Abstract:
An electronic paper includes: a main body that is provided with a display unit that displays an image; a storage unit that stores the image data; a controller that controls the display unit to display the image data stored in the storage unit; a battery that supplies electric power to the display unit and the controller; and an cartridge unit that is detachable from the main body and causes the image to be erased from the main body when detached from the main body.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electronic paper and a security system that are improved in security.  
         [0003]     2. Description of the Related Art  
         [0004]     Electronic papers have a probability that they will spread widely as a tool for assisting intellectual collaboration work done in a prescribed area. The term “prescribed area” means a space (reading place) in which electronic papers are distributed to individuals who join collaboration work and the collaboration work is done on the basis of information displayed thereon, and which the individuals who joined collaboration work exit after its end (the electronic papers are collected).  
         [0005]     Secret information may be displayed on the electronic papers, and hence the displayed information should be erased when the individuals exit the prescribed area. Further, since electronic papers are still expensive as a display device, the current situation is such that taking out each electronic paper from the above space is restricted.  
         [0006]     For example, a conventional security system that is intended to prevent leakage of information displayed on electronic papers and taking-out of electronic papers employs a method in which each electronic paper is provided with a communication device and the display on each electronic paper is erased when it comes to be unable to receive particular radio waves that are emitted from a prescribed area where a transmission source of the particular radio waves is installed (refer to JP-A-2004-037829).  
         [0007]     However, in the conventional security system, each electronic paper needs to be provided with the communication device and the transmission source of the particular radio waves needs to be installed in the prescribed area, which is costly. Further, the carrying-out of an electronic paper itself cannot be prevented. Still further, since information to be displayed is delivered to electronic papers by radio, the information may be radio-intercepted outside the prescribed area or may be radio-intercepted inside the prescribed area and recorded in another recording medium. As such, the use of radio waves is, in itself, a source of security-related problems.  
       SUMMARY OF THE INVENTION  
       [0008]     According to an aspect of the invention, there is provided an electronic paper including: a main body that is provided with a display unit that displays an image; a storage unit that stores the image data; a controller that controls the display unit to display the image data stored in the storage unit; a battery that supplies electric power to the display unit and the controller; and a cartridge unit that is detachable from the main body and causes the image to be erased from the main body when detached from the main body. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     In the accompanying drawings:  
         [0010]      FIG. 1  is a perspective view of an electronic paper according to a first embodiment;  
         [0011]      FIGS. 2A and 2B  show a cartridge according to the first embodiment of the invention, wherein  FIG. 2A  is a plan view and  FIG. 2B  shows a storage area of a memory unit;  
         [0012]      FIG. 3  shows an exemplary security system using the electronic paper according to the first embodiment;  
         [0013]      FIG. 4  is a block diagram of a control system of the security system of  FIG. 3 ;  
         [0014]      FIG. 5A  shows an electronic paper according to a second embodiment of the invention, and  FIG. 5B  is a sectional view taken along line Vb-Vb in  FIG. 5A ;  
         [0015]      FIG. 6  shows an electronic paper according to a third embodiment; and  
         [0016]      FIG. 7  shows an electronic paper according to a fourth embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     Embodiments of the invention are described in detail hereinunder optionally with reference to the drawings attached hereto. In the following description, the same reference is given to the same or the corresponding part, and an overlapping description for it is omitted.  
       First Embodiment  
       [0018]      FIG. 1  is a perspective view of an electronic paper according to a first embodiment.  FIGS. 2A and 2B  show a cartridge, wherein  FIG. 2A  is a plan view and  FIG. 2B  shows a storage area of a memory unit. As shown in  FIG. 1 , the electronic paper  1 A is provided with a thin, rectangular main unit  2  and a cartridge  5 A as a cartridge unit that is attached to and detached from the main unit  2 .  
         [0019]     As shown in  FIG. 1 , the main unit  2  is equipped with a display unit  3  for displaying an image, a page-down key  6 , and a controller  4  for reading image data from a memory unit (described later) and causing the image data to be displayed on the display unit  3  and for paging down images to be displayed on the display unit  3  according to a manipulation on the page-down key  6 .  
         [0020]     It is preferable that the display unit  3  is able to be driven by a detachable thin-film power source and the display disappears instantaneously or in a short time (several seconds to a little more than 10 seconds) after the detachment of the power source. For example, the display unit  3  may, have a general configuration as described in JP-A-2002-22918 in which a bi-stable “contrast medium” such as an electrochromic material, an electroluminescence material, or a liquid crystal material is driven by an electronically addressable driving circuit. Alternatively, as described in JP-A-2004-037829, the display unit  3  may be of an electrophoresis type, a twist ball type, a type in which the degree of absorption of a dye is varied by applying a voltage to a guest-host liquid crystal, or a type composed of a cholesteric liquid crystal and an organic photosensitive material composite film. However, the display unit  3  is not limited to those examples because the storage time of a display can be controlled from a long time to a short time by, for example, properly doing material designing, selecting a device structure, or selecting a driving method.  
         [0021]     As shown in  FIG. 1 , the cartridge  5 A is equipped with a thin, rectangular case  50  which as approximately as thick as the main unit  2 , a guide groove  50   a  to be fitted with a guide projection  20  of the main unit  2 , a wireless IC tag  51  that is provided on the surface of the case  50 , and a male connector  52 A for electrically connecting a power source unit  53  and a memory unit  54  (see  FIG. 2A ) to the controller  4 .  
         [0022]     The main unit  2  is equipped with a female connector  52 B having plural female terminals  52   b . The male connector  52 A has plural male terminals  52   a  to be electrically connected to the plural female terminals  52   b  of the female connector  52 B, respectively. The size, shape, position, etc. of the cartridge  5 A are not limited to those shown in  FIGS. 1, 2A  and  2 B.  
         [0023]     The power source unit  53 , which serves to supply electric power for driving of the display unit  3  and the controller  4 , may be, for example, a “FLEXIBLE THIN LAYER OPEN ELECTROCHEMICAL CELL” as disclosed in JP-A-2003-297374 (U.S. Pat. No. 5,652,043). This battery can be made as thin as 1 mm or less and can provide sufficient energy for driving of a display device that is used for a meeting of several hours. Therefore, when attached to the main unit  2 , the battery fits the main body  2  without causing an incongruous feeling and can supply power without causing any problems relating to the use of the electronic paper  1 A.  
         [0024]     As shown in  FIG. 2B , the memory unit  54  is provided with an image data area to which image data are to be written and an ID area  54   b  to which identification information (ID) of the electronic paper  1 A is to be written.  
         [0025]     To prevent damaging of the power source unit  53 , the memory unit  54 , the male connector  54 A, and other portions by reducing impact that occurs when the cartridge  5 A is input through an insertion slot of an exit gate section (described later), it is preferable that the cartridge  5 A is provided with a protective layer.  
         [0026]      FIG. 3  shows an exemplary security system using the electronic paper  1 A shown in  FIGS. 1, 2A  and  2 B. A use space (prescribed area)  200  where the use of the electronic paper  1 A is permitted is defined by walls  201 , and a presentation display  202  is disposed at the front position of the use space  200 .  
         [0027]     In the security system  100 , an entrance gate section  110  and an exit gate section  120  are provided at an entrance and an exit of the use space  200 , respectively.  
         [0028]      FIG. 4  shows a control system of the security system  100 . The security system  100  has a personal computer (PC)  101  for controlling the entire system  100 . A storage device  102 , an image writing device  103 , an ID writing device  111 , an entrance gate  112 , an ID reading device  121 , a cartridge collecting section  122 , and an exit gate  123  are connected to the PC  101 . The ID writing device  111  and the entrance gate  112  are installed in the entrance gate section  110 , and the ID reading device  121 , the cartridge collecting section  122 , and the exit gate  123  are installed in the exit gate section  120 .  
         [0029]     The PC  101  is equipped with input devices such as a keyboard and a mouse, a display such as a liquid crystal display, a CPU for controlling the entire system  100 , and storage units such as a ROM and a RAM.  
         [0030]     Image data to be displayed on the display unit  3  of each electronic paper  1 A and an ID list in which IDs of electronic papers  1 A are registered are stored in the storage device  102 . Pieces of personal information such as names, company names, etc. of users of the electronic papers  1 A are registered in the ID list so as to correspond to the respective IDs. The storage device  102  maybe a hard disk drive, for example.  
         [0031]     The image-writing device  103  is configured so as to write, via the male connector  52 A, image data of plural pages transmitted from the PC  101  to the image data area  54   a  of the memory unit  54  of the cartridge  5 A that is pulled out of each electronic paper  1 A. Further, the image-writing device  103  is configured so as to perform a power check on the power source unit  53  in writing image data to the memory unit  54  and, in the event of insufficient charging, turn on a lamp to indicate it. Image data may be written by a different method. For example, image data may be written directly to the memory unit  54  by pulling out the memory unit  54  from the cartridge  5 A and connecting it to the image-writing device  103 . Alternatively, image data may be written to the memory unit  54  via the wireless IC tag  51 .  
         [0032]     The ID writing device  111  is configured so as to write an ID transmitted from the PC  101  to the ID area  54   b  of the memory unit  54  via the wireless IC tag  51  in a state that the cartridge  5 A is attached to the main unit  2 . An ID may be written by a different method. For example, an ID may be written to the ID area  54   b  of the memory unit  54  via the male connector  52 A after pulling out the cartridge  5 A from the main unit  2 . Alternatively, an ID may be written directly to the memory unit  54  by pulling out the memory unit  54  from the cartridge  5 A and connecting it to the ID writing device  111 .  
         [0033]     The cartridge collecting section  122  is provided with an insertion slot (not shown) through which cartridges  5 A are input and a collection box (not shown) for collecting cartridges  5 A that have been input through the insertion slot.  
         [0034]     The ID reading device  121  is configured so as to read, via the wireless IC tags  51 , IDs from the ID areas  54   b  of the memory units  54   b  of cartridges  5 A that have been input to the cartridge collecting section  122  through the insertion slot.  
         [0035]     Next, the operation of the security system  100  using the electronic paper  1 A according to the first embodiment will be described.  
         [0000]     ( 1 ) Writing of Image  
         [0036]     First, an organizer of a presentation writes image data to cartridges  5 A that are the same in number as attendees. That is, the organizer manipulates the input devices of the PC  101  to cause image data read from the storage device  102  to be displayed on the display of the PC  101 . Then, organizer manipulates the input devices to select image data of plural pages to be written to each memory unit  54 . The CPU of the PC  101  transmits the selected image data to the image-writing device  103 .  
         [0037]     The image-writing device  103  writes, via the male connector  52 A, the image data of the plural pages transmitted from the PC  101  to the image data area  54   a  of the memory unit  54  of the cartridge  5 A that is pulled out of each electronic paper  1 A. Further, the image-writing device  103  performs a power check on the power source nit  53  and, in the event of insufficient charging, turns on the lamp to indicate it. In the case of insufficient charging, image-writing device  103  recharges the power source unit  53 . Alternatively, the power source unit  53  may be replaced by a charged-up one. This eliminates a probability that an electronic paper  1 A is rendered unusable due to power-down during its use.  
         [0000]     (2) Writing of ID  
         [0038]     In the entrance gate section  110 , the ID writing device  111  writes an ID to an electronic paper  1 A and hands over it to each attendee. More specifically, the organizer manipulates the input devices of the PC  101  to cause an ID list read from the storage device  102  to be displayed on the display of the PC  101 . Then, the organizer manipulates the input devices to select an ID to be written to the memory unit  54 . The CPU of the PC  101  transmits the selected ID to the ID writing device  111 . The ID writing device  111  writes the ID transmitted from the PC  101  to the ID area  54   b  of the memory unit  54  via the wireless IC tag  51 , and transmits an ID writing completion signal to the PC  101 . Upon receiving the ID writing completion signal from the ID writing device  111 , the PC  101  opens the entrance gate  112 . The organizer attaches the ID-written cartridge  5 A to the main unit  2  and hands over the electronic paper  1 A to an attendee Pb. The attendee Pb passes through the entrance gate  112  bringing the electronic paper  1 A, enters the electronic paper use space  200 , and sits down. Each main unit  2  may be handed over to an attendee either inside or outside the use space  200 .  
         [0000]     (3) Presentation  
         [0039]     A presenter Pa faces attendees Pb and gives a presentation to the attendees Pb while displaying images of a presentation materials etc. on the presentation display  202 . Having an electronic paper  1 A, each attendee Pb manipulates the page-down key  6  of the electronic paper  1 A to cause the controller  4  to switch the display of the display unit  3  according to the progress of the presentation. Each attendee joins a discussion or the like on the basis of the information displayed on the electronic paper  1 A and the presentation display  202 .  
         [0040]     The information to be displayed on the electronic paper  1 A and that to be displayed on the presentation display  202  need not always be identical. This allows the presenter Pa to separately use information to be used for the presentation by himself or herself and information to be presented to the attendees Pb to allow them to be involved in the meeting. For example, to check the degree of understanding of a lecture given by the presenter Pa, the information to be displayed on the presentation display  202  and that to be displayed on the electronic papers  1 A may be the contents of the lecture and problems of a check test, respectively.  
         [0000]     (4) Collection of Cartridges and Reading of IDs  
         [0041]     After completion of the presentation, the organizer requests each attendee Pb to pull out the cartridge  5 A from the main unit  2 . When the cartridge  5 A is pulled out of the main unit  2 , the display unit  3  no longer receives power and hence the display on the display unit  3  disappears.  
         [0042]     Each attendee leaves his or her seat with the main unit  2  left on the desk and inputs the cartridge  5 A to the cartridge collecting section  122  installed in the exit gate section  120  through the insertion slot (not shown). The ID reading device  121  reads, via the wireless IC tag  51 , the ID from the ID area  54   b  of the cartridge  5 A that has been input through the insertion slot, and transmits the ID to the PC  101 .  
         [0043]     The CPU of the PC  101  judges whether the ID transmitted from the ID reading device  121  coincides with one of the IDs in the ID list that is stored in the storage device  102 . If ID coincidence is found, the PC opens the exit gate  123 . The attendee  123  exits through the exit gate  123 . The cartridge  5 A is put into the collection box (not shown) of the cartridge collecting section  122 .  
         [0044]     If the read-out ID is not found in the ID list or the ID cannot be read, the exit gate  123  is not opened and the cartridge  5 A is ejected through an ejection slot.  
       Advantages of First Embodiment  
       [0045]     The first embodiment provides the following advantages:  
         [0046]     (a) When the cartridge  5 A is removed from the main unit  2 , power is no longer supplied to the controller  4  and the display unit  3  is rendered incapable of display. Further, the cartridge  5 A having the memory unit  54  is subjected to collection. Therefore, secret information on the electronic paper  1 A can be prevented from being taken out.  
         [0047]     (b) Each attendee cannot exit without detaching the cartridge  5 A from the main unit  2 , which prevents taking-out of the electronic paper  1 A.  
         [0048]     (c) Display on each electronic paper  1 A is performed via a signal line on the basis of image data stored in the memory unit  54  of the electronic paper  1 A, which makes the probability of data tapping in or in the vicinity of the use space  200  lower than in the conventional case of data delivery by radio and hence enables realization of high security.  
         [0049]     (d) Each electronic paper  1 A is of a stand-along type and hence its display is not linked with the display of the presentation display  202 . And part of or a summarized version of the information used by the presenter Pa for the presentation is displayed on each electronic paper  1 A. Therefore, the number of pages to be displayed on each electronic paper  1 A is reduced and hence the memory capacity of the memory unit  54  and the load of the power source unit  53  can be reduced.  
         [0050]     (e) The information to be displayed on each electronic paper  1 A is written to the memory unit  54  in advance, which makes it possible to supply a minimum necessary amount of secret data to each attendee.  
         [0051]     To increase the security, the cartridge  5 A may be configured so that the image data in the memory unit  54  are erased automatically as soon as the cartridge  5 A is removed from the main unit  2 . For example, the cartridge  5 A may be configured in such a manner that the memory unit  54  employs a volatile memory and the supply of power from the power source unit  53  to the volatile memory is stopped as soon as the cartridge  5 A is removed from the main unit  2 .  
       Second Embodiment  
       [0052]      FIG. 5A  shows an electronic paper according to a second embodiment of the invention, and  FIG. 5B  is a sectional view taken along line Vb-Vb in  FIG. 5A . This electronic paper  1 B is configured in the same manner as the electronic paper  1 A according to the first embodiment except for a cartridge  5 B. In these figures, an electric connection portion between the cartridge  5 B and the main unit  2  is omitted.  
         [0053]     The cartridge  5 B is equipped with a thin, circular case  50  which is thinner than the main unit  2 , a power source unit  53  and a memory unit  54  disposed inside the case  50 , plural pins  55  which are led out of the power source unit  53  and the memory unit  54  and are exposed from the bottom surface of the cartridge  5 B, and a cap  56  for preventing the case  50  from coming off.  
         [0054]     Made of an elastic material such as rubber, the cap  56  fits into the main unit  2  and prevents the case  50  from coming off by its elasticity. An alternative structure is possible in which the cap  56  is made of a resin or a metal and is pressed against the case  50  by a spring member.  
         [0055]     The main unit  2  has a fitting recess  21  to be fitted with the case  50  and the cap  56  and connection holes  22  into which the pins  55  of the cartridge  5 B are to be inserted. When the pins  55  are connected to the connection holes  21  and the case  50  and the cap  56  are fitted into the fitting recess  21 , the power source unit  53  and the memory unit  54  are electrically connected to the display unit  3  and the controller  4  via the pins  55  and the connection holes  22 .  
         [0056]     According to the second embodiment, as in the case of the first embodiment, leakage of information displayed on the electronic paper  1 B and taking-out of the electronic paper  1 B can be prevented. Further, having a thin, circular shape, the cartridge  5 B can easily be input through the insertion slot of the exit gate section  120 .  
       Third Embodiment  
       [0057]      FIG. 6  shows an electronic paper according to a third embodiment of the invention. The third embodiment is the same as the first embodiment except that in the first embodiment the memory unit is moved from the cartridge  5 A to the main unit  2 . In this figure, an electric connection portion between a cartridge  5 C and the main unit  2  is omitted.  
         [0058]     It is preferable that a memory unit  7  disposed in the main unit  2  be a volatile memory. With this measure, when the cartridge  5 C having the power source unit  53  is removed from the main unit  2 , power is no longer supplied to the memory unit  7  and hence the storage content of the memory unit  7  can be erased. Alternatively, the memory unit  7  may be a nonvolatile memory. In this case, an appropriate operation is such that the controller  4  detects removal of the cartridge  5 C from the main unit  2  and erases the storage content of the memory unit  7 .  
         [0059]     In this embodiment, whereas image data are stored in the memory unit  7 , an ID is stored in the wireless IC tag  51  by the ID writing device  111 .  
         [0060]     The third embodiment provides the following advantages:  
         [0061]     (a) When the cartridge  5 C is removed from the main unit  2 , power is no longer supplied to the controller  4  and the display unit  3  is rendered incapable of display. And the storage content of the memory unit  7  disappears because it employs a volatile memory. Therefore, secret information on the electronic paper  1 C can be prevented from being taken out.  
         [0062]     (b) Each attendee cannot exit without detaching the cartridge  5 C from the main unit  2 , which prevents taking-out of the electronic paper  1 C.  
         [0063]     (c) The cartridge  5 C is equipped with only the wireless IC tag  51  and the power source unit  53 , which makes it possible to reduce the cost of the cartridge  5 C.  
       Fourth Embodiment  
       [0064]      FIG. 7  shows an electronic paper according to a fourth embodiment of the invention. The fourth embodiment is same as the first embodiment except that the power source unit  53  is removed from the cartridge  5 A of the first embodiment and a power source unit  58  is provided in the main unit  2 . In this figure, an electric connection portion between a cartridge  5 D and the main unit  2  is omitted.  
         [0065]     The controller  4  of this embodiment is configured so as to erase the display on the display unit  3  upon detecting removal of the cartridge  5 D from the main unit  2 .  
         [0066]     The fourth embodiment provides the following advantages:  
         [0067]     (a) When the cartridge  5 D is removed from the main unit  2 , the controller  4  controls the display unit  3  so as to erase its display. Further, the cartridge  5 D having the memory unit  54  is subjected to collection. Therefore, secret information on the electronic paper  1 D can be prevented from being taken out.  
         [0068]     (b) Each attendee cannot exit without detaching the cartridge  5 D from the main unit  2 , which prevents taking-out of the electronic paper  1 D.  
         [0069]     (c) The cartridge  5 C is equipped with only the wireless IC tag  51  and the memory unit  54 , which makes it possible to reduce the cost of the cartridge  5 D.  
         [0070]     The invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit and scope of the invention. The components of the embodiments can be combined with each other arbitrarily without departing from the spirit and scope of the invention.  
         [0071]     The entire disclosure of Japanese Patent Application No. 2005-179077 filed on Jun. 20, 2005 including specification, claims, drawings and abstract is incorporated herein by reference in its entirety.