Image display medium driving method and image display device

• US 20020033793A1
• Filed: 09/20/2001
• Published: 03/21/2002
• Est. Priority Date: 09/21/2000
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Inventors: Machida, Yoshinori, Shigehiro, Kiyoshi, Sakamaki, Motohiko, Matsunaga, Takeshi, Yamaguchi, Yoshiro
• Granted Patent: US 6,657,612 B2
• Time in Patent Office: Days
• US Class Current: 345/107
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1677 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167

Abstract

An image display device and driving method thereof produce a multiple color display without inviting a drop in resolution, or with the drop in resolution suppressed. Between a back substrate and a transparent display substrate forming the image display surface, the image display part has in order a display electrode on which a transparent surface coating is formed, a spacer, and a back electrode on which a surface coating is formed. A voltage control part applies a −350 V dc voltage, for example, to the display electrode to display black by black particles, applies an approximately +350 dc voltage to the display electrode to display white by white particles, and applies, for example, a +/−500 V particle drive voltage pulse repeatedly to the display electrode to make the black and white particles clump together inside the unit cell, thereby making the unit cell transparent to produce a transparent display.

Claims

1. A driving method for an image display medium, the image display medium having a plurality of facing substrates of which at least a display-side substrate is transparent, a unit cell delimited between the substrates, and at least two types of particle groups of different color and charge characteristics sealed inside the unit cells, the driving method comprising the steps of:

producing a color display by applying a particle drive voltage pulse of a saturation voltage, the saturation voltage being high enough to saturate the color density of the at least one particle group of the at least two particle group types that moves to the display-side substrate as a result of a field produced by applying voltage to a unit cell; and

producing a transparent display by applying a particle drive voltage pulse of an absolute voltage greater than the saturation voltage so that the two particle group types inside the unit cells agglomerate and make the unit cell transparent.

2. The image display medium driving method as described in claim 1, wherein to produce the transparent display, a particle drive voltage pulse of a frequency higher than the frequency of the saturation voltage particle drive voltage pulse is applied.

3. The image display medium driving method as described in claim 1, wherein to cancel the transparent display, a particle drive voltage pulse of a voltage lower than the voltage causing particle groups to agglomerate, and a frequency higher than the frequency of the saturation voltage particle drive voltage pulse, is applied.

5. The image display medium driving method as described in claim 2, wherein to produce the transparent display, a particle drive voltage pulse of a frequency higher than the frequency of the saturation voltage particle drive voltage pulse is applied.

6. The image display medium driving method as described in claim 2, wherein to cancel the transparent display, a particle drive voltage pulse of a voltage lower than the voltage causing particle groups to agglomerate, and a frequency higher than the frequency of the saturation voltage particle drive voltage pulse, is applied.

4. A driving method for an image display medium, the image display medium having a transparent display substrate, a back substrate disposed opposite the display substrate with a gap therebetween, and two types of particles of different color and charge characteristics sealed between the substrates so that particles can move between the substrates when a field is applied therebetween, wherein the color particles are driven by means of at least two particle drive voltage pulses, including:

a first particle drive voltage pulse for producing a color display by applying a saturation voltage causing particles of at least one color to adhere to the display substrate, the saturation voltage being high enough so that the color density of particles of the one color of the at least two particle types is saturated; and

a second particle drive voltage pulse for producing a transparent display by causing particles to agglomerate.

7. An image display device comprising:

a plurality of facing substrates of which at least a display-side substrate is transparent;

a support member disposed between each of the plural substrates and delimiting a unit cell;

particle groups of at least two types sealed in the unit cell, having different color and charge characteristics, and moving in mutually opposite directions between the substrates in response to an applied field;

a pair of electrodes disposed between the plurality of facing substrates to form a field in the unit cell; and

display control means for displaying the color of at least one of the particle groups by applying a particle drive voltage pulse of a saturation voltage, the saturation voltage being high enough so that the color of the at least one particle group of the at least two particle groups that moves to the display side substrate due to the applied field reaches a saturation density, and producing a transparent display by applying a particle drive voltage pulse of an absolute voltage greater than the saturation voltage so that the two particle group types inside the unit cells agglomerate and make the unit cell transparent.

8. The image display device as described in claim 7, wherein the display control means applies a particle drive voltage pulse of a frequency higher than the frequency of the saturation voltage particle drive voltage pulse when producing the transparent display.

9. The image display device as described in claim 7, wherein the display control means applies a particle drive voltage pulse of a voltage lower than the voltage causing particle groups to agglomerate, and a frequency higher than the frequency of the saturation voltage particle drive voltage pulse, to cancel the transparent display.

10. The image display device as described in claim 7, wherein the color of one substrate of a facing pair of substrates in the plural substrates is different from the color of either of the at least two types of particle groups.

11. The image display device as described in claim 7, wherein a plurality of said unit cells are disposed between said facing plural substrates,

a filter of a specific color is disposed to each unit cell, and

the plural unit cells having different color filters are driven as a single pixel unit to produce a color display.

12. The image display device as described in claim 7, comprising unit cells having at least two types of particle groups sealed therein disposed between three or more parallel substrates having gaps therebetween, wherein stacked unit cells in upper and lower layers form one display cell, and the colors of the at least two types of particles sealed in each of the stacked unit cells are all different.

13. The image display device as described in claim 7, further comprising a color filter disposed to the lowest layer substrate in the display cell, wherein the color of particles sealed in the unit cell on the upper layer, the color of particles sealed in the unit cell on the lower layer, and the color of the color filter are all different.

14. The image display device as described in claim 7, wherein all substrates are transparent, and light emitting means for emitting light toward the display-side substrate from back-side substrate is further disposed behind the back substrate.