Electrochemical display element and electrochemical display
An electrochemical display device and an electrochemical display apparatus, having preferable cycle properties and preferable display quality, and a method for producing the same. The electrochemical display device according to the present invention is characterized in that it has: a first transparent electrode; an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution; a second electrode having the electrolyte layer disposed between the first transparent electrode and the second electrode; and a third electrode independent of the first transparent electrode and the second electrode.
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The present invention relates to an electrochemical display device using a principle such that the color of a material is changed utilizing electrochemical oxidation or reduction.
BACKGROUND ARTIn recent years, as the network widely spreads, documents, which have conventionally been delivered in the form of prints, are being delivered in the form of so-called electronic documents. Further, books, magazines and the like are frequently provided through so-called electronic publication.
The information has been read conventionally from a CRT or liquid crystal display of a computer. However, it is pointed out that a light emission type display causes severe fatigue for the reasons of ergonomics, making long-time reading difficult. In addition, there is a drawback in that information can be read only at the place in which a computer is located.
Laptop computers widely spread currently, and some of them are used as portable display, but they cannot be used in reading for several hours or longer because they are of a light emission type using a back light and further consume the power soon. Recently, a reflection type liquid crystal display is developed, and the use of this enables driving of a computer with low power consumption; however, the liquid crystal has only a reflectance of plain display (white display) as low as 30%, and hence has markedly poor visibility, as compared to printed paper, and is likely to cause fatigue, thus also making long-time reading difficult.
For solving these problems, recently, so-called paper-like display or electronic paper is being developed. They are colored mainly by making coloring particles to move between electrodes by an electrophoresis method, or rotating particles having dichroism in an electric field. However, these methods have disadvantages in that spaces between the particles absorb a light to lower the contrast, and the driving voltage required for obtaining a practical writing speed (1 second or faster) is as high as 100 V or more.
An electrochromic display apparatus (ECD), which achieves coloring based on an electrochemical action, is preferable in contrast, as compared to the above display using an electrophoresis method, and it has already been put into practical use in photochromic glass and clock display. However, the photochromic glass and clock display essentially have no need of matrix driving, and hence cannot be applied to display use of electronic paper, and they generally have poor black quality and low reflectance.
A display of electronic paper is always exposed to a light, such as sunlight or room light, when being used. In the electrochromic display apparatus practically used in photochromic glass and clock display, a predetermined organic material is used to form a black portion. However, an organic material generally has poor light resistance and hence poses a problem in that black color is faded and the black density is lowered after being used for a long time. In addition, the display apparatus of a matrix driving type described in Japanese Patent Application Publication No. Hei 4-73764 is known, but the driving device merely constitutes a part of the liquid crystal display apparatus.
For solving the above technical problems, there have been proposed an electrochemical display device and an electrochemical display apparatus, using metal ions as a material which changes in color by electrochemical oxidation and reduction, and using a white colored polymer electrolyte for dissolving the metal ions, and being capable of matrix driving and improving the contrast and the black density. However, the properties, especially cycle properties are unsatisfactory, and it is desired that the cycle properties are improved. In addition, there is a problem in that appropriate control of the oxidation reduction reactions is not satisfactorily achieved and the image remains upon display switching, that is, afterimage is caused, thus lowering the image quality.
In view of the above problems accompanying the prior art, the present invention has been made, and it is an object to provide an electrochemical display device and an electrochemical display apparatus, having preferable cycle properties and preferable display quality, and a method for producing the same.
DISCLOSURE OF THE INVENTIONThe electrochemical display device according to the present invention for attaining the above object is characterized in that it has: a first transparent electrode; an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution; a second electrode having the electrolyte layer disposed between the first transparent electrode and the second electrode; and a third electrode independent of the first transparent electrode and the second electrode.
In the electrochemical display device according to the present invention having the above configuration, by virtue of having the third electrode independent of the first transparent electrode and the second electrode, the reaction state during the deposition or dissolution of the coloring material is precisely detected without being affected by the first transparent electrode and second electrode. Therefore, a point in time when the deposition or electrochemical reaction satisfactorily proceeds at the electrode is precisely detected, and driving is controlled based on the result of detection, achieving precise control of the driving. In addition, the precise control of the driving prevents the reaction from proceeding to an excess extent, so that the occurrence of a side reaction due to the excess reaction is prevented.
In addition, the electrochemical display apparatus according to the present invention for attaining the above object includes a plurality of electrochemical display devices arranged in a plane form, wherein each electrochemical display device has: a first transparent electrode; an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution; a second electrode having the electrolyte layer disposed between the first transparent electrode and the second electrode; and a third electrode independent of the first transparent electrode and the second electrode.
In the electrochemical display apparatus according to the present invention having the above configuration, the electrochemical display device constituting the electrochemical display apparatus has the third electrode independent of the first transparent electrode and the second electrode, and hence the reaction state during the deposition or dissolution of the coloring material is precisely detected without being affected by the first transparent electrode and second electrode. Therefore, a point in time when the deposition or electrochemical reaction satisfactorily proceeds at the electrode is precisely detected, and driving is controlled based on the result of detection, achieving precise control of the driving. In addition, the precise control of the driving prevents the reaction from proceeding to an excess extent, so that the occurrence of a side reaction due to the excess reaction is prevented.
Further, the method for producing an electrochemical display device according to the present invention for attaining the above object has: a step for forming a first transparent electrode on a transparent support; a step for forming an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution; a step for forming a second electrode having the electrolyte layer disposed between the first transparent electrode and the second electrode; and a step for forming a third electrode independent of the first transparent electrode and the second electrode.
In the above method for producing an electrochemical display device according to the present invention, the third electrode independent of the first transparent electrode and the second electrode is formed, and therefore a device is produced in which the reaction state during the deposition or dissolution of the coloring material is precisely detected without being affected by the first transparent electrode and second electrode. Thus, there is produced an electrochemical display device advantageous in that driving is precisely controlled to prevent the occurrence of a side reaction due to the excess reaction.
Furthermore, the method for producing an electrochemical display apparatus according to the present invention for attaining the above object has: a step for forming a first transparent electrode on a transparent support; a step for forming an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution; a step for forming a second electrode having the electrolyte layer disposed between the first transparent electrode and the second electrode; and a step for forming a third electrode independent of the first transparent electrode and the second electrode.
In the above method for producing an electrochemical display apparatus according to the present invention, the third electrode independent of the first transparent electrode and the second electrode is formed when forming an electrochemical display device, and therefore a display apparatus is produced in which the reaction state during the deposition or dissolution of the coloring material is precisely detected without being affected by the first transparent electrode and second electrode. Thus, there is produced an electrochemical display apparatus advantageous in that driving is precisely controlled to prevent the occurrence of a side reaction due to the excess reaction.
BRIEF DESCRIPTION OF THE DRAWINGS
Hereinbelow, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following descriptions, and can be modified or changed as long as the effect aimed at by the present invention is not deviated.
The electrochemical display device according to the present invention is characterized in that it has a first transparent electrode, an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution, a second electrode having the electrolyte layer disposed between the first transparent electrode and the second electrode, and a third electrode independent of the first transparent electrode and the second electrode. The electrochemical display apparatus according to the present invention is characterized in that it includes a plurality of the electrochemical display devices having the above configuration and being arranged in a plane form.
In the electrodeposition type display apparatus 1, one transparent picture element electrode 3 and one TFT 4 are combined to constitute one picture element, and the picture elements are arranged in a matrix form on the transparent support 2.
As the transparent support 2, a transparent glass substrate, such as a quartz glass plate or a white glass plate, can be used, but it is not limited to these, and examples include esters, such as polyethylene naphthalate and polyethylene terephthalate; polyamide; polycarbonate; cellulose esters, such as cellulose acetate; fluorine polymers, such as polyvinylidene fluoride and polytetrafluoroethylene-cohexafluoropropylene; polyethers, such as polyoxymethylene; polyacetal; polystyrene; polyolefins, such as polyethylene, polypropylene, and methylpentene polymer; and polyimide, such as polyimide-amide and polyetherimide. When a synthetic resin is used as the support, either a rigid substrate unlikely to be bent or a flexible structure in a film form can be made.
The transparent picture element electrode 3 is comprised of a transparent conductive film formed in a substantially rectangular or square pattern, and, as shown in FIGS. 1 to 3, the picture elements are separated from one another, and, in part of them, the TFT 4 is disposed per picture element. In the transparent picture element electrode 3, it is preferred to use a so-called ITO film included mainly of In2O3, SnO2, or a mixture thereof or a thin film coated with SnO2 or In2O3. Alternatively, one obtained by doping the ITO film or SnO2- or In2O3-coated film with Sn or Sb may be used, or MgO, ZnO or the like can be used.
The TFT 4 formed in each picture element is selected by not shown wiring and controls the corresponding transparent picture element electrode 3. The TFT 4 is extremely effective in prevention of the occurrence of cross talk between the picture elements. The TFT 4 may be formed, for example, so as to occupy a corner of the transparent picture element electrode 3, but a structure may be employed in which the transparent picture element electrode 3 is stacked on the TFT 4. In FIGS. 1 to 3, the TFT 4 is formed so as to occupy a corner of the transparent picture element electrode 3, but the TFT 4 may be formed so as to occupy a corner of the second electrode as described below. In this case, a structure may be employed in which the second electrode is stacked on the TFT 4, and, when the TFT 4 is disposed at a corner of the second electrode, this structure is general.
To the TFT 4, specifically, are connected a gate line and a data line, and to each gate line is connected a gate electrode of each TFT 4, and one end of source/drain of each TFT 4 is connected to the data line, and another end of source/drain is electrically connected to the transparent picture element electrode 3. When the TFT 4 is provided at the second electrode, another end of source/drain is electrically connected to the second electrode. A driving device other than the TFT 4, such as a driving driver IC, may be comprised of other materials which can be formed on a transparent substrate as a matrix driving circuit used in flat display.
The electrolyte layer 5 containing metal ions can be constituted by an electrolytic solution or a polymer electrolyte. As the electrolytic solution, one containing a metal salt or a quaternary alkylammonium salt in a solvent can be used. As the solvent for the electrolytic solution, water, ethyl alcohol, isopropyl alcohol, propylene carbonate, dimethyl carbonate, ethylene carbonate, γ-butyrolactone, acetonitrile, sulfolane, dimethoxyethane, dimethylformamide, dimethyl sulfoxide, or a mixture thereof can be used.
As a matrix polymer used in the polymer electrolyte, preferred is a polymer material having a repeating unit of alkylene oxide, alkylenimine, or alkylene sulfide in a main skeleton unit or a side chain unit, or both of them; a copolymer containing a plurality of these different units; or a polymethyl methacrylate derivative; polyvinylidene fluoride; polyvinylidene chloride; polyacrylonitrile; a polycarbonate derivative; or a mixture thereof. When the electrolyte layer is comprised of a polymer electrolyte, the electrolyte layer comprised of a polymer electrolyte may be either of a single layer or a laminate structure obtained by stacking a plurality of polymer electrolyte layers.
The above-mentioned matrix polymer can be used in the form of polymer swollen with water or an organic solvent. Especially when a high response speed or the like is required, the addition of the plasticizer facilitates movement of the ions contained, and therefore it is preferred that water or an organic solvent is added to the matrix polymer.
When hydrophilicity is required according to the properties of the matrix polymer and the desired electrochemical reaction, it is preferred that water, ethyl alcohol, isopropyl alcohol, or a mixture thereof is added, and, when hydrophobicity is required, it is preferred that propylene carbonate, dimethyl carbonate, ethylene carbonate, γ-butyrolactone, acetonitrile, sulfolane, dimethoxyethane, ethyl alcohol, isopropyl alcohol, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, n-methylpyrrolidone, or a mixture thereof is added.
In the electrodeposition type display apparatus 1 according to the present invention, the electrolyte layer 5 contains metal ions as a coloring material which colors by electrochemical reduction or oxidation, accompanied by deposition or dissolution. The electrochemical deposition or dissolution reaction of the metal ions causes coloring or decoloring to achieve display. In other words, a main principle is such that so-called plating and a dissolution reaction are advanced reversibly. With respect to the metal ions capable of coloring or decoloring by electrochemical deposition or dissolution, there is no particular limitation, and examples include ions of bismuth, copper, silver, sodium, lithium, iron, chromium, nickel, or cadmium and ions comprised of a combination thereof. Of these, especially preferred metal ions are bismuth and silver. The reason for this resides in that bismuth or silver can facilitate the reversible reaction, and exhibits high degree of color change in the deposition.
When a salt containing an ion species different from the metal ion species to be deposited or dissolved is added as a supporting electrolyte salt to the electrolyte layer 5, the electrochemical deposition or dissolution reaction can be carried out more effectively and stably. Examples of supporting electrolytes include lithium salts, such as LiCl, LiBr, LiI, LiBF4, LiClO4, LiPF6, and LiCF3SO3; potassium salts, such as KCl, KI, and KBr; sodium salts, such as NaCl, NaI, and NaBr; and quaternary tetraalkylammonium salts, such as tetraethylammonium borofluoride, tetraethylammonium perchlorate, tetrabutylammonium borofluoride, tetrabutylammonium perchlorate, and tetrabutylammonium halides. There may be a variation in the length of alkyl chains in the above quaternary ammonium salts.
As a coloring means for improving the contrast, the electrolyte layer 5 contains a coloring agent, such as an inorganic pigment or an organic pigment. When the color of the metal ions is black as mentioned above, a white material having high opacifying properties is introduced as a background color. As this material, for example, white particles for coloring are used, and, as the white particles for coloring, titanium dioxide, calcium carbonate, silica, magnesium oxide, or aluminum oxide can be used. Alternatively, a dye for coloring can be used.
When inorganic particles are used as a coloring agent, the amount of the coloring agent added is preferably 1 to 20 wt %, more preferably 1 to 10 wt %, further preferably 5 to 10 wt %. In this case, when the amount of the coloring agent added is too small, desired coloring cannot be obtained, and, conversely, when the amount of the coloring agent added is too large, the ion content is lowered and further the conductivity of the electrolyte is lowered. Accordingly, by using the coloring agent in the above amount, preferable coloring conditions can be realized without causing the above problems.
When inorganic particles as a coloring agent are mixed into the electrolyte layer 5 comprised of a polymer electrolyte layer, the thickness of the electrolyte layer is preferably 20 to 200 μm, more preferably 50 to 150 μm, further preferably 70 to 150 μm. When the electrolyte layer has a smaller thickness, the resistance between the electrodes is lowered, leading to advantages in that the time required for coloring or decoloring becomes shorter and the power consumption is reduced. However, when the thickness of the electrolyte layer is 20 μm or less, the mechanical strength is disadvantageously lowered to cause a pinhole or crack. Further, when the thickness of the electrolyte layer is too small, the content of the white particles is lowered, so that the whiteness (optical density) is not satisfactory.
On the other hand, when a dye is used as the coloring means, the amount of the dye added may be as small as about 10 wt %. The reason for this resides in that the coloring efficiency of the dye is considerably high, as compared to that of inorganic particles. Therefore, a dye which is electrochemically stable can exhibit a satisfactory contrast even in a small amount. Generally, as the dye, it is preferred to use an oil-soluble dye.
When the electrolyte layer 5 is comprised of a polymer electrolyte, the electrolyte layer 5 comprised of a polymer electrolyte may have a laminate structure obtained by stacking a plurality of polymer electrolyte layers, and, in this case, by providing the coloring means only in part of the layers, the above-mentioned effect can be obtained.
For reversibly and efficiently advancing the electrochemical reactions, especially deposition and dissolution of a metal, it is preferred that at least one additive selected from a growth inhibitor, a stress relaxing agent, a brightener, a complexing agent, and a reducing agent is added to the electrolyte layer 5. As the additive, an organic compound having a group having an oxygen atom or a sulfur atom is preferred, and, for example, at least one member selected from the group comprised of thiourea, 1-allyl-2-thiourea, mercaptobenzimidazole, coumarin, phthalic acid, succinic acid, salicylic acid, glycolic acid, dimethylamineborane (DMAB), trimethylamineborane (TMAB), tartaric acid, oxalic acid, and D-glucono-1,5-lactone can be added. Particularly, in the present invention, when adding mercaptobenzimidazole according to a mercaptoalkylimidazole represented by the chemical formula 1 below, not only be the reversibility improved, but also preferable effects can be advantageously obtained in long-term storage properties and high-temperature storage properties.
Chemical Formula 1
where each of R1, R2, and R3 is a hydrogen atom or alkyl substituent represented by CnH2+1 (wherein n is an integer of 0 or more).
In the electrodeposition type display apparatus of a system having the above configuration, a side reaction other than the predetermined reactions may be caused during the electrochemical reactions. For example, when the electrolyte layer 5 contains a salt containing a halide, the halide in the form of ions is oxidized depending on the potential according to the reaction represented by the chemical formula 2 below, thus causing coloring other than the desired coloring.
I2+2e−2I−(0.536V) Chemical formula 2
Br2+2e−2Br−(1.065V)
Cl2+2e−2Cl−(1.360V)
(The values indicate standard electrode potentials in an aqueous solution.)
Therefore, for preventing the occurrence of unnecessary coloring, it is required to suppress the above side reaction and reduce the halide oxidized. In this case, as a reducing agent, a general reducing agent can be used and added as an additive to the electrolyte layer 5. As the reducing agent, for example, an ascorbic acid compound, a trialkylalcoholamine having a general formula represented by the chemical formula 3 below, or the like is preferred.
Chemical Formula 3
Particularly, in the present invention, when triethanolamine represented by the chemical formula 4 below which is a trialkylalcoholamine species is added to the electrolyte layer 5, preferable effects can be advantageously obtained in long-term storage properties and high-temperature storage properties.
When a reduction reaction is caused due to a side reaction other than the predetermined reaction, an oxidizing agent is added. Therefore, it is preferred that the electrolyte layer contains a reducing agent or an oxidizing agent for suppressing a side reaction which is possibly caused in any of the first transparent electrode and the second electrode mainly due to an anion species during the deposition of the coloring material.
Chemical Formula 4
As the second electrode disposed opposite to the first transparent electrode, a common electrode 6 is formed. The common electrode 6 may be comprised of any metal which is electrochemically stable, but preferred are platinum, chromium, aluminum, cobalt, palladium, bismuth, and silver, and it can be prepared by forming a film comprised of a good conductor, such as a metallic thin film, on the support 7. Further, when it is possible to preliminarily or successively, satisfactorily make up for the metal used in the main reaction, carbon can be used in the common electrode. The use of carbon can lower the cost for the electrode. As an example of a method for carrying carbon on the electrode, there can be mentioned a method in which an ink is formed from carbon using a resin and printed on the surface of the substrate.
In the system in which bismuth or silver is deposited or dissolved, when the same metal species as that to be deposited or dissolved is used as the second electrode, electrochemically stable electrode reactions can be realized.
The support 7 is not necessarily transparent, and a substrate or a film, which can surely support the common electrode 6 and the electrolyte layer 5, can be used. For example, a quartz glass plate, a white glass plate, a ceramic substrate, a paper substrate, a wooden substrate, or the like can be used, but the support is not limited to these, and, as a synthetic resin substrate, ester, such as polyethylene naphthalate or polyethylene terephthalate; polyamide; polycarbonate; cellulose ester, such as cellulose acetate;
a fluorine polymer, such as polyvinylidene fluoride or polytetrafluotoethylene-cohexafluoropropylene; polyether, such as polyoxymethylene; polyacetal; polystyrene; polyolefin, such as polyethylene, polypropylene, or methylpentene polymer; or polyimide, such as polyimide-amide or polyetherimide can be used.
When the above synthetic resin is used as the support 7, either a rigid substrate unlikely to be bent or a flexible structure in a film form can be made. When the second electrode is integrally constituted as the common electrode and has satisfactory rigidity, there is no need to form the support 7.
For disposing the first transparent electrode opposite to the second electrode as shown in FIGS. 1 to 3, sealing resin portions 9 for holding both the supports 2, 7 are formed on the periphery. The sealing resin portions 9 surely hold the both supports 2, 7, and the transparent picture element electrodes 3, TFTs 4, electrolyte layer 5, and common electrode 6 disposed between the supports.
The third electrode 8 is formed as a member which is independent of and electrically insulated from the transparent picture element electrode 3 and the common electrode 6. The third electrode 8, which is formed as a member independent of and electrically insulated from the transparent picture element electrode 3 and the common electrode 6, can precisely detect the state of the reaction which proceeds during the deposition or dissolution of the coloring material without being affected by the transparent picture element electrode 3 and common electrode 6.
As a material for the third electrode 8, a stable metal material which is not involved in the reaction at all and is not dissolved in the reaction medium is selected and, for example, the same material as that for the common electrode 6, such as platinum, chromium, aluminum, cobalt, palladium, or silver, can be selected.
In the electrodeposition type display apparatus 1 according to the present invention having the above-described configuration, matrix driving using the TFT 4 is possible. In addition, by utilizing the metal ions and coloring agent contained in the electrolyte layer 5, there can be realized an electrodeposition type display apparatus which is advantageous not only in that it enables display with preferable contrast and high black density, but also in that it exhibits preferable display quality and preferable visibility.
Further, in the electrodeposition type display apparatus according to the present invention having the above configuration, electricity is conducted between the transparent picture element electrode 3 as the first transparent electrode and the second electrode 6 to allow ions in the electrolyte layer disposed between the transparent picture element electrode 3 and the second electrode 6 to move, so that an electrochemical reaction proceeds to cause deposition or dissolution of the metal, thus changing a color and coloring. The electrolyte layer 5 contains a coloring agent as the coloring means, and hence can improve the contrast when the coloring material changes in color.
In an electrodeposition type display apparatus having a structure including only the first transparent electrode and the second electrode and having no third electrode, for example, when being controlled by a voltage waveform, not only the potential of the first transparent electrode but also the potential of the second electrode vary due to the electrochemical reaction, so that the potential difference between the two electrodes is controlled by an external voltage waveform in a state such that both the potentials are varying. When such controlling is conducted, the inherent potential of the first transparent electrode cannot be known, making desired controlling difficult. This means that the coloring material cannot be controlled to be in a desired dissolved or deposited state. Therefore, in systems other than the system in which there is almost no variation in the potential of the second electrode, control of the potential difference between the two electrodes by an external voltage waveform is poor in reliability.
By contrast, in the electrodeposition type display apparatus 1, when display is achieved by conducting electricity between the transparent picture element electrode 3 as the first transparent electrode and the common electrode 6 to change a color, the third electrode 8 as a reference electrode, which is insulated from and independent of the transparent picture element electrode 3 and the common electrode 6, is not directly involved in the electrochemical reaction.
Thus, the state of the reaction which proceeds during the deposition or dissolution of the coloring material can be precisely detected without being affected by the transparent picture element electrode 3 and common electrode 6. In other words, using as a reference the potential of the third electrode 8 which does not vary, the reaction state during the deposition or dissolution of the coloring material can be detected or swept as a potential, thus making it possible to precisely detect a point in time when deposition or electrochemical reaction satisfactorily proceeds at the electrode. Then, based on the result of detection, driving, i.e., conduction between the transparent picture element electrode 3 and the second electrode 6 is controlled, enabling control of the electrochemical reaction with high reliability.
This means that the coloring material can be controlled to be in a desired dissolved or deposited state, so that control of coloring or decoloring of the coloring material, namely, control of display can be appropriately conducted, thus enabling control of display with high reliability.
Accordingly, the occurrence of a phenomenon in which the color remains upon decoloring, i.e., so-called afterimage can be prevented, thus making it possible to constitute an electrodeposition type display apparatus having preferable visibility. Therefore, in the electrodeposition type display apparatus 1, an electrodeposition type display apparatus having preferable display quality is realized.
When appropriate control of driving is not made in the electrodeposition type display apparatus, the reaction proceeds to an excess extent to cause a side reaction, leading to deterioration of the cycle properties.
However, in the electrodeposition type display apparatus 1, as mentioned above, the third electrode 8 is formed as a member which is independent of and electrically insulated from the transparent picture element electrode 3 and the common electrode 6, making it possible to precisely detect a point in time when deposition or electrochemical reaction satisfactorily proceeds at the electrode. Then, based on the result of detection, driving, i.e., conduction between the transparent picture element electrode 3 and the second electrode 6 is controlled to prevent the reaction from further proceeding. That is, this control can prevent a side reaction due to the excess deposition or dissolution reaction of the coloring material, so that deterioration of the cycle properties due to a side reaction other than the predetermined reactions can be prevented, thus remarkably improving the cycle properties. Therefore, in the electrodeposition type display apparatus 1, the use of the third electrode 8 has realized an electrodeposition type display apparatus having preferable cycle properties.
Next, a method for producing the above-described electrodeposition type display apparatus 1 is described. In the production of the electrodeposition type display apparatus 1, first, as shown in
Then, an electrolyte layer 5 is formed on the transparent support 2. When, for example, a polymer electrolyte layer is formed as the electrolyte layer 5, first, a synthetic resin as a matrix polymer for the polymer solid electrolyte, a salt constituting the electrolyte and containing a metal species to be deposited or dissolved, and a supporting electrolyte salt are mixed together, and white particles as a coloring agent and a plasticizer are added thereto and dispersed.
Separately, as shown in
Then, as shown in
Then, as shown in
Then, as shown in
Then, the matrix polymer in the polymer electrolyte having high fluidity may be permitted to undergo a cross-linking reaction by a heating or ultraviolet irradiation means to make gelation. In this case, a cross-linking agent or a photosensitizer can be used to efficiently promote the gelation.
Alternatively, before forming the electrolyte layer 5 comprised of a polymer electrolyte, the transparent support 2 and the support 7 maybe stacked in a state such that a desired gap between the electrodes is formed using a partition or the like to secure an injection inlet for a polymer electrolyte solution having fluidity. Then, as conducted in the process for liquid crystal, a polymer electrolyte solution having fluidity is injected by an injection method utilizing capillary phenomena, and then the injection inlet is sealed up, thus producing the electrodeposition type display apparatus 1. By using the injection method, an electrolytic solution containing no resin and a solution containing a coloring agent are injected, thus constituting the electrodeposition type display apparatus 1.
For keeping the gap between the transparent support 2 and the support 7 stacked to face each other constant in the in-plane direction, a frame-form gap-forming member comprised of a resin, an inorganic material or the like may be provided at the outer periphery portion of the transparent support 2 and the support 7, or fine spheres used in a liquid crystal device or the like can be dispersed in the polymer electrolyte to form a desired gap. Alternatively, nonwoven fabric or a porous film containing a polymer electrolyte can be used as a gap-forming member.
The active matrix type in which the third electrode 8 is disposed on the first transparent electrode side, i.e., transparent picture element electrode side is described above, but the present invention is not limited to this type. The above-described electrochemical display device is roughly classified into an active matrix type and a passive matrix type (simple matrix type). The active matrix type includes a type having the TFT incorporated to the side of the first transparent electrode as a working electrode as mentioned above, and a type having the TFT incorporated to the side of the second electrode as a counter electrode.
In the active matrix type, considering the opening ratio of the display picture element, the latter type having the TFT incorporated to the side of the second electrode is preferred since the TFT does not reduce the opening area. For further utilizing the effectiveness of the third electrode as a reference electrode disposed on the side of the first transparent electrode, it is preferred that the third electrode is close to the working electrode, and, in this case, the former type having the TFT incorporated to the side of the first transparent electrode is preferred. Further, the structure for the third electrode includes a structure in which the third electrode is disposed on the side of the first transparent electrode and a structure in which the third electrode is disposed on the side of the second electrode as a counter electrode.
The third electrode can be formed by weaving a thin metal wire into a mesh form, and a structure can be employed in which the thus formed third electrode is sandwiched with nonwoven fabric and disposed between the first transparent electrodes and the second electrodes so as to prevent the occurrence of short-circuiting between the third electrode and the other electrodes.
On the other hand, the passive matrix type includes a type having the third electrode disposed on the side of the first transparent electrode as a working electrode and a type having the third electrode disposed on the side of the second electrode as a counter electrode.
Hereinbelow, examples of arrangement of the third electrode in the electrodeposition type display device according to the present invention are shown as specific embodiments of the present invention.
First, examples of the configuration of a passive matrix-electrodeposition type display device in which the third electrode is arranged on the side of the transparent picture element electrode are described. In the following first to seventh embodiments, the basic configuration of the electrodeposition type display device is the configuration of a conventional standard passive matrix-electrodeposition type display device in which no third electrode is provided, i.e., configuration shown in
The first embodiment is an example of the arrangement in which a third electrode 59 in a line form is arranged on the transparent picture element electrode substrate so as to surround the whole of the effective picture elements on the side of the transparent picture element electrodes 52 as shown in
The second embodiment is an example of the arrangement in which top and bottom third electrodes 59 in a line form are arranged, on the transparent picture element electrode substrate, in the direction parallel to the stripe structure of the transparent picture element electrodes 52 so that the whole of the effective picture elements are disposed between the two third electrodes as shown in
The third embodiment is an example of the arrangement in which right and left third electrodes 59 in a line form are arranged, on the transparent picture element electrode substrate, in the direction perpendicular to the stripe structure of the transparent picture element electrodes 52 so that the whole of the effective picture elements are disposed between the right and left third electrodes as shown in
The forth embodiment is an example of the arrangement in which third electrodes 59 in a line form in the same number as that of the stripes of the transparent picture element electrodes 52 are formed, on the transparent picture element electrode substrate, in the direction parallel to the stripe structure of the transparent picture element electrodes 52 between the stripes of the transparent picture element electrodes 52 as shown in
The fifth embodiment is an example of the arrangement in which third electrodes 59 in a line form are formed, on the transparent picture element electrode substrate, in the direction parallel to the stripe structure of the transparent picture element electrodes 52 at intervals of the predetermined number of the stripes of the transparent picture element electrodes 52 as shown in
The sixth embodiment is an example of the arrangement in which third electrodes 59 in a line form are formed, on the transparent picture element electrode substrate, in the direction perpendicular to the stripe structure of the transparent picture element electrodes 52 between the picture elements in the lengthwise direction as shown in
The seventh embodiment is an example of the arrangement in which third electrodes 59 in a line form are formed, on the transparent picture element electrode substrate, in the direction perpendicular to the stripe structure of the transparent picture element electrodes 52 between the picture elements in the lengthwise direction at predetermined intervals as shown in
Next, examples of the configuration of a passive matrix-electrodeposition type display device in which the third electrode is arranged on the side of the second electrode are described. In the following eighth to twelfth embodiments, the basic configuration of the electrodeposition type display device is the same as that in the first to seventh embodiments, i.e., configuration shown in
The eighth embodiment is an example of the arrangement in which a third electrode 74 in a line form is arranged on the second electrode substrate so as to surround the whole of the effective picture elements on the side of the second electrodes 54 as shown in
The ninth embodiment is an example of the arrangement in which right and left third electrodes 74 in a line form are formed, on the second electrode substrate, in the direction parallel to the stripe structure of the second electrodes 54 so that the whole of the effective picture elements are disposed between the right and left third electrodes 74 as shown in
The 10th embodiment is an example of the arrangement in which top and bottom third electrodes 74 in a line form are arranged, on the second electrode substrate, in the direction perpendicular to the stripe structure of the second electrodes 54 so that the whole of the effective picture elements are disposed between the two third electrodes as shown in
The 11th embodiment is an example of the arrangement in which third electrodes 74 in a line form in the same number as that of the stripes of the second electrodes 54 are formed, on the second electrode substrate, in the direction parallel to the stripe structure of the second electrodes 54 between the stripes of the second electrodes 54 as shown in
The 12th embodiment is an example of the arrangement in which third electrodes 74 in a line form are formed, on the second electrode substrate, in the direction parallel to the stripe structure of the second electrodes 54 at intervals of the predetermined number of the stripes of the second electrodes 54 as shown in
Next, an example of the configuration of a passive matrix-electrodeposition type display device in which the third electrode is disposed between the first transparent electrode and the second electrode is described.
13TH EMBODIMENT In the 13th embodiment, as shown in
Next, examples of the configuration of an active matrix type, electrodeposition type display device in which the TFT for driving and further the third electrode are arranged on the side of the transparent picture element electrode are described. In the following 14th to 20th embodiments, the basic configuration of the electrodeposition type display device is the configuration of a conventional standard active matrix type, electrodeposition type display device in which no third electrode is provided, i.e., configuration shown in
As shown in
The 14th embodiment is an example of the arrangement in which a third electrode 101 in a line form is arranged on the transparent picture element electrode substrate so as to surround the whole of the effective picture elements on the side of the transparent picture element electrodes 92 as shown in
The 15th embodiment is an example of the arrangement in which top and bottom third electrodes 101 in a line form are arranged on the transparent picture element electrode substrate so that the whole of the effective picture elements on the side of the transparent picture element electrodes 92 are disposed between the two third electrodes 101 as shown in
The 16th embodiment is an example of the arrangement in which third electrodes 101 in a line form are arranged on the transparent picture element electrode substrate so that the two third electrodes 101 cross at the almost central portion of the whole of the effective picture elements on the side of the transparent picture element electrodes 92 as shown in
The 17th embodiment is an example of the arrangement in which third electrodes 101 are formed between all the picture element lines arranged in the fixed direction on the plane of the effective picture elements on the side of the transparent picture element electrodes as shown in
The 18th embodiment is an example of the arrangement in which third electrodes 101 are formed, on the plane of the effective picture elements on the side of the transparent picture element electrodes, between the picture element lines arranged in the fixed direction at intervals of the predetermined number of lines, namely, a plurality of picture element lines as shown in
The 19th embodiment is an example of the arrangement in which a third electrode point 106 is formed per one picture element on the plane of the effective picture elements on the side of the transparent picture element electrodes as shown in
The 20th embodiment is an example of the arrangement in which a third electrode point 106 is formed per predetermined plurality of picture elements on the plane of the effective picture elements on the side of the transparent picture element electrodes as shown in
Next, examples of the configuration of an active matrix type, electrodeposition type display device in which the TFT for driving is disposed on the side of the transparent picture element electrode and the third electrode is arranged on the side of the second electrode as a counter electrode are described. In the following 21st to 25th embodiments, the basic configuration of the electrodeposition type display device is substantially the same as that in the above 14th to 20th embodiments except that the second electrodes are formed in a stripe form and are not a common electrode, i.e., configuration shown in
Hereinbelow, examples of the configuration of the third electrode are described with reference to the plan view of the third electrode disposed on the support 113 on which the second electrodes 116 are formed (hereinafter, frequently referred to as “second electrode substrate”), as viewed from the counter electrode side, and the enlarged view of the essential portion with respect to each embodiment.
21ST EMBODIMENT The 21st embodiment is an example of the arrangement in which the second electrode substrate having the similar structure as that of the second electrode substrate in the above eighth embodiment is used, and a third electrode 117 in a line form is arranged on the second electrode substrate so as to surround the whole of the effective picture elements on the side of the second electrodes 116 as shown in
The 22nd embodiment is an example of the arrangement in which the second electrode substrate having the similar structure as that of the second electrode substrate in the above ninth embodiment is used, and right and left third electrodes 117 in a line form are arranged on the second electrode substrate so that the whole of the effective picture elements on the side of the second electrodes 116 are disposed between the right and left third electrodes 117 as shown in
The 23rd embodiment is an example of the arrangement in which the second electrode substrate having the similar structure as that of the second electrode substrate in the above 10th embodiment is used, and top and bottom third electrodes 117 in a line form are arranged on the second electrode substrate so that the whole of the effective picture elements on the side of the second electrodes 116 are disposed between the top and bottom third electrodes 117 as shown in
The 24th embodiment is an example of the arrangement in which the second electrode substrate in the above 11th embodiment is used as the second electrode substrate, and third electrodes 117 in a line form in the same number as that of the stripes of the second electrodes 116 are formed, on the second electrode substrate, in the direction parallel to the stripe structure of the second electrodes 116 between the stripes of the second electrodes 116 as shown in
The 25th embodiment is an example of the arrangement in which the second electrode substrate in the above 12th embodiment is used as the second electrode substrate, and third electrodes 117 in a line form are formed, on the second electrode substrate, in the direction parallel to the stripe structure of the second electrodes 116 at intervals of the predetermined number of the stripes of the second electrodes 116 as shown in
Next, examples of the configuration of an active matrix type, electrodeposition type display device in which the third electrode is disposed between the first transparent electrode and the second electrode are described.
26TH EMBODIMENT In the 26th embodiment, as shown in
A third electrode 137 is disposed between the transparent picture element electrodes 132 and the second electrode 136. As the third electrode 137, a twill type Ag mesh having about 30-μm one side of the mesh structure is used, and the third electrode 137 is sandwiched with nonwoven fabric 138 and disposed between the transparent picture element electrodes 132 and the second electrode 136 so as to prevent the occurrence of short-circuiting between the third electrode and the other electrodes.
27TH EMBODIMENT In the 27th embodiment, as shown in
A third electrode 137 is disposed between the transparent picture element electrodes 132 and the second electrodes 136. As the third electrode 137, a twill type Ag mesh having about 30-μm one side of the mesh structure is used, and the third electrode 137 is sandwiched with nonwoven fabric 138 and disposed between the transparent picture element electrodes 132 and the second electrodes 136 so as to prevent the occurrence of short-circuiting between the third electrode and the other electrodes.
Next, examples of the configuration of an active matrix type, electrodeposition type display device in which the TFT for driving is disposed on the side of the second electrode and the third electrode is arranged on the side of the transparent picture element electrode are described. In the following 28th to 34th embodiments, as shown in
The 28th embodiment is an example of the arrangement in which a third electrode 147 in a line form is formed on the transparent picture element electrode substrate so as to surround the whole of the effective picture elements on the side of the transparent picture element electrodes 142 as shown in
The 29th embodiment is an example of the arrangement in which right and left third electrodes 147 in a line form are formed, on the transparent picture element electrode substrate, in the direction parallel to the stripe structure of the transparent picture element electrodes 142 so that the whole of the effective picture elements are disposed between the right and left third electrodes 147 as shown in
The 30th embodiment is an example of the arrangement in which top and bottom third electrodes 147 in a line form are formed, on the transparent picture element electrode, in the direction perpendicular to the stripe structure of the transparent picture element electrodes 142 so that the whole of the effective picture elements are disposed between the top and bottom third electrodes 147 as shown in
The 31st embodiment is an example of the arrangement in which third electrodes 147 in a line form in the same number as that of the stripes of the transparent picture element electrodes 142 are formed in the direction parallel to the stripe structure of the transparent picture element electrodes 142 between the stripes of the transparent picture element electrodes 142 as shown in
The 32nd embodiment is an example of the arrangement in which third electrodes 147 in a line form are formed in the direction parallel to the stripe structure of the transparent picture element electrodes 142 at intervals of the predetermined number of the stripes of the transparent picture element electrodes 142 as shown in
In the present invention, with respect to the configuration of the transparent picture element electrode, second electrode, and third electrode, a configuration may be employed in which only electrode lines are formed and no insulating layer is provided. Specifically, there may be employed a configuration shown in, for example,
Alternatively, a configuration in which insulating layers are provided on electrode lines by patterning in the direction perpendicular to the electrode lines may be employed. Specifically, there can be employed a configuration shown in, for example,
Further alternatively, a configuration in which insulating layers are formed by patterning so as to expose only the picture element portion and the third electrode portion may be employed. Specifically, there can be employed a configuration shown in, for example,
Here, an explanation is made on the transparent picture element electrode substrate, but the similar configuration can be applied to the second electrode substrate.
EXAMPLESHereinbelow, the present invention will be described in more detail with reference to the following specific Examples. The following Examples should not be construed as limiting the scope of the present invention.
Example 1(Preparation of Display Electrode)
First, on a glass substrate having a thickness of 1.5 mm and a size of 10 cm×10 cm, as transparent picture element electrodes 201, ITO films arranged in a line form at a pitch of 150 μm were formed by a known method. Then, one third electrode 202 was formed at the central portion of the lines of the ITO films so as to be parallel to the lines. The third electrode 202 was formed using Ag to have a width of 1 μm. Then, effective picture element portions and their periphery portions were coated and patterned to form insulating layers 203 perpendicular to the lines of the ITO films. Subsequently, lead portions connected from the substrate to driving circuits were formed by a known method, to connect the transparent picture element electrodes 201 to transparent picture element electrode withdrawal portions 204, 205, and connect the third electrode 202 to third electrode withdrawal portions 206, 207, thus preparing display electrodes shown in
(Preparation of Counter Electrode)
On a glass substrate having a thickness of 1.5 mm and a size of 8 cm×12 cm, a Cr film was vapor-deposited by a known method, and Ag films having a thickness of 1,000 nm arranged in a line form at a pitch of 150 μm were formed on the Cr film by a known method. Then, effective picture element portions and their periphery portions were patterned to form insulating layers on the ITO films perpendicular to the lines of the ITO films, thus preparing counter electrodes.
(Preparation of Polymer Electrolyte Layer)
1 Part by weight of polyether having a molecular weight of about 350,000, 10 parts by weight of dimethylformamide (DMSO), 1.7 part by weight of sodium iodide, and 1.7 part by weight of silver iodide were mixed with one another, and heated to 120° C. to prepare a uniform solution. Then, to the uniform solution were added triethanolamine represented by the chemical formula 5 below, coumarin represented by the chemical formula 6 below, and benzimidazole represented by the chemical formula 7 below so that the respective concentrations became 10 g/l, 5 g/l, and 5 g/l.
Then, 0.2 part by weight of titanium dioxide having an average particle size of 0.5 μm was added to the resultant mixture, and uniformly dispersed together by means of a homogenizer. The resultant dispersed mixture was applied by means of a doctor blade onto the glass substrate of the above-prepared display electrodes so that the thickness became 100 μm, and then immediately the counter electrodes as the second electrodes were attached on the substrate to form a gelled polymer electrolyte between the two electrodes. Then, the edges of the resultant laminate were sealed with an adhesive, thus preparing a passive matrix-electrodeposition type display apparatus in Example 1.
(Evaluation of Driving and Display Properties)
A reduction reaction was caused on the display electrode side at an electrical quantity of 10 mC/cm2 per one picture element during coloring, and oxidation was caused at the same electrical quantity during decoloring by means of a known passive matrix driving circuit to switch colored display and colorless (white) display. In the driving, the input waveform controlled may be either current or voltage.
For confirming effectiveness of the third electrode as a reference electrode, with respect to the selected transparent picture element electrodes having different distances from the third electrode, cyclic voltammogram measurements were conducted per predetermined picture elements. The cyclic voltammogram measurements were conducted with respect to the counter electrode picture element line A (35 mm from the center of the effective picture element portion) and the counter electrode picture element line B (5 mm from the center of the effective picture element portion), and, in each case, measurements were conducted with respect to the distances from the third electrode of 50 μm, 500 μm, 2 mm, 10 mm, and 40 mm. As the input waveform, a voltage triangular wave at 50 mV/sec was applied in the range of from −1.0 to −1.5 V on the reduction side and in the range of from +1.0 to +1.4 V on the oxidation side, relative to the potential of Ag as a reference electrode of the third electrode. The results with respect to the counter electrode picture element line A are shown in
As can be seen in
Specifically, for achieving arrangement such that the third electrode more effectively operates to obtain higher reliability, it is preferred that the third electrodes in the same number as that of the stripes of the transparent picture element electrodes are disposed between the stripes of the transparent picture element electrodes. However, considering the opening ratio on the side of the transparent picture element electrodes and the trade-off, the structure in the present Example in which one third electrode in a line form is disposed at the central portion of the effective picture element portion has no problem, and is considered to make it possible to effectively operate the third electrode and effectively utilize the effect.
In addition, from the above results, it is found that, in the driving according to a linear successive method or the like as a method for picture element display, there is no need to provide the third electrode separately, and part of the counter electrodes which are not selected and are inactive as electrical signals can serve as a quasi-third electrode.
Example 2(Preparation of Display Electrode)
First, on a glass substrate having a thickness of 1.5 mm and a size of 10 cm×10 cm, as transparent picture element electrodes, ITO films and TFTs (thin film transistors) arranged in a plane form at a pitch of 150 μm were prepared by a known method to form picture element portions 211. Then, third electrodes 212 were disposed so that the two third electrodes crossed each other at the almost central portion of the effective picture element portions. The third electrodes 212 were formed using silver to have a width of 1 μm. Then, effective picture element portions and their periphery portions, excluding the picture element portions 211 and third electrodes 212, were coated and patterned to form insulating layers 213 perpendicular to the picture element lines of the ITO films. Lead portions connected from the substrate to driving circuits were formed by a known method, to connect the picture element portions 211 to transparent picture element electrode withdrawal portions 214, 215, and connect the third electrodes 212 to third electrode withdrawal portions 216, 217, 218, 219, thus preparing display electrodes shown in
(Preparation of Counter Electrode)
On a glass substrate having a thickness of 1.5 mm and a size of 8 cm×12 cm, a Cr film was vapor-deposited by a known method, and an Ag alloy thin film having a thickness of 1,000 nm was formed on the Cr film by a known method, thus preparing counter electrodes.
(Preparation of Polymer Electrolyte Layer)
A polymer electrolyte was prepared in the same manner as in Example 1 above, and applied by means of a doctor blade onto the glass substrate of the above-prepared display electrodes so that the thickness became 100 μm, and then immediately the counter electrodes as the second electrodes were attached on the glass substrate to form a gelled polymer electrolyte between the two electrodes. Then, the edges of the resultant laminate were sealed with an adhesive, thus preparing an active matrix type, electrodeposition type display apparatus in Example 2.
(Evaluation of Driving and Display Properties)
With respect to the counter electrode picture element line A (35 mm from the center of the effective picture element portion) and the counter electrode picture element line B (5 mm from the center of the effective picture element portion), cyclic voltammogram measurements were conducted per predetermined picture elements with respect to the selected transparent picture element electrodes having different distances from the third electrode in the same manner as in Example 1. The results with respect to the counter electrode picture element line A are shown in
As can be seen in
Specifically, for achieving arrangement such that the third electrode more effectively operates to obtain higher reliability, it is preferred that the third electrode is disposed per picture element portion. However, considering the opening ratio on the side of the transparent picture element electrodes and the trade-off, the structure in the present Example in which the two third electrodes cross at the almost central portion of the effective picture element portions has no problem, and is considered to make it possible to effectively operate the third electrode and effectively utilize the effect.
Example 3(Preparation of Display Electrode)
Display electrodes were prepared in substantially the same manner as in Example 1 except that no third electrode was formed.
(Preparation of Counter Electrode)
Counter electrodes shown in
(Preparation of Polymer Electrolyte Layer)
A polymer electrolyte was prepared in the same manner as in Example 1 above, and applied by means of a doctor blade onto the glass substrate of the above-prepared display electrodes so that the thickness became 100 μm, and then immediately the counter electrodes as the second electrodes were attached on the substrate to form a gelled polymer electrolyte between the two electrodes. Then, the edges of the resultant laminate were sealed with an adhesive, thus preparing a passive matrix-electrodeposition type display apparatus in Example 3.
(Evaluation of Driving and Display Properties)
With respect to the counter electrode picture element line A (35 mm from the center of the effective picture element portion) and the counter electrode picture element line B (5 mm from the center of the effective picture element portion), cyclic voltammogram measurements were conducted per predetermined picture elements with respect to the selected transparent picture element electrodes having different distances from the third electrode in the same manner as in Example 1. The results with respect to the counter electrode picture element line A are shown in
As can be seen in
Specifically, for achieving arrangement such that the third electrode more effectively operates to obtain higher reliability, the structure in Example 1 above is preferred, but the structure in the present Example in which the third electrode is not disposed on the side of the transparent picture element electrodes has no particular problem, and the highest opening ratio on the side of the transparent picture element electrodes can be advantageously secured.
Example 4(Preparation of Electrodeposition Type Display Apparatus)
A passive matrix-electrodeposition type display apparatus was prepared in substantially the same manner as in Example 1 except that the third electrode was formed from an ITO instead of Ag.
(Evaluation of Driving and Display Properties)
With respect to the counter electrode picture element line A (35 mm from the center of the effective picture element portion), cyclic voltammogram measurements were conducted per predetermined picture elements with respect to the selected transparent picture element electrodes having different distances from the third electrode in the same manner as in Example 1. The results are shown in
As can be seen in
With respect to the active matrix type, electrodeposition type display apparatus prepared in Example 2, an actual display waveform was applied in the same manner as in Example 1 to repeat a cycle of coloring and decoloring. In addition, with respect to the apparatus in which the third electrode was not effective, namely, no third electrode was provided, a waveform was applied to two electrodes, i.e., the display electrode and the counter electrode to repeat a cycle of coloring and decoloring in the same manner. The results of above two were compared to each other. The electrodeposition type display apparatus had initial properties such that the reflectance during colorless (white) was 70% and the optical density (OD) of the display portion during coloring (black) was about 0.8 (reflectance: 13%). Accordingly, the contrast of reflectance obtained was 1:5.
In the apparatus for comparison which had no effective third electrode and operated in a dual electrode mode, the repetition of the cycles until the black density during coloring became 1.0 or less was about 80,000,000, whereas, in the apparatus in which the third electrode was effective, the black density was not lowered to be 1.0 or less even after repetition of the double cycles of the above, and further a phenomenon in which the color remained upon decoloring did not occur. This result indicates that the use of the third electrode can considerably improve the cycle properties, as compared to a conventional apparatus having no third electrode. Further, the use of the third electrode can appropriately control the display switching, as compared to a conventional apparatus having no third electrode. That is, the use of the third electrode can realize an electrodeposition type display apparatus having preferable cycle properties and preferable display quality.
Example 6Using the display electrodes prepared in Example 3 in which no third electrode was formed and the counter electrodes prepared in Example 1 in which no third electrode was formed, and using a twill type silver mesh having about 30-μm one side of the mesh structure as a third electrode, the third electrode was sandwiched with nonwoven fabric and disposed between the display electrodes and the counter electrodes so as to prevent the occurrence of short-circuiting between the third electrode and the other electrodes, thereby preparing an electrodeposition type display apparatus. A polymer electrolyte layer was formed in the same manner as in Example 1.
With respect to the thus-prepared passive matrix-electrodeposition type display apparatus in Example 6, cyclic voltammogram measurements were conducted in the same manner as in Example 1. As a result, there were obtained results substantially similar to those obtained in Example 1. This has confirmed that, in the passive matrix-electrodeposition type display apparatus in which the third electrode having a mesh structure is disposed between the display electrodes and the counter electrodes, the third electrode effectively operates, and thus effectiveness of the use of the third electrode is confirmed.
Example 7Display electrodes were prepared in substantially the same manner as in Example 2 except that no third electrode was formed, and, on a glass substrate having a thickness of 1.5 mm and a size of 8 cm×12 cm, no third electrode was formed, and second electrodes having a stripe structure were formed from an Ag thin film by a known method to prepare counter electrodes. Lead portions connected from these substrates to driving circuits were formed by a known method. Then, as a third electrode, a twill type silver mesh having about 30-μm one side of the mesh structure was used, and the third electrode was sandwiched with nonwoven fabric and disposed between the display electrodes and the counter electrodes so as to prevent the occurrence of short-circuiting between the third electrode and the other electrodes, thereby preparing an active matrix type, electrodeposition type display apparatus. A polymer electrolyte layer was formed in the same manner as in Example 1.
With respect to the thus-prepared electrodeposition type display apparatus in Example 7, cyclic voltammogram measurements were conducted in the same manner as in Example 2. As a result, there were obtained results substantially similar to those obtained in Example 2. This has confirmed that, in the active matrix type, electrodeposition type display apparatus in which the third electrode having a mesh structure is disposed between the display electrodes and the counter electrodes, the third electrode effectively operates, and thus effectiveness of the use of the third electrode is confirmed.
Example 8(Preparation of Display Electrode)
First, on a glass substrate having a thickness of 1.5 mm and a size of 10 cm×10 cm, as transparent picture element electrodes, ITO films were formed by a known method to prepare display electrodes.
(Preparation of Counter Electrode)
On a glass substrate having a thickness of 1.5 mm and a size of 8 cm×12 cm, Ag alloy films and TFTs (thin film transistors) arranged in a plane form at a pitch of 150 μm were prepared by a known method to form picture elements. Then, third electrodes were disposed so that the two third electrodes crossed each other at the almost central portion of the effective picture element portions to prepare counter electrodes. The third electrodes were formed using silver to have a width of 1 μm. Then, an active matrix type, electrodeposition type display apparatus was prepared in the same manner as in Example 2.
With respect to the thus-prepared electrodeposition type display apparatus in Example 8, cyclic voltammogram measurements were conducted in the same manner as in Example 2. As a result, there were obtained results substantially similar to those obtained in Example 2, and substantially similar results were obtained with respect to all the device electrodes from the device electrode immediately adjacent to the third electrode to the farthest one. Generally, it is preferred that the transparent picture element electrode which is a working electrode and the third electrode are as close as possible, but, from the above results, it has been found that the third electrode effectively operates, almost irrespective of the distance between the third electrode and the transparent picture element electrode as a working electrode, even when the third electrode is disposed on the counter electrode side as in the present Example.
Example 9(Preparation of Display Electrode)
Fist, on a glass substrate having a thickness of 1.5 mm and a size of 10 cm×10 cm, as transparent picture element electrodes, ITO films arranged in a line form at a pitch of 150 82 m were formed by a known method. Then, one third electrode was formed at the central portion of the lines of the ITO films so as to be parallel to the lines. The third electrode was formed using Ag to have a width of 1 μm. Then, effective picture element portions and their periphery portions were coated and patterned to form insulating layers perpendicular to the lines of the ITO films. Subsequently, lead portions connected from the substrate to driving circuits were formed by a known method, thus preparing display electrodes.
(Preparation of Counter Electrode)
Counter electrodes were prepared in substantially the same manner as in Example 8 except that no third electrode was formed. Then, an active matrix type, electrodeposition type display apparatus was prepared in the same manner as in Example 2.
With respect to the thus-prepared electrodeposition type display apparatus in Example 9, cyclic voltammogram measurements were conducted in the same manner as in Example 2. As a result, there were obtained results substantially similar to those obtained in Example 2, and substantially similar results were obtained with respect to all the device electrodes from the device electrode immediately adjacent to the third electrode to the farthest one. Generally, it is preferred that the transparent picture element electrode which is a working electrode and the third electrode are as close as possible, but the above results have confirmed that the third electrode effectively operates almost irrespective of the distance between the third electrode and the transparent picture element electrode serving as a working electrode.
Industrial Applicability
The electrochemical display device and electrochemical display apparatus according to the present invention can achieve matrix driving per picture element, and utilize the coloring material and coloring means contained in the electrolyte layer, and further have a third electrode independent of the first transparent electrode and the second electrode.
Therefore, according to the electrochemical display device and electrochemical display apparatus of the present invention, there can be provided an electrodeposition type display device and an electrodeposition type display apparatus having preferable cycle properties and preferable display quality such that display with high contrast and high black density can be achieved.
In addition, by the method for producing an electrochemical display device and the method for producing an electrochemical display apparatus according to the present invention, an electrochemical display device and an electrochemical display apparatus having the above-described structure can be easily produced.
Claims
1. An electrochemical display device characterized by comprising:
- a first transparent electrode;
- an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution;
- a second electrode having said electrolyte layer disposed between said first transparent electrode and said second electrode; and
- a third electrode independent of said first transparent electrode and said second electrode.
2. The electrochemical display device according to claim 1, characterized in that said third electrode is provided as an electrically insulated member on a substrate on which said first transparent electrode is formed.
3. The electrochemical display device according to claim 1, characterized in that said third electrode is provided as an electrically insulated member on a substrate on which said second electrode is formed.
4. The electrochemical display device according to claim 1, characterized in that said third electrode is provided as an electrically insulated member between said first transparent electrode and said second electrode.
5. The electrochemical display device according to claim 4, characterized in that said third electrode is comprised of a metal wire or a mesh structure obtained by weaving said metal wire.
6. The electrochemical display device according to claim 5, characterized in that said third electrode is disposed between insulating materials.
7. The electrochemical display device according to claim 1, characterized in that said third electrode is provided in a state in which said third electrode surrounds an effective picture element portion of said first transparent electrode or said second electrode.
8. The electrochemical display device according to claim 1, characterized in that said third electrode is provided in a state in which said third electrode sandwiches an effective picture element portion of said first transparent electrode or said second electrode.
9. The electrochemical display device according to claim 1, characterized in that a plurality of said third electrodes are provided in a state in which a plurality of said third electrodes cross one another in an effective picture element portion of said first transparent electrode or said second electrode.
10. The electrochemical display device according to claim 1, characterized in that said first transparent electrode is included mainly of SnO2, In2O3, or a mixture thereof.
11. The electrochemical display device according to claim 1, characterized in that said second electrode is a metallic thin film.
12. The electrochemical display device according to claim 1, characterized in that said third electrode is a metallic thin film.
13. The electrochemical display device according to claim 1, characterized in that said third electrode is a transparent electrode included mainly of SnO2, In2O3, or a mixture thereof.
14. The electrochemical display device according to claim 1, characterized in that said third electrode is part of said first transparent electrode or said second electrode, which is in a display inactive state.
15. The electrochemical display device according to claim 1, characterized in that said electrolyte layer is d of an electrolytic solution or a polymer electrolyte layer.
16. The electrochemical display device according to claim 15, characterized in that said electrolytic solution or polymer electrolyte layer contains a metal salt or a quaternary alkylammonium salt.
17. The electrochemical display device according to claim 15, characterized in that a solvent for said electrolytic solution is comprised of water, ethyl alcohol, isopropyl alcohol, propylene carbonate, dimethyl carbonate, ethylene carbonate, γ-butyrolactone, acetonitrile, sulfolane, dimethoxyethane, dimethylformamide, dimethyl sulfoxide, or a mixture thereof.
18. The electrochemical display device according to claim 15, characterized in that a matrix polymer constituting said polymer electrolyte layer is a polymer material having a repeating unit of alkylene oxide, alkylenimine, or alkylene sulfide in a main skeleton unit or a side chain unit, or both of them; a copolymer including a plurality of these different units; or a polymethyl methacrylate derivative; polyvinylidene fluoride; polyvinylidene chloride; polyacrylonitrile; a polycarbonate derivative; or a mixture or laminate thereof.
19. The electrochemical display device according to claim 18, characterized in that said polymer electrolyte layer includes said matrix polymer containing a solvent which is comprised of water, ethyl alcohol, isopropyl alcohol, propylene carbonate, dimethyl carbonate, ethylene carbonate, γ-butyrolactone, acetonitrile, sulfolane, dimethoxyethane, dimethylformamide, dimethyl sulfoxide, or a mixture thereof.
20. The electrochemical display device according to claim 15, characterized in that said polymer electrolyte layer is comprised of a plurality of layers, wherein said coloring means is contained in part of the layers.
21. The electrochemical display device according to claim 1, characterized in that said electrolyte layer contains at least one member selected from a growth inhibitor, a stress relaxing agent, and a brightener for the deposition of said coloring material.
22. The electrochemical display device according to claim 21, characterized in that said growth inhibitor, stress relaxing agent, or brightener is an organic compound having a group having an oxygen atom or a sulfur atom.
23. The electrochemical display device according to claim 1, characterized in that said electrolyte layer contains a reducing agent or an oxidizing agent for suppressing a side reaction which is possibly caused in any of said first transparent electrode and said second electrode mainly due to an anion species during the deposition of said coloring material.
24. The electrochemical display device according to claim 1, characterized in that said coloring material is ions of bismuth, copper, silver, sodium, lithium, iron, chromium, nickel, or cadmium, or ions comprised of a combination thereof.
25. The electrochemical display device according to claim 1, characterized in that said coloring means is an inorganic pigment or an organic pigment, or a dye.
26. The electrochemical display device according to claim 25, characterized in that said inorganic pigment is comprised of powder of titanium dioxide, calcium carbonate, magnesium oxide, or aluminum oxide.
27. The electrochemical display device according to claim 1, characterized in that said electrochemical display device is driven by detecting or sweeping a potential between said third electrode and said first transparent electrode.
28. The electrochemical display device according to claim 1, characterized in that said electrochemical display device has a driving device in said first transparent electrode or said second electrode and said driving device is driven in an active matrix mode.
29. The electrochemical display device according to claim 1, characterized in that said first transparent electrode and said second electrode are arranged in a matrix form, and said device is driven in a passive matrix mode.
30. An electrochemical display apparatus characterized by comprising a plurality of electrochemical display devices arranged in a plane form, each electrochemical display device having: a first transparent electrode; an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution; a second electrode having said electrolyte layer disposed between said first transparent electrode and said second electrode; and a third electrode independent of said first transparent electrode and said second electrode.
31. A method for producing an electrochemical display device, characterized by comprising the steps of:
- forming a first transparent electrode on a transparent support;
- forming an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution;
- forming a second electrode having said electrolyte layer disposed between said first transparent electrode and said second electrode; and
- forming a third electrode independent of said first transparent electrode and said second electrode.
32. A method for producing an electrochemical display apparatus, characterized by comprising the steps of:
- forming a first transparent electrode on a transparent support;
- forming an electrolyte layer containing a coloring material which colors by a coloring means and electrochemical reduction or oxidation, accompanied by deposition or dissolution;
- forming a second electrode having said electrolyte layer disposed between said first transparent electrode and said second electrode; and
- forming a third electrode independent of said first transparent electrode and said second electrode.
Type: Application
Filed: Feb 7, 2003
Publication Date: Apr 28, 2005
Applicant: Sony Corporation (Tokyo)
Inventor: Kenichi Takahashi (Kanagawa)
Application Number: 10/503,122
