JP2827247B2 - Electrochromic element that uniformly colors - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrochromic device that uniformly discolors and colors, particularly a large-sized electrochromic device.

[Conventional technology]

When a voltage is applied, a phenomenon in which an electrolytic oxidation or reduction reaction occurs reversibly and coloring occurs reversibly is called electrochromism.

Electrochromic exhibiting such a phenomenon (hereinafter, referred to as
An EC element (hereinafter, abbreviated as EC) that discolors by voltage or current operation using a substance such as tungsten trioxide (hereinafter, referred to as EC)
ECD is abbreviated, and this ECD is used as a light control element (for example,
Attempts to use it for an anti-glare mirror) and a numerical display element using 7 segments have been made for more than 20 years.

For example, an ECD in which a transparent lower electrode layer, a tungsten trioxide thin film, an insulating layer such as silicon dioxide, and an upper electrode layer are sequentially laminated on a glass substrate in the order of four layers has been proposed as an all-solid-state ECD ( (See Japanese Patent Publication No. 52-46098).

When a voltage is applied to this ECD, tungsten trioxide (W
O ₃ ) The thin film is colored blue. Thereafter, when a reverse voltage is applied to the ECD, the blue color of the WO ₃ thin film disappears and the WO ₃ thin film becomes colorless.
This colored, decolored mechanism is not understood in detail, a small amount of water contained in the WO ₃ film and the insulating film is WO ₃
It is understood that it controls the coloring and decoloring of

 The reaction formula for coloring is estimated as follows.

As another ECD, a reduction coloring EC layer (for example, WO ₃ ), an ion conductive layer, and a reversible electrolytic oxide layer (for example, iridium oxide or hydroxide) are laminated between an upper electrode layer and a lower electrode layer. Layered structures are known.

At least one of the pair of electrode layers sandwiching the intermediate layer including the EC layer (the layer between the upper and lower electrode layers) must be transparent in order to show the color-discoloration of the EC layer to the outside.
In the case of a transmissive ECD, both electrode layers must be transparent.

At present, SnO ₂ , In
₂ O ₃ , ITO (mixture of SnO ₂ and In ₂ O ₃ ), ZnO, etc. are known, but these materials have to be thinned due to relatively poor transparency, and this and other reasons From, ECD
Is usually formed on a substrate (for example, a glass plate or a plastic plate).

The ECD is used by arranging a sealing substrate for protecting the element depending on the application so as to face the element substrate, and hermetically sealing it using, for example, an epoxy resin.

[Problems to be solved by the invention]

By the way, the conventional ECD has a problem that even if a coloring voltage is applied, the color gradually increases from the end and is not uniformly colored, and even if a decoloring voltage is applied, the color is not uniformly erased. Had.

Particularly in the case of a large-sized ECD used for an auto-dimming mirror of an automobile or a window of a building, the tendency is remarkable, and the above problem has been a problem in practical use.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ECD capable of uniformly discoloring and discoloring, particularly a large ECD.

[Means for solving the problem]

Therefore, as a result of diligent research, in the conventional ECD,
When the resistance of the upper electrode layer is R ₁ , the resistance of the lower electrode layer is R ₂ , and the internal resistance of the intermediate layer (excluding the electronically conductive auxiliary electrode layer) sandwiched between both electrode layers is R ₃ , The following equation (5) is used: Had become.

However, the definitions of the resistors R ₁ , R ₂ , and R ₃ are defined by the following equations (2) to
(4): The meanings of the symbols in the formulas (2) to (4) are as follows.

ρ ₁ : resistivity of the upper electrode layer ρ ₂ : resistivity of the lower electrode layer ρ ₃ : ionic resistivity of the intermediate layer d ₁ : thickness of the upper electrode layer d ₂ : thickness of the lower electrode layer d ₃ : intermediate layer L: Length of the extraction electrode (if it differs between the upper electrode layer and the lower electrode layer, the smaller value) S: Area of the electrochromic element The resistance of the extraction electrode is assumed to be almost zero.

FIG. 3 is a diagram schematically showing how a current I flows when a voltage is applied to an ECD having such a resistance relationship. Since the resistance in the vertical direction of the intermediate layer is smaller than that in the horizontal direction of the upper electrode layer, as shown in the figure, most of the current I is transmitted from one end of the upper electrode layer close to the extraction electrode to the inside of the intermediate layer. As a result, the above-described reaction proceeds in the portion close to the extraction electrode of the ECD, and the color is rapidly and deeply colored.However, almost no current flows from the central portion away from the extraction electrode to the other end, and coloring is performed. It turned out to be very slow and thin.

This causes uneven coloring, especially for large ECDs.
It was also found that this tendency was remarkable.

Further, it has been found that the colorlessness tends to be nonuniform at the time of erasing compared to the coloring, but the color is unevenly erasable for the same reason.

Therefore, as a result of further research, the relationship between the three was expressed by the following equation (1): Then, the inventors have found that the above problems can be solved, and have accomplished the present invention.

Therefore, the present invention provides: “at least an intermediate layer including an upper electrode layer and an electrochromic layer (not including an electron conductive auxiliary electrode layer);
In an electrochromic device in which lower electrode layers are laminated and a low-resistance extraction electrode is provided in a part of both electrode layers, the resistances of the upper electrode layer and the lower electrode layer are respectively R ₁ ,
R ₂ , when the internal resistance of the intermediate layer is R ₃ , the following equation (1): And an electrochromic device characterized by satisfying the following.

[Action]

FIG. 2 is a conceptual diagram showing the flow of current I when a voltage is applied between the upper and lower electrode layers (upper electrode layer: positive polarity, lower electrode layer: negative polarity) in the ECD of the present invention. .

In the present invention, since the internal resistance of the intermediate layer is sufficiently higher than that of the electrode layer, the current I input from the extraction electrode of the upper electrode layer (in the case of FIG. 2) first spreads sufficiently to the upper electrode layer, After the gradient has been eliminated, it flows uniformly into the entire intermediate layer and then to the lower electrode layer. Therefore, the voltage between the upper and lower electrode layers becomes almost equal regardless of the horizontal portion of the electrode layer.

Therefore, the color erasing and discoloring reactions occur almost at the same time in the entire EC layer.

In order to make coloring more uniform, R ₁ and R ₂
It is preferable to make R ₃ as large as possible. The following equation (6): (R ₁ + R ₂ ) <R ₃ Equation (6) Particularly, the following equation (7): 4 (R ₁ + R ₂ ) <R ₃ It is preferable to satisfy the expression (7).

In the present invention, the magnitude relationship between the resistances R ₁ and R ₂ of the two electrode layers may be any one. When both layers are transparent electrodes, when they are actually formed, the upper electrode layer formed on the uppermost layer tends to have a higher resistance than the electrode layer formed directly on the substrate.

The multilayer structure of the ECD in the present invention has an upper electrode layer, EC
Layers and a lower electrode layer as long as the EC layer is in a liquid state, for example, a layer containing an electrolyte layer in an intermediate layer, or a layer using an organic EC substance. , A metal ion such as Li ion instead of proton may be used. For example, a four-layer structure such as an electrode layer / EC layer / ion conductive layer / electrode layer, or an electrode layer / reduced coloring type EC layer / Ion conductive layer / reversible electrolytic oxidation layer /
An all solid thin film type having a five-layer structure such as an electrode layer is preferable.

As a material of the transparent electrode, for example, SnO ₂ , In ₂ O ₃ , ITO, or the like is used. Such an electrode layer is generally formed by a vacuum thin film forming technique such as vacuum deposition, ion plating, and sputtering.

(Reduction coloring) WO ₃ , MoO _{3 and the} like are generally used as the EC layer.

As the ion conductive layer, for example, silicon oxide, tantalum oxide, titanium oxide, aluminum oxide, niobium oxide, zirconium oxide, hafnium oxide, lanthanum oxide, magnesium fluoride, and the like are used. Thin films of these substances are insulators for electrons depending on the manufacturing method, but are good conductors for protons (H ⁺ ) and hydroxy ions (OH ⁻ ).

A cation is required for the color decoloring reaction of the EC layer, and it is necessary to include H ⁺ ions and Li ⁺ ions in the EC layer and the like. H ⁺ ions need not be ion from the beginning, it may be the H ⁺ ions when a voltage is applied Shojire, therefore H ⁺
Water may be contained instead of ions. This water is very small and sufficient, and often discolors even water that naturally enters from the atmosphere.

Either the EC layer or the ionic conductive layer may be on the upper side or the lower side. Further, a reversible electrolytic oxide layer or a catalyst layer may be provided on the EC layer with an ion conductive layer interposed therebetween (in some cases, an oxidative coloring EC layer).

Examples of such a layer include iridium oxide or hydroxide, nickel, chromium, vanadium, ruthenium, rhodium, and the like. These substances may be dispersed in the ionic conductive layer or the transparent electrode, or may be dispersed on the contrary.

The opaque electrode layer may also serve as the reflection layer, and for example, a metal such as gold, silver, aluminum, chromium, tin, zinc, nickel, ruthenium, rhodium, and stainless steel is used.

Both the upper and lower electrode layers need to be connected to external wiring in order to supply charges (current) from an external power supply. But,
When a transparent electrode is used as the electrode, the transparent electrode has a higher resistance than the external wiring. Therefore, a low-resistance extraction electrode is provided so as to overlap (ie, contact) the transparent electrode with a large area as long as there is no problem. Usually, a low-resistance extraction electrode is provided in a strip shape around the transparent electrode layer. As the low-resistance electrode material, the constituent material of the opaque electrode layer, for example, aluminum is generally used.

When an opaque electrode layer is used as the electrode layer, the resistance is generally low.

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

〔Example〕

FIG. 1 is a schematic sectional view showing an example of an ECD according to the present invention.

(1) First, a rectangular or parallelogram glass element substrate 10
Thickness throughout (vertical 25 cm × horizontal 15cm;; area S = 375cm ² upper, length l = 25 cm of each extraction electrode of the lower electrode layer) surface of the of d ₂ =
An ITO electrode layer (resistivity ρ ₂ = 2 × 10 ⁻⁴ Ωcm) of 2 × 10 ⁻⁵ cm was formed.

(2) Next, a thin groove was formed by etching or laser cutting at the end of the ITO electrode layer to divide the ITO electrode layer into two, thereby forming the upper electrode extraction portion 7 and the lower electrode layer 2.

Note that these patterns may be directly formed on the upper electrode extraction portion 7 and the lower electrode layer 2 by mask vapor deposition of ITO.

(3) On the lower electrode 2, a reversible electrolytic oxide layer 5 composed of a mixture of iridium oxide and tin oxide, an ion conductive layer 4 composed of tantalum oxide, and a reduction coloring EC layer 3 composed of tungsten oxide were sequentially laminated.

The thickness of the intermediate layer composed of these three layers (3, 4, 5) is
d ₃ = 1.5 × 10 ⁻⁴ cm, and the ionic resistivity is ρ ₃ = 2 × 10 ⁸
Ωcm.

(4) Further, on the EC layer 3, as the upper electrode layer 1, the thickness d ₁
= 2 × 10 ^-5 cm ITO electrode layer (resistivity ρ ₁ = 4 × 10 ^-4 Ωcm)
Was deposited. At this time, the ITO was formed such that one end thereof was in contact with the upper electrode extraction portion 7 already formed on the substrate 10.

The resistivity and ionic resistivity of each layer can be changed by selecting conditions such as the Ar / O ₂ ratio of the gas at the time of film formation, the degree of vacuum, the film formation speed, the substrate temperature, and the power of the applied high frequency. be able to.

Here, when we calculate the resistance R _1, R _2, R ₃ of the respective layers becomes as follows.

It has become.

That is, 4 (R ₁ + R ₂ ) <R ₃ <5 (R ₁ + R ₂ ) is satisfied.

(5) Next, prepare conductive clips (extraction electrodes) 8a and 8b made of phosphor bronze having a U-shaped cross section and a length of 25 cm, to which external wirings 11a and 11b are soldered or conductive respectively. They were connected with an adhesive. Then, the clips 8a and 8b were attached to the ends of the element substrate 10, respectively, so that the clip 8a and the clip 8b were pressed against the upper electrode extraction portion 7 and a part of the lower electrode layer 2, respectively. In this case, the clips 8a and 8b corresponding to the extraction electrodes are regarded as having virtually zero resistance (equipotential in any part).

Note that the shapes and dimensions of the conductive layer clips 8a and 8b are set so that positioning of the sealing substrate 6 (described later) and masking of a non-display portion around the ECD can be performed.

(6) Finally, a glass sealing substrate 6 coated with an epoxy resin sealing material 9 is overlaid (the substrate 6 is made of clips 8a, 8b
The sealing material 9 is cured to complete the ECD of this embodiment.

When a coloring voltage (+3 V) is applied from the driving power supply 12 between the upper electrode layer 1 and the lower electrode layer 2 of the ECD manufactured as described above, the ECD is quickly and uniformly colored over the entire surface.
After a second, the transmittance of incident light having a wavelength of 633 nm decreased to 10%.

This transmittance is maintained for a while even when the voltage application is stopped,
Thereafter, when a decoloring voltage (-3 V) was applied, the transmittance was restored to 70% after 20 seconds.

(Comparative example)

The resistances R ₁ = 12Ω, R ₂ = 6Ω, R ₃ = 0.15Ω by changing the resistivity ρ ₁ , ρ ₂ and the ionic resistivity ρ _{3 of} each layer without changing the size and thickness. And the relationship between the three ECD was produced.

When this ECD is subjected to a color erasure / decoloration experiment in the same manner as the example,
The color was unevenly discolored and the appearance was poor.

〔The invention's effect〕

As described above, according to the present invention, the color can be uniformly applied and erased over the entire ECD surface.

Further, in the present invention, since local current concentration does not occur, depending on the application, a higher voltage than that of the conventional ECD is applied to increase the responsiveness or increase the variable width of the color erasing density. be able to.

Such an ECD is particularly useful as an anti-glare mirror of an automobile or a window for a building (light control glass) because there is no unevenness in color erasing even when the ECD is enlarged.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an ECD according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a state in which a current flows in the ECD according to the present invention. FIG. 3 is a schematic diagram showing how a current flows in a conventional ECD. [Description of Signs of Main Parts] 1... Upper electrode layer 2... Lower electrode layer 3... Reduction coloring EC layer (intermediate layer) 4... Ion conductive layer (intermediate layer) 5. (Intermediate layer) 6: Sealing substrate 8a, 8b: Clip (an example of an extraction electrode) 9: Sealing agent 10: Element substrate

Claims (1)

(57) [Claims] At least an upper electrode layer, an intermediate layer including an electrochromic layer (not including an electronically conductive auxiliary electrode layer), and a lower electrode layer are laminated. In an electrochromic device provided with an extraction electrode, the resistances of the upper electrode layer and the lower electrode layer are R ₁ ,
R ₂ , when the internal resistance of the intermediate layer is R ₃ , the following equation (1): (R ₁ + R ₂ ) / 10 <R ₃ ... Equation (1) is satisfied. Electrochromic device. However, the definitions of the resistors R ₁ , R ₂ , and R ₃ are defined by the following equations (2) to (4): R ₁ = (ρ ₁ · S) / (d ₁ · l ² ) ··· 2) R ₂ = (ρ ₂ · S) / (d ₂ · l ² ) ··· Formula (3) R ₃ = (ρ ₃ · d ₃ ) / S ··· As shown in formula (4) And the meaning of the symbols in the formulas (2) to (4) is
It is as follows. ρ ₁ : resistivity of the upper electrode layer ρ ₂ : resistivity of the lower electrode layer ρ ₃ : ionic resistivity of the intermediate layer d ₁ : thickness of the upper electrode layer d ₂ : thickness of the lower electrode layer d ₃ : intermediate layer L: Length of the extraction electrode (the smaller value if different for the upper and lower electrode layers) S: Area of the electrochromic element