JP2006276801A - Image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain droplets surely when voltage is not applied with respect to an image display to be used excellently for electronic paper display or the like which uses an electro-wetting phenomenon for moving liquid mass by using an external electric field. <P>SOLUTION: The display is provided with an upper part layer to be a display side and a lower part layer arranged with a display space from the upper part layer. The display space is filled with a colored conductive droplet and oil which does not mix with the droplet or air. While an upper face in the lower part layer on the lower face side of the display space or a lower face in the upper part layer on the upper face side of the display space is provided with a planar electrode, a needle electrode vertically protrudes into the display space from either the upper part layer or the lower part layer. The planar electrode is lipophilic, whereas the needle electrode is hydrophilic. When circuits of the planar electrode and needle electrode are opened and the voltage is not applied, the droplet is held in a state that it adheres surroundings of the needle electrode in the vertical direction in a ball shape. When the voltage is applied at the closure of the circuits, the droplet is displayed in color in a state that it spreads in the horizontal direction on the lower face side or the upper face side in the display space provided with the planar electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image display device, and more particularly to an image display device suitably used for an electronic paper display using an electrowetting phenomenon in which a liquid is moved using an external electric field.

  2. Description of the Related Art Conventionally, an electronic display that performs display using a movement phenomenon of a transparent or colored liquid has been proposed. For example, there are an electroosmosis method and an electrowetting method as a method for moving and displaying a liquid using an external electric field.

The electroosmosis method controls the liquid impregnation rate on the surface of the porous body to scatter external light, controls the light reflectivity and light transmittance for external light, and matches the refractive index of the porous body and the transparent liquid in advance. In addition, when the liquid is filled in the through hole of the porous body, the liquid crystal becomes transparent and a background color is displayed. On the other hand, when the liquid flows out of the through hole, light scattering occurs and the white color is displayed.
The electrowetting method uses a phenomenon in which the liquid is moved along the through-hole by changing the interfacial tension of the liquid by applying an electric field to the liquid in the pores, while the liquid flows out from the pores by removing the electric field. . Specifically, when a voltage is applied to the electrode provided on the inner surface of the pore, the wettability of the liquid with respect to the inner surface of the pore changes due to the generated electric field, and the contact angle of the liquid with respect to the inner surface of the pore decreases. The liquid moves inside. On the other hand, when the electric field with respect to the liquid is removed, the wettability of the liquid with respect to the inner surface of the pore changes, the contact angle increases rapidly, and the liquid flows out from the pore.

  Conventionally, as a display device using electrowetting, Japanese Patent Application Laid-Open No. 10-39800 (Patent Document 1) and Japanese Patent Application Laid-Open No. 9-311643 (Patent Document 2) provide an apparatus shown in FIG. In the sealed space 3 between the two transparent sheets 1 and 2, the apparatus encloses a plurality of sets of small droplets 4A, 4B,... In addition to providing one electrode 5, a low surface energy insulating film 6 is provided on the first electrode 5, and a small area planar high surface energy plate serving as the second electrode 8 is disposed on the upper surface of the insulating film 3. I am letting. In the display device, the circuit between the first electrode 5 and the second electrode 8 is closed and a voltage is applied, and electrolysis is directly applied to the liquid droplets to expand the liquid droplets and display in color. ing.

  Furthermore, as an electronic display using electrowetting, Japanese Patent Application Laid-Open No. 2004-287008 (Patent Document 3) and Japanese Patent Application Laid-Open No. 2004-252444 (Patent Document 4) provide an apparatus shown in FIG. As in FIG. 9, the apparatus encloses the colored droplets 4 in the sealed space 3 formed between the sheets 1 and 2, provides the sheet 1 with the first electrode 5, and the first electrode The second electrode 8 is provided on the insulating film 6 on the surface 5, and the third electrode 9 is provided in an insulating state around the second electrode 8. The third electrode 9 promotes the spherical return of the colored droplet 4. Is.

JP-A-10-39800 Japanese Patent Laid-Open No. 9-311643 JP 2004-287008 A JP 2004-252444 A

In the display device having the configuration disclosed in Patent Documents 1 to 4, it is essential to hold the droplet in a state of being in reliable contact with the electrode while the droplet has a small spherical shape. However, none of the devices of Patent Documents 1 to 4 give sufficient consideration to this droplet retention.
First, Patent Documents 3 and 4 do not describe a droplet holding mechanism that holds a droplet in a small spherical shape when a mechanical impact is applied from the outside.
In Patent Documents 1 and 2, as shown in FIG. 9B, by providing a cavity 10 for each droplet 4 with an acrylic plate or the like and partially encapsulating, mechanical shock can be avoided. ,Are listed.
However, if the droplet itself is not fixed by an effective means, the droplet will be detached from the electrode when there is a mechanical impact, so the electric field in the liquid is disturbed and the electrocapillary phenomenon does not work effectively. Pixels will be generated. As a result, the critical color reproducibility of the display deteriorates.
Since the cavity 10 has a volume that expands the droplet when a voltage is applied, the droplet expands into the cavity 10 when an impact is applied, and cannot be held in a small sphere when no voltage is applied. There is a risk of colored display. Furthermore, when the cavity 10 for storing droplets is provided by an acrylic plate, there is a problem that the light transmittance is lowered and the contrast is lowered.

  The present invention has been made in view of the above problems, and even when an external mechanical shock is applied, the liquid droplet can be retained in a small spherical shape without being detached from the electrode, and the liquid droplet does not hinder the contrast. An object of the present invention is to provide an image display device having a holding function.

In order to solve the above problems, the present invention comprises an upper layer on the display side, and a lower layer disposed with a space for display with the upper layer,
The display space is filled with colored conductive droplets and oil or air that does not mix with the droplets,
While a planar electrode is provided on the upper surface of the lower layer on the lower surface side of the display space or the lower surface of the upper layer on the upper surface side of the display space,
In the display space, needle-like electrodes protrude vertically from the upper layer or the lower layer,
While the planar electrode is oleophilic, the needle electrode is hydrophilic,
When the circuit between the planar electrode and the needle electrode is opened and no voltage is applied, the droplet is held in a spherical shape around the needle electrode in the vertical direction, while the voltage is applied when the circuit is closed. There is provided an image display device characterized in that the liquid droplets are colored and displayed in a state of spreading horizontally on the lower surface side or the upper surface side of the display space provided with the planar electrodes.

As described above, in the present invention, when no voltage is applied, the droplet returns around the needle-like electrode protruding into the display space, and the droplet is attached to the needle-like electrode and held in a spherical shape. Therefore, even if a mechanical impact is applied from the outside, the liquid droplets do not leave the needle-like electrode, and the durability can be improved.
As described above, since one of the pair of electrodes that performs display control by expanding the droplet to expand the surface area and reducing the surface area by reducing the surface to a spherical shape is also used for holding the droplet, There is no need to provide additional means for holding the droplet, and the droplet itself can be attached to the electrode and held. Therefore, the liquid droplet is not detached from the electrode, and the electric field in the liquid is not disturbed, and the deterioration of color reproducibility can be surely prevented. Furthermore, it is not necessary to provide a cavity with an acrylic plate or the like to accommodate droplets as described in Patent Documents 3 and 4, and the contrast is not lowered.

As described above, the planar electrode is made oleophilic, while the needle-like electrode is hydrophilic, specifically, a needle-like electrode made of platinum, copper, or the like, which needs to be conducted to a conductive droplet. The platinum needle and the copper needle are exposed without applying an insulating coating or the like. Note that a thin film of SiO ₂ that can be conductive may be coated by sputtering.
With this configuration, when no electrode is applied, the conductive liquid is repelled by the oleophilic planar electrode, and the liquid droplets can be sucked into the hydrophilic needle electrode at high speed. Can be speeded up.
An insulating film and a water repellent film are sequentially laminated on the surface of the planar electrode. The insulating film preferably contains, for example, parylene or alumina oxide, and the film thickness is preferably about 1 to 0.1 μm. The water repellent film is preferably composed of a fluororesin that becomes a hydrophilic layer when a voltage is applied.

It is preferable that the protrusion dimension L3 of the needle-like electrode protruding in the vertical direction to the display space is 1/4 or more than the vertical dimension L1 of the display space.
The projecting dimension of the needle-like electrode needs to be projected by 1/4 or more in order to attach the droplet to the periphery of the needle-like electrode and keep it in a spherical shape. A necessary insulating space must be provided between them. The upper limit is preferably 9/10 or less because discharge occurs and the insulating film breaks when the distance between the needle electrode and the planar electrode is moderately close.

  The vertical dimension (display space thickness) L1 of the display space and the orthogonal horizontal dimension (display space width) L2 are such that L1: L2 is 1: 200 to 5: 2. It is preferable to set.

Moreover, it is preferable that the said acicular electrode is provided in the center part of the length direction of the said display space extended in a horizontal direction.
This is because when a needle-like electrode is placed in the center of the display space, the droplets attached and held on the needle-like electrode can be quickly expanded on both sides when a voltage is applied, and the display can be switched at high speed. Can do.

It is preferable that a liquid reservoir portion communicating with the display space is provided in the lower layer, and the needle-like electrode protrudes into the display space through the center of the liquid reservoir portion. The liquid reservoir is preferably provided at the center of the lower layer, but may be provided at one end.
When the structure has a liquid reservoir, the liquid can be retained in the liquid reservoir, and the retention of liquid droplets is always increased regardless of the voltage ON / OFF, making it more durable against mechanical impact. It can be. Furthermore, by passing the needle electrode through the center of the liquid reservoir and projecting it into the display space, it is possible to reliably store the liquid droplet in the liquid reservoir with the liquid droplet attached to the needle electrode, Since the droplet diameter in the state where no voltage is applied can be made to correspond to the diameter of the liquid reservoir without depending on the diameter of the droplet itself, the reliability of contrast between the image display and the white display can be improved. it can.

  Furthermore, the droplets adhering to the needle electrode in the liquid reservoir move on the needle electrode when voltage is applied and diffuse to the display surface space, and follow the needle electrode from the liquid reservoir. Since the discharge of the droplet and the accompanying air or oil drawing along the inner wall of the liquid reservoir occur, smooth circulation of the droplet and air or the droplet and oil can be realized. As a result, the resistance applied to the discharge of the liquid droplet from the liquid reservoir is reduced, and a lower voltage drive than before is possible.

In the image display device of the present invention, the upper layer is a substantially transparent layer through which the colored liquid spreading in the display space can be seen through, the planar electrode is a transparent electrode, and is mixed with the colored droplets. The oil or air is not colorless and transparent, and the lower layer is provided with a light scattering layer,
When a voltage is applied in which the droplet spreads horizontally in the display space, the display is colored. On the other hand, when no voltage at which the droplet adheres to the needle electrode is applied, white display is performed by light scattering by the light scattering layer.
Alternatively, instead of providing a light scattering layer in the lower layer, a light scattering material is blended with the oil that does not mix with the colored droplets, and the oil adheres to the needle-like electrode when no voltage is applied. It is good also as a structure which displays white by the light scattering by the inside light-scattering material.

As the conductive droplet, any conductive liquid may be used. However, an ionic liquid which is a room temperature molten salt having thermal stability and does not contain water is preferably used.
Furthermore, the image display device of the present invention may have any configuration of a reflection type, a transmission type provided with a backlight, and a transflective type using both the reflection type and the transmission type.

The display space is separated from the display space of adjacent pixels by a partition.
That is, the colored conductive liquid of each pixel is any one of R, G, and B, and the colored conductive liquid is introduced into the display space and spreads to display a full color image. In addition, the image display apparatus performs full-color moving image display by moving the conductive liquid at high speed.
When it is considered that one pixel is constituted by R, G, and B, a pixel enclosing one colored liquid according to the present invention is a picture element constituting one pixel.

  In the image display device of the present invention, the upper layer and the lower layer are formed into a sheet shape having a thickness of about 10 to 300 μm, and the vertical dimension L1 of the display space is set to about 1 to 500 μm. And a sheet-like image display device.

As described above, the image display device according to the present invention is configured to hold the droplet by adhering to the needle electrode when no voltage is applied, so that the droplet is detached from the needle electrode even when a vibration or impact is applied. Can be suppressed. Therefore, the liquid droplets are not detached from the electrode and the electric field in the liquid is not disturbed, the deterioration of the color reproducibility can be surely prevented, and the durability can be improved.
In addition, since one of the electrodes to which the voltage is applied is also used for holding the droplet, it is not necessary to provide another means for holding the droplet. In addition, the droplet itself can be attached to the electrode and held.

  In addition, when a liquid reservoir portion that communicates with the display space is provided and the needle reservoir electrode protrudes into the display space through the liquid reservoir portion, the liquid reservoir portion adheres to the needle electrode in the liquid reservoir portion and In this case, the droplet diameter when no voltage is applied can be defined by the diameter of the liquid reservoir without depending on the droplet itself.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 and 2 show a sheet-like image display device 11 according to the first embodiment.
An upper layer 12 made of a transparent substrate on the display side, and a lower space 14 are stacked with a display space 13 extending in the horizontal direction with the upper layer 12. The lower layer 14 has a structure in which the substrate 15 and the light scatterer 16 are stacked and integrated on the upper surface thereof.
The display space 13 is partitioned by adjacent pixels and partition walls 19 to form a sealed space, and a colored conductive droplet Q and a transparent oil O that does not cross the droplet Q are filled in a sealed state. Yes.

A thin transparent electrode 20 made of ITO is provided on the entire upper surface of the light scatterer 16 on the lower surface side of the display space 13. A transparent insulating film 21 and a water repellent film 22 are sequentially laminated on the entire upper surface of the planar electrode 20.
The insulating film 21 contains parylene or alumina oxide and has a thickness of about 1 to 0.1 μm.
The water repellent film 22 is made of a fluorine resin or the like that becomes a hydrophilic layer when a voltage is applied. In order to enable moving image display, it is necessary to increase the moving speed of the liquid droplets. Therefore, the outermost surface exposed to the display space 13 is hydrophilic when voltage is applied and hydrophobic when voltage is not applied. It is effective to form the water repellent film 22.
Further, a water-repellent film 29 is also provided on a region of the display space 13 excluding the lower surface side where the planar electrode 20 is disposed, that is, on the lower surface of the upper layer 12 on the upper surface side and on the space side inner surface of the partition wall 19.

The needle-like electrode 25 is suspended from the upper layer 12 to the display space 13 at the center position in the length direction of the display space 13, and its tip 25 a is spaced from the water repellent film 22 on the lower surface side of the display space 13. The position is opened. That is, the hydrophilic needle-like electrode 25 is projected from the center of the display space 13 extending in the horizontal direction so as to cross in the vertical direction.
The needle electrode 25 is formed from a hydrophilic conductive wire having a diameter of about 1 μm to 10 μm, and platinum is used in this embodiment.
When the vertical dimension L1 of the display space 13 is set, the protruding dimension L3 of the needle electrode 25 is set to 1/4 or more, and in this embodiment, about 4/5.

The transparent substrate forming the upper layer 12 is made of a glass plate or an insulating resin sheet. However, a white paint may be applied only to a micro portion where the needle-like electrode 25 is provided. A fine line transparent circuit 26 connected to the needle electrode 25 is provided in the upper layer 12.
The substrate 15 of the lower layer 14 is made of the same transparent glass as that of the upper layer 12, but it need not be transparent. The light scatterer 16 laminated on the substrate 15 has a refractive index in the transparent polymer resin sheet so that the surface screen is white like paper when the transparent oil O spreads in the display space 13. Large particles of titanium oxide and alumina, and hollow polymer particles having a small refractive index are included to cause irregular reflection on the display surface side, thereby producing paper-like whiteness.
As the matrix resin of the light scatterer 16, any of thermoplastic resin and thermosetting resin can be used. Epoxy resin, acrylic resin, polyimide resin, polyamide resin, polycarbonate, Teflon (registered trademark), etc. Used. In addition, not only resin but glass, ceramic, etc. may be sufficient.

  The upper layer 12 and the lower layer 14 have a sheet shape of 10 to 300 [mu] m, and the vertical dimension L1 of the display space 13 is 1 to 500 [mu] m, and in this embodiment is about 10 [mu] m. It is said.

As described above, the display space 13 partitions and seals the display space of the adjacent pixels and the partition wall 19, and the adjacent pixels have different colors.
The conductive colored droplet Q has a vapor pressure of zero, is excellent in thermal stability, and has a high conductivity, so that an ionic liquid is preferably used. In this embodiment, a conductive aqueous solution is used. ing.
The colorless and transparent oil O not intermingled with the conductive droplet Q is an insulating oil, and is selected from one or more kinds selected from side chain higher alcohols, side chain higher fatty acids, alkane hydrocarbons, silicone oils, and matching oils. Nonpolar oil is used. Of these oils, silicone oil is preferably used.
The oil O may not be transparent and may be colored in a color different from the droplet Q. Further, instead of the oil O, a gas such as air may be used.

  As shown in the figure, the planar electrode 20 and the needle electrode 25 are connected to a power source 28 via an open / close switch 27 so that a voltage is applied to the electrodes 20 and 25 when the open / close switch 27 is turned on. .

Next, driving of the image display device will be described.
The initial state is the white state shown in FIG. 1, the switch 27 between the planar electrode 20 and the needle electrode 25 is off, and the droplet Q adheres only around the needle electrode 25 and exhibits a spherical shape. Transparent oil O spreads along the planar electrode 20 on the lower side of the display space 13. In this state, the display surface is white due to irregular reflection from the light scatterer 16.
FIG. 2 shows the state in which the switch 27 is turned on, and the droplet Q held around the needle electrode 25 moves to the planar electrode 20 side and enters the display space 13 along the planar electrode 20. It spreads and changes to the colored display attached to the droplet Q.
The surface area of the droplet Q shown in FIG. 2 is about 20 times that of the surface of the droplet Q facing the display side shown in FIG.

  Specifically, when the switch 27 is turned on and a voltage is applied to the planar electrode 20 and the needle electrode 25, the wettability of the droplet Q with respect to the planar electrode 20 changes in the display space 13. That is, ions (charges) of the droplet Q existing in the electric double layer near the surface of the planar electrode 20 are attracted to the surface of the planar electrode 20 by the electric field. The ions (charges) having increased density repel each other, and as a result, the interfacial tension between the droplet Q and the surface of the planar electrode 20 is reduced, and the external tension (solid phase) in which the droplet Q becomes relatively large. Tension between the gas phase and the gas phase), and the droplet Q is moved in the direction of both ends in the length direction of the display space 13. The droplet Q spreads in the display space 13 and the oil O is applied to the droplet Q. Move to the upper layer.

When the switch 25 is turned off, the electric field of the planar electrode 20 is removed, the interfacial tension of the droplet Q is returned to the inherent surface tension of the droplet Q itself, and the droplet Q in the display space 13 is returned. Is pulled back to the needle-like electrode 25 having hydrophilicity, and becomes a spherical shape attached to the peripheral surface of the needle-like electrode 25. Since colored droplets are located only around the needle-like electrode in this way, the colored liquid does not enter the field of view from the display surface side, and white display is performed.
At the time of this white display, the spherical shape is not held only by the surface tension of the droplet itself, but the droplet Q is attached to the needle electrode 25 to hold the droplet in a spherical shape. Even if external vibration or the like is applied, it can be prevented from being separated from the needle electrode 25 and spreading in the display space 13.

By turning the switch 27 off and on in this way, the colored droplets Q are spread and displayed in the display space 13 while the droplets Q are attached to the periphery of the needle-like electrode 25 to form a small sphere. By holding, white display can be obtained.
As described above, the display space 13 is partitioned by the adjacent display space and the partition wall 19, and the display space 13 encloses droplets Q colored in a specific color.
In this embodiment, R (red) droplets, G (green liquid) droplets, and B (blue) droplets are wind-filled in adjacent display spaces, and full-color image display is performed in RGB display. ing.

"Example 1"
The image display device of the first embodiment was created by the following manufacturing process.
A light scatterer 16 made of E-60 (trade name) manufactured by Toray Industries, Inc. was laminated and fixed on the surface of a non-alkali glass substrate 15 (manufactured by Asahi Glass) having a thickness of 0.7 mm of the lower layer 14. The light scatterer 16 has a thickness of 50 μm and includes an air layer in a polyester resin, and white color is expressed by a difference in refractive index between air and the polyester resin.
A planar electrode 20 made of a planar ITO film having a thickness of 170 nm was adhered to the surface of the light scatterer 16 with a UV curable adhesive. An insulating film 21 made of a parylene film having a thickness of 1 μm was formed on the surface of the planar electrode 20 made of the ITO film. Next, a water repellent film 22 having a thickness of 20 nm was formed on the surface of the insulating film 21 using FG-5010 manufactured by Fluoro Technology.

A white partition wall 19 having a height of 10 μm was formed on the surface of the lower layer 14 using a white UV curable resin by an inkjet method to form a display space 13.
The display space was filled with color droplets Q (1 mM / L + magenta 3 wt%) composed of transparent silicone oil and a conductive aqueous solution in which pigments were dispersed and colored. The droplet diameter was 2 mm.

The transparent glass substrate of the upper layer 12 is a non-alkali glass substrate (manufactured by Asahi Glass) having a thickness of 0.7 μm, and an electrode circuit made of a transparent thin wire is provided inside the substrate and connected to the tip of the electrode circuit. The base of the needle electrode 25 made of platinum having a diameter of 5 μm was embedded and fixed in the substrate. The needle-like electrode 25 had a protruding dimension of 2 μm from the substrate 12.
The substrate of the upper layer 12 and the upper end of the partition wall 19 were adhered and fixed, and the needle electrode 25 and the planar electrode 20 were connected to the power source 28 via the switch 27.

A droplet was moved by applying an AC voltage of 60 V at a frequency of 1 KHz from the power source 28 to the planar electrode 20 and the needle electrode 25.
The contrast ratio between the state where the droplet was held on the needle electrode when no voltage was applied and the state where the droplet spread along the planar electrode when the voltage was applied was measured.
During the measurement, variable frequency vibration (10-57 Hz / 0.075 mm, 58-500 Hz / 1G sweep time 11 minutes, 2 h / ± (X, Y, Z)) and impact (490 m / s 2, 11 msec, 1 time / ± (X, Y, Z)) was applied, and the contrast ratio was compared and evaluated with and without vibration.
The contrast ratio is “display side area in a state where a droplet spreads / display side area when attached around a needle electrode”.

As a result, the average contrast ratio without vibration was 20. On the other hand, the average contrast ratio with vibration was 19.
From this measurement result, even when external vibration or impact is applied, droplets are securely held around the needle-like electrode when no voltage is applied, and the same contrast ratio can be obtained as when there is no vibration. Was confirmed.

2 and 3 show the second embodiment, and the difference from the first embodiment is that the needle-like electrode 25 protrudes upward from the lower layer 14 side and protrudes into the display space 13. .
In the second embodiment, the line electrode 30 is provided on the surface of the substrate 15 of the lower layer 14, the lower end of the needle electrode 25 is connected to the center position of the line electrode 30, and the needle electrode 25 protrudes upward. is doing. On the upper surface side of the substrate 15, a light scatterer 16 is laminated as in the first embodiment, and the needle-like electrode 25 is passed through the light scatterer 16. Although the planar electrode 20 is formed on the upper surface of the light scatterer 16, the light scatterer 16 is interposed between the planar electrode 20 and the needle electrode 25 for insulation.
As in the first embodiment, an insulating film 21 and a water repellent film 22 are laminated on the upper surface of the planar electrode 20, and the needle-like electrode 25 penetrates the water repellent film 22 and enters the display space 13 upward from below. It is protruding. Since other configurations are the same as those of the first embodiment, the same reference numerals are given and description thereof is omitted.

The operation of the colored droplet Q in the second embodiment is the same as that in the first embodiment. FIG. 3 shows that the switch 27 is off and no voltage is applied, and the colored droplet Q adheres around the needle electrode 25. It is held in a small droplet state.
On the other hand, when the switch 27 shown in FIG. 4 is turned on, the droplet Q spreads along the planar electrode 20 on the lower surface side of the display space 13 and is colored.

"Example 2"
An apparatus having the configuration of the second embodiment was created in the same manner as in Example 1.
In addition, the material used was the same as in Experimental Example 1, the color droplets were KCL aqueous solution 1 mM / L + magenta 3 wt%, and silicone oil was used as the oil.
In the evaluation test, a 60 V AC voltage is applied to the planar electrode 20 and the needle electrode 25 from the power source 28 to move the droplet, and the droplet is held on the needle electrode when no voltage is applied. The contrast ratio between the state and the state where the droplet spreads along the planar electrode when a voltage was applied was measured. During measurement, variable frequency vibration (10-57 Hz / 0.075 mm, 58-500 Hz / 1G sweep time 11 minutes, 2 h / ± (X, Y, Z)) and impact (490 m / s 2, 11 msec, 1 time / ± (X, Y, Z)) was loaded, and the contrast ratio was compared and evaluated when there was vibration and when there was no vibration.
As a result, as in Example 1, the average contrast ratio without vibration was 20. On the other hand, the average contrast ratio with vibration is 19, and even when external vibration or impact is applied, when no voltage is applied, the liquid droplets are securely held around the needle-shaped electrode, and there is no vibration. It was confirmed that a contrast ratio was obtained in the same manner as.

5 and 6 show a third embodiment.
In the third embodiment, the light scatterer 16 and the liquid reservoir 35 having a circular cross section at the center of the planar electrode 20 on the upper surface, the insulating film 21 and the water repellent film 22 are provided, and the liquid reservoir 35 is provided at the center of the liquid reservoir 35. The needle-like electrode 25 was inserted and protruded into the display space 13.
In 3rd Embodiment, the acicular electrode 25 was formed from the copper wire.
The other structure is the same as that of 2nd Embodiment, the same member attaches | subjects the same code | symbol and abbreviate | omits description.

  The display operation is the same as in the first and second embodiments. FIG. 5 shows a white display state in which the switch 27 is off and no voltage is applied to the electrodes 20 and 25. FIG. A voltage is applied to and a colored display state is shown.

With the structure having the liquid reservoir 35, the conductive colored droplet Q can be adhered and held around the needle-like electrode 25 in the liquid reservoir 35, and the droplet Q when no voltage is applied can be held. The holding force can be further increased, and durability against external vibration and impact can be increased.
In addition, the liquid droplets Q can be reliably accommodated in the liquid reservoir 35, and the diameter of the liquid droplets when no voltage is applied can be made to correspond to the diameter of the liquid reservoir diameter 35 without depending on the diameter of the liquid droplets themselves. Therefore, the reliability of contrast between the image display and the white display can be improved.
Further, the liquid droplets adhering to the needle electrode 25 in the liquid reservoir 35 move on the needle electrode 25 and flow into the display surface space 13 when a voltage is applied, and the needle from the liquid reservoir 35. The droplet Q along the electrode 25 and the accompanying oil Q along the inner wall of the liquid reservoir 35 are rapidly generated, and the smooth circulation of the droplet Q and the oil O can be realized. As a result, the resistance applied to the discharge of the droplet Q from the liquid reservoir 35 is reduced, and low voltage driving is possible.

"Example 3"
An apparatus having the configuration of the third embodiment was created in substantially the same manner as in Example 1. The needle electrode was made of a conductive material.
In addition, the material used was the same as in Experimental Example 1, and the color droplet was KCL aqueous solution 1 mM / L + magenta 3 wt%.
In the evaluation test, a 60 V AC voltage is applied to the planar electrode 20 and the needle electrode 25 from the power source 28 to move the droplet, and the droplet is held on the needle electrode when no voltage is applied. The contrast ratio between the state and the state where the droplet spreads along the planar electrode when a voltage was applied was measured. During measurement, variable frequency vibration (10-57 Hz / 0.075 mm, 58-500 Hz / 1G sweep time 11 minutes, 2 h / ± (X, Y, Z)) and impact (490 m / s 2, 11 msec, 1 time / ± (X, Y, Z)) was loaded, and the contrast ratio was compared and evaluated when there was vibration and when there was no vibration.
As a result, there was no change in contrast ratio due to the presence or absence of vibration compared to Examples 1 and 2, and the average contrast ratio without vibration and the average contrast ratio with vibration were both 20.

7 and 8 show a fourth embodiment.
In the fourth embodiment, the planar electrode 20 is formed on the lower surface of the transparent glass substrate of the upper layer 12, and the insulating film 21 and the water repellent film 22 are formed on the surface (lower surface) of the planar electrode 20.
The lower layer 14 disposed across the upper layer 12 and the display space 13 is composed of a light scatterer 16 and a substrate 15, and a liquid reservoir 35 is provided in the center of the light scatterer 16.
Similar to the third embodiment, the line electrode 30 is formed on the upper surface of the substrate 15, and the needle electrode 25 having the lower end connected to the line electrode 30 is passed through the center of the liquid reservoir 35 to enter the display space 13. Protruding.
Since other members are the same as those in the above embodiment, the same reference numerals are given and description thereof is omitted.

In the fourth embodiment, since the planar electrode 20 is provided on the lower surface of the substrate of the upper layer 12, the colored droplets Q are transparently spread along the substrate of the upper layer 12 when a voltage is applied, and the coloring is more vivid. Can be displayed.
That is, in the first to third embodiments, the droplets spread along the upper surface of the lower layer 14 during the color display, and the transparent oil O exists on the display side of the color droplet Q, and the color is displayed through the oil O. However, in the fourth embodiment, the colored droplet Q can be directly visually recognized without passing through the oil O.

Example 4
An apparatus having the configuration of the fourth embodiment was created in substantially the same manner as in Example 1. The needle electrode was made of a conductive material.
In addition, the material used was the same as in Experimental Example 1, and the color droplet was KCL aqueous solution 1 mM / L + magenta 3 wt%.
In the evaluation test, a 60 V AC voltage is applied to the planar electrode 20 and the needle electrode 25 from the power source 28 to move the droplet, and the droplet is held on the needle electrode when no voltage is applied. The contrast ratio between the state and the state where the droplet spreads along the planar electrode when a voltage was applied was measured. During measurement, variable frequency vibration (10-57 Hz / 0.075 mm, 58-500 Hz / 1G sweep time 11 minutes, 2 h / ± (X, Y, Z)) and impact (490 m / s 2, 11 msec, 1 time / ± (X, Y, Z)) was loaded, and the contrast ratio was compared and evaluated when there was vibration and when there was no vibration.
As a result, like Example 3, there was no change in the contrast ratio due to the presence or absence of vibration, and the average contrast ratio without vibration and the average contrast ratio with vibration were both 20.

In any of the first to fourth embodiments, a colored electrolytic aqueous solution is used as the conductive droplet Q, but an ionic liquid not containing water is used instead of the electrolytic aqueous solution, and the average particle diameter is 5 μm or less. Alternatively, ionic colored droplets in which the above pigment is dispersed may be used.
Specifically, the droplet Q is an ionic liquid that is a room temperature molten salt composed of a 1-1 salt in which one kind of cation and anion each having a monovalent charge are combined, and contains almost no water.
The cations and anions are selected so that the droplet Q has a combination having the following melting point, viscosity, and ionic conductivity.
It must be liquid at room temperature with a melting point of -4 to -90 ° C, it is non-volatile, has a vapor pressure of zero, has a wide liquid temperature range, and has excellent thermal stability.
The ionic conductivity (s / cm) at room temperature (25 ° C.) is 0.1 × 10 ⁻³ or more.
The viscosity at room temperature (25 ° C.) is 300 cp or less.
As the conductive liquid having the physical properties described above, a liquid containing a chemical species composed of 1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, or dimethyl-3-propylimidazolium is used. It is done.
The droplet Q is preferably the ionic droplet, but other droplets may be used and are not limited.
Further, the colorless and transparent may be replaced with oil and air may be used.
Moreover, it is preferable that the coloring material mix | blended with the said normal temperature molten salt shall be 5 micrometers or less in volume average particle diameter.

  Further, a backlight may be provided below the lower layer substrate to form a transmissive display device. At that time, the light scatterer layer may be omitted. In addition, a light scatterer layer may be partially disposed and a backlight may be partially disposed, and a semi-transmissive type using both a reflective type and a transmissive type may be used.

  The present invention relates to an electric field including an electrophoretic method in which image display is performed by changing the surface energy of a liquid in accordance with whether or not a voltage is applied to the liquid, and moving the liquid or increasing or decreasing the surface area of the surface of the liquid. It can be used for any of the induction-type sheet display devices.

FIG. 2 is a cross-sectional view of the image display device according to the first embodiment, in white display when no voltage is applied with the switch off. It is sectional drawing at the time of the coloring display at the time of the switch-on of 1st Embodiment and a voltage application. It is sectional drawing at the time of the white display when the image display apparatus of 2nd Embodiment is shown and a voltage is not applied by switch-off. It is sectional drawing at the time of the colored display at the time of the switch-on of 2nd Embodiment at the time of a voltage application. It is sectional drawing at the time of white display when the image display apparatus of 3rd Embodiment is shown and a voltage is not applied by switch-off. It is sectional drawing at the time of the colored display at the time of the switch-on of 3rd Embodiment at the time of a voltage application. It is sectional drawing at the time of the white display when the image display apparatus of 4th Embodiment is shown and a voltage is not applied by switch-off. It is sectional drawing at the time of the colored display at the time of the switch-on of 4th Embodiment and a voltage application. (A) (B) is drawing which shows a prior art example. It is drawing which shows another prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Image display apparatus 12 Upper layer 13 Display space 14 Lower layer 15 Board | substrate 16 Light-scattering body 19 Partition 20 Planar electrode 21 Insulating film 22, 26 Water-repellent film 25 Needle-shaped electrode 27 Switch 28 Power supply 35 Liquid storage part Q Colored liquid Drop O Oil

Claims (7)

An upper layer on the display side, and a lower layer arranged with a space for display with the upper layer,
The display space is filled with colored conductive droplets and oil or air that does not mix with the droplets,
While a planar electrode is provided on the upper surface of the lower layer on the lower surface side of the display space or the lower surface of the upper layer on the upper surface side of the display space,
In the display space, needle-like electrodes protrude vertically from the upper layer or the lower layer,
While the planar electrode is oleophilic, the needle electrode is hydrophilic,
When the circuit between the planar electrode and the needle electrode is opened and no voltage is applied, the droplet is held in a spherical shape around the needle electrode in the vertical direction, while the voltage is applied when the circuit is closed. An image display device characterized in that the liquid droplets are colored and displayed in a state of spreading horizontally on the lower surface side or the upper surface side of the display space provided with the planar electrodes.   2. The image display device according to claim 1, wherein a protrusion dimension L <b> 3 of the needle-like electrode protruding in the vertical direction to the display space is set to ¼ or more of a dimension L <b> 1 in the vertical direction of the display space. .   The image display device according to claim 1, wherein the needle-like electrode is provided at a central portion in a length direction of the display space extending in a horizontal direction.   2. A liquid reservoir that communicates with a central portion in the length direction of the display space is provided in the lower layer, and the needle electrode protrudes into the display space through the center of the liquid reservoir. The image display device according to claim 3. The upper layer is a substantially transparent layer through which the colored liquid spreading in the display space can be seen through, the planar electrode is a transparent electrode, and the oil or air that does not mix with the colored droplets is colorless and transparent. In addition, a light scattering layer is provided in the lower layer,
The colored display is performed when a voltage is applied in which the droplet spreads in the display space in the horizontal direction, while the white display is performed by light scattering by the light scattering layer when no voltage is applied to the needle electrode. The image display device according to any one of claims 1 to 4. The upper layer is a substantially transparent layer through which the colored liquid spreading in the display space can be seen through, the planar electrode is a transparent electrode, and a light scattering material is blended in the oil that does not cross the colored droplets. And
When a voltage is applied in which the droplet spreads horizontally in the display space, the display is colored, while when no voltage is applied to the needle electrode, the light is scattered by the light scattering material in the oil to display white. The image display device according to any one of claims 1 to 4.   7. The upper layer and the lower layer are formed in a sheet shape of 10 to 300 [mu] m, and the vertical dimension L1 of the display space is set to 1 to 500 [mu] m. The image display device according to item.

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