JP3298792B2 - Optical recording medium initialization method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium initialization method, and more particularly, to irradiating a light beam to cause an optical change in a recording layer material, thereby enabling information recording, reproduction and rewriting. The present invention relates to a method for initializing a phase change type optical recording medium, and is used for manufacturing an optical recording medium.

[0002]

2. Description of the Related Art By irradiating a laser beam,
By causing an optical change in the recording layer material, information recording,
A phase-change optical recording medium that can be reproduced and rewritten has an initial phase in which, in a manufacturing process, a recording layer is heated by irradiating a laser beam to the optical recording medium to change the recording layer from an amorphous state to a crystallized state. Is performed.
In the initialization step, conventionally, an initialization method of irradiating a small laser beam (spot diameter of about 1 μm, output several mW to 10 mW) subjected to focusing servo one track at a time has been adopted. Therefore, there was a problem that productivity was poor.

Therefore, conventionally, a high-power laser beam of several hundred mW to several tens of W is applied to irradiate a plurality of tracks with one track.
A pretreatment apparatus for an optical recording medium initialized by a beam has been proposed (see JP-A-60-106031).

When a plurality of tracks are initialized with a high-power laser beam, uniformity of the laser beam becomes a problem. That is, if the intensity distribution of the laser beam in the direction perpendicular to the direction of relative movement between the optical recording medium (optical disk) and the laser beam is non-uniform, the crystallization progresses in adjacent places, causing a difference in disc characteristics. For example, there arises a problem that non-uniformity occurs in the reflectance.
In particular, when a high-power gas laser such as a helium neon laser is used, it is important to make the intensity distribution uniform in the direction perpendicular to the relative movement direction between the optical disk and the laser beam.

Therefore, in the pre-processing apparatus for an optical recording medium described in Japanese Patent Application Laid-Open No. 60-106031, the orthogonal coordinate system XYZ with the optical axis direction of the first radiation light as the Z axis is used. Radiation light from a radiation light source passes through a first unidirectional lens having a lens function only in the X direction and a second unidirectional lens having a lens function only in the Y direction, and is recorded by a third lens. By focusing the light on the upper side, initialization is performed while considering the uniformity of the optical disk and the laser beam intensity, as shown in the beam profile in FIG.

[0006]

However, in such a conventional method for initializing an optical recording medium, as described above, uniformity can be achieved to some extent, but nonuniformity still remains. The challenge remains with uniform initialization. In particular,
In order to ensure the uniformity of the optical disk, it is necessary to irradiate the laser beam many times, and due to the multiple thermal shocks at the time of initialization, the repetitive characteristics of the disk characteristics such as jitter and modulation deteriorate, There was a problem that productivity deteriorated.

As disclosed in “Laser Research” Vol. 18, No. 8 (pp. 555 to 572), in a high-power semiconductor laser, a near-field image and a far-field image parallel to a bonding surface are trapezoidal. Although it has a similar shape, it still has remaining irregularities, and it is difficult to initialize the optical recording medium using the laser beam of the semiconductor laser as it is.

As described above, it is extremely difficult to obtain good disk characteristics (reflectance distribution, jitter, repetitive writing characteristics, etc.) with good productivity by the conventional initialization technique using a high-power laser beam.

Therefore, the first aspect of the present invention provides an objective lens.
A light scatterer is disposed in the laser beam path between the laser beam and the laser beam irradiation surface of the optical recording medium to irradiate the optical recording medium.
By uniforming the light intensity distribution of the laser beam that will be the reflectance of the high-output non-uniform light intensity of the laser beam of a large diameter is uniform in the light scattering body, fractional times optical recording medium in the laser beam irradiation It is an object of the present invention to provide a method for initializing an optical recording medium with improved productivity by improving the distribution.

According to a second aspect of the present invention, the light scatterer has a particle or a surface having an average roughness smaller than the wavelength of the laser beam, so that the incident laser beam can be scattered with a small scattering angle. It is an object of the present invention to provide an optical recording medium initialization method that can raise the efficiency of using a laser beam.

According to a third aspect of the present invention, as the light scatterer,
By using a material whose scattering power has a spatial distribution, for example, the light scattering power of the light scatterer corresponding to the center of the beam is increased, and the light scattering power of the light scatterer relative to the periphery of the beam is reduced. Accordingly, an object of the present invention is to provide an optical recording medium initialization method capable of further improving the uniformity of a laser beam and improving the in-circumferential reflectance distribution of the optical recording medium.

According to a fourth aspect of the present invention, as the light scatterer,
By using a diffraction grating that has the property of scattering light only in a direction perpendicular to the predetermined uniaxial direction, anisotropy is given to the light scattering direction, and an elliptical or rectangular shape with the light scattering direction as the long axis Of the laser beam in the long axis direction to increase the initializing linear velocity, improve the productivity of the initializing process, and further improve the disk characteristics such as repetitive writing characteristics. It is an object of the present invention to provide a method for initializing an optical recording medium that can be performed.

According to a fifth aspect of the present invention, a semiconductor laser is used as a laser light source, and a light scatterer is disposed at a position where the scattering direction is parallel to light in a direction parallel to the active layer of the semiconductor laser. Small, low-cost, highly operable semiconductor laser beam with excellent operability. Highly uniform light intensity of laser beam. High-energy density laser beam enables low-cost, high-speed initialization. An object of the present invention is to provide an optical recording medium initialization method.

According to a sixth aspect of the present invention, the light scatterer is supported by a slider which floats by a predetermined hydrodynamic force, and the distance from the optical recording medium is maintained at a predetermined distance, so that the laser beam is emitted. With constant light intensity and distribution,
It is an object of the present invention to provide an optical recording medium initialization method that can improve reliability while preventing defects of the optical recording medium due to contact between the light scatterer and the optical recording medium.

According to a seventh aspect of the present invention, the recording layer of the optical recording medium is heated by heat conduction from the light absorbing layer by coating a predetermined light absorbing layer on the laser beam irradiation surface before the laser beam irradiation. It is another object of the present invention to provide a method for initializing an optical recording medium capable of improving the laser absorption efficiency by lowering the reflectance by a light absorbing layer.

[0016]

According to a first aspect of the present invention, there is provided an optical recording medium initializing method, wherein a laser beam from a laser light source is optically recorded via a collimating lens and an objective lens.
Recording layer (optical recording information carrying layer) by irradiating the medium
An optical recording medium initializing method for performing initialization by heating the objective lens and a laser beam of the optical recording medium.
It arranged a predetermined light scatterer laser beam path between the irradiation surface, light of the laser beam irradiation surface of the optical recording medium
The above object is achieved by making the intensity distribution of the laser beam emitted uniform.

Here, the optical recording medium initialization includes a laser light source, an initialization optical system for irradiating the laser beam emitted from the laser light source to the optical recording medium, and a relative movement between the optical recording medium and the laser beam. Initialization mechanical system to be performed,
This is performed using a light scatterer and a focus mechanism installed in the laser beam optical path between the optical recording medium and the objective lens near the optical recording medium, and the laser beam is applied to the optical recording medium.
Irradiation is performed from the side of the optical recording information carrying layer opposite to the substrate, and initialization is performed.

The vicinity of the optical recording medium is a proximity area where the distance from the optical recording medium is, for example, approximately several μm to 1 mm.
In particular, it refers to a proximity region equal to or less than the thickness of the substrate of the optical recording medium.

The light scatterer is a transparent fine powder, a solution or glass in which these are dispersed, and has the property of scattering light. The shape of the light scatterer is arbitrary.

That is, a laser beam which does not pass through the substrate is irradiated onto the optical recording medium on the optical recording information carrying layer on the substrate which is the back surface of the optical recording medium , in the vicinity of the irradiation surface of the optical recording medium. A light scatterer is disposed in a laser beam optical path between the laser beam and the objective lens . Therefore, even when a laser beam having a non-uniform light intensity is incident on the light scatterer, the light intensity distribution of the laser beam passing through the light scatterer in the main part of the beam becomes uniform. In particular, the non-uniformity of the light intensity in a spatially short cycle is eliminated. At this time, if the light scattering body is a glass body in which fine particles are dispersed,
The light becomes diffuse transmitted light, and as the distance from the light scatterer increases, the light intensity decreases.However, since the light scatterer is present near the irradiation surface of the optical recording medium, light suitable for initialization is used. Strength can be maintained. In particular, since the laser beam is radiated from the opposite side of the substrate, the light scatterer can be brought arbitrarily close to the optical recording medium without being limited by the thickness of the substrate.

According to the above arrangement, a light scatterer is arranged in the laser beam optical path near the laser beam irradiation surface of the optical recording medium to make the intensity distribution of the laser beam uniform, so that a high-power large-diameter laser beam is obtained. The non-uniform light intensity of the laser beam can be made uniform by the light scatterer, and the reflectance distribution of the optical recording medium in a few times of laser beam irradiation is improved.
The optical recording medium can be initialized with high productivity.

In this case, for example, as described in claim 2, the light scatterer has an average roughness of a particle or a surface that scatters the laser beam, and a particle diameter of the particle or an average of the plane. The magnitude of the roughness may be equal to or less than the wavelength of the laser beam.

Here, if the average roughness of the particles or the surface of the light scatterer is less than the wavelength of the laser beam, the light scatter in the light scatterer is predominantly scattered at a small scattering angle, and the reflected light is suppressed. Then, the utilization efficiency of the laser beam is improved.

According to the above configuration, since the light scatterer has the average roughness of the particles or the surface of the wavelength of the laser beam or less, it is possible to cause the incident laser beam to scatter with a small scattering angle. In addition, the efficiency of using a laser beam can be improved.

Further, for example, the light scatterer may have a spatial distribution of light scattering ability.

Here, in order to make the intensity distribution of the main part of the laser beam having the intensity distribution approximated by Gaussian uniform, the light scattering ability of the light scatterer corresponding to the center of the laser beam is increased. When the light scattering ability of the light scatterer corresponding to the peripheral portion of the beam is weakened, the laser beam that has passed through the light scatterer can be a direct beam that passes without being scattered, and a diffuse transmitted light that has been scattered and transmitted, Are mixed, but the intensity distribution of the main part of the laser beam can be made highly uniform. In addition, the outer part of the main part of the laser beam is irradiated with weak diffused light or direct light, but this does not contribute much to heating of the optical recording medium, so that the initial crystallization of the phase change type optical recording medium is performed. Does not occur. The uniformity of the laser beam in the portion of the optical recording medium parallel to the track reduces thermal damage due to initialization, and the uniformity of the beam in the direction traversing the track improves uniformity of the reflectance distribution. Is important in the development.

Therefore, the light intensity can be made more uniform by changing the intensity of the light scattering ability of the light scatterer for each location according to the spatial intensity distribution of the laser beam.

According to the above configuration, as the light scatterer, a light scatterer having a spatial distribution is used. For example, the light scatterer corresponding to the center of the beam has a stronger light scatterer, The light scattering ability of the light scattering body with respect to the peripheral portion of the optical recording medium can be weakened, the uniformity of the laser beam can be further improved, and the reflectance distribution in the circumference of the optical recording medium can be improved.

Further, for example, the light scatterer may be a diffraction grating having a property of scattering light only in a direction perpendicular to a predetermined uniaxial direction.

Here, as the diffraction grating, for example, a diffraction grating having a groove or the like extending in a one-dimensional direction and having a spatial change in the depth and pitch of the groove can be used. .

If the light scatterer is a diffraction grating that scatters light only in a direction perpendicular to one axis, it is possible to have anisotropy in the light scattering direction, and the scattering ability (intensity and / or intensity) of a portion having a high energy density is increased. Alternatively, if the scattering angle) is increased and the scattering power of the portion having a relatively low energy density is reduced, the light intensity can be made highly uniform. In addition, a direct beam (a beam that is not scattered by light) can be brought into a focus state, and a beam with high energy density can be obtained.

Therefore, the initializing linear velocity can be increased, the productivity of the initializing step can be improved, and the time during which the optical recording medium is exposed to the thermal shock can be shortened. Characteristic deterioration can be suppressed. As a result, the repetitive writing characteristics and the like can be improved.

According to the above configuration, since the diffraction grating having the property of scattering light only in the direction perpendicular to the predetermined uniaxial direction is used as the light scatterer, the light scattering direction is made anisotropic. The long axis direction of the elliptical or rectangular laser beam whose light scattering direction is the long axis can be made uniform, the initializing linear velocity can be increased, and the productivity of the initializing step can be improved. In addition, the disk characteristics such as the repetitive writing characteristics can be further improved.

Further, for example, as set forth in claim 5, the laser light source is a semiconductor laser, and the light scatterer has a scattering direction parallel to light in a direction parallel to the active layer of the semiconductor laser. It may be arranged at a position where

Here, in the initialization using a high-power semiconductor laser, a beam having a shape similar to a rectangle or an ellipse is irradiated. The light intensity distribution in the longitudinal direction corresponds to the light parallel to the active layer. ing. The near-field image of light in the direction parallel to the active layer of this semiconductor laser has a trapezoidal light intensity distribution as shown in FIG. 5, but the light intensity distribution of the main part of the laser beam is not completely uniform. And a light intensity distribution of ± 10% or more remains. The cycle at which the light intensity of the laser beam becomes maximum is in the range of several μm to several tens of μm. It is important to eliminate the non-uniformity of the light intensity in this range and to approach an ideal trapezoidal beam profile. It is. Therefore, if the light in the direction parallel to the active layer of the semiconductor laser and the scattering direction of the light scatterer are made to have a parallel positional relationship, the beam profile is made uniform mainly in the longitudinal direction of the laser beam, and the length of the short axis is increased. The size (several μm) is not changed much. Therefore, initialization at a high linear velocity by a laser beam having a high energy density can be performed.

According to the above configuration, a semiconductor laser is used as the laser light source, and the light scatterer is disposed at a position where the scattering direction is parallel to the light parallel to the active layer of the semiconductor laser. Small, low-cost, highly operable laser beam of a semiconductor laser with excellent operability can be homogenized with high precision, and initialization with a high energy density laser beam at low cost and high linear velocity Can be.

Further, for example, the light scatterer is supported by a predetermined slider which floats by a predetermined hydrodynamic force, and a distance from the optical recording medium is a predetermined distance. May be maintained.

Here, the floating principle of the slider is as follows.
By fluid force due to relative motion with the optical recording medium,
Alternatively, a material that floats by injecting pressurized air or the like can be used.

In the initialization of the optical recording medium, the light intensity and distribution of the laser beam on the optical recording medium depend on the distance between the optical recording medium and the light scatterer. It is important to precisely control the distance to the optical recording medium in order to properly initialize the optical recording medium. Then, the slider is moved 0.1 mm by relative movement with the optical recording medium.
It floats from 1 μm to several tens of μm, but under a constant linear velocity,
The flying height is extremely stable, and is suitable as a support for the light scatterer. Also, by using a slider,
Defects due to contact between the light scatterer and the optical recording medium are extremely small, which contributes to improvement in reliability.

According to the above arrangement, the light scatterer is supported by the slider that floats by a predetermined hydrodynamic force, and the distance from the optical recording medium is maintained at a predetermined distance. The distribution can be made constant, the defect of the optical recording medium due to the contact between the light scatterer and the optical recording medium can be prevented, and the reliability can be improved.

Further, for example, before the laser beam is irradiated on the optical recording medium, a predetermined light absorbing layer may be coated on a laser beam irradiation surface of the optical recording medium.

Here, the light absorbing layer is made of carbon, fine metal particles,
Alloy fine particles, metal thin film (thickness: several nm to several tens nm),
An element having light absorption such as an alloy thin film, a compound film of chromium oxide, aluminum oxide, aluminum nitride, iron oxide or the like, or a mixed film thereof can be used. Metal compounds or alloy compounds in which the stoichiometric compound does not have light absorption are used as a light absorbing layer in the form of a thin film with a non-stoichiometric composition or a mixture of metal and stoichiometric fine particles. I do.

The layer structure of an optical recording medium to which the method for initializing an optical recording medium of the present invention can be applied varies depending on the type, but when the light absorbing layer is formed on the back surface of the reflective layer, The laser for recording and reproducing optical information does not reach the light absorbing layer. In this case, the light absorbing layer is, in an optical sense,
It does not directly affect recording and reproduction. The layer structure of the optical recording medium to which the present invention is applied is, for example, a layer structure in which a substrate / first protective layer / recording layer / second protective layer / reflective layer / light absorbing layer are laminated in this order. is there. The coating of an ultraviolet-curable resin having poor heat resistance is usually performed after the implementation of the present invention.

Therefore, the recording layer of the optical recording medium is heated by the heat conduction from the light absorbing layer, and the reflectivity is reduced by the action of the light absorbing layer, so that the efficiency of using the laser beam is improved.

According to the above configuration, since the predetermined light absorbing layer is coated on the laser beam irradiation surface before the laser beam irradiation, the recording layer of the optical recording medium can be heated by heat conduction from the light absorbing layer. At the same time, the reflectance can be reduced by the light absorbing layer, and the laser absorption efficiency can be improved.

[0046]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.

FIGS. 1 to 5 show an embodiment of the optical recording medium initialization method of the present invention. FIG. 1 shows an embodiment of the optical recording medium initialization method of the present invention. 1 is a side view of a main part of an optical recording medium initialization device 1 to be performed.

In FIG. 1, an optical recording medium initialization device 1
Is provided with an initialization mechanical system 20 for rotating and moving the optical recording medium 10 to be initialized, an initialization optical system 30 for initializing the optical recording medium 10, a focus mechanism 40, and the like.

In the optical recording medium 10, a lower protective layer 12, a recording layer (optical recording information carrying layer) 13, an upper protective layer 14, and a reflective heat radiation layer 15 are sequentially laminated on a substrate 11. Immediately after the optical recording medium 10 is manufactured, the recording layer 13 is in an amorphous state, and changes its phase from an amorphous state to a crystallized state by being irradiated with a laser beam and heated. Changing the phase of the recording layer 13 from an amorphous state to a crystallized state is called initialization.

The initialization mechanical system 20 includes the disk rotating mechanism 2
1 and a disk feed mechanism 22 and the like. The disk rotation mechanism 21 drives the optical recording medium 10 to rotate at a predetermined rotation speed. The disk feed mechanism 22 translates the optical recording medium 10 in parallel with the rotation of the optical recording medium 10.

The focusing mechanism 40 includes a pair of focusing lasers 41a and 41b, a pair of focusing laser collimating lenses 42a and 42b, a pair of focusing laser objective lenses 43a and 43b, a pair of polarization beam splitters 44a and 44b, and a pair of focusing lasers. 1/4 wavelength plate 45
a, 45b, a pair of focus signal generators 46a,
6b and focusing actuators 47a and 47b. Focusing lasers 41a, 41b
For example, a He-Ne laser or the like is used, and a focusing laser beam is emitted to the focusing laser collimating lenses 42a and 42b. The focusing laser collimating lenses 42a and 42b convert the incident laser beam into parallel light and enter the focusing laser objective lenses 43a and 43b via the polarizing beam splitters 44a and 44b and the quarter-wave plates 45a and 45b. Focusing laser objective lens 43a, 43b
Collects and irradiates the laser beam incident through the quarter-wave plates 45a and 45b onto the surface of the optical recording medium 10, and reflects the reflected light from the optical recording medium 10 into the quarter-wave plates 45a and 45b. Incident on. Quarter wave plates 45a, 45
b is a focusing laser objective lens 43a, 43b
And the polarization beam splitters 44a and 44b, and changes the plane of polarization of the laser beam reflected from the optical recording medium 10 with respect to the polarization beam splitters 44a and 44b. The polarization beam splitters 44a and 44b
The laser beams incident from the quarter-wave plates 45a and 45b are reflected by focus signal generators 46a and 46b. The focus signal generators 46a and 46b determine a focus shift based on the incident laser beam and output a focus signal to the focus actuators 47a and 47b. Focus actuator 4
7a and 47b are focus signal generators 46a and 46
The position of the focus laser objective lenses 43a and 43b is adjusted based on the focus signal from b to adjust the focus shift.

The initialization optical system 30 includes an initialization high-power laser 31, a high-power laser collimator lens 32, a high-power laser objective lens 33, a light scatterer 34, and the like. 31 is, for example, A
An r laser is used. High power laser 31 for initialization
Emits a high-power laser to the high-power laser collimating lens 32, and makes the laser beam from the initialization high-power laser 31 incident on the high-power laser objective lens 33 as parallel light. High power laser objective lens 33
Irradiates an incident laser beam onto the surface of the optical recording medium 10 via the light scatterer 34 in a predetermined focus state. The high-power laser objective lens 33 is connected to the focus laser objective lenses 43a and 43b of the focus mechanism 40, and the focus laser objective lenses 43a and 43b are defocused so that the optical recording medium 10 is adjusted. The position is adjusted so that the distance with the distance becomes a predetermined distance. In the present embodiment, the laser beam focused by the high-power laser objective lens 33 is in a focused state in the light scatterer 34, and the size of the incident surface of the laser beam to the light scatterer is
It is adjusted so that the beam diameter becomes smaller.

The light scatterer 34 is formed of a cylindrical glass body. The side surface of the light scatterer 34 irradiated with the laser beam has irregularities having an average roughness of several μm by polishing or the like.
For example, irregularities of φ50 μm × 50 μm are provided. This light scatterer 34 is held by a holding mechanism (not shown).
It is held near the surface of the optical recording medium 10. The term “in the vicinity of the optical recording medium 10” means that the distance from the optical recording medium 10 is, for example, a proximity area of approximately several μm to 1 mm, and in particular, a proximity area equal to or less than the thickness of the substrate of the optical recording medium 10. .

Next, the initialization processing of the optical recording medium 10 by the optical recording medium initialization apparatus 1 of the present embodiment will be described. When the optical recording medium initialization apparatus 1 initializes the optical recording medium 10, the disk rotation mechanism 2 of the initialization mechanical system 20 is used.
1 while rotating the optical recording medium 10 and moving the optical recording medium 10 in parallel by the disk feed mechanism 22,
The optical recording medium 10 is initialized by irradiating a laser beam with a high output and a large diameter according to 0.

At this time, the initialization optical system 30 is focused by the focusing mechanism 40, the position of the high-power laser objective lens 33 is adjusted, and the laser beam emitted from the initialization high-power laser 31 is scattered. Body 34
The laser beam is focused inside, and the size of the incident surface of the laser beam on the light scatterer 34 is adjusted to be smaller than the beam diameter.

The light scatterer 34 is formed of a cylindrical glass body, and has irregularities with an average roughness of several μm, which is equal to or smaller than the laser beam wavelength, on the side surface to which the laser beam is irradiated.

Therefore, the laser beam having a large light output and having a non-uniform light intensity incident on the light scatterer 34 is scattered by the unevenness existing on the side surface of the light scatterer 34, and transmitted through the light scatterer 34. The light beam intensity (light intensity) is made uniform. A laser beam having a uniform light intensity is applied to the optical recording medium 10, and a small number of laser beam irradiations are used to improve the reflectance distribution of the optical recording medium and initialize the optical recording medium with high productivity. Can be.

In this case, the light scatterer 34 is not limited to the light scatterer 34 having the irregularities formed on the side surface as described above. For example, as shown in FIG.
May have a large number of light scattering particles 52 inside a cylindrical glass body 51. The light scattering particles 52
When the particle diameter is formed to be equal to or less than the wavelength of the laser beam irradiated on the light scatterer 50, backscattering, that is, scattering toward the high-power laser objective lens 33 side can be suppressed, and suitable small-angle scattering Can be caused to dominate. As a result, the efficiency of laser beam irradiation on the optical recording medium 10 can be improved, and the utilization efficiency of the laser beam used for initializing the optical recording medium 10 can be improved.

Further, as shown in FIG.
May be formed such that a light scattering layer 58 having minute light scattering particles 57 is formed on at least one of the incident surface and the emission surface of the laser beam of the cylindrical glass body 56. Similar effects can be obtained.

Further, as shown in FIG.
May be formed by dispersing light scattering particles 62 having a small particle diameter in a convex lens-shaped glass body 61. The light scattering body 60 may be disposed in the vicinity of the laser beam emission side of the light scattering body 60. A transparent concave lens 63 is provided. The transparent concave lens 63 corrects the influence of light refraction by the light scatterer 60.

Since the light scatterer 60 has a large thickness at the central portion, the scattering power at the central portion becomes large in a plane perpendicular to the optical axis of the incident laser beam, and the light scattering power is spatially distributed. have. Therefore, the light intensity distribution of the incident laser beam approximated by a curve such as Gaussian,
That is, the light of the central portion is greatly scattered with respect to the profile of the incident beam in which the beam intensity is maximized at the central portion, and is radiated to the peripheral portion. As described above, since the light intensity distribution of the main part of the laser beam having the light intensity distribution approximated by Gaussian is made uniform, the light scattering ability of the light scatterer 60 corresponding to the central part of the laser beam is increased, When the light scattering ability of the light scatterer 60 corresponding to the peripheral portion of the beam is weakened, the light that has passed through the light scatterer 60 has a direct beam that passes without being scattered, and a diffuse transmitted light that has been scattered and transmitted. Are mixed, but the light intensity distribution of the main part of the laser beam can be made highly uniform. The outer periphery of the main part of the laser beam is irradiated with weak diffused light or direct light.
Since it does not contribute much to the heating of 0, unevenness in the initial crystallization of the optical recording medium 10 of the phase change type does not occur.
The uniformity of the laser beam in a portion parallel to the track of the optical recording medium 10 reduces thermal damage caused by the initialization, and the uniformity of the beam in the direction crossing the track is one of the reflectivity distribution. Important in the specification. Therefore, the light intensity can be made more uniform by changing the intensity of the light scattering ability of the light scatterer 60 at each location according to the spatial intensity distribution of the laser beam.

As described above, since the light scatterer 60 has a spatial distribution of the scattering power, for example, the light scatterer 60 corresponding to the center of the beam has a high light scattering power and the light The light scattering ability of the light scatterer 60 with respect to the light is weakened, the light intensity distribution at the center and the periphery of the beam is made uniform, and light having a gentle gradient near the maximum value is applied to the optical recording medium 10. Therefore, the uniformity of the laser beam can be further improved. In this case, the light scatterer 60
The same effect can be obtained even when the light scattering particles are non-uniformly thinly coded on a flat plate.

The light scatterer 34 is not limited to the one using the light scattering particles or the roughness such as unevenness formed on the surface. For example, a diffraction grating that scatters light only in a direction perpendicular to one axis is used. It may be. As a diffraction grating, for example,
A diffraction grating having a groove or the like extending in a one-dimensional direction and having a spatial change in the depth and pitch of the groove can be used. In this case, the light scattering angle of the diffraction grating is in the range of several degrees to 70 degrees, and the light scattering body 34 having an appropriate scattering angle is selected according to the set distance between the light scattering body 34 and the optical recording medium 10. I do. When a high degree of uniformity of the beam intensity is required, at least one of the scattering angle and the scattering power of the portion where the beam intensity is large is increased.

As described above, when the light scatterer 34 is a diffraction grating that scatters light only in a direction perpendicular to one axis, the light scatterer 34 can have anisotropy in the light scattering direction and can scatter light in a portion having a high energy density. Performance (intensity and / or scattering angle)
By reducing the scattering power of the portion having a relatively low energy density, the light intensity can be made highly uniform. Also,
A direct beam (a beam that is not scattered by light) can be brought into a focus state, and a beam with a high energy density can be obtained.

Therefore, the initializing linear velocity can be increased, the productivity of the initializing step can be improved, and the time during which the optical recording medium is exposed to the thermal shock can be shortened. Characteristic deterioration can be suppressed. As a result, the repetitive writing characteristics and the like can be improved.

The initialization high-power laser 31
Is not limited to an Ar laser, but may be a semiconductor laser. As the high power laser 31 for initialization,
When a semiconductor laser is used, the light scatterer 34 is disposed at a position where the scattering direction is parallel to the light parallel to the active layer of the semiconductor laser.

That is, when a high-power semiconductor laser is used as the high-power laser 31 for initialization, a laser beam having a rectangular or elliptical shape is irradiated. It corresponds to light in the direction parallel to the layer. The near-field pattern (near-field pattern) of light in the direction parallel to the active layer has a trapezoidal intensity distribution as shown in FIG. 5, but the light intensity distribution of the main part of the laser beam is completely uniform. But not ±
An intensity distribution of 10% or more remains. The cycle at which the light intensity of the laser beam becomes maximum is in the range of several μm to several tens of μm, and in order to properly initialize the optical recording medium 10, the non-uniformity of the light intensity in this range is eliminated. It is important to approach an ideal trapezoidal beam profile.

Therefore, when a semiconductor laser is used as the high power laser 31 for initialization, the light in the direction parallel to the active layer of the semiconductor laser and the scattering direction of the light scatterer 34 are in a parallel positional relationship. In this manner, the beam profile is made uniform in the longitudinal direction of the laser beam, and the length of the minor axis (several μm) is not changed much. Therefore, initialization at a high linear velocity by a laser beam having a high energy density can be performed.

That is, when a semiconductor laser is used as the high-power laser 31 for initialization, the light scatterer 34 is arranged at a position where the scattering direction is parallel to the light parallel to the active layer of the semiconductor laser. With this, the light intensity of the laser beam of the semiconductor laser, which is small, low-cost, and excellent in operability, can be made uniform with high accuracy.
Initialization can be performed at a low cost and at a high linear velocity by using a laser beam having a high energy density.

When the light scatterer 34 is held by the slider, the distance between the optical recording medium 10 and the light scatterer 34 is always kept constant, and the light intensity and distribution of the laser beam can be made constant. The defect of the optical recording medium 10 due to the contact between the scatterer 34 and the optical recording medium 10 can be prevented, and the reliability can be improved.

That is, the light scatterer 34 is supported at the end of the slider that floats by a predetermined hydrodynamic force,
The distance from the optical recording medium 10 is maintained at a predetermined interval. As the floating principle of the slider, it is possible to use the one based on a fluid force caused by the relative movement with the optical recording medium 10, or the one floating by injecting pressurized air. In the initialization of the optical recording medium 10, the light intensity and distribution of the laser beam on the optical recording medium 10 depend on the distance between the optical recording medium 10 and the light scatterer 34. It is important to accurately control the distance from the scatterer 34 in order to properly initialize the optical recording medium 10. The slider moves from 0.1 μm to several tens μm depending on the relative movement with the optical recording medium 10.
Although floating, the floating amount is extremely stable under a constant linear velocity, and is suitable as a support for the light scattering member 34.
For example, when the light scatterer 34 is supported at the end of a slider having a linear velocity of 6 m / s and a flying height of 5 μm, the distance between the optical recording medium 10 and the light scatterer 34 is about 30 μm. Further, by using the slider, defects due to contact between the light scatterer 34 and the optical recording medium 10 are extremely small, and reliability can be improved.

Further, the optical recording medium 10 may be coated with a predetermined light absorbing layer on the laser beam irradiation surface before the laser beam irradiation. As the light absorbing layer,
Carbon, metal fine particles, alloy fine particles, metal thin film (thickness: several n
m to several tens of nm), a light-absorbing element such as an alloy thin film, or a compound film such as chromium oxide, aluminum oxide, aluminum nitride, or iron oxide, or a mixed film thereof. For example, coating, spin coating, vacuum deposition, sputtering, anodic oxidation or CVD (Chemic
al Vapor Deposition). A metal compound or alloy compound in which a compound having a stoichiometric composition does not have light absorption is used as a light absorbing layer as a non-stoichiometric composition or a thin film in which fine particles of a metal and a stoichiometric composition are mixed. . When the reflective film 15 of the optical recording medium 10 is formed by coding an Al alloy or the like by sputtering, the reflective film 15 is used.
Following the codec of No. 3, nitrides of several nm to several tens n
An effective light absorption layer can be formed by m-coding. The nitride has a non-stoichiometric composition (A
l-rich) nitride, and a composition having an appropriate light absorption coefficient is selected. Since the light absorption coefficient of this nitride decreases with an increase in the nitrogen concentration, an appropriate gradient is applied to the nitrogen concentration (for example, the nitrogen concentration is low on the Al alloy side and the nitrogen concentration is high on the surface side). Lower the reflectance,
Set an appropriate light absorption coefficient.

The coding of the reflection layer 15 and the light absorption layer is performed using the same sputtering chamber.
Can be coded continuously. For example, rf sputtering of the reflection layer 15 is performed using Ar gas as an introduction gas.
(200 sccm) and 1kW input power, 1
The light absorbing layer was sputtered under rf sputtering conditions and an introduced gas of Ar (200).
sccm) + N2 (5-10sccm), input power 1k
W is formed to a thickness of 20 nm. The flow rate of nitrogen at this time is increased with time.

Although the layer structure of the optical recording medium 10 varies depending on the type, when the light absorbing layer is formed on the back surface of the reflective heat radiation layer 15, a laser for recording and reproducing optical information is used. However, it does not reach the light absorbing layer.

Therefore, the recording layer 13 of the optical recording medium 10 can be heated by the heat conduction from the light absorbing layer, and the reflectance of the recording medium 13 decreases due to the action of the light absorbing layer, thereby improving the efficiency of using the laser beam. be able to.

Although the invention made by the inventor has been specifically described based on the preferred embodiments, the invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the invention. It goes without saying that it is possible.

[0077]

According to the optical recording medium initialization method of the present invention , a light scatterer is provided in a laser beam optical path between an objective lens and a laser beam irradiation surface of the optical recording medium. In order to make the intensity distribution of the laser beam irradiated on the laser irradiation surface of the optical recording medium uniform, the non-uniform light intensity of the high-power large-diameter laser beam is made uniform by the light scatterer. By improving the reflectance distribution of the optical recording medium in a few times of laser beam irradiation, the optical recording medium can be initialized with high productivity.

According to the optical recording medium initialization method of the second aspect of the present invention, since the light scatterer has the average roughness of the particles or the surface smaller than the wavelength of the laser beam, the incident laser beam In this case, scattering with a small scattering angle can be caused, and the efficiency of using a laser beam can be improved.

According to the method for initializing an optical recording medium according to the third aspect of the present invention, since a light scattering body having a spatial distribution of scattering power is used, it corresponds to, for example, a beam center. The light scattering ability of the light scatterer is increased, and the light scattering ability of the light scatterer with respect to the periphery of the beam is reduced, so that the uniformity of the laser beam can be further improved. The distribution can be improved.

According to the optical recording medium initializing method of the invention described in claim 4, since the diffraction grating having the property of scattering light only in a direction perpendicular to the predetermined uniaxial direction is used as the light scatterer, By giving anisotropy to the light scattering direction, the long axis direction of the rectangular or elliptical laser beam whose long axis is the light scattering direction can be made uniform, and the initializing linear velocity is increased, The productivity of the initialization step can be improved, and the disk characteristics such as the repetitive writing characteristics can be further improved.

According to the optical recording medium initialization method of the present invention, a semiconductor laser is used as a laser light source, and a light scatterer is scattered parallel to light whose direction is parallel to the active layer of the semiconductor laser. The laser beam of the semiconductor laser, which is compact, low-cost, and excellent in operability, can be uniformized with high precision at high accuracy. , And can be initialized at a high linear velocity.

According to the optical recording medium initializing method of the invention, the light scatterer is supported by the slider which floats by a predetermined hydrodynamic force, and the distance from the optical recording medium is set to a predetermined distance. , The light intensity and distribution of the laser beam can be kept constant, the defect of the optical recording medium due to the contact between the light scatterer and the optical recording medium can be prevented, and the reliability can be improved. Can be.

According to the optical recording medium initializing method of the present invention, since a predetermined light absorbing layer is coated on the laser beam irradiation surface before the laser beam irradiation, light by heat conduction from the light absorbing layer is applied. The recording layer of the recording medium can be heated, and the reflectance can be reduced by the light absorbing layer, so that the laser absorption efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of an optical recording medium initialization apparatus to which an embodiment of an optical recording medium initialization method according to the present invention is applied.

FIG. 2 is an enlarged front view of the light scatterer of FIG.

FIG. 3 is an enlarged front view showing another example of the light scatterer.

FIG. 4 is an enlarged front view showing still another example of the light scatterer.

FIG. 5 is a diagram showing an example of a near-field pattern of a semiconductor laser.

FIG. 6 is a diagram showing a beam profile used in conventional optical recording medium initialization.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Optical recording medium 11 Substrate 12 Lower protective layer 13 Recording layer 14 Upper protective layer 15 Reflection heat dissipation layer 20 Initialization mechanical system 21 Disk rotation mechanism 22 Disk feed mechanism 30 Initialization optical system 31 High power laser for initialization 32 High power laser Collimating lens 33 for high power laser objective lens 34 light scatterer 40 focusing mechanism 41a, 41b focusing laser 42a, 42b focusing laser collimating lens 43a, 43b focusing laser objective lens 44a, 44b polarizing beam splitter 45a, 45b1 / Four-wavelength plates 46a, 46b Focus signal generators 47a, 47b Focusing actuators 50, 55, 60 Light scattering bodies 51, 56, 61 Glass bodies 52, 57, 62 Light scattering particles 58 Light scattering layers 63 Transparent concaves Lens

Claims (7)

(57) [Claims] 1. A laser beam from a laser light source,
An optical recording medium initialization method for heating and initializing a recording layer by irradiating an optical recording medium through a collimating lens and an objective lens , wherein the objective lens and the laser beam of the optical recording medium are Arranging a light scatterer in a laser beam optical path between the irradiation surface and the laser beam of the optical recording medium
A method for initializing an optical recording medium, comprising equalizing the intensity distribution of a laser beam applied to a beam irradiation surface . 2. The light scatterer has an average roughness of particles or a surface that scatters the laser beam, and the particle diameter of the particles or the average roughness of the plane is determined by the wavelength of the laser beam. 2. The method for initializing an optical recording medium according to claim 1, wherein: 3. The optical recording medium initialization method according to claim 1, wherein the light scatterer has a light scattering ability having a spatial distribution. 4. The optical recording medium according to claim 1, wherein the light scatterer is a diffraction grating having a characteristic of scattering light only in a direction perpendicular to a predetermined uniaxial direction. Method. 5. The method according to claim 1, wherein the laser light source is a semiconductor laser, and the light scatterer is disposed at a position where its scattering direction is parallel to light in a direction parallel to an active layer of the semiconductor laser. The method for initializing an optical recording medium according to any one of claims 1 to 4, wherein: 6. The light scatterer is supported by a predetermined slider that floats by a predetermined hydrodynamic force, and a distance from the optical recording medium is maintained at a predetermined distance. The method for initializing an optical recording medium according to claim 1. 7. The optical recording medium according to claim 1, wherein a predetermined light absorbing layer is coated on a laser beam irradiation surface of the optical recording medium before the laser beam irradiation. The optical recording medium initialization method according to the above.