Abstract:
Optical storage media with limited useful life include a substrate having a data storage portion containing readable data. A reservoir associated with the substrate releasably retains a preselected chemical agent that interacts with the data storage portion to render it unreadable a preselected period of time after the chemical agent is released. Alternatively, the invention includes an optical storage medium including a substrate supporting a metallic data storage layer for storing optically readable data, a reservoir located in proximity to the data storage layer for storing a chemical agent in contact with the data storage layer on a first side of the reservoir, and a flexible metallic lamina in contact with the chemical agent on an opposite side of the reservoir. A nonconductive member is located intermediate the data storage layer and the lamina for holding apart the data storage layer and the lamina, and has at least a portion through which the lamina can be deformed and come into contact with the data storage layer to complete a voltaic circuit from the data storage layer through the chemical agent to the lamina. Opening the storage container releases the chemical agent or completes the voltaic circuit, and starts the interaction with the optical storage medium, which will become unreadable after a preselected period of time.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 09/436,538, filed Nov. 9, 1999, now abandoned by the same inventor. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to optical storage media. In particular, the present invention relates to an optical storage medium including an agent that renders the optical storage medium unreadable after a preselected period of time. 
     BACKGROUND OF THE INVENTION 
     Optical storage media are well known in the art. Optical storage media, such as audio and/or visual compact discs (CD) or digital versatile discs (DVD), permit large amounts of data or information to be stored and retrieved. Because of their capacity to store large amounts of data, optical storage media have become enormously popular in the content media industry for delivering computer software, compilations of music, movies, and other types of audio and/or visual materials to the consumer. 
     Typically,data stored in an optical storage medium remains available to the consumer without any practical limit as to the length of time over which the data may be read. Being most of the time read only memory, there are no software limitations introduced in the data to otherwise prevent or limit the availability or readability of the data. However, the absence of any limit to the availability or readability of the data is a drawback in some cases. 
     A significant factor contributing to the price charged for an optical storage medium is the useful life of the data stored thereon. Because the data remains available for the life of the particular optical storage medium, the data may be repeatedly copied by the consumer without remitting any payment to the content media distributor or royalties to the author of the work or data. As a result, significant monies may be lost due to the length of time over which the data is available. Although the risk that the data may be repeatedly copied is typically passed on to the consumer in the form of higher prices for the sale or rental of the optical storage medium, the higher prices do little to curtail copying. However, by controlling the useful life or the availability of the data, there is the potential to create a new revenue stream in repeat purchases (similar to rentals) of optical storage media. 
     Accordingly, it is desirable to provide an optical storage medium having limited useful life. In particular, it is desired to provide an optical storage medium to control the period over which the data stored in the optical storage medium becomes unreadable. 
     SUMMARY OF THE INVENTION 
     In a preferred embodiment, the invention comprises an optical storage medium comprising a substrate supporting a data storage layer for storing optically readable data. A reservoir is attached to the substrate for storing a chemical agent. The reservoir is rupturable to release the chemical agent when subjected to an applied force. The reservoir is located in proximity to the data storage layer to permit the chemical agent released from the reservoir upon rupture to contact the data storage layer. 
     In a narrower aspect of the invention, the invention comprises an optical storage medium as described above, and a substantially airtight container having an interior in which the substrate and attached reservoir are housed. The interior of the container is under a vacuum. The container includes a lid having an opening sealed by a frangible seal for admitting air under atmospheric pressure into the interior when the frangible seal is broken. The atmospheric pressure exerts a force on the reservoir sufficient to rupture the reservoir and release the chemical agent. 
     In a different aspect of the invention, the invention comprises an optical storage medium including a substrate supporting a metallic data storage layer for storing optically readable data, a reservoir located in proximity to the data storage layer for storing a chemical agent in contact with the data storage layer on a first side of the reservoir, and a flexible metallic lamina in contact with the chemical agent on an opposite side of the reservoir. The lamina is more electronegative than the data storage layer. A nonconductive member is located intermediate the data storage layer and the lamina for holding apart the data storage layer and the lamina. The nonconductive member has at least a portion through which the lamina can be deformed and come into contact with the data storage layer to complete a voltaic circuit from the data storage layer through the chemical agent to the lamina. As a result, the material of the data storage layer will degrade over time due to voltaic action. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     For purposes of illustrating the invention, there is shown in the drawings forms of the invention which are presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown. 
     FIG. 1 is a perspective view of an optical storage medium of the present invention removably stored in a case. 
     FIG. 2 is a perspective view of the optical storage medium shown in FIG. 1, removed from the case. 
     FIG. 3 is a detailed section view of a portion of the optical storage medium shown in FIG. 2, taken along line  3 — 3 . 
     FIG. 4 is an enlarged cross sectional view of the optical storage medium and case shown in FIG. 1, taken along line  4 — 4 . 
     FIG. 5 is a perspective view of a second embodiment of an optical storage medium of the present invention. 
     FIG. 6 is a partially cut away perspective view of a third embodiment of an optical storage medium of the present invention. 
     FIG. 7 is a view of a cross-section of the optical storage medium shown in FIG.  6 . 
     FIG. 8 is an enlarged cross sectional view of the optical storage medium shown in FIG. 6, taken along line  8 — 8 . 
     FIG. 9 is an isometric view of a fourth embodiment of an optical storage medium of the present invention in an unopened vacuum sealed case. 
     FIG. 10 is a partial sectional view, on an enlarged scale, of a portion of the edge of the case illustrated in FIG.  9 . 
     FIG. 11 is an exploded view of the optical storage medium stored in the unopened vacuum sealed case shown in FIG.  9 . 
     FIG. 12 is an enlarged cross sectional view of the optical storage medium stored in the unopened vacuum sealed case shown in FIG. 9, take along the line  12 — 12  in FIG.  9 . 
     FIG. 13 is an enlarged cross sectional view of a portion of the optical storage medium as shown in FIG. 12, the case having been unsealed and subjected t o atmospheric pressure prior to opening. 
     FIG. 14 is an enlarged cross sectional view, partially broken away, of a fifth embodiment of an optical storage medium of the present invention, shown apart from an unopened vacuum sealed case, but shown as it would be in the vacuum sealed case. 
     FIG. 15 is an enlarged cross sectional view, partially broken away, of the embodiment of an optical storage medium shown in FIG. 14, also shown apart from an unopened vacuum sealed case, but shown as it would be after the vacuum sealed case has been opened. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings, where like numerals identify like elements, there is shown an embodiment of an optical storage medium  10  of the present invention. The optical storage medium  10  is a storage device in which data or other types of information may be stored and read, such as an audio and/or video compact disc (CD), a digital versatile disc (DVD), and the like. The optical storage medium  10  described herein is preferably a CD or DVD). 
     FIG. 1 shows the optical storage medium  10  in an environment presently known in the art, namely, removably stored within a case or storage container  12 . The case  12  includes a base  16  having a storage housing  18  that is shaped and dimensioned to receive the optical storage medium  10 . A recess  20  in communication with the storage housing  18  provides a finger or thumb receiving portion of the base  16  so that the optical storage medium  10  may be grasped for easy removal. The base  16  is pivotably joined to a lid  14  by a living hinge. The lid  14  rotates about the hinge to enclose the optical storage medium  10  within the case  12 . The case  12  shown in FIG. 1 is merely exemplary of the type of CD or DVD cases presently known in the art and is not critical to the invention. Therefore, it is contemplated that the optical storage medium  10  of the present invention may be utilized and sold independent of the case  12 . 
     Turning now to FIG. 2, the optical storage medium  10  is shown in isolation, after having been removed from the case  12 , for example. The optical storage medium  10  is circular, having an edge  22  that defines an outer periphery. The optical storage medium  10  includes a rigid substrate  26 , as shown in FIGS. 2 and 3. The substrate  26  includes a central aperture or opening  24  and is made of transparent material, such as glass or plastic. Preferably, the substrate  26  is made of transparent polycarbonate plastic having a first or top surface  25  and a second or bottom surface  27 . The top and bottom surfaces  25  and  27  are spaced apart from each other by the thickness of the substrate  26 , as best seen in FIG.  3 . 
     The substrate  26  includes a data storage portion associated therewith on one surface, usually the bottom. The data storage portion includes readable data or information represented by pits or bumps formed within one or more radial tracks of the substrate  26  that are scanned by a laser to read the data. The data storage portion has a leading edge that is radially outward of the aperture  24 , but inward of the edge  22 . 
     The data storage portion has been described as being formed within the substrate  26 . However, other embodiments are contemplated. For example, it is contemplated that the data storage portion may be a separate layer of recordable and/or readable material that is supported by the substrate  26 . In this way, the substrate  26  will provide support for the recording layer that provides the primary source of the readable data stored on the optical storage medium  10 . Other suitable structures may be used. 
     As best seen in FIG. 3, a relatively thin reflective layer  28  overlies the substrate  26 . The reflective layer  28  provides a necessary reflective surface for the output of a laser so that the data stored on the optical storage medium  10  may be read. The reflective layer  28  is disposed on the top  25  surface of the substrate  26 , having an inner edge  30  positioned radially outward of the aperture  24  and an outer edge  31  that is radially inward of edge  22 . Preferably, the reflective layer  28  is a thin sheet of reflective metallic material, such as aluminum. 
     A reservoir or cavity  34  is associated with the substrate  26 , as shown in FIG.  2 . The reservoir  34  is provided to releasably retain a preselected chemical agent that will render the optical storage medium  10  unreadable after a preselected period of time, as discussed in more detail below. The reservoir  34  is in communication with the reflective layer  28  or data storage portion of the substrate  26  and as shown in FIG. 2, is located intermediate aperture  24  and edge  30 . The reservoir  34  may be formed by a recess or well formed within the substrate  26 . Preferably, the reservoir  34  is a capsule that sits within the recess or on the top surface  25  of the substrate  26 . The capsule has a relatively thin shell and releasably retains the preselected chemical agent. It should be understood that the location of the reservoir  34  shown in FIG. 2 is merely exemplary, and may be located anywhere on or within the optical storage medium  10  to releasably retain the chemical agent. 
     The chemical agent interacts with the optical storage medium  10  to render it unreadable after a preselected period of time by disrupting the ability of the laser to read the data stored in substrate  26 . The chemical agent reacts with or dissolves the metallic material of reflective layer  28  so that the laser cannot read select portions of the data. Those of ordinary skill in the art will appreciate that aluminum has relatively low reactivity in that, due to its characteristics, it is instantly protected by a cover of oxide at any time. Despite this low reactivity, aluminum is known to react to certain chemicals under certain conditions and circumstances when the aluminum oxide is dissolved by a chemical agent that can, because of the dissolution of the oxide, react with the aluminum. For example, aluminum is sensitive to bases such as NaOH or KOH, acids such as HCl, H 2 SO 4 , NHO 3 , and several metallic salts, such as CuSO 4 , as a few examples. 
     The properties of these chemical agents may be advantageously used to facilitate and control the rate of dissolution or corrosion of the aluminum. For example, the corrosion of an aluminum reflective layer  28  may be steady and uniform with certain agents, such as NaOH or HCl, or may become pitted upon exposure to agents such as CuSO 4 . In particular, a solution of NaOH with a concentration of 0.06 g/l and a pH of  11  generates a rate of dissolution of the aluminum reflective layer  28  ranging anywhere between approximately 0.3 micron per hour and approximately 1.0 micron per hour. Inhibitors like soda silicate can reduce or delay the action of NaOH, thereby reducing the rate of dissolution of the aluminum of the reflective layer  28 , but extending the period over which the data will become unreadable. 
     As an additional example, a solution of HCl with a concentration of 5.0% produces a rate of dissolution of the aluminum of the reflective layer  28  ranging anywhere between approximately 1.0 microns per 24 hours and approximately 3.0 microns per 24 hours. Inhibitors can reduce or delay the effects of the HCI even further, thereby reducing the rate of dissolution, but extending the period over which the data will be readable. 
     As yet another example, a solution of CuSO 4  with a concentration of 1.0% produces a rate of dissolution of the aluminum of the reflective layer  28  ranging anywhere between approximately 1.0 microns per 24 hours to approximately 2.0 microns per 24 hours. 
     Those of ordinary skill will appreciate that the dissolution of the aluminum, and the period after which the optical storage medium  10  will become unreadable, will depend on many factors. Those factors include the thickness of the aluminum and the characteristics of the chemical agent. For example, the relative thickness of the aluminum may be selectably adjusted to control the time needed by the chemical agent to at least partially dissolve the aluminum sufficiently to reach the polycarbonate layer or substrate  26  so as to destroy the availability of the data. The chemical properties of the chemical agent may also be selectably adjusted to control the period over which the data of a particular optical storage medium  10  will become unreadable. Another factor is the type of metallic material used for the reflective layer  28 . Although aluminum is presently preferred, other types of metallic material having properties similar to aluminum may be used with the optical storage medium  10 . Therefore, the type of metallic material used for the reflective layer  28  should be taken into account to determine the type, concentration, and amount of the chemical agent needed. 
     A supply path  36  is provided on one side of the reflective layer  28  to control the distribution or flow of the chemical agent. As shown in FIG. 2, the supply path  36  is in fluid communication with the reservoir  34  and is defined by borders or guides  38  that extends around the reservoir  34  and have an end that terminates radially inward of the edge  31  of the reflective layer  28 . The borders  38  direct the flow of the chemical agent to the select portions of the reflective layer  28  when the chemical agent is released. Preferably, each border  38  is a thin bead of material, such as glue, on the top surface of the reflective layer  28  so that they will not interfere with the reading of the data. 
     Preferably, as shown in FIGS. 2 and 3, a protective layer of material  32  is provided to prevent the spread of the chemical agent external to the optical storage medium  10  when released. The protective layer  32  is disposed over the reflective layer  28 , and has an outer edge secured to the edge  22  of the substrate  26 . The protective layer  32  may be made of plastic or other suitable material, such as an acrylic. The protective layer  32  is vacuum sealed to the substrate  26  to encapsulate the reservoir  34  and chemical agent in an airtight and liquid tight environment. In this way, the protective layer  32  enables the optical storage medium  10  to have the capacity to store in airtight conditions gases such as hydrogen that are generated by the chemical reaction between the chemical agent and the reflective layer  28 . Once the protective layer  32  is sealed to the substrate  26 , the chemical agent in the reservoir  34  will be stable until released. 
     It is contemplated that the protective layer  32  described above may be transparent or opaque. It is also contemplated that the exposed surface of the protective layer  32  may have applied thereon graphic or alphanumeric indica, advertising material, labels, and the like. 
     The storage medium is held in place in case  12  by a retainer which also functions as a chemical reaction starting device  40  to selectably control the release of the chemical agent when the retainer is removed to permit removal of the storage medium. As shown in FIG. 1, the starting device  40  is removably joined or secured to the optical storage medium  10  to prevent the optical storage medium  10  from being used until it is removed and the chemical agent released. As shown in FIG. 1, the starting device includes a pair of rigid members or arms, a first  42  and a second  44 , that extend radially outward from a central portion or bridge  45 . Each rigid member  42  or  44  forms a handle so that the user may operate or remove the starting device  40 , as discussed below. 
     As best seen in FIG. 4, the starting device  40  is joined to the case by a screw  46 . The screw  46  has an outer surface that is threaded and a hollow center. The center of the screw  46  includes an annular flange  49  that extends radially inwardly of the outer surface. The flange  49  has an inner edge that defines a hole that provides access to the hollow center of the screw  46 . The flange  49  is provided to engage a locking collar  47  that extends downwardly from the bridge  45 . The locking collar  47  includes a cylindrical body having an outer diameter that is slightly smaller than the hole formed by the flange  49 . An annular flange or detent mechanism  51  extends radially outwardly from the distal end of the body of the collar  47 , and is provided to snap-fit into the hollow portion of the screw  46 . The bottom edge of the flange  51  is beveled to facilitate insertion of the locking collar  47  into the screw  46 . 
     As shown in FIG. 4, the screw  46  terminates in a frangible portion  52  that is releasably joined to a hub  53 . The hub  53  projects upwardly from the base  16  and is preferably cylindrical, having an outer surface with a diameter that is the same or slightly shorter than the central aperture  24  of the optical storage medium  10 . The upper portion of the hub  53  is joined to the bottom portion of the screw  46  at a portion of reduced wall thickness to define the frangible portion  52 . The frangible portion  52  is provided so that the starting device  40  and screw  46  may be removed from the optical storage medium  10 . 
     The bridge  45  supports a heel or projection member  50 . The heel  50  projects downwardly from the rigid members  42  and  44  and includes a lower surface that sits over or lightly contacts the portion of the protective layer  32  that is positioned over the reservoir  34 . Preferably, the heel  50  extends radially and continuously around the screw  46  so that the lower portion will be in constant contact with the reservoir  34  no matter how the optical storage medium  10  is placed in the case  10 . The heel  50  includes a drive  57  and a finger  59 . The drive  57  extends around the inner portion of the heel  50  and engages the threads of the screw  46 . The finger  59  extends downwardly at an angle relative to the rigid members  42  and  44 , terminating at an end that lightly contacts the surface of the protective layer  32 . The finger  59  conceals the screw  46  and prevents objects from getting underneath the heel  50 . 
     To assemble the case  12  as shown in FIGS. 1 and 4, the optical storage medium  10  is seated within the housing  18  of the case  12 , such that the screw  46  projects though the central aperture  24 . Once the storage medium  10  is positioned within the housing  18 , the starting device  40  is joined. The starting device  40  is joined by inserting the locking collar  47  into the hole of the screw  46 . The annular flange  51  of the locking collar  47  will engage the flange of  49  the screw  46  until its snaps in place such that the upper surface of the flange  51  of the locking collar  47  engages the lower surface of the flange  49  of the screw  46 , as illustrated in FIG.  4 . In this way, the starting device  46  cannot be easily removed from the screw  46  by simply pulling it upwardly. As a result, the starting device  40  prevents the optical storage medium  10  from being used until the starting device  40  is removed. Once the starting device  40  is in place, a portion of the heel  50  will be positioned over the reservoir  34 , as shown. 
     In operation, to use the optical storage medium  10 , the starting device  40  must be removed. To remove the starting device  40 , the rigid members  42  are rotated about the screw  46 . As the rigid members  42  and  44  are rotated, the drive  57  will follow the grooves of the thread, moving generally downwardly toward the base  16 . As the drive  57  moves downwardly the heel  50  will exert a downwardly directed force or pressure on the reservoir  34  or capsule. The pressure exerted on the reservoir  34  facilitates or causes the release of the chemical agent, which then flows onto the preselected portion of the reflective layer  28  through the supply path  36 , thereby starting the interaction between the chemical agent and optical storage medium  10 . After a preselected period of time, the chemical agent will dissolve the reflective layer  28  to render the optical storage medium  10  unreadable, after which it has to be discarded. The dissolution of the reflective layer  28  can be observed by the consumer, indicating that the optical storage medium is unreadable. 
     As the rigid members  42  and  44  are further rotated, pressure will be created about the frangible portion  52  such that the screw  46  breaks off from the hub  53 . Once the screw  46  breaks off, both the screw  46  and rigid members  42  and  44  are removed and the optical storage medium  10  may be removed from the housing  18 . The hub  53  can then be used in conventional fashion for removably securing the optical storage medium  10  in the case  12 . 
     In an alternative embodiment, the rigid members  42  and  44  may be joined by screw  46  disposed within a hole or channel formed within the hub  53  of the case  12 . When the screw  46  is tightened to a preselected level of tension, the screw  46  will break apart so that the rigid members  42  and  44  may be removed from the case  12 . Tightening screw  46  will also cause the head of the screw  46  to move downwardly toward the base  18 , taking with it the drive  57  of the heel  50 . As the drive  57  moves downwardly toward the base  18 , the heel  50  will exert sufficient pressure on the reservoir  34  or capsule to release the chemical agent. 
     The operation of the release of the chemical agent has been described by the use of the starting device  40  as shown in FIGS. 1 and 4. However other devices may be used. For example, the starting device  40  may be replaced by other types of mechanical devices or mechanisms, such as pressure release couplings, push-button devices, and other mechanical means. 
     FIG. 5 shows an alternative embodiment of an optical storage medium  54 . The optical storage medium  54  shown in FIG. 5 is similar to the optical storage medium  10 , described with reference to FIGS. 1-4 above. The optical storage medium  54  includes a substrate  26 , a reflective layer  28 , and a protective layer  32 . A reservoir or capsule  56  is formed within the substrate  26 , as described above, and is in communication with a supply path  58 . The reservoir  56  is provided to releasably retain a preselected chemical agent in much the same way reservoir  34  releasably retains the chemical agent described with reference to the optical storage medium  10  of FIGS. 1-4. The chemical agent is provided to render the optical storage medium  54  unreadable after a preselected period of time. 
     As shown in FIG. 5, the reflective layer  28  includes small segments or pieces of a metal or metallic material  60  (two shown), such as copper, iron or any suitable alloy. Preferably, the metal segments  60  are added to the surface of the reflective layer  28  that faces the protective layer  32 . The segments  60  have an electrochemical potential different from the metallic material of the reflective layer  28 . The chemical agent retained in the reservoir  56  to interact with the optical storage medium  54  is a solution having preselected electric conductivity with a pre-set level of concentration, such as NaCl. When the chemical agent is released, the chemical agent will flow onto select areas of the reflective layer  28  through supply path  58  toward the segments  60 . Once the chemical agent contacts the two metals (i.e., the segment  60  and reflective layer  28 ), the chemical agent facilitates an electrochemical reaction which dissolves selected portions of the reflective layer  28 . The dissolution of the reflective layer  28  will form pits in the area of contact with the segments  60 , which, in turn, disrupts the ability of the laser to read the data of the substrate  26  after a preselected period of time. As a result, the optical storage medium  54  or the data stored in the data storage portion  30  will become unreadable, after which it must be discarded. The dissolution of the reflective layer  28  should be observable to the user. 
     It is contemplated that the type and thickness of the metal segments  60  and the type of chemical agent may be selectably adjusted to control the period over which the select portions of the reflective layer  28  will be dissolved. It is also contemplated that one or a series of segments  60  may be used, in keeping with the scope of the present invention. 
     FIGS. 6-8 show an alternative embodiment of an optical storage medium  62 , which is in the form similar to a double sided DVD. As shown in FIGS. 6 and 7, the optical storage medium  62  includes a first substrate  64  and a second substrate  68 . Both the first substrate  64  and second substrate  68  have a central hole or opening  66  and are made of transparent material, such as polycarbonate plastic, glass, ceramic, or the like. Each substrate  64  and  68  include a data storage portion for storing readable data (not shown) or include a separate layer of recording material to store the data. 
     A reflective layer  72  is provided intermediate substrates  64  and  68 . The reflective layer  72  provides a reflective surface so that data stored on each exposed side of substrates  64  and  68  may be read. Preferably, the data is in the form of pits or bumps formed in radial tracks of the substrates  64  and  68  may be read by a laser. To read the data, the laser passes through the corresponding substrate  64  or  68  and is reflected from the reflective layer  72 . Preferably, the reflective layer  72  is made of metallic material, such one or a pair of thin aluminum sheets that are bonded together, having an edge  76  that is radially inward of the hole  66 , thereby creating a gap  73 . 
     As shown in FIG. 6, a reservoir  78  is formed on one side of the optical storage medium  62 . The reservoir  78  is provided to releasably retain a preselected chemical agent that is in communication with the data storage portion of the substrates  64  and  68 . The chemical agent will render select portions of the data storage portion or reflective layer  72  unreadable after a preselected period of time when released. Preferably, the chemical agent is in the form of a capsule similar to that described with reference to reservoir  34  of optical storage medium  10 , described with reference to FIGS. 1-4. 
     As best seen in FIG. 8, the reservoir  78  is in communication with a hole  80  that extends downwardly from the top of substrate  68 . The hole  80  operates as a supply path and is in communication with the gap  73  that receives the chemical agent from the reservoir  78 . The gap  73  is used as a means for directing the flow of the chemical agent onto the reflective layer  72  or data storage portion. 
     Preferably, a protective layer  79  will overlie the side of the optical storage medium  62  having the reservoir  78 . The protective layer  79  is provided to encapsulate the reservoir  78  and its chemical agent in an airtight and liquid tight environment, in much the same way as the protective layer  32  described with reference to optical storage medium  10  creates an airtight and liquid tight environment, illustrated in FIGS. 1-4. As such, the release of the chemical agent will not flow outside of the optical storage medium  62 . 
     The release of the chemical agent of reservoir  78  is selectably caused or controlled by a chemical reaction starting device (not shown) that operates in much the same way as the chemical reaction starting device  40  illustrated in FIGS. 1 and 4, and described above in reference to optical storage medium  10 . The starting device is removably secured to the optical storage medium  62 . The starting device prevents the optical storage medium  62  from being used until it is removed and the chemical agent is released. 
     The optical storage medium  62  is placed in a case, such as the type illustrated in FIGS. 1 and 4 described above. The starting device will prevent the optical storage medium  62  from being used until the starting device is removed. To use the optical storage medium  62 , the rigid members of the starting device are rotated about the screw such that the heel will exert pressure on the reservoir  78 . The pressure created on the reservoir  78  will cause the release of the chemical agent. When released, the chemical agent from the reservoir  78  will flow through the hole and enter the gap  73 . Upon entering the gap  73 , the chemical agent will contact preselected areas of the reflective layer  74  which will start the interaction with the optical storage medium  62 . The chemical agent will then dissolve the reflective layer  72  after a preselected period of time. The dissolution of the reflective layer  72  will disrupt the ability of the data of each substrate  64  and  68  to be read by a laser. As a result, the optical storage medium  62  will become unreadable. 
     The operation of the optical storage medium  62  has been described using a preselected chemical agent stored in reservoir  78 . However, it is contemplated that metal segments (not shown) may be provided on select portions of the reflective layer  72 , having an electrochemical potential different than the metallic material used for the reflective layer  72 . When the chemical agent is released an electrochemical reaction occurs between the two metals (i.e., the metal segment and the metallic material of the reflective layer  74 ) to form pits in the reflective layer  72 , in much the same way as segments  60  dissolve reflective layer  28  of optical storage medium  54 , described and illustrated in reference to FIG.  5 . 
     The optical storage media  10 ,  54  and  62  of the present invention have been described and illustrated relative to a case  12 , for purposes of discussion only. The case  12  is not critical to the invention. Indeed, it is contemplated that the embodiments of the optical storage media of the present invention may be sold and utilized independent of or without the case  12 . The starting device may include or be removably coupled to a support element that would support a screw or similar type of member removably joined to the hub. In this way, the starting device would still prevent the optical storage medium from being used until the chemical agent is released. However, the optical storage media (with the starting device releasably attached thereto) may be offered for sale and sold independent of the case  12 . This would help reduce costs associated with the sale of the optical storage media, which is particularly useful if the optical storage media are sold as one-time purchase items. Other embodiments of the starting device are contemplated which can be releasably secured to the optical storage media without a case. 
     FIGS. 9-13 show an alternative embodiment of the invention, in which the chemical agent is released not by mechanical action but by atmospheric pressure. 
     FIG. 9 illustrates a case or storage container  100  which holds an optical storage medium and a quantity of chemical agent in a reservoir. The case  100  has a lid  102  and a body  104 , which is in the form of a shallow dish. Case  100  is illustrated as circular in shape, but may be square or rectangular, or any other shape, without departing from the scope of the invention. Both lid  102  and body  104  are made of an air-impermeable material, such as plastic. The lid  102  has an opening  106  in the center, shown in dashed lines in FIG. 9, sealed by a frangible seal  108 . Seal  108  is preferably a thin metallic foil, and is also air-impermeable. As best seen in FIG. 10, body  104  has a circumferential side wall  110  which extends upward from a bottom  112 . Side wall  110  has a groove  114  around the inner surface thereof which receives a complementary tongue  116  in lid  102 . The tongue  116  and groove  114  are sized and shaped to form an air-tight seal between lid  102  and body  104 . 
     As best seen in the exploded view of FIG. 11, case  100  contains a storage medium  118 , such as for example a CD. Conventionally, CD  118  comprises a transparent substrate  120  and a thin reflective layer  122  on which are stored data to be read from the CD. As already noted, the reflective layer  122  is a thin sheet of reflective metallic material, such as aluminum. Usually, a layer  124  of barrier material is applied to the reflective layer  122 , and covers the entire reflective layer  122 . The barrier layer  124  is usually printed with indicia to identify the CD and its contents, and also serves to protect the reflective layer from exposure to external elements. In the present invention, a CD to be rendered unreadable after a preselected time is provided with a barrier layer  124  over only about half of the reflective layer  122 , leaving the remaining portion of reflective layer  122  exposed. 
     A thin carrier layer  126 , which carries a reservoir  128  of chemical agent, is placed over and adhered to the barrier layer  124  and reflective layer  122 . The carrier layer is orientated so that the reservoir  128  lies over about the center of the barrier layer. If desired, body  104  of case  100  is provided with a recess  130  to receive reservoir  128  without subjecting reservoir  128  to mechanical pressure or deformation. At least one, and preferably two, beads  132  of adhesive are applied to the carrier layer  126  to attach it to CD  118 . The beads  132  of adhesive also serve to define a channel  134  between them through which chemical agent released from reservoir  128  can flow onto reflective layer  122 . 
     With this embodiment of the invention, the various parts are fabricated and assembled in a vacuum, such as inside a vacuum chamber. That is, the reservoir  128  is filled with chemical agent and the carrier layer  126  glued to CD  118  within the vacuum chamber. Then, CD  118 , along with carrier layer  126  and reservoir  128 , are placed into body  104  of case  100 . Finally, lid  102  is snapped into place so that tongue  116  on lid  102  enters groove  114  on side wall  110  of body  104  to form an airtight seal. Since the CD  118  and attached carrier layer  126  are placed into case  100  in a vacuum environment, and since lid  102  is attached to body  104  in the same environment, the interior of case  100  will be under vacuum. The difference in pressure between the outside of case  100  (atmospheric pressure) and the inside of case  100  (vacuum) serves to hold lid firmly in place and prevent case  100  from being inadvertently opened. 
     FIG. 12 is a cross-sectional view of an assembled case  100  containing a CD  118  and attached carrier layer  126  and reservoir  128 , showing the interrelationship of the parts. In the condition illustrated in FIG. 12, the reservoir  128  is stable, and chemical agent can be retained in the reservoir indefinitely. In that condition, the case  100  containing CD  118  can be shipped, stacked on shelves for storage, and otherwise handled without deleterious effect. 
     Once it is desired to use CD  118 , however, case  100  must be opened to remove the CD. In order to open case  100 , frangible seal  108  is broken, as indicated by the arrow in FIG.  13 . Once seal  108  is broken, air at atmospheric pressure is admitted to the interior of case  100 . This subjects reservoir  128  to atmospheric pressure, rupturing it and forcing the chemical agent contained in reservoir  128  to flow out of the reservoir and onto the surface of CD  118 . Channel  134 , defined by beads  132  of adhesive, constrains the chemical agent to flow circumferentially and thus onto the portion of reflective layer  122  unprotected by barrier layer  124 . Once the chemical agent reaches the unprotected portion of reflective layer  122 , it begins to interact with the reflective layer, as in the previously described embodiments, eventually rendering the reflective layer unreadable. 
     Breaking seal  108  and admitting air at atmospheric pressure into case  100  also makes it easy to remove lid  102  to permit removal of CD  118  from the case. 
     Turning now to FIGS. 14 and 15, there is shown yet another embodiment of the present invention. As in the previously described embodiments, the embodiment shown in FIGS. 14 and 15 comprises an optical storage medium, which may be any optical storage medium such as, for example, a DVD or CD. In the illustrated embodiment, the optical storage medium is in the form of a CD  118 , which includes a substrate  120  having a center opening  106 , a reflective layer  122 , and a protective layer  124  overlying reflective layer  122 . However, in this embodiment, protective layer  124  is provided with at least two openings  136  and  138  through it, to expose portions of reflective layer  122 . In the region where protective layer  124  is provided with openings  126  and  138 , protective layer is overlain with a thin metallic lamina, such as a metallic foil,  140 . Lamina  140  is thin enough to be flexible, for the reasons given in more detail below. In addition, while a metallic foil is illustrated, a thin membrane of flexible polymer or other non-metal, coated with metal on the surface facing reflective layer  122 , can be used without departing from the invention. In either case, the metal comprising lamina  140  is one that is electrochemically dissimilar to, and more electronegative than, the metal which comprises reflective layer  122 . A typical, but not the only, suitable metal for lamina  140  is copper. Gold can also be used, for example, but is obviously more expensive than copper. 
     One of the openings, such as opening  138  in the illustrated embodiment, is filled with a chemical agent  142  having a preselected conductivity. An example of a suitable agent is a solution of sodium chloride (NaCl). The other of the openings, such as opening  136  in the illustrated embodiment, is not filled with a chemical agent. Rather, the opening is under vacuum, which can be achieved by assembling the optical storage medium in a vacuum environment, as already described in connection with the embodiment of FIGS. 9-13. Once assembled, the optical storage medium is placed inside a vacuum sealed case (not shown in FIG. l 4 - 15 ), in the same manner as the embodiment of FIGS. 9-13. 
     After assembly and placement in the vacuum sealed case, the optical storage medium according to this embodiment will appear as illustrated in FIG.  14 . As can be seen from that figure, lamina  140  is in contact with chemical agent  142 , which fills opening  138 , but is spaced apart from reflective layer  122  by protective layer  124  and is, therefore, not in contact with reflective layer  122 . 
     Once the vacuum sealed case is opened, the optical storage medium is subjected to atmospheric pressure. The pressure of the atmosphere now surrounding the optical storage medium deforms lamina  140  inward into opening  136 , which is under vacuum, and causes lamina  140  to contact reflective layer  122 . This state is illustrated in FIG. 15, which shows the deformation of lamina  140  such that it contacts reflective layer  122 . That action completes an electrical circuit from lamina  140  to reflective layer and then back to lamina  140  through the sodium chloride solution  142  in opening  138 . Because reflective layer  122 , typically aluminum, is less electronegative than the lamina  140 , typically copper, an electrolytic current flows through the circuit. Electrons begin to flow from the aluminum to the copper and, as a consequence, the aluminum begins to break down because of voltaic action. When the aluminum has broken down to a sufficient degree, the reflective layer will no longer be readable, and the optical storage medium will have reached the end of its useful life. 
     The optical storage media of the present invention described above provides several advantages in the content media market. For example, the optical storage media of the present invention may be used as promotional material in point of sale purchases. When used as promotional material, the data stored in the optical storage media of the present invention may be used to offer on a trial basis software, music, movies, or other types of audio or visual data over a preselected period of time, such as a number of hours or days. At the expiration of the period of time, the optical storage media will have to be discarded and the consumer will have to purchase the data on a more permanent storage medium. In addition, the optical storage media may be used by hotels to offer movies, either free or at a price, that must be used within a specific period of time, such as in a day or in a couple of hours, after which it must be discarded. 
     As another example, the optical storage media of the present invention may be used in the movie rental industry. Often, movies in today&#39;s market are available to consumers as rental items in which the particular storage medium, such as a video cassette containing the movie, is rented for a fee. In exchange for paying the rental fee, the consumer is permitted to use the storage medium over a set period of time, such as three days, after which it has to be returned. At the end of three days, the video cassette is returned (if at all) and must be checked to ensure that it is rewound so that it may be rented again. However, by using the optical storage media of the present invention (such as an audio and/or visual DVD) as a rental item, the optical storage medium may be offered as a one-time purchase. As a one time purchase, the optical storage medium may be used for a preselected period of time, such as a couple of days, as desired. After the preselected period of time has expired, the optical storage media is discarded. In comparison to video cassettes, the content media distributor does not have to worry about the optical storage media being returned (if at all) and/or rewound. Rather, the content media distributor will simply have to maintain a supply of optical storage media to be purchased by the consumer. Thus, the costs associated with rental items such as movies may be reduced. 
     Furthermore, by utilizing optical storage media of the present invention, the content media distributor can have more control over the extent to which copies of the data are made. By limiting the availability of the data, the content media distributor may reduce the extent to which consumers will have the opportunity to make multiple copies of the data to avoid paying the cost to purchase the optical storage media. By reducing the risk of multiple copies, there is the potential to increase in the amount of optical storage media that is purchased. As a result, the increased purchases have the potential to generate revenue to the content media distributor or the author or inventor of the work or data. 
     The present invention has been described in reference to an optical storage medium such as the type shown in FIGS. 2,  5 , and  6 . However, it is contemplated that the optical storage medium can have any shape or size, such that the cylindrically shape of the optical storage medium  10  shown in FIGS. 1-8 is only exemplary. It is also contemplated that the optical storage medium may be replaced by other types of audio, visual, or computer software data storage devices on which data or information may be selectably stored and read. Furthermore, the application of incorporating a preselected chemical agent to render the storage device unreadable over a pre-selected period of time may be incorporated into other types of data storage devices known in the art. 
     Persons skilled in the art will recognize that there may be different devices, mechanisms, and methods of operation which are within the spirit and scope of the invention as defined in the claims. Also, it should be understood that the drawings, while useful in illustrating the invention, are not intended to be necessarily to scale. The dimensions and relative sizes and locations of the various parts shown can be varied, depending upon the particular optical storage media being used, without departing from the scope of the invention. To the extent that the drawings imply dimensions and relative size positions, the drawings should be regarding as illustrative only and not limiting the invention to particular dimensions, sizes, position, and location of parts. 
     Finally, the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.