Abstract:
An optical data storage medium includes a first substrate, the first substrate including a plurality of first data structures; a second substrate positioned above the first substrate, the second substrate including a plurality of second data structures; a reflective layer positioned on the second substrate to cover the second data structures; and a masking layer interposed between the reflective layer and the first substrate to cover the first data structures, the masking layer having a varying reflectivity to thereby render the second data structures unreadable.

Description:
Background of Invention  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an optical data storage medium, and more particularly, to an optical data storage medium of limiting play times.  
           [0003]    2. Description of the Prior Art  
           [0004]    While a typical compact disc (CD) or a typical compact disc-read only memory (CD-ROM) available at the present has a recording capacity of 640M bytes, a digital versatile disc (DVD) with a high recording capacity of 4.7 Gbytes is also available with the recent increase in the density. There has also been proposed a dual-layer DVD having its recording surface double-layered to obtain a higher recording capacity of 8.5 Gbytes.  
           [0005]    Please refer to FIG. 1 of a cross-sectional diagram of a DVD  10  according to the prior art. The DVD  10  is a single-layer DVD, such as a DVD- 5  disc, having a single readable information layer. As shown in FIG. 1, the DVD  10  includes a first substrate  12 , a reflective layer  14  coated on a plurality of data structures  12   a  on the first substrate  12 , and a bonding layer  16  formed on the reflective layer  14  for connecting the first substrate  12  to a second substrate  18 . Normally, the first substrate  12  and the second substrate  18  are made of polycarbonate, and the reflective layer  14  is a metallic layer. The data structures  14   a  are readable by a laser beam  20  of a predetermined focusing depth during a play process. The laser beam  20  is emitted from a picked head (not shown) installed under the first substrate  12  and is penetrating through the first substrate  12  and the data structures  12   a . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  20  from the reflective layer  14  for identifying the data structures  12   a.    
           [0006]    Please refer to FIG. 2 of a cross-sectional diagram of a DVD  30  according to the prior art. The DVD  30  is a dual-layer DVD, such as a DVD- 9  disc, having two readable information layers. As shown in FIG. 2, the DVD  30  includes a first substrate  32 , a semi-reflective layer  34  coated on the first substrate  32 , a reflective layer  38  coated on a plurality of data structures  32   a  on the first substrate  32 , a reflective layer  38  coated on a plurality of data structures  40   a  on a second substrate  40 , and a bonding layer  36  interposed between the semi-reflective layer  34  and the reflective layer  38  for bonding the first substrate  32  and the second substrate  40  together. Normally, the first substrate  32  and the second substrate  40  are made of polycarbonate. The semi-reflective layer  34  is a metallic layer, such as a gold layer, and the reflective layer  38  is also a metallic layer, such as an aluminum layer.  
           [0007]    For reading lower data of the DVD  30 , such as the data structures  32   a , a laser beam  42  of a predetermined focusing depth is emitted from a picked head (not shown) installed under the first substrate  32  and is penetrating through the first substrate  32  and the data structures  32   a . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  42  from the semi-reflective layer  34  for identifying the data structures  32   a . Similarly, for reading upper data of the DVD  30 , such as the data structures  40   a , a laser beam  44  of a predetermined focusing depth is emitted from the picked head installed under the first substrate  32  and is penetrating through the first substrate  32 , the semi-reflective layer  34 , the bonding layer  36  until the reflective layer  38 . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  44  from the reflective layer  38  for identifying the data structures  40   a.    
           [0008]    With the development of the high storage capacity, DVD has become a popular storage medium to store application software or audio/video information. Researches on preventing an illegal copying from the DVD, such as distributing software or other information that is recorded on the DVD by additional computer programs have been made. Since the protection mechanism that relies on computer programs has the potential to be defeated, other protection mechanisms are required to effectively prevent the illegal copying problems.  
         SUMMARY OF INVENTION  
         [0009]    It is therefore an objective of the claimed invention to provide an optical data storage medium of limiting plat times to solve the above-mentioned problems.  
           [0010]    According to the claimed invention, an optical data storage medium includes a first substrate, the first substrate including a plurality of first data structures; a second substrate positioned above the first substrate, the second substrate including a plurality of second data structures; a reflective layer positioned on the second substrate to cover the second data structures; and a masking layer interposed between the reflective layer and the first substrate to cover the first data structures, the masking layer having a varying reflectivity to thereby render the second data structures unreadable.  
           [0011]    It is an advantage of the present invention that with the play times increasing, the accumulated energy in the optical data storage medium changes the reflectivity of the masking layer. Specifically, when a laser beam cannot penetrate through the masking layer, users can only read a warning statement of the first data structures showing that the second data structures are unreadable. Therefore, the optical data storage medium of the present invention use the reflectivity change rate of the masking layer for defining its play times, thus preventing the information stored therein from being unlimitedly read or copied.  
           [0012]    These and other objectives of the claimed invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0013]    [0013]FIG. 1 is a cross-sectional diagram of a DVD according to the prior art;  
         [0014]    [0014]FIG. 2 is a cross-sectional diagram of a dual layer DVD according to the prior art;  
         [0015]    [0015]FIG. 3 is a cross-sectional diagram of a first embodiment of an optical data storage medium according to the present invention;  
         [0016]    [0016]FIG. 4 is a cross-sectional diagram of a second embodiment of an optical data storage medium according to the present invention;  
         [0017]    [0017]FIG. 5 is a cross-sectional diagram of a third embodiment of an optical data storage medium according to the present invention; and  
         [0018]    [0018]FIG. 6 is a cross-sectional diagram of a fourth embodiment of an optical data storage medium according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]    Please refer to FIG. 3 of a cross-sectional diagram of a first embodiment of an optical data storage medium  50  according to the present invention. The optical data storage medium  50  is a single-layer DVD, such as a DVD- 5  disc, having a single readable information layer. However, the an optical data storage medium  50  is not limited to have a single readable information layer, and other optical data storage medium having multiple readable information layers (such as double or triple readable information layers) are also applicable to the first embodiment of the present invention. As shown in FIG. 3, the an optical data storage medium  50  includes a plurality of data structures  52   a  formed by etching a surface of a first substrate  52 , a masking layer  54  positioned on the first substrate  52  and the data structures  52   a , a plurality of data structures  60   a  formed by etching a surface of a second substrate  60 , a reactive layer  58  positioned on the second substrate  60  and the data structures  60   a , and a bonding layer  56  interposed between the reflective layer  58  and the masking layer  54  for bonding the first substrate  52  with the second substrate  60 . Normally, the first substrate  52  and the second substrate  60  are made of polycarbonate, the reflective layer  58  is a metallic layer, and the masking layer  54  is made of phase change materials for defining readable times of the optical data storage medium  50 . Specifically, according to the present invention, storage data of the DVD- 5  disc  50  (the data structures  60   a ) is formed by etching the surface of the upper substrate  60  counterclockwise, which is different from an ordinary DVD- 5  disk having storage data formed by etching a surface of a lower substrate clockwise.  
         [0020]    For reading data of the optical data storage medium  50  (i.e., the data structures  60   a ), a laser beam  62  of a predetermined focusing depth is emitted from a picked head (not shown) installed under the first substrate  52  and is penetrating through the first substrate  32 , the masking layer  54 , the bonding layer  56  until the reflective layer  58 . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  62  from the reflective layer  58  for identifying the data structures  60   a.    
         [0021]    With the play times increasing, the accumulated energy in the optical data storage medium  50  changes the reflectivity of the phase change materials composing the masking layer  54 . For example, transparent phase change materials of amorphous phase will gradually transform into non-transparent phase change materials of crystal phase. In other words, as play time increasing, the ratio of crystal structures within the masking layer  54  raises, which results in an increasing of reflectivity of the masking layer  54  until a laser beam cannot penetrate through the masking layer  54  for reading the date structures  60   a . At that time, the laser beam will be reflected from the masking layer  54 , such as the laser beam  64  shown in FIG. 3, and users can only read a warning statement of the data structures  52   a  showing that the data structures  60   a  are unreadable.  
         [0022]    Please refer to FIG. 4 of a cross-sectional diagram of a second embodiment of an optical data storage medium  70  according to the present invention. The optical data storage medium  70  is a single-layer DVD, such as a DVD- 5  disc, having a single readable information layer. However, the an optical data storage medium  70  is not limited to have a single readable information layer, and other optical data storage medium having multiple readable information layers (such as double or triple readable information layers) are also applicable to the second embodiment of the present invention. As shown in FIG. 4, the optical data storage medium  70  includes a plurality of data structures  72   a  formed by etching a surface of a first substrate  72 , a reflective layer  76  positioned on the first substrate  72  and the data structures  72   a , a reactive layer  73  positioned adjacent to the reflective layer  76  (such as above the reflective layer  76  or below the reflective layer  76 ), a barrier layer  74  interposed between the reactive layer  73  and the reflective layer  76 , and a bonding layer  78  positioned on the reflective layer  76  for bonding the first substrate  72  with a second substrate  80 . Normally, the first substrate  72  and the second substrate  80  are made of polycarbonate, the reflective layer  58  is a metallic layer, and the reactive layer  73  is made of reactive compounds for defining readable times of the optical data storage medium  70 .  
         [0023]    For reading data of the optical data storage medium  70  (i.e., the data structures  72   a ), a laser beam  72  of a predetermined focusing depth is emitted from a picked head (not shown) installed under the first substrate  72  and is penetrating through the first substrate  72 , the reactive layer  73 , the barrier layer  74  until the reflective layer  76 . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  82  from the reflective layer  76  for identifying the data structures  72   a.    
         [0024]    With the play times increasing, the accumulated energy in the optical data storage medium  70  achieves diffusion of the reactive compounds from within the reactive layer  73  to the barrier layer  74  and the reflective layer  76 . Therein, the barrier layer  74  is used to control the time of the reactive compounds diffusing to the reflective layer  76 . Furthermore, the diffused reactive compounds react with the reflective layer  76  so as to change the reflectivity of the reflective layer  76 . Specifically, with the play times increasing, the reflectivity of the reflective layer  76  covering a portion of the data structures  72   a  also changes, resulting in magnitude decay or direction deviation of the reflected laser beam  82  for reading the portion of the data structures  72   a . Therefore, the photo detector of the picked head is unable to detect the reflected laser beam  82  correctly, and the optical data storage medium  70  of the present invention is limitedly read.  
         [0025]    Please refer to FIG. 5 of a cross-sectional diagram of a third embodiment of an optical data storage medium  90  according to the present invention. The optical data storage medium  90  is a single-layer DVD, such as a DVD- 5  disc, having a single readable information layer. However, the an optical data storage medium  90  is not limited to have a single readable information layer, and other optical data storage medium having multiple readable information layers (such as double or triple readable information layers) are also applicable to the third embodiment of the present invention. As shown in FIG. 5, the optical data storage medium  90  includes a plurality of data structures  92   a  formed by etching a surface of a first substrate  92 , a masking layer  93  positioned on the first substrate  92  and the data structures  92   a , a reflective layer  96  positioned on the masking layer  93 , a reactive layer  95  positioned adjacent to the masking layer  93  (such as above the masking layer  93  or below the masking layer  93 ), a barrier layer  94  interposed between the reactive layer  95  and the masking layer  93 , and a bonding layer  98  positioned on the reflective layer  96  for bonding the first substrate  92  with a second substrate  100 . Normally, the first substrate  92  and the second substrate  100  are made of polycarbonate, the reflective layer  96  is a metallic layer, and the reactive layer  73  is made of reactive compounds for defining readable times of the optical data storage medium  90 .  
         [0026]    For reading data of the optical data storage medium  90  (i.e., the data structures  92   a ), a laser beam  102  of a predetermined focusing depth is emitted from a picked head (not shown) installed under the first substrate  92  and is penetrating through the first substrate  92 , the masking layer  93 , the barrier layer  94 , the reactive layer  95  until the reflective layer  96 . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  102  from the reflective layer  96  for identifying the data structures  92   a.    
         [0027]    With the play times increasing, the accumulated energy in the optical data storage medium  90  achieves diffusion of the reactive compounds from within the reactive layer  95  to the barrier layer  94  and the masking layer  93 . Therein, the barrier layer  94  is used to control the time of the reactive compounds diffusing to the masking layer  93 . Furthermore, the diffused reactive compounds react with the masking layer  93  so as to change the reflectivity of the masking layer  93 . Specifically, with the play times increasing, the reflectivity of the masking layer  93  covering a portion of the data structures  92   a  also changes, resulting in magnitude decay or direction deviation of the reflected laser beam  102  for reading the portion of the data structures  92   a . Therefore, the photo detector of the picked head is unable to detect the reflected laser beam  102  correctly, and the optical data storage medium  90  of the present invention is limitedly read.  
         [0028]    Please refer to FIG. 6 of a cross-sectional diagram of a forth embodiment of an optical data storage medium  110  according to the present invention. The optical data storage medium  110  is a dual-layer DVD, such as a DVD- 9  disc, having two readable information layers. The forth embodiment of the present invention applies the method of the second embodiment, which uses reactive compounds to change the reflectivity of the reflective layer, for limiting play times of the optical data storage medium  110  having two readable information layers. As shown in FIG. 6, the optical data storage medium  110  includes a plurality of data structures  112   a  formed by etching a surface of a first substrate  112 , a semi-reflective layer  114  positioned on the first substrate  112  and the data structures  112   a , a first reactive layer  16  positioned adjacent to the semi-reflective layer  114  (such as above the semi-reflective layer  114  or below the semi-reflective layer  114 ), a reflective layer  120  positioned on a second substrate  124  and a plurality of data structures  124   a  formed by etching a surface of the second substrate  124 , a second reactive layer  122  positioned adjacent to the reflective layer  120  (such as above the reflective layer  120  or below the reflective layer  120 ), and a bonding layer  118  interposed between the semi-reflective layer  114  and the reflective layer  120  for bonding the first substrate  112  with the second substrate  124 . Normally, the first substrate  112  and the second substrate  124  are made of polycarbonate the semi-reflective layer  114  is a metallic layer, such as a gold layer, the reflective layer  122  is also a metallic layer, such as an aluminum layer, and the first and the second reactive layer  116 ,  122  is made of reactive compounds for defining readable times of the optical data storage medium  110 .  
         [0029]    For reading lower data of the optical data storage medium  110  (i.e., the data structures  112   a ), a laser beam  126  of a predetermined focusing depth is emitted from a picked head (not shown) installed under the first substrate  112  and is penetrating through the first substrate  112 , the data structures  112   a , until the semi-reflective layer  114 . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  126  from the semi-reflective layer  114  for identifying the data structures  112   a . Similarly, for reading upper data of the optical data storage medium  110  (i.e., the data structures  124   a ), a laser beam  128  of a predetermined focusing depth is emitted from the picked head installed under the first substrate  112  and is penetrating through the first substrate  112 , the semi-reflective layer  114 , the first reactive layer  116 , the bonding layer  118  until the reflective layer  120 . As a result, a photo detector of the picked head can be used to detect a reflected laser beam  128  from the reflective layer  120  for identifying the data structures  124   a.    
         [0030]    With the play times increasing, the accumulated energy in the optical data storage medium  110  achieves diffusion of the reactive compounds from within the first reactive layer  116  and the second reactive layer  122  respectively to the semi-reflective layer  114  and the reflective layer  120  for changing the reflectivity of the semi-reflective layer  114  and the reflective layer  120 . Specifically, with the play times increasing, the reflectivity of the semi-reflective layer  114  covering a portion of the data structures  112   a  and the reflective layer  120  covering a portion of the data structures  124   a  also change, resulting in magnitude decay or direction deviation of the reflected laser beam  126 , 128  for reading the portion of the data structures  112   a ,  124   a . Therefore, the photo detector of the picked head is unable to detect the reflected laser beam  112   a ,  124   a  correctly, and the optical data storage medium  110  of the present invention is limitedly read. Additionally, for controlling the diffusion time of the reactive compounds diffused from within the first reactive layer  116  to the semi-reflective layer  114  and from within the second reactive layer  122  to the reflective layer  120 , a barrier layer (not shown) is respectively formed between the first reactive layer  116  and the semi-reflective layer  114  and between the second reactive layer  122  and the reflective layer  120 . The barrier layer is used to control the reflectivity change rate of the semi-reflective layer  225  and the reflective layer  120  and further to limit the readable times or readable hours of the optical data storage medium  110 .  
         [0031]    Moreover, according to other embodiments of the present invention, a detection device, such as a program of a counting function, is installed in a lead-in area of an optical data storage medium for computing whether read times or read hours of the optical data storage medium exceed the defined readable times or readable hours of the optical data storage medium so as to control the lifetime of the optical data storage medium more effectively.  
         [0032]    In contrast to the prior art, the present invention uses the energy accumulating during the play process of the optical data storage medium to change the reflectivity of particular layers included in the optical data storage medium. Therefore, signals for reading the data stored in the optical data storage medium decay with the play times increasing, and finally the data stored in the optical data storage medium is unreadable. As a result, a lifetime of the optical data storage medium can be defined by changing construction materials of the optical data storage medium itself, thus preventing the information stored in the optical data storage medium from being unlimitedly read or copied.  
         [0033]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.