JPS63301028A - Solution type electrochromic element - Google Patents

Abstract

PURPOSE:To obtain stable color formation by providing a translucent film which is disposed to face a transparent display electrode and isolates a color forming soln. to one side of the electrode to the inside of a soln. layer. CONSTITUTION:The translucent film 7 which is disposed to face the transparent display electrode 2 and isolates the color forming soln. to one side of the electrode 2 is provided in the soln. layer. Migration of molecules, which are macromolecules and make coloration and decoloration, between the electrodes 2 and 4 is selectively blocked by the translucent film 7 at the time when electric current flows in the soln. or the molecules disperse by impressing two voltages on the electrodes. Namely, a color forming layer 5 contg. the color forming soln. isolated by the translucent film 7 is disposed on the transparent display electrode 2 side and a negative potential is impressed on the transparent display electrode 2 side. Then, the molecules which are reduced to form a color on the surface of the transparent display electrode 2 cannot migrate to the other electrode 4 side and stay near the transparent display electrode 2, since there is the translucent film 7. The stable color formation is thereby attained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a solution type electrochromic device (hereinafter referred to as EC
It is called a D element. ), and in particular relates to an ECD element with improved color developing and fading characteristics.

[Conventional technology]

ECD elements are beginning to be used in various display devices as non-emissive display elements. Figure 3 is a typical conventional ECD
FIG. 3 is a schematic cross-sectional view of the element. In FIG. 3, 21 is a glass substrate on which a transparent display electrode 22 made of a tin-doped indium oxide (hereinafter referred to as ITO) film is attached, and 23 is arranged as a counter electrode via a spacer 24 to maintain a gap. A stainless steel plate 25 is an epoxy resin that seals the joint. Further, 26 is a solution layer filled with a solution in which appropriate amounts of heteropolyacid, solvent, and oxide powder are mixed.

Next, the operation of the ECD element configured as described above will be explained with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing the state of reaction and diffusion on the electrode surface of a conventional 0ECD element, and FIG. 5 is a diagram showing the distribution of color-forming molecules and color-erasing molecules after a certain period of time has elapsed.

In FIGS. 4 and 5, 31a is a coloring molecule of a heteropolyanion, 31b is a decolorizing molecule of a heteropolyanion, and E is a DC power source.

Now, when a negative potential is applied to the transparent display electrode 22 side as shown in FIG. 4 and FIG. The molecules 31a are reduced and colored blue, and the colored molecules 31a diffuse into the solution layer 26 as they are.

On the other hand, on the surface of the stainless steel plate 23, which is the counter electrode, the colored molecules 31a are oxidized by taking electrons from N1m, and are decolored to become colorless molecules 31b, which diffuse into the solution [26]. In this way, when a voltage is applied, a reduction reaction at the negative electrode and an oxidation reaction at the positive electrode occur simultaneously. The molecules that have finished reacting on the electrode surface move into the solution Ji26 by diffusion, and the molecules that were inside the solution N2G reach the electrode surface by diffusion and react.

As time passes, molecules 31a colored at the negative electrode and molecules 31b decolored at the positive electrode mix in the solution and become uniform in the center B of the solution layer 26, as shown in FIG. However, in the vicinity A of the transparent display electrode 22, which is the negative electrode, there are overwhelmingly blue molecules 31a, and in the vicinity C of the positive electrode, the molecules 3 are decolored.
1b. Therefore, while a negative potential is applied to the transparent display electrode 22 side, the ECD element appears blue.

Also, if the polarity of the applied voltage is reversed, will the surface of the transparent display electrode 22, which is the positive electrode, dissolve? The colored molecules 31a that have diffused from inside the flN 26 are oxidized and decolored, and then diffused into the solution layer 26 again, and the stainless steel plate 23, which is the negative electrode, is oxidized and decolored.
On the surface, the decolored molecules 31b are colored. and,
In the same manner as described above, the colorless molecules 31b are placed on the transparent display electrode 22 side which is the positive electrode, and the stainless steel plate 23 which is the negative electrode.
Many colored molecules 31a will be present on the side.

By the way, since white oxide powder is mixed in the solution layer 26, when a positive potential is applied to the transparent display electrode 22, external light incident from the transparent display electrode 22 is reflected by this oxide powder. , the colored molecules 31a existing inside the solution layer 26 are not visible, and the ECD element appears white. Previously 0
In the ECD element, the color development/decolorization reaction is performed in this manner.

[Problem that the invention seeks to solve]

By the way, in the conventional ECD element, when a potential is applied to the electrode, a coloring reaction always occurs on the negative electrode side regardless of the applied polarity, and the reacted molecules diffuse into the solution layer 26. Therefore, if the ECD element contains only a heteropolyacid solution, when a voltage is applied, it always appears blue from the outside regardless of the applied polarity. Since an actual ECD element contains white oxide powder in addition to heteropolyacid, when a positive potential is applied to the transparent display electrode 22, the colored molecules 31a that have reached the surface of the transparent display electrode 22 are oxidized. The colored molecules 31a inside the solution 11i26 and the colored molecules 31a present in large numbers near the stainless steel plate 23 are hidden by the oxide powder, so only the blue molecules 31a are not visible from the outside.

In other words, even if the polarity is reversed and a potential is applied to the conventional 0ECD element, the color does not disappear in principle. A solution containing oxide powder is required. Further, if the solution layer 26 between the electrodes is made thin, the blue molecules 31a can be seen through the oxide powder solution even if the polarity is reversed, so a certain thickness is required.

As described above, the conventional ECD element requires a certain thickness of solution Ji26 between the electrodes, and because of the thickness of this solution N26, the opposing surfaces of the electrodes do not have a uniform potential. '8 Diffusion into the interior of the liquid layer 26 not only causes uneven color development, but also slows down the rate of color development and fading (approximately 100
ms to about 1 second).

In addition, when the conventional ECD element stops applying voltage,
During color development, the colored molecules 31a diffuse, so the color becomes lighter as time passes, and conversely, during decolorization, the decolored molecules 31b expand +1i 1. It gradually becomes colored, eventually becoming a uniform blue color in both cases. That is, when the application of voltage is stopped, the conventional ECD element cannot maintain the coloring state or the colorless state, and has no memory effect.

The present invention has been made based on the above-mentioned circumstances, and is an EC that can obtain stable color development and has a fast color development/discoloration speed.
The purpose is to provide a D element.

[Means for solving problems]

In order to achieve the above object, the present invention comprises a small number of electrodes (one of which is a transparent display electrode, which are arranged facing each other, and a solution layer containing a coloring solution and an electrolyte solution provided between the electrodes). A solution type electrocomic element having a solution layer disposed in the solution layer so as to face the electrode,
In addition, a semipermeable membrane is provided on one side of the electrode to isolate the coloring liquid.

[Effect]

By having the above-described structure, the present invention reduces the movement of macromolecules that change color and fade between the electrodes by half when a voltage is applied to the electrodes and a current flows through the solution, or when the molecules diffuse. selectively blocked by a permeable membrane. This results in
For example, if a coloring layer containing a coloring solution isolated by a semi-i3 film is placed on the transparent display electrode side and a negative potential is applied to the transparent display electrode side, molecules that are reduced and colored on the surface of the transparent display electrode will become semitransparent. Because of the film, it cannot move to the other electrode and remains near the transparent display electrode.

Furthermore, when a positive potential is applied to the transparent display electrode side, the colored molecules are oxidized and decolored by the transparent display electrode. At this time, a negative potential is applied to the other electrode, but since there are no molecules that perform color development/decolorization on this electrode side, no color development reaction occurs on either electrode surface. By reversing the polarity in this way, there are no colored molecules in the solution, so oxide powder to hide the color is not needed, and the solution layer can be reduced to one, resulting in improved color development and fading properties. You can improve your performance. Furthermore, since there is no oxide powder, once the color develops, the color can be seen even if the voltage application is stopped, and when the color is erased, the color molecules dissolve and diffuse from inside the layer. Therefore, once the color is erased, it will not become colored even if the voltage application is stopped. In other words, a memory effect occurs in which the state at the time of color development and color erasure is stored.

〔Example〕

The following is a first example of an ECD element according to an embodiment of the present invention.
This will be explained with reference to the figures. FIG. 1 is a schematic cross-sectional view of an ECD element that is an embodiment of the present invention.

In FIG. 1, 1 is a transparent insulating substrate, for example, a glass substrate, and 2 is a transparent display electrode with a thickness of approximately 2000 angstroms formed of tin-doped indium oxide (ITO) on one surface of the glass substrate 1 by high-frequency sputtering. ,
3 is a stainless steel plate mirror-polished using a 9 μm diamond paste, 4 is a counter electrode formed by silver plating the inner surface of the stainless steel plate 3, and 5 is a silicotungstic acid hydrate or a non-aqueous electrolyte. 6 is an electrolyte layer in which an electrolytic MN solution using a sodium chloride solution is encapsulated; 7 is made of hydrated cellulose to which 10 to 20% glycerin has been added. A semi-permeable membrane with a thickness of 40 μm; 8a is a spacer for maintaining the distance between the glass substrate 1 and the semi-permeable membrane 7; and 8b is a spacer for maintaining the distance between the semi-I3 film 7 and the stainless steel plate 3.

Note that the bonding surfaces of the glass substrate 1 and the spacers 8a, etc. are sealed with epoxy resin.

Next, the operation of the embodiment configured as described above will be explained with reference to FIG. 2 as well. FIG. 2 is a diagram showing the principle of operation of this embodiment. In Figure 2, 11a is a cation when sodium chloride is ionized, 11b is an anion when sodium chloride is ionized, 12a is a coloring molecule of silicotungstic acid, and 12b is a decolorizing molecule of silicotungstic acid. .

Further, the semipermeable membrane 7 is one that allows the cations lla and anions llb generated when sodium chloride is ionized to pass therethrough, but does not allow the molecules 12 of silicic tungstic acid to pass therethrough.

When a voltage is applied to the electrode, electrical conduction occurs through the semipermeable membrane 7, including the cations lla and anions llb of sodium chloride.
carried out by Then, when a negative potential is applied to the transparent display electrode 2, as shown in FIG. 2, the colored molecules 12a colored by the reduction of silicic tungstic acid cannot reach the counter electrode 4 side because of the semi-transparency wi7. Therefore, it remains near the transparent display electrode 2. Therefore, when a negative potential is applied to the transparent display electrode 2, no decoloring reaction occurs, and the color development of silicotungstic acid can be seen from the outside.

Here, in the case of this example, since there is no oxide powder in the solution, the color development does not disappear even if the voltage application is stopped.

In other words, it has a memory effect that memorizes the state of color development.

Next, when a positive potential is applied to the electrode 2 of the transparent display, the silicotungstic acid is oxidized and decolored. Of course, the decolorizing molecules 12b cannot pass through the semi-permeable membrane 7, so they remain near the transparent display electrodes 2. At this time, a negative potential is applied to the counter electrode 4, but since the molecules 12 of the silicic tungstic acid that perform coloring and decolorization cannot move to the counter electrode 4 due to the semipermeable membrane 7, no coloring reaction occurs. Therefore, the transparent display electrode 2
By applying a positive potential to , the colored molecules 12a in the solution can be reduced and completely erased. That is, when decoloring, the coloring molecules 12a no longer exist, so even if the application of potential is stopped, the coloring molecules will not diffuse from inside the solution layer and develop color, as in conventional ECD elements. It has a memory effect that remembers the colorless state. In this way, in this embodiment, the color can be erased in principle by reversing the polarity of the applied voltage, and the structure that has a memory effect hides coloring, and is different from the conventional 0ECD which does not have a memory effect. Different from element.

Further, the color development and fading speed was experimentally measured by applying a cyclic potential to both electrodes of the ECD element of this example, with the coloring layer 6 having a thickness of 50 μm and the electrolyte 15 having a thickness of 700 μm. Even when the number of color development and fading cycles was 10', cyclic voltammetry drew a stable redox loop. The time required for coloring was approximately half that of the conventional ECD element (approximately 50 msec).

As mentioned above, this embodiment can theoretically erase color and does not require oxide powder to hide the color development, unlike conventional 0ECD elements, so the thickness between the electrodes of the ECD element can be reduced. This increases the reaction rate and improves the rate of color development and fading.

In addition, according to the above embodiment, since the solution layer consisting of the coloring layer and the electrolyte layer is thin, natural convection due to temperature difference is reduced, there is no diffusion, and the entire surface of the electrode has almost the same potential. Uneven color development is reduced and stable color development can be obtained.

In the above embodiment, a reflective ECD element using a stainless steel plate as one electrode was explained, but the present invention is not limited to this, and both electrodes are made of tin-doped indium oxide (tin-doped indium oxide) on a glass substrate. A material formed with an ITO film may also be used.

As a result, the present invention can be used as a transmission type ECD element since no oxide powder is mixed in the solution.

Furthermore, in the above embodiment, the case where the coloring layer is placed on the side of the transparent display bridge is explained, but this coloring layer may be placed on the side of the counter electrode. Since the solution can be stored on the stainless steel plate side, it is possible to prevent the tin-doped indium oxide (ITO) film of the transparent display electrode from being corroded by the strongly acidic coloring solution.

〔Effect of the invention〕

As explained above, according to the present invention, by isolating the coloring solution to one electrode side using a semipermeable membrane, stable coloring can be obtained by thinning the solution layer between the electrodes, and coloring and decoloring can be achieved. A fast ECD element can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an ECD element that is an embodiment of the present invention, FIG. 2 is a diagram of the operating principle of this embodiment, FIG. 3 is a schematic sectional view of a typical conventional ECD element, and FIG. 4・Figure 5 is a diagram of the operating principle of a conventional 0ECD element. l...Glass substrate, 2...Transparent display electrode, 3.・Stainless steel plate, 4... Counter electrode, 5... Coloring layer,
6... Electrolyte layer, 7... Semipermeable membrane, 8... Spacer. Applicant Iwasaki Electric Co., Ltd. 1 Do b Figure 2

Claims (1)

[Claims] (1) A solution-type electrochromic device having electrodes disposed opposite to each other using a transparent display electrode as at least one electrode, and a solution layer containing a coloring solution and an electrolyte solution provided between the electrodes, the solution layer 1. A solution-type electrochromic device, characterized in that a semipermeable membrane is provided inside the device so as to face the electrode, and isolates the coloring solution to one side of the electrode.