Title: A Novel Thin Film Layer Configuration for the Development of High-Speed Phase Change Digital Versatile Disc
Background of Invention
In the present invention, a novel thin film layer structure has been designed for the development of high speed (8X) Digital Versatile Disc + Rewritable (DVD+RW). The present invention is broadly attributed to the evolution of high speed (8X) DVD+RW optical discs, where different materials e.g., dielectric, chalcogenide and metal are sputtered one after another to obtain a thin film layer structure. This novel thin film layer configuration was found to be suitable to obtain high-speed (8X) digital versatile discs, which have quality parameters well within the specification. Prior Art
The re-writable optical data storage device also known as phase change recording medium is found to be an excellent tool to provide and promote the facility for a data to be written and over written many times. The phase change media of optical data storage are typically deposited in thin film form on a polycarbonate substrate, sandwiched between protective dielectric layer that play a crucial role in determining the storage medium's optical and thermal behaviour. In addition, rewritable phase change medium employ a thin metal film to optimize the absorption of the focused laser beam during writing/erasing, to enhance the contrast between amorphous marks and the crystalline background during readout, and to promote rapid thermal quenching that is so critical to amorphous mark formation during recording. After the discovery of digital versatile disc technology by Sony in 1995, many players at the international level came forward to develop their own design and formats. The re-writable digital versatile media actually highlighted in late 1997 by DVD+RW alliance and became popular in late 2002. In the present invention, higher speed (8X) digital versatile disc has been developed using a novel thin film layer structure as shown in Figure 1.

Statement of Invention
The present invention relates to a novel thin film layer stack design for the development of re-writable phase change digital versatile disc of recording speed (8X). On a blank, active and grooved polycarbonate substrate, a new thin film layer structure has been obtained after depositing nano-meter thin films of dielectric, chalcogenide and metal materials, one after another. The entire thin film layer stack design and original disc structure for the present invention is depicted in the Figure 1.
(Figure Removed 1)

As per the present invention of thin film layer stack configuration, a re-writable phase change digital versatile disc of speed 8X has been obtained wherein:
The mechanical quality parameters of optical storage media are well within characteristic specification as per the Orange Book.
The electrical quality parameters e.g.. Jitter, Block Error Rate (BLER), Carrier to Noise Ratio (CNR) and Modulation of optical storage media are well within characteristic specification as per the Orange Book.
The optical storage media so obtained is able to record, write and erase the information.
The optical storage medium is environmentally stable at room as well as at high temperature (80°C).
The invented thin film layer stack configuration is suitable to produce re-writable digital versatile disc having 8X recording speed.
Detailed Description of the Invention
In the recent time, phase change re-writable optical media have been highly investigated and extensively exploited for data storage applications. Due to its unique reversible characteristics of writing and erasing stored information, this media is currently considered as paradigm in communication and information sectors.
During the manufacturing operation of re-writable phase change optical data storage media, thin layers of different materials e.g., dielectrics, chalcogenide alloys and metals are deposited one after another on a blank, active and grooved polycarbonate substrate of diameter 120.00mm and thickness 0.6mm. In the present development, films of different materials as described above are uniformly deposited according to the design and structure shown in Figure 1. Uniformity of as deposited thin films has been evaluated using standard equipment. After the deposition of various thin films, the active substrate was bonded with an inactive (dummy) polycarbonate substrate, which has the same order of diameter and
thickness as that of an active substrate. UV rays were flashed on the disc to cure the bonding glue. UV cured disc was induced by a laser beam to create changes in the structure of recording film. The mechanical and electrical quality parameters were evaluated. It has been found that disc exhibits excellent quality characteristics and is able to record and erase the data successfully.
Example
Grooved polycarbonate circular substrate of thickness 0.6mm and diameter 120.00mm was replicated using an injection molding. The substrate so obtained is named as active substrate. An un-grooved polycarbonate substrate of same thickness and diameter has been also replicated by injection molding and named as dummy substrate.
Both the substrates were cooled to an optimum temperature. The active substrate was allowed to undergo into the sputtering system for the deposition of different materials one after another in sequence.
Immediately after the sputtering, the active substrate was cooled and bonded with the dummy substrate using organic bonding glue. Bonded disc was cured using UV radiations and then allowed to undergo for the process of initialization where a laser beam is irradiated on the recording film to change the structure from an amorphous to crystalline phase.
After the process of initialization, the mechanical and electrical quality parameters were evaluated using variety of equipments. All the quality parameters were found to be well within specification and disc shows excellent capabilities to record and erase the data. The quality parameters as evaluated in the present invention are shown in the Figure 2 and 3.

(Figure Removed 2)

(Figure Removed 3)

We claim
1. A novel thin film layer configuration for the development of high speed (8X)
re-writable phase change digital versatile disc (DVD+RW)
Wherein,
Electrical and mechanical parameters are within specification as per the Orange
Book.
The uniformity of each of the thin films deposited is within an accuracy of 2% or
less.
The disc so obtained exhibits excellent performance to record and erase the data.
2. A new thin film layer stack configuration as claimed in claim 1
Wherein,
The high-speed digital versatile disc is capable to overwrite the data for more than 1000 times.
The jitter and error rate are maintained under specification limit even after an overwriting of more than 1000 times.
3. A new thin film deposition procedure and thin film layer configuration to
manufacture high-speed (8X) re-writable phase change digital versatile disc
substantially as herein described.