OPTICAL RECORDING MEDIUMS
BACKGROUND
The present Invention relates, in general, to optical recording mediums.
A typical optical recording medium includes a reflective layer made from a highly-reflective material, such as gold and silver. Apart from the requirement of high reflectivity, it is required that an optical recording medium be tolerant to moisture and temperature.
The use of gold and silver increases the cost of the optical recording mediums. Attempts to find a cheaper substitute to gold and silver have failed, largely due to requirements of high reflectivity and high tolerance to moisture and temperature.
In light of the foregoing discussion, there is a need for an optical recording medium that uses a low-cost reflective material and has a lower cost, compared to conventional optical recording mediums.
SUMMARY
An object of the present invention is to provide an optical recording medium.
Another object of the present invention is to provide an optical recording medium that uses a low-cost reflective material and has a lower cost, compared to conventional optical recording mediums.
An embodiment of the present invention provides an optical recording medium that includes a substrate, a recordable layer formed over the substrate.

a reflective layer formed over the recordable layer, and a protective layer formed over the reflective layer. The optical recording medium may, for example, be a Compact Disc (CD) or a Digital Versatile Disc (DVD).
Another embodiment of the present invention provides an optical recording medium that includes a substrate, a reflective layer formed over the substrate, a recordable layer formed over the reflective layer, and a protective layer formed over the recordable layer. The optical recording medium may, for example, be a Blu-ray Disc (BD).
The reflective layer includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.
In accordance with an embodiment of the present invention, the reflective layer also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, the reflective layer includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, the reflective layer includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
As the reflective layer is made from low-cost reflective materials, the optical recording medium has a lower cost, compared to conventional optical recording mediums.
BRIEF DESCRIPTION OF DRAWINGS
Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings provided to illustrate and not to limit the

scope of the claims, wherein like designations denote like elements, and in which:
FIG. 1 depicts various layers of an optical recording medium, in accordance with
an embodiment of the present invention;
FIG. 2 depicts various layers of an optical recording medium, in accordance with
another embodiment of the present invention;
FIG. 3 depicts a system for manufacturing an optical recording medium, in
accordance with an embodiment of the present invention;
FIG. 4 depicts a system for manufacturing an optical recording medium, in
accordance with another embodiment of the present invention;
FIG. 5 depicts a method of manufacturing an optical recording medium, in
accordance with an embodiment of the present invention; and
FIG. 6 depicts a method of manufacturing an optical recording medium, in
accordance with another embodiment of the present invention.
DETAILED DESCRIPTION
Various embodiments of the present invention provide an optical recording medium. The optical recording medium includes a substrate on which a recordable layer and a reflective layer are formed. The reflective layer includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.
Referring now to figures, FIG. 1 depicts various layers of an optical recording medium 100, in accordance with an embodiment of the present invention. With reference to FIG. 1, optical recording medium 100 includes a substrate 102, a recordable layer 104 formed over substrate 102, a reflective layer 106 formed over recordable layer 104, and a protective layer 108 formed over reflective layer 106.

Substrate 102 may, for example, be made of a polycarbonate or a plastic.
Recordable layer 104 may, for example, be made of an organic dye, such as Cyanine, Phthalocyanine, Azo compounds, Formazan, Dipyrromethene compounds, or combinations thereof. Recordable layer 104 may be configured to record data.
Reflective layer 106 includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.
In addition to copper and zinc, reflective layer 106 may also include any other suitable metal. In accordance with an embodiment of the present invention, reflective layer 106 also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, reflective layer 106 includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, reflective layer 106 includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
An arrow 110 represents the direction of a light ray incident on optical recording medium 100. The light ray is reflected off reflective layer 106, and is received by a light detector. This enables tracking of the light ray over optical recording medium 100.
Protective layer 108 is capable of protecting recordable layer 104 and reflective layer 106 against damage. Protective layer 108 may, for example, be made of an acrylic lacquer. Alternatively, protective layer 108 may include a bonding layer and a dummy substrate.

In accordance with an embodiment of the present invention, optical recording medium 100 is stable at a temperature of 55 degree Celsius, a relative humidity of 50 %, and duration of 96 hours.
Optical recording medium 100 may, for example, be of any suitable type, shape and size. Examples of optical recording medium 100 include, but are not limited to, Compact Discs (CDs), Digital Versatile Discs (DVDs), High Definition -DVDs (HD-DVDs), and MiniDiscs (MDs). Optical recording medium 100 may, for example, be recordable, re-writable, read-only memory, or random access memory.
It is to be understood that the specific designation for optical recording medium 100 is for the convenience of reading and is not to be construed as limiting optical recording medium 100 to specific numbers, shapes, sizes, types, or arrangements of various layers of optical recording medium 100.
FIG. 2 depicts various layers of an optical recording medium 200, in accordance with another embodiment of the present invention. With reference to FIG. 2, optical recording medium 200 includes a substrate 202, a reflective layer 204 formed over substrate 202, a recordable layer 206 formed over reflective layer 204, and a protective layer 208 formed over recordable layer 206.
Substrate 202 may, for example, be made of a polycarbonate or a plastic.
In accordance with an embodiment of the present invention, reflective layer 204 includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.

In addition to copper and zinc, reflective layer 204 could include any other suitable metal. In accordance with an embodiment of the present invention, reflective layer 204 also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, reflective layer 204 includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, reflective layer 204 includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
An arrow 210 represents the direction of a light ray incident on optical recording medium 200. The light ray Is reflected off reflective layer 204, and is received by a light detector. This enables tracking of the light ray over optical recording medium 200.
Recordable layer 206 may, for example, be made of an organic dye or a phase-changing inorganic material. Examples of organic dyes include, but are not limited to, Cyanine, Phthalocyanine, Azo compounds, Formazan, and Dipyrromethene compounds. Recordable layer 206 may be configured to record data.
Protective layer 208 is capable of protecting recordable layer 206 against damage. Protective layer 208 may, for example, be made of an acrylic-based polymer.
In accordance with an embodiment of the present invention, optical recording medium 200 is stable at a temperature of 55 degree Celsius, a relative humidity of 50 %, and duration of 96 hours.
Optical recording medium 200 may, for example, be of any suitable type, shape and size. Optical recording medium 200 may, for example, be a Blu-ray

Disc (BD). Optical recording medium 200 may, for example, be recordable, re¬writable, read-only memory, or random access memory.
It is to be understood that the specific designation for optical recording medium 200 is for the convenience of reading and is not to be construed as limiting optical recording medium 200 to specific numbers, shapes, sizes, types, or arrangements of various layers of optical recording medium 200. For example, optical recording medium 200 may include a first buffer layer between reflective layer 204 and recordable layer 206, and a second buffer layer between recordable layer 206 and protective layer 208, in accordance with an additional embodiment of the present invention.
FIG. 3 depicts a system 300 for manufacturing an optical recording medium, in accordance with an embodiment of the present invention. System 300 includes a substrate-obtaining unit 302, a recordable-layer forming unit 304, a reflective-layer forming unit 306, and a protective-layer forming unit 308.
Substrate-obtaining unit 302 obtains a substrate. For this purpose, substrate-obtaining unit 302 may, for example, mold a polymeric material to form a substrate of a desired shape and size. The polymeric material may, for example, be a polycarbonate or a plastic.
Substrate-obtaining unit 302 may, for example, be an injection molding unit that injection molds the polymeric material against an injection mold.
Recordable-layer forming unit 304 then forms a recordable layer over the substrate. The recordable layer may, for example, be made of an organic dye, such as Cyanine, Phthalocyanine, Azo compounds, Formazan, Dipyrromethene compounds, or combinations thereof.

Recordable-layer forming unit 304 may, for example, perform spin coating using a solution of a dye in an appropriate solvent, followed by drying of the solvent.
Recordable-layer forming unit 304 may be used to form more than one recordable layer. The number of recordable layers may, for example, depend on the type of an optical recording medium to be manufactured.
Subsequently, reflective-layer forming unit 306 forms a reflective layer over the recordable layer. The reflective layer includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.
Reflective-layer forming unit 306 may, for example, be a sputtering unit that sputter-deposits a reflective material over the recordable layer. Accordingly, the reflective material could be in the form of a sputter target made as per the predefined proportion.
As described earlier, the reflective layer may also include other suitable metals. In accordance with an embodiment of the present invention, the reflective layer also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, the reflective layer includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, the reflective layer includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
Finally, protective-layer forming unit 308 forms a protective layer over the reflective layer. For example, the protective layer may be made of an acrylic lacquer. In such a case, protective-layer forming unit 308 may perform spin

coating, followed by Ultra-Violet (UV) curing. In another example, the protective layer may include a bonding layer and a dummy substrate. In such a case, protective-layer forming unit 308 may form the bonding layer, and place the dummy substrate over the bonding layer.
In accordance with an embodiment of the present invention, the optical recording medium so manufactured is stable at a temperature of 55 degree Celsius, a relative humidity of 50 %, and duration of 96 hours.
FIG. 3 is merely an example, which should not unduly limit the scope of the claims herein.
FIG. 4 depicts a system 400 for manufacturing an optical recording medium, in accordance with another embodiment of the present invention. System 400 includes a substrate-obtaining unit 402, a reflective-layer forming unit 404, a recordable-layer forming unit 406, and a protective-layer forming unit 408.
Substrate-obtaining unit 402 obtains a substrate. For this purpose, substrate-obtaining unit 402 may, for example, mold a polymeric material to form a substrate of a desired shape and size. The polymeric material may, for example, be a polycarbonate or a plastic.
Substrate-obtaining unit 402 may, for example, be an injection molding unit that injection molds the polymeric material against an injection mold.
Reflective-layer forming unit 404 then forms a reflective layer over the substrate. The reflective layer includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.

Reflective-layer forming unit 404 may, for example, be a sputtering unit that sputter-deposits a reflective material over the substrate. Accordingly, the reflective material could be in the form of a sputter target made as per the predefined proportion.
As described earlier, the reflective layer could include other suitable metals as well. In accordance with an embodiment of the present invention, the reflective layer also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, the reflective layer includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, the reflective layer includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
Subsequently, recordable-layer forming unit 406 forms a recordable layer over the reflective layer. The recordable layer may, for example, be made of an organic dye or a phase-changing inorganic material. Examples of organic dyes include, but are not limited to, Cyanine, Phthalocyanine, Azo compounds, Formazan, and Dipyrromethene compounds.
Recordable-layer forming unit 406 may, for example, perform spin coating using a solution of an organic dye in an appropriate solvent, followed by drying of the solvent. Alternatively, recordable-layer forming unit 406 may perform sputter-deposition of a phase-changing inorganic material.
Recordable-layer forming unit 406 may be used to form more than one recordable layer. The number of recordable layers may, for example, depend on the type of an optical recording medium to be manufactured.

Finally, protective-layer forming unit 408 forms a protective layer over the recordable layer. For example, protective-layer forming unit 408 may spin coat an acrylic-based polymer over the recordable layer.
In accordance with an additional embodiment of the present invention, system 400 may include a buffer-layer forming unit that forms a first buffer layer between the reflective layer and the recordable layer, and a second buffer layer between the recordable layer and the protective layer.
In accordance with an embodiment of the present invention, the optical recording medium so manufactured is stable at a temperature of 55 degree Celsius, a relative humidity of 50 %, and duration of 96 hours.
FIG. 4 is merely an example, which should not unduly limit the scope of the claims herein.
FIG. 5 depicts a method of manufacturing an optical recording medium, in accordance with an embodiment of the present invention. At step 502, a substrate is obtained. Step 502 may, for example, include molding a polymeric material to form a substrate of a desired shape and size. The polymeric material may, for example, be a polycarbonate or a plastic.
Step 502 may, for example, include injection molding the polymeric material against an injection mold.
At step 504, a recordable layer Is formed over the substrate. The recordable layer may, for example, be made of an organic dye, such as Cyanine, Phthalocyanine, Azo compounds, Formazan, Dipyrromethene compounds, or combination thereof.

step 504 may, for example, include spin coating using a solution of a dye in an appropriate solvent, followed by drying of the solvent.
In addition, more than one recordable layer may be formed at step 504. The number of recordable layers may, for example, depend on the type of the optical recording medium to be manufactured.
At step 506, a reflective layer is formed over the recordable layer. The reflective layer includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.
Step 506 may, for example, include sputter-depositing a reflective material over the recordable layer. Accordingly, the reflective material could be in the form of a sputter target made as per the predefined proportion.
As described earlier, the reflective layer may also include other suitable metals. In accordance with an embodiment of the present invention, the reflective layer also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, the reflective layer includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, the reflective layer includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
At step 508, a protective layer is formed over the reflective layer. For example, the protective layer may be made of an acrylic lacquer. In such a case, step 508 may include spin coating, followed by UV curing. In another example, the protective layer may include a bonding layer and a dummy substrate. In such

a case, step 508 may include forming the bonding layer, and placing the dummy substrate over the bonding layer.
In accordance with an embodiment of the present invention, the optical recording medium so manufactured is stable at a temperature of 55 degree Celsius, a relative humidity of 50 %, and duration of 96 hours.
It should be noted here that steps 502-508 are only illustrative and other alternatives can also be provided where steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein.
FIG. 6 depicts a method of manufacturing an optical recording medium, in accordance with another embodiment of the present invention. At step 602, a substrate is obtained. Step 602 may, for example, include molding a polymeric material to form a substrate of a desired shape and size. The polymeric material may, for example, be a polycarbonate or a plastic.
Step 602 may, for example, include injection molding the polymeric material against an injection mold.
At step 604, a reflective layer is formed over the substrate. The reflective layer includes a predefined proportion of copper and zinc. In accordance with an embodiment of the present invention, the predefined proportion includes 55-75 % copper and 15-45 % zinc by mass.
Step 604 may, for example, include sputter-depositing a reflective material over the substrate. Accordingly, the reflective material could be in the form of a sputter target made as per the predefined proportion.

As described earlier, the reflective layer could include other suitable metals as well. In accordance with an embodiment of the present invention, the reflective layer also includes at least one of: nickel or bismuth.
In accordance with a specific embodiment of the present invention, the reflective layer includes 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass. In accordance with another specific embodiment of the present invention, the reflective layer includes 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
At step 606, a recordable layer is formed over the reflective layer. The recordable layer may, for example, be made of an organic dye or a phase-changing inorganic material. Examples of organic dyes include, but are not limited to, Cyanine, Phthalocyanine, Azo compounds, Formazan, and Dipyrromethene compounds.
Step 606 may, for example, include spin coating using a solution of an organic dye in an appropriate solvent, followed by drying of the solvent. Alternatively, step 606 may include sputter-depositing a phase-changing inorganic material.
In addition, more than one recordable layer could be formed at step 606. The number of recordable layers may, for example, depend on the type of an optical recording medium to be manufactured.
At step 608, a protective layer is formed over the recordable layer. Step 608 may, for example, include spin coating an acrylic-based polymer over the recordable layer.
In accordance with an additional embodiment of the present invention, a step of forming a first buffer layer between the reflective layer and the recordable

layer may be performed. In accordance with another additional embodiment of the present invention, a step of forming a second buffer layer between the recordable layer and the protective layer may be performed.
In accordance with an embodiment of the present invention, the optical recording medium so manufactured is stable at a temperature of 55 degree Celsius, a relative humidity of 50 %, and duration of 96 hours.
It should be noted here that steps 602-608 are only illustrative and other alternatives can also be provided where steps are added, one or more steps are removed, or one or more steps are provided in a different sequence without departing from the scope of the claims herein.
Embodiments of the present invention provide an optical recording medium that satisfies various testing parameters specified as per lEC 68-2-2Ba mentioned in the Specification Book. These testing parameters are measured for an optical recording medium subjected to a temperature of 55 degree Celsius and a relative humidity of 50 % for duration of 96 hours.
For example, in case of DVDs, following testing parameters may be used:
Reflectivity: Reflectivity is the measure of the percentage of light returning from a program area (including lead-in, lead-out, middle and data area) of an optical recording medium. Too low a value of reflectivity may result in problems with reading of data.
Modulation: Modulation reveals information about the shape of pits, and therefore, about the quality of recording on an optical recording medium.
Asymmetry: Asymmetry is used to determine the signal values including deviation and Jitter as well as digital errors.
Parity Outer Fail (POF): A POF indicates the number of uncorrectable blocks present in an optical recording medium.

PISumS: A PISumS indicates the sum of Parity Inner Errors (PIE) per eight consecutive blocks of an optical recording medium.
Data to Clock Jitter (DC Jitter): DC Jitter indicates the occurrence of deviations from an ideal duration.
Embodiments of the present invention provide an optical recording medium, and a method and system for manufacturing the optical recording medium. The optical recording medium includes a reflective layer including a predefined proportion of copper and zinc.
The reflective layer has a high reflectivity, and is suitable for use in various types of optical recording mediums.
Moreover, the reflective layer is made from low-cost reflective materials. This reduces the cost of the optical recording mediums so manufactured.
Furthermore, the optical recording mediums so manufactured are stable at conditions prescribed by various standards defined for optical recording mediums, and therefore, are reliable.
In the description herein for the embodiments of the present invention, numerous specific details are provided, such as examples of components and/or methods, to provide a thorough understanding of the embodiments of the present invention. One skilled in the relevant art will recognize, however, that an embodiment of the present invention can be practiced without one or more of the specific details, or with other apparatus, systems, assemblies, methods, components, materials, parts, and/or the like. In other instances, well-known structures, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of the embodiments of the present invention.

Reference throughout this specification to "one embodiment", "an embodiment", or "a specific embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of an embodiment of the present invention and not necessarily in all embodiments. Thus, respective appearances of the phrases "in one embodiment", "in an embodiment", or "in a specific embodiment" in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics of any specific embodiment of the present invention may be combined in any suitable manner with one or more other embodiments. It is to be understood that other variations and modifications of the embodiments of the present invention described and illustrated herein are possible in light of the teachings herein and are to be considered as part of the spirit and scope of the present invention.
It will also be appreciated that one or more of the elements depicted in the drawings/figures can also be implemented in a more separated or integrated manner, or even removed or rendered as inoperable in certain cases, as is useful in accordance with a particular application.
As used in the description herein and throughout the claims that follow, "a", "an", and "the" includes plural references unless the context clearly dictates othenwise. Also, as used in the description herein and throughout the claims that follow, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
The foregoing description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the present invention to the precise forms disclosed herein. While specific embodiments of, and examples for, the present invention are described herein for illustrative purposes only, various equivalent modifications

are possible within the spirit and scope of the present invention, as those skilled in the relevant art will recognize and appreciate. As indicated, these modifications may be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention and are to be included within the spirit and scope of the present invention.
Thus, while the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosures, and it will be appreciated that in some instances some features of the embodiments of the present invention will be employed without a corresponding use of other features without departing from the scope and spirit of the present invention as set forth. Therefore, many modifications may be made to adapt a particular situation or material to the essential scope and spirit of the present invention. It is intended that the present invention not be limited to the particular terms used in following claims and/or to the particular embodiment disclosed as the best mode contemplated for carrying out this present invention, but that the present invention will include any and all embodiments and equivalents falling within the scope of the appended claims.

CLAIMS WHAT IS CLAIMED IS:
1. An optical recording medium comprising:
a substrate;
a recordable layer formed over the substrate;
a reflective layer formed over the recordable layer, the reflective layer comprising a predefined proportion of copper and zinc, the predefined proportion comprising 55-75 % copper and 15-45 % zinc by mass; and
a protective layer formed over the reflective layer.
2. The optical recording medium of claim 1, wherein the reflective layer further comprises at least one metal selected from the group consisting of nickel and bismuth.
3. The optical recording medium of claim 1, wherein the reflective layer comprises 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass.
4. The optical recording medium of claim 1, wherein the reflective layer comprises 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
5. The optical recording medium of claim 1 is a Compact Disc (CD).
6. The optical recording medium of claim 1 is a Digital Versatile Disc (DVD).
7. An optical recording medium comprising:
a substrate;
a reflective layer formed over the substrate, the reflective layer comprising a predefined proportion of copper and zinc, the predefined proportion comprising 55-75 % copper and 15-45 % zinc by mass;

a recordable layer formed over the reflective layer; and a protective layer formed over the recordable layer.
8. The optical recording medium of claim 7, wherein the reflective layer further comprises at least one metal selected from the group consisting of nickel and bismuth.
9. The optical recording medium of claim 7, wherein the reflective layer comprises 60-70 % copper, 15-30 % zinc, and 5-20 % nickel by mass.
10. The optical recording medium of claim 7, wherein the reflective layer
comprises 50-65 % copper, 30-45 % zinc, and 1-10 % bismuth by mass.
11. The optical recording medium of claim 7 is a Blu-ray Disc (BD).
12. An optical recording medium substantially as herein above described in the
specification with reference to the accompanying drawings.