JPH0945048A - Recovering method for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method capable of reading the information already written on a disk board when the information becomes impossible to be read due to the flaw occurred on the board. SOLUTION: The optical disk in which already written information becomes impossible to be read due to the flaw occurred on a disk board 1 is polished with abrasive material on a recess 2 generated by the flaw. Thereafter, grease is buried in the recess 2 to form a grease layer 3 to be flattened so that the information written on the disk can be made readable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing an optical disc in order to read information that has once become unreadable.

[0002]

2. Description of the Related Art In recent years, in the field of information recording, research on optical information recording methods has been actively pursued. This optical information recording system can record / reproduce in a non-contact manner, can achieve a recording density higher than the magnetic recording system by one digit or more, and has a read-only type, a write-once type and a rewritable type. It has a number of advantages such as compatibility, and is considered to be applicable to a wide range of applications from industrial to consumer as a method for realizing inexpensive large-capacity files.

The recording / reproducing system of these optical discs differs depending on the memory type such as a read-only type, a write-once type, and a rewritable type, but information is recorded as an array of pits of a predetermined track pitch and is reproduced. Therefore, a laser spot is used to detect the intensity change of the reflected light depending on the presence or absence of a pit.

For example, a digital audio disc, an optical video disc, and the like, which are widely used as an optical disc compatible with a read-only memory type, are transparent in which an uneven pattern such as pits or grooves indicating information is formed. A reflection film made of a metal such as aluminum is formed on the optical disc substrate, and a protection film for protecting the reflection film from moisture and oxygen in the atmosphere is formed. In such an optical disk, a laser spot is irradiated from the optical disk substrate side to the concave-convex pattern, and information is detected by the difference in reflectance between the incident light and the return light (reflected light).

[0005]

By the way, in the above-mentioned optical disc, the disc substrate is scratched due to contact with a foreign substance, erosion by a solvent, etc. during use, transportation, storage, etc. It may not be possible to read the stored information. In addition, when an ultraviolet curable resin or the like is applied as the top coat, coating unevenness may occur, which may make it impossible to read information.

As described above, this is because the reproduction of the information on the optical disc is performed by detecting the intensity change of the reflected light depending on the presence or absence of the pits. This is because if the reflected light is disturbed, the track position is erroneously detected and accurate servo operation cannot be performed.

Therefore, the present invention has been proposed in view of such a conventional situation, and in order to make it possible to read the information written on the optical disc whose disc substrate is scratched, the optical disc is read. The purpose is to provide a method of repair.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above-mentioned object, and is intended for an optical disc in which already written information cannot be read due to scratches on the disc substrate. On the other hand, after polishing the scratched portion with an abrasive, the recesses caused by the scratch are filled with resin or grease to flatten the surface, thereby making it possible to read the information written on the optical disc. .

The scratched portion is polished to prevent incident light or reflected light from being diffusely reflected here. It should be noted that, although it depends on the type, width, direction with respect to the track direction, number, etc. of scratches, when the depth of scratches is less than several tens of μm, scratches are generated by this polishing without embedding resin or grease. In some cases, it is possible to read out the information only by smoothing the surface of the existing portion.
Here, in polishing, it is necessary to optimize the polishing conditions such as the type of polishing agent, polishing pressure, polishing direction, etc., so as not to deteriorate the scratched state.

Further, after polishing, the resin or grease is embedded in the recesses caused by the scratches by flattening the surface of the disk substrate so that the incident light and the reflected light can be absorbed at the scratched portion and other portions. This is to make the length of the optical path uniform. However, even if the surface of the substrate is flattened, if the refractive index of the resin or grease is significantly different from the refractive index of the disk substrate, or if birefringence occurs in the resin or grease, the optical path of incident light or reflected light is disturbed. , The track position is erroneously detected. Therefore, as the resin and grease, those having optical characteristics close to those of the disk substrate are preferable.

The disk substrate has a refractive index of 1.46.
It is required to be about 1.60, and specifically, polyvinyl chloride, acrylic resin, polycarbonate, epoxy resin and the like can be used. For this reason, it is preferable to use a material having a refractive index within the above range as the resin or grease that is embedded in the concave portion caused by the scratch.

The present invention can be applied to any of a read-only type, a write-once type, and a rewritable type optical disc, but a read-only type duplicated based on pits recorded on a master disc. It is more suitable to be applied to the write-once type and rewritable type optical discs on which the user records information than the optical discs of the above.

The write-once type optical disk utilizes the fact that information is recorded by irradiating a recording material layer with a laser spot and thermally irreversibly changing the reflectivity. Is reproduced. This irreversible change may be a hole in the recording material layer, a phase change, or a film deformation. Further, the structure of such an optical disc may be a single layer type in which only a recording material layer is formed on a disc substrate or a multilayer type in which a plurality of thin films are formed in addition to the recording material layer. .

On the other hand, as a rewritable optical disc,
Information is recorded or erased by reversibly changing the atomic arrangement of the recording material layer between the crystalline state and the amorphous state. Utilizing the fact that the reflectance is different between the crystalline state and the amorphous state. Examples of the optical disc include a phase change recording type optical disc in which reproduction is performed and an optical disc to which a magneto-optical recording type is applied.

In an optical disk to which a magneto-optical recording method is applied (so-called magneto-optical disk), a laser beam is used as a heat source, and an external magnetic field is applied while the perpendicular magnetization film is raised above the Curie temperature to magnetize it. Recording or erasing is carried out by changing the direction of, and reproduction is carried out by utilizing the phenomenon (Kerr effect) in which the plane of polarization of reflected light rotates depending on the direction of this magnetization.

As described above, by applying the present invention, it becomes possible to re-read information that could not be read. However, even if the present invention makes it possible to read information, it is not always possible to endure repeated use thereafter. Therefore, if the information can be read, it is preferable to copy the information to a new optical disc instead of using the optical disc as it is.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Here, a write-once type optical disc in which information cannot be read was repaired. This optical disc is made by stacking tellurium (Te) -selenium (Se) on a disc substrate made of polycarbonate having a refractive index of about 1.58.
The recording material layer of the system was formed and used as an image document file.

Specifically, first, a clean cloth having a smooth surface is spread on a flat work table free from dust and scratches so as not to wrinkle, and the optical disk taken out from the cartridge is placed on the work table with a laser beam. It was placed with the light irradiation surface facing up.

Here, when the surface of this optical disk is observed, as shown in FIG.
The recess 2 was formed due to the scratch. The surface of the recess 2 was rough.

After that, dust and foreign matters on the surface of the optical disk are removed by an air gun or a clean cloth, and then the cloth is coated with an abrasive containing relatively coarse abrasive particles (trade name: rubbing compound RB9 manufactured by Holtz Co.), and the recess 2 is formed. Was rubbed in the vicinity of and was polished with a polishing agent (trade name: Rubbing Compound RB6 manufactured by Holtz Co., Ltd.) containing relatively fine polishing particles for finishing. At this time, as the cloth, a cloth which is hard to be scratched and to which fibers are hard to come out, such as an eyeglass cleaner, is used. Although the compound depends on the degree of scratches, it is preferable to use a compound containing medium abrasive particles at the beginning and a compound containing fine abrasive particles for finishing. The polishing was performed from the inner peripheral side toward the outer peripheral side without applying an excessive force.

The standard for finishing polishing was when the concave portion 2 was obliquely irradiated with the light of a fluorescent lamp and the difference with the surroundings became almost unknown.

By the above polishing, the surface of the recess 2 in the disk substrate 1 became smooth as shown in FIG.

Then, after the excess abrasive was wiped off, the cloth was moistened with ethyl alcohol to wipe the surface and further cleaned with pure water.

Next, grease (product name by Dow Corning: silicon grease for high vacuum) is attached to the cloth,
After embedding this grease in the recesses 2, the grease adhering to the areas other than the recesses 2 was wiped off with a clean cloth.

As a result, as shown in FIG. 3, the grease layer 3 was formed in the recess 2 of the disk substrate 1, and the surface of the disk substrate 1 was substantially flattened.

Then, when the optical disc having the scratch thus repaired was mounted on a reproducing apparatus and reproduced, accurate servo operation could be performed and information could be read out as usual. This is because the concave portion 2 caused by the scratch was filled with the grease layer 3 to be flattened, and the difference in the refractive index between the surface of the disk substrate 1 and the grease layer 3 in the concave portion 2 was small. This is because the disturbance of the incident light and the reflected light is prevented, the intensity change of the reflected light depending on the presence or absence of the pit can be accurately detected, and the erroneous detection of the track position is prevented.

Here, instead of using this optical disk as it is, information is copied to a new optical disk.

Although the method for repairing an optical disk according to the present invention has been described above, the present invention is not limited to the above-mentioned embodiment, and various modifications and changes are possible. For example, the type of abrasive used for polishing the disk substrate 1, the type of grease filling the recess 2 and the like can be appropriately changed. Further, it is not limited to the write-once type optical disc, but may be applied to a read-only type or rewritable type optical disc.

[0030]

As is apparent from the above description, when the present invention is applied, it is possible to read out the information written on the optical disc whose disc substrate has been scratched. You can prevent loss.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a surface of a disk substrate having scratches.

FIG. 2 is a schematic cross-sectional view showing a state in which a concave portion caused by a scratch is smoothed.

FIG. 3 is a schematic cross-sectional view showing a state where grease is embedded in a concave portion caused by a scratch.

[Explanation of symbols]

 1 disk substrate 2 recess 3 grease layer

Claims (1)

[Claims] 1. An optical disc in which the information already written cannot be read due to the scratch on the disk substrate, the scratched portion is polished with an abrasive, and then the scratch is generated by the scratch. A method of repairing an optical disc, wherein the concave portion is filled with resin or grease to be flattened so that information written on the optical disc can be read.