JPS641775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for manufacturing electrochromic display elements.

Electrochromism is a phenomenon in which a redox reaction occurs reversibly when a voltage is applied, and the substance reversibly develops and disappears in color. Attempts have been made to use materials that exhibit such phenomena, that is, electrochromic materials, to create display elements that repeatedly develop and discolor by applying and removing voltage, and to display clock numbers and computer numbers using these display elements. , has been going on for over 15 years. For example, a transparent electrode film (cathode), a tungsten trioxide thin film,
2. Description of the Related Art Electrochromic display elements are already known, which are formed by sequentially laminating an insulating film such as silicon dioxide and an electrode film (anode). When a voltage is applied to this display element, the tungsten trioxide (WO ₃ ) thin film is colored blue. Then, when a reverse voltage is applied to this display element, the blue color of the WO ₃ thin film disappears and it becomes colorless. Although the mechanism of coloring and decoloring has not been elucidated in detail, it is known that a trace amount of water contained in the WO ₃ thin film and the insulating film controls the coloring and decoloring of WO ₃ . The reaction formula for coloring is estimated as follows.

H ₂ O→H ⁺ +OH ^- (WO ₃ film = cathode side) WO ₃ +nH ⁺ +ne ^- →HnWO ₃ colorless blue (insulating film = anode side) 2OH ^- →H ₂ O+1/2O ₂ ↑+e ^- Therefore, this The disadvantage of such display elements is that during the coloring reaction, the moisture content is consumed by an undesirable side reaction of oxygen gas generation, and water is not produced in the reverse decoloring reaction, so it is difficult to repeat coloring. Water needs to be replenished from the atmosphere. Particularly for the latter reason, this type of display element has the disadvantage that the reproducibility of coloring is affected by moisture in the atmosphere.

Recently, the same amount of water is produced by the decoloring reaction as is consumed by the coloring reaction, and therefore coloring and decoloring can be repeated without the need for water supply from the outside world. An all-solid-state electrochromic display element whose color density is not affected by the external environment has been proposed (see Japanese Patent Laid-Open No. 73749/1983). This display element basically consists of a transparent electrode, an electrolytic reduction color forming thin film such as WO ₃ , an electrolytic oxidizing thin film such as Cr ₂ O ₃ , and a counter electrode stacked one after another. Furthermore, according to the disclosure in the above-mentioned publication, when the voltage is removed after being colored by applying a voltage, a phenomenon in which the coloring gradually disappears due to spontaneous discharge is observed, and the property that the coloring is preserved even after the voltage is removed (this is stored in the memory). In order to provide this display element with the desired properties (referred to as "transparent"), it is necessary to provide an insulating film, such as a thin film of silicon dioxide, magnesium fluoride, etc., at any position between the transparent electrode and the counter electrode. According to the inventors' speculation, this insulating film is not a good conductor of electrons, but it is a good conductor of protons (H ⁺ ).
It is a substance that can freely move hydroxy ions (OH ^- ).

The present inventor has now conducted research on a method of manufacturing an electrochromic display element, which is partially known per se.

When using nickel hydroxide or iridium hydroxide as an electrolytically oxidized thin film, the metals themselves are first vacuum-deposited and then electrolytically oxidized (anodized) in a sulfuric acid aqueous solution or a sodium hydroxide aqueous solution. An attempt was made to convert metals into hydroxides. However, such electrolytic oxidation in an acid or alkaline aqueous solution is extremely troublesome, including subsequent washing and drying steps, and increases manufacturing equipment and manufacturing costs. However, as we proceeded with our research, the present inventors happened to deposit metal nickel or metal iridium, then deposited an electrode layer on it, and when we passed an alternating current through the resulting structure for a while in the atmosphere, these metals gradually disappeared. discovered that it reacts with moisture in the atmosphere or other layers and turns into hydroxide, exhibiting electrochromism.

Therefore, the present invention provides at least the following five layers: A: Electrode layer B: Layer capable of reversibly electrolytically reducing color development C: Electronically insulating and ionically conductive layer D: The hydroxide thereof is reversibly electrolytically reducible. Oxidizable metal layer E: Production of an electrochromic display element characterized by applying an alternating current voltage between the electrodes of a structure consisting of an electrode layer in a gas atmosphere containing water vapor to convert layer D into a hydroxide. provide a method.

A gas atmosphere containing water vapor includes not only the atmosphere but also a closed space containing water vapor, and the pressure is not particularly limited to atmospheric pressure.

When carrying out the present invention, a substrate may be provided outside the electrode layer if necessary. In this case, for example, a strong and transparent material such as glass, ceramics, or plastic may be used, but a reflective type substrate may be used. In the case of a display element, the substrate on the side that is not observed does not necessarily have to be transparent.

As the electrode layers of A and E, Nesa (SnO ₂ ), ITO
(indium oxide mixed with about 5% SnO ₂ - good transparency), indium oxide (In ₂ O ₃ ),
Copper iodide, gold, platinum, palladium, aluminum, silver, conductive resin, etc. are used, but A,
At least the observation side electrode of the E2 layer must be transparent. A thickness of 0.01 to 0.5 μm is sufficient for the electrode layer, but it may be thicker if a thicker layer is desired.

Examples of the layer B, which can be reversibly colored by electrolytic reduction, include tungsten trioxide and molybdenum trioxide, and among them, tungsten trioxide is preferable.

The electronically insulating and ionically conductive layer of the C layer may be a liquid electrolyte...for example, an acid or aqueous solution thereof such as sulfuric acid or hydrochloric acid, an aqueous alkali solution such as sodium hydroxide or potassium hydroxide, sodium chloride, or lithium chloride. , aqueous solutions of solid strong electrolytes such as potassium chloride, lithium sulfate, semi-solid gel electrolytes...For example, electrolyte aqueous solutions can be mixed with gelling agents such as polyvinyl alcohol, CMC, etc.
Gelled with agar, gelatin, etc., <<P-TsOH + urea (mixed at a molar ratio of 12:1)>> Solid electrolyte...For example, HVP, B-Al ₂ O ₃ ,
Na ₃ Zr ₂ Si ₂ PO ₁₂ , Na ₁ +xZr ₂ SixP ₃ −
xO ₁₂ Na ₅ YSi ₄ O ₁₂ , RbAg ₄ I ₅ , etc. Water or ion-containing synthetic resin solids...For example, copolymer of β-hydroxyethyl methacrylate and 2-acrylamido-2-methylpropanesulfonic acid, hydrated methacrylate Hydrous vinyl polymers such as acid methyl copolymers, hydrous polyesters, etc. Others... tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), zirconium oxide (ZrO ₂ ),
Titanium oxide (TiO ₂ ), hafnium oxide (HfO ₂ ), yttrium oxide (Y ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), silicon oxide (SiO ₂ ), magnesium fluoride, zirconium phosphate, or a mixture thereof. However, among these, tantalum oxide is preferred. These materials are insulators for electrons, but good conductors for protons (H ⁺ ) and hydroxy ions (OH ⁻ ).

When the C layer is in liquid or semi-solid gel form, it exists in a sandwiched form with the B and D layers, but in the case of water or ion-containing synthetic resin solids, the B and D layers may also serve as an adhesive layer. This method is well known in the specification of Japanese Patent Application No. 56-98404 filed by the present applicant. in this case,
A thickness of about 0.1 to 1000 μm is sufficient for the C layer.

It is preferable to use a so-called solid insulator in order to make the C layer thinner or to solve the problem of liquid leakage.
It is possible to set it to 0.001-10 micrometers.

If a transmission type display element is desired for the C layer,
It must be as transparent as possible.

Examples of metals to which the hydroxide of the D layer can be reversibly electrolytically oxidized include iridium, nickel, mutenium, rhodium, and chromium, among which iridium and nickel are preferred. These metals exhibit electrochromism when converted into hydroxides.

The thickness of layer D is the same as layer B, but is usually 0.001
~ several μm is sufficient.

Layers A to E are formed by a thin film forming technique such as vacuum evaporation or sputtering, except when layer C is made of liquid, semi-solid gel, or synthetic resin.

In addition, when displaying in a pattern is desired, at least one layer other than the C layer may be patterned, or a patterned light-shielding layer or an electron/ion insulating layer may be placed between or on any layer. It may be provided.

Layers A to E can be formed by laminating A to E in order depending on the selection of layer C, or by preparing an A-B laminate and a D-E laminate in advance and sandwiching layer C between them. A structure is created.

The structure thus obtained is placed in the atmosphere, and an alternating current voltage is applied between the A and E electrodes according to the present invention. An AC frequency of 0.01 to 10Hz is sufficient;
The waveform may be a triangular wave, a rectangular wave, a sawtooth wave, or a sine wave. A voltage of about 0.5 to 3 volts is sufficient.

When an alternating current voltage is applied, the metal in layer D reacts with moisture from the atmosphere or other layers, gradually loses its metallic color and becomes transparent, and eventually begins to exhibit electrochromism.

In this way, an excellent electrochromic display element is obtained.

According to the present invention, compared to a method of electrolytic oxidation in an acid or alkaline aqueous solution, manufacturing equipment and processes are simplified, and a significant reduction in manufacturing costs is expected.

The electrochromic display element manufactured according to the present invention can be repeatedly colored and decolored with low voltage, and can be used as a means for displaying numbers or characters in calculators and watches.
It can be used for warning display means in the viewfinder of camera surveying instruments, display means for automobile instrument panels, advertising displays, etc.

Next, examples of the present invention will be shown.

Example 1 A transparent electrode film (ITO; made of indium oxide mixed with a trace amount of tin oxide) with a thickness of 0.15 μm supported on a glass plate was coated with a vacuum evaporation method (degree of vacuum 1 to 5 × 10 ^-5 Torr. Vapor deposition rate 0.001μm/sec)
A thin film of iridium metal with a thickness of 0.01 μm was formed.

Furthermore, a thickness of 0.25 μm was obtained using a vacuum evaporation method (degree of vacuum: 1 to 2×10 ^-4 Torr. Deposition rate: 2 to 3×10 ^-4 μm/sec).
A transparent thin film of tantalum pentoxide of m was formed.
Vacuum evaporation method (vacuum degree 1) on tantalum pentoxide thin film
~2×10 ^-4 Torr. Vapor deposition rate 5 to 10×10 ^-4 μm/sec)
A transparent thin film of tungsten trioxide with a thickness of 0.25 μm was formed.

Finally, transparent indium oxide was used as the counter electrode.
It was deposited to a thickness of 0.12 μm.

Of the two electrodes of the resulting structure, the electrode in contact with tungsten trioxide was connected to the cathode of an external power source, and the electrode in contact with metal iridium was connected to the anode of an external power source. When a wave alternating current voltage was applied, the metallic iridium layer gradually changed from opaque dark gray to transparent and colored repeatedly after 5 minutes.

Example 2 A transparent electrode film (ITO) with a thickness of 0.15 μm supported on a glass plate was coated with a vacuum evaporation method (degree of vacuum 1 to 5 ×
An iridium metal thin film with a thickness of 0.01 μm was formed at a deposition rate of 10 ⁻⁵ Torr. (10×10 ⁻⁴ μm/sec).

Next, a vacuum evaporation method (degree of vacuum 1 to 2 × 10 ^-4 Torr, deposition rate 2 to 3 × 10 ^-4 μm/
sec) to form a tantalum pentoxide film with a thickness of 0.25 μm, and then vacuum evaporation method (vacuum degree 1 to 2
A transparent tungsten trioxide film with a thickness of 0.25 μm was formed at a deposition rate of 5 to 10×10 ⁻⁴ μm/sec (10 ⁻⁴ Torr.).

The formed tungsten trioxide film was patterned into a desired pattern by photolithography.

Finally, transparent indium oxide was evaporated to a thickness of 0.12 μm over the entire surface as a counter electrode.

The obtained structure was heated at 0.5 Hz and 1.5 Hz as in Example 1.
When a square wave AC voltage of volts was applied, after 5 minutes, the tungsten trioxide film began to repeat the pattern of colorless and transparent←→coloring. Since the portion excluding the pattern did not exhibit electrochromic properties, it can be said that the metal iridium layer corresponding to that portion was not converted into hydroxide.

Example 3 In Example 1, ruthenium was used instead of iridium, but a substantially similar display element was obtained.

Example 4 In Example 1, rhodium was used instead of iridium, but a substantially similar display element was obtained.

Example 5 A vacuum evaporation method (degree of vacuum 1 to 2×
A thin film (thickness: 0.12 μm) of nickel metal was formed at a deposition rate of 2 ^to 3×10 ⁻⁴ μm/sec). This metallic nickel thin film was patterned into a predetermined shape by photolithography. Thereafter, as in Example 1, a tantalum pentoxide thin film, a tungsten trioxide thin film, and a counter electrode film (indium oxide) were sequentially deposited, and a triangular wave AC voltage of 0.5 Hz and 1.5 volts was applied to the resulting structure. After 5 minutes, the display area corresponding to the nickel pattern began to cycle from colorless and transparent to blackish gray. The contrast ratio before and after coloring was approximately 1:2.

Example 6 A transparent ITO electrode layer with a thickness of 0.15 μm was deposited on a mirror with a width of 30 mm, a length of 20 mm, and a thickness of 1 mm. On top of this ITO layer, the thickness was
Form a thin layer of 0.25μm tungsten trioxide,
As a result, a first member was obtained. Vacuum evaporation method (vacuum degree 1 to 5
×10 ^-5 Torr; Vapor deposition rate 1 × 10 ^-4 μm/sec; Temperature
30° C.) to form a thin layer of iridium metal with a thickness of 0.01 μm, thereby producing a second member.

Next, both members are placed facing each other so that the tungsten trioxide layer and the metal iridium layer are on the inside of each other, shifted slightly laterally, and placed on top of each other, and a mixture of water/acrylic acid = 20/80 (weight ratio) is placed in the middle of both members. The solution was allowed to penetrate and the acrylic acid was polymerized and cured by irradiating it with ultraviolet light for 10 minutes from a 500W mercury lamp placed approximately 20cm above.

In this way, a structure having an ion-permeable electronically insulating resin layer with a thickness of about 10 μm was obtained. of both parts
Take out the lead wire from the ITO layer and make sure that the tungsten trioxide side is negative and the metal iridium side is positive.
A square wave AC voltage of 0.5 Hz and 1.3 volts was applied. Ten
As minutes passed, the element gradually became colorless and transparent←→blue repeatedly. The contrast ratio was 1:3.

Example 7 Oxygen partial pressure 2 x 10 ^-4 Torr, evaporation rate 6 x 10 ^-4 μ on a quartz plate of width 30 mm x length 20 mm x thickness 25 μm.
Transparent ITO with a thickness of 0.15μm was produced using the RF ion plating method under the conditions of m/sec and temperature of 100℃.
An electrode layer was formed. Next, on top of this ITO layer, vacuum evaporation method (degree of vacuum: 1 to 2 × 10 ^-4 Torr; deposition rate: 5
~10×10 ^-4 μm/sec; room temperature) thickness 0.25μm
A thin layer of tungsten trioxide was formed to obtain a first member.

Vacuum evaporation method (vacuum degree 1 to 5 x 10 ^-5 Torr, evaporation rate 1
×10 ⁻⁴ μm/sec; room temperature) to form a thin layer of nickel metal with a thickness of 0.01 μm, thereby forming a second member.

Next, these two members are overlapped with a slight shift, and 2-acrylamide-2- is placed in the middle of both members.
It was filled with methylpropanesulfonic acid/2-hydroxyacrylate=40/60 (weight ratio) and irradiated with gamma rays (0.4 Mrad/hr) for about 5 minutes, completing polymerization and curing. In this way, a structure having an ion-permeable electronically insulating resin layer with a thickness of 10 μm was obtained.

When the lead wires were pulled out from the ITO layers of both components and an AC voltage of 0.5 Hz and 1.3 V was applied to the cell in the same manner as in Example 1, after 10 minutes, the color changed from colorless and transparent to blackish gray. The contrast ratio was approximately 1:2.

Example 8 A transparent ITO electrode layer with a thickness of 0.15 μm was deposited on a glass substrate with a width of 100 mm, a length of 150 mm, and a thickness of 2 mm.

Vacuum evaporation method (vacuum degree 1 to 5 ×
10 ^-5 Torr. Vapor deposition rate 1×10 ^-4 μm/sec, temperature 150
℃) to form a thin film of iridium metal with a thickness of 0.04 μm. Furthermore, vacuum evaporation method (vacuum degree 1 to 2
A transparent thin film of tantalum pentoxide with a thickness of ^0.75 μm was formed at a deposition rate of 2 to 3×10 ⁻⁴ μm/sec. Vacuum evaporation method (vacuum degree 1 to 2 x 10 ^-4 Torr, evaporation rate 5 to
10×10 ⁻⁴ μm/sec) to form a transparent thin film of tungsten trioxide with a thickness of 0.5 μm.

Finally, use aluminum metal as the counter electrode.
A reflective element was fabricated by vapor deposition to a thickness of 0.12 μm.

Of the two electrodes of the resulting structure, the electrode in contact with tungsten trioxide was connected to the cathode of an external power source, and the electrode in contact with metal iridium was connected to the anode of an external power source. A wave alternating current voltage was applied. After 30 minutes, the element gradually becomes
Transparent reflection ← → Blue reflection now repeats.

When a coloring voltage (+1.3V) is applied, the reflectance of this element decreases to 14% (5
seconds later), this reflectance was maintained for a while even after the voltage application was stopped. When a decolorizing voltage (-1.3V) was applied this time, the reflectance recovered to 70% (after 1 second).

Claims (1)

[Claims] 1 A: Electrode layer B: Layer capable of reversibly electrolytically reductively coloring C: Electronically insulating and ionically conductive layer D: Layer of metal whose hydroxide can be reversibly electrolytically oxidized E: A method for producing an electrochromic display element, which comprises applying an alternating current voltage between the electrodes of a structure consisting of electrode layers in a gas atmosphere containing water vapor to convert the D layer into a hydroxide.