JP4433669B2 - Electrodeposition type display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an electrodeposition type display device that performs display by electrodeposition (electrodeposition) of metal ions, which is one of electrochemical display devices.In placeRelated.
[0002]
[Prior art]
In recent years, with the spread of networks, documents that have been distributed in the form of printed materials are now being distributed as so-called electronic documents, and books and magazines are also provided in the form of electronic publications. Is increasing.
[0003]
In order to view this information, a conventional method is to read from a computer CRT or a liquid crystal display. However, it has been pointed out that light-emitting displays are extremely fatigued for ergonomic reasons and cannot withstand long-time reading. In addition, there is a difficulty in that the reading place is limited to the place where the computer is installed.
[0004]
Recently, some notebook computers can be used as portable displays, but they cannot be used for reading for more than a few hours due to power consumption in addition to light-emitting displays. In recent years, reflective liquid crystal displays have also been developed, and if such reflective liquid crystal displays are used, they can be driven with low power consumption. However, the reflectance when liquid crystal is not displayed (white display) is approximately 30%. However, the visibility is remarkably poor compared to the printed matter on paper, and fatigue tends to occur.
[0005]
In order to solve these problems, a so-called paper-like display or electronic paper has been developed recently. These are colored by moving the colored particles between the electrodes mainly by electrophoresis or by rotating the dichroic particles with an electric field. However, in these methods, the gap between particles absorbs light, resulting in poor contrast, and the practical writing speed (within 1 second) cannot be obtained unless the driving voltage is set to 100 V or higher. There is.
[0006]
Electrochemical display devices (ECD) that perform color development based on electrochemical action are superior to the electrophoretic methods described above in terms of high contrast. It has been put into practical use. However, since there is no need for matrix driving in the light control glass or watch display, it cannot be applied to display applications such as electronic paper, and the quality of black is generally poor. However, its application is limited to display devices with low values.
[0007]
In addition, displays such as electronic paper continue to be exposed to light such as sunlight and room light because of their use, but they are used in light control glass and watch displays. In a chemical display device, a required organic material is used to form a black portion. However, in general, organic materials have poor light resistance, and when used for a long period of time, there arises a problem that the black density is lowered due to fading. In addition, a matrix driving type is known as a display device (see, for example, Patent Document 1), but the driving element only constitutes a part of the liquid crystal display device.
[0008]
As a solution to such technical problems, a metal ion is used as a material that undergoes a color change by electrochemical oxidation and reduction, and a white solid polymer electrolyte is used as a material to dissolve the metal ion. There have been proposed an electrochemical display element and an electrochemical display device that can be driven and can increase contrast and black density. Also known is an apparatus (for example, see Non-Patent Document 1) in which a gel electrolyte membrane is formed between opposing electrodes and writing or erasing is performed by electrodeposition of bismuth-based metal ions.
[0009]
[Patent Document 1]
Japanese Examined Patent Publication No. 4-73764
[0010]
[Non-Patent Document 1]
B. Warszawski, Matrix Addressing and Driving in a New Electrochemical Display Technology, Polyvision France, Paris, France, SID 93 DIGEST 993
[0011]
[Problems to be solved by the invention]
In the electrochemical display element having such a configuration, a polymer solid electrolyte existing between the first transparent electrode and the second electrode is energized between the first transparent electrode and the second electrode. Electrodeposition due to metal ions contained in the polymer solid electrolyte layer occurs in the layer, resulting in a color change. Since this solid polymer electrolyte layer contains a colorant, it is possible to increase the contrast when a color change occurs, and it is also possible to drive the matrix by a drive element.
[0012]
However, in the case of this device using a conventional electrochemical reaction, it takes several hundred ms or more from applying a voltage to coloring. This has been a serious problem when this device is applied to display applications such as electronic paper. In order to express an image freely, it is necessary to form a pixel electrode and perform matrix driving. However, if line-sequential scanning is performed at the time of driving, it is the product of the product of the pixel coloring time and the number of scanning lines. Because it only takes time. For example, an SVGA screen will take several minutes.
[0013]
When used as electronic paper, the response speed is not necessarily as high as video playback, but considering the practical aspect, it is necessary to set the writing speed on the entire screen to within about 1 second. It is necessary to shorten the time required for erasing to about 100 ms or less.
[0014]
  Accordingly, in view of the above technical problems, the present invention provides an electrodeposition type display device having a structure capable of shortening the time required for writing and erasing.PlaceThe purpose is to provide.
[0015]
[Means for Solving the Problems]
  In order to solve the above-mentioned problem, an electrodeposition type display device of the present invention isA substantially flat substrate disposed on the back side of the electrolyte layer, a plurality of strip-like back electrodes provided on the substrate, and a back electrode, which is disposed so as to deposit metal ions by passing current. A polymer electrolyte layer, a strip-shaped transparent electrode facing the back electrode across the polymer electrolyte layer and provided in a direction orthogonal to the back electrode, a transparent substrate provided on the transparent electrode, and transparent A transparent insulating film that covers the electrode, and an opening in the insulating film in which the transparent electrode and the polymer electrolyte layer are directly connected are formed in the pixel, and the area of the opening is 100 μm. ² More than 5mm ² It is as follows.
[0016]
The electrolyte membrane containing the metal ions is sandwiched between a pair of opposed electrodes, and a current is passed between the pair of electrodes, whereby the metal ions can be electrodeposited or dissolved on the electrode portion. According to experiments conducted by the inventors, it has been found that the size of such opposing electrodes strongly depends on the rate of electrochemical reaction, and the electrode area is about 5 mm.²The data that the coloring time can be reduced to 100 ms or less, which is practically useful, is obtained below. Unlike a liquid crystal device that responds to an applied voltage, an electrochemical device requires charge transfer at the electrode interface, and considering the current injection efficiency from the power supply side, the response speed is relative to the current collector area. This greatly depends on the ratio of the pixel area. In other words, even when the response speed equal to that of a video signal cannot be expected, the maximum electrode that satisfies this requirement is provided with a standard of 100 ms or less as a coloring time in view of loss of practicality if metal ion deposition takes several minutes. Area is 5mm²Therefore, the electrode area is 5mm²It is as follows. In addition, the lower limit is about 100 μm from the viewpoint of human visual ability because it is difficult to recognize visually by a size of about 10 μm square.²That's it.
[0017]
  Also,It is composed of an electrodeposition type display device having the above structure. In particular, at least one of the opposing electrodes is composed of a transparent electrode, and the size of the transparent electrode in a pixel is 100 μm.²More than 5mm²You may set so that it may become the following areas. When the electrode is made of a transparent material, it can be formed in a structure in which the electrode pattern is covered with an insulating film, and the size of the opening formed in the insulating film is an electrode area that functions for electrodeposition. Even in such an electrode structure, the response speed greatly depends on the ratio of the pixel area to the current collector area, and the upper limit area is 5 mm from the practical point of view.²The lower limit area is 100 μm from the viewpoint of visibility.²It is said above.
[0018]
  The electrodeposition type display device of the present invention is also provided.IsCausing contrast by electrodeposition and dissolution of metal ionsDrive, Multiple arrayPixelAnd having a structure in which the electrolyte membrane containing the metal ions is sandwiched between a pair of opposing electrodes, and has a thickness of 100 μm.²More than 5mm²Drive using one of the electrodes whose pixel size is set to the following area:The
[0019]
  With the above driving, the electrode area is 100 μm²More than 5mm²Since it is set as follows, the response speed depending on the ratio of the pixel area to the current collector area satisfies the respective conditions from the viewpoints of practicality and visibility. Therefore, it is possible to display an image with good responsiveness.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an electrochemical display device according to an embodiment of the present invention will be described with reference to the drawings.
[0021]
First, the structure of the electrochemical display device of this embodiment will be described with reference to FIG. The electrochemical display device of the present embodiment includes an electrolyte layer sandwiched between parallel row electrodes and column electrodes extending in the row direction and the column direction, respectively, and a voltage is applied between the row electrodes and the column electrodes. In this case, the display is a passive matrix drive type and electrodeposition type (electrodeposition) type display device in which metal ions are deposited from the substrate.
[0022]
This passive matrix drive type electrochemical display device includes a substantially flat substrate 11 disposed on the back side of an electrolyte layer, and a plurality of strip-like back electrodes 12 each extending in the row direction of the substrate, for example. The polymer electrolyte layer 13 disposed so as to cover the back electrode 12 and the back electrode 12 extending in the direction perpendicular to the back electrode 12 across the polymer electrolyte layer 13. A plurality of strip-shaped transparent electrodes 14 and a transparent base material 15 provided on the plurality of strip-shaped transparent electrodes 14 are the main constituent elements and are omitted in FIG. 14 is covered with a transparent insulating film, and an opening for directly connecting the transparent electrode 14 to the polymer electrolyte layer 13 with a relatively small size is formed in the pixel corresponding portion. By depositing metal ions through such a small opening, efficient deposition is performed, and writing in a short time is realized as described later.
[0023]
The substantially flat substrate 11 is a plate functioning as a support for the electrodes 12, 14 and the polymer electrolyte layer 13, and is not necessarily transparent, and reliably holds the electrodes 12, 14 and the polymer electrolyte layer 13. A usable substrate, film, sheet, or the like can be used. Examples of the substrate 11 include a glass substrate such as a quartz glass plate and a white plate glass plate, a ceramic substrate, a paper substrate, and a wood substrate. However, the substrate 11 is not limited thereto, and a polyethylene resin naphthalate is used as a synthetic resin substrate. , Esters such as polyethylene terephthalate, cellulose esters such as polyamide, polycarbonate, cellulose acetate, fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene-cohexafluoropropylene, polyethers such as polyoxymethylene, polyacetal, polystyrene, polyethylene, Examples thereof include polyolefins such as polypropylene and methylpentene polymer, and polyimides such as polyimide-amide and polyetherimide. When these synthetic resins are used as a support, it is possible to form a rigid substrate that does not easily bend, but it is also possible to form a film-like structure having flexibility.
[0024]
On the substrate 11, a plurality of back electrodes 12 are formed extending in parallel. The back electrode 12 has, for example, a belt-like pattern extending in the row direction. Such an electrode material may be any electrochemically stable metal, but is preferably silver, platinum, They are chromium, aluminum, cobalt, palladium, etc., and can be formed by forming a film made of a good conductor such as a metal film on the substrate 11. In addition, the electrode may be configured by a composite material. For example, an electrode having a structure in which silver is deposited on an electrode material such as copper may be used. The back electrode 12 can use carbon as an electrode if the metal used for the main reaction can be sufficiently supplemented in advance or at any time. As a method for supporting carbon on the electrode, there is a method of forming an ink using a resin and printing it on the substrate surface. By using carbon, it is possible to reduce the price of the electrode. Note that signal lines (not shown) for supplying signals are respectively connected to the end portions of the back electrodes 12, and a drive circuit for the back electrodes 12 is connected to these signal lines.
[0025]
The polymer electrolyte layer 13 is disposed between the opposing electrodes 12 and 14, and deposits metal ions according to the current passing through the polymer electrolyte layer 13, and the deposited metal ions function as a coloring material. It is a layer to do. The polymer electrolyte layer 13 has a configuration including a polymer material for a base material, a metal salt, a plasticizer, and the like, and the polymer electrolyte layer 13 has a white pigment or the like for exhibiting a background color. included.
[0026]
As the polymer material for the base material used for the solid polymer electrolyte constituting the polymer electrolyte layer 13, the skeleton unit is represented by-(CCO) n-,-(CCN) n-, or-(CCS) n-, respectively. And polyethylene oxide, polyethyleneimine, and polyethylene sulfide. A structure having a branch may be used as a main chain structure. Polymethyl methacrylate, polyvinylidene fluoride, polyvinylidene chlorite, polycarbonate and the like are also preferable.
[0027]
When forming the polymer electrolyte layer 13, it is preferable to add a necessary plasticizer to the matrix polymer. As a preferable plasticizer, when the matrix polymer is hydrophilic, water, ethyl alcohol, isopropyl alcohol and a mixture thereof are preferable. When the matrix polymer is hydrophobic, propylene carbonate, dimethyl carbonate, ethylene carbonate, γ-butyrolactone, Acetonitrile, sulfolane, dimethoxyethane, ethyl alcohol, isopropyl alcohol, dimethylformamide, dimethyl sulfoxide, dimethylacetamide, n-methylpyrrolidone and mixtures thereof are preferred.
[0028]
The polymer electrolyte layer 13 is formed by dissolving an electrolyte in the matrix polymer. Examples of the electrolyte include silver nitrate, silver borofluoride, silver halide, silver perchlorate, silver cyanide, and silver thiocyanide. In addition to at least one silver salt selected from quaternary ammonium halides (F, Cl, Br, I) and alkali metal halides (LiCl, LiBr, LiI, NaCl, NaBr, NaI, etc.), alkali metal cyanide A solution containing at least one kind of supporting electrolyte selected from a salt and an alkali metal thiocyanide is dissolved as an electrolyte.
[0029]
The polymer electrolyte layer 13 contains a colorant in order to improve contrast. When the coloring is black, a white highly concealing material is introduced as the background color. As such a material, for example, white particles for coloring are used, and titanium dioxide, calcium carbonate, silica, magnesium oxide, and aluminum oxide can be used as the white particles for coloring.
[0030]
In the case of using inorganic particles, the mixing ratio of the colorant is preferably about 1-20 wt%, more preferably about 1-10 wt%, and further preferably about 5-10 wt%. This is because inorganic white particles such as titanium oxide are not soluble in the polymer and only disperse. When the mixing ratio increases, the inorganic particles aggregate, resulting in non-uniform optical density. . Moreover, since inorganic particles do not have ionic conductivity, an increase in the mixing ratio causes a decrease in the conductivity of the solid polymer electrolyte. Considering both, the upper limit of the mixing ratio is about 20 wt%.
[0031]
When inorganic particles are mixed as a colorant, the thickness of the polymer electrolyte layer 13 is preferably 10 μm-200 μm, more preferably 10 μm-100 μm, and even more preferably 10 μm-50 μm. The thinner one is preferable because the resistance between the electrodes becomes smaller, which leads to reduction in coloring / decoloring time and power consumption. However, when the thickness is 10 μm or less, the mechanical strength is lowered, and pinholes and cracks are generated, which is not preferable. On the other hand, if it is too thin, the amount of white particles mixed becomes small, and the whiteness (optical density) becomes insufficient.
[0032]
The mixing ratio of the colorant may be 10 wt% in the case of using a pigment. This is because the coloring efficiency of the dye is much higher than that of inorganic particles. Therefore, if the dye is electrochemically stable, contrast can be obtained even with a small amount. Usually, an oil-soluble dye is preferred as the pigment.
[0033]
The transparent electrode 14 arranged on the side facing the back electrode 12 across the polymer electrolyte layer 13 has, for example, a belt-like pattern extending in a direction substantially perpendicular to the back electrode 12, that is, in the column direction. Have. The transparent electrode 14 is made of a transparent conductive film, and is made of In.₂O_ThreeAnd SnO₂Of so-called ITO film and SnO₂Or In₂O_ThreeIt is preferable to use a film coated with. These ITO films and SnO₂Or In₂O_ThreeA film coated with Sn may be doped with Sn or Sb, and MgO, ZnO, or the like can also be used. Note that signal lines (not shown) for supplying signals are respectively connected to the end portions of the transparent electrodes 14, and a drive circuit for the transparent electrode 14 is connected to the signal lines.
[0034]
A transparent base material 15 is attached on the transparent electrode 14. As the transparent substrate 15, a transparent glass substrate such as a quartz glass plate or a white plate glass plate can be used, but is not limited thereto. Esters such as polyethylene naphthalate and polyethylene terephthalate, polyamide, polycarbonate, cellulose acetate Cellulose esters such as polyvinylidene fluoride, fluoropolymers such as polytetrafluoroethylene-cohexafluoropropylene, polyethers such as polyoxymethylene, polyacetals, polystyrene, polyethylene, polypropylene, polyolefins such as methylpentene polymer, and polyimide-amide And polyimide such as polyetherimide. When these synthetic resins are used as the transparent base material 15, it is possible to form a rigid substrate that does not easily bend, but it is also possible to form a flexible film-like structure. .
[0035]
Next, the basic operation of the electrodeposition type display device of this embodiment having such a structure will be described with reference to FIGS. In the electrodeposition type display device of this embodiment, metal ions such as silver ions dissolved in the polymer electrolyte layer 13 tend to precipitate by controlling the transparent electrode 14 to the minus side, and particularly in FIG. As shown in the cyclic volta monogram, by applying a potential exceeding the precipitation overpotential of about −0.7 V, metal ions such as silver ions are reduced, and the reduced metal ions are transferred onto the transparent electrode 14. It precipitates in.
[0036]
Therefore, when the deposition is performed, a negative potential lower than the deposition overpotential is once applied to the transparent electrode 14 to promote the deposition. Subsequently, electrodeposition of metal ions can be promoted by maintaining a deposition potential of about −0.5 V in the cyclic volta monogram of FIG. In FIG. 2, the pixel that is blackened by the electrodeposition is indicated by “B”, and the pixel that has not been reduced by the metal ions is left as “W” in white. This white portion has a high light reflectance and is maintained at, for example, 70% or more. The reflectance of the black part is set to 2.7% or less, for example.
[0037]
On the other hand, in the case of erasing, the deposited metal is dissolved by applying a reverse potential to the transparent electrode 14. The black color gradually disappears due to the deposition of the metal, and the white color of the polymer electrolyte layer 13 appears. By switching the potential with respect to the transparent electrode 14 between plus and minus, the display color can be switched between black and white. This potential switching control can be performed, for example, by switching and controlling the switch 18 in FIG. 2 to the battery 16 side or the potential 17 side having a reverse potential relationship with the battery 16. FIG. 3B is a diagram showing the relationship between the charge density and the optical density. In general, the higher the charge density, the higher the optical density tends to be.
[0038]
FIG. 4 is a perspective view of the transparent electrode portion. A plurality of transparent electrodes 14 are formed in a band-like pattern on the transparent substrate 15, and an insulating film 19 is formed so as to cover each transparent electrode 14. The insulating film 19 is provided with an opening 20 having a small size on the transparent electrode 14, and the opening size of the opening 20 functions as an in-pixel size of the transparent electrode. In form, the area is 100 μm²More than 5mm²Set to: By providing such a small opening 20, the transparent electrode 14 contacts the internal polymer electrolyte layer 13 with a small area of the opening 20. Therefore, in the portion in the opening 20 of the polymer electrolyte layer 13, current concentration occurs in the opening 20 having a small size while the transparent electrode 14 functions as a current collector, and writing in a short time is realized. become. In this embodiment, the pixel electrode size is 100 μm.²More than 5mm²Although it is as follows, preferably 400 μm²4mm or more²It is also possible to: The thickness of the polymer electrolyte layer can be, for example, 10 μm to 200 μm, preferably 10 μm to 100 μm, and more preferably 10 μm to 50 μm.
[0039]
Next, a segment display cell structure created as an embodiment of the display device will be described with reference to FIGS. The segment display cells are formed with openings of different sizes, each having a circular shape or a square shape, and the size of the opening is examined by changing the optical density.
[0040]
First, the structure of the manufactured segment display cell will be described with reference to FIG. A polymer electrolyte layer 23 held between the spacers 22 is formed on the back electrode 21, and a plurality of transparent electrodes 24 each covered with an insulating film 26 are formed on the polymer electrolyte layer 23. It has a structure in which a transparent substrate 25 is formed on the transparent electrode 24. The segment display cell having such a structure is specifically manufactured by the following procedure.
[0041]
First, for the transparent electrode 24 as a display electrode, a 40 mm square or 30 mm square glass substrate having a thickness of 0.8 mm is used as the transparent base material 25, and a strip-like transparent material is formed on the transparent base material 25 by the following procedure. An electrode 24 and an insulating film 26 were formed. First, an ITO film having a film thickness of 500 nm and a sheet resistance value of 12Ω / □ was formed on a glass substrate by sputtering. Next, a photoresist was applied on the ITO film, and the photoresist was formed in a strip shape by a lithography method. Next, the glass substrate was eroded in an ITO etching solution, and the ITO film in a portion not covered with the photoresist was removed to form a transparent electrode 24. Thereafter, the photoresist is removed with an organic solvent such as acetone, and TEOS (ethyl silicate Si (OC₂H_Five)_Four: Tetra-Ethoxyortho-Silicate) and O₂SiO used as the insulating film 26 by the plasma CVD method using₂Was deposited to 200 nm. Next, SiO₂Photoresist is applied on the film, the photoresist is formed into a desired shape by lithography, and this substrate is eroded in a mixed solution of ammonium fluoride, hydrofluoric acid, etc. SiO₂The membrane was removed. Thereafter, the photoresist was removed with an organic solvent such as acetone. Here, a plurality of desired shapes are formed by changing the diameter of the circular opening as shown in FIGS. 5 and 6, or a plurality of shapes are formed by changing the diameter of the square opening as shown in FIG. The shape is such as These shapes will be described later.
[0042]
The back electrode 21 which is a counter electrode was produced by the following procedure. First, a copper electrode was first formed on the entire surface of an epoxy resin such as polycarbonate or PET (polyethylene terephthalate) or a glass epoxy resin used for a circuit board. Subsequently, an electric field was applied to the formed electrode, and it was immersed in a solution in which silver (or a desired metal) was dissolved, and silver was deposited on the electrode by an electroplating method, whereby the back electrode 21 was produced. The copper electrode was about 15 μm, for example, and the silver electrode was about 15 μm, for example, and the total thickness was about 30 μm. There is an electroless method in which silver or metal is deposited without applying an electric field, but the electroplating method is desirable because the deposited metal becomes thicker.
[0043]
After forming such a back electrode 21, in order to form the polymer electrolyte layer 23, 1 part by weight of polyvinyl alcohol having a molecular weight of about 350,000, 10 parts by weight of a 1: 1 mixed solvent of water and isopropyl alcohol, bromide 1.7 parts by weight of lithium and 1.7 parts by weight of silver iodide were mixed and heated to 120 ° C. to prepare a uniform solution. Next, 0.2 parts by weight of aluminum oxide having an average particle size of 0.5 μm was added thereto, and the mixture was uniformly dispersed with a homogenizer.
[0044]
After the solution uniformly dispersed by the homogenizer was applied to the insulating film 26 of the base material 25 with a doctor blade at a thickness of 100 μm, the back electrode 21 on the opposite electrode side was immediately bonded, and this was applied at 110 ° C. and 0.1 MPa. A gelled polymer electrolyte layer 23 was formed between the two electrodes by drying under reduced pressure for 1 hour. Subsequently, the end face of bonding was sealed with the spacer 22 and the adhesive.
[0045]
FIG. 5B and FIG. 6 are examples in which a plurality of openings are formed by changing the diameter of the circular opening. Here, each size of the opening will be described. The size of the largest opening 31a is the diameter. The next largest opening 31b has a diameter of 2.0 mm, the next largest opening 31c has a diameter of 1.0 mm, and the smallest opening 31d has a diameter of 0.00 mm. 5 mm. For each dimension shown in FIG. 6, the transparent electrode width R₁Is about 9 mm, and the size R from the edge of the display cell to the position of the opening is R₂Is about 14mm, R₃And R₄Are the substrate sizes, each about 40 mm.
[0046]
Similarly, FIG. 7 shows an example in which a plurality of openings are formed in the insulating film 47 covering the electrode 46 so as to change the diameter of the square openings. The structure of the electrolyte layer has the same structure as the segment display cell having the structure shown in FIG. 5 described above. Here, each size of the opening will be described. The largest opening 33a has a size of 3.0 mm square, the next largest opening 33 b has a size of 2.0 mm square, and the next largest opening 33 c has a size of 3.0 mm square. The size is 1.0 mm square, and the size of the smallest opening 33 d is 0.5 mm square. For each dimension shown in FIG. 7, the transparent electrode width L₁Is approximately 6 mm, and the size L from the edge of the display cell to the position of the opening₂Is about 12mm, L₃Is a substrate size of about 30 mm.
[0047]
Using the segment display cell having the circular opening of FIG. 6 and the square opening of FIG. 7, the drive, drive, and display characteristics were evaluated. First, a desired display side electrode is selected, and at the time of color development, a voltage of -2 V is applied to the second electrode having a display electrode as a back electrode made of a metal such as silver, and the display electrode side In the case of decoloring, the color display and the colorless [white] display were switched by causing the oxidation reaction of the voltage of +2.4 over 1.0 to 1.2 times the time of the reduction reaction. .
[0048]
In the structure of the segment display cell shown in FIG. 6, the reflectance when colorless (white) is ˜63% (OD˜0.2), and the coloring behavior (coloring speed) at the time of color development is shown in FIG. 8. The vertical axis in FIG. 8 is the optical density, and indicates that black is dark when the numerical value is higher. The horizontal axis of the graph of FIG. 8 shows the time of logarithmic display. As is apparent from the graph of FIG. 8, when the diameter φ of the circular opening is in the range of 0.5 mm to 2.0 mm, the coloring behavior at the time of color development shows a steep rise, and in the openings 31b, 31c, and 31d, It can be seen that the coloring is performed quickly. On the other hand, when the diameter φ of the circular opening is as large as 7.0 mm, the coloring is slow, and it takes 0.1 seconds or longer even when the OD is 0.5. That is, it is shown that when the opening is large, the coloring reaction rate is slow, and the size of the opening is 4 to 5 mm.²It has been shown that the electric field concentration at the opening is good when the area is as follows.
[0049]
FIG. 9 is a graph showing the response times of the circular opening shown in FIG. 6 and the square opening shown in FIG. 7, the vertical axis is the response time (seconds), and the horizontal axis is the area (mm²). In FIG. 9, (1) is a circular opening 31d with a diameter of 0.5 mm, (2) is a circular opening 31c with a diameter of 1.0 mm, (3) is a circular opening 31b with a diameter of 2.0 mm, and (4) is The circular opening 31a has a diameter of 7.0 mm. In addition, (5) is a 0.5 mm square opening 33 d, (6) is a 1.0 mm square opening 33 c, (7) is a 2.0 mm square opening 33 b, and (8) is 3. A square opening 33a of 0 mm square is shown.
[0050]
As is apparent from FIG. 9, regardless of whether the display portion is circular or square, the small size opening tends to have a shorter response time, and the time to reach OD = 1.0 is shorter. . Further, in the circular opening 31a having a diameter of 7.0 mm of (4) and the square opening 33a of 3.0 mm square of (8), the area becomes too large to achieve a required response speed. That is, the display area is ~ 5mm²If it is below, it is extrapolated that the response time is 0.1 sec or less. From a practical aspect, when the response speed is up to about 0.1 sec, a circular opening having a diameter of 2.0 mm or less or 2 A square opening of less than 0.0 mm square will be selected. In each example of FIGS. 8 and 9, the measurement is performed with the detector focused on the center of the display unit.
[0051]
As an electrodeposition type display device according to another embodiment, as shown in FIGS. 10 and 11, a potential detection electrode 56 independent of the transparent electrode 54 and the back electrode 52 may be formed as the third electrode. Good. These potential detection electrodes 56 are generally referred to as reference electrodes, and are the same surface as the back electrode 52 on the substrate 51 facing the transparent electrode 54 or the polymer electrolyte layer 53 on the transparent base material 55. These electrodes 54 and 52 are disposed as electrically insulated members, and are used to detect the potential of the transparent electrode 54 on the transparent base 55 or the back electrode 52 on the substrate 51. It is done.
[0052]
The potential detection electrode 56 serving as a reference electrode can be installed on the same surface as the transparent electrode 54 or the back electrode 52. In order to accurately detect the potential in the course of the reaction, it is preferable to form it on the transparent electrode 54 side, but this is not preferable in this respect because the aperture ratio decreases. The electrode material is preferably silver, and one to a plurality of electrodes are provided between the stripe electrodes in parallel to the electrodes, and one to a plurality of them are installed at right angles to the electrodes so as to be connected at an orthogonal intersection. In addition, in the portion where the potential detection electrode 56 perpendicular to the striped electrodes 52 and 54 crosses the striped electrodes 52 and 54, the surfaces of the striped electrodes 52 and 54 are coated with an insulating film. There is a need.
[0053]
Further, a passive matrix display device as still another embodiment will be described with reference to FIGS. Similar to the display device of FIG. 5, first, the transparent electrode side structure, which is a display electrode, is formed on a polycarbonate substrate having a size of 10 cm × 10 cm and a thickness of 0.2 mm on the polycarbonate transparent substrate 73 and the insulating film by the following procedure. Formed. Specifically, the stripe width P of the transparent electrode 73₂Is 150 μm and the pitch P of the transparent electrode 73 is₃Is 170 μm pitch, and the size P of the opening 74 (the portion not covered by the insulating film) is P₁First, an ITO film having a film thickness of 500 nm and a sheet resistance value of 12 Ω / □ is formed on a polycarbonate substrate by sputtering, and then a photoresist is applied on the ITO film, and the photoresist is applied by lithography. A desired stripe shape was formed. Next, the polycarbonate substrate was eroded in an ITO etching solution, and the ITO film in a portion not covered with the photoresist was removed. Thereafter, the photoresist was removed with an organic solvent such as acetone. Next, TEOS (ethyl silicate Si (OC) is formed on the striped ITO film.₂H₅)₄: Tetra-Ethoxyortho-Silicate) and O₂By the plasma CVD method using₂Was deposited to 200 nm.
[0054]
Next, SiO₂Photoresist is applied on the film, the photoresist is formed into a desired shape by lithography, and this substrate is eroded in a mixed solution of ammonium fluoride, hydrofluoric acid, etc. SiO₂The membrane was removed. Thereafter, the photoresist was removed with an organic solvent such as acetone.
[0055]
The back electrode 71 which is a counter electrode arranged facing this was produced by the following procedure. First, copper electrodes were formed in stripes on a substrate 72 made of an epoxy resin such as polycarbonate, PET, or a glass epoxy resin used for a circuit board. As a method for forming a striped copper electrode, first, copper is formed on the entire surface by sputtering or the like. Subsequently, a photoresist is applied to the copper electrode on the entire surface, covered with a stripe-shaped metal mask or a mask for blocking ultraviolet rays, and irradiated with ultraviolet rays. The portions of the photoresist and electrodes masked by the lithography method are removed by wet etching or dry etching so that the stripe-shaped electrodes 71 are insulated. Subsequently, an electric field is applied to the formed striped electrode 71 so as to be immersed in a solution in which silver or a desired metal is dissolved, and silver or metal is deposited on the electrode 71 by an electroplating method. Is made.
[0056]
The copper electrode portion is about 15 μm, the silver electrode portion is about 15 μm, and the total thickness is about 30 μm. There is an electroless method in which silver or metal is deposited without applying an electric field, but the electroplating method is preferable because the thickness of the deposited metal becomes thicker. It is desirable for the substrate 72 to make the interval between pixels to be displayed as narrow as possible. The pixel gap is covered with a solid electrolyte, but it is desirable to use a white substrate 72 as much as possible, assuming that the solid electrolyte can be seen through.
[0057]
For production of the display electrode and preparation and application of the polymer solid electrolyte, 1 part by weight of polyvinyl alcohol having a molecular weight of about 350,000, 10 parts by weight of a 1: 1 mixed solvent of water and isopropyl alcohol, and 1.7 parts by weight of lithium bromide Then, 1.7 parts by weight of silver iodide was mixed and heated to 120 ° C. to prepare a uniform solution. Next, 0.2 part by weight of titanium dioxide having an average particle size of 0.5 μm was added thereto, and the resulting mixture was uniformly dispersed with a homogenizer.
[0058]
After coating this onto the substrate with a doctor blade at a thickness of 60 μm, the second electrode was immediately bonded together, and this was dried under reduced pressure at 110 ° C. and 0.1 MPa for 1 hour to obtain a gelled polymer solid electrolyte. Formed between two electrodes. Next, the bonded end surfaces were sealed with an adhesive to obtain a configuration as shown in FIG.
[0059]
Next, driving and display characteristics of the passive matrix display device according to this example were evaluated. A desired pair of stripe electrodes 73 and 71 are selected by a known method, and at the time of color development, an electric quantity of 5 μC per pixel is supplied to the display electrode for 0.1 second, causing a reduction reaction on the display electrode side and decoloring. Occasionally, oxidation was performed with the same amount of electricity to switch between colored and colorless (white) display.
[0060]
The reflectance when colorless (white) was 70%, and the optical density (OD) of the display portion when colored (black) was about 1.4 (reflectance 4%). Further, as shown in FIG. 13, pixels that were not selected did not develop or lose color. Note that the time required to reach OD = 1 was about 30 ms. After leaving the colored state, the circuit was opened and allowed to stand, and it was found that the optical density of the display part after one week did not change and had sufficient memory properties. When the coloring and decoloring cycles were repeated, the number of repeated cycles until the black density at the time of coloring became 1.0 or less was about 8 million.
[0061]
In the above-described embodiment, the method for setting the size of the opening formed in the insulating film has been described as a method for limiting the area of the electrode in the pixel. Can also be made smaller.
[0062]
【The invention's effect】
Electrodeposition type display device of the present inventionIn placeAccording to this, the size of the electrode inside the pixel is adjusted to 100 μm by adjusting the size of the opening²More than 5mm²Since the following areas are set, the response speed depending on the ratio of the pixel area to the current collector area satisfies the conditions from the viewpoints of practicality and visibility. Therefore, it is possible to display an image with good responsiveness.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an example of an electrodeposition type display device according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view for explaining the operation of an example of an electrodeposition type display device according to an embodiment of the present invention.
FIGS. 3A and 3B are graphs for explaining the operation of an example of an electrodeposition type display device according to an embodiment of the present invention, where FIG. 3A is a cyclic volta monogram, and FIG. 3B is an optical density with respect to charge density; It is a graph of.
FIG. 4 is an enlarged perspective sectional view of the vicinity of a transparent electrode of an example of an electrodeposition type display device according to an embodiment of the present invention.
5A and 5B are diagrams showing a structure of a segment display cell as an example of an electrodeposition type display device according to an embodiment of the present invention, wherein FIG. 5A is a schematic cross-sectional view, and FIG. 5B is a plan view. It is.
FIG. 6 is a plan view showing various circular openings formed in the segment display cell.
FIG. 7 is a plan view showing various square openings formed in the segment display cell.
FIG. 8 is a coloring characteristic diagram illustrating that the coloring speed varies depending on the size of the circular opening.
FIG. 9 is a response characteristic diagram explaining that the response speed varies depending on the size of the opening.
FIG. 10 is a schematic perspective view showing an example of an electrodeposition type display device according to another embodiment of the present invention.
11 is a plan view of an example of the electrodeposition type display device of FIG.
FIG. 12 is a schematic plan view showing the structure of an embodiment according to an example of an electrodeposition type display device of the present invention.
13 is a diagram showing a display state of a pixel when the apparatus of FIG. 12 is operated.
[Explanation of symbols]
11 Substrate
12 Back substrate
13 Polymer electrolyte layer
14 Transparent electrode
15 Transparent substrate
21 Back electrode
22 Spacer
23 Polymer electrolyte layer
24 Transparent electrode
25 Transparent substrate
31a-31d, 33a-33d opening
51 substrates
52 Back electrode
53 Polymer electrolyte layer
54 Transparent electrode
55 Transparent substrate
56 Potential detection electrode
71 Back electrode
72 substrates
73 Transparent electrode
74 opening

Claims (5)

A substantially flat substrate disposed on the back side of the electrolyte layer;
A plurality of strip-shaped back electrodes provided on the substrate;
A polymer electrolyte layer disposed over the back electrode and depositing metal ions by passing current;
A strip-shaped transparent electrode facing the back electrode across the polymer electrolyte layer and provided in a direction orthogonal to the back electrode;
A transparent substrate provided on the transparent electrode;
A transparent insulating film covering the transparent electrode;
In the insulating film, an opening for directly connecting the transparent electrode and the polymer electrolyte layer is formed in the pixel,
The area of the opening is 100 μm ² More than 5mm ² Is
Electrodeposition type display device. The pixels arranged in a matrix, electrodeposition type display apparatus 請 Motomeko 1 wherein that will be passive matrix driving. 2. The electrodeposition display device according to claim 1, wherein the polymer electrolyte layer is formed by dissolving an electrolyte in a base polymer, and the electrolyte is composed of a silver salt and a supporting electrolyte. The electrodeposition type display device 請 Motomeko 1, wherein the colorant Ru is introduced to improve the contrast in the polyelectrolyte layer. Electrodeposition type display device adjacent 請 Motomeko 1 reference electrode for sensing the potential of the pixel electrode is Ru is formed according to the pixel.

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