Abstract:
A head mounted on various kinds of storage mediums such as a hard disc drive is moved along a storage face to destruct data on the storage medium. Therefore, the data on a storage medium is destructed without disassembling a hard disk drive or the like.

Description:
This is a continuation of Application PCT/JP2003/003523, filed on Mar. 24, 2003. 

   TECHNICAL FIELD  
   The present invention relates to a destruction technology for destroying a storage medium. 
   BACKGROUND ARTS  
   Generally, an information processing apparatus including an existing computer involves employing a hard disc device as an information storage medium. 
   The hard disc device is the most standard type of data storage device in a computer system. The hard disc device is stored with operating system (OS) and application programs. Further, the hard disc device is stored with user data and operation data. A 3.5-in. type hard disc device, which is a mainstream type of device at the present, has a storage capacity that is equal to or larger than 100 gigabytes per device. 
   The hard disc device magnetically records the data by rotating at a high speed a disc (also called a [platter]) constructed of a glass or aluminum circular plate coated or vapor-deposited with a magnetic substance. A multiplicity of tracks are disposed concentrically on this platter. Further, sectors (a sector is a unit for reading and writing the data, and one sector normally consists of 512 bytes through several kilobytes) are regularly arranged within the track. 
   In the hard disc device, when reading and writing the data, at first, a head slider (which will hereinafter be referred to as a head portion) including a read/write head is moved onto a target track. Note that the movement of this head portion is called a ‘seek’. After the seek, the hard disc device, when the head is moved to a position just under the target sector, starts reading and writing the data. Total time of a period of seek waiting time and a period of rotation waiting time becomes a period of access time (a period of time till a data transfer is started) to the hard disc. This access time to the hard disc device generally requires several milliseconds. Then, once the data transfer is started, a data transfer speed of the hard disc device is determined corresponding to a rotating speed and a record density of the platter. 
   Note that in the hard disc device, the head can access a plurality of tracks existing in the same position through one seek by using double sides of the single platter or by simultaneously employing a plurality of platters. Accordingly, performance of the hard disc device is improved by such methods. By the way, in the hard disc device, according to the methods such as erasing the data or formatting (initializing) the disc, etc., the stored data simply look disappeared from the computer. 
   Namely, the data erasing method given above is a method of deleting, e.g., connection information (initial entry) among blocks configuring a file. In this method, though the connection information among the blocks is deleted, the blocks for storing the data still remain undeleted. Further, the data erasing method described above, for instance, intends to make the data unable to be read by writing the same information (Ex.: 0) to all the files. This method has a possibility that the original data might be decoded by a difference from the same written information. 
   The hard disc device with the data appearing as if erased can be read if using a special piece of software. Hence, unless a proper measure is taken for the data in the hard disc device in case of disposal or a transfer of a personal computer, a malicious third party might reuse the data of the previous user. 
   Therefore, when discarding the hard disc device described above, the data can not be completely erased unless the disc medium (storage medium) is destroyed by deassembling the hard disc device. 
   Accordingly, the general user, inconveniently enough, must destroy the hard disc device by deassembling the computer when discarding the computer. Moreover, even when a waste disposal company conducts a discarding treatment of the computer, this treatment involves a manual work, and consequently it is not so easy to discard a tremendous quantity of hard disc devices. A problem arising when discarding the storage medium is the same with other types of storage mediums such as a CD (Compact Disc), a (DVD (Digital Video or Digital Versatile Disc), an MD (Mini Disc), an FD (Flexible Disk) and so on. 
   By the way, a technology (refer to, e.g., Patent document 1) for destroying, e.g., an optical disc is disclosed as a technology for destroying the storage medium. 
   Patent Document 1 
   Japanese Patent Application Laid-Open Publication No. 64-30024 
   SUMMARY OF THE INVENTION 
   Even by the technology in Patent document 1, however, the destruction of the storage medium must involve removing the storage medium from the hard disc device by deassembling a computer. 
   It is an object of the present invention, which was devised in view of the items described above, to provide a technology for completely destroying the storage surface when discarded without deassembling the hard disc device. 
   The present invention adopts the following means in order to solve the aforementioned problems. 
   Namely, the present invention has a contrivance that a head portion including a head for reading or writing information from or to a storage medium is moved along a storage surface of a storage medium, thereby destroying the storage medium. 
   In the present invention, the head provided in each of a variety of storage mediums of hard disc devices, etc. is moved along the storage surface, thereby destroying the storage medium. 
   Therefore, according to the present invention, the storage medium can be destroyed without deassembling the hard disc device, etc. 
   Further, in the present invention, when the head portion moves above the storage surface, a perpendicular position of the head portion with respect to the storage surface may be controlled. 
   Hence, according to the present invention, the perpendicular position of the head portion when destroying the storage medium can be changed in relation to the perpendicular position at the normal reading/writing time by controlling the perpendicular position of the head portion. 
   Then, in the present invention, when the head portion moves above the storage surface, the head portion is pressed against the storage surface. 
   Hence, according to the present invention, the storage surface is destroyed by pressing the head portion against the storage surface, whereby the data can be neither read from nor written to the storage medium any more. 
   Further, in the present invention, the storage medium is a circular storage medium, and the number of revolutions of the storage medium may be reduced. 
   The head portion of the storage device gets afloat by a pressure difference of the air between the storage medium and the head portion, which is caused by rotating the storage medium. Then, the perpendicular position of the head portion is lowered by decreasing the number of revolutions of the storage medium, thus pressing the head portion against the storage surface. 
   Hence, according to the present invention, the storage surface is destroyed by pressing the head portion against the storage surface, whereby the data can be neither read from nor written to the storage medium any more. 
   Then, in the present invention, storage medium is a circular storage medium, and a rotating direction of the storage medium may be changed. 
   A force for floating the head portion is generated depending on a shape of the head portion. Then, in the present invention, the force for floating the head portion is prevented from being generated in a way that changes the rotating direction of the storage medium. 
   Hence, according to the present invention, the storage surface is destroyed by pressing the head portion against the storage surface, whereby the data can be neither read from nor written to the storage medium any more. 
   Moreover, in the present invention, the head may be supplied with an electric current equal to or larger than an allowable value of an electric current when written to the storage medium. 
   According to the present invention, the storage surface of the storage medium is destroyed by supplying the head with the electric current equal to or larger than the allowable value of the electric current when written to the storage medium. 
   Therefore, according to the present invention, the storage surface of the storage medium is destroyed by supplying the head with the electric current, whereby the data can be neither read from nor written to the storage medium any more. 
   Additionally, in the present invention, a magnetic field equal to or larger than an allowable value of a magnetic field when written to the storage medium may be generated from the head. 
   In the present invention, the storage surface of the storage medium is destroyed by generating from the head the magnetic field equal to or larger than the allowable value of the magnetic field when written to the storage medium. 
   Therefore, according to the present invention, the storage surface of the storage medium is destroyed by generating the magnetic field from the head, whereby the data can be neither read from nor written to the storage medium any more. 
   Moreover, the present invention may also be a program for actualizing any one of the functions given above. Further, in the present invention, a storage medium readable by a computer may be stored with such a program. 
   Still further, the present invention may also be an apparatus that actualizes any one of the functions described above. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing a hard disc device according to an embodiment of the present invention; 
       FIG. 2  is a sectional view (side view) when a storage surface of a disc of the hard disc device according to a first embodiment is set on the surface side; 
       FIG. 3  is an explanatory view illustrating a principle on which a head portion of the hard disc device gets afloat; 
       FIG. 4  is an explanatory view showing a state where the head portion is pressed against the disc in the hard disc device according to the first embodiment; 
       FIG. 5  is an explanatory flowchart of a storage surface destruction process by the storage device in the first embodiment; 
       FIG. 6  is a sectional view (side view) showing a normal state when the storage surface of the disc of the hard disc device according to a second embodiment is set on the surface side; 
       FIG. 7  is a sectional view showing a state where the storage surface destruction process according to the second embodiment is executed; 
       FIG. 8  is an explanatory flowchart of the storage surface destruction process by the storage device in the second embodiment; and 
       FIG. 9  is a block diagram showing a normal type of hard disc device. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Preferred embodiments of the present invention will hereinafter be described with reference to the drawings in  FIGS. 1 through 9 . 
   &lt;First Embodiment&gt; 
   A first embodiment will be explained with reference to  FIGS. 1 through 5 . In the first embodiment, the present invention is applied to an information processing device such as a computer, etc. Further, the first embodiment will give one example of a hard disc device as a storage device including a storage medium from and to which the information is read and written in the information processing device. Then, a storage device, a storage medium destruction program and a storage medium destruction method of the present invention are applied to a storage medium discarding process of the hard disc device. 
   In the first embodiment, the hard disc device given by way of one example of the storage device is preinstalled with a function of executing the storage medium destruction method of the present invention. Then, the hard disc device may be built in the information processing apparatus. Moreover, the hard disc device may also be connected from outside to the information processing device. 
   The hard disc device is connected to the information processing apparatus and is thereby stored with operating system (OS) and an application program, wherein pieces of information thereof are read and written. Further, the hard disc device is connected to the information processing device and is thereby stored with user data and operation data, wherein pieces of information thereof are read and written. 
   &lt;Configuration of Device&gt; 
   Next, the hard disc device including the function of destroying the storage medium according to the first embodiment, will be described. 
     FIG. 1  is a block diagram showing one example of a hard disc device  100  according to the first embodiment. The hard disc device  100  according to the first embodiment is constructed of the following components. The hard disc device  100  includes an MPU (Micro Processing Unit)  101 , a storage medium destruction control unit  102 , a read/write control unit  103 , an exchange management information memory  104 , a servo control unit  105 , a rotating position detecting unit  106 , a read/write circuit  107 , a positioning control unit  108 , a rotation control unit  109  and a DE (Disc Enclosure)  110 . 
   Next, the components will be explained. The MPU  101  accepts an access command to the data to be stored, which is given from a computer (unillustrated). Moreover, the MPU  101 , when storing the data, accepts a storage command from the computer. Then, in response to the access command and the storage command, the MPU  101  instructs the respective components to execute processes for carrying out these commands. 
   The storage medium destruction control unit  102  gives instructions, as exemplified below, to respective elements of the DE  110  in order to execute a storage surface destruction process of the storage medium destruction method according to the first embodiment. To be specific, the storage medium destruction control unit  102  presses a head portion against a storage surface to execute the storage medium destruction method according to the first embodiment. Further, the storage medium destruction control unit  102  generates, from the head, a magnetic field equal to or higher than an allowable value of the magnetic field caused by an electric current for reading and writing in order to execute the storage medium destruction method according to the first embodiment. 
   Note that the storage medium destruction control unit  102  may also give the instructions to the respective elements of the DE  110  for performing the storage surface destruction process through the read/write control unit  103 , the read/write circuit  107 , the servo control unit  105 , the positioning control unit  108 , the rotation control unit  109  and the rotating position detecting unit  106 . 
   For reading and writing the data, the read/write control unit  103  and the read/write circuit  107  (current control means) control the current for generating the magnetic field from the head existing at the DE  110  for reading and writing the data to and from the disc in accordance with a command from the MPU  101  and with rotating position information that will be mentioned later on. 
   The servo control unit  105  connects to the positioning control unit  108 , the rotation control unit  109  and the rotating position detecting unit  106 . The servo control unit  105  instructs, through the positioning control unit  108 , a moving portion to move a position, above the storage surface of the disc, of the head portion to a predetermined read/write position. Further, the servo control unit  105  controls, through the rotation control unit  109 , the number of revolutions of a spindle motor so that the disc reaches the number of revolutions necessary for reading and writing. 
   The rotating position detecting unit  106  transmits, to the read/write control unit  103 , the rotating position information of the disc that is acquired from the rotation control unit  109  via the servo control unit  105 . The DE  110  is a generic name of the mechanical components in the hard disc device  100 , such as the head portion including the head and a head/slider that serve to effect the read/write, the disc (a platter) defined as the storage medium, the spindle motor (a rotating portion) for rotating the disc, the moving portion for moving the head portion to a sector on the disc, and a perpendicular position moving portion (a pressing portion) for determining a perpendicular position of the head portion with respect to the storage surface of the disc. 
   &lt;Example of Storage Surface Destruction Process&gt; 
   Next, one example of the disc storage surface destruction process in the hard disc device  100  according to the first embodiment, will be described. 
     FIG. 2  is a sectional view (side view) when the storage surface of the disc of the hard disc device  100  according to the first embodiment is set on the surface side. The hard disc device  100  includes a disc  100   a,  a head portion  100   b,  and a head  100   c.    
   Normally, the hard disc device  100  performs, as illustrated in  FIG. 2 , reading and writing in such a way that the head  100   c  is set afloat by approximately 15 nm from the storage surface of the disc  100   a.  At this time, the hard disc device  100  stops the head portion  100   b  above the predetermined sector where the head  100   c  performs reading and writing. Then, the hard disc  100  generates, from the head  100   c,  the magnetic field caused by the current that is required for reading and writing, thereby reading and writing the data. 
     FIG. 3  is an explanatory view illustrating a principle on which the head portion  100   b  of the hard disc device  100  gets afloat. In  FIG. 3 , the disc  100   a  is rotated (moved) in a direction indicated by an arrow. 
   Normally, the head portion  100   b  of the hard disc device  100  gets afloat above the surface (the storage surface) of the disc  100   a  by dint of airflow caused when the disc  100   a  rotates about a rotating shaft  100   d.  At this time, a pressure is produced by viscosity of the air between the disc  100   a  and the head portion  100   b.  Then, the head portion  100   b  gets afloat from the disc  100   a  with equilibration between the pressure and a spring force of a spring  100   e  that acts in such a direction as to get pulled apart from the disc  100   a.  Note that a contrivance is given to a sectional shape of the head portion  100   b  for generating the pressure. 
   In the hard disc device  100  according to the first embodiment, the head portion  100   b  which is usually kept afloat above the disc  100   a  is pressed against the disc  100   a.  The hard disc device  100  performs a full-seek in a state where the head portion  100   b  is pressed against the disc  100   a.  Through this operation, the hard disc device  100  executes the storage surface destruction process over the disc  100   a.  As a result, the data stored on the hard disc device  100  can be neither read nor written any more. The storage surface destruction process over the disc  100   a  according to the first embodiment includes control of reducing the number of revolutions of the disc, control of changing the rotating direction of the disc, and the process of pressing the head portion (pressed against the head by the pressing portion). 
   The reduction control of the number of revolutions of the disc is the control of decreasing the pressure for floating the head portion  100   b  by reducing the number of revolutions of the disc  100   a,  and of thus pressing the head portion  100   b  against the disc  100   a.  Under this reduction control of the number of revolutions of the disc, the storage medium destruction control unit  102 , in response to an instruction, given from the computer (unillustrated), purporting that the storage surface destruction process be executed, instructs the DE  110  to reduce the number of revolutions of the spindle motor. Further, the storage medium destruction control unit  102  moves the head portion  100   b  to the storage surface of the disc  100   a.    
   The change control of the rotating direction of the disc is the control of preventing the pressure for floating the head portion  100   b  from being produced in a way that reverses the normal rotating direction of the disc  100   a,  and of thus pressing the head portion  100   b  against the disc  100   a.  Under this rotating direction change control, the storage medium destruction control unit  102 , in response to an instruction, given from the computer, purporting that the storage surface destruction process be executed, instructs the DE  110  to change the rotating direction of the spindle motor. Moreover, the storage medium destruction control unit  102  also instructs the DE  110  to move the head portion  100   b  to the storage surface of the disc  100   a.    
   The head portion pressing control is the process of forcibly pressing the head portion  100   b  against the disc  100   a  by an actuator (unillustrated), etc. In this head portion pressing process, the storage medium destruction control unit  102  instructs the DE  110  so that a perpendicular position of the head portion  100   b  comes to a position of pressing the head portion  100   b  against the disc  100   a.    
     FIG. 4  is an explanatory view showing the state where the head portion  100   b  is pressed against the disc  100   a  in the hard disc device according to the first embodiment. In  FIG. 4 , the head portion  100   b  is pressed against the disc  100   a.  Then, the storage medium destruction control unit  102  rotates the spindle motor when the head portion  100   b  is kept pressing, and simultaneously moves the head portion  100   b  along the storage surface. Through this operation, the entire storage surface of the disc  100   a  of the hard disc device  100  is destroyed, whereby the data can be neither read nor written any more. 
   &lt;Flowchart in First Embodiment&gt; 
   Next, the storage surface destruction process by the hard disc device  100  according to the first embodiment will be explained with reference to a flowchart. 
     FIG. 5  is an explanatory flowchart of the storage surface destruction process by the hard disc device  100  in the first embodiment. 
   To begin with, the storage medium destruction control unit  102  judges whether the data given from the computer should be destroyed or not (the storage surface destruction process should be executed or not) (in step  101  in  FIG. 5 , which will hereinafter be abbreviated such as S 101 ). At this time, if given an instruction purporting that the data be kept undestroyed, the storage medium destruction control unit  102  finishes this process. 
   The storage medium destruction control unit  102  accepting the instruction purporting that the data be destroyed, for example, under the reduction control of the number of revolutions of the disc, presses the head portion  100   b  against the storage surface of the disc  100   a  (S 102 ). Further, the storage medium destruction control unit  102  accepting the instruction purporting that the data be destroyed, for example, under the change control of the rotating direction of the disc, presses the head portion  100   b  against the storage surface of the disc  100   a  (S 102 ). Moreover, the storage medium destruction control unit  102  accepting the instruction purporting that the data be destroyed, for example, by the head portion pressing process described above, presses the head portion  100   b  against the storage surface of the disc  100   a  (S 102 ). 
   Then, the storage medium destruction control unit  102 , after pressing the head portion  100   b  against the disc  100   a,  executes the so-called full-seek of moving the head portion  100   b  along the entire storage surface while rotating the disc  100   a  (S 103 ). 
   After completion of the full-seek, the storage medium destruction control unit  102  finishes this process. 
   &lt;Effects of First Embodiment&gt; 
   The following effects are acquired by actualizing the hard disc device  100  according to the first embodiment. According to the hard disc device  100  in the first embodiment, the storage medium of the hard disc device, etc. built in the computer can be destroyed without any deassembly. 
   Moreover, according to the hard disc device  100  in the first embodiment, the storage medium destruction process can be surely executed. 
   &lt;Second Embodiment&gt; 
   A second embodiment will be described with reference to  FIGS. 6 through 8 . The first embodiment is that the storage surface is destroyed by pressing the head portion against the storage surface of the storage medium in the storage device. The second embodiment is that the storage surface is destroyed by an electric current that generates a magnetic field equal to or higher than an allowable value when writing. 
   Other configurations and operations in the second embodiment are the same as those in the first embodiment. Accordingly the explanations of the same configurations and operations as those in the first embodiment are omitted. Further, in the second embodiment,  FIGS. 1 through 5  are referred to according to the necessity. 
   &lt;Example of Storage Surface Destruction Process&gt; 
     FIG. 6  is a sectional view (side view) showing the normal state when the storage surface of the disc  100   a  of the hard disc device  100  according to the second embodiment is set on the surface side. Further,  FIG. 7  is a sectional view showing a state where the storage surface destruction process of the disc  100   a  according to the second embodiment is executed. The hard disc device  100  includes the disc  100   a,  the head portion  100   b  and the head  100   c.    
   Normally, the hard disc device  100  performs, as illustrated in  FIG. 6 , writing in such a way that the head  100   c  is set afloat by approximately 15 nm from the storage surface of the disc  100   a.  At this time, the hard disc device  100  stops the head portion  100   b  above the predetermined sector where the head  100   c  performs writing. Then, the hard disc  100  generates, from the head  100   c,  the magnetic field caused by the current that is required for writing, thereby writing the data. 
   In the storage surface destruction process according to the second embodiment, as shown in  FIG. 7 , the magnetic field equal to or larger than a tolerance is generated from the head  100   c  by the current when writing the data. Then, the magnetic field generated by the current, which is equal to or larger than the tolerance, destroys the magnetic field over the storage surface of the disc  100   a,  whereby the data can be neither read from nor written to the storage medium any more. 
   &lt;Flowchart in Second Embodiment&gt; 
   Next, the storage surface destruction process by the hard disc device  100  according to the second embodiment will be described with reference to a flowchart. 
     FIG. 8  is an explanatory flowchart of the storage surface destruction process by the hard disc device  100  in the second embodiment. 
   To start with, the storage medium destruction control unit  102  judges whether the data given from the computer should be destroyed or not (the storage surface destruction process should be executed or not) (in step  201  in  FIG. 8 , which will hereinafter be abbreviated such as S 201 ). At this time, if given an instruction purporting that the data be kept undestroyed, the storage medium destruction control unit  102  finishes this process. 
   The storage medium destruction control unit  102  accepting the instruction purporting that the data be destroyed, supplies the head  100   c  with the current equal to or larger than the tolerance of the current supplied when reading and writing as described above. Then, the head  100   c  destroys the magnetic field over the storage surface of the disc  100   a  by dint of the magnetic field generated by the current equal to or larger than the tolerance (S 202 ). 
   Then, the storage medium destruction control unit  102 , in the state of generating the magnetic field from the head  100   c  by the current that is equal to or larger than the tolerance, executes the so-called full-seek of moving the head  100   c  along the entire storage surface while rotating the disc  100   a  (S 203 ). 
   After completion of the full-seek, the storage medium destruction control unit  102  finishes this process. 
   &lt;Effects of Second Embodiment&gt; 
   The following effects are acquired by actualizing the hard disc device  100  according to the second embodiment. 
   According to the hard disc device  100  in the second embodiment, the storage medium of the hard disc device, etc. built in the computer can be destroyed without any deassembly. 
   Moreover, according to the hard disc device  100  in the second embodiment, the storage medium destruction process can be surely executed. 
   Still further, according to the hard disc device  100  in the second embodiment, the storage surface destruction process can be executed so that the data can be neither read nor written without damaging the storage medium. 
   &lt;Modifies Example&gt; 
   In the present embodiment, the storage device of the present invention has been discussed by giving one example mainly of the hard disk device of the information processing apparatus, however, the present invention is not limited to this type of storage device and can be broadly carried out for other types of storage devices. 
     FIG. 9  is a block diagram showing one example of a normal type of hard disc device  200  according to the present embodiment. For instance, the storage medium destruction method according to the present embodiment is installed as a program executable by the computer into the computer or an MPU  201  of the hard disc device  200 , whereby the storage surface destruction process of the disc can be executed even in the hard disc device  200  that does not include the storage device of the present invention. In this case, even when the hard disc device  200  is not connected to the computer, the storage surface destruction process of the disc can be executed by manipulating a jumper switch, etc. on condition that the present program is installed into the MPU  201 . 
   Note that in the present embodiment, the storage medium destruction control unit  102  can be also actualized as so-called firmware for giving an instruction of executing the storage surface destruction process according to the present embodiment to, e.g., the read/write control unit  103  and the read/write circuit  107  (current control means), and the servo control unit  105 , the positioning control unit  108 , the rotation control unit  109  and the rotating position detecting unit  106 . In this case, even when the hard disc device  200  is not connected to the computer, the storage surface destruction process of the disc can be executed by manipulating the jumper switch, etc. on condition that the present program is installed as the firmware into the present hard disc device. 
   Moreover, the storage device according to the present embodiment may execute a combination of the disc storage surface destruction processes in the first embodiment and in the second embodiment. 
   Moreover, the storage device according to the present embodiment is applied to the hard disc device of the computer, however, the present invention is not limited to this hard disc device and can be applied to all other types of storage mediums. The storage device of the present invention can be applied to, e.g., a CD (Compact Disc), a DVD (Digital Video or Digital Versatile Disc), an MD (Mini Disc), an FD (Flexible Disk) and so on. Among the storage mediums given above, the CD and the DVD are classified as optical recording mediums, and therefore, in the storage surface destruction process according to the second embodiment, data are destroyed by irradiating the storage surface with laser beams. Moreover, among the storage mediums given above, the MD is classified as a magneto-optic disc, and hence, in the storage surface destruction process according to the second embodiment, the data are destroyed by irradiating the storage surface with the laser beams and thus generating the magnetic field. 
   &lt;Readable-by-Computer Recording Medium&gt; 
   The control program in this embodiment may be recorded on a readable-by-computer recording medium. Then, a computer reads the control program on this recording medium, and executes this program, whereby the computer functions as the image processing system  200  demonstrated in this embodiment. 
   Herein, the readable-by-computer recording medium embraces recording mediums capable of storing information such as data, programs, etc electrically, magnetically, optically and mechanically or by chemical action, which can be all read by the computer. What is demountable out of the computer among those recording mediums may be, e.g., a flexible disk, a magneto-optic disk, a CD-ROM, a CD-R/W, a DVD, a DAT, an 8 mm tape, a memory card, etc. 
   Further, a hard disk, a ROM (Read Only Memory) and so on are classified as fixed type recording mediums within the computer. 
   INDUSTRIAL APPLICABILITY 
   The storage device of the present invention is capable of completely destroying the storage surface when discarded without deassembling the hard disc device, and can be therefore applied to an industry for providing the storage medium destruction technology. 
   &lt;Others&gt; 
   The disclosures of international application PCT/JP2003/003523, filed on Mar. 24, 2003 including the specification, drawings and abstract are incorporated herein by reference.