JPS6159317A - Electrochromic element provided with heating circuit - Google Patents

Abstract

PURPOSE:To improve the response speed in low-temp. environment and to prevent dimming by providing a heating circuit which generates heat by passing electric current to a lower electrode or upper electrode which sandwiches an electrochromic layer and at least one of which is a transparent electrode. CONSTITUTION:For example, an antidazzle mirror which ECD is formed of a transparent glass substrate S on the front, thin ITO film E as the transparent lower electrode, thin film D as an oxidation colorable EC layer, thin film C as a transparent ion conductive layer, a thin film B as a reduction colorable EC layer and the upper electrode layer A in common use as a reflecting layer. Heat is generated in the electrode A when the electric current passes thereto from a low-voltage power source F via a switch SW2, level shift circuit LA and SW4. On the other hand, the heat is generated in the electrode E as well as the current flows to said electrode as well. As a result, the EC layers B, D are warmed, by which the response speed in the low-temp. environment is improved. The substrate S is also warmed and the dimming can be prevented even if the substrate S contacts with the moist and warm air in the low-temp. environment. The colored state is maintained even if the SW1, 3, 5 are turned off after the coloring.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to an improvement in an electrochromic display device that can be colored or erased by applying a voltage.

(Background of the Invention) An electrochromic element is basically a thin film of an electrochromic layer, such as WO, sandwiched between a pair of electrode layers, at least one of which is transparent.
When a voltage of 4 volts is applied, WO.

The thin film is colored blue, and the coloration is retained even after the application of the voltage is stopped, and when the same amount of reverse voltage is applied, the color disappears and returns to its original colorless and transparent state, and the coloration is maintained even when the application of the reverse voltage is stopped. Ru. Such an EC element (hereinafter referred to as ECD) has a small driving power supply, low power consumption, a relatively fast response speed for coloring/decoloring, a relatively thin overall element, and a low power consumption when decoloring. Due to its high light transmittance, relatively low light transmittance when colored, and relatively high brightness, it is being used for displays using seven segments and devices for controlling the amount of transmitted or reflected light. .

As a type of reflected light amount control device, an anti-glare mirror has also been proposed in which the amount of reflected light can be adjusted by installing an ECD on the interior mirror of an automobile and electrically coloring and decolorizing the ECD (Utility Model No. 21120). When a car's rearview mirror reflects the lights of a car following you at night,
The driver feels dazzled, so use EC when the lights are reflected.
D is colored to reduce the amount of reflected light, and at other times ECD is decolored to increase the amount of reflected light (in other words, to make it brighter).

By the way, the response speed of an ECD depends on the surrounding temperature, and generally the response speed is 0.5 in a low temperature environment below O'c.
It has the disadvantage that it is slow at ~10 seconds or less.

Another drawback is that the surface of the ECD becomes cloudy when it comes into contact with moist, warm air (for example, human breath) in a low-temperature environment.

(Object of the Invention) Therefore, the object of the present invention is to provide an ECD equipped with a heating means for the purpose of improving response speed and preventing fogging in a low-temperature environment.
Our goal is to provide the following.

(Summary of the Invention) The present inventors came up with the idea of using the upper or lower electrode itself that sandwiches the electrochromic layer of an ECD as a heating element, and have accomplished the present invention.

Accordingly, the present invention provides an electrochromic element comprising a lower electrode, an electrochromic layer, and an upper electrode, in which at least one of the lower electrode and the upper electrode is a transparent electrode, in which a current is passed through the lower electrode or the upper electrode. Provided is an electrochromic element characterized by having a heating circuit that generates heat.

Electrochromic devices (ECDs) are basically
It consists of an EC layer and a pair of electrodes sandwiching it, but generally, in addition to the EC layer, a transparent ion conductive layer or electrolyte (
A layer (which may be an electrolytic solution) is required, and a pair of two layers, a reduction color-forming EC layer and an oxidation color-forming EC layer, may be used as the EC layer. Therefore, ECr) in the present invention also
4-layer structure of "electrode/ECEC transparent ion conductive layer or electrolyte (electrolyte may be used) layer/electrode" or "electrode/reductive coloring EC layer/transparent ion conductive layer or electrolyte (electrolyte may be used) layer" It is preferable to have a five-layer structure: /oxidative color-forming EC layer, reversible electrolytic redox layer, catalyst layer/electrode.

Cations are required for the coloring and decoloring reaction of the EC layer, particularly the reduction color-forming EC layer, and it is necessary to contain H+ ions and ions in the EC layer and other parts. H+ ions do not need to be ions from the beginning; it is only necessary that ■(+ ions are generated when a voltage is applied. Therefore, water may be contained instead of 11+ ions. This water is very small. Examples of transparent electrode materials that are sufficient and often change color and fade even with moisture that naturally enters from the atmosphere include, for example, SnO2, In
2O3, ITO (indium oxide mixed with about 5% tin oxide), etc. are used.

Examples of materials used for the opaque electrode include metals such as gold, metal, aluminum, chromium, tin, zinc, nickel, ruthenium, rhodium, and stainless steel. Electrodes made of these metals can also serve as a reflective layer.

WO3 is generally used as the reduction color-forming EC substance.

Examples of the transparent ion conductive layer include silicon oxide, tantalum oxide, titanium oxide, aluminum oxide, niobium oxide, zirconium oxide, hafnium oxide, lanthanum oxide,
Magnesium fluoride etc. are used. When these thin films of materials contain a small amount of water during manufacture, they become insulators for electrons, but become good conductors for protons H (+') and hydroxy ions (OH-). An electrolyte or an electrolytic solution may be used as the ion conductive layer or in its place, for example, an acid such as sulfuric acid, hydrochloric acid, phosphoric acid, acetic acid, butyric acid, oxalic acid or an aqueous solution thereof, sodium hydroxide, potassium hydroxide, etc. aqueous alkali solution, sodium chloride,
Aqueous solutions of potassium chloride, lithium chloride, lithium sulfate, etc. are used. Further, an electrolyte or an electrolyte aqueous solution gelled with a gelling agent such as PVA, CMC, agar, gelatin, etc. may also be used. Furthermore, synthetic resins containing water or having hydroxyl or carboxyl groups, such as copolymers of β-hydroxyethyl methacrylate and other vinyl monomers, copolymers of 2-acrylamide-2-methylpropanesulfone and other vinyl monomers, etc. Polymers, polyacrylic acids, hydrous polyesters, etc. can also be used.

Li+ ions may be used instead of H+ ions, in which case lithium salts such as LiCIO4, LiBF4, etc. may be mixed with methanol, ethanol, ethylene glycol, ethyl cellosolve, tetrahydrofuran, acetonitrile,
Pyridine, T-butyrolactone, dimethyl sulfoxide, dimethylform 1, amide, propylene carbonate 1.
or solid lithium electrolyte dissolved in a solvent such as 1. i, WoiLi3N, LiN, etc. are used.

Examples of the oxidative color-forming EC layer or reversible electrolytic redox layer or catalyst layer that may be used include iridium oxide or hydroxide, nickel, chromium, vanadium, ruthenium, rhodium, etc. . These materials may also be dispersed in other transparent ionic conductors or transparent electrode materials. In any case, it must be colorless and transparent when no voltage is applied, and colorless and transparent or colored when a voltage is applied.

Hereinafter, the present invention will be explained in detail with reference to Examples, but the present invention is not limited thereto.

(Example) FIG. 1 is a conceptual diagram illustrating an anti-glare mirror with ECD according to this example.

In Figure 1, (S) is a transparent glass substrate on the surface, (E) is an I-To thin film as a transparent lower electrode, (D) is an iridium hydroxide thin film as an oxidative color-forming EC layer, and (C) is transparent. A tantalum oxide thin film containing a trace amount of water is used as an ion conductive layer, (B) is a WO thin film as a reduction coloring EC layer,
(A) is an An layer serving as an upper electrode that also serves as a reflective layer.

In addition, (F) is a constant voltage power supply, (LA) and (L
B) is a level shift.

(SI'L) is a main switch, which turns the constant voltage power supply ON-OFF. (S6) and (5W3) are ECD
It is a switch for coloring and decoloring, and both can be turned ON and OFF at the same time.
It is necessary to perform F, and when it is ON, it colors, and when it is OFF, it decolors. <5u4) and (!J5) are switches that maintain the colored state or decolored state even when the voltage is stopped (that is, have memory properties), and both must be turned on and off at the same time. Therefore, it is turned on when driving coloring/decoloring, and turned off when the memory is temporarily activated.

FIG. 2 is an electrical circuit diagram showing an example of the level shift shown in FIG. 1.

Turn on the main switch (Sl'l+), apply current (ro) from the constant voltage power supply (F), and turn on the switch (!l).
When Jz ) and (5ILK) are turned on, the current (IA) is divided into the current (IA) and the current (IE) so that a constant potential difference (-V, ) is generated by the level shift (LA), and the current (IA) is also used as a reflective layer. flows to the upper Al electrode (A), where Al
If the resistance of the electrode (A) is RA, then QA = (IA)
Generates heat from 2XRA. On the other hand, the current (IE) flows to the lower rTo electrode (E) where it flows to the ITO electrode (
If the resistance of E) is R1, then QE - (IE)"XR
Generates heat of E. For example, A1 has an electrical resistance of about 3 ohms, so when a current of about 0.5 to 2 amperes is passed through it, it generates heat that can be felt in the hand. As a result, EC1i (B) and (D) are warmed and the response speed does not slow down even in low-temperature environments, and the transparent substrate (S)
It also warms the air, so even if it comes in contact with warm, humid air in a low-temperature environment, it won't become cloudy.

On the other hand, since a constant voltage (-1) is applied between the electrodes (A) and (E) at any position, the EC layer (B),
(D) is colored. As a result, the amount of reflected light decreases. Once colored, turn off the switches (SWa) and (SWs), and the main switch (
The colored state is maintained even if SW+) is turned off. If the switches (SW, ) and (S) are not turned off, a short circuit will occur between electrodes (A) and (E), so
The color will fade eventually. However, in terms of keeping warm,
It is preferable not to turn off the main switch (SW+).

To erase the color, turn on the main switch (SH+), then turn on switches (SWg) and (5W3).
When the FF is turned on, the current (Io) is level shifted (L
A) is divided into a current (I,) and a current (I, ) with a constant potential difference (+VI), the current (IA) flows to the upper A1 electrode (A) which also serves as a reflective layer, and the current (I,) is Lower ITO
flows to the electrode (E), and as a result, each electrode (A>, (
E) generates heat. Since a constant potential difference (→-V+) is applied between the electrodes (A) and (B) at any position, the EC layer is immediately decolored. Once the color is erased, switch <SUa) and (sW5) are turned off.
When set to FF, turn the main switch (SW+) to 6FF.
However, the decolored state is maintained. However, from the standpoint of keeping warm, it is preferable not to turn off the main switch (SW+).

(Effects of the Invention) As described above, according to the present invention, the electrodes of the ECD can be used as they are as heating elements, and simply by attaching a heating circuit.
The ECD can be easily heated, and as a result, it is possible to eliminate the decrease in response speed in a low-temperature environment and to prevent fogging.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram illustrating the overall configuration of an ECD-equipped anti-glare mirror according to an embodiment of the present invention. FIG. 2 is an electrical circuit diagram showing an example of the level shift shown in FIG. 1. [Explanation of symbols of main parts] S... Transparent substrate SW,... Main switch SWz, SL
, 5IAa, SWs... Switch LA
, I, B... Level shift
4F ・・・・・・ Constant voltage power supply

Claims (1)

[Claims] In an electrochromic element comprising a lower electrode, an electrochromic layer, and an upper electrode, in which at least one of the lower electrode and the upper electrode is a transparent electrode, heat is generated by passing a current through the lower electrode or the upper electrode. An electrochromic element characterized in that it is provided with a heating circuit.