Rewritable thin image display sheet, image display apparatus and image display system

Abstract

Discloses is a rewritable thin image display sheet, an image display apparatus and an image display system. In the image display system, a low-melting-point wax 18 with a magnetic powder 16 dispersed therein is held between a heat-generation layer 12 and a transparent layer 14 which are disposed spaced apart from one another, and a zone of the low-melting-point wax 18 corresponding to a pixel for image display is selectively heated and molted by the heat-generation layer 12 . Then, the magnetic powder 16 in the molten zone is displaced toward the transparent layer 14 so as to display a given image on the transparent layer. The rewritable thin image display sheet, the image display apparatus and the image display system can reliably display an image in a rewritable state while achieving a significantly simplified structure.

1 . An image display apparatus for displaying an image in a rewritable state on an image display sheet including: a base layer; a transparent layer disposed apart from said base layer by a given distance; and a medium which is filled in the space between said base layer and said transparent layer while containing a magnetic powder dispersed therein, and adapted to be changeable between a first phase where said magnetic powder is allowed to be displaced and a second phase where said magnetic powder is prohibited from being displaced, said image display apparatus comprising:
 phase change means for allowing a zone of said medium corresponding to a pixel to be selectively changed from said second phase into said first phase; and   displacement means for allowing the magnetic powder dispersed in said medium zone changed into said first phase to be displaced toward said transparent layer, whereby a given image is displayed on said image display sheet in accordance with said displaced magnetic powder on said transparent layer.   
   
   
       2 . The image display apparatus as defined in  claim 1 , wherein:
 said medium is made of a low-temperature-melting material which exhibits a liquid phase as said first phase at a high temperature and a solid phase as said second phase at a low temperature; and   said phase change means is heating/melting means for heating said medium up to said high temperature.   
   
   
       3 . The image display apparatus as defined in  claim 2 , wherein said base layer includes a resistive layer having a given electrical resistance, and an electrode layer disposed to cover a surface of said resistive layer on the side of said transparent layer. 
   
   
       4 . The image display apparatus as defined in  claim 3 , wherein said electrode layer is an overall electrode covering over the entire surface of said resistive layer on the side of said transparent layer. 
   
   
       5 . The image display apparatus as defined in  claim 4 , wherein said heating/melting means includes current supply means for passing a current through an arbitrarily selected region of said resistive layer to selectively generate heat in said current-passing region of said resistive layer. 
   
   
       6 . The image display apparatus as defined in  claim 5 , wherein said current supply means includes a current supply head, wherein said current supply means is adapted to pass a current between a region of said resistive layer in contact with said current supply head and said electrode layer so as to selectively generate heat in said current-passing region of said resistive layer. 
   
   
       7 . The image display apparatus as defined in  claim 2 , wherein said base layer includes a resistive layer having a given electrical resistance, and a pair of electrode layers each disposed to cover a corresponding one of the opposite surfaces of said resistive layer and formed with a matrix-shaped conductive pattern, wherein said respective conductive patterns of said electrode layers have plural pairs of opposed intersection points to be selectively supplied with a current therebetween, whereby a current is passed through a region of said resistive layer located between the selected intersection points of said respective conductive patterns to selectively generate heat in said current-passing region of said resistive layer. 
   
   
       8 . The image display apparatus as defined in  claim 2 , wherein said displacement means is adapted to displace said magnetic powder in accordance with a magnetic force. 
   
   
       9 . The image display apparatus as defined in  claim 8 , wherein said displacement means includes a permanent magnet disposed on the side of said transparent layer. 
   
   
       10 . The image display apparatus as defined in  claim 8 , wherein said displacement means includes a magnetic head having an electromagnet disposed on the side of said transparent layer. 
   
   
       11 . The image display apparatus as defined in  claim 10 , wherein said electromagnet is adapted to vary said magnetic force depending on the value of current to be supplied thereto. 
   
   
       12 . The image display apparatus as defined in  claim 2 , wherein:
 said heating/melting means is disposed on the side of said base layer; and   said displacement means is disposed on the side of said transparent layer in opposed relation to said heating/melting means while interposing said low-temperature-melting material between said heating/melting means and said displacement means.   
   
   
       13 . The image display apparatus as defined in  claim 12 , wherein said displacement means is disposed spaced apart from said transparent layer. 
   
   
       14 . The image display apparatus as defined in  claim 2 , wherein said base layer is composed of a transparent layer. 
   
   
       15 . The image display apparatus as defined in  claim 2 , which further includes cooling means for cooling and solidifying said low-temperature-melting material in a liquid phase. 
   
   
       16 . The image display apparatus as defined in  claim 15 , wherein said cooling means is disposed adjacent to said displacement means. 
   
   
       17 . The image display apparatus as defined in  claim 15 , wherein said cooling means is disposed in contactable relation to said transparent layer. 
   
   
       18 . The image display apparatus as defined in  claim 2 , which further includes image erasing means for erasing an image displayed on said image display sheet. 
   
   
       19 . The image display apparatus as defined in  claim 18 , wherein said image erasing means includes a magnetic erasing head disposed on the side of said base layer, and a selective erasing head disposed on the side of said transparent layer. 
   
   
       20 . The image display apparatus as defined in  claim 19 , wherein said selective erasing head is adapted to be moved in synchronous with said magnetic erasing head. 
   
   
       21 . The image display apparatus as defined in  claim 19 , wherein said selective erasing head includes an infrared lamp, and a reflecting mirror for reflecting light and heat emitted from said infrared lamp toward said image display sheet. 
   
   
       22 . The image display apparatus as defined in  claim 21 , wherein said reflecting mirror is a parabolic mirror. 
   
   
       23 . The image display apparatus as defined in  claim 21 , wherein said reflecting mirror is an elliptic mirror. 
   
   
       24 . The image display apparatus as defined in  claim 19 , wherein said selective erasing mirror is adapted to be movable along a direction orthogonal to said image display sheet. 
   
   
       25 . The image display apparatus as defined in  claim 2 , wherein said heating/melting means includes a laser system. 
   
   
       26 . An image display apparatus for displaying an image in a rewritable state on at least either one of the opposite surfaces of an image display sheet including: a first transparent layer; a second transparent layer disposed apart from said first transparent layer by a given distance; an intermediate heat-generation layer disposed between said first and second transparent layers and adapted to generate heat at an arbitrary position thereof; a first low-temperature-melting material filled in the space between said intermediate heat-generation layer and said first transparent layer while containing a magnetic powder dispersed therein; and a second low-temperature-melting material filled in the space between said intermediate heat-generation layer and said second transparent layer while containing a magnetic powder dispersed therein; said image display apparatus comprising:
 heating/melting means for heating a region of said intermediate heat-generation layer corresponding to a pixel to melt said first low-temperature-melting material; and   displacement means for displacing the magnetic powder dispersed in said molten zone of said first low-temperature-melting material, toward said first transparent layer, whereby a given image is displayed on said first transparent layer of said image display sheet in accordance with said displaced magnetic powder on said first transparent layer.   
   
   
       27 . The image display apparatus as defined in  claim 26 , wherein said displacement means is adapted to displace said magnetic powder in accordance with a magnetic force. 
   
   
       28 . The image display apparatus as defined in  claim 27 , wherein said displacement means includes a permanent magnet disposed on the side of said second transparent layer. 
   
   
       29 . The image display apparatus as defined in  claim 27 , wherein said displacement means includes a magnetic head having an electromagnet disposed on the side of said second transparent layer. 
   
   
       30 . The image display apparatus as defined in  claim 29 , wherein said electromagnet is adapted to vary said magnetic force depending on the value of current to be supplied thereto. 
   
   
       31 . The image display apparatus as defined in  claim 27 , wherein said displacement means is disposed spaced apart from said second transparent layer. 
   
   
       32 . The image display apparatus as defined in  claim 26 , which further includes cooling means for cooling and solidifying said molten first low-temperature-melting material. 
   
   
       33 . The image display apparatus as defined in  claim 32 , wherein said cooling means is disposed in opposed relation to said displacement means while interposing said image display sheet therebetween. 
   
   
       34 . The image display apparatus as defined in  claim 33 , wherein said cooling means is disposed in contactable relation to said first transparent layer. 
   
   
       35 . An image display system comprising:
 holding a low-temperature-melting material with a magnetic powder dispersed therein, between a heat-generation layer and a transparent layer which are disposed spaced apart from one another;   allowing a zone of said low-temperature-melting material corresponding to an image display to be selectively heated and molted by said heat-generation layer; and   displacing the magnetic powder in said molten zone toward said transparent layer so as to display a given image on said transparent layer.   
   
   
       36 . The image display system as defined in  claim 35 , wherein said magnetic powder in said molten zone is displaced toward said transparent layer by means of a magnetic force. 
   
   
       37 . The image display system as defined in  claim 35 , wherein said heat-generation layer includes a resistive layer capable of generating heat in response to a current passed therethrough, wherein said zone of said low-temperature-melting material corresponding to a pixel in said image display is heated and molten by said resistive layer. 
   
   
       38 . The image display system as defined in  claim 35 , which including, after the image is displayed in accordance with said displaced magnetic powder, cooling and solidifying said molten zone to fix said image. 
   
   
       39 . The image display system as defined in  claim 38 , which including heating and melting a part of said solidified low-temperature-melting material, and then displacing said magnetic powder on said transparent layer toward said base layer to erase a part of said image. 
   
   
       40 . The image display system as defined in  claim 38 , which including heating and melting said solidified low-temperature-melting material in its entirety, and then displacing said magnetic powder on said transparent layer toward said base layer to erase said image in its entirety.