Patent Publication Number: US-8114579-B2

Title: Manufacturing data-storage media using light-curable material

Description:
This application is a continuation of U.S. patent application Ser. No. 11/247,478, filed on Oct. 11, 2005, incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to techniques for manufacturing data-storage media, such as compact discs (CDs) and digital video discs (DVDs). 
     2. Description of the Related Art 
     A conventional DVD player reads digital data stored on a DVD by illuminating the DVD with light from a laser and detecting and processing light reflected from different portions of the DVD (e.g., by rotating the DVD and moving the illuminating laser light radially). Portions of the DVD that store instances of the logical data value “1” have optical characteristics that are different from the optical characteristics of portions of the DVD that store instances of the logical data value “0”, such that the reflected laser light is different for logical “1”s and “0”s. 
     There are different ways to manufacture a DVD, including stamping and burning. 
       FIG. 1  shows a schematic cross-section of a portion of a conventional stamped DVD  100 . Stamped DVD  100  comprises a plastic (e.g., polycarbonate) substrate  102  and a protective layer  106  with an intervening reflective (e.g., aluminum) coating  104 . The interface between substrate  102  and protective layer  106  is defined by physical characteristics referred to as pits  108  and lands  110 , which are distinguished by their different elevation levels in the Z direction represented in  FIG. 1 . As viewed in  FIG. 1 , lands correspond to plateaus (i.e., regions of relatively elevated elevation) in the topology of the upper surface of substrate  102 , while pits corresponds to valleys (i.e., regions of relatively depressed elevation) in that topology. Depending on the DVD storage scheme, transitions between pits  108  and lands  110  may correspond to logical “1”s and “0”s. 
     According to one prior-art technique, substrate  102  is formed by physically pressing a heat-softened plastic disc (corresponding to substrate  102 ) against a master disc having “a mirrored image” of the pits and lands of substrate  102  to create pits and lands on the upper surface (as viewed in  FIG. 1 ) of substrate  102 . Reflective coating  104  is then applied (e.g., by sputtering or vapor deposition) to the upper surface of substrate  102 , followed by application of protective layer  106  to form DVD  100  (e.g., by applying a spun coating of clear enamel). Note that protective layer  106  may also function as the label for stamped DVD  100 . Stamped DVDs are typically manufactured in large quantities using sophisticated and expensive machinery. 
     An alternative to stamping DVDs is burning, where selected portions of a “blank” disc are illuminated with laser light that alters the optical characteristics of the disc material in those selected portions, thereby creating “optical” pits and lands that function analogously to the “topological” pits and land of a stamped DVD. One of the advantages of burning DVDs is that the technique can be implemented using equipment that is less expensive than the conventional machinery used to stamp DVDs. One of the disadvantages is that certain copyright protection schemes, such as the Contents Scramble System (CSS), are designed for stamped DVDs, but not for burnt DVDs. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention is a method and apparatus for manufacturing a data-storage medium having pits and lands. A layer of a uncured, light-curable material is applied to a substrate. Selected regions of the layer are illuminated with material-curing light to cure portions of the material corresponding to the selected regions. Uncured portions of the material are removed from the substrate to create lands corresponding to the cured portions, and the manufacturing of the data-storage medium is completed, as appropriate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other aspects, features, and advantages of the present invention will become more fully apparent from the following detailed description, the appended claims, and the accompanying drawings in which like reference numerals identify similar or identical elements. 
         FIG. 1  shows a schematic cross-section of a portion of a conventional stamped DVD; 
       FIGS.  2 (A)-(C) represent a technique for manufacturing a DVD, according to one embodiment of the present invention; 
       FIGS.  3 (A)-(C) represent a technique for manufacturing a DVD, according to another embodiment of the present invention; 
       FIGS.  4 (A)-(D) represent a technique for manufacturing a DVD employing a mask having one or more opaque portions corresponding to false pits, according to one embodiment of the present invention; 
       FIGS.  5 (A)-(D) represent a technique for manufacturing a DVD employing a mask having one or more transparent portions corresponding to false lands, according to one embodiment of the present invention; 
         FIG. 6  shows a block diagram of a DVD manufacturing system, according to one embodiment of the present invention; and 
         FIG. 7  shows a flow diagram of the processing implemented by the DVD manufacturing system of  FIG. 6 , according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     FIGS.  2 (A)-(C) represent a technique for manufacturing a DVD, according to one embodiment of the present invention. As represented in  FIG. 2(A) , a layer  204  of uncured (e.g., semi-fluid), light-curable material is applied to the upper (as viewed in  FIG. 2 ) surface of a substrate  202 . 
     Different portions of layer  204  are then selectively illuminated with appropriate (i.e., material-curing) light under appropriate conditions (e.g., temperature, pressure and composition of ambient air, duration and intensity of illumination) to cure (i.e., make solid) the light-curable material corresponding to those different portions. This selective illumination can be accomplished using a variety of methods. 
     One such method is represented in  FIG. 2(A) , where an optical mask  206  having appropriate transparent portions  208  and opaque portions  210  is positioned over layer  204  and a broad beam of material-curing light is applied from above to selectively illuminate different portions of layer  204 . If substrate  202  is transparent to the material-curing light, then optical mask  206  could alternatively be positioned below substrate  202  with the material-curing light applied from below. 
     Other methods of selectively illuminating different portions of layer  204  with material-curing light involve the selective application of a relatively narrow beam of laser light, similar to what is done in the prior-art technique of burning DVDs. Here, too, depending on the implementation, the laser light can be applied either from above or from below. Note that the material-curing light can be any electromagnetic radiation suitable for curing the curable material, and can be, but need not be visible light. 
     No matter which method is employed for selectively illuminating different portions of layer  204 , the result is that the light-curable material corresponding to the illuminated portions will be cured, while the light-curable material that was not illuminated will remain in its uncured state. By removing (e.g., washing away) the uncured material from the substrate, the cured material will remain, as represented in  FIG. 2(B) , as plateaus  212  of cured material separated by valleys  214  (corresponding to the removed uncured material) on the upper surface of substrate  202 . An appropriate reflective coating (not shown) can then be applied over the plateaus and valleys, using a conventional sputtering or vacuum deposition technique. 
     As represented in  FIG. 2(C) , the manufacturing process is completed by applying a protective coating  216  to the upper surface to produce a DVD  200  having land structures  218  and pit structures  220  physically and functionally analogous to the lands and pits of prior-art DVD  100  of  FIG. 1 . 
     Different suitable materials may be used in manufacturing DVD  200 . In one possible implementation, substrate  202  may be a polycarbonate plastic, the light-curable material of layer  204  may be Accura® LaserForm® ST-200 material or DuraForm® polyamide and glass-filled laser-sintering material from 3D Systems Corporation of Valencia, Calif., the reflective coating may be aluminum, and protective coating  216  may be enamel. 
     FIGS.  3 (A)-(C) represent a technique for manufacturing a DVD, according to another embodiment of the present invention. The initial steps of this technique are similar to those for the technique of  FIG. 2 , except that, as represented in  FIG. 3(A) , plateaus  312  of cured material and corresponding valleys  314  are formed on a press-machine (e.g., polycarbonate) substrate  302 , instead of being formed on substrate  202  of  FIG. 2 . If press-machine substrate  302  is opaque to the material-curing light, then the material-curing light will be applied from above (as viewed in  FIG. 3 ), using either mask-based illumination or selective laser illumination. 
     As represented in  FIG. 3(B) , plateaus  212  of cured material are physically transferred from press-machine substrate  302  to blank substrate  202  by pressing substrate  202  onto the upper surface of press-machine substrate  302  for under suitable conditions (e.g., time, temperature, and physical pressure). 
     The resulting structure is shown in  FIG. 3(C) , where the plateaus  212  of cured material and corresponding valleys have been transferred and fused onto the lower surface of substrate  202 . The manufacture of a DVD similar to DVD  200  of  FIG. 2  can be completed by applying reflective and protective coatings similar to those applied in the technique of  FIG. 2 . 
     Note that the structure shown in  FIG. 3(C)  is identical to the structure shown in  FIG. 2(B) , albeit flipped over (i.e., rotated 180 degrees about the normal to the page). To achieve this identical structure, the locations of the pits and lands formed press-machine substrate  302  of  FIG. 3  should be a mirrored image of the pits and lands formed on substrate  202  of  FIG. 2(B) . When mask-based illumination is employed, this mirrored image can be achieved by flipping over mask  206  of  FIG. 2(A) . 
     Note that the materials used in the technique of  FIG. 3  may be, but do not have to be the same as those used in the technique of  FIG. 2 . 
     As is the case with the master discs used in the conventional DVD stamping technique, one of the dangers of using optical masks, similar to mask  206  of  FIG. 2(A) , is the risk of the masks being stolen and used to manufacture unauthorized DVDs containing the content encoded in the mask. One possible solution to this problem is to employ optical masks having one or more extra opaque portions (corresponding to features referred to herein as “false pits”) that do not correspond to pits in the completed DVD. 
     FIGS.  4 (A)-(D) represent a technique for manufacturing a DVD employing a mask having one or more opaque portions corresponding to false pits, according to one embodiment of the present invention. As represented in  FIG. 4(A) , the initial steps of this technique are similar to those for the technique of  FIG. 2 , except that mask  406  has one or more opaque, false-pit portions  410  corresponding to particular portions of mask  206  of  FIG. 2  that are transparent in mask  206 . 
     As a result, as represented in  FIG. 4(B) , after illuminating layer  204  of light-curable material through mask  406 , layer  204  has cured “true-land” regions  401  and uncured “true-pit” regions  403 , corresponding to actual lands and pits, respectively, in the completed DVD. In addition, layer  204  has an uncured false-pit region  405  corresponding to each false-pit portion  410  in mask  406 . 
     As represented in  FIG. 4(C) , prior to removing the uncured material from layer  204 , uncured false-pit region  405  of  FIG. 4(B)  is selectively illuminated using laser light  407  to cure the light-curable material in that region to convert the false-pit region into a cured true-land region  401 . 
     As represented in  FIG. 4(D) , after the uncured material is removed from layer  204 , the resulting structure is identical to the structure represented in  FIG. 2(B) . The DVD manufacturing process can then be completed as described in reference to  FIG. 2 . 
     Another possible solution to the problem of employing optical masks that accurately represent DVD content is to employ optical masks having one or more extra transparent portions (corresponding to features referred to as “false lands”) that do not correspond to lands in the completed DVD. 
     FIGS.  5 (A)-(D) represent a technique for manufacturing a DVD employing a mask having one or more transparent portions corresponding to false lands, according to one embodiment of the present invention. As represented in  FIG. 5(A) , the initial steps of this technique are similar to those for the technique of  FIG. 2 , except that mask  506  has one or more transparent, false-land portions  508  corresponding to particular portions of mask  206  of  FIG. 2  that are opaque in mask  206 . 
     As a result, as represented in  FIG. 5(B) , after illuminating layer  204  of light-curable material through mask  506 , layer  204  has cured true-land regions  501 , uncured true-pit regions  503 , and an cured false-land region  505  corresponding to each false-land portion  508  in mask  506 . 
     As represented in  FIG. 5(C) , after the uncured material is removed from layer  204 , the structure include a false land  509  for every false-land region  505  in  FIG. 5(B) . False land  509  is selectively burned off using laser light  507  to convert the false land into a true pit. 
     As represented in  FIG. 5(D) , the resulting structure is identical to that represented in  FIG. 2(B)  and  FIG. 4(D) . The DVD manufacturing process can then be completed as described in reference to  FIG. 2 . 
     The two-step illumination process (i.e., mask-based illumination followed by selective laser illumination) of either  FIG. 4  or  FIG. 5  can also be employed to create a structure similar to that shown in  FIG. 3(A)  employing techniques analogous to the machine-press technique of  FIG. 3 . 
     Other embodiments of two-step illuminations processes are possible. For example, a hybrid two-step process involving both false pits and false lands can be implemented using a mask that has both one or more extra opaque portions and one or more extra transparent portions. Furthermore, a mask having one or more extra transparent portions can be used to create false pits by failing to illuminate those extra transparent portions of the mask during the mask-based step. The resulting false pits can then be selectively cured during the selective laser illumination step. 
     In general, two-step illumination processes, such as those represented in  FIGS. 4 and 5 , can be used to create DVDs identical to those manufactured using the techniques of either  FIG. 2  or  FIG. 3  using a mask, like mask  406  of  FIG. 4  or mask  506  of  FIG. 5 , that does not, by itself, accurately represent the content of the resulting DVDs. If such a mask is stolen, then, without knowledge of the location of the false pits/lands, any unauthorized DVDs manufactured using the mask will contain inaccurate content. Depending on the number and location of the false pits/lands, the resulting DVDs may be rendered inoperative (e.g., unable to be played in a conventional DVD player), thereby effectively inhibiting unauthorized copying. 
     Two-step illumination processes also enable the manufacture of different instances of DVDs having content that differs in known ways, even when the different DVD instances are manufactured using the same optical mask, by selectively illuminating a different set of false pits/lands during the selective laser illumination step(s) for each different DVD instance. Such selective generation of (potentially unique) content for each DVD instance can be used to encode one or more of the following types of instance-specific information into each DVD:
         Forensic tracking information such as time, date, and location of manufacture and intended seller and/or owner of DVD instance;   Serial number; and   Cryptographic information such as Digital Rights Management (DRM) keys/signatures.       

     The DVD manufacturing techniques of the present invention can be employed in a variety of different contexts, including mass production in a factory setting. Another possible manufacturing context is a relatively small DVD-manufacturing apparatus such as a kiosk that enables users (e.g., customers/store employees) to manufacture individual DVD instances locally (e.g., in the presence of the user). 
       FIG. 6  shows a block diagram of a DVD manufacturing system  600 , according to one embodiment of the present invention. DVD manufacturing system  600  includes one or more distributed kiosks  602  and a centralized server  604  that is able to communicate with the remotely located kiosks via a suitable communication network  606 , which could, but does not have to, include the Internet. 
     Each kiosk  602  may contain one or more optical masks, each of which is an accurate mask, such as mask  206  of  FIG. 2 , or an inaccurate mask, such as mask  406  of  FIG. 4  or inaccurate mask  506  of  FIG. 5 . In addition, each kiosk  602  contains suitable equipment for implementing manufacturing techniques according to one or more embodiments of the present invention, such as those represented in  FIGS. 2-5 . 
       FIG. 7  shows a flow diagram of the processing implemented by DVD manufacturing system  600  of  FIG. 6  when a user uses a kiosk  602  to manufacture a single DVD instance, according to one embodiment of the present invention. The processing begins with the kiosk presenting the user with different choices of DVD content that are available (i.e., supported by that kiosk), and the kiosk receives the user&#39;s DVD content selection (step  702  of  FIG. 7 ). 
     Using cryptographic principles, a copy count is checked and incremented and, if appropriate, a fee is paid (step  704 ). 
     If the kiosk does not have an optical mask corresponding to the user&#39;s DVD content selection (step  706 ), then, using cryptographic principles, the kiosk retrieves the content for the user&#39;s selection and performs selective laser illumination to cure corresponding portions of the light-curable material (e.g., corresponding to layer  204 ) (step  708 ). Depending on the particular implementation and/or the particular user selection, the kiosk may retrieve the DVD content either from its local memory resources or from the server via the communication network. Note that the kiosk&#39;s local memory resources may include an actual DVD instance corresponding to the user&#39;s selection. Processing then continues to step  718 . 
     If the kiosk does have an optical mask corresponding to the user&#39;s DVD content selection (step  706 ), then the kiosk performs mask-based illumination to cure corresponding portions of the light-curable material (step  710 ). 
     If the mask contains an accurate representation of the final DVD content (step  712 ), then processing continues to step  718 . 
     If the mask does not contain an accurate representation of the final DVD content (step  712 ), then the mask contains one or more “false-feature” portions, where each false-feature region is either a false-pit portion corresponding to a false pit or a false-land portion corresponding to a false land. In that case, using cryptographic principles, the kiosk retrieves information about the locations of those false pits and/or lands (step  714 ). As in step  708 , depending on the particular implementation and/or the particular user selection, the kiosk may retrieve the false-pit/land information either from its local memory resources or from the server via the communication network. 
     Depending on the particular manufacturing technique being implemented, the kiosk then performs selective laser illumination either to cure false-pit regions in layer  204  (as in  FIG. 4(C) ) or to burn off false lands in layer  204  (as in  FIG. 5(C) ) (or both in a hybrid technique) (step  716 ). Processing continues to step  718 . 
     In step  718 , the kiosk performs the appropriate steps to complete the DVD manufacturing process to provide the user with a DVD instance that, depending on which subset of false pits/lands are illuminated in step  716 , may contain a unique set of DVD content. 
     Note that the present invention can also be implemented in the context of stand-alone kiosks that do not rely on a centralized server, such as server  604  of  FIG. 6 . 
     Although the present invention has been described in the context of DVDs, it can also be implemented in the context of other types of data-storage media having pits and lands, such as CDs and even media corresponding to technology not yet developed or standardized. 
     One of the advantages of the present invention over the prior art is that data-storage media manufacturing techniques of the present invention can be implemented using equipment that is less expensive than the conventional machinery used to stamp DVDs, while enabling the manufacture of DVD instances whose content may conform to certain copyright protection schemes, such as the Contents Scramble System (CSS). 
     The present invention may be implemented using circuit-based processes, including possible implementation as a single integrated circuit (such as an ASIC or an FPGA), a multi-chip module, a single card, or a multi-card circuit pack. As would be apparent to one skilled in the art, various functions of circuit elements may also be implemented as processing steps in a software program. Such software may be employed in, for example, a digital signal processor, micro-controller, or general-purpose computer. 
     The present invention can be embodied in the form of methods and apparatuses for practicing those methods. The present invention can also be embodied in the form of program code embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. The present invention can also be embodied in the form of program code, for example, whether stored in a storage medium, loaded into and/or executed by a machine, or transmitted over some transmission medium or carrier, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the invention. When implemented on a general-purpose processor, the program code segments combine with the processor to provide a unique device that operates analogously to specific logic circuits. 
     It will be further understood that various changes in the details, materials, and arrangements of the parts which have been described and illustrated in order to explain the nature of this invention may be made by those skilled in the art without departing from the scope of the invention as expressed in the following claims. 
     Although the steps in the following method claims, if any, are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those steps, those steps are not necessarily intended to be limited to being implemented in that particular sequence. 
     Reference herein to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments necessarily mutually exclusive of other embodiments. The same applies to the term “implementation.”