Image displaying method and image forming apparatus utilizing a reversible image display medium having a high resolution image display

Abstract

A method and apparatus capable of displaying a high-quality image using a reversible image display medium in which a cell(s) formed between two substrates accommodates at least two kinds of frictionally chargeable dry developing particles having different chargeable polarities and different optical reflection densities. in image display, an electric field strength of, e.g., 0.3 V/μm to 3.0 V/μm is applied to the developer. An oscillating force (e.g. oscillating magnetic filed) is applicable and the oscillating force is substantially stopped during application of the electrostatic field. After completion of the electrostatic field, the surface of the medium on the image observation side may be charged to a potential holding the displayed image. Optionally before image display, an alternating electric field may be applied to stir the developer for initialization of the medium.

1 . A method for displaying an image, comprising the steps of: 
 providing a reversible image display medium comprising;    two substrates opposed to each other with a gap therebetween;    one or more developer accommodating cells formed between the two substrates, each having a periphery surrounded by a partition wall; and    a dry developer contained in each of the cells, the dry developer containing at least two kinds of frictionally chargeable dry developing particles having different chargeable polarities and different optical reflection densities; and    displaying an image by driving the frictionally charged developing particles having different chargeable polarities in an electrostatic field corresponding to the image to be displayed, wherein    in the image display step, strength of the electric field to be applied to the developer is 0.3 V/μm to 3.0 V/μm.    
   
   
       2 . The method according to  claim 1 , wherein at least one kind of the developing particles among the dry developing particles are magnetic particles, and a magnetic stirring force is applied to the developer by a magnetic field in relation to driving the developing particles in the electrostatic field.  
   
   
       3 - 7 . (canceled)  
   
   
       8 . A method for displaying an image, comprising the steps of: 
 providing a reversible image display medium comprising;    two substrates opposed to each other with a gap therebetween;    one or more developer accommodating cells formed between the two substrates, each having a periphery surrounded by a partition wall; and    a dry developer contained in each of the cells, the dry developer containing at least two kinds of frictionally chargeable dry developing particles having different chargeable polarities and different optical reflection densities;    displaying an image by applying from outside an electrostatic field corresponding to the image to be displayed to the frictionally charged developing particles having different chargeable polarities to drive the developing particles for image display; and    charging a surface of the image display medium on image observation side to carry a potential holding the displayed image after completion of application of the electrostatic field.    
   
   
       9 . (canceled)  
   
   
       10 . The method according to  claim 8 , wherein the potential holding the displayed image is 100 V or less in terms of absolute value.  
   
   
       11 . A method for displaying an image, comprising the steps of: 
 providing a reversible image display medium comprising;    two substrates opposed to each other with a gap therebetween;    one or more developer accommodating cells formed between the two substrates, each having a periphery surrounded by a partition wall; and    a dry developer contained in each of the cell(s), the dry developer containing at least two kinds of frictionally chargeable dry developing particles having different chargeable polarities and different optical reflection densities;    initializing the reversible image display medium by stirring the developer in the image display medium before image display on the display medium; and    displaying an image by driving the frictionally charged dry developing particles having different chargeable polarities within the above-initialized reversible image display medium in an electrostatic field corresponding to the image to be displayed.    
   
   
       12 . The method according to  claim 11 , wherein the initialization is conducted by application of an alternating electric field to the developer in the medium.  
   
   
       13 . The method according to  claim 12 , wherein strength of the alternating electric field to be applied to the developer is 0.5 V/μm or more.  
   
   
       14 . The method according to  claim 12 , wherein frequency of the alternating electric field to be applied to the developer is 5 kHz or less.  
   
   
       15 . The method according to  claim 12 , wherein the application of alternating electric field to the developer in the medium is performed to satisfy a condition: (frequency[Hz] of alternating electric field.times.time[second(s)] for application of alternating electric field)=20 or more.  
   
   
       16 . An image forming apparatus which displays an image using a reversible image display medium comprising: two substrates opposed to each other with a gap therebetween; one or more developer accommodating cells formed between the two substrates, each having a periphery surrounded by a partition wall; and a dry developer contained in each of the cell(s), the dry developer containing at least two kinds of frictionally chargeable dry developing particles having different chargeable polarities and different optical reflection densities, 
 the apparatus comprising:    a device for initializing the reversible image display medium by stirring the developer in the image display medium before image display on the medium; and    an image forming portion for displaying an image by driving the frictionally charged developing particles having different chargeable polarities within the initialized medium in an electrostatic field corresponding to the image to be displayed.    
   
   
       17 . The image forming apparatus according to  claim 16 , wherein the initializing device is one in which the developer is stirred by application of an alternating electric field to the developer in the reversible image display medium.  
   
   
       18 . The image forming apparatus according to  claim 17 , wherein the initializing device applies the alternating electric field having an electric field strength of 0.5 V/μm or more to the developer.  
   
   
       19 . The image forming apparatus according to  claim 17 , wherein the initializing device applies the alternating electric field having a frequency of 5 kHz or less to the developer.  
   
   
       20 . The image forming apparatus according to  claim 17 , wherein the initializing device applies the alternating electric field to the developer to satisfy a condition: (frequency[Hz] of alternating electric field) X (time[second(s)] for application of alternating electric field)=20 or more.  
   
   
       21 - 36 . (canceled)