Dynamic information storage or retrieval – Specific detail of information handling portion of system – Electrical modification or sensing of storage medium
Reexamination Certificate
1998-04-06
2003-05-27
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Electrical modification or sensing of storage medium
C365S113000
Reexamination Certificate
active
06570833
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for initializing optical data storage media, and more particularly to a method and an apparatus for initializing an optical disk of a phase transformation type in a short time therefor.
2. Description of the Prior Art
Optical media of a phase transformation type are utilized as multimedia data storage media because of their large capacity as well as their high portability and reliability. This type of media is composed of an optical disk of a phase transformation type and an optical disk reproducing unit.
An optical disk of a phase transformation type stores and erases data based on an irradiating of laser beams on a recording film to heat a substrate, thereby inducing a phase transformation between two crystallographically divided phases to record and erase data. Two phases have the separate reflectance, respectively, so that data is reproduced by detecting the reflectance variation. That is, data is recorded by using laser beams to reversibly transform the phase of the material use to fabricate the recording film, the data being read based on the difference in an optical characteristic(reflectance) between the phases(crystalline phase/amorphous phase).
In the phase transformation between amorphous and crystalline phases, the amorphous phase is obtained by using laser beams to heat the recording film material over its melting point and then rapidly cooling it, while the crystalline phase is obtained by heating the material over its crystallizing temperature.
This phase transformation typed optical disk has the advantage that purely optical systems are simplified because only optical devices are employed to read and erase data. Also, the disk is useful in digital moving picture recording and voice recording because the overwriting operation can be directly performed using a single beam to shorten the recording time. Further, data recording can be performed without a magnet which generates a magnetic field. Thus, the optical unit may be thin. Additionally, a light source having a short wavelength is employed to get a high densified unit.
More specifically, recording and reproducing can be performed only by laser beams, without a magnetic head to apply a bias magnetic field, because an external magnetic field is not required in a recording process. Thus, the optical system becomes simplified, effectively decreasing the production cost, increasing compatibility and decreasing thickness.
Further, recording and erasing operations are each performed by the power modulation of laser beams, so that the direct overwriting is possible.
Because reproducing signals are obtained based on the variations in the intensity of reflected light which is generated by the reflectance difference between the two phases, these optical storage media are very compatible with the read-only typed disk such as a CD(compact disk) and the write-once and read-many typed disk.
Hereinafter, the general manufacturing process of the phase transformation typed optical disk will be described.
A digital master tape is made by the digital processing through a digital console, and then a code encoding process is performed to insert the sub-code representing the information related to a disk and to cut the disk using laser beams.
Then, several drops of photoresistor are dropped during the rotation of a spinner on glass that is ground evenly and precisely and is cleaned ultrasonically. The photoresistor forms a coating that is about 0.1 um thick, depending upon the rotation number of the spinner and the viscosity of the photoresistor.
A glass master is manufactured by exposing and developing the photoresistor with argon laser (wavelength of 457.9 nm) or He—Cd laser (wavelength of 441.6 nm).
A sheet of metal master is manufactured by plating the original photoresistor plate, and then several sheets of mother are manufactured. Several sheets of stamper are manufactured from the mother, and the stamper is subject to trimming to be provided for a molding device.
Next, as shown in
FIG. 1
, a polycarbonate substrate
1
is manufactured by injectedly molding the melted polycarbonate. A first dielectric layer
2
, a recording film
3
, a second dielectric layer
4
and a reflective layer
5
are stacked successively, and a protective layer(not shown) is formed thereon with the spinning technique to prevent the deterioration of film. Finally, a recording film is initialized, and the disk is tested to evaluate its quality.
The initializing process is necessary for the phase transformation typed optical disk, where the process of “initializing” involves crystallizing a stacked recording film which is made of materials constituting the recording film by sputtering to have a thickness of 50 to 500 Å by heating that stacked recording film over the crystallizing temperature.
FIGS. 2
a
and
2
b
are schematic views showing the pre-transformation and post-transformation atomic arrangements of the materials constituting the recording film of the phase transformation typed optical disk, respectively.
Japanese Patent Unexamined Publication Nos. sho 60-106031 and sho 62-250533 disclose the conventional initializing methods.
In Japanese Patent Unexamined Publication No. sho 60-106031, a method is disclosed for using a laser beam to successively heat the optical disk track-by-track from its inner circumference to its outer circumference Specifically, according to the publication, a first laser diode is used to read/reproduce data A second higher powered laser diode capable of obtaining a laser spot of several to several hundred micrometers in size (generally 0.5 to 1 micrometers) is used to initialize the optical disk by successively heating the disk track-by-track. As a result, the conventional method effectively reduces the initializing and preventing the occurrence of cracks because the track-by-track heating leads to the lower heat load. However, using this method, even the reduced initializing time is to long, i.e. overall, it requires 30 min. to 1 hour to initialize disk since the initialization is performed track-by-track. Therefore in case of mass-producing the disk, the productivity is reduced, and the manufacturing cost is increased.
In order to overcome the above problems, Japanese Patent Unexamined Publication No. sho 62-250533 discloses a method for crystallizing an entire region of a recording film simultaneously by irradiating that region with a flash of light from a lamp. First, to initialize, the disk is heates to a temperature that exceeds the crystallizing temperature by applying 1 MW of power for the exposing time of 500 us (i.e. with the heat energy of about 500 J. A xenon lamp is employed as a light source in the publication. The instant exposure induces the stress which curves the disk. The curved disk restores its flat shape by annealing a stacked plurality of the curved disk with the irradiated light from a mercury lamp. The initializing process is completed by re-initializing the disk which rotates at a high speed according to the method disclosed in the Japanese Patent Unexamined Publication No. sho 60-106031.
However, this method has the problem that an additional process for making the disk flat such as an annealing process is required, because the heat energy which is instantly and unevenly irradiated to the disk with the xenon lamp of a relatively high power curves the disk. Thus, the productivity is reduced and the manufacturing cost is increased.
SUMMARY OF THE INVENTION
The present invention is devised to solve the foregoing problems. It is an object of the present invention to provide a method for initializing a phase transformation typed optical disk and an apparatus therefor capable of enhancing the productivity as well as the yield by means of initializing the disk simultaneously to shorten the initializing time and minimize the deformation of the disk.
To achieve the above object of the present invention, a method is proposed which comprises the steps of, applying electrical energy to a recording fil
Kim Chang-Jong
Kim Myong-Ryeong
Seo Hun
Yeo Woon-Seng
LG Electronics Inc.
Psitos Aristotelis M.
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