Patent Application
20060177622
1. Field of the Invention
The present invention relates to a structure of an optical storage medium, particularly to a structure of a double-side optical storage medium.
2. Description of Related Art
Evolving with the age of information and multi-media, a storage medium needs a higher data-storage density and data-storage capacity to satisfy the current demand of the data storage, and the high-capacity Digital Versatile Disc (DVD) plays an important role therein. The capacity of DVD depends on the disc structure itself and the spot size of the laser light used in the read/write device. The optical system of the conventional 23.3 GB blu-ray disc (BD) adopts a laser light of about 405 nm wavelength and a focusing lens of about 0.85 numerical aperture (NA), which enables the focused laser light to has a spot size of about 0.3 μm in diameter; the disc structure thereof adopts a structure of single side-double layer.
As shown in
In the aforementioned structure of the conventional optical storage medium, a 0.1 mm cover layer needs to be formed, which makes the fabrication of that optical storage medium difficult, needless to mention that a space layer needs to be formed between two read/write layers 12; thus, the fabricating cost thereof is pretty high. Further, owing to the reading/writing of the double layers, a layer cross talk is apt to occur, which induces a signal interference. Besides, the write power must be enhanced in order to overcome the problem of reading/writing of the double layers, which induces the technical threshold and price of that read/write device to be rather high.
As shown in
As the red light, which has a longer wavelength, is adopted in the above-mentioned conventional technology, the focused point is relatively large, which results in a lower read/write density; thus, the data-storage capacity thereof decreases.
In re the problems of the conventional technology mentioned above, the present invention provides a structure of double-side optical storage medium utilizing a blue laser light in order to overcome the drawbacks thereof.
The primary objective of the present invention is to provide a structure of double-side optical storage medium, wherein via installing read/write structures separately onto the top and the bottom surface of the substrate, the data-storage capacity is doubled.
Another objective of the present invention is to provide a structure of double-side optical storage medium, which is distinct from the conventional single-side/double-layer optical storage medium, wherein, via installing read/write structures separately onto the top and the bottom surface of the substrate, the manufacturing process thereof is exempt from the fabrication of the space layer; thus the fabricating cost is reduced.
Further another objective of the present invention is to provide a structure of double-side optical storage medium, wherein as the read/write structure is installed on the surface of the substrate, the read/write distance decreases, and a laser light source of shorter wavelength and a larger numerical aperture can be adopted, so that the extent of the data densification of the optical storage medium increases.
According to the present invention, the structure of double-side optical storage medium comprises a substrate, which possesses a top surface and a bottom surface, and two read/write structures, which are separately installed onto the top and the bottom surface.
Via the following detailed description of the embodiments in cooperation with the attached drawings, the objectives, technical contents, characteristics, and accomplishments of the present invention are to be more easily understood.
As shown in
Referring to
After the above description of the read/write structure 22, the materials of each layer thereof will be described below. The material of the phase-transformation recoding layer 28 is composed of Germanium (Ge), Indium (In), Antimony (Sb) and Tellurium (Te), GeBiTe or GeSbTe-related materials. The material of the top and the bottom dielectric layer is composed of materials with thermal conductivity lower than that of the recording material, such as Germanium compound, Silicon Nitride (SiN), or ZnS—SiO2, etc. The material of the reflective layer 24 is selected from Silver (Ag) or silver alloy.
After sequentially installing the read/write structures 22 and the transparent protective cover layers 32 onto two transparent plates 20, the bottom surfaces of two transparent plates 20 are joined together face to face to form a substrate 34 with two read/write structures 22 separately on two externally-fronting surfaces of two transparent plates 20. Then, the optical storage medium is initialized to enable the phase-transformation recoding layer 28 to crystallize, and thus, the fabrication of the optical storage medium is completed. The abovementioned embodiment is the present invention's application in the phase-transformation type optical storage medium. Besides, the structure of the present invention also applies to the read-only type optical storage medium.
When reading/writing the optical storage medium, the laser light of wavelength ranging from 385 to 435 nm illuminates the optical storage medium to enable the phase-transformation recoding layer 28 to shift between a crystalline and an amorphous phase, and then, via the high reflectivity of the crystalline phase and the low reflectivity of the amorphous phase, the signal of 0 or 1 is identified.
As shown in
Accordingly, via installing two read/write structures 22 separately onto the top and the bottom surface of the substrate 34, the data-storage capacity of the optical storage medium is doubled. Further, via installing the read/write structure 22 onto the surface of the substrate 34, when the read/write device operates, the read/write distance can be reduced, and thus, the laser light source of shorter wavelength and larger numerical aperture can be adopted in order to promote the extent of the data densification of the optical storage medium.
