JPS63189844A - Electrochromic display element - Google Patents

Abstract

PURPOSE:To improve an initial response characteristic so that the response characteristic is stably exhibited for a long period of time and a preservable property is enhanced by incorporating a carbon material adsorbed with an anionic or nonionic surfactant into a counter electrode material layer. CONSTITUTION:An electrochromic material layer 3 consisting of tungsten oxide is provided via transparent display electrodes 2 on the inside surface of a light transmittable display side substrate 1 and display electrodes 4 fractionated to the segments to constitute required patterns are formed. The counter electrode material layer 7 contg. the carbon material adsorbed with the surfactant is provided via a counter electrode 6 on the inside surface of a substrate 5 on the opposite side thereof to form a counter pole 8. Both the substrates 1, 5 are disposed to confront each other via a spacer 9 consisting of a synthetic resin, etc., and an electrolyte 10 contg. a lithium salt and nonaq. solvent is sealed between the two electrodes 4 and 8. The material layer 7 contains the carbon material adsorbed with the anionic or nonionic surfactant.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is an electrochromic material that displays characters, patterns, etc. by color change of a reactant between an electrochromic material of a display electrode and a counter electrode material of a counter electrode through an electrolytic solution. This invention relates to a chromic display element.

[Conventional technology]

A typical example of this type of display element is, for example, a display device in which an electrochromic material layer is provided on the inner surface of a light-transmitting display substrate via a transparent display electrode, and the display is divided into segments constituting a required pattern. A counter electrode material layer is provided on the inner surface of the opposite substrate via a counter electrode to make it a counter homopolar,
A device is known in which an electrolytic solution is sealed between the two electrodes of both substrates which are placed facing each other with a spacer in between.

In such a display element, by applying a voltage to the display electrodes corresponding to the required segments using the above-mentioned counter electrode as a common electrode, color change of the reactant through the electrolyte between the electrochromic substance and the counter electrode substance is performed. , the required display is made on the surface of the display side substrate. For example, in the case of blue display, tungsten oxide (WOs) is generally used as the electrochromic substance, but the color change in this case occurs when lithium salt dissolved in a non-aqueous solvent is used as the electrolyte. It is based on the following reaction.

By the way, in a display element using tungsten oxide as an electrochromic substance as described above and a lithium salt dissolved in a non-aqueous solvent as an electrolyte, tungsten oxide, iron tungstate, iron tungstate, In addition to oxide-based materials such as manganese dioxide, carbon materials such as carbon powder, carbon fiber, and activated carbon fiber are used as materials that can obtain a particularly high amount of injected electricity and provide excellent response characteristics (reference unknown). ).

[Problem that the invention seeks to solve]

However, as mentioned above, although conventional display elements using carbon materials as counter electrode materials exhibit excellent response characteristics initially, the amount of injected electricity decreases significantly during storage, and the initial response characteristics remain stable for a long time. There was a problem that it was difficult to make full use of the system.

Therefore, the present invention has a high amount of injected electricity and a small drop in this amount of electricity during storage, which means it has excellent initial response characteristics and is capable of stably exhibiting these response characteristics over a long period of time. The purpose of the present invention is to provide an electrochromic display element with excellent storage stability.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventor used a counter electrode material made of a carbon material for an electrochromic material made of tungsten oxide, and used an electrolyte containing a lithium salt and a non-aqueous solvent. In this case, by adsorbing a specific substance to the carbon material, an electrochromic display element with good storage stability that can stably exhibit the excellent response characteristics based on the carbon material over a long period of time can be obtained. Knowing this led me to complete this invention.

That is, in the present invention, a display electrode is formed by disposing a pair of substrates facing each other and having at least the display side transparent, and providing an electrochromic material layer made of tungsten oxide on the inner surface of the display side substrate via a display electrode. In an electrochromic display element in which a counter electrode is formed by providing a counter electrode material layer on the inner surface of a counter substrate via a counter electrode, and an electrolytic solution containing a lithium salt and a non-aqueous solvent is sealed between the two materials. , an electrochromic display element characterized in that the counter electrode material layer includes a carbon material adsorbing an anionic or nonionic surfactant.

[Structure and operation of the invention]

In this invention, as described above, by including the carbon material in which the counter electrode material layer has adsorbed an anionic or nonionic surfactant, a high amount of electricity can be initially injected based on the carbon material. This achieves the effect that the injection cap can be held stably for a long period of time. The reason for this is not necessarily clear at present, but according to the inventor's speculation, it is thought to be as follows.

That is, first, in a conventional electrochromic display element comprising an electrochromic material layer made of tungsten oxide and a counter electrode material layer containing a normal carbon material, and using a lithium salt dissolved in a non-aqueous solvent as an electrolytic solution. It is thought that the carbon material has an adverse effect on the liquid properties of the electrolytic solution, which inactivates the tungsten oxide in the electrochromic material layer and causes a decrease in the amount of electricity injected. Although the mechanism that causes the above-mentioned adverse effects is not clear, the anions constituting the lithium salt in the electrolyte (for example, the lithium salt is
In the case of Os, Cl0a-) is easily adsorbed to the carbon material of the counter electrode material layer, and as a result of this adsorption, the electrolyte composition gradually changes to an excessive amount of lithium ions, causing lithium ions to enter the electrochromic material layer made of tungsten oxide. It is thought that this makes it easier to produce substances that cannot function as electrochromic substances, such as Li and WO.

On the other hand, when an anionic or nonionic surfactant is adsorbed to the carbon material of the counter electrode material layer as in the present invention, the anion that constitutes the lithium salt of the electrolyte is selected from the carbon material. As a result, the electrolyte composition is less likely to change, and deactivation of tungsten oxide in the electrochromic material layer during storage is avoided, and the amount of electricity injected into the device decreases over time. It is presumed that this suppresses the response characteristics and enables stable and excellent response characteristics to be exhibited over a long period of time.

The above-mentioned effect of suppressing the decrease in the amount of injected electricity over time is noticeable when the surfactant adsorbed to the carbon material is anionic or nonionic, but cationic surfactant This is because the adsorption points of the cationic surfactant on the surface of the carbon material are different from the adsorption points of the anions constituting the lithium salt of the electrolyte, and the adsorption of the ions is cationic. This is thought to be because it is not inhibited by ionic surfactants.

In this invention, the carbon material used for the counter electrode material layer includes carbon powder, carbon fiber, activated carbon fiber, etc., and activated carbon fiber is particularly suitable.

and a counter electrode material layer containing such a carbon material.

In the case of carbon powder, in the case of carbon powder, a paint containing this and a binder resin may be applied to a counter electrode previously formed on the opposite substrate by a screen printing method or the like, and then dried and hardened. In the case of carbon fibers and activated carbon fibers, these cross-like materials may be attached onto the counter electrode via a conductive adhesive containing conductive particles such as the carbon powder. Note that the counter electrode material layer containing carbon powder or the conductive adhesive layer may contain powder of an oxide counter electrode active material such as tungsten oxide or iron tungstate.

Examples of anionic surfactants to be adsorbed to these carbon materials include fatty acids, alkyl sulfates, alkylbenzenesulfonic acids, α-olefinsulfonic acids, N-acylamino acids, higher alcohol sulfonic acids, alkylnaphthalenesulfonic acids, and perfluoroalkylcarboxylic acids. Examples include Na salts, K salts, Ca salts of acids, perfluoroalkylsulfonic acids, and the like.

On the other hand, examples of nonionic surfactants include alkyl polyoxyethylene ether, fatty acid polyethylene glycol ester, alkyl carbonyloxy polyoxyethylene, p-alkylphenyl polyoxyethylene ether, fatty acid alcohol ester, fluorinated alkyl ester, and perfluorinated surfactant. Examples include alkyl polyoxyethylene ethanol and the like.

Means for adsorbing these surfactants onto carbon materials include a method of directly adsorbing them onto the carbon material and a method of adding the surfactant to the electrolyte. As a method of directly adsorbing the above carbon material, the carbon material may be treated with an aqueous solution containing a surfactant in advance, and a counter electrode material layer may be formed using the carbon material to which the surfactant has been adsorbed after this treatment. However, it is preferable to form a counter electrode material layer containing a carbon material on the counter electrode of the counter substrate, and to immerse the entire substrate in an aqueous solution of a surfactant for adsorption. According to the method of adding a surfactant, the surfactant in the electrolyte is immediately adsorbed onto the surface of the carbon material when the electrolyte comes into contact with the carbon material of the counter electrode material layer after the device is assembled.

The amount of surfactant adsorbed varies considerably depending on the type of carbon material and surfactant, but is generally about 0.3 to 100 cm per gram of carbon material, preferably 3 to 30 cm per gram of carbon material.
It is better to set it as a degree. When a surfactant is added to the electrolytic solution, the amount added is preferably about 0.05 to 50 g per electrolytic solution IIl in order to achieve the above adsorption amount.

The electrolytic solution used in this invention contains a lithium salt and a non-aqueous solvent, and contains propylene carbonate, γ
- LiCJlOas LIPF&, in a non-aqueous solvent such as butyrolactone, dimethoxyethane, dioxolane, etc.
LiBF4, LiAsFa, LiCFs SOs, L
In addition to a solution in which a lithium salt such as i$F4 ($ is a phenyl group) is dissolved, 0.1~
There are electrolytic solutions that contain about 3% by volume of water, and the latter type of electrolytic solution that contains water has the advantage of increasing the initial amount of electricity injected. The non-aqueous solvent is particularly propylene carbonate, and the lithium salt is particularly L.
iCJOa is preferred.

As described above, the electrochromic display element of the present invention has an electrochromic material layer made of tungsten oxide and uses an electrolytic solution containing a lithium salt and a nonaqueous solvent, and the counter electrode material layer is anionic or nonaqueous. The device is characterized by containing a carbon material adsorbed with an ionic surfactant, but the other configurations of this device may be the same as those of conventional devices.
An example of the electrochromic display element of the present invention, including the other configurations mentioned above, will be described with reference to the drawings.

In the figure, 1 is a light-transmitting display-side substrate, and an electrochromic material layer 3 is provided on the inner surface of this substrate 1 via a transparent display electrode 2, and the display is divided into segments constituting a required pattern. Pole 4 is formed. Reference numeral 5 denotes a counter substrate, and a counter electrode material layer 7 containing a carbon material adsorbing the above-mentioned surfactant is provided on the inner surface of the substrate 5 via a counter electrode 6 to form a counter electrode 8. The side substrates 1.5 are placed opposite to each other with a spacer 9 made of synthetic resin or glass interposed therebetween, and the inside thereof, that is, the two poles 4.
The electrolytic solution 10 described above is sealed between the spaces 8 and 8.

Although a translucent material such as glass is generally used for the above-mentioned side substrates 1 and 5, the opposing substrate 5 may be non-transparent. Further, the display electrode 2 is made of indium-
It is made of a transparent conductive material such as tin composite oxide (hereinafter referred to as ITO), and is usually made of 1,000~ It is formed to a thickness of about 3,000 people. Furthermore, the counter electrode 6 is made of gold.

Precious metals such as platinum, alloys of these metals with other metals, or materials similar to those for the display electrode 2 are used, and in addition to the same thin film forming techniques described above, in the case of metals, the opposing electrodes are formed by pressing or bonding foil-like materials. Usually 1 on the inner surface of the side board 5
,000 to 3,000 people in thickness.

The electrochromic material layer 3 is made of tungsten oxide (W
O3) It is made of a thin film and is formed on the display electrode 2 to a thickness of usually about 3.000 to 10,000 by using the same thin film forming technique as described above. When a cross-like material of carbon fiber or activated carbon fiber is used as the carbon material of the counter electrode material layer 7, the thickness of the cross-like material is preferably about 200 to 800 μm.

In addition, when using carbon powder as the above carbon material,
The thickness of the counter electrode material layer formed by binding this powder with a binder is preferably about 20 to 500 μm.

In addition, 11 and 12 are lead terminals on the display electrode side and the counter electrode side fixed to the side edge of the display side substrate 1, and 13 is a material such as conductive paste or metal foil that constitutes the external lead-out portion of the counter electrode 6. 14 is an insulating layer consisting of sio for protecting the display electrode 2, etc. 15 is a background material that hides the counter electrode 8 and uses its own color tone as the background of the display, and expresses the color tone. It is composed of an electrolyte-impregnated sheet-like molded product in which a pigment is dispersed in a binder component such as polytetrafluoroethylene, or a gel body of a pigment and an electrolyte.

〔Effect of the invention〕

As described above, according to the present invention, in a device having an electrochromic material layer made of tungsten oxide and using an electrolytic solution containing a lithium salt and a non-aqueous solvent, the counter electrode material layer of the counter electrode is anionic or non-ionic. An electrochromic display element with good storage stability that stably exhibits excellent initial response characteristics based on the carbon material over a long period of time by being composed of a carbon material to which an ionic surfactant is adsorbed. can be provided.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 An IT panel with a thickness of 1.500 people was placed on one side of the display side substrate made of transparent glass with a length of 40n+, a width of 120m, and a thickness of 1.1fi.
A display electrode with a predetermined pattern made of O and a thickness of 5.
An electrochromic material layer in the shape of six 8-shaped numbers display patterns (consisting of 7 segments) made of tungsten oxide thin film arranged in the lateral direction of the substrate is formed by vacuum evaporation, respectively. 5,000 ml of Si0g on the exposed surface of the substrate and display electrodes
An insulating film was provided to serve as a display electrode.

On the other hand, on the entire surface of the opposing substrate, which is made of transparent glass with a length of 361 m, a width of 116 fins, and a thickness of 1.1 fl,
A counter electrode made of 0.00% ITO was formed by vacuum evaporation, and carbon resin ink (product name RP-10: Too 10, manufactured by Tokurikisha Co., Ltd.: a paste containing phenol novolac resin and carbon particles) and propylene were applied. A conductive adhesive solution consisting of a mixture with carbonate at a weight ratio of 5:1.5 was screen printed to a thickness of 20 μm, and an activated carbon fiber cloth (trade name: CH-20 manufactured by Kuraray Co., Ltd.) was pressed onto this and heated at 200°C. The mixture was heat-treated for 4 hours. Next, this opposing substrate was coated with an anionic surfactant, higher alcohol sodium sulfate (trade name Emerua 1, manufactured by Kao Soap Co., Ltd.).
After immersing in a 2 g/l aqueous solution at a liquid temperature of 80°C for 30 minutes, thoroughly washing with pure water and further heating at 120°C for 1 hour, the anionic surfactant adsorbed activity was removed. A counter electrode material layer was formed by bonding carbon fiber cloth onto the counter electrode via a conductive adhesive to serve as a counter electrode. Note that the adsorption amount of the anionic surfactant was 20rnIZ per gram of activated carbon fiber.

Then, the above-mentioned side substrate was placed in such a manner that the display electrode and the counter electrode faced each other, and between the two electrodes, a 200 μm thick sheet-like molded product (manufactured by Sumitomo Electric Industries, Ltd.) of a mixture of titanium dioxide pigment and polytetrafluoroethylene powder was used. A background material made of Boaron (trade name: Boaron) is interposed, and a thickness of 0.8 mm is added to the periphery.
They were placed facing each other with rectangular annular spacers made of polyester resin of 50 m in size interposed therebetween, and were tightly sealed with an epoxy resin adhesive. Approximately 3 ml of an electrolytic solution containing pure water was sealed. Next, lead terminals were attached and a conductive layer was formed by applying silver paste, thereby producing an electrochromic display element having the configuration shown in the drawings.

Examples 2 to 8 Example 1 except that the anionic or nonionic surfactants listed in Table 1 below were used as the anionic or nonionic surfactants to be adsorbed onto the activated carbon fiber cloth, and the adsorption amounts were the same as those listed in the same table. An electrochromic display element was produced in the same manner as described above.

Example 9 A counter electrode material layer was formed on the activated carbon fiber cloth without adsorbing a surfactant to serve as a counter electrode, and higher alcohol sulfate (described above) was added to the electrolyte at a ratio of Ig/#. Except for this, an electrochromic display element was produced in the same manner as in Example 1.

Examples 1O to 16 Electrochromic was prepared in the same manner as in Example 9, except that the anionic or nonionic surfactants listed in Table 2 below were added at a rate of 1 g/lt to the electrolytic solution. A display element was manufactured.

Comparative Example An electrochromic display element was produced in the same manner as in Example 1, except that a counter material layer was formed on the activated carbon fiber cloth to form a counter electrode without adsorbing a surfactant.

For each display element according to the above example and comparative example, ±
When we measured the initial amount of injected electricity when applying a square wave AC voltage of 1.2V for 0.6 seconds, it was 12mG in both cases.
Next, after storing these display elements at 45°C for 3 months, the amount of electricity injected under the same conditions and the amount of electricity injected after storage when the initial amount of electricity injected is taken as 100%. The relative value, that is, the retention rate (%) was investigated. The results are shown in Table 1 for Examples 1 to 8, and for Examples 9 to 8.
16 are shown in Table 2.

Note that comparative examples are also listed in Tables 1 and 2.

Table 2 From the results in Tables 1 and 2 above, it can be seen that the display element of the present invention (Example 1-16
) has excellent response characteristics, with extremely little decrease in the amount of electricity injected after storage, compared to a display element with a conventional structure (comparative example) in which the counter electrode is ordinary activated carbon fiber that does not adsorb the surfactant. It is clear that the effect is stable over a long period of time.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of an electrochromic display element of the present invention. DESCRIPTION OF SYMBOLS 1... Display side substrate, 2... Display electrode, 3... Electrochromic material layer, 4... Display electrode, 5... Opposite side substrate, 6... Counter electrode, 7... Counter electrode layer, 8
...Counter electrode, 10... Electrolyte

Claims (1)

[Claims] (1) A pair of substrates whose display sides are translucent at least are placed opposite each other, a display electrode is formed by providing an electrochromic material layer made of tungsten oxide on the inner surface of the display side substrates via a display electrode, and the opposite side A counter electrode is formed by providing a counter electrode material layer on the inner surface of the substrate via a counter electrode,
In an electrochromic display element in which an electrolytic solution containing a lithium salt and a non-aqueous solvent is sealed between these two electrodes, the counter electrode material layer includes a carbon material adsorbing an anionic or nonionic surfactant. An electrochromic display element characterized by: