Patent Publication Number: US-2011051584-A1

Title: Optical recording mediums

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority under 35 U.S.C 119 to co-pending India Patent Application No. 2109/CHE/2009 filed on Aug. 31, 2009. The entire disclosure of the prior application is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The embodiments herein relate, in general, to optical recording mediums. 
     2. Description of the Prior Art 
     A typical optical recording medium includes a reflective layer made from a highly reflective material. Gold and silver are most common reflective materials used today. 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 in manufacturing of optical recording mediums increases the cost of the optical recording mediums. Various attempts have been made in the past, to find a cheaper substitute to gold and silver. However, these attempts 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. In this regard, the present invention substantially fulfills this need. In this respect, the optical recording mediums according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of providing a low-cost reflective material and has a lower cost, compared to conventional optical recording mediums. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing disadvantages inherent in the known types of optical recording mediums now present in the prior art, the present invention provides an improved optical recording medium, and overcomes the above-mentioned disadvantages and drawbacks of the prior art. As such, the general purpose of the present invention, which will be described subsequently in greater detail, is to provide a new and improved optical recording medium and method which has all the advantages of the prior art mentioned heretofore and many novel features that result in an optical recording medium which is not anticipated, rendered obvious, suggested, or even implied by the prior art, either alone or in any combination thereof. 
     An embodiment is to provide an optical recording medium (and a manufacturing method and system thereof). 
     Another embodiment 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 herein 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 herein 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 at least copper and zinc. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45% zinc by mass. 
     In accordance with an embodiment herein, the reflective layer also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, the reflective layer includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, 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 cost of manufacturing of the optical recording medium is reduced. Therefore, the optical recording medium has a lower cost, compared to conventional optical recording mediums. 
     There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood and in order that the present contribution to the art may be better appreciated. 
     Numerous objects, features and advantages of the present invention will be readily apparent to those of ordinary skill in the art upon a reading of the following detailed description of presently preferred, but nonetheless illustrative, embodiments of the present invention when taken in conjunction with the accompanying drawings. In this respect, before explaining the current embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of descriptions and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     These together with other objects of the invention, along with the various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments herein 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 herein; 
         FIG. 2  depicts various layers of an optical recording medium, in accordance with another embodiment herein; 
         FIG. 3  depicts various layers of an optical recording medium, in accordance with yet another embodiment herein; 
         FIG. 4  depicts a system for manufacturing an optical recording medium, in accordance with an embodiment herein; 
         FIG. 5  depicts a system for manufacturing an optical recording medium, in accordance with another embodiment herein; 
         FIG. 6  depicts a method of manufacturing an optical recording medium, in accordance with an embodiment herein; 
         FIG. 7  depicts a method of manufacturing an optical recording medium, in accordance with another embodiment herein; and 
         FIG. 8  depicts an optical drive for reading and writing on an optical recording medium so manufactured, in accordance with an embodiment herein. 
     
    
    
     The same reference numerals refer to the same parts throughout the various figures. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a reflective layer” may include a plurality of reflective layers unless the context clearly dictates otherwise. 
     Embodiments herein provide optical recording mediums, methods and systems for manufacturing an optical recording medium, and an optical drive for reading and writing on an optical recording medium. In the description of the embodiments herein, numerous specific details are provided, such as examples of components and/or mechanisms, to provide a thorough understanding of embodiments herein. One skilled in the relevant art will recognize, however, that an embodiment herein 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 embodiments herein. 
     GLOSSARY 
     Optical recording medium: An optical recording medium is an optical medium that is capable of recording and reproducing data. Examples of optical recording mediums include, but are not limited to, Compact Discs (CDs), Digital Versatile Discs (DVDs), High-Definition DVDs (HD-DVDs), Blu-ray Discs (BDs), and MiniDiscs (MDs). One of ordinary skill in the art would appreciate that the term ‘optical recording medium’ is not limited to these examples only. 
     Substrate: A substrate provides support to various layers of an optical recording medium. 
     Recordable layer: A recordable layer is configured to record data. 
     Reflective layer: A reflective layer is capable of reflecting off a light ray incident on the optical recording medium. The reflected light could then be received by a light detector. 
     Protective layer: A protective layer is capable of protecting underlying layers against damage from external factors, such as scratches and dirt. 
     Buffer layer: A buffer layer is capable of controlling heat transfer between various layers of an optical recording medium. 
     Substrate-obtaining unit: A substrate-obtaining unit is configured to obtain a substrate of a desired shape and size. 
     Recordable-layer forming unit: A recordable-layer forming unit is configured to form a recordable layer. 
     Reflective-layer forming unit: A reflective-layer forming unit is configured to form a reflective layer. The reflective-layer forming unit could, for example, be configured to sputter-deposit a reflective material to form the reflective layer. 
     Protective-layer forming unit: A protective-layer forming unit is configured to form a protective layer. 
     Optical device: An optical device is a device that is capable of reading and writing on an optical recording medium. 
     Tray: A tray is configured to receive an optical recording medium. 
     Light source: A light source is configured to emit light rays of a predefined wavelength. 
     Optical lens: An optical lens is configured to focus the light rays on the optical recording medium. 
     Light detector: A light detector is configured to detect light rays reflected off the optical recording medium. 
     Rotator: A rotator is configured to rotate the optical recording medium, such that light rays are guided over the optical recording medium. 
     In accordance with an embodiment herein, an optical recording medium 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 CD or a DVD. 
     In accordance with another embodiment herein, an optical recording medium 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 BD. 
     In accordance with an embodiment herein, the reflective layer includes a predefined proportion of at least copper and zinc. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45% zinc by mass. 
     In addition to copper and zinc, the reflective layer could also include other suitable metals. In accordance with an embodiment herein, the reflective layer also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, the reflective layer includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, the reflective layer includes 50-65% copper, 30-45% zinc, and 1-10% bismuth by mass. 
     In accordance with an embodiment herein, the reflective layer is formed by sputter-depositing a reflective material that includes at least copper and zinc in a proportion substantially similar to the desired predefined proportion. Accordingly, the reflective material could be in the form of a sputter target made as per the predefined proportion. 
     In accordance with an embodiment herein, the optical recording medium satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for duration of 96 hours. 
       FIG. 1  depicts various layers of an optical recording medium  100 , in accordance with an embodiment herein. 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  is configured to record data. Recordable layer  104  may, for example, be made of an organic dye, such as Cyanine, Phthalocyanine, Azo compounds, Formazan, Dipyrromethene compounds, or combinations thereof. 
     In accordance with an embodiment herein, reflective layer  106  includes a predefined proportion of at least copper and zinc. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45% zinc by mass. 
     In addition to copper and zinc, reflective layer  106  could include any other suitable metal. In accordance with an embodiment herein, reflective layer  106  also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, reflective layer  106  includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, 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 herein, optical recording medium  100  satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for 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, CDs, DVDs, HD-DVDs, and MDs. Optical recording medium  100  may, for example, be recordable, re-writable, read-only memory, or random access memory. 
       FIG. 1  is merely an example, which should not unduly limit the scope of the claims herein. 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 . One of ordinary skill in the art would recognize many variations, alternatives, and modifications of embodiments herein. 
       FIG. 2  depicts various layers of an optical recording medium  200 , in accordance with another embodiment herein. 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 herein, reflective layer  204  includes a predefined proportion of at least copper and zinc. In accordance with an embodiment herein, the predefined proportion includes 50-75% 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 herein, reflective layer  204  also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, reflective layer  204  includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, 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  is configured to record data. 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. 
     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 herein, optical recording medium  200  satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for 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 BD. Optical recording medium  200  may, for example, be recordable, re-writable, read-only memory, or random access memory. 
       FIG. 2  is merely an example, which should not unduly limit the scope of the claims herein. 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 . One of ordinary skill in the art would recognize many variations, alternatives, and modifications of embodiments herein. 
       FIG. 3  depicts various layers of an optical recording medium  300 , in accordance with yet another embodiment herein. With reference to  FIG. 3 , optical recording medium  300  includes a substrate  302 , a reflective layer  304  formed over substrate  302 , a buffer layer  306  formed over reflective layer  304 , a recordable layer  308  formed over buffer layer  306 , a buffer layer  310  formed over recordable layer  308 , and a protective layer  312  formed over buffer layer  310 . 
     Substrate  302  may, for example, be made of a polycarbonate or a plastic. 
     In accordance with an embodiment herein, reflective layer  304  includes a predefined proportion of at least copper and zinc. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45% zinc by mass. 
     In addition to copper and zinc, reflective layer  304  could include any other suitable metal. In accordance with an embodiment herein, reflective layer  304  also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, reflective layer  304  includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, reflective layer  304  includes 50-65% copper, 30-45 zinc, and 1-10% bismuth by mass. 
     An arrow  314  represents the direction of a light ray incident on optical recording medium  300 . The light ray is reflected off reflective layer  304 , and is received by a light detector. This enables tracking of the light ray over optical recording medium  300 . 
     Buffer layer  306  is capable of controlling heat transfer between reflective layer  304  and recordable layer  308 . Buffer layer  306  may, for example, be made of a dielectric material. 
     Recordable layer  308  is configured to record data. Recordable layer  308  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. 
     Buffer layer  310  is capable of controlling heat transfer between recordable layer  308  and protective layer  312 . Buffer layer  310  may, for example, be made of a dielectric material. 
     Protective layer  312  is capable of protecting recordable layer  308  against damage. Protective layer  312  may, for example, be made of an acrylic-based polymer. 
     In accordance with an embodiment herein, optical recording medium  300  satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for duration of 96 hours. 
     Optical recording medium  300  may, for example, be of any suitable type, shape and size. Optical recording medium  300  may, for example, be a BD. Optical recording medium  300  may, for example, be recordable, re-writable, read-only memory, or random access memory. 
       FIG. 3  is merely an example, which should not unduly limit the scope of the claims herein. It is to be understood that the specific designation for optical recording medium  300  is for the convenience of reading and is not to be construed as limiting optical recording medium  300  to specific numbers, shapes, sizes, types, or arrangements of various layers of optical recording medium  300 . One of ordinary skill in the art would recognize many variations, alternatives, and modifications of embodiments herein. 
       FIG. 4  depicts a system  400  for manufacturing an optical recording medium, in accordance with an embodiment herein. System  400  includes a substrate-obtaining unit  402 , a recordable-layer forming unit  404 , a reflective-layer forming unit  406 , and a protective-layer forming unit  408 . 
     Substrate-obtaining unit  402  is configured to obtain a substrate. 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 configured to injection mold the polymeric material against an injection mold. 
     Recordable-layer forming unit  404  is configured to form a recordable layer over the substrate. The recordable layer may, for example, be made of an organic dye. Examples of organic dyes include, but are not limited to, Cyanine, Phthalocyanine, Azo compounds, Formazan, and Dipyrromethene compounds. 
     Recordable-layer forming unit  404  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  404  could be configured 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. 
     Reflective-layer forming unit  406  is configured to form a reflective layer over the recordable layer. The reflective layer is formed using a reflective material that includes a predefined proportion of at least copper and zinc. Consequently, the reflective layer so formed includes at least copper and zinc in the predefined proportion. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45 zinc by mass. 
     Reflective-layer forming unit  406  may, for example, be a sputtering unit configured to sputter-deposit the 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 could include other suitable metals as well. In accordance with an embodiment herein, the reflective layer also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, the reflective layer includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, the reflective layer includes 50-65% copper, 30-45% zinc, and 1-10% bismuth by mass. 
     Protective-layer forming unit  408  is configured to form 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  408  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  408  may form the bonding layer, and place the dummy substrate over the bonding layer. 
     In accordance with an embodiment herein, the optical recording medium so manufactured satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for duration of 96 hours. 
       FIG. 4  is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many variations, alternatives, and modifications of embodiments herein. 
       FIG. 5  depicts a system  500  for manufacturing an optical recording medium, in accordance with another embodiment herein. System  500  includes a substrate-obtaining unit  502 , a reflective-layer forming unit  504 , a recordable-layer forming unit  506 , and a protective-layer forming unit  508 . 
     Substrate-obtaining unit  502  is configured to obtain a substrate. Substrate-obtaining unit  502  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  502  may, for example, be an injection molding unit configured to injection mold the polymeric material against an injection mold. 
     Reflective-layer forming unit  504  is configured to form a reflective layer over the substrate. The reflective layer is formed using a reflective material that includes a predefined proportion of at least copper and zinc. Consequently, the reflective layer so formed includes at least copper and zinc in the predefined proportion. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45% zinc by mass. 
     Reflective-layer forming unit  504  may, for example, be a sputtering unit configured to sputter-deposit the 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 herein, the reflective layer also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, the reflective layer includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, the reflective layer includes 50-65% copper, 30-45% zinc, and 1-10% bismuth by mass. 
     Recordable-layer forming unit  506  is configured to form 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  506  may, for example, perform spin coating using a solution of a dye in an appropriate solvent, followed by drying of the solvent. Alternatively, recordable-layer forming unit  506  may perform sputter-deposition of a phase-changing inorganic material. 
     Recordable-layer forming unit  506  could be configured 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. 
     Protective-layer forming unit  508  is configured to form a protective layer over the recordable layer. For example, protective-layer forming unit  508  may spin coat an acrylic-based polymer over the recordable layer. 
     In accordance with an additional embodiment herein, system  500  includes a buffer-layer forming unit configured to form 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 herein, the optical recording medium so manufactured satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for duration of 96 hours. 
       FIG. 5  is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many variations, alternatives, and modifications of embodiments herein. 
       FIG. 6  depicts a method of manufacturing an optical recording medium, in accordance with an embodiment herein. The method is illustrated as a collection of steps in a logical flow diagram, which represents a sequence of steps that can be implemented in hardware, software, or a combination thereof. 
     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 recordable layer is formed over the substrate. The recordable layer may, for example, be made of an organic dye. Examples of organic dyes include, but are not limited to, Cyanine, Phthalocyanine, Azo compounds, Formazan, and Dipyrromethene compounds. 
     Step  604  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 could be formed at step  604 . The number of recordable layers may, for example, depend on the type of an optical recording medium to be manufactured. 
     At step  606 , a reflective layer is formed over the recordable layer. As described earlier, the reflective layer is formed using a reflective material that includes a predefined proportion of at least copper and zinc. Consequently, the reflective layer so formed includes at least copper and zinc in the predefined proportion. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45 zinc by mass. 
     Step  606  may, for example, include sputter-depositing the 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 could include other suitable metals as well. In accordance with an embodiment herein, the reflective layer also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, the reflective layer includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, the reflective layer includes 50-65% copper, 30-45% zinc, and 1-10% bismuth by mass. 
     At step  608 , 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  608  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  608  may include forming the bonding layer, and placing the dummy substrate over the bonding layer. 
     In accordance with an embodiment herein, the optical recording medium so manufactured satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for 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. 
       FIG. 7  depicts a method of manufacturing an optical recording medium, in accordance with another embodiment herein. The method is illustrated as a collection of steps in a logical flow diagram, which represents a sequence of steps that can be implemented in hardware, software, or a combination thereof. 
     At step  702 , a substrate is obtained. Step  702  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  702  may, for example, include injection molding the polymeric material against an injection mold. 
     At step  704 , a reflective layer is formed over the substrate. As described earlier, the reflective layer is formed using a reflective material that includes a predefined proportion of at least copper and zinc. Consequently, the reflective layer so formed includes at least copper and zinc in the predefined proportion. In accordance with an embodiment herein, the predefined proportion includes 50-75% copper and 15-45% zinc by mass. 
     Step  704  may, for example, include sputter-depositing the 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 herein, the reflective layer also includes at least one of: nickel or bismuth. 
     In accordance with a specific embodiment herein, the reflective layer includes 60-70% copper, 15-30% zinc, and 5-20% nickel by mass. In accordance with another specific embodiment herein, the reflective layer includes 50-65% copper, 30-45% zinc, and 1-10% bismuth by mass. 
     At step  706 , 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  706  may, for example, include spin coating using a solution of a dye in an appropriate solvent, followed by drying of the solvent. Alternatively, step  706  may include sputter-depositing a phase-changing inorganic material. 
     In addition, more than one recordable layer could be formed at step  706 . The number of recordable layers may, for example, depend on the type of an optical recording medium to be manufactured. 
     At step  708 , a protective layer is formed over the recordable layer. Step  708  may, for example, include spin coating an acrylic-based polymer over the recordable layer. 
     In accordance with an additional embodiment herein, 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 herein, a step of forming a second buffer layer between the recordable layer and the protective layer may be performed. 
     In accordance with an embodiment herein, the optical recording medium so manufactured satisfies various testing parameters when subjected to a temperature of 55 degree Celsius and a relative humidity of 50% for duration of 96 hours. 
     It should be noted here that steps  702 - 708  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. 8  depicts an optical device  800  for reading and writing on an optical recording medium, in accordance with an embodiment herein. Optical device  800  includes a tray  802 , a light source  804 , an optical lens  806 , and a light detector  808 . 
     Tray  802  is configured to receive the optical recording medium. Tray  802  may, for example, be extendable and retractable between a loading position and an operating position. 
     Light source  804  is configured to emit light rays of a predefined wavelength, while optical lens  806  is configured to focus the light rays on the optical recording medium. 
     In accordance with an embodiment herein, the predefined wavelength is based on the type of the optical recording medium. Consider, for example, two different types of optical recording mediums, namely, a DVD and a BD. In case of the DVD, light rays of a first predefined wavelength could be used. While, in case of the BD, light rays of a second predefined wavelength, which is smaller than the first predefined wavelength, could be used. 
     In addition, light source  804  could include a controller configured to control the amount of light rays, depending on the type of operation required. For example, different amounts of light rays could be used to write data onto and read data from the optical recording medium. 
     Light detector  808  is configured to detect light rays reflected off the optical recording medium. Data recorded onto the optical recording medium could, for example, be read by determining the change in the reflected light rays. 
     In case of an optical recording medium of a circular shape, optical device  800  may also include a rotator configured to rotate the optical recording medium. When the optical recording medium is rotated, light rays are guided over various portions of the optical recording medium. 
     Optical device  800  may, for example, be implemented in a personal computer or a laptop. A computer typically includes a processor for executing various programs, a display screen for displaying one or more user interfaces to a user, and one or more input devices for receiving inputs from the user. The computer may, for example, include a single integrated device that is capable of reading and writing on optical recording mediums. 
       FIG. 8  is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many variations, alternatives, and modifications of embodiments herein. 
     Embodiments herein provide an optical recording medium that satisfies various testing parameters specified as per IEC 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. 
     PISum8: A PISum8 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 herein provide optical recording mediums, and methods and systems for manufacturing an optical recording medium. An optical recording medium includes a reflective layer including a predefined proportion of at least 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 overall cost of manufacturing of optical recording mediums, and hence reduces the cost of the optical recording mediums so manufactured. 
     Furthermore, the optical recording mediums so manufactured are stable at conditions prescribed by the standards, and therefore, are reliable. 
     Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.