied to an optical disk of a type for optically accessing an information signal. Will be described with reference to.

As shown in FIG. 1, the optical disc D according to this embodiment has a reproduction-only area Zr spatially allocated on the outer peripheral side and a recordable area Zw on the inner peripheral side. The TOC area Zt is assigned to the side.

Structurally, as shown in FIG. 2, after melting and crystallizing on a transparent substrate 1 made of a disk-shaped glass substrate or a polycarbonate substrate having phase pits P partially formed on one main surface, A laminated film 3 including a phase-change material film 2 that can be turned is formed and configured.

More specifically, the phase pits P are formed on the surface of the transparent substrate 1 corresponding to the reproduction-only area Zr and the surface corresponding to the TOC area Zt, and the phase-pits P are continuously formed over the reproduction-only area Zr, the recordable area Zw, and the TOC area Zt. Specifically, the laminated film 3 including the phase change material film 2 is formed.

The laminated film 3 including the phase change material film 2 comprises a first dielectric film 4, a phase change material film 2 and a phase change material film 2 in this order from the transparent substrate side.
The second dielectric film 5, the light reflecting film 6 and the third dielectric film 7 are sequentially laminated and configured, and the optical disc D is formed by the first, second and third dielectric films 4, 5 and 7. The optical characteristics, such as the light reflectance, are set. A guide groove (not shown) for tracking control is formed along the recording track on the surface of the transparent substrate 1 corresponding to the recordable area Zw.

The phase change material film 2 is made of Sb ₂ Se ₃ , Sb.
₂ Te ₃ , Se, Te, BiTe, BiSe, In-S
e, In-Sb-Te, In-SbSe, In-Se-
It is at least one selected from Tl, Ge-Te-Sb, and Ge-Te. In this example, as the phase change material film 2, Ge-Te-Sb having a thickness of 20 nm was deposited.

The above-mentioned first, second and third dielectric films 4, 5
And 7 are AlN, Si ₃ N ₄ , SiO ₂ , Al ₂ O ₃ and Z.
It is a film selected from nS and MgF ₂ , and in this embodiment, as the first dielectric film 4, ZnS having a thickness of 100 nm is used.
/ SiO ₂ is deposited and formed as the second dielectric film 5, a ZnS / SiO ₂ with a thickness of 70nm was deposited and formed, as the third dielectric film 7, the thickness of 400 nm ZnS / SiO ₂ Adhered and formed.

On the other hand, the phase pit P is the reproduction-only area Z.
Track pitch is 1.6 for both r and TOC area Zt
μm, pit depth is about 120 nm, pit length is 0.3 μm
It is formed under the setting condition of m. In addition, the recordable area Z
The pit length of the recording pit formed on the w phase change film is
It is 0.83 μm, and the reproduction-only areas Zr and TO
It is set larger than the pit length of the phase pit P in the C area Zt.

Here, when compared with the spot diameter of the light beam which is the reading light, the read-only areas Zr and TOC
In area Zt, there are 2 phase pits P in the spot.
The recording area is formed with a high density so that one recording pit is included in the spot. Therefore, the optical disc D has a significantly increased recording capacity in the read-only area Zr.

Next, a schematic structure of a disc recording / reproducing apparatus for recording / reproducing information signals on / from the optical disc D according to this embodiment will be described with reference to FIGS.

This recording / reproducing apparatus, as shown in FIG.
A spindle motor 11 for rotating the optical disc D,
It has an optical head 12 that optically records and reproduces information signals on and from the optical disc D.

The spindle motor 11 has its rotating shaft 11
A turntable 13 to which the central portion of the optical disc D is mounted is provided at the tip of a. The optical head 12 is installed at a position opposite to the position where the spindle motor 11 is installed and the optical disc D mounted on the turntable 13 is separated. For example, a known slide mechanism (not shown) mainly including a linear motor and a guide shaft is used. , Optical disc D
It is supposed to be movable in the radial direction. The slide mechanism is also provided with a slide encoder 14 that electrically detects the position of the optical head 12.

The optical head 12 is provided with an objective lens 16 for focusing the light beam L from the laser light source 15 on the optical disc D. The objective lens 16 is slightly moved in the contact / separation direction of the optical disc D and the radial direction of the optical disc D by the two-dimensional actuator 17.
Although not shown, the two-dimensional actuator 17 has a magnetic circuit including, for example, a focus coil, a tracking coil and a magnet.

The circuit system of this disk recording / reproducing apparatus has at least a motor drive control circuit 21, a signal selection circuit 22, a demodulation circuit 23, a laser drive control circuit 24, a focus servo circuit 25, a tracking servo circuit 26, and various types thereof. System controller 27 that controls the circuit
Is configured.

The motor drive control circuit 21 drives the spindle motor 11 based on the drive control signal Sm from the system controller 27 to rotate the optical disc D in the CLV (constant linear velocity) system or the CAV (constant angular velocity) system. It is a circuit to make.

The signal selection circuit 22 is a circuit for selecting the reproduction information signal Sr including address information, the focusing error signal Sf and the tracking error signal St from the detection signal S from the light detection means 28 of the optical head 12. Of the signals selected by the signal selection circuit 22, the reproduction information signal Sr is supplied to the demodulation circuit 23, the focusing error signal Sf is supplied to the focus servo circuit 25, and the tracking error signal St is supplied to the tracking servo circuit 2.
6 respectively.

The demodulation circuit 23 converts the reproduction information signal Sr from the signal selection circuit 22 into digital data, decodes the encoding processing such as error correction added to the converted digital data, and reproduces it. Information data Dr
Is a circuit that outputs as. The reproduction information data Dr from this demodulation circuit 23 is supplied to the system controller 27, and is also connected to this recording / reproducing apparatus via an interface circuit 41 and an interface bus (for example, a SCSI bus) 42 (not shown). ) Is supplied to.

The laser drive control circuit 24 drives the laser light source 15 installed in the optical head 12 based on the drive control signal Sc from the system controller 27, and based on the signal level of the drive control signal Sc and the like. And a circuit for controlling the output (power) and pulse width of the light beam L emitted from the laser light source 15.

The focus servo circuit 25 drives the two-dimensional actuator 17 of the optical head 12 based on the focusing error signal Sf from the signal selection circuit 22.
It is a circuit that controls and moves the objective lens 16 in the contact and separation direction of the optical disc D to adjust its focus.
The tracking servo circuit 26, based on the tracking error signal St from the signal selection circuit 22,
This is a circuit for driving and controlling the two-dimensional actuator 17 to move the objective lens 16 in the radial direction of the optical disc D to perform tracking adjustment thereof.

The system controller 27 has a built-in memory therein, and this memory has information (hereinafter, simply referred to as area) indicating the range of the read-only area Zr and the recordable area Zw recorded in the TOC area Zt. An array variable area for storing range information) is logically allocated.

That is, the system controller 27 stores the area range information in the array variable area of the reproduced data from the reproduced TOC area Zt, and the reproduction-only area Zr or the recordable area Zw by the optical head 12 is stored.
At the time of accessing, the position detection data Dp of the optical head 12 from the slide encoder 14 is compared with the area range information to determine in which area the optical head 12 is currently located.

As shown in the enlarged view of FIG. 4, the optical head 12 includes the laser light source 15 made of a semiconductor laser which is a light source of the light beam L, the objective lens 16 for focusing the light beam L on the optical disc D, and The entire optical system including the light detection means 73 for detecting the return light beam Lr reflected on the optical disc D and converting it into an electric signal (detection signal S) of a current level or a voltage level according to the amount of light is It is configured as one unit, and is moved along the radial direction of the optical disc D by a known moving means (for example, a linear motor or the like).

In this optical system, in addition to the above optical components,
The collimator lens 31 that collimates the light beam L emitted from the laser light source 15 and the light beam L is at least three.
The phase diffraction grating 32 for separating the light beam component of the book, the polarization beam splitter 33 for separating the light beam L from the laser light source 15 and the return light beam Lr from the optical disc D, and 1 /
An optical isolator 35 including a four-wave plate 34 is provided, and the focal length of the return light beam Lr is adjusted between the polarization beam splitter 33 and the light detecting means 28 in the optical path of the return light beam Lr. The multi-lens 36 including a cylindrical lens and a concave lens for generating astigmatism, and the return light beam Lr are detected by the light detecting means 2.
And an image forming lens 37 that converges on the upper surface.

Next, the operation of the optical head 12 will be described. First, the light beam L emitted from the laser light source 15 is collimated by the collimator lens 31 and is incident on the phase diffraction grating 32. The light beam L separated into at least three luminous flux components (0th order light, + 1st order light and −1st order light) by the phase diffraction grating 32 is linearly polarized with only the P component by the polarization beam splitter 33, that is, P Only polarized light passes through.

The P-polarized light that has passed through the polarization beam splitter 33 passes through the quarter-wave plate 34,
The phase difference becomes π / 2, and, for example, clockwise circularly polarized light.
The clockwise circularly polarized light focused on the optical disc D by the objective lens 16 is reflected by the surface of the optical disc D to become counterclockwise circularly polarized light whose rotation direction is opposite.

At this time, of the three light beams L (circularly polarized light), the central one (0th order light) illuminates the center of the recording track on the optical disc D, and the remaining two light beams L ( ± 1
Next light) illuminates the guide groove in the recordable area Zw. Therefore, when the irradiated position is the reproduction-only area Zr, the light beam L irradiating the center of the recording track is subjected to modulation corresponding to the phase pits P formed along the recording track. When the irradiation position of the light beam L is the recordable area Zw, the light beam L applied to the guide groove is subjected to modulation corresponding to the edge of the guide groove.

The counterclockwise circularly polarized light which has been subjected to the above-mentioned modulation passes through the objective lens 16 again and the quarter wavelength plate 34. In the quarter-wave plate 34, since the phase difference is further π / 2, the incident left-handed circularly polarized light becomes linearly polarized light having only the S component, that is, S polarized light. This S-polarized light is reflected by the boundary surface 33 a of the polarization beam splitter 33.

Boundary 3 of this polarization beam splitter 33
The three return light beams Lr reflected by 3 a pass through the multi-lens 36 and the imaging lens 37, and the photo-detecting means 28.
Is incident on. In the photo-detecting means 28, the three incident return light beams Lr are photoelectrically converted into conversion signals S, which are supplied to the signal selection circuit 22 shown in FIG.

By the way, the phase change material film 2 generally undergoes the following state changes according to the output of the irradiated light beam L and its pulse width (see FIG. 5). That is, even if the phase change material film 2 is not melted but is in a crystallized state while maintaining the initial state even when irradiated with the light beam L (hereinafter, referred to as a non-melted state), the phase change material film 2 is irradiated with the light beam L. While it is in a liquid phase while being melted while it is in a liquid phase, it returns to a crystallization state when it is solidified by cooling after passing through the light beam L (hereinafter referred to as a melt crystallization state). ), And after passing through the light beam L, when it changes to a solid phase by cooling, it may change to an amorphous state, that is, an amorphous state (hereinafter, referred to as a molten amorphized state).

Here, for convenience of explanation, the range (area) of the output and pulse width of the light beam L corresponding to the above-mentioned three kinds of state changes is defined as follows. First, the range of the output and pulse width of the light beam L in which the phase change material film 2 is in the non-melting state is the non-melting region A, and the output of the light beam L in which the phase change material film 2 is in the melt crystallization state and the pulse width are The range is defined as a melt crystallization region B, and the range of the output and pulse width of the light beam L in which the phase change material film 2 is in a melt amorphized state is defined as a melt crystallization region C.

Normally, in data access to a recording medium, there are two behaviors of reading data and writing data. For this optical disc D, data is written to the TOC area Zt, the read-only area Zr and the recordable area Zw. Read-out is performed and data writing is
It is performed only for the recordable area Zw.

Concretely, the case where the above-mentioned disc recording / reproducing apparatus records / reproduces data on / from the optical disc D will be described.

First, the turntable 13 of the optical disc D
Based on the completion of mounting to the system controller 27
Outputs a drive control signal Sm to the motor drive control circuit 21. The motor drive control circuit 21 drives the spindle motor 11 to rotate by the CAV method or the CLV method based on the drive control signal Sm from the system controller 27. In this embodiment, the optical disc D is rotated by the CLV method, and its linear velocity is set to 7 m / s.

Next, the system controller 27 supplies a drive signal to a known slide mechanism (not shown) for the optical head 12. This slide mechanism moves the optical head 12 in the radial direction of the optical disc D based on the drive signal from the system controller 27. Then, the optical head 12 is moved to the innermost side of the optical disc D, that is, the TOC area Zt.
And the TOC data including the area range information is read from the TOC area Zt. The TOC data including the read area range information is stored in a predetermined array variable area of the memory incorporated in the system controller 27.

The specific reading of the TOC data will be collectively described in the following description of reading the data from the reproduction-only area Zr.

That is, regarding the reading of data from the TOC area Zt and the read-only area Zr of the optical disc D, the output of the light beam L is set in the range of the melt crystallization region B, and the optical disc D is continuously irradiated. Thus, the pit information on the TOC area Zt and the reproduction-only area Zr is read. The output of the light beam L is set based on the drive control signal Sc supplied from the system controller 27 to the laser drive control circuit 24.

That is, in the system controller 27, based on the position detection data Dp supplied from the slide encoder 14 and the area range information stored in the memory, the irradiation position of the light beam L is currently the reproduction-only area Zr. If the system controller 27 determines that the drive control signal Sc has a signal level indicating the range of the melt crystallization region B, the system controller 27 instructs the laser drive control circuit 24.
Is output. The laser drive control circuit 24 drives and controls the laser light source 15 according to the signal level of the drive control signal Sc from the system controller 27. In this case, the output of the light beam L is set within the range of the melt crystallization region B (output = 10 mW in this embodiment). Since the light beam L is continuously irradiated in this reading operation, the pulse width that determines the range of the melt crystallization region B is obtained by converting the spot diameter / linear velocity of the light beam L. You can

At this time, the scanning spot SP of the light beam L
The light intensity inside has an intensity distribution substantially conforming to a Gaussian distribution, as indicated by the broken line A in FIG. In addition, the light beam L
As shown by the solid line B, the temperature distribution of the phase-change material film 2 due to the irradiation of 1) has a peak at a position delayed from the center of the scanning spot SP by a distance corresponding to the scanning speed of the light beam L in the scanning direction. It will have a distribution.

Now, it is assumed that the pitch between the phase pits P is so narrow that two phase pits P are included in the scanning spot SP. A phase pit that first enters the scanned spot SP is defined as a head pit Pa, and a phase pit that next enters is defined as a next-stage pit Pb. Then, when the scanning spot SP moves on the head pit Pa, the temperature of the phase change material film 2 on the head pit Pa gradually rises, but before the temperature of the phase change material film becomes liquid phase is reached. The leading pit Pa is optically read.

After that, when the scanning spot SP is applied to the next-stage pit Pb by the scanning, the temperature of the phase change material film 2 on the next-stage pit Pb rises. However, the temperature rise does not reach the phase of the phase change material film 2 on the next-stage pit Pb becoming liquid phase. On the other hand, since the phase change material film 2 on the leading pit Pa in the same scanning spot SP continues to be irradiated with light by the scanning spot SP, its temperature further rises above the melting temperature MT and its phase change occurs. The material film 2 becomes a liquid phase.

Therefore, in this case, for example, the phase change material film 2 on the leading pit Pa has a lowered liquid reflectivity due to its liquid phase, and it becomes impossible to optically read the leading pit Pa by the scanning spot SP. Optical reading by this scanning spot SP is possible only for the next-stage pit Pb.

That is, when reading data from the TOC area Zt and the read-only area Zr, the temperature distribution within the scanning spot SP on the optical disc D due to the relative movement of the light beam L with respect to the optical disc D is utilized. A liquid phase state is partially generated in the phase change material film 2 in the high temperature region Px generated in the scanning spot SP, whereby, for example, the light reflectance of that portion is lowered, and the liquid state is in the liquid state portion Px, for example. Optical reading is disabled for the phase pit Pa.

That is, a region Px for optically extinguishing the phase pit P is formed in a part of the scanning spot SP,
Equivalently, the area of the effective area Pz of the scanning spot SP is reduced. As a result, the array pitch of the phase pits P can be made smaller than the diameter of the scanning spot SP, and even if the phase pits P are formed with high density, the numerical aperture N of the lens system is N.
A, the reading can be performed with high resolution without being limited by the wavelength λ of the light beam, and the recording capacity of the read-only area can be substantially increased. After passing through the scanning spot SP, the phase change material film 2 on the leading pit Pa and the next pit Pb returns to the crystallized state by cooling after passing.

In reading data from the TOC area Zt and the read-only area Zr, phase pits (pit length = 0 when the output of the light beam L is 10 mW and the linear velocity is 7 m / S as described above). .3μ
C / N when reproducing m) is 51 dB, and high C / N
The phase pit can be optically read out with N (S / N).

Next, the case where data is written in the recordable area Zw will be described. This writing operation is performed by supplying the recording data sent from a computer or the like connected to the interface bus 64 to the system controller 27.

As described above, the phase change material film 2 changes to the non-melting state, the melting crystallization state and the melting amorphization state depending on the output of the light beam L and the pulse width. Therefore, in this writing operation, the output of the light beam L and the pulse width are set within the range of the molten amorphized region C, and the data (pit) is written. The output setting and the pulse width setting of the light beam L are performed as follows.

That is, the system controller 27 outputs the drive control signal Sc to the laser drive control circuit 24, which has a signal level indicating the range of the molten amorphous region C and is on / off controlled according to the recording data. To do. The laser drive control circuit Sc drives / controls the laser light source 15 according to the signal level of the drive control signal Sc from the system controller 27 and its on / off timing. In this case, the output of the light beam L is set in the range of the molten amorphized region C (output = 10 mW, pulse width = 118 ns (duty 50%) in this embodiment),
A pulse laser (pulse width = 118n) that is partially irradiated by on / off control by a laser drive control circuit
s) is output.

Then, as described above, by partially irradiating the light beam L set in the range of the molten amorphized region C, the irradiated portion becomes amorphous,
The pit information is optically newly written. The pit length of the recording pit at this time is 0.83 μm.

Next, when reading data from the recordable area Zw, the output of the light beam L is set within the range of the non-melting area A and reading is performed. That is,
In the system controller 27, based on the position detection data Dp supplied from the slide encoder 14 and the area range information stored in the memory of the system controller 27, the irradiation position of the light beam L is currently in the recordable area Zw. When it is determined that the laser drive control circuit 24 is present, the system controller 27
A drive control signal S having a signal level indicating the range of the non-melting region A
Output c.

The laser drive control circuit 24 drives and controls the laser light source 15 according to the signal level of the drive control signal Sc from the system controller 27. In this case, the output of the light beam L is set within the range of the non-melting region A (output = 1 mW in this embodiment). Since the light beam L is continuously irradiated also in the read operation for the recordable area Zw, the pulse width that determines the range of the non-melting area A is converted by the spot diameter / linear velocity of the light beam L. You can ask for it.

The recorded pit information is optically converted by the difference between the light reflection in the crystallized portion of the phase change material film 2 on the recordable area Zw and the light reflection in the amorphized portion (pit information). read out. In this case, since the output of the light beam L is set within the range of the non-melting region A, the amorphized portion (pit information) at the time of reading
Is not erased, that is, is not crystallized.

In reading data from the recordable area Zw, when the output of the light beam L is 1 mW and the linear velocity is 7 m / S as described above, recording pits (pit length = 0.83 μm) are formed. C when played
/ N is 45 dB, and the recording pit can be optically read with a high C / N (S / N).

As described above, in the optical disc according to this embodiment, the TOC area Zt in which the phase pit P is formed is formed.
Since the phase change material film 2 is formed from the read-only area Zr to the recordable area Zw, the read-only area Zw can be formed without reducing the recording capacity of the recordable area Zw.
The recording capacity of r can be increased.

Data can be read and recorded in the TOC area Zt and the reproduction-only area Zr.
Since the output of the light beam L only needs to be varied in reading data from and writing data to the recordable area Zw, the laser light source 15 that is the generation source of the light beam L is composed of one light source as in the conventional case. can do. As a result, there is an advantage that the conventional optical system can be used as it is without having to complicate the structure of the optical system.

Further, since the laminated film 3 including the phase change material film 2 is formed from the read-only area Zr (and the TOC area Zt) where the phase pits P are formed in advance to the recordable area Zw, the read-only area can be formed. The optical disk D in which Zr and the recordable area Zw are formed on the same plane can be manufactured by a simple manufacturing process, which is advantageous in manufacturing cost.

The phase change material film 2 in the above example is formed by the light beam L
Although the film having the characteristic that the light reflectance thereof is lowered by the temperature rise due to the irradiation of is used, a phase change material film having the opposite characteristic may be used.

Further, in the above example, the output of the light beam emitted from the laser light source is set in the melting and crystallization area B or the non-melting area A, and the optical disk is continuously irradiated, so that the information signal for the optical disk is changed. Although the reading is performed, in addition, by setting the output and pulse width of the light beam in the melting crystallization area B or the non-melting area A and irradiating the optical disk with pulses, the reading of the information signal from the optical disk is performed. May be performed.

[0082]

As described above, according to the disc-shaped recording medium of the present invention, a disc-shaped recording medium having phase pits formed on a transparent substrate is spatially divided into a read-only area and a recordable area. Separate, form phase pits on the surface corresponding to the reproduction-only area of the transparent substrate, continuously melt from the reproduction-only area of the transparent substrate to the recordable area, after melting,
When a phase-change material film that can be crystallized is formed, and at least when the information signal is read to the read-only area, the phase-change material film is partially liquefied in the melting crystallization region within the scanning spot of the reading light, Since the reflectivity changes and it returns to the crystalline state after reading, the recording capacity of the read-only area can be increased without reducing the recording capacity of the recordable area, and the structure of the optical system is complicated. Therefore, the conventional optical system can be used as it is.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment (hereinafter simply referred to as an optical disk according to an embodiment) in which a disc-shaped recording medium according to the present invention is applied to an optical disk of a type for optically accessing an information signal.

FIG. 2 is a cross-sectional view showing an optical disc in the example.

FIG. 3 is a block diagram showing a schematic configuration of a disc recording / reproducing apparatus for recording / reproducing information signals on / from the optical disc according to the present embodiment.

FIG. 4 is a configuration diagram showing an optical system of an optical head for recording / reproducing information signals on / from the optical disc according to the present embodiment.

FIG. 5 is a characteristic diagram showing a state change (phase change state) of the phase change material film corresponding to the output of the light beam and the pulse width.

FIG. 6 is a characteristic diagram showing light intensity and temperature distribution of a scanning spot of a light beam.

[Explanation of symbols]

 D Optical disk Zr Reproduction-only area Zw Recordable area Zt TOC area 1 Transparent substrate 2 Phase change material film 3 Laminated film 4 First dielectric film 5 Second dielectric film 6 Light reflection film 7 Third dielectric film P Phase pit 11 Spindle motor 12 Optical head 13 Turntable 14 Slide encoder 15 Laser light source 16 Objective lens 17 Two-dimensional actuator 21 Motor drive control circuit 22 Signal selection circuit 23 Demodulation circuit 24 Laser drive control circuit 27 System controller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Kasami 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (2)

[Claims] 1. A disk-shaped recording medium having phase pits formed on a transparent substrate, which is spatially divided into a read-only area and a recordable area, and the transparent substrate is provided on a surface corresponding to the read-only area. Phase pits are formed, and a phase change material film that can be crystallized after melting is formed continuously from the read-only area of the transparent substrate to the recordable area, and at least when the information signal is read to the read-only area. A disk characterized in that the phase-change material film is partly liquid-phased in the melting and crystallization region within the scanning spot of the reading light, the light reflectance changes, and returns to the crystalline state after reading. Recording medium. 2. The disc-shaped recording medium according to claim 1, wherein the phase change material film is formed of a chalcogenite-based material.