JP6497099B2 - Electrochromic display device driving method and electrochromic display device - Google Patents

Description

  The present invention relates to a driving method of an electrochromic display device and an electrochromic display device.

  In recent years, electronic paper has been actively developed as an electronic medium replacing paper. Since electronic paper is characterized in that the display device is used like paper, characteristics different from those of a conventional display device such as a CRT or a liquid crystal display are required. For example, it is a reflection type display device, has a high white reflectance and a high contrast ratio, can display a high definition, has a memory effect in display, can be driven even at a low voltage, is thin and light, and is inexpensive It is necessary to have characteristics such as

Among the above, the degree of demand for white reflectance / contrast ratio equivalent to that of paper is high as a characteristic that affects display quality. Until now, as a display device for electronic paper, for example, a method using a reflective liquid crystal, a method using electrophoresis, a method using toner migration, and the like have been proposed.
However, it is very difficult for any of the above methods to perform multicolor display while ensuring white reflectance / contrast ratio. In general, in order to perform multicolor display, a color filter is provided. However, if a color filter is provided, the color filter itself absorbs light, and the reflectance decreases. Furthermore, since the color filter divides one pixel into red (R), green (G), and blue (B), the reflectance of the display device is lowered, and the contrast ratio is lowered accordingly. When the white reflectance / contrast ratio is significantly reduced, the visibility is very poor and it is difficult to use as electronic paper.

On the other hand, as a promising technique for realizing a reflective display device without providing the color filter as described above, there is a method using an electrochromic phenomenon.
A phenomenon in which a redox reaction occurs reversibly and a color changes reversibly by applying a voltage is called electrochromism. An electrochromic display device is a display device that utilizes the coloring / decoloring (hereinafter referred to as color erasing) of an electrochromic compound that causes this electrochromic phenomenon. Since this electrochromic display device is a reflective display device, has a memory effect, and can be driven at a low voltage, it is a leading candidate for display device technology for electronic paper use, from material development to device design. R & D has been conducted extensively.

On the other hand, the electrochromic display device has a drawback in that the response speed of color development / decoloration is slow because of the principle of performing color development / decoloration utilizing an oxidation-reduction reaction. In Patent Document 1, it is proposed to improve the response speed of color development and decoloration by fixing an electrochromic compound in the vicinity of an electrode. According to the description in Patent Document 1, the time required for color development and decoloration, which has been about several tens of seconds, has been improved to about 1 second for both the color development time from colorless to blue and the color erase time from blue to colorless. Yes.
However, this is not sufficient, and in the research and development and practical application of electrochromic display devices, it is necessary to further improve the response speed of color development and decoloration.

  On the other hand, the electrochromic display device is expected as a multicolor display device because various colors can be developed depending on the structure of the electrochromic compound. Several technologies have been reported for multicolor display devices using such electrochromic display devices. For example, Patent Document 2 reports a multicolor display device using an electrochromic compound in which fine particles of a plurality of types of electrochromic compounds are stacked. Patent Document 2 describes an example of a multicolor display device in which a plurality of electrochromic compounds, which are polymer compounds having a plurality of functional functional groups having different voltages that exhibit color development, are stacked to form a multicolor display electrochromic compound. Yes.

  Further, Patent Document 3 discloses a display device in which a plurality of electrochromic layers are formed on an electrode, and multiple colors are developed using a difference in voltage value or current value necessary for the color development. Patent Document 3 discloses a multicolor display device having a display layer that is formed by laminating or mixing a plurality of electrochromic compounds that develop different colors and have different threshold voltages for color development and different charge amounts necessary for color development. An example is given.

  Patent Document 4 describes an example of a multicolor display device in which a plurality of structural units each having an electrochromic layer and an electrolyte sandwiched between a pair of transparent electrodes are stacked. Further, Patent Document 5 describes an example of a multicolor display device corresponding to RGB three colors by forming a passive matrix panel and an active matrix panel using the structural units described in Patent Document 4.

  In a display device, display density and resolution are important factors, and in an electrochromic display device, memory performance is also an important factor. Therefore, device configurations and driving methods are being studied for these controls. Patent Document 5 discloses an apparatus, method and system for controlling a cell of an electrochromic display. In the display device as shown in [0043] and [FIG. 6] of Patent Document 5, attempts are being made to improve by driving the central area and the surrounding area. Attempts have also been made to improve the gradation by how many of the plurality of electrodes in the pixel are operated.

  In an electrochromic display device, it is necessary to improve memory performance, and not only memory performance but also color development intensity and uniformity are important. If the charge or potential spread is large, the color development during color development of the color development drive pixel is further reduced, the temporal stability (memory property) is also deteriorated, and the color development over time is further reduced.

  However, in the conventional techniques as described above, the contrast between the colored portion and the non-colored portion (decolored portion) is not sufficient, and the memory performance is not satisfactory. Therefore, an electrochromic display device with improved contrast and memory characteristics and a driving method thereof are desired even when an electrochromic display device capable of maintaining a good response speed of color development / erasing and capable of multicolor display is desired. It was.

  In view of the above problems, an object of the present invention is to provide a driving method of an electrochromic display device in which the contrast between a color-developing pixel and a decoloring pixel is good and the memory property is excellent.

In order to solve the above problems, the present invention is formed so as to be in contact with a display substrate, a display electrode formed in contact with the display substrate, a counter substrate facing the display substrate, and the counter substrate. A plurality of pixel electrodes and a counter electrode made of a transparent conductive thin film formed so as to be in contact with the pixel electrode; an electrolyte layer provided between the display electrode and the counter electrode; the display electrode and the counter electrode And an electrochromic layer formed so as to be in contact with the display electrode, wherein the color is selected from the display electrode and the plurality of pixel electrodes to drive the pixels, and the color development step of color development by applying a coloring voltage, prior to the color development step, decoloring step of decoloring driving only the peripheral pixels including a pixel adjacent to the color drive pixel , Characterized by having a.

  According to the present invention, it is possible to provide a driving method for an electrochromic display device in which the contrast between the color-developing pixels and the decoloring pixels is good and the memory property is excellent.

It is a schematic diagram of the cross section in an example of the electrochromic display apparatus which can apply this invention. It is a schematic diagram of the cross section in the other example of the electrochromic display apparatus which can apply this invention. It is a figure which shows the color development state when the electrochromic display device obtained by the Example and the comparative example was color-driven. It is a figure which shows the color development state when the electrochromic display device obtained by the Example and the comparative example is color-driven, and fixed time passes.

  Hereinafter, a method for driving an electrochromic display device and an electrochromic display device according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

  The present invention includes a display substrate, a display electrode formed in contact with the display substrate, a counter substrate facing the display substrate, a plurality of pixel electrodes formed in contact with the counter substrate, and the pixel electrode A counter electrode made of a transparent conductive thin film formed so as to be in contact with the electrode, an electrolyte layer provided between the display electrode and the counter electrode, and between the display electrode and the counter electrode, An electrochromic display device comprising: an electrochromic layer formed in contact with a display electrode, wherein a coloring voltage is applied to a coloring driving pixel selected from the display electrode and the plurality of pixel electrodes And a color erasing step of causing a peripheral pixel including a pixel adjacent to the color development drive pixel to be decolored before the color development step.

(Configuration of electrochromic display device)
An embodiment of an electrochromic display device according to the present invention will be described with reference to FIG. FIG. 1 is a schematic cross-sectional view of an electrochromic display device according to this embodiment. FIG. 1 shows a display substrate 10, a display electrode 12 formed so as to be in contact with the display substrate 10, a counter substrate 24 facing the display substrate 10, and a plurality of pixel electrodes formed so as to be in contact with the counter substrate 24. 20 and the counter electrode 22 made of the transparent conductive thin film 18 formed in contact with the pixel electrode 20, the electrolyte layer 16 provided between the display electrode 12 and the counter electrode 22, the display electrode 12 and the counter electrode 22. The electrochromic layer 14 formed between and in contact with the display electrode 12 is illustrated. Further, FIG. 1 shows a sealing support member 26.
The details of the electrochromic display device used in the present invention will be described below.

<Display substrate and counter substrate>
As the display substrate 10 and the counter substrate 24, glass, transparent resin, or the like can be used.
Examples of the transparent resin include polycarbonate resin, acrylic resin, polyethylene, polyvinyl chloride, polyester, epoxy resin, melamine resin, phenol resin, polyurethane resin, and polyimide resin. Other examples include metal oxides such as aluminum oxide, silicon oxide, titanium oxide, and zinc oxide, and composite materials thereof.
When the electrochromic device is a reflective display device, the transparency of either the display substrate 10 or the counter substrate 24 is not necessary.

  In addition, the surface of the display substrate 10 or the counter substrate 24 may be coated with a transparent insulating layer, an antireflection layer, or the like in order to improve water vapor barrier properties, gas barrier properties, and visibility.

  The thicknesses of the display substrate 10 and the counter substrate 24 can be appropriately changed. For example, when glass is used, 0.5 to 2.0 mm is preferable, and when a transparent resin film is used, 0.5 to 0 is used. .1 mm is preferred. The display substrate 10 and the counter substrate 24 may be made of the same material or different materials.

<Display electrode>
The material of the display electrode 12 is preferably a metal oxide such as indium oxide, zinc oxide, tin oxide, indium tin oxide, indium zinc oxide. Also useful are network electrodes such as transparent silver, gold, carbon nanotubes, metal oxides, and composite layers thereof.

  As a manufacturing method, a vacuum deposition method, a sputtering method, an ion plating method, or a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, a bar as long as the display electrode material can be applied and formed. Coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing method, flexographic printing method, offset printing method, reverse printing Various printing methods such as a printing method and an ink jet printing method can also be used.

  The transmittance of the display electrode 12 is preferably 60% or more and less than 100%, and more preferably 90% or more and less than 100%. Among these, indium tin oxide (ITO) formed by vacuum deposition using a sputtering method is excellent in conductivity and transparency, and can be suitably used.

  The thickness of the display electrode 12 is adjusted so that an electrical resistance value necessary for the oxidation-reduction reaction of the electrochromic layer 14 described later can be obtained. Therefore, although it is difficult to define a suitable range of thickness, for example, when ITO vacuum film formation is used as the material of the display electrode 12, 20 nm to 500 nm is preferable, and 50 nm to 200 nm is more preferable.

<Counter electrode>
The counter electrode 22 includes a plurality of pixel electrodes 20 formed in contact with the counter substrate 24 and the transparent conductive thin film 18 formed in contact with the pixel electrode 20.

  The counter electrode 22 is not particularly limited as long as it is a conductive material. As a material for the counter electrode, use metal oxide such as indium oxide, zinc oxide, tin oxide, indium tin oxide, indium zinc oxide, metal such as zinc or platinum, carbon, or a composite film thereof. Can do. Further, a protective layer may be formed so as to cover the counter electrode so that the counter electrode is not irreversibly corroded by the oxidation-reduction reaction.

  As a manufacturing method of the counter electrode, a vacuum deposition method, a sputtering method, an ion plating method, or a spin coating method, a casting method, a micro gravure coating method, a gravure coating method, as long as the counter electrode material can be formed by coating, Bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing method, flexographic printing method, offset printing method, inversion Various printing methods such as a printing method and an inkjet printing method can also be used.

The pixel electrode 20 can have the same configuration as the display electrode 12 described above. The number of pixel electrodes 20 is not particularly limited and can be changed as appropriate.
The transparent conductive thin film 18 is not particularly limited as long as it is a material that plays a role of preventing corrosion due to an irreversible oxidation-reduction reaction of the counter electrode. Al ₂ O ₃ or SiO ₂ or an insulator containing them Various materials such as a material, zinc oxide, titanium oxide, tin oxide or a semiconductor material containing them, or an organic material such as polyimide can be used. In particular, materials that exhibit a reversible redox reaction are useful.

For example, conductive or semiconducting metal oxide fine particles such as antimony tin oxide and nickel oxide are fixed on the counter electrode with a binder such as acrylic, alkyd, isocyanate, urethane, epoxy or phenol. It has been known.
As a method for forming the transparent conductive thin film 18, a vacuum deposition method, a sputtering method, an ion plating method, or a spin coating method, a casting method, a micro gravure coating method, a gravure as long as the protective layer material can be applied and formed. Coating method, bar coating method, roll coating method, wire bar coating method, dip coating method, slit coating method, capillary coating method, spray coating method, nozzle coating method, gravure printing method, screen printing method, flexographic printing method, offset printing Various printing methods such as a printing method, a reverse printing method, and an inkjet printing method can also be used.

<Electrochromic layer>
The electrochromic layer 14 indicates a layer containing an electrochromic material, and any of an inorganic electrochromic compound and an organic electrochromic compound may be used as the electrochromic material. In addition, a conductive polymer known to exhibit electrochromism can also be used.

Examples of the inorganic electrochromic compound include tungsten oxide, molybdenum oxide, iridium oxide, and titanium oxide.
Examples of the organic electrochromic compound include viologen, rare earth phthalocyanine, and styryl.
Examples of the conductive polymer include polypyrrole, polythiophene, polyaniline, and derivatives thereof.

Further, as the electrochromic layer in the display element of the present invention, it is particularly desirable to use a structure in which an organic electrochromic compound is supported on conductive or semiconductive fine particles.
Specifically, it is a structure in which fine particles having a particle size of about 5 nm to 50 nm are sintered on the electrode surface, and an organic electrochromic compound having a polar group such as phosphonic acid, carboxyl group, or silanol group is adsorbed on the surface of the fine particle. . In this structure, since electrons are efficiently injected into the organic electrochromic compound by utilizing the large surface effect of the fine particles, the structure responds faster than a conventional electrochromic display element. Furthermore, since a transparent film can be formed as a display layer by using fine particles, a high color density of the electrochromic dye can be obtained. Also, a plurality of types of organic electrochromic compounds can be supported on conductive or semiconductive fine particles.

  Specifically, polymer-based and dye-based electrochromic compounds include azobenzene, anthraquinone, diarylethene, dihydroprene, dipyridine, styryl, styryl spiropyran, spirooxazine, spirothiopyran, thioindigo, tetra Thiafulvalene, terephthalic acid, triphenylmethane, triphenylamine, naphthopyran, viologen, pyrazoline, phenazine, phenylenediamine, phenoxazine, phenothiazine, phthalocyanine, fluorane, fulgide, A low molecular organic electrochromic compound such as benzopyran or metallocene, or a conductive polymer compound such as polyaniline or polythiophene is used.

  In particular, a viologen compound or a dipyridine compound is preferably included. These materials have a low color development / discoloration potential and exhibit good color values even in a plurality of display electrode configurations. Examples of the viologen type are described in Japanese Patent No. 39555641, Japanese Patent Application Laid-Open No. 2007-171781, and examples of the dipyridine type are described in Japanese Patent Application Laid-Open No. 2007-171781 and Japanese Patent Application Laid-Open No. 2008-116718.

  Among the above, it is particularly preferable to include a dipyridine compound represented by the following general formula (1). Since these materials have a low color development / discoloration potential, even when an electrochromic display device having a plurality of display electrodes is configured, a good color value is exhibited by the reduction potential.

[In General Formula (1), R 1 and R 2 each independently represent a C 1-8 alkyl group which may have a substituent, or an aryl group, and at least one of R 1 or R 2 is COOH, PO It has a substituent selected from (OH) ₂ and Si (OC _k H _{2k + 1} ) ₃ . X represents a monovalent anion. n represents 0, 1 or 2. k represents 0, 1 or 2. A represents an alkylene group having 1 to 20 carbon atoms, an arylene group or a divalent heterocyclic group which may have a substituent. ]

  On the other hand, inorganic electrochromic compounds such as titanium oxide, vanadium oxide, tungsten oxide, indium oxide, iridium oxide, nickel oxide, and Prussian blue are used as the metal complex-based and metal oxide-based electrochromic compounds.

  Although it does not specifically limit as electroconductive or semiconductive fine particle, A metal oxide is desirable. Materials include titanium oxide, zinc oxide, tin oxide, zirconium oxide, cerium oxide, yttrium oxide, boron oxide, magnesium oxide, strontium titanate, potassium titanate, barium titanate, calcium titanate, calcium oxide, ferrite, oxide A metal oxide mainly composed of hafnium, tungsten oxide, iron oxide, copper oxide, nickel oxide, cobalt oxide, barium oxide, strontium oxide, vanadium oxide, aluminosilicate, calcium phosphate, aluminosilicate, or the like is used.

  Moreover, these metal oxides may be used independently and 2 or more types may be mixed and used. In view of physical properties such as electrical properties and optical properties such as electrical conductivity, a kind selected from titanium oxide, zinc oxide, tin oxide, zirconium oxide, iron oxide, magnesium oxide, indium oxide, tungsten oxide, Or when those mixtures are used, the multicolor display excellent in the response speed of color development / erasure is possible. In particular, when titanium oxide is used, multicolor display with a more excellent response speed of color development and decoloration is possible.

The shape of the conductive or semiconductive fine particles is not particularly limited, but a shape having a large surface area per unit volume (hereinafter referred to as specific surface area) is used in order to efficiently carry the electrochromic compound. For example, when the fine particle is an aggregate of nanoparticles, it has a large specific surface area, so that the electrochromic compound is more efficiently supported, and multicolor display with an excellent display contrast ratio of color development and decoloration is possible. .
Moreover, it is preferable that the electrochromic layer is composed of a porous electrode made of a transparent conductive film of a porous film having through-holes capable of transmitting ions and electrochromic molecules modified on the surface of the porous electrode.

<Electrolyte layer>
The electrolytic solution used for the electrolyte layer 16 includes an electrolyte and a solvent for dissolving the electrolyte. The electrolytic solution can be impregnated in these layers after forming the counter electrode, the display electrode, and the electrochromic layer. It is also possible to distribute the electrolyte in each layer at the stage of producing display electrodes, electrochromic layers, insulating layers (if necessary), and impregnate only the solvent when bonding the display substrate and the counter substrate. is there. In this method, the impregnation rate of each layer can be improved by the osmotic pressure of the electrolytic solution.

As the electrolyte material, for example, inorganic ion salts such as alkali metal salts and alkaline earth metal salts, quaternary ammonium salts, acids, and alkali supporting salts can be used. Specifically, LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ COO, KCl, NaClO ₃ , NaCl, NaBF ₄ , NaSCN, KBF ₄ , Mg (ClO ₄ ) ₂ , Mg (BF ₄ ) ₂ etc. can be used.

An ionic liquid can also be used. As the ionic liquid, any substance that is generally studied and reported can be used. In particular, an organic ionic liquid has a molecular structure that exhibits a liquid in a wide temperature range including room temperature. Examples of molecular structures include cation components such as N, N-dimethylimidazole salt, N, N-methylethylimidazole salt, N, N-methylpropylimidazole salt, N, N-dimethylpyridinium salt, N, Aromatic salts such as pyridinium derivatives such as N-methylpropylpyridinium salts or aliphatic quaternary ammonium systems such as tetraalkylammonium such as trimethylpropylammonium salt, trimethylhexylammonium salt and triethylhexylammonium salt can be mentioned. As the anion component, a compound containing fluorine is preferable in terms of stability in the atmosphere, and examples thereof include BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , PF ₄ ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ . An ionic liquid formulated by a combination of these cationic components and anionic components can be used.

  Examples of the solvent include propylene carbonate, acetonitrile, γ-butyrolactone, ethylene carbonate, sulfolane, dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, polyethylene glycol. Alcohols or a mixed solvent thereof can be used.

  Further, the electrolytic solution does not need to be a low-viscosity liquid, and can take various forms such as a gel, a polymer cross-linking type, and a liquid crystal dispersion type. In particular, the electrolytic solution is preferably formed in a gel or solid form from the viewpoint of improving the element strength, improving the reliability, and preventing the color diffusion. As a solidification method, it is preferable to hold the electrolyte and the solvent in the polymer resin. This is because high ionic conductivity and solid strength can be obtained. Further, the polymer resin is preferably a photocurable resin. This is because the device can be manufactured at a low temperature and in a short time compared to thermal polymerization or a method of thinning the film by evaporating the solvent.

<Support material for encapsulation>
The encapsulating support member 26 is formed as necessary, and is formed so as to physically and chemically protect the side surface portion of the electrochromic device. The encapsulating support material 26 can be formed by, for example, applying an ultraviolet curable or thermosetting insulating resin or the like so as to cover the side surface and / or the upper surface, and then curing. Moreover, it is more preferable to set it as the laminated protective layer of curable resin and an inorganic material. By using a laminated structure with an inorganic material, barrier properties against oxygen and water are improved.

  As the inorganic material, a material having high insulation, transparency, and durability is preferable, and specific materials include oxides or sulfides such as silicon, aluminum, titanium, zinc, and tin, or a mixture thereof. Can be mentioned. These films can be easily formed by a vacuum film forming process such as sputtering or vapor deposition.

  Although it does not restrict | limit especially as said curable resin, For example, photocuring resins, such as an acrylic resin, a urethane resin, an epoxy resin, a vinyl chloride resin, an ethylene resin, a melamine resin, a phenol resin, a thermosetting resin Etc.

  The thickness of the encapsulating support material 26 is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.5 μm to 10 μm.

(Driving method of electrochromic display device)
The driving method of the electrochromic display device according to the present invention includes a coloring step of applying a coloring voltage to a coloring driving pixel selected from the display electrode 12 and the plurality of pixel electrodes 20 and coloring before the coloring step. And a decoloring step of performing decoloring driving on peripheral pixels including pixels adjacent to the color driving pixels.
Details will be described below. Hereinafter, the applied voltage when the peripheral pixels are driven to be erased may be referred to as an erased voltage.

In the coloring process, a coloring voltage is applied to the coloring driving pixel selected from the display electrode 12 and the plurality of pixel electrodes 20 to develop a color. Needless to say, the range of the color driving pixels to be selected can be changed as appropriate, and is changed depending on the image to be displayed.
Further, a coloring voltage is applied between the selected display electrode 12 and the pixel electrode 20 to perform coloring driving. The magnitude of the coloring voltage at this time is appropriately changed depending on the configuration of the electrochromic display device, and the time for applying the coloring voltage is also changed as appropriate.

In the present invention, the decoloring step is performed before the coloring step. In the decoloring step, the peripheral pixels including the pixels adjacent to the color driving pixels are driven to be decolored.
The peripheral pixels can be changed as appropriate, and it is difficult to define the range in general. However, a range including at least a pixel adjacent to the color driving pixel is selected.
For example, when the pixel electrode 20 indicated by reference numerals 20c and 20d is selected as the color driving pixel among the plurality of pixel electrodes 20 shown in FIG. 1, at least the pixel electrodes indicated by reference numerals 20b and 20e are driven to be decolored. . In this way, by positively reacting in the vicinity of the coloring drive pixel, the color difference between the coloring portion (coloring driving pixel) and the decoloring portion (peripheral pixel) increases, and excellent contrast is achieved. can get.

On the other hand, when the color-development drive pixel is developed in a naturally stable state without performing the above-described decoloring process on peripheral pixels including pixels adjacent to the color-development drive pixel, good contrast cannot be obtained.
If the erasing process is not performed, it is considered that the past color development history in the peripheral pixels is not erased and a slight color development remains, so that the difference from the color development drive pixels becomes small. As another reason, it is considered that when the coloring driving pixel is colored, the peripheral pixels are also affected by the coloring, and the color is slightly developed, and this can be suppressed by the above-described decoloring process.

  In addition, as described above, a good contrast can be obtained when the peripheral pixel is driven to decolorize and then the coloring driving pixel is colored, but this is maintained even after a certain period of time has passed. Therefore, according to the present invention, good memory performance can be obtained.

  When the color developing voltage is a negative value when driving peripheral pixels, the peripheral pixel is driven to erase by applying a voltage larger than the color developing voltage, or the color developing voltage is a positive value. Preferably, the peripheral pixels are driven to be decolored by applying a voltage having a value smaller than the coloring voltage. For example, when a color development voltage is applied to a color development drive pixel by applying a color development voltage at −3.5 V, a voltage having a value larger than the color development voltage −3.5 V is applied to drive the peripheral pixels to be decolored. The coloring voltage and the erasing voltage may be the same sign.

It is preferable to increase an applied voltage in the erasing direction when the peripheral pixels are driven to erasing. When the coloring voltage is a negative value, the range of the voltage value for driving the peripheral pixels to be decolored varies depending on the configuration of the electrochromic display device and the image to be displayed and is appropriately changed. difficult. Therefore, it can be changed as appropriate within the range where the effects of the present invention can be obtained. Preferably there is. The same tendency occurs when the coloring voltage is a positive value.
In addition, when only one of positive and negative can be obtained from 0V, and positive / negative inversion by connection reversal is not possible, that is, when coloring, decoloring, holding or the like is originally performed only with the same sign, it is larger than the coloring voltage (minus value) and smaller than 0V. It can be a range. Similarly, it can be set in a range smaller than the coloring voltage (plus value) and larger than 0V.
By doing so, it is possible to further improve the contrast between the coloring driving pixels and the peripheral pixels driven to be decolored.

In addition, it is preferable to increase the time for applying the applied voltage when the peripheral pixels are driven to be decolored. The time for applying the decoloring voltage varies depending on the configuration of the electrochromic display device and the image to be displayed, and is appropriately changed. Therefore, it is difficult to define a suitable range. Therefore, it can be changed as appropriate within the range where the effects of the present invention can be obtained. It is preferable that the time is within the range of time for decoloring. When the color development time is longer than the decoloring time, the color development time or longer is preferable.
By doing so, it is possible to further improve the contrast between the coloring driving pixels and the peripheral pixels driven to be decolored.

  Also, when the time for applying the decoloring voltage is changed, the contrast improvement may be slightly inferior to when the value of the decoloring voltage is changed, but the burden on the sample can be reduced. This is advantageous. For this reason, it is important to appropriately select the voltage and time for decoloring driving in consideration of the configuration of the electrochromic display device and the image to be displayed.

(Other embodiment 1)
The present invention can be applied to an electrochromic display device as shown in FIG. 2 in addition to the electrochromic display device as shown in FIG. The electrochromic display device shown in FIG. 2 includes a plurality of sets of the display electrode and the electrochromic layer. In FIG. 2, the display electrode indicated by reference numeral 12 includes the first display electrode, the electrochromic layer indicated by reference numeral 14 includes the first electrochromic layer, and in addition, the second display electrode 32, the second display electrode An electrochromic layer 34, a third display electrode 42, and a third electrochromic layer 44 are provided.

  In the present embodiment, a plurality of pixel electrodes 20 and first to third display electrodes are arbitrarily selected, and a color development driving pixel is selected. A coloring voltage is applied between the selected pixel electrode and the display electrode to drive the coloring. About the decoloring process performed before a coloring process, it can carry out similarly to the above.

  In the electrochromic display device shown in FIG. 2, full color display is possible by changing the color type of the electrochromic layer. For this reason, according to the present embodiment, an electrochromic display device capable of full-color display with improved contrast as compared with the prior art can be obtained.

In the present embodiment, it is preferable that the second display electrode 32, the second electrochromic layer 34, the third display electrode 42, and the third electrochromic layer 44 have through holes. It is preferable to have a through-hole because charge transfer with the electrolyte layer 16 becomes easier.
The shape of the through hole is not particularly limited. For example, in the case of a film formed by collecting particles, even a gap between particles is included in the through hole referred to here. In addition, the method for manufacturing the through hole can be changed as appropriate, and can be manufactured by a known manufacturing method.

(Other embodiment 2)
As described above, the electrochromic display device driven by the method for driving an electrochromic display device of the present invention can be appropriately changed as long as it can perform the color developing step and the color erasing step.

  An example of an electrochromic display device according to an embodiment different from the above-described electrochromic display device will be described. The electrochromic display device according to the present embodiment includes, inside or outside, a coloring unit that performs the coloring step and a erasing unit that performs the erasing step. The erasing means exchanges image data to be displayed, and selects a color development drive pixel and peripheral pixels based on the image data. At this time, based on the image data and the configuration of the electrochromic display device, the erasing voltage for erasing driving the peripheral pixels and the erasing voltage application time for applying the erasing voltage are appropriately determined. As a result, the peripheral pixels are driven to be decolored, and thereafter, the coloring driving pixels are colored by the coloring means. The color forming unit and the color erasing unit may be configured to exchange information with each other. For example, the color developing voltage and the color erasing time may be mutually exchanged between the color developing voltage and the color developing time. .

  According to such an aspect, a driving device capable of setting the erasing voltage or time as the erasing setting is obtained. In addition, the erasing voltage is not fixed, and can be changed according to, for example, the reverse sign of the coloring voltage, a short circuit, or the coloring voltage, and can be varied as a whole or for each pixel. Further, the erasing time is not fixed, and, for example, it is not always erased for the same time, but can be varied for the whole or for each pixel. A device capable of applying a time gradation or a voltage gradation in an arbitrary pattern in the erasing direction and a device capable of bidirectional control of color erasing driving can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to the following Example.

Example 1
<Production of electrochromic display device>
A display substrate 12 was formed by preparing a glass substrate as the display substrate 10 and depositing an ITO film to a thickness of about 20 nm by sputtering on the upper surface region.
On the glass substrate on which the display electrode 12 is formed, SP210 (manufactured by Showa Titanium Co., Ltd.) as a titanium oxide nanoparticle dispersion is applied by a spray method, and annealed at 120 ° C. for 15 minutes to form a titanium oxide particle film. did. Subsequently, a coating solution in which a 5 wt% 2,2,3,3-tetrafluoropropanol solution of a viologen compound and the above-mentioned SP210 were mixed at a ratio of 2.4 / 4 was applied by a spin coating method at 120 ° C. By annealing for 10 minutes, titanium oxide particles and electrochromic compound [4,4 '-(1-phenyl-1H-pyrrole-2,5-diyl) bis (1- (4- (phosphonomethyl) benzyl) pyridinium ) bromide] to form a 1000 nm thick electrochromic layer 14.

On the other hand, as the counter substrate 24, a substrate with electrodes capable of active matrix driving (AM driving) having 240 × 320 pixel electrodes was prepared. The electrode here is made of Ti. A transparent conductive thin film 18 made of tin oxide was formed on the upper surface to form a counter electrode 22 having a thickness of 200 nm.
Then, the display substrate 10 and the counter substrate 24 were bonded together.

  Next, as preparation of the electrolyte solution, 35 wt% of titanium oxide particles having a primary particle size of 300 nm (manufactured by Ishihara Sangyo Co., Ltd.) were dispersed in a solution in which 0.1 M of tetrabutylammonium perchlorate was dissolved in propylene carbonate. This was enclosed in a cell to produce an electrochromic display device.

  The obtained electrochromic display device had a cross section as shown in FIG. Although only six pixel electrodes 20 are shown in FIG. 1, this is only a part, and a large number of pixel electrodes 24 are formed in the obtained electrochromic display device. A plurality of pixel electrodes 20 are also formed in the depth direction, and when viewed from the display substrate 10 side, an arbitrary pattern such as a character, a sentence, or a picture can be displayed in units of the pixel electrodes 24.

<Driving of electrochromic display device>
The obtained electrochromic display device was driven by the following method.
Select a pixel electrode in an area of approximately 1.4 mm x 1.4 mm as the color development drive pixel, and select a pixel electrode around the area (a range of about 1.4 mm width from the color development drive pixel) as the pre-erasing drive pixel. , + 1.5V, 250 ms in advance. Next, a coloring voltage was applied at −3.5 V to the area selected as the coloring driving pixel to drive the coloring.

(Example 2)
In the driving of the electrochromic display device of Example 1, the electrochromic display device was driven in the same manner as in Example 1 except that the pre-erasing application voltage was changed from +1.5 V to +3.5 V.

(Example 3)
In driving the electrochromic display device of Example 1, the electrochromic display device was driven in the same manner as in Example 1 except that the pre-erasing application time was doubled.

Example 4
In driving the electrochromic display device of Example 2, the electrochromic display device was driven in the same manner as in Example 2 except that the pre-erasing application time was doubled (500 ms).

(Comparative Example 1)
In the driving of the electrochromic display device of Example 1, the electrochromic display device was driven in the same manner as in Example 1 except that the previous decoloring application was not performed.

(Evaluation)
The resulting electrochromic display device is shown in FIG. 3 in a color developing state when color driving is performed. FIG. 3 is an overhead view when viewed from the display substrate 10 side. In the color driving pixel in FIG. 3, magenta color was obtained. In FIG. 3, the magenta coloring in Examples 1 and 2 is stronger than the magenta coloring in Comparative Example 1 although it is slightly difficult to understand on the paper surface.

Next, for Examples 1 to 4 and Comparative Example 1, color development / decoloration values defined below were obtained.
[Color value]
When the color development voltage is applied and the application is terminated, the average value obtained for the characteristic value of about 0.6 mm width inside the area selected as the color development drive pixel is Av1, and about the outside of the area selected as the color development drive pixel. The average value obtained for the characteristic value of 0.6 mm width is Av2. This difference (Av1-Av2) was defined as the color-decoloring value.
The characteristic values were obtained by processing image data taken under a constant illuminance using a digital camera. In order to make a comparison without variations due to shooting conditions, black-and-white charts were shot at the same time, and the comparison was performed using values corrected by the values.

  About the comparison of the color development / decoloration value in an Example and a comparative example, the relative value was calculated | required and compared based on the color development / decoloration value of a comparative example. The results are shown in Table 1 below.

From Table 1, when Example 1 and Example 2 were compared, the color development was improved by increasing the pre-color application voltage. Moreover, when Example 1 and Example 3 were compared, the improvement in color development was seen by doubling the pre-erasing application time.
For these reasons, it is possible to improve color erasing by changing pre-erasing conditions. Further, from the results of Table 1, the difference between Example 1 and Example 3 is +0.4 point, whereas the difference between Example 1 and Example 2 is as large as +1.7 point, and the voltage change is large. You can see that it has an effect.

  In Example 2, the area that had been previously erased was slightly colored compared to Example 1. When the average of the characteristic values is obtained for the width of about 0.6 mm outside the area selected as the color driving pixel, when Comparative Example 1 is used as a reference, +1.7 points in Example 1 and +7.2 points in Example 2 Met.

Next, after the color was driven as described above and color was developed, the memory property was evaluated by allowing a certain period of time to elapse. FIG. 4 shows the color development state (memory state) of Examples 1 and 2 and Comparative Example 1 when a certain time has elapsed. Although slightly difficult to understand on paper, the color development in Examples 1 and 2 was stronger than the color development in Comparative Example 1.
When the color erasing value is obtained as described above, when the color erasing value of Comparative Example 1 is used as a reference, Example 1 is +2.4 points, Example 2 is +4.9 points, and Example 3 is +4. .7 points. From this, Examples 1-3 showed the high memory property compared with the comparative example 1. FIG.

10 display substrate 12 display electrode (first display electrode)
14 Electrochromic layer (first electrochromic layer)
16 Electrolyte Layer 18 Transparent Conductive Thin Film 20 Pixel Electrode 22 Counter Electrode 24 Counter Substrate 26 Encapsulating Support Material 32 Second Display Electrode 34 Second Electrochromic Layer 42 Third Display Electrode 44 Third Electrochromic Layer

Special table 2001-510590 gazette JP 2003-121883 A JP 2006-106669 A JP 2003-270671 A JP 2008-532055 A

Claims (6)

A display board;
A display electrode formed in contact with the display substrate;
A counter substrate facing the display substrate;
A plurality of pixel electrodes formed in contact with the counter substrate, and a counter electrode made of a transparent conductive thin film formed in contact with the pixel electrodes;
An electrolyte layer provided between the display electrode and the counter electrode;
An electrochromic display device comprising: an electrochromic layer formed between and in contact with the display electrode between the display electrode and the counter electrode,
A color development step of applying a color voltage to the color development drive pixel selected from the display electrode and the plurality of pixel electrodes to cause color development;
A method for driving an electrochromic display device, comprising: a color erasing step for erasing only peripheral pixels including pixels adjacent to the color development driving pixels before the color development step.   When the coloring voltage is a negative value, a voltage greater than the coloring voltage is applied to drive the peripheral pixels to be decolored, or when the coloring voltage is a positive value, the value is smaller than the coloring voltage. 2. The method of driving an electrochromic display device according to claim 1, wherein a voltage is applied to drive the peripheral pixels to be decolored.   3. The method of driving an electrochromic display device according to claim 1, wherein an applied voltage when the peripheral pixels are driven to be decolored is increased in a decoloring direction.   The method of driving an electrochromic display device according to claim 1, wherein a time for applying an applied voltage when the peripheral pixels are driven to be decolored is increased.   The method of driving an electrochromic display device according to claim 1, wherein the electrochromic display device includes a plurality of sets of the display electrode and the electrochromic layer. An electrochromic display device for performing the method of driving an electrochromic display device according to claim 1 ,
A coloring means for carrying out the coloring step and a decoloring means for carrying out the erasing step;
The decoloring means receives and transmits image data to be displayed, selects the peripheral pixels based on the image data, and decolorizes only the peripheral pixels before performing the coloring process. Display device.