JPH10106045A - Optical recording medium and its manufacturing method and equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain an uniform initialization characteristic all over the initialization area by varying a laser light power according to variations in film thickness of a filmformed recording layer at the time of initialization. SOLUTION: A substrate 1 of an optical recording medium is driven by a rotation driving means 2, for example, so as to rotate with a constant linear velocity. A laser light beam 4 emitted from a laser generation means 3 is focused through conversion lenses 5a, 5b, and emitted onto the substrate l to crystallize and initialize the recording layer. A power of the emitted laser beam is controlled by a power control device 7. This power control device 7 operates based on signals set at a data input device 8. To the data input device 8, a feed pitch of the laser beam, an initialization range, an emitted power reference as well as a pre-grasped film thickness of the recording layer, more precisely, variations in the film thickness, are inputted.

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, a method of manufacturing the same, and a manufacturing apparatus thereof, and more particularly, to an improvement in an optical recording medium initialization technique.

[0002]

2. Description of the Related Art An optical recording medium is provided with an information recording section capable of optically recording and reproducing information on a substrate, and is used as a disk for files such as documents and data. While rotating the optical recording medium at a high speed, a laser beam narrowed down to about 1 μm is irradiated to read data from the recording layer or record data on the recording layer while performing focus adjustment and position detection.

[0003] This recording layer is made of a specific alloy which can be reversibly changed between a crystal and an amorphous by a laser beam,
An optical recording medium of a phase change type or the like that enables overwrite recording in which data is read based on a difference in reflectance of a recording layer is already known. In this phase-change type optical recording medium, after forming another layer such as a recording layer and a protective layer on a substrate, initialization for crystallizing the recording layer using a laser beam or the like is performed.

In this initialization, (1) when irradiating a laser beam while rotating the substrate on which the recording layer and the like are formed, the substrate is rotated so that the linear velocity at the irradiation position becomes constant, A method of initializing while keeping the irradiation power of the laser beam constant in the initialization region; and (2) keeping the angular velocity of the substrate rotation constant and reducing the linear velocity caused by the movement of the irradiation position of the laser beam in the radial direction of the substrate. There is known a method of changing the irradiation power of laser light by an amount corresponding to the change.

[0005]

However, the film formed on the substrate of the optical recording medium has a variation in film thickness and is not always uniform. In particular, when the thickness of the recording layer varies, the degree of initialization is affected. For example, it affects the obtained reflectance and the crystal grain size.

Therefore, it is difficult to make the reflectivity and the crystal grain size uniform by the method of (1) in which the irradiation power is constant and the recording layer has a variation in film thickness.

In the above method (2), the variation in the film thickness of the recording layer is taken into account only by changing the irradiation power of the laser beam by an amount corresponding to the change in the linear velocity. As a result, the variation in the initializing characteristics due to the variation in the thickness of the recording layer, that is, the variation in the reflectance and the variation in the crystal grain size also occurred.

When the reflectance of the optical recording medium varies, the probability of reading and writing errors increases. If this is to be corrected by the improvement of the recording / reproducing apparatus, the signal processing circuit becomes complicated. In addition, when the crystal grain size varies, the jitter characteristic is deteriorated as compared with the case where the crystal grain size is uniform.

An object of the present invention is to make it possible to perform more uniform desired initialization by controlling the irradiation power of laser light more appropriately.

[0010]

In order to solve the above-mentioned problems, a method of manufacturing an optical recording medium according to the present invention comprises: forming a recording layer on a substrate; The method is characterized in that the light irradiation power is changed according to the thickness of the recording layer.

This method is particularly suitable for application to a phase change type optical recording medium in which the recording layer to be formed is made of a material which undergoes a phase change. The control is performed so that the crystal grain size of the recording layer is as uniform as possible, or the obtained reflectance is as uniform as possible.

In this method, any one of the above-described method of rotating the substrate so that the linear velocity at the laser beam irradiation point is constant and the method of rotating the substrate at a constant angular velocity upon initialization are described. It can also be applied to In the latter method, while rotating the substrate at a constant angular velocity, the irradiation power of the laser beam is changed in accordance with the change in the thickness of the recording layer in addition to the change in the linear velocity. .

An optical recording medium according to the present invention is manufactured by the above-described method and uses a substrate having a thickness of 1.2 mm or less.

Further, the method of manufacturing an optical recording medium according to the present invention comprises: means for rotating a substrate on which a recording layer is formed; means for irradiating the substrate with a laser beam for initialization; It comprises means for controlling the irradiation power, and means for sending a signal for changing the irradiation power according to the thickness of the recording layer to the irradiation power control means.

In the present invention, at the time of initialization, the irradiation power of the laser beam is appropriately changed and controlled in accordance with the previously grasped change in the thickness of the recording layer. Therefore, even when the thickness of the recording layer varies, the influence of the variation on the initialization characteristics is eliminated, and uniform characteristics, that is, uniform crystal grain size and uniform reflectance can be obtained over the entire surface.
As a result, the initialized optical recording medium has uniform recording characteristics over the entire recording area.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. As an optical recording medium according to the present invention, a medium for writing data using light or a change or difference in optical properties (light reflectance, spectral reflectance, light polarization state of reflected light, etc.) of each part of a recording portion is used. Read-only or rewritable optical recording media such as a magneto-optical recording medium and a phase-change optical recording medium may be used as long as they can read data. It is suitable for a recording medium.

A phase change type optical recording medium is generally provided with a recording layer on a transparent substrate, and a specific metal which can be reversibly changed between crystal and amorphous by a laser beam is used for the recording layer. ing. The layer configuration on the substrate may be, for example, a layer configuration having at least a first protective layer / recording layer / second protective layer / reflective layer on a transparent substrate.

The recording layer of the phase-change optical recording medium includes, for example, a Te-Ge-Sb-Pd alloy, Te-Ge-Sb-
Pd-Nb alloy, Nb-Ge-Sb-Te alloy, Pt-
Ge-Sb-Te alloy, Ni-Ge-Sb-Te alloy,
Ge-Sb-Te alloy, Co-Ge-Sb-Te alloy,
In-Sb-Te alloys, In-Se alloys, and alloys containing these as main components are used. Especially Te-Ge-
Sb-Pd alloys and Te-Ge-Sb-Pd-Nb alloys are preferable because they hardly deteriorate even when recording / erasing / reproducing is repeated, and have excellent thermal stability. A particularly desirable recording film composition is, for example, in the range represented by the following formula, from the viewpoint of excellent thermal stability and repetition stability. M _z (Sb _x Te _(1-x) ) _1-yz (Ge _0.5 Te _0.5 )
_y 0.35 ≦ x ≦ 0.5 0.20 ≦ y ≦ 0.50 ≦ z ≦ 0.05 where M is at least one metal selected from palladium, niobium, platinum, silver, gold and cobalt, Sb Represents antimony, Te represents tellurium, and Ge represents germanium. Also,
x, y, z and numerals represent the number of atoms of each element (the number of moles of each element). In particular, palladium and niobium preferably contain at least one kind. In this case, z is 0.
It is preferably at least 0005. These alloys are applied on the first protective layer provided on the substrate by, for example, sputtering to form a recording layer.

The first protective layer and the second protective layer mechanically protect the recording layer, and also prevent the substrate and the recording layer from being deformed by heat due to recording and from deteriorating the recording / erasing / reproducing characteristics. In addition, it plays a role in giving the recording layer moisture and heat resistance and oxidation resistance. ZnS,
SiO ₂ , Ta ₂ O ₅ , ITO, ZrC, TiC, Mg
An inorganic film such as F ₂ or a mixed film thereof can be used. In particular, a mixed film of ZnS and SiO ₂ and a mixed film of ZnS and MgF ₂ are excellent in moist heat resistance, and furthermore, are preferable because deterioration of the recording layer at the time of recording / erasing / reproduction is suppressed.

As the reflection layer, a mixture of a metal or a metal oxide, a metal nitride, a metal carbide and the like, for example, Zr, Cr, Ta, Mo, Si, Al, Au, P
Metals such as d and Hf, alloys thereof, and mixtures thereof with Zr oxide, Si oxide, Si nitride, Al oxide, and the like can be used. In particular, Al, Au, Ta, alloys thereof, and alloys of Al, Hf, and Pd are preferable because the film can be easily formed.

The first protective layer, the recording layer, the second protective layer, and the reflective layer are formed on the substrate by a method of forming a thin film in a vacuum atmosphere, for example, a sputtering method, a vacuum deposition method, an ion plating method. Etc. can be used. In particular, the sputtering method is preferable because the composition and the film thickness can be easily controlled.

As the substrate, it is preferable to use a material through which laser light can be transmitted in order to perform recording and reproduction from the substrate side. For example, polymethyl methacrylate resin,
Organic polymer resins such as polycarbonate resin, polyolefin resin, and epoxy resin, mixtures thereof, copolymers, and glass can be used. Above all, recently, polycarbonate resins have become mainstream.

The substrate is formed into a disk.
The molding method is not particularly limited. For example, injection molding can be used. A stamper having a predetermined groove or male pit formed on the surface is mounted in a mold, and a desired track is formed on the surface by transfer from the stamper. Can be formed.

The size of the substrate needs to conform to the standard required by the optical recording medium drive. For example, it is specified that the substrate is formed into a substrate having a diameter of 90 mm, 120 mm, or 130 mm. In the present invention, the thickness of the substrate is preferably 1.2 mm or less.

On such a substrate, at least a first protective layer / recording layer / second protective layer / reflective layer are sequentially laminated.
An organic resin protective layer may be further provided on this reflective layer. As the organic resin protective layer, a photocurable resin composition containing a polymerizable monomer or oligomer as a main component or a thermosetting resin composition can be used.

Initialization is performed in the state where the film is formed on the substrate as described above. In the case of an optical recording medium provided with an organic resin protective layer, the initialization is performed even before the organic resin protective layer is provided. Good. In the present invention, in addition to the linear velocity, the laser beam irradiation power, the laser beam feed pitch, and the initialization range, parameters for changing the irradiation power of the laser beam are added as parameters of the initialization condition. For example, the initialization range is generally indicated by the radius of the optical recording medium, but can be achieved by setting the power for each radial position. The power at the innermost circumference or the outermost circumference may be used as a reference value, and the power may be changed in the radial direction at an arbitrary ratio based on the reference value. The change in irradiation power is 40% of the reference value.
%.

In the above state, in the present invention, the irradiation power of the laser beam is controlled to be changed in accordance with the change in the thickness of the recording layer. The change in the film thickness of the recording layer is measured in advance and input as data. The irradiation power is changed and controlled according to the input data so that the crystal grain size and the reflectance become uniform.

The crystal of the initialized phase change type optical recording medium can be observed with a TEM (transmission electron microscope), and its size can be measured at the same time. Generally, in a power range that can be initialized, the crystal grain size tends to increase as the power increases. By utilizing this tendency, the crystal grain size can be controlled.

The initialization and the control of the irradiation power of the laser beam are performed using, for example, an apparatus as shown in FIG.
In FIG. 1, reference numeral 1 denotes a substrate of an optical recording medium on which at least a recording layer is formed, and the substrate 1 of the optical recording medium has a constant linear velocity at a laser beam irradiation position, for example, by a rotation driving unit 2. Is rotated as follows.

The laser light 4 emitted from the laser generating means 3 is condensed through appropriate condenser lenses 5a and 5b.
The converged laser light is applied to the substrate 1 to crystallize and initialize the recording layer.

Reference numeral 6 denotes a laser driving device. The power of the laser light to be irradiated is controlled by a power control device 7. The power control device 7 includes a data input device 8
Activated based on a setting signal from The data input device 8 receives, in addition to the feed pitch of the laser beam, the initialization range, and the reference irradiation power, a previously grasped film thickness of the recording layer, more precisely, a change in the film thickness. In the present invention, the irradiation power of the laser light is changed and controlled according to the thickness of the recording layer. Specifically, the change control is performed within a range of 40% or less of the reference power.

By changing the laser beam irradiation power in accordance with the change in the thickness of the recording layer, the entire initialization area can be changed.
A uniform reflectance characteristic and a uniform crystal grain size can be obtained.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on more specific embodiments. Diameter 1 made of polycarbonate resin
A thin film having the following structure was formed on a 20 mm transparent substrate using a sputtering apparatus. The second layer among the following is the recording layer. The first layer _{80.0ZnS-20.0Si0 2 (atm%)} 155nm second layer 55.0Te-25.4Sb-19.0Ge -0.5Nb-0.08Pd (atm%) 23nm third layer 80.0ZnS- 20.0Si0 ₂ of (atm%) 36 nm fourth layer 98.1Al-1.7Hf-0.2Pd (atm% ) 90nm resulting optical recording medium by irradiating a semiconductor laser beam having a wavelength of 810nm optical recording medium recording After the layer was crystallized and initialized, the reflectance was measured at the outer peripheral side, the inner peripheral side, and the middle (middle) position (Table 1).

In the optical recording medium used in the present invention, the film thickness of the recording layer becomes larger toward the inner peripheral portion of the substrate than the outer peripheral portion. Therefore, when the optical recording medium is initialized at a constant power as in the comparative example, the reflectance does not become constant. . On the other hand, in the embodiment, since the power is adjusted to be reduced at the inner circumference as compared with the outer circumference, the reflectance can be made substantially the same. Table 2 shows the thickness of the recording layer measured in advance.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

As described above, according to the present invention,
At the time of initialization, the irradiation power of the laser beam is changed according to the variation in the thickness of the formed recording layer, so that uniform initialization characteristics can be obtained over the entire initialization region, and uniform characteristics can be obtained. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for manufacturing an optical recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate on which the recording layer of the optical recording medium was formed 2 Rotation driving means 3 Laser generation means 4 Laser light 5a, 5b Condensing lens 6 Laser driving device 7 Power control device 8 Data input device

Claims (8)

[Claims] 1. A method for optical recording, comprising: forming a recording layer on a substrate; and irradiating the recording layer with a laser beam to initialize the recording layer by changing the irradiation power of the laser beam in accordance with the thickness of the recording layer. The method of manufacturing the medium. 2. The method for manufacturing an optical recording medium according to claim 1, wherein the ratio of changing the irradiation power of the laser beam is 40% or less. 3. The method for manufacturing an optical recording medium according to claim 1, wherein the recording layer to be formed is made of a material that undergoes a phase change, and the crystal grain size in the recording layer is controlled in the initialization. 4. The method for manufacturing an optical recording medium according to claim 1, wherein the recording layer to be formed is made of a material that undergoes a phase change, and the reflectance is controlled during the initialization. 5. The method of manufacturing an optical recording medium according to claim 1, wherein, during the initialization, the substrate is rotated so that a linear velocity at a laser beam irradiation point becomes constant. 6. The method of manufacturing an optical recording medium according to claim 1, wherein the substrate is rotated at a constant angular velocity during the initialization. 7. An optical recording medium manufactured by the method according to claim 1, wherein the substrate has a thickness of 1.2 mm or less. 8. A means for rotating a substrate on which a recording layer is formed, a means for irradiating the substrate with a laser beam for initialization,
An apparatus for manufacturing an optical recording medium, comprising: means for controlling the irradiation power of the laser light; and means for sending a signal for changing the irradiation power according to the thickness of the recording layer to the irradiation power control means. .