FIELD OF INVENTION
[0002] The invention disclosed herein relates, in general, to a printable optical storage media. More specifically, the present invention relates to an optical storage media that is capable of being offset printed.
BACKGROUND
[0003] Compact Discs (CDs) are widely used these days. Recordable CDs such as those of movies etc are labeled. The labeling of CDs is generally done by screen printing method. In screen printing, a woven mesh supporting an ink-blocking stencil is placed over a CD and then a squeegee containing a required ink(s) is moved across the stencil. This pumps the ink to form an image on the optical storage media. However, screen printing consumes more time, provides low resolution images, and limits the numbers of ink colors can be in the label.
[0004] There is certainly a need of printing high resolution images with multiple colors and high contrast. This can be achieved by offset printing method. The offset printing method uses heavy ink rollers to transfer the ink to the print layer of the optical storage media. This force, generated due to heavy roller, causes separation of various layers in a CD. Commonly used bonding agents and adhesives are not capable of holding the layers intact. Use of specialized bonding agents or adhesives increases the cost of a CD significantly, making high resolution printing on a CD unsuitable for mass manufacturing. Also, there is high possibility of deformation of printable layer, especially at the edges.
[0005] There is, therefore, a need for an optical storage media that is capable of being offset printed in a cost effective way.
BRIEF DESCRIPTION OF FIGURES
[0006] The features of the present invention, which are believed to be novel, are set forth with particularity in the appended claims. The invention may best be understood by reference to the following,description, taken in conjunction with the accompanying drawings. These drawings and the associated description are provided to illustrate some embodiments of the invention, and not to limit the scope of the invention.
[0007] FIG. 1a is a cross sectional view of an optical storage media (prior art), in accordance with the state of the art prior to the present invention;
[0008] FIG. 1b is a zoomed-in view of a region 110 of the optical storage media (prior art) shows in FIG. 1a, in accordance with the state of the art prior to the present invention;
[0009] FIG. 2a is a cross sectional view of an optical storage media, in accordance with an embodiment of the present invention;
[0010] FIG. 2b is a zoomed-in view of a region 204 of the optical storage media shown in FIG. 2a, in accordance with an embodiment of the present invention;
[0011] FIG. 2c is a blown-up view depicting different layers of the optical storage media shown in FIG. 2a, in accordance with an embodiment of the present invention;
[0012] FIG. 3 is a cross sectional view of an optical storage media, in accordance with another embodiment of the present invention in which a printable layer bonds with a polycarbonate layer on one or more substantially flat portions of the polycarbonate layer;
[0013] FIG. 4 is a cross sectional view of an optical storage media, in accordance with yet another embodiment of the present invention in which a printable layer bonds with a polycarbonate layer on inner and outer perimeter of the polycarbonate layer; and
[0014] FIG. 5 illustrates a customized top view of an exemplary optical storage media to illustrate a pattern of depressions, in accordance with an embodiment of the present invention.
[0015] Those with ordinary skill in the art will appreciate that the elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated, relative to other elements, in order to improve the understanding of the present invention.
[0016] There may be additional structures described in the foregoing application that are not depicted on one of the described drawings. In the event such a structure is described, but not "depicted in a drawing, the absence of such a drawing should not be considered as an omission of such design from the specification.
SUMMARY
[0017] The instant exemplary embodiments provide an optical storage media that can be offset printed.
[0018] Some embodiments provide an optical storage media having strong adhesion between its layers.
[0019] Some embodiments provide an optical storage media, in which a reflective layer has substantially lesser chances of separating from remaining layers.
[0020] Some embodiments of the present invention provide an optical storage media capable of being offset printed. The optical storage media includes a polycarbonate substrate having a pattern of depressions and one or more substantially flat portions. The polycarbonate substrate is substantially transparent to facilitate a transmission of laser. A dye layer is confined in the pattern of depressions. The dye layer is optically active to a predefined incident laser which, thereby, facilitates data storage on the dye layer. A reflective layer is substantially bonded to the one or more substantially flat portions of the polycarbonate substrate, such that there is an increased adhesion between the reflective layer and the polycarbonate substrate, and physical strength is imparted to the optical storage media. The optical storage media also includes a printable layer substantially bonded to the reflective layer. The printable layer is capable of being offset printed without being separated from the reflective layer and the polycarbonate substrate.
[0021] In one embodiment of the optical storage media, the dye is confined to the pattern of depressions by using dispensing, spraying and/or layering.
[0022] In one embodiment of the optical storage media, the pattern of depressions is a spiral pattern.
[0023] In one embodiment of the optical storage media, the dye is a cyanine-based dye, a phthalocyanine dye, or an azo dye.
[0024] In one embodiment of the optical storage media, the material of the reflective layer is Silver, Gold, an alloy of Silver or an alloy of Gold.
[0025] In one embodiment of the optical storage media, the printable layer is bonded to the polycarbonate substrate along an outer perimeter and/or an inner perimeter, which imparts physical strength to the optical storage media.
[0026] In one embodiment of the optical storage media, a print layer is formed on the printable layer by offset printing.
[0027] In one embodiment of the optical storage media, the printable layer is bonded to the one or more substantially flat portions proximal to at least one of an outer perimeter and an inner perimeter of the polycarbonate substrate.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0028] Before describing the present invention in detail, it should be observed that the present invention utilizes a combination of method steps and apparatus components related to an optical storage media. Accordingly the apparatus components and the method steps have been represented where appropriate by conventional symbols in the drawings, showing only specific details that are pertinent for an understanding of the present invention so as not to obscure the disclosure with details that will be readily apparent to those with ordinary skill in the art having the benefit of the description herein.
[0029] While the specification concludes with the claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawings, in which like reference numerals are carried forward.
[0030] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.
[0031] The terms "a" or "an", as used herein, are defined as one or more than one. The term "another", as used herein, is defined as at least a second or more. The terms "including" and/or "having" as used herein, are defined as comprising (i.e. open transition). The term "coupled" or "operatively coupled" as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically.
GLOSSARY
[0032] Optical Storage Media: These are electronic data storage devices, usually circular discs that encode binary data in the form of pits (binary value of 0 or off, due to lack of reflection when read) and lands (binary value of 1 or on, due to a reflection when read) on an optically active material, more specifically, a material optically sensitive to laser. These devices have multiple layers, a substrate layer to provide strength to the optical storage media and allow the transmission of an incident laser through itself, a recording layer to facilitate recording of data by creating pits or lands when incident by a recording laser, a reflective layer to reflect a reading laser back and facilitate reading of the recorded data. One example of an optical storage media is a Recordable Compact Disc (CD-R).
[0033] Dye: It is an optically active material that changes its optical properties w.r.t. reflection of the reading laser when a recording laser is incident on it. This characteristic makes a dye suitable to be used as a recording material in optical storage media, for example, a CD-R. Some examples of dye include, but are not limited to, a cyanine-based dye, a phthalocyanine dye, and an azo dye.
[0034] Polycarbonate Substrate: This is a substrate layer in the optical storage media that provides strength to the optical storage media. It is transparent to allow transmission of recording as well as reading laser through itself. It also has a pattern of depressions, preferably a spiral groove, on its surface. In accordance with the present invention, the dye is confined to this pattern of depressions.
[0035] Reflective Layer: Reflective layer is provided in an optical storage media to facilitate reading of the stored data. The reflective layer is so provided that the reading laser reaches it after passing through the pits and/or lands on the dye, after which the reflective layer reflects the reading laser, which is read by an optical storage media reading device.
[0036] Printable Layer: Printable layer is a protective layer provided over the reflective layer. Labels or data identifiers are printed on the printable layer. This layer is termed as printable layer for the purpose of this description, however, in some real life applications, this layer may be provided to only provide strength and protection without being printable.
[0037] Print layer: This is the layer of the label or identifier information that is formed by subjecting the printable layer of the optical storage media to offset printing. This layer may include different combinations of inks that constitute the label or identifier information.
[0038] Offset Printing: It is a widely used printing process for producing high resolution printing. It is called offset printing because the ink is not directly pressed onto a printable layer, but is distributed from a metal roller to a rubber roller where it is then pressed onto the printable layer. In offset printing, the printable layer is under a high pressure and at the same time the rubber roller may have a tendency to pull the printable layer depending upon a degree of adhesion between the printable layer and the roller. Accordingly, when using offset printing on an optical storage media, as per the state of the art prior to the present invention, the reflective layer tends to separate from the dye layer due to strong adhesion between the printable layer and the rubber roller, and weak adhesion between the reflective layer and the dye layer. This separation damages the optical storage media, rendering, the offset printing process ineffective or unsuitable for printing on the optical storage media.
[0039] Referring now to the drawings, FIG. 1a is a cross sectional view of an optical storage media 100, in accordance with the state of the art prior to the present invention (prior art) and FIG." 1b is a zoomed-in view of a region 110 of the optical storage media 100. The zoomed-in view is provided for clear illustration of different layers of the optical storage media 100. For the purpose of this description, the optical storage media 100 is considered to be an annular disc having an axis 101, and with a hole at the centre. In this specific illustration the optical storage media 100 is defined as a Compact Disc (CD). It will, however, be readily apparent to those skilled in the art that the invention can be implemented on other optical storage media as well.
[0040] The optical storage media 100 is shown to include a polycarbonate substrate 102, a dye layer 104, a reflective layer 106 and a printable layer 108. The polycarbonate substrate has a pattern of depressions 103 and one or more substantially flat portions 105 (refer FIG. 5). For example, the polycarbonate substrate 102 can have a spiral groove on its surface, and portions of the surface that are not covered by the grooves are referred to as substantially flat portions 105. A dye layer 104 is provided over the polycarbonate substrate 102, such that the dye layer 104 fills the pattern of depressions 103 and also forms an annular layer 107 over the polycarbonate substrate 102.
[0041] The dye of the dye layer 104 is translucent to a reading laser beam that is used for reading data from optical storage media 100, i.e., a low power laser beam of a wavelength substantially close to 780 nm. However, the dye is optically active to a recording laser, i.e., a high-power laser beam of a predefined wavelength substantially close to 780nm. The recording laser has been referred to as the predefined incident laser in claims. When the high-power incident laser beam is incident on a portion of the dye, it chemically alters that portion of the dye, thereby, changing its opacity to the laser reading laser beam. For example, the dye which was translucent to the reading laser becomes substantially opaque to the reading laser after the high-power incident laser beam is incident on it. This characteristic of the dye makes it suitable for recording or storing data on the optical storage media 100. Some examples of the dyes used for the
dye layer 104 include, but are not limited to, a cyanine-based dye, a phthalocyanine dye, and an azo dye.
[0042] For the purpose of this description, surfaces of each layer are referred to as lower and upper surfaces according to their relative position when the optical storage media is viewed from side. In other words, a surface on which an incident laser becomes incident is referred to as the lower layer, and an opposite surface is referred to as the upper surface.
[0043] The reflective layer 106 is provided above the dye layer 104, such that a lower surface of the reflective layer 106 is adhering or bonding to an upper surface of the dye layer 104. Some examples of the materials used for the reflective layer 106 include, but are not limited to, gold, silver, an alloy of gold and an alloy of silver.
[0044] The printable layer 108 is provided above the reflective layer such that a lower surface of the printable layer 108 adheres or bonds to an upper surface of the reflective layer 106.
[0045] When the optical storage media 100, according to the prior art, is subject to offset printing, the printable layer 108 is under a high pressure and at the same time the rubber roller may have a tendency to exert shear force on the optical storage media 100 across the surfaces where different layers interface. An adhesion between the reflective layer 106 and the dye is weak and cannot withstand the shear force exerted by the rubber roller. Accordingly, the reflective layer 106 tends to separate from the dye layer 104. Further, there can be deformation at an outer and/or an inner perimeter of the optical storage media 100 in a direction of movement of the rubber roller. This separation and/or deformation damages the optical storage media 100, rendering it unusable.
[0046] Referring to FIG. 2a, there is shown a cross sectional view of an optical storage media 200, in accordance with an embodiment of the present invention. FIG. 2b is a zoomed-in view of a region 204 of the optical storage media 200 and FIG. 2c is a blown-up view depicting different layers of the optical storage media 200. For the purpose of this description, the optical storage media 200 is considered to be a CD with an annular disc having an axis 101, and with a hole at the centre. It will be appreciated by those with ordinary skilled in the art that the present invention can be practiced with optical storage media 200 of other shapes and type as well.
[0047] The optical storage media 200 is shown to include the polycarbonate substrate 102, a dye layer 202, the reflective layer 106 and the printable layer 108.
[0048] The polycarbonate substrate 102 has the pattern of depressions 103 and the one or more substantially flat portions 105 (refer FIG. 5). The pattern of depressions 103 are filled with the dye and the filled pattern of depressions 103 forms the dye layer 202 (Refer FIG. 2c for ease in understanding). In other words the dye layer 202 includes the dye confined to the pattern of depressions 103, such that there is practically no dye on the one or more substantially flat portions 105. The dye filled in the dye layer 202 is substantially same as the dye filled in the dye layer 104 of optical storage media 100 (Prior Art).
[0049] Since in optical storage media 200, there is practically no dye on the one or more substantially flat portions 105, the reflective layer 106 is directly bonded to the polycarbonate substrate 102. Thereby, the dye layer 104 is encapsulated between the reflective layer 106 and the polycarbonate layer 102.
[0050] In one embodiment, the reflective layer 106 is directly bonded to the polycarbonate layer 102 only near an inner perimeter 306 and an outer perimeter 304.
[0051] The dye layer 202 can be confined to the pattern of depressions 103, by disposing the dye using dispensing, spraying and/or layering. In all these techniques, the dye is applied or disposed only in the pattern of depressions 103, while ensuring that the dye does not gets disposed on the one or more substantially flat portions 105.
[0052] For example, one such process for depositing the dye confined to the pattern of depressions 103 may include precision dispensing of the dye directly into the pattern of depressions 103 using a nozzle that has a fine hole, with a diameter in the range of a fraction of microns, In this exemplary process, a synchronization between linear movement of the nozzle along a radius of the optical storage media and a rotation of the optical storage media can facilitate depositing the dye confined to the pattern of depressions 103.
[0053] Another.exemplary process for depositing the dye confined to the pattern of depressions 103 may include, spin coating a layer of dye on the polycarbonate layer 102 such that the pattern of'depressions 103 are completely filled and an additional layer similar to the annular layer 107 is formed. Thereafter, the annular layer 107 can be removed by chemical or non-chemical cleaning.
[0054] The adhesion between the reflective layer 106 and the polycarbonate substrate 102 is greater than the adhesion between the reflective layer 106 and the dye, therefore, the chances of separation of the reflective layer 106 on application of a force are substantially reduced in the optical storage media 200 as compared to the optical storage media 100.
[0055] The printable layer 108 is provided above the reflective layer 106, and is bonded to the reflective layer 106. The printable layer 108 can be provided by using multiple methods, for example, spin coating. The printable layer 108 is a protective layer to protect the reflective layer 106 from direct contact with the environment, corrosion and scratches, etc. An example of the printable material 108 includes, but is not limited to, a lacquer.
[0056] When the optical storage media 200 is subject to offset printing, i.e., the printable layer 108 is under a high pressure while also being under a pulling force due to the adhesion with the rubber roller, the reflective layer 106 does not separate from the polycarbonate substrate 102 or the dye layer 202. Therefore, the optical storage media 200, in accordance with the present invention, can be offset printed.
[0057] After offset printing, a layer of the printed content or a print layer 206 (Refer FIG. 2c) is formed on the printable layer 108.
[0058] In some embodiments of the present invention, to further enhance the physical strength of the optical storage media, it is so manufactured that the printable layer 108 not only bonds to the reflective layer 106 but also bonds to the one or more substantially flat portions 105 near an inner and outer perimeter of the optical storage media. The strength is further enhanced in this embodiment, as the adhesion between the printable layer 108 and the polycarbonate substrate 102 is greater than the adhesion between the reflective layer 106 and the polycarbonate substrate 102.
[0059] This embodiment is shown as the optical storage media 300 in FIG. 3. For the purpose of this description, the optical storage media 300 is considered to be an annular disc with an outer perimeter represented by lines 304 and an inner perimeter represented by lines 306 in the cross sectional view of the optical storage media 300 depicted in FIG. 3 (refer FIG. 5 for top view of inner perimeter 306 and outer perimeter 304). The printable layer 108 is shown to be bonded to the reflective layer 106 and also at the substantially flat portions 302 of the polycarbonate substrate 102 proximal to the inner perimeter 306 and the outer perimeter 304.
[0060] The above embodiment can be achieved by keeping the substantially flat portions 302 proximal to the inner perimeter 306 and the outer perimeter 304 free from the reflective layer 106 during disposition of the reflective layer 106 on the polycarbonate substrate 102. For example, when the reflective layer 106 is being disposed using spin coating, then one or more parameters of the spin coating process,like, location of spraying the material, speed of rotation or spin and the duration of rotation or spin can be controlled to achieve the above embodiment.
[0061] Thereafter, when the printable layer 108 is applied, it can bond to both the reflective layer 106 and also at the substantially flat portions 302 of the polycarbonate substrate 102 proximal to the inner perimeter 306 and the outer perimeter 304.
[0062] In some other embodiments of the present invention, to further enhance the strength of the optical storage media, it is so manufactured that the printable layer 108 not only bonds to the surface of the reflective layer 106 but also bonds to the reflective layer 106 and the polycarbonate substrate 102 along the inner perimeter and/or the outer perimeter.
[0063] This embodiment is shown as the optical storage media 400 in FIG. 4. For the purpose of this description, the optical storage media 400 is considered to be an annular disc with an outer perimeter represented by lines 304 and an inner perimeter represented by lines 306 in the cross sectional view of the optical storage media 400 depicted in FIG. 4. The printable layer 108 is shown to adhere to the surface of the reflective layer 106 and also to the outer perimeter 304 of the reflective layer 106 and the polycarbonate substrate 102.
[0064] Various embodiments of the present invention, as described above, provide an optical storage media, which has several advantages. One of the several advantages of some embodiments of this optical storage media is that it can be offset printed. Another advantage is that the reflective layer strongly adheres to the polycarbonate substrate, thereby imparting strength to the optical storage device. Another advantage of this optical storage device is that high resolution labels and multi-colored images can be printed on it.
[0065] While the invention has been disclosed in connection with the preferred embodiments shown and described in detail, various modifications and improvements thereon will become readily apparent to those ordinarily skilled in the art. Accordingly, the spirit and scope of the present invention is not to be limited by the foregoing examples, but is to be understood in the broadest sense allowable by law.
[0066] All documents referenced herein are hereby incorporated by reference.

CLAIMS
What is claimed is:
1. An optical storage media capable of being offset printed, the optical storage
media comprising:
a polycarbonate substrate having a pattern of depressions and one or more substantially flat portions, wherein the polycarbonate substrate is substantially transparent to facilitate a transmission of an incident laser;
a dye layer confined in the pattern of depressions, wherein the dye layer is optically active to a predefined incident laser, thereby facilitating data storage on incidence of the incident laser;
a reflective layer substantially bonded to the one or more substantially flat portions of the polycarbonate substrate, whereby increasing an adhesion between the reflective layer and the polycarbonate substrate, and whereby imparting physical strength to the optical storage media; and
a printable layer substantially bonded to the reflective layer, wherein the printable layer is capable of being offset printed without being separated from the reflective layer and the polycarbonate substrate.
2. The optical storage media of claim 1, wherein the optical storage media is a recordable compact disc (CD-R).
3. The optical storage media of claim 1, wherein the printable layer is bonded to the polycarbonate substrate along at least one of an outer perimeter and an inner perimeter, whereby imparting strength to the optical storage media.
4. The optical storage media of claim 1, wherein a print layer is formed on the printable layer by offset printing.
5. The optical storage media of claim 1, wherein the printable layer is bonded to the one or more substantially flat portions proximal to at least one of an outer perimeter and an inner perimeter of the polycarbonate substrate.