JPH09212918A - INFORMATION RECORDING MEDIUM, ITS INITIALIZATION METHOD, AND INITIALIZATION DEVICE - Google Patents

Abstract

(57) Abstract: In the conventional initialization of a rewritable phase change optical recording medium, the degree of distortion of a reproduced signal waveform largely changed depending on the number of overwrites. A high-power semiconductor laser or flash,
Alternatively, the beam is shaped so that the shape of the beam spot emitted from the strobe light source becomes an ellipse on the recording film surface,
Further, a beam is irradiated in a state in which the major axis direction of the elliptical spot is arranged to be substantially perpendicular to the recording track direction, and at least a part of the recording film is melted at least once. [Effect] Due to the melting of the recording film due to the initialization, the bond of each element in the recording film became stable, and good characteristics were obtained regardless of the number of overwrites.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal obtained by FM-modulating an analog code such as video and audio by a recording beam such as a laser beam, digital data such as computer data, facsimile signals and digital audio signals. The present invention relates to an information recording medium capable of recording information in real time, an initialization method thereof, and a recording / reproducing apparatus.

[0002]

2. Description of the Related Art In a phase-change type optical disk for recording information by utilizing a phase change between a crystal and an amorphous phase, high-speed erasing in which crystallization can be performed in substantially the same time as the laser irradiation time for recording. When a possible recording film is used, the power of one energy beam is changed between two levels higher than the read power level, that is, between a high power level and an intermediate power level. By changing, it is possible to perform so-called overwriting (rewriting by overwriting) in which new information is recorded while erasing existing information. Immediately after such a recording film is formed by a vacuum deposition method, a sputtering method or the like (as depo. State), at least a part thereof is in an amorphous state or in a metastable crystalline state. Such an as depo. Condition is usually
The reflectivity is low and auto focus and tracking tend to be unstable. Therefore, the recording film is initialized in advance. Conventionally, as one of the means for this initialization,
-45247, for example, a laser beam of an argon laser is emitted as an elliptical light spot so that its longitudinal direction substantially coincides with the radial direction of the recording medium,
The recording film has been crystallized in a temperature range from the crystallization temperature to the melting point.

[0003]

When the information recording medium is initialized by using the conventional technique, the recording film is crystallized at 400 to 500 ° C., which is lower than the melting point, so that the crystal grains are entirely dispersed. The crystallization speed is small and the crystallization speed after the initial overwriting is slightly slow, and the crystallization speed is increased by rewriting by overwriting 100 times and gradually reaches a steady state.
Therefore, if the recording waveform is determined so that optimum recording / reproduction can be performed after the steady state is reached, in the initial overwrite, the reproduction signal waveform, especially in the time axis direction of the portion corresponding to the trailing end position of the recording mark Shifts and fluctuations (jitter) are large, and it becomes maximum after overwriting 2 to 5 times
It becomes smaller by 0 times and then reaches a steady state. Therefore, if the number of overwrites is 2 to 100, a read error may occur in some cases. Such a change in the crystallization rate is often caused by disorder of interatomic bonds in a recording film that has just been formed and crystallized, and the crystallization rate is limited. It is thought to happen because it is less. Furthermore, in the prior art device, the laser beam emitted from the Ar laser is
There is a problem that the device becomes complicated, for example, it is separated into two spots for initialization.

Therefore, an object of the present invention is to solve the above problems in the prior art and to provide an information recording medium initialization method and an initialization device for reliably recording information regardless of the number of overwrites. To do.

[0005]

In order to solve the above-mentioned problems in the prior art, in the initialization method of the present invention, for example, a high power laser for initialization (output about 2 W) is used.
A beam is shaped so that the single beam spot shape emitted from this high-power laser becomes an ellipse on the recording film surface, and the major axis direction (longitudinal direction) of this elliptical spot is recorded on the recording track. The recording medium is rotated or moved while being arranged so as to be substantially perpendicular to the direction, and irradiation is performed while focusing on the recording film. Then, the initialization beam is moved in the radial direction of the recording medium to perform initialization. In the present invention, at least a part of the recording film is emitted from the energy source for initialization, and the melting process is performed by irradiation with an energy beam of a particularly high power, in which the maximum width of the beam spot on the disk is larger than the recording track pitch. Is. As high-energy energy beams, flash light generated from a light source such as a xenon lamp, strobe light (repeated pulsed light flash light),
Use one or more of a mask (slit), a lens, and a reflecting mirror that allows a part of light to pass therethrough, so that the area of the recording medium is 1/3 or less, more preferably 1/10, rather than the entire surface. A beam-shaped one may be used. The advantage of using a laser is that the beam can be focused sufficiently.
The irradiation time per time is short, and damage due to heat of the recording medium can be avoided. However, the price of the initialization device is high.

On the other hand, in the case of flash light or strobe light, if the film is defective, cracks and the like are likely to occur, but it is easy to make the initialization device inexpensive. Here, the temperature of the recording film reaches the melting point or higher due to laser irradiation or the like, the recording film is melted, and then cooled. Thereby, the atomic arrangement of the recording film became stable, and good characteristics were obtained from the first overwriting. Here, since the cooling rate of the recording film is lower than the cooling rate at the time of recording on the disk, after the recording film is melted, it is at least partially recrystallized into a crystalline state.
If the recrystallized region is small in a recording film with a low crystal growth rate, laser beam irradiation in the temperature range from the crystallization temperature to the melting point, flash light, strobe light irradiation, etc. is performed to crystallize the recording film. May be. At this time, when the recording film is melted and then recrystallized, a crystalline state of a coarse crystal grain size with a uniform maximum width of 0.1 μm or more (larger than the crystal grain form after erasing the recording mark) is obtained over the entire surface of the disc. There is a possibility that The width of the coarse crystal grain region corresponding to one irradiation of the initialization energy beam at this time is wider than the recording track width.

Of the above-mentioned initializations, the elliptical spot used in the example of the present invention is shaped by the optical system in the initialization device in order to reduce the damage due to heat in the initialization by the high-power laser. By doing so, the light intensity in the short-axis direction (short-side direction) is close to a Gaussian distribution, and the cross-sectional shape of the light-intensity distribution in the long-axis direction (longitudinal direction) is close to a trapezoid (the vertex is flat). The disc is rotated with the major axis direction (longitudinal direction) of the elliptical spot arranged substantially perpendicular to the recording track direction so that the beam is focused on the recording film and continuous light (DC) is generated. Light) irradiation was used for initialization. Since the spot width in the recording track direction (short axis direction) is narrow and does not differ much from the spot width of the recording / reproducing device, rapid heating and quenching are possible and less damage due to heat. Furthermore, by making the maximum width of the initialization beam spot on the disk larger than the recording track pitch, the time required for the initialization is reduced. For example, in order to enable initialization of a large area in a short time, a high-power laser (pulse output of about 2 W) with an elliptical spot whose beam spot shape is about 1.5 μm × 100 μm on the recording film surface is used. I was there. By continuously irradiating a beam in a state where the major axis direction (longitudinal direction) of this elliptical spot is substantially perpendicular to the recording track direction (radial direction of the disk), one disk rotation is performed. Can be initialized at a feed pitch of 100 μm at maximum.

For example, a disc having a diameter of 5 inches is 180
If initialization is performed by rotating the beam at 0 rpm and moving the beam at a feed pitch of 100 μm from a radius of 30 mm to a radius of 60 mm toward the outer periphery, the initialization will be completed in about 10 seconds. In this case, the beam irradiation power may be increased from the inner circumference to the outer circumference in order to securely initialize the entire surface of the disk. Also, although the initialization time becomes longer, the feed pitch is shorter than 100 μm,
In some cases, initialization can be performed more reliably by increasing the number of irradiations to the same location on the recording medium. Further, the linear velocity of the recording medium at the time of initialization is preferably 4 m / s or more and 30 m / s or less. Particularly, 6 m / s or more and 15 m / s or less are preferable. Further, it is more preferable that the linear velocity at the time of initialization be constant regardless of the position in the radial direction of the disk so that the state after initialization becomes uniform. Further, in order to reduce the thermal damage to the recording film, in the case of high-power laser light, it is preferable to perform pulsed irradiation instead of continuous light irradiation. In this case,
At least three levels are set as the power level of the beam, and the value of each power level, the pulse irradiation frequency of the beam, the duty ratio, the linear velocity of the disk, etc. are set according to the crystallization speed of the recording film and the cooling speed of the recording film. Just change it. For example, the power level of each beam for initialization is set to a high power level (PH): a power level equal to or higher than the power level at which the recording film melts at the center of the beam spot, an intermediate power level (PM): as the linear velocity of the recording medium increases. high. (Relationship of PH>PM> PL) Low power level (PL): playback power level.

It suffices to perform the initialization under the condition satisfying the condition of. When the linear velocity of the recording medium at the time of initialization is v, the half width of the initialization beam in the recording track direction is x, and the pulse irradiation frequency of the initialization beam is f, the condition of f ≧ (v / x) is satisfied. By performing the initialization under the condition that satisfies, the initialization can be performed in a uniform state over the entire initialization area. In the case of such initialization by pulse irradiation, a large number of arcs are gathered at least on one side edge of the coarse grain region at the boundary between the initialized region and the uninitialized region. The shape.

Further, depending on the recording medium, first, the beam power is irradiated so that the temperature is lower than the melting point of the recording film, and thereafter, the beam power having at least two stages of the beam power at which the temperature is higher than the melting point at which the recording film melts. It may be better to irradiate. Alternatively, the irradiation may be initialized by first irradiating with beam power having a temperature equal to or higher than the melting point of the recording film, and then irradiating with beam power having a temperature lower than the melting point of the recording film. Even if a high-power laser with an elliptical beam is not used, by irradiating with a laser beam having a shape almost the same as the beam shape for actual recording, the recording film is initialized through the melting process, or the actual recording is performed. Although the initialization may be performed by melting the recording film with the laser beam to be performed, the number of disks that can be initialized per day by one device used for the initialization decreases.

There are cases where the wavelength of the laser for initialization and the laser wavelength for actual reading of information are different. At this time, as at the wavelength of the laser to be initialized
The reflectance in the depo. state or the reflectance in the amorphous state is
As at the wavelength of the laser that actually reads information
3 of reflectance in depo. state or reflectance in amorphous state
By using the recording medium with a double or less, reliable initialization and good recording characteristics were obtained. In particular, it is preferably 1.5 times or less. At this time, as at the laser wavelength for initialization
When the initializing laser beam is difficult to focus due to the low reflectance in the depo. state, weak flash light irradiation is performed before initialization by the initializing laser to increase the reflectance of the disk, then Crystallization may be performed by irradiation with a laser beam for chemical conversion. Even if the reflectivity in the as depo. State is low, the power of the read light of the initialization laser for focusing is made close to the power at the time of initialization to try to focus. Since the recording film is crystallized at the moment when the focal point is reached in the middle of the process, and the reflectance is increased thereby, it may be possible to focus stably thereafter.

The present invention can also be applied to the case of initializing an optical disk medium capable of high-density reproduction or recording by providing a mask layer which causes a region where the amount of light transmission decreases in the beam spot. For example, when a dye is used as the mask layer or when an inorganic layer having a low melting point is used. Further, the present invention can be applied to a case where a mask layer for generating a region where the amount of light transmission decreases in a beam spot is provided to initialize an optical disk medium capable of high-density reproduction or recording. For example, when a dye such as naphthalocyanine is used as the mask layer, or when an inorganic layer having a low melting point is used.

The initialization device used in the present invention includes means for emitting an initialization energy beam, means for rotating or moving a recording medium, means for focusing the initialization beam on a recording film, and an initialization beam. It has at least means for moving the position on the recording medium, means for controlling the power level and irradiation time of the initialization beam to temporarily melt the recording film. Furthermore, the beam emitted from the energy source has a spot shape on the recording film surface with a light intensity distribution in the minor axis direction close to a Gaussian distribution, and a cross-sectional shape of the light intensity distribution in the major axis direction is trapezoidal (the vertex is flat). Of the elliptical spot, positioning means of the recording head for arranging the major axis direction of the elliptical spot in a direction substantially perpendicular to the recording track direction, rotation or movement of the recording medium and radius of the energy beam recording medium Means for controlling the mutual relationship of directional movement,
It has at least one or more of a means for irradiating with flash light and a means for deciding the irradiation order of flash light irradiation and energy beam irradiation.

In the present invention, at least a protective layer on the substrate,
A recording medium having an optical recording film, an intermediate layer, and a reflective layer formed in this order is used. At this time, good characteristics were obtained by setting the thickness of each layer in the following range. First, the thickness of the protective layer is 50
The thickness is preferably from 150 nm to 150 nm, particularly preferably from 60 nm to 130 nm. The thickness of the optical recording film is 10 n
m to 50 nm, preferably 12 nm to 40 nm.
nm or less is preferable. The thickness of the intermediate layer is 5 nm or more and 50
nm or less, preferably 10 nm or more and 30 nm or less. The thickness of the reflective layer is preferably 30 nm or more and 300 nm or less, and particularly preferably 50 nm or more and 200 nm or less. As a recording film to be used, a crystal-amorphous phase-change optical recording film capable of high-speed crystallization, a recording film utilizing an amorphous-amorphous change, a crystal such as a change in a crystal system or a crystal grain size, etc. -An intercrystalline phase change recording film is preferred, but other recording films may be used. In particular, Ge-Sb-Te based recording films and Ag-In-Sb
A recording film using a phase change, such as a -Te recording film, may be used. In addition, a recording film in which a high melting point material such as Cr ₂ Te ₃ having a higher melting point than the main component material is added to the recording film,
It is preferable to use a recording medium having two reflective layers, because it is possible to suppress a change in the thickness of the recording film due to the flow of the recording film. Here, when the number of the reflective layers is two, the thickness of the first layer is preferably 20 nm or more and 300 nm or less, more preferably 50 nm or less.
It is preferably not less than 100 nm and not more than 100 nm. The thickness of the second layer is preferably 30 nm or more and 300 nm or less, and particularly 50
It is preferably not less than 200 nm and not more than 200 nm.

It is preferable that the operation of melting the recording film is performed after forming each layer such as the recording film on the substrate and at least performing a protective coating of, for example, an ultraviolet curable resin, since the recording film is less damaged. In particular, after the optical recording medium having a structure coated with a protective layer of an ultraviolet curable resin and the protective plate are adhered to each other by an adhesive such as an ultraviolet curable resin or a hot melt method, laser irradiation or flashing is performed from the substrate side. It is preferable to perform light irradiation. Alternatively, irradiation may be performed on both surfaces after the optical recording media are adhered to each other to form a double-sided recording medium.

In the initialization of the present invention, at least a part of the recording film has once undergone a melting process by irradiation with an energy beam, and as an energy source for melting the recording film, a semiconductor laser, an Ar laser, Kr is used. laser,
Alternatively, an electron beam or the like can be used. Among these, a semiconductor laser is preferable because it does not require downsizing of the device or cooling water. When the energy source is a light source, its main wavelength is
The wavelength difference from at least one of the reproduction wavelengths is preferably 100 nm or less, and particularly preferably 50 nm or less. Further, it can be used if at least a part of the recording film can be melted only by irradiation with flash light or strobe light from a xenon lamp or the like.
A little below the melting point of the recording film (within 100 ° C below the melting point)
Even at this temperature, if the number of irradiations at one location was doubled or more, an effect similar to that obtained when melting was obtained. In particular, in the case of flash light or strobe light, since the irradiation time is long, the effect can be obtained even below the melting point. Since the recording film is in an amorphous state before the irradiation with the energy beam, there is actually no clear melting point, and when it is rapidly cooled, it does not crystallize but softens from a temperature slightly below the melting point of the crystal. When fine crystals are formed during the temperature rise, they melt at a temperature slightly lower than the melting point (melting point of large crystals) which is usually known. Therefore, it is considered that the effect is effective even just below the melting point. It can be known from the fact that when such a temperature is reached, coarse crystals are usually formed during cooling.

The operation of melting the recording film is performed at the same time as certifying the recording medium (defect inspection by reading).
Alternatively, it may be performed before or after that. The above-described operation of melting the recording film is performed at the stage when the manufacturer manufactures the recording medium (related to the manufacturing method) or before the trial writing is performed by the device that actually records / reproduces information (related to the pretreatment method).
You can go to

Further, the present invention is not limited to a disk shape,
The present invention is also applicable to other forms of recording medium such as a card.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below using embodiments.

Embodiment 1 FIG. 1 is a structural sectional view of a rewritable optical disk having a guide groove used in this embodiment. First, the diameter 1
20mm, 0.6mm thick guide groove (track pitch 1.
Polycarbonate substrate 1 having 48 μm, U-shaped groove)
On top, the thickness is about 1 by magnetron sputtering.
A ZnS-SiO ₂ protective layer 2 having a thickness of 10 nm was formed. Next, the recording film 3 having a composition of Cr ₂ Ge ₂₀ Sb ₂₂ Te ₅₆ is applied to about 2
It was formed to a thickness of 5 nm. Then was formed ZnS-SiO ₂ intermediate layer 4 to a thickness of approximately 20 nm. Then, a Si layer (first reflection layer) 5 having a thickness of 80 nm and an Al-Ti layer (second reflection layer) 6 having a thickness of about 100 nm were formed. These films were formed sequentially in the same sputtering apparatus. After that, an ultraviolet curable resin layer 7 was applied on this, and then a two-liquid mixed room temperature effect adhesive 8 was used to adhere and adhere to another disk of the same structure.

Initialization of the disk manufactured as described above was performed as follows. First, the spot shape of a beam emitted from a high-power semiconductor laser (wavelength: about 810 nm) with an output of about 2 W is about 1.5 μm × 100 μ on the recording film surface.
Beam shaping was performed so as to form an oval spot of m, and the long axis direction of the oval spot 9 was arranged substantially at right angles to the recording track 10 direction as shown in FIG. Then, the disk was rotated at a linear velocity of 8 m / s, and about 1 was recorded on the recording film surface.
A continuous light (DC light) of 50 mW was irradiated to perform automatic focusing. Next, while the elliptical spot 9 was moved from the outer circumference to the inner circumference of the disc at a constant speed, the laser power was increased to the power for melting the recording film and pulse irradiation was performed. The initialization conditions are a linear velocity of the disk of 8 m / s, an initialization pulse frequency of 9 MHz, a duty ratio of the initialization pulse of 50%, and a power ratio of a high power level (Ph) to an intermediate power level (Pm) of 2: 1. And the initialization was performed under the conditions that the high power levels were set to 900 mW and 1800 mW in two radial regions on the disk, respectively. For comparison, DC light (light without pulse modulation)
Initialization of 700 mW was also performed. Then, the recording was performed by using a recording device with a laser wavelength of 680 nm and an NA of 0.55, and overwriting was performed with the ternary waveform shown in FIG. Here, the recording power was 9 mW, the erasing power was 4 mW, and the reading power was 1 mW. FIG. 4 shows the results of examining the dependence of jitter on the number of overwrites in each initialization region. From this figure, the initialization power is DC light 700
It can be seen that in the case of mW and pulsed light of 900 mW, the jitter is large when the number of overwrites is small. The reason for this is that when the initialization power is low, the temperature until the recording film melts has not reached,
It is considered that the structure of the recording film gradually changed due to overwriting because the recording film was crystallized from the as depo. State without melting. On the other hand, the initialization power is 180
When it is as high as 0 mW, the recording film temperature reaches the melting point, and once the recording film has melted, it was recrystallized during cooling and became mostly in a crystalline state. Therefore, good characteristics were obtained from the first overwrite. It is believed that If coarse crystal grains are formed at this time, the width of the coarse crystal grain region is wider than the recording track width.

In the present invention, the value of each power level and its power ratio, the pulse irradiation frequency of the beam, the linear velocity of the disk, etc. may be changed according to the crystallization speed of the recording film and the cooling speed of the recording film. . For example, the power level of each beam for initialization is set to a high power level (PH): a power level equal to or higher than the power level at which the recording film melts at the center of the beam spot, an intermediate power level (PM): as the linear velocity of the recording medium increases. high. (Relationship of PH>PM> PL) Low Power Level (PL): Below Reproduction Power Level.

It suffices to perform the initialization under the condition satisfying the condition of. In this embodiment, PH is 1800 mW, which is higher than the power level (1200 mW) at which the recording film melts, PM is 900 mW in the range of PH>PM> PL, and P
L is each condition of the reproducing power level of 150 mW.

Further, depending on the irradiation frequency value of the beam at the time of initialization, the regions where the recording films are melted do not overlap in the traveling direction of the initialization beam, and the reflectance may be uneven. Therefore, the characteristics vary depending on the location of the initialization area. Therefore, the linear velocity of the recording medium at the time of initialization is set to v [m /
s], the half-width of the initialization beam in the recording track direction is x
[Μm], the pulse irradiation frequency of the initialization beam is f [M
Hz], the initialization was performed so that the condition of f ≧ (v / x) was satisfied. As a result, initialization can be performed in a uniform state over the entire initialization area.

In the initialization method of the present embodiment, when pulse irradiation with a high initialization pulse frequency is performed, pulsed light is continuously irradiated at a short distance, so the cooling rate of the recording film is slow. Coarse crystals are formed over the entire initialization region by recrystallization. In the case of pulse initialization, at least one edge of the coarse crystal grain region at the boundary between the initialized region and the non-initialized region is
It becomes a shape where a large number of arcs are gathered.

In addition, although the initialization time becomes longer, there are cases where the initialization can be surely performed by setting the feed pitch shorter than 100 μm and increasing the number of irradiations to the same place on the recording medium. Furthermore, as the linear velocity of the recording medium at the time of initialization,
At 4 m / s or less, damage due to heat accumulation becomes large, and at 30 m / s or more, initialization becomes insufficient. Therefore, the linear velocity of the recording medium at initialization is preferably 4 m / s or more and 30 m / s or less. In particular, it is preferably 6 m / s or more and 15 m / s or less, which widens the initialization margin.

Depending on the recording medium, the beam power is first irradiated so that the temperature is equal to or lower than the melting point of the recording film, and then the beam power is at least 2 which is equal to or higher than the melting point at which the recording film is melted. It may be better to perform a stepwise irradiation. On the contrary, the initialization may be performed by first irradiating with beam power having a temperature equal to or higher than the melting point of the recording film, and then irradiating with beam power having a temperature equal to or lower than the melting point of the recording film. When the recording film is recrystallized after melting, coarse crystal grains are generated. Good recording / reproducing characteristics were obtained by setting the recording medium and the initialization method such that the maximum width of the coarse crystal grains was 0.1 μm or more. More preferably, it is 0.3 μm or more, which is close to the maximum width of coarse crystal grains formed during actual overwriting. Even if a high-power semiconductor laser with an elliptical beam is not used, by irradiating a semiconductor laser beam with a beam shape that is almost the same as the beam shape for actual recording, the recording film is initialized through the melting process, Initialization may be performed through a melting process of the recording film with a semiconductor laser beam for recording. In this case, the number of discs that can be initialized in one day by one device used for initialization decreases. Flash light from a xenon lamp or strobe light may be used as the energy beam. In this case, the entire surface of the disk may be irradiated at the same time, but thermal damage such as crack generation is likely to occur. Therefore, after arranging a concave reflecting mirror after the lamp, a slit and a lens for passing a part of the light in front, and irradiating a beam on a part of the disk while rotating the disk at 2000 rpm, good initialization can be performed. It was

The present invention can also be applied to the case of initializing an optical disk medium capable of high-density reproduction or recording by providing a mask layer which causes a region where the amount of light transmission decreases in the recording or reproduction beam spot. For example, when a dye is used as the mask layer or when an inorganic layer having a low melting point is used. Furthermore, the present invention can be applied to the case of initializing an optical disk medium capable of reproducing or recording high density recording information by providing a mask layer that causes a region where the laser beam does not penetrate to the recording film in the beam spot. For example, when a pigment such as phthalocyanine is used as the mask layer, or when an inorganic layer having a low melting point is used.

The initialization device used in the present embodiment comprises means for emitting an initialization energy beam, means for rotating the recording medium, means for focusing the initialization beam on the recording film, and initialization beam. Means for moving the position on the recording medium,
A means for temporarily controlling the power level and irradiation time of the initialization beam to melt the recording film temporarily, and the beam emitted from the energy source has a spot shape with a light intensity distribution in the short axis direction on the recording film surface. Means for shaping an elliptical spot having a trapezoidal (vertical flat) cross-sectional shape of the light intensity distribution in the major axis direction, which is close to a Gaussian distribution, and the major axis direction of the elliptical spot is substantially perpendicular to the recording track direction. It has a positioning means for the recording head to be arranged, and means for controlling the mutual relationship between the rotation or movement of the recording medium and the movement of the energy beam in the radial direction of the recording medium. However, when using a flash light source or a strobe light source, it is not necessary to focus the light, and the beam may be guided onto the recording film. Further, the light intensity may be shaped into an oval or rectangular light spot, but it is not necessary to make the light intensity in the minor axis direction a Gaussian distribution.

In the initial crystallization by the high power semiconductor laser, it is necessary to reduce the damage due to heat. Therefore, the elliptical spot used in the present invention converges to the diffraction limit in the short-axis direction (short-side direction) and has a Gaussian distribution. Further, in order to uniformly initialize a large area at one time, the cross-sectional shape of the light intensity distribution in the major axis direction (longitudinal direction) is close to a trapezoid. That is, the apex of the light intensity distribution has a flat portion. At this time, 10 from the flat part of the apex
%, The length in the major axis direction is set to about 70% or more of the length in the major axis direction when sliced at a power of 1 / e ² of the intensity distribution in the minor axis direction. In this embodiment, the elliptical spot has a short axis of about 1.5 μm (1 / e ² ).
The major axis direction is about 100 μm. Initial crystallization is carried out by rotating the disk in a state in which the major axis direction of the elliptical spot is arranged substantially perpendicular to the recording track direction so that the beam is focused on the recording film. In this case, since the light intensity distribution in the recording track direction (short axis direction) has a Gaussian distribution, rapid heating and rapid cooling are possible and damage due to heat is small.

As described above, using a high-power semiconductor laser (output of about 2 W), the beam is shaped so that the beam spot shape emitted from this high-power semiconductor laser becomes an ellipse on the surface of the recording film. By irradiating the beam with a pulse in a state where the major axis direction of this elliptical spot is arranged so as to be substantially perpendicular to the recording track direction,
Irradiation number 10 times (optical head feed amount: 10 μm / revolution), high power 1800 mW, intermediate power 900 m
Initial crystallization was performed under the conditions of W and linear velocity of 8 m / s, and the diameter was 12
It is possible to initialize a 0 mm disc in about 100 seconds with little change in the jitter of the reproduced signal due to the number of overwrites, which is more than 10 times that of the conventional method (initialization for each recording track on the groove and between grooves). The initialization time was shortened. Here, when the output of the high-power semiconductor laser is 1 W, the shape of the elliptical spot should be approximately
By beam-shaping m (1 / e ² ) in the major axis direction to about 50 μm, the same effect was obtained although the shortening of the initialization time was reduced.

In the present invention, at least a protective layer on the substrate,
A recording medium having an optical recording film, an intermediate layer, and a reflective layer formed in this order is used. At this time, the film thickness of each layer was set within the following range. First, if the thickness of the protective layer is less than 50 nm, the recording film tends to flow due to overwriting, and
If it is thicker than 50 nm, damage by heat during recording becomes large. Therefore, the thickness is preferably 50 nm or more and 150 nm or less, and in particular, a large absorption rate with a laser for initialization can be taken.
It is preferably not less than nm and not more than 130 nm. When the film thickness of the optical recording film is 10 nm or less, a large signal level cannot be obtained. When the film thickness is 50 nm or more, the flow of the recording film due to overwriting tends to occur.
The following are preferable, and particularly, 12 with good overwrite characteristics
It is preferably not less than 40 nm and not more than 40 nm. The thickness of the intermediate layer is 5
If it is less than 50 nm, it may be deformed at the time of overwriting or diffusion may occur between the recording film and the reflective layer. If it is 50 nm or more, a slow cooling structure is formed and the power margin of the erasing ratio becomes narrow. The thickness is preferably 10 nm or more and 30 nm or less, in which the recording film hardly flows. When the thickness of the reflective layer is 30 nm or less, the effect as a reflective layer is small, and when the thickness is 300 nm or more, the film is easily peeled. Therefore, the thickness is preferably 30 nm or more and 300 nm or less, and particularly preferably 50 nm or more and 200 nm or less, which have large thermal and mechanical effects. . As a recording film to be used, a crystal-amorphous phase-change optical recording film capable of high-speed crystallization, a recording film utilizing an amorphous-amorphous change, a crystal such as a change in a crystal system or a crystal grain size, etc. -An intercrystalline phase change recording film is preferred, but other recording films may be used. In particular, Ge-Sb-Te-based recording films and Ag-
A recording film utilizing a phase change, such as an In-Sb-Te recording film, may be used. Further, if a recording film in which a high melting point material such as Cr ₂ Te ₃ having a higher melting point than the main component material is added to the recording film, or a recording medium having two reflective layers as in this embodiment is used, This is preferable because a change in the thickness of the recording film due to the flow of the recording film can be suppressed. Here, when the number of the reflective layers is two, the thickness of the first layer is preferably from 20 nm to 300 nm, and particularly preferably from 50 nm to 100 nm. When the film thickness of the second layer is 30 nm or less, it is difficult to suppress the change of the recording film thickness due to the flow of the recording film.
When the thickness is 00 nm or more, the structure has a gradual cooling and the power margin of the erasing ratio is narrowed. Therefore, the thickness is preferably 30 nm or more and 300 nm or less, and particularly preferably 50 nm or more and 200 nm or less in which the recording film flow due to overwriting does not easily occur.

It is preferable that the operation of melting the recording film is performed after the two discs are adhered to each other as in this embodiment, but it is preferable that the operation is performed at least after the protective coat is applied to the recording film. May be less.

When the thickness of the lower protective layer is changed to read or reduce the light reflectance at the recording wavelength to obtain the maximum reproduction signal intensity, the reflectance at other wavelengths increases and the initialization power is insufficient. Therefore, the wavelength of the initialization laser is preferably within a range of ± 50 nm from the recording or reading wavelength. Considering the ease of making a high-power laser, it is particularly preferable to use a high-power semiconductor laser having a wavelength of 680 nm ± 30 nm.

In this embodiment, the melting of the recording film was performed after certifying the disc (defect inspection by reading). However, the same effect can be obtained by performing the certifying of the disc at the same time or before the certifying.

Although the above description is about the method of manufacturing the information recording medium (the stage in which the manufacturer manufactures the recording medium) in which the information can be rewritten by the irradiation of the energy beam, the recording medium of the present invention is actually used. The above-mentioned effect can be obtained even in the case of performing the trial writing (related to the preprocessing method) in the apparatus for recording / reproducing information.

Embodiment 2 The structure of the rewritable optical disk used in this embodiment is basically the same as that of FIG. However, the film thickness of each layer is different. First, a ZnS—SiO ₂ protective layer having a thickness of about 80 nm was formed by a magnetron sputtering method on a polycarbonate substrate having a guide groove (track pitch 1.48 μm, U-shaped groove) having a diameter of 120 mm and a thickness of 0.6 mm. Next, a recording film having a composition of Cr ₃ Ge ₂₁ Sb ₂₀ Te ₅₆ is used for about 25
It was formed to a film thickness of nm. Then was formed ZnS-SiO ₂ intermediate layer to a thickness of approximately 20 nm. Then, a Si layer (first reflective layer) of 50 nm and an Al-Ti layer (second reflective layer) of about 100 nm were further formed. These films were formed sequentially in the same sputtering apparatus. After that, an ultraviolet-curing resin layer was applied on this, and then a hot-melt adhesive was used to adhere and adhere to another disk of the same structure.

Initialization of the disk manufactured as described above is almost the same as that of the first embodiment, but this disk uses as depo in order to obtain a large reflectance difference between the crystalline state and the amorphous state at the reading wavelength. The structure has a low reflectance in the state. Therefore, in the vicinity of 680 nm which is the wavelength of the semiconductor laser used for recording / erasing / reading,
The reflectance is as low as 5% in the as depo. state, and automatic focusing is very difficult to apply. Therefore, in this embodiment, in order to raise the reflectance of the manufactured disk to the extent of focusing before the initial crystallization by the high-power semiconductor laser,
First, flash light irradiation was performed at a temperature slightly lower than the melting point. This flash light irradiation power is about 2 joules /
cm ² . This increases the reflectance to 13%,
The focus is on stability. In addition, by increasing the power of the read light of the high-power semiconductor laser for focusing without flash light irradiation to about 500 mW, the moment when there is a focus during the operation of focusing. Since the recording film is crystallized to increase the reflectance, it may be possible to focus stably thereafter.

In some cases, the wavelength (810 nm) of the semiconductor laser for initialization as in this embodiment is different from the wavelength (680 nm) of the semiconductor laser for actually reading information. At this time, a recording medium in which the reflectance in the as depo. State at the wavelength of the semiconductor laser to be initialized is 3 times or less than the reflectance in the as depo. State at the wavelength of the semiconductor laser to actually read information is used. By using
Reliable initialization and good recording characteristics were obtained. In particular, the effect was great when the reflectance difference in the as depo. State at each wavelength was 1.5 times or less.

The initialization device used in the present embodiment includes means for emitting an initialization energy beam, means for rotating or moving the recording medium, means for focusing the initialization beam on the recording film, and initialization means. A means for moving the position of the beam on the recording medium, a means for temporarily melting the recording film by controlling the power level and irradiation time of the initialization beam, and a beam emitted from the energy source whose spot shape is on the recording film surface. The means for shaping the light intensity distribution in the short-axis direction close to the Gaussian distribution and the cross-sectional shape of the light intensity distribution in the long-axis direction into a trapezoidal (flat top) flattened spot, the long-axis direction of the spot is recorded. Positioning means for the recording head, which is arranged substantially perpendicular to the track direction, and means for controlling the mutual relationship between the rotation or movement of the recording medium and the radial movement of the energy beam of the recording medium. Means for irradiating a flash light, and has a means for determining the irradiation sequence of the flash light irradiation and energy beam irradiation.

[0041]

According to the present invention, a high output energy beam is used for initialization, and the beam is shaped so that the beam spot shape becomes an ellipse or a rectangle on the surface of the recording film. By irradiating the beam with the axial direction almost perpendicular to the recording track direction and at least partially melting the recording film, the change in characteristics due to the difference in the number of overwrites can be reduced. I was able to.

[Brief description of drawings]

FIG. 1 is a sectional view of a disk structure according to the present invention.

FIG. 2 is a layout view of an elliptical beam according to the present invention.

FIG. 3 is a ternary recording waveform according to the present invention.

FIG. 4 shows the dependence of jitter on the number of overwrites in the present invention.

[Explanation of symbols]

1,1 'polycarbonate substrate 2, 2' ZnS-SiO ₂ dielectric layer 3,3 'recording layer _{(Cr 2 Ge 20 Sb 22 Te} 56) 4,4' ZnS-SiO 2 dielectric layer 5,5 'Si reflective Layer 6,6 ′ Al—Ti alloy reflective layer 7,7 ′ UV curable resin protective layer 8 Hot melt adhesive layer 9 Elliptical spot 10 Recording track.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Miyamoto 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd. Hitachi, Ltd. Video Information Media Division (72) Inventor Akemi Hirotsune 1-chome, East Koikeku, Kokubunji, Tokyo 280 In Hitachi Central Research Laboratory (72) Inventor Yoshihiro Shiroishi 1-chome Higashi Koikeku, Kokubunji, Tokyo 280 Address Central Research Laboratory Hitachi, Ltd. (72) Hiroyuki Awano 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Central Research Laboratory

Claims (27)

[Claims] 1. An optical recording medium capable of recording information by irradiation with an energy beam, at least a part of a recording film of which is emitted from an energy source for initialization, and the maximum width of a beam spot on a disk is a recording track pitch. An information recording medium, characterized in that it undergoes a melting process by irradiation with a larger energy beam. 2. The information recording medium according to claim 1, wherein
A recording medium for information, characterized in that a beam emitted from an energy source is irradiated in pulses. 3. The information recording medium according to claim 1,
An information recording medium characterized in that the maximum width of crystal grains after initialization is 0.1 μm or more (coarse crystal grains). 4. The information recording medium according to claim 3,
An information recording medium characterized in that the width of the coarse crystal grain region is wider than the recording track width. 5. The information recording medium according to claim 3,
An information recording medium, characterized in that at least one edge of a coarse crystal region at a boundary between an initialized region and a non-initialized region has a shape in which a large number of arcs are gathered. 6. The information recording medium according to claim 1, wherein
As dep at the wavelength of the energy beam used for initialization
An information recording medium characterized in that the reflectance in the o. state is 3 times or less than the reflectance in the as depo. state at the wavelength of the energy beam used for reading information. 7. The information recording medium according to claim 1, wherein
An information recording medium having at least a protective layer, an optical recording film, an intermediate layer, and a reflective layer on a substrate, the protective layer having a thickness of 50 nm or more and 150 nm or less. 8. The information recording medium according to claim 1, wherein
An information recording medium having at least a protective layer, an optical recording film, an intermediate layer, and a reflective layer on a substrate, the thickness of the optical recording film being 10 nm or more and 50 nm or less. 9. The information recording medium according to claim 1, wherein
An information recording medium having at least a protective layer, an optical recording film, an intermediate layer, and a reflective layer on a substrate, the thickness of the intermediate layer being 5 nm or more and 50 nm or less. 10. The information recording medium according to claim 1, wherein a protective layer, an optical recording film, an intermediate layer and a reflective layer are provided on at least the substrate, and the thickness of the reflective layer is 30 nm or more and 300 n or more.
An information recording medium characterized by being m or less. 11. The information recording medium according to claim 1, comprising a protective layer, an optical recording film, an intermediate layer, a first reflective layer and a second reflective layer on at least a substrate, and the film of the second reflective layer. The thickness is
An information recording medium having a thickness of 20 nm or more and 300 nm or less. 12. A method of initializing an information recording medium, wherein an optical recording medium capable of recording information by irradiating an energy beam is first brought into a recordable state. An initialization method for an information recording medium, characterized in that a melting process is performed by irradiation of an energy beam having a maximum width of a beam spot larger than a recording track pitch. 13. The information initializing method according to claim 12, wherein the energy source is a light source, and the main wavelength thereof has a wavelength difference of 100 nm or less with at least one of the recording and reproducing wavelengths of the recording medium. A method for initializing a recording medium of characteristic information. 14. The method for initializing an information recording medium according to claim 12, wherein the initialization is performed by a single beam spot. 15. The information initializing method according to claim 12, wherein the recording film is initialized under the condition that the recording film is recrystallized during cooling after the recording film is melted. Method. 16. The information recording medium initialization method according to claim 12, wherein the beam spot emitted from the energy source is shaped into an ellipse or a rectangle on the surface of the recording film, and the light spot is formed. The information is characterized in that initialization is performed by moving the light spot in the radial direction of the recording medium while rotating the recording medium with the long axis direction of the recording medium being arranged substantially perpendicular to the recording track direction. Recording medium initialization method. 17. The method for initializing the information recording medium according to claim 12, wherein the linear velocity of the recording medium is 4 m / s or more.
An initialization method for an information recording medium, characterized in that initialization is performed under conditions of m / s or less. 18. The method for initializing an information recording medium according to claim 12, wherein the energy beam emitted from the energy source is irradiated in pulses on the recording medium. . 19. An information recording medium initialization method according to claim 18, wherein the power level of the initialization beam is set to a high power level (PH) and an intermediate power level (P).
M), a method for initializing an information recording medium, characterized in that initialization is performed in a state of being set to at least three levels of a low power level (PL). 20. The information recording medium initialization method according to claim 19, wherein each power level of the initialization beam has a high power level (PH): a power level at which the recording film melts at the center of the beam spot. As described above, the intermediate power level (PM): the higher the linear velocity of the recording medium, the higher. (Relationship of PH>PM> PL) Low power level (PL): playback power level. The method for initializing an information recording medium, characterized in that the initialization is performed under the condition satisfying the condition of. 21. The method for initializing an information recording medium according to claim 19, wherein the linear velocity of the recording medium at the time of initialization is v, the half width of the initialization beam in the recording track direction is x, and the initialization beam is An initialization method of an information recording medium is characterized in that initialization is performed under the condition that f ≧ (v / x) is satisfied, where f is the pulse irradiation frequency. 22. The method for initializing an information recording medium according to claim 12, wherein flash light irradiation is first performed,
Next, the beam spot emitted from the energy source is shaped so that the shape of the beam spot becomes elliptical or rectangular on the surface of the recording film, and the long axis direction of this light spot is arranged almost at right angles to the recording track direction. An initialization method of an information recording medium, wherein the initialization is performed by moving the light spot in the radial direction of the recording medium while rotating the recording medium. 23. The information recording medium initialization method according to claim 12, wherein the light intensity distribution of the light spot in the minor axis direction is close to a Gaussian distribution, and the cross-sectional shape of the light intensity distribution in the major axis direction is trapezoidal ( A method for initializing an information recording medium, characterized in that the vertices are close to flat. 24. The method for initializing an information recording medium according to claim 12, wherein irradiation is first performed with a power that is lower than a melting point and is a temperature that facilitates crystallization, and then at least a part of the recording film is melted. A method for initializing an information recording medium, characterized in that irradiation is performed with power. 25. The method for initializing an information recording medium according to claim 12, wherein irradiation is first performed with a power that melts at least a part of the recording film, and then a temperature lower than the melting point of recording and easily crystallized. And a method for initializing an information recording medium, characterized in that irradiation is performed with a power of 26. An information recording medium initializing device for initially recording an optical recording medium capable of recording information by irradiation of an energy beam, a means for emitting an initializing energy beam, and a recording medium. Means for rotating or moving the beam, means for focusing the beam for initialization on the recording film, means for moving the position of the beam for initialization on the recording medium, control of the power level and irradiation time of the beam for recording, and the recording film An apparatus for initializing an information recording medium, comprising at least a means for temporarily melting at least a part of the above. 27. The information recording medium initialization device according to claim 25, wherein the means for condensing the spot shape of the beam emitted from the energy source into an ellipse on the surface of the recording film, said ellipse. Positioning means of the recording head for arranging the major axis direction of the spot in a direction substantially perpendicular to the recording track direction, means for controlling the mutual relation between the rotation or movement of the recording medium and the movement of the energy beam in the radial direction of the recording medium, A means to irradiate flash light for crystallization at a temperature lower than the melting point and a temperature at which it easily crystallizes, a means to determine the irradiation order of flash light irradiation and energy beam irradiation, and a Gaussian distribution of the light intensity distribution in the minor axis direction of the elliptical spot. Of at least one of means for shaping an elliptical spot having a trapezoidal (flat top) cross-sectional shape in the light intensity distribution in the major axis direction close to
An information recording medium initialization device, characterized by comprising one or more means. 27. The information recording medium initialization device according to claim 25, wherein the energy source is a light source, and a main wavelength thereof is 100 nm or less with respect to at least one of recording and reproducing wavelengths of the recording medium. An initialization device for an information recording medium characterized by being present.