JP2013164538A - Image display medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display medium capable of being a memory property compatible with responsiveness in display using electrophoresis of phoretic particles, more excellently, as compared with a case where the present configuration is not used.SOLUTION: Electronic paper 100 includes: a display side electrode 2 and a back side electrode 4 for applying voltage; cells 70 arranged between the display side electrode 2 and the back side electrode 4; solvent 82 stored in the cells 70; phoretic particles 80R, 80C, 80W which move in the solvent 82 by electrophoresis caused by first applied voltage applied between the display side electrode 2 and the back side electrode 4; and liquid crystal 81 of which orientation is made anisotropic in the solvent 82, by second applied voltage applied to the display side electrode 2 and the back side electrode 4.

Description

  The present invention relates to an image display medium.

  As a conventional image display medium, there is an electrophoretic display using microcapsules in which threshold characteristics are given to electrophoresis of electrophoretic particles (see, for example, Patent Document 1).

  An image display medium described in Patent Document 1 includes a microcapsule filled with an electrophoretic liquid containing negatively charged electrophoretic particles and a positively charged nematic liquid crystal, and electrodes disposed at positions facing each other across the microcapsule. The voltage applied to the electrodes is controlled so that the selection voltage for displaying the pixel in the display state or the erasing voltage for non-display state reaches the threshold voltage at which the molecules of the nematic liquid crystal are aligned in the electric field direction. The applied voltage is controlled so that the voltage condition does not reach the threshold voltage of the nematic liquid crystal.

JP 2004-191694 A

  An object of the present invention is to provide an image display medium that has both good memory performance and excellent response in display using electrophoresis of migrating particles, compared to the case where this configuration is not used.

  One embodiment of the present invention provides the following image display medium in order to achieve the above object.

[1] a display cell disposed between opposing electrodes;
A solvent contained in the display cell;
Migrating particles that move in the solvent by electrophoresis at a first applied voltage applied between the opposing electrodes;
An image display medium comprising: a liquid crystal having an anisotropic orientation in the solvent at a second applied voltage applied to the opposing electrodes.

[2] The image display medium according to [1], wherein the first applied voltage applied between the opposing electrodes is a direct current, and the second applied voltage is an alternating current.

[3] The image display medium according to [1], wherein an absolute value of the second applied voltage is smaller than an absolute value of the first applied voltage applied between the opposing electrodes.

[4] Voltage application means for applying a voltage between the opposing electrodes of the image display medium according to any one of [1] to [3];
And a control unit that controls the voltage applying unit to apply the first voltage after applying the second voltage.

  According to the first aspect of the present invention, it is possible to satisfactorily achieve both memory performance and responsiveness in the display using electrophoresis of electrophoretic particles, compared to the case where this configuration is not used.

  According to the second aspect of the present invention, migrating particles that are moved by a DC voltage are less susceptible to the influence of the second applied voltage than when a second DC applied voltage is used.

  According to the third aspect of the present invention, the migrating particles that are moved by the direct current voltage have a second applied voltage that is higher than that of the second applied voltage that has an absolute value equal to or greater than the absolute value of the first applied voltage. Difficult to be affected.

  According to the fourth aspect of the present invention, the image display medium according to any one of the first to third aspects can be driven so that both the memory performance and the responsiveness can be satisfactorily compared with the case where the present configuration is not used. it can.

FIG. 1A is a perspective view showing an example of the configuration of electronic paper as an image display medium according to the first embodiment, and FIG. 1B is a partial cross-sectional view taken along the line AA. FIGS. 2A to 2D are schematic cross-sectional views illustrating an operation example of display control of the image display medium according to the first embodiment. 3A to 3D are schematic cross-sectional views illustrating the configuration of the image display medium according to the second embodiment and an example of display control operation.

(First embodiment)
(Configuration of image display medium)
FIG. 1A is a perspective view showing an example of the configuration of electronic paper as an image display medium according to the first embodiment, and FIG. 1B is a partial cross-sectional view taken along the line AA.

  An electronic paper 100 as an image display medium has a display-side substrate 1 that is a transparent substrate in which a display-side electrode 2 that is a transparent electrode is formed on the entire back surface 1b, and a back-side electrode 4 that is formed in a two-dimensional matrix. The back side substrate 3 and the electrophoretic liquid 8 encapsulated in the cell 70 of the rib 7 and containing the electrophoretic particles 80R, 80C, 80W, the liquid crystal 81, and the solvent 82 are included. The display side substrate 1 and the back side substrate 3 are bonded together with an adhesive.

  For example, the display-side substrate 1 is configured using a transparent resin such as an acrylic resin, a polycarbonate resin, a polyethylene terephthalate resin, a polyethylene sulfide resin (PES), a polysulfone resin, and a polyethersulfone resin.

  The display-side electrode 2 is formed of a transparent conductive oxide such as indium-tin oxide (ITO) and indium-zircon oxide (IZO). The display-side electrode 2 may be provided on the entire back surface 1b of the display-side substrate 1 or may be a line-like electrode provided at a constant pitch.

  The back side substrate 3 may be formed of the same transparent material as that of the display side substrate 1, or may be formed of an opaque material such as ABS resin or glass epoxy resin.

  The back side electrode 4 may be formed of a transparent conductive oxide such as ITO or IZO as with the display side electrode 2, or may be formed of a metal material such as a gold foil or a copper foil. However, when the display-side electrode 2 is provided on the entire back surface 1b of the display-side substrate 1, the back-side electrode 4 is formed in a two-dimensional matrix, and the display-side electrodes 2 are formed at a constant pitch. In the case of the electrode, the back side electrode 4 is a line electrode formed so as to be orthogonal to the display side electrode 2.

  That is, when the display-side electrode 2 is provided on the entire back surface 1b of the display-side substrate 1, the display-side electrode 2 operates as a common line, and the back-side electrode 4 operates as a scan line and a data line.

  A TFT (Thin Film Transistor) or the like may be provided between the back side substrate 3 and the back side electrode 4.

  The rib 7 has a plurality of cells 70 having a square planar shape, which are partitioned corresponding to display pixels, in a grid pattern. Note that the cell 70 may have a rectangular shape or a polygonal shape.

  The height of the rib 7 is not particularly limited, but about 10 to 100 μm is preferable from the viewpoint of flexibility of the electronic paper 100. The width is preferably about 5 to 20 μm. The length of one side of the cell is preferably about 0.1 to 1 mm.

  The rib 7 may be formed by a photolithography method using a photosensitive resin, or may be cured by pressing a concave mold against a photocurable liquid resin or a photocurable film. Alternatively, the thermoplastic resin film may be formed by heating and softening and pressing the concave mold to cool and solidify, or by pressing the thermosetting resin and thermosetting it. Further, a predetermined pattern may be printed by screen printing or ink jet printing with a transparent liquid resin, and cured by an appropriate means such as heat, light, or electron beam.

  Moreover, the rib 7 does not necessarily need to be transparent, and may be an achromatic color of black, gray, or white.

  As the electrophoretic particles 80R, 80C, and 80W of the electrophoretic liquid 8, fine particles colored in colors of R (red), C (cyan), and W (white) are used. The diameter of the migrating particles 80R, 80C, and 80W is preferably 1 μm or less, and particularly preferably about 10 to 200 nm. However, in order to make the applied voltage thresholds different from each other, the charge amount is set so that the diameters thereof are different. I have control. A predetermined number of the migrating particles 80 </ b> R, 80 </ b> C, and 80 </ b> W is accommodated in each cell of the rib 7.

  The liquid crystal 81 of the electrophoretic liquid 8 is a positive nematic liquid crystal, and is aligned by an alternating voltage applied by the display side electrode 2 and the back side electrode 4. In addition, you may use what is orientated by the DC applied voltage lower than the electrophoretic particle 80R, 80C, and 80W.

  The solvent 82 of the electrophoretic solution 8 is not particularly limited as long as it is an electrically insulating liquid. Usually, silicone oil, knitted silicone oil, fluorine oil, isoparaffin, and the like are used. The viscosity is preferably 1 and about 100 mPa · s. A surfactant may be added to the solvent 82 in order to improve the dispersion of the migrating particles 80R, 80C, and 80W.

  In the above configuration, the display-side electrode 2 of the display-side substrate 1 and the back-side electrode 4 of the back-side substrate 3 are connected to a drive circuit (5) (not shown) via a driver (not shown), and the display-side electrode 2 (common line ) Is set to 0 V, and a voltage is applied to the back side electrode 4 (scan line and data line) to change, so that one or more of the migrating particles 80R, 80C, 80W move to the display side substrate 1 side, An arbitrary color is displayed in each cell.

(Operation of image display medium)
Hereinafter, an operation example of the image display medium will be described with reference to the drawings.

  FIGS. 2A to 2D are schematic cross-sectional views illustrating an operation example of display control of the image display medium according to the first embodiment.

  First, when the applied voltage between the display-side electrode 2 and the back-side electrode 4 is 0 V, the orientation of the liquid crystal 81 is isotropic in the solvent 82 as shown in FIG. The viscosity of the solvent 82 and the liquid crystal 81 as a whole with respect to the migrating particles 80R, 80C, and 80W is high. That is, it can be said that the migrating particles 80R, 80C, and 80W are not easily moved by an external force and have a high memory property. At this time, when the cell 70 is viewed from the direction of the display-side substrate 1, black is recognized by the user by the migrating particles 80R and 80C.

  Next, when an AC voltage is applied by the AC circuit 50 between the display-side electrode 2 and the back-side electrode 4 (between the data line and the common line) by the driving device 5 in order to write on the electronic paper 100, FIG. As shown in (b), the liquid crystal 81 is aligned in the direction of the electric field, and the alignment direction of the liquid crystal 81 is anisotropic in the solvent 82. As a result, the solvent 82 and the liquid crystal 81 as a whole with respect to the migrating particles 80R, 80C, 80W The viscosity in the longitudinal direction of the drawing is low. That is, it can be said that the migrating particles 80R, 80C, and 80W are easily moved by an external force and have high responsiveness. The frequency of the alternating voltage is a frequency at which the migrating particles 80R, 80C, and 80W do not move, and a high frequency (for example, kHz order or more) that is a frequency at which the alignment of the liquid crystal 81 changes is selected. In the present embodiment, this AC voltage corresponds to the second applied voltage. The AC circuit 50 is controlled by the control means 52.

  Next, as shown in FIG. 2B, in the state where the alignment direction of the liquid crystal 81 is anisotropic, the DC voltage corresponding to the written image is applied by the DC circuit 51 to the display side electrode 2 and the back side electrode 4. 2C, the migrating particles 80R, 80C, 80W receive a DC voltage exceeding their own threshold value and move in a direction corresponding to the voltage, as shown in FIG. In the present embodiment, this DC voltage corresponds to the first applied voltage. The DC circuit 51 is controlled by the control means 52.

  Next, in a state where the migrating particles 80R, 80C, and 80W have finished moving in the direction corresponding to the voltage, the driving of the driving device 5 is stopped and the applied voltage between the display side electrode 2 and the back side electrode 4 is set to 0V. Then, as shown in FIG. 2D, the orientation of the liquid crystal 81 becomes isotropic again in the solvent 82, and the viscosity of the solvent 82 and the liquid crystal 81 as a whole with respect to the migrating particles 80R, 80C, and 80W is high. It becomes a state. That is, the memory property is again high, and the migrating particles 80R, 80C, and 80W remain in the state shown in FIG. At this time, when the cell 70 is viewed from the direction of the display-side substrate 1, white is recognized by the user by the migrating particles 80W.

  The arrangement of the migrating particles 80R, 80C, and 80W is not limited to that shown in the figure, and can be arranged in various patterns. The cell 70 changes the color recognized by the user depending on the arrangement.

(Effects of the first embodiment)
According to the embodiment described above, by adding the liquid crystal 81 in the solvent 82, the electrophoretic particles 80R, 80C, and 80W are applied when the applied voltage between the display-side electrode 2 and the back-side electrode 4 is 0V. The solvent 82 and the liquid crystal 81 as a whole have a high viscosity, that is, a high memory property. This can suppress a decrease in memory performance of the electrophoretic particles having a larger diameter (larger mass) when the electrophoretic particles having different diameters are used.

  In addition, in the state where an AC voltage is applied between the display side electrode 2 and the back side electrode 4 by the AC circuit 50, the orientation of the liquid crystal 81 is anisotropic in the solvent 82, and the migrating particles 80R, 80C, The solvent 82 and the liquid crystal 81 with respect to 80 W have a low viscosity in the longitudinal direction of the drawing, that is, a high responsiveness.

  Since the viscosity can be adjusted by the orientation of the liquid crystal 81 as described above, it is not necessary to use the solvent 82 having a high viscosity in order to improve the memory property, and the solvent 82 having a low viscosity can be used. There is no need to sacrifice responsiveness. From the above, it is possible to achieve both memory performance and responsiveness to the migrating particles 80R, 80C, and 80W.

  Note that the threshold value of the applied voltage at which the liquid crystal 81 is aligned may be lower than the threshold value of the applied voltage at which the migrating particles 80R, 80C, 80W migrate, and the alignment of the liquid crystal 81 may be controlled by a DC voltage. The drive circuit 5 may be configured separately from the electronic paper 100 and connected when writing an image.

(Second Embodiment)
3A to 3D are schematic cross-sectional views illustrating the configuration of the image display medium according to the second embodiment and an example of display control operation.

  The cell 70 of the electronic paper 100 according to the second embodiment is filled with the electrophoresis solution 8A in which the electrophoresis particles 80W in the electrophoresis solution 8 of the first embodiment are omitted.

  First, when the applied voltage between the display-side electrode 2 and the back-side electrode 4 is 0 V, the orientation of the liquid crystal 81 is isotropic in the solvent 82 as shown in FIG. The viscosity of the solvent 82 and the liquid crystal 81 as a whole with respect to the migrating particles 80R and 80C is high. That is, it can be said that the migrating particles 80R and 80C are not easily moved by an external force and the memory property is high. At this time, when the cell 70 is viewed from the direction of the display-side substrate 1, black is recognized by the user by the migrating particles 80R and 80C.

  Next, when an AC voltage is applied by the AC circuit 50 between the display-side electrode 2 and the back-side electrode 4 by the driving device 5 for writing to the electronic paper 100, as shown in FIG. The liquid crystal 81 is aligned in the direction of the electric field, and the alignment direction of the liquid crystal 81 is anisotropic in the solvent 82, and the viscosity in the longitudinal direction of the drawing of the solvent 82 and the entire liquid crystal 81 with respect to the migrating particles 80 R and 80 C is low. . That is, it can be said that the migrating particles 80R and 80C are easily moved by an external force and have high responsiveness. In the present embodiment, this AC voltage corresponds to the second applied voltage. The AC circuit 50 is controlled by the control means 52.

  Next, in the state where the orientation of the liquid crystal 81 is anisotropic as shown in FIG. 3B, the DC voltage corresponding to the written image is applied by the DC circuit 51 to the display side electrode 2 and the back side electrode 4. When applied during the period, as shown in FIG. 3C, the migrating particles 80R and 80C receive a DC voltage exceeding their own threshold value and move in a direction corresponding to the voltage. In the present embodiment, this AC voltage corresponds to the first applied voltage. The DC circuit 51 is controlled by the control means 52.

  Next, in a state where the migrating particles 80R and 80C have finished moving in the direction corresponding to the voltage, when the driving of the driving device 5 is stopped and the applied voltage between the display side electrode 2 and the back side electrode 4 is set to 0V. As shown in FIG. 3D, the orientation of the liquid crystal 81 is isotropic again in the solvent 82, and the viscosity of the solvent 82 and the entire liquid crystal 81 as a whole with respect to the migrating particles 80R and 80C becomes high. That is, the memory property is again high, and the migrating particles 80R and 80C remain in the state shown in FIG. At this time, when the cell 70 is viewed from the direction of the display-side substrate 1, white is recognized by the user due to light scattering by the liquid crystal 81.

(Effect of the second embodiment)
According to the above-described embodiment, the same effect as that of the first embodiment can be achieved, and since the white light is scattered by the liquid crystal 81, the migrating particles 80W can be omitted. Moreover, you may add the electrophoretic particle of another color instead of the electrophoretic particle 80W.

[Other embodiments]
The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the display cell 70 formed by the rib 7 has been described, but the present invention can be similarly applied to a microcapsule. Further, the display device may be configured by combining the electronic paper 100 and the drive circuit 5. Further, a plurality of sets of electrodes may be disposed in one cell 70.

DESCRIPTION OF SYMBOLS 1 Display side board | substrate 2 Display side electrode 3 Back side board | substrate 4 Back side electrode 5 Drive circuit 7 Rib 8, 8A Electrophoretic liquid 50 AC circuit 51 DC circuit 52 Control means 70 Cell 80R, 80C, 80W Electrophoretic particle 81 Liquid crystal 82 Solvent 100 Electron Paper

Claims (4)

A display cell disposed between opposing electrodes;
A solvent contained in the display cell;
Migrating particles that move in the solvent by electrophoresis at a first applied voltage applied between the opposing electrodes;
An image display medium comprising: a liquid crystal having an anisotropic orientation in the solvent at a second applied voltage applied to the opposing electrodes.   The image display medium according to claim 1, wherein the first applied voltage applied between the opposing electrodes is a direct current, and the second applied voltage is an alternating current.   The image display medium according to claim 1, wherein an absolute value of the second applied voltage is smaller than an absolute value of the first applied voltage applied between the opposing electrodes. Voltage applying means for applying a voltage between the opposing electrodes of the image display medium according to any one of claims 1 to 3,
And a control unit that controls the voltage applying unit to apply the first voltage after applying the second voltage.

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