JP7134455B2 - Electrochromic display element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a light modulating device and a product including the same, and more particularly, a device including an electrochromic material that modulates light by changing the optical properties of the electrochromic material and a product using the same, such as a display. display device, a dimmer filter for adjusting the amount of light incident from the outside, an anti-glare mirror, and the like.

Elements for adjusting the amount of transmitted light are currently on the market as, for example, display devices and dimmer filters. 2. Description of the Related Art Devices for displaying information (display devices) such as televisions, personal computer monitors, mobile phone displays, etc. are indispensable devices in the recent information society. In addition, dimmer filters, anti-glare mirrors, etc., which adjust the amount of light entering from the outside, have the same effect as curtains, etc., because they can adjust the light from the outside in spaces such as indoors, cars, and aircrafts. , is very useful in life.

Among the above, the display method of the display device can generally be broadly classified into three types: reflective type, transmissive type, and luminescent type. A person who manufactures a display device generally selects a preferable display method in consideration of the environment in which the display device is placed.

By the way, in recent years, the portability of display devices has improved due to the miniaturization and thinning of display devices, and the opportunities to use display devices by carrying them around in environments with various brightnesses have increased significantly. are also diversifying. As for the mode of the display device, for example, there is a demand for not only a bright and dark display, but also a display screen having a mirror surface state. This point is the same for the light control filter and the like.

Patent Literature 1 describes an element that enables a reversible color change from a transparent state to a mirror state or a black state by depositing silver on a transparent electrode.

WO2012/118188

In the invention described in Patent Document 1, if the circuit of the element is opened while a voltage is being applied, the colored state is not maintained and returns to the decolored state. must be continuously applied, there is a problem that power is consumed in order to maintain the coloring state.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electrochromic display element capable of maintaining a coloring state for a certain period of time even when the circuit of the element is open.

According to one aspect of the present invention, in order to solve the above problems, an electrochromic display element comprises a pair of electrodes, an electrolytic solution held between the pair of electrodes, and a voltage applied to the pair of electrodes. voltage applying means for applying voltage, and the electrolytic solution contains a solvent, an electrochromic material containing silver ions, a mediator, and a thiol derivative.

Furthermore, the mediator preferably contains copper ions.

According to another aspect of the present invention, an electrochromic display element comprises a pair of electrodes, an electrolytic solution held between the pair of electrodes, and voltage applying means for applying a voltage to the pair of electrodes. wherein the electrolytic solution contains a solvent, an electrochromic material containing silver ions, a mediator and a thiol derivative, and when a voltage is applied to the pair of electrodes, a self-assembled membrane is formed on at least one of the pair of electrodes is formed. It is preferable that the transmittance of the electrochromic display element is 40% or less when 3000 seconds have passed since the circuit of the voltage applying means was opened after the voltage applying means applied the voltage to the pair of electrodes.

According to the present invention, in the electrochromic element, the coloring state can be maintained for a certain period of time even when the circuit of the element is open, and power consumption can be reduced.

It is a figure which shows the schematic sectional drawing of the display apparatus of this embodiment. It is a figure explaining the display principle of this embodiment. 1 is a diagram showing an outline of a display device of Example 1; FIG. It is a figure which shows the applied voltage to an element, the transmittance|permeability, and the relationship of an electric current. FIG. 10 is a diagram showing changes in transmittance when the circuit is opened after application of a coloring voltage; FIG. 10 is a diagram showing changes in transmittance when the circuit is opened after applying a coloring voltage when 1-octanethiol is added to the electrolytic solution. It is a figure which shows a frequency change.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. This invention may, however, be embodied in many different ways and should not be construed as limited to the embodiments set forth below.

FIG. 1 is a schematic cross-sectional view of a display device (also referred to as an electrochromic display device, hereinafter referred to as “the present display device”) 1 according to the present embodiment, which is an example of the light control device of the present invention. As shown in FIG. 1, the present display device 1 is sandwiched between a pair of substrates 2 and 3, a pair of electrodes 21 and 31 formed on opposite surfaces of the pair of substrates, and a pair of electrodes 21 and 31. an electrochromic material containing silver and an electrolyte layer 4 containing a mediator.

In the present embodiment, the pair of substrates 2 and 3 are used to sandwich and hold the electrolyte layer 4. At least one of the substrates 2 and 3 should be transparent. type display can be realized. In this embodiment, for the sake of explanation, a case where both sides are transparent will be explained. The material of the substrate is not limited as long as it has a certain degree of hardness and chemical stability and can stably hold the material layer, but glass, plastic, metal, semiconductor, etc. can be employed, and when used as a transparent substrate, glass or plastic can be used.

Further, in this embodiment, electrodes 21 and 31 are formed on the opposing surface sides (inner sides) of the pair of substrates 2 and 3, respectively. This electrode is used to apply a voltage to the material layer sandwiched between the pair of substrates 2,3. The electrode material is not limited as long as it has suitable conductivity. For example, when the material of the substrate is a transparent substrate, a transparent material containing at least one of ITO, IZO, SnO ₂ , ZnO, and the like is used. It is preferably an electrode.

Further, the electrodes according to the present embodiment may be formed on the substrate in a shape matching a pattern such as characters to be displayed. It may be If the area is divided into a plurality of areas, there is an advantage that each area is used as a pixel, display is controlled for each pixel, and display of a complicated shape can be handled.

The distance between the electrodes is not limited as long as an electric field can be applied so that the silver in the electrochromic material, which will be described in detail later, is sufficiently deposited as fine particles and disappears, but it can be 1 μm or more and 10 mm or less. , desirably in the range of 1 μm or more and 1 mm or less.

Note that the electrodes according to this embodiment are each connected to a power source via conductive wiring, and the application and release of voltage to the material layer can be controlled by turning the power source on and off.

The electrolyte layer (electrolyte solution) 4 according to the present embodiment contains an electrolyte as a supporting salt, an electrochromic material containing silver ions, and a mediator. The electrolyte layer 4 according to the present embodiment contains the electrochromic material 41 containing silver and the mediator 42 as well as a solvent for retaining these materials.

Furthermore, this embodiment is characterized in that a thiol or a thiol derivative is dissolved in the electrolyte layer 4 . A thiol is a type of organic compound having a terminal sulfur hydride represented by R-SH (where R is a hydrocarbon group). Thiol groups (SH) of thiols form self-assembled membranes (SAM) on metal surfaces (silver, gold, etc.).

The electrolyte in the electrolyte layer of the present embodiment is for promoting the oxidation-reduction of the electrochromic material, and is preferably a supporting salt. The electrolyte preferably contains bromide ions, and examples thereof include LiBr, KBr, NaBr, and tetrabutylammonium bromide (TBABr). Although the concentration of the electrolyte is not limited, it is preferably about 5 times the electrochromic material in terms of molarity, specifically 3 times or more and 6 times or less, for example, 3 mM or more and 6 M or less. more preferably 5 mM to 5 M, more preferably 6 mM to 3 M, still more preferably 15 mM to 600 mM, still more preferably 25 mM to 500 mM, and 30 mM to 300 mM.

In the present embodiment, the solvent is not limited as long as it can stably hold the electrochromic material, the electrochemiluminescent material and the electrolyte, but it may be a polar solvent such as water, Ordinary solvents such as non-polar organic solvents can also be used. Examples of solvents that can be used include, but are not limited to, dimethylsulfoxide (DMSO).

In the present embodiment, the electrochromic material is a material that causes an oxidation-reduction reaction when a DC voltage is applied, and is preferably a salt containing silver ions. This electrochromic material deposits or disappears silver fine particles by oxidation-reduction reaction, and can display by causing a color change based on this. Electrochromic materials containing silver include, but are not limited to, _AgNO3 , _AgClO4 , AgBr _, AgBr3. The concentration of the electrochromic material is not particularly limited as long as it has the above functions, and can be adjusted as appropriate depending on the material. Desirably, it is 5 mM to 100 mM.

In the present embodiment, the mediator refers to a material that can be oxidized and reduced with electrochemically lower energy than silver. The oxidant of the mediator can give and receive electrons from silver at any time to assist the decoloring reaction due to oxidation. Although the mediator is not limited as long as it has the above function, it is preferably a salt of copper (II) ions, such as CuCl ₂ , CuSO ₄ and CuBr ₂ .

The concentration of the mediator is not limited as long as it exhibits the above functions, and can be adjusted as appropriate depending on the material. Excessive coloring can be prevented by making it 20 mM or less. The concentration ratio of silver ions and copper (II) ions is not particularly limited, but the concentration of copper (II) ions is preferably in the range of 1 or more and 3 or less when silver ions are 10.

Moreover, in this embodiment, a thickener, for example, can be added in addition to the above constituent elements. By adding a thickener, the memory property of the electrochromic device can be improved. Examples of the thickener include, but are not limited to, polyvinyl alcohol. Although the concentration of the thickening agent is not particularly limited, it is preferable that the thickening agent is contained in the range of 5% by weight or more and 20% by weight or less with respect to the total weight of the electrolyte layer.

This display device can achieve a reflective state, for example, in a state in which a voltage is applied. FIG. 2 shows a conceptual diagram of the state of the element according to this embodiment. FIG. 2 shows the mirror state.

In this display device, when a voltage is applied between the electrodes, silver ions in the electrochromic are reduced at one of the electrodes and deposited as silver. In this case, if the silver is formed in the form of a smooth electrode, it will be in a mirror state. Note that the strength of the voltage when applying the DC voltage can be appropriately adjusted depending on the distance between the pair of substrates and the distance between the pair of electrodes, and is not limited. It is preferably in the range of ×10 ³ V/m or more and 1.0×10 ⁵ V/m or less, more preferably in the range of 1.0×10 ⁴ V/m or less.

In the element of the prior art, copper (II) chloride, which is a decoloring aid, causes dissolution of deposited silver, making it difficult to maintain the state of color development of the element. Therefore, by adding thiol to this electrolyte, a self-assembled film was formed on the deposited silver, and by preventing copper mediation, the color retention property of the device after voltage application was improved.

In addition to the present embodiment, when the electrode 31 is modified with particles, silver is formed on the particles by applying a voltage, and light is irregularly reflected to create a black state. The effect of maintaining the color development of the present invention can be obtained even with the element having the above structure.

Here, a display device was actually produced and its effect was confirmed. It is explained below.

FIG. 3 is a diagram showing an outline of the display device of this embodiment. Electrolytic solution 4 was prepared by adding 300 mM AgBr, 5 mM LiCl ₂ and 5 mM CuCl ₂ to DMSO solvent, stirring the solution with a mix rotor, and then preparing 10 mM 1-dodecanethiol.

The upper part of FIG. 4 shows the relationship between the voltage applied to the element and the transmittance, and the lower part of FIG. 4 shows the relationship between the voltage applied to the element and the current. When the voltage was swept in the negative direction, the reduction current increased from -2.3V due to the deposition of silver, and the transmittance decreased. In addition, when the positive sweep was reversed at -2.5V, the oxidation current due to silver dissolution increased from -0.2V.

FIG. 5 shows changes in transmittance when the circuit is opened after application of the coloring voltage. In the element using the conventional electrolyte containing no thiol, the transmittance immediately increased to the initial transmittance when the circuit was opened, and the color development was not maintained. On the other hand, the element of this example showed good color retention characteristics even after about 3500 seconds had elapsed after the transmittance increased to about 30%. Compared to conventional electrochromic devices, the addition of thiol prevents the mediation of copper, so even after the circuit is opened, the precipitated silver does not dissolve and is retained on the working electrode, improving the color retention characteristics. It is considered that If the transmittance is 40% or less at 3500 seconds after the circuit is opened, sufficient color retention and energy saving can be obtained, and it is desirable to be 30% or less.

FIG. 6 shows changes in transmittance and color retention characteristics when 10 mM of 1-octanethiol is added instead of 1-dodecanethiol. It was confirmed that even when 1-octanethiol was added, good color retention characteristics were exhibited.

In addition, in the same electrolyte, the quartz crystal micro balance method (QCM method) was used to observe the self-assembled film formation of thiol molecules on the metal. Measurements were performed using a gold crystal electrode as the working electrode, a platinum wire as the counter electrode, and Ag/Ag ⁺ as the working electrode. FIG. 7 shows the measurement results. A decrease in frequency was observed from about 0 seconds to about 1200 seconds when the working electrode was inserted into the electrolyte, indicating that the mass on the electrode increased. From this, it was shown that a self-assembled film is formed on the noble metal even when a voltage is applied by using an electrolytic solution to which thiol molecules are added.

As described above, it was confirmed that an electrochromic display device having a high color retention property can be obtained according to this example.

INDUSTRIAL APPLICABILITY The present invention has industrial applicability as an electrochromic display element.

2, 3 substrates 21, 31 electrode 4 electrolyte layer 41 electrochromic material 42 mediator

Claims (3)

A pair of electrodes, an electrolytic solution held between the pair of electrodes, and voltage applying means for applying a voltage to the pair of electrodes, wherein the electrolytic solution contains a solvent and silver ions dissolved in the solvent . contains an electrochromic material, a mediator, and a thiol derivative, the molar concentration of halogen atoms in the electrolytic solution is higher than the molar concentration of the electrochromic material, and when a voltage is applied to the pair of electrodes, the pair of electrodes An electrochromic display element in which a self-assembled film of the thiol derivative is formed on deposited silver directly deposited on at least one of the above. The transmittance of the electrochromic display element is 40% or less when 3000 seconds have passed since the circuit of the voltage applying means was opened after the voltage applying means applied the voltage to the pair of electrodes. The electrochromic display element according to claim 1 . 3. The electrochromic display element according to claim 1, wherein said mediator contains copper ions.

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