JP2005099408A - Electrophoretic display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an electrophoretic display device which responds fast, and has a high reflectance and a long life. <P>SOLUTION: The electrophoretic display device is characterized in that: a dispersion layer having colored electrified particulates which have fullerene or its association body and a surface-active agent and are colored in a 1st color and insulating liquid in which the particulates are dispersed is interposed between 1st and 2nd substrates; the 1st substrate is provided with a 1st electrode and a 2nd electrode smaller in area than the 1st electrode, and the 2nd substrate is provided with a 3rd electrode facing the 2nd electrode; and voltage is not applied to the 1st, 2nd, and 3rd electrodes when the 1st color is displayed and the voltage is applied between the 2nd electrode and 3rd electrode so that the polarities are alternated when a 2nd color different from the 1st color is displayed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device using electrophoretic particles.

  Expectations for reflective display devices are increasing from the standpoint of reducing power consumption and reducing the burden on the eyes. Until now, an electrophoretic display device has been known as one of reflection type display devices. This electrophoretic display device is composed of a dispersion composed of electrophoretic particles having electric charge and an insulating liquid, and a pair of electrodes facing each other with the dispersion interposed therebetween. Then, by applying an electric field to the dispersion liquid through this electrode, the electrophoretic particles are moved onto an electrode having a polarity opposite to that of the electric charge, and display is performed.

  In the electrophoretic display device, the electrophoretic particles are colored, and the contrast color of the electrophoretic particles is borne by the dispersion liquid in which the dye is dissolved. More specifically, when the electrophoretic particles adhere to the surface of one electrode close to the observer, the color of the electrophoretic particles is observed. In addition, when the electrophoretic particles adhere to the surface of the other electrode far from the observer, the color of the electrophoretic particles is concealed by the dispersion and the color of the dispersion is observed.

  The electrophoretic display device has the advantages of a wide viewing angle, high contrast, and low power consumption. However, high reflectivity, that is, brightness and high contrast due to adverse effects such as adsorption of the dye dissolved in the dispersion to the electrophoretic particles and penetration of the dispersion between the electrode surface on which the electrophoretic particles are adsorbed and the electrophoretic particles. There was a big problem that it was essentially impossible to achieve both.

In order to solve this problem, an electrophoretic display device that performs display using a transparent dispersion liquid has been proposed (see Patent Documents 1 and 2). In these methods, when displaying the first color (for example, black), the colored particles are migrated over the entire pixel electrode substantially equal to the pixel size, and when displaying the second color (for example, white), the non-pixel portion, Alternatively, colored particles are collected in a small area portion of the pixel so that the pixel portion is in a transmissive state. Since the pigment is not dissolved in the dispersion, the dispersion is highly stable, and good white display can be realized by controlling the scattering characteristics of the reflective electrode.
Japanese Patent Laid-Open No. 9-211499 (page 2-7, FIG. 1) Japanese Patent Laid-Open No. 11-202804 (page 3-8, FIG. 1)

  However, these electrophoretic display devices have a problem that display characteristics such as response speed and reflectance, and a lifetime are insufficient.

  In view of these problems, an object of the present invention is to obtain an electrophoretic display device having a high-speed response, a high reflectance, and a long lifetime.

Accordingly, the present invention provides a first substrate, a second substrate facing the first substrate, colored charged fine particles sandwiched between the first substrate and the second substrate and colored in a first color, and colored charged fine particles A dispersion layer having an insulating liquid that disperses the liquid, a first electrode provided on a surface of the first substrate on the dispersion layer side, a surface provided on the surface of the first substrate on the dispersion layer side, and having an area larger than that of the first electrode. A small second electrode, a third electrode provided on the surface of the second substrate on the dispersion layer side, facing the second electrode, and a drive circuit for applying a voltage to the first electrode, the second electrode, and the third electrode. And the colored charged fine particles include fullerene or an aggregate of fullerenes and a nonionic or ionic surfactant, and in the first display state displaying the first color, the first electrode, the second The electrode and the third electrode are all in a voltage-free state, and a second color different from the first color is displayed. The second display state, to provide an electrophoretic display device, characterized in that the polarity is a state of applying a voltage to alternating between the second electrode and the third electrode.

  In the present invention, the fullerene or the aggregate of fullerenes may be a fullerene derivative having an ionic functional group or an aggregate of fullerene derivatives having an ionic functional group.

  In the present invention, the fullerene or the fullerene aggregate may be a fullerene encapsulating a metal or a fullerene aggregate encapsulating a metal.

  In addition, the present invention is sandwiched between a first substrate, a second substrate facing the first substrate, and the first substrate and the second substrate, and has an average particle diameter of 600 nm or less and colored in the first color. A dispersion layer having colored charged fine particles, an insulating liquid for dispersing the colored charged fine particles, a first electrode provided on the dispersion layer side surface of the first substrate, and a dispersion layer side surface of the first substrate. A second electrode having a smaller area than the first electrode, a third electrode provided on the surface of the second substrate on the dispersion layer side and facing the second electrode, the first electrode, the second electrode, and the third electrode And a driving circuit that applies a voltage to the colored charged fine particles. The colored charged fine particles include a pigment particle and a polymer film that has an ionic functional group and covers the pigment particle, and displays a first color. In the state, the first electrode, the second electrode, and the third electrode are all in a state in which no voltage is applied, and is different from the first color. In the second display state that displays the color, to provide an electrophoretic display device, characterized in that the polarity is a state of applying a voltage to alternating between the second electrode and the third electrode.

  In the present invention, when the drive circuit switches from the first display state to the second display state, the first electrode and the third electrode are arranged so that the polarity of the third electrode is opposite to the polarity of the colored charged fine particles. When the voltage is applied between the second display state and the third electrode, and then the polarity is alternately changed between the second electrode and the third electrode, the second display state is switched to the first display state. A voltage is applied between the first electrode and the third electrode so that the polarity of one electrode is opposite to the polarity of the colored charged fine particles, and then the voltages of the first electrode, the second electrode, and the third electrode May be in a non-application state.

  In the present invention, an insulating protrusion facing the first electrode may be provided on the surface of the second substrate on the dispersion layer side.

  In the present invention, the surfaces of the first substrate and the second substrate including the first electrode, the second electrode, and the third electrode may be coated with a polymer having a surface potential of the same polarity as the colored charged fine particles. .

  In the present invention, the surfaces of the first substrate and the second substrate including the first electrode, the second electrode, and the third electrode may be coated with a polymer having a surface tension of 30 mN / m or less.

  According to the present invention, it is possible to obtain an electrophoretic display device having a high response speed and a high reflectance and a long lifetime.

Hereinafter, the electrophoretic display device according to each embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments.
(First embodiment)
First, an electrophoretic display device according to a first embodiment of the present invention will be described. The electrophoretic display device of this embodiment comprises colored charged fine particles having fullerenes or aggregates of fullerenes and ionic or nonionic surfactants that impart dispersion stability thereto, and the electrophoretic phenomenon Display is performed using both diffusion phenomena.

  FIG. 1A and FIG. 1B are cross-sectional views showing a part of the electrophoretic display device of the present embodiment, showing a colored state and a decolored state, respectively.

  In FIG. 1, a first substrate 4 and a second substrate 3 are provided to face each other, and an insulating liquid 1 is sandwiched between these substrates. The insulating liquid 1 is transparent and colored charged fine particles 2 are dispersed. The colored charged fine particles 2 have fullerene or a fullerene aggregate and a surfactant that imparts dispersion stability to the fullerene or fullerene aggregate, and are colored, for example, black (first color). The first color can be changed to another color (purple or the like) in combination with a solvent or a surfactant. In the present embodiment, a dispersion layer is formed by the insulating liquid 1 and the colored charged fine particles 2. A part of the surfactant is dispersed around the fullerene or the aggregate of fullerenes, and the rest is dispersed in the insulating liquid 1. A first electrode 6 and a second electrode 5 are provided on the first substrate 4, and a third electrode 7 is provided on the second substrate 3. The first electrode 6 has a larger area than the second electrode 5. The third electrode 7 is provided at a position facing the second electrode 5. The first electrode 6, the second electrode 5, and the third electrode 7 form one pixel, and actually such pixels are formed in a two-dimensional matrix. In addition, a drive circuit 100 that applies a voltage to the first electrode 6, the second electrode 5, and the third electrode 7 is provided.

In this embodiment, the insulating liquid 1 is colorless and transparent, and the colored charged fine particles 2 are colored black. The colored charged fine particles 2 can be charged to either positive or negative polarity by a surfactant or a dispersed insulating liquid. Here, description will be made on colored charged fine particles that are negatively charged. And the display method of the electrophoretic display device of this embodiment is as follows. In the colored state displaying the color of the colored charged fine particles 2 shown in FIG. 1A, the color of the colored charged fine particles 2 can be observed from the observation surface by dispersing the colored charged fine particles 2 over the entire pixel. Further, in the decolored state displaying the transparent (white) (second color) shown in FIG. 1B, the colored charged fine particles 2 are locally present between the second electrode 5 and the third electrode 7. Thus, since the insulating liquid 1 is colorless, white, which is the color of the diffuse reflector made of Al, Ag, TiO ₂ film or the like provided on the outer surface of the substrate on the surface opposite to the observation surface. Observable. Here, the observation surface may be the second substrate 3 side with the second substrate 3 as a transparent substrate, or the first substrate 4 side with the first substrate 4 and the first electrode 6 as the transparent substrate and transparent electrode. Further, the colored charged fine particles 2 are moved to the colored state or the decolored state for each pixel.

  Next, a method for realizing the coloring state (first display state) and the decoloring state (second display state) of the electrophoretic display device of the present embodiment will be described with reference to FIGS.

  First, FIG. 1 and FIG. 1 show switching from black display to white display when the colored state is the color (black) display of the colored charged fine particles 2 and the decolored state is the diffused reflector color (white) display. 2 and FIG. FIG. 2 shows (a) black display, (b) a transition state from black display to white display, and (c) and (c ′) white display. FIG. 3 shows a waveform diagram of the first electrode 6 in the upper stage, a waveform diagram of the second electrode 5 in the middle stage, and a waveform chart of the third electrode 7 in the lower stage. The transition state and the white display state are shown.

As shown in FIGS. 1, 2A, and 3, during black display, the first electrode 6, the second electrode 5, and the third electrode 7 are all in a voltage-free state, and the colored charged fine particles 2 are pixels. Distributed throughout.

  In order to perform white display from this state, first, a voltage is applied between the first electrode 6 and the third electrode 7 as shown in FIGS. Here, a voltage having a polarity opposite to that of the colored charged fine particles 2 is applied to the third electrode 7, and no voltage is applied to the second electrode 5. Then, the colored charged fine particles 2 temporarily gather on the third electrode 7 side. It is not necessary to apply the voltage between the first electrode 6 and the third electrode 7 until the colored charged fine particles 2 are completely collected in the vicinity of the third electrode 7. It only needs to be away from the surroundings.

  Next, as shown in FIGS. 2C and 2C and FIG. 3, a voltage is applied while changing the polarity between the second electrode 5 and the third electrode 7. Here, no voltage is applied to the first electrode 6. Then, the colored charged fine particles 2 vibrate between the second electrode 5 and the third electrode 7, and the colored charged fine particles 2 are localized between the second electrode 5 and the third electrode 7. Thus, switching from black display to white display is completed. At this time, it is preferable that the voltage applied between the second electrode 5 and the third electrode 7 is about 0.1 V to 1 V, and the applied voltage in the state (b) is 1 V to 10 V or more.

  Next, switching from white display to black display will be described with reference to FIGS. FIG. 4 shows (a) and (a ′) white display, (b) transition from white display to black display, and (c) black display. FIG. 5 shows a waveform diagram of the first electrode 6 in the upper stage, a waveform diagram of the second electrode 5 in the middle stage, and a waveform diagram of the third electrode 7 in the lower stage, and from each of the white display from the left side, from white display to black display The transition state and black display state are shown.

  As shown in FIGS. 1, 4 (a), (a ′) and FIG. 5, a voltage is applied while changing the polarity between the second electrode 5 and the third electrode 7 during white display. Since the colored charged fine particles 2 are present in the vicinity of the second electrode 5 and the third electrode 7, white display is performed. In order to perform black display from this state, first, a voltage is applied between the first electrode 6 and the third electrode 7 as shown in FIGS. Here, a voltage having a polarity opposite to that of the colored charged fine particles 2 is applied to the first electrode 6, and no voltage is applied to the second electrode 5. Then, the colored charged fine particles 2 temporarily spread to the first electrode 6 side, that is, the entire pixel. The voltage application between the first electrode 6 and the third electrode 7 does not need to be performed until the colored charged fine particles 2 are completely spread over the entire pixel, and may be applied to the extent that promotes the diffusion phenomenon of the colored charged fine particles 2. .

  Next, as shown in FIGS. 4C and 5, the first electrode 6, the second electrode 5, and the third electrode 7 are all brought into a voltage-free state. Then, the colored charged fine particles 2 that are attracted toward the first electrode 6 are diffused throughout the pixel due to the diffusion phenomenon, resulting in black display, and switching from white display to black display is completed.

  By performing such display switching for each pixel, in this embodiment, electrophoretic display using electrophoretic phenomenon and diffusion phenomenon using fullerene or an aggregate of fullerene provided with a surfactant as a colored charged fine particle. A device can be obtained.

  In the present embodiment, the colored charged fine particles 2 are not completely adsorbed by any electrode in white display or black display, and FIG. 2B or FIG. The state of 4 (b) does not last long. Therefore, it is possible to improve the deterioration due to the aggregation of the colored charged fine particles 2 and the adsorption to each electrode, and it is possible to realize a long life.

In the decolored state, a voltage is applied between the second electrode 5 and the third electrode 7 while always changing the polarity in order to collect the colored charged fine particles 2 in the vicinity of the second electrode 5 and the third electrode 7. Must. However, the electrophoretic phenomenon is generated by applying a voltage as much as possible, that is, since the colored charged fine particles 2 move to the opposite polarity electrode, the second electrode 5 and the third electrode 7 in the decolored state The electric power required to apply a voltage during this period is extremely small. Therefore, it can be said that the power consumption due to the constant application of the voltage with the polarity changed, such as alternating current, can be ignored. In FIG. 2 (b) or FIG. 4 (b), the voltage applied when the colored charged fine particles 2 are temporarily moved to collect or spread is applied, for example, about 1 V or more while changing the polarity in the decolored state. The voltage to be applied can be, for example, about 0.1 V or more. In the colored state, no voltage is applied to any electrode and no voltage is applied, so that power consumption can be kept small.

  Further, as the relationship between the first electrode 6, the second electrode 5, and the third electrode 7, in order to increase the contrast ratio between the colored state and the decolored state, the area of the first electrode 6 is preferably large, The first electrode 6 is preferably about 5 to 10 times the second electrode 5 or the third electrode 7. In order to reduce the non-pixel region as much as possible, it is preferable that the second electrode 5 and the third electrode 7 face each other and have the same area.

In the present embodiment, fullerene or an aggregate of fullerenes means closed cage-like carbon molecules such as C ₆₀ and C ₇₀ , or a clustered form in which they are gathered. FIG. 6 shows colored charged fine particles 2 containing fullerene 9 and surfactant 10. The fullerene 9 and the surfactant 10 are in a state in which the surfactant 10 surrounds the fullerene 9 by adsorption or the like due to electrostatic or hydrophilic / hydrophobic interaction. Further, the surfactant 10 is not only adsorbed around the fullerene 9 but also dispersed in the insulating liquid, and a part of the surfactant is adsorbed on the fullerene. . When the surfactant 10 is adsorbed on the fullerene 9, the charged charged fine particles 2 are obtained, in which charge is imparted to the fullerene 9 or dispersion stability is imparted due to electrostatic or steric repulsion. A phenomenon occurs. Since the fullerene 9 is as small as about 0.76 nm as shown in FIG. 6, the diffusion coefficient becomes large and high-speed response is possible, and since it is an electrophoretic display device, an effect of high reflectivity can be obtained.

As the fullerene, C ₆₀ , C ₇₀ or the like can be used. As the surfactant, a nonionic low molecular active agent, a nonionic high molecular active agent, an ionic low molecular active agent, an ionic high molecular active agent, or the like can be used. By adding the surfactant to the liquid in which the fullerene is dispersed, the fullerene charged with the surfactant can be obtained.
(Second Embodiment)
Next, an electrophoretic display device according to a second embodiment of the invention will be described. In the electrophoretic display device of this embodiment, colored charged fine particles are different from those of the first embodiment. In the present embodiment, only differences from the first embodiment will be described, and description of similar parts will be omitted.

  In the present embodiment, the colored charged fine particles 2 are different from those in the first embodiment. The colored charged fine particles 2 of this embodiment are shown in FIG.

First, FIG. 7A shows a basic structure of a fullerene derivative in which an ionic functional group 11 is adsorbed around the fullerene 9. By using the fullerene derivative having such a structure as the colored charged fine particles 2, it is difficult to remove the ionic functional group, so that the effect of high dispersion stability of the colored charged fine particles 2 can be obtained. For fullerene derivatives, use should be made of fullerene bonded with an anionic functional group such as carboxylic acid or sulfonic acid as an ionic functional group and a cationic functional group such as quaternary ammonium as a cationic functional group. Can do. Examples of fullerene derivatives that can be used in this embodiment are shown in FIGS. 7B, 7C,
And shown in FIG.

  FIG. 7E shows a case where an aggregate of fullerene derivatives in which ionic functional groups 11 are adsorbed around fullerene 9 is used as colored charged fine particles 2. By using such colored charged fine particles 2, the charge amount of the colored charged fine particles 2 as a whole increases, so that it is possible to increase the speed of electrophoresis. In order to make fullerene or a fullerene derivative into an aggregate, an appropriate fullerene or fullerene derivative may be added to an appropriate solvent. For example, an aggregate can be obtained by using toluene as a solvent. In some cases, fullerene and aggregates of fullerene derivatives can be dispersed in other solvents, particularly nonpolar solvents, by further solvent substitution.

  FIG. 7F shows the case where fullerene 9 containing metal atoms 12 is used as colored charged fine particles 2. By using such colored charged fine particles 2, the charge of the colored charged fine particles 2 is increased, so that high speed electrophoresis can be realized. Examples of metal atoms encapsulated in fullerene include Li.

  FIG. 7G shows the use of colored charged fine particles 2 having pigment particles 13 and a polymer coating 14 having ionic functional groups 11 covering the pigment particles 13 and having an average particle size of 600 nm or less. Is. Since the pigment particles 13 bear a display color and the polymer film 14 having the ionic functional group 11 covers the pigment particles 13, the colored charged fine particles 2 are given an electric charge. As the pigment particles 13, inorganic pigments such as carbon black and titania, organic pigments such as metal phthalocyanine, and the like can be used. Examples of the polymer film 14 having the ionic functional group 11 include anionic polymers such as acrylate polymers (acrylic acid, methacrylic acid, glycidyl acid), polystyrene sulfonic acid, polyethyleneimine, polyvinylamine, polyallylamine, and polyornithine. Cationic polymers such as polylysine can be used. In order to coat the pigment particles 13 with the polymer film 14, methods such as a coacervation method, an in-situ polymerization method, and a submerged drying method can be used. In the case of having a polymer film having an ionic functional group, since the polymer film having an ionic functional group causes electrostatic repulsion to the electrode, adsorption to the electrode and the like is reduced, and there is an effect that the life is improved. . Furthermore, the average particle diameter of the colored charged fine particles 2 is preferably 600 nm or less in order to increase the diffusion rate. Here, the average particle diameter includes not only fullerene 9 and pigment particles 13 but also functional groups and the like. If the average particle size is larger than 600 nm, the diffusion rate may be slow.

As described above, also in this embodiment, an electrophoretic display device using an electrophoresis phenomenon and a diffusion phenomenon can be obtained as in the first embodiment.
(Third embodiment)
Next, an electrophoretic display device according to a third embodiment of the invention will be described. In the electrophoretic display device of this embodiment, an insulating projection is provided on the surface of the second substrate on the side of the dispersion layer to guide the colored charged fine particles in a predetermined direction when moving. In the present embodiment, only differences from the first embodiment will be described, and description of similar parts will be omitted.

  The present embodiment is different from the first embodiment in that an insulating projection facing the first electrode is provided for each pixel on the surface of the second substrate on the dispersion layer side. It is sectional drawing which shows a part of electrophoretic display device which concerns on this embodiment, and shows a decoloring state. Actually, the pixels are formed in a two-dimensional matrix.

As shown in FIGS. 8A and 8B, the electrophoretic display device of this embodiment has insulating protrusions 15a and 15b on the second substrate 3 at positions facing the first electrode 6. Have. The protrusions 15a and 15b are such that the colored charged fine particles 2 easily spread over the entire pixel when switching from the decolored state to the colored state. Any shape that guides when the colored charged fine particles 2 move so as to easily gather between the electrodes 7 may be used. By adopting such a shape, the movement of the colored charged fine particles 2 is assisted, so that the colored charged fine particles 2 can move efficiently and display with a high contrast ratio can be performed.

  For example, in FIG. 8A, the shape of the protrusion 15a is a triangular prism, and an isosceles triangle whose cross-sectional shape is the bottom surface of the triangular prism. Further, in FIG. 8B, the shape of the protrusion 15b is a triangular prism, and a right-angled triangle whose cross-sectional shape is the bottom surface of the triangular prism. In the case of FIG. 8B, the protrusion 15b not only guides in a predetermined direction when the colored charged fine particles 2 move, but also functions as a wall between adjacent pixels. Therefore, there is no problem that the colored charged fine particles 2 are moved to the adjacent pixels, and the density of each pixel can be changed. However, the protrusions 15a and 15b may have any shape that guides when the colored charged fine particles 2 move, and are not limited to these shapes.

  The protrusions 15a and 15b are preferably made of an insulating material in order to prevent the colored charged fine particles 2 from being adsorbed. When the second substrate 3 side is used as the observation surface, the protrusions 15a and 15b are preferably transparent, and a method such as photolithography using a material such as an acrylic polymer, a carbonate polymer, or an imide polymer. Can be formed. When the first substrate 4 side is the observation surface, the projections 15a and 15b may be transparent or may bear the contrasting color of the colored charged fine particles 2, and may be colored by mixing the dye with the above materials. Can be formed in a similar manner.

  Also in the present embodiment, as in the first embodiment, not only can an electrophoretic display device utilizing the electrophoretic phenomenon and the diffusion phenomenon be obtained, but also the colored charged fine particles 2 can move efficiently, and the contrast ratio can be improved. High display can be performed.

In these embodiments, the first substrate 4 and the second substrate 3 can be made of glass, plastic such as PET, PES, or the like. The first electrode 6, the second electrode 5, and the third electrode 7 can be formed by depositing ITO, SnO ₂ or the like by vapor deposition or sputtering, and patterning by photolithography.

  Further, as the insulating liquid 1, it is preferable to use a hydrocarbon solvent, a silicone solvent, or the like, which is a nonpolar solvent, because an electric current hardly flows.

  Further, the surfaces of the first substrate 4 and the second substrate 3 including the first electrode 6, the second electrode 5, and the third electrode 7 are coated with a polymer having a surface potential having the same polarity as the colored charged fine particles 2. Also good. By covering with such a polymer, it is possible to prevent the colored charged fine particles 2 from being adsorbed to the electrodes and the like, and an electrophoretic display device having a high contrast ratio and a long life can be obtained. Examples of the polymer having a surface potential with the same polarity as the colored charged fine particles 2 include polyimide and acrylate polymers. The range covered with this polymer does not have to be the entire surface of the first substrate 4 and the second substrate 3, and only the electrode portion may be covered.

Moreover, you may coat | cover the surface of the 1st board | substrate 4 and the 2nd board | substrate 3 containing the 1st electrode 6, the 2nd electrode 5, and the 3rd electrode 7 with the polymer whose surface tension is 30 mN / m or less. By coating with such a polymer, since the surface tension of the polymer is small, it is possible to prevent the colored charged fine particles 2 from being adsorbed to the electrode and the like, and an electrophoretic display device having a high contrast ratio and a long life. Can be obtained. In addition, when the surface tension is 30 mN / m or less, it is possible to obtain an effect that the insulating liquid 1 and the colored charged fine particles 2, particularly the colored charged fine particles 2 are difficult to adsorb, and when the surface tension is greater than 30 mN / m. These may be adsorbed. Examples of the polymer having a surface tension of 30 mN / m or less include fluorine-based polymers such as polyfluoroacrylate. The range covered with this polymer does not have to be the entire surface of the first substrate 4 and the second substrate 3, and only the electrode portion may be covered.

Hereinafter, specific examples will be described in more detail with reference to the drawings.
(Example 1)
Example 1 relating to the first embodiment will be described with reference to FIGS. 1 and 6. Tetralin solvent, 0.4 wt% of C ₆₀ as fullerene 9, AOT as the surfactant 10 (bis - (2-ethylhexyl) sodium sulfosuccinate) was added 0.5 wt% was subjected to dispersion treatment in a homogenizer. The dispersed liquid was subjected to solvent substitution using Isopar M manufactured by Esso as nonpolar solvent 1 (insulating liquid) to prepare a colored charged particle dispersion.

  As the first substrate 4 and the second substrate 3, transparent glass plates with an ITO film having a thickness of 1.1 mm were used.

  The ITO films of the first substrate 4 and the second substrate 3 were patterned like the first electrode 6, the second electrode 5, and the third electrode 7. The gap between the first substrate 4 and the second substrate 3 is set to about 30 μm using a bead spacer having a particle size of 30 μm, and these substrates are bonded together via the bead spacer, as shown in FIG. It was. The colored charged particle dispersion described above was injected into the cell, and the injection port was sealed. Further, an Al diffuse reflector was attached to the back of the second substrate 3 to obtain a reflective display panel with the surface on the first substrate 4 side as the observation surface.

The AC voltage applied between the second electrode 5 and the third electrode 7 during white display is 0.5 V, and between the first electrode 6 and the third electrode 7 during display switching between white display and black display. A reflection display characteristic having a reflectance of 70% was obtained at a voltage applied to 8V. Further, it was found from the microscopic observation that the aggregation after driving was not observed and the deterioration hardly occurred.
(Example 2)
Example 2 regarding the second embodiment will be described with reference to FIGS. 1 and 7G. Add 1.0% by weight of carbon black as pigment particles 13 and 5% by weight of alkyl acrylate / dimethicone copolymer (KP-541, manufactured by Shin-Etsu Polymer Co., Ltd.) as material for polymer coating 14 in isopropyl alcohol and disperse with a homogenizer. Went. About 10 wt% of this liquid subjected to the dispersion treatment was added to dimethyl silicone (KF96L-1, manufactured by Shin-Etsu Polymer Co., Ltd.) used as an insulating liquid, and further subjected to dispersion treatment using a homogenizer. The liquid that had undergone the two dispersion treatments was subjected to fractional distillation treatment to remove isopropyl alcohol to prepare a colored charged particle dispersion.

  As the first substrate 4 and the second substrate 3, transparent glass plates with an ITO film having a thickness of 1.1 mm were used.

  The ITO films of the first substrate 4 and the second substrate 3 were patterned like the first electrode 6, the second electrode 5, and the third electrode 7. The gap between the first substrate 4 and the second substrate 3 is set to about 30 μm using a bead spacer having a particle size of 30 μm, and these substrates are bonded together via the bead spacer, as shown in FIG. It was. The colored charged particle dispersion described above was injected into the cell, and the injection port was sealed. Further, an Al diffuse reflector was attached to the back of the second substrate 3 to obtain a reflective display panel with the surface on the first substrate 4 side as the observation surface.

The AC voltage applied between the second electrode 5 and the third electrode 7 during white display is 0.5 V, and between the first electrode 6 and the third electrode 7 during display switching between white display and black display. A reflection display characteristic with a reflectivity of 65% was obtained with a voltage applied to the voltage of 15V. Further, it was found from the microscopic observation that there was almost no deterioration because no aggregation was observed after driving.
(Example 3)
Example 3 relating to the third embodiment will be described with reference to FIG. First, a colored charged particle dispersion was prepared using the same materials and methods as in Example 2.

  As the first substrate 4 and the second substrate 3, transparent glass plates with an ITO film having a thickness of 1.1 mm were used.

  The ITO films of the first substrate 4 and the second substrate 3 were patterned like the first electrode 6, the second electrode 5, and the third electrode 7. An insulating layer made of a photosensitive acrylic resin (transparent in the visible light region) is formed on the second substrate 3, and this insulating layer is insulated by photolithography using an oblique exposure process so as to have a shape as shown by 15a in FIG. Sexual protrusions were formed. The height of the insulating projection was 15 μm.

  The gap between the first substrate 4 and the second substrate 3 is set to about 30 μm using a bead spacer having a particle diameter of 30 μm, and these substrates are bonded together via the bead spacer, as shown in FIG. It was. The colored charged particle dispersion described above was injected into the cell, and the injection port was sealed. Further, an Al diffuse reflector was attached to the back of the second substrate 3 to obtain a reflective display panel with the surface on the first substrate 4 side as the observation surface.

  The AC voltage applied between the second electrode 5 and the third electrode 7 during white display is 0.5 V, and between the first electrode 6 and the third electrode 7 during display switching between white display and black display. A reflection display characteristic with a reflectance of 62% was obtained at a voltage applied to the voltage of 17V. Further, it was found from the microscopic observation that the aggregation after driving was not observed and the deterioration hardly occurred.

It is sectional drawing which shows a part of electrophoretic display device which concerns on the 1st Embodiment of this invention, (a) is a colored state, (b) is a decoloring state. It is sectional drawing which shows a part of electrophoretic display device which concerns on the 1st Embodiment of this invention, (a) is black display, (b) is the transition state from black display to white display, ( c) and (c ′) are white display. It is a wave form diagram which shows the voltage applied to the 1st electrode, the 2nd electrode, and the 3rd electrode at the time of switching from black display to white display. It is sectional drawing which shows a part of electrophoretic display device concerning a 1st embodiment of the present invention, (a) and (a ') are white displays, and (b) is a transition from white display to black display. This is a state, and (c) is black display. It is a wave form diagram which shows the voltage applied to the 1st electrode, the 2nd electrode, and the 3rd electrode at the time of switching from white display to black display. It is a schematic diagram which shows the colored charged fine particle of the electrophoretic display device which concerns on the 1st Embodiment of this invention. (A), (b), (c), (d), (e), (f), and (g) are schematic views showing colored charged fine particles according to the second embodiment of the present invention. (A), (b) is sectional drawing which shows a part of electrophoretic display device based on the 3rd Embodiment of this invention, and shows a decoloring state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating liquid 2 ... Colored charged fine particle 3 ... 2nd board | substrate 4 ... 1st board | substrate 5 ... 2nd electrode 6 ... 1st electrode 7 ... 3rd electrode 9 ... Fullerene 10 ... Surfactant 11 ... Ionic functional group 12 ... Metal atoms 13 ... Pigment particles 14 ... Polymer coatings 15a, 15b ... Protrusions

Claims (8)

A first substrate;
A second substrate facing the first substrate;
A dispersion layer comprising colored charged fine particles sandwiched between the first substrate and the second substrate and colored in a first color; and an insulating liquid for dispersing the colored charged fine particles;
A first electrode provided on a surface of the first substrate on the dispersion layer side;
A second electrode provided on a surface of the first substrate on the dispersion layer side and having a smaller area than the first electrode;
A third electrode provided on a surface of the second substrate on the dispersion layer side and facing the second electrode;
A drive circuit for applying a voltage to the first electrode, the second electrode, and the third electrode;
The colored charged fine particles have fullerene or an aggregate of fullerenes, and a nonionic or ionic surfactant.
In the first display state for displaying the first color, the first electrode, the second electrode, and the third electrode are all in a voltage non-application state,
In a second display state in which a second color different from the first color is displayed, a voltage is applied so that polarity is alternately changed between the second electrode and the third electrode. An electrophoretic display device. 2. The electrophoretic display device according to claim 1, wherein the fullerene or an aggregate of fullerenes is a fullerene derivative having an ionic functional group or an aggregate of fullerene derivatives having an ionic functional group. 2. The electrophoretic display device according to claim 1, wherein the fullerene or a fullerene aggregate is a fullerene encapsulating a metal or a fullerene aggregate encapsulating a metal. A first substrate;
A second substrate facing the first substrate;
A colored charged fine particle sandwiched between the first substrate and the second substrate and having an average particle diameter of 600 nm or less and colored in the first color, and an insulating liquid for dispersing the colored charged fine particle. A dispersion layer;
A first electrode provided on a surface of the first substrate on the dispersion layer side;
A second electrode provided on a surface of the first substrate on the dispersion layer side and having a smaller area than the first electrode;
A third electrode provided on a surface of the second substrate on the dispersion layer side and facing the second electrode;
A drive circuit for applying a voltage to the first electrode, the second electrode, and the third electrode;
The colored charged fine particles have pigment particles and a polymer film having an ionic functional group and covering the pigment particles,
In the first display state for displaying the first color, the first electrode, the second electrode, and the third electrode are all in a voltage non-application state,
In a second display state in which a second color different from the first color is displayed, a voltage is applied so that polarity is alternately changed between the second electrode and the third electrode. An electrophoretic display device. The drive circuit is
When switching from the first display state to the second display state, the polarity of the third electrode is between the first electrode and the third electrode so that the polarity of the third electrode is opposite to the polarity of the colored charged fine particles. Applying a voltage, and then applying a voltage so that the polarity alternates between the second electrode and the third electrode;
When switching from the second display state to the first display state, the polarity of the first electrode is between the first electrode and the third electrode so that the polarity of the first electrode is opposite to the polarity of the colored charged fine particles. The electrophoretic display device according to claim 1, wherein a voltage is applied, and then the voltages of the first electrode, the second electrode, and the third electrode are not applied. 5. The electrophoretic display device according to claim 1, wherein an insulating projection facing the first electrode is provided on a surface of the second substrate on the dispersion layer side. 6. The surfaces of the first substrate and the second substrate including the first electrode, the second electrode, and the third electrode are coated with a polymer having a surface potential having the same polarity as the colored charged fine particles. The electrophoretic display device according to claim 1 or 4. The surface of the first substrate and the second substrate including the first electrode, the second electrode, and the third electrode is covered with a polymer having a surface tension of 30 mN / m or less. 5. The electrophoretic display device according to 1 or 4.

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