JP2000067476A - Production of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to improve the production yield and to reduce the cost by inspecting the reflectivity right after initialization of an optical recording medium having a recording layer of a phase transition type at the time of producing this medium. SOLUTION: The initialization is executed while a disk is rotated at a constant linear speed of 5 m/sec and while an optical head is fed at a feed speed of 86 μm/revolution. Whether the initialization is normally executed or not may be decided by inspecting the reflectivity right after the initialization and monitoring the reflectivity. The reflectivity is inspected right after the initialization and a disk defective in the initialization is removed from a production line, by which the waste in the ensuing stages may be omitted. In addition, the disk defective in the initialization is not an intrinsic defect and inevitably occurs at a certain probability and, therefore, the yield is improved by subjecting the defective disk to the initialization again. The improvement in the quality by the uniform initialization is thus made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing an optical recording medium having a phase-change recording layer.

[0002]

2. Description of the Related Art A phase-change type optical recording medium uses a reversible structural change (phase change) between an amorphous state and a crystalline state of a substance caused by light irradiation, mainly laser light irradiation, to store information. Used for recording / erasing. Such a phase-change optical recording medium has a large recording capacity in addition to a high-speed information processing capability. Another advantage is that the drive structure is simpler than that of a magneto-optical recording drive, so that the cost can be reduced.

[0003] In a phase-change optical recording medium, the erasing state of information is usually set to the crystalline state of the recording film, and the recording state is usually set to the amorphous state generated by melting and quenching of the film with high laser power. The medium has a high reflectance in the crystalline state and a low reflectance in the amorphous state. The difference between the reflectances becomes a reproduced signal. The recording layer of the phase-change type optical recording medium is in an amorphous state immediately after the film formation by sputtering, and is used after being subjected to an overall annealing treatment to be in a crystalline state, that is, an erased state. The annealing process on the entire surface is, for example, about 1 watt,
This is performed by irradiating the recording film surface with a laser beam having a width of 1 to 2 μm × about 100 μm. This step is called initialization (initial crystallization).

The manufacturing process of the phase change type optical recording medium includes injection molding of a plastic substrate, spattering of a recording film, coating and forming an organic protective layer on the recording film, initialization, assembling in a case,
Usually, inspection and shipping are performed in this order.

The phase-change optical recording medium has a basic structure including a lower dielectric layer, a recording layer, an upper dielectric layer, and a reflective layer formed on a plastic substrate by a thin film forming method such as a sputtering method. . Condensed laser light used for initialization and recording / reproduction is generally applied to a recording film (recording layer) through a plastic substrate. However, a reflective layer, a lower dielectric layer, a recording layer, The present invention is also applied to a phase change type optical recording medium having a basic structure including an upper dielectric layer and being initialized and recorded / reproduced by irradiating a condensed laser beam from a film surface without passing through a substrate.

[0006]

In the above initialization, the laser beam is focused on the recording film surface while rotating the disk, and the focused beam is moved in the radial direction to initialize the entire disk surface. Done. It has been found that there are two problems in the initialization process that lower the production yield.

The first problem is that when mass-produced, a disc that has been initialized but intended to be initialized with a probability of about several percent has occurred. The cause is presumed to be that the focus (focal point) of the initialization laser beam is not focused on the recording film surface and the other reflective surface (for example, a laser beam incident surface of a plastic substrate) is focused. Was done. The device intends to emit a laser beam with normal power and initialize the front surface of the disk while moving in the radial direction. However, in fact, the focus has shifted and the recording film has not risen to a predetermined temperature. This problem is related to the extremely low medium reflectivity of the amorphous state immediately after sputter deposition. That is, the reflectance is small, the amount of returning light is small, and automatic focus control (autofocus control) is difficult to operate.

[0008] A second problem is that spots are easily generated on the disk surface by a single initialization operation. This is also supposed to be mainly because the focal position is locally fluctuated due to surface run-out (Run-out) at the time of disk rotation, because the medium reflectance immediately after the film formation by sputtering is low.

An object of the present invention is to solve such a problem that has become apparent in the mass production of phase-change optical recording media, improve the production yield, and provide a low-cost phase-change optical recording medium.

[0010]

According to the method of manufacturing an optical recording medium of the present invention, a step of inspecting the reflectivity immediately after initializing the medium is provided at the time of manufacturing an optical recording medium having a phase change type recording layer. It is characterized by the following. Here, in the step of inspecting the reflectance immediately after the initialization, it is more preferable to perform the initialization again on the medium in which the abnormality of the reflectance is detected.

Further, the method of manufacturing an optical recording medium according to the present invention is characterized in that when manufacturing an optical recording medium having a phase change type recording layer, initialization of the medium is repeatedly performed a plurality of times.

Alternatively, according to the method of manufacturing an optical recording medium of the present invention, when manufacturing an optical recording medium having a phase change type recording layer, the medium has a disk shape, and initialization of the medium is started from the inner peripheral portion of the disk. It is characterized by doing. This is more preferable in combination with the present invention. Further, at that time, it is more preferable that the reflectance test of the medium is performed within a range of 10 mm from the outer periphery of the disk.

In the present invention, the initialization of the medium is repeatedly performed two or three times, in which case the initialization of the post-process is performed in a wider range than the range initialized in the previous process, and after the final initialization, More preferably, the final medium reflectivity inspection is performed on the area initialized only in the final initialization.

Further, in the present invention, the initialization of the medium is repeatedly performed two or three times, and the initialization of the subsequent process is started from a region having a higher reflectance within the range initialized in the previous process. Is more preferable.

By incorporating each of the above means into the manufacturing process, it has become possible to greatly improve the production yield.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An optical recording medium produced by the method for producing an optical recording medium according to the present invention has a plastic substrate on one side.
A phase change optical recording medium having a basic structure consisting of a lower dielectric layer, a recording layer, an upper dielectric layer, and a reflective layer in the order from the substrate surface is the most common, but is directly or adhered to the substrate. It has a basic structure consisting of a reflective layer, a lower dielectric layer, a recording layer, and an upper dielectric layer, bordering layers and heat insulating layers. The present invention is also applied to a phase change type optical recording medium of a type which is formed and recorded / reproduced.

As the substrate, a polycarbonate disc having a diameter of 120 mm produced by injection molding is preferably used. The dielectric layer is made of a material having heat resistance, being transparent and having a refractive index of about 2.0. A typical example of such a dielectric is ZnS (80 mo).
1%) and SiO ₂ (20 mol%), and ZnS · S obtained by sputtering film formation in Ar gas.
It is an iO ₂ film. The recording layer is a GeSbTe film or AgInS
A phase change recording film such as a bTe film is used. Immediately after these recording films are formed by sputtering, the recording films are amorphous films, and when the medium is used as a medium, the disk has a small reflectance of about 10% or less. Reflective film is T on Al
An aluminum alloy film to which i or Cr is added by several% is preferably used.

The phase-change optical recording medium is manufactured by injection molding of a plastic substrate, spattering of a recording film, coating and forming an organic protective layer on the recording film, initialization, mounting in a case,
Usually, inspection and shipping are performed in this order. The manufacturing method of the present invention provides an improvement in the initialization step,
This is to provide a reflectance inspection step immediately after the initialization step.

Here, a bulk eraser device (model LK101A) manufactured by Shibasoku Co., Ltd. was used as the initialization device.
However, the optical head has a laser beam intensity of about 1 watt on the disk surface, a wavelength of 810 nm, an NA (objective lens numerical aperture) of 0.34, and a spot size of 125 μm.
(Long axis length) × 1.27 μm (short axis length) was used with the beam major axis inclined at 30 ° from the disk radial direction. Initialization is performed by rotating the disk at a constant linear velocity of 5 m / sec while moving the optical head at a feed speed of 86 μm /
Rotation (the optical head moves 86
Advance by μm. ).

In the initialization step of the present invention, the reflectance is inspected immediately after the initialization. The medium reflectance immediately after sputter deposition is about 1
0% or less. If the initialization is completed normally, the medium reflectance will be about 20 to 40%. However, if the initialization is incomplete due to the above-described reasons, a predetermined reflectance cannot be obtained. Thus, by monitoring the reflectance, it can be determined whether or not the initialization has been normally performed. Immediately after the initialization, the reflectivity can be inspected, and the defective initialization disk can be quickly removed from the production line, so that the subsequent steps can be omitted. In addition, the inventor has found that a poorly initialized disk is not an essential defect, but inevitably occurs with some probability. It turned out that many disks complete initialization without any problem by performing initialization again. Therefore, in the production line of the present invention, it is preferable from the viewpoint of the yield to perform the initialization again even if the initialization failure is found in the reflectance inspection. Re-initialization is usually sufficient once. 1
If performed more than once, there is a disadvantage that the speed of the entire production line is reduced. Further, if the initialization is attempted twice and the initialization fails, it is suspected that there is a defect such that the disk is larger than other disks, and it is a waste of time to attempt the initialization three or more times. Great potential.

In the initialization step of the present invention, it is preferable to initialize the entire surface by moving the optical head from the inner circumference of the disk to the outer circumference. When the reason for the initialization failure was examined, it was found that when the disc wobble (Run-out in the axial direction) was large, the probability that the focus was not properly adjusted to the recording film was large. In the case of an optical disk substrate manufactured by injection molding of a thermoplastic resin, there is generally a tendency for the outer peripheral surface to be larger than the inner peripheral surface. In such a case, it has been found that good results can be obtained by moving the optical head to the outer periphery after performing auto-focusing on the inner periphery with small surface deviation. The reflectance test when starting from the inner circumference and initializing to the outer circumference is preferably performed near the end of initialization on the outer circumference. This is because if the optical head is out of focus during the movement of the optical head from the inner circumference to the outer circumference, it can be recognized as a defective disk. Usually within 10 mm from the outer circumference, preferably 5 m
If it is within the range of m, it is sufficient to judge from this purpose.

Further, as described above, the present inventor has found that spots are easily generated on the disk surface by only one initialization operation. In severe cases, spots of the uninitialized portion were visually observed. This is also supposed to be mainly because the focal position is locally fluctuated due to surface run-out (Run-out) at the time of disk rotation, because the medium reflectance immediately after the film formation by sputtering is low. In a disk that has been initialized and has a high reflectance over the entire surface, autofocus can be easily achieved even if a small amount of uninitialized portion remains (the laser beam focuses on the recording film. , The focal point is hard to deviate from the film surface). Therefore, in the present invention, it is desirable to perform the initialization twice or more, and usually it is sufficient to perform the initialization twice.

In the method in which the initialization is repeated twice, there is no guarantee that the second initialization is performed 100% completely. There may be a case where the second initialization fails even though the first initialization succeeds. If the first initialized area (radius) matches the second initialized area, the reflectivity of the medium has increased during the first initialization, and there is no quick method for detecting the second initialization failure. To cope with such a situation, the second initialization is performed in a range wider than the first initialization range,
It is desirable that the final reflectance inspection be performed on the area initialized only in the final initialization step. For example, on an optical disc,
In many cases, an area for inspection and a lead-out area are provided closer to the outer periphery than the data recording area. However, a method in which the outside of the data area is divided into two and used is considered. That is, for example, the first initialization may be started from the inner periphery and proceed to a position before the lead-out region on the outer periphery, and the second initialization may be performed on the entire region up to the outer periphery. Note that the reflectance test is performed centering on the place where the first initialization is completed (that is, reflecting the boundary between the area where the initialization is repeated twice and the area where only the second initialization is performed finally). A method of measuring the reflectance (as the center of the reflectance measurement part) is conceivable. In this case, the reflectance at the end of the first initialization is to measure the initialized high reflectance portion and the uninitialized low reflectance portion together, and the obtained reflectance value is The value becomes an intermediate value between the final reflectance and the reflectance of the uninitialized portion, and a predetermined reflectance is obtained when the second initialization is completed. In this method, it is possible to measure whether or not the first initialization has been completed without failure and whether or not the second initialization has also been completed without failure with a single reflectance sensor.

In the method in which the above initialization is repeated twice, in order to perform the second initialization more reliably, the subsequent (second) initialization should be started from the previously initialized high reflectance area. Is desirable. That is, the initialization failure often occurs at the first start of auto-focusing (that is, when the focus servo is pulled in). It is more reliable to start the focus control at the place where the reflectivity is increased by the first initialization than to start the focus control from the place of the uninitialized low reflectivity (that is, the return light amount is small). This is because initialization can be started. When the initialization is started from the inner periphery, the second initialization may be started from the outer periphery by about 0.1 mm from the first initialization start radius.

As described above, by incorporating the reflectance inspection means immediately after the initialization step and the initialization step of the present invention into the manufacturing process, the number of defective initial products is drastically reduced, and the quality can be improved by uniform initialization. , And the production yield has improved significantly.

The reflectance measurement is preferably performed with light having a wavelength in the vicinity of the recording / reproducing laser wavelength of the drive using the medium. However, any wavelength can be selected as long as a change in reflectance due to initialization can be detected. . Further, by simultaneously using two or more wavelengths, the color tone of the medium can be easily determined.
Since the color tone of the medium is related to the thicknesses of the recording film and the dielectric film, there is an advantage that an abnormality in the film thickness can be inspected at the same time.

[0027]

As described above, according to the method for manufacturing a phase change type optical recording medium of the present invention, the number of defective products can be reduced and the quality can be improved.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Ebina 4-3-2 Asahigaoka, Hino-shi, Tokyo Teijin Incorporated Tokyo Research Center (72) Inventor Junichi Ishimaru 4-2-2 Asahigaoka, Hino-shi, Tokyo Teijin Tokyo Research Center F term (reference) 5D121 AA01 GG26 HH11

Claims (8)

[Claims] 1. A method for manufacturing an optical recording medium, comprising the step of inspecting the reflectance immediately after initializing the medium when manufacturing an optical recording medium having a phase-change recording layer. 2. The optical recording medium according to claim 1, wherein, in the step of inspecting the reflectance immediately after the initialization, the medium in which the abnormality of the reflectance is detected is initialized again. Production method. 3. A method of manufacturing an optical recording medium having a phase-change recording layer, wherein the medium has a disk shape and initialization of the medium is started from an inner peripheral portion of the disk. Method. 4. A method for manufacturing an optical recording medium, comprising: repeating the initialization of the medium a plurality of times when manufacturing an optical recording medium having a phase-change type recording layer. 5. The method for manufacturing an optical recording medium according to claim 1, wherein the medium has a disk shape, and initialization of the medium is started from an inner peripheral portion of the disk. 6. The method for manufacturing an optical recording medium according to claim 5, wherein the inspection of the reflectance of the medium is performed within a range of 10 mm from the outer periphery of the disk. 7. Initialization of a medium is repeatedly performed two or three times, and in that case, initialization of a post-process is performed in a wider range than the range initialized in the previous process, and after the final initialization, the final medium reflection is performed. 7. The method of manufacturing an optical recording medium according to claim 1, wherein the rate inspection is performed in an area initialized only in final initialization. 8. The method according to claim 1, wherein the initialization of the medium is repeatedly performed two or three times, and the initialization of the subsequent process is started from a region having a higher reflectance within the range initialized in the previous process. Item 8. The method for producing an optical recording medium according to any one of Items 1 to 3 and 5 to 7.